CN111033199A

CN111033199A - Torque detector

Info

Publication number: CN111033199A
Application number: CN201880051952.2A
Authority: CN
Inventors: 瀬戸祐希; 石仓义之; 小笠原里奈
Original assignee: Azbil Corp
Current assignee: Azbil Corp
Priority date: 2017-08-23
Filing date: 2018-07-19
Publication date: 2020-04-17
Also published as: JP6698595B2; KR20200019245A; KR102332884B1; JP2019039708A; WO2019039146A1

Abstract

The invention comprises the following steps: a base plate (2) fixed to a rotating shaft body (5) so as to straddle two flange sections (51, 52), wherein the rotating shaft body (5) includes the two flange sections (51, 52) and a strain generating section (53), and the strain generating section (53) is provided between the two flange sections (51, 52) and has a smaller shaft diameter than the two flange sections (51, 52); a strain sensor (1) mounted on the base plate (2) at a position facing the strain generating section (53); and a recess (21) that is formed on both side surfaces of the base plate (2) that face the strain generating section (53), and that is narrower than the width of the strain sensor (1).

Description

Torque detector

Technical Field

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

Background

As one of the methods of detecting the torque applied to the rotary shaft body, there is a method of: metal strain gauges (strain gauges) are attached to the circumferential surface of the rotary shaft body, and the magnitude of shear stress generated in the circumferential surface of the rotary shaft body by torque is detected by the change in resistance values of the metal strain gauges.

In the above aspect, when a minute torque change is detected with high accuracy, the following method may be adopted: sensitivity is improved by reducing the shaft diameter of the strain generating portion of the rotation shaft body to reduce torsional rigidity (see, for example, patent document 1).

Documents of the prior art

Patent document

Patent document 1: japanese patent laid-open publication No. 2002-139391

Disclosure of Invention

Problems to be solved by the invention

However, if the rigidity is reduced by reducing the shaft diameter of the strain generating portion of the rotating shaft body, a problem of hysteresis (hysteresis) due to an increase in stress (trade-off problem of sensitivity and hysteresis) occurs, and improvement of accuracy cannot be expected.

In addition, when the shaft diameter of the strain generating portion is reduced with respect to the outer dimension of the rotation shaft body required for facilitating the connection with the drive system and the load system, a metal strain gauge is attached to a narrow and deep portion. Therefore, there are problems as follows: it is difficult to mount the metal strain gauges with high positional accuracy and uniformity.

The present invention has been made to solve the above-described problems, and an object thereof is to provide a torque detector with improved torque detection accuracy.

Means for solving the problems

The torque detector of the present invention is characterized by comprising: a base plate fixed to a rotating shaft body across two flange portions, the rotating shaft body including the two flange portions and a strain generating portion provided between the two flange portions and having a smaller shaft diameter than the two flange portions; a strain sensor mounted on the base plate at a position facing the strain generating section; and a recess formed on both side surfaces of the base plate facing the strain generating section, the recess being narrower than the width of the strain sensor.

ADVANTAGEOUS EFFECTS OF INVENTION

According to the present invention, the torque detection accuracy is improved because of the above configuration.

Drawings

Fig. 1A and 1B are views showing a configuration example of a torque detector according to embodiment 1 of the present invention (a view showing a state in which a strain sensor is attached to a rotary shaft body via a base plate), fig. 1A is a side view, and fig. 1B is a perspective view as viewed from above.

Fig. 2A to 2C are diagrams showing a configuration example of a strain sensor according to embodiment 1 of the present invention, fig. 2A is a top view, fig. 2B is a side view, and fig. 2C is a sectional view taken along line a-a'.

Fig. 3A is a top view showing an example of arrangement of a resistance meter according to embodiment 1 of the present invention, and fig. 3B is a diagram showing an example of configuration of a full bridge circuit including the resistance meter shown in fig. 3A.

Fig. 4 is a flowchart showing an example of a method for manufacturing a strain sensor according to embodiment 1 of the present invention.

Fig. 5 is a top view showing a structural example of a base plate according to embodiment 1 of the present invention (a view showing a state where a strain sensor is mounted).

