WO2019087946A1 - 電動パワーステアリング装置用ギヤハウジングおよびその製造方法、並びに、電動パワーステアリング装置 - Google Patents

電動パワーステアリング装置用ギヤハウジングおよびその製造方法、並びに、電動パワーステアリング装置 Download PDF

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Publication number
WO2019087946A1
WO2019087946A1 PCT/JP2018/039781 JP2018039781W WO2019087946A1 WO 2019087946 A1 WO2019087946 A1 WO 2019087946A1 JP 2018039781 W JP2018039781 W JP 2018039781W WO 2019087946 A1 WO2019087946 A1 WO 2019087946A1
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WO
WIPO (PCT)
Prior art keywords
worm
worm wheel
electric power
power steering
housing
Prior art date
Application number
PCT/JP2018/039781
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English (en)
French (fr)
Japanese (ja)
Inventor
貴之 石井
Original Assignee
日本精工株式会社
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Filing date
Publication date
Application filed by 日本精工株式会社 filed Critical 日本精工株式会社
Priority to JP2019550305A priority Critical patent/JP6911934B2/ja
Publication of WO2019087946A1 publication Critical patent/WO2019087946A1/ja

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    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22C—FOUNDRY MOULDING
    • B22C9/00—Moulds or cores; Moulding processes
    • B22C9/22—Moulds for peculiarly-shaped castings
    • B22C9/24—Moulds for peculiarly-shaped castings for hollow articles
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B22—CASTING; POWDER METALLURGY
    • B22D—CASTING OF METALS; CASTING OF OTHER SUBSTANCES BY THE SAME PROCESSES OR DEVICES
    • B22D17/00—Pressure die casting or injection die casting, i.e. casting in which the metal is forced into a mould under high pressure
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B29—WORKING OF PLASTICS; WORKING OF SUBSTANCES IN A PLASTIC STATE IN GENERAL
    • B29C—SHAPING OR JOINING OF PLASTICS; SHAPING OF MATERIAL IN A PLASTIC STATE, NOT OTHERWISE PROVIDED FOR; AFTER-TREATMENT OF THE SHAPED PRODUCTS, e.g. REPAIRING
    • B29C45/00—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor
    • B—PERFORMING OPERATIONS; TRANSPORTING
    • B62—LAND VEHICLES FOR TRAVELLING OTHERWISE THAN ON RAILS
    • B62D—MOTOR VEHICLES; TRAILERS
    • B62D5/00—Power-assisted or power-driven steering
    • B62D5/04—Power-assisted or power-driven steering electrical, e.g. using an electric servo-motor connected to, or forming part of, the steering gear

Definitions

  • the present invention relates to a gear housing for an electric power steering apparatus for housing a worm reduction gear, and an electric power steering apparatus.
  • FIG. 12 shows an example of a conventional structure of an electric power steering apparatus.
  • the electric power steering apparatus includes a steering shaft 2 and a cylindrical steering column 3 rotatably supporting the steering shaft 2 inward, and auxiliary power for reducing the force required for the driver to operate the steering wheel 1.
  • a universal joint 5a, an intermediate shaft 6, and a universal joint 5b for transmitting the rotation of the steering shaft 2 to the pinion shaft 8 of the steering gear unit 7 are provided.
  • the steering wheel 1 is fixed to the rear end of the steering shaft 2. The movement of the steering wheel 1 at the time of steering is transmitted to the pinion shaft 8 via the steering shaft 2, the electric assist device 4, the universal joint 5a, the intermediate shaft 6, and the universal joint 5b.
  • the rotation of the pinion shaft 8 pushes and pulls the pair of tie rods 9 arranged on both sides of the steering gear unit 7, and a steering angle according to the amount of operation of the steering wheel 1 is given to the pair of left and right steered wheels.
  • the front-rear direction refers to the front-rear direction of the vehicle body on which the electric power steering apparatus is assembled.
  • FIG. 13 shows a specific structure of the electric assist device described in WO 2016/084659.
  • the electric assist device 4a is disposed in front of the steering column 3, and controls the energization based on measurement signals from the torque sensor 10 and the torque sensor 10 that measure the steering torque input from the steering wheel 1 to the steering shaft 2. It is fixed to the front end of the electric motor 11 and the worm reduction gear 12 which applies the auxiliary power from the electric motor 11 to the output shaft 13 to generate the auxiliary power in a fixed state, the torque sensor 10 and the worm A gear housing 14 is provided to accommodate the reduction gear 12.
  • the gear housing 14 includes a front housing 15 and a rear housing 16 disposed in the front-rear direction and coupled by a plurality of bolts.
