Torque sensor

A torque sensor includes: a torsion bar coaxially connecting a first shaft and a second shaft; a multipole magnet; a pair of magnetic yokes; and a magnetic sensor capable of detecting a density of magnetic flux formed by the pair of the magnetic yokes and having an inner magnetosensitive surface facing inward in a radial direction and an outer magnetosensitive surface facing outward in the radial direction when viewed along a central axis of the torsion bar. The torque sensor includes: a magnetic flux guiding member capable of magnetically coupling the magnetic yoke and the outer magnetosensitive surface of the magnetic sensor; and a water blocking portion capable of housing the magnetic sensor and the magnetic flux guiding member to restrict the magnetic sensor from coming into contact with water.

TECHNICAL FIELD

The present disclosure relates to a torque sensor.

BACKGROUND

A torque sensor includes a set of magnetic yokes forming a magnetic circuit with a multipole magnet provided on a rotating shaft, and a magnetic sensor provided between the set of magnetic yokes to detect the magnetic flux density of the magnetic circuit.

SUMMARY

According to an aspect of the present disclosure, a torque sensor includes: a torsion bar coaxially connecting a first shaft and a second shaft; a multipole magnet having N poles and S poles alternately provided in a circumferential direction to generate magnetic flux in a radial direction; a pair of magnetic yokes to form a magnetic circuit in a magnetic field formed by the multipole magnet; a magnetic sensor capable of detecting a density of the magnetic flux formed by the pair of the magnetic yokes, the magnetic sensor having an inner magnetosensitive surface facing inward in the radial direction and an outer magnetosensitive surface facing outward in the radial direction when viewed along a central axis of the torsion bar; a magnetic flux guiding member capable of magnetically coupling the magnetic yoke and the outer magnetosensitive surface of the magnetic sensor; and a water blocking portion capable of housing the magnetic sensor and the magnetic flux guiding member to restrict the magnetic sensor from coming into contact with water.

DESCRIPTION OF EMBODIMENTS

A torque sensor detects an axial torque acting on a rotational shaft based on a change in magnetic flux density of a magnetic circuit. For example, a torque sensor includes a set of magnetic yokes, a set of magnetic collection rings, and a magnetic sensor provided between the set of magnetic collection rings. The set of magnetic yokes have plural claws formed to extend in the radial direction with respect to a multipole magnet that is magnetized to generate magnetic flux in the axial direction. The set of magnetic collection rings are provided radially outward of the magnetic yoke and magnetically coupled to the magnetic yoke.

When the torque sensor is applied to, for example, an electric power steering device of a vehicle, the torque sensor needs to reliably operate even in a situation where water may be splashed, and needs to be downsized to enlarge the engine room of the vehicle. The magnetic sensor and an electric circuit for the magnetic sensor are sealed for the waterproofness, such that there is no path through which water can infiltrate. However, in the case where a magnetic sensor is provided between a pair of magnetic collection rings, water may flow through an interface between the magnetic collection ring and the sealing material while the magnetic sensor is sealed. For this reason, not only the structure for the sealing is complicated but also the size is increased in the torque sensor, when the magnetic sensor and the magnetic collection ring are integrally and annularly sealed.

Further, in the torque sensor, the magnetic sensor is formed such that the magnetic sensitive surface is along the axial direction, and the wiring of the magnetic sensor is formed to project radially outward from the magnetic sensor. Thus, the size of the torque sensor is relatively large in the radial direction. If there is nothing blocking the leakage flux between the magnetic sensor and the surface of the multipole magnet, the leakage flux from the multipole magnet affects the detection sensitivity of the magnetic sensor. In this case, a protrusion is provided to protrude from the magnetic collection ring in the radial direction to support the magnetic sensor. For this reason, the size of the torque sensor is further increased in the radial direction.

The present disclosure provides a torque sensor in which the waterproofness is improved while the size is reduced.

