WO2019039146A1

WO2019039146A1 - Torque detector

Info

Publication number: WO2019039146A1
Application number: PCT/JP2018/027075
Authority: WO
Inventors: 祐希瀬戸; 石倉　義之; 里奈小笠原
Original assignee: アズビル株式会社
Priority date: 2017-08-23
Filing date: 2018-07-19
Publication date: 2019-02-28
Also published as: JP2019039708A; KR20200019245A; JP6698595B2; KR102332884B1; CN111033199A

Abstract

The present invention is provided with: a base plate (2) fixed across two flange parts (51, 52) to a rotary shaft body (5) which has the two flange parts (51, 52) and a strain generating part (53) provided between the two flange parts (51, 52) and having a smaller diameter than the two flange parts (51, 52); a strain sensor (1) mounted at a position, facing the strain generating part (53), on the base plate (2); and a recess part (21) formed on both strain generating part-facing surfaces of the base plate (2) and having a smaller width than the strain sensor (1).

Description

Torque detector

The present invention relates to a torque detector that detects torque applied to a rotating shaft.

A metal strain gauge is attached to the peripheral surface of the rotating shaft as one of the methods to detect the torque applied to the rotating shaft, and the magnitude of shear stress generated on the peripheral surface of the rotating shaft by torque There is a method of detecting by value change.
In this method, in order to detect a minute torque change with high accuracy, the sensitivity is improved by reducing the shaft diameter of the strain generating portion in the rotating shaft to lower the torsional rigidity (for example, a patent). Reference 1).

Japanese Patent Laid-Open No. 2002-139391

However, if the shaft diameter of the strain generating portion of the rotating shaft is reduced to lower the rigidity, a problem of hysteresis due to stress increase (a problem of trade-off between sensitivity and hysteresis) occurs, and improvement in accuracy can not be expected.
In addition, when the shaft diameter of the strain generating portion is reduced with respect to the external size of the rotary shaft necessary for the connection with the drive system and the load system, a metal strain gauge is attached to the narrow and recessed portion. Therefore, there is a problem that it is difficult to uniformly attach the metal strain gauges with high positional accuracy.

The present invention has been made to solve the problems as described above, and it is an object of the present invention to provide a torque detector that improves the detection accuracy of torque.

The torque detector according to the present invention includes two flanges and a rotary shaft provided between the two flanges and having a strained portion having a smaller shaft diameter than the two flanges. A base plate fixed across two flanges, a strain sensor mounted at a position opposite to the strained portion of the base plate, and both sides facing the strained portion of the base plate, the width of the strain sensor And a recessed portion narrower than the recessed portion.

According to this invention, since it comprised as mentioned above, detection accuracy of a torque improves.

FIGS. 1A and 1B are diagrams showing a configuration example of a torque detector according to Embodiment 1 of the present invention (a diagram showing a state in which a strain sensor is attached to a rotary shaft via a base plate), 1A is a side view and FIG. 1B is a perspective view seen from above. FIGS. 2A to 2C are diagrams showing a configuration example of the strain sensor according to the first embodiment of the present invention, FIG. 2A is a top view, FIG. 2B is a side view, and FIG. FIG. FIG. 3A is a top view showing an arrangement example of the resistance gauges according to the first embodiment of the present invention, and FIG. 3B is a view showing a construction example of a full bridge circuit composed of the resistance gauges shown in FIG. 3A. It is a flowchart which shows an example of the manufacturing method of the distortion sensor in Embodiment 1 of this invention. It is a top view (figure which shows the state in which the distortion sensor was mounted) which shows the structural example of the base board in Embodiment 1 of this invention. 6A and 6B are diagrams for explaining the basic operation principle of the torque detector, FIG. 6A is a side view showing a torque applied to the rotating shaft, and FIG. 6B is a strain sensor based on the torque shown in FIG. It is a figure which shows an example of the stress distribution which generate | occur | produced in. FIGS. 7A and 7B are diagrams showing the effect of the torque detector according to the first embodiment of the present invention, FIG. 7A is a diagram showing the width (necking width) between the recesses of the base plate, and FIG. It is a figure which shows an example of the relationship between a constriction width and the sensitivity of a torque detector. It is sectional drawing (figure which shows the state in which the strain sensor was attached to the rotating shaft via the base board) which shows another structural example of the rotating shaft in Embodiment 1 of this invention. 9A to 9C are top views showing another example of arrangement of the resistance gauges according to the first embodiment of the present invention. FIG. 10A is a top view showing another arrangement example of the resistance gauge in accordance with the first embodiment of the present invention, and FIG. 10B is a view showing a construction example of a half bridge circuit constituted by the resistance gauge shown in FIG. 10A. 11A to 11C are back views showing another configuration example of the silicon layer in the first embodiment of the present invention. 12A and 12B are top views (figures showing a state in which a strain sensor is mounted) showing another configuration example of the base plate in the first embodiment of the present invention.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
Embodiment 1
FIG. 1 is a view showing a configuration example of a torque detector according to Embodiment 1 of the present invention. FIG. 1 shows a state in which the strain sensor 1 is attached to the rotating shaft 5 via the base plate 2.
In the rotating shaft 5, a drive system 6 such as a motor is connected to one end in the axial direction, and a load system such as a robot hand is connected to the other end. As shown in FIG. 1, the rotary shaft 5 has a flange portion 51, a flange portion 52, and a strain generating portion 53.

