JP6345458B2 - Rotating shaft holding mechanism and rotational viscometer using the same - Google Patents

Description

  The present invention relates to a rotating shaft holding mechanism that can be used for a mechanism and a device that require a rotating shaft and requires a small amount of rotation, and to solve problems in fields that require highly accurate torque measurement. The invention has been devised and is particularly suitable for use in torque measurement in a rotational viscometer or a rotational viscometer type rheometer (hereinafter simply referred to as a rotational viscometer). .

Many of the rotating shaft holding mechanisms have a structure in which a rotating body such as a ball bearing is sandwiched. This reduces the accuracy and frictional resistance of the rotating shaft. However, the rotating body sandwiched between the bearings affects the accuracy of the rotating shaft, and further, the resistance of rotation varies finely with the rotation of the shaft. In applications where this is a problem, particularly when high accuracy and low friction resistance are required, an air bearing having a structure in which an air film is sandwiched is used. However, the air bearing requires a separate high-pressure air source, and cannot be made too compact, resulting in a drawback that the rotational moment increases. In addition, the air pressure supplied to the air bearing is a source of torque in some cases, and is a matter requiring attention when using the air bearing as a bearing for high-accuracy torque measurement.
Among the mechanisms that require a highly accurate rotating shaft, a holding mechanism having a structure that can ensure the necessary rotation by deformation of the spring can be adopted for a mechanism that hardly rotates, and the present inventors also have an elastic hinge mechanism. An application for a bearing mechanism that uses the above has already been filed (see Patent Document 1). As shown in FIG. 3, the rotating shaft holding mechanism of Patent Document 1 uses (1) a plurality of parallel spring links, and (2) the length and angle of the side on which the parallel spring links are deformed, and the parallel spring and the rotating shaft. It is the structure made to correspond to the distance and direction from the rotating shaft center of a junction point. By using the parallel spring link structure of (1) above, high rigidity can be imparted to deformations other than the rotation direction, and by matching the lengths of (2) above, movement of the shaft due to deformation of the parallel springs can be achieved. It can be lost.

JP 2012-132856 A

The bearing by the elastic hinge mechanism having the parallel spring link of Patent Document 1 is ideally changed by the rotation of the shaft due to the thin elastic hinge portion (plate spring) and the plate spring twice as thick as that. A configuration that is not possible is possible. However, since the restoring force due to the elasticity of the spring works, when this restoring force becomes a problem, it is necessary to make the leaf spring thin.
However, when the leaf spring is made thin, according to the configuration of Patent Document 1, there is a problem that the limit of the load bearing performance of the bearing is lowered due to the buckling limit which is always a problem in the thin leaf spring structure.
Therefore, an object of the present invention is to provide a rotating shaft holding mechanism that solves the above-described problems and improves the decrease in load bearing performance due to buckling.

Since buckling is a phenomenon when a thin beam is compressed from the longitudinal direction, the elastic hinge element set that supports the shaft is subjected only to compression instead of the conventional structure of Patent Document 1 that receives both compression and tension at the same time. The configuration is changed so that only the pull is combined. By using a plurality of elastic hinge elements that support the lateral load applied to the shaft, there can be an elastic hinge element that supports the shaft with a tensile stress with respect to a lateral load from any direction. This element protects the compressive stress element with the buckling mode and prevents the bearing from breaking. For this reason, the problem can be solved by reversing the direction of the elastic hinge element that connects the movable part of the parallel spring link and the shaft structure to the fixed part of the parallel spring link.
The parallel spring link ideally has a structure in which only the angle of the vertex of the parallelogram changes, and one side is fixed, and the two sides connected to it are deformed to translate the other side. . Since objects do not move, they can move very smoothly, and are used for mechanical parts where high-precision measurement is required. When the movement of the movable side is viewed in detail, it is a circular motion with the radius of the deformed side, and an arbitrary point fixed to the movable side is centered on a point determined by the length and orientation of the deformed side. Move around the circle. Therefore, it can be seen that if a variable angle hinge is arranged at this position, it becomes an element constituting the rotation axis. With one parallel spring link, the angle of the hinge is free, so the rotation axis cannot be defined. Therefore, the hinges having the center of circular motion on the same axis are parallel from two or more directions that are not 180 degrees. The rotating shaft is arranged by a spring link and coincides with this axis.

