WO2012015183A2

WO2012015183A2 - Torque index sensor having structure for magnetic shielding

Info

Publication number: WO2012015183A2
Application number: PCT/KR2011/005045
Authority: WO
Inventors: Minchul Kang
Original assignee: LG Innotek Co Ltd
Current assignee: LG Innotek Co Ltd
Priority date: 2010-07-27
Filing date: 2011-07-11
Publication date: 2012-02-02
Anticipated expiration: 2013-01-27
Also published as: KR101637597B1; KR20120010695A; WO2012015183A3

Abstract

The present invention relates to a TIS (torque index sensor) having a magnetic shielding structure, formed with a shield plate between a torque sensor unit and an index unit to minimize the magnetic interference therebetween for operational reliability and to make the TIS compact for maximization of utilization of space, the TIS including: a torque sensor unit including a rotor connected to the input shaft, a stator connected to the output shaft, a collector and a torque sensor magnetic device; an index unit including an index magnet rotating along with the output shaft, and an index magnetic device detecting changes in magnetic field in response to rotation of the index magnet; and a shield plate interposed between the torque sensor unit and the index unit for shielding a magnetic interference between the torque sensor unit and the index unit.

Description

TORQUE INDEX SENSOR HAVING STRUCTURE FOR MAGNETIC SHIELDING

The teachings in accordance with the exemplary embodiments of this invention relate generally to a torque index sensor in a steering system, and more particularly to a torque index sensor having magnetic shielding structure capable of shielding interference of magnetic field between a torque sensor and an index unit to thereby enhance operational reliability and to maximize utilization of space.

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 steering system is proposed. The power steering system serves to provide a power transfer device to operation of the steering wheels, thereby reducing operating force.

In order for the power steering system to provide a force of operating the steering wheels, needs arise to measure a torque applied to a steering axis, a steering angel and an angular velocity. Apparatus of various methods are proposed for measuring torques of steering wheel. Particularly, a method for detecting a torque is largely employed for economic reasons in which a magnetic field of a magnet coupled to a steering axis is measured to detect the torque. Furthermore, a method for detecting an electromagnetic rotation is widely used to detect the steering angle and the angular velocity by employing a gear rotating along with a steering wheel and a driven gear meshed with the gear.

However, the device or system detecting the steering angle or the angular velocity suffers from disadvantages such as complicated fabrication processes, and a high probability of error occurrences from malfunction or erroneous operation, such that a method using an index sensor is employed.

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

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

An index sensor is provided for measuring angular velocity and angular acceleration by detecting rotation of a magnet rotating with the output shaft. The torque sensor and the index sensor may be modularized, and a modularized device is called a torque index sensor (TIS). That is, a torque index sensor (TIS) is an integrated device of a torque sensor for detection of steering torque in steering manipulation and an index sensor for detection of number of turns of a steering shaft, wherein these sensors are installed in a steering system of an automobile for example.

The TIS is advantageous due to structural simplicity and economic reasons, but concurrently disadvantageous due to inevitable occurrence of magnetic field interference caused by a structure in which two types of magnetization detection device are adjacently arranged. In order to solve the disadvantage, the torque sensor and the index sensor are needed to maintain a predetermined distance, such that a distance of 35mm is generally secured to avoid occurrence of magnetic field interference.

As a result, there is generated a disadvantage of unnecessarily increasing a size of the TIS and of considering a magnetic field interference for fabricating the TIS into a compact size.

The present invention is provided to solve the abovementioned problems, and it is an object of the present invention to provide a TIS (torque index sensor) having magnetic shielding structure capable of shielding interference of magnetic field between a torque sensor and an index unit to thereby enhance operational reliability and to maximize utilization of space.

Technical problems to be solved by the present invention are not restricted to the above-mentioned, 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 TIS (torque index sensor) having a magnetic shielding structure, the TIS in a steering system connected to an input shaft and an output shaft, comprising: a torque sensor unit including a rotor connected to the input shaft, a stator connected to the output shaft, a collector and a torque sensor magnetic device; an index unit including an index magnet rotating along with the output shaft, and an index magnetic device detecting changes in magnetic field in response to rotation of the index magnet; and a shield plate interposed between the torque sensor unit and the index unit for shielding a magnetic interference between the torque sensor unit and the index unit.

