JP2016121882A - Steering column for electrically-driven power steering device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a steering column for an electrically-driven power steering device that can contain a torque sensor in a housing without generating operational failures of the torque sensor even when the dimensional tolerance of the steering column in the housing is comparatively large.SOLUTION: A steering column A1 for an electrically-driven power steering device includes: an input shaft 11; an output shaft 12; a torsion bar 13 connecting the input shaft 11 and the output shaft 12 to each other; a torque sensor 2 detecting relative rotational displacement of the output shaft 12 with respect to the input shaft 11 caused by torsional deformation of the torsion bar 13; a housing 3 containing the torque sensor 2; and an elastic member 4 disposed between the torque sensor 2 and the housing 3, the elastic member 4 supporting the torque sensor 2 in the housing 3.SELECTED DRAWING: Figure 3

Description

  The present invention relates to a support structure for a torque sensor housed in a steering column for an electric power steering apparatus.

  Of the electric power steering devices for automobiles, the column assist type is a steering column provided with an electric motor and a reduction gear for assisting steering. Among these, the worm wheel which comprises the said reduction gear is being fixed to the steering shaft accommodated in the said steering column. Driving the electric motor and the speed reducer increases the torque of the steering shaft, thereby reducing the burden on the driver's steering effort.

  The electric motor and the speed reducer are driven in accordance with a control signal output from an ECU (Electronic Control Unit) based on a detection result of a torque sensor housed in the steering column. The torque sensor is a device that detects a relative rotational displacement of the steering shaft. Some of the torque sensors are disclosed in Patent Document 1, for example, in which a rotor and a stator are housed in a synthetic resin case. In housing the torque sensor in the assembly of the steering column, the case is generally fixed to the steering column housing, and the rotor and the stator are fixed to the steering shaft. In this case, when the dimensional tolerance of the inner surface of the housing of the steering column at the time of machining is relatively large, the gap between the case of the torque sensor, the rotor, and the stator is biased in the direction perpendicular to the steering shaft. Therefore, the case, the rotor, and the stator may be brought into contact with each other due to vibrations when the vehicle travels, and an operation failure of the torque sensor may occur.

  Further, the torque sensor detects a relative rotational displacement of the steering shaft using a change in magnetic flux. Therefore, it is suggested that the detection accuracy of the torque sensor is lowered due to an unintended magnetic influence from the outside.

JP2013-113845A

  In view of the above circumstances, the present invention allows the torque sensor to be accommodated in the housing without causing an operational failure even if the dimensional tolerance in the housing of the steering column is relatively large. An object of the present invention is to provide a steering column for an electric power steering apparatus.

  A steering column for an electric power steering apparatus provided by the present invention is generated by an input shaft, an output shaft, a torsion bar that interconnects the input shaft and the output shaft, and a torsional deformation of the torsion bar. A steering column for an electric power steering apparatus, comprising: a torque sensor that detects a relative rotational displacement of the output shaft with respect to the input shaft; and a housing that houses the torque sensor, wherein the steering column is provided between the torque sensor and the housing. An elastic member is disposed, and the torque sensor is supported in the housing by the elastic member.

  According to the present invention, the case of the torque sensor is supported in the housing via the elastic member. Therefore, the torque sensor is accommodated in the housing in a state where the case is not in contact with the inner surface of the housing. Even if a dimensional tolerance in the housing at the time of processing becomes relatively large, the elastic member deforms following the shape of the inner surface of the housing, and the dimensional tolerance is absorbed by the deformation. At this time, in the torque sensor housed in the housing, the distance in the direction perpendicular to the steering axis between the case and the rotor and stator of the torque sensor is kept constant over the circumferential direction of the shaft. Therefore, even if the dimensional tolerance in the housing becomes relatively large, the torque sensor can be accommodated in the housing without causing an operation failure in the torque sensor.

  Other features and advantages of the present invention will become more apparent from the detailed description given below with reference to the accompanying drawings.