Fig. 6A and 6B are views for explaining a basic operation principle of the torque detector, fig. 6A is a side view showing a torque applied to the rotational shaft body, and fig. 6B is a view showing an example of a stress distribution generated in the strain sensor by the torque shown in fig. 6A.

Fig. 7A and 7B are views showing the effect of the torque detector according to embodiment 1 of the present invention, fig. 7A is a view showing the width (neck width) between the concave portions of the base plate, and fig. 7B is a view showing an example of the relationship between the neck width and the sensitivity of the torque detector.

Fig. 8 is a sectional view showing another example of the structure of the rotary shaft body according to embodiment 1 of the present invention (a view showing a state in which a strain sensor is attached to the rotary shaft body via a base plate).

Fig. 9A to 9C are top views showing another arrangement example of the resistance meter according to embodiment 1 of the present invention.

Fig. 10A is a top view showing another example of the arrangement of a resistance meter according to embodiment 1 of the present invention, and fig. 10B is a diagram showing an example of the configuration of a half-bridge circuit including the resistance meter shown in fig. 10A.

Fig. 11A to 11C are rear views showing another example of the structure of the silicon layer in embodiment 1 of the present invention.

Fig. 12A and 12B are top views showing another example of the structure of the base plate according to embodiment 1 of the present invention (views showing a state where a strain sensor is mounted).

Detailed Description

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

Embodiment 1.

Fig. 1 is a diagram 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 rotation shaft body 5 via the base plate 2.

The rotational shaft body 5 is connected at one end in the axial direction to a drive system 6 such as a motor, and connected at the other end to a load system such as a robot (robot). As shown in fig. 1, the rotation shaft body 5 includes a flange 51, a flange 52, and a strain generating portion 53.

One end of the flange portion 51 in the axial direction engages with a shaft (draft) of the drive system 6.

One end of the flange portion 52 in the axial direction engages the shaft of the load system.

The strain generating portion 53 is provided between the flange portion 51 and the flange portion 52, and is configured to have a smaller axial diameter than the flange portion 51 and the flange portion 52. For example, the diameter of the strain generating portion 53 is set to a minimum diameter that can maintain the rigidity required as the rotation shaft body 5. The strain generating portion 53 has one end in the axial direction connected to the other end of the flange portion 51, and the other end connected to the other end of the flange portion 52.

As described above, the rotation shaft body 5 is configured as an H-type strain generator, and has the strain generating portion 53 having a smaller shaft diameter than the

flange portions

51 and 52 between the

flange portions

51 and 52.

On the other hand, the torque detector detects the torque applied to the rotation shaft body 5. As shown in fig. 1, the torque detector includes a strain sensor 1 and a base plate 2. Hereinafter, a case where a semiconductor strain gauge is used as the strain sensor 1 will be described.

The strain sensor 1 is a semiconductor strain gauge that is attached to the rotational shaft body 5 via a base plate 2 and outputs a voltage corresponding to external shear stress (tensile stress and compressive stress). The strain sensor 1 is implemented by Micro Electro Mechanical Systems (MEMS). The strain sensor 1 is mounted on the base plate 2 at a position facing the strain generating section 53. As shown in fig. 2 and 3, the strain sensor 1 includes a silicon layer (substrate layer) 11 and an insulating layer 12.

The silicon layer 11 is a single crystal silicon which is strained by an external force, and is a sensor layer including a Wheatstone bridge circuit (diffusion circuit) including a plurality of resistance meters (diffusion resistors) 13. The silicon layer 11 has a groove 111 formed in the center of the back surface (one surface). The thin portion 112 is formed in the silicon layer 11 by the groove portion 111. The resistance meter 13 is formed on the thin portion 112.

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

Further, single crystal silicon has crystal anisotropy, and the piezoelectric resistivity is the largest in the <110> direction on the p-type silicon (100) plane. Therefore, the resistance meter 13 is formed, for example, in the <110> direction of the silicon layer 11 having the crystal orientation (100) on the surface.

