Abstract:
Disclosed is a torque sensor comprising: a first casing comprising a first opening; a second casing comprising a second opening; a stator comprising a stator holder that is placed in the interior of the first casing and the second casing and at least one stator tooth that is secured to the stator holder; and a rotor that is rotatably disposed in the stator, wherein the stator comprises a protrusion facing the inner peripheral surface of the first opening.

Description:
FIELD 
       [0001]    The present invention relates to a torque sensor, and more particularly, to a torque sensor mounted on vehicles to measure a torque about a steering axis. 
       BACKGROUND 
       [0002]    Generally, an electronic power steering system (EPS) is an apparatus for ensuring steering stability of a vehicle and provides a torque in the direction that a driver steers using a motor for smooth handling. 
         [0003]    Unlike the existing hydraulic power steering (HPS), the EPS may improve steering performance and steering feel by controlling an operation of a motor according to driving condition. 
         [0004]    A torque load about a steering axis, a steering angle, and an angular velocity of steering need to be measured for the EPS to provide an appropriate torque. 
         [0005]    A conventional steering structure includes an input axis coupled with a steering wheel, an output axis joined with a pinion which is coupled to a rack bar at a wheel and a torsion bar which connects the input axis and the output axis. 
         [0006]    When a steering wheel is rotated, rotation power is delivered to the output axis and directions of wheels are changed by the operation of a pinion and a rack bar. Here, when a resistance force is great, the input axis becomes more rotated so that the torsion bar becomes twisted, and a magnetic field type torque sensor measures the degree of twist of the torsion bar. 
         [0007]    The torque sensor is provided to be accommodated in an upper casing and a lower casing with a rotor, a stator, a collector and a circuit board, and the torque sensor provided as such is accommodated in a housing to connect with the input axis and the output axis. Here, a stator holder is fixed in the axis direction by coupling the upper casing and the lower casing. 
         [0008]    However, there is a problem in that the stator holder vibrates in a case in the case of not being fixed in a direction perpendicular to the axis direction, i.e. the horizontal direction. When the stator holder vibrates as such, a gap of the stator tooth delivering a magnetic force is changed, and thus there is a problem in that reliability of the torque sensor operation is lowered. 
       DISCLOSURE 
     Technical Problem 
       [0009]    The present invention provides a torque sensor where reliability of a torque sensor operation is improved by preventing a stator from vibrating in a lateral direction perpendicular to an axis direction. 
       Technical Solution 
       [0010]    According to an aspect of the present invention, a torque sensor includes a first casing including a first opening, a second casing including a second opening, a stator including a stator holder disposed inside the first casing and the second casing and at least a stator tooth fixed to the stator holder, and a rotor rotatably disposed in the stator wherein the stator includes a protrusion facing an inner peripheral surface of the first opening. 
         [0011]    In the torque sensor according to an aspect of the present invention, a diameter of the first opening may be greater than that of the second opening. 
         [0012]    In the torque sensor according to an aspect of the present invention, the protrusion may be formed in a plurality of numbers along a first virtual circle, and a diameter of the first virtual circle may be equal to or smaller than that of the first opening. 
         [0013]    In the torque sensor according to an aspect of the present invention, the diameter of the first opening may be greater than that of an outer peripheral surface of the rotor. 
         [0014]    In the torque sensor according to the aspect of the present invention, the diameter of the first virtual circle may be greater than that of an outer peripheral surface of the rotor. 
         [0015]    In the torque sensor according to an aspect of the present invention, a diameter of an outer peripheral surface of the stator may be greater than those of the first opening and the first virtual circle. 
         [0016]    In the torque sensor according to an aspect of the present invention, the protrusion may protrude from the stator tooth in an axis direction. 
         [0017]    In the torque sensor according to an aspect of the present invention, the protrusion may protrude from the stator holder in an axis direction. 
         [0018]    In the torque sensor according to an aspect of the present invention, the torque sensor may include a collector connected to the stator tooth, and a magnetic device configured to detect a magnetization level collected by the collector. 
