JPH0743287B2 - 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 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 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 a torsional displacement, and a predetermined pair of N pole and S pole is arranged as a fixed magnetic pole so as to surround the periphery of this connection portion, and the shaft is attached to the second shaft. Fixed, the first number of the same number as the logarithm of the fixed magnetic pole
The pickup path has N poles and S poles that form a pair of fixed magnetic poles.
A second pickup path is provided so as to face the middle position of the poles and returns the magnetic flux flowing through the first pickup path to each of the magnetic poles, and the amount of magnetic flux flowing through the first and second pickup paths. First magnetic detection element for detecting
The first and second pickup paths are provided in a non-contact manner with the shaft, and depending on which side of the first pickup path or the second pickup path the N pole approaches when the first shaft is torsionally displaced with respect to the second shaft. Change the amount of magnetic flux flowing through the
The torsional displacement of the shaft is detected.

(Operation) In the present invention, the first shaft is connected to the second shaft so that the distal end portion has a structure capable of generating torsional displacement, and the predetermined pair of N pole and S pole 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 number of pairs of the fixed magnetic poles are arranged so as to face an intermediate position between the N pole and the S pole forming the pair of fixed magnetic poles. A second pickup path is provided for returning the magnetic flux flowing through the first pickup path to each of the magnetic poles. 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, it flows through the first and second pickup paths depending on which side of the pair of N pole or S pole the first pickup path is located. The amount of magnetic flux 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, eight magnetic bodies 5a arranged so that the N pole faces the end surface 4c and eight magnetic bodies 5b arranged so that the S pole face the end surface 4c are alternately concentric and equally spaced. It is arranged so that. Further, the other end of each magnetic body 5a, 5b is connected to an annular common ring 6, and the common ring 6 forms a part of a closed loop magnetic path for the magnetic field emitted from each magnetic body 5a, 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, as shown in FIG. 2, a cylindrical flange type magnetic path material (second pickup path) 7 is fitted and fixed to the outer peripheral surface 1a of the first shaft on the side of the small diameter portion 2, and the cylindrical flange type magnetic path is formed. One end 7a of the material 7 is extended to the second shaft 3 side so as to have a minute gap (pivot air gap) with the inner peripheral surface 6a of the common ring 6. The other end 7b of the cylindrical flange type magnetic path member 7 is axially arranged so as to face an inner peripheral surface 9b of an annular magnetic path member (first pickup path) 9 described later with a predetermined minute gap. The pickup member 8 made of a non-magnetic material is fitted and fixed to the outer peripheral surface 7c of the cylindrical flange type magnetic path material 7. The pickup member 8 has a small gap from the tip end side of the end portion 7b toward the axial direction side.
8a is defined, and the outer peripheral side end surface of the pickup member 8 is formed.
An annular magnetic path material 9 is arranged on 8b so as to face the end surface 4c and to have a minute gap with the end surface 4c. The annular magnetic path member 9 is formed with eight tooth-shaped protrusions 9a facing the intermediate positions of the magnetic bodies 5a and 5b and forming a pair with the magnetic bodies 5a and 5b. , 5b and the tooth-shaped protruding portion 9a form one set each. Therefore, the annular magnetic path material 9
As shown in the front view of FIG. 3, the N pole is located on the right side and the S pole is located on the left side across the tooth profile protrusion 9a, and the gap space l _A from the N pole to the tooth profile protrusion 9a and the S pole are located. It becomes equal to each other and the gap space l _B to toothed protrusion 9a from. In the present embodiment, the N pole is shown on the right side and the S pole is shown on the left side. However, the present invention is not limited to this, and an S pole on the right side and an N pole on the left side may be used. Here, the common ring 6, the cylindrical flange type magnetic path material 7 and the annular magnetic path material 9 are preferably made of a material that easily allows the magnetic field lines to pass therethrough, and are made of, for example, permalloy or ferrite. To form a predetermined magnetic path corresponding to the twist angle. By the way, the cylindrical flange type magnetic path material 7 and the annular magnetic path material 9 are the magnetic material 5 described above.
Like the a and 5b, it is integrally formed with the pickup member 8 made of a non-magnetic material, and in the steady state (that is, when the torque is 0), the magnetic material 5a or 5b is the cylindrical flange type magnetic path material 7 as described above. It is configured to be located exactly in the middle of. 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. Further, between the tooth-shaped protruding portion 9a of the annular magnetic path member 9 and the end portion 7b of the cylindrical flange type magnetic-path member 7 described above, the tooth-shaped protruding portion 9a is not in contact with the magnetic path member or the pickup member 8. One or a plurality of Hall elements (magnetism detecting elements) 11 are arranged at a position perpendicular to the magnetic field applied from the end portion 7b to the tooth shape protruding portion 9a (or from the end portion 7b), and the Hall element 11 is a printed circuit board. It is fixed to 12 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 uses the torsional displacement generated between the first shaft 1 and the second shaft 3 as the change in the gap spaces l _A and l _B between the magnetic bodies 5a and 5b and the tooth profile protrusion 9a. The Hall element 11 detects the torque by detecting the flow of magnetic flux (magnetic path) and the change in the amount of magnetic flux caused by the change in the gap spaces l _A and l _{B in} a non-contact manner. Subsequently, the basic idea of the present invention will be described with reference to FIG. Figure 4 (a)
Is a perspective view schematically showing a part of the torque detection mechanism 21 in a steady state, FIG. 7B shows a case where a rotational force is applied in the circumferential direction A, and FIG. The case where the force is applied in the direction of the circumferential direction B is schematically shown.

