Patent Description:
Patent Literature <NUM> discloses a magnetostrictive torque sensor in which a sensor section is covered with an inner mold. The sensor section has a detection coil, a resin bobbin arranged on an inner peripheral side of the detection coil, and a magnetic body ring made of a ferromagnetic material arranged on an outer peripheral side of the detection coil.

In the magnetostrictive torque sensor disclosed in Patent Literature <NUM>, there is a possibility that a resin for forming the inner mold may enter an arrangement space for the detection coil from between the bobbin and the magnetic body ring during molding of the inner mold. If the inner mold enters the arrangement space for the detection coil, the position of the detection coil may shift from a desired position, or the detection coil may break.

Therefore, it is an object of the present invention to provide a magnetostrictive torque sensor capable of suppressing an entry of a resin mold section around a detection coil.

So as to achieve the above object, one aspect of the present invention, as defined in independent claim <NUM>, provides: a magnetostrictive torque sensor for detecting a torque applied to a magnetostrictive member having magnetostrictive properties.

According to the present invention, it is possible to provide a magnetostrictive torque sensor capable of suppressing an entry of a resin mold section around the detection coil.

An embodiment of the present invention will be described with reference to <FIG>. It should be noted that the embodiment described below is shown as a preferred specific example for carrying out the present invention, and there are portions that specifically illustrate various technically preferable technical matters. However, the technical scope of the present invention is not limited to this specific embodiment.

<FIG> is a perspective view of a magnetostrictive torque sensor <NUM> according to an embodiment of the present invention. <FIG> is a cross-sectional view around a detection coil <NUM> of the magnetostrictive torque sensor <NUM> in the embodiment of the present invention. <FIG> is an enlarged view around a plug member <NUM> in <FIG>. <FIG> is a cross-sectional view around a heat shrinkable tube <NUM> of the magnetostrictive torque sensor <NUM> in the embodiment of the present invention. <FIG> is a schematic diagram showing the state of using the magnetostrictive torque sensor <NUM> in the embodiment of the invention.

The magnetostrictive torque sensor <NUM> is used to measure the rotational torque applied to a magnetostrictive member <NUM> (see <FIG>) having magnetostrictive properties. Magnetostriction is a phenomenon in which distortion (strain) appears in a ferromagnetic material when a magnetic field is applied to the ferromagnetic material to magnetize it. The magnetostrictive torque sensor <NUM> reversely utilizes this phenomenon and detects the torque acting on the magnetostrictive member <NUM> by detecting the magnetic field generated by the distortion of the magnetostrictive member <NUM> with the detection coil <NUM>. The magnetostrictive member <NUM> whose rotational torque is to be measured (i.e., measuring object) can be, e.g., a predetermined rotating shaft used in a vehicle. The magnetostrictive torque sensor <NUM> comprises a detection coil <NUM>, a housing <NUM>, a magnetic ring <NUM>, a plug member <NUM>, a resin mold section <NUM>, a cable <NUM>, and a heat shrinkable tube <NUM>.

As shown in <FIG>, the detection coil <NUM> is arranged so as to surround the magnetostrictive member <NUM> from the outer peripheral side. The detection coil <NUM> outputs an electric signal corresponding to the magnitude of torque applied to the magnetostrictive member <NUM> to a control device or the like outside the magnetostrictive torque sensor <NUM> through the cable <NUM>. The detection coil <NUM> can be configured by, for example, a pattern formed on a flexible substrate, or can be configured by winding an insulated wire (i.e., electrically insulated electric wire) in a coil shape. The configuration of the detection coil <NUM>, such as the shape and number, can adopt the configuration of detection coils of conventional magnetostrictive torque sensors. The detection coil <NUM> is fixed to housing <NUM>.