That is, in the conventional structure of Patent Document 1 (see FIG. 3), the above-described arbitrary point fixed to the movable side where the hinge is arranged is connected to a member including a shaft center (solid rotating shaft). However, in the present invention, an arbitrary point fixed to the movable side on which the hinge is arranged has a structure that does not include an axis as a substance (hollow rotation axis), and rotates around a virtual axis. Joined to the member (see FIG. 1). More realistically, the rotation shaft having the configuration shown in FIG. 1 is the fixed portion side, and the fixed portion having the configuration shown in FIG. 1 is the movable shaft side (rotation shaft) including the shaft center as an entity (see FIG. 2). It becomes.
In the present invention, a movable side joined to the rotary shaft by an elastic hinge at a position of an execution length h in the radial direction from the rotation center of the rotary shaft, one end joined to the movable side by an elastic hinge, and the other end fixed by the elastic hinge A rotating shaft holding mechanism that allows rotation of the rotating shaft by providing at least two parallel spring links formed of a plurality of parallel deformed sides having an execution length h that are joined to a portion, The joining direction of the elastic hinge that joins the rotating shaft is the joining of the joint portion of the movable side that is located inward from the effective length h in the radial direction from the center of rotation and the rotating shaft that is located outside the effective length h. The part is joined with an elastic hinge.
The present invention also provides a movable side joined to the fixed portion by an elastic hinge at a position of an execution length h in the radial direction from the rotation center of the rotary shaft, and one end joined to the movable side by an elastic hinge and the other end is an elastic hinge. A rotating shaft holding mechanism that allows rotation of the rotating shaft by providing at least two parallel spring links formed of a plurality of parallel deformable sides having an execution length h joined to the rotating shaft, The joining direction of the elastic hinge that joins the movable part and the movable side is located at the joint part of the movable side located inside the effective length h in the radial direction from the rotation center of the rotating shaft, and outside the effective length h. It is characterized in that the joint portion of the fixed portion to be joined is joined.
The present invention is also a rotational viscometer, characterized in that the above-described rotational shaft holding mechanism is used as a torque measuring shaft retaining mechanism of the rotational viscometer.

According to the present invention, since a parallel spring link mechanism is adopted, a precise rotating shaft holding mechanism having high rigidity against deformations other than the rotating direction can be provided, and maintenance and handling are easy at low cost compared to air bearings and the like. In addition, when a lateral load is applied to the rotating shaft, all the elastic hinges in the link support the rotating shaft with tensile stress in at least one parallel spring link. Load bearing performance is improved.
In the rotational viscometer using the rotating shaft holding mechanism of the present invention, the elastic hinge portion can be made thinner by improving the load bearing performance due to buckling, and the stress torque due to the elastic hinge can be reduced. Torque can be detected.

FIG. 1 is a diagram for explaining the principle of the rotary shaft holding mechanism of the present invention. FIG. 2 is a view showing an embodiment of the rotating shaft holding mechanism of the present invention. In the structure of FIG. 2, B can be used as the rotating shaft side and E can be used as the fixed portion side. Conversely, B can be used as the fixed portion side and E can be used as the rotating shaft side. FIG. 3 is a diagram illustrating the principle of the conventional rotating shaft holding mechanism disclosed in Patent Document 1. In FIG. FIG. 4 is a diagram for explaining an application example of the rotating shaft holding mechanism of the present invention to a rotating shaft holding mechanism of a rotational viscometer.