  • the front housing 15 is a cylindrical worm disposed at a part in the circumferential direction (upper end in the illustrated example) of the cup-shaped worm wheel accommodating portion 17 whose rear is open and the outer diameter side portion of the worm wheel accommodating portion 17 And a housing portion 18.
  • the worm wheel accommodating portion 17 is provided with a mounting stay 19 which protrudes forward and supports the gear housing 14 with respect to the vehicle body.
  • the worm reduction gear 12 includes a worm wheel 20 externally fitted and fixed to the output shaft 13 and a worm shaft 21 coupled to the output shaft of the electric motor 11.
  • the worm wheel 20 is accommodated inside the worm wheel accommodating portion 17.
  • the worm shaft 21 is accommodated inside the worm accommodating portion 18.
  • the worm shaft 21 includes a worm 22 at an intermediate portion thereof, and the worm 22 and the worm wheel 20 mesh with each other.
  • the output shaft 13 is rotatably supported in the gear housing 14, and is connected to the input shaft 23 coaxially disposed with each other via a torsion bar 24.
  • the front end portion of the output shaft 13 is connected to the pinion shaft 8 through a pair of universal joints 5a, 5b and an intermediate shaft 6, as shown in FIG.
  • the rear end of the input shaft 23 is connected to the front end of the steering shaft 2.
  • the input shaft 23 and the output shaft 13 twist the torsion bar 24 by the steering torque applied to the input shaft 23 via the steering shaft 2 and the resistance to the rotation of the output shaft 13. Relative to the rotational direction while being elastically deformed.
  • the relative displacement between the input shaft 23 and the output shaft 13 is measured by the torque sensor 10.
  • a controller (not shown) controls the electric motor 11 according to the measurement signal of the torque sensor 10, and the auxiliary power (auxiliary torque) from the electric motor 11 is applied to the output shaft 13 via the worm reduction gear 12. .
  • the worm wheel accommodating portion constituting the front housing is provided with a through hole at the radial center portion in order to rotatably arrange the output shaft inside thereof.
  • the front housing having such a through hole is manufactured by casting or injection molding, the material which has flowed on both sides of the column portion for forming the through hole, which is a part of the mold, Since the merging is performed on the rear side (downstream with respect to the flow direction of the material), a weld line is easily generated at the merging portion. For this reason, the quality of the confluence tends to deteriorate, and the product strength may decrease.
  • An object of the present invention is to realize a structure of a gear housing for an electric power steering apparatus, which can secure rigidity and can suppress a reduction in strength of a material joining portion occurring at the time of manufacture. .
  • the gear housing for an electric power steering apparatus constitutes an electric power steering apparatus, and includes a front housing and a rear housing which are combined in the front-rear direction directly or through other members such as an intermediate plate. Prepare.
  • the front housing includes a worm wheel receiving portion for receiving a worm wheel inside, a worm receiving portion for receiving a worm shaft inside, and a thick portion.
  • the worm wheel accommodating portion includes a worm wheel cylinder portion disposed around the worm wheel, a circular worm wheel bottom portion bent radially inward from a front end portion of the worm wheel cylinder portion, and a diameter And a through hole axially extending in the worm wheel receiving portion.
  • the worm accommodating portion is provided in a circumferential direction part of the outer diameter side portion of the worm wheel accommodating portion, and has a motor mounting flange projecting radially outward at an opening side end.
  • the thick portion has a thickness dimension larger than a portion present in the periphery, and is disposed on a side far from the worm accommodating portion and close to the motor mounting flange in the bottom portion for a worm wheel Ru. More specifically, the thick portion is a side opposite to the worm accommodating portion across the central axis of the worm wheel accommodating portion in the bottom portion for the worm wheel, and an axial direction of the worm accommodating portion With respect to the motor mounting flange.
  • the gear housing for an electric power steering apparatus is provided with the thick-walled part on the side far from the worm accommodating part and close to the motor mounting flange in the bottom part for the worm wheel.
  • a rib having a large thickness dimension can optionally be provided at any other position of the bottom portion of the worm wheel as compared to the portion present at the periphery.
  • the opening edge portion of the through hole in the radial direction central portion of the worm wheel bottom portion may be provided with an annular protrusion protruding forward.
  • the front side surface of the thick portion can be disposed at the same position as the front side surface of the annular projection, or rearward of the front side surface of the annular projection.
  • the thick portion may be arranged to extend radially from the annular projection.
  • the electric power steering apparatus comprises a worm reduction gear having a worm shaft rotationally driven by an electric motor, a worm provided at an intermediate portion of the worm shaft, and a worm wheel meshing with the worm.
  • a gear housing is provided for receiving the worm reduction gear inside.
  • the gear housing is configured by the gear housing for the electric power steering apparatus of the present invention.
