WO2019035289A1

WO2019035289A1 - Torque detector, and method for producing torque detector

Info

Publication number: WO2019035289A1
Application number: PCT/JP2018/025893
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: 2017-08-14
Filing date: 2018-07-09
Publication date: 2019-02-21
Also published as: KR20200020957A; JP2019035636A; CN111033200A; CN111033200B; JP6843019B2; KR102333526B1

Abstract

The present invention is provided with: a silicon layer (11); a resistance gauge (13) which is formed in the silicon layer (11); slit portions (111) which are formed in the silicon layer (11), and which define a place where the resistance gauge (13) in the silicon layer (11) is formed as a local portion (112); and an insulation layer (12) which is joined to the silicon layer (11).

Description

Torque detector and method of manufacturing torque detector

The present invention relates to a torque detector that detects a torque applied to a rotating shaft and a method of manufacturing the torque detector.

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, a bridge circuit is configured by mounting four or more metal strain gauges at 45 degrees with respect to the axial direction of the rotating shaft.
However, with a metal strain gauge, it is difficult to detect minute strain with high accuracy because the gauge factor is small.

On the other hand, as a method of increasing the detection sensitivity of torque, there is considered a method of decreasing the rigidity of the rotating shaft and increasing the amount of distortion. In patent document 1, the improvement of sensitivity is implement | achieved by giving various processes to a rotating shaft and forming a beam part.

JP, 2016-109568, A

However, in the method of reducing the rigidity of the rotating shaft, 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 the conventional method, it is necessary to arrange at least four metal strain gauges. Therefore, it is necessary to exactly match the relative positions and angles of the metal strain gauges, which causes a problem of difficulty.

Here, in an industrial robot, detection of torque is essential to control its operation. Therefore, conventionally, a torque detector is attached to the industrial robot to detect the torque of each joint of the robot arm.
On the other hand, in recent years, in order for industrial robots to coexist with people without being separated, there is a demand for safety that instantaneously detects contact and stops operation when touching an object such as a person or a thing. There is. However, since the industrial robot has its own weight and the weight of the object to be held, and it is a robust casing in consideration of the operation speed, it is not possible to detect the torque with high accuracy with the conventional metal strain gauge. difficult.

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 a substrate layer in which strain occurs in response to an external force, a resistance gauge formed on the substrate layer, and a substrate layer formed on the substrate layer, and a local portion where the resistance gauge of the substrate layer is formed. And an insulating layer bonded to the substrate layer.

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

1A to 1C are diagrams showing a configuration example of a torque detector according to Embodiment 1 of the present invention, FIG. 1A is a top view, FIG. 1B is a side view, and FIG. 1C is AA FIG. FIG. 2A is a top view showing an arrangement example of the resistance gauges according to the first embodiment of the present invention, and FIG. 2B is a view showing a construction example of a full bridge circuit constituted by the resistance gauges shown in FIG. 2A. It is a flowchart which shows an example of the manufacturing method of the distortion sensor in Embodiment 1 of this invention. FIGS. 4A and 4B are diagrams showing a state in which the strain sensor according to Embodiment 1 of the present invention is attached to a rotating shaft, FIG. 4A is a top view, and FIG. 4B is a side view. 5A and 5B are diagrams for explaining the basic operation principle of the torque detector, and FIG. 5A is a side view showing the torque applied to the rotating shaft, and FIG. 5B 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. 6A and 6B are top views showing another configuration example of the strain sensor in accordance with the first embodiment of the present invention. 7A and 7B are side views showing another configuration example of the strain sensor in the first embodiment of the present invention. FIG. 8A is a top view showing another arrangement example of the resistance gauge in accordance with the first embodiment of the present invention, and FIG. 8B is a view showing a construction example of a half bridge circuit constituted by the resistance gauge shown in FIG. 8A. 9A to 9F are a top view and a side view showing an example of the size of the strain sensor in the first embodiment of the present invention, and FIG. 9G is a view showing the difference in sensitivity depending on the size of the strain sensor. It is a figure which shows the difference in the sensitivity by the thickness of the insulating layer in Embodiment 1 of this invention, and the thickness of a joining layer. 11A and 11B show a top view and a side view of the strain sensor according to the first embodiment of the present invention, and FIG. 11C shows a difference in sensitivity depending on the width of the slit portion and the width of the local portion. .