As shown in <FIG>, the housing <NUM> is made of an electrically insulating resin or the like. In this embodiment, the housing <NUM> is a combination of a first housing <NUM> and a second housing <NUM>. The first housing <NUM> has a substantially cylindrical facing portion <NUM> facing the magnetic ring <NUM> across the detection coil <NUM>, and an extending portion <NUM> extending from one end portion of the facing portion <NUM> to the outer peripheral side of the facing portion <NUM>. The facing portion <NUM> is formed substantially coaxially with the magnetostrictive member <NUM>, the detection coil <NUM>, and the magnetic ring <NUM>. Hereinafter, a direction in which a central axis C of the magnetostrictive member <NUM>, the facing portion <NUM>, the detection coil <NUM>, and the magnetic ring <NUM> extends is referred to as an axial direction. Also, one side in the axial direction, the side where the facing portion <NUM> stands against the extending portion <NUM> (for example, the upper side in <FIG>) is referred to as an upper side, and the opposite side (for example, the lower side in <FIG>) is referred to as a lower side. Note that a vertical direction is for convenience, and does not limit the posture of the magnetostrictive torque sensor <NUM> with respect to the vertical direction when the magnetostrictive torque sensor <NUM> is used.

The detection coil <NUM> is fixed to an outer peripheral surface of the facing portion <NUM>. For example, when the detection coil <NUM> is composed of a pattern on a surface of a flexible substrate, the flexible substrate may be adhered to the outer peripheral surface of the facing portion <NUM> using an adhesive or the like.

The extending portion <NUM> is formed to extend in one direction perpendicular to the axial direction from the lower end portion of the facing portion <NUM>. A wiring (not shown) between the detection coil <NUM> and the cable <NUM> is arranged on the upper side of the extending portion <NUM>. This wiring (not shown) is accommodated in a wiring space <NUM> surrounded by the first housing <NUM> and the second housing <NUM>.

The second housing <NUM> is arranged above the extending portion <NUM> and surrounds the wiring space <NUM> together with the first housing <NUM>. The second housing <NUM> is formed to extend in one direction perpendicular to the axial direction, like the extending portion <NUM>. An end portion of the second housing <NUM> closer to the facing portion <NUM> is provided with a retaining protrusion (i.e., retaining projection) <NUM> protruding upward. The retaining protrusion <NUM> is arranged to fill a retaining recess 411a provided on a lower surface of the magnetic ring <NUM>. When the second housing <NUM> is molded, a resin for forming the second housing <NUM> enters the retaining recess 411a, so that the retaining protrusion <NUM> has the same shape as the space in the retaining recess 411a In this embodiment, an inner peripheral surface of the retaining recess 411a is formed in a screw groove shape, and accordingly, the outer peripheral surface of the retaining protrusion <NUM> is formed in a screw thread shape. Note that the inner peripheral surface of the retaining recess 411a and the outer peripheral surface of the retaining protrusion <NUM> may adopt other concave and convex shapes as long as they are secured against each other.

The magnetic ring <NUM> is formed to face the facing portion <NUM> across the detection coil <NUM>. The magnetic ring <NUM> forms an arrangement space <NUM> in which the detection coil <NUM> is arranged between the facing portion <NUM> and the magnetic ring <NUM>. The magnetic ring <NUM> is formed by forming a substantially cylindrical ferromagnetic material (soft magnetic material) made of metal (including an alloy) such as iron. By covering the detection coil <NUM> from the outer peripheral side, the magnetic ring <NUM> has the function of preventing the magnetic flux generated by the detection coil <NUM> from leaking to the outside and reducing the torque measurement accuracy of the magnetostrictive torque sensor <NUM>. The arrangement space <NUM> is closed (plugged) at its lower side by the first housing <NUM>, partially connected to the wiring space <NUM>, and closed at its upper side by the plug member <NUM>.

The magnetic ring <NUM> has a large-diameter portion <NUM> at the lower end portion, and a small-diameter portion <NUM> having a smaller outer diameter than the large-diameter portion <NUM> above the large-diameter portion <NUM>. A fitting recess <NUM> that is recessed upward and is fitted to the second housing <NUM> is formed on a lower surface of the large-diameter portion <NUM>. The retaining recess 411a is formed so as to open to a bottom surface of the fitting recess <NUM>. A portion of the lower surface of the large-diameter portion <NUM> other than the portion where the fitting recess <NUM> is formed faces the upper surface of the first housing <NUM>.