It is a longitudinal cross-sectional view which shows the steering column concerning this invention. It is a principal part perspective view which shows the torque sensor of the steering column of FIG. It is sectional drawing which follows the III-III line of FIG. It is a principal part front view which shows the elastic member of the steering column of FIG.

  An embodiment of a steering column according to the present invention will be described with reference to the accompanying drawings.

  The steering column A1 according to the present invention will be described with reference to FIGS. The steering column A1 of this embodiment includes a steering shaft 1, a torque sensor 2, a housing 3, an elastic member 4, and a speed reducer 5. FIG. 1 is a longitudinal sectional view of the steering column A1 in the steering shaft 1 direction (N1-N2 direction in FIG. 1). FIG. 2 is a perspective view showing a main part of the torque sensor 2 constituting the steering column A1. 3 is a cross-sectional view taken along line III-III in FIG. FIG. 4 is a main part front view showing the elastic member 4 constituting the steering column A1. In the present embodiment, the steering column A1 is the main configuration of the column assist type electric power steering apparatus.

  The steering shaft 1 is a rotating shaft for transmitting a steering force input from a steering wheel (not shown) to a steering gear (not shown) by a rack and pinion mechanism. By the steering gear, the rotational motion around the steering shaft 1 is converted into a linear motion along the left-right direction of the vehicle. Thereby, steering of a wheel (not shown) is achieved. The steering shaft 1 has an input shaft 11, an output shaft 12 and a torsion bar 13.

  The input shaft 11 is positioned on the input side N1 of the steering shaft 1, and the steering wheel is connected to the end of the input side N1. The output shaft 12 is positioned on the output side N2 of the steering shaft 1, and an intermediate shaft (not shown) connected to the steering gear is connected to the end of the output side N2 via a universal joint (not shown). The torsion bar 13 is a member for relatively rotating the input shaft 11 and the output shaft 12, and is located between the input shaft 12 and the output shaft 13. By the torsion bar 13, the input shaft 11 and the output shaft 12 are connected to each other on the same axis. In the present embodiment, the torsion bar 13 is included in the input shaft 11 and the output shaft 12. When the steering force from the steering wheel is input to the input shaft 11, the torsion bar 13 is elastically torsionally deformed, so that the input shaft 11 and the output shaft 12 are relatively rotated.

  The torque sensor 2 is a device that detects a relative rotational displacement of the output shaft 12 with respect to the input shaft 11 of the steering shaft 1, which is generated by elastic torsional deformation of the torsion bar 13 of the steering shaft 1. The torque sensor 2 includes a case 21, a rotor 22, a stator 23, a collector 24, and a circuit board 25. The torque sensor 2 is fixed to each end of the output side N2 of the input shaft 11 of the steering shaft 1 and the input side N1 of the output shaft 12.

  The case 21 is a member that accommodates the rotor 22, the stator 23, the collector 24, and the circuit board 25. The case 21 includes an upper case 21a and a lower case 21b. In the upper case 21a and the lower case 21b, a hole for allowing the steering shaft 1 to pass therethrough is formed in the center of each. The upper case 21a and the lower case 21b are engaged with each other to form the case 21. Case 21 is made of, for example, a synthetic resin.

  The rotor 22 and the stator 23 are both circular rotating members provided with magnets. Further, the rotor 22 and the stator 23 are arranged so that their centers are on the axis X of the steering shaft 1. The rotor 22 has a first magnet portion 22a and a first engagement portion 22b. The first magnet portion 22 a is a cylindrical magnet disposed along the outer peripheral surface of the rotor 22. The first engaging portion 22b is a portion protruding along the inner edge of the rotor 22 and in the axis X direction, and the end portion of the steering shaft 1 is fixed to the portion. In the present embodiment, the end portion on the input side N1 of the output shaft 12 of the steering shaft 1 is fixed to the first engagement portion 22b.