The present disclosure provides a torque sensor including a torsion bar, a multipole magnet, a pair of magnetic yokes, a magnetic sensor, a magnetic flux guiding member, and a water blocking portion. The torsion bar coaxially connects the first shaft and the second shaft, and converts torque applied between the first shaft and the second shaft into torsional displacement. The multipole magnet is fixed to the first shaft or one end of the torsion bar, and N poles and S poles are alternately provided in the circumferential direction to generate magnetic flux in the radial direction. The pair of magnetic yokes is fixed to the second shaft or the other end of the torsion bar to form a magnetic circuit in the magnetic field formed by the multipole magnet. The magnetic sensor is provided radially outward of the pair of magnetic yokes. The magnetic sensor has an inner magnetosensitive surface formed to be directed radially inward when viewed along the central axis of the torsion bar, and an outer magnetosensitive surface formed to be directed radially outward when viewed along the central axis of the torsion bar. The magnetic sensor can detect the magnetic flux density of the magnetic circuit formed in the pair of magnetic yokes. The magnetic flux guiding member is made of a soft magnetic material, is located radially outward of the outer magnetosensitive surface, and can magnetically couple the magnetic yoke to the outer magnetosensitive surface of the magnetic sensor. The water blocking portion is formed to house the magnetic sensor and the magnetic flux guiding member, and restricts the magnetic sensor from contacting with water.

In the torque sensor of the present disclosure, the magnetic sensor is formed such that the two magnetosensitive surfaces extend in the radial direction. The magnetic sensor is provided such that, of the two magnetosensitive surfaces the inner magnetosensitive surface is directed radially inward in cross-section passing the center axis of the torsion bar. When the inner magnetosensitive surface faces the magnetic yoke, the magnetic sensor is easy to magnetically couple with the magnetic circuit of one of the magnetic yokes. When the inner magnetosensitive surface is formed to be directed radially inward as viewed along the central axis of the torsion bar, the inner magnetosensitive surface faces the torsion bar. The outer magnetosensitive surface formed to be directed radially outward magnetically couples the magnetic sensor with the other magnetic yoke of the pair of magnetic yokes via the magnetic flux guiding member. When the outer magnetosensitive surface is oriented radially outward as viewed along the central axis of the torsion bar, the outer magnetosensitive surface is oriented opposite to and away from the torsion bar. Thus, the magnetic sensor of the torque sensor according to the present disclosure can reliably detect the magnetic flux density of the magnetic circuit of the pair of magnetic yokes, and can have the wiring extended in a direction other than the radially outward direction of the magnetic yoke. Therefore, the torque sensor of the present disclosure can reduce the size in the radial direction as compared to a torque sensor formed so that the wiring projects outward from the magnetic sensor in the radial direction.

Further, in the torque sensor of the present disclosure, the magnetic sensor and the magnetic flux guiding member, which are provided radially outward of the pair of magnetic yokes, are housed in the water blocking portion.

Thereby, the shape of the water blocking portion is simplified as compared with a case where, for example, the torque sensor includes a magnetic collection ring and the magnetic sensor, which are integrally and annularly sealed. Since there is no path through which water can penetrate from outside, such as interface between components, the magnetic sensor can be reliably prevented from water.

As described above, the torque sensor of the present disclosure includes the magnetic sensor having the inner magnetosensitive surface and the magnetic flux guiding member capable of magnetically coupling the outer magnetosensitive surface of the magnetic sensor and the magnetic yoke. Accordingly, the magnetic flux density is reliably detected, at the same time, the size can be reduced in the radial direction. Further, the magnetic sensor can be reliably protected from water by the simple configuration of the water blocking portion, to improve the waterproofness.

Hereinafter, embodiments of the present disclosure will be described based on the drawings. In the embodiments, the same reference marks are used for substantially the same element, and description thereof will be omitted.

First Embodiment

As shown inFIG. 2, a torque sensor1according to a first embodiment is applied to, for example, an electric power steering apparatus90for assisting a steering operation of a vehicle.FIG. 2shows an entire configuration of a steering system including the electric power steering apparatus90.

The torque sensor1is provided on a steering shaft94connected to a steering wheel93. A pinion gear96is provided at an axial end of the steering shaft94. The pinion gear96meshes with a rack shaft97. A pair of road wheels98is rotatably coupled to ends of the rack shaft97via a tie rod or the like. The rotational movement of the steering shaft94is converted into linear movement of the rack shaft97by the pinion gear96, and the pair of road wheels98is steered.

The torque sensor1is provided between an input shaft11as a “first shaft” and an output shaft12as a “second shaft.” The input shaft11and the output shaft12define the steering shaft94. The torque sensor1detects a steering torque applied to the steering shaft94and outputs the detected steering torque to an ECU91. The ECU91controls the output of a motor92in accordance with the detected steering torque. The steering assist torque generated by the motor92is transmitted to the steering shaft94after speed reduction by the reduction gear95.

