JP2011080870A - Torque sensor and electric power steering device - Google Patents

Abstract

A torque sensor and an electric power steering device capable of simplifying the shape of a yoke are provided.
A torque sensor includes a plate spring that connects an input shaft and a lower shaft so as to be relatively rotatable, and a pair of yokes that constitute a magnetic circuit together with a magnet fixed to the plate spring. And prepared. In addition, a Hall IC 56 for detecting the magnetic flux generated in the magnetic circuit is provided, and the input torque is detected based on the magnetic flux detected by the Hall IC 56. Then, in accordance with the relative rotation of the input shaft 31 and the lower shaft 32, the magnet 51 is moved to the leaf spring 33 so that the positions of the magnetic poles in the axial direction (axial position) of the shafts 31 and 32 change in opposite directions. Fixed.
[Selection] Figure 2

Description

  The present invention relates to a torque sensor and an electric power steering device.

  Conventionally, as a torque sensor used in an electric power steering device (EPS) or the like, a magnetic detection unit such as a Hall IC is provided, and the input torque to the first axis and the second axis that are coaxially arranged is detected by the magnetic detection unit. Some are detected based on the magnetic flux generated. For example, in the torque sensor described in Patent Document 1, a pair of ring magnets that are magnetized with different polarities alternately in the circumferential direction are provided on the first shaft, and the ring magnets that form a magnetic circuit together with the ring magnets. A yoke is provided coaxially with respect to the second axis, and the input torque is detected based on the magnetic flux passing through the air gap between the yokes.

  More specifically, as shown in FIG. 10A, the torque sensor described in Patent Document 1 includes a first shaft 91 and a second shaft 92 that are coaxially arranged with each other, and the first shaft 91 has a ring magnet. 93 is fixed, and a pair of yokes 94 and 95 disposed on the radially outer side of the ring magnet 93 are fixed to the second shaft 92. Each of the yokes 94 and 95 is formed with a plurality of isosceles triangular claws 96 and 97 extending in the axial direction of the first shaft 91 (second shaft 92) at predetermined intervals in the circumferential direction. 96 and 97 are adapted to face the ring magnet 93 in the radial direction. Specifically, as shown in the figure, each of the yokes 94 and 95 is a ring magnet that faces the claws 96 and 97 when no input torque is applied to the first shaft 91 and the second shaft 92. The areas of the 93 N poles and the S poles are arranged to be equal to each other. Therefore, in this state, the magnetic flux does not pass through the axial gap (air gap 98) between the yokes 94 and 95.

  On the other hand, when the torque is input and the first shaft 91 and the second shaft 92 rotate relative to each other, as shown in FIG. 10B or FIG. The circumferential position of the magnetic pole of the ring magnet 93 with respect to 97 changes. As a result, the area of the N pole and the area of the S pole of the ring magnet 93 facing the claws 96 and 97 become different, so that the magnetic flux passes through the air gap 98. At this time, the magnetic flux passing through the air gap 98 changes in accordance with the ratio between the area of the N pole and the area of the S pole of the ring magnet 93 facing the claws 96 and 97. That is, since the magnetic flux passing through the air gap 98 changes according to the relative rotation (the magnitude of the input torque) between the first shaft 91 and the second shaft 92, the input torque is based on the magnetic flux detected by the Hall IC 99. Can be detected.

JP 2005-69994 A

  However, in Patent Document 1 described above, the circumferential position of the magnetic pole of the ring magnet 93 with respect to the yokes 94 and 95 is changed by the relative rotation of the first shaft 91 and the second shaft 92, thereby passing through the air gap 98. In order to change the magnetic flux, it is necessary to form claws 96 and 97 extending in the axial direction with respect to the respective yokes 94 and 95. As a result, in the conventional configuration, the shapes of the yokes 94 and 95 have to be complicated, which is a cause of an increase in the manufacturing cost of the torque sensor.

  The present invention has been made to solve the above-described problems, and an object thereof is to provide a torque sensor and an electric power steering device that can simplify the shape of a yoke.

  In order to achieve the above object, the first aspect of the present invention includes a first shaft and a second shaft that are coaxially arranged with each other, and a connecting means that connects the first shaft and the second shaft so as to be relatively rotatable. A magnet disposed between the first axis and the second axis, a pair of yokes that form a magnetic circuit together with the magnet, and a magnetic detection unit that detects a magnetic flux generated in the magnetic circuit, A torque sensor for detecting an input torque applied to at least one of the first axis and the second axis based on a magnetic flux detected by the magnetic detection unit, wherein the magnet includes the first axis and the first axis. The gist is that the axial positions of the magnetic poles in the axial direction of the magnetic poles are supported so as to change in opposite directions in response to relative rotation with the two axes.

  In the above configuration, the axial positions of the magnetic poles (N pole and S pole) in the magnet are opposite to each other according to the relative rotation of the first axis and the second axis, that is, the axial position of the N pole is the upper side in the axial direction. Is changed to the lower side in the axial direction, and when the axial position of the N pole is changed to the lower side in the axial direction, the axial position of the S pole is changed to the upper side in the axial direction. Since the first axis and the second axis rotate relative to each other according to the input torque, the axial positions of the magnetic poles in the magnet change in opposite directions according to the input torque. Therefore, since the magnetic flux generated in the magnetic circuit changes according to the input torque, the input torque applied to at least one of the first axis and the second axis is detected based on the magnetic flux detected by the magnetic detection unit. can do.