  • the front housing is manufactured by injection molding of cast or synthetic resin using a mold having a cavity. At this time, the material is made to flow from the side of the worm accommodating portion forming space for forming the worm accommodating portion to the worm wheel accommodating portion forming space for forming the worm wheel accommodating portion in the cavity.
  • a thick portion forming space for forming the thick portion is disposed on the rear side of the portion for forming the through hole with respect to the flow of the material in the mold.
  • the material may be merged on the rear side of the portion for forming the through hole, and the thick portion may be formed at the merging portion of the material.
  • rigidity can be secured, and a reduction in strength of the material joining portion occurring at the time of manufacture can be suppressed.
  • FIG. 1 is a side view of an electric power steering apparatus according to a first example of the embodiment.
  • FIG. 2 is a front view of the electric power steering apparatus according to the first example of the embodiment.
  • FIG. 3 is a cross-sectional view of an essential part of the electric power steering apparatus according to the first example of the embodiment.
  • FIG. 4 is a cross-sectional view taken along line AA of FIG.
  • FIG. 5 is a front view showing the front housing taken out of the electric power steering apparatus according to the first example of the embodiment.
  • FIG. 6 is a perspective view showing the front housing of the electric power steering apparatus according to the first example of the embodiment.
  • FIG. 7 is a schematic view of a mold for illustrating a process of forming the front housing of the first example of the embodiment by casting or injection molding.
  • FIG. 8 is a front view corresponding to FIG. 5 regarding the electric power steering apparatus according to the second example of the embodiment.
  • FIG. 9 is a perspective view corresponding to FIG. 6 regarding the electric power steering apparatus of the second example of the embodiment.
  • FIG. 10 is a front view corresponding to FIG. 5 regarding the electric power steering apparatus according to the third example of the embodiment.
  • FIG. 11 is a perspective view corresponding to FIG. 6 regarding the electric power steering apparatus according to the third example of the embodiment.
  • FIG. 12 is a partially cutaway side view showing an example of a conventional electric power steering apparatus.
  • FIG. 13 is a cross-sectional view corresponding to FIG. 3 regarding the electric assist device of the conventional structure.
  • the electric power steering apparatus includes a tilt / telescopic mechanism capable of adjusting the vertical position and the longitudinal position of the steering wheel 1 (see FIG. 12) in accordance with the driver's physique and driving posture, and the steering wheel 1
  • An electric assist device 4b is provided to reduce the force required for the operation.
  • the steering shaft 2a is rotatably supported inside the steering column 3a via a plurality of rolling bearings (not shown).
  • the steering wheel 1 is fixed to a portion of the rear end portion of the steering shaft 2a that protrudes rearward beyond the rear end opening of the steering column 3a.
  • the steering shaft 2a includes an inner shaft 25 and an outer shaft 26, which can transmit a rotational force and allow relative displacement in the axial direction by spline engagement or the like.
  • the inner shaft 25 and the outer shaft 26 are axially displaced relative to each other to adjust the longitudinal position of the steering wheel 1 and to reduce the overall length of the steering shaft 2a in the event of a collision.
  • the steering column 3a has a hollow cylindrical shape as a whole, and includes an inner column 27 and an outer column 28. A front portion of the outer column 28 is fitted loosely to allow a relative displacement in the axial direction to a rear portion of the inner column 27 Have a structure that The steering column 3a has a function of enabling adjustment of the front-rear position of the steering wheel 1, and a function of shortening the total length of the steering column 3a together with the steering shaft 2a in the event of a collision.
  • the gear housing 14a which comprises the electrically-driven assist apparatus 4b is fixed to the front end part (left end part of FIG. 1) of the inner column 27. As shown in FIG.
  • the gear housing 14a is supported so as to be able to pivot about a tilt shaft 30 disposed in the width direction with respect to the lower bracket 29 fixed to the vehicle body.
  • the width direction refers to the width direction of the vehicle body on which the electric power steering apparatus is assembled, and corresponds to the left-right direction.
  • the outer column 28 is supported by the upper bracket 31 on the vehicle body.
  • the upper bracket 31 is configured to be detachable forward from the vehicle body when a strong impact directed to the front is applied.
  • the outer column 28 is supported movably in the front and rear direction and in the up and down direction with respect to the upper bracket 31, and the front and rear position and the up and down position of the steering wheel 1 can be adjusted.
  • the pair of held portions 32 constituting the outer column 28 are provided with telescopic adjustment long holes 33 which are long in the front-rear direction.
  • the pair of support plate portions 34 constituting the upper bracket 31 disposed on both sides in the width direction of the pair of held portions 32 are provided with long tilt adjustment long holes 35 in the vertical direction.
  • the adjustment rod 36 is inserted in the width direction into the telescopic adjustment long hole 33 and the tilt adjustment long hole 35.
