JP2019124526A - Torque sensor and electric power steering device - Google Patents

Abstract

To provide a torque sensor and an electric power steering device with which it is possible to detect the torque transmitted between shafts without using a torsion bar.SOLUTION: A torque sensor 10 comprises: an upper shaft 21 and an output-side shaft 20 coupled by serration fitting; an input-side rotation angle sensor 61 for detecting the rotation angle of the upper shaft 21; and an output-side rotation angle sensor 62 for detecting the rotation angle of the output-side shaft 20. A buffer material 24 that is elastically deformed by transmitted torque is interposed between a serration protrusion 211 of the upper shaft 21 and a serration protrusion 221 of an intermediate shaft 22 in the output-side shaft 20. Due to the elastic deformation of the buffer material 24, an angle difference that corresponds to transmitted torque occurs between the rotation angle detected by the input-side rotation angle sensor 61 and the rotation angle detected by the output-side rotation angle sensor 62, and transmitted torque is obtained on the basis of the angle difference.SELECTED DRAWING: Figure 4

Description

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

  Conventionally, in a steering apparatus that steers the steered wheels of a vehicle according to a steering operation of a steering wheel, a steering torque applied to the steering wheel is detected, and a steering assist torque corresponding to the steering torque is generated by an electric motor There is.

  For example, as described in Patent Documents 1 and 2, such an electric power steering apparatus has a torsion bar (torsion shaft) disposed in a transmission path of steering torque, and one or the other end of the torsion bar is disposed. The steering torque is detected by the relative rotational displacement of the input and output shafts fixed respectively. A controller (ECU) that controls the electric motor supplies a current corresponding to the detection result of the steering torque to the electric motor. The output rotation of the electric motor is decelerated by the reduction mechanism and transmitted to the steering shaft, and a steering assist torque corresponding to the steering torque is applied to the steering shaft.

  For example, as described in detail in Patent Document 2, the torsion amount of the torsion bar is such that the magnetic flux density detected by the pair of Hall elements and these Hall elements changes in accordance with the torsion amount of the torsion bar. And a torque sensor having a configured magnetic circuit.

JP, 2015-85805, A JP, 2016-88208, A

  In the conventional electric power steering apparatus configured as described above, the torsion bar is disposed in the transmission path of the steering torque, so that, for example, in a sports car where movement performance is emphasized, the steering is particularly rigid near the neutral position. There may be a lack of sexual feeling. In addition, it may be difficult for the road surface condition to be transmitted to the driver via the steering wheel. Furthermore, since there are many components of the magnetic circuit of a torque sensor, much man-hours are needed for the assembly.

  Therefore, an object of the present invention is to provide a torque sensor and an electric power steering device capable of detecting a torque transmitted between shafts without using a torsion bar.

  In order to achieve the above object, the present invention provides an input side shaft and an output side shaft connected by serration fitting, an input side rotation angle sensor for detecting a rotation angle of the input side shaft, and the output side shaft An output side rotation angle sensor for detecting a rotation angle, wherein the serration fitting is made by interposing a shock absorbing material elastically deformed by a transmission torque from the input side shaft to the output side shaft, A torque sensor is provided in which an angular difference corresponding to the transmission torque is generated between an angle of rotation detected by the input side rotation angle sensor and a rotation angle detected by an output side rotation angle sensor by elastic deformation.

  Further, in order to achieve the above object, the present invention provides an input shaft to which a steering torque is input, an output shaft connected to the input shaft by serration fitting, and a rotation angle of the input shaft. It comprises: an input side rotation angle sensor to be detected; an output side rotation angle sensor to detect a rotation angle of the output side shaft; and a steering assist device to apply a steering assist torque to the output side shaft by rotation of an electric motor. The serration fitting is performed by interposing a shock absorbing material elastically deformed by the transmission torque from the input side shaft to the output side shaft, and the rotation detected by the input side rotation angle sensor by the elastic deformation of the shock absorbing material An angle difference corresponding to the transmission torque occurs between the angle and the rotation angle detected by the output side rotation angle sensor, and the steering assist device is based on the angle difference. A steering assist torque of the magnitude corresponding to the steering torque obtained by There is imparted to the output side shaft, to provide an electric power steering apparatus.

