JP2001255218A - Torque sensor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a torque sensor with excellent detection accuracy and detection sensitivity. SOLUTION: A magnetic flux passage part made of magnetic material on the periphery of a first shaft 3 is surrounded, with a gap left between, by an outer tube part made of insulating synthetic resin of a tubular member 12 rotating together with a second shaft 4. The periphery of the member 12 is surrounded by coils 33, 34 that induce magnetic flux to set up an alternating magnetic field. Elastic relative rotation of the two shafts 3, 4 changes radially- overlapping areas of the periphery of the passage part joining to an edge of a groove 40 formed in the passage part with openings 43, 44 in a conductive inner tube part made of nonmagnetic metal embedded in the outer tube part, and accordingly changes magnetic flux passing through the passage part. Torque transmitted between the two shafts 3, 4 is detected based on the change of the flux.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque sensor suitable for detecting a steering torque in, for example, a power steering device for applying a steering assist force according to the steering torque.

[0002]

2. Description of the Related Art In a power steering apparatus for a vehicle, for example, when the rotation of a steering wheel is transmitted to wheels via a steering shaft, torque transmitted by the steering shaft is detected by a torque sensor, and the magnitude of the detected torque is increased. The steering assist force is applied accordingly.

For example, in the torque sensors disclosed in Japanese Patent Application Laid-Open Nos. 8-240481, 9-61263, and 9-61264, a first rotating shaft made of a magnetic metal material is connected to a torsion bar. A cylindrical member made of a non-magnetic metal material having conductivity is connected to the second rotating shaft connected so as to rotate together, and a magnetic flux generating coil surrounding the cylindrical member is provided, and a window is formed in the cylindrical member. A groove is formed on the outer periphery of the first rotating shaft surrounded by the cylindrical member. The overlapping state of the window and the groove is changed by the relative rotation of the two rotating shafts due to the torque transmission. Since the magnetic flux reaching the first rotating shaft is blocked by the cylindrical member, the magnetic flux passing through the first rotating shaft is changed by the change in the overlapping state between the window and the groove due to the relative rotation of the two rotating shafts according to the transmission torque. Change. Further, the magnetic flux reaching the first rotating shaft is also blocked by the eddy current generated in the cylindrical member in the alternating magnetic field generated due to the generation of the magnetic flux of the coil. That is, the magnetic flux passing through the first rotating shaft changes according to the relative rotation of the two rotating shafts according to the transmission torque. The coil output is changed by electromagnetic induction due to the change in magnetic flux, and the transmission torque is detected based on the change in the coil output.

[0004]

In the above conventional torque sensor, a gap is formed between the outer periphery of the first rotating shaft and the inner periphery of the cylindrical member. However, the gap is small because the magnetic flux passes therethrough. Therefore, when the axis of the first rotation shaft and the axis of the second rotation shaft are relatively inclined due to the action of an external force or the like, the outer circumference of the first rotation shaft and the inner circumference of the cylindrical member may make metal contact. is there. Since the relative rotation of both rotating shafts is hindered by the metal contact, there is a problem that torque detection accuracy is reduced.

An object of the present invention is to provide a torque sensor that can solve the above-mentioned problem.

[0006]