  • a lever (not shown) fixed to the end of the adjustment rod 36 and expanding / contracting the expansion / contraction device (not shown) arranged around the adjustment rod 36 in the width direction, a pair of support plates 34 hold a pair of clamped
  • the force holding the portion 32 from both sides in the width direction can be adjusted.
  • the outer column 28 can be fixed to the upper bracket 31 or can be released from the fixing.
  • the outer column 28 moves back and forth within the range in which the adjustment rod 36 can be displaced inside the telescopic adjustment long hole 33, and the longitudinal position of the steering wheel 1 can be adjusted. Further, the vertical position of the steering wheel 1 can be adjusted by vertically moving the steering column 3a within a range in which the adjusting rod 36 can be displaced inside the tilt adjusting long hole 35. At this time, the steering column 3 a swings in the vertical direction about the tilt shaft 30.
  • An electric assist device 4b for reducing the operation force of the steering wheel 1 is disposed in front of the steering column 3a, and includes a torque sensor 10a, an electric motor 11a, a worm reduction gear 12a, an output shaft 13a, and a gear housing 14a. Equipped with
  • the gear housing 14a includes a front housing 15a and a rear housing 16a combined in the front-rear direction via an intermediate plate 37, and accommodates the worm reduction gear 12a inside.
  • the front housing 15a and the rear housing 16a are both cast products (including die cast molded products) of light alloys such as iron-based alloys or aluminum alloys, or injection molded products of synthetic resin.
  • the front housing 15a swings and displaces the vehicle body through the lower bracket 29 and the worm wheel housing portion 17a housing the worm wheel 20a inside, the worm housing portion 18a housing the worm shaft 21a inside, and the gear housing 14a. And a pair of mounting stays 19a for possible support.
  • the thickness of each part of the front housing 15a is reduced for weight reduction.
  • the gear housing 14a of this example includes one radial rib 59 corresponding to the thick portion in the present invention. Furthermore, the gear housing 14a of the present example is provided with a plurality (three in the illustrated example) of bridging ribs 38a, 38b and 38c.
  • the worm wheel accommodating portion 17a has a cup shape opened at the rear and a central axis extending in a substantially horizontal direction.
  • the worm wheel accommodating portion 17a is disposed around the worm wheel 20a, and is disposed forward of the worm wheel cylindrical portion 39 and the worm wheel 20a, and radially from the front end portion of the worm wheel cylindrical portion 39.
  • an annular worm wheel bottom 40 bent substantially at a right angle toward the inside.
  • the worm wheel bottom portion 40 is provided with a substantially cylindrical inner diameter side cylindrical portion 41 at an inner peripheral edge portion.
  • the bottom portion 40 for the worm wheel is provided with a bearing holding hole 42 corresponding to the through hole in the present invention in the radial direction inner portion of the inner diameter side cylindrical portion 41 which is the radial direction central portion.
  • the worm wheel bottom portion 40 is provided with an annular projection 43 at the opening edge portion on the front side of the bearing holding hole 42, which protrudes forward more than the radial direction intermediate portion and the outer portion of the worm wheel bottom portion 40.
  • the annular projection 43 is constituted by the front end portion of the inner diameter side cylindrical portion 41.
  • the worm accommodating portion 18a has a substantially bottomed cylindrical shape.
  • the worm accommodating portion 18a is a part of the outer diameter side of the worm wheel accommodating portion 17a in the circumferential direction, and is disposed at a portion located below in the assembled state of the electric power steering apparatus.
  • the internal space of the worm accommodating portion 18a communicates with the internal space of the worm wheel accommodating portion 17a.
  • the worm accommodating portion 18a extends in a substantially horizontal direction, but has a central axis which is in a twisted positional relationship with the central axis of the worm wheel accommodating portion 17a.
  • the worm accommodating portion 18 a includes a motor mounting flange 44 protruding radially outward at an opening side end.
  • the pair of mounting stays 19 a project forward from the vertical middle portion of the front side surface of the worm wheel bottom 40. Specifically, the pair of mounting stays 19a are arranged at positions mutually sandwiching the bearing holding holes 42 in the width direction of the vehicle body in the worm wheel bottom portion 40 of the front housing 15a, being mutually separated. . Each of the pair of mounting stays 19a has mounting holes 45 at its tip end, which pass through in the width direction and into which the tilt shaft 30 is inserted.
  • the front half portion of the mounting stay 19a has a tapered shape in which the dimension in the vertical direction decreases toward the tip end, whereas the base half portion of the mounting stay 19a does not change in the dimension in the vertical direction.
  • the widthwise outer surface of the base end portion of the mounting stay 19a is continuous with the outer peripheral surface of the worm wheel cylindrical portion 39, while the widthwise inner surface of the base end portion of the mounting stay 19a is annular projection 43 To be continuous. Further, the lower end portion of the widthwise outer surface of the mounting stay 19a positioned on the opening side (left side in FIGS. 2 and 5) of the worm accommodating portion 18a in the width direction is the upper end portion of the inner surface of the motor mounting flange 44 in the width direction. Be continuous.
