WO2019069683A1

WO2019069683A1 - Torque detector

Info

Publication number: WO2019069683A1
Application number: PCT/JP2018/034570
Authority: WO
Inventors: 里奈小笠原; 石倉　義之; 祐希瀬戸
Original assignee: アズビル株式会社
Priority date: 2017-10-03
Filing date: 2018-09-19
Publication date: 2019-04-11
Also published as: JP2019066374A

Abstract

The present invention comprises: a plurality of strain sensors (1) that have a circuit comprising a plurality of active gauges (13), and are attached to a rotary shaft body (5) at equal intervals around the axis thereof; and a measurement unit (2) that measures the sum of the outputs of the plurality of strain sensors (1). The active gauges (13) are slanted relative to the axial direction of the rotary shaft body (5).

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.
However, in this method, even when another shaft load (a thrust load or a radial load) other than torque is applied to the rotating shaft, sensitivity is obtained to some extent, and only torque can not be detected accurately.

Therefore, for example, in the method disclosed in Patent Document 1, when a plurality of metal strain gauges are applied to the circumferential surface of the rotating shaft, the change in resistance value of the paired metal strain gauges is reversed when another axial load is applied. It has been arranged. This makes it possible to cancel the influence of the other axis load.

JP 09-021709 A

However, in the method disclosed in Patent Document 1, it is necessary to arrange eight or more 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.

The present invention has been made to solve the above-described problems, and it is an object of the present invention to provide a torque detector which can detect torque accurately even when another axis load is applied and which can be easily manufactured. There is.

A torque detector according to the present invention measures the sum of outputs of a plurality of strain sensors having a circuit formed of a plurality of active gauges and mounted on a rotating shaft at equal intervals around an axis and a plurality of strain sensors. And a measuring unit, wherein the active gauge is obliquely directed to the axial direction of the rotating shaft.

According to this invention, since it was comprised as mentioned above, even when the other-axis load is added, a torque can be detected accurately, and it can manufacture simply.

It is a front view (figure which shows the state in which the distortion sensor was attached to the rotating shaft) which shows the structural example of the torque detector which concerns on Embodiment 1 of this invention. 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. 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 to 6C are diagrams showing a case where a radial load is applied in the sensor mounting direction in the torque detector according to Embodiment 1 of the present invention, and FIGS. 6A and 6B show the mounting position of the strain sensor. FIG. 6C is a front view and a side view, and FIG. 6C is a side view showing a state in which a radial load is applied in the sensor mounting direction. FIGS. 7A to 7D are diagrams showing a case where a radial load is applied in the sensor non-mounting direction in the torque detector according to Embodiment 1 of the present invention, and FIGS. 7A and 7B show mounting positions of strain sensors. 7C is a side view showing a state in which a radial load is applied in the sensor mounting direction, and FIG. 7D is a view showing a state of two strain sensors in FIG. 7C. 8A to 8C are top views showing another example of arrangement of the resistance gauges according to the first embodiment of the present invention. FIG. 9A is a top view showing another arrangement example of the resistance gauges according to the first embodiment of the present invention, and FIG. 9B is a view showing a construction example of a half bridge circuit constituted by the resistance gauges shown in FIG. 9A. 10A to 10C are diagrams showing another configuration example of the silicon layer 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 front 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.
The torque detector detects the torque applied to the rotating shaft 5. 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 torque detector includes a plurality of strain sensors 1 and a measurement unit 2. FIG. 1 shows the case where two strain sensors 1 are used. 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 rotary shaft 5 and outputting a signal 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 which is strained in response to an external force, and is a sensor layer having a circuit composed of a plurality of resistance gauges (diffusion resistance) 13 which are active gauges. FIG. 3 shows the case where the circuit is a full bridge circuit of a Wheatstone bridge circuit. 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 in the <110> direction of the silicon layer 11.
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).

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.

Further, the plurality of strain sensors 1 are arranged at equal intervals so that the resistance gauges 13 are directed obliquely (with 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. The plurality of strain sensors 1 have the same sensitivity. In FIG. 1, two strain sensors 1 are disposed opposite to each other on the rotating shaft 5.