A torque sensor according to the present invention comprises a first shaft, a second shaft coaxially and elastically connected to the first shaft so as to be relatively rotatable, and a coaxial shaft to the second shaft. A cylindrical member connected so as to rotate together with the core, and a coil arranged to surround the outer periphery of the cylindrical member and generating a magnetic flux so as to generate an alternating magnetic field, and the cylindrical member includes An insulating synthetic resin outer cylinder portion disposed so as to surround the outer periphery of the first shaft with a gap therebetween, and a conductive nonmagnetic metal material inner cylinder portion embedded in the outer cylinder portion. A magnetic flux passage portion made of a magnetic metal material arranged at a passage position of the generated magnetic flux of the coil by the outer periphery of the first shaft, and the inner cylindrical portion surrounds the magnetic flux passage portion. Arranged at the position where the magnetic flux generated by the coil passes A groove is formed in the magnetic flux passage portion along the direction of the relative rotation axis of both shafts, and an opening is formed in the magnetic flux restriction portion. The overlapping area between the outer periphery of the magnetic flux passage portion connected to the edge of the groove along the opening and the opening is changed according to the relative rotation of the two shafts, so that the groove and the opening partially overlap in the radial direction of the two shafts. And the torque transmitted by both shafts is detected based on a change in the magnetic flux passing through the magnetic flux passing portion according to a change in the overlapping area. As the magnetic metal material forming the magnetic flux passage portion of the first shaft, for example, a soft magnetic metal material having excellent magnetic characteristics required for forming the torque sensor can be used. As the insulating synthetic resin material constituting the outer cylindrical portion, it is preferable to use a material having a small friction at the time of contact with the magnetic flux passage portion and having excellent wear resistance. As the conductive non-magnetic metal material forming the inner cylindrical portion, a paramagnetic metal material having excellent conductivity and low magnetic permeability such as aluminum can be used. In the above configuration, by the relative rotation of the two shafts during torque transmission, the groove formed in the magnetic flux passage portion of the first shaft and the opening formed in the magnetic flux regulating portion of the inner cylinder that rotates together with the second shaft. The state of overlap changes.
Thereby, in the radial direction of both shafts, the overlapping area between the outer periphery of the magnetic flux passage portion connected to the edge of the groove and the opening changes according to the relative rotation of both shafts. Since the magnetic flux passing portion is made of a magnetic material and the inner cylindrical portion is made of a non-magnetic material, the magnetic flux passing through the magnetic flux passing portion changes due to a change in the overlapping area. Further, the magnetic flux reaching the magnetic flux passage is also blocked by an eddy current generated in the conductive inner cylinder portion in an alternating magnetic field generated due to the generation of the magnetic flux of the coil. Thus, the magnetic flux passing through the magnetic flux passing portion can be changed according to the change in the overlapping area. Since the area change corresponds to the relative rotation of both shafts corresponding to the transmission torque, the torque transmitted by both shafts can be detected based on the magnetic flux change. Since the outer cylinder in which the inner cylinder is embedded is insulative, eddy current does not occur and does not affect torque detection. According to the above configuration, since the outer cylindrical portion surrounding the outer periphery of the first shaft through the gap is made of a synthetic resin, the axis of the first shaft and the axis of the second shaft are relatively moved by the action of an external force or the like. Even when the first shaft is inclined, the outer periphery of the first shaft is in contact with the synthetic resin. Therefore, the frictional force for preventing the relative rotation of the two shafts at the contact portion can be reduced as compared with the case where the metal members are in contact with each other, and a decrease in torque detection accuracy can be prevented.

A coil holder made of a magnetic material for holding the coil is provided. The coil holder includes a cylindrical outer peripheral portion surrounding the coil, a portion extending inward from one end of the outer peripheral portion, and an outer peripheral portion. Inward from the other end side of the two shafts, in the direction of the relative rotation axis of both shafts,
The size of the opening is larger than the size of the coil and smaller than the size of the coil holder, the opening is arranged between both ends of the coil holder, and the coil is preferably arranged between both ends of the opening. . This allows
Even if the relative positions in the axial direction of the first shaft, the second shaft, the cylindrical member, and the coil fluctuate due to manufacturing tolerances and assembly tolerances, the passage of the magnetic flux generated by the coil through the opening in the relative rotational axis direction of both shafts. Can be placed in Therefore, fluctuation due to the tolerance of the magnetic flux passing through the magnetic flux passing portion can be eliminated, and a decrease in detection accuracy can be prevented.

[0008] The opening has a shape along a quadrilateral having an edge parallel to the rotation axis direction of both shafts and an edge parallel to the rotation circumferential direction, and the opening is formed in the relative rotation axis direction of both shafts. When both shafts are located at the detection origin position where both shafts are not relatively rotated, the edge along the relative rotation axis of both shafts in the groove is located at the center of the opening along the relative rotation axis of both shafts. And it is preferable to be arranged so as to overlap in the radial direction. Thus, the torque corresponding to the relative rotation amount can be detected both when the two shafts rotate relative to each other in one direction and when the two shafts rotate relative to each other.