In fig. 3, the following is shown: four resistance meters 13(R1 to R4) constituting a full bridge circuit (wheatstone bridge circuit) are formed in an oblique direction (45-degree direction) with respect to the side direction of the silicon layer 11, and the strain sensor 1 detects shear stress in both directions. Here, although a case in which the inclination direction is 45 degrees is shown as a specific example of the inclination direction, the inclination direction is not limited to the 45 degrees, and some deviation (for example, 44 degrees or 46 degrees) is allowed in the characteristics of the strain sensor 1.

The insulating layer 12 is a pedestal having an upper surface bonded to the back surface of the silicon layer 11 and a back surface bonded to the rotation shaft 5. As the insulating layer 12, for example, glass, sapphire, or the like can be used.

Next, an example of a method for manufacturing the strain sensor 1 will be described with reference to fig. 4.

In the method of manufacturing the strain sensor 1, as shown in fig. 4, first, a plurality of resistance meters 13 are formed in the silicon layer 11 by ion implantation (step ST 1). Next, a wheatstone bridge circuit is formed by the plurality of resistance meters 13.

Next, the groove 111 is formed in the back surface of the silicon layer 11 by etching (step ST 2). Therefore, the portion of the silicon layer 11 where the resistance meter 13 is formed is the thin portion 112.

Next, the back surface of the silicon layer 11 and the upper surface of the insulating layer 12 are bonded by, for example, anodic bonding (step ST 3).

The base plate 2 is a plate member on which the strain sensor 1 is mounted and which is directly fixed across the

flange portions

51 and 52. As the base plate 2, for example, a metal member such as kovar can be used. In fig. 1, the following is shown: base plate 2 is fixed across the peripheral surfaces of flange 51 and flange 52. As shown in fig. 5, the base plate 2 has a recess 21 formed in the center of both side surfaces facing the strain generating section 53. The recess 21 is formed narrower than the width of the strain sensor 1. The recess 21 is formed narrower than the distance (axial interval) between the flange 51 and the flange 52.

When the strain sensor 1 manufactured as described above is mounted on the base plate 2, the back surface of the insulating layer 12 is bonded to the base plate 2 by, for example, solder bonding. In this case, the back surface of the insulating layer 12 and the joint portion of the base plate 2 are metallized, and then solder-joined. When the base plate 2 is attached to the rotation shaft body 5, the base plate is also joined by, for example, solder joining as described above.

The strain sensor 1 is disposed such that the resistance meter 13 is oriented in an oblique direction (45-degree direction) with respect to the axial direction of the rotation shaft body 5. That is, the resistance meter 13 is disposed so as to face the direction of generation of shear stress generated when torque is applied to the rotation shaft body 5. Here, although a case in which the inclination direction is 45 degrees is shown as a specific example of the inclination direction, the inclination direction is not limited to the 45 degrees, and some deviation (for example, 44 degrees or 46 degrees) is allowed in the characteristics of the strain sensor 1.

Next, the basic operation principle of the torque detector will be described with reference to fig. 6. In fig. 6A, the following state is shown: a drive system 6 is connected to one end of the rotational shaft body 5 to which the strain sensor 1 is attached, and torque is applied to the rotational shaft body 5 by the drive system 6. Fig. 6 shows a case where the strain sensor 1 is directly attached to the rotary shaft body 5 by using the cylindrical rotary shaft body 5.

As shown in fig. 6A, the strain sensor 1 attached to the rotational shaft body 5 is strained by applying a torque to the rotational shaft body 5, and a shear stress as shown in fig. 6B is generated on the surface of the strain sensor 1. In fig. 6, the following state is shown: the darker the color, the stronger the tensile stress, and the lighter the color, the stronger the compressive stress. The resistance meter 13, which is inclined in the direction (45 degrees) with respect to the axial direction of the rotation shaft body 5, changes the resistance value in accordance with the shear stress, and the strain sensor 1 outputs a voltage in accordance with the change in the resistance value. Next, the torque detector detects the torque applied to the rotary shaft body 5 based on the voltage output from the strain sensor 1.

