WO2011145820A2

WO2011145820A2 - Torque sensor of steering system

Info

Publication number: WO2011145820A2
Application number: PCT/KR2011/003304
Authority: WO
Inventors: Minchul Kang
Original assignee: Lg Innotek Co., Ltd.
Priority date: 2010-05-20
Filing date: 2011-05-03
Publication date: 2011-11-24
Also published as: WO2011145820A3; KR20110127815A; KR101680898B1

Abstract

The present invention relates to a torque sensor including an input axis, an output axis and a torsion bar connecting the input axis to the output axis, the torque sensor characterized by: a plurality of magnets connected to one of the input axis and the output axis of steering system, and axially magnetized for arrangement to a circumferential direction; and a stator including a ring-shaped body connected to one of the input axis and the output axis that is not connected to the plurality of magnets and discretely arranged from the magnets, and a plurality of lugs facing an axial distal end of the magnets, whereby a conventional collector is eliminated to allow a magnetic device to be directly coupled to a stator, thereby providing an operational reliability and structural simplicity.

Description

TORQUE SENSOR OF STEERING SYSTEM

The teachings in accordance with the exemplary embodiments of this invention relate generally to a torque sensor of steering system, and more particularly to a torque sensor of steering system, configured to simplify structure and enhance an operation reliability by omitting a collector through vertical magnetization of a magnet and horizontal arrangement of a lug at a stator.

In a conventional vehicle, a steering wheel connected to wheels is operated to manipulate a traveling direction. However, an operating force may decrease to make it difficult to quickly operate the vehicle, in case there is a large resistance between wheels and road surface, or there is generated an obstacle to steering operation. In order to solve the problem, a power system is proposed. The power system serves to intervene a power transfer device to operation of the steering wheels, thereby reducing operating force.

In order for the power system to intervene to force of operating the steering wheels, need arises to measure a torque applied to a steering axis. Apparatus of various methods are proposed to an apparatus for measuring torques of steering wheel. Particularly, a method of detecting a torque is largely employed for economic reason in which a magnetic field of a magnet coupled to a steering axis is measured to detect the torque.

A steering structure generally includes an input axis coupled to a steering wheel, an output axis coupled to a pinion meshed to a rack bar of wheel side, and a torsion bar connecting the input axis to the output axis.

In case a steering wheel is turned, a rotational force is transmitted to the output axis to change wheel directions responsive to operation of pinion and rack bar. In this case, if resistance is great, the input axis is more rotated to twist the torsion bar, where a twist level of torsion bar is measured by a torque sensor of magnetic field method.

A magnet is coupled to the input axis of a conventional torque sensor, whereby the magnet forms a ring. An output axis is arranged with a stator which is discretely arranged on a periphery of the magnet, and includes a vertical lug that is bent to an axis direction.

In case a twist is generated on the torsion bar due to a difference of rotational amount between the input axis coupled to the magnet and the output axis coupled to the stator, the magnet and the stator are relatively rotated, where an opposite surface between the periphery of the magnet and the vertical lug is changed to change a magnetization value. At this time, a torque can be measured using the change of magnetization value.

A collector is arranged to concentrate the magnetization value, where a magnetic element detects the magnetization value concentrated by the collector. Meantime, FIG.1 is a perspective view illustrating a magnet (10) and a direction of magnetic field according to prior art.

A conventional torque sensor is such that the direction of magnetic field is perpendicular to an axial direction, that is, a radial direction of the magnet (10), whereby the stator requires a bent surface to a direction perpendicular to the axis. However, there is a limit in obtaining an area for magnetizing the stator in the abovementioned arrangement, and as a result, a torque signal, that is, a magnetic signal disadvantageously becomes weak. In order to overcome the disadvantage, a further complicated structure is called for where a bent surface for stator is needed, and a collector has to be arranged to the ineffective detection of magnetization.

The present invention is provided to solve the abovementioned problems, and it is an object of the present invention to provide a torque sensor of steering system configured to simplify the structure and to increase operational reliability by axially arranging a magnetic direction of a magnet and broadening an effective area capable of detecting magnetization and removing a collector.

Technical problems to be solved by the present invention are not restricted to the above-mentioned descriptions, and any other technical problems not mentioned so far will be clearly appreciated from the following description by skilled in the art.

An object of the invention is to solve at least one or more of the above problems and/or disadvantages in a whole or in part and to provide at least the advantages described hereinafter. In order to achieve at least the above objects, in whole or in part, and in accordance with the purposes of the invention, as embodied and broadly described, and in one general aspect of the present invention, there is provided a torque sensor of steering system, the torque sensor including an input axis, an output axis and a torsion bar connecting the input axis to the output axis, the torque sensor characterized by: a plurality of magnets connected to one of the input axis and the output axis of steering system, and axially magnetized for arrangement to a circumferential direction; and a stator including a ring-shaped body connected to one of the input axis and the output axis that is not connected to the plurality of magnets and discretely arranged from the magnets, and a plurality of lugs facing an axial distal end of the magnets.

Preferably, the stator includes an upper stator facing a distal end of the magnet, and a bottom stator facing the other distal end of the magnet.

