JPH0875573A - Holding member and magnetostrictine torque sensor using it - Google Patents

Abstract

PURPOSE: To provide a no-zero point drift or small magnetostrictive torque sensor without causing position dislocation between constitution members by temperature change. CONSTITUTION: Holding members 10 of a magnetostrictive torque sensor have a space as a clearance in which the inside diameter of an annular body 11, whose outside diameter is in contact with a housing 2, is not in contact with anything. It has a space as a clearance wherein the outside diameter of a projection part 13, whose inside diameter is in contact with yoke members 5, is not in contact with anything. When each member expands due to temperature change (temperature increase), the yoke members 5, the housing 2 and a rotation shaft (not shown) whose thermal expansion coefficients are nearly same, hold mutual position relation, and only the holding members 10 of a larger thermal expansion coefficient expand relatively. At this time, the annular body 11 of the holding member 10 expands in the inside having the clearance, and the projection part 13 holding the yoke member 5 is deformed in the form of a divergence to the outside having the clearance, and production of compression stresses is avoided respectively. Strains produced between each members caused by thermal stress accompanying the temperature change are eliminated, and the mutual position relation of each member is held constant. Thereby accurate torque detection is made possible.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a holding member that holds a winding member that surrounds a rotary shaft in a housing that engages with the rotary shaft in a non-contact manner, and a magnetostrictive torque sensor using the same.

[0002]

2. Description of the Related Art Conventionally, there is a magnetostrictive torque sensor as shown in FIG. To briefly explain this, the magnetostrictive torque sensor shown in FIG. 1 has a housing (frame) 2 arranged at an appropriate position on a torque transmission shaft (rotary shaft) 1 (the rotary shaft 1 shown in FIG. 1). (Cross section except for). This housing 2
Is engaged with the rotating shaft 1 via the bearing 3 and is fixed to an appropriate portion of the external device. The rotary shaft 1 is rotatable with respect to the housing 2, and the magnetostrictive films 4-1 and 4-2 surrounding the shaft circumferential surface are attached to the shaft located inside the housing 2 at appropriate intervals. There is. These magnetostrictive films 4-1 and 4-2 are magnetostrictive elements whose magnetic permeability changes due to stress, and the surface thereof is provided with notches inclined in directions opposite to the width direction of the film. When the rotating shaft 1 rotates and a strain is generated in the shaft due to a twist due to a load, the one of the magnetostrictive films 4-1 (or 4-2) is formed due to the presence of the notch.
Compressive stress is applied to the other magnetostrictive film 4-2 (or 4-
Tensile stress is applied to 1). As a result, the magnetic permeability of each magnetostrictive film increases on the one hand and decreases on the other hand. A yoke (joint beam) member 5 is disposed so as to surround the rotary shaft 1 in a non-contact manner at a position facing the magnetostrictive films 4-1 and 4-2, and is attached to the housing 2 by the holding members 6-1 and 6-2. Is held.

FIG. 1B is a perspective view showing only the yoke member 5 shown in the above sectional view. As shown in FIG. 3B, the yoke member 5 is made of hard resin or metal and has annular grooves 5-1 and 5-2 formed in the portions corresponding to the two magnetostrictive films 4-1 and 4-2. Has been done.
Magnetostriction detecting coils 7-1 and 7-2 shown in FIG. 9A are held in these grooves 5-1 and 5-2, respectively. These magnetostriction detection coils 7-1 and 7-2 are generally
It is held in the grooves 5-1 and 5-2 while being wound on the bobbin.

FIG. 1C shows the magnetostriction detecting coil 7-1 (or 7-2) wound on the bobbin 8.
(d) shows the cross-sectional view. Magnetostriction detection coil 7-1
(Or 7-2) is a normal enameled copper wire having an appropriate thickness, and is composed of a primary coil and a secondary coil. From these primary coil and secondary coil, a primary coil terminal and a secondary coil terminal are drawn out to the outside of the bobbin 8 and further to the outside of the housing 2 to be connected to a predetermined circuit.