  Thus, in the above configuration, the magnetic flux generated in the magnetic circuit is changed by changing the axial position of each magnetic pole in the magnet in the opposite direction, so the circumferential position of each magnetic pole in the ring magnet is changed as before. Unlike the case of making them, it is not necessary to form a portion (claw) extending in the axial direction with respect to each yoke. Accordingly, the shape of the yoke can be simplified, and the manufacturing cost can be reduced.

The invention according to claim 2 is summarized in that, in the torque sensor according to claim 1, the pair of yokes and the magnetic detection unit are each fixed to a non-rotating part.
The size of the air gap between the pair of yokes varies depending on the position of the yoke in the circumferential direction due to an assembly error or the like. In general, since the magnetic detection unit is fixed to a non-rotating part (such as a housing), when a pair of yokes is fixed to the first shaft or the second shaft, the magnetic force in the yokes is rotated as these shafts rotate. The circumferential position of the detection unit changes, and the size of the air gap in which the magnetic detection unit is arranged changes. On the other hand, since the magnetic resistance of the air gap is very large, the magnetic flux passing through the air gap changes greatly even if its size changes slightly. For this reason, when each yoke is fixed to the first axis or the second axis, there is a possibility that a change in magnetic flux caused by a change in the axial position of each magnetic pole cannot be detected with high accuracy.

  In this regard, according to the above configuration, each yoke and the magnetic detection unit are fixed to the non-rotating part, and therefore the circumferential position of the magnetic detection unit in the yoke does not change even if the first shaft and the second shaft rotate. First, the magnetic detection unit can detect the magnetic flux passing through the air gap of a certain size, and can accurately detect the change in the magnetic flux due to the change in the axial position of each magnetic pole.

  In the conventional configuration, in order to detect relative rotation between the first shaft and the second shaft, it is necessary to provide a ring magnet on the first shaft and a yoke on the second shaft. Therefore, in order to enable the magnetic detection unit to detect the magnetic flux passing through a certain air gap as described above, a pair of yokes are prepared in addition to the yoke provided on the second shaft, and non-rotation is performed. It is necessary to fix to a site | part (refer patent document 1).

  In this regard, according to the above configuration, since the relative rotation between the first axis and the second axis is a change in the axial position of each magnetic pole, the first axis and the second axis can be provided even if the yoke is provided in the non-rotating part. The magnetic flux which changes according to relative rotation with can be detected. Therefore, the number of parts can be reduced as compared with the conventional one while accurately detecting a change in magnetic flux due to a change in the axial position of each magnetic pole in the magnet. In addition, the number of air gaps in the magnetic circuit can be reduced compared to the conventional one by reducing the pair of yokes and eliminating the air gap between the yoke provided on the second shaft and the yoke provided on the non-rotating portion. Therefore, the strength of the magnetic flux detected by the magnetic detection unit can be ensured and the noise resistance can be improved.

  According to a third aspect of the present invention, in the torque sensor according to the first or second aspect, the connecting means is elastic in a circumferential direction of the respective shafts with relative rotation between the first shaft and the second shaft. A leaf spring provided in a deformable manner, wherein a support shaft is formed on the first shaft, the support shaft extends toward the second shaft in the axial direction and abuts on the second shaft, and the magnet Is summarized in that the axial positions of the magnetic poles are fixed to the leaf springs so as to change in opposite directions according to the elastic deformation of the leaf springs.

  In the above configuration, when the axial force acts on the first shaft or the second shaft, the leaf spring is prevented from being elastically deformed by the contact of the support shaft with the second shaft, and erroneous detection of the input torque. Can be prevented. In addition, since the position of each magnetic pole in the axial direction changes when the magnet rotates due to elastic deformation of the leaf spring, when the axial position of each magnetic pole changes, the member (plate spring) to which the magnet is fixed is changed. Generation of abnormal noise can be suppressed without sliding with other members.

According to a fourth aspect of the present invention, there is provided a torque sensor according to the third aspect, wherein the magnet is a bonded magnet and is integrally formed with the leaf spring by injection molding.
According to the above configuration, since the magnet is a bonded magnet and is integrally formed with the leaf spring by injection molding, for example, the magnet can be easily replaced with the leaf spring as compared with the case where the magnet is fixed to the leaf spring by an adhesive or a screw. Can be fixed.

  According to a fifth aspect of the present invention, in the torque sensor according to the third or fourth aspect, the tip of the support shaft is formed in a sharp shape so as to make point contact with the second shaft. The gist.

  According to the above configuration, since the support shaft makes point contact with the second shaft, even if the first shaft and the second shaft rotate relative to each other, the friction generated between the support shaft and the second shaft is reduced. Therefore, it is not necessary to interpose a bearing between the support shaft and the second shaft, and an increase in the number of components can be suppressed.