Next, configuration of the torque sensor1will be described with reference toFIG. 1,FIG. 3andFIG. 4.

The torque sensor1includes a torsion bar13, a multipole magnet20, a pair of magnetic yokes31and32, two magnetic sensors41and42, a magnetic flux guiding member43, and a connector portion45corresponding to a “water blocking portion”.

The torsion bar13is a rod-like resilient member, and is provided between the input shaft11and the output shaft12. One end of the torsion bar13is fixed to the input shaft11by a fixing pin14. The other end of the torsion bar13is fixed to the output shaft12by a fixing pin15. Thereby, the torsion bar13connects the input shaft11and the output shaft12along the rotation axis O as the “central axis”. The torsion bar13converts a steering torque applied to the steering shaft94into a torsional displacement.

The multipole magnet20is a cylindrical member and is fixed to the input shaft11. In the multipole magnet20, N poles and S poles are alternately provided in the circumferential direction to generate magnetic flux in the radial direction. In the first embodiment, the multipole magnet20has, for example,12pairs of N poles and S poles, that is,24poles in total.

The magnetic yoke31,32is an annular body made of a soft magnetic material. The pair of magnetic yokes31and32is fixed to the output shaft12so as to be located radially outward of the multipole magnet20. The pair of magnetic yokes31and32form a magnetic circuit in the magnetic field formed by the multipole magnet20.

The magnetic yoke31has an annular portion311and plural claws312. The annular portion311has a ring shape, and is provided radially outward of the end portion of the multipole magnet20adjacent to the input shaft11. The claws312are formed to extend from the radially inner edge of the annular portion311along the rotation axis O toward the output shaft12. In the first embodiment, twelve claws312are provided at equal intervals around the entire circumference of the annular portion311.

The magnetic yoke32has an annular portion321and plural claws322. The annular portion321has a ring shape, and is provided radially outward of the end portion of the multipole magnet20adjacent to the output shaft12. The claws322are formed to extend from the radially inner edge of the annular portion321along the rotation axis O toward the input shaft11. In the first embodiment, twelve claws322are provided at equal intervals all around the annular portion321.

The claws312and the claws322are alternately arranged in the circumferential direction. That is, as shown inFIG. 4, the magnetic yoke31and the magnetic yoke32face each other in the direction along the rotation axis O (hereinafter, referred to as “rotation axial direction”) via an air gap. In the first embodiment, the pair of magnetic yokes31and32are resin-sealed to be integrated by the resin portion33and fixed to the output shaft12so as to face each other in the rotation axial direction via the air gap.

As shown inFIGS. 3 and 4, the magnetic sensors41and42are provided radially outward of the magnetic yoke31. In the first embodiment, the magnetic sensors41and42are provided in the vicinity of the magnetic yoke31and arranged in the direction perpendicular to the rotation axial direction. As shown inFIGS. 3 and 4, the two magnetic sensors41and42are housed in the connector portion45, and are respectively mounted on the circuit boards410and420. In the first embodiment, the two magnetic sensors41,42are used.

Even if one of the magnetic sensors fails to function, it is possible to detect the magnetic flux density of the magnetic circuit formed in the pair of magnetic yokes31,32by the other magnetic sensor. The probability that the two magnetic sensors41and42fail simultaneously is considered to be extremely low.

The magnetic sensor41is an IC package formed in a rectangular parallelepiped shape whose height is smaller than the width and depth, and includes a Hall element411, a power supply line41p,a ground line41g,and a signal line41s.

The Hall element411has two magnetosensitive surfaces412and413formed substantially in parallel. The two magnetosensitive surfaces412and413are formed to be substantially parallel to the direction perpendicular to the rotation axis O. The magnetosensitive surface412corresponds to an inner magnetosensitive surface formed to be directed inward of the magnetic yoke31in the radial direction as viewed along the central axis of the torsion bar. Specifically, the magnetosensitive surface412is formed to face the radially outer end surface of the annular portion311of the magnetic yoke31. The magnetosensitive surface413corresponds to an outer magnetosensitive surface formed to be directed outward of the magnetic yoke31in the radial direction as viewed along the central axis of the torsion bar. The Hall element411detects the magnetic flux density passing through the magnetosensitive surface412,413as the strength of the magnetic field, and outputs an output signal corresponding to the detected strength of the magnetic field.