  The stator 23 has a second magnet part 23a and a second engagement part 23b. The second magnet part 23 a is a magnet arranged in a comb shape along the inner peripheral surface of the stator 23. The second engaging portion 23b is a portion that protrudes in the direction of the axis X along the inner edge having a smaller diameter than the inner periphery of the stator 23, and the end portion of the steering shaft 1 is fixed to the portion. In the present embodiment, the end portion on the output side N2 of the input shaft 11 of the steering shaft 1 is fixed to the second engagement portion 23b.

  The rotor 22 and the stator 23 are arranged in the case 21 so that the outer peripheral surface of the rotor 22 is covered by the inner peripheral surface of the stator 23. Therefore, the first magnet portion 22a of the rotor 22 and the second magnet portion 23a of the stator 23 face each other. Moreover, since the 1st magnet part 22a and the 2nd magnet part 23a are arrange | positioned in the non-contact state, the clearance gap is formed between this magnet part. Since the rotor 22 and the stator 23 rotate integrally with the steering shaft 1, the rotor 22 and the stator 23 rotate relative to each other. The relative rotation causes a change in the magnetic flux formed between the first magnet portion 22a and the second magnet portion 23a.

  The collector 24 and the circuit board 25 are components that detect the relative rotational displacement of the steering shaft 1 based on the change of the magnetic flux and input the detection result to the ECU (not shown) as a voltage signal. In addition to the detection result, detection results such as the traveling speed of the automobile and the rotation angle of the steering wheel are input to the ECU. The collector 24 is a metal piece that performs the function of consolidating changes in the magnetic flux. The collector 24 has a shape along a part of the outer edge of the stator 23 and is disposed on the inner surface of the lower case 21 b of the case 21. The circuit board 25 is fixed to the lower case 21b side. A Hall element 25 a is mounted on the circuit board 25. The hall element 25a has a function of converting the change in the magnetic flux collected by the collector 24 into a voltage signal. The hall element 25a and the collector 24 are arranged close to each other in the case 21 in a non-contact state.

  The housing 3 is a member that houses the steering shaft 1, the torque sensor 2, the elastic member 4, and the speed reducer 5. In the present embodiment, the reduction gear 5 is disposed on the output side N2 of the torque sensor 2.

  The elastic member 4 is a member that is disposed between the torque sensor 2 and the housing 3 and supports the torque sensor 2 in the housing 3. In the present embodiment, the elastic member 4 is a leaf spring having a curved portion. In the present embodiment, the material of the elastic member 4 is, for example, mild steel. The elastic member 4 has a pair of first support part 41 and second support part 42, respectively.

  As shown in FIGS. 3 and 4, the first support portion 41 of the elastic member 4 is a portion that sandwiches the outer surface of the case 21 of the torque sensor 2, and has a flat shape. Further, the second support portion 42 of the elastic member 4 is a portion that contacts the inner surface of the housing 3, and its shape protrudes in a mountain shape toward the outer side of the elastic member 4. Since the rotor 22 and the stator 23 of the torque sensor 2 are fixed to the input shaft 11 and the output shaft 12 of the steering shaft 1, the elastic member 4 supports the case 21 of the torque sensor 2. FIG. 4 shows the elastic member 4 in a state where no external force is acting. In this state, the separation distance lb of the second support portion 42 is set longer than the separation distance la of the first support portion 41.

  A procedure for supporting the torque sensor 2 by the elastic member 4 in the housing 3 will be described. First, the rotor 22 and the stator 23 of the torque sensor 2 are respectively fixed to the input shaft 11 and the output shaft 12 of the steering shaft 1. Next, an external force is applied to the end portion of the elastic member 4 in a direction in which the curved portion of the member closes, and the outer surface of the case 21 of the torque sensor 2 is held by the first support portion 41 of the elastic member 4. At this time, in the elastic member 4, both the separation distance la of the first support portion 41 and the separation distance lb of the second support portion 42 are shortened.