  According to a sixth aspect of the present invention, in the torque sensor according to the first or second aspect, the connecting means is a torsion bar, the magnet is provided with a gear, and the first shaft and the second shaft. The tooth portions are formed along the circumferential direction on the facing surfaces of the gears, and the tooth portions mesh with the gear, and the gears according to relative rotation between the first shaft and the second shaft. The gist is that the axial position of each magnetic pole in the magnet changes in the opposite direction by rotating.

  According to the above configuration, the magnets rotate together with the gears to change the axial positions of the magnetic poles in the opposite directions. Therefore, the first shaft is independent of changes in material properties (such as elastic modulus) caused by aging. The axial position of each magnetic pole can be accurately changed according to the relative rotation between the magnetic pole and the second axis. Therefore, the axial position of each magnetic pole can be changed stably over a long period of time.

  The invention according to claim 7 is the torque sensor according to claim 1 or 2, wherein the connecting means is a torsion bar, and a guide groove is formed in one of the magnet and the first shaft, The guide groove extends along the axial direction of each axis, and a projection is formed on the other of the magnet and the first axis, and the projection protrudes in the radial direction of each axis. The magnet is inserted into the guide groove, and the magnet is rotatably supported with respect to the second shaft in a state where the protrusion is inserted into the guide groove, and the first shaft and the second shaft are supported. The gist of the invention is that the axial positions of the magnetic poles of the magnet change in directions opposite to each other as the protrusion moves in the guide groove in accordance with relative rotation with the shaft.

  According to the above configuration, since the protrusion moves in the guide groove and the magnet rotates, the axial position of each magnetic pole is changed in the opposite direction to each other, so the change in material characteristics (elastic coefficient, etc.) caused by secular change Regardless, the axial position of each magnetic pole can be accurately changed according to the relative rotation between the first axis and the second axis. Therefore, the axial position of each magnetic pole can be changed stably over a long period of time.

The gist of an eighth aspect of the invention is an electric power steering apparatus including the torque sensor according to any one of the first to seventh aspects.
According to the above configuration, the shape of the yoke can be simplified, and the manufacturing cost of the torque sensor can be reduced. As a result, an inexpensive electric power steering device can be provided.

  ADVANTAGE OF THE INVENTION According to this invention, the torque sensor and electric power steering apparatus which can simplify the shape of a yoke can be provided.

The schematic block diagram of an electric power steering device (EPS). FIG. 3 is a cross-sectional view illustrating a schematic configuration of a torque sensor according to the present embodiment. AA sectional view taken on the line in FIG. (A)-(c) The schematic diagram which shows the change aspect of the axial direction position of each magnetic pole in the torque sensor of this embodiment. The graph which shows the change of the output voltage of Hall IC with respect to input torque. Sectional drawing which shows schematic structure of another torque sensor. The schematic diagram which shows the change aspect of the axial direction position of each magnetic pole in another torque sensor. Sectional drawing which shows schematic structure of another torque sensor. (A), (b) The schematic diagram which shows the change aspect of the axial direction position of each magnetic pole in another torque sensor. (A) Side view showing a schematic configuration in a state where no input torque is applied in a conventional torque sensor, (b), (c) Side view showing a schematic configuration in a state where an input torque is applied in a conventional torque sensor. .

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, an embodiment of the invention will be described with reference to the drawings.
As shown in FIG. 1, in an electric power steering apparatus (EPS) 1, a steering shaft 3 to which a steering 2 is fixed is connected to a rack shaft 5 via a rack and pinion mechanism 4. The rotation of the shaft 3 is converted into a reciprocating linear motion of the rack shaft 5 by the rack and pinion mechanism 4. The steering shaft 3 is formed by connecting a column shaft 8, an intermediate shaft 9, and a pinion shaft 10. Then, the reciprocating linear motion of the rack shaft 5 accompanying the rotation of the steering shaft 3 is transmitted to a knuckle (not shown) via tie rods 11 connected to both ends of the rack shaft 5, so that the steering angle of the steered wheels 12 is increased. That is, the traveling direction of the vehicle is changed.

  The EPS 1 also includes an EPS actuator 22 that applies an assist force to assist the steering operation in the steering system using the motor 21 as a drive source, and an ECU 23 that controls the operation of the EPS actuator 22.

  The EPS actuator 22 is a so-called column type EPS actuator, and a motor 21 as a driving source thereof is drivingly connected to the column shaft 8 via a speed reduction mechanism 25. The rotation of the motor 21 is decelerated by the speed reduction mechanism 25 and transmitted to the column shaft 8 so that the motor torque is applied to the steering system as an assist force.

  On the other hand, a vehicle speed sensor 27 and a torque sensor 28 are connected to the ECU 23. Then, the ECU 23 controls the operation of the EPS actuator 22 based on the vehicle speed V and the steering torque τ detected by these sensors, specifically, the torque generated by the motor 21 to control the assist force applied to the steering system. It is configured to execute control (power assist control).

