CN117588548A - Speed reducer of electric power steering device and manufacturing method thereof - Google Patents

Speed reducer of electric power steering device and manufacturing method thereof Download PDF

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Publication number
CN117588548A
CN117588548A CN202311045603.9A CN202311045603A CN117588548A CN 117588548 A CN117588548 A CN 117588548A CN 202311045603 A CN202311045603 A CN 202311045603A CN 117588548 A CN117588548 A CN 117588548A
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CN
China
Prior art keywords
gear
boss
gear portion
tooth groove
decelerator
Prior art date
Legal status (The legal status is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the status listed.)
Pending
Application number
CN202311045603.9A
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Chinese (zh)
Inventor
金宗汉
Current Assignee (The listed assignees may be inaccurate. Google has not performed a legal analysis and makes no representation or warranty as to the accuracy of the list.)
HL Mando Corp
Original Assignee
Mando Corp
Priority date (The priority date is an assumption and is not a legal conclusion. Google has not performed a legal analysis and makes no representation as to the accuracy of the date listed.)
Filing date
Publication date
Priority claimed from KR1020230063706A external-priority patent/KR20240026076A/en
Application filed by Mando Corp filed Critical Mando Corp
Publication of CN117588548A publication Critical patent/CN117588548A/en
Pending legal-status Critical Current

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Classifications

    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H55/00—Elements with teeth or friction surfaces for conveying motion; Worms, pulleys or sheaves for gearing mechanisms
    • F16H55/02—Toothed members; Worms
    • F16H55/22—Toothed members; Worms for transmissions with crossing shafts, especially worms, worm-gears
    • 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
    • B29C45/14—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor incorporating preformed parts or layers, e.g. injection moulding around inserts or for coating articles
    • B29C45/14336—Coating a portion of the article, e.g. the edge of the article
    • 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
    • B29C45/14—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor incorporating preformed parts or layers, e.g. injection moulding around inserts or for coating articles
    • B29C45/14778—Injection moulding, i.e. forcing the required volume of moulding material through a nozzle into a closed mould; Apparatus therefor incorporating preformed parts or layers, e.g. injection moulding around inserts or for coating articles the article consisting of a material with particular properties, e.g. porous, brittle
    • B29C45/14786—Fibrous material or fibre containing material, e.g. fibre mats or fibre reinforced material
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H55/00—Elements with teeth or friction surfaces for conveying motion; Worms, pulleys or sheaves for gearing mechanisms
    • F16H55/02—Toothed members; Worms
    • F16H55/06—Use of materials; Use of treatments of toothed members or worms to affect their intrinsic material properties
    • F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F16—ENGINEERING ELEMENTS AND UNITS; GENERAL MEASURES FOR PRODUCING AND MAINTAINING EFFECTIVE FUNCTIONING OF MACHINES OR INSTALLATIONS; THERMAL INSULATION IN GENERAL
    • F16H—GEARING
    • F16H55/00—Elements with teeth or friction surfaces for conveying motion; Worms, pulleys or sheaves for gearing mechanisms
    • F16H55/02—Toothed members; Worms
    • F16H55/08—Profiling

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  • Engineering & Computer Science (AREA)
  • General Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • Manufacturing & Machinery (AREA)
  • Physics & Mathematics (AREA)
  • Electromagnetism (AREA)
  • Thermal Sciences (AREA)
  • Power Steering Mechanism (AREA)

Abstract

The present embodiment provides a decelerator of an electric power steering apparatus and a method of manufacturing the same, the decelerator including: a boss having a coupling hole formed in a center portion to allow the steering shaft to be coupled to the boss; and a gear portion located at an outer peripheral side of the boss and having a tooth groove portion engaged with the worm at an outer peripheral surface of the boss, wherein the tooth groove portion has a first end and a second end in an axial direction of the gear portion, the first end being axially open, and the second end being closed.

