JPH0678955B2 - Torque sensor - Google Patents

Description

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a torque sensor, and more particularly to a torque sensor that measures rotational torque in a non-contact manner.

(Prior Art) In general, the number of devices driven by rotational driving force is very large, and its application fields are diverse. Torque control often occupies an important position in controlling such devices. That is, the torque is one of the most basic and important parameters when controlling the rotary drive system,
When the information on the torque and the number of revolutions is obtained, the product of them is proportional to the horsepower, so that it becomes possible to grasp the generation state and transmission state of power.

As a conventional torque sensor, for example, there is one disclosed in Japanese Patent Application Laid-Open No. 54-17228, which may be applied to a steering force detecting device for detecting a steering force applied to a steering wheel of a vehicle. In this device, a steering wheel and a steering shaft are connected via an elastic body, and a relative torsional displacement generated between the steering wheel and the steering shaft due to a torsional action generated in the elastic body according to the magnitude of the steering torque during steering. It is detected by turning on and off the contacts that are interposed between the steering wheel and the steering shaft. However, in such a device, contacts and microswitches that are turned on and off by twisting displacement are provided, so high work accuracy is required for the placement of these contacts, and the amount of relative twisting displacement that turns on is large. There is a problem that it is difficult to individually set the relative torsional displacement amount that turns OFF or OFF. Further, the device disclosed in Japanese Patent Laid-Open No. 55-44013 is provided with an electric displacement detector such as a strain gauge on an input shaft to which steering torque is transmitted from the steering wheel, and inputs from the steering wheel in proportion to road surface resistance. It detects the relative twisting displacement of the input shaft that occurs according to the steering torque.However, in order to detect the twisting displacement of the input shaft, an electrical displacement detector such as a strain gauge was fixed to the input shaft, so the temperature change However, there is a problem in that the operation is unstable and the reliability is low.

Therefore, as a solution to such a problem,
JP-A-58-194664, JP-A-58-218627, JP-A-58-
No. 105877, No. 57-192872, No. 58-101153,
The ones disclosed in JP-A-58-5626 and JP-A-61-21861 are known.

For example, in the device described in JP-A-58-194664, a column shaft having one end connected to a steering wheel and the other end connected to a steering gear is divided, and the two divided shafts are connected via an elastic body. The steering device is connected to enable relative rotational displacement, and the relative rotational displacement of these two shafts is converted into an axial displacement, which is added to the steering wheel according to the magnitude of the axial displacement. The steering force applied is detected. Further, there is the one described in the above-mentioned JP-A-61-21861 as one in which the twist of the torsion bar mechanism is converted into a change in electrostatic capacity.

(Problems to be Solved by the Invention) However, in such a conventional device, the torsional displacement of the torsion bar mechanism is detected by using a member such as a switch, or the relative rotational displacement is determined as the axial displacement. In the case of so-called contact type torque sensors such as those that convert, the structure is complicated, the number of mechanical and electrical parts of the detector is large, and considerable accuracy is required for mounting, which not only increases the manufacturing cost. Detection accuracy may deteriorate due to environmental changes such as temperature and humidity. That is, when the torque is detected as the sensor, the non-contact type torque sensor is desirable from the viewpoint of reliability such as wear resistance and safety because the rotational axis is the target. On the other hand, even a non-contact type torque sensor, for example, one that photoelectrically detects the amount of torsional displacement (see Japanese Patent Laid-Open No. 58-5626) cannot be used particularly in a heavily soiled place. Sometimes. In addition to the above-mentioned problems, in the conventional device, whether the torque sensor is a contact type or a non-contact type, the conventional device detects the rotational displacement direction (that is, the direction in which the torque acts) and the stationary torque. Is quite difficult, and a torque sensor that solves these problems has not been realized yet.

As described above, there is a demand for the appearance of a torque sensor that can accurately detect rotation and static torque, which are extremely important parameters when controlling a rotation drive unit such as an engine or an electric motor, in a non-contact manner at low cost.

(Object of the invention) Therefore, the present invention focuses on a physical quantity called a magnetic field that is not affected by environmental changes such as temperature and humidity and dirt, and converts a torsional displacement into a change in the magnetic flux by a predetermined structure. The purpose of the present invention is to provide a non-contact type torque sensor that has a simple structure, has a good responsiveness, and can detect torque at low cost regardless of whether it is stationary or rotating, by detecting the change in a non-contact manner and measuring the torsional displacement. There is.

