KR20100037882A - Worm geared speed reducer and electric power steering system having the same - Google Patents

Abstract

The present invention relates to a worm reducer and an electric power assisted steering apparatus including the same, wherein at least one of the worm gears or worm gears of the worm reducer is provided such that the pressure angle at its tip is greater than the pressure angle at the tooth root. Since it is formed, greatly reducing wear and durability and life is improved, there is an effect of preventing the transmission of vibration and noise generated by the backlash.

Description

Worm reducer and electric power steering with same {Worm geared speed reducer and electric power steering system having the same}

The present invention relates to a worm reducer, and more particularly, to a worm reducer including a worm and a worm wheel, wherein the pressure angle at the tip of the worm is larger than the pressure angle at the root of the worm to improve durability. . The present invention also relates to an electric power assisted steering apparatus provided with such a worm reducer.

Recent technical trends of the steering apparatus provided in the vehicle has been researched and developed in the direction of pursuing the convenience of the driver with safety, such as stability of the steering state and smooth and comfortable steering. According to this development trend, various power assist steering devices, such as hydraulic or electric, are being developed as a way to improve the driver's steering feeling.The electric power is reduced due to the advantages of lighter electric, less energy consumption and improved vehicle fuel economy than hydraulic. The use of auxiliary steering devices is on the rise.

In general, the electric power assist steering device assists the driver's steering torque by driving the motor in the electronic control device according to the driving conditions of the vehicle detected by the vehicle speed sensor and the steering torque sensor, thereby providing a light and comfortable steering state at low speed driving. In addition, it provides a heavy and stable steering state at high speeds, and provides steering performance to maintain the optimal steering feeling for the driver, such as enabling rapid steering operation in response to sudden emergency situations.

The electric power assisted steering system can be divided into various types according to the mounting position. The column-type electric power assisted steering system (C-EPS) is a steering wheel of the driver's seat and the lower part of the vehicle. By installing a power assisted steering device with an electric motor in the steering column part for fixing the steering shaft connecting the gearbox to the vehicle body, the rotational force of the steering wheel operated by the driver can be transmitted to the gearbox by the power assisted steering device. Device to ensure that

1 is a cross-sectional view showing the internal structure of a worm reducer provided in a commonly used column type electric power assisted steering device.

Such a worm reducer is provided with a worm shaft 104 made of steel having a worm 102 formed in an intermediate portion thereof, and worm bearings 106 are provided at both ends of the worm shaft 104 to provide a worm shaft 104. The worm shaft 104 and the motor shaft 108 are connected to each other, and the worm shaft 104 is rotated by the driving of the motor 110.

A worm wheel 114 made of, for example, a plastic material is provided at one side of the outer diameter of the worm 102 so that the worm 102 formed in the middle portion of the worm shaft 104 may be separated from the worm 102. Mounted on the steering shaft 112 for transmitting the rotational force of the steering wheel (not shown), the rotational force of the worm shaft 104 by the drive of the motor 110 is transmitted to the steering shaft (112). These worm wheels 114 and worm shafts 104, which are engaged in a worm gear manner, are mounted inside the housing 116 for protection from the outside.

Accordingly, a steering wheel in which the driving of the motor 110 is controlled by the electronic control device provided in the vehicle according to the vehicle driving condition, and the rotational force of the worm shaft 104 by the driving of the motor 110 is manipulated by the driver. In addition to the rotational force of the si) is transmitted to the steering shaft 112, it is possible to keep the driver's steering driving state smooth and stable.

However, in recent years, as the power output of steering assistance increases, wear of both worm gears increases. In particular, when the worm wheel is made of a material having a lower strength than that of the worm, for example, the teeth of the worm wheel are relatively As a disadvantage in terms of durability there was a problem that the wear proceeds more severely.

Moreover, the occurrence of backlash cannot be avoided due to such wear, and there is a problem in that vibrations and rattle noises due to such backlash are transmitted to the interior of the vehicle.

Accordingly, the present invention has been made to solve the above problems, in the worm reducer comprising a worm and a worm wheel, by increasing the pressure angle at the end of the worm gear than the pressure angle at the root, significantly reduce wear and improve durability It is an object of the present invention to provide a worm reducer which can be used to extend the life of the device.

In addition, another object of the present invention is to provide an electric power assisted steering device that is provided with such a worm reducer to ultimately eliminate vibrations and noise caused by backlash caused by wear.

The present invention for achieving the above object is a worm wheel mounted on the shaft, a worm which is entangled in the worm wheel is formed and at least one side of the worm shaft is supported by a worm bearing, the housing for receiving the worm wheel and the worm shaft, and In a worm reducer comprising a motor mounted to the housing for driving the worm shaft, at least one of the worm wheel or the worm may have a pressure angle at the tip of the worm gear so as to be larger than a pressure angle at the tooth root. It is characterized in that the tooth surface is formed.

The present invention also provides a worm wheel mounted on a steering shaft, a worm shaft which is entangled with the worm wheel, and at least one side of which is supported by a worm bearing, a housing accommodating the worm wheel and the worm shaft, and the housing An electric power assisted steering apparatus comprising a worm reducer including a motor mounted and driving a worm shaft, wherein at least one of the worm wheel or the worm of the worm reducer has a pressure angle at its tip. It is characterized in that the side surface is formed to be larger than the pressure angle at.

As described above, according to the present invention, the pressure angle at the tip of the worm gear is larger than the pressure angle at the tooth root, thereby greatly reducing wear and improving durability and life, and at the same time preventing vibration and noise caused by backlash. It is effective to provide an electric power assisted steering device having a worm reducer.