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.
The torque detector detects the torque applied to the rotating shaft 5 (see FIG. 4). 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. The torque detector includes a strain sensor 1 as shown in FIG.

The strain sensor 1 is a semiconductor strain gauge attached to the rotating shaft 5 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 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. In the silicon layer 11, a plurality of slit portions 111 are formed. A local portion 112 is formed at the center of the silicon layer 11 by the slit portion 111. The resistance gauge 13 is formed on the local portion 112.

In FIG. 1, slit portions 111 are formed on a pair of side surfaces of the silicon layer 11 respectively. Thus, the silicon layer 11 is a local portion 112 provided between the silicon layer (first substrate layer) 113, the silicon layer (second substrate layer) 114, and the silicon layer 113 and the silicon layer 114. And a bridge unit 115. Further, in FIG. 1, the corner of the slit portion 111 is formed in an arc shape.

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. 2, 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.
In FIG. 1, the insulating layer 12 is composed of two plate-like insulating layers (a first insulating layer and a second insulating layer) 121 and 122 disposed with a gap, and the upper surface of the insulating layer 121 is a silicon layer. The upper surface of the insulating layer 122 is bonded to the back surface of the silicon layer 114.

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. 3, first, a plurality of resistance gauges 13 are formed in the silicon layer 11 by ion implantation (Step ST1). Then, a plurality of resistance gauges 13 form a Wheatstone bridge circuit.
Next, the slit portion 111 is formed in the silicon layer 11 by etching (step ST2). Thus, the portion of the silicon layer 11 where the resistance gauge 13 is formed is made to be the local 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).

When the strain sensor 1 manufactured as described above is attached to the rotating shaft 5, the back surface of the insulating layer 12 and the rotating shaft 5 are joined by, for example, solder bonding. At this time, the rear surface of the insulating layer 12 and the bonding portion of the rotary shaft 5 are metallized and then solder bonding is performed. FIG. 4 shows a state in which the strain sensor 1 is attached to the rotating shaft 5.

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. 5A, 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. 5, the case where the distortion sensor 1 of rectangular shape is used is shown.
As shown in FIG. 5A, by applying torque to the rotating shaft 5, the strain sensor 1 attached to the rotating shaft 5 is strained, and shear stress as shown in FIG. 5B is generated on the surface of the strain sensor 1. . FIG. 5 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 local portion 112 is formed by forming a plurality of slits 111 in the silicon layer 11, and the resistance gauge 13 is formed in the local portion 112. Thereby, stress can be concentrated on the local 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.
Further, as shown in FIG. 1, the insulating layer 12 is formed of the insulating layer 121 and the insulating layer 122, and the center of the insulating layer 12 is divided, so that the detection sensitivity to the torque applied to the rotating shaft 5 is further improved.

Moreover, in FIG. 1, the corner of the slit part 111 is comprised by circular arc shape. Thereby, the stress concentrated locally can be dispersed to the case where the slit portion 111 has a corner, and the risk of breakage of the bridge portion 115 can be reduced.

Note that FIG. 1 shows the case where the slit portions 111 are formed on the pair of side surfaces of the silicon layer 11 and the silicon layer 11 has a one bridge structure having one bridge portion 115. However, the bridge shape is not limited to this. For example, as shown in FIG. 6A, two slits 111 may be formed in the silicon layer 11, and the silicon layer 11 may have a three-bridge structure having three bridge portions 115 including the local portion 112. By the configuration shown in FIG. 6A, the strength of silicon layer 11 can be increased. Further, as shown in FIG. 6B, the silicon layer 11 may have a cross bridge structure having two bridge portions 115 crossed each other which is a local portion 112.

