KR101450320B1 - Rack Assist Type Electric Power Steering Apparatus having Ball Reducer - Google Patents

Rack Assist Type Electric Power Steering Apparatus having Ball Reducer Download PDF

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KR101450320B1
KR101450320B1 KR1020100036176A KR20100036176A KR101450320B1 KR 101450320 B1 KR101450320 B1 KR 101450320B1 KR 1020100036176 A KR1020100036176 A KR 1020100036176A KR 20100036176 A KR20100036176 A KR 20100036176A KR 101450320 B1 KR101450320 B1 KR 101450320B1
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South Korea
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ball
output shaft
steering
rack bar
rack
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KR1020100036176A
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Korean (ko)
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KR20110116643A (en
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이충성
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주식회사 만도
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  • Mechanical Engineering (AREA)
  • Chemical & Material Sciences (AREA)
  • Combustion & Propulsion (AREA)
  • Transportation (AREA)
  • General Engineering & Computer Science (AREA)
  • Power Steering Mechanism (AREA)

Abstract

According to the present invention, there is provided a ball reducer which is coupled to a rack bar coaxially so as to transmit a steering assist force to a rack bar, thereby providing a rack-driven electromotive steering system It is possible to reduce noise, vibration and friction caused by an increase in backlash as compared with the apparatus, to smooth steering operation to provide a pleasant steering feeling to the driver, and to greatly reduce size and weight.

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention [0001] The present invention relates to a rack driving type electric power steering apparatus having a ball reducer,

The present invention relates to a rack-driven electric steering system. More specifically, the present invention provides a ball reducer that is coupled to a rack bar coaxially to transmit a steering assist force to a rack bar, thereby reducing noise, vibration, and frictional force due to an increase in backlash as compared with a conventional rack- To a rack-driven electromotive steering system equipped with a ball reducer which is capable of providing a comfortable steering feeling to a driver and greatly reducing size and weight.

BACKGROUND ART Generally, a hydraulic power steering apparatus using a hydraulic pressure of a hydraulic pump is used as a power assist steering apparatus of an automobile. Recently, an electric power steering apparatus using a motor has become commonplace.

A typical electric steering apparatus comprises a steering system extending from the steering wheel to both wheels and an auxiliary power mechanism for supplying steering assist power to the steering system.

The auxiliary power mechanism includes a torque sensor for sensing a steering torque applied to the steering wheel by the driver and outputting an electric signal proportional to the detected steering torque, an electronic control unit (ECU) for generating a control signal based on an electric signal transmitted from the torque sensor, An electronic control unit), a motor for generating a steering assist power based on a control signal transmitted from the electronic control unit, and a transmission for transmitting auxiliary power generated by the motor to the rack bar via a belt.

FIG. 1 is a partial cross-sectional view schematically showing a conventional rack-driven electromotive steering system, and FIG. 2 is a cross-sectional view schematically showing a part of a conventional rack-driven electromotive steering system.

1 and 2, a rack driving type electric steering apparatus according to the related art includes a rack bar 140 extending in the lateral direction of the automobile and having a rack gear on one side and a screw groove 145 on the outer side, A ball 220 moving in rolling contact with the screw groove 145 and the intermediate path 215 of the rack bar, a pinion shaft 110 having a pinion gear engaged with the rack gear, An end cap 230 attached to an end of the ball nut 210, a ball nut 210, and a ball nut 210. The ball nut 210 has an intermediate path 215 through which the ball 220 circulates, A belt-type power transmission device 160 for connecting the motor shaft 155, a motor 150, and the like.

The pinion shaft 110 is connected to the steering wheel through the steering shaft and the rack bar 140 having the screw groove 145 of a predetermined length formed on one side of the outer circumferential surface thereof is housed in the rack housing 120.

The belt-type power transmission device 160 is formed to include a belt connecting the motor shaft 155 and the ball nut 210. The belt-type power transmission device 160 is configured to receive the steering assist force generated by the motor 150 in proportion to the steering torque applied to the steering wheel. And transmits it to the rack bar 140 through the nut 210.

The conventional method is a method in which the ball 220 contacts the screw groove 145 of the rack bar 140 and the screw groove of the ball nut 210 to form a linear intermediate path 215).

However, such a conventional rack-driven electric power steering apparatus has a complicated structure in which a belt-type power transmission apparatus is separately provided outside the rack bar and connected with a ball nut and a belt. After the running of the vehicle, the backlash increases, There is a problem that an uncomfortable steering feeling is generated to the driver.

Further, the structure is complicated, the size and weight are increased, and the friction between the ball and the ball is increased due to the difficulty in manufacturing the intermediate path through which the ball circulates and errors.

