JP3645143B2 - Torque sensor - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a torque sensor suitable for detecting the steering torque in, for example, a power steering apparatus that applies a steering assist force according to the steering torque.
[0002]
[Prior art]
For example, in a power steering device for a vehicle, when the rotation of a steering wheel is transmitted to a wheel via a steering shaft, torque transmitted by the steering shaft is detected by a torque sensor, and steering is performed according to the magnitude of the detected torque. Auxiliary power is given.
[0003]
As such a torque sensor, a sensor that detects torque based on a change in magnetic resistance in accordance with a torque change has been conventionally used. A torque sensor based on the detection principle includes a first shaft, a second shaft elastically coupled to the first shaft so as to be relatively rotatable, and a first detection ring made of a magnetic material fixed to the first shaft. And a second detection ring made of a magnetic material fixed to the second shaft, and a coil covering between the opposing faces of the two detection rings, and a plurality of teeth are provided along the circumferential direction on the end face of each detection ring, The teeth of this detection ring and the teeth of the other detection ring face each other through an air gap. In this torque sensor, when the two detection rings rotate relative to each other due to torque transmission by both shafts, the facing area between the teeth of one detection ring and the teeth of the other detection ring changes. Due to the change in area, the magnetic resistance to the magnetic flux generated by the coil passing through the air gap between the teeth of both detection rings changes. Based on the change in the magnetic resistance, the torque transmitted by both shafts is detected. Furthermore, in order to compensate for fluctuations in the detected torque value due to temperature changes, a magnetic flux generating coil having the same specifications as the above coils and a magnetic circuit for detecting changes due to temperature changes in the magnetic resistance with respect to the magnetic flux are provided. .
[0004]
[Problems to be solved by the invention]
The conventional torque sensor is large in size because it requires first and second detection rings projecting radially from both shafts. In addition, since a plurality of detection rings are required, the number of parts, the number of assembly steps, an increase in cost, a complicated structure, an increase in size, and a decrease in detection accuracy due to accumulation of assembly errors become problems. In addition, in order to increase the detection sensitivity, it is necessary to increase the number of teeth provided on each detection ring, but if this is done, the projecting dimension from each shaft of each detection ring is large, resulting in an increase in detection sensitivity. Is limited. Furthermore, a dedicated magnetic circuit is required only for compensation due to temperature changes.
[0005]
An object of this invention is to provide the torque sensor which can solve the said problem.
[0006]
[Means for Solving the Problems]
The torque sensor of the present invention includes a first shaft, a second shaft that is elastically and relatively connected to the first shaft, a cylindrical member that is connected to the second shaft so as to rotate together, A coil disposed so as to surround the outer periphery of the cylindrical member, and at least a part of the cylindrical member is a magnetic flux passing portion made of a magnetic material covering the outer periphery of the first shaft, and the first shaft At least a part of the outer periphery of the cylindrical member is a magnetic material magnetic flux passage portion covered by the magnetic flux passage portion of the cylindrical member, an opening is formed in the magnetic flux passage portion of the cylindrical member, and the magnetic flux passage of the first shaft A stepped surface that overlaps the opening in the radial direction is formed in the portion, and the inner peripheral surface and the stepped surface of the opening have opposing portions that face each other through an air gap through which the magnetic flux passes, In the direction of the relative rotation axis At least one of the facing portion on the inner peripheral surface of the opening and the facing portion on the step surface is a relative rotation of both shafts so that the dimension of the air gap changes according to the change in the relative rotation amount of both shafts. Torque transmitted along both shafts is detected on the basis of a change in the magnetic resistance with respect to the magnetic flux according to a change in the size of the air gap.
As the magnetic material, for example, a soft magnetic metal material, a magnetic resin material formed by dispersing soft magnetic powder in a synthetic resin base material, or the like can be used.
According to the structure of this invention, it forms in the internal peripheral surface of the opening formed in the magnetic flux passage part made from a magnetic material in a cylindrical member, and the magnetic flux passage part in a 1st shaft by relative rotation of both shafts at the time of torque transmission. The relative position with the stepped surface changes. The inner peripheral surface and the step surface of the opening have opposing portions facing each other through an air gap, and at least one of the opposing portions follows a spiral around the relative rotation axis of both shafts. The dimension of the air gap in the relative rotation axis direction can be changed according to the change in the relative rotation amount of both shafts. Since the magnetic flux generated by the coil passes through the air gap, the magnetic resistance to the magnetic flux changes according to the change in the air gap dimension. Based on the change in the magnetic resistance, the torque transmitted by both shafts can be detected.