As shown inFIGS. 1 and 4, the power supply line41p,the ground line41g,and the signal line41sare electrically connected to the Hall element411through the circuit board410on which the magnetic sensors41and42are mounted. The power supply line41preceives power supplied from the outside. The ground line41gis electrically connected to the ground. The signal line41soutputs an output signal according to the magnetic flux density of the magnetic circuit detected by the Hall element411to the outside. The power supply line41p,the ground line41g,and the signal line41sare formed to extend in the rotation axial direction as shown inFIG. 1. The power supply line41p,the ground line41g,and the signal line41sare electrically connected to the ECU91through the terminal452of the connector portion45.

The magnetic sensor42is an IC package formed in a rectangular parallelepiped shape whose height is smaller than the width and the depth, and includes a Hall element421, a power supply line42p,a ground line42g,and a signal line42s.

The Hall element421has two magnetosensitive surfaces422and423formed substantially in parallel. The two magnetosensitive surfaces422and423are formed to face in a direction perpendicular to the rotation axis O. The magnetosensitive surface422corresponds to an inner magnetosensitive surface formed to be directed inward of the magnetic yoke31in the radial direction as viewed along the central axis of the torsion bar. Specifically, the magnetosensitive surface422is formed to face the radially outer end surface of the annular portion311of the magnetic yoke31. The magnetosensitive surface423corresponds to an outer magnetosensitive surface formed to be directed radially outward of the magnetic yoke31as viewed along the central axis of the torsion bar. The Hall element421detects the magnetic flux density passing through the magnetosensitive surface422,423as the strength of the magnetic field, and outputs an output signal corresponding to the detected strength of the magnetic field.

As shown inFIGS. 1 and 4, the power supply line42p,the ground line42g,and the signal line42sare electrically connected to the Hall element421through the circuit board420. The power supply line42preceives power supplied from the outside. The ground line42gis electrically connected to the ground. The signal line42soutputs an output signal according to the magnetic flux density of the magnetic circuit detected by the Hall element421to the outside. The power supply line42p,the ground line42g,and the signal line42sare formed to extend in the rotation axial direction as shown inFIG. 1. The power supply line42p,the ground line42g,and the signal line42sare electrically connected to the ECU91via the terminal452of the connector portion45.

The magnetic flux guiding member43is made of a soft magnetic material, and is provided radially outward of the magnetic sensor41,42and radially outward of the magnetic yoke32when viewed from the rotation axis O. As shown inFIGS. 3 and 4, the magnetic flux guiding member43is housed in the connector portion45together with the two magnetic sensors41and42and the circuit boards410and420.

The magnetic flux guiding member43has a first radial portion431extending in the radial direction, an axial portion432extending in the axial direction, and a second radial portion433extending in the radial direction. The first radial portion431, the axial portion432, and the second radial portion433are integrally formed. The magnetic flux guiding member43is magnetically coupled to the magnetic yoke31, the magnetic sensors41and42, and the magnetic yoke32to induce the magnetic flux of the magnetic circuit formed in the magnetic yokes31and32.

The first radial portion431is located radially outward of the magnetic sensors41and42when viewed from the rotation axis O. As shown inFIG. 4, the first radial portion431has an end surface434facing the magnetosensitive surface413,423of the magnetic sensor41,42. The first radial portion431is formed to extend from the vicinity of the magnetic sensors41and42outward in the radial direction of the magnetic yoke31. The first radial portion431can be magnetically coupled to the magnetosensitive surfaces413and423of the magnetic sensors41and42. As shown inFIG. 3, the first radial portion431has a length L43in a solid arrow direction A1in which the magnetic sensors41and42are arranged and perpendicular to the rotation axis O. The length L43is set to cover the magnetosensitive surfaces412and422from the radially outer side of the magnetic sensor41.

The axial portion432is formed to extend from the radially outer end of the first radial portion431along the output shaft12. The axial portion432is formed to have the same length in the solid arrow direction A1in which the magnetic sensors41and42are arranged, as the length L43of the first radial portion431.

The second radial portion433is formed to extend inward in the radial direction of the magnetic yoke32from the end of the axial portion432adjacent to the output shaft12. The second radial portion433has the radially inner end surface435that faces the radially outer end surface of the annular portion321of the magnetic yoke32. The second radial portion433can be magnetically coupled to the magnetic yoke32.

The connector portion45is a substantially rectangular member. The connector portion45has a hollow case450made of resin, a connector451, a terminal452, and a potting material453.

