KR20240026076A - Reducer of electric power steering apparatus and manufacturing method of the same - Google Patents

Abstract

The present embodiments include a boss having a coupling hole in the center for coupling the steering shaft, a gear part provided on the outer part of the boss and having a tooth groove formed on the outer peripheral surface to engage with the worm, and the tooth groove is located on one side of the gear part in the axial direction. Provided is a reducer for an electric steering system in which the end is open in the axial direction and the other axial end of the gear portion is closed, and a method of manufacturing the same.

Description

Reducer for electric steering system and method of manufacturing same {REDUCER OF ELECTRIC POWER STEERING APPARATUS AND MANUFACTURING METHOD OF THE SAME}

These embodiments relate to a reducer for an electric steering system, and more specifically, when a worm and a worm wheel are engaged, the tooth contact rate is increased, thereby increasing the power transmission rate, reducing clearance, reducing noise, and making the tooth groove of the worm wheel easier to process. This relates to a reducer for an electric steering system that shortens the process, reduces production costs, and increases the precision and mechanical durability of the worm wheel, allowing the reducer to be used stably for a long time.

In general, power steering has been developed and applied to the steering system of a vehicle to provide convenience in driving by assisting the driver's steering wheel operation force. Power steering is a hydraulic steering device using hydraulic pressure, and electric power from hydraulic pressure and a motor. Electric-hydraulic steering devices that use both simultaneously and electric-powered steering devices that use only the electric power of the motor have been developed and applied.

However, in such an electric steering device, the worm wheel is formed with tooth grooves open at both ends in the axial direction, so processing is easy, but there is a problem in that the power transmission rate is lowered due to the low tooth contact rate.

In addition, because the clearance between the worm and the worm wheel is large, the vibration and noise generated by rotation are transmitted directly to the driver, and there is a problem that the durability of the reducer's internal parts is reduced or, in severe cases, parts are damaged. .

Accordingly, there is a need for research to increase the durability of the reducer of the electric steering system by increasing the power transmission rate by increasing the tooth contact rate of the worm wheel and reducing vibration and noise.

Accordingly, the present embodiments were developed from the above-mentioned background, and in the reducer of an electric steering device, the tooth contact rate is increased when the worm and the worm wheel are engaged, thereby increasing the power transmission rate, reducing noise, and facilitating processing of the tooth groove of the worm wheel. Thus, it is possible to provide a reducer for an electric steering system and a manufacturing method thereof that can reduce the manufacturing process and manufacturing cost and increase the precision and mechanical durability of the worm wheel.

In addition, the problems to be solved by the embodiments of the present invention are not limited thereto, and other problems not mentioned will be clearly understood by those skilled in the art from the description below.

According to the present embodiments, it includes a boss having a coupling hole in the center in which the steering shaft is coupled, a gear part provided on the outer part of the boss and having a tooth groove formed on the outer peripheral surface to engage with the worm, and the tooth groove is the axis of the gear part. A reducer for an electric steering device may be provided, wherein one end of the gear unit is open in the axial direction and the other end of the gear unit in the axial direction is closed.

Additionally, in the present embodiments, the gear unit may have a radius length of the other end where the tooth grooves are closed than a radius length of one end where the tooth grooves are open.

In addition, in the present embodiments, the gear portion includes a first gear portion formed with a constant thickness and a constant radius length at one end where the tooth grooves are opened, and a first gear portion formed with a constant thickness and a constant radius length at the other end where the tooth grooves are closed. It may include a second gear unit having a larger radius than the first gear unit.

Additionally, in the present embodiments, the gear unit may further include a connection gear unit that connects the first gear unit and the second gear unit in the axial direction and whose radial length increases from the first gear unit to the second gear unit.

Additionally, in these embodiments, the first gear portion may have a uniform tooth groove width in the circumferential direction.

Additionally, in the present embodiments, the second gear unit may be formed such that the circumferential width of the tooth groove portion gradually becomes smaller toward the other end.