[0009] As the coil, a first coil and a second coil of the same specification are arranged in parallel along the direction of the relative rotation axis of the two shafts, and the openings are arranged at intervals in the direction of the relative rotation axis of the two shafts. First opening and second
An opening, wherein the first coil is arranged at a position where a magnetic flux passing through the first opening is generated, and the second coil is arranged at a position where a magnetic flux passing through the second opening is generated.
The opening and the outer circumference of the magnetic flux passing portion connected to the edge of the groove increase the overlapping area with each other when both shafts rotate in one direction, and with each other when both shafts rotate relative to each other. Are relatively arranged so that the overlapping area is reduced,
The second opening and the outer periphery of the magnetic flux passing portion connected to the edge of the groove reduce the overlapping area with each other when the two shafts relatively rotate in one direction, and when the two shafts relatively rotate in the other direction. The first and second shafts are arranged relative to each other so as to increase the overlapping area with each other.
The absolute value of the change in the overlap area between the opening and the outer periphery of the magnetic flux passage portion and the absolute value of the change in the overlap area between the second opening and the outer periphery of the magnetic flux passage portion are made equal to each other, and according to the change in the overlap area. Changes in the magnetic flux passing through the magnetic flux passing portion,
It is preferable that the torque transmitted by both shafts is detected based on a difference between a change in the magnetic flux passing through the magnetic flux passing portion and a change in the overlapping area. According to this configuration,
When both shafts rotate in one direction during torque transmission,
The overlapping area between the first opening and the outer periphery of the magnetic flux passing portion connected to the edge of the groove increases according to the relative rotation amount, and the overlapping area between the second opening and the outer periphery of the magnetic flux passing portion connected to the edge of the groove decreases. When the two shafts rotate relative to each other in the other direction during torque transmission, the overlapping area between the first opening and the outer periphery of the magnetic flux passage decreases in accordance with the amount of relative rotation, and the overlapping area between the second opening and the outer periphery of the magnetic flux passage increases. Increase. The magnetic flux passing through the magnetic flux passage changes according to the change of each overlapping area. The absolute value of the change in the overlap area between the first opening and the outer periphery of the magnetic flux passage portion and the absolute value of the change in the overlap area between the second opening and the outer periphery of the magnetic flux passage portion during relative rotation of the two shafts. Are equal to each other. Therefore, the change in the magnetic flux passing through the magnetic flux passage portion according to the change in the overlapping area between the first opening and the outer periphery of the magnetic flux passage portion, and the change in the magnetic flux passing according to the change in the overlap area between the second opening and the outer periphery of the magnetic flux passage portion. The torque transmitted by both shafts can be detected based on the difference from the change in the magnetic flux passing through the section, and the torque detection sensitivity can be increased. Moreover, when the temperature fluctuates, the magnetic flux passing through the magnetic flux passing portion overlapping the first opening and the magnetic flux passing through the magnetic flux passing portion overlapping the second opening change by the same amount. , The fluctuation of the detected torque due to the temperature fluctuation can be offset.

A plurality of the first openings are formed in parallel at equal intervals in the circumferential direction of the cylindrical member, and the second openings are arranged in parallel at equal intervals in the circumferential direction of the cylindrical member. And a plurality of the grooves are provided so as to be arranged in parallel at equal intervals in a circumferential direction of the first shaft, and a circumferential dimension of each groove is equal to a circumferential dimension of the magnetic flux passage portion between the grooves. And the circumferential dimension of the magnetic flux passage between the grooves is made larger than the circumferential dimension of each opening. Each second opening is arranged in the circumferential direction, and in the relative rotation range of both shafts corresponding to the torque detection range, each first opening overlaps one edge of the groove along the relative rotation axis of both shafts, 2
The opening is preferably arranged so as to overlap the other edge of the groove along the axis of relative rotation of the two shafts. Thereby, the number of the first and second openings and the grooves can be increased to improve the torque detection sensitivity.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A torque sensor 1 shown in FIGS.
Detects the steering torque in the power steering device of the vehicle. The torque sensor 1 includes a housing 2 and
A first shaft 3 and a second shaft 4 are provided. 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.