  According to the torque sensor and the electric power steering apparatus according to the present invention, the torque transmitted between the shafts can be detected without using a torsion bar. As a result, the sense of rigidity when steering the steering wheel is enhanced, the road surface condition can be easily transmitted to the driver accurately, and a magnetic circuit and the like are not required, which can contribute to cost reduction.

FIG. 1 is a block diagram of an electric power steering apparatus according to an embodiment of the present invention. It is the sectional view on the AA line of FIG. It is the elements on larger scale of FIG. It is the BB sectional drawing of FIG.

Embodiment
Embodiments of the present invention will be described with reference to FIGS. 1 to 4. Note that the embodiments described below are shown as preferable specific examples for carrying out the present invention, and there are portions that specifically exemplify various technical matters that are technically preferable. The technical scope of the present invention is not limited to this specific embodiment.

(Whole structure of steering device)
FIG. 1 is a block diagram showing an electric power steering apparatus according to an embodiment of the present invention. FIG. 2 is a cross-sectional view taken along line AA of FIG. FIG. 3 is a partial enlarged view of FIG. FIG. 4 is a cross-sectional view taken along line B-B of FIG. Note that FIG. 1 schematically shows a part of the steering device.

  The electric power steering apparatus 1 includes a steering shaft 11 including a column shaft 2 rotating with a steering wheel 100, a rack shaft 12 moving in the vehicle width direction with the rotation of the steering shaft 11, and a steering column through which the column shaft 2 is inserted. 3, a support mechanism 4 for supporting the steering column 3 with respect to the vehicle body, and a steering assist device 5 for assisting the steering operation of the steering wheel 100 by the driver. The column shaft 2, the steering column 3, the support mechanism 4, and the steering assist device 5 constitute a steering column device 1A.

  As shown in FIG. 1, the steering shaft 11 is connected to the column shaft 2, an intermediate shaft 112 connected to the column shaft 2 via a universal joint 111, and a joint to the intermediate shaft 112 via a universal joint 113. And the pinion shaft 114. At one end of the pinion shaft 114, pinion teeth 114a are formed, and the pinion teeth 114a mesh with the rack teeth 12a of the rack shaft 12. A pair of tie rods 13 and 13 is swingably connected to both end portions of the rack shaft 12, and the rack shaft 12 moves in the vehicle width direction as the steering shaft 11 rotates, whereby the left and right front wheels 14 are moved. , 14 are steered.

  The column shaft 2 has an output side shaft 20 to which a universal joint 111 is attached at an end, and an upper shaft 21 as an input side shaft to which a steering wheel 100 is attached at one end. As shown in FIG. 4, the output side shaft 20 includes an intermediate shaft 22 as a first shaft member connected to the other end of the upper shaft 21 by serration fitting, and a worm wheel 54 of the steering assist device 5 described later. It consists of the lower shaft 23 as a fixed 2nd shaft member. The intermediate shaft 22 and the lower shaft 23 are relatively non-rotatably fixed by press fitting the end of the lower shaft 23 into a cylindrical fitting portion 220 provided on the intermediate shaft 22. The output side shaft 20 may be a single shaft member in which a first shaft portion corresponding to the intermediate shaft 22 and a second shaft portion corresponding to the lower shaft 23 are integrally formed.

  A steering torque is input to the upper shaft 21 from the steering wheel 100. The upper shaft 21, the intermediate shaft 22, and the lower shaft 23 are made of a cylindrical steel material, and rotate around the rotation axis O together with the steering wheel 100. Hereinafter, a direction parallel to the rotation axis O is referred to as an axial direction. The intermediate shaft 22 and the lower shaft 23 are not limited to the cylindrical shape, but may be a solid cylindrical shape without a cavity at the center.

  The upper shaft 21 is provided at its end opposite to the steering wheel 100 with a fitting hole 210 in which the intermediate shaft 22 is fitted. A plurality of serration projections 211 are formed on the inner peripheral surface of the fitting hole 210. The plurality of serration protrusions 211 extend in parallel to one another along the axial direction.

