Torque detecting apparatus and method for manufacturing the same

A torque detecting apparatus includes an annular magnetic flux collecting ring, a magnetic flux collecting holder surrounding and holding the magnetic flux collecting ring, and a magnetic shield including a circumferential end and attached to the outer periphery of the magnetic flux collecting holder. The magnetic flux collecting holder includes a housing portion that houses in its inner space the circumferential end of the magnetic shield. The housing portion includes an outer wall radially inwardly facing an outer peripheral surface of the circumferential end of the magnetic shield such that a first clearance is provided between the housing portion and the outer peripheral surface of the circumferential end of the magnetic shield.

INCORPORATION BY REFERENCE

The disclosure of Japanese Patent Application No. 2016-226315 filed on Nov. 21, 2016, including the specification, drawings and abstract, is incorporated herein by reference in its entirety.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The invention relates to torque detecting apparatuses and methods for manufacturing torque detecting apparatuses.

2. Description of the Related Art

A torque detecting apparatus to detect a relative rotational displacement amount between shafts axially coupled to each other is known in the related art. A torque detecting apparatus disclosed in Japanese Patent Application Publication No. 2015-031600 (JP 2015-031600 A) includes a cylindrical magnetic flux collecting holder, a magnetic shield, and a housing. The magnetic flux collecting holder is integral with a magnetic flux collecting ring. The magnetic shield is attached to the outer peripheral surface of the magnetic flux collecting holder so as to reduce influence that an external magnetic field exerts on the magnetic flux collecting ring. The housing is integral with the magnetic flux collecting holder.

A change in temperature causes the magnetic shield, the magnetic flux collecting holder, and the housing to expand or contract. The magnetic shield, the magnetic flux collecting holder, and the housing expand or contract to different degrees as a result of a change in temperature. Thus, a change in temperature causes the magnetic shield to be pressed against the magnetic flux collecting holder and/or the housing. Circumferential ends of the magnetic shield, in particular, expand or contract to a large degree owing to a change in temperature. This concentrates stress on portions of the magnetic flux collecting holder and/or the housing that are in contact with the circumferential ends. Such stress concentration may unfortunately form cracks in these portions.

SUMMARY OF THE INVENTION

An object of the invention is to provide a torque detecting apparatus that prevents formation of cracks in components surrounding a magnetic shield caused by contact of circumferential ends of the magnetic shield with the surrounding components, and a method for manufacturing such a torque detecting apparatus.

A torque detecting apparatus according to an aspect of the invention includes an annular magnetic flux collecting ring, a magnetic flux collecting holder, and a magnetic shield. The magnetic flux collecting holder surrounds and holds the magnetic flux collecting ring. The magnetic shield is attached to an outer periphery of the magnetic flux collecting holder. The magnetic shield includes a circumferential end. The magnetic flux collecting holder includes a housing portion housing the circumferential end of the magnetic shield. The housing portion includes an outer wall radially inwardly facing an outer peripheral surface of the circumferential end of the magnetic shield such that a clearance is provided between the housing portion and the outer peripheral surface of the circumferential end of the magnetic shield.

DETAILED DESCRIPTION OF EMBODIMENTS

An embodiment of the invention will be described in detail below with reference to the accompanying drawings.FIG. 1is a diagram illustrating a schematic configuration of an electric power steering system5including a torque detecting apparatus1according to the embodiment of the invention. The torque detecting apparatus1includes a torque sensor2and a housing3that houses the torque sensor2. The torque sensor2and the housing3are integral with each other. The electric power steering system5equipped with the torque sensor2is a dual pinion electric power steering system, for example. The electric power steering system5includes a rack shaft6, a first pinion shaft7, and a second pinion shaft8. The first pinion shaft7is provided with a first pinion7athat meshes with a first rack6aof the rack shaft6. Thus, the first pinion shaft7serves to transmit a steering assist force. The second pinion shaft8is provided with a second pinion8athat meshes with a second rack6bof the rack shaft6. Thus, the second pinion shaft8serves to transmit a manual steering force.

