JP5071407B2 - Torque sensor and electric power steering apparatus using the same - Google Patents

Description

  The present invention relates to a torque sensor and an electric power steering apparatus using the torque sensor.

  An electric power steering device mounted on an automobile or the like is provided with a torque sensor that detects torque input from the steering. In the electric power steering apparatus, the operator can rotate the steering with a smaller force by assisting the rotation of the steering by a motor or the like based on the torque detected by the torque sensor. The electric power steering apparatus is also provided with a rotation angle sensor that detects the rotation angle of the steering in order to accurately control the steering. In recent years, torque sensors that detect both torque and rotation angle have been proposed.

  For example, Patent Document 1 discloses a torque sensor for obtaining a steering torque applied to a steering shaft that couples a steering wheel and a steering mechanism based on the twist of the steering shaft detected by a torsion detection means, and a rotation integrally with the steering shaft. In a steering device comprising: a rotation angle sensor that detects a rotation angle of an external gear meshing with an internal gear that is detected by a rotation angle detection means and obtains a rotation angle of a steering shaft based on a detection result of the rotation angle detection means; It is described that the torsion detection means of the torque sensor is fitted and held in the holding portion of the casing of the angle sensor.

  Patent Document 2 discloses an integrated sensor for measuring a relative rotational motion between an input shaft and an output shaft and measuring an angular position of both shafts, and rotates around the input shaft and an axis. An output shaft axially aligned with the input shaft, a support housing for rotatably supporting the output shaft for rotation about an axis, and a relative rotational motion between the two shafts in response to a predetermined torque A torsion bar that interconnects the shafts to allow for rotation, a wheel supported by the output shaft for rotation with the output shaft, and the both to measure relative rotational motion between the input shaft and the output shaft. A torque detection mechanism disposed around the shaft and an incremental detection that generates an incremental output indicative of the incremental angular position of the wheel in response to wheel rotation. An integrated sensor comprising: a mechanism; a segment detection mechanism for providing a segment output indicating the angular segment in which the wheel is placed; and a sensor casing supported by the housing and supporting at least a portion of the detection mechanism. Is described. Patent Document 3 also describes a sensor having a torque sensor and a rotation angle sensor.

JP 2007-269281 A US Pat. No. 7,174,795 US Patent Application Publication No. 2007/157740

  As described in Patent Documents 1 to 3, the sensor can be made small by providing the torque sensor and the rotation angle sensor integrally. However, in the devices described in Patent Documents 1 to 3, the torque sensor and the rotation angle sensor are merely arranged in the vicinity. For this reason, there is a limit to downsizing and a reduction in manufacturing cost because a member (printed circuit board, etc.), a connection member, a housing, and the like for fixing the detection element can be shared.

  The present invention has been made in view of the above, and an object of the present invention is to provide a torque sensor that can be further reduced in size and that can reduce the manufacturing cost, and an electric power steering device using the torque sensor. To do.

  In order to solve the above-described problems and achieve the object, the present invention provides a torque sensor, a connecting shaft that connects a first shaft body and a second shaft body, and the first shaft body. A permanent magnet that is fixed and ring-shaped, with the first surface and the second surface magnetized, and is fixed to the second shaft body and disposed within the magnetic field of the first surface of the permanent magnet. A plurality of magnetic bodies, an auxiliary magnetic body that is arranged in proximity to the magnetic body and forms a magnetic circuit with the permanent magnet and the magnetic body, and a first magnet that detects a magnetic flux induced by the auxiliary magnetic body A detector, a torque detector for detecting torque acting on the first shaft body or the second shaft body based on the detection output of the first magnetic detector, and the second surface. And a second magnetic detector for detecting magnetism generated from the outer peripheral surface of the permanent magnet, and the second magnetic detection There based on magnetism detection, and having an a-axis position detecting unit for detecting at least one of rotation angle and rotation speed of the first shaft.

  Here, it is preferable that the first surface is a surface orthogonal to the rotation axis of the permanent magnet, and the second surface is an outer peripheral surface.

  In addition, it is preferable that the permanent magnet is multipolarly magnetized on the second surface.

  Moreover, it is preferable that the said 2nd surface of the said permanent magnet is magnetized in parallel.

  The second magnetic detector preferably detects the direction of magnetism generated from the second surface.

  A drive gear disposed on the permanent magnet so as not to rotate; a driven gear configured to transmit rotation of the drive gear; a two-pole magnet disposed on the driven gear so as not to rotate; and A third magnetic detector disposed in the magnetic field, wherein the shaft body position detector is based on magnetism detected by the second magnetic detector and magnetism detected by the third magnetic detector. Preferably, the rotation angle of the first shaft body is detected as an absolute angle.

  In order to solve the above-described problems and achieve the object, the present invention is an electric power steering apparatus described in any of the above, and a torque sensor for detecting a steering torque, and an auxiliary steering force is applied to the steering mechanism. And an electric motor drive control means for driving and controlling the electric motor based on at least the steering torque.

  The torque sensor according to the present invention can detect the rotation angle and / or the rotation speed in addition to the torque, and it is possible to further reduce the size and to reduce the manufacturing cost. In addition, the electric power steering apparatus of the present invention can reduce the size of the torque sensor and reduce the manufacturing cost, so that the steering shaft can be shortened and the manufacturing cost can be reduced.