  A plurality of serration projections 221 are formed on the outer peripheral surface of the end of the intermediate shaft 22 fitted to the fitting hole 210 of the upper shaft 21. The plurality of serration projections 221 of the intermediate shaft 22 and the plurality of serration projections 211 of the upper shaft 21 mesh with each other, and the steering torque is transmitted from the upper shaft 21 to the intermediate shaft 22 by this meshing. Further, the upper shaft 21 is axially movable relative to the intermediate shaft 22 while maintaining the meshing state of the serration protrusions 211 and 221.

  The intermediate shaft 22 has a weakened portion 222 which is partially weakened. The fragile portion 222 is formed to have an outer diameter smaller than that of the other portion of the intermediate shaft 22 and a smaller thickness. With this configuration, for example, when an excessive steering torque is input from the steering wheel 100 to the upper shaft 21 with one of the left and right front wheels 14 fitted in the groove, the fragile portion 222 is broken or plastically deformed, Damage to other parts of the electric power steering apparatus 1 is suppressed.

  As shown in FIG. 3, a shock absorbing material 24 is disposed between the serration projections 211 of the upper shaft 21 and the serration projections 221 of the intermediate shaft 22 so as to prevent the steel materials from contacting each other. In the present embodiment, the cushioning material 24 is made of a resin coated on the outer peripheral surface of the intermediate shaft 22. The shock absorbing material 24 has an elasticity that is elastically deformed by a transmission torque (steering torque) from the upper shaft 21 to the intermediate shaft 22. That is, when the steering torque is transmitted from the upper shaft 21 to the intermediate shaft 22, the side surface 211a on the front side in the rotational direction among the side surfaces 211a of the serration projection 211 of the upper shaft 21 The buffer material 24 interposed between the protrusion 221 and the side surface 221 a is elastically compressed.

  In the present embodiment, the plurality of serration projections 211 formed on the inner peripheral surface of the fitting hole 210 provided on the upper shaft 21 are engaged with the plurality of serration projections 221 formed on the outer peripheral surface of the intermediate shaft 22. However, on the contrary, a plurality of serration projections formed on the inner peripheral surface of the fitting hole provided on the intermediate shaft 22 are on a plurality of serration projections formed on the outer peripheral surface of the upper shaft 21 Both shafts 21 and 22 may be serrated to engage. In this case, it is preferable in terms of manufacture to coat the resin on the outer peripheral surface of the upper shaft 21 to form a shock absorbing material. However, the inner circumferential surface of the fitting hole may be coated with a resin.

  The steering column 3 has an outer tube 31 and an inner tube 32 partially accommodated in the outer tube 31, and the outer tube 31 is disposed closer to the steering wheel 100 than the inner tube 32. An upper shaft 21 and an intermediate shaft 22 are inserted through the steering column 3, and a first bearing 33 is disposed between the inner peripheral surface of the outer tube 31 and the outer peripheral surface of the upper shaft 21. The first bearing 33 is a ball bearing in which a plurality of spherical rolling elements are disposed between an outer ring and an inner ring.

  As shown in FIG. 2, the support mechanism 4 supports the control lever 40, a frame 41 fixed to the outer tube 31, and a pair of side plate portions 421 and 422 to support the frame 41 in the vehicle width direction. Body 42, a tilt bolt 43 that rotates with the operation lever 40, a pressing member 44 that rotates integrally with the tilt bolt 43 to press the inner tube 32 against the outer tube 31, and a cam mechanism 45 that operates by the operation of the operation lever 40. , An upper bracket 46 to which the support 42 is fixed, and a lower bracket 47 (see FIG. 1) disposed in front of the upper bracket 46 in the vehicle. The upper bracket 46 is fixed to the vehicle body via a pair of capsules 48 which are detachable at the time of a secondary collision. The lower bracket 47 is fixed to the vehicle body by a plurality of bolts inserted into the bolt insertion holes 471.