  • the pair of mounting stays 19 a is disposed between the pair of side plate portions 46 that constitute the lower bracket 29.
  • the radial ribs 59 are provided on the front side of the worm wheel bottom 40, and are solid, having a thickness dimension in the front-rear direction larger than the portion present at the periphery.
  • the thickness dimension of the portion of the front housing 15a provided with the radial rib 59 is, for example, 10 times or less the thickness dimension of the portion existing around the radial rib 59 of the front housing 15a. The range is set large enough.
  • the thickness dimension of the portion where the bridging ribs 38a, 38b, 38c are installed is set such that the bridging ribs 38a, 38b, 38c do not project axially from the annular projection 43. Is preferred.
  • the formation positions (ranges) of the radial ribs 59 are through holes in the mold (casting mold, injection molding mold) 61 when the front housing 15a is manufactured by casting or injection molding, as shown in FIG. Assuming that the molten metal flowing on both sides of the column portion 62 for forming the bearing holding holes 42 merges, the following restriction is performed. That is, of the bottom portions 40 for the worm wheel, the motor mounting flange 44 is on the side (upper side in FIGS. 2, 5, 6 and 7) far from the worm accommodating portion 18a in the vertical direction and in the width direction of the vehicle body.
  • the radial ribs 59 are arranged in the range (the range with the oblique grid pattern in FIG.
  • the radial rib 59 extends in the radial direction, and its radially inner end is connected to the annular projection 43, and its radially outer end is located at the radially outer end of the worm wheel bottom 40.
  • the radial rib 59 has a cross-sectional shape such as a trapezoidal shape, a convex arc shape, or the like in which the dimension in the width direction (short direction) decreases toward the front. Releasability from the mold 61 is ensured by providing drafts to the lateral side surfaces of the radial ribs 59. Further, the front side surface of the radial rib 59 is disposed at the same position as the front side surface of the annular projection 43 or at the rear of the front side surface of the annular projection 43. This prevents the deterioration of the layout of the other members disposed in front of the front housing 15a due to the radial ribs 59.
  • the three bridging ribs 38a, 38b and 38c are respectively solid and arranged on the front side of the front housing 15a so as to bridge the worm housing 18a and the worm wheel bottom 40. Further, the bridging ribs 38a, 38b, 38c act on the meshing reaction force between the worm wheel 20a and the worm 22a provided on the worm shaft 21a in the alignment direction of the worm wheel accommodating portion 17a and the worm accommodating portion 18a. It extends in the direction (up and down in FIGS. 2, 4 and 5).
  • hung passing ribs 38a, 38b, a 38c are substantially arranged parallel to the imaginary straight line L that is perpendicular to the central axis O 11 of the output shaft of the central axis O 20 and the electric motor 11a of the worm wheel 20a .
  • the term "substantially parallel” includes the case where the forming direction of the bridging ribs 38a, 38b, 38c is inclined with respect to the imaginary straight line L due to a manufacturing error or an assembly error of the electric power steering apparatus.
  • the extension direction of the bridging ribs 38a, 38b and 38c is inclined with respect to the imaginary straight line L as long as the rigidity of the front housing 15a against the engagement reaction force between the worm wheel 20a and the worm 22a can be improved.
  • the angle between the extending direction of the bridging ribs 38a, 38b and 38c and the imaginary straight line L can be set to any angle of 45 degrees or less, that is, 0 degrees, that is, the bridging ribs 38a and 38b.
  • 38c and the imaginary straight line L are preferably parallel to each other.
  • the angle between the extending direction of the bridging ribs 38b and 38c and the virtual straight line Lto is an arbitrary angle of 45 degrees or less, where the angle between the extending direction of the bridging rib 38a and the virtual straight line L is 0 degrees. You can also.
  • the meshing reaction force is a force acting in the opposite direction so that the worm wheel 20a and the worm shaft 21 are separated.
  • the bridging ribs 38a, 38b and 38c are extended in the acting direction of the meshing reaction force, the rigidity of the front housing 15a with respect to the meshing reaction force can be effectively improved. For this reason, even when the front housing 15a is thinned, it is possible to prevent the occurrence of harmful deformation or the like due to the meshing reaction force in the front housing 15a.
  • the cross-over ribs 38a, 38b and 38c have cross-sectional shapes such as trapezoidal or convex circular arc shapes whose dimension in the width direction (shorter direction) decreases toward the front, like the cross-sectional shape of the radial ribs 59.