         [0019]    According to another aspect of the present invention, a torque sensor includes a first casing in which a first opening is formed, a second casing in which a second opening is formed, a stator including a stator holder disposed inside the first casing and the second casing and at least a stator tooth fixed to the stator holder, and a rotor rotatably disposed in the stator, wherein the first casing includes a first guide groove formed inside thereof, and the stator includes a first protrusion rotatably coupled to the first guide groove. 
         [0020]    In the torque sensor according to another aspect of the present invention, the protrusion may be formed in a plurality of numbers along a first virtual circle, and a diameter of the first virtual circle may be greater than that of the first opening. 
         [0021]    In the torque sensor according to another aspect of the present invention, the first protrusion may protrude from the stator holder in an axis direction. 
         [0022]    In the torque sensor according to another aspect of the present invention, the second casing may include a second guide groove formed inside thereof, and the stator may include a second protrusion rotatably coupled to the second guide groove. 
         [0023]    In the torque sensor according to another aspect of the present invention, the torque sensor may include a collector connected to the stator tooth, and a magnetic device configured to detect a magnetization level collected by the collector. 
         [0024]    According to still another aspect of the present invention, a torque sensor includes a first casing in which a first opening is formed, a second casing in which a second opening is formed, a stator including a stator holder disposed inside the first casing and the second casing and at least a stator tooth fixed to the stator holder, and a rotor rotatably disposed in the stator, wherein the stator includes a first protrusion which protrudes in an axis direction to face an inner peripheral surface of a first opening, and a second protrusion rotatably coupled to a guide groove formed in the second casing. 
       Advantageous Effects 
       [0025]    According to an embodiment of the present invention, a stator can be prevented from vibrating in a case in a lateral direction perpendicular to an axis direction, and thus reliability of the torque sensor operation can be improved. 
     
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
         [0026]      FIG. 1  is an exploded perspective view of a torque sensor according to an embodiment of the present invention. 
           [0027]      FIG. 2  is a cross-sectional view of a torque sensor according to an embodiment of the present invention. 
           [0028]      FIG. 3  is an exploded perspective view of a torque sensor according to another embodiment of the present invention. 
           [0029]      FIG. 4  is an exploded perspective view of a torque sensor according to still another embodiment of the present invention. 
           [0030]      FIG. 5  is a modified example of a torque sensor according to still another embodiment of the present invention. 
       
    
    
     DETAILED DESCRIPTION 
       [0031]    While the present invention is susceptible to various modifications and alternative embodiments, specific embodiments thereof are shown by way of examples in the drawings and described. However, it should be understood that there is no intention to limit the present invention to the particular embodiments disclosed, but on the contrary, the present invention is to cover all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. 
         [0032]    It will be understood that, although the terms including ordinal numbers such as “first,” “second,” etc. may be used herein to describe various elements, these elements are not limited by these terms. These terms are only used to distinguish one element from another. For example, a second element could be termed a first element without departing from the teachings of the present inventive concept, and similarly a first element could be also termed a second element. The term “and/or” includes any and all combination of one or more of the associated listed items. 
         [0033]    It will be understood that when an element or layer is referred to as being “on,” “connected to,” or “coupled with” another element or layer, it can be directly on, connected, or coupled to the other element or layer or intervening elements or layers may be present. In contrast, when an element is referred to as being “directly on,” “directly connected to,” or “directly coupled with” another element or layer, there are no intervening elements or layers present. 
         [0034]    The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the present invention. As used herein, the singular forms “a,” “an,” and “the,” are intended to include the plural forms as well, unless the context clearly indicates otherwise. It will be further understood that the terms “comprises” and/or “comprising,” when used in this specification, specify the presence of stated features, integers, steps, operations, elements, and/or components, but do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, components, and/or groups thereof. 
         [0035]    Unless otherwise defined, all terms including technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skill in the art to which this inventive concept belongs. It will be further understood that terms, such as those defined in commonly used dictionaries, should be interpreted as having a meaning that is consistent with their meaning in the context of the relevant art and will not be interpreted in an idealized or overly formal sense unless expressly so defined herein. 
         [0036]    Hereinafter, embodiments of the present invention will be described in detail with reference to the accompanying drawings, and regardless of the numbers in the drawings, the same or corresponding elements will be assigned with the same numbers and overlapping descriptions will be omitted. 