The above primary coil is an induction coil, which is energized from the outside to generate a magnetostriction detecting coil 7-1 (or 7-2).
Magnetic flux is generated along the inner diameter of the magnetostrictive detection coil 7-1 (or 7-2) and penetrates the magnetostrictive film 4-1 (or 4-2) on the rotating shaft 1 that penetrates the inner diameter of the magnetostrictive detection coil 7-1 (or 7-2). Magnetostrictive film 4-1
(Or 4-2) corresponds to the strain according to the load due to the rotation of the rotary shaft 1 as described above, and the magnetic permeability is increased (or higher than that when the rotary shaft 1 is rotating without load). descend. That is, the magnetic flux density transmitted through the magnetostrictive film 4-1 (or 4-2) becomes high (or low). On the other hand, the secondary coil is a detection coil, and is the magnetostrictive film 4-1 (or 4).
The secondary current is induced by the magnetic flux passing through -2). The secondary current induced on the secondary coil side increases or decreases as compared with when the rotating shaft 1 is rotating without a load, depending on the level of the magnetic flux density. These two magnetostrictive detection coils 7
-1 and 7-2 are used to detect the values of the secondary current increase or decrease in two opposite directions at the same time, which is the same as the electrical differential amplification that cancels the offset component and doubles the sensitivity. It depends on the principle.

As described above, the magnetostrictive torque sensor detects the degree of distortion of the rotating shaft 1, that is, the load applied to the rotating shaft 1, that is, the torque by detecting the degree of increase or decrease of the secondary current. are doing.

The intensity of magnetic flux (magnetic flux density) is inversely proportional to the square of the distance from the magnetic flux generating source. Therefore, if there is a slight change in the vertical or horizontal distance between the magnetostrictive film 4-1 (or 4-2) on the rotating shaft 1 and the magnetostrictive detection coil 7-1 (or 7-2), the primary The density of the magnetic flux generated by the coil and passing through the magnetostrictive film 4-1 (or 4-2) fluctuates greatly. That is, if there is a slight positional deviation between the magnetostrictive film 4-1 (or 4-2) and the magnetostrictive detection coil 7-1 (or 7-2), it is detected by the secondary current when the rotating shaft 1 is unloaded. The reference current should fluctuate (zero point drift), and accurate torque cannot be detected. The holding members 6-1 and 6-2 shown in FIG. 1 are used to position the magnetostrictive film and the magnetostriction detecting coil (to keep the magnetic path constant).

FIGS. 5A and 5B show another example 2 of the holding member. In both cases, a cut groove is provided in the yoke member (a peripheral surface of the yoke member circumference for the yoke member 5a in FIG. 1A, and a side surface of the yoke member for the yoke member 5b in FIG. 2B), and fitted into the cut groove. Holding the protrusion (6
-1a or 6-1b), and as shown in FIGS. 1 (a) and (b), the notch groove of the yoke member and the protrusion of the holding member are fitted to each other, whereby the housing 2 is provided. The held yoke member 5a (or 5b) is prevented from being displaced and the magnetic path is kept constant. In the holding member, the yoke member 5 has a fitting stress due to thermal stress due to temperature change and accumulation of tolerance due to assembly of each component.
In order not to adversely affect a (or 5b),
It is composed of an elastic body.

[0009]

However, even if the yoke member 5a (or 5b) is positioned by various fitting methods by forming the holding member with an elastic body as described above, the holding member and the yoke are not formed. Members, housings, etc. cause thermal expansion or thermal contraction due to temperature changes in the environment. Normally, the yoke member and the housing are made of metal like the rotating shaft, and the coefficient of thermal expansion does not differ so much, so that the yoke member and the housing expand or contract to the same extent with respect to temperature changes. Therefore, originally, the mutual positional relationship does not change. However, since the holding member, which is a positioning member interposed in the middle, is made of resin, it has an extremely large expansion coefficient as compared with metal. However, as shown in FIGS. 4 (a) and 5 (a), (b), this holding member is in contact with the yoke member inside the portion in contact with the housing. In other words, the holding member is held by the housing at the outer diameter portion thereof, and the yoke member is held by the inner diameter portion of the same portion held by the outer diameter portion. That is, it is sandwiched between the housing and the yoke member. Therefore, even though the holding member is made of an elastic body, it is hard to say that it completely absorbs thermal stress, and distortion occurs at the abutting portion, which causes a gap between the members. As a result, a positional shift due to temperature change occurs in the component parts of each member. When the positional deviation, especially the eccentricity from the axis of the rotary shaft 1 occurs in the yoke member 5, the magnetic path changes, and as a result, the zero point drift occurs and accurate torque detection cannot be performed. Occurs.

In view of the above conventional circumstances, the object of the present invention is to
It is an object of the present invention to provide a magnetostrictive torque sensor that does not cause a positional shift between constituent members even if the temperature changes and has no zero-point drift or has a very small zero-point drift.