(Means for Solving Problems) The torque sensor according to the present invention has the first object to achieve the above object.
The tip portion of the shaft is connected to the second shaft as a structure capable of generating torsional displacement, and a predetermined number of N poles and S poles are alternately arranged as fixed magnetic poles so as to surround the periphery of the connection portion. The first pickup path and the second pickup path, which are fixed to the shaft and have the same number of N poles and S poles, are arranged so as to face the intermediate positions of the respective magnetic poles, and flow through the first and second pickup paths. A magnetic detection element that detects a change in magnetic flux is provided on the first shaft in a non-contact manner, and when the first shaft is twisted and displaced with respect to the second shaft, the N pole is located on either side of the first pickup path or the second pickup path. The amount of magnetic flux flowing through the first and second pickup paths is changed depending on whether the first shaft and the second shaft are close to each other, and the torsional displacement of the first shaft with respect to the second shaft is detected from the change in the magnetic flux. And a torque sensor, characterized in that.

(Operation) In the present invention, the tip portion of the first shaft is connected to the second shaft as a structure capable of generating torsional displacement, and a predetermined number of N poles and S poles are fixed magnetic poles so as to surround the periphery of the connection portion. Are alternately arranged and fixed to the second shaft, and the same number of first pickup paths and second pickup paths as the N poles and the S poles are arranged so as to face the intermediate positions of the respective magnetic poles. It Further, a magnetic detection element that detects a change in magnetic flux flowing through the first and second pickup paths is provided on the first shaft in a non-contact manner. And
When the first shaft is twisted and displaced with respect to the second shaft, the amount of magnetic flux flowing through the first and second pickup paths changes depending on which side of the first pickup path or the second pickup path the N pole approaches. From the change of the magnetic flux, the torsional displacement of the first shaft with respect to the second shaft is detected in a non-contact manner. Therefore, the structure is simple, the response is good, and the torque can be accurately measured at low cost regardless of whether it is stationary or rotating.

(Example) Hereinafter, the present invention will be described with reference to the drawings.

1 to 6 are views showing an embodiment of the present invention, FIG. 1 is an exploded perspective view of this embodiment, FIG. 2 is a vertical side view, and FIG. 3 is a front view.

First, the configuration will be described. In FIG. 1, reference numeral 1 is a first shaft, and the first shaft 1 is connected to a second shaft 3 via a small diameter portion 2 for slightly lowering torsional rigidity, as shown by A and B in the figure. The rotational force of the first shaft in the circumferential direction is transmitted to the second shaft 3 via the small diameter portion 2. Further, as shown in the vertical side view of FIG. 2, the outer peripheral surface 3a of the second shaft 3 has a projecting end portion 4a of a cylindrical mold member (nonmagnetic material) 4 formed so as to enclose the small diameter portion 2. It is fitted and fixed, and the mold member 4 forms a pair with a pickup member 7 and a Hall element 13 which will be described later to form a torque detection mechanism 21. On the other hand, the mold member 4
A donut-shaped magnetic material embedded portion 4b is formed on the other end side of the magnetic material embedded portion 4b, and the magnetic material embedded portion 4b has a cut surface (end surface) 4c perpendicular to the axial direction. Is the end face
The magnetic body 5a arranged so as to face the N pole on 4c, and S on the end surface 4c
Eight magnetic bodies 5b arranged so as to face the poles are arranged alternately in concentric circles and at equal intervals. Furthermore, the other end of each magnetic body 5a, 5b is connected to an annular common ring 6, and the common ring 6 is used for each magnetic body.
It forms part of a closed-loop magnetic path for the magnetic fields emitted from 5a and 5b. Common ring 6 and each magnetic body 5a, 5b
Is embedded in the magnetic material embedded portion 4b and is integrally formed with the magnetic material embedded portion 4b made of a non-magnetic material. In the present embodiment, the number of the magnetic bodies 5a and 5b is eight, respectively, but of course the number is not limited to this, and another number may be used as long as the north pole and the south pole alternately face the end surface 4c at equal intervals. It may be one of the embodiments.