FIG. 1 is a block diagram showing a schematic configuration of a vehicle having an electric power steering device of the present invention. FIG. 2 is a cross-sectional view around the torque sensor of the electric power steering apparatus shown in FIG. FIG. 3 is an exploded perspective view for explaining main components of the torque sensor shown in FIG. FIG. 4 is a perspective view showing a schematic configuration of the permanent magnet. FIG. 5 is an explanatory diagram for explaining the principle of torque detection by the torque sensor. FIG. 6 is a graph showing the relationship between the output voltage from the second magnetic detector and the rotation angle. FIG. 7 is a perspective view showing a schematic configuration of a permanent magnet used in the torque sensor of the second embodiment. FIG. 8 is an explanatory diagram showing magnetic flux generated from the outer peripheral surface of the permanent magnet shown in FIG. FIG. 9 is a graph showing the relationship between the output voltage from the second magnetic detector and the rotation angle. FIG. 10 is a graph showing the relationship between the output voltage from the second magnetic detector and the rotation angle. FIG. 11 is a perspective view illustrating a schematic configuration of the torque sensor according to the third embodiment. FIG. 12 is an exploded perspective view for explaining the main components of the torque sensor shown in FIG. FIG. 13 is a schematic perspective view showing a partial configuration of the second magnetic detector shown in FIG. FIG. 14 is a graph showing the relationship between the output voltage from the second magnetic detector and the third magnetic detector and the rotation angle. FIG. 15 is a schematic diagram illustrating a schematic configuration of another example of the rotation angle detection mechanism. FIG. 16 is a graph showing another example of the relationship between the output voltage from the second magnetic detector and the third magnetic detector and the rotation angle. FIG. 17 is a graph showing another example of the relationship between the output voltage from the second magnetic detector and the third magnetic detector and the rotation angle.

  Hereinafter, embodiments of a torque sensor according to the present invention and an electric power steering apparatus using the torque sensor will be described in detail with reference to the drawings. In addition, this invention is not limited by this embodiment.

<First Embodiment>
First, a torque sensor and an electric power steering device according to a first embodiment of the present invention will be described. Here, FIG. 1 is a block diagram showing a schematic configuration of an embodiment of a vehicle having the electric power steering of the present invention. The electric power steering apparatus shown in FIG. 1 has the torque sensor of the present invention. The vehicle 1 includes an electric power steering device 2, a steering mechanism 3, a control unit 4, an ignition switch 5, a battery 6, and a vehicle speed sensor 7. In addition to the components shown in FIG. 1, the vehicle 1 has various components that are normally passed as a vehicle, such as an engine and wheels.

  The electric power steering device 2 detects a steering wheel 11 operated by an operator, a steering shaft 12 that transmits rotation input from the steering wheel 11, a torque input to the steering shaft 12, and a rotation angle of the steering shaft. And an auxiliary steering mechanism 14 that assists the rotation of the steering shaft 12 based on the torque detected by the torque sensor 13. The electric power steering device 2 detects the steering torque generated in the steering shaft 12 by the torque sensor 13 when the steering wheel 11 is operated. Furthermore, the electric power steering device 2 assists the steering force of the steering wheel 11 by generating the auxiliary steering torque by controlling the drive of the electric motor 16 by the control unit 4 based on the detected signal.

  A steering shaft 12 connected to the steering wheel 11 has an input shaft 12a and an output shaft 12b on which a driver's steering force acts, and a torque sensor 13 and a reduction gear box are interposed between the input shaft 12a and the output shaft 12b. 15 is interposed. The steering force transmitted to the output shaft 12 b of the steering shaft 12 is transmitted to the steering mechanism 3.

  The torque sensor 13 detects the steering force transmitted to the input shaft 12a via the steering wheel 11 as a steering torque. The torque sensor 13 will be described in detail later.

  The auxiliary steering mechanism 14 is connected to the output shaft 12b of the steering shaft 12, and transmits auxiliary steering torque to the output shaft 12b. The auxiliary steering mechanism 14 includes a reduction gear box 15 connected to the output shaft 12b, and an electric motor 16 connected to the reduction gear box 15 and generating auxiliary steering torque. The steering shaft 12, the torque sensor 13, and the reduction gear box 15 constitute a column, and the electric motor 16 applies auxiliary steering torque to the output shaft 12b of the column. That is, the electric power steering apparatus in this embodiment is a column assist type.

  The steering mechanism 3 includes a universal joint 20, a lower shaft 21, a universal joint 22, a pinion shaft 23, a steering gear 24, and a tie rod 25. The steering force transmitted from the electric power steering device 2 to the steering mechanism 3 is transmitted to the lower shaft 21 via the universal joint 20, further transmitted to the pinion shaft 23 via the universal joint 22, and then transmitted to the pinion shaft 23. The steering force thus transmitted is transmitted to the tie rod 25 via the steering gear 24 to steer a steered wheel (not shown). The steering gear 24 is configured as a rack-and-pinion type having a pinion 24a connected to the pinion shaft 23 and a rack 24b meshing with the pinion 24a. It has been converted.

  A control unit (ECU, Electronic Control Unit) 4 controls driving of various parts of the vehicle 1 such as the electric motor 16 and the engine. The control unit 4 is supplied with electric power from the battery 6 when the ignition switch 5 is on. The control unit 4 calculates an assist steering command value of the assist command based on the steering torque T detected by the torque sensor 13 and the traveling speed V detected by the vehicle speed sensor 7, and based on the calculated assist steering command value. Thus, the supply current value to the electric motor 16 is controlled.

  Next, the torque sensor 13 will be described in detail. Here, FIG. 2 is a sectional view around the torque sensor of the electric power steering apparatus shown in FIG. 1, and FIG. 3 is an exploded perspective view for explaining main components of the torque sensor shown in FIG.

  First, the steering shaft 12 has a connecting shaft 12c in addition to the input shaft 12a and the output shaft 12b described above. A steering wheel 11 (FIG. 1) is attached to the other axial end of the input shaft 12a. The output shaft 12b is rotatably supported by the reduction gear box 15 by a bearing 30. A steered wheel (not shown) is attached to the other axial end of the output shaft 12b via a universal joint 20 or the like. The connecting shaft (torsion bar) 12c is a connecting shaft that connects one axial end of the input shaft 12a (second shaft) and one axial end of the output shaft (first shaft) 12b. As shown in FIG. 2, the hollow shaft 12d covers the input shaft 12a. The gear cover 12 e is connected to the hollow shaft 12 d and attached to the reduction gear box 15. The gear cover 12e covers the outer periphery of the reduction gear box 15, and protects the structure (the reduction gear and the torque sensor 13) in the reduction gear box 15.