SUMMARY OF THE INVENTION The present invention has been conceived in order to solve these problems, and it is an object of the present invention to provide a ball reducer for transmitting a steering assist force to a rack bar by being coupled to a rack bar coaxially, And to reduce frictional force and smooth steering operation, thereby providing a comfortable steering feeling to the driver, and to reduce the size and weight of the steering apparatus to a large extent.

To achieve these and other advantages and in accordance with the purpose of the present invention, as embodied and broadly described herein, there is provided an automatic transmission control system comprising: an ECU for receiving steering wheel steering information and vehicle driving information through at least one sensor and calculating a control value for a target steer- And a ball reducer having an output shaft connected to a shaft of the motor and a rack shaft coaxially with the motor shaft and transmitting a rotation ratio of the ball circulated inside the motor shaft to the rack bar through the output shaft. A rack-driven electric power steering apparatus provided with a ball reducer is provided.

According to the present invention, by providing a ball reducer which is coupled to a rack bar coaxially so as to transmit a steering assist force to a rack bar, noise, vibration and friction caused by an increase in backlash can be reduced and steering operation is smooth Thereby providing a comfortable steering feeling to the driver and greatly reducing the size and weight of the vehicle.

1 is a partial cross-sectional view schematically showing a conventional rack-driven electromechanical steering apparatus;
FIG. 2 is a cross-sectional view schematically showing a part of a conventional rack-driven electromechanical steering apparatus; FIG.
3 is a perspective view schematically showing an active front wheel steering apparatus having a ball reducer according to an embodiment of the present invention;
4 is a sectional view of a ball reducer according to an embodiment of the present invention;
5 is an exploded perspective view of the ball reducer of FIG. 4;
FIG. 6 is an exploded perspective view showing a coupling state of the transmission disc and the output disc in the ball reducer of FIG. 4;

Hereinafter, some embodiments of the present invention will be described in detail with reference to exemplary drawings. It should be noted that, in adding reference numerals to the constituent elements of the drawings, the same constituent elements are denoted by the same reference symbols as possible even if they are shown in 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 describing the components of the present invention, terms such as first, second, A, B, (a), and (b) may be used. These terms are intended to distinguish the constituent elements from other constituent elements, and the terms do not limit the nature, order or order of the constituent elements. When a component is described as being "connected", "coupled", or "connected" to another component, the component may be directly connected to or connected to the other component, It should be understood that an element may be "connected," "coupled," or "connected."

FIG. 3 is a perspective view schematically showing an active front wheel steering apparatus having a ball reducer according to an embodiment of the present invention, FIG. 4 is a sectional view of a ball reducer according to an embodiment of the present invention, FIG. 6 is an exploded perspective view showing a coupling state of the transmission disk and the output disk in the ball reducer of FIG. 4; FIG.

As shown in these drawings, a rack-driven electric steering apparatus 300 having a ball reducer 320 according to an embodiment of the present invention includes steering wheel 311 steering information and vehicle driving information A motor 330 driven by a control value calculated by the ECU 310 and a control unit 330 for controlling the shaft 403 of the motor 330, And an output shaft 430 coaxially connected to the rack bar 140. The epicyclic curved surface 420 and the hypocyloid curved surface 417 are connected to the output shaft 430 in such a manner that the ball 425 circulates, And a ball decelerator 320 for transmitting the ball decelerator 320 to the rack bar 140.

The ball reducer 320 includes an input disk 410 that is rotatably supported by a fixing plate 405 via a ball when the shaft 403 of the motor 330 rotates and transmits rotational force, , A transfer disk 415 having a side surface opposed to the transfer disk 415 via a ball and having a hypocyloid curved surface 417 formed on the other side thereof and a side surface opposed to the transfer disk 415 via a ball And an epicycloidal curved surface 420 corresponding to the hypocrocyclic curved surface 417 is formed on both sides of the axle 403 of the motor 330 so as to be coaxial with the rack bar 140, And an output disk 420 having an output shaft 430 coupled therewith.

The ECU 310 includes a steering angle sensor 301 such as an input angle sensor and an output angle sensor and a torque sensor 303, a vehicle speed sensor 305, a lateral acceleration sensor 307, a yaw rate sensor 309, The steering wheel 311 steering information of the driver and the running information of the vehicle are inputted through the sensors of various sensors such as the steering wheel 311 and the like to calculate a control value for the target steering ratio of the output shaft 430 based on the information And drives the motor 330.

That is, in the rack-driven electric steering system 300 having the ball reducer 320 according to the present invention, the steering information caused by the operation of the steering wheel 311 of the driver is transmitted through the steering angle sensor 301 or the torque sensor 303 The ECU 310 continuously receives the steering information that changes frequently and compares the steering information with various kinds of information of the automobile and then transmits it as an electric signal to the motor 330 that controls the linear motion of the rack bar 140, And a ball speed reducer 320 is provided as a speed reducing device for changing the output speeds of the motor 330 and the rack bar 140.