On the other hand, the outer peripheral surface 1a on the small diameter portion 2 side of the first shaft has an end surface 4c.
A disk-shaped pickup member (non-magnetic body) 7 facing the end face 4c and having a minute gap is fitted and fixed, and the end face 7a on the input side of the pickup member 7 is circumscribed to the end face 7a. An outer ring 8 and an inner ring 9 are provided inside the outer ring 8. Further, on the end surface 7b of the pickup member 7 facing the end surface 4c, a magnetic path piece 10a and a magnetic path piece 10b which become magnetic paths by receiving a magnetic force from the magnetic material 5a or 5b and the magnetic materials 5a and 5b are respectively formed. In order to respond by pair 1, eight magnetic pole pieces are alternately arranged in concentric circles and at equal intervals.
The a is connected to the outer ring 8 and the magnetic path piece 10b is connected to the inner ring 9. The magnetic path piece 10a and the outer ring 8 form a first pickup path 11, and the magnetic path piece 10b and the inner ring 9 form a second pickup path 12. Here, it is desirable that the common ring 6, the magnetic path pieces 10a and 10b, the outer ring 8 and the inner ring 9 are made of a material through which magnetic lines of force easily pass, and are made of, for example, permalloy or ferrite, and the magnetic bodies 5a and 5b described above are used. The magnetic force generated from the magnetic path piece 10
Guide to the outer ring 8 and the inner ring 9 via a and 10b. By the way, the magnetic path pieces 10a and 10b are made of a non-magnetic material like the magnetic materials 5a and 5b.
It is integrally formed inside, so that in a steady state (that is, when the torque is 0), the magnetic body 5a or 5b is located exactly in the middle of the magnetic path pieces 10a and 10b as shown in the front view of FIG. It is configured. Therefore, from the magnetic body 5a to the magnetic path piece
Gap space l _A up to 10a and magnetic body 5a to magnetic path piece 1
The gap space l _B up to 0b is equal to each other, and similarly, the gap space l _A from the magnetic body 5b to the magnetic path piece 10b is equal to the gap space l _B from the magnetic body 5b to the magnetic path piece 10a. Therefore, as shown in FIG. 1, when a rotational force in the circumferential direction A (or B) is applied to the first shaft 1, the gap spaces l _A and l _B respectively change by a predetermined amount according to the rotational force. Furthermore, the outer ring 8 and the inner ring 9 described above are not in contact with these rings or the pickup member 7 and are perpendicular to the magnetic field applied from the outer ring 8 to the inner ring 9 (or from the inner ring 9 to the outer ring 8). The Hall element (magnetic detecting element) 13 is arranged at such a position that the Hall element 13 is fixed to the printed board 14 with an adhesive or the like. A member (not shown) for detecting and processing a signal from the Hall element 13 is provided on the printed circuit board 14, and the printed circuit board 14 is mounted on the printed circuit board 14 via a support member 14a fixed to the printed circuit board. 1 is rotatably displaced and fitted. In addition, Hall element
Reference numeral 13 denotes a sensor utilizing the solid Hall effect, which is an element for generating an output voltage proportional to the strength of a magnetic field, but the same element as that conventionally known can be used, and its detailed description will be omitted.

Next, the operation will be described.

The torque sensor according to the present invention uses the first shaft 1 when the Hall element 13 detects the magnetic force generated from the magnetic bodies 5a and 5b.
The mechanical torsional displacement generated between the second shaft 3 and the second shaft 3, the gap space l _A between the magnetic body 5a, 5b and the magnetic path piece 10a, 10b,
It is regarded as a change in l _B (in other words, a change in space magnetic path length), and the change in the magnetic flux flow (magnetic path) and the amount of magnetic flux caused by the change in the gap spaces l _A and l _B is not detected by the hall element 13. The torque is detected by contact. Then, the 4th and 5th
The basic idea of the present invention will be described with reference to the drawings. FIG. 4 (a) is a diagram schematically showing a part of the torque detection mechanism 21 in a steady state, and FIG. 4 (b) is a diagram showing the rotational force in the circumferential direction A as shown in FIG. A case where the rotational force is applied in the circumferential direction B is schematically shown in FIG. Further, FIG. 5 is a perspective view schematically showing a part of the torque detection mechanism 21 in the steady state.

Since no constant torque is applied, the gap space l _A from the magnetic body 5a to the magnetic path piece 10a and the magnetic body 5 as shown in FIG.
The gap space l _B from a to the magnetic path piece 10b is equal, and the positional relationship between each magnetic body and the magnetic path piece is uniform at any place. Therefore, as shown in FIG.
The pair of magnetic bodies 5a and 5b and the magnetic path pieces 10a and 10b can be described as representative examples. Now, the magnetic flux generated from the N pole of the magnetic body 5a is the gap space l _{A as} shown by the solid arrow.
The enters the magnetic path pieces 10a through, through the distal end portion of the magnetic path pieces 10a to reach the S pole of the magnetic body 5b through the gap space l _B. Similarly, the magnetic flux emitted from the N pole of the magnetic body 5a is one in enters the magnetic path piece 10b via the gap space l _B passes through the gap space l _A through the distal end portion of the magnetic path piece 10b of the magnetic 5b Reach the south pole. Any magnetic flux generated from the N pole of 5b reaches the S pole of the magnetic body 5a through the common ring 6. Thus, the magnetic body
5a, 5b, the magnetic path piece 10a (or 10b) and the common ring 6 form one closed loop magnetic path with the gap spaces l _A , l _B sandwiched therebetween, and this magnetic path is called the main magnetic path, The magnetic flux at this time is called φ ₁ .