Description

Speed reducer of electric power steering device and manufacturing method thereof
Cross Reference to Related Applications
The present application claims priority from korean patent application No. 10-2022-0103927 filed on day 19 of 8, 2022 and application No. 10-2023-0063706 filed on day 17 of 2023, which are incorporated herein by reference for all purposes as if fully set forth herein.
Technical Field
The present embodiment relates to a decelerator of an electric power steering apparatus, and more particularly, to a decelerator of an electric power steering apparatus, which can improve a power transmission rate by improving a tooth contact rate during tooth engagement between a worm and a worm wheel, reduce noise by reducing a gap, reduce manufacturing processes and costs by simplifying machining of tooth grooves of the worm wheel, and improve accuracy and mechanical durability of the worm wheel so that the decelerator can be stably used for a long period of time.
Background
In general, a vehicle steering apparatus employs a power steering apparatus to assist a driver in steering a steering wheel and provide steering convenience. Power steering apparatuses that have been developed and employed include hydraulic power steering apparatuses that use hydraulic power, electro-hydraulic power steering apparatuses that use both hydraulic power and motor power, and electric power steering apparatuses that use only motor power.
In the conventional electric power steering apparatus, the worm wheel is formed such that the tooth grooves have openings at both opposite side ends in the axial direction to provide easier processing. However, the tooth contact rate is lowered, so that the power transmission rate is deteriorated.
Further, since there is a large gap between the tooth meshing portions of the worm and the worm wheel, significant vibration and noise generated during rotation may be directly transmitted to the driver, and durability of internal components of the reduction gear may be deteriorated or those components may be damaged.
Therefore, in the decelerator of the electric power steering apparatus, it is necessary to improve the durability of the decelerator by reducing vibration and noise, while increasing the power transmission rate by increasing the tooth contact rate of the worm wheel.
Disclosure of Invention
In view of the above-described background art, the present embodiment can provide a speed reducer of an electric power steering apparatus and a manufacturing method thereof, which can improve a power transmission rate by improving a tooth contact rate during tooth engagement between a worm and a worm wheel, reduce noise by reducing a gap, reduce manufacturing processes and costs by simplifying machining of tooth grooves of the worm wheel, and improve accuracy and mechanical durability of the worm wheel so that the speed reducer can be stably used for a long period of time.
The objects of the embodiments of the present disclosure are not limited to the foregoing, and other objects will be apparent to those of ordinary skill in the art from the following detailed description.
According to the present embodiment, there can be provided a speed reducer of an electric power steering apparatus including: a boss having a coupling hole formed in a center portion to allow the steering shaft to be coupled to the boss; and a gear portion located at an outer peripheral side of the boss and having a tooth groove portion engaged with the worm at an outer peripheral surface of the boss, wherein the tooth groove portion has a first end and a second end in an axial direction of the gear portion, the first end being axially open, and the second end being closed.
Further, in the present embodiment, in the gear portion, the radial length of the closed second end of the spline portion may be greater than the radial length of the open first end of the spline portion.
Further, in the present embodiment, the gear portion may include: a first gear part formed to have a constant thickness and a constant radial length in a first end of an opening of the slot part; and a second gear portion formed to have a gradually decreasing thickness and a constant radial length in the closed second end of the spline portion, wherein the radial length of the second gear portion is greater than the radial length of the first gear portion.
Further, in the present embodiment, the gear portion may further include: the connecting gear portion axially connects the first gear portion and the second gear portion at a constant thickness and has a radial length that increases from the first gear portion to the second gear portion.
Further, in the present embodiment, the first gear portion may be formed such that the circumferential width of the tooth groove portion is constant.
Further, in the present embodiment, the second gear portion may be formed such that the circumferential width of the tooth groove portion gradually decreases toward the second end of the gear portion.
Further, in the present embodiment, the connecting gear portion may be formed such that the circumferential width of the tooth groove portion is constant.
Further, in the present embodiment, the first gear portion may be formed such that the depth of the tooth groove portion is constant.
Further, in the present embodiment, the second gear portion may be formed such that the depth of the tooth groove portion gradually decreases toward the second end of the gear portion.