Additionally, in the present embodiments, the connection gear portion may be formed to have a constant circumferential width of the tooth groove portion.

Additionally, in these embodiments, the depth of the tooth grooves of the first gear may be formed to be constant.

Additionally, in the present embodiments, the second gear portion may be formed so that the depth of the tooth groove portion gradually decreases toward the other end.

Additionally, in the present embodiments, the connection gear portion may be formed with a constant depth of the tooth groove portion.

Additionally, in the present embodiments, the second gear unit may be formed with a rounded curved end at the other end of the tooth groove.

In addition, in the present embodiments, the boss is provided with a spline groove on the outer peripheral surface and includes a gear coupling portion surrounding the gear portion, a cylindrical shaft coupling portion provided with a coupling hole, and an annular boss coupling portion connecting the gear coupling portion and the shaft coupling portion. may include.

Additionally, in these embodiments, the gear coupling portion and the shaft coupling portion may be formed to protrude in the axial direction more than the boss coupling portion.

Additionally, in these embodiments, the spline groove may be formed to have a constant circumferential width.

Additionally, in these embodiments, the spline groove may be formed to have a constant depth.

Additionally, in these embodiments, the gear coupling portion may be provided with a side protrusion protruding in the axial direction.

Additionally, in the present embodiments, the side protrusions are spaced apart from the spline grooves in the radial direction and may be disposed between adjacent spline grooves.

Additionally, in these embodiments, a key groove formed in the axial direction may be provided on the inner peripheral surface of the shaft coupling portion.

In addition, according to the present embodiments, a boss forming step of forming a coupling hole through which the steering shaft is coupled to the central axis, forming a spline groove on the outer peripheral surface, and forming a side protrusion protruding in the axial direction on the side, and a boss forming step are formed in the boss forming step. Electric steering that includes a gear and tooth groove forming step of forming the gear and tooth grooves by injecting plastic resin to surround the spline groove and side protrusion on the outer portion of the boss and having a radius length of the other end larger than that of one end in the axial direction. A method of manufacturing the reducer of the device may be provided.

In addition, in the present embodiments, a tooth processing step of cutting the inner surface of the tooth groove formed in the gear portion and tooth groove forming step to be the same as the contact surface of the worm may be further included.

According to these embodiments, in the reducer of an electric steering device, the tooth contact rate is increased when the worm and the worm wheel are engaged, thereby increasing the power transmission rate and reducing the noise by reducing the clearance.

In addition, processing of the tooth groove of the worm wheel becomes easier, shortening the manufacturing process and reducing manufacturing costs, and the precision and mechanical durability of the worm wheel are increased, allowing the reducer to be used stably for a long time.

1 is a perspective view showing some of the reducers of electric steering devices according to the present embodiments;
Figure 2 is a front view showing some of the reducers of the electric steering device according to the present embodiments;
3 and 4 are perspective views showing some of the reducers of the electric steering system according to the present embodiments;
5 and 6 are side views showing some of the reducers of the electric steering system according to the present embodiments;
Figure 7 is a cross-sectional view taken along line AA of Figure 6;
Figure 8 is a schematic diagram showing some of the reducers of the electric steering device according to the present embodiments;
Figure 9 is a flowchart showing a method of manufacturing a reducer for an electric steering device according to the present embodiments;
Figure 10 is a reference diagram showing a method of manufacturing a reducer for an electric steering device according to the present embodiments.

Hereinafter, some embodiments of the present disclosure will be described in detail with reference to illustrative drawings. In adding reference numerals to components in each drawing, the same components may have the same reference numerals as much as possible even if they are shown in different drawings. Additionally, in describing the present embodiments, if it is determined that a detailed description of a related known configuration or function may obscure the gist of the present technical idea, the detailed description may be omitted. When “comprises,” “has,” “consists of,” etc. mentioned in the specification are used, other parts may be added unless “only” is used. When a component is expressed in the singular, it can also include the plural, unless specifically stated otherwise.