  • each of the widthwise side surfaces of the bridging ribs 38a, 38b, 38c have a draft, releasability from the casting mold or the injection mold is secured.
  • the front side surfaces of the bridging ribs 38a, 38b and 38c are also arranged at the same position as the front side surface of the annular projection 43 or at the rear than the front side surface of the annular projection 43. This prevents the deterioration of the layout of the other members disposed in front of the front housing 15a due to the bridging ribs 38a, 38b and 38c.
  • the bridging rib 38a installed at the widthwise middle part is the lower end portion of the annular projection 43 closest to the worm housing 18a and the shaft of the worm housing 18a. It is arranged to be bridged to the direction middle part. Therefore, the upper end portion of the bridging rib 38 a is connected to the lower end portion of the annular projection 43.
  • the two bridging ribs 38b and 38c provided on both sides in the width direction are bridged between the lower surface of the base end of the pair of mounting stays 19a and the two axial sides of the worm accommodating portion 18a. Arranged as.
  • the upper ends of the bridging ribs 38b and 38c are connected to the lower surface of the proximal end of the mounting stay 19a. That is, the bridging ribs 38b and 38c and the pair of mounting stays 19a are arranged to be continuous in the vertical direction.
  • the thickness dimension in the width direction of the bridging rib 38a is substantially constant over the entire length
  • the thickness dimension in the width direction of the bridging ribs 38b and 38c is the attachment stay 19a. It gets bigger as it approaches.
  • the front housing 15a is provided with a plurality of (three in the illustrated example) bosses 47 projecting forward relative to a portion present in the periphery at a plurality of locations on the front side.
  • bosses 47 project more forward than the portions present around them, and are thus thicker.
  • the two bosses 47 arranged at the outer peripheral edge of the worm wheel housing 17a are continuous with the bridging ribs 38b and 38c, respectively.
  • the front housing 15a having the above-described configuration is produced by casting or injection molding using a mold (casting mold, injection molding mold) 61 having a cavity 63.
  • a worm accommodating portion forming space 64 for forming the worm accommodating portion 18a, of the gate G of the mold 61 serving as a supply port of a material (molten metal, synthetic resin). are disposed on the opposite side of the worm wheel accommodating portion forming space 65 for forming the worm wheel accommodating portion 17a. That is, the gate G is disposed such that the worm accommodating portion forming space 64 is on the upstream side.
  • the material having passed through the worm accommodating portion forming space 64 flows to the worm wheel accommodating portion forming space 65 side.
  • the worm accommodating portion 18a is positioned upstream of the worm wheel accommodating portion 17a in the material flow direction.
  • the rear housing 16 a is formed of a cast or a synthetic resin injection-molded article having a hollow cylindrical shape as a whole, and includes a fixed cylindrical portion 48, a large diameter cylindrical portion 49 and a continuous portion 50.
  • the fixed cylindrical portion 48 has a cylindrical shape and is fixedly fitted to the front end portion of the inner column 27.
  • the large diameter cylindrical portion 49 is disposed around the torque sensor 10 a and abuts on the rear end opening of the front housing 15 a via the intermediate plate 37.
  • the continuous portion 50 connects the front end portion of the fixed cylindrical portion 48 and the rear end portion of the large diameter cylindrical portion 49.
  • the front housing 15a and the rear housing 16a are connected to each other by a plurality of (three in the illustrated example) bolts 57 in a state where they are combined via the intermediate plate 37.
  • the front fitting portion 51 provided on the outer diameter side portion of the front side surface of the intermediate plate 37 which is generally formed in a substantially annular shape
  • the front housing 15a (cylindrical portion 39 for worm wheel
  • the front end portion of the rear housing 16 large diameter cylindrical portion 49) is externally fitted to the rear fitting portion 52 provided on the outer diameter side portion of the rear side.
  • a plurality of (three in the illustrated example) rear coupling flanges 58 formed on the outer peripheral surface are coupled to one another by bolts 57, respectively.
  • the output shaft 13a is rotatably supported by the pair of rolling bearings 54a and 54b inside the gear housing 14a having the above-described configuration.
  • the rolling bearing 54a on the front side is internally fitted and held in the bearing holding hole 42 constituting the front housing 15a, and the rolling bearing 54b on the rear side is on the inner circumferential surface of the intermediate plate 37. Internally held.
  • the outer ring forming the front side rolling bearing 54 a is fitted and fixed to the axially intermediate portion of the inner peripheral surface of the bearing holding hole 42 by press-fitting.
  • the outer ring constituting the rolling bearing 54 a on the front side is provided at a portion near the front end of the bearing holding hole 42 and is formed at a step surface facing rearward and a portion near the rear end of the inner circumferential surface of the bearing holding hole 42 It is clamped from both sides by the snap ring locked by the locking groove.