  2 and 3, the torque sensor 13 includes a permanent magnet assembly 31 including a permanent magnet 31a, a sensor yoke assembly 32 and a magnetic collecting yoke assembly 33 that form a magnetic circuit, and a sensor yoke 32a and a magnetic collecting yoke 33a. A first magnetic detector 34a that detects a magnetic flux by induction of the first magnetic detector 34 and a detector 34 that includes a second magnetic detector 34b that detects the magnetic force of the permanent magnet 31a. When torque acts on the input shaft 12a, the first magnetic detector 34a Torque is detected based on the detection output of the magnetic detector 34a, and the rotation angle of the steering shaft is detected based on the detection output of the second magnetic detector 34b. The constituent elements of the torque sensor include the input shaft 12a, the output shaft 12b, and the connecting shaft 12c of the steering shaft 12 described above.

  As shown in FIG. 2, the permanent magnet assembly 31 includes a permanent magnet 31a formed as a plate-shaped annular body surrounding the output shaft 12b (and the connecting shaft 12c), and a metal back yoke fixed to the permanent magnet 31a. 31b.

  Here, FIG. 4 is a perspective view showing a schematic configuration of the permanent magnet 31a. As shown in FIG. 4, the permanent magnet 31 a has a ring shape, and a surface (hereinafter referred to as “upper surface”) 31 c on the steering wheel 11 side has different magnetic poles (N pole and S pole) in the circumferential direction. The outer peripheral surface 31d is alternately magnetized with different magnetic poles (N pole and S pole) in the circumferential direction. In the present embodiment, the upper surface 31c and the outer peripheral surface 31d of the permanent magnet 31a are each magnetized to 16 poles. Further, the upper surface 31c and the outer peripheral surface 31d are magnetized with the S pole and the N pole in the same phase. That is, in the permanent magnet 31a, the outer peripheral surface 31d at a position corresponding to the portion where the upper surface 31c is magnetized to the N pole is magnetized to the N pole, and the upper surface 31c corresponds to the portion magnetized to the S pole. The outer peripheral surface 31d at the position is magnetized to the S pole. Here, as a magnet material constituting the permanent magnet 31a, a ferrite magnet, a rare earth magnet (Nd—Fe—B magnet, Sm—Co magnet, etc.), a metal magnet, a sintered magnet, or the like can be employed. Moreover, you may employ | adopt as a permanent magnet the bond magnet (rubber magnet or plastic magnet) integrally molded with the back yoke 31b.

  The back yoke 31b is press-fitted and fixed to the output shaft 12b, and the permanent magnet 31a is fixed by adhesion. The back yoke 31b has a ring shape with an L-shaped cross section, and supports the permanent magnet 31a with the inner surface and the lower surface of the permanent magnet 31a being in contact with the other surfaces exposed. In the present embodiment, the example in which the permanent magnet 31a is attached to the back yoke 31b in order to effectively use the magnetic flux is shown, but the permanent magnet 31a can also be attached directly to the output shaft 12b.

  2 and 3, the sensor yoke assembly 32 covers and fixes the sensor yoke 32a, a metal sleeve 32b inserted in the center of the sensor yoke 32a, the sensor yoke 32a, and the sleeve 32b. And a resin molded body 32c. The sensor yoke 32a is an annular magnetic body formed by arranging two short cylindrical sensor yoke components (first sensor yoke component 32aA and second sensor yoke component 32aB) in the axial direction, and is a permanent magnet. The magnetic circuit of the permanent magnet 31a is formed in the magnetic field of the 31a. As shown in FIG. 3, the first sensor yoke constituting portion 32aA has a plurality of flat plate trapezoidal claw portion constituting portions 32dA constituting the claw portions 32d and a side wall portion 32eA constituting the outer peripheral portion 32e. ing. The second sensor yoke constituting part 32aB has a plurality of flat plate-like claw constituting parts 32dB constituting the claw parts 32d and a side wall part 32eB constituting the outer peripheral part 32e.

  As shown in FIG. 3, the sensor yoke 32a has a plurality of plate-like claw portions 32d that face each other on one side in the axial direction of the permanent magnet 31a and are arranged on a substantially flat surface so as to surround the input shaft 12a. ing. These claw portions 32d are formed by combining the claw portion constituting portion 32dA of the first sensor yoke constituting portion 32aA and the claw portion constituting portion 32dB of the second sensor yoke constituting portion 32aB in the circumferential direction. They are arranged at equal intervals. The sensor yoke 32a has an outer peripheral portion 32e that is arranged in a non-contact state on the radially inner side of the magnetism collecting yoke 33a described later and extends in the axial direction. This outer peripheral part 32e is comprised from the side wall part 32eA of 1st sensor yoke structure part 32aA, and the side wall part 32eB of 2nd sensor yoke structure part 32aB.

  The sleeve 32b is fixed to the input shaft 12a by caulking after being fitted to the input shaft 12a. The sensor yoke 32a and the sleeve 32b are covered with a resin molded body 32c, and the sleeve 32b is fixed to the sensor yoke 32a. By fixing the sleeve 32b to the input shaft 12a in this way, the phase adjustment between the sensor yoke 32a and the permanent magnet 31a can be performed with the sensor yoke assembly 32 inserted into the input shaft 12a. Can be improved. The sleeve 32b is preferably made of a non-magnetic material because leakage flux from the claw portion 32d of the sensor yoke 32a to the input shaft 12a can be reduced. Further, if the sleeve 32b is made of a softer material than the input shaft 12a, the input shaft 12a is not deformed during caulking, so that positioning can be performed with high accuracy.

  In the present embodiment, the sleeve 32b is fixed to the input shaft 12a by caulking. However, the sleeve 32b may be fixed to the input shaft 12a by means such as screwing from the side, welding, or bonding. it can. Further, in the present embodiment, an example in which the planar shape is the trapezoidal claw portion 32d (the claw portion constituting portions 32dA and 32dB) is shown, but the planar shape is a triangular shape or a rectangular shape. Also good.

  As shown in FIGS. 2 and 3, the magnetic flux collecting yoke assembly 33 includes a magnetic flux collecting yoke 33a disposed in a non-contact state in the vicinity of the outer peripheral portion 32e of the sensor yoke 32a, and a magnetic flux collecting yoke holder 33b. Yes. The magnetism collecting yoke holder 33b accommodates and fixes the magnetism collecting yoke 33a therein, is made of a non-magnetic material, and is fixed to the reduction gear box 15 as shown in FIG. The magnetism collecting yoke 33a includes two magnetism collecting yoke constituent parts (first sensor yoke constituent parts (first sensor yoke constituent part 32aA and second sensor yoke constituent part 32aB)) that constitute the sensor yoke 32a. 1 is an annular auxiliary magnetic body configured by arranging one magnetic flux collecting yoke component 33aA and second magnetic flux collecting yoke component 33aB) in the axial direction, and is arranged in the magnetic field of the permanent magnet 31a to be a magnetic circuit of the permanent magnet 31a. Form.