The ball decelerator 320 is an epicyclic ball decelerator of a kind and increases or decreases the rotation rate of the output disk 420 in the forward and reverse directions with respect to the rotation speed of the input disk 410 rotating in conjunction with the motor shaft 403 And the ball is coupled to the epicyclic curve surface 420 and the hypocyloid curve surface 417 which are opposed to each other so as to transmit the steering output value corrected for the input of the driver's steering wheel 311 to the rack bar 140. [

That is, when the rotational force of the motor 330 is transmitted through the input disc 410, the transfer disc 415, and the output disc 420, the ball 425 is transferred to the transfer disc 415 and the output disc 420 The epicyclic curved surface 420 and the hypocyloid curved surface 417 which are formed are circulated only at a certain reduction ratio to reduce the rotation rate of the output disc 420. [

The ball reducer 320 includes a fixed plate 405, an input disk 410, a transmission disk 415, and an output disk 420, which are sequentially connected to each other through a ball.

The shaft 403 of the motor 330 is formed hollow so that the output shaft 430 of the ball reducer 320 passes through the shaft 403. An eccentric shaft 404 and an eccentric weight 402 are provided on one side, An eccentric rotational force is transmitted to the input disc 410 by the eccentric weight 402 when the input disc 410 is rotated and the input disc 410 and the input disc 410 are disposed on one side of the input disc 410 and the opposite side of the transfer disc 415, A hypoid cycloid curved surface 417 is formed on the other side surface of the transfer disc 415 and the transfer disc 415 is opposed to the output disc 415 on the output disc 420. [ An epicycloidal curved surface 420 is formed on the surface.

A ball 425 circulates on the epicycloidal curved surface 420 and the hypocyloid curved surface 417 between the transfer disc 415 and the output disc 420 and a change in the rotation ratio occurs at a constant reduction ratio.

The epicycloidal curved surface 420 and the hypocyloid curved surface 417 are formed as grooves so as to be opposed to each other on the transfer disc 415 and the output disc 420. The epicycloid curves the circle while circumscribing the circumferential phase Hypocycloid is a trajectory drawn by a point of a circle when rolling a circle while inscribing the circumference image.

At this time, the ball 425 is disposed at a position where these contact points, that is, the epicycloidal curved surface 420 and the hypocycloid curved surface 417 intersect.

These balls 425 are driven while being in contact with the respective epicycloidal curved surface 420 and the hypocroved curved surface 417 while being in contact with the respective curved surfaces so that when the transfer disc 415 makes one revolution, And the hypocyloid curved surface 417. Therefore, when the epicycloidal curved surface 420 is formed of N waves, the reduction ratio is

Figure 112010025032276-pat00001
.

Therefore, the reduction ratio determines the wavenumbers of the epicycloidal curved surface 420 and the hypocyloid curved surface 417 in accordance with the required target value. Such an epicyclic ball decelerator is generally used, and the operating principle is described in further detail Is omitted.

The output shaft 430 is coupled to the rack bar 140 and transmits the converted rotation ratio to the rack bar 140. The output shaft 430 is coaxial with the rack bar 140, The output shaft 430 provided on the other side is coupled to the rack bar 140 through the shaft 403 of the motor 330 so that the output shaft 430 is coupled to the rack bar 140, do.

The output shaft 430 and the rack bar 140 are inserted and coupled with each other to allow the rack bar 140 to linearly move in the direction of the central axis when the output shaft 430 rotates. The outer and inner circumferential surfaces oppose each other, When the output shaft 430 rotates, the rack bar 140 linearly moves toward one side or the other side in accordance with the rotation direction.

Screw grooves 435a and 435b corresponding to the outer circumferential surface and the inner circumferential surface of the output shaft 430 and the rack bar 140 are formed to be opposed to each other and the balls 437 are engaged with the screw grooves 435a and 435b When the ball 437 is coupled to the screw grooves 435a and 435b in this way, the driving force of the motor is reduced by reducing the frictional force compared with the case where the balls 437 roll in the rolling motion during the rotation of the output shaft 430 .

According to the present invention having such a structure and shape, a ball reducer which is coupled to a rack bar coaxially and transmits a steering assist force to a rack bar provides noise reduction and vibration due to an increase in backlash The frictional force can be reduced, the steering operation can be smoothly performed, a pleasant steering feeling can be provided to the driver, and the size and weight can be significantly reduced.