The housing3is attached to, for example, a rack housing10that houses the rack shaft6. The torque sensor2is attached to, for example, the second pinion shaft8. The second pinion shaft8includes an input shaft15, an output shaft16, and a torsion bar17. The input shaft15is coupled to a steering wheel13through a steering shaft11and an intermediate shaft12. The output shaft16is provided with the second pinion8a. The torsion bar17is coaxially coupled to the input shaft15and the output shaft16. The input shaft15and the output shaft16are rotatable relative to each other within a predetermined angular range.

Steered wheels20are each coupled to an associated one of the ends of the rack shaft6through an associated tie rod18and an associated steering knuckle arm19. A driver manipulates the steering wheel13so as to steer the steered wheels20through the steering shaft11, the intermediate shaft12, the second pinion shaft8, the rack shaft6, the tie rods18, and the steering knuckle arms19. When the driver manipulates the steering wheel13in order to steer the steered wheels20, the input shaft15and the output shaft16of the second pinion shaft8rotate relative to each other so as to twist the torsion bar17.

The torque sensor2detects the amount of twist of the torsion bar17of the second pinion shaft8. A torque detection signal from the torque sensor2is provided to an electronic control unit (ECU)25. The ECU25drives and controls, through an internal driving circuit, an electric motor26in accordance with, for example, the torque detection signal and/or a vehicle speed detection signal provided from a vehicle speed sensor (not illustrated). Rotation of the electric motor26is reduced in speed through a speed reducing mechanism27. The resulting rotation is transmitted to the first pinion shaft7and converted into a linear motion of the rack shaft6. This linear motion assists the driver in steering a vehicle.

The configuration of the torque detecting apparatus1will be described in detail below.FIG. 2is a schematic cross-sectional view of the torque detecting apparatus1and components adjacent thereto.FIG. 3is an exploded perspective view of the torque sensor2.FIG. 4is a perspective view of the torque sensor2. The torque sensor2includes a permanent magnet40and a pair of magnetic yokes41magnetically connected to the permanent magnet40. The permanent magnet40is secured to the input shaft15such that the permanent magnet40is concentric with and rotatable together with the input shaft15. The pair of magnetic yokes41are secured to the output shaft16such that the magnetic yokes41are concentric with and rotatable together with the output shaft16. The input shaft15and the output shaft16rotate relative to each other so as to change the positions of the pair of magnetic yokes41and the permanent magnet40relative to each other. This results in a change in magnetic flux.

The torque sensor2is electrically connected to the ECU25. The torque sensor2detects magnetic flux from the magnetic yokes41. The torque sensor2includes a first circuit portion51having an annular shape. The first circuit portion51includes a central axis C1corresponding to the central axis of the input shaft15. A radial direction defined with respect to the central axis C1will be referred to as a “radial direction R”. The radial direction R includes a radially inward direction and a radially outward direction. The radially inward direction is a direction toward the central axis C1. The radially outward direction is a direction away from the central axis C1. A direction extending along the central axis C1will be referred to as an “axial direction X”. A direction extending around the central axis C1will be referred to as a “circumferential direction C”.

The first circuit portion51includes a pair of annular magnetic flux collecting rings53and an annular magnetic flux collecting holder55. The pair of magnetic flux collecting rings53are each magnetically connected to an associated one of the magnetic yokes41. The magnetic flux collecting holder55surrounds and holds the magnetic flux collecting rings53. The torque sensor2further includes a second circuit portion52having a block shape. The second circuit portion52is protruded radially outward from the outer periphery of the first circuit portion51. The second circuit portion52includes a first magnetic element61, a second magnetic element62, an electronic component60, and a holder63. The first magnetic element61and the second magnetic element62each output a signal responsive to magnetic flux flowing through a magnetic circuit56. The electronic component60is electrically connected to a pair of the first and second magnetic elements61and62. The holder63houses and holds the pair of first and second magnetic elements61and62and the electronic component60.