Opposing portions facing each other through the air gap are constituted by a step surface formed on the outer periphery of the first shaft and an inner peripheral surface of an opening formed in a cylindrical member covering the outer periphery of the first shaft. Therefore, the structure is simple, and since it does not protrude greatly from both shafts in the radial direction, the size can be reduced.
[0007]
The dimension of the opening in the relative rotational axis direction of both shafts is less than the dimension of the coil in the relative rotational axis direction of both shafts, and the opening is disposed between both ends of the coil in the relative rotational axis direction of both shafts. It is preferable.
Thereby, even if the relative position in the axial direction of the first shaft, the second shaft, and the coil fluctuates due to manufacturing tolerances and assembly tolerances, the opening can be disposed between both ends of the coils in the relative rotational axis direction of both shafts. Therefore, the fluctuation of the magnetic resistance due to the tolerance can be eliminated, and the decrease in detection accuracy can be prevented.
[0008]
It is preferable that a groove is formed along the spiral on the outer periphery of the first shaft, and the step surface is constituted by an inner side surface of the groove.
This makes it possible to form a stepped surface along the spiral simply by processing the outer periphery of the first shaft, reducing the number of parts, assembly man-hours, cost, simplifying the structure, downsizing, and reducing assembly error accumulation. Improvements can be made.
[0009]
The coil includes a first coil and a second coil of the same specification arranged in parallel along the relative rotational axis direction of both shafts, and the opening is disposed at an interval in the relative rotational axis direction of both shafts. 1 step and 2nd opening are comprised, The said level | step difference surface is comprised by each of the mutually opposing internal side surfaces in the said groove | channel, The 1st opening is comprised by one of the mutually opposing internal side surfaces The second opening is disposed so as to overlap with the step surface in the radial direction, and the second opening is disposed so as to overlap with the step surface constituted by the other of the opposing inner side surfaces in the radial direction. A first air gap is formed between the facing portions of the inner peripheral surface and the step surface, and a second air gap is formed between the inner peripheral surface of the second opening and the facing portions of the step surface. The first coil is the first coil. Through the air gap The second coil is disposed at a position where the magnetic flux is generated, and the second coil is disposed at a position where the magnetic flux passing through the second air gap is generated. Are equal to each other when both shafts are at the detection origin position, and the absolute value of the amount of change in both air gap dimensions at the time of relative rotation of both shafts is equal to each other, and the first value corresponding to the change in the first air gap size is The torque transmitted by both shafts is detected based on the difference between the change in magnetic resistance with respect to the magnetic flux generated by one coil and the change in magnetic resistance with respect to the magnetic flux generated by the second coil according to the change in the second air gap dimension. It is preferable.
According to this configuration, the step surface formed by one of the opposing inner side surfaces of the groove along the spiral overlaps the first opening in the radial direction, and the step formed by the other of the inner side surfaces Since the surface overlaps the second opening in the radial direction, when both shafts rotate relative to each other during torque transmission, one of the first air gap dimension and the second air gap dimension increases according to the relative rotation amount, The other decreases according to the relative rotation amount. According to the change of each air gap dimension, the magnetic resistance to the magnetic flux generated by each coil changes. Therefore, the torque detection sensitivity is increased by detecting the torque based on the difference between the change in magnetoresistance corresponding to the dimensional change of the first air gap and the change in magnetoresistance corresponding to the dimensional change of the second air gap. be able to. In addition, since both magnetoresistances change by the same amount due to temperature changes, the detected torque fluctuation due to temperature fluctuations can be offset by detecting the torque based on the difference between the two magnetoresistance changes.