On the other hand, the magnetic flux generated from the N pole of the magnetic body 5a is simply the magnetic path piece 10
In addition to forming the main magnetic path as described above that passes through a (or the magnetic path piece 10b) and reaches the S pole of the magnetic body 5b, the magnetic path piece
Some of them are directed in the axial direction of 10a, 10b (toward the outer ring 8 and the inner ring 9). That is, a part of the magnetic flux generated from the N pole of the magnetic body 5a reaches the Hall element 13 via the gap space l _A , the magnetic path piece 10a, and the outer ring 8 as shown by the dashed-dotted arrow in FIG. _A bypass magnetic path that is orthogonal to 13 and passes through the inner ring 9, the magnetic path piece 10b, and the gap space l _A to return to the S pole of the magnetic body 5b is formed (the magnetic flux passing through the bypass magnetic path in this direction is φ ₂ ). By the way, the magnetic force generated at the N pole of the magnetic body 5a is equally applied to the magnetic path piece 10b side (however, the polarity is different) on the one hand, and it is the same as the case described above as shown by the arrow of the broken line in the figure. Forms a bypass magnetic path in the reverse route (the magnetic flux passing through the bypass magnetic path by this reverse flow is referred to as -φ ₂ ). In this case, the strength of the magnetic field applied to the Hall element 13 is actually the gap space having extremely small magnetic permeability as compared with the magnetic path material having large magnetic permeability or the common ring 6.
It is determined by the difference in the size of l _A or l _B. Also,
Magnetic path pieces 10a, 10b, outer ring 8, inner ring 9
Further, since each member of the common ring 6 forms a common magnetic path both in the steady state and in the non-steady state, the torque detection accuracy is deteriorated even if these members are deteriorated due to aging or the like. Absent.

Thus, in the steady state where no torque is applied, the magnetic flux φ ₁ flowing in the main magnetic path is the magnetic flux | φ flowing in the bypass magnetic path.
_Since it is much larger than ₂ | (φ ₁ >> | φ ₂ |),
In reality, almost no magnetic flux flows into the bypass magnetic path in which the Hall element 13 is arranged. Also, the gap spaces l _A and l _B
Are equal to each other, the magnetic fluxes φ ₂ and −φ ₂ have the same magnitude (φ ₂ = −) even if there is some leakage flux | φ ₂ |.
φ ₂ ), which cancel each other out and the Hall element 11 is insensitive and torque is not detected.

Here, in the present invention, the change in magnetic flux in the bypass magnetic path is used as a parameter for torque detection. That is, the Hall element 13 is provided in the middle of the bypass magnetic path. On the other hand, in the main magnetic path, although the magnetic flux changes due to the torque change, it is not detected. However, the torque can be detected by the magnetic flux of the main magnetic path, and the applicant intends to propose this as another application. Therefore, hereinafter, the specific operation will be described focusing on the magnetic flux change in the bypass magnetic path.

At non-steady state (when torque is applied) As shown in FIG. 4 (b), when the rotational force is applied in the circumferential direction A, the gap space l _A from the magnetic body 5a to the magnetic path piece 10a and the magnetism Gap space l _A from body 5b to magnetic path piece 10b
Are all increased, both smaller than the gap space l _B from the gap space l _B and the magnetic body 5b of the opposite magnetic bodies 5a to magnetic path piece 10b to the magnetic path piece 10a. Along with this, the magnetic path resistance of the magnetic flux −φ ₂ of the bypass magnetic path decreases, and the magnetic path resistance of the main magnetic path φ ₁ increases. Therefore, the flow of the magnetic flux shifts from φ _{1 of} the main magnetic path, which was dominant in the steady state, toward the bypass magnetic path, and the magnetic flux −φ ₂ becomes larger than the magnetic flux φ ₂ , and the degree thereof is A It is proportional to the magnitude of the twist angle applied in the direction (see Fig. 6). For example, the direction of the magnetic field applied to the Hall element 13 by the rotational force in the A direction is set to the positive direction, and the output voltage of the Hall element 13 becomes a positive value.
By setting the output of 13, it is possible to properly detect the magnitude and direction of the generated torque and the static torque as shown in FIG. Further, as shown in FIG. 4 (c), when the rotational force is applied in the circumferential direction B, the magnetic flux φ ₂ is −
It becomes larger than φ ₂ and the torque in the opposite direction to the above case can be detected.