Each of the first and second magnetic elements61and62is a Hall integrated circuit (IC), for example. In the cross-sectional view ofFIG. 2, the pair of first and second magnetic elements61and62are actually invisible, but both of the pair of first and second magnetic elements61and62are indicated by dashed lines for convenience of description. The electronic component60includes a substrate70and a capacitor71mounted on the substrate70. The substrate70is electrically connected with metal terminals72. The terminals72each include: a first portion72acoupled to the substrate70; and a second portion72bextending downward from an end of the first portion72a. The electronic component60further includes: pins73that couple the pair of first and second magnetic elements61and62to the substrate70; and a cover74covering the capacitor71.

The holder63is made of resin. The holder63has a block shape (i.e., a substantially rectangular cuboid shape). The holder63includes a pair of sub-holders63afitted to each other, with the electronic component60sandwiched therebetween. The housing3includes a tubular body80, a holder retainer82, and a connector portion83. The body80, the holder retainer82, and the connector portion83are made of a single material and integral with each other. The body80surrounds the input shaft15of the second pinion shaft8. The body80includes an inner space80a. The pair of magnetic flux collecting rings53and the magnetic flux collecting holder55are housed in the inner space80a. The holder retainer82is protruded from the outer peripheral surface of the body80. The holder retainer82retains the holder63. The connector portion83is extended from a protruded end of the holder retainer82. A waterproof connector30is fitted to the connector portion83. Connecting the connector30to the connector portion83electrically connects the second portions72bof the terminals72to the ECU25.

The housing3is waterproofed with a seal member31, a seal member32, a bearing33, and a seal member34so as to prevent entry of liquid into the housing3. The seal member31is provided between the body80and the input shaft15. The seal member32is provided between the body80and the rack housing10. The bearing33is provided between the rack housing10and the output shaft16. The seal member34is provided between the connector30and the connector portion83.

The magnetic flux collecting holder55is made of resin. The magnetic flux collecting holder55is housed in the housing3made of resin. The magnetic flux collecting holder55is integral with the housing3. The magnetic flux collecting holder55includes an annular portion55b. The annular portion55bincludes a pair of sub-portions55afitted to each other in the axial direction X. Each of the sub-portions55ais integral with an associated one of the sub-holders63aof the holder63. Each of the magnetic flux collecting rings53includes an annular portion53a, a first element facing portion53b, and a second element facing portion53c. The first element facing portion53bis protruded radially outward from the annular portion53aand faces the first magnetic element61. The second element facing portion53cis protruded radially outward from the annular portion53aand faces the second magnetic element62.

Each of the magnetic flux collecting rings53is molded with the resin of an associated one of the sub-portions55asuch that each of the magnetic flux collecting rings53is integral with the associated sub-portion55aof the magnetic flux collecting holder55. Thus, each of the magnetic flux collecting rings53and the associated sub-portion55aare formed into an annular shape as a whole. In other words, the magnetic flux collecting rings53are each held by an associated one of the sub-portions55a. Each of the sub-portions55aof the magnetic flux collecting holder55and each of the magnetic flux collecting rings53surround the outer periphery of an associated one of the magnetic yokes41in a concentric and noncontact manner. The first magnetic element61is disposed between the first element facing portions53bof the pair of magnetic flux collecting rings53. The second magnetic element62is disposed between the second element facing portions53cof the pair of magnetic flux collecting rings53. Magnetic flux that has changed in accordance with a change in the position of the permanent magnet40relative to each magnetic yoke41is guided to the pair of first and second magnetic elements61and62by the pair of magnetic flux collecting rings53.

The first circuit portion51further includes a magnetic shield57to reduce influence exerted on the magnetic circuit56by an external magnetic field. The magnetic circuit56is provided by the magnetic flux collecting rings53, the magnetic yokes41, and the permanent magnet40. The magnetic shield57is attached to the outer periphery of the magnetic flux collecting holder55. Thus, the magnetic flux collecting holder55is disposed adjacent to the magnetic shield57. The housing3housing the magnetic flux collecting holder55and integrally molded with the magnetic flux collecting holder55is disposed around the magnetic shield57attached to the outer periphery of the magnetic flux collecting holder55.