First, a rotation shaft holding mechanism using a conventional parallel spring link of Patent Document 1 will be described with reference to FIG. In FIG. 3, A: movable side, B: fixed part, C1, C2: deformation side, D: elastic hinge, O: rotating shaft (rotates integrally as a rigid body without deformation from O to D) The movable side A of the parallel spring link draws an arc having a radius h equal to the execution length h of the deformation sides C1 and C2 that are parallel to each other. An elastic hinge D that joins the rotary shaft O and the movable side A at a point where the inclination (inclination of the deformation sides C1 and C2) and the length (h) coincide with the parallel spring link from the position where the rotation axis O is desired to be the center. Provide. At this time, the elastic hinge D is joined to the rotating shaft toward the center position side of the rotating shaft O when viewed from the movable side A. Then, the rotation axis O constitutes a rotation axis that follows the arcuate motion of the movable side A. Since the position of the elastic hinge D is not specified, the position of the rotation axis O can be freely set. If the number of the parallel spring links in FIG. 3 is only one, the position of the rotation axis O is not fixed by the elastic hinge D. Therefore, two or more parallel spring links having different directions with respect to one rotation axis O are combined. Thus, the position of the rotation axis O can be determined.
In the rotary shaft holding mechanism using the conventional parallel spring link described above, when a lateral load is applied to the rotary shaft, for example, if a tensile load is applied to the elastic hinge D that joins the movable side A and the rotary shaft O, the deformation is deformed. A compression load (buckling mode) is applied to the elastic hinges D at both ends of the sides C1, C2, and conversely, if a compression load (buckling mode) is applied to the elastic hinge D that joins the movable side A and the rotating shaft O, A tensile load is applied to the elastic hinges D at both ends of the deformed sides C1 and C2, and the elastic hinges in one parallel spring link are simultaneously subjected to compression and tensile. In order to prevent buckling failure of the elastic hinge portion to which a compressive load is applied, there is a limit to the thinning of the elastic hinge portion, and the stress torque due to the elastic hinge cannot always be sufficiently reduced.