The case450can hold the circuit board410on which the magnetic sensors41and42are mounted and the magnetic flux guiding member43.

The connector451is a bottomed substantially cylindrical portion provided on the outer wall surface of the case450.

The terminal452is housed in the connector451. The terminal452is electrically connected to each of the power supply line41p,the ground line41g, the signal line41s,the power supply line42p,the ground line42g,and the signal line42sof the magnetic sensors41and42.

The potting material453is filled inside the case450.

The connector portion45is provided such that the magnetosensitive surfaces412and422of the magnetic sensors41and42face the radially outer end surface of the annular portion311of the magnetic yoke31.

When the torque sensor1is assembled, the circuit board410on which the magnetic sensors41and42are mounted and the magnetic flux guiding member43are disposed inside the case450. At this time, each of the power supply line41p,the ground line41g,the signal line41s,the power supply line42p,the ground line42g,and the signal line42sis connected to the terminal452.

Next, the potting material453is filled in the case450in which the circuit board410and the magnetic flux guiding member43are disposed. Thereby, the magnetic sensors41and42can be protected from water.

Next, the operation of the torque sensor1will be described.

In a neutral state where no steering torque is applied between the input shaft11and the output shaft12, no torsional displacement occurs in the torsion bar13. At this time, the boundary between the N pole and the S pole of the multipole magnet20is in agreement with the center of the claw312or the claw322. In the neutral state, the magnetic flux does not leak to the gap between the magnetic yoke31and the magnetic yoke32because the same number of lines of magnetic force enter and exit relative to each of the claws312and322from the N pole and the S pole of the multipole magnet20. The magnetic flux density detected by the magnetic sensors41and42is zero. When a steering torque is applied between the input shaft11and the output shaft12and a torsional displacement occurs in the torsion bar13, a relative position between the multipole magnet20fixed to the input shaft11and the pair of magnetic yokes31and32fixed to the output shaft12changes in the circumferential direction.

For example, when the claw312of the magnetic yoke31faces the N pole and the claw322of the magnetic yoke32faces the S pole, the magnetic line having N poles and the magnetic line having S poles are respectively increased in the magnetic yoke31and the magnetic yoke32. As a result, the density of magnetic flux passing through the magnetic sensor41,42changes substantially proportionally to the amount of torsional displacement of the torsion bar13and changes the polarity in accordance with the direction of torsion of the torsion bar13. The magnetic sensors41,42detect the magnetic flux density passing in the direction perpendicular to the magnetosensitive surfaces412,413,422,423, that is, the strength of the magnetic field. The torque sensor1thus detects the steering torque between the input shaft11and the output shaft12by outputting a voltage corresponding to the detected magnetic field strength as an output signal.

In the torque sensor1according to the first embodiment, the magnetic sensor41,42has: the magnetosensitive surface412,422formed to face the radially outer end face of the annular portion311of the magnetic yoke31; and the magnetosensitive surface413,423formed to be directed radially outward. Since the magnetosensitive surface412,422is provided to face the magnetic yoke31, the magnetic sensor41,42can be easily magnetically coupled to the magnetic circuit of the magnetic yoke31. The magnetosensitive surface413,423magnetically couples the magnetic yoke32and the magnetic sensor41,42via the magnetic flux guiding member43. Thus, the magnetic sensors41and42can reliably detect the magnetic flux density of the magnetic circuit of the magnetic yokes31and32. Therefore, the body size can be made smaller in the radial direction in the first embodiment, compared with a torque sensor formed so that the wiring protrudes radially outward from the magnetic sensor since the magnetosensitive surface is formed along the axial direction.

Further, in the torque sensor1, the magnetic sensors41and42and the magnetic flux guiding member43are housed in the substantially rectangular connector portion45. Therefore, the water blocking structure for the magnetic sensors41and42can be made simple as compared with a case where, for example, the magnetic sensor and a magnetic collecting ring are integrally and annularly sealed in a torque sensor. Therefore, there is no path through which water can penetrate from the outside, such as interface between the members in the member, to prevent contact between the magnetic sensor41,42and water. Thus, the contact between the magnetic sensor41,42and water is surely prevented.

As described above, in the torque sensor1, the magnetic flux density is reliably measured by the magnetic sensors41and42having the magnetosensitive surfaces412and422, and the magnetic flux guiding member43capable of magnetically coupling the magnetosensitive surface413,423and the magnetic yoke32, while reducing the physical size in the radial direction. Waterproofness can be improved by reliably blocking contact between the magnetic sensor41,42and water by the connector portion45having a simple configuration.