The magnetic shield57is C-shaped by bending a metal plate. The magnetic shield57includes a pair of circumferential ends110. The circumferential ends110of the magnetic shield57are ends of the magnetic shield57in the circumferential direction C. The circumferential ends110of the magnetic shield57are disposed on both sides of the second circuit portion52. The magnetic flux collecting holder55further includes a pair of housing portions100. The pair of housing portions100each house an associated one of the circumferential ends110of the magnetic shield57. The pair of housing portions100are disposed on the outer periphery of the annular portion55b, with an interval between the housing portions100in the circumferential direction C. The housing portions100are disposed on both sides of the second circuit portion52. The magnetic flux collecting holder55is provided by integrally molding the pair of housing portions100with the annular portion55b. Alternatively, the annular portion55band the pair of housing portions100may be molded separately. In such a case, the magnetic flux collecting holder55may be provided by assembling the separately molded annular portion55band housing portions100to each other.

Dividing the magnetic flux collecting holder55in a direction perpendicular to the axial direction X divides the pair of housing portions100in a direction perpendicular to the axial direction X. Thus, each of the housing portions100includes a pair of sub-portions100afitted to each other in the axial direction X such that an inner space101is defined. Each of the housing portions100includes the inner space101, and an opening102through which the inner space101is in communication with the outside of the housing portion100. The opening102is provided at an end of each housing portion100in the circumferential direction C.

Examples of metal used for the magnetic shield57include iron and magnetic stainless steel. Iron has a linear thermal expansion coefficient of 1.21×10−5/° C. Magnetic stainless steel has a linear thermal expansion coefficient of 1.02×10−5/° C. Examples of resin used for the magnetic flux collecting holder55and the housing3include PA6T/6I and PA612. PA6T/6I has a linear thermal expansion coefficient of 5.0×10−5/° C. PA612 has a linear thermal expansion coefficient of 8.0×10−5/° C.

The magnetic flux collecting holder55and the housing3made of resin each greatly differ in linear thermal expansion coefficient from the magnetic shield57made of metal. Thus, the degree of expansion or contraction of each of the magnetic flux collecting holder55and the housing3caused by a change in temperature greatly differs from the degree of expansion or contraction of the magnetic shield57caused by a change in temperature.FIG. 5is a schematic cross-sectional view of the torque sensor2and the housing3taken along the line V-V inFIG. 4. Although the housing3is not illustrated inFIG. 4, the housing3is illustrated inFIG. 5for convenience of description. Each housing portion100includes an outer wall103, an inner wall104, a pair of axial walls105(seeFIG. 4), and a bottom wall106. The outer wall103defines a radially outward portion of the inner space101. The inner wall104defines a radially inward portion of the inner space101. The pair of axial walls105define ends of the inner space101in the axial direction X. The bottom wall106defines a portion of the inner space101located opposite to the opening102in the circumferential direction C.

The outer wall103radially inwardly faces an outer peripheral surface110aof the circumferential end110of the magnetic shield57such that a first clearance S1is provided between the outer wall103and the outer peripheral surface110aof the circumferential end110. The inner wall104radially outwardly faces an inner peripheral surface110bof the circumferential end110of the magnetic shield57such that a second clearance S2is provided between the inner wall104and the inner peripheral surface110bof the circumferential end110. The bottom wall106located opposite to the opening102faces a circumferential end face110cof the magnetic shield57in the circumferential direction C such that a third clearance S3is provided between the bottom wall106and the circumferential end face110cof the magnetic shield57.

The opening102of each of the pair of housing portions100is provided at an end of the housing portion100located opposite to the second circuit portion52in the circumferential direction C (seeFIG. 4). Each of the circumferential ends110of the magnetic shield57is inserted into the associated housing portion100in the circumferential direction C and thus housed in the associated housing portion100. Resin120that forms the housing3is not present in the inner space101including the clearances S1to S3. The outer wall103of each housing portion100includes a contact region103ain contact with an outer peripheral surface57aof the magnetic shield57at a location closer to the opening102of the housing portion100than to the associated circumferential end110(i.e., at a location away from the associated circumferential end110in the circumferential direction C). Specifically, the magnetic shield57is interposed between the inner wall104of each housing portion100and the contact region103aof the associated outer wall103at a location closer to the opening102than to the first clearance S1. The outer peripheral surface57aof the magnetic shield57includes: the outer peripheral surface110aof each circumferential end110of the magnetic shield57; and an outer peripheral surface57bof a portion of the magnetic shield57other than the circumferential ends110. This means that each contact region103ais in contact with the outer peripheral surface57b.