Therefore, in the present invention, when a lateral load is applied to the rotating shaft, the elastic hinge in one parallel spring link is improved so as to be a combination of only compression or only tension, and a plurality of parallel spring links are provided. Thus, with respect to the lateral load from all directions, in the at least one parallel spring link, all the elastic hinges in the link support the shaft with a tensile stress.
FIG. 1 is a diagram for explaining the principle of the present invention. The difference from the prior art of FIG. 3 is that the joining direction of the elastic hinge D that joins the rotating shaft and the movable side is reversed, that is, This is a point where the elastic hinge D is joined to a part E of the rotating body on the opposite side, not the direction of the center position of the rotating shaft as viewed from the movable side A. A: movable side, B: fixed part, C1, C2: deformed side, D: elastic hinge, O: rotating shaft, E: part of rotating body of rotating shaft, and the movable side A of the parallel spring link is mutually An arc having a radius h equal to the execution length h of the parallel deformation sides C1 and C2 is drawn. From the location where the center of the rotation axis O is desired, the rotation axis O (in the figure, the center axis portion of the rotation axis having a hollow center axis) is located at a point where the inclination (the inclination of the deformation sides C1 and C2) and the length (h) coincide with the parallel spring link. An elastic hinge D that joins a part E) of the rotating body and the movable side A is provided. Then, the rotation axis O constitutes a rotation axis that follows the arcuate motion of the movable side A. However, it should be noted that a part E of the rotating body of the rotating shaft joined by the movable side A and the elastic hinge D is not in the rotational center side of the rotating shaft O as viewed from the elastic hinge D at the joining point. It is important to adopt a joining direction in which the movable side A is arranged on the rotation center side when viewed from the elastic hinge D at the joining point. In other words, the joining direction of the elastic hinge D that joins the movable side A and the rotation axis O is a joint portion of the movable side A located radially inside the effective length h from the center of rotation and outside the effective length h. In FIG. 1, from the part E of the rotating body of the rotating shaft to the elastic hinge D at the joining point, the connecting portion of the rotating shaft O (E) positioned is joined by the elastic hinge D. The extending member indicates that it rotates as a rigid body integrally with the rotating shaft, like the part E of the rotating body. Further, in FIG. 1, in order to make the explanation of the joining direction of the elastic hinge that joins the rotating shaft and the movable side easy to understand, the hollow rotating shaft having no substance in the central shaft portion has been explained. Since the shaft holding mechanism is based on the premise that the rotation amount required is small, even a solid rotation shaft is provided with holes, recesses, deformation grooves, etc. in the solid rotation shaft It is also possible to realize the joining direction by putting a part or all of a parallel spring link such as a movable side inside the hole, the concave portion or the deformation groove.
If there is only one parallel spring link element of the present invention in FIG. 1, the position of O is not fixed by the hinge D. However, the position of the rotation axis O can be determined by combining two or more parallel spring link elements having different directions with respect to one O. However, in the case of two parallel spring link elements, depending on the direction of the force, a compressive stress is applied to all hinge portions. Normally, this is avoided by combining three or more parallel spring link elements (three or more are not an absolute condition when the axes described later are arranged horizontally, for example).
More realistically, the rotary shaft side E in the configuration of FIG. 1 is fixed, and the fixed side B of the parallel spring link is a movable shaft including the axis as a substance (hatching in FIG. 2 described later). See section structure). In the component in this case, the force acting in the direction in which the fixed portion of the fixed shaft and the movable shaft are moved away from each other becomes a pulling force with respect to each elastic hinge element. Conversely, the force in the approaching direction acts as a compressive force on each elastic hinge element, and a buckling mode occurs. When the parallel spring link elements configured in this way are connected to the shaft from three or more directions, the stress with respect to the lateral load of the shaft is only tensile stress in one or more parallel spring link elements, and the seats of the other parallel spring link elements. Eliminate bending stress. Here, the direction of three or more is not an absolute condition. For example, in an axis in which a load is applied only in the direction in which the axis is suspended horizontally, an element that pulls downward can be omitted. With this configuration, it is possible to configure an elastic hinge structure using a thinner member, and it is possible to create a rotating shaft with a small restoring force against rotation. In addition, the present invention can be used for usage in a configuration in which the shaft is easily subjected to a force in a direction perpendicular to the shaft, for example, the shaft is disposed horizontally.

In the example of FIG. 1 illustrating the principle of the present invention, since the part E of the rotating body does not have a substance in the central axis part, the fixed part B can be moved to a region including the central axis. If it does in this way, it can replace and use so that the part which was a fixed part containing a central axis may be used as a rotation part, and the part which was a rotary body may be used as a fixed part. In order to connect this structure to the region B in FIG. 1 including the central axis from three directions, it is necessary to shift the position of the elastic hinge on B in the movable side direction.
An embodiment constructed in this way is shown in FIG. In FIG. 2, A: movable side, B: rotating portion, D0 to D2: elastic hinge, O: rotating shaft center, E: fixed portion, and a bearing that supports the rotating shaft using parallel spring links is created from three directions. Is done. The hatched portion in FIG. 2 corresponds to one parallel spring link element in FIG. 1, except that the fixed portion E and the rotating portion B are interchanged (in FIG. 1, B is the fixed portion and E is a part of the rotating body). Met). In FIG. 2, the portion E which has become the fixing portion is fixed by an appropriate method, the rotating shaft entity is passed through the central hole on the rotating portion B, and the rotating shaft entity and the rotating portion B are fixed to each other. It rotates integrally with the rotating shaft entity. In the bearing, the most important point is that the effective length h and direction of the elastic hinges D1 to D2 coincide with the effective length h from the rotational axis O to the elastic hinge D0 in all three parallel spring elements. Further, the joining direction of the elastic hinge D0 that joins the fixed portion E and the movable side A is the movable side A that is located on the inner side of the execution length h in the radial direction from the rotation axis (rotation center) of the rotation shaft. And the joint part of the fixed part E located outside the effective length h.
In this embodiment, in order to reduce the stress torque with respect to rotation, the elastic hinge portion is manufactured using a leaf spring. However, the present invention is not limited to this, and a thin hinge can also be manufactured. In this embodiment, the three parallel spring links are used. However, it goes without saying that four or more parallel spring links can be used. Further, only the direction in which the above-mentioned shaft is suspended horizontally is used. For a shaft on which a load is applied, two parallel spring links can be used.