         [0037]      FIG. 1  is an exploded perspective view of a torque sensor according to an embodiment of the present invention, and  FIG. 2  is a cross-sectional view of a torque sensor according to an embodiment of the present invention. Meanwhile,  FIG. 3  is an exploded perspective view of a torque sensor according to another embodiment of the present invention. 
         [0038]    Referring to  FIG. 1  and  FIG. 2 , the torque sensor according to an embodiment of the present invention includes a first casing  110 , a second casing  120 , a stator  200 , and a rotor  300 . Here, the first casing  110  may be an upper casing and the second casing  120  may be a lower casing, but without a strict limitation. 
         [0039]    The first casing  110  and the second casing  120  are coupled with each other to form an exterior of the torque sensor, and the stator  200  and the rotor  300  are disposed inside thereof. Here, the first casing  110  and the second casing  120  may be coupled by couplers  112  and  122  formed on one side. 
         [0040]    A first opening  111  and a second opening  121  are formed in the first casing  110  and the second casing  120 , respectively. An input axis (not shown) is connected to the rotor  300  through the first opening  111  of the first casing  110 , and an output axis (not shown) is connected to the stator  200  through the second opening  121  of the second casing  120 . 
         [0041]    Here, diameters of the first opening  111  and the second opening  121  formed in the first casing  110  and the second casing  120  may be smaller than outer diameter of the stator  200 . Accordingly, the stator  200  may be fixed in an axis direction z by coupling the first casing  110  and the second casing  120 . 
         [0042]    The stator  200  is disposed inside the first casing  110  and the second casing  120  to be rotated with the output axis. The stator  200  includes a stator holder  210  and a stator tooth  220 . The stator tooth  220  is formed as a pair ( 221  and  222 ), and each is fixed in an upper and a lower portions of the stator holder  210 , respectively. The stator tooth  220  is disposed to face a magnet  310  which is disposed on an outer peripheral surface of the rotor  300 . 
         [0043]    The stator holder  210  forms the body of the stator  200  and is coupled with the output axis. The stator holder  210  may be manufactured by an injection molding process to fix the stator tooth  220 . The manner of coupling the stator tooth  220  and the stator holder  210  may have all configurations of a conventional torque sensor applied. 
         [0044]    The stator  200  according to the embodiment of the present invention includes a protrusion  230  supported by an inner peripheral surface of the first opening  111  formed in the first casing  110 . However, the protrusion  230  is not limited to thereto and may be supported at the second opening  121  formed in the second casing  120 . 
         [0045]    The protrusion  230  may be formed to protrude in plurality in the axis direction z along a first virtual circle Cl. In this case, the diameters of the openings  111  and  121  formed in the first casing  110  and the second casing  120  may be equal to or smaller than a rotational diameter of the protrusion  230  (diameter of the first virtual circle). 
         [0046]    The diameters of the first opening  111  and the second opening  121  may be flexibly selected within a tolerance range in which a rotation of the protrusion  230  is supported. For example, when rotated, the protrusion  230  may be in contact with or separated by a certain distance from the inner peripheral surface of the first opening  111 . 
         [0047]    The rotor  300  is disposed inside the stator  200  and is rotated with the input axis. The magnet  310  in a ring shape is attached on the outer peripheral surface of the rotor  300 , and the stator tooth  220  is disposed on an outer surface of the magnet  310 . 
         [0048]    When a torsion bar is twisted due to a difference between rotation angles of the input axis and the output axis, a rotation angle of the magnet  310  mounted on the rotor  300  become different from that of the stator  200 , and thus the surfaces facing each other between the magnet  310  and the stator tooth  220  are relatively moved . Therefore, torque may be measured by detecting a change in magnetization level of the stator  200 . 
         [0049]    To this end, the torque sensor further includes at least one collector (not shown) which is coupled with the stator tooth  220  to collect magnetic flux, a magnetic device (not shown) to detect the magnetization level collected by the collector, and a circuit board (not shown) in which the magnetic device is disposed 
         [0050]    Referring to  FIG. 2 , a diameter R 1  of the first opening may be formed to be larger than a diameter R 3  of the second opening, and a diameter R 2  of the first virtual circle may be equal to or smaller than the diameter R 1  of the first opening. In such a configuration, the protrusion  230  disposed along the first virtual circle is disposed to face an inner peripheral surface  111   a  of the first opening to support rotation of the stator. 