  As shown in FIG. 2, the first magnetic flux collecting yoke component 33aA and the second magnetic flux collecting yoke component 33aB are arranged on the outer peripheral portion 32e of the first sensor yoke component 32aA and the second sensor yoke component 32aB, respectively. It arrange | positions so that it may oppose the surface of the radial direction outer side. The first (second) magnetism collecting yoke component 33aA (33aB) is formed on the surface of the second (first) magnetism collecting yoke component 33aB (33aA) so as to protrude radially outward. A convex portion 33c is provided. The convex part 33c functions as a magnetic flux concentration part. Here, the interval in the axial direction between the convex portions 33c is narrower than the interval in the axial direction between the first magnetic flux collecting yoke component 33aA and the second magnetic flux collecting yoke component 33aB. Thereby, the magnetic flux generated from the permanent magnet 31a can be concentrated. The magnetic detector 34a of the detector 34 is disposed on the convex portion 33c as the magnetic flux concentration portion.

  As shown in FIGS. 2 and 3, the detector 34 includes a first magnetic detector 34 a inserted into a gap in the axial direction of the convex portion 33 c as a magnetic flux concentrating portion provided in the magnetism collecting yoke 33 a, and a permanent magnet. And a second magnetic detector 34b provided at a position facing the second surface of 31a. The first magnetic detector 34a is fixed in a gap in the axial direction of the magnetic flux concentrating portion (the convex portion 33c) and detects the density of the magnetic flux passing therethrough. The first magnetic detector 34a may be any element that can measure the magnetic flux density, such as a Hall element, MR element, MI element, or the like. The first magnetic detector 34 a sends the detected amount of magnetic flux to the control unit 4.

  The second magnetic detector 34b is disposed to face the outer peripheral surface 31d of the permanent magnet 31a, and detects a magnetic field formed by the outer peripheral surface 31d of the permanent magnet 31a. Here, in the present embodiment, a Hall switch that detects magnetic flux is used for the second magnetic detector 34b. The second magnetic detector 34b detects the density of the magnetic flux of the radial component generated from the outer peripheral surface 31d of the permanent magnet 31a at the opposite position, and within the two of the high voltage and the low voltage according to the detected value One of the voltages is output as a signal. The second magnetic detector 34 b sends an output voltage (output signal) to the control unit 4.

  Next, the principle of torque detection of the torque sensor 13 according to this embodiment will be described with reference to FIG. FIG. 5 shows the permanent magnet 31 a and the sensor yoke 32 a that constitute the torque sensor 13. In FIG. 5, in order to clarify the positional relationship between the claw portion 32d of the sensor yoke 32a and the permanent magnet 31a, the second sensor yoke constituting portion 32aB constituting the sensor yoke 32a is not shown. However, in actuality, the claw portion constituting portion 32dB of the second sensor yoke constituting portion 32aB is arranged on both sides of the claw portion constituting portion 32dA of the first sensor yoke constituting portion 32aA, and a plurality of claw portions 32d are formed.

  When there is no torque input, each of the claw portions 32d of the sensor yoke 32a is located on the boundary between the magnetic poles (N pole and S pole) constituting the permanent magnet 31a, and the permanent magnet 31a viewed from each claw portion 32d. Since the permeance (reciprocal of the magnetic resistance) with respect to the N pole and the S pole is equal, the magnetic flux flows as shown in FIG. Specifically, the magnetic flux generated from the N pole of the permanent magnet 31a enters the claw portion 32d of the sensor yoke 32a and enters the S pole of the permanent magnet 31a as it is. Therefore, the magnetic flux does not flow through the first magnetic detector 34a.

  When torque is input to the input shaft 12a by the driver rotating the steering wheel 11 in a certain direction, for example, rightward, the input side of the connecting shaft 12c rotates in the same manner as the steering wheel 11 and the connecting shaft 12c itself. Twist occurs according to the input torque. This twist causes a relative angular displacement between the input side and the output side of the connecting shaft 12c. The relative angular displacement generated between the input side and the output side of the connecting shaft 12c appears as a relative angular displacement between the permanent magnet 31a of the torque sensor 13 and the sensor yoke 32a.

  When a relative angular displacement occurs between the permanent magnet 31a and the sensor yoke 32a, the balance of permeance as shown in FIG. 5 is lost, and the magnetic circuit including the first magnetic detector 34a (that is, generated from the N pole of the permanent magnet 31a). The magnetic flux that has flowed flows into the claw portion constituting portion 32dA of the first sensor yoke constituting portion 32aA and passes through the first magnetism collecting yoke constituting portion 33aA and the convex portion 33c from the first sensor yoke constituting portion 32a. A magnetic flux passes through the detector 34a and flows through the second magnetism collecting yoke component 33aB to the south pole of the permanent magnet 31a via the claw component component 32dB. By detecting the magnetic flux generated in the magnetic circuit including the first magnetic detector 34a with the first magnetic detector 34a, the relative angular displacement can be measured, and the torque applied to the connecting shaft 12c can be detected. When the driver rotates the steering wheel 11 in the reverse direction (in this case, the left direction), the magnetic flux flows through the magnetic circuit including the first magnetic detector 34a in the direction opposite to the above-described direction. Thereby, it is possible to detect the direction in which the torque is acting depending on the direction of the magnetic flux as well as the magnitude of the torque.