  In the frame body 41, long holes 41a and 41b which are long in a direction parallel to the rotation axis O are formed, and the tilt bolt 43 is inserted through the long holes 41a and 41b. In the support body 42, long holes 42a and 42b long in the vehicle vertical direction are formed in the side plate portions 421 and 422, respectively, and the tilt bolts 43 are inserted through the long holes 42a and 42b. The cam mechanism 45 has a first cam member 451 fixed to the side plate portion 422 of the support 42 and a second cam member 452 that rotates together with the operation lever 40. When the first cam member 451 and the second cam member 452 rotate relative to each other and the cam mechanism 45 operates, the side plate portions 421 and 422 of the support 42 hold the frame 41 by the cam thrust.

  The pressing member 44 integrally includes a cylindrical portion 441 that rotates integrally with the tilt bolt 43 and a pressing ring 442 that is eccentric to the cylindrical portion 441. The pressing ring 442 is provided via the opening 31 b provided in the outer tube 31 when the operating lever 40 is rotated so that the grip portion 401 (see FIG. 1) provided at the tip of the operating lever 40 is lifted upward. The outer peripheral surface 32 a of the lower end portion of the inner tube 32 is pressed against the inner peripheral surface 31 a of the outer tube 31. In addition, when the operation lever 40 is rotated so that the grip portion 401 is pushed downward, the pressing ring 442 is separated from the inner tube 32.

  With the above-described configuration of the support mechanism 4, when the operation lever 40 is pivoted so that the grip portion 401 is pushed downward, the frame 41 can move up and down relative to the support 42 so that tilt adjustment is possible. Also, the outer tube 31 can be moved in the axial direction with respect to the inner tube 32 to enable telescopic adjustment. In the present embodiment, since the shock absorbing material 24 made of resin is coated on the outer peripheral surface of the intermediate shaft 22, the upper shaft 21 can be smoothly axially moved relative to the intermediate shaft 22 at the time of telescopic adjustment. Further, when the operation lever 40 is pivoted so that the grip portion 401 can be lifted upward, the position of the steering wheel 100 is fixed.

  As shown in FIGS. 1 and 4, the steering assist device 5 includes an electric motor 51, a controller 52 for controlling the electric motor 51, a worm gear 53 rotationally driven by the electric motor 51, and a worm engaged with the worm gear 53. A wheel 54 and a housing 55 supported by the vehicle body via a lower bracket 47 are provided. A support bolt 49 for inserting the lower bracket 47 is screwed into the housing 55, and at the time of tilt adjustment, the housing 55 can swing with the central axis of the support bolt 49 as a tilt central axis.

  The housing 55 has a first housing member 56 for housing the worm gear 53 and the worm wheel 54, and a second housing member 57 having a cylindrical portion 571 on which the inner tube 32 is fitted and fixed. The second housing member 57 is fastened by a bolt (not shown). The worm wheel 54 is fixed to the lower shaft 23 in the first housing member 56, and a steering assist torque is applied to the lower shaft 23 from the worm wheel 54.

  In addition, the first housing member 56 is provided with a cylindrical holding portion 561 for holding the second bearing 34 for rotatably supporting the lower shaft 23. The second bearing 34 is disposed between the inner circumferential surface of the holding portion 561 and the outer circumferential surface of the lower shaft 23. Like the first bearing 33, the second bearing 34 is a ball bearing in which a plurality of spherical rolling elements are disposed between the outer ring and the inner ring.

  The controller 52 supplies the electric motor 51 with a current corresponding to the steering torque. The steering assist torque applied to the lower shaft 23 by the rotation of the electric motor 51 increases as the steering torque increases. The electric power steering apparatus 1 according to the present embodiment does not have a torsion bar that is twisted by a steering torque or a magnetic circuit that magnetically detects the amount of torsion of the torsion bar, and the input side rotation angle sensor described below The steering torque is detected based on the difference between the rotation angle detected at 61 and the rotation angle detected by the output side rotation angle sensor 62.