Preferably, the shield plate is arranged at a bottom surface of the collector, and takes the shape of a shape corresponding to that of the collector for shielding the magnetic interference from the index magnet if the index magnet is positioned at the bottom surface of the collector.

Preferably, the shield plate is extended to an area where the torque sensor magnetic device is mounted for shielding the collector and the torque sensor magnetic device from the magnetic interference of the index magnet.

Preferably, the TIS (torque index sensor) having a magnetic shielding structure further includes a housing forming an external appearance of the TIS and supportively accommodating therein the torque sensor unit, the index unit and the shield plate.

Preferably, the magnetic device is a Hall element (Hall integrated circuit).

Preferably, the shield plate is formed with a magnetic substance.

Preferably, the stator includes an upper stator arranged at an upper surface of the stator, and a bottom stator arranged at a bottom surface of the stator, and the collector includes an upper collector connected to the upper stator, and a bottom collector connected to the bottom stator.

In another general aspect of the present invention, there is provided a TIS (torque index sensor) having a magnetic shielding structure, the TIS comprising: a rotor and a stator connected to a steering shaft; a collector concentrating changes in magnetization values caused by rotation of the stator relative to the rotor; a torque sensor magnetic device detecting the changes in magnetization values; an index magnet arranged at a bottom surface of a collector to rotate along with rotation of the steering shaft; an index magnetic device detecting changes in magnetization values of the index magnet; and a plate-shaped shield plate arranged at the bottom surface of the collector for shielding magnetic flux facing upwards from the index magnet.

Preferably, the shield plate takes the shape of a form corresponding to that of the collector for shielding the magnetic interference from the index magnet if the index magnet is positioned at the bottom surface of the collector.

Preferably, the magnetic device is a Hall element (Hall integrated circuit).

Preferably, the shield plate is formed with a magnetic substance.

The a TIS (torque index sensor) having a magnetic shielding structure according to the present invention has an advantageous effect in that a magnetic field shielding structure is formed between the torque sensor unit and the index unit to minimize the magnetic interference therebetween and to make the TIS compact.

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 torque index sensor;

FIG. 2 is a perspective view illustrating an essential part of a torque index sensor;

FIG. 3 is a perspective view illustrating a torque index sensor installed with a shield plate according to an exemplary embodiment of the present invention;

FIG. 4 is a visual view illustrating a magnetic interference between a torque index sensor free from a shield plate and a torque index sensor installed with a shield plate; and

FIG. 5 is a graph illustrating a difference of magnetic flux between A point and B point illustrated in FIG. 4.

The following description is not intended to limit the invention to the form disclosed herein. Consequently, variations and modifications commensurate with the following teachings, and skill and knowledge of the relevant art are within the scope of the present invention. The embodiments described herein are further intended to explain modes known of practicing the invention and to enable others skilled in the art to utilize the invention in such, or other embodiments and with various modifications required by the particular application(s) or use(s) of the present invention.

The disclosed embodiments and advantages thereof are best understood by referring to FIGS. 1-5 of the drawings, like numerals being used for like and corresponding parts of the various drawings. Other features and advantages of the disclosed embodiments will be or will become apparent to one of ordinary skill in the art upon examination of the following figures and detailed description. It is intended that all such additional features and advantages be included within the scope of the disclosed embodiments, and protected by the accompanying drawings. Further, the illustrated figures are only exemplary and not intended to assert or imply any limitation with regard to the environment, architecture, or process in which different embodiments may be implemented. Accordingly, the described aspect is intended to embrace all such alterations, modifications, and variations that fall within the scope and novel idea of the present invention.