An outer peripheral surface of the large-diameter portion <NUM> is a covered outer peripheral surface <NUM>, which is covered with the resin mold section <NUM>, and an outer peripheral surface of the small-diameter portion <NUM> is an exposed outer peripheral surface <NUM>, which is exposed from the resin mold section <NUM>. The covered outer peripheral surface <NUM> has an enlarged diameter surface portion 412a that expands downward. By forming the enlarged diameter surface portion 412a on the covered outer peripheral surface <NUM>, the magnetic ring <NUM> is prevented from slipping upward from the resin mold section <NUM>. In this embodiment, the enlarged diameter surface portion 412a is tapered. The shape of the enlarged diameter surface portion 412a is not limited to a tapered shape as long as it can prevent the magnetic ring <NUM> from slipping off the resin mold section <NUM> upward. For example, the enlarged diameter surface portion 412a may be formed to have a step portion in which an outer diameter gradually increases as progresses downward.

An upward-facing annular surface <NUM> is provided between the covered outer peripheral surface <NUM> and the exposed outer peripheral surface <NUM> on the surface of the magnetic ring <NUM>. The annular surface <NUM> has an annular shape and is formed in a plane perpendicular to the axial direction.

The exposed outer peripheral surface <NUM> has a cylindrical surface 421a, and a concave surface 421b that is formed below the cylindrical surface 421a and recessed radially inwardly from the cylindrical surface 421a. The cylindrical surface 421a is formed from the upper end of the exposed outer peripheral surface <NUM> to the concave surface 421b, and is formed in a cylindrical shape parallel to the axial direction. The concave surface 421b is formed along the entire circumference of a lower end portion of the exposed outer peripheral surface <NUM>.

As shown in <FIG>, the magnetostrictive torque sensor <NUM> is fixed to an attachment target <NUM> made of metal, to which the magnetostrictive torque sensor <NUM> is attached, by fitting the magnetic ring <NUM> to an inner peripheral surface of an attachment hole 100a of the attachment target <NUM> in such a manner that the exposed outer peripheral surface <NUM> faces the inner peripheral surface of the attachment hole 100a. The magnetic ring <NUM> is fitted onto the inner peripheral surface of the attachment hole 100a so as to have a loose fit or a tight fit. Here, in order to fit the magnetic ring <NUM> onto the inner peripheral surface of the attachment hole 100a as intended, the cylindrical surface 421a and the attachment hole 100a must be formed with high precision. In the present embodiment, both the magnetic ring <NUM> constituting the cylindrical surface 421a and the attachment target <NUM> constituting the attachment hole 100a are made of metal, so the cylindrical surface 421a and the attachment hole 100a can be formed with high precision. The magnetostrictive torque sensor <NUM> is inserted into the attachment hole 100a until the annular surface <NUM> abuts the attachment target <NUM>. At this time, since the concave surface 421b is formed at the lower end portion of the exposed outer peripheral surface <NUM>, the magnetostrictive torque sensor <NUM> can be inserted into the attachment hole 100a until the annular surface <NUM> abuts the attachment target <NUM>.

Here, measures for preventing the magnetostrictive torque sensor <NUM> from rotating about the central axis C with respect to the attachment target <NUM> and from slipping out of the attachment hole 100a in the axial direction, in a state where the magnetostrictive torque sensor <NUM> is attached to the attachment target <NUM>, will be explained. In the resin mold section <NUM>, an annular portion formed around the magnetic ring <NUM> is referred to as a first portion 6a, and a portion extending from the first portion 6a and covering the extending portion <NUM> of the first housing <NUM> and the second housing <NUM> is referred to as a second portion 6b. Although not shown, in order to prevent the magnetostrictive torque sensor <NUM> from rotating with respect to the attachment target <NUM>, the attachment target <NUM> can be formed with a recess for fitting the second portion 6b. In this case, the magnetostrictive torque sensor <NUM> is restricted from rotating with respect to the attachment target <NUM> by the second portion 6b interfering with the recess of the attachment target <NUM>. Although not shown, in order to prevent the magnetostrictive torque sensor <NUM> from slipping out of the attachment hole 100a, it is possible to adopt a configuration in which a part of the attachment target <NUM> is brought into contact with the annular surface <NUM>, and the lower side of the magnetostrictive torque sensor <NUM> is held by a retaining ring fitted in a circumferential groove provided in the attachment hole 100a. Alternatively, it is possible to adopt a configuration in which a part of the attachment target <NUM> is brought into contact with the annular surface <NUM>, and a protrusion protruding outward which is provided on the first portion 6a of the resin mold section <NUM> is fitted into a circumferential groove provided in the attachment hole 100a, to prevent the magnetostrictive torque sensor <NUM> from slipping out of the inner peripheral surface of the attachment hole 100a. Furthermore, although not shown, a flange projecting outward is provided on the first portion 6a of the resin mold section <NUM>, and a bolt is inserted through a collar provided on the flange and screwed into a female threaded hole provided on the attachment target <NUM>, so that the magnetostrictive torque sensor <NUM> may be bolted to the attachment target <NUM>. Furthermore, when the magnetic ring <NUM> is attached to the inner peripheral surface of the attachment hole 100a in a tight fit, the magnetic ring <NUM> can be attached to the inner peripheral surface of the attachment hole 100a by, for example, press fitting. In addition, as long as the magnetic ring <NUM> is configured to fit into the attachment hole 100a, it is possible to adopt various aspects.