(Application to rotational viscometer)
FIG. 4 is a perspective view of an outer cylinder rotation type coaxial double cylindrical rotational viscometer which is one of typical rotational viscometers in order to explain the application of the rotating shaft holding mechanism of the present invention to a rotational viscometer. It is the figure which showed the structure. 4, a, e, and f are torque detection mechanisms, b is a precise rotating shaft holding mechanism, c is an inner cylinder / outer cylinder, d is a thermostatic chamber, g and h are rotating mechanisms of the outer cylinder, and i is a thermostatic chamber. This is a lifting mechanism. In the coaxial double-cylindrical rotational viscometer of the outer cylinder rotation type in FIG. 4, the inner cylinder shaft is provided with torque that acts on the inner cylinder when the sample cylinder is inserted between the inner cylinder and the outer cylinder and the outer cylinder is rotated The viscosity of the sample fluid is measured by detecting with a torque detection mechanism. In the example shown in the figure, when the inner cylinder shaft is rotationally displaced, a torque sufficient to cancel the rotational displacement is applied to the inner cylinder shaft, and the torque is detected by calculating the value of the loaded torque. Although the cylindrical shaft hardly rotates, it is necessary to use a precise rotating shaft holding mechanism with a small rotational load fluctuation in order to accurately detect the torque. Therefore, conventionally, the use of an air bearing having a small rotational load variation and the rotating shaft holding mechanism of Patent Document 1 by the present inventors have been proposed. However, air bearings have drawbacks in both cost and ease of handling, and the rotating shaft holding mechanism of Patent Document 1 is resistant to buckling of a thin elastic hinge when a lateral load is applied to the shaft as described above. There was the difficulty that the limit of load performance would become low.
Therefore, both the cost and ease of handling can be achieved by replacing the conventional air bearing and the holding mechanism of Patent Document 1 with the rotating shaft holding mechanism of the present invention as the rotating shaft holding mechanism of the rotary viscometer. Therefore, it is possible to provide a rotational viscometer having a higher limit of load bearing performance against a lateral load applied to the rotating shaft.
The rotational viscometer thus obtained is ideal as a torque meter for a rotational viscometer because the shaft rigidity and load-bearing performance are limited and the moment of inertia can be reduced. Thereby, the measurable area can be expanded. The small moment of inertia increases the response speed, and in particular contributes to the expansion of the rheometer frequency range. In addition to price, it is expected to improve performance, reduce maintenance and improve ease of handling.

  The rotating shaft holding mechanism of the present invention has been developed as a mechanism for holding the rotating shaft of a rotational viscometer that requires highly accurate torque measurement. It can be widely used as a holding mechanism for a small rotating shaft.

Claims (3)

The movable by one end comprises at least two deformation sides or Ranaru parallel spring links joined plurality of mutually parallel run length h in the fixing portion and the other end is joined to the soluble Dohen an elastic hinge with elastic hinge Between the sides, a rotating shaft holding mechanism that holds the hollow rotating body so as to allow rotation around its rotation center ,
A joint portion of the movable side located inward of the execution length h along the front Symbol rotation center to the deformation parallel to the side radially, towards the said hollow rotating body to the center of rotation along the radially rotary shaft holding mechanism from said center of rotation of the extending member, characterized in that the junction you positioned outside the said run length h along the radial direction and joined by an elastic hinge. The rotary shaft holding mechanism according to claim 1, wherein the elastic hinge includes a leaf spring .   A rotary viscometer using the rotary shaft holding mechanism according to claim 1 or 2 as a torque measuring shaft holding mechanism of a rotary viscometer.

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