Further, in the present embodiment, the connecting gear portion may be formed such that the depth of the tooth groove portion is constant.
Further, in the present embodiment, the second gear portion may be formed to have a curved tip in a direction toward the second end of the tooth groove portion.
Further, in the present embodiment, the boss may include: a gear portion coupling portion having spline grooves on an outer peripheral surface of the boss and surrounded by the gear portion; a cylindrical shaft coupling part having a coupling hole; and an annular boss connecting portion connecting the gear portion coupling portion and the shaft coupling portion.
Further, in the present embodiment, the gear portion coupling portion and the shaft coupling portion may be formed to axially protrude beyond the boss connecting portion.
Further, in the present embodiment, the spline grooves may be formed to have a constant circumferential width.
Further, in the present embodiment, the spline grooves may be formed to have a constant depth.
Further, in the present embodiment, the gear portion coupling portion may have a side projection protruding in the axial direction.
Further, in this embodiment, the side projections may be radially spaced from the spline grooves and may be disposed between adjacent spline grooves.
Further, in the present embodiment, a key groove may be formed in an inner peripheral surface of the shaft coupling portion in the axial direction.
Further, in the present embodiment, there may be provided a method for manufacturing a decelerator of an electric power steering apparatus, including: a boss forming step of forming a coupling hole at the center shaft to allow the steering shaft to be coupled to the boss, forming a spline groove on an outer peripheral surface of the boss, and forming an axially protruding side protrusion on a side surface of the boss; and a gear portion and tooth groove portion forming step of forming the gear portion and the tooth groove portion by injection molding a plastic resin such that a radial length of the second end in the axial direction is greater than a radial length of the first end, and surrounding the spline groove and the side protrusion on the outer peripheral side of the boss formed in the boss forming step.
Further, in this embodiment, the method may further include: a tooth groove portion processing step of cutting an inner surface of the tooth groove portion formed in the gear portion and tooth groove portion forming step to match a contact surface of the worm.
According to the present embodiment, the power transmission rate can be increased by increasing the tooth contact rate during the tooth engagement between the worm and the worm wheel, and the noise can be reduced by reducing the backlash in the speed reducer of the electric power steering apparatus.
The manufacturing process and cost can be reduced by more simply processing the tooth grooves of the worm wheel, and the accuracy and mechanical durability of the worm wheel can be improved, so that the speed reducer can be stably used for a long time.
Drawings
The foregoing and other objects, features, and advantages of the disclosure will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings in which:
fig. 1 is a perspective view showing a part of a speed reducer of an electric power steering apparatus according to the present embodiment;
fig. 2 is a front view showing a part of a speed reducer of the electric power steering apparatus according to the present embodiment;
fig. 3 and 4 are perspective views showing a part of a decelerator of the electric power steering apparatus according to the present embodiment;
fig. 5 and 6 are side views showing a part of a decelerator of the electric power steering apparatus according to the present embodiment;
FIG. 7 is a cross-sectional view of section A-A' of FIG. 6;
fig. 8 is a perspective view showing a part of a speed reducer of the electric power steering apparatus according to the present embodiment;
fig. 9 is a flowchart showing a manufacturing method of a decelerator of the electric power steering apparatus according to the present embodiment; and is also provided with
Fig. 10 is a reference diagram showing a method of manufacturing a speed reducer of an electric power steering apparatus according to the present embodiment.
Detailed Description
In the following description of examples or embodiments of the present disclosure, reference will be made to the accompanying drawings in which specific examples or embodiments that may be practiced are shown by way of illustration, and in which like reference numerals and symbols, even though they are shown in different drawings from one another, may be used to designate the same or similar components. Further, in the following description of examples or embodiments of the present disclosure, detailed descriptions of well-known functions and components incorporated herein will be omitted when it may be determined that the description may obscure the subject matter in some embodiments of the present disclosure. Unless these terms are used with the term "only," such as "comprising," "having," "including," "constituting," "making up," "forming," etc., as used herein are generally intended to allow for the addition of other components. As used herein, the singular is intended to include the plural unless the context clearly indicates otherwise.
Terms such as "first," second, "" a, "" B, "" a, "or" (B) may be used herein to describe elements of the present disclosure. Each of these terms is not intended to define an element, sequence, order, quantity, etc., but is only used to distinguish the corresponding element from other elements.