Additionally, in describing the components of the present disclosure, terms such as first, second, A, B, (a), and (b) may be used. These terms are only used to distinguish the component from other components, and the nature, sequence, order, or number of the components are not limited by the term.

In the description of the positional relationship of components, when two or more components are described as being “connected,” “coupled,” or “connected,” the two or more components are directly “connected,” “coupled,” or “connected.” ", but it should be understood that two or more components and other components may be further "interposed" and "connected," "combined," or "connected." Here, other components may be included in one or more of two or more components that are “connected,” “coupled,” or “connected” to each other.

In the description of temporal flow relationships related to components, operation methods, production methods, etc., for example, temporal precedence relationships such as “after”, “after”, “after”, “before”, etc. Or, when a sequential relationship is described, non-continuous cases may be included unless “immediately” or “directly” is used.

On the other hand, when a numerical value or corresponding information (e.g., level, etc.) for a component is mentioned, even if there is no separate explicit description, the numerical value or corresponding information is related to various factors (e.g., process factors, internal or external shocks, It can be interpreted as including the error range that may occur due to noise, etc.).

Figure 1 is a perspective view showing some of the reducers of the electric steering device according to the present embodiments, Figure 2 is a front view showing some of the reducers of the electric steering device according to the present embodiments, and Figures 3 and 4 are the present embodiment. A perspective view showing some of the reducers of the electric steering device according to the present embodiments, Figures 5 and 6 are side views showing some of the reducers of the electric steering device according to the present embodiments, Figure 7 is a cross-sectional view of the area A-A of Figure 6, and Figure 8 is a FIG. 9 is a schematic diagram showing some of the reducers of the electric steering device according to the present embodiments, FIG. 9 is a flow diagram showing a method of manufacturing the reducer of the electric steering device according to the present embodiments, and FIG. 10 is a diagram showing the electric steering device according to the present embodiments. This is a reference diagram showing the method of manufacturing the reducer of the device.

As shown in these drawings, the reducer of the electric steering device according to the present embodiments includes a boss 110 having a coupling hole 111 in the center where the steering shaft is coupled, and an outer portion of the boss 110. It includes a gear unit 120 with a tooth groove 123 formed on the outer peripheral surface that engages with the worm, and the tooth groove 123 has one axial end 125a of the gear unit 120 opened in the axial direction. The other axial end 125b of the gear unit 120 is characterized in that it is formed to be closed.

The reducer of the electric steering device according to the present embodiments assists the driver's steering force by rotating the steering shaft by decelerating or accelerating the gear ratio of the worm and the worm wheel 100 rotating with the driving force of the motor.

This reducer is mounted on an electric steering device, and the worm and the worm wheel 100 are interlocked by the driving force of the motor to rotate the steering shaft to assist the driver's steering force. When the motor is driven, there are two ends of the worm interlocked with the motor shaft. A worm shaft bearing is fastened to support the rotation of the worm, and the worm wheel 100 and the worm interlocked with the steering shaft are built into the gear housing.

In addition, the steering shaft, which transmits the rotational force of the steering wheel to the rack bar when the driver operates the steering wheel, is connected from the steering wheel to a gearbox containing a column, universal joint, rack gear, and pinion gear, and the reducer is connected to the column and gearbox. It can be coupled to a built-in steering shaft or pinion.

Therefore, when the worm rotates due to the driving of the motor, the worm wheel 100 rotates interlocked, and at this time, the worm wheel 100 is coupled to the steering shaft of the steering column or the steering shaft of the gearbox to assist the driver's steering force.

The worm wheel 100 is largely composed of a boss 110 and a gear unit 120, and the gear unit 120, which is provided by injection molding on the outer portion of the boss 110, has a tooth groove 123 on the outer peripheral surface that engages with the worm. is formed.

The tooth groove portion 123 is formed such that one axial end 125a of the gear portion 120 is open and the other axial end 125b of the gear portion 120 is closed.