         [0051]    Here, since a diameter R 4  of an outer peripheral surface of the stator is manufactured to have greater than the diameter R 1  of the first opening and the diameter R 3  of the second opening, the stator may be securely confined in the first casing  110  and the second casing  120 . 
         [0052]    Further, the diameter R 1  of the first opening may be greater than a diameter R 5  of the outer peripheral surface of the rotor  300 . In this structure, since the rotor  300  is not confined in the first casing  110  and the second casing  120  and easily separated from the stator, there is an advantage where manufacturing and maintenance are easy. Further, when the torque sensor is mounted on a vehicle, since the rotor  300  and the stator  200  are confined in the axial direction of a steering axis (the input axis and the output axis), performance of the sensor is not lowered. 
         [0053]    The protrusion  230  may be formed to protrude from the stator holder  210  or the stator tooth  220 . Here, the protrusion  230  is formed in the axis direction z or the lateral directions x and y to be supported by an inner peripheral surface of the first casing  110  or the second casing  120 . 
         [0054]    In such a configuration, the stator  200  may be fixed in the lateral directions x and y perpendicular to the axis direction z inside the first casing  110  and the second casing  120 . That is, since the stator  200  may rotate while being supported by the inner peripheral surface of the first casing  110  or the second casing  120 , the stator  200  is prevented from vibrating in the horizontal directions x and y during rotating. Therefore, reliability of the torque sensor operation may be improved. 
         [0055]    Referring to  FIG. 3 , a protrusion  230  may also protrude toward a second casing  120 . Therefore, the protrusion  230  may be supported by an inner peripheral surface of a second opening  121 . 
         [0056]      FIG. 4  is an exploded perspective view of a torque sensor according to still another embodiment of the present invention, and  FIG. 5  is a modified example of a torque sensor according to still another embodiment of the present invention. In the embodiment, configuration of the case and configuration of the protrusion formed in plurality along the first virtual circle are the same as described above, and since only a structure which supports the protrusion is different from the above, the structure will be described in detail. 
         [0057]    Referring to  FIG. 4 , a first guide groove  113  in a ring shaped may be formed on an inner peripheral surface of a first casing  110  to guide rotation of a first protrusion  231 , and the first protrusion  231  formed by the stator  200  may be rotatably supported by the first guide groove  113 . 
         [0058]    Here, the protrusion  231  may be formed to protrude from a stator holder  210  in the axis direction z, and a diameter of an opening  111  formed in the first casing  110  may be smaller than that of a path outlined by rotation of the protrusion  231  (diameter of the first virtual circle). 
         [0059]    In such a configuration, since the stator  200  may rotate while being supported by the guide groove  113  formed in the inner peripheral surface of the first casing  110 , the stator  200  may be prevented from vibrating in the lateral directions x and y during rotating. Therefore, reliability of the torque sensor operation may be improved. 
         [0060]    However, the supporting structure of the protrusion is not necessarily limited to the above. For example, as illustrated in  FIG. 5 , a second guide groove  123  formed on an inner peripheral surface of a second casing  120  may guide a second protrusion  232 . 
         [0061]    Further, the first protrusion  231  and the second protrusion  232  may be formed in the stator  200  and configured to be supported by the first guide groove  113  of the first casing  110  and the second guide groove  123  of the second casing  120 . 
         [0062]    Further, the first protrusion  231  formed in the stator  200  may be disposed to face an inner peripheral surface of the first opening  111  of the first casing  110  (see  FIG. 1 ), and the second protrusion  232  formed in the stator  200  may be disposed to be rotatably coupled to the guide groove  123  formed in the second casing  120 . In such a configuration, vibration of the stator in the horizontal direction may be further effectively controlled. 
         [0063]    Although exemplary embodiments of the present invention have been referenced and described above, it will be understood that it is possible for those of ordinary skill in the art to implement modifications and variations on the present invention without departing from the concept and scope of the present invention listed in the following appended claims.