Next, the configuration of the torque sensor 28 of the present embodiment will be described.
As shown in FIG. 2, the torque sensor 28 includes an input shaft 31 as a first axis, a lower shaft 32 as a second axis coaxially arranged with the input shaft 31, the input shaft 31 and the lower shaft 32. And a plurality (four in this embodiment) of leaf springs 33 are connected. The steering 2 (see FIG. 1) is fixed to the upper end (upper side in FIG. 2) of the input shaft 31, and the intermediate shaft 9 (see FIG. 1) is attached to the lower end (lower side in FIG. 2) of the lower shaft 32. It is connected. That is, the column shaft 8 is configured by the input shaft 31, the lower shaft 32, and each leaf spring 33.

  More specifically, a first large-diameter portion 35 extending outward in the radial direction is formed at the lower end (lower side in FIG. 2) of the input shaft 31, and an annular shape extending from the outer peripheral edge downward in the axial direction. The first fixing portion 36 is formed. On the other hand, at the upper end of the lower shaft 32 (upper side in FIG. 2), a second large-diameter portion 38 extending outward in the radial direction is formed, and an annular second fixing extending from the outer periphery to the upper side in the axial direction. A portion 39 is formed. Each leaf spring 33 is formed in a rectangular plate shape. The input shaft 31 and the lower shaft 32 have first and second fixing portions 36 at both ends of each leaf spring 33 by screws (not shown) or the like. , 39 are fixedly connected to each other.

  As shown in FIG. 3, each leaf spring 33 is arranged so that its short direction is along the radial direction, and along the relative rotation of the input shaft 31 and the lower shaft 32, the circumferential direction of both the shafts 31, 32. Are provided so as to be elastically deformable. In the present embodiment, the leaf springs 33 are fixed at equal angular intervals in the circumferential direction of the shafts 31 and 32.

  The input shaft 31 and the lower shaft 32 are configured such that each leaf spring 33 is elastically deformed according to an input torque applied to at least one of the input shaft 31 and the lower shaft 32 (for example, a steering torque τ applied to the input shaft 31). , They rotate relative to each other about the axis L.

  As shown in FIG. 2, the first large-diameter portion 35 of the input shaft 31 is integrally formed with a support shaft 41 that extends axially downward from the center thereof, and the second large-diameter portion 38 of the lower shaft 32. It is in contact with the upper end of. Thereby, when the force along an axial direction acts on the input shaft 31 or the lower shaft 32, each leaf | plate spring 33 is prevented from elastically deforming. Further, the tip 42 of the support shaft 41 of the present embodiment is formed in a sharp shape, and is in point contact with the upper end of the second large diameter portion 38 of the lower shaft 32.

  A plurality of (two in this embodiment) stoppers 43 are formed on the distal end side of the support shaft 41 so as to extend radially outward. On the other hand, as shown in FIG. 3, the second fixing portion 39 of the lower shaft 32 has a plurality of (two in this embodiment) recesses 45 that are recessed from the inner peripheral surface 44 toward the radially outer side. It is formed at a position corresponding to the stopper 43. Specifically, the stopper 43 is located when the relative position between the input shaft 31 and the lower shaft 32 is at a position where the input torque is not applied to the shafts 31 and 32 (hereinafter, neutral position). The concave portion 45 is disposed at the center in the circumferential direction. When the relative rotation angle between the input shaft 31 and the lower shaft 32 increases, the stopper 43 and the recess 45 come into contact with each other, so that the relative rotation is restricted and the leaf spring 33 is deformed beyond its elastic limit. This has been prevented.

  As shown in FIGS. 2 and 3, the torque sensor 28 includes a plurality of magnets 51 fixed to the leaf springs 33. More specifically, the magnet 51 is fixed so that the positions of the magnetic poles in the axial direction (axial position) of the shafts 31 and 32 change in opposite directions in accordance with the elastic deformation of the leaf spring 33. That is, in the magnet 51, when the axial position of the N pole changes to the upper side in the axial direction, the axial position of the S pole changes to the lower side in the axial direction, and the axial position of the N pole changes to the lower side in the axial direction. Sometimes, the axial position of the south pole is fixed so as to change upward in the axial direction. Since the leaf springs 33 are elastically deformed according to the input torque as described above, the axial positions of the magnetic poles in the magnet 51 are changed in opposite directions according to the input torque.

  In the present embodiment, the magnet 51 is a bonded magnet, and is fixed to both side surfaces in the thickness direction of the leaf spring 33. Specifically, a through hole 33a that penetrates in the thickness direction is formed in the center of the leaf spring 33, and the magnet 51 is fixed to the leaf spring 33 by being integrally formed with the leaf spring 33 by injection molding. ing. Each magnet 51 is formed so that different polarities (N pole, S pole) appear on both sides in the thickness direction of the leaf spring 33, and the magnets 51 are magnetic poles having different polarities alternately along the circumferential direction. It is arranged to become. In the present embodiment, the magnet 51 is arranged along the direction in which each magnetic pole is orthogonal to the axial direction in a state where the input shaft 31 and the lower shaft 32 are in a neutral position, that is, in a state where the leaf spring 33 is not elastically deformed. It is being fixed to the leaf | plate spring 33 so that it may arrange | position.