The inner wall104of each housing portion100is provided with a step107by which the inner wall104is recessed radially inward in a region of the housing portion100located between the opening102and the bottom wall106. The housing3is radially inwardly in intimate contact with the outer wall103of each housing portion100and is radially inwardly in contact with a portion of the magnetic shield57other than the circumferential ends110. Each circumferential end110of the magnetic shield57includes at its extremity a pair of corners111. One of the pair of corners111is provided on a connection between the circumferential end face110cof the magnetic shield57and the outer peripheral surface110aof the associated circumferential end110of the magnetic shield57. The other one of the pair of corners111is provided on a connection between the circumferential end face110cof the magnetic shield57and the inner peripheral surface110bof the associated circumferential end110of the magnetic shield57. Each circumferential end110of the magnetic shield57includes a curved portion112radially inwardly curved such that each circumferential end face110cfaces the inner wall104of the associated housing portion100.

A method for manufacturing the torque detecting apparatus1described above will be described in detail below. A first step involves preparation of the torque sensor2including the magnetic flux collecting holder55and the magnetic shield57attached to the outer periphery of the magnetic flux collecting holder55, with the circumferential ends110of the magnetic shield57housed in the housing portions100. As used herein, the term “preparation” refers to preparing component(s) and/or jig(s) to be used for manufacture of an apparatus. This means that the preparation does not necessarily involve manufacturing the component(s) and/or jig(s) by a manufacturer of the apparatus. In other words, preparing component(s) and/or jig(s) may involve commissioning other manufacturer(s) to manufacture component(s) and/or jig(s) to be used in manufacturing steps for an apparatus. In one example, the torque sensor2that is a component of the torque detecting apparatus1may be manufactured by a manufacturer of the torque detecting apparatus1, or other manufacturer(s) may be commissioned to manufacture the torque sensor2.

As illustrated inFIG. 6, an insert-molding mold90is prepared. The torque sensor2is placed in the mold90. As with the torque sensor2, the mold90that is a jig to be used for manufacture of the torque detecting apparatus1may be manufactured by the manufacturer of the torque detecting apparatus1, or other manufacturer(s) may be commissioned to manufacture the mold90.FIG. 6is a schematic diagram illustrating a step included in the method for manufacturing the torque detecting apparatus1. For convenience of description, illustration of the torque sensor2is simplified inFIG. 6. The same goes forFIGS. 7 and 9described below. Specifically, illustration of the magnetic flux collecting rings53and the magnetic shield57of the first circuit portion51, and illustration of the pair of first and second magnetic elements61and62and the electronic component60of the second circuit portion52are omitted inFIGS. 6, 7, and 9. InFIGS. 6, 7, and 9, the holder63and the magnetic flux collecting holder55are illustrated as if the holder63and the magnetic flux collecting holder55are a single member.

Referring toFIG. 6, the mold90includes an upper mold91and a lower mold92facing each other in an up-down direction Z. The lower surface of the upper mold91and the upper surface of the lower mold92face each other in the up-down direction Z. Bringing a portion of the lower surface of the upper mold91into contact with a portion of the upper surface of the lower mold92closes the mold90. Separating the lower surface of the upper mold91and the upper surface of the lower mold92from each other opens the mold90. The mold90includes an inner space95that is defined by the lower surface of the upper mold91and the upper surface of the lower mold92, with the mold90closed. The lower surface of the upper mold91is provided with a first uneven portion91athat defines an upper portion of the inner space95. The upper surface of the lower mold92is provided with a second uneven portion92athat defines a lower portion of the inner space95.

The mold90further includes a columnar support94protruded upward from the upper surface of the lower mold92. The support94is configured to support the first circuit portion51of the torque sensor2. With the mold90closed, the support94is protruded toward the upper mold91. With the mold90closed, a surface94aof the support94, the first uneven portion91a, and the second uneven portion92aprovide an inner wall surface90aof the mold90. The inner space95is defined by the inner wall surface90a.