[0010]
The plurality of grooves are formed to be arranged in parallel at equal intervals in the circumferential direction of the first shaft, and the plurality of first openings are provided to be arranged in parallel at equal intervals in the circumferential direction of the cylindrical member. A plurality of the second openings are provided so as to be arranged in parallel at equal intervals in the circumferential direction of the cylindrical member, and in the relative rotation range of both shafts corresponding to the torque detection range, the respective step surfaces overlap each other. The circumferential interval between the first opening that overlaps one step surface and the second opening that overlaps the other step surface in each groove is less than 1/2 of the circumferential interval between adjacent first openings. It is preferable that
According to this configuration, in the relative rotation range of both shafts corresponding to the torque detection range, the step surface where each opening overlaps is made single, so that the change in magnetic resistance according to the relative rotation amount of both shafts is achieved. Abrupt fluctuations can be prevented. Furthermore, since the circumferential interval between the first opening that overlaps one step surface and the second opening that overlaps the other step surface in each groove is less than ½ of the circumferential interval between adjacent first openings, The range in which both shafts can be rotated relative to each other without overlapping the second opening on one of the stepped surfaces can be made larger than in the case of being 1/2 or more. Therefore, if the torque detection range corresponding to the relative rotation range of both shafts is constant, the distance between both step surfaces in each groove can be reduced. Thereby, the number of grooves can be increased without increasing the size, the number of openings can be increased, and the detection sensitivity can be improved.
[0011]
DETAILED DESCRIPTION OF THE INVENTION
A torque sensor 1 shown in FIGS. 1 to 4 detects a steering torque in a power steering device of a vehicle. The torque sensor 1 includes a housing 2, a first shaft 3, and a second shaft 4. The first shaft 3 is supported by the housing 2 via a bearing 5 and is supported by an inner periphery of a recess 4 a formed at one end of the second shaft 4 via a bush 6. The second shaft 4 is supported by the housing 2 via a bearing 7. A steering assist force is applied according to the detected torque.
[0012]
A torsion bar 8 is inserted into the axial hole 3 a formed in the first shaft 3 and the recess 4 a of the second shaft 4. One end of the torsion bar 8 is connected to the first shaft 3 by a pin 9 so as to rotate along with the first shaft 3, and the other end is connected via the serration 10 to rotate along with the second shaft 4. Thus, the second shaft 4 is disposed coaxially with the first shaft 3 and is elastically coupled to the first shaft 3 so as to be relatively rotatable. One end side of the first shaft 3 is connected to a steering wheel (not shown), and the other end side of the second shaft 4 is connected to a steering gear such as a rack and pinion type steering gear. Thereby, the rotation of the steering wheel for steering is transmitted to the wheels via the first and second shafts 3 and 4, and the steering angle changes.
[0013]
A cylindrical tubular member 11 is connected to the second shaft 4 so as to rotate together. In the present embodiment, the cylindrical member 11 is fitted to the outer periphery on one end side of the second shaft 4 and integrated by an appropriate fixing means such as a screw or welding. The cylindrical member 11 is disposed coaxially with the first and second shafts 3 and 4 in the housing 2 and covers the outer periphery of the first shaft 3.
[0014]
A first coil holder 31 made of a magnetic material and a second coil holder 32 made of a magnetic material are inserted into the inner periphery of the housing 2. As shown in FIG. 2, each of the coil holders 31 and 32 includes cylindrical outer peripheral portions 31a and 32a, and annular peripheral wall portions 31b and 32b extending inwardly from one end side of the outer peripheral portions 31a and 32a, and It is comprised from the annular | circular shaped cover parts 31c and 32c which go inward from the other end side of the outer peripheral parts 31a and 32a. Each coil holder 31 is sandwiched via a leaf spring 54 by a step 2 a formed on the inner periphery of the housing 2 and a retaining ring 53 fitted to the inner periphery of the housing 2, thereby being fixed to the housing 2. The
[0015]
A first coil 33 and a second coil 34 having the same specifications are arranged in parallel along the relative rotational axis direction of both shafts 3 and 4. That is, the first coil 33 is inserted into the inner periphery of the first coil holder 31, and the second coil 34 is inserted into the inner periphery of the second coil holder 32. Each of the coils 33 and 34 is configured by winding conductive wires 33a and 34a around bobbins 33b and 34b made of an insulating material around the axis of the first shaft 3. Each coil holder 31 and 32 and the coils 33 and 34 are arrange | positioned so that the outer periphery of the said cylindrical member 11 may be enclosed through a clearance gap.
[0016]
The cylindrical member 11 is made of a magnetic material, and thus has a magnetic flux passage portion through which the magnetic flux generated by each of the coils 33 and 34 passes. The cylindrical member 11 may be composed of a magnetic material portion and a non-magnetic material portion. In short, at least a part of the cylindrical member 11 passes through the magnetic material magnetic flux covering the outer periphery of the first shaft 3. It only has to be a part.