  As shown in FIGS. 2 and 3, the torque sensor 28 includes a pair of yokes 53 and 54 that form a magnetic circuit together with the magnet 51, and a Hall IC 56 as a magnetic detection unit that detects magnetic flux generated in the magnetic circuit. And. In the present embodiment, the pair of yokes 53, 54 are spaced apart from each other on both axial sides of the shafts 31, 32 with respect to the magnet 51, and the Hall IC 56 is a shaft formed between the yokes 53, 54. The magnetic flux passing through the directional gap (air gap 55) is detected.

  More specifically, the yokes 53 and 54 are formed in an annular shape and are arranged coaxially with the input shaft 31 and the lower shaft 32. The yokes 53 and 54 are resin-molded integrally with a holding portion 58 made of a resin material, and are press-fitted and fixed in a housing 59 as a non-rotating part fixed to the vehicle body. Further, the yokes 53 and 54 are respectively formed with extending portions 61 and 62 extending in the radial direction, and the Hall IC 56 is disposed in the air gap 55 between the extending portions 61 and 62. The Hall IC 56 is fixed to the housing 59 and is connected to the ECU 23 (see FIG. 1) via a signal line (not shown). The Hall IC 56 outputs a voltage at which the magnetic flux passing through the air gap 55 changes to the ECU 23 as an output signal, and the ECU 23 detects the input torque (steering torque τ) based on the output signal.

Next, the operation of the torque sensor 28 of the present embodiment will be described.
As shown in FIG. 4A, in a state where the input shaft 31 and the lower shaft 32 are in the neutral position, each magnetic pole (N pole, S pole) of the magnet 51 is arranged along a direction orthogonal to the axial direction. Therefore, the distance between the N pole and the yoke 53 of each magnet 51 is equal to the distance between the S pole and the yoke 53, the distance between the N pole and the yoke 54, and the distance between the S pole and the yoke 54. Are equal. Therefore, the magnetic flux that has flowed from the N pole of each magnet 51 to the upper yoke 53 does not pass through the air gap 55, goes around the yoke 53, and returns to the S pole of each magnet 51. Similarly, the magnetic flux that has flowed from the N pole of each magnet 51 to the lower yoke 54 does not pass through the air gap 55 but goes around the yoke 54 and returns to the S pole of the magnet 51. Therefore, when no torque is input, the magnetic flux does not pass through the air gap 55 between the yokes 53 and 54, and the magnetic flux is not detected by the Hall IC 56.

  On the other hand, for example, when the driver steers the steering wheel 2 to one side in the circumferential direction and the input shaft 31 and the lower shaft 32 rotate relative to each other, the leaf spring 33 is elastically deformed as shown in FIG. Rotates, and the axial positions of the magnetic poles change in opposite directions. Specifically, since the axial position of the N pole of each magnet 51 approaches the upper yoke 53 side and the axial position of the S pole of each magnet 51 approaches the lower yoke 54 side, as shown in FIG. A part of the magnetic flux that flows from the N pole of each magnet 51 to the upper yoke 53 flows through the air gap 55 to the lower yoke 54 and returns to the S pole of each magnet 51. Here, the magnetic flux (absolute value) flowing from the yoke 53 through the air gap 55 to the yoke 54 is such that the N pole axial position of the magnet 51 approaches the yoke 53 (the S pole axial position approaches the yoke 54). ). Since the axial position of each magnetic pole in each magnet 51 changes according to the input torque as described above, the output voltage (absolute value) of the Hall IC 56 is the input torque (absolute value) as shown in FIG. It increases in proportion to.

  For example, when the driver steers the steering wheel 2 to the other side in the circumferential direction and the input shaft 31 and the lower shaft 32 rotate relative to each other, the leaf spring 33 is elastically deformed as shown in FIG. Rotates, and the axial positions of the magnetic poles change in opposite directions. Specifically, since the axial position of the N pole of each magnet 51 approaches the yoke 54 side and the axial position of the S pole of each magnet 51 approaches the yoke 53 side, as shown in FIG. Part of the magnetic flux flowing from the pole to the lower yoke 54 passes through the air gap 55 and flows to the upper yoke 53, and returns to the S pole of each magnet 51. Also in this case, the magnetic flux (absolute value) flowing from the yoke 54 through the air gap 55 to the yoke 53 is such that the N pole axial position of the magnet 51 approaches the yoke 54 (the S pole axial position is Therefore, the output voltage (absolute value) of the Hall IC 56 increases in proportion to the input torque (absolute value) (see FIG. 5).

As described above, according to the present embodiment, the following operational effects can be achieved.
(1) The torque sensor 28 includes a plate spring 33 that connects the input shaft 31 and the lower shaft 32 so as to be relatively rotatable, and magnets 51 fixed to the plate spring 33 on both axial sides of the shafts 31 and 32. A pair of yokes 53 and 54 which are arranged apart from each other and constitute a magnetic circuit together with the magnet 51 are provided. Further, a Hall IC 56 for detecting a magnetic flux passing through the air gap 55 between the yokes 53 and 54 is provided, and the input torque is detected based on the magnetic flux detected by the Hall IC 56. Then, in accordance with the relative rotation of the input shaft 31 and the lower shaft 32, the magnet 51 is moved to the leaf spring 33 so that the positions of the magnetic poles in the axial direction (axial position) of the shafts 31 and 32 change in opposite directions. Fixed.