[0011]

[Means and Action for Solving the Problems] First, claim 1
The holding member of the invention according to the invention has a ring body formed in a ring shape, and at one side surface portion of the ring body at a position concentric with the ring body and away from a side end of an outer diameter portion of the ring body. A protrusion that is elastically deformable and that protrudes from the side surface is provided, and when the protrusion is interposed between the housing and the magnetic member disposed in the housing, the protrusion holds the magnetic member and the ring member The outer diameter portion is formed so as to be held by the housing.

As a result, the position of the magnetic member is kept constant regardless of the temperature change. Next, the invention according to claim 2 is a magnetostriction detecting coil comprising a rotating shaft, a magnetostrictive element provided on a peripheral surface of the rotating shaft, and a primary coil and a secondary coil facing the magnetostrictive element in a non-contact manner. And a yoke member that holds the magnetostrictive detection coil in a non-contact manner with the rotary shaft and the magnetostrictive element, and a housing that holds the yoke member and engages with the rotary shaft via a bearing. Applied to.

In the magnetostrictive torque sensor of the present invention, the holding member according to the first aspect of the present invention is interposed between the housing and the yoke member, and the holding member is formed by the inner diameter portion of the protrusion of the yoke. It is configured to hold the member and to be held from the housing by its annular outer diameter portion.

As a result, even if the temperature changes, a large positional deviation does not occur between the members of the magnetostrictive torque sensor, and the zero point drift of magnetostriction detection is kept small.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. FIG. 1 (a) is a plan view of a holding member according to one embodiment, and FIG. 1 (b) is a view taken along the line AA 'of FIG.
1A and 1B, the holding member 10 is made of a non-electrical conductor such as PBT, epoxy resin, Teflon (a fluorocarbon resin, trade name of DuPont, USA). Of these, Teflon is a preferable material from the viewpoint of hardness and ease of handling during assembly. The holding member 10 has an annular body 11 formed in an annular shape, and on one side surface portion 12 of the annular body 11, a side end of an outer diameter portion of the annular body 11 is concentric with the annular body 11. At a position away from the side portion 1
It has a projection 13 which projects from 2 and forms an annular shape. When the inner diameter of the protrusion 13 receives an external force in the centrifugal direction indicated by an arrow B in FIG. 1B, the protrusion 13 has an appropriate elasticity to bend toward the centrifugal direction and is elastically deformable. Is configured.

The holding member 10 includes, for example, a housing 2 for rotatably engaging the rotary shaft 1 shown in FIG. 1, and a yoke member 5 disposed in the housing 2 and surrounding the rotary shaft 1 in a non-contact manner. When it is interposed between
Thus, the yoke member 5 is held by the outer diameter portion of the ring body 11 and is held by the housing 2. The yoke member 5 is made of a magnetic material.

Next, an embodiment of a magnetostrictive torque sensor using the holding member 10 will be described. Figure 2
It is sectional drawing of the Example of a magnetostrictive torque sensor. In the structure of the magnetostrictive torque sensor shown in FIG.
Other than that, the other components are the same as those of the magnetostrictive torque sensor shown in FIG. 1. Therefore, in FIG. 2, the rotating shaft, the magnetostrictive film, the magnetostriction detecting coil, the bobbin, etc. shown in FIG. Is omitted and only the holding member 10, the housing 2 and the yoke member 5 are shown.

As shown in the figure, in the magnetostrictive torque sensor of this embodiment, the holding member 10 described in FIG. 1 is interposed between the housing 2 and the yoke member 5, and the holding member 10 is The yoke member 5 is held by the inner diameter of the protrusion 13 and is held from the housing 2 by the outer diameter of the ring 11.

Next, the operation of the holding member corresponding to the temperature change in the magnetostrictive torque sensor having the above-described structure will be described with reference to FIG.
This will be described with reference to the operation state diagram shown in (b). Same figure (a), (b)
Shows an enlarged part of the left side of the configuration of FIG. As shown in FIG. 3 (a), the holding member 10, on the other hand, has a portion 11-1 (the outer diameter of the ring body 11) that is in contact with the housing 2 and an inner portion 11-2 (the inner diameter of the ring body 11) that is in contact with the holding member 10. Has a free space (relief allowance), and on the other hand, also contacts the outer side 13-1 (outer diameter of the protruding portion 13) of the portion 13-2 (inner diameter of the protruding portion 13) in contact with the yoke member 5. It has a free space (escape allowance) without objects.