Since no constant torque is applied, as shown in FIG. 4 (a), the gap space l _A from the magnetic body 5a to the tooth profile protrusion 9a of the annular magnetic path material 9 and the tooth profile protrusion 9a to the magnetic body 5b Gap spaces I _B are equal to each other, and the positional relationship between each magnetic body and the tooth-shaped protrusion 9a is uniform at any place.

Therefore, as shown in the figure, the pair of magnetic bodies 5a and 5b and the tooth-shaped protruding portion 9a can be described as a representative example. Now, the magnetic flux emitted from the N pole of the magnetic body 5a enters the tooth profile protrusion 9a of the annular magnetic path member 9 through the gap space l _A as shown by the arrow, passes through the tooth profile protrusion 9a, and passes through the gap space.
It reaches the south pole of the magnetic body 5b via l _B. The magnetic flux generated from the N pole of the magnetic body 5b passes through the common ring 6 and the magnetic body 5a.
To reach the south pole. In this way, the magnetic bodies 5a and 5b, the tooth-shaped protruding portion 9a of the annular magnetic path member 9 and the common ring 6 form one closed loop with the gap spaces l _A and l _B sandwiched between them. It is called the main magnetic path, and 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 not only forms the main magnetic path that reaches the S pole of the magnetic body 5b by passing through the tooth-shaped protruding portion 9a, but also in the center direction of the annular magnetic path material 9. There are also those that go toward (inner circumferential surface 9b direction). That is, part of the magnetic flux emitted from the N pole of the magnetic member 5a as shown by the arrows in FIG. (C), the gap space l _A, toothed protrusion 9a of the annular magnetic path member 9 and the inner peripheral surface 9b To the Hall element 11, and the Hall element 11 is orthogonal to the end portion 7 of the cylindrical flange type magnetic path material 7.
b, 7a, Pivot air gap and common ring 6
To form a bypass magnetic path that returns to the S pole of the original magnetic body 5a via (the magnetic flux passing through the bypass magnetic path in this direction is referred to as φ ₂ ). However, not only the magnetic flux of the magnetic body 5a but also the magnetic flux from the magnetic body 5b is applied to the tooth-shaped protruding portion 9a (however, the polarity is different), which is different from the case described above as shown by the arrow in FIG. 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 11 is, in fact, very small as compared with the magnetic path material having a large magnetic permeability or the common ring 6 in the gap space.
It is determined by the difference in size of l _A , l _B or the pivot air gap. In addition, 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 are aged. Even if there is deterioration due to, for example, the accuracy of torque detection does not decrease.