Furthermore, "exemplary" is merely meant to mean an example, rather than the best. It is also to be appreciated that features, layers and/or elements depicted herein are illustrated with particular dimensions and/or orientations relative to one another for purposes of simplicity and ease of understanding, and that the actual dimensions and/or orientations may differ substantially from that illustrated.

As may be used herein, the terms "substantially" and "approximately" provide an industry-accepted tolerance for its corresponding term and/or relativity between items.

That is, in the drawings, the size and relative sizes of layers, regions and/or other elements may be exaggerated or reduced for clarity. Like numbers refer to like elements throughout and descriptions of well-known functions and constructions are omitted for clarity and conciseness.

Now, the present invention will be described in detail with reference to the accompanying drawings.

FIG. 1 is a perspective view illustrating a torque index sensor, and FIG. 2 is a perspective view illustrating an essential part of a torque sensor unit and an index unit of a torque index sensor free from a shield plate.

Referring to FIGS. 1 and 2, an input shaft that is inserted into TIS (Torque Index Sensor) from an upper side is coupled to a rotor (12) coupled to a magnet, where the rotor (12) takes the shape of a ring. An output shaft is coupled by a stator (11), where the stator (11) is discretely arranged from a periphery of the rotor (12) and includes an axially-bent vertical lug piece (13).

In a case a twist is generated to a torsion bar by a rotational difference between the input shaft coupled to the rotor (12) and the output shaft coupled to the stator (11), the rotor (12) and the stator (11) are relatively rotated, where a facing surface between the periphery of the rotor (12) and the axially-bent vertical lug piece (13) is changed to change a magnetization value, and where the changed magnetization value may be utilized to measure a torque.

A collector (14) is arranged to concentrate the magnetization value, and a torque sensor magnetic device (15) detects the magnetization value concentrated by the collector (14).

Meanwhile, an index unit is arranged at a bottom side of the torque sensor unit. The index unit includes an index magnet (31) and an index magnet device (35), where the index magnet (31) is connected to the output shaft along with the stator (11) and rotated therewith.

Although the torque sensor unit and the index unit are modularized inside a housing (22) and form an integrated configuration, each of the torque sensor unit and the index unit functions differently. That is, the torque sensor unit measures a torque change in response to change in magnetization value and sends a detection signal to a PCB (Printed Circuit Board, 21), while the index unit sends a detection signal of an amount of magnetization that is changed by the index magnet device in response to rotation of the index magnet (31).

FIG. 3 is a perspective view illustrating a torque index sensor installed with a shield plate according to the present invention.

Referring to FIG. 1 again, the TIS according to the present invention includes a torque sensor unit and an index unit that are modularized and coupled in a housing that forms an external appearance of the TIS.

The torque sensor unit generally includes a ring-shaped rotor (112), a magnet (not shown) coupled to a periphery of the rotor (112), stator (111) discretely arranged from the periphery of the rotor (112), a collector (114) coupled to one side of the stator (111) to concentrate a magnetization change, and a torque sensor magnetic device (115) connected to the collector (114) to detect the magnetization change.

The rotor (112) generally takes the shape of a ring, and is arranged at a periphery of an input shaft and is rotated with the input shaft. Furthermore, the stator (111) is connected to an output shaft and rotated with the output shaft. In a case an amount of rotation of the input shaft and that of the output shaft are different due to wheel resistance, torsion is generated, and the difference is measured by magnetic field as explained above. However, it should be apparent that the rotor (112) can be connected to the output shaft and the stator (111) can be connected to the input shaft.

Furthermore, a axially-bent vertical lug piece (113) is changed in magnetization value by relative rotation with a magnet arranged at the periphery of the rotor (112). The stator (111) is arranged at one side thereof with the collector (114) in which the changed magnetization is concentrated.

A part of the collector (114) is arranged with the torque sensor magnetic device (115). The torque sensor magnetic device (115) is electrically connected to the collector (114) to detect the amount of magnetization of the stator (111) magnetized by magnetization mutual action between the magnet of the rotor (112) and the lug piece (113). Preferably, the torque sensor magnetic device (115) is a Hall element (Hall integrated circuit) capable of detecting intensity of magnetic field.