Further, the connector portion45houses the magnetic sensors41and42and the magnetic flux guiding member43, and the magnetosensitive surfaces412and422of the magnetic sensors41and42face the radially outer end surface of the annular portion311of the magnetic yoke31. Therefore, the magnetic sensors41and42and the magnetic flux guiding member43can be provided at the optimum position in detection of the magnetic flux density only by adjusting the positional relationship between the pair of magnetic yokes31and32and the connector portion45, compared with a torque sensor provided with a magnetic collecting ring where a magnetic sensor is provided. That is, the detection sensitivity of the magnetic flux density of can be improved.

Further, since the magnetic sensors41and42and the magnetic flux guiding member43are housed in the connector portion45and integrally formed, the connector portion45can be easily separated from the pair of magnetic yokes31and32fixed to the output shaft12. Thus, the magnetic sensors41and42can be easily attached and detached.

The magnetic sensors41and42are provided to be opposed to the radially outer end surface of the annular portion311of the magnetic yoke31. Thereby, the leakage flux from the multipole magnet20is blocked by the magnetic yoke31. Thereby, a fall in the detection sensitivity of the magnetic sensor41,42caused by the leakage flux from the multipole magnet20can be prevented.

The end surface434of the first radial portion431of the magnetic flux guiding member43is provided in the vicinity of the magnetosensitive surfaces413and423. Thus, the magnetic flux guiding member43functions as a magnetic shield that prevents a magnetic flux of external magnetic noise from passing through the magnetosensitive surfaces413and423. Therefore, it is possible to prevent a decrease in detection sensitivity of the torque sensor1due to the external magnetic noise.

Second Embodiment

A torque sensor according to a second embodiment will be described based onFIG. 5. In the second embodiment, the configuration of the connector portion is different from that of the first embodiment.

The torque sensor2according to the second embodiment includes a torsion bar13, a multipole magnet20, a pair of magnetic yokes31and32, two magnetic sensors41and42, a magnetic flux guiding member53, and a connector portion55as a “water blocking portion.”

In the second embodiment, unlike the first embodiment, the two magnetic sensors41and42are not mounted on the circuit board. The magnetic sensor41,42has a wiring electrically connected to the Hall element411,421and formed to extend linearly along the rotation axis O (only the power supply line51pis shown inFIG. 5, which is electrically connected to the magnetic sensor41), and the wiring is electrically connected to the ECU91through a terminal551of the connector portion55.

The magnetic flux guiding member53is made of a soft magnetic material, and is provided radially outward of the magnetic sensors41and42and radially outward of the magnetic yoke32when viewed from the rotation axis O. As shown inFIG. 5, the magnetic flux guiding member53is housed in the connector portion45together with the two magnetic sensors41and42.

The magnetic flux guiding member53has an axial portion531and a radial portion532. The axial portion531and the radial portion532are integrally formed. The magnetic flux guiding member53is magnetically coupled to the magnetic yoke31, the magnetic sensors41and42, and the magnetic yoke32to induce the magnetic flux of the magnetic circuit formed in the magnetic yokes31and32.

The axial portion531is formed to extend along the output shaft12from the radially outer side of the magnetic sensor41,42when viewed from the rotation axis O. The axial portion531has the end face533in the vicinity of the magnetic sensor41,42, and the end face533faces the magnetosensitive surfaces413and423. The axial portion531can be magnetically coupled to the magnetosensitive surfaces413and423of the magnetic sensors41and42.

The radial portion532is formed to extend inward of the magnetic yoke32in the radial direction from the end of the axial portion531adjacent to the output shaft12. The radial portion532is formed such that the radially inner end surface534faces the radially outer end surface of the annular portion321of the magnetic yoke32. The radial portion532can be magnetically coupled to the magnetic yoke32.

The connector portion55is a substantially rectangular member. The connector portion55has a sealing portion550and a terminal551.

The sealing portion550is a substantially rectangular portion formed of a resin. The sealing portion550houses the magnetic sensors41and42and the magnetic flux guiding member53inside.

The terminal551is formed to protrudes from the sealing portion550. The terminal551is electrically connected to each of the electrical wirings of the magnetic sensors41and42.

When assembling the torque sensor2, the magnetic sensors41and42, the magnetic flux guiding member43, and the terminals551electrically connected to the electrical wirings of the magnetic sensors41and42are sealed with resin or the like. Thereby, the magnetic sensors41and42are restricted from contacting water.

