JPH0743288B2 - 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 a torque sensor described in Japanese Patent Application Laid-Open No. 54-17228, which is 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 described in Japanese Patent Laid-Open No. 55-44013 is provided with an electric displacement detection unit such as a strain gauge on an input shaft to which steering torque is transmitted from the steering wheel, and the steering torque and steering resistance input from the steering wheel. It detects the relative torsional displacement of the input shaft that occurs depending on the difference between the temperature and the temperature.Because an electrical displacement detector such as a strain gauge was fixed to the input shaft to detect the torsional displacement of the input shaft, There is a problem that it is susceptible to changes, its operation is unstable, and its reliability is poor.

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 whose one end is connected to a steering wheel and the other end is connected to a steering gear is divided, and the two divided shafts are separated by 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, since the rotary shaft is the target, a non-contact type torque sensor is desirable from the viewpoint of reliability such as wear resistance and safety. 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 problems described above, it is quite difficult to detect static torque with conventional devices in any of contact type and non-contact type torque sensors. Sensors have 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 which has a simple structure, has a good responsiveness, and can detect a torque at low cost regardless of whether it is stationary or rotating by detecting the change without contact 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 pair of N poles or S poles are arranged as fixed magnetic poles so as to surround the periphery of the connection portion and the second shaft is provided. The second pickup path is fixed, and the same number of the first pickup paths as the fixed magnetic poles are arranged so as to face the intermediate position of each fixed magnetic pole, and the magnetic flux flowing through the first pickup path is returned to the respective magnetic poles. And a magnetic detection element that detects the amount of magnetic flux flowing through the first and second pickup paths is provided on the first shaft in a non-contact manner.
When the first shaft is twisted and displaced with respect to the shaft, the first pickup path located at the intermediate position of each fixed path pole before the displacement deviates from the intermediate position after the displacement and comes close to the fixed magnetic pole side. The amount of magnetic flux flowing through the pickup path is changed, and the torsional displacement of the first shaft with respect to the second shaft is detected from the change in the magnetic flux.

(Operation) In 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 or S poles are fixed magnetic poles so as to surround the periphery of the connection portion. Is fixed to the second shaft, and the same number of first pickup paths as the fixed magnetic poles are arranged so as to face the intermediate position of each fixed magnetic pole, and the magnetic flux flowing through the first pickup path is A second pickup path is provided for returning to each magnetic pole. Further, a magnetic detection element that detects the amount of magnetic flux flowing through the first and second pickup paths is provided on the first shaft in a non-contact manner. Then, when the first shaft is twisted and displaced with respect to the second shaft, the first pickup path, which is located at the intermediate position of each fixed path pole before the displacement, deviates from the intermediate position after the displacement and comes close to the fixed magnetic pole side. The amount of magnetic flux flowing through the first and second pickup paths changes, and the torsional displacement of the first shaft with respect to the second shaft is detected in a non-contact manner from the change in the magnetic flux. 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 5 are views showing an embodiment of the present invention, FIG. 1 is an exploded perspective view of this embodiment, FIG. 2 is a vertical sectional 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 cross-sectional side view of FIG. 2, the outer peripheral surface 3a of the second shaft 3 has a cylindrical tip member 4a of a cylindrical mold member (non-magnetic material) 4 formed so as to enclose the small diameter portion 2.
, And the mold member 4 is paired with a pickup member 8 and a Hall element 11, which will be described later, to form a torque detection mechanism 21. On the other hand, a donut-shaped magnetic material embedded portion 4b is formed on the other end of the mold member 4, and the magnetic material embedded portion 4b has a cut surface (end surface) 4c perpendicular to the axial direction. In the body-embedded portion 4b, 16 magnetic bodies 5 arranged so as to face the N pole on the end face 4c are concentrically arranged at equal intervals. further,
The other end of each magnetic body 5 is connected to an annular common ring 6, and the common ring 6 forms part of a closed loop magnetic path for the magnetic field emitted from each magnetic body 5. The common ring 6 and each magnetic body 5 are embedded in the magnetic material embedded portion 4b and are integrally formed with the magnetic material embedded portion 4b made of a non-magnetic material. In this embodiment, the number of the magnetic bodies 5 is set to 16, but the number of magnetic bodies 5 is not limited to this, and any other number may be used as long as they face at equal intervals. It may be one that faces the pole.