A torsion bar 8 is inserted into an axial hole 3 a formed in the first shaft 3 and a concave portion 4 a of the second shaft 4. One end of the torsion bar 8 is connected by a pin 9 so as to rotate with the first shaft 3, and the other end is connected through the serration 10 to rotate with the second shaft 4. This allows
The second shaft 4 is arranged coaxially with the first shaft 3 and is elastically connected to the first shaft 3 so as to be relatively rotatable. One end of the first shaft 3 is connected to a steering wheel (not shown), and the other end of the second shaft 4 is connected to a steering gear such as a rack and pinion steering gear. Thereby, the rotation of the steering wheel for steering is first,
The power is transmitted to the wheels via the second shafts 3 and 4, and the steering angle changes.

The second shaft 4 is connected to a cylindrical member 12 so as to rotate coaxially with the cylindrical member 12.
In the present embodiment, the cylindrical member 12 is press-fitted to the outer periphery of one end of the second shaft 4, but may be integrated by a suitable fixing means such as a screw. 2 and 3 (1),
As shown in (2), the cylindrical member 12 is composed of a cylindrical outer cylindrical portion 12a made of insulating synthetic resin and a cylindrical inner cylindrical portion 12b made of a conductive non-magnetic metal material. Examples of the synthetic resin include PA6 (nylon) and POM (polyacetal), which have good slidability when coming into contact with the first shaft 3 and can be injection-molded with the inner cylindrical portion 12b made of aluminum or the like. .
The outer cylindrical portion 12a is arranged in the housing 2 so as to surround the outer periphery of the first shaft 3 via a gap ε.
The inner cylinder part 12b is embedded in the outer cylinder part 12a.

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 has a cylindrical outer peripheral portion 31a, 32.
a, annular peripheral wall portions 31b, 32b directed inward from one end sides of the outer peripheral portions 31a, 32a, and annular lid portions 31c, 32c directed inward from the other end sides of the outer peripheral portions 31a, 32a. It is composed of Each of the coil holders 31 and 32 includes a step 2 a formed on the inner periphery of the housing 2 and a retaining ring 5 fitted on the inner periphery of the housing 2.
3 are sandwiched by a leaf spring 54 and are thereby fixed to the housing 2.

The first coil 33 held by the first coil holder 31 and the second coil 34 held by the second coil holder 32 are connected to both shafts 3, 4.
Are arranged in parallel along the direction of the relative rotation axis. Both coils 33, 3
Reference numeral 4 denotes the same specification, which 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, and inserted into the inner periphery of each coil holder 31. Each of the coil holders 31 and 32 and the coils 33 and 34 are arranged so as to surround the outer periphery of the tubular member 12 via a gap. Each coil 33, 34
A torque detection circuit is configured as described below, and generates a magnetic flux so as to generate an alternating magnetic field.

The first shaft 3 is made of a magnetic metal material.
A magnetic flux passing portion made of a magnetic metal material is disposed at a position where the generated magnetic fluxes of the magnetic fluxes 3 and 34 pass, and the outer periphery thereof is along the cylindrical surface. In the present embodiment, the first shaft 3 is formed of a single member. However, the first shaft 3 is formed by integrating a member constituting a magnetic flux passage portion and a member constituting a portion other than the magnetic flux passage portion. May be formed.

As shown in FIGS. 3A, 3B and 4, a plurality of grooves 40 are formed in the magnetic flux passage along the direction of the relative rotation axis of the shafts 3, 4. Those grooves 40
Are arranged in parallel at equal intervals in the circumferential direction of the first shaft 3. The dimensions of each groove 40 are equal to each other. The circumferential dimension S1 of each groove 40 is larger than the circumferential dimension S2 of the magnetic flux passage between the grooves 40.

The inner cylindrical portion 12b has a first shaft 3
And a magnetic flux restricting portion disposed at a position where the magnetic flux generated by each of the coils 33 and 34 passes. A plurality of first openings 43 and a plurality of second openings 44 are formed in the magnetic flux restricting portion. The first opening 43 and the second opening 44 are arranged at an interval in the direction of the relative rotation axis of the shafts 3 and 4. The first openings 43 are arranged side by side at equal intervals in the circumferential direction of the tubular member 12. The second openings 44 are arranged side by side at equal intervals in the circumferential direction of the tubular member 12. Each opening 43, 44
In this embodiment, the shafts 3 and 4 have a shape along a quadrilateral having edges parallel to the rotation axis direction and edges parallel to the rotation circumferential direction. The first
The coil 33 is disposed at a position where a magnetic flux passing through each first opening 43 is generated, and the second coil 34 is disposed at each second opening 44.
Is arranged at a position where a magnetic flux passing through is generated.