The torque sensor2according to the second embodiment includes the magnetic sensors41and42, the magnetic flux guiding member53capable of magnetically coupling the magnetosensitive surfaces413and423and the magnetic yoke32, and the connector portion55housing the magnetic sensors41and42and the magnetic flux guiding member53. In this way, the second embodiment achieves the advantages that are the same as those of the first embodiment.

Further, in the torque sensor2, the electric wirings such as the power supply lines51pof the magnetic sensors41and42are formed to extend linearly from the magnetic sensors41and42along the rotation axis O unlike the first embodiment. Further, unlike the first embodiment, the axial portion531of the magnetic flux guiding member53located in the vicinity of the magnetic sensors41and42is formed to extend in the direction of the output shaft12from the radially outer side of the magnetic sensors41and42. Thereby, the physical size of the connector portion55in the radial direction can be further reduced as compared with the first embodiment.

Third Embodiment

A torque sensor according to a third embodiment will be described based onFIG. 6andFIG. 7. The third embodiment differs from the first embodiment in that two magnetic collection rings are provided.

The torque sensor3according to the third embodiment includes a torsion bar13, a multipole magnet20, a pair of magnetic yokes31and32, two magnetic sensors41and42, two magnetic collection rings46and47, a magnetic flux guiding member43, and a connector portion45.

The magnetic collection ring46is a substantially annular member formed of a soft magnetic material. The magnetic collection ring46has a main body461and two collecting parts462and463. The main body461and the collecting parts462and463are integrally formed.

The main body461is an annular portion provided on the radially outer side of the magnetic yoke31. A portion of the main body461is located between the annular portion311of the magnetic yoke31and the magnetic sensors41and42. The main body461is magnetically coupled to the magnetic yoke31.

The collecting part462is a substantially flat portion provided on the main body461located between the annular portion311and the magnetic sensor41. The collecting part462is formed to face the magnetosensitive surface412in the vicinity of the magnetic sensor41. The collecting part462guides the magnetic flux formed in the main body461to the magnetic sensor41.

The collecting part463is a substantially flat portion provided on the main body461located between the annular portion311and the magnetic sensor42. The collecting part463is formed to face the magnetosensitive surface422in the vicinity of the magnetic sensor42. The collecting part463guides the magnetic flux formed in the main body461to the magnetic sensor42.

The magnetic collection ring47is an annular member formed of a soft magnetic material. The magnetic collection ring47has a main body471and a collecting part472. The main body471and the collecting part472are integrally formed.

The main body471is an annular portion provided on the radially outer side of the magnetic yoke32. A part of the main body471is located between the annular portion321of the magnetic yoke32and the magnetic flux guiding member43. The main body471is magnetically coupled to the magnetic yoke32.

The collecting part472is a substantially flat portion provided on the main body471located between the annular portion321and the magnetic flux guiding member43. The collecting part472is formed to face the end surface435in the vicinity of the magnetic flux guiding member43. The collecting part472guides the magnetic flux formed in the main body471to the magnetic flux guiding member43.

In the third embodiment, as shown inFIGS. 6 and 7, the two magnetic collection rings46and47are resin-sealed by the resin portion48and formed integrally. The resin portion48is provided to be separated from the connector portion45.

The torque sensor3according to the third embodiment includes the magnetic sensors41and42, the magnetic flux guiding member43, and the connector portion45. The third embodiment achieves the advantages that are the same as those of the first embodiment.

The magnetic collection ring46is formed to face the magnetosensitive surfaces412and422in the vicinity of the magnetic sensors41and42. The magnetic collection ring47is located in the vicinity of the end surface435of the second radial portion433of the magnetic flux guiding member43. Thus, the magnetic collection rings46and47function as a magnetic shield that prevents magnetic flux of external magnetic noise from passing through the magnetosensitive surfaces412and422and the end surface435. Therefore, the detection sensitivity of the torque sensor3can be prevented from falling.

Further, in the torque sensor3, when the torsion bar13is twisted, a magnetic circuit is formed to pass through the magnetic yoke31, the magnet collection ring46, the magnetic sensors41and42, the magnetic flux guiding member43, the magnetic collection ring47and the magnetic yoke32. Thereby, the magnetic flux density passing through the magnetic sensors41and42can be increased as compared with a case where there is no magnetic collection ring. Therefore, the third embodiment can improve the detection sensitivity of the magnetic flux density by the magnetic sensors41and42.