  In the above configuration, the axial positions of the magnetic poles in the magnet 51 change in opposite directions according to the input torque, and the pair of yokes 53, 54 are located on both axial sides of the shafts 31, 32 with respect to the magnet 51. Therefore, the magnetic flux passing through the air gap 55 between the yokes 53 and 54 changes according to the input torque. Therefore, the input torque can be detected based on the magnetic flux detected by the Hall IC 56. Thus, in order to change the magnetic flux passing through the air gap 55 by changing the axial positions of the magnetic poles in the magnet 51 in opposite directions, the yokes 53 and 54 are arranged on both sides of the magnet 51 in the axial direction. There is no need to form portions (claws) extending in the axial direction with respect to the yokes 53 and 54 as in the prior art. Therefore, the shapes of the yokes 53 and 54 can be simplified, the manufacturing cost of the torque sensor 28 can be reduced, and the inexpensive electric power steering apparatus 1 can be provided.

(2) The pair of yokes 53 and 54 and the Hall IC 56 are fixed to the housing 59, respectively.
Here, the size of the air gap between the pair of yokes 53 and 54 varies depending on the circumferential positions of the yokes 53 and 54 due to causes such as assembly errors. In general, since the Hall IC 56 is fixed to a non-rotating part, when the pair of yokes 53 and 54 are fixed to the input shaft 31 or the lower shaft 32, the yokes 53 and 54 are rotated in accordance with the rotation of these shafts. The circumferential position of the Hall IC 56 changes, and the size of the air gap in which the Hall IC 56 is arranged changes. On the other hand, since the magnetic resistance of the air gap is very large, the magnetic flux passing through the air gap changes greatly even if its size changes slightly. Therefore, when the yokes 53 and 54 are fixed to the input shaft 31 or the lower shaft 32, there is a possibility that a change in magnetic flux caused by a change in the axial position of each magnetic pole cannot be detected with high accuracy.

  In this regard, according to the above configuration, the yokes 53 and 54 and the Hall IC 56 are fixed to the housing 59 which is a non-rotating part. Therefore, even if the input shaft 31 and the lower shaft 32 rotate, the circumferential position of the Hall IC 56 in the yokes 53 and 54 does not change, and the Hall IC 56 can detect the magnetic flux passing through the air gap of a certain size. Thus, a change in magnetic flux due to a change in the axial position of each magnetic pole can be detected with high accuracy.

  In the conventional configuration, in order to detect the relative rotation between the input shaft 31 and the lower shaft 32, it is necessary to provide a ring magnet on the input shaft 31 and a yoke on the lower shaft 32. Therefore, in order to enable the Hall IC 56 to detect the magnetic flux passing through a certain air gap, it is necessary to prepare a pair of yokes separately from the yoke provided on the lower shaft 32 and fix it to the housing. .

  In this respect, according to the above-described configuration, since the relative rotation between the input shaft 31 and the lower shaft 32 is a change in the axial position of each magnetic pole, even if the yokes 53 and 54 are provided in the housing 59, the relative rotation depends on the relative rotation. Can be detected. Therefore, it is possible to reduce the number of parts as compared with the prior art while accurately detecting a change in magnetic flux due to a change in the axial position of each magnetic pole in the magnet 51. In addition, the number of air gaps in the magnetic circuit is reduced compared to the prior art by eliminating a pair of yokes and eliminating the air gap between the yoke provided on the lower shaft (second shaft) and the yoke provided on the housing. Therefore, the strength of the magnetic flux detected by the Hall IC 56 can be secured, and the noise resistance can be improved.

  (3) The leaf spring 33 disposed so as to be elastically deformable in the circumferential direction couples the input shaft 31 and the lower shaft 32, and extends in the axial direction to the input shaft 31, and the second large diameter portion 38 of the lower shaft 32. A support shaft 41 is formed in contact with the leaf spring 33, and the magnet 51 is fixed to the leaf spring 33 so that the axial positions of the magnetic poles are changed by elastic deformation of the leaf spring 33. In the above configuration, the leaf spring 33 is elastically deformed when an axial force is applied to the input shaft 31 or the lower shaft 32 by the support shaft 41 coming into contact with the second large diameter portion 38 of the lower shaft 32. And erroneous detection of input torque can be prevented. Further, since the axial position of each magnetic pole changes due to elastic deformation of the leaf spring 33, when the axial position of each magnetic pole changes, the member to which the magnet is fixed (the leaf spring 33) slides with other members. It does not move and the generation of abnormal noise can be suppressed.

  (4) When the through-hole 33a is formed in the leaf spring 33, the magnet 51 is composed of a bonded magnet, and is integrally formed with the leaf spring 33 by injection molding. For example, the magnet is fixed to the leaf spring by an adhesive or a screw. As compared with the above, the magnet 51 can be easily fixed to the leaf spring 33.

  (5) The tip 42 of the support shaft 41 is formed in a sharp shape, and the support shaft 41 is formed so as to make point contact with the second large diameter portion 38 of the lower shaft 32. Therefore, even if the input shaft 31 and the lower shaft 32 rotate relative to each other, the friction generated between the support shaft 41 and the second large diameter portion 38 can be kept low. It is not necessary to interpose a bearing between the portion 38 and the increase in the number of parts can be suppressed.