The torque sensor unit is arranged at a bottom surface with an index unit, where the index unit includes an index magnet (131) and an index magnetic element (135). The index magnet (131) is generally connected to an output shaft and rotated with the output shaft. The index magnetic element (135) takes the shape of a predetermined circumferential length only, unlike the magnet of the rotor (112), such that the index magnetic element (135) takes the shape of an arc when viewed from a cross-section.

The index magnetic element (135) arranged near to the torque sensor magnetic device (115) repeats a process of approaching and distancing from the index magnet (131) in response to the rotation of the output shaft, whereby the magnetization is changed. The index magnet element (135) detects the changed magnetization and outputs a detection signal capable of analyzing angular velocity and angular acceleration based on algorithm. That is, the index unit outputs an impulse signal at every period of 360 degrees.

It is therefore apparent that the magnetic interference is generated by a mutual adjacency between the torque sensor unit and the index unit, each being closely arranged, as explained in the above. As a measure to solve the abovementioned shortcoming and based on the concept of the present invention, a shield plate (140) is arranged between the torque sensor unit and the index unit to shield the magnetic field interference.

To be more specific, there may be generated a chance of the index magnet (131) and the collector (114) being aligned when axially viewed according to rotation of the index magnet (131), and the magnet flux from the index magnet (131) passing through the collector (114). Under this circumstances, there is generated a difference in magnetization values of each collector (114) arranged on an upper and a bottom side, whereby an accurate value is outputted from the detected signal of the torque sensor magnetic device (115), leading to generation of an error in rotational torque.

Therefore, in order to prevent the abovementioned occurrences, the shield plate (140) is preferably arranged underneath the collector (114). The shield plate (140) is formed with a plated material and is also formed with a magnetic substance to prevent the magnetic flux of the index magnet (131) from flowing upwards. More preferably, the shield plate (140) is shaped to correspond with the shape of the collector (114). It suffices, on the part of the shield plate (140), to shield the magnetic flux of an area crossing the collector (114) in response to rotation of the index magnet (131). The shield plate (140) is therefore shaped to correspond to the shape of the collector (114), preferably a bit larger than the collector (114).

Furthermore, the shield plate (140) may be extended to one side of an area leading to the torque sensor magnetic device (115) to shield the magnetic flux. Although the shield plate (140) may be formed at the area that is arranged with the collector (114) as described above, the shield plate (140) may be also formed across the board of the bottom side of the stator (111) to shield the lion s share of influence from the magnetic flux. In this case, the shield plate (140) may substantially take the shape of a ring-like plate.

The installation of shield plate between the torque sensor unit and the index unit can substantially reduce the influence of magnetic flux to the collector (114) from the index magnet. To be more specific, a difference of magnetization value between an upper collector and a bottom collector connecting an upper stator and a bottom stator is reduced, which means that accuracy of torque data can be improved.

FIG. 4 is a visual view illustrating a magnetic interference between a torque index sensor free from a shield plate and a torque index sensor installed with a shield plate.

A left side view of FIG. 4 illustrates an amount of magnetization at the torque index sensor free from a shield plate, a right side view of FIG. 4 illustrates an amount of magnetization at the torque index sensor installed with a shield plate, and a bottom view of FIG. 4 illustrates an amount of magnetization based on color saturation of magnet flux. An A point in FIG. 4 illustrates an area of a collector installed on an upper side, while a B point of FIG. 4 illustrates an area of a collector installed on a bottom side. Both models show a larger amount of magnetization at the bottom side in bright color, which is caused by influence of magnetic flux from the index magnet arranged at the bottom side.

However, unlike the case where there is no shield plate, it can be noted that a color difference between an upper and a bottom side of the collector of the torque index sensor according to the present invention is greatly reduced. That is, the shield plate (140) arranged at the bottom side of the collector (114) absorbs the magnetic flux to minimize the influence of index magnet (131) to the bottom collector (114).