As shown in FIG. 2, the size of each opening 43, 44 exceeds the size of each coil 33, 34 and less than the size of each coil holder 31, 32 in the direction of the relative rotation axis of both shafts 3, 4. The first opening 43 is disposed between both ends of the first coil holder 31, the second opening 44 is disposed between both ends of the second coil holder 32, and the first coil 33 is disposed between both ends of the first opening 43. And the second coil 3
4 is arranged between both ends of the second opening 44. This allows
Even if the relative positions in the axial direction of the first shaft 3, the second shaft 4, the first coil 33, the second coil 34, and the tubular member 12 fluctuate due to manufacturing tolerances or assembly tolerances,
Each opening 4 in the direction of the relative rotation axis of both shafts 3 and 4
3 and 44 can be arranged at the positions where the magnetic fluxes generated by the coils 33 and 34 pass. Therefore, fluctuation due to the tolerance of the magnetic flux passing through the magnetic flux passing portion can be eliminated, and a decrease in detection accuracy can be prevented.

In the radial direction of the shafts 3 and 4, the overlapping area between the outer circumference of the magnetic flux passage portion connected to the edge of the groove 40, that is, the outer circumference of the portion between the grooves 40 in the first shaft 3, and the openings 43 and 44. Is changed according to the relative rotation of the shafts 3 and 4 so that the groove 40 and the opening 4
The shafts 3 and 44 are arranged so as to partially overlap in the radial direction of the shafts 3 and 4.

That is, as shown in FIG. 4, the circumferential dimension S2 of the magnetic flux passage between the grooves 40 is different from that of each opening 4
Each of the second openings 44 is arranged between the first openings 43 in the circumferential direction, and is larger than the circumferential dimension P1 of the first and third openings 44.
The first and second openings 43 and 44 are arranged between both ends of the groove 40 in the direction of the relative rotation axis of the shafts 3 and 4.
In the relative rotation range of the shafts 3 and 4 corresponding to the torque detection range, each of the first openings 43 is one of the first openings 43 along the relative rotation axis of the shafts 3 and 4 in the groove 40 in the radial direction of the shafts 3 and 4. It overlaps with the edge 40a. The second opening 44
In the relative rotation range of the shafts 3 and 4 corresponding to the torque detection range, in the radial direction of the shafts 3 and 4, the other edge 40b of the groove 40 along the relative rotation axis of the shafts 3 and 4 overlaps. As a result, when the first shaft 43 and the outer periphery of the magnetic flux passage portion connected to the edge 40a of each groove 40 rotate relative to each other in one direction, the overlapping area with each other increases, and the first shaft 43 and the first shaft 43 increase. When the members 3 and 4 rotate relative to each other in the other direction, they are arranged so that the overlapping area with each other is reduced. Further, the outer circumference of the magnetic flux passing portion connected to each second opening 44 and the edge 40b of each groove 40 is defined by both shafts 3,
When the shafts 4 rotate relatively in one direction, the overlapping area with each other decreases, and when the shafts 3 and 4 rotate relatively in the other direction, the overlapping areas with each other increase. . That is, the groove 40 in which the first opening 43 overlaps
Edge 40a of the groove 40 and the edge 40b of the groove 40 where the second opening 44 overlaps
Means that the two shafts 3 and 4 are located on mutually opposite sides in the rotational circumferential direction of the shaft 40 when viewed from the center of the groove 40.