The inner space95includes a first chamber96and a second chamber97. With the torque sensor2placed in the mold90, the first circuit portion51is disposed in the first chamber96. With the torque sensor2placed in the mold90, the second circuit portion52is disposed in the second chamber97. The second chamber97is in communication with the first chamber96. As used herein, the phrase “with the torque sensor2placed in the mold90” refers to a state where the first circuit portion51of the torque sensor2is supported by the support94, and the mold90is closed. The support94supports the first circuit portion51from below.

The mold90further includes gates93. Resin is to be injected into the first chamber96through the gates93. The gates93may be provided in an uppermost region of the first uneven portion91aof the upper mold91. In one example, the gates93are provided at a plurality of positions in such a manner that the gates93surround the periphery of the support94. The gates93are in communication with the first chamber96. The second chamber97includes a holder forming portion97aand a connector forming portion97beach having a substantially rectangular shape when viewed in a horizontal direction. The second circuit portion52is disposed in the holder forming portion97a. The second portions72bof the terminals72extending from the second circuit portion52are disposed in the connector forming portion97b.

Alternatively, the upper mold91may include a convex portion (not illustrated) that abuts against the upper end of the support94, and the gate(s)93may be provided in a region of the convex portion that abuts against the support94. Subsequently, the method involves placing the torque sensor2in the mold90. This step will be referred to as a “placing step”. InFIG. 6, the upper and lower molds91and92of the mold90in an opened state are indicated by the long dashed double-short dashed lines.

The placing step involves placing the torque sensor2between the upper mold91and the lower mold92, and then bringing the upper mold91and the lower mold92close to each other so as to close the mold90. Thus, the torque sensor2is placed in the mold90such that the inner peripheral surface of the magnetic flux collecting holder55of the first circuit portion51is supported by the support94.FIG. 7is a schematic diagram illustrating a step subsequent to the placing step illustrated inFIG. 6. The subsequent step illustrated inFIG. 7is a molding step involving injecting the resin120into the mold90, and molding the housing3, with the clearances S1to S3maintained. Specifically, as illustrated inFIG. 7, the molding step first involves a sub-step of injecting the resin120that is molten into the mold90having the torque sensor2placed therein. This sub-step will be referred to as an “injecting step”. The resin120is injected into the first chamber96through the gates93(see the thick arrows inFIG. 7). The resin120injected into the first chamber96partially flows to the second circuit portion52. Thus, the space between the mold90and the torque sensor2is filled with the resin120. The resin120that is being injected into the mold90is illustrated inFIG. 7. Specifically, the resin120that is flowing into the second chamber97is also illustrated inFIG. 7. The resin120that has flowed into the second chamber97is indicated by the long dashed double-short dashed line.

As illustrated inFIG. 8, during the molding step, pressure applied from the resin120inside the mold90presses the housing portion100against the outer peripheral surface57a(or more specifically, the outer peripheral surface57b) of the magnetic shield57at a location closer to the opening102of the housing portion100than to the associated circumferential end110. Specifically, the outer wall103is elastically deformed such that a portion of the outer wall103of the housing portion100defining the opening102is brought into intimate contact with and pressed against the outer peripheral surface57aof the magnetic shield57(see the hollow arrows inFIG. 8). This radially narrows the opening102so as to prevent entry of the resin120into the inner space101(or more specifically, the first clearance S1). The outer wall103is in contact with the outer peripheral surface57bof the magnetic shield57before pressure applied from the resin120presses the outer wall103against the outer peripheral surface57a(or more specifically, the outer peripheral surface57b) of the magnetic shield57at a location closer to the opening102than to the associated circumferential end110.

Referring to the long dashed double-short dashed line inFIG. 8, the outer wall103does not necessarily have to be in contact with the outer peripheral surface57bof the magnetic shield57before being pressed against the outer peripheral surface57bof the magnetic shield57by pressure applied from the resin120. The outer wall103may be configured to be brought into contact with the outer peripheral surface57bof the magnetic shield57by being pressed against the outer peripheral surface57bby pressure applied from the resin120.