  Next, the principle of detection of the rotation angle by the torque sensor 13 will be described. Here, FIG. 6 is a graph showing the relationship between the output voltage (output signal) from the second magnetic detector 34b and the rotation angle. In the second magnetic detector 34b, the magnetic flux to be detected changes depending on the state of the outer peripheral surface 31d of the permanent magnet 31a at the facing position. Specifically, when the steering wheel 11 and the steering shaft 12 are rotated by an operator's operation with an arbitrary position of the output shaft 12b (for example, the center position of the steering shaft 12) as a reference, the output shaft 12b and the output shaft 12b are permanent. The magnet 31a also rotates. When the permanent magnet 31a rotates in this way, the S pole portion and the N pole portion of the outer peripheral surface 31d of the permanent magnet 31a alternately pass through the positions facing the second magnetic detector 34b. Every time the position facing the second magnetic detector 34b is switched between the S pole and the N pole, the magnetic flux detected by the second magnetic detector 34b also changes. That is, as shown in FIG. 6, when the rotation angle of the output shaft 12b changes in one direction, that is, when the rotation angle is simply increased or decreased, the voltage output from the second magnetic detector 34b is a high voltage, Alternates to low voltage. The voltage output from the second magnetic detector 34b is sent to the control unit 4 as an output signal.

  The control unit 4 controls the steering shaft 12 and the steering wheel 11 based on the number of changes in the voltage output from the second magnetic detector 34b, information on the reference position, and information on the rotational direction calculated based on torque and the like. Can be calculated as an absolute angle. Further, an estimated value of the absolute angle of the rotational angle of the steering shaft 12 and the steering wheel 11 is calculated from the difference between the rotational speeds of the left and right steered wheels, and the estimated value and a change in the voltage output from the second magnetic detector 34b are calculated. The rotation angle of the steering shaft 12 and the steering wheel 11 may be calculated as an absolute angle based on the number of times.

  The torque sensor 13 according to the above embodiment can detect both the torque applied to the steering shaft 12 and the rotation angle of the steering shaft 12. Moreover, the permanent magnet used for detecting the torque and the permanent magnet used for calculating the rotation angle are a common permanent magnet, that is, one permanent magnet, thereby simplifying the device configuration of the torque sensor 13. be able to. Moreover, since both a torque and a rotation angle can be detected using one permanent magnet, the axial dimension of the torque sensor 13 can be shortened, and the torque sensor 13 can be reduced in size.

  Moreover, since the electric power steering apparatus according to the above embodiment includes the torque sensor 13 that can be downsized (reduced axial dimension), the axial dimension of the entire apparatus can be shortened. Moreover, installation of the electric power steering apparatus with a limited mounting space can be facilitated.

  In the present embodiment, a detection element that outputs a detection result in binary is used as the second magnetic detector 34b. However, it is preferable to use a linear Hall IC as the detection element. In this case, it is preferable that the outer peripheral surface 31d of the permanent magnet 31a is sine-wave magnetized. In this way, the second magnetic detector 34b is a linear Hall IC, and the outer peripheral surface 31d is sinusoidally magnetized, so that not only the N pole faces the S pole but the S pole faces the N pole. It is possible to detect which part of the surface magnetized in the surface is facing, and which part of the surface magnetized in the S pole is facing, and the resolution of the detected rotation angle. Can be made higher.

  In the present embodiment, an example is shown in which an annular (planar shape is circular) magnetism collecting yoke 33a is employed. However, a planar shape of the magnetism collecting yoke 33d (or semicircular shape) is employed. You can also. When the magnetic collecting yoke 33d having a sector shape or a semicircular shape is employed as described above, the magnetic collecting yoke 33d can be assembled from the lateral direction (radial direction) of the sensor yoke 32a, and the magnetic collecting yoke 33d is connected to the input shaft 12a. As a result, it is not necessary to penetrate through, so that the assembling work can be greatly facilitated.

  In the present embodiment, the magnetism collecting yoke 33a is disposed so as to face the radially outer surface of the outer peripheral portion 32e (side wall portions 32eA, 32eB) of the sensor yoke 32a. 33a can also be arranged so as to face the axial surface of the outer peripheral portion 32e of the sensor yoke 32a. Further, the magnetism collecting yoke 33a may be arranged so as to face both the radially outer surface and the axial surface of the outer peripheral portion 32e of the sensor yoke 32a. When the magnetism collecting yoke 33a is disposed so as to face the axial surface of the outer peripheral portion 32e of the sensor yoke 32a, the magnetism collecting yoke 33a is disposed even when the input shaft 12a is displaced relative to the magnetism collecting yoke 33a. There is little fluctuation in the amount of magnetic flux passing through.

  If an alloy containing nickel is used as the material for the sensor yoke 32a and the magnetism collecting yoke 33a, the magnetic characteristics (output hysteresis) can be improved, and good performance as the torque sensor 13 can be obtained. Become. If hysteresis is not a problem, the sensor yoke 32a and the magnetism collecting yoke 33a are configured using other magnetic metal (for example, a silicon steel plate or a rolled steel plate such as SPCC generally used as a material for a motor or the like). can do. Further, either one of the sensor yoke 32a and the magnetism collecting yoke 33a may be configured using an alloy containing nickel.

Second Embodiment
Then, the torque sensor which concerns on 2nd Embodiment of this invention is demonstrated using FIGS. 7-9. The torque sensor according to the present embodiment is obtained by changing the configurations of the permanent magnet assembly 31 and the detector 34 of the torque sensor 13 according to the first embodiment, and the other configurations are substantially the same. For this reason, it demonstrates focusing on a different structure, about the overlapping structure, the code | symbol same as 1st Embodiment is attached | subjected and detailed description is abbreviate | omitted. Here, FIG. 7 is a perspective view showing a schematic configuration of a permanent magnet used in the torque sensor of the second embodiment, and FIG. 8 is an explanatory diagram showing a magnetic flux generated from the outer peripheral surface of the permanent magnet shown in FIG. FIG. 9 is a graph showing the relationship between the output voltage (output signal) from the second magnetic detector and the rotation angle.

  The permanent magnet assembly in this embodiment includes a permanent magnet 101a formed as a flat annular body surrounding the output shaft 12b (and the connecting shaft 12c), and a metal back yoke (not shown) fixed to the permanent magnet 101a. And have. The permanent magnet 101a has a ring shape, and the surface (upper surface) 101c on the steering wheel 11 side is alternately magnetized with different magnetic poles (N pole and S pole) in the circumferential direction, and the outer peripheral surface 101d has two poles. Parallel magnetized. That is, half of the outer peripheral surface 101d is magnetized to the N pole, and half is magnetized to the S pole. By parallel magnetizing the outer peripheral surface 101d of the permanent magnet 101a, the magnetic flux generated from the outer peripheral surface 101d of the permanent magnet 101a differs in the direction and magnitude of the magnetic field depending on the position, as shown in FIG.