When the shafts 3 and 4 are at the detection origin position where they are not relatively rotating, that is, when the steering angle is zero, the overlapping area between the first opening 43 and the outer periphery of the magnetic flux passage portion, and the second opening 44 The overlapping area with the outer periphery of the magnetic flux passage portion is equal to each other. That is, as shown in FIG. 4, when both shafts 3 and 4 are at the detection origin position, one edge 40 a of each groove 40 along the relative rotation axis of both shafts 3 and 4 is
The first openings 43 are arranged so as to overlap radially with the center of the first shaft 43 along the relative rotation axis of the shafts 3 and 4. The other edge 40b of each groove 40 along the relative rotation axis of both shafts 3 and 4 is arranged so as to overlap the center of each second opening 44 along the relative rotation axis of both shafts 3 and 4 in the radial direction. ing. Accordingly, when the shafts 3 and 4 rotate relative to each other, the absolute value of the change in the overlapping area between the first opening 43 and the outer periphery of the magnetic flux passage portion is expressed by:
The absolute value of the change in the overlapping area between the second opening 44 and the outer periphery of the magnetic flux passing portion is made equal to each other.

As shown by the two-dot chain line β in FIG. 2, the magnetic flux generated by the first coil 33 passes through the first coil holder 31, the first opening 43 of the tubular member 12, and the magnetic flux passage of the first shaft 3. Thus, a first magnetic circuit including the first coil holder 31 and the magnetic flux passage portion of the first shaft 3 as constituent elements is formed, and the magnetic flux generated by the second coil 34 is generated by the second coil holder 32 and the cylindrical member. By passing through the second opening 44 of 12 and the magnetic flux passage of the first shaft 3,
A second magnetic circuit including the second coil holder 32 and the magnetic flux passage of the first shaft 3 as constituent elements is configured.

In the above configuration, the first shaft 3 is rotated by the relative rotation of the shafts 3 and 4 during torque transmission.
The overlapping state of the groove 40 formed in the magnetic flux passage portion and the openings 43 and 44 formed in the magnetic flux regulating portion of the inner cylindrical portion 12b rotating together with the second shaft 4 changes. This allows
In the radial direction of both shafts 3, 4, the edge 4 of the groove 40
0a, 40b and the opening 43,
The overlapping area with the shaft 44 changes according to the relative rotation of the shafts 3 and 4. Since the magnetic flux passage portion is made of a magnetic material and the inner cylindrical portion 12b is made of a non-magnetic material, the magnetic flux passing through the magnetic flux passage portion changes due to a change in the overlapping area. Further, the magnetic flux reaching the magnetic flux passage is also blocked by the eddy current generated in the conductive inner cylindrical portion 12b in the alternating magnetic field generated by the magnetic flux generated in the coils 33 and 34. Thus, the magnetic flux passing through the magnetic flux passing portion can be changed according to the change in the overlapping area. The change in the area corresponds to the relative rotation of the shafts 3 and 4 corresponding to the transmission torque. The coil 3 is driven by electromagnetic induction based on the change in magnetic flux.
It is assumed that the outputs 3, 34 change, and the transmission torque is detected based on the change in the coil output. Since the outer cylinder portion 12a in which the inner cylinder portion 12b is buried is insulative, no eddy current is generated and does not affect torque detection.

In the above configuration, when the shafts 3 and 4 rotate in one direction relative to each other during torque transmission, the first opening 43 and one edge 40 of the groove 40 are formed according to the relative rotation amount.
The overlapping area with the outer periphery of the magnetic flux passing portion connected to a increases, and the overlapping area with the outer periphery of the magnetic flux passing portion connected to the second opening 44 and the other edge 40b of the groove 40 decreases. When the shafts 3 and 4 rotate relative to each other in the other direction during torque transmission, the overlapping area between the first opening 43 and the outer periphery of the magnetic flux passing portion decreases according to the relative rotation amount, and the second opening 44 and the outer periphery of the magnetic flux passing portion. And the overlapping area increases. The magnetic flux passing through the magnetic flux passage changes according to the change of each overlapping area. Further, when the shafts 3 and 4 rotate relative to each other, the absolute value of the change in the overlap area between the first opening 43 and the outer periphery of the magnetic flux passage portion, and the overlap area between the second opening 44 and the outer periphery of the magnetic flux passage portion. Are made equal to each other. Therefore, the change in the magnetic flux passing through the magnetic flux passage portion according to the change in the overlapping area between the first opening 43 and the outer periphery of the magnetic flux passage portion, and the change in the second opening 44
The torque transmitted by the shafts 3 and 4 is detected based on the difference between the change in the magnetic flux passing through the magnetic flux passing portion according to the change in the overlapping area between the magnetic flux passing portion and the outer circumference of the magnetic flux passing portion, thereby increasing the torque detection sensitivity. Further, the torque corresponding to the relative rotation amount can be detected both when the shafts 3 and 4 are relatively rotated in one direction and when the shafts are relatively rotated in the other direction. Moreover, when the temperature fluctuates, the magnetic flux passing through the magnetic flux passing portion overlapping the first opening 43 and the magnetic flux passing through the magnetic flux passing portion overlapping the second opening 44 change by the same amount. By detecting the torque based on this, the fluctuation of the detected torque due to the temperature fluctuation can be offset.