Further, FIG. 1 shows the case where the thickness of the local portion 112 is the same as the thickness of the silicon layer 11 (silicon layers 113 and 114). However, the thickness of the local portion 112 may be thinner than the thickness of the silicon layer 11 (silicon layers 113 and 114), for example, as shown in FIG. 7A. Thereby, the detection sensitivity to the torque applied to the rotating shaft 5 is further improved. The thickness of the local portion 112 is appropriately designed in accordance with the rigidity and the like of the silicon layer 11. For example, if the stiffness of the silicon layer 11 is low, the local portion 112 is designed to be thick, and if the stiffness of the silicon layer 11 is high, the local portion 112 is designed to be thin.
Further, FIG. 1 shows the case where the insulating layer 12 is composed of the insulating layer 121 and the insulating layer 122, and the center of the insulating layer 12 is divided. However, not limited to this, for example, as shown in FIG. 7B, the insulating layer 12 may not be divided.

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. 8, a half bridge circuit composed of two resistance gauges 13 (R1 and R2) may be used as a Wheatstone bridge circuit. Note that R in FIG. 8B is a fixed resistance.

Finally, parameters that affect the sensitivity of the strain sensor 1 (MEMS chip) will be described together with experimental data.
The parameters that affect the sensitivity of the strain sensor 1 according to the first embodiment of the present invention include the size of the strain sensor 1 (chip size), the thickness of the insulating layer 12, and the bonding layer between the silicon layer 11 and the insulating layer 12. And the width of the slit portion 111 and the width of the local portion 112.

First, the difference in sensitivity depending on the size of the strain sensor 1 will be described with reference to FIG. 9A and 9B show the case where the size of the strain sensor 1 is (a × 3a), and FIGS. 9C and 9D show the case where the size of the strain sensor 1 is (1.5a × 1.5a), 9E and 9F show the case where the size of the strain sensor 1 is (3a × 3a). a is a constant. And FIG. 9G shows the difference in sensitivity depending on the size of the strain sensor 1. The strain sensor 1 shown in FIGS. 9A to 9F shows the case where the slit portion 111 is provided. Further, FIG. 9G shows the sensitivity ratio when the sensitivity of a general metal strain gauge is 1.
As shown in FIG. 9, the larger the size of the strain sensor 1, the higher the sensitivity. In the case of the same area, the strain sensor 1 has a higher sensitivity in the case of a square than in the case of a rectangle. That is, the strain sensor 1 shown in FIGS. 9C and 9D is smaller in area than the strain sensor 1 shown in FIGS. 9A and 9B, but has high sensitivity as shown in FIG. 9G.

Further, while the gauge factor is about 2 to 3 in a general metal strain gauge, the gauge factor is about several tens to about 100 in the strain sensor 1. Therefore, this strain sensor 1 can achieve a sensitivity of 100 times or more with respect to a metal strain gauge. In addition, since the strain sensor 1 has high sensitivity, the strain sensor 1 can be downsized significantly with respect to the metal strain gauge, and the degree of freedom on the fixed side (rotation shaft 5 side) is increased.
As described above, although the size and sensitivity of the strain sensor 1 are in a trade-off relationship, the strain sensor 1 can be made highly sensitive by dividing the insulating layer 12 or forming the slit portion 111 because the size is reduced.

Next, differences in sensitivity due to the thickness of the insulating layer 12 and the thickness and hardness of the bonding layer will be described with reference to FIG. In FIG. 10, the sensitivity ratio when the thickness when the thickness of the bonding layer is T and the thickness ratio of the insulating layer 12 (the ratio to the reference thickness) is 2 when the thickness is 1 is used. It shows. Further, in FIG. 10, when the thickness of the bonding layer is T, the thickness ratio of the insulating layer 12 is 1 and the solder bonding is performed, the thickness ratio of the insulating layer 12 is 1 and the thickness of the bonding layer is 4T. The case is shown.
If the insulating layer 12 is thick, strain is absorbed, and the strain transmission efficiency decreases. Therefore, as shown in FIG. 10, the strain sensor 1 has higher sensitivity as the thickness of the insulating layer 12 is thinner. On the other hand, a minimum thickness considering the withstand voltage necessary for the insulating layer 12 is required. When an adhesive is used as the bonding layer, the sensitivity changes depending on the thickness and hardness. That is, in the strain sensor 1, the sensitivity is higher when an adhesive having a high Young's modulus, such as an epoxy type, is used or the bonding layer is thinner. Further, the sensitivity of the strain sensor 1 is higher in the case of using a solder joint than in the case of using an adhesive.