  Here, the detector 34 of the present embodiment uses a Hall ASIC (Application Specific Integrated Circuit) that is a detector that detects the direction of the magnetic field for the second magnetic detector 34b. The detector 34 has the same configuration as that of the detector 34 described above except for the second magnetic detector 34b, and a description thereof will be omitted. By detecting the direction of the magnetic field by the second magnetic detector 34b, it is possible to detect which direction the permanent magnet 101a has a different magnetic field direction depending on the position as shown in FIG. Specifically, as shown in FIG. 9, the output voltage can be linearly changed with respect to the rotation angle. Thereby, the control unit 4 can detect a rotation angle from the voltage sent from the 2nd magnetic detector 34b. Thus, according to this embodiment, the absolute angle in one rotation can be detected only from the detection result from the second magnetic detector. As a result, the rotation angle can be calculated more easily.

  In the second embodiment, the outer peripheral surface 101d of the permanent magnet 101a is magnetized in two poles in parallel and the direction of the magnetic field is detected by the second magnetic detector 34b. However, the present invention is not limited to this, and the first embodiment is not limited thereto. As described above, the outer peripheral surface of the permanent magnet may be magnetized in multiple poles, and the direction of the magnetic field may be detected by the second magnetic detector as in the second embodiment. Here, FIG. 10 is a graph showing the relationship between the output voltage (output signal) from the second magnetic detector and the rotation angle. The graph shown in FIG. 10 shows the relationship between the output voltage and the rotation angle when the outer peripheral surface is magnetized to 16 poles and the direction of the magnetic field is detected by the second magnetic detector. As shown in FIG. 10, by magnetizing the outer peripheral surface to 16 poles, an output signal having 8 cycles is output while the permanent magnet rotates once, that is, while the steering shaft rotates once. Thus, by detecting the direction of the magnetic field, it is possible to more accurately detect the angle of the permanent magnet during one period, for example, between 0 degrees and 45 degrees. Note that the cycle number of the permanent magnet in the repetition cycle is calculated from the number of repetitions from the reference position, the direction of torque, and the like, as in the first embodiment.

<Third Embodiment>
Then, the torque sensor which concerns on 3rd Embodiment of this invention is demonstrated using FIGS. The torque sensor according to this embodiment is obtained by changing the configuration of the detector 34 of the torque sensor 13 according to the first embodiment, and the other configurations are substantially the same. For this reason, it demonstrates focusing on a different structure, about the overlapping structure, the code | symbol same as 1st Embodiment is attached | subjected and detailed description is abbreviate | omitted. Here, FIG. 11 is a perspective view showing a schematic configuration of the torque sensor of the third embodiment, and FIG. 12 is an exploded perspective view for explaining main components of the torque sensor shown in FIG. 13 is a schematic perspective view showing a configuration of a part of the third magnetic detector shown in FIG. 12, and FIG. 14 shows output voltages (output signals) from the second magnetic detector and the third magnetic detector; It is a graph which shows an example of the relationship with a rotation angle.

  11 and 12, the torque sensor 202 includes a permanent magnet assembly 31 including a permanent magnet 31a, a sensor yoke assembly 32 and a magnetic flux collecting yoke assembly 33 that form a magnetic circuit, and a sensor yoke 32a and a magnetic flux collecting yoke. A rotation angle detection mechanism 210 including a first magnetic detector 34a for detecting a magnetic flux induced by 33a, a second magnetic detector 208 for detecting the magnetic force of the permanent magnet 31a, and a third magnetic detector 218, and an input shaft 12a. Torque is detected based on the detection output of the first magnetic detector 34a, and the rotation angle of the steering shaft is determined based on the detection outputs of the second magnetic detector 208 and the third magnetic detector 218. To detect.

  The first magnetic detector 34a is the same as the first magnetic detector 34a of the detector 34 described above. The second magnetic detector 208 is a sensor that detects the direction of the magnetic field of the outer peripheral surface 31d of the permanent magnet 31a at the opposing position. Here, since the permanent magnet 31a of the present embodiment magnetizes the outer peripheral surface 31d to 16 poles, the output (voltage value) of the output signal of the second magnetic detector 208 at each rotation angle is the above-described figure. The output is the same as the graph shown in FIG.

  The rotation angle detection mechanism 210 includes a first gear 212 fixed to the lower surface (the surface opposite to the upper surface 31c) of the permanent magnet 31a, a second gear 214 meshed with the first gear 212, and a second gear 214. And a third magnetic detector 218 disposed opposite to the magnetized surface of the dipole magnet 216.

  The first gear 212 is a gear fixed to the lower surface of the permanent magnet 31a (the surface opposite to the upper surface 31c), and rotates together with the permanent magnet 31a. The method for fixing the first gear 212 to the permanent magnet 31a is not particularly limited, and the first gear 212 may be bonded by an adhesive, mechanically joined or fixed, or may be integrally formed.

  The second gear 214 is a gear meshed with the first gear 212. The second gear 214 is formed with a gear having a number of teeth different from that of the first gear 212. As described above, since the second gear 214 is meshed with the first gear 212, when the first gear 212 is rotated together with the rotation of the output shaft 12b, the meshed second gear 214 is also rotated. At this time, the second gear 214 rotates at a rotation angle (rotational speed) different from that of the first gear 212. In the present embodiment, the number of teeth of the first gear 212 is set to 36, and the number of teeth of the second gear 214 is set to 11. Thus, since the second gear 214 has fewer gear teeth than the first gear 212, the second gear 214 rotates a plurality of times while the first gear 212 rotates once.

  The two-pole magnet 216 is a permanent magnet whose upper surface is magnetized to two poles, and the lower surface is fixed to the second gear 214. The dipole magnet 216 rotates with the second gear 214. The method of fixing the dipole magnet 216 to the second gear 214 is not particularly limited, and may be formed by bonding with an adhesive, mechanically joining and fixing, or integrally.