As described above, in the present embodiment, when the magnetic force generated from the magnetic bodies 5a and 5b is detected by the hall element 13, the torsional displacement generated between the first shaft 1 and the second shaft 3 causes the magnetic body 5a, It is perceived as a change in the gap space l _A , l _B between the 5b and the magnetic path piece 10a, 10b, and this change in the gap space l _A , l _{B is} a change in the magnetic field strength without contact with the pickup member 7. It is accurately detected by the Hall element 13 provided. Therefore, as described in the conventional problem, compared with the conventional device such as a device that converts the relative rotational displacement into the axial displacement, there is no rotational portion, and the structure can be extremely simplified, and the responsiveness and It is possible to realize a torque sensor with excellent reliability and high measurement accuracy at low cost. Further, in addition to the simple structure, since the Hall element 13 and the like can be adjusted after the mold member 4 and the pickup member 7 are attached, it is necessary to perform a difficult work requiring high precision in attaching each of these members. Not. Moreover, since the information of the rotating torque is detected in a non-contact manner in the present invention, not only the improvement of the measurement accuracy, but also the abrasion resistance, the reliability such as the safety can be dramatically improved, The static torque can be detected with high accuracy as in the conventional device.

If the present invention having the above features is applied to a steering device for detecting a steering force of an automobile, for example, it is extremely suitable for controlling the steering force.

In this embodiment, the rotation angle is detected as an example in which the rotation angle is only ± 6 °. However, the present invention is not limited to this. For example, by adjusting the torsional rigidity of the magnetic body, the magnetic path piece, and the shaft, a wide range is obtained. Of course, even static torque can be detected.

Further, in the present invention, although the tip end portion of the first shaft is connected to the second shaft as a structure capable of generating a torsional displacement, the first shaft and the second shaft may be separate members, Alternatively, as in this embodiment, the first and second
It goes without saying that the embodiment may be formed of one member.

(Effect) According to the present invention, the tip end portion of the first shaft is connected to the second shaft as a structure capable of generating torsional displacement, and a predetermined number of N poles and S poles are provided so as to surround the periphery of the connection portion. The fixed magnetic poles are alternately arranged and fixed to the second shaft, and the same number of the first pickup paths as the N poles and the S poles are provided.
The pickup path and the second pickup path are arranged so as to face the intermediate positions of the respective magnetic poles, and a magnetic detection element for detecting a change in the magnetic flux flowing through the first and second pickup paths is provided in a non-contact manner with the first shaft. When the first shaft is twisted and displaced with respect to the second shaft, the amount of magnetic flux flowing through the first and second pickup paths is determined depending on which side of the first pickup path and the second pickup path the N pole approaches. Since the torsional displacement of the first shaft with respect to the second shaft is detected from this change in the magnetic flux, the structure is simple and the response is good. Can be detected.

[Brief description of drawings]

1 to 6 are views showing an embodiment of the present invention. FIG. 1 is an exploded perspective view thereof, FIG. 2 is a longitudinal side view thereof, FIG. 3 is a front view thereof, and FIG. Schematic diagram for explaining
FIG. 5 is a perspective view schematically shown for explaining the action, and FIG. 6 is a characteristic diagram of rotational torque for explaining the effect. 1 ... 1st shaft, 2 ... small diameter part, 3 ... 2nd shaft 5a, 5b ... magnetic material, 10a, 10b ... magnetic path piece, 11 ... first pickup path, 12 ... second pickup Road, 13 ... Hall element (magnetic detection element).

Claims (1)

[Claims] 1. A tip portion of a first shaft is connected to a second shaft as a structure capable of generating a torsional displacement, and a predetermined number of N poles and S poles are alternately arranged as fixed magnetic poles so as to surround the periphery of the connection portion. The first pickup path and the second pickup path as many as the N poles and the S poles are arranged so as to face the intermediate positions of the respective magnetic poles. , A magnetic detection element for detecting a change in magnetic flux flowing through the second pickup path is provided on the first shaft in a non-contact manner, and when the first shaft is twisted and displaced with respect to the second shaft, the N pole is the first pickup path or the first pickup path. The amount of magnetic flux flowing through the first and second pickup paths is changed depending on which side of the two pickup paths is approached, and the twist displacement of the first shaft with respect to the second shaft is changed from the change in the magnetic flux. Torque sensor is characterized in that so as to output.