On the other hand, a cylindrical flange type magnetic path material (second pickup path) 7 is fitted and fixed to the outer peripheral surface 1a on the small diameter portion 2 side of the first shaft, and one end portion 7a of the cylindrical flange type magnetic path material 7 is The common ring 6 is extended to the second shaft 3 side so as to have an inner peripheral surface 6a and a minute gap (pivot air gap). The other end 7b of the cylindrical flange type magnetic path material 7 is an inner peripheral surface 9b of an annular magnetic path material (first pickup path) 9 described later.
Is bent perpendicularly to the axial direction so as to face each other with a predetermined minute gap, and the cylindrical flange type magnetic path member 7
A pickup member 8 made of a non-magnetic material is fitted and fixed to the outer peripheral surface 7c of the. The other end of the pickup member 8
A minute gap 8a is defined from the tip side of 7b to the axial side, and an annular magnetic path material 9 faces the cut surface 4c on the outer peripheral side end surface 8b of the pickup member 8 and is minute with the cut surface 4c. It is arranged so as to have a void. The annular magnetic path member 9 is formed with 16 tooth-shaped protrusions 9a facing the intermediate position of each magnetic body 5. By the way, the cylindrical flange type magnetic path material 7 and the annular magnetic path material 9 are integrally formed on the pickup member 8 made of a non-magnetic material like the magnetic material 5, and in a steady state (that is, when the torque is 0). At the time), as shown in the front view of FIG. 3, the magnetic body 5 is located exactly in the middle of the cylindrical flange type magnetic path material 7. Therefore, the gap spaces from the magnetic body 5 to the tooth-shaped protruding portion 9a of the annular magnetic path member 9 are equal. Here, the common ring 6, the cylindrical flange type magnetic path material 7 and the annular magnetic path material 9 are desirably made of a material that easily allows the magnetic force lines to pass therethrough, and are made of, for example, permalloy or ferrite. further,
There is no contact between the tooth profile protrusion 9a of the annular magnetic path material 9 and the end 7b of the cylindrical flange type magnetic path material 7 and the end portion from the tooth profile projection 9a without contact with the magnetic path material or the pickup member 8. One or a plurality of Hall elements (magnetism detecting elements) 11 are arranged at positions perpendicular to the magnetic field applied to 7b (or to the tooth-shaped protruding section 9a from the end 7b).
Is fixed to the surface with an adhesive or the like. A member (not shown) for detecting and processing a signal from the Hall element 11 is arranged on the printed circuit board 12, and the printed circuit board 12 is provided with a support member 12a fixed to the printed circuit board to form a first shaft. 1 is rotatably displaced and fitted. The Hall element 11 is a sensor that utilizes the solid Hall effect, and is an element that generates an output voltage proportional to the strength of the magnetic field. Omit it.

Next, the operation will be described.

The torque sensor according to the present invention regards the torsional displacement generated between the first shaft 1 and the second shaft 3 as a change in the gap space between the magnetic body 5 and the tooth profile protrusion 9a, and changes in this gap space. The Hall element 11 detects the change in the amount of magnetic flux generated by the non-contact to detect the torque. Subsequently, the basic idea of the present invention will be described with reference to FIG. FIG. 4 (a) is a perspective view schematically showing a part of the torque detection mechanism 21 in a steady state, and FIG. 4 (b) shows a case where a rotational force is applied in the circumferential direction A. Figure (c)
Shows schematically the case where the rotational force is applied in the direction of the circumferential direction B.

Since no constant torque is applied, the gap space from the magnetic body 5 to the tooth-shaped protrusion 9a of the annular magnetic path member 9 is uniform at any place as shown in FIG. 4 (a). Therefore, as shown in the figure, the tooth profile protrusion 9a and the tooth profile protrusion
This can be explained by taking a pair of magnetic bodies 5 sandwiching 9a as an example. Now, the magnetic flux generated from the N pole of the magnetic body 5 reaches the Hall element 11 through the gap space tooth-shaped projection 9a and the inner peripheral surface 9b as shown by the arrow, and the Hall element 11 is orthogonal to the cylindrical flange type magnetic path material. A closed loop that returns to the S pole of the original magnetic body 5 via the ends 7b and 7a of 7, the pivot air gap, and the common ring 6 is formed (the magnetic flux at this time is referred to as φ). In this case, the strength of the magnetic field applied to the Hall element 11 depends on the difference in the size of the gap space or the pivot air gap whose magnetic permeability is extremely smaller than that of the magnetic path material having a large magnetic permeability or the common ring 6 in practice. Although it is determined, since the gap space is relatively large in the steady state, the strength of the magnetic field applied to the Hall element 11 is almost zero, and no torque is detected. By the way, since each member of the cylindrical flange type magnetic path member 7, the annular magnetic path member 9 and the common ring 6 forms a common magnetic path during steady state and non-steady state, these members change over time. Even if there is deterioration due to, for example, the accuracy of torque detection does not decrease.