  As shown in FIG. 13, the third magnetic detector 218 is provided at a position facing the magnetized surface (upper surface in the present embodiment) of the dipole magnet 216 and spaced from the upper surface by a predetermined distance. It has been. Similar to the second magnetic detector 208, the third magnetic detector 218 uses a detector that detects the direction of the magnetic field, and detects the direction of the magnetic field of the upper surface portion of the dipole magnet 216 at the opposite position. Here, since the two-pole magnet 216 is magnetized to two poles, the signal output from the third magnetic detector 218 is detected so that the original output value is obtained when the two-pole magnet 216 makes one rotation. The That is, the signal output from the third magnetic detector 218 detects one rotation of the dipole magnet 216 as one cycle.

  With the above configuration, the relationship between the signal output from the second magnetic detector 208 and the signal output from the third magnetic detector 218 and the rotation angle of the output shaft 12b is as shown in FIG. It becomes a relationship. Here, FIG. 14 shows the rotation angle when the output shaft 12b is rotated until it rotates twice in both directions (−720 degrees to +720 degrees) with the reference position (0 degree) as a reference, and the second magnetic detector 208. 4 is a graph showing a relationship with an output voltage (output signal) output from the third magnetic detector 218. As shown in FIG. 14, while the output shaft 12b makes one rotation, the output signal from the second magnetic detector 208 changes by 8 cycles, and the output signal from the third magnetic detector 218 becomes 3 strong cycles. Change. In this way, the output signal cycle is set to a different cycle, and the combination of the output signal from the second magnetic detector 208 and the output signal from the third magnetic detector 218 is performed between the rotation angle of −720 degrees and +720 degrees. However, the absolute angle of the rotation angle of the output shaft can be calculated from the two output signals by making sure that there are no angles that have the same combination.

  In the present embodiment, the number of teeth of the first gear 212 is set to 36, the number of teeth of the second gear 214 is set to 11, and the gear ratio of the two gears is set to about 3.27. However, the gear ratio is limited to this. Not. If the output signal from the second magnetic detector 208 and the output signal from the third magnetic detector 218 within the range of the rotation angle of the output shaft 12b do not have the same value, various gear ratios can be used. It can be. Here, the gear ratio is preferably a non-integer. By setting the gear ratio to a non-integer (non-integer value), the two output signals can be made different output signals even if the output shaft 12b is rotated a plurality of times, that is, 360 degrees or more.

  In the above embodiment, the second gear 214 is smaller than the first gear 212, but the ratio of the sizes is not limited. Hereinafter, another example of the rotation angle detection mechanism will be described with reference to FIG. Here, FIG. 15 is a schematic diagram illustrating a schematic configuration of another example of the rotation angle detection mechanism. The rotation angle detection mechanism 230 shown in FIG. 15 is the same as the rotation angle detection mechanism 230 except for the size of the second gear. Therefore, the following description focuses on the points peculiar to the rotation angle detection mechanism 230. The rotation angle detection mechanism 230 includes a first gear 212, a second gear 234, a dipole magnet 216, and a third magnetic detector 218. The second gear 234 is a gear meshed with the first gear 212. The second gear 234 is a gear having approximately the same size as the first gear 212. In the present embodiment, the first gear 212 has 36 gear teeth, and the second gear 234 has 37 gear teeth. Thus, since the second gear 234 has fewer gear teeth than the first gear 212, the second gear 234 also rotates approximately one time while the first gear 212 rotates once.

  By configuring the rotation angle detection mechanism 230 as described above, the relationship between the signal output from the second magnetic detector 208 and the signal output from the third magnetic detector 218 and the rotation angle of the output shaft 12b. Is as shown in FIG. Here, FIG. 16 is a graph showing the relationship between the rotation angle and the output signals from the second magnetic detector and the third magnetic detector when the rotation angle detection mechanism 230 is used. In the present embodiment, as shown in FIG. 16, the output signal from the second magnetic detector 208 changes by eight periods while the output shaft 12b rotates once, and the output signal from the third magnetic detector 218 is It changes by a little less than one cycle. As described above, even when the gear ratio between the first gear 212 and the second gear 234 is substantially the same, by setting the number of teeth of the gear to a different number of teeth, the rotation angle is between −720 degrees and +720 degrees. The combination of the output signal from the second magnetic detector 208 and the output signal from the third magnetic detector 218 can be such that there is no angle at which the combination is the same. Thereby, the absolute angle of the rotation angle of the output shaft can be calculated from the two output signals, and the amount of calculation by the control unit can be reduced.

  Further, the number of teeth of the second gear may be larger than the number of teeth of the first gear. For example, the number of teeth of the first gear may be 8, and the number of teeth of the second gear may be 32. In this embodiment, if the angle range of rotation of the output shaft is −720 degrees to +720 degrees, the second gear is configured to rotate once by rotating the output shaft from −720 degrees to +720 degrees. When the gear ratio between the first gear and the second gear is as described above, the signal output from the second magnetic detector 208 and the signal output from the third magnetic detector 218, and the rotation angle of the output shaft 12b. The relationship is as shown in FIG. Here, FIG. 17 shows the output voltage (output signal) from the second magnetic detector and the third magnetic detector when the gear ratio of the first gear to the second gear is 1: 4, and the rotation angle. It is a graph which shows a relationship. As shown in FIG. 17, in this embodiment, the output signal from the second magnetic detector 208 changes by 32 periods while the output shaft 12 b rotates four times, and the output signal from the third magnetic detector 218. Changes for one period. Therefore, also in the present embodiment, the combination of the output signal from the second magnetic detector 208 and the output signal from the third magnetic detector 218 becomes the same combination between the rotation angles of −720 degrees and +720 degrees. There can be no angle. In this embodiment, the approximate value of the absolute angle of the rotation angle is calculated using the output signal from the third magnetic detector, and the final absolute angle of the rotation angle is calculated using the output signal from the second magnetic detector. You may make it calculate by a value, ie, a finer value. This can reduce the resources required for the arithmetic processing.

  In the present embodiment, the permanent magnet fixed on the second gear is a two-pole magnet. However, the present invention is not limited to this, the outer peripheral surface is magnetized in multiple poles, and the third magnetic detector is used. May be arranged at a position facing the outer peripheral surface of the dipole magnet.