(Method of detecting steering torque)
An input side rotation angle sensor 61 is disposed adjacent to the first bearing 33 between the inner peripheral surface of the outer tube 31 and the outer peripheral surface of the upper shaft 21. Further, an output side rotation angle sensor 62 is disposed adjacent to the second bearing 34 between the inner peripheral surface of the holding portion 561 of the first housing member 56 and the outer peripheral surface of the lower shaft 23. The input side rotation angle sensor 61 and the output side rotation angle sensor 62, together with the output side shaft 20 and the upper shaft 21 connected via the buffer material 24, function as a torque sensor 10 for detecting a steering torque.

  In the present embodiment, the input-side rotation angle sensor 61 is disposed adjacent to the first bearing 33 on the vehicle front side, but the order of arrangement may be reversed. Further, in the present embodiment, the output side rotation angle sensor 62 is disposed adjacent to the vehicle front side of the second bearing 34, but the arrangement order may be reversed. Furthermore, the input side rotation angle sensor 61 and the first bearing 33, and the output side rotation angle sensor 62 and the second bearing 34 may not necessarily be adjacent to each other.

  The input side rotation angle sensor 61 and the output side rotation angle sensor 62 are known per se, and for example, an optical sensor or a magnetic sensor can be appropriately used. The rotation angles of the upper shaft 21 and the output shaft 20 relative to the steering column 3 can be detected by the input side rotation angle sensor 61 and the output side rotation angle sensor 62. More specifically, the input side rotation angle sensor 61 detects the rotation angle of the upper shaft 21 with respect to the outer tube 31, and the output side rotation angle sensor 62 detects the rotation angle of the lower shaft 23 with respect to the housing 55. Detection signals indicating detection results of the input side rotation angle sensor 61 and the output side rotation angle sensor 62 are sent to the controller 52 by signal lines not shown.

  The detection results of the input side rotation angle sensor 61 and the output side rotation angle sensor 62 are used to detect the steering torque, and the detection results of the input side rotation angle sensor 61 or the detection results of the output side rotation angle sensor 62 are steered. It is also possible to use, for example, automatic driving as corner information.

  As described above, the shock absorbing material 24 has elasticity to be elastically deformed by the transmission torque from the upper shaft 21 to the intermediate shaft 22. Therefore, when the steering wheel 100 is steered, the elastic deformation of the shock absorbing material 24 causes the upper The shaft 21 and the intermediate shaft 22 slightly rotate relative to each other. As a result, an angular difference corresponding to the steering torque occurs between the rotation angle detected by the input side rotation angle sensor 61 and the rotation angle detected by the output side rotation angle sensor 62. The steering torque can be obtained by calculating this angle difference in the controller 52. The steering assist device 5 obtains a steering torque based on the above-mentioned angle difference, and applies a steering assist torque having a magnitude corresponding to the obtained steering torque to the output side shaft 20 (specifically, the lower shaft 23).

  Further, in the present embodiment, the intermediate shaft 22 has the fragile portion 222, and the output side rotation angle sensor 62 detects the rotation angle of the lower shaft 23 on the torque transmission downstream side of the intermediate shaft 22, so When the fragile portion 222 of the intermediate shaft 22 is twisted within the range of the steering torque, the rotation angle detected by the input side rotation angle sensor 61 and the rotation detected by the output side rotation angle sensor 62 also by the torsion component There is an angular difference with the corners. Thereby, the detection accuracy of the steering torque is improved as compared with the case where the intermediate shaft 22 does not have the fragile portion 222. However, even if the intermediate shaft 22 is a rigid body which is not twisted by the steering torque over the entire axial direction, it is possible to obtain the steering torque by the angular difference caused by the elastic deformation of the cushioning material 24.

  In order to further improve the detection accuracy of the steering torque, the input side rotation angle sensor 61 and the output side rotation angle sensor 62 when a torque is applied to the upper shaft 21 after the steering column device 1A is assembled in the manufacturing process. It is desirable to measure the angular difference of the rotational angle detected in the above and store information indicating the relationship between the steering torque and the angular difference determined based on the measurement result in the non-volatile memory of the controller 52. This measurement can be performed, for example, by applying a torque to the upper shaft 21 in a state where the lower shaft 23 is non-rotatably fixed. The controller 52 calculates steering torque with reference to stored information in a state where the electric power steering apparatus 1 is mounted on a vehicle, for example, due to variations in thickness and hardness of the shock absorbing material 24 and the like. The detection error of the generated steering torque can be reduced.