In the flange portion 51, the shaft of the drive system 6 is joined to one end in the axial direction.
In the flange portion 52, the shaft of the load system is joined to one end in the axial direction.
The strain generating portion 53 is provided between the flange portion 51 and the flange portion 52, and has a smaller shaft diameter than the flange portion 51 and the flange portion 52. For example, the shaft diameter of the strain generating portion 53 is set to the minimum diameter capable of maintaining the rigidity necessary for the rotating shaft 5. One end of the strain generating portion 53 in the axial direction is connected to the other end of the flange portion 51, and the other end is connected to the other end of the flange portion 52.

As described above, the rotary shaft 5 is configured as an H-type straining member having the strained portion 53 having a smaller shaft diameter than the flange portion 51 and the flange portion 52 between the flange portion 51 and the flange portion 52. .

On the other hand, the torque detector detects the torque applied to the rotating shaft 5. The torque detector comprises a strain sensor 1 and a base plate 2 as shown in FIG. Below, the case where a semiconductor strain gauge is used as the strain sensor 1 is shown.

The strain sensor 1 is a semiconductor strain gauge attached to the rotating shaft 5 via the base plate 2 and outputting a voltage according to external shear stress (tensile stress and compressive stress). The strain sensor 1 is realized by MEMS (Micro Electro Mechanical Systems). The strain sensor 1 is mounted at a position facing the strain generating portion 53 of the base plate 2. The strain sensor 1 has a silicon layer (substrate layer) 11 and an insulating layer 12 as shown in FIGS.

The silicon layer 11 is a single crystal silicon in which strain is generated in response to an external force, and is a sensor layer having a Wheatstone bridge circuit composed of a plurality of resistance gauges (diffusion resistances) 13. A groove 111 is formed in the center of the back surface (one surface) of the silicon layer 11. The thin portion 112 is formed in the silicon layer 11 by the groove portion 111. The resistance gauge 13 is formed on the thin portion 112.

The thickness of the thin portion 112 is appropriately designed in accordance with the rigidity and the like of the silicon layer 11. For example, when the rigidity of the silicon layer 11 is low, the thin portion 112 is thick, and when the rigidity of the silicon layer 11 is high, the thin portion 112 is thin.

In addition, single crystal silicon has crystal anisotropy, and in the p-type silicon (100) plane, the piezoresistance coefficient is largest in the <110> direction. Therefore, the resistance gauge 13 is formed, for example, in the <110> direction of the silicon layer 11 whose crystal orientation on the surface is (100).
In FIG. 3, four resistance gauges 13 (R1 to R4) constituting a full bridge circuit (Wheatstone bridge circuit) are formed in a diagonal direction (45 degrees direction) with respect to the side direction of the silicon layer 11. Shows the case of detecting shear stress in two directions. Here, although the case where it is 45 degrees direction was shown as a specific example of the above-mentioned oblique direction, the above-mentioned oblique direction is not limited to 45 degrees direction, but the characteristic of distortion sensor 1 46 degrees direction etc) is acceptable.

The insulating layer 12 is a pedestal whose upper surface is joined to the back surface of the silicon layer 11 and whose back surface is joined to the rotary shaft 5. For example, glass or sapphire can be used as the insulating layer 12.