When referring to a first element "connected or coupled," "contacting or overlapping" with a second element, it should be construed that not only the first element may be "directly connected or coupled" or "directly contacting or overlapping" with the second element, but also a third element may be "interposed" between the first element and the second element, or the first element and the second element may be "connected or coupled," "contacting or overlapping" with each other through a fourth element, etc. Here, the second element may be included in at least one of two or more elements that are "connected or coupled", "contact or overlap" with each other, etc.
When relative terms such as "after," subsequent, "" next, "" before, "and the like are used to describe a process or operation of an element or configuration or a flow or step in an operation, process, method of manufacture, these terms may also be used to describe a non-continuous or non-sequential process or operation unless otherwise indicated by the term" directly "or" immediately.
In addition, when referring to any dimensions, relative dimensions, etc., even if the relevant description is not specified, it should be considered that the numerical values of the elements or features or the corresponding information (e.g., levels, ranges, etc.) includes tolerances or ranges of errors that may be caused by various factors (e.g., process factors, internal or external influences, noise, etc.). Further, the term "may" is intended to fully cover all meanings of the term "may".
Fig. 1 is a perspective view showing a part of a speed reducer of an electric power steering apparatus according to the present embodiment. Fig. 2 is a front view showing a part of a speed reducer of the electric power steering apparatus according to the present embodiment. Fig. 3 and 4 are perspective views showing a part of a decelerator of the electric power steering apparatus according to the present embodiment. Fig. 5 and 6 are side views showing a part of a speed reducer of the electric power steering apparatus according to the present embodiment. FIG. 7 is a cross-sectional view of section A-A' of FIG. 6. Fig. 8 is a perspective view showing a part of a speed reducer of the electric power steering apparatus according to the present embodiment. Fig. 9 is a flowchart showing a method of manufacturing a decelerator of an electric power steering apparatus according to the present embodiment. Fig. 10 is a reference diagram showing a method of manufacturing a speed reducer of an electric power steering apparatus according to the present embodiment.
As shown in the figure, the decelerator of the electric power steering apparatus according to the present embodiment includes: a boss 110 having a coupling hole 111 formed in a central portion to allow a steering shaft to be coupled to the boss 110; and a gear part 120 located at an outer circumferential side of the boss 110 and having a tooth groove part 123 engaged with the worm screw a at an outer circumferential surface of the boss 110. The spline portion 123 has a first end 125a and a second end 125b along the axial direction of the gear portion 120. The first end is axially open and the second end is closed.
The decelerator of the electric power steering apparatus according to the present embodiment assists the manipulation of the driver by rotating the steering shaft while reducing the gear ratio between the worm screw rotated by the driving force of the motor and the worm wheel 100.
The speed reducer is installed in the electric power steering apparatus. The worm is coupled with the worm wheel 100 to rotate the steering shaft by a motor driving force, thereby assisting the driver in steering. When the motor is operated, worm shaft bearings are fastened to both ends of the worm in linkage with the shaft of the motor, thereby supporting the worm to rotate. A worm wheel 100 and a worm screw that are linked with the steering shaft are placed in the gear box.
A steering shaft that transmits a rotational force of the steering wheel to the rack bar when the driver manipulates the steering wheel is connected from the steering wheel to a gear box having a rack and a pinion through a steering column and a universal joint, and a decelerator may be coupled to a pinion shaft or a steering shaft installed in the gear box and the steering column.
Therefore, if the worm is rotated by the driving of the motor, the worm wheel 100 is also rotated, and at this time, the worm wheel 100 is coupled to the steering shaft of the steering column or the steering shaft of the gear box to assist the steering force of the driver.
The worm wheel 100 includes a boss 110 and a gear portion 120. The gear portion 120 is formed on the outer peripheral portion of the boss 110 by injection molding. The gear portion 120 has a tooth groove portion 123 on an outer peripheral surface thereof, which meshes with the worm.
The first end 125a of the spline portion 123 in the axial direction of the gear portion 120 is axially open, and the second end 125b in the axial direction of the gear portion 120 is closed.
The gear portion 120 is formed such that the radial lengths of the first end 125a and the second end 125b in the axial direction are different from each other to increase the rigidity of the gear portion 120.