In this embodiment, the coils 33 and 34 are
Printed circuit board 3 attached to outer surface side of housing 2
5 via a wiring. The printed circuit board 35
In FIG. 5, a torque detection circuit shown in FIG. 5 is formed. In the circuit, the first coil 33 is connected to an oscillator 46 via a resistor 45, the second coil 34 is connected to an oscillator 46 via a resistor 47, and the coils 33 and 34 are connected to a differential amplifier circuit 48. You. Thereby, both shafts 3, 4
When the torsion bar 7 is twisted by torque transmission between the two, the shafts 3 and 4 elastically rotate relative to each other, and the overlapping area between the openings 43 and 44 and the outer periphery of the magnetic flux passing portion changes according to the transmitted torque. When the magnetic flux passing through the magnetic flux passing portion changes due to the change in the overlapping area, the first and second coils 3
The outputs of 3, 34 change. Based on the output of the differential amplifier circuit 48 corresponding to the difference between the change in the magnetic flux passing through the magnetic flux passing portion overlapping the first opening 43 and the change in the magnetic flux passing through the magnetic flux passing portion overlapping the second opening 44, the two shafts 3 are used. , 4 are detected. A steering assist force is applied by an actuator (not shown) such as a motor driven according to a signal corresponding to the transmission torque output from the differential amplifier circuit 48. A known configuration can be employed for the mechanism for applying the steering assist force.

According to the above configuration, since the outer cylindrical portion 12a surrounding the outer periphery of the first shaft 3 via the gap ε is made of synthetic resin, the axial center of the first shaft 3 and the axial center of the second shaft 4 Even when the outer peripheral surface of the first shaft 3 contacts the outer peripheral surface of the first shaft 3 even when the outer peripheral surface is inclined by an external force or the like, the synthetic resin is used. Therefore, the frictional force for preventing the relative rotation of the two shafts 3 and 4 at the contact portion can be reduced as compared with the case where the metals are in contact with each other, and a decrease in torque detection accuracy can be prevented.

The present invention is not limited to the above embodiment. For example, one end of the first shaft 3 may be connected to a steering gear, and the other end of the second shaft 4 may be connected to a steering wheel. Further, the torque sensor of the present invention may be used for detecting torque in a device other than the steering device.

[0029]

According to the present invention, it is possible to provide a torque sensor excellent in detection accuracy and detection sensitivity.

[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 sectional view of a main part of the torque sensor according to the embodiment of the present invention.

FIG. 3 is a cross-sectional view of a main part of a torque sensor according to an embodiment of the present invention, and FIG.

FIG. 4 is a partial development view of a cylindrical member of the torque sensor according to the embodiment of the present invention.

FIG. 5 is a diagram showing a torque detection circuit according to the embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Torque sensor 3 1st shaft 4 2nd shaft 12 Cylindrical member 12a Outer cylinder part 12b Inner cylinder part 31, 32 Coil holder 33 First coil 34 Second coil 40 Groove 43 First opening 44 Second opening

Claims (5)