  In order to suppress the influence of the magnetic field generated by the dipole magnet on the magnetic detector other than the third magnetic detector, that is, the first magnetic detector and the second magnetic detector, the dipole magnet and the first magnetic It is preferable to provide a magnetic shield between the detector and the second magnetic detector. By providing a magnetic shield, the rotation angle and torque can be calculated more accurately.

  In the above embodiment, the case where the permanent magnet is magnetized to 16 poles and the case where the permanent magnet is magnetized to 2 poles have been described, but the number of magnetized poles is not particularly limited. For example, it may be magnetized to 8 poles, 10 poles, or 32 poles. Further, the magnetic detector only needs to be able to detect the magnetic state of the permanent magnet at the opposing position, and may detect the magnitude of the magnetic flux and magnetic field, or the direction of the magnetic flux and magnetic field. In the above embodiment, the rotation angle of the output shaft is calculated based on the detection results of the second magnetic detector and further the third magnetic detector. However, instead of or in addition to the rotation angle, the rotation speed is calculated. May be. In the above embodiment, the first shaft body that fixes the permanent magnet is used as the output shaft, and the second shaft body that fixes the sensor yoke is used as the input shaft (the shaft to which the steering wheel is connected). The shaft and the output shaft may be reversed. That is, the input shaft may be the first shaft body, the permanent magnet may be fixed to the input shaft, the output shaft may be the second shaft body, and the sensor yoke may be fixed to the output shaft.

  In each of the above embodiments, an example in which the present invention is applied to a torque sensor of an electric power steering apparatus for an automobile has been described. However, the present invention can be widely applied to torque sensors of various other apparatuses.

  As described above, the torque sensor according to the present invention and the electric power steering using the torque sensor are useful for detecting the torque applied to the rotating shaft, and are particularly applied to the steering for controlling the traveling direction of the vehicle. Suitable for use in torque detection.

DESCRIPTION OF SYMBOLS 1 Vehicle 2 Electric power steering apparatus 3 Steering mechanism 4 Control unit 5 Ignition switch 6 Battery 7 Vehicle speed sensor 11 Steering wheel 12 Steering shaft 12a Input shaft 12b Output shaft 12c Connecting shaft (torsion bar)
12d hollow shaft 12e gear cover 13 torque sensor 14 auxiliary steering mechanism 15 reduction gear box 16 electric motor 20 universal joint 21 lower shaft 22 universal joint 23 pinion shaft 24 steering gear 24a pinion 24b rack 25 tie rod 30 bearing 31a permanent magnet 31b back yoke (annular) Element)
32a Sensor yoke (magnetic material)
32b Sleeve (cylindrical member)
32c Resin molded body 32d Claw portion 32e Outer peripheral portion 33 Magnetic flux collecting yoke assembly 33a Magnetic flux collecting yoke (auxiliary magnetic material)
33aA Concentration yoke component 33aB Concentration yoke component 33b Concentration yoke holder 33c Convex portion (magnetic flux concentration portion)
34 detector 34a first magnetic detector 34b second magnetic detector

Claims (7)

A connecting shaft that connects the first shaft body and the second shaft body;
A permanent magnet fixed to the first shaft body, having a ring shape, and magnetized on the first surface and the second surface;
A plurality of magnetic bodies fixed to the second shaft body and disposed in the magnetic field of the first surface of the permanent magnet;
An auxiliary magnetic body that is disposed in proximity to the magnetic body and forms a magnetic circuit with the permanent magnet and the magnetic body;
A first magnetic detector for detecting a magnetic flux induced by the auxiliary magnetic body;
A torque detector that detects torque acting on the first shaft body or the second shaft body based on a detection output of the first magnetic detector;
A second magnetic detector disposed opposite to the second surface for detecting magnetism generated from the outer peripheral surface of the permanent magnet;
Based on magnetism said second magnetic detector detects, have a, a shaft position detecting unit for detecting at least one of rotation angle and rotation speed of the first shaft,
The first surface is a surface orthogonal to the rotation axis of the permanent magnet,
The torque sensor , wherein the second surface is an outer peripheral surface . The permanent magnet, a torque sensor according to claim 1, wherein the second surface is parallel magnetized. The permanent magnet, a torque sensor according to claim 1, wherein the second surface is multi-pole magnetized.   A connecting shaft that connects the first shaft body and the second shaft body;
  A permanent magnet fixed to the first shaft body, having a ring shape, and magnetized on the first surface and the second surface;
  A plurality of magnetic bodies fixed to the second shaft body and disposed in the magnetic field of the first surface of the permanent magnet;
  An auxiliary magnetic body that is disposed in proximity to the magnetic body and forms a magnetic circuit with the permanent magnet and the magnetic body;
  A first magnetic detector for detecting a magnetic flux induced by the auxiliary magnetic body;
  A torque detector that detects torque acting on the first shaft body or the second shaft body based on a detection output of the first magnetic detector;
  A second magnetic detector disposed opposite to the second surface for detecting magnetism generated from the outer peripheral surface of the permanent magnet;
  A shaft body position detector that detects at least one of a rotation angle and a rotation speed of the first shaft body based on magnetism detected by the second magnetic detector;
  The permanent magnet is a torque sensor characterized in that the second surface is magnetized in parallel. The second magnetic detector, a torque sensor according to claims 2 to any one of 4, characterized in that to detect the magnetic orientation generated from the second surface. A drive gear disposed on the permanent magnet so as not to rotate;
A driven gear for transmitting rotation of the drive gear;
A dipole magnet disposed on the driven gear so as not to rotate;
A third magnetic detector disposed in the magnetic field of the dipole magnet,
The shaft body position detecting unit detects the rotation angle of the first shaft body as an absolute angle based on magnetism detected by the second magnetic detector and magnetism detected by the third magnetic detector. The torque sensor according to any one of claims 1 to 5, characterized in that: A torque sensor according to any one of claims 1 to 6, which detects a steering torque,
An electric motor for applying an auxiliary steering force to the steering mechanism;
An electric power steering device comprising: electric motor drive control means for driving and controlling the electric motor based on at least the steering torque.

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