In other words, as shown in fig. 2, the radial length Lb of the closed second end 125b in the spline portion 123 is formed to be greater than the radial length La of the open first end 125a of the spline portion 123, thereby enhancing the tip rigidity of the spline portion 123 when the tip of the spline portion 123 is forced to be widened by the supporting force of the worm engaged with the spline portion 123.
The worm support surfaces 123a are formed on two opposite inner surfaces of the spline portion 123 to have the same tooth shape as that of the worm. The worm support surface 123a is formed by a polishing tool, which is a cutting tool having the same tooth shape as the worm.
Therefore, when the spline portion 123 is in contact with the worm, the contact area increases so that the supporting force of the worm can be uniformly transmitted, and the rigidity of the spline portion 123 to withstand the bending stress and the shearing stress generated at the spline portion 123 is maintained, thereby preventing deformation and damage.
The gear portion 120 includes: a first gear part 121a having a constant thickness and a constant radial length in a first end 125a where the spline part 123 is opened; and a second gear part 121b having a gradually decreasing thickness and a constant radial length in the second end 125b where the spline part 123 is closed, the radial length of the second gear part 121b being greater than the radial length of the first gear part 121 a.
Further, the gear part 120 may further include: the connecting gear portion 121c connects the first gear portion 121a and the second gear portion 121b with a constant thickness, and has a radial length increasing from the first gear portion 121a to the second gear portion 121 b.
As shown in fig. 3, the first gear portion 121a is formed such that the circumferential width Wg of the tooth groove portion 123 is constant, the second gear portion 121b is formed such that the circumferential width Wg of the tooth groove portion 123 gradually decreases toward the second end 125b of the gear portion 120, and the connecting gear portion 121c is formed such that the circumferential width Wg of the tooth groove portion 123 is constant.
Accordingly, the supporting force of the worm engaged with the connecting gear portion 121c and the first gear portion 121a can be constantly transmitted, and deformation and damage of the tooth groove portion 123 are prevented by the rigidity of the second gear portion 121 b.
Further, the first gear portion 121a is formed such that the depth Dg of the tooth groove portion 123 is constant, the second gear portion 121b is formed such that the depth Dg of the tooth groove portion 123 gradually decreases toward the second end 125b of the gear portion 120, and the connection gear portion 121c is formed such that the depth Dg of the tooth groove portion 123 is constant.
Accordingly, the worms engaged with the first gear portion 121a and the connecting gear portion 121c are engaged at the same depth, so that a constant force can be transmitted to the first gear portion 121a and the connecting gear portion 121c.
As shown in fig. 3, the second gear portion 121b is formed such that its tip 123e in a direction toward the second end 125b of the spline portion 123 is curved. Therefore, as described above, when the tip 123e of the spline portion 123 is forced to be widened, as described above, stress is prevented from being concentrated on the tip 123e of the spline portion 123 by the supporting force of the worm, thereby preventing the tip 123e of the spline portion 123 from being broken.
The boss 110 has a spline groove 113a formed in an outer peripheral surface of the boss 110, and includes a gear portion coupling portion 113 surrounded by a gear portion 120, a cylindrical shaft coupling portion 115 having a coupling hole 111, and an annular boss connecting portion 117 connecting the gear portion coupling portion 113 and the shaft coupling portion 115.
The spline groove 113a is spaced apart from the spline portion 123 of the gear portion 120 in the radial direction, is formed between the spline portions 123 adjacent in the circumferential direction, and is embedded while being surrounded by the gear portion 120 during injection molding of the gear portion 120.
The gear portion coupling portion 113 and the shaft coupling portion 115 are formed to axially protrude beyond the boss connecting portion 117, and are formed to have an axial thickness greater than the boss connecting portion 117.
This increases the rigidity of the gear portion 120 and the gear portion coupling portion 113 biased by the worm, and at the same time increases the rigidity of the shaft coupling portion 115 transmitting the force to the steering shaft, thereby preventing the entire boss 110 from being deformed and damaged.
The spline groove 113a is formed to have a constant circumferential width Wb and a constant depth from the first end 125a to the second end 125b in the axial direction of the boss 110.
Accordingly, the coupling strength with the spline protrusion 113a-1 formed on the inner circumferential surface of the gear part 120 can be maintained constant during the injection molding of the gear part 120. Accordingly, the coupling strength and supporting force between the boss 110 and the gear part 120 can be increased, and the resin can flow better between the spline protrusion 113a-1 and the spline groove 113a inside the gear part 120, so that the gear part 120 as a whole has uniform physical properties.
Further, the gear portion coupling portion 113 has a side projection 119 protruding in the axial direction. The side projections 119 are radially spaced from the spline grooves 113a and are disposed between adjacent spline grooves 113 a.