Next, an example of a method of manufacturing the strain sensor 1 will be described with reference to FIG.
In the method of manufacturing the strain sensor 1, as shown in FIG. 4, first, a plurality of resistance gauges 13 are formed on the silicon layer 11 by ion implantation (step ST1). Then, a plurality of resistance gauges 13 form a Wheatstone bridge circuit.
Next, the groove portion 111 is formed on the back surface of the silicon layer 11 by etching (step ST2). Thereby, the portion of the silicon layer 11 where the resistance gauge 13 is formed is made to be the thin portion 112.
Next, the back surface of the silicon layer 11 and the top surface of the insulating layer 12 are bonded by, for example, anodic bonding (step ST3).

The base plate 2 is a plate member on which the strain sensor 1 is mounted and directly fixed to the flange portion 51 and the flange portion 52. As the base plate 2, for example, a metal member such as Kovar can be used. FIG. 1 shows the case where the base plate 2 is fixed across the peripheral surfaces of the flange portion 51 and the flange portion 52. Further, as shown in FIG. 5, in the base plate 2, a recess 21 is formed at the center of both side surfaces facing the strain generating portion 53. The recess 21 is narrower than the width of the strain sensor 1. Further, the recess 21 is configured to be narrower than the space between the flange portion 51 and the flange portion 52 (the interval in the axial direction).

When the strain sensor 1 manufactured as described above is attached to the base plate 2, the back surface of the insulating layer 12 and the base plate 2 are joined by, for example, solder bonding. At this time, solder bonding is performed after the back surface of the insulating layer 12 and the bonding portion of the base plate 2 are metallized. Further, when the base plate 2 is attached to the rotary shaft 5, it is joined by, for example, solder bonding in the same manner as described above.

Further, the strain sensor 1 is disposed such that the resistance gauge 13 is directed obliquely (45 degrees) with respect to the axial direction of the rotating shaft 5. That is, the resistance gauge 13 is disposed so as to face the generation direction of the shear stress generated when the torque is applied to the rotating shaft 5. Here, although the case where it is 45 degrees direction was shown as a specific example of the above-mentioned oblique direction, the above-mentioned oblique direction is not limited to 45 degrees direction, but the characteristic of distortion sensor 1 46 degrees direction etc) is acceptable.

Next, the basic operation principle of the torque detector will be described with reference to FIG. In FIG. 6A, the drive system 6 is connected to one end of the rotary shaft 5 to which the strain sensor 1 is attached, and a state where torque is applied to the rotary shaft 5 by the drive system 6 is shown. Moreover, in FIG. 6, the case where the strain sensor 1 is directly attached to the rotating shaft 5 using the cylindrical rotating shaft 5 is shown.
As shown in FIG. 6A, by applying torque to the rotating shaft 5, the strain sensor 1 attached to the rotating shaft 5 is distorted, and shear stress as shown in FIG. 6B is generated on the surface of the strain sensor 1. . FIG. 6 shows that the deeper the color, the stronger the tensile stress, and the lighter the color, the stronger the compressive stress. And resistance gauge 13 which turned to a diagonal direction (45 degrees direction) to the axial direction of axis of rotation 5 changes resistance value according to this shear stress, and strain sensor 1 changes according to change of resistance value. Output voltage. The torque detector detects the torque applied to the rotating shaft 5 from the voltage output by the strain sensor 1.

In the torque detector according to the first embodiment, the strain sensor 1 is disposed radially outward of the strain generating portion 53 via the base plate 2 with respect to the rotary shaft 5, which is an H-type strain generating body. .
Thereby, the allowable torque can be secured, and the strain sensor 1 can be effectively distorted. That is, the magnitude of distortion generated when torque is applied to the rotating shaft 5 increases in the radially outward direction from the axial center. Therefore, by disposing the strain sensor 1 at a position away from the axial center, the detection sensitivity to the torque applied to the rotating shaft 5 is improved. In addition, the base plate 2 is disposed radially outward of the strain generating portion 53, whereby the mounting of the base plate 2 is facilitated.