At unsteady state (when torque is applied) When the rotational force is applied in the direction of the circumferential direction A as shown in FIG. 4 (b), or the rotational force is applied in the circumferential direction B as shown in FIG. 4 (c). In any case, the gap space from the magnetic body 5 to the tooth-shaped protruding portion 9a becomes smaller, and the magnetic path resistance decreases accordingly. Therefore, the magnetic flux increases according to the rotational force, and the degree thereof is proportional to the magnitude of the twist angle applied in the A or B direction. As a result, the magnitude of the generated torque and the static torque can be appropriately detected as shown in FIG.

As described above, in the present embodiment, when the magnetic force generated from the magnetic body 5 is detected by the Hall element 11, the torsional displacement generated between the first shaft 1 and the second shaft 3 causes the magnetic body 5 and the tooth profile to project. It is perceived as a change in the gap space with the portion 9a, and the change in the amount of magnetic flux caused by the change in the gap space is accurately detected by the Hall element 11 provided in non-contact with the pickup member 8 as indicating the torque. It 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. In particular, in this embodiment, the structure of the magnetic path is very simple, so that it is possible to reduce the number of parts and the mounting cost. Moreover, in addition to the simple structure, the mold member 4 and the pickup member 8 are provided.
Since the Hall element 11 and the like can be adjusted after the mounting, the mounting of these members does not require a difficult work requiring high accuracy. 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, Both static torque and rotational torque, which were difficult to measure with the conventional device, can be accurately detected.

If the present invention having the above characteristics 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 invention is not limited to this. For example, the torsional rigidity of the magnetic body, the magnetic piece, and the shaft can be adjusted to be used. It goes without saying that the corresponding rotation torque can also 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.

Further, in this embodiment, the magnetic detection element (hall element) is
Although an example in which one piece is used is shown, the present invention is not limited to this, and a plurality of magnetic detection elements may be provided. For example, if two magnetic detection elements are provided at positions facing each other at an angle of 180 ° about the axis of the first shaft 1, the torque ripple component due to the influence of eccentricity or the like can be offset, and the detection can be performed. The accuracy can be further enhanced.

(Effect) According to 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 or S poles are provided so as to surround the periphery of the connection portion. The magnetic poles are arranged as fixed magnetic poles and fixed to the second shaft, and the same number of the first pickup paths as the fixed magnetic poles are arranged so as to face the intermediate position of each fixed magnetic pole, and the magnetic flux flowing through the first pickup paths is A second pickup path for returning to each magnetic pole is arranged, and a magnetic detection element for detecting the amount of magnetic flux flowing through the first and second pickup paths is provided on the first shaft in a non-contact manner, and a magnetic detection element is provided for the second shaft. When one shaft is twisted and displaced, the first pickup path, which is located at the intermediate position between the fixed path poles before the displacement, deviates from the intermediate position after the displacement and comes close to the fixed magnetic pole side, so that the first and second pickup paths flow. The amount of magnetic flux generated is changed, and the torsional displacement of the first shaft with respect to the second shaft is detected based on the change in the magnetic flux.
It is possible to provide a non-contact type torque sensor that can detect torque at low cost regardless of rotation.

[Brief description of drawings]

1 to 5 are views showing an embodiment of the torque sensor according to the present invention. FIG. 1 is an exploded perspective view thereof, FIG. 2 is a longitudinal side view thereof, and FIG. 3 is a front view thereof. FIG. 4A is a perspective view schematically shown for explaining the operation in the steady state, and FIG. 4B is a schematic view for explaining the operation when torque is applied in one direction. The perspective view shown in FIG. 4 (c) is a perspective view schematically shown for explaining the action when the torque is applied in the other direction, and FIG. 5 is the rotational torque for explaining the effect. FIG. 1 ... 1st shaft, 2 ... small diameter part, 3 ... 2nd shaft, 5 ... magnetic material, 7 ... cylindrical flange type magnetic path material (2nd
Pickup path), 9 ... annular magnetic path material (first pickup path), 9a ... Tooth-shaped protrusion, 11 ... 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 or S poles are arranged as fixed magnetic poles so as to surround the periphery of the connection portion. Is fixed to the second shaft, the same number of first pickup paths as the fixed magnetic poles are arranged so as to face the intermediate position of each fixed magnetic pole, and the magnetic flux flowing through the first pickup path is returned to each magnetic pole. The second pickup path is provided, and a magnetic detection element that detects the amount of magnetic flux flowing through the first and second pickup paths is provided on the first shaft in a non-contact manner, and the first shaft is twisted with respect to the second shaft. When displaced, the first pickup path at the intermediate position of each fixed path pole before the displacement deviates from this intermediate position after the displacement and approaches the fixed magnetic pole side, so that the amount of magnetic flux flowing through the first and second pickup paths is reduced. It is of the torque sensor, characterized in that the change in the magnetic flux and to detect the torsional displacement of the first shaft to the second shaft.