Accordingly, the coupling strength with the protrusion support groove 119-1 formed inside the gear portion can be maintained constant in the circumferential direction, thereby increasing the coupling strength between the tooth groove portion 123 and the spline groove 113a, while increasing the coupling strength between the gear portion 120 and the gear portion coupling portion 113.
On the other hand, key grooves 111a are formed in the inner peripheral surface of the shaft coupling portion 115 in the axial direction so that during injection molding of the gear portion 120, the spline grooves 113a and the spline grooves 123 are phase-matched in the rotational direction, and the gear portion 120 is injection molded, thereby positioning the gear portion 120 and the boss 110.
The manufacturing method of the decelerator of the electric power steering apparatus according to the present embodiment includes: a boss forming step S100 of forming a coupling hole 111 on the center shaft to allow the steering shaft to be coupled to the boss, forming a spline groove 113a in an outer peripheral surface of the boss, and forming an axially protruding side protrusion 119 on a side surface of the boss; and a gear portion and tooth groove portion forming step S200 of forming the gear portion 120 and the tooth groove portion 123 by injection molding a plastic resin such that the radial length of the second end 125b is greater than the radial length of the first end 125a in the axial direction while surrounding the spline groove 113a and the side protrusion 119 on the outer peripheral side of the boss 110 formed in the boss forming step S100.
The boss 110 is formed of a metal material such as steel, and has a coupling hole 111 on the center shaft to allow the steering shaft to be coupled to the boss. The boss 110 has spline grooves 113a formed in the outer peripheral surface and side protrusions formed on the side surfaces, and the gear portion 120 and the spline groove portion 123 are injection molded.
As shown in fig. 10, the method further comprises: a tooth groove portion processing step S300 of cutting the inner peripheral surface of the tooth groove portion 123 formed in the gear portion and tooth groove portion forming step S200 by the cutting tool 310 to match the contact surface of the worm.
A polishing tool formed to match the tooth shape of the worm is used as the cutting tool 310 instead of a hobbing tool for manufacturing a worm wheel, so that a worm support surface 123a is formed on the inner surface of the tooth groove portion 123, the worm support surface 123a having the same curved surface as the contact surface of the worm.
Therefore, the contact area increases during contact with the worm, so that the supporting force of the worm can be constantly transmitted, thereby improving the power transmission efficiency, maintaining the rigidity of the spline portion 123, and preventing deformation and damage of the spline portion 123.
The metal boss 110 formed in a hollow shape (e.g., ring shape) passes the steering shaft through and is coupled through the center portion thereof, and the gear portion 120 is formed by injection molding of a polyamide resin reinforced by mixing with glass fibers.
Here, the polyamide resin used for injection molding the gear portion 120 and the tooth groove portion 123 is one of polyamide 6, polyamide 66, polyamide 46, and polyamide 12, and is mixed with glass fibers in a weight ratio of 30% to 50%. Therefore, it can have enhanced hardness, tensile strength, elongation, bending strength and high temperature characteristics, as well as excellent friction characteristics and durability, compared to when it is manufactured with only polyamide resin.
As described above, according to the present embodiment, the power transmission rate can be increased by increasing the tooth contact rate during the tooth engagement between the worm and the worm wheel, and the noise can be reduced by reducing the clearance in the speed reducer of the electric power steering apparatus.
The manufacturing process and cost can be reduced by more simply machining the tooth grooves of the worm wheel, and the accuracy and mechanical durability of the worm wheel can be improved so that the speed reducer can be stably used for a long period of time.
The above description is presented to enable any person skilled in the art to make and use the disclosed technical ideas, and is provided in the context of a particular application and its requirements. Various modifications, additions and substitutions to the described embodiments will be apparent to those skilled in the art and the generic principles defined herein may be applied to other embodiments and applications without departing from the spirit and scope of the disclosure. The above description and the accompanying drawings provide examples of the technical ideas of the present disclosure for illustrative purposes only. That is, the disclosed embodiments are intended to illustrate the scope of the technical ideas of the present disclosure. Thus, the scope of the present disclosure is not limited to the embodiments shown, but is to be accorded the broadest scope consistent with the claims. The protection scope of the present disclosure should be construed based on the appended claims, and all technical ideas falling within the equivalent scope thereof should be construed to be included in the scope of the present disclosure.