Next, the difference in sensitivity depending on the width of the slit portion 111 and the width of the local portion 112 will be described with reference to FIG. 11A and 11B show, as an example, the case where the size of the strain sensor 1 is (3a × 3a). Further, as shown in FIG. 11A, the width of the slit portion 111 is h1 and the width of the local portion 112 is h2. Moreover, in FIG. 11C, similarly to FIG. 9G, the sensitivity ratio when the sensitivity of a general metal strain gauge is 1 is shown.
As shown in FIG. 11, by forming the slit portion 111 and the local portion 112 in the strain sensor 1, it is possible to increase the sensitivity approximately twice that in the case where the slit portion 111 and the local portion 112 are not provided. Become. Further, the width of the slit portion 111 and the width of the local portion 112, which become the highest sensitivity, are almost the same even if the size of the strain sensor 1 is changed (in the example of FIG. The case where the width of the portion 111 is 0.25a and the width of the local portion 112 is 0.25a is the highest sensitivity).

As described above, according to the first embodiment, the silicon layer 11, the resistance gauge 13 formed on the silicon layer 11, and the silicon layer 11 are formed, and the resistance gauge 13 of the silicon layer 11 is formed. Since the slit part 111 which makes a part a local part 112 and the insulating layer 12 joined to the silicon layer 11 are provided, the detection accuracy of torque is improved.

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-mentioned insulator or metal is used as the substrate layer, the gauge factor becomes 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.

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 and the method of manufacturing the torque detector according to the present invention can be used, for example, in a method of manufacturing the torque detector and the torque detector that detects the torque applied to the rotating shaft because the accuracy of torque detection is improved. Is suitable.

Reference Signs List 1 strain sensor 5 rotating shaft 6 driving system 11 silicon layer (substrate layer)
12 insulation layer 13 resistance gauge (diffusion resistance)
111 Slit portion 112 Local portion 113 Silicon layer 114 Silicon layer 115 Bridge portion 121 Insulating layer 122 Insulating layer

Claims

A substrate layer which is distorted in response to an external force,
A resistance gauge formed on the substrate layer;
A slit portion which is formed on the substrate layer and which makes a portion where the resistance gauge of the substrate layer is formed be a local portion;
A torque detector comprising: an insulating layer bonded to the substrate layer.
The torque detector according to claim 1, wherein the substrate layer is a silicon layer.
The crystal orientation of the surface of the said silicon layer is (100). The torque detector of Claim 2 characterized by the above-mentioned.
The torque detector according to any one of claims 1 to 3, wherein the resistance gauge is formed by forming a film on the substrate layer.
The said resistance gauge was formed in the <110> direction of the said silicon layer. The torque detector of Claim 2 or Claim 3 characterized by the above-mentioned.
The torque detector according to any one of claims 1 to 5, wherein a corner of the slit portion is formed in an arc shape.
The substrate layer is
A first substrate layer,
A second substrate layer,
It has one bridge part which is the said local part provided between the said 1st board | substrate layer and the said 2nd board | substrate layer. Any one of Claim 1 to 6 characterized by the above-mentioned. Torque detector.
The substrate layer is
A first substrate layer,
A second substrate layer,
It has three bridge parts containing the said local part provided between the said 1st board | substrate layer and the said 2nd board | substrate layer. It is characterized by the above-mentioned. Torque detector.
The substrate layer is
A first substrate layer,
A second substrate layer,
It has two crossed bridge parts which are the local parts provided between the 1st substrate layer and the 2nd substrate layer. Any one of claims 1 to 6 The torque detector according to the item.
The insulating layer is
A first insulating layer bonded to the first substrate layer;
The torque detector according to any one of claims 7 to 9, further comprising: a second insulating layer bonded to the second substrate layer.
The torque detector according to any one of claims 1 to 10, wherein the local portion is configured to be thinner than the thickness of the substrate layer.
Forming a resistance gauge on the substrate layer that is strained in response to an external force;
Forming, in the substrate layer, a slit portion which makes a portion where the resistance gauge of the substrate layer is formed be a local portion;
Bonding the substrate layer and the insulating layer.