A graph in which trapezoids are connected illustrates a magnetization change between A point and B point of the torque index sensor according to the present invention, and a graph in which rectangles are connected illustrates a magnetization change of a torque index sensor which is not installed with the shield plate. The horizontal axis defines a magnetic calculation position and the vertical axis defines a magnet flux density.

As evidenced from FIG. 5, in a case the shield plate (140) is installed at a bottom side of the collector (114), a difference of the amount of magnetization of collectors at the upper and bottom sides is greatly reduced. A difference of amount of magnetization between A point and B point according to the present invention is approximately 2.97% based on the present experiment, and the case where there is no shield plate shows approximately 6.80%, which is a big difference.

Although embodiments have been described with reference to a number of illustrative embodiments thereof, it should be understood that numerous other modifications and embodiments can be devised by those skilled in the art that will fall within the spirit and scope of the principles of this invention. More particularly, various variations and modifications are possible in the component parts and/or arrangements of the subject combination arrangement within the scope of the disclosure, the drawing and the appended claims. In addition to variations and modifications in the component parts and/or arrangements, alternative uses will also be apparent to those skilled in the art.

The TIS (torque index sensor) having a magnetic shielding structure according to the present invention has an industrial applicability in that a shield plate is formed between a torque sensor unit and an index unit to minimize the magnetic interference therebetween for operational reliability and to make the TIS compact for maximization of utilization of space.

Claims

A TIS (torque index sensor) having a magnetic shielding structure, the TIS in a steering system connected to an input shaft and an output shaft, comprising:

a torque sensor unit including a rotor connected to the input shaft, a stator connected to the output shaft, a collector and a torque sensor magnetic device;

an index unit including an index magnet rotating along with the output shaft, and an index magnetic device detecting changes in magnetic field in response to rotation of the index magnet; and

a shield plate interposed between the torque sensor unit and the index unit for shielding a magnetic interference between the torque sensor unit and the index unit.
The TIS of claim 1, wherein the shield plate is arranged at a bottom surface of the collector, and takes the shape of a shape corresponding to that of the collector for shielding the magnetic interference from the index magnet if the index magnet is positioned at the bottom surface of the collector.
The TIS of claim 2, wherein the shield plate is extended to an area where the torque sensor magnetic device is mounted for shielding the collector and the torque sensor magnetic device from the magnetic interference of the index magnet.
The TIS of claim 1, further comprising a housing forming an external appearance of the TIS and supportively accommodating therein the torque sensor unit, the index unit and the shield plate.
The TIS of claim 1, wherein the magnetic device is a Hall element (Hall integrated circuit).
The TIS of claim 1, wherein the shield plate is formed with a magnetic substance.
The TIS of claim 1, wherein the stator includes an upper stator arranged at an upper surface of the stator, and a bottom stator arranged at a bottom surface of the stator, and the collector includes an upper collector connected to the upper stator, and a bottom collector connected to the bottom stator.
A TIS (torque index sensor) having a magnetic shielding structure, the TIS comprising:

a rotor and a stator connected to a steering shaft; a collector concentrating changes in magnetization values caused by rotation of the stator relative to the rotor;

a torque sensor magnetic device detecting the changes in magnetization values;

an index magnet arranged at a bottom surface of a collector to rotate along with rotation of the steering shaft; an index magnetic device detecting changes in magnetization values of the index magnet; and

a plate-shaped shield plate arranged at the bottom surface of the collector for shielding magnetic flux facing upwards from the index magnet.
The TIS of claim 8, wherein the shield plate takes the shape of a form corresponding to that of the collector for shielding the magnetic interference from the index magnet if the index magnet is positioned at the bottom surface of the collector.
The TIS of claim 9, wherein the shield plate is extended to an area where the torque sensor magnetic device is mounted for shielding the collector and the torque sensor magnetic device from the magnetic interference of the index magnet.
The TIS of claim 8, wherein the magnetic device is a Hall element (Hall integrated circuit).
The TIS of claim 8, wherein the shield plate is formed with a magnetic substance.