  As described above, according to the present embodiment, the steering torque can be detected without using the torsion bar used in the conventional electric power steering apparatus. As a result, the rigidity at the time of steering the steering wheel 100 is enhanced, and the road surface condition can be easily transmitted to the driver accurately, and a magnetic circuit or the like for detecting the amount of torsion of the torsion bar becomes unnecessary. Can be achieved.

(Supplementary note)
As mentioned above, although this invention was demonstrated based on embodiment, these embodiments do not limit the invention which concerns on a claim. In addition, it should be noted that not all combinations of features described in the embodiments are essential to the means for solving the problems of the invention.

  Further, the present invention can be appropriately modified and implemented without departing from the scope of the invention. For example, although the above embodiment describes the case where the present invention is applied to the column shaft 2 to which the steering wheel 100 is attached at one end, the present invention is not limited to this. For example, the present invention is applied to the pinion shaft 114 Is also possible. Furthermore, the application target of the torque sensor according to the present invention is not limited to the electric power steering device of a vehicle, and the torque sensor according to the present invention can be used for various devices such as various mechanical devices and measuring devices. .

DESCRIPTION OF SYMBOLS 1 ... Electric-power-steering apparatus 10 ... Torque sensor 100 ... Steering wheel 20 ... Output side shaft 21 ... Upper shaft (input side shaft) 211 ... Serration protrusion 22 ... Intermediate shaft 221 ... Serration protrusion 222 ... Fragile part 23 ... Lower shaft 24 ... Buffer material 33: first bearing 34: second bearing 5: steering assist device 61: input side rotation angle sensor 62: output side rotation angle sensor

Claims (5)

An input shaft and an output shaft connected by serration fitting;
An input side rotation angle sensor for detecting a rotation angle of the input side shaft;
An output side rotation angle sensor for detecting a rotation angle of the output side shaft;
The serration fitting is performed by interposing a buffer material elastically deformed by a transmission torque from the input side shaft to the output side shaft,
The elastic deformation of the buffer material causes an angular difference corresponding to the transmission torque between the rotation angle detected by the input side rotation angle sensor and the rotation angle detected by the output side rotation angle sensor.
Torque sensor. The input shaft and the output shaft are serrated projections formed on the outer peripheral surface of the other shaft, serration projections formed on the inner peripheral surface of the fitting hole provided on one of the shafts. Serrated to engage with the
The shock absorbing material is a resin coated on the outer peripheral surface of the other shaft,
The torque sensor according to claim 1. An input shaft to which a steering torque is input,
An output side shaft connected to the input side shaft by serration fitting;
An input side rotation angle sensor for detecting a rotation angle of the input side shaft;
An output side rotation angle sensor for detecting a rotation angle of the output side shaft;
And a steering assist device that applies a steering assist torque to the output side shaft by rotation of an electric motor.
The serration fitting is performed by interposing a buffer material elastically deformed by a transmission torque from the input side shaft to the output side shaft,
The elastic deformation of the buffer material causes an angular difference corresponding to the transmission torque between the rotation angle detected by the input side rotation angle sensor and the rotation angle detected by the output side rotation angle sensor.
The steering assist device applies a steering assist torque having a magnitude according to the steering torque obtained based on the angle difference to the output side shaft.
Electric power steering device. The input side shaft is provided at one end with a fitting hole into which the output side shaft is fitted, and a serration projection is formed on the inner peripheral surface of the fitting hole,
In the output side shaft, a serration projection is formed on an outer peripheral surface of an end portion fitted to the fitting hole,
The shock absorbing material is a resin coated on the outer peripheral surface of the output side shaft,
The electric power steering apparatus according to claim 3. The output side shaft is connected to the input side shaft by serration fitting and is fixed to the first shaft member having a weakened portion whose strength is partially weakened, and is fixed to the first shaft member, and the steering assist torque And a second shaft member to which
The output side rotation angle sensor detects a rotation angle of the second shaft member,
The electric power steering apparatus according to claim 3.

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