As shown in <FIG>, a step portion <NUM> is formed between an upper end surface 4a and an inner peripheral surface 4b of the magnetic ring <NUM>. A plug member <NUM> is fitted to the step portion <NUM>. The step portion <NUM> has a first surface 422a facing upward and connected to the inner peripheral surface 4b of the magnetic ring <NUM>, and a second surface 422b facing radially inwardly and connected to the upper end surface 4a of the magnetic ring <NUM>. The plug member <NUM> is arranged to contact both the first surface 422a and the lower end portion of the second surface 422b. The plug member <NUM> has an outer diameter greater than an inner diameter of the lower end portion of the second surface 422b in a free state before being assembled to the step portion <NUM>, and is press-fitted into the step portion <NUM>. As a result, when the plug member <NUM> is assembled to the step portion <NUM>, an outer peripheral end portion of the plug member <NUM> is in elastic contact with the second surface 422b, ensuring sealing between the plug member <NUM> and the second surface 422b. As described above, the magnetic ring <NUM> is made of metal, and the surface including the second surface 422b can be formed with high precision. It becomes easier to ensure the sealing property between the plug member <NUM> and the second surface 422b with the second surface 422b being formed with high precision.

In addition, an inward protrusion (i.e., inner periphery protrusion) 422c that protrudes radially inwardly is formed above the plug member <NUM> on the second surface 422b. The inward protrusion 422c has the function of preventing the plug member <NUM> from slipping out of the step portion <NUM> upward. The inner peripheral surface of the inward protrusion 422c has, at its upper end portion, an upper end tapered surface 422d with a tapered configuration in which a diameter decreases downward, and at its lower end portion, a lower end tapered surface 422e with a tapered configuration in which a diameter expands downward. Accordingly, when inserting the plug member <NUM> into the step portion <NUM>, the plug member <NUM> is smoothly guided to a predetermined position within the step portion <NUM>.

The plug member <NUM> closes an opening <NUM>, which is formed between the upper end portion of the magnetic ring <NUM> and the upper end portion of the facing portion <NUM> and opens upward. The plug member <NUM> is formed over the entire circumferences of the magnetic ring <NUM> and the facing portion <NUM>. The plug member <NUM> has a core portion <NUM> made of a cold-rolled steel plate such as SPCC (Steel Plate Cold Commercial) and maintaining the shape of the plug member <NUM>, and an elastic portion <NUM> made of elastically deformable rubber covering the core portion <NUM>. The core portion <NUM> is formed to have an L-shaped cross-section. The core portion <NUM> is embedded in the elastic portion <NUM> so as not to be exposed upward from the elastic portion <NUM>. The elastic portion <NUM> has a portion <NUM> configured to be accommodated in the step portion <NUM> on its outer peripheral portion, and an elastic contact piece <NUM> that elastically contacts the upper end surface of the facing portion <NUM> in the axial direction. The elastic contact piece <NUM> is bent upward, so that a downward restoring force is always generated in the elastic contact piece <NUM>. Due to this restoring force, the elastic contact piece <NUM> abuts on the upper surface of the facing portion <NUM> and the sealing property between the elastic contact piece <NUM> and the upper surface of the facing portion <NUM> is ensured.