The gear unit 120 has one axial end 125a and the other end 125b having different radial lengths to increase the rigidity of the gear unit 120.

That is, the radius length (Lb) of the other end (125b) where the tooth groove portion (123) is closed is formed to be larger than the radius length (La) of one end (125a) where the tooth groove portion (123) is open, so that the tooth groove portion (123) ) When the force to spread the end of the tooth groove portion 123 acts due to the support force of the worm engaged with ), the radius length (Lb) of the other end 125b of the gear portion 120 is formed to be large, so that the tooth groove portion 123 Reinforces end rigidity.

This gear portion 120 includes a first gear portion 121a formed with a constant radius length and a constant thickness at one end 125a where the tooth groove portion 123 is opened, and a first gear portion 121a where the tooth groove portion 123 is closed at the other end. At 125b, the second gear portion 121b is formed with a constant thickness and a constant radius length and has a greater radius length than the first gear portion 121a.

In addition, the gear unit 120 connects the first gear unit 121a and the second gear unit 121b in the axial direction, and the radial length increases from the first gear unit 121a to the second gear unit 121b. It may further include an enlarged connection gear portion 121c.

Here, the first gear portion 121a has a uniformly formed circumferential width (Wg) of the tooth groove portion 123, and the second gear portion 121b has a circumferential width (Wg) of the tooth groove portion 123 at the other end. It is formed to gradually become smaller toward (125b), and the connection gear portion (121c) has a constant circumferential width (Wg) of the tooth groove portion (123).

Accordingly, the support force of the worm meshed with the first gear portion 121a and the connecting gear portion 121c can be transmitted consistently, and the rigidity of the second gear portion 121b prevents deformation and damage of the tooth portion.

In addition, the first gear unit 121a has a constant depth Dg of the tooth groove 123, and the second gear unit 121b has the depth Dg of the tooth groove 123 at the other end 125b. It is formed to become gradually smaller, and the depth (Dg) of the tooth groove portion 123 of the connection gear portion 121c is formed to be constant.

Accordingly, the worms meshed with the first gear portion 121a and the connecting gear portion 121c are meshed at the same depth, making it possible to transmit a certain force to the first gear portion 121a and the connecting gear portion 121c.

The second gear unit 121b is formed with an end 123e in the direction of the other end 125b of the tooth groove 123 as a round curved surface, and as described above, the end 123e of the tooth groove 123 is spread by the support force of the worm. By preventing stress from being concentrated on the end 123e of the tooth groove 123 when a force is applied, fracture of the end 123e of the tooth groove 123 is prevented.

The boss 110 is provided with a spline groove 113a on the outer peripheral surface and includes a gear coupling portion 113 surrounded by a gear portion 120, a cylindrical shaft coupling portion 115 provided with a coupling hole 111, and a gear portion. It includes an annular boss connection portion 117 connecting the sub-coupling portion 113 and the shaft coupling portion 115.

The spline groove 113a is radially spaced apart from the tooth groove 123 of the gear portion 120 and is formed at a position facing each tooth groove 123. When the gear portion 120 is injection molded, the gear portion 120 ) is surrounded and embedded.

The gear coupling portion 113 and the shaft coupling portion 115 are formed to protrude in the axial direction more than the boss coupling portion 117, so that the thickness of the gear coupling portion and the shaft coupling portion 115 is thicker than that of the boss coupling portion 117.

Therefore, the rigidity of the gear part 120 and the gear part coupling part 113 through which force is transmitted by the worm is increased, and the rigidity of the shaft coupling part 115 through which force is transmitted to the steering shaft is increased, thereby increasing the boss 110. Prevents overall deformation and damage.

The spline groove 113a has a constant circumferential width Wb from one axial end 125a to the other end 125b of the boss 110 and a constant depth.