Corresponding to a sufficiently low environmental temperature, the same figure (a)
Changes in temperature (temperature rise) when configured as shown in
When each member expands due to the above, as described above, the yoke member 5, the housing 2, and the rotating shaft (not shown) have the same thermal expansion coefficients and expand in a state of maintaining their positional relationship with each other. To do. Therefore, only the holding member 10 having a larger coefficient of thermal expansion expands relative to the yoke member 5 and the housing 2. At this time, as shown in FIG. 2B, the expanded ring member 11 of the holding member 10
Since the outer diameter portion is in contact with the housing 2, it expands to the inside with a clearance, as indicated by arrow C in the figure, and avoids the occurrence of compressive stress in this portion. On the other hand, the protrusion 13 provided on the ring body 11 and having the inner diameter portion in contact with the yoke member 5 is further pressed to the yoke member 5 by the ring body 11 that expands inward. It opens in a flared shape to the outside where there is a clearance, as shown by D, and avoids the occurrence of compressive stress in this portion.

As described above, since there is a clearance in the engagement relationship between the housing and the holding member, and there is a clearance in the engagement relationship between the holding member and the yoke member, even if the environmental temperature changes. The compressive stress is eliminated by the deformation of the protrusion 13 and the distortion due to the thermal stress due to the temperature change does not occur between the respective members, so that the mutual positional relationship is kept constant, whereby the zero point drift of the magnetostriction detection is caused. There is no
Alternatively, it is kept small, and therefore accurate torque detection becomes possible.

In addition, since there are clearances between the holding member and the yoke member and between the holding member and the housing in this way, a larger tolerance can be taken in assembling as compared with the conventional case, and therefore, the design of the parts. , Easy to manufacture and improve work efficiency.

Further, it is not necessary to provide a cut groove or the like on the yoke member side, and it is sufficient to change only the shape of the holding member using the conventional yoke member shown in FIG. 4 (a), which is easy to improve. is there.

[0024]

As described above, according to the present invention,
Even if the environmental temperature changes, the deformation of the protrusion of the holding member eliminates the compressive stress in the holding portion between the housing and the yoke member, and the distortion due to the thermal stress due to the temperature change does not occur between the members. The positional relationship of is constant and the zero-point drift of the magnetostriction detection is not present or is kept small, and therefore accurate torque detection is possible.

[Brief description of drawings]

FIG. 1A is a plan view of a holding member according to an embodiment,
(b) is the AA 'arrow line view.

FIG. 2 is a sectional view of an embodiment of a magnetostrictive torque sensor using the holding member of FIG.

3 (a) and 3 (b) are views for explaining an operating state of a holding member of the magnetostrictive torque sensor.

FIG. 4A is a sectional view of a conventional magnetostrictive torque sensor,
(b) is a perspective view showing only the yoke from the cross-sectional view, (c) is a perspective view of the magnetostrictive detection coil wound around a bobbin, and (d) is its cross-sectional view.

5A and 5B are views showing an example 2 of a conventional holding member.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Torque transmission shaft (rotating shaft) 2 Housing 3 Bearings 4-1 and 4-2 Magnetostrictive film 5, 5a, 5b Magnetic flux collecting yokes 5-1 and 5-2 Grooves 6-1, 6-2, 6-1a and 6 -1b Holding member 7-1, 7-2 Magnetostriction detection coil 8 Bobbin 10 Holding member 11 Ring body 11-1 A portion in contact with the housing (outer diameter of the ring body) 11-2 A portion having a clearance (the inner diameter of the ring body 12 Plane part 13 Projection part 13-1 Part having clearance (projection part outer diameter) 13-2 Part in contact with yoke member (projection part inner diameter)

Claims (2)

[Claims] 1. A ring-shaped ring body, which is concentric with the ring body on one side surface of the ring body and is located away from the side end of the outer diameter portion of the ring body from the side surface section. A protrusion is provided and is elastically deformable. When the protrusion is interposed between the housing and a magnetic member disposed in the housing, the protrusion holds the magnetic member and the outer diameter portion of the annular body. The holding member is formed so as to be held by the housing. 2. A rotating shaft, a magnetostrictive element provided on a peripheral surface of the rotating shaft, a magnetostrictive detecting coil including a primary coil and a secondary coil facing the magnetostrictive element in a non-contact manner, and the magnetostrictive detecting coil. 2. A magnetostrictive torque sensor comprising: a yoke member that holds the rotating shaft and the magnetostrictive element in non-contact with each other; and a housing that holds the yoke member and engages with the rotating shaft via a bearing. The holding member is interposed between the housing and the yoke member, and the holding member holds the yoke member by the inner diameter portion of the protrusion and is held from the housing by the outer diameter portion of the annular body. Magnetostrictive torque sensor characterized by.