As shown in <FIG> and <FIG>, the resin mold section <NUM> is molded to cover the housing <NUM> while exposing the magnetic ring <NUM> and the plug member <NUM>. The resin mold section <NUM> generally covers a surface of a portion of the magnetostrictive torque sensor <NUM> below the annular surface <NUM> of the magnetic ring <NUM>. On the other hand, the resin mold section <NUM> does not cover a portion of the magnetostrictive torque sensor <NUM> above the annular surface <NUM>, the inner peripheral surface of the facing portion <NUM> of the first housing <NUM>, and a portion <NUM> around the facing portion <NUM> on the lower surface of the first housing <NUM>. The portion <NUM> is a portion where the die abuts with the housing <NUM> when molding the resin mold section <NUM>.

A part of the resin mold section <NUM> is also provided on the covered outer peripheral surface <NUM> of the magnetic ring <NUM>. The resin mold section <NUM> is provided with an outer annular surface <NUM> formed substantially flush or coplanar with the annular surface <NUM> of the magnetic ring <NUM>. As shown in <FIG> and <FIG>, the cable <NUM> is drawn out from the housing <NUM> and the resin mold section <NUM>.

The cable <NUM> includes one or more wires (i.e., electric wires) <NUM> electrically connected to the detection coil <NUM>, and a sheath <NUM> surrounding the one or more wires <NUM>. As shown in <FIG>, there are plural wires <NUM> in the present embodiment, and the sheath <NUM> collectively covers the plural wires <NUM>. Each wire <NUM> is a covered wire (i.e., coated wire) with a core wire and a coating. The sheath <NUM> is formed by forming a resin or the like having electrically insulating property into a cylindrical shape.

The plural wires <NUM> exposed from the sheath <NUM> are arranged in the wiring space <NUM> in the housing <NUM> (i.e., the first housing <NUM> and the second housing <NUM>), and the sheath <NUM> is drawn out from an end portion <NUM> on the far side from the facing portion <NUM> in the housing <NUM>. The end portion <NUM> of the housing <NUM> is annularly formed by the first housing <NUM> and the second housing <NUM> and exposed from the resin mold section <NUM>. The heat shrinkable tube <NUM> is provided to prevent liquid or the like from entering the housing <NUM> through a gap between the housing <NUM> and the resin mold section <NUM> and the cable <NUM>.

The heat shrinkable tube <NUM> is formed so as to collectively cover the boundary between the cable <NUM> and the housing <NUM> and the resin mold section <NUM> when viewed from the outside. The heat shrinkable tube <NUM> is configured to shrink at least toward the inner peripheral side (i.e., radially inwardly) of the heat shrinkable tube <NUM> when the temperature reaches a predetermined temperature or higher. The heat shrinkable tube <NUM> covers the end portion of the resin mold section <NUM> on the far side from the facing portion <NUM>, the end portion <NUM> of the housing <NUM>, and the end portion of the sheath <NUM> of the cable <NUM> on the housing <NUM>-side. In the present embodiment, the heat shrinkable tube <NUM> is configured in such a manner that the length in a cable longitudinal direction of a portion covering the sheath <NUM> is longer than the length in the cable longitudinal direction of a portion covering the end portion <NUM> of the housing <NUM> and the resin mold section <NUM>. In addition, a so-called hot melt, which is an adhesive material that melts at a predetermined temperature or higher and hardens again at a temperature lower than a predetermined temperature, may be provided on the inner peripheral portion of the heat shrinkable tube <NUM>.

The heat shrinkable tube <NUM> is provided by the following method. First, the heat shrinkable tube <NUM> before heat shrinking, which has an outer diameter larger than the parts to be covered by the heat shrinkable tube <NUM> in the housing <NUM>, the resin mold section <NUM>, and the cable <NUM>, is arranged so as to surround the parts to be covered by the heat shrinkable tube <NUM> in the housing <NUM>, the resin mold section <NUM>, and the cable <NUM>. Next, by heating and shrinking the heat shrinkable tube <NUM>, the heat shrinkable tube <NUM> is brought into close contact with the surfaces of the housing <NUM>, the resin mold section <NUM>, and the cable <NUM>, either directly or via the hot melt, if any. The heat shrinkable tube <NUM> is provided as described above.