  • the output shaft 13a is coupled to the front end portion of the inner shaft 25 constituting the steering shaft 2a via a torsion bar 24a. Further, a universal joint 5a is coupled to a portion of the front end portion of the output shaft 13a that protrudes to the outside of the gear housing 14a.
  • a worm wheel 20a constituting the worm reduction gear 12a is externally fitted and fixed between the pair of rolling bearings 54a and 54b. In this state, the worm wheel 20a is disposed inside the worm wheel receiving portion 17a that constitutes the front housing 15a.
  • the worm shaft 21a constituting the worm reduction gear 12a is rotatably supported inside the worm accommodating portion 18a via a pair of rolling bearings 55a and 55b.
  • the worm 22a provided at the middle portion of the worm shaft 21a meshes with the worm wheel 20a.
  • the output shaft of the electric motor 11a is connected to the proximal end of the worm shaft 21a. Thereby, the auxiliary power of the electric motor 11a can be transmitted to the worm wheel 20a.
  • the electric motor 11a is supported and fixed to the gear housing 14a via a motor mounting flange 44 that constitutes the front housing 15a.
  • the tip end of the worm shaft 21a is directed to the worm wheel 20a side between the rolling bearing 55a externally fitted to the tip end of the worm shaft 21a and the inner peripheral surface of the worm accommodating portion 18a.
  • a torque sensor 10a is disposed around the front end of the inner shaft 25 inside the large diameter cylindrical portion 49 that constitutes the rear housing 16a.
  • the electric motor 11a rotationally drives the worm shaft 21a according to the direction and the magnitude of the steering torque applied from the steering wheel 1 to the steering shaft 2a detected by the torque sensor 10a, and the auxiliary power (assist torque Give).
  • the operation force of the steering wheel 1, which is necessary when giving the steering angle to the pair of left and right steered wheels is reduced.
  • rigidity can be secured for the front housing 15a constituting the gear housing 14a, and a reduction in the strength of the material joining portion occurring at the time of manufacture can be suppressed. That is, in this example, radial ribs 59 extending in the radial direction are disposed on the front side surface of the worm wheel bottom portion 40 constituting the front housing 15a. Therefore, the rigidity of the front housing 15a, in particular, the rigidity in the radial direction is improved.
  • the gate G is disposed so that the worm accommodating portion forming space 64 is on the upstream side, and the material flows.
  • the flowed material flows on both sides of the column portion 62 for forming the bearing holding hole 42 which is a through hole existing in the radial direction central portion of the worm wheel housing portion 17 a in the mold 61, and the rear side of the column portion 62 Merge at (downstream with respect to the material flow direction).
  • the worm accommodating portion forming space 64 has a larger volume (longer flow path) than the other portions on the side provided with the portion forming the motor mounting flange 44 (left side in FIG. 7).
  • the motor attachment flange 44 is more than the flow ⁇ passing through the portion forming the motor attachment flange 44.
  • the flow [beta] passing through the opposite side reaches the worm wheel container formation space 65 earlier. Therefore, flows ⁇ and ⁇ of the two materials are on the side far from worm housing formation space 64 of worm wheel housing formation space 65 and close to the space for forming motor mounting flange 44. It merges in the range which exists (The range which attached the diagonal lattice pattern in FIG. 5).
  • bridging ribs 38a, 38b, 38c are arranged on the front side of the front housing 15a so as to bridge between the worm accommodating portion 18a and the worm wheel bottom 40 and bridging ribs 38a. , 38b and 38c are made to coincide with the action direction of the meshing reaction force between the worm wheel 20a and the worm 22a. Therefore, the rigidity of the front housing 15a against the engagement reaction force can be effectively improved. Therefore, even when the front housing 15a is thinned, it is possible to prevent the occurrence of harmful deformation or the like due to the meshing reaction force in the front housing 15a.
  • the bridging ribs 38a, 38b, 38c in the front housing 15a, the bridging ribs 38a, 38b, 38b, 38b, 38c,.
  • the cross-sectional area of the space through which the material flows can be increased by the space for forming 38c.
  • the extending direction of the bridging ribs 38a, 38b, 38c is the same as the action direction of the meshing reaction force directed in the arrangement direction of the worm wheel accommodating portion 17a and the worm accommodating portion 18a, from the gate G
  • the supplied material can be efficiently supplied to the space for forming the worm wheel receiving portion 17a through the space for forming the bridging ribs 38a, 38b and 38c in the cavity 63.
  • the flowability (flowability of the material) of the material can be improved, and the formability at the time of manufacture can be improved.