Positioning of each housing portion100in the circumferential direction C is preferably effected such that the contact region103aof the outer wall103of each housing portion100does not overlap with a weld line of the housing3(i.e., the gates93of the mold90) when viewed in the axial direction X.FIG. 9is a schematic diagram illustrating a step subsequent to the step illustrated inFIG. 7. As illustrated inFIG. 9, the molding step subsequently involves a sub-step of cooling the resin120through the mold90, with the mold90filled with the resin120, so as to solidify the resin120. This sub-step will be referred to as a “cooling step”. As a result of performing these steps, the housing3is integrally molded with the torque sensor2.

Specifically, referring toFIG. 9, the body80of the housing3is molded by solidifying the resin120filled into the first chamber96. The holder retainer82of the housing3is molded by solidifying the resin120filled into the holder forming portion97aof the second chamber97. The connector portion83of the housing3is molded by solidifying the resin120filled into the connector forming portion97bof the second chamber97. The method then involves opening the mold90in the up-down direction Z, and removing the housing3and the torque sensor2integral with each other from the mold90. This step will be referred to as a “removing step”. Performing the removing step completes the torque detecting apparatus1including the torque sensor2integral with the housing3housing the torque sensor2.

When the torque detecting apparatus1to be used is installed on a vehicle, the magnetic shield57, the magnetic flux collecting holder55, and the housing3expand or contract owing to a change in temperature. The greater the distance from the central axis C1, the greater the degree of expansion or contraction of each member in the radial direction R caused by a change in temperature. Thus, if the circumferential end110of the magnetic shield57comes into contact with the magnetic flux collecting holder55and/or the housing3, stress is likely to be concentrated, in particular, on region(s) of the magnetic flux collecting holder55and/or the housing3that come(s) into contact with the outer peripheral surface110aof the circumferential end110. This makes it likely that cracks will be formed in the region(s) of the magnetic flux collecting holder55and/or the housing3.

In this embodiment, however, the magnetic flux collecting holder55, surrounding and holding the annular magnetic flux collecting rings53, includes the housing portions100that house the circumferential ends110of the magnetic shield57. The first clearance S1is provided between the outer wall103radially inwardly facing the outer peripheral surface110aof the associated circumferential end110and the outer peripheral surface110aof the associated circumferential end110of the magnetic shield57. This makes it possible to prevent contact between the magnetic flux collecting holder55(including the housing portions100each located around the associated circumferential end110of the magnetic shield57) and the outer peripheral surface110aof each circumferential end110of the magnetic shield57. Consequently, this embodiment prevents formation of cracks in the magnetic flux collecting holder55caused by contact of the circumferential end(s)110of the magnetic shield57with the magnetic flux collecting holder55.

In this embodiment, the circumferential ends110of the magnetic shield57each include the corners111. This prevents contact of the magnetic flux collecting holder55with the outer peripheral surface110aof each circumferential end110of the magnetic shield57so as to more effectively prevent formation of cracks. This embodiment makes it unnecessary to provide cushioning materials to prevent stress concentration between the circumferential ends110of the magnetic shield57and the magnetic flux collecting holder55and/or between the circumferential ends110of the magnetic shield57and the housing3. Thus, this embodiment prevents an increase in cost.

In this embodiment, the outer wall103of each housing portion100includes the contact region103ain contact with the outer peripheral surface57a(or more specifically, the outer peripheral surface57b) of the magnetic shield57at a location closer to the opening102of the housing portion100than to the associated circumferential end110. This makes it possible to prevent contact of the magnetic flux collecting holder55with the outer peripheral surface110aof each circumferential end110of the magnetic shield57, and to allow the magnetic flux collecting holder55to hold the magnetic shield57in a favorable manner.

The above-described magnetic flux collecting holder55having the magnetic shield57attached thereto is usable for insert molding. Suppose that the magnetic flux collecting holder55having the magnetic shield57attached thereto is placed in the mold90, and the resin120is injected into the mold90, so that the housing3is integrally molded with the magnetic flux collecting holder55. In this case, each contact region103aprevents entry of the resin120into the inner space of the associated housing portion100through the opening102. This makes it possible to prevent contact of the housing3, molded by insert molding, with the circumferential ends110of the magnetic shield57. Consequently, this embodiment prevents formation of cracks in the housing3caused by contact of the circumferential ends110of the magnetic shield57with the housing3.