In the torque detector according to embodiment 1, the strain sensor 1 is disposed on the radial outer side of the strain generating section 53 with respect to the rotational shaft body 5 as the H-type strain generator via the base plate 2.

Therefore, it is possible to ensure allowable torque and strain the strain sensor 1 effectively. That is, the magnitude of strain generated when torque is applied to the rotation shaft body 5 increases as the strain is directed radially outward from the shaft center. Therefore, by disposing the strain sensor 1 at a position away from the axial center toward the outside, the sensitivity of detecting the torque applied to the rotary shaft body 5 is improved. Further, by disposing the base plate 2 radially outward of the strain generating portion 53, the base plate 2 can be easily attached.

In the torque detector according to embodiment 1, the recesses 21 are formed on both side surfaces of the base plate 2 facing the strain generating section 53, and the recesses 21 are configured to be narrower than the width of the strain sensor 1.

Here, when the strain sensor 1 is attached to the rotation shaft body 5 via the base plate 2, the transmission efficiency when the deformation of the rotation shaft body 5 is transmitted to the strain sensor 1 is reduced. Therefore, by providing the concave portion 21 in the base plate 2, the base plate 2 is easily strained in the rotational direction, and by generating deformation in a region narrower than the width (chip length) of the strain sensor 1, the detection sensitivity of the torque applied to the rotational shaft body 5 is improved.

The recess 21 is formed narrower than the distance (axial interval) between the flange 51 and the flange 52. Therefore, the deformation of the base plate 2 is locally concentrated, the strain amount is increased, and the detection sensitivity of the torque applied to the rotation shaft body 5 is improved.

Fig. 7 shows an effect of the torque detector according to embodiment 1.

As shown in fig. 7A, the width between the recesses 21 of the base plate 2 is a constriction width w. In this case, the relationship between the neck width w and the sensitivity of the torque detector is shown in fig. 7B, for example. In fig. 7B, the relationship between the neck width ratio and the sensitivity ratio is shown by setting the neck width ratio to 1 when there is no neck (no recess 21) in the base plate 2 and setting the sensitivity ratio to 1 at this time. As shown in fig. 7B, it is understood that the sensitivity ratio of the torque detector is improved by providing the concave portion 21 in the base plate 2.

Further, by mounting the strain sensor 1 on the base plate 2, the fixing and power-taking steps of the strain sensor 1 can be performed on the base plate 2. Therefore, the strain sensor 1 is easy to use and has few restrictions on process equipment.

In addition, in the joining of the strain sensor 1 and the base plate 2, heat is applied by solder joining. Therefore, by appropriately selecting the material of the base plate 2, deterioration of the temperature characteristics due to the difference in the linear expansion coefficient can be reduced. For example, when silicon is used as the strain sensor 1, kovar is used as the base plate 2.

In the torque detector, a groove 111 is formed in the center of the back surface of the silicon layer 11 to form a thin portion 112, and the resistance meter 13 is formed in the thin portion 112. Therefore, stress can be concentrated on the thin portion 112 where the resistance meter 13 is formed, and the sensitivity of detecting the torque applied to the rotation shaft body 5 can be improved.

In the above description, the base plate 2 is fixed across the peripheral surfaces of the

flange portions

51 and 52. However, the strain sensor 1 is not limited to this, and may be arranged to face the strain generating section 53 at a position radially outward of the strain sensor. Therefore, for example, as shown in fig. 8, a housing groove 54 may be formed in the peripheral surface of the rotation shaft body 5 (the flange portion 51, the flange portion 52), and the base plate 2 may be housed in the housing groove 54.

The arrangement of the four resistance meters 13 is not limited to the arrangement shown in fig. 3, and may be, for example, the arrangement shown in fig. 9.

In addition, the above description shows the case where a full bridge circuit including four resistance meters 13(R1 to R4) is used as a wheatstone bridge circuit. However, the present invention is not limited to this, and a half-bridge circuit including two resistance meters 13(R1, R2) may be used as the wheatstone bridge circuit as shown in fig. 10. In addition, R in fig. 10B is a fixed resistance.