Therefore, during injection molding of the gear unit 120, the coupling force with the spline protrusion 113a-1 formed on the inner peripheral surface of the gear unit can be maintained constant in the circumferential direction, so that the coupling force and support force between the boss 110 and the gear unit 120 This improves and the flowability of the resin between the inner spline protrusion 113a-1 and the spline groove 113a of the gear unit 120 improves, so that the entire gear unit 120 has uniform physical properties.

In addition, the gear coupling portion 113 is provided with a side protrusion 119 that protrudes in the axial direction, and the side protrusion 119 is spaced apart from the spline groove 113a in the radial direction and is disposed between adjacent spline grooves 113a. do.

Therefore, the coupling force with the protrusion support groove 119-1 formed on the inside of the gear portion can be maintained constant in the circumferential direction, thereby increasing the coupling force between the tooth groove portion 123 and the spline groove 113a and at the same time, the gear portion. The coupling force between (120) and the gear coupling portion 113 is increased.

Meanwhile, the inner peripheral surface of the shaft coupling portion 115 is provided with a key groove 111a formed in the axial direction, so that the rotational direction phase of the spline groove 113a and the tooth groove portion 123 are matched when injection molding the gear portion 120. Then, injection molding of the gear unit 120 is performed, so that the gear unit 120 and the boss 110 can be formed in the correct position.

In addition, the method of manufacturing the reducer of the electric steering device according to the present embodiments forms a coupling hole 111 through which the steering shaft is coupled to the central axis, forms a spline groove 113a on the outer peripheral surface, and forms an axially protruding part on the side. A boss forming step (S100) forming the side protrusion 119, and one end in the axial direction surrounding the spline groove (113a) and the side protrusion (119) on the outer portion of the boss (110) formed in the boss forming step (S100). It includes a gear portion and tooth groove forming step (S200) in which the gear portion 120 and the tooth groove portion 123 are formed by injecting plastic resin so that the radius length of the other side end 125b is larger than that of the other side end 125b (125a).

The boss 110 is made of a metal material such as steel and forms a coupling hole 111 where the steering shaft is coupled to the central axis, and a spline groove 113a is formed on the outer peripheral surface and a side protrusion 119 is formed on the side, and the gear portion ( 120) and the tooth groove portion 123 are injection molded.

And, as shown in Figure 10, a tooth groove processing step ( S300) is further included.

The cutting tool 310 does not use a hobbing tool used in manufacturing a worm wheel, but uses a burnishing tool formed identical to the tooth shape of the worm to form a worm support surface having the same curved surface as the contact surface of the worm on the inner surface of the tooth groove 123. It forms (123a).

Therefore, when in contact with the worm, the contact area is increased and the support force of the worm is transmitted consistently, thereby increasing power transmission efficiency and maintaining the rigidity of the tooth portion 123, thereby preventing deformation and damage of the tooth portion 123. It becomes possible.

The boss 110 made of metal, which is formed in a hollow shape roughly like a ring, has a steering shaft penetratingly coupled to its center, and the gear unit 120 is molded by injection of polyamide resin reinforced with a mixture of glass fibers.

Here, the polyamide resin 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 glass fiber is mixed at 30 to 50% by weight. As a result, compared to when it is formed only of polyamide resin, hardness, tensile strength, elongation, flexural strength, high-temperature properties, etc. are improved, and durability is improved by having excellent friction characteristics.

As described above, according to the present embodiments, in the reducer of an electric steering device, the tooth contact rate is increased when the worm and the worm wheel are meshed, thereby increasing the power transmission rate and reducing the clearance, thereby reducing noise.

In addition, processing of the tooth groove of the worm wheel becomes easier, shortening the manufacturing process and reducing manufacturing costs, and the precision and mechanical durability of the worm wheel are increased, allowing the reducer to be used stably for a long time.

The above description is merely an illustrative explanation of the technical idea of the present disclosure, and those skilled in the art will be able to make various modifications and variations without departing from the essential characteristics of the present disclosure. In addition, since the present embodiments are not intended to limit the technical idea of the present disclosure, but rather to explain it, the scope of the technical idea of the present disclosure is not limited by these embodiments. The scope of protection of this disclosure should be interpreted in accordance with the claims below, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of rights of this disclosure.