[Claims] 1. A first shaft, a second shaft coaxially and resiliently connected to the first shaft so as to be relatively rotatable, and a cylinder connected to the second shaft so as to be coaxial and rotatable therewith. And a coil arranged to surround the outer periphery of the cylindrical member and generating a magnetic flux so as to generate an alternating magnetic field, and the cylindrical member has an outer periphery of the first shaft through a gap. An outer cylindrical portion made of an insulative synthetic resin, and an inner cylindrical portion made of a conductive non-magnetic metal material embedded in the outer cylindrical portion. Thereby, a magnetic flux passing portion made of a magnetic metal material is arranged at a position where the generated magnetic flux of the coil passes, and the inner cylindrical portion surrounds the magnetic flux passing portion and is arranged at a passing position of the generated magnetic flux of the coil. And a magnetic flux passing portion. A groove is formed along the direction of the relative rotation axis of both shafts, an opening is formed in the magnetic flux regulating portion, and in the radial direction of both shafts, the outer periphery of the magnetic flux passing portion connected to the edge of the groove along the direction of the relative rotation axis and the opening So that the overlap area with changes according to the relative rotation of both shafts,
The groove and the opening are arranged so as to partially overlap each other in the radial direction of both shafts, and the torque transmitted by both shafts is detected based on a change in the magnetic flux passing through the magnetic flux passing portion according to a change in the overlapping area. Torque sensor. 2. A coil holder made of a magnetic material for holding the coil, the coil holder comprising a cylindrical outer peripheral portion surrounding the coil, a portion inward from one end of the outer peripheral portion, and a A portion that faces inward from the other end of the outer peripheral portion, and in the direction of the relative rotation axis of both shafts,
The size of the opening is larger than the size of the coil and smaller than the size of the coil holder, the opening is arranged between both ends of the coil holder, and the coil is arranged between both ends of the opening. 2. The torque sensor according to 1. 3. The opening has a shape along a quadrilateral having an edge parallel to the rotation axis direction of both shafts and an edge parallel to the rotation circumferential direction, and the opening is a relative rotation axis of both shafts. When both shafts are located at the detection origin position where both shafts are not relatively rotating in the direction, the edge along the relative rotation axis of both shafts in the groove is aligned with the relative rotation axis of both shafts at the opening. The torque sensor according to claim 1, wherein the torque sensor is disposed so as to overlap a center along the radial direction. 4. The coil includes a first coil and a second coil of the same specification which are arranged in parallel along the direction of the relative rotation axis of both shafts, and the opening is formed at an interval in the direction of the relative rotation axis of both shafts. The first opening and the second
An opening, wherein the first coil is arranged at a position where a magnetic flux passing through the first opening is generated, and the second coil is arranged at a position where a magnetic flux passing through the second opening is generated.
The opening and the outer circumference of the magnetic flux passing portion connected to the edge of the groove increase the overlapping area with each other when both shafts rotate in one direction, and with each other when both shafts rotate relative to each other. Are relatively arranged so that the overlapping area is reduced,
The second opening and the outer periphery of the magnetic flux passing portion connected to the edge of the groove reduce the overlapping area with each other when the two shafts relatively rotate in one direction, and when the two shafts relatively rotate in the other direction. The first and second shafts are arranged relative to each other so as to increase the overlapping area with each other.
The absolute value of the change in the overlap area between the opening and the outer periphery of the magnetic flux passage portion and the absolute value of the change in the overlap area between the second opening and the outer periphery of the magnetic flux passage portion are made equal to each other, and according to the change in the overlap area. Changes in the magnetic flux passing through the magnetic flux passing portion,
The torque sensor according to any one of claims 1 to 3, wherein a torque transmitted by both shafts is detected based on a difference between a change in a magnetic flux passing through the magnetic flux passing portion and a change in the overlapping area. 5. A plurality of said first openings are formed in parallel at equal intervals in the circumferential direction of said tubular member, and said second openings are formed at equal intervals in the circumferential direction of said tubular member. And a plurality of grooves are provided so as to be arranged in parallel at equal intervals in a circumferential direction of the first shaft, and a circumferential dimension of each groove is a magnetic flux passing portion between the grooves. And the circumferential dimension of the magnetic flux passage between the grooves is made larger than the circumferential dimension of each opening. Each second opening is arranged in the circumferential direction of the opening, and in the relative rotation range of both shafts corresponding to the torque detection range, each first opening overlaps one edge along the relative rotation axis of both shafts in the groove, Each second
The torque sensor according to claim 4, wherein the opening is arranged so as to overlap the other edge of the groove along the relative rotation axis of the two shafts.