In this embodiment, no resin120that forms the housing3is present between each outer wall103and the associated circumferential end110of the magnetic shield57. This makes it possible to prevent contact of portions of the housing3, located around the circumferential ends110of the magnetic shield57, with the outer peripheral surfaces110aof the circumferential ends110of the magnetic shield57. In this embodiment, the circumferential ends110of the magnetic shield57each include the curved portion112curved radially inward. This makes it possible to successfully maintain the first clearance S1between the outer peripheral surface110aof each circumferential end110of the magnetic shield57and the outer wall103of the associated housing portion100. In other words, this embodiment effectively prevents contact of each outer wall103with the associated circumferential end110of the magnetic shield57.

In this embodiment, the second clearance S2is provided between the inner peripheral surface110bof each circumferential end110of the magnetic shield57and the inner wall104of the associated housing portion100radially outwardly facing the inner peripheral surface110bof the circumferential end110of the magnetic shield57. This makes it possible to prevent contact of the magnetic flux collecting holder55with the inner peripheral surface110bof each circumferential end110of the magnetic shield57. Consequently, this embodiment more effectively prevents formation of cracks in the magnetic flux collecting holder55caused by contact of the circumferential ends110of the magnetic shield57with the magnetic flux collecting holder55.

In this embodiment, the third clearance S3is provided between each circumferential end face110cof the magnetic shield57and the bottom wall106of the associated housing portion100facing the circumferential end face110cof the magnetic shield57in the circumferential direction C. This makes it possible to prevent contact of the magnetic flux collecting holder55with each circumferential end face110cof the magnetic shield57. Consequently, this embodiment more effectively prevents formation of cracks in the magnetic flux collecting holder55caused by contact of the circumferential ends110of the magnetic shield57with the magnetic flux collecting holder55.

This embodiment prevents contact of the magnetic flux collecting holder55with the circumferential ends110of the magnetic shield57. Thus, although the linear thermal expansion coefficient of the magnetic flux collecting holder55is greatly different from the linear thermal expansion coefficient of the magnetic shield57, this embodiment more effectively prevents formation of cracks. In this embodiment, the magnetic flux collecting holder55having the magnetic shield57attached thereto is placed in the mold90, and the resin120is injected into the mold90having the magnetic flux collecting holder55placed therein. Consequently, the housing3is formed integrally with the magnetic flux collecting holder55. The molding step is carried out, with the first clearance S1maintained between the outer wall103of each housing portion100of the magnetic flux collecting holder55, radially inwardly facing the outer peripheral surface110aof the associated circumferential end110of the magnetic shield57, and the outer peripheral surface110aof the associated circumferential end110of the magnetic shield57. This makes it possible to prevent contact of portions of the magnetic flux collecting holder55and the housing3that are located around the circumferential ends110of the magnetic shield57with the circumferential ends110of the magnetic shield57. Accordingly, this embodiment prevents formation of cracks in the magnetic flux collecting holder55and the housing3caused by contact of the circumferential ends110of the magnetic shield57with the magnetic flux collecting holder55and the housing3.

In this embodiment, pressure applied from the resin120inside the mold90presses each outer wall103against the outer peripheral surface57a(or more specifically, the outer peripheral surface57b) of the magnetic shield57at a location closer to the opening102of the associated housing portion100than to the associated circumferential end110. This makes it possible to prevent entry of the resin120into the inner space101while maintaining the first clearance S1. Consequently, this embodiment effectively prevents contact of the magnetic flux collecting holder55and the housing3with the circumferential ends110of the magnetic shield57.

The invention is not limited to the embodiment described above, but various changes and modifications may be made within the scope of the claims.

In an alternative example, each housing portion100may be configured such that at least one of the second clearance S2and the third clearance S3is not provided. When no second clearance S2is provided, each inner wall104does not have to be provided with the step107.

Unlike this embodiment, the torque sensor2does not necessarily have to be attached to the second pinion shaft8. In an alternative example, the torque sensor2may be attached to the steering shaft11.