Preferably, the magnet is such that two or more magnetic substances are circumferentially arranged each spaced at an equal distance apart.

Preferably, the number of lugs in the upper and bottom stators are same as the number of poles formed at one distal end and the other distal end of the magnets.

Preferably, the torque sensor of steering system further includes a magnetic device connected to the stator to detect a magnetization amount of the stator.

Preferably, the lugs are protruded to an inner circumferential direction of the body.

The torque sensor of steering system according to the present invention has an advantageous effect in that a concept for axially forming a magnetic flux is proposed to enable a precise and easy measurement of magnetization amount, whereby a conventional collector is eliminated to allow a magnetic device to be directly coupled to a stator, thereby providing an operational reliability and structural simplicity. The torque sensor of steering system according to the present invention has another advantageous effect in that information on rotary deviation can be linearly detected, whereby rotation compensation of output shaft can be accurately realized by an auxiliary power system.

The teachings of the present invention can be readily understood by considering the following detailed description in conjunction with the accompanying drawings, in which:

FIG. 1 is a perspective view illustrating a direction of magnetic flux of a magnet in a torque sensor according to prior art;

FIG. 2 is a perspective view illustrating a torque sensor according to the present invention;

FIG. 3 is a perspective view illustrating a direction of magnetic flux of a magnet in a torque sensor according to the present invention;

FIG. 4 is schematic views experimentally illustrating changes in magnetization amount of a stator in a torque sensor according to the present invention; and

FIG. 5 is a graph illustrating changes in magnetization amount based on changes in revolution detected by a torque sensor according to the present invention.

The exemplary embodiments described here in detail for illustrative purposes are subject to many variations in structure and design. It should be emphasized, however, that the present invention is not limited to a particular disclosure, as shown and described. It is understood that various omissions and substitutions of equivalents are contemplated as circumstances may suggest or render expedient, but these are intended to cover the application or implementation without departing from the spirit or scope of the claims of the present invention.

The torque sensor of steering system according to the present invention will be best understood by referring to FIGS. 1-5 of the drawings.

FIG. 2 is a perspective view illustrating a torque sensor according to the present invention.

A magnet (100) takes the shape of a ring, and is generally arranged on a periphery of an input axis to rotate with the input axis. Stators (200, 300) are connected to an output axis to rotate with the output axis. Torsion is understandably generated by wheel resistance in case there is a difference of revolution between the input axis and the output axis, and the difference is measured by way of magnetic field as noted above. However, it should be apparent that the magnet (100) is connected an output axis, and each of the stators (200, 300) is connected to an input axis.

The magnet (100) is preferably configured in such a manner that two or more magnetic pieces are connected. Therefore, a plurality of arch-shaped magnet pieces forms the ring-shaped magnet (100). Each magnet piece is axially magnetized based on the concept of the present invention.

In case the magnet (100) is axially magnetized, the magnetic flux is likewise inputted and outputted axially, such that the magnetic flux can be measured across the magnet (100).

The stator includes an upper stator (200) and a bottom stator (300), each formed at an upper distal end and a bottom distal end of the magnet (100). Each of the stator (200, 300) includes a ring-shaped plate bodies (210, 310) and lug pieces (220, 320) that are horizontally formed with the body, that is, radially protruded.

The upper and bottom stators (200, 300) are such that the ring-shaped upper body (210) and the bottom body (310) are connected to the output axis, and discreted from the upper distal end and the bottom distal end of the magnet (100). The lug pieces (220, 320) may be protruded inwardly or outwardly from the ring-shaped body, but it is preferable that each lug piece (220, 230) face both distal ends of the magnet (100), and it is more preferable that each lug piece (220, 230) is inwardly protruded. The stators (200, 300) are preferably formed with a soft magnetizable material by way of injection molding method.

Meanwhile, a part of the stators (200, 300) is arranged with a magnetic device (500). The magnetic device (500) is electrically contacted by the stators (200, 300) to detect the magnetization amount of the stators (200, 300) magnetized by mutual magnetic action between the magnet (100) and the upper and bottom lug pieces (220, 320). It should be apparent that the magnetic device (500) can be attached to the upper stator (200), to the bottom stator (300), or to both the stators (200, 300). The magnetic device (500) is preferably comprised of a Hall IC (Hall IC).

As described above, the magnet (100) is formed in a ring shape by magnet pieces connected together, and each of the lug pieces (220, 320) facing the upper and bottom distal ends of the magnet (100) faces an N pole and a S pole. As a result, the number of upper and bottom lug pieces (220, 320) is preferably formed in the same number of poles arranged on the magnet (100).

FIG. 3 is a perspective view illustrating a direction of magnetic flux of a magnet in a torque sensor according to the present invention.

Unlike a conventional prior art, a magnetic flux of the magnet faces an axial direction, and based on this concept, each of the lug pieces (220, 320) can face the distal end of the magnet (100) from the axial direction. It should be appreciated that four poles are respectively formed as the magnetic pieces are four, as illustrated in FIG. 4.