Furthermore, in the torque detector according to the first embodiment, the recess 21 is formed on both side surfaces of the base plate 2 facing the strained portion 53, and the recess 21 is narrower than the width of the strain sensor 1.
Here, when the strain sensor 1 is attached to the rotary shaft 5 via the base plate 2, the transmission efficiency when the deformation of the rotary shaft 5 is transmitted to the strain sensor 1 decreases. Therefore, by providing the recess 21 in the base plate 2, the base plate 2 is easily distorted in the rotational direction, and by causing deformation in a region narrower than the width (chip length) of the strain sensor 1, the rotary shaft 5 Sensitivity to torque applied to the
Further, the recess 21 is configured to be narrower than the space between the flange portion 51 and the flange portion 52 (the interval in the axial direction). As a result, the deformation of the base plate 2 can be locally concentrated, the amount of strain is increased, and the detection sensitivity to the torque applied to the rotating shaft 5 is improved.

FIG. 7 shows the effect of the torque detector according to the first embodiment.
As shown to FIG. 7A, let the width | variety between the recessed parts 21 of the base board 2 be constriction width w. In this case, the relationship between the constriction width w and the sensitivity of the torque detector is, for example, as shown in FIG. 7B. FIG. 7B shows the relationship between the constriction width ratio and the sensitivity ratio, where the constriction width ratio is 1 when there is no constriction in the base plate 2 (there is no recess 21), and the sensitivity ratio at that time is 1. . As shown in FIG. 7B, it can be seen that by providing the recess 21 in the base plate 2, the sensitivity ratio of the torque detector is improved.

Further, by mounting the strain sensor 1 on the base plate 2, the process of fixing the strain sensor 1 and extracting the electricity can be performed on the base plate 2. Therefore, the strain sensor 1 is easy to handle, and there are few restrictions on the process device.

In addition, in the bonding of the strain sensor 1 and the base plate 2, heat is applied by solder bonding. Therefore, by appropriately selecting the material of the base plate 2, it is possible to reduce the temperature characteristic deterioration due to the difference in linear expansion coefficient. For example, when silicon is used as the strain sensor 1, Kovar is used as the base plate 2.

In the torque detector described above, the thin portion 112 is formed by forming the groove portion 111 in the center of the back surface of the silicon layer 11, and the resistance gauge 13 is formed in the thin portion 112. Thereby, the stress can be concentrated on the thin portion 112 in which the resistance gauge 13 is formed, and the detection sensitivity to the torque applied to the rotating shaft 5 is improved.

Moreover, the case where the base board 2 was straddled over the surrounding surface of the flange part 51 and the flange part 52 was shown above. However, the present invention is not limited to this, as long as the strain sensor 1 is disposed so as to be opposed to the radially outer side than the strain generating portion 53. Therefore, for example, as shown in FIG. 8, the storage groove 54 may be formed on the peripheral surface of the rotating shaft 5 (flanges 51 and 52), and the base plate 2 may be stored in the storage groove 54.

Further, the arrangement of the four resistance gauges 13 is not limited to the arrangement shown in FIG. 3, but may be an arrangement as shown in FIG. 9, for example.

Also, in the above description, the case where a full bridge circuit composed of four resistance gauges 13 (R1 to R4) is used as the Wheatstone bridge circuit is shown. However, the present invention is not limited to this, and as shown in FIG. 10, a half bridge circuit composed of two resistance gauges 13 (R1 and R2) may be used as a Wheatstone bridge circuit. R in FIG. 10B is a fixed resistance.

Further, as shown in FIG. 11, a communication groove portion 113 may be formed on the back surface of the silicon layer 11 so as to communicate the groove portion 111 with the side surface of the silicon layer 11. Here, in the bonding of the silicon layer 11 and the insulating layer 12, a temperature of about 400 ° C. is applied by anodic bonding. Therefore, when the communication groove portion 113 is not present, the air present in the groove portion 111 between the silicon layer 11 and the insulating layer 12 is sealed in a high temperature state at the time of anodic bonding, and when the temperature drops to normal temperature As a result, the thin-walled portion 112 may be deformed and the zero point of the strain sensor 1 may be displaced. On the other hand, by providing the communication groove portion 113, air present in the groove portion 111 can be released to the outside at the time of anodic bonding, and deformation of the thin portion 112 can be avoided.
The silicon layer 11 needs to be configured so as to be partially thinned by the groove portion 111 and the communication groove portion 113 so as not to be entirely thinned.