In addition, the said embodiment can also be implemented in the following aspects which changed this suitably.
In the above embodiment, the input shaft 31 and the lower shaft 32 are connected by the leaf spring 33 and the magnet 51 is fixed to the leaf spring 33. However, the present invention is not limited to this, and the relative rotation between the input shaft 31 and the lower shaft 32 ( Other configurations may be used as long as the axial positions of the magnetic poles in the magnet 51 change in opposite directions according to the input torque.

  For example, a torsion bar may be used as the connecting means, and the axial positions of the magnetic poles may be changed in opposite directions by a gear mechanism. Specifically, as shown in FIG. 6, in the torque sensor 28 according to another embodiment, the input shaft 31 and the lower shaft 32 are connected by a torsion bar 71 as a connecting means. A plurality of gears 72 are arranged between the input shaft 31 and the lower shaft 32, and the opposing surfaces of the first and second fixing portions 36 and 39 are along the circumferential direction meshing with the gears 72. Teeth 73 and 74 are formed respectively. A magnet 75 is fixed to each gear 72 such that each magnetic pole is disposed along a direction orthogonal to the axial direction in a state where the input shaft 31 and the lower shaft 32 are in the neutral position. In the torque sensor 28 thus configured, as shown in FIG. 7, the magnet 75 rotates together with the gear 72 in accordance with the relative rotation between the input shaft 31 and the lower shaft 32, so that the axial position of each magnetic pole is set. They change in opposite directions. According to this configuration, since the axial position of each magnetic pole is changed using a gear mechanism, the relative rotation of the input shaft 31 and the lower shaft 32 is not affected by changes in material properties (such as elastic modulus) caused by aging. Accordingly, the axial position of each magnetic pole can be changed with high accuracy. Therefore, the axial position of each magnetic pole can be changed stably over a long period of time.

  In addition, for example, a torsion bar may be used as the connecting means, and the protrusions may move along the guide groove due to the relative rotation of the input shaft 31 and the lower shaft 32 to change the axial positions of the magnetic poles in the opposite directions. Good. Specifically, as shown in FIG. 8, in the torque sensor 28 according to another embodiment, the input shaft 31 and the lower shaft 32 are connected by a torsion bar 81 as a connecting means. Further, the magnet 82 is formed with a guide groove 83 extending along the axial direction of the shafts 31 and 32, and the lower shaft 32 is formed with a protrusion 84 that protrudes in the radial direction and is inserted into the guide groove 83. Has been. The magnet 82 is rotatably supported by the pin 85 with respect to the input shaft 31 in a state where the protrusion 84 is inserted into the guide groove 83. In the torque sensor 28 configured as described above, when the input shaft 31 rotates relative to the one side in the circumferential direction with respect to the lower shaft 32 from the state shown in FIG. As described above, when the protrusion 84 moves in the guide groove 83 and the magnet 82 rotates, the axial position of each magnetic pole changes. Even when the input shaft 31 rotates relative to the other side in the circumferential direction with respect to the lower shaft 32, similarly, the protrusion 84 moves in the guide groove 83 and the magnet 82 rotates, so that each magnetic pole in the magnet 82 is rotated. The axial position changes in opposite directions. According to this configuration, since the protrusion 84 moves in the guide groove 83 to change the axial position of each magnetic pole, the input shaft 31 and the input shaft 31 are not affected by changes in material properties (such as elastic modulus) caused by aging. The axial position of each magnetic pole can be accurately changed according to the relative rotation of the lower shaft 32. Therefore, the axial position of each magnetic pole can be changed stably over a long period of time. In the torque sensor 28 shown in FIG. 8, the projecting portion may be formed on the magnet 82 and the guide groove may be formed on the lower shaft 32.

In the above embodiment, the input shaft 31 and the lower shaft 32 are connected by the plurality of plate springs 33. However, the present invention is not limited to this, and the number of the plate springs 33 may be one.
In the above embodiment, the yokes 53 and 54 are formed in an annular shape. However, the present invention is not limited to this, and when the magnet 51 rotates, the magnetic flux flowing from the magnets 51 to the yokes 53 and 54 forms the air gap 55. It only has to pass back to each magnet 51 and may be formed in a circular arc shape with a part cut away.

  In the above embodiment, the pair of yokes 53 and 54 and the Hall IC 56 are fixed to the housing 59. However, the invention is not limited thereto, and the Hall IC 56 is fixed to the housing 59 so as to rotate integrally with the input shaft 31 or the lower shaft 32. May be. Further, the Hall IC 56 may be rotated integrally with the input shaft 31 or the lower shaft 32 by using a slip ring or the like.

In the above embodiment, the magnets 51 are fixed to both side surfaces in the thickness direction of the leaf spring 33. However, the present invention is not limited to this, and the magnets 51 may be fixed to one side surface of the leaf spring 33 in the short direction.
In the above embodiment, the Hall IC 56 detects the magnetic flux passing through the axial gap (air gap 55) formed between the yokes 53, 54. However, the invention is not limited to this. The yokes 53 and 54 may be configured such that a circumferential gap is formed in the gap, and a magnetic flux passing through the circumferential gap may be detected.