Hereinafter, exemplary embodiments of the present invention will be described in detail with reference to the accompanying drawings. First of all, in adding reference numerals to the components of each drawing, it should be noted that the same reference numerals are used as much as possible even if displayed on different drawings. In the following description of the present invention, a detailed description of known functions and configurations incorporated herein will be omitted when it may make the subject matter of the present invention rather unclear.

In addition, in the following description, for the convenience of description, an example in which the worm reducer according to the present invention is applied to an electric power assisted steering apparatus is described in detail, but the application example of the worm reducer according to the present invention is not limited thereto. Of course, it can be used for any required machine, apparatus or equipment.

Figure 2 is a perspective view showing the main portion of the worm reducer provided in the electric power assisted steering apparatus according to the present invention, a steering shaft 112 for transmitting a rotational force of a steering wheel (not shown) that the driver operates as shown therein: 1, a worm wheel 114 is mounted, and a worm bearing 106 is installed at both ends of the worm shaft 104 formed at an intermediate portion of the worm wheel 114 and the worm 102 which is bited off. It supports 104, one end of the worm shaft 104 is connected to the motor shaft 108 (see Fig. 1) is a structure in which the worm shaft 104 is rotated by the drive of the motor 110 (see Fig. 1) have. The worm wheel 114 and the worm shaft 104 are housed inside the housing 116 (see FIG. 1) for protection from the outside.

By the rotation of the worm shaft 104 by the driving of the motor, the worm 102 formed on the worm shaft 104 and the worm wheel 114 which are bitten off are rotated, so that the rotational force of the worm shaft 104 is reduced in the axial direction thereof. The steering shaft 112 is transmitted at right angles. Therefore, the rotational force of the steering wheel operated by the driver and the rotational force of the driving of the motor 110 are synthesized, so that steering operation can be made smoothly and stably.

The worm bearing 106 is provided at both ends of the worm shaft 104, the first bearing is provided on the inner side of the worm shaft 104, that is, the worm shaft is connected to the motor shaft of the motor, and the worm shaft 104 It is preferable to include a second bearing which is provided at a position opposite to the outer side, that is, the first bearing and connected to the worm shaft, but is not limited thereto. At least one bearing may be used.

3 is an enlarged view of a main portion of a worm gear used in a worm reducer according to a preferred embodiment of the present invention. One worm gear is characterized in that the tooth surface 120 is formed such that the pressure angle α _A at the tip thereof is larger than the pressure angle α _D at the root.

For example, if the pressure angle α _D at the root is 14.5 °, the pressure angle α _A at the tip is preferably about 14.5 ° <α _A ≦ 25 °. On the contrary, in an exceptional case, the pressure angle α _A at the tip may be 14.5 °, in which case the pressure angle α _D at the root may be 11 ° ≦ α _D <14.5 °.

In this way, by forming the facets such that the pressure angles at the tip and the root are different from each other and exactly the pressure angle at the tip is larger than the pressure angle at the tip, it prevents partial wear on the face (particularly at the tip). It will be able to contribute to strengthening the strength of the li and improving the durability of the worm gear as a whole.

As described above, according to the present invention, the wear and tear of the worm gear is greatly reduced, and durability and lifespan are improved, and vibration and noise generated by the backlash can be prevented from being transmitted.

Ultimately, when such a worm reducer is applied to an electric power assisted steering system, it prevents the transmission of vibration and noise along with extending the life of the steering system, thereby providing the driver with the reliability and smooth and comfortable steering feeling of the product. Will be.

The foregoing description is merely illustrative of the technical idea of the present invention, and various changes and modifications may be made by those skilled in the art without departing from the essential characteristics of the present invention. Therefore, the embodiments disclosed in the present invention are not intended to limit the technical idea of the present invention but to describe the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The protection scope of the present invention should be interpreted by the following claims, and all technical ideas within the equivalent scope should be interpreted as being included in the scope of the present invention.

1 is a cross-sectional view showing the internal structure of a worm reducer provided in a commonly used column type electric power assisted steering device.

Figure 2 is a perspective view showing the main portion of the worm reducer provided in the electric power assisted steering apparatus according to the present invention.

3 is an enlarged view of the main part shape of the worm gear used in the worm reducer according to the preferred embodiment of the present invention.

Claims (4)

A worm wheel mounted on the shaft, a worm shaft which is formed on the worm wheel, and a worm shaft having at least one side supported by a worm bearing, a housing accommodating the worm wheel and the worm shaft, and the worm shaft mounted on the housing. In a worm reducer comprising a motor for driving, At least one of the worm wheel and the worm gear is a worm reducer, characterized in that the tooth surface is formed such that the pressure angle at its tip is larger than the pressure angle at the root. The worm reducer of claim 1, wherein the pressure angle at the tip is greater than the pressure angle at the root and is 25 ° or less. The worm reducer of claim 1, wherein the pressure angle at the root is smaller than the pressure angle at the tip and is 11 ° or more. A worm wheel mounted on a steering shaft, a worm shaft which is formed on the worm wheel, and a worm shaft, at least one side of which is supported by a worm bearing; a housing accommodating the worm wheel and the worm shaft; and a worm shaft mounted on the housing. In the electric power assisted steering apparatus having a worm reducer comprising a motor for driving the motor, The at least one worm gear of the worm wheel or the worm of the worm reducer is provided with a tooth surface such that the pressure angle at its tip is larger than the pressure angle at the tooth root.

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