[0017]
The first shaft 3 is made of a magnetic material, and thus has a magnetic flux passage portion through which the magnetic flux generated by the coils 33 and 34 passes on the outer periphery thereof. The magnetic flux generating part of the first shaft 3 is covered by the magnetic flux passing part of the cylindrical member 11 via the gap δ. The first shaft 3 may be composed of a magnetic material portion and a non-magnetic material portion. In short, at least a part of the outer periphery of the first shaft 3 is a gap δ due to the magnetic flux passage portion of the cylindrical member 11. What is necessary is just to be made into the magnetic flux passage part made from a magnetic material covered via.
[0018]
A plurality of first openings 41 and a plurality of second openings 42 are formed as openings in the magnetic flux passage portion of the cylindrical member 11. The first opening 41 and the second opening 42 are arranged at an interval in the relative rotational axis direction of the shafts 3 and 4. The first openings 41 are juxtaposed at equal intervals in the circumferential direction of the tubular member 11. The second openings 42 are arranged in parallel with each other at equal intervals in the circumferential direction of the cylindrical member 11. The shapes and dimensions of the openings 41 and 42 are equal to each other. In this embodiment, the openings 41 and 42 have a shape along a quadrilateral having an edge parallel to the rotation axis direction and an edge parallel to the rotation circumferential direction of the shafts 3 and 4. .
[0019]
As shown in FIG. 2, the dimension L1 of each opening 41, 42 in the relative rotational axis direction of both shafts 3, 4 is less than the dimension L2 of the coils 33, 34 in the relative rotational axis direction of both shafts 3, 4. The first opening 41 is disposed between both ends of the first coil 33 in the relative rotational axis direction of the shafts 3 and 4, and the second opening 42 is disposed at both ends of the second coil 34 in the relative rotational axis direction of the shafts 3 and 4. Arranged between. Thereby, even if the relative position in the axial direction of the first shaft 3, the second shaft 4, the first coil 33, and the second coil 34 fluctuates due to manufacturing tolerances and assembly tolerances, the relative rotational axes of the shafts 3, 4 Openings 41, 42 can be arranged between the ends of the coils 33, 34 in the direction. Therefore, fluctuations in magnetic resistance, which will be described later due to tolerances, can be eliminated, and deterioration in detection accuracy can be prevented.
[0020]
On the outer periphery of the magnetic flux passage portion of the first shaft 3, step surfaces 51 and 52 that overlap the openings 41 and 42 in the radial direction are formed. That is, on the outer periphery of the first shaft 3, a plurality of grooves 55 are formed along the spiral around the relative rotational axis of the shafts 3 and 4. The grooves 55 are arranged in parallel at equal intervals in the circumferential direction of the first shaft 3. The step surfaces 51 and 52 are constituted by the inner side surfaces facing each other in each groove 55.
[0021]
As shown in FIG. 3, each first opening 41 is disposed so as to overlap in a radial direction with a step surface 51 formed by one inner side surface in each groove 55, and the second opening 42 is formed in each groove 55. It arrange | positions so that it may overlap with the level | step difference surface 52 comprised by the other internal side surface in radial direction. In the relative rotation range of the shafts 3 and 4 corresponding to the torque detection range, the dimensions and arrangement pitch of the grooves 55 and the openings 41 and 42 are determined so that each of the openings 41 and 42 faces only a single step surface. It has been. In other words, in the relative rotation range of both shafts 3 and 4 corresponding to the torque detection range, each opening 41 and 42 faces a step surface other than the step surface facing when both shafts 3 and 4 are at the detection origin position. Never do.
[0022]
The circumferential interval θb between the first opening 41 facing one step surface 51 and the second opening 42 facing the other step surface 52 in each groove 55 is equal to the circumferential interval θa of the adjacent first openings 41. It is assumed that it is less than 1/2.
[0023]
The inner peripheral surfaces of the openings 41 and 42 and the step surfaces 51 and 52 have opposing portions 41a, 42a, 51a, and 52a facing each other through air gaps α1 and α2 through which the magnetic flux passes. In each groove 55, a space between the facing portion 41 a on the inner peripheral surface of the first opening 41 and the facing portion 51 a on the one step surface 51 is defined as a first air gap α 1, and the facing portion on the inner peripheral surface of the second opening 42. A second air gap α2 is defined between 42a and the facing portion 52a on the other step surface 52. The dimension of the first air gap α1 and the dimension of the second air gap α2 in the direction of the relative rotation axis of the shafts 3 and 4 are as follows when the shafts 3 and 4 are at the detection origin position, that is, when the steering angle is zero. Are equal to each other.