Based on the abovementioned configuration, the torque sensor of steering system according to the present invention is such that a torsion ratio is twisted by wheel resistance if a steering wheel is manipulated to steer wheels, to thereby generate a rotary deviation between an input axis connected to the magnet and an output axis connected to the stators (200, 300). That is, the magnet (100) is rotated relative to the stators (200, 300) in response to the twist of the torsion bar.

Portions facing the lug pieces (220, 320) of the stators (200, 300) are changed by the rotation of the magnet (100), which may be measured by variation of magnetization value in the lug pieces.

FIG. 4 is schematic views experimentally illustrating changes in magnetization amount of a stator in a torque sensor according to the present invention.

A left hand side figure of FIG. 4 illustrates a magnetization amount at an initial state where the magnet (100) and the stators (200, 300) are arranged, where a bright portion defines an area where the magnetization amount is great. The poles of magnet (100) are initially arranged about a concave area between the lug pieces (220, 320) to thereby minimize the magnetization amount of the lug pieces (220, 320). Furthermore, the magnetization amount becomes maximized at the lug pieces (220, 320) as shown in the right hand side of FIG. 4, if the magnet (100) is rotated relative to the stators (200, 300) to generate a maximum revolution.

The magnetic device (500) is arranged adjacent to a particular area of the lug pieces (220, 320) to measure the detected magnetization amount, whereby the measurement is outputted as an electrical signal. The torque sensor of steering system provides a concept where magnetic flux is axially formed, whereby measurement of magnetization amount can be precisely and easily performed. In short, the conventional collector is removed to allow the magnetic device (500) to directly contact the stators, whereby operational reliability and structural simplicity can be provided.

As shown in FIG. 5, in case the magnetic flux is axially formed based on the concept according to the present invention, it should be noted that data on the measurement value takes the shape similar to a linear one. At this time, in case a set-up value within an appropriate scope is established, a magnetization value proximate to the linear shape can be extracted, which means that information on rotary deviation can be linearly detected, and that rotation compensation of an output shaft can be accurately realized by an auxiliary power system according to the information.

The previous description of the present invention is provided to enable any person skilled in the art to make or use the invention. Various modifications to the invention will be readily apparent to those skilled in the art, and the generic principles defined herein may be applied to other variations without departing from the spirit or scope of the invention. Thus, the invention is not intended to be limited to the examples and designs described herein but is to be accorded the widest scope consistent with the principles and novel features disclosed herein.

The torque sensor of steering system according to the present invention has an industrial applicability in that simplify the structure can be simplified and operational reliability can be increased by axially arranging a magnetic direction of a magnet and broadening an effective area capable of detecting magnetization and removing a collector.

Claims

A torque sensor of steering system, the torque sensor including an input axis, an output axis and a torsion bar connecting the input axis to the output axis, the torque sensor characterized by: a plurality of magnets connected to one of the input axis and the output axis of steering system, and axially magnetized for arrangement to a circumferential direction; and a stator including a ring-shaped body connected to one of the input axis and the output axis that is not connected to the plurality of magnets and discretely arranged from the magnets, and a plurality of lugs facing an axial distal end of the magnets.
The torque sensor of claim 1, characterized in that the lugs are radially protruded from the body to be parallel with a distal end of the magnet.
The torque sensor of claim 1, characterized in that the lugs are protruded to an inner circumferential direction of the body.
The torque sensor of claim 1, characterized in that the stator includes an upper stator facing a distal end of the magnet, and a bottom stator facing the other distal end of the magnet.
The torque sensor of claim 1, characterized in that the magnet is such that two or more magnetic substances are circumferentially arranged each spaced at an equal distance apart.
The torque sensor of claim 4, characterized in that the number of lugs in the upper and bottom stators are same as the number of poles formed at one distal end and the other distal end of the magnets.
The torque sensor of any one claim of 1 to 6, further characterized by a magnetic device connected to the stator to detect a magnetization amount of the stator.
The torque sensor of claim 7, characterized in that the magnetic device is a Hall IC.
The torque sensor of claim 7, characterized in that the magnetic device is directly coupled to the stator.
The torque sensor of steering system, characterized by: a plurality of magnets connected to one of an input axis and an output axis of steering system for axial magnetization; and a stator connected to one of the input axis and the output axis that is not connected to the plurality of magnets and arranged at an axial distal end of the magnet to detect an axial magnetization amount that changes in response to a relative rotation of the magnet.
The torque sensor of claim 10, characterized in that the stator includes a ring-shaped body, and a plurality of lugs radially extended from the body to face a distal end of the magnet.
The torque sensor of claim 11, characterized in that the lugs are protruded to an inner circumferential direction of the body.
The torque sensor of claim 10, characterized in that the stator includes an upper stator facing a distal end of the magnet, and a bottom stator facing the other distal end of the magnet.
The torque sensor of claim 10, characterized in that the magnet is such that two or more magnetic substances are circumferentially arranged each spaced at an equal distance apart.
The torque sensor of claim 13, characterized in that the number of lugs in the upper and bottom stators are same as the number of poles formed at one distal end and the other distal end of the magnets.