In addition, although the case where the silicon layer 11 was used as a board | substrate layer was shown in the above, it does not restrict to this, and should just be a member which distortion produces according to external force. For example, as the substrate layer, an insulator (such as glass) or a metal can be used. Here, when the substrate layer is an insulator, the resistance gauge 13 is formed by depositing a film on the insulator by sputtering or the like. When the substrate layer is metal, the resistance gauge 13 is formed by sputtering the metal via an insulating film. Alternatively, the silicon layer 11 may be used as a substrate layer, and the resistance gauge 13 may be formed on the silicon layer 11 by sputtering or the like.
Even when the above-described insulator or metal is used as the substrate layer, the gauge factor is higher than that of a general metal strain gauge. Further, when the resistance gauge 13 is formed by film formation, the gauge ratio does not change depending on the crystal orientation as opposed to the case where the resistance gauge 13 is formed in the silicon layer 11 by ion implantation, that is, the direction needs to be limited. There is no
On the other hand, the gauge factor is 4 to 10 times higher in the case where the resistance gauge 13 is formed by ion implantation in the silicon layer 11 than when the resistance gauge 13 is formed by film formation.

Moreover, as shown in FIG. 5, the case where the recessed part 21 was comprised by the rectangular shape was shown above. However, the present invention is not limited to this. For example, the recess 21 may be configured to have a semicircular shape as shown in FIG. 12A or a shape having R at the corners as shown in FIG. 12B. Here, when the base plate 2 is deformed, stress concentrates on the corners of the recess 21. Therefore, stress dispersion and stress relaxation can be achieved when the base plate 2 is deformed by forming the recess 21 in a semicircular shape or in a shape having R at the corner.

In the above, the case of using a semiconductor strain gauge having a shape as shown in FIG. 2 as the strain sensor 1 is shown. However, the present invention is not limited to this, and semiconductor strain cages of other shapes may be used. In addition, as the strain sensor 1, another strain gauge (for example, a metal strain gauge) may be used.
Further, when the rigidity of the strain sensor 1 is low, as in a thin film strain gauge, the base plate 2 also plays a role of adjusting the rigidity of the strain sensor 1.

As mentioned above, according to this Embodiment 1, it is provided between two

flange parts

51 and 52, and the two

flange parts

51 and 52 concerned, and, from the two

flange parts

51 and 52 concerned, shaft diameter is The base plate 2 fixed across the two

flanges

51 and 52 with respect to the rotary shaft 5 having the small strain generating portion 53, and the strain mounted at a position facing the strain generating portion 53 of the base plate 2 Since the sensor 1 and the concave portions 21 formed on both side surfaces of the base plate 2 facing the strain generating portion 53 and narrower than the width of the strain sensor 1 are provided, torque detection accuracy is improved.

In the present invention, within the scope of the invention, modifications of optional components of the embodiment or omission of optional components of the embodiment is possible.

The torque detector according to the present invention is suitable for use in a torque detector that detects a torque applied to a rotating shaft, because the detection accuracy of the torque is improved.

Reference Signs List 1 strain sensor 2 base plate 5 rotating shaft 6 driving system 11 silicon layer (substrate layer)
12 insulation layer 13 resistance gauge (diffusion resistance)
Reference Signs List 21 recessed portion 51 52 flange portion 53 strain generation portion 54 storage groove 111 groove portion 112 thin wall portion 113 communication groove portion

Claims

It is fixed across the two flanges with respect to a rotary shaft provided with two flanges and a strain-flexing part provided between the two flanges and having a smaller shaft diameter than the two flanges. Base plate,
A strain sensor mounted at a position opposite to the strain generating portion of the base plate;
And a recessed portion formed on both side surfaces of the base plate facing the strained portion.
The said recessed part is narrower than the width | variety of the said distortion sensor. The torque detector of Claim 1 characterized by the above-mentioned.
The said recessed part is narrower than the space | interval in the axial direction of the said two flange parts. The torque detector of Claim 1 characterized by the above-mentioned.
The torque detector according to any one of claims 1 to 3, wherein the concave portion is formed in a semicircular shape or a shape having an R at a corner.
The torque sensor according to any one of claims 1 to 4, wherein the strain sensor is a semiconductor strain gauge.
The strain sensor includes a substrate layer in which strain occurs in response to an external force, and a resistance gauge formed by forming a film on the substrate layer. The torque detector according to any one of the preceding claims.
The torque detector according to claim 5, wherein the base plate is made of kovar.