[0024]
The first coil 33 is disposed at a position where a magnetic flux passing through the first air gap α1 is generated. The second coil 34 is disposed at a position where a magnetic flux passing through the second air gap α2 is generated. Thereby, as indicated by a two-dot chain line β in FIG. 2, the magnetic flux generated by the first coil 33 is changed to the first coil holder 31, the magnetic flux passing portion of the cylindrical member 11, the magnetic flux passing portion of the first shaft 3, and the first By passing through the air gap α1, a first magnetic circuit including the first coil holder 31, the magnetic flux passage portion of the cylindrical member 11, the magnetic flux passage portion of the first shaft 3, and the first air gap α1 as components. Composed. Further, the magnetic flux generated by the second coil 34 generates magnetic flux that passes through the second coil holder 32, the magnetic flux passage portion of the cylindrical member 11, the magnetic flux passage portion of the first shaft 3, and the second air gap α2. A second magnetic circuit including the second coil holder 32, the magnetic flux passage portion of the cylindrical member 11, the magnetic flux passage portion of the first shaft 3, and the second air gap α2 is configured.
[0025]
According to the said structure, the opposing parts 51a and 52a in each level | step difference surface 51 and 52 follow a spiral, and the opposing parts 41a and 42a in the internal peripheral surface of each opening 41 and 42 follow the circumferential direction of both the shafts 3 and 4. Therefore, the dimensions of the air gaps α1 and α2 in the direction of the relative rotation axis of both shafts 3 and 4 change according to the change in the relative rotation amount of both shafts 3 and 4. That is, due to the relative rotation of the shafts 3 and 4 during torque transmission, the inner peripheral surface of the openings 41 and 42 formed in the magnetic material magnetic flux passage portion of the cylindrical member 11 and the magnetic flux passage portion of the first shaft 3. The relative position with respect to the step surfaces 51 and 52 formed on the surface changes. In FIG. 3, two-dot chain lines 51 ′ and 52 ′ indicate a change in position of the step surfaces 51 and 52 when the shafts 3 and 4 are relatively rotated in one direction. 4 shows the change in position of the step surfaces 51 and 52 when they are relatively rotated in one direction. The inner peripheral surfaces of the openings 41, 42 and the step surfaces 51, 52 have opposing portions 41a, 42a, 51a, 52a facing each other through the air gaps α1, α2, and the opposing portions 51a of the step surfaces 51, 52. , 52a is along a spiral around the relative rotational axis of the shafts 3 and 4, so that the dimensions of the air gaps α1 and α2 in the direction of the relative rotational axis of the shafts 3 and 4 are the relative rotational amounts of the shafts 3 and 4. It can be changed in response to changes. Further, the step surface 51 constituted by one of the opposing inner side surfaces of the groove 55 along the spiral overlaps the first opening 41 in the radial direction, and the step surface constituted by the other of the inner side surfaces. 52 overlaps with the second opening 42 in the radial direction, so that when the shafts 3 and 4 are rotated relative to each other during torque transmission, the size of the first air gap α1 and the size of the second air gap α2 in the relative rotation axis direction are One increases according to the relative rotation amount, and the other decreases according to the relative rotation amount.
[0026]
Therefore, when the shafts 3 and 4 rotate relatively in one direction, the first air gap α1 increases and the second air gap α2 decreases as the relative rotation amount increases. When the shafts 3 and 4 rotate relatively in the other direction, the first air gap α1 decreases and the second air gap α2 increases as the relative rotation amount increases. That is, the absolute value of the amount of change in the dimensions of the air gaps α1 and α2 increases as the relative rotation amount of the shafts 3 and 4 increases. Further, the absolute values of the change amounts of the dimensions of the air gaps α1 and α2 when the shafts 3 and 4 are relatively rotated are made equal to each other.
[0027]
Since the magnetic flux generated by the coils 33 and 34 passes through the air gaps α1 and α2, the magnetic resistance to the magnetic flux changes according to the change in the dimensions of the air gaps α1 and α2. Based on the change in the magnetic resistance, the torque transmitted by both shafts 3 and 4 can be detected. In addition, the torque detection sensitivity is improved by detecting the torque based on the difference between the change in the magnetic resistance corresponding to the dimensional change of the first air gap α1 and the change in the magnetic resistance corresponding to the dimensional change of the second air gap α2. Can be increased. Further, since both the magnetoresistances change by the same amount due to the temperature change, the detected torque fluctuation due to the temperature fluctuation can be offset by detecting the torque based on the difference between the two magnetoresistance changes.