  Next, the torque sensor 2 and the elastic member 4 are accommodated in the housing 3 while the external force is applied to the elastic member 4. Next, when the action of the external force is finished, the second support portion 42 comes into contact with the inner surface of the housing 3 by the restoring force of the elastic member 4. At this time, the first support portion 41 holds the state where the case 21 is sandwiched. Through the above procedure, the torque sensor 2 is supported by the elastic member 4 in the housing 3.

  The speed reducer 5 is an electric drive device for assisting steering. The reduction gear 5 includes an electric motor 51 and a reduction gear 52. The electric motor 51 is a drive source for generating a steering assist force that is driven according to a control signal output from the ECU. In the present embodiment, the electric motor 51 is disposed above the steering shaft 1.

  The speed reducer 52 is a mechanism that decelerates the output rotation of the electric motor 51 and increases the torque of the output shaft 12 of the steering shaft 1. The speed reducer 52 includes a worm 52a and a worm wheel 52b. The worm 52a is concentrically connected to an output shaft (not shown) of the electric motor 51, and transmits the output rotation of the electric motor 51 to the worm wheel 52b. The worm wheel 52b meshes with the worm 52a to decelerate the output rotation of the electric motor 51 and increase the torque of the output shaft 12. The output shaft 12 passes through a hole provided in the center of the worm wheel 52b, and the worm wheel 52b is fixed to the output shaft 12 by fitting. In this embodiment, the worm 52a is made of metal, and the worm wheel 52b is made of synthetic resin.

  Next, the function and effect of the steering column A1 will be described.

  According to this embodiment, the case 21 of the torque sensor 2 is supported in the housing 3 via the elastic member 4. Therefore, the torque sensor 2 is accommodated in the housing 3 in a state where the case 21 is not in contact with the inner surface of the housing 3. Even if the dimensional tolerance in the housing 3 during processing becomes relatively large, the elastic member 4 deforms following the shape of the inner surface of the housing 3, and the dimensional tolerance is absorbed by the deformation. At this time, in the torque sensor 2 accommodated in the housing 3, the space in the direction perpendicular to the steering shaft 1 between the case 21 and the rotor 22 and the stator 23 of the torque sensor 2 is ensured uniformly over the circumferential direction of the shaft. . Therefore, even if the dimensional tolerance in the housing 3 becomes relatively large, the torque sensor 2 can be accommodated in the housing 3 without causing an operation failure in the torque sensor 2.

  By making the material of the elastic member 4 a magnetic material such as mild steel, the elastic member 4 functions as a magnetic shield against unintended magnetism from the outside. Therefore, it can suppress that the detection accuracy of the torque sensor 2 falls by the influence of the said magnetism.

  The steering column according to the present invention is not limited to the embodiment described above. The specific configuration of each part of the steering column according to the present invention can be variously changed in design.

A1: Steering column 1: Steering shaft 11: Input shaft 12: Output shaft 13: Torsion bar 2: Torque sensor 21: Case 21a: Upper case 21b: Lower case 22: Rotor 22a: First magnet portion 22b: First engagement Part 23: Stator 23a: Second magnet part 23b: Second engagement part 24: Collector 25: Circuit board 25a: Hall element 3: Housing 4: Elastic member 41: First support part 42: Second support part 5: Deceleration Device 51: Electric motor 52: Reducer 52a: Worm 52b: Worm wheel N1: Input side N2: Output side X: Shaft la, lb: Separation distance

Claims (1)

An input shaft;
An output shaft;
A torsion bar that interconnects the input shaft and the output shaft;
A torque sensor for detecting a relative rotational displacement of the output shaft with respect to the input shaft, which occurs due to torsional deformation of the torsion bar;
A steering column for an electric power steering device comprising a housing for accommodating the torque sensor,
An elastic member is disposed between the torque sensor and the housing,
The steering column for an electric power steering apparatus, wherein the torque sensor is supported in the housing by the elastic member.

Images