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 11 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 = | −φ) even if there is some leakage flux | φ ₂ |.
₂ |) and cancel each other out, and the Hall element 11 is insensitive and torque is not detected.

At unsteady 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 tooth profile protrusion 9a increases. On the other hand, the gap space l _A from the magnetic body 5b to the tooth profile protrusion 9a decreases conversely. Along with this, the magnetic path resistance of the magnetic flux −φ ₂ of the bypass magnetic path decreases, and both the magnetic flux φ _{2 of the} bypass magnetic path and the magnetic path resistance of the main magnetic path φ ₁ increase. 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 to the direction (see Fig. 5). For example, if the direction of the magnetic field applied to the Hall element 11 by the rotational force in the A direction is positive and the output of the Hall element 11 is set so that its output voltage has a positive value, as shown in FIG. It is possible to properly detect the magnitude and direction of the generated torque and the static torque. Further, as shown in FIG. 4 (c), when the rotational force is applied in the direction of the circumferential direction B, the tooth-shaped protrusion 9a approaches the magnetic body 5a, so that the magnetic flux φ ₂ increases and becomes large. The torque in the opposite direction to that in the 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 11, the torsional displacement generated between the first shaft 1 and the second shaft 3 causes the magnetic displacement of the magnetic bodies 5a and 5a. gap space l _a between 5b and toothed protrusions 9a, seen as a change in l _B, the gap space l _a, assuming that the change in the magnetic flux flow and the magnetic flux amount caused by changes in l _B indicates torque Hall element 11 provided without contact with the pickup member 8
Is accurately detected by. 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. Further, in addition to the simple structure, since the Hall element 11 and the like can be adjusted after the mold member 4 and the pickup member 8 are mounted, it is necessary to perform difficult work requiring high precision in mounting 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, 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 end portion of the first shaft is connected to the second shaft as a structure capable of generating torsional displacement, and a predetermined pair of N pole and S pole is provided so as to surround the periphery of the connection portion. It is arranged as a fixed magnetic pole and is fixed to the second shaft, and the same number of first pickup paths as the number of pairs of the fixed magnetic poles are arranged so as to face the intermediate position between the N pole and the S pole forming the pair of fixed magnetic poles. A second pickup path for returning the magnetic flux flowing through the first pickup path to each of the magnetic poles is provided, and a magnetic detection element for detecting the amount of the magnetic flux flowing through the first and second pickup paths is provided on the first shaft. Provided by contact, second
When the first shaft is twisted and displaced with respect to the shaft, the amount of magnetic flux flowing in the first and second pickup paths is changed depending on which side of the pair of N pole or S pole the first pickup path approaches. Since the torsional displacement of the first shaft with respect to the second shaft is detected from the change of the magnetic flux, the structure is simple and the response is good,
Torque can be detected accurately 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, 5a, 5b ... magnetic material, 7 ... cylindrical flange type magnetic path material (second pickup path), 9 ... annular shape Magnetic path material (first
Pickup path), 9a ... Toothed protrusion, 11 ... Hall element (magnetic detection element).

Claims (1)

[Claims] 1. A front end portion of a first shaft is connected to a second shaft as a structure capable of generating a torsional displacement, and a predetermined pair of N pole and S pole is arranged as a fixed magnetic pole so as to surround the periphery of the connection portion. Is fixed to the second shaft, and the same number of the first pickup paths as the number of pairs of the fixed magnetic poles are arranged so as to face the intermediate position between the N pole and the S pole forming the pair of fixed magnetic poles. A second pickup path for returning the magnetic flux flowing through the pickup path to each of the magnetic poles 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 when the first shaft is torsionally displaced with respect to the second shaft, the first
The amount of magnetic flux flowing through the first and second pickup paths is changed depending on which side of the N pole or the S pole of the pair the pickup path is located. A torque sensor characterized by detecting a twist displacement.