[0028]
In the present embodiment, the coils 33 and 34 are connected to a printed circuit board 35 attached to the outer surface side of the housing 2 via wiring. A signal processing circuit shown in FIG. 4 is formed on the printed circuit board 35. In the circuit, the first coil 33 is connected to the oscillator 46 through the resistor 45, the second coil 34 is connected to the oscillator 46 through the resistor 47, and the coils 33 and 34 are connected to the differential amplifier circuit 48. The Thus, when the torsion bar 8 is twisted by torque transmission between the shafts 3 and 4 and the shafts 3 and 4 are elastically rotated relative to each other, the air gaps α1 in the relative rotational axis directions of the shafts 3 and 4 , Α2 changes. The magnetoresistance of the first and second magnetic circuits changes due to the dimensional change of the air gaps α1 and α2. Based on the change in the magnetic resistance, the outputs of the first and second coils 33 change. The change in the magnetic resistance with respect to the magnetic flux generated by the first coil 33 according to the change in the size of the first air gap α1, and the magnetic resistance with respect to the magnetic flux generated in the second coil 34 according to the change in the size of the second air gap α2. Based on the output of the differential amplifier circuit 48 corresponding to the difference from the change in torque, the torque transmitted by both shafts 3 and 4 is detected. A steering assist force is applied by an unillustrated actuator such as a motor driven in accordance with a signal corresponding to the transmission torque output from the differential amplifier circuit 48. A known configuration can be adopted as the steering assist force applying mechanism.
[0029]
According to the above configuration, the opposing portions 41 a, 42 a, 51 a, 52 a facing each other through the air gaps α 1, α 2 are the step surfaces 51, 52 formed on the outer periphery of the first shaft 3 and the first shaft 3. Since it is comprised by the inner peripheral surface of the opening 41 and 42 formed in the cylindrical member 11 which covers the outer periphery of this, while simplifying a structure, it does not protrude greatly from both shafts 3 and 4 in the radial direction, Miniaturization can be achieved. In addition, the step surfaces 51 and 52 along the spiral can be formed simply by machining the outer periphery of the first shaft 3, and the number of parts, the number of assembly steps, the cost can be reduced, the structure can be simplified, the size can be reduced, and the assembly error can be reduced. The detection accuracy can be improved.
Further, in the relative rotation range of both shafts 3 and 4 corresponding to the torque detection range, the step surface where each of the openings 41 and 42 overlap is made single, so that it corresponds to the relative rotation amount of both shafts 3 and 4. Abrupt fluctuations in the change in magnetoresistance can be prevented. Further, the circumferential interval θb between the first opening 41 facing one step surface 51 and the second opening 42 facing the other step surface 52 in each groove 55 is the circumferential interval between the adjacent first openings 41. Since it is less than ½ of θa, the range in which both shafts 3 and 4 can be relatively rotated without overlapping the second opening 42 on one stepped surface 51 can be made larger than when ½ or more. . Therefore, if the torque detection range corresponding to the relative rotation range of both shafts 3 and 4 is constant, the interval between both step surfaces 51 and 52 in each groove 55 can be reduced. Accordingly, the number of grooves 55 can be increased without increasing the size, the number of openings 41 and 42 can be increased, and the detection sensitivity can be improved.
[0030]
The present invention is not limited to the above embodiment. For example, one end side of the first shaft 3 may be connected to the steering gear, and the other end side of the second shaft 4 may be connected to the steering wheel. Further, the opposing portions 41a and 42a on the inner peripheral surfaces of the openings 41 and 42 are formed along the spirals around the relative rotational axes of the shafts 3 and 4 together with the opposing portions 51a and 52a on the step surfaces 51 and 52, The opposing portions 51a, 52a on the surfaces 51, 52 are set along the rotational circumferential direction of the shafts 3, 4, and the opposing portions 41a, 42a on the inner peripheral surfaces of the openings 41, 42 are the relative rotational axes of the shafts 3, 4. You may form along the surrounding spiral. In addition, the torque sensor of the present invention may be used to detect torque other than the steering device.
[0031]
【The invention's effect】
ADVANTAGE OF THE INVENTION According to this invention, the torque sensor which can aim at the simplification of a structure, size reduction, the number of parts, the number of assembly steps, cost reduction, detection accuracy, and an improvement in sensitivity can be provided.