In the magnetostrictive torque sensor <NUM> of the present embodiment, the resin mold section <NUM> covers the housing <NUM> while exposing the magnetic ring <NUM> and the plug member <NUM>. Therefore, since the resin mold section <NUM> is not arranged around the opening <NUM>, the resin mold section <NUM> is prevented from entering the periphery of the detection coil <NUM> through the opening <NUM> when the resin mold section <NUM> is molded. Moreover, the magnetostrictive torque sensor <NUM> of the present embodiment includes the plug member <NUM> that closes the opening <NUM>. As a result, even if the magnetic ring <NUM> is exposed from the resin mold section <NUM>, it is possible to prevent foreign matters from entering the periphery of the detection coil <NUM> through the opening <NUM>. Furthermore, a part of the housing <NUM> and the resin mold section <NUM> and the end portion of the exposed cable <NUM> from the housing <NUM> and the resin mold section <NUM> are covered with the heat shrinkable tube <NUM>. As a result, the foreign matters such as oil, and liquid can be prevented from entering the interior of the magnetostrictive torque sensor <NUM> through the gap between the housing <NUM> and the resin mold section <NUM> and the cable <NUM>.

The step portion <NUM> is formed between the upper end surface 4a and the inner peripheral surface 4b of the magnetic ring <NUM>, and the plug member <NUM> is fitted in the step portion <NUM>. This facilitates positioning (e.g., alignment) of the plug member <NUM> with respect to the magnetic ring <NUM>. Here, the shape of the step portion <NUM> is desired to be formed with high precision because it affects the sealing property between the plug member <NUM> and the step portion <NUM>. Therefore, by forming the step portion <NUM> on the magnetic ring <NUM> made of a ferromagnetic material (i.e., metal), the step portion <NUM> can be formed with higher precision than when the step portion <NUM> is formed on a resin member or the like. Thus, it is easy to secure the sealing property with the plug member <NUM>. For example, in the case of a resin member, the surface shape tends to be different from the desired shape due to molding shrinkage of the resin member. However, the surface of the magnetic ring <NUM> made of the ferromagnetic material is formed with relatively high precision.

In addition, the inner peripheral surface of the step portion <NUM> has the inward protrusion 422c protruding toward the inner peripheral side (i.e., radially inwardly) at a position above the plug member <NUM>. Therefore, it is possible to prevent the magnetic ring <NUM> from slipping out from the step portion <NUM>.

The outer peripheral surface of the magnetic ring <NUM> has the covered outer peripheral surface <NUM> covered by the resin mold section <NUM>, and the exposed outer peripheral surface <NUM> located above the covered outer peripheral surface <NUM> and exposed from the resin mold section <NUM>. The surface of the magnetic ring <NUM> made of ferromagnetic material (i.e., metal) is formed with higher precision than the surface of the resin member. Therefore, by forming the outer surface of the magnetostrictive torque sensor <NUM> with the exposed outer peripheral surface <NUM>, it is possible to prevent the outer shape of the magnetostrictive torque sensor <NUM> from deviating from a desired shape. If the outer shape of the magnetostrictive torque sensor <NUM> deviates from the desired shape, for example, when the magnetostrictive torque sensor <NUM> is attached to the member to be attached (i.e., attachment object), the magnetostrictive torque sensor <NUM> may easily interfere with the attachment object and parts arranged around it. However, this can be suppressed in the present embodiment.

In addition, the lower surface of the magnetic ring <NUM> faces the housing <NUM>, and the covered outer peripheral surface <NUM> has the enlarged diameter surface portion 412a whose diameter increases downward. Therefore, the housing <NUM> prevents the magnetic ring <NUM> from slipping out of the resin mold section <NUM> downward, and the resin mold section <NUM> provided on the enlarged diameter surface portion 412a prevents the magnetic ring <NUM> from slipping out of the resin mold section <NUM> upward.