Claims (20)

1. A decelerator of an electric power steering apparatus, comprising:
a boss having a coupling hole formed in a center portion to allow a steering shaft to be coupled thereto; and
a gear part which is positioned at the outer peripheral side of the boss and is provided with a tooth groove part meshed with the worm on the outer peripheral surface of the boss,
wherein the spline portion has a first end and a second end in an axial direction of the gear portion, the first end being axially open, and the second end being closed.
2. The reduction gear according to claim 1, wherein in the gear portion, a radial length of the closed second end of the spline portion is greater than a radial length of the open first end of the spline portion.
3. The decelerator of claim 2, wherein the gear part includes:
a first gear part formed to have a constant thickness and a constant radial length in a first end of an opening of the tooth groove part; and
a second gear portion formed to have a gradually decreasing thickness and a constant radial length in a closed second end of the spline portion, the radial length of the second gear portion being greater than the radial length of the first gear portion.
4. A decelerator according to claim 3 wherein the gear portion further comprises: and a connecting gear portion axially connecting the first gear portion and the second gear portion at a constant thickness, and having a radial length increasing from the first gear portion to the second gear portion.
5. The decelerator according to claim 4, wherein the first gear part is formed such that a circumferential width of the tooth groove part is constant.
6. The speed reducer according to claim 4, wherein the second gear portion is formed such that a circumferential width of the tooth groove portion gradually decreases toward the second end of the gear portion.
7. The decelerator according to claim 4, wherein the connection gear part is formed such that a circumferential width of the tooth groove part is constant.
8. The decelerator according to claim 4, wherein the first gear part is formed such that the depth of the tooth groove part is constant.
9. The decelerator according to claim 4, wherein the second gear part is formed such that the depth of the tooth groove part gradually decreases toward the second end of the gear part.
10. The decelerator according to claim 4, wherein the connection gear part is formed such that the depth of the tooth groove part is constant.
11. The decelerator according to claim 9, wherein the second gear part is formed to have a curved tip in a direction toward the second end of the tooth groove part.
12. The decelerator of claim 1, wherein the boss comprises:
a gear portion coupling portion having spline grooves on an outer peripheral surface of the boss and surrounded by the gear portion;
a cylindrical shaft coupling part having the coupling hole; and
and the annular boss connecting part is used for connecting the gear part connecting part and the shaft connecting part.
13. The decelerator of claim 12, wherein the gear portion coupling portion and the shaft coupling portion are formed to axially protrude beyond the boss connection portion.
14. The reduction gear of claim 12, wherein the spline grooves are formed with a constant circumferential width.
15. The decelerator of claim 12, wherein the spline grooves are formed to have a constant depth.
16. The decelerator according to claim 12 wherein the gear portion coupling portion has an axially protruding side projection.
17. The reducer of claim 16, wherein said side projections are radially spaced from said spline grooves and are disposed between adjacent spline grooves.
18. The decelerator according to claim 12, wherein a key groove is axially formed in an inner peripheral surface of the shaft coupling part.
19. A method for manufacturing a decelerator of an electric power steering apparatus, comprising:
a boss forming step of forming a coupling hole at a central shaft to allow a steering shaft to be coupled to a boss, forming a spline groove on an outer peripheral surface of the boss, and forming an axially protruding side protrusion on a side surface of the boss; and
a gear portion and tooth groove portion forming step of forming the gear portion and the tooth groove portion by injection molding a plastic resin so that a radial length of the second end is longer than a radial length of the first end in the axial direction while surrounding the spline groove and the side protrusion on the outer peripheral side of the boss formed in the boss forming step.
20. The method of claim 19, further comprising: a tooth groove portion processing step of cutting an inner surface of the tooth groove portion formed in the gear portion and tooth groove portion forming step to match a contact surface of the worm.
CN202311045603.9A 2022-08-19 2023-08-18 Speed reducer of electric power steering device and manufacturing method thereof Pending CN117588548A (en)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
KR10-2022-0103927 2022-08-19
KR10-2023-0063706 2023-05-17
KR1020230063706A KR20240026076A (en) 2022-08-19 2023-05-17 Reducer of electric power steering apparatus and manufacturing method of the same

Publications (1)

Publication Number Publication Date
CN117588548A true CN117588548A (en) 2024-02-23

Family

ID=89912164

Family Applications (1)

Application Number Title Priority Date Filing Date
CN202311045603.9A Pending CN117588548A (en) 2022-08-19 2023-08-18 Speed reducer of electric power steering device and manufacturing method thereof

Country Status (1)

Country Link
CN (1) CN117588548A (en)

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