  • the material can be supplied directly. Therefore, the material can be sufficiently supplied to the space for forming the mounting stay 19a, and the strength and rigidity of the mounting stay 19a can be improved. Moreover, material can also be directly supplied to the space for forming the annular protrusion 43 (inner diameter side cylinder part 41) through the space for forming the bridging rib 38a. Therefore, according to the present embodiment, the deterioration of the quality of the front housing 15a is prevented (the occurrence of defective products is reduced). Also, the substantial strength of the front housing 15a can be improved. Furthermore, as described above, the rigidity can be secured, and the formability at the time of manufacture can be secured, so weight reduction by thinning can be achieved.
  • the rigidity of the front housing 15a and the rigidity of the mounting stay 19a can be improved. For this reason, the operation feeling and operation efficiency of the electric power steering apparatus can be improved, and the generation of vibration and noise can be suppressed.
  • the rigidity of the mounting stay 19a can be improved, the behavior of the contraction operation of the steering shaft 2a and the steering column 3a can be stabilized, and the absorption characteristic of collision energy can also be improved.
  • the worm wheel bottom 40 further includes a radially extending second radial rib 60 on the front side.
  • Second radial rib 60 passes through the central axis O 17 of the worm wheel housing portion 17a, and, with respect to the imaginary plane S perpendicular to the center axis O 18 of the worm accommodating portion 18a, are arranged in the radial ribs 59 symmetrically.
  • the second radial rib 60 is similar to the radial rib 59 with respect to the cross-sectional shape and the amount of forward projection.
  • the rigidity of the worm wheel bottom 40 can be made to be uniform in the circumferential direction.
  • the 2nd radial rib 60 does not contribute to suppression of the strength reduction of a material confluence
  • Other configurations and effects are the same as the first example of the embodiment.
  • the merging part (weld line generating part) of the material is located in the space for forming the boss 47a. For this reason, by setting the bosses 47a larger in thickness than the surrounding portions at the merging portion of the material, the reduction in strength of the merging portion is suppressed.
  • Other configurations and effects are the same as the first example of the embodiment.
  • the present invention is not limited to the structure in which the worm accommodating portion forming the front housing is disposed at the lower end portion of the worm wheel accommodating portion in the assembled state of the electric power steering apparatus. That is, a structure in which the worm accommodating portion is disposed at an arbitrary position, such as a portion positioned on the side of the output shaft with respect to the upper end portion of the worm wheel accommodating portion and the width direction of the vehicle body in the assembled state of the electric power steering apparatus.
  • the present invention is also applicable to

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Transportation (AREA)
  • Manufacturing & Machinery (AREA)
  • Power Steering Mechanism (AREA)
  • Molds, Cores, And Manufacturing Methods Thereof (AREA)
  • Injection Moulding Of Plastics Or The Like (AREA)
PCT/JP2018/039781 2017-10-30 2018-10-25 電動パワーステアリング装置用ギヤハウジングおよびその製造方法、並びに、電動パワーステアリング装置 WO2019087946A1 (ja)

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Cited By (2)

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CN115401182A (zh) * 2022-09-23 2022-11-29 荆州荆龙航天科技有限公司 一种转向器壳体及其压铸加工方法
CN117980631A (zh) * 2021-10-25 2024-05-03 恩斯克转向及控制公司 齿轮箱以及电动辅助装置

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JP2002517694A (ja) * 1998-06-11 2002-06-18 プレシジョン プロダクツ システムズ， エルエルシー ギヤハウジング
JP2012020647A (ja) * 2010-07-14 2012-02-02 Jtekt Corp 電動パワーステアリング装置
JP2017024702A (ja) * 2015-04-16 2017-02-02 日本精工株式会社 減速機及び電動式パワーステアリング装置

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JP2003072562A (ja) * 2001-08-30 2003-03-12 Koyo Seiko Co Ltd 電動式動力舵取装置
WO2004040734A1 (ja) * 2002-10-31 2004-05-13 Nsk Ltd. 電動パワーステアリング装置
JP5281353B2 (ja) * 2008-09-30 2013-09-04 トヨタ自動車株式会社 車両用操舵力伝達装置
JP2012176632A (ja) * 2011-02-25 2012-09-13 Nsk Ltd 電動パワーステアリング装置
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JP2002517694A (ja) * 1998-06-11 2002-06-18 プレシジョン プロダクツ システムズ， エルエルシー ギヤハウジング
JP2012020647A (ja) * 2010-07-14 2012-02-02 Jtekt Corp 電動パワーステアリング装置
JP2017024702A (ja) * 2015-04-16 2017-02-02 日本精工株式会社 減速機及び電動式パワーステアリング装置

Cited By (2)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
CN117980631A (zh) * 2021-10-25 2024-05-03 恩斯克转向及控制公司 齿轮箱以及电动辅助装置
CN115401182A (zh) * 2022-09-23 2022-11-29 荆州荆龙航天科技有限公司 一种转向器壳体及其压铸加工方法

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