Also, the magnetostrictive torque sensor <NUM> is configured to be attached to the attachment target <NUM> by fitting the magnetic ring <NUM> to the inner peripheral surface of the attachment hole 100a in such a manner that the exposed outer peripheral surface <NUM> faces the inner peripheral surface of the attachment hole 100a. This makes it possible to easily attach the magnetostrictive torque sensor <NUM> to the attachment target <NUM>. As an example, the magnetostrictive torque sensor <NUM> can be attached to the attachment target <NUM> without using bolts. In addition, since the magnetic ring <NUM> that can be formed with high precision is fitted to the inner peripheral surface of the attachment hole 100a at the exposed outer peripheral surface <NUM>, the magnetic ring <NUM> can be easily fitted to the inner peripheral surface of the attachment hole 100a. That is, for example, when a resin member, which is difficult to form with high precision, is fitted to the inner peripheral surface of the attachment hole 100a, the resin member may be formed too large to fit into the attachment hole 100a. The occurrence of such a situation can be suppressed in the present embodiment.

In addition, the outer diameter of the covered outer peripheral surface <NUM> is larger than the outer diameter of the exposed outer peripheral surface <NUM>, and the upward-facing annular surface <NUM> is formed between the covered outer peripheral surface <NUM> and the exposed outer peripheral surface <NUM> on the surface of the magnetic ring <NUM>. Therefore, the magnetostrictive torque sensor <NUM> can be easily positioned (e.g., aligned) with respect to the attachment target <NUM> by making the attachment target <NUM> abut the annular surface <NUM> when the magnetic ring <NUM> is fitted to the inner peripheral surface of the attachment hole 100a.

The concave surface 421b recessed toward the inner peripheral side (i.e., radially inwardly) is formed at the end portion of the exposed outer peripheral surface <NUM> on the covered outer peripheral surface <NUM>-side. Therefore, it is possible to fit the magnetic ring <NUM> to the inner peripheral surface of the attachment hole 100a until the annular surface <NUM> abuts the attachment target <NUM>. Here, for example, if the concave surface 421b is not formed on the exposed outer peripheral surface <NUM>, it is difficult to form a corner between the exposed outer peripheral surface <NUM> and the annular surface <NUM> at <NUM> degrees in terms of manufacturing. A slight curved surface (i.e., round surface) is formed between the exposed outer peripheral surface <NUM> and the annular surface <NUM>. Therefore, if the concave surface 421b is not formed on the exposed outer peripheral surface <NUM>, when the magnetic ring <NUM> is fitted to the inner peripheral surface of the attachment hole 100a, the curved surface interferes with the attachment target <NUM>, so that the exposed outer peripheral surface <NUM> cannot fit into the inner peripheral surface of the attachment hole 100a until the annular surface <NUM> abuts the attachment target <NUM>. Therefore, in the present embodiment, by providing the concave surface 421b at the lower end portion of the exposed outer peripheral surface <NUM>, the annular surface <NUM> and the attachment target <NUM> can abut with each other when the magnetic ring <NUM> is fitted into the inner peripheral surface of the attachment hole 100a.

Claim 1:
A magnetostrictive torque sensor (<NUM>) for detecting a torque applied to a magnetostrictive member (<NUM>) having magnetostrictive properties, comprising:
a detection coil (<NUM>) arranged on an outer peripheral side of the magnetostrictive member (<NUM>);
a magnetic ring (<NUM>) comprising a ferromagnetic material arranged on an outer peripheral side of the detection coil (<NUM>);
a housing (<NUM>) having a facing portion (<NUM>) facing the magnetic ring (<NUM>) across the detection coil (<NUM>);
a plug member (<NUM>) closing an opening (<NUM>) formed between the magnetic ring (<NUM>) and the facing portion (<NUM>);
a resin mold section (<NUM>) covering the housing (<NUM>) while exposing the magnetic ring (<NUM>) and the plug member (<NUM>);
a cable (<NUM>) electrically connected to the detection coil (<NUM>) and drawn out from the housing (<NUM>) and the resin mold section (<NUM>); and
a heat shrinkable tube (<NUM>) covering and configured to be brought by heating into close contact with the surfaces of the housing (<NUM>), a portion of the resin mold section (<NUM>), and an end portion of the cable (<NUM>) exposed from the housing (<NUM>) and the resin mold section (<NUM>).