Fourth Embodiment

A torque sensor according to a fourth embodiment will be described based onFIG. 8. The fourth embodiment is different from the first embodiment in that one magnetic collection ring is provided.

The torque sensor4according to the fourth embodiment includes a torsion bar13, a multipole magnet20, a pair of magnetic yokes31and32, two magnetic sensors41and42, a magnetic collection ring46, a magnetic flux guiding member43, and a connector portion45.

The torque sensor4according to the fourth embodiment includes the magnetic sensors41and42, the magnetic flux guiding member43, and the connector portion45. The fourth embodiment thus achieves the same advantage as that of the first embodiment.

Further, as shown inFIG. 8, in the torque sensor3, the magnetic collection ring46is provided in the radially outer side of the magnetic yoke31. Thus, in the fourth embodiment, as in the third embodiment, the detection sensitivity of the magnetic sensors41and42can be prevented from being lowered. In other words, the detection sensitivity of the magnetic sensors41and42can be improved.

Other Embodiments

In the above embodiment, the torque sensor is applied to the electric power steering apparatus. However, the device to which the torque sensor of the present disclosure is applied is not limited thereto. The present disclosure may be applied to other device in which a torsion bar converts torque to torsional displacement.

In the above embodiment, one magnetic flux guiding member is provided for two magnetic sensors. However, a magnetic flux guiding member may be provided for each of the magnetic sensors. That is, there may be plural magnetic flux guiding members. Also, the number of magnetic sensors may be one.

Specifically, as shown inFIG. 9, as a modification of the first embodiment, one magnetic flux guiding member43may be provided for one magnetic sensor41in a torque sensor1.

In the above embodiment, the magnetosensitive surface is oriented in a direction substantially parallel to the direction perpendicular to the rotation axis O. However, the orientation of the magnetosensitive surface is not limited to this. The magnetosensitive surface may be oriented in a direction different from the rotation axial direction.

FIG. 10shows a torque sensor2as a modification of the second embodiment. Note that, inFIG. 10, in order to avoid complication of the drawing, the terminals551and portions for housing the terminals551are omitted.

In the torque sensor2shown inFIG. 10, the magnetosensitive surfaces412and422of the two magnetic sensors41and42are formed inward of the magnetic yoke31in the radial direction. Specifically, the magnetosensitive surfaces412and422are formed along the radially outer end surface313of the annular portion321of the magnetic yoke31formed in a curved shape. At this time, the magnetosensitive surface413of the magnetic sensor41and the magnetosensitive surface423of the magnetic sensor42are formed to be oriented outward of the magnetic yoke31in the radial direction.

The torque sensor2shown inFIG. 10includes two magnetic flux guiding members53corresponding to the magnetic sensors41and42, respectively. The end face533of the axial portion531of the magnetic flux guiding member53facing the magnetosensitive surfaces413and423is formed to be substantially parallel to the magnetosensitive surfaces413and423, as shown inFIG. 10.

As described above, the detection sensitivity of the magnetic flux density of the magnetic sensors41and42can be improved by forming the magnetosensitive surfaces412and422of the two magnetic sensors41and42along the radially outer end face of the annular portion321of the magnetic yoke31. Further, the detection sensitivity of the magnetic flux density of the magnetic sensors41and42can be further improved by forming the end face533of the magnetic flux guiding member53to be substantially parallel to the magnetosensitive surfaces413and423.

In the above embodiment, the power supply line, the ground line, and the signal line are formed to extend in the rotation axial direction. However, the power supply line, the ground line, and the signal line may not be formed to extend in the rotation axial direction. For example, the power supply line, the ground line, and the signal line may be formed to extend in a tangential direction of an imaginary circle having a center at the rotation axis.

In the above embodiment, the magnetic collection ring is a substantially annular member. However, the shape of the magnetic collection ring is not limited to this. The shape of the magnetic collection ring may be an arc shape.

The present disclosure should not be limited to the embodiments described above, and various other embodiments may be implemented without departing from the scope of the present disclosure.

The present disclosure has been described in accordance with embodiments. However, the present disclosure is not limited to the embodiments and structures. This disclosure also encompasses various modifications and variations within the scope of equivalents. Furthermore, various combination and formation, and other combination and formation including one, more than one or less than one element may be made in the present disclosure.