[Brief description of the drawings]
FIG. 1 is a sectional view of a torque sensor according to an embodiment of the present invention.
FIG. 2 is a cross-sectional view of a main part of a torque sensor according to an embodiment of the present invention.
FIG. 3 is a partial development view of a cylindrical member of the torque sensor according to the embodiment of the present invention.
FIG. 4 is a circuit diagram of a torque sensor according to an embodiment of the present invention.
[Explanation of symbols]
1 Torque sensor
3 First shaft
4 Second shaft
11 Tubular member
33 First coil
34 Second coil
41 1st opening
42 Second opening
51, 52 Step surface
α1 1st air gap
α2 2nd air gap

Claims (5)

A first shaft;
A second shaft that is elastically and relatively rotatably coupled to the first shaft;
A cylindrical member connected to the second shaft so as to rotate along with the second shaft;
A coil disposed so as to surround the outer periphery of the cylindrical member,
At least a part of the cylindrical member is a magnetic flux passage made of a magnetic material that covers the outer periphery of the first shaft,
At least a part of the outer periphery of the first shaft is a magnetic flux passage made of a magnetic material covered by the magnetic flux passage of the cylindrical member,
An opening is formed in the magnetic flux passage part of the cylindrical member,
A stepped surface overlapping with the opening in the radial direction is formed in the magnetic flux passage portion of the first shaft,
The inner peripheral surface and the step surface of the opening have opposing portions facing each other through an air gap through which the magnetic flux passes,
The dimension of the air gap in the direction of the relative rotation axis of both shafts changes at least of the facing portion on the inner peripheral surface of the opening and the facing portion on the step surface so as to change according to the change in the relative rotation amount of both shafts. One is formed along a spiral around the relative rotational axis of both shafts,
A torque sensor for detecting a torque transmitted by both shafts based on a change in magnetic resistance with respect to the magnetic flux in accordance with a change in dimension of the air gap. The dimension of the opening in the relative rotational axis direction of both shafts is less than the dimension of the coil in the relative rotational axis direction of both shafts, and the opening is disposed between both ends of the coil in the relative rotational axis direction of both shafts. The torque sensor according to claim 1. The torque sensor according to claim 1 or 2, wherein a groove is formed along the spiral on the outer periphery of the first shaft, and the step surface is constituted by an inner side surface of the groove. As the coil, comprising a first coil and a second coil of the same specification arranged in parallel along the relative rotational axis direction of both shafts,
As the opening, provided with a first opening and a second opening arranged with an interval in the relative rotational axis direction of both shafts,
The stepped surfaces are formed by the opposing internal side surfaces of the groove, and the first opening is disposed so as to overlap the stepped surface formed by one of the opposing internal side surfaces in the radial direction. And the second opening is disposed so as to overlap in a radial direction with a step surface constituted by the other of the opposing inner side surfaces,
Between the inner peripheral surface of the first opening and each facing portion of the step surface is a first air gap, and between the inner peripheral surface of the second opening and each facing portion of the step surface is a second air gap,
The first coil is disposed at a position for generating a magnetic flux passing through the first air gap, and the second coil is disposed at a position for generating a magnetic flux passing through the second air gap. The first air gap dimension and the second air gap dimension are equal to each other when both shafts are at the detection origin position, and the absolute values of changes in both air gap dimensions at the time of relative rotation of both shafts are equal to each other,
The difference between the change in magnetoresistance with respect to the magnetic flux generated by the first coil in accordance with the change in the first air gap dimension and the change in magnetoresistance with respect to the magnetic flux generated in the second coil according to the change in the second air gap dimension. The torque sensor according to claim 3, wherein the torque transmitted by both shafts is detected based on the torque sensor. A plurality of the grooves are formed so as to be arranged at equal intervals in the circumferential direction of the first shaft,
A plurality of the first openings are provided so as to be arranged at equal intervals in the circumferential direction of the cylindrical member,
A plurality of the second openings are provided so as to be arranged in parallel at equal intervals in the circumferential direction of the cylindrical member,
In the relative rotation range of both shafts corresponding to the torque detection range, the step surface where each opening overlaps is made single,
The circumferential interval between the first opening that overlaps one step surface and the second opening that overlaps the other step surface in each groove is less than ½ of the circumferential interval between adjacent first openings. 4. The torque sensor according to 4.

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