  In the above embodiment, the through-hole 33a is formed in the leaf spring 33, the magnet 51 is composed of a bond magnet, and the leaf spring 33 and the magnet 51 are integrally formed by injection molding. May be made of a ferrite magnet or the like and fixed to the leaf spring 33 with an adhesive or a screw.

  In the above embodiment, the magnet 51 is fixed to the leaf spring 33 so that the magnetic poles are arranged along the direction orthogonal to the axial direction in a state where the input shaft 31 and the lower shaft 32 are in the neutral position. Not limited to this, the magnetic poles may be fixed to the leaf spring 33 so that the magnetic poles are arranged along the direction intersecting the axial direction in the neutral position.

  In the above embodiment, the tip end 42 of the support shaft 41 is formed in a sharp shape, and the support shaft 41 is formed so as to make point contact with the second large diameter portion 38 of the lower shaft 32. The tip of the support shaft 41 may be formed in a flat shape, and a bearing may be interposed between the support shaft 41 and the second large diameter portion 38.

In the above embodiment, the Hall IC 56 is used as the magnetic detection unit. However, the magnetic detection unit is not limited to this, and other magnetic sensors such as an MR element may be used as the magnetic detection unit.
In the above embodiment, the input shaft 31 is the first axis and the lower shaft 32 is the second axis. However, the present invention is not limited to this, and the input shaft 31 may be the second axis and the lower shaft 32 may be the first axis. .

In the above embodiment, the torque sensor 28 is provided on the column shaft 8, but it may be provided on the pinion shaft 10.
-In above-mentioned embodiment, although this invention was actualized to the electric power steering apparatus (EPS), you may apply to the torque detection apparatus used for uses other than EPS.

  DESCRIPTION OF SYMBOLS 1 ... Electric power steering apparatus (EPS), 28 ... Torque sensor, 31 ... Input shaft, 32 ... Lower shaft, 33 ... Leaf spring, 41 ... Support shaft, 42 ... Tip, 51, 75, 82 ... Magnet, 53, 54 ... Yoke, 55 ... Air gap, 56 ... Hall IC, 59 ... Housing, 71, 81 ... Torsion bar, 72 ... Gear, 73,74 ... Tooth part, 83 ... Guide groove, 84 ... Protrusion part.

Claims (8)

A first axis and a second axis arranged coaxially with each other;
Connecting means for connecting the first shaft and the second shaft so as to be relatively rotatable;
A magnet disposed between the first axis and the second axis;
A pair of yokes constituting a magnetic circuit together with the magnet;
A magnetic detection unit for detecting magnetic flux generated in the magnetic circuit,
A torque sensor for detecting an input torque applied to at least one of the first axis and the second axis based on a magnetic flux detected by the magnetic detection unit;
The magnet is supported such that the axial positions of the magnetic poles in the axial direction of the respective axes change in opposite directions in response to relative rotation between the first axis and the second axis. Torque sensor. The torque sensor according to claim 1,
The torque sensor, wherein the pair of yokes and the magnetic detection unit are respectively fixed to non-rotating portions. The torque sensor according to claim 1 or 2,
The connection means is a leaf spring provided so as to be elastically deformable in a circumferential direction of each axis in accordance with relative rotation between the first axis and the second axis.
A support shaft is formed on the first shaft, the support shaft extends toward the second shaft in the axial direction and abuts on the second shaft.
2. The torque sensor according to claim 1, wherein the magnet is fixed to the leaf spring so that the axial positions of the magnetic poles change in opposite directions according to elastic deformation of the leaf spring. The torque sensor according to claim 3, wherein
The torque sensor according to claim 1, wherein the magnet is a bonded magnet and is integrally formed with the leaf spring by injection molding. The torque sensor according to claim 3 or 4,
The torque sensor according to claim 1, wherein a tip of the support shaft is formed in a sharp shape and is formed so as to make point contact with the second shaft. The torque sensor according to claim 1 or 2,
The connecting means is a torsion bar;
The magnet is provided with a gear,
A tooth portion is formed along each circumferential direction on each facing surface of the first shaft and the second shaft, and the tooth portion meshes with the gear.
A torque sensor characterized in that the axial position of each magnetic pole in the magnet changes in the opposite direction when the gear rotates according to relative rotation between the first axis and the second axis. The torque sensor according to claim 1 or 2,
The connecting means is a torsion bar;
A guide groove is formed on one of the magnet and the first shaft, and the guide groove extends along the axial direction of each of the shafts.
A protrusion is formed on the other of the magnet and the first shaft, and the protrusion protrudes in the radial direction of each shaft and is inserted into the guide groove.
The magnet is supported so as to be rotatable with respect to the second shaft in a state where the protrusion is inserted into the guide groove, and the protrusion according to relative rotation between the first shaft and the second shaft. The torque sensor, wherein the axial position of each magnetic pole in the magnet changes in the opposite direction by moving the guide groove.   The electric power steering apparatus provided with the torque sensor as described in any one of Claims 1-7.

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