Claims (20)

A boss having a coupling hole in the center where the steering axis is coupled;
a gear portion provided on the outer portion of the boss and having a tooth groove portion engaged with a worm formed on the outer circumferential surface;
Includes,
A reducer for an electric steering device, wherein the tooth groove portion is formed so that one axial end of the gear portion is open in the axial direction and the other axial end of the gear portion is closed. According to claim 1,
A reducer for an electric steering device, wherein the gear part has a radius length of the other end where the tooth grooves are closed than a radius length of one end where the tooth grooves are open. According to claim 2,
The gear part,
a first gear portion formed at a constant thickness and a constant radius length at one end where the tooth groove portion is opened;
a second gear portion formed at a constant thickness and a constant radius length at the other end where the tooth groove portion is closed, and a radius length larger than that of the first gear portion;
A reducer for an electric steering system including a. According to claim 3,
The gear part,
A reducer for an electric steering device that connects the first gear unit and the second gear unit in the axial direction and further includes a connecting gear unit whose radial length increases from the first gear unit to the second gear unit. According to claim 4,
A reducer for an electric steering device, wherein the first gear unit has a constant circumferential width of the tooth groove. According to claim 4,
The second gear unit is a reducer for an electric steering device, wherein the circumferential width of the tooth groove portion is formed to gradually become smaller toward the other end. According to claim 4,
A reducer for an electric steering device, wherein the connection gear portion has a constant circumferential width of the tooth groove portion. According to claim 4,
A reducer for an electric steering device, wherein the first gear unit has a constant depth of the tooth groove. According to claim 4,
The second gear unit is a reducer for an electric steering device, wherein the depth of the tooth groove portion is formed to gradually decrease toward the other end. According to claim 4,
A reducer for an electric steering device, wherein the connecting gear portion has a constant depth of the tooth groove portion. According to clause 9,
The second gear unit is a reducer for an electric steering device, wherein an end of the second gear unit toward the other end of the tooth groove is formed with a round curved surface. According to claim 1,
The boss said,
A gear coupling portion provided with a spline groove on the outer peripheral surface and surrounding the gear portion;
A cylindrical shaft coupling portion provided with the coupling hole;
An annular boss connection part connecting the gear part coupling part and the shaft coupling part;
A reducer for an electric steering system including a. According to claim 12,
A reducer for an electric steering device, wherein the gear coupling portion and the shaft coupling portion are formed to protrude in the axial direction more than the boss coupling portion. According to claim 12,
A reducer for an electric steering system, characterized in that the spline groove is formed with a constant circumferential width. According to claim 12,
A reducer for an electric steering system, characterized in that the spline groove is formed with a constant depth. According to claim 12,
A reducer for an electric steering system, characterized in that the gear coupling part is provided with a side protrusion protruding in the axial direction. According to claim 16,
The side protrusion is spaced apart from the spline groove in the radial direction and is disposed between adjacent spline grooves. According to claim 12,
A reducer for an electric steering system, characterized in that a key groove formed in the axial direction is provided on the inner peripheral surface of the shaft coupling portion. A boss forming step of forming a coupling hole through which the steering shaft is coupled to the central axis, forming a spline groove on the outer peripheral surface, and forming a side protrusion protruding in the axial direction on the side surface;
A gear portion and a tooth groove portion are formed by injecting plastic resin to surround the spline groove and the side protrusion on the outer portion of the boss formed in the boss forming step and having a radius length of the other end larger than that of one end in the axial direction. formation stage;
A method of manufacturing a reducer for an electric steering device comprising a. According to claim 19,
A reducer for an electric steering device further comprising a tooth groove processing step of cutting the inner surface of the tooth groove formed in the gear portion and tooth groove forming step to be the same as the contact surface of the worm.

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