While the present invention has been described in connection with what is presently considered to be the most practical and preferred embodiments, it is to be understood that the invention is not limited to the disclosed embodiments. That is, within the scope of the present invention, all of the components may be selectively coupled to one or more of them.

It is also to be understood that the terms such as " comprises, "" comprising," or "having ", as used herein, mean that a component can be implanted unless specifically stated to the contrary. But should be construed as including other elements. All terms, including technical and scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs, unless otherwise defined. Commonly used terms, such as predefined terms, should be interpreted to be consistent with the contextual meanings of the related art, and are not to be construed as ideal or overly formal, unless expressly defined to the contrary.

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 intended to illustrate rather than limit the scope of the present invention, and the scope of the technical idea of the present invention is not limited by these embodiments. The scope of protection of the present invention should be construed according to the following claims, and all technical ideas falling within the scope of the same shall be construed as falling within the scope of the present invention.

310: ECU 320: ball reducer
330: motor 403: motor shaft
405: Fixing plate 410: Input disk
415: Transfer Disk 420: Epicycloid Surface
425: ball 430: output shaft

Claims (5)

An ECU for receiving steering wheel steering information and vehicle running information through at least one sensor and calculating a control value for the target steering ratio according to the steering wheel steering information and the vehicle running information;
A motor driven by a control value calculated by the ECU; And
And a ball reducer having an output shaft connected to a shaft of the motor and a rack bar coaxially and transmitting a rotation ratio of the balls circulated in the ball bar to the rack bar through the output shaft,
The ball-
An input disk which is rotatably supported on the fixed plate through a ball when the axis of the motor rotates;
A transfer disk having one side opposed to the input disk coupled through a ball and a hypocyloid curved surface formed on the other side; And
An output disc having an output shaft connected to the rack bar on both sides thereof on both sides thereof, the output disc having an output shaft connected to one side of the transmission disc through a ball, wherein the output disc has an epicyclic curved surface corresponding to the hypocyloid curved surface,
Wherein the rack-drive type electric-powered steering system comprises a ball-reducer. delete The method according to claim 1,
Wherein the shaft of the motor is formed hollow so as to allow the output shaft of the ball reducer to pass therethrough, and eccentricity is further provided at one end of the motor. The method according to claim 1,
Wherein the output shaft and the rack bar are inserted and coupled to each other and have a threaded portion that engages with an outer circumferential surface and an inner circumferential surface which are opposed to each other so that the rack bar linearly moves in the direction of the central axis when the output shaft rotates Rack-driven electric steering. The method according to claim 1,
Wherein the output shaft and the rack bar are inserted and coupled with each other and have a screw groove formed in an outer circumferential surface and an inner circumferential surface opposed to each other and a ball is coupled to the screw groove so that the rack bar linearly moves in the direction of the central axis when the output shaft rotates And a ball decelerator for driving the rack-driven electric motor.
KR1020100036176A 2010-04-20 2010-04-20 Rack Assist Type Electric Power Steering Apparatus having Ball Reducer KR101450320B1 (en)

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KR1020100036176A KR101450320B1 (en) 2010-04-20 2010-04-20 Rack Assist Type Electric Power Steering Apparatus having Ball Reducer

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KR1020100036176A KR101450320B1 (en) 2010-04-20 2010-04-20 Rack Assist Type Electric Power Steering Apparatus having Ball Reducer

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Publication number Priority date Publication date Assignee Title
KR101450322B1 (en) * 2011-01-31 2014-10-21 주식회사 만도 Rack Assist Type Electric Power Steering Apparatus having Ball Reducer

Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR900007362B1 (en) * 1985-06-27 1990-10-08 가모 세이꼬오 가부시끼가이샤 Ball-type differential speed reducer structure
US20050016789A1 (en) * 2002-10-24 2005-01-27 Toyoda Koki Kabushiki Kaisha Electric power steering device and method and apparatus for manufacturing the same
KR20080042651A (en) * 2006-11-09 2008-05-15 미쓰비시덴키 가부시키가이샤 Transmission ratio varying mechanism
US20080184838A1 (en) * 2005-02-14 2008-08-07 Toyota Jidosha Kabushiki Kaisha Steering Device

Patent Citations (4)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
KR900007362B1 (en) * 1985-06-27 1990-10-08 가모 세이꼬오 가부시끼가이샤 Ball-type differential speed reducer structure
US20050016789A1 (en) * 2002-10-24 2005-01-27 Toyoda Koki Kabushiki Kaisha Electric power steering device and method and apparatus for manufacturing the same
US20080184838A1 (en) * 2005-02-14 2008-08-07 Toyota Jidosha Kabushiki Kaisha Steering Device
KR20080042651A (en) * 2006-11-09 2008-05-15 미쓰비시덴키 가부시키가이샤 Transmission ratio varying mechanism

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