Here, in the torque detector disclosed in Patent Document 1, it is necessary to mount eight or more metal strain gauges in precise relative position and angle. On the other hand, in the torque detector according to the first embodiment, since a bridge circuit is formed in one strain sensor 1, at least two strain sensors 1 may be mounted, and the torque detector can be manufactured more easily. It becomes. In the case where a plurality of resistance gauges 13 are formed in one strain sensor 1, each resistance gauge 13 can be precisely positioned because it is patterned by photolithography.

The measuring unit 2 measures the sum of the signals output by the plurality of strain sensors 1 as a torque. In FIG. 1, the measuring unit 2 measures the sum of the signals output by the two strain sensors 1 as a torque.

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. Further, FIG. 5 shows a case where one strain sensor 1 is used.
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 a signal. The torque detector detects the torque applied to the rotating shaft 5 from the signal output from the strain sensor 1.

In the torque detector according to the first embodiment, the plurality of strain sensors 1 are arranged on the rotating shaft 5 at equal intervals around the axis. Further, the four resistors constituting the full bridge circuit of the strain sensor 1 are arranged to face 45 degrees with respect to the axial direction of the rotary shaft 5.
The effects of the torque detector according to the first embodiment will be described below with reference to FIGS. FIGS. 6 and 7 show a case where two

strain sensors

1a and 1b are disposed opposite to each other on the rotating shaft 5.

Here, the stresses produced when torque is applied to the rotating shaft 5 are equal on the circumferential surface of the same radius. Therefore, the sum of the signals output by the two

strain sensors

1 a and 1 b is twice as large as the signal output by the single strain sensor 1.

On the other hand, when a thrust load or a radial load in the sensor mounting direction shown by the arrow in FIG. 6B is applied to the rotating shaft 5, the change in resistance value of the two pairs in the

strain sensors

1a and 1b is reversed and offset. Therefore, there is no output from the

strain sensors

1a and 1b.
When a radial load to the sensor non-mounting side shown by the arrow in FIG. 7B is applied to the rotating shaft 5, as shown in FIG. 7D, the

strain sensors

1a and 1b are strained in opposite directions to each other. The output by 1b is inverted. Therefore, the measurement unit 2 cancels the sum by taking the sum.
Therefore, the influence by other axis load can be controlled. Further, in the case where two

strain sensors

1a and 1b are used, the assembly may be easy since they may be disposed so as to be opposed to each other on the rotary shaft 5.

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.

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. 8, 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. 9, 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. 9B is a fixed resistance.

Further, as shown in FIG. 10, on the back surface of the silicon layer 11, a communication groove portion 113 may be formed, which communicates 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.

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.

As described above, according to the first embodiment, the plurality of strain sensors 1 having the circuit including the plurality of resistance gauges 13 and attached to the rotating shaft 5 at equal intervals around the axis, and the plurality of strains Since the resistance gauge 13 is directed obliquely with respect to the axial direction of the rotating shaft 5, the torque is accurately measured even when another shaft load is applied. It can be detected and easily manufactured.

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 can accurately detect a torque even when a load is applied to another shaft, can be easily manufactured, and is suitable for use as a torque detector that detects a torque applied to a rotating shaft. .

Reference Signs List 1 strain sensor 2 measurement unit 5 rotary shaft 6 drive system 11 silicon layer (substrate layer)
12 insulation layer 13 resistance gauge (diffusion resistance)
111 Groove 112 Thin portion 113 Communication groove

Claims

A plurality of strain sensors, each having a circuit composed of a plurality of active gauges, and mounted on the rotating shaft at equal intervals around an axis;
And a measuring unit that measures the sum of the outputs of the plurality of strain sensors,
The said active gauge turned in the diagonal direction with respect to the axial direction of the said rotating shaft. The torque detector characterized by the above-mentioned.
The torque detector according to claim 1, wherein the circuit is a full bridge circuit of a Wheatstone bridge circuit.
The torque detector according to claim 1, wherein the circuit is a half bridge circuit of a Wheatstone bridge circuit.
The torque sensor according to any one of claims 1 to 3, wherein the strain sensor is a semiconductor strain gauge.