As shown in fig. 11, a communication groove 113 that communicates the groove 111 with the side surface of the silicon layer 11 may be formed on the back 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 degrees is applied by anodic bonding. Therefore, if the groove 113 is not connected, air in the groove 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 if the temperature is lowered to normal temperature, the air is contracted, and therefore the thin portion 112 may be deformed, and the zero point of the strain sensor 1 may be displaced. On the other hand, by providing the communicating groove portion 113, air existing 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.

In addition, the silicon layer 11 needs to be configured so that only a part of the silicon layer is thinned by the groove portion 111 and the communicating groove portion 113 without thinning the entire silicon layer.

In addition, although the case where the silicon layer 11 is used as the substrate layer has been described above, the present invention is not limited thereto, and any member may be used as long as it generates strain according to an external force. For example, as the substrate layer, an insulator (glass or the like) or a metal can be used. Here, when the substrate layer is an insulator, the resistance meter 13 is formed by forming a film on the insulator by sputtering or the like. When the substrate layer is made of a metal, the resistance meter 13 is formed by forming a film on the metal through an insulating film by sputtering or the like. The resistance meter 13 may be formed by forming a film on the silicon layer 11 by sputtering or the like using the silicon layer 11 as a substrate layer.

In the case of using the insulator or the metal as a substrate layer, the gauge factor is also higher than that of a general metal strain gauge. Further, when the resistance meter 13 is formed by film formation, the gauge factor does not change due to crystal orientation, that is, it is not necessary to define the direction, as compared with the case where the resistance meter 13 is formed on the silicon layer 11 by ion implantation.

On the other hand, when the resistance meter 13 is formed on the silicon layer 11 by ion implantation, the gauge factor is higher by 4 to 10 times or more than that in the case where the resistance meter 13 is formed by film formation.

As described above, the recess 21 is formed in a rectangular shape as shown in fig. 5. However, the concave portion 21 is not limited to this, and may be formed in a semicircular shape as shown in fig. 12A or a shape having R at a corner as shown in fig. 12B, for example. Here, when the base plate 2 is deformed, stress concentrates on the corners of the concave portions 21. Therefore, by forming the recess 21 in a semicircular shape or a shape having an R shape at a corner, stress dispersion and stress relaxation when the base plate 2 is deformed can be achieved.

In addition, the case where the semiconductor strain gauge having the shape shown in fig. 2 is used as the strain sensor 1 is described above. However, the present invention is not limited to this, and semiconductor strain gauges of other shapes may be used. Further, as the strain sensor 1, other strain gauges (for example, metal strain gauges) may be used.

Further, when the rigidity of the strain sensor 1 is low, such as a film strain gauge, the base plate 2 also plays a role of rigidity adjustment for the strain sensor 1.

As described above, according to the embodiment 1, the present invention includes: a base plate 2 fixed to a rotating shaft body 5 across two

flange portions

51, 52, the rotating shaft body 5 including the two

flange portions

51, 52 and a strain generating portion 53, the strain generating portion 53 being provided between the two

flange portions

51, 52 and having a smaller shaft diameter than the two

flange portions

51, 52; a strain sensor 1 mounted on the base plate 2 at a position facing the strain generating section 53; and the concave portion 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, so that the torque detection accuracy is improved.

In the present invention, any constituent elements of the embodiments may be modified or omitted within the scope of the invention.

Industrial applicability

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

Description of the symbols

1: strain sensor

2: base plate

5: rotary shaft body

6: drive system

11: silicon layer (base layer)

12: insulating layer

13: resistance meter (diffusion resistance)

21: concave part

51. 52: flange part

53: strain generating part

54: storage groove

111: trough part

112: thin wall part

113: communicating groove part

Claims

1. A torque detector, comprising:

a base plate fixed to a rotating shaft body across two flange portions, the rotating shaft body including the two flange portions and a strain generating portion provided between the two flange portions, the shaft diameter being smaller than the two flange portions;

a strain sensor mounted on the base plate at a position facing the strain generating section; and

and a recess formed on both side surfaces of the base plate facing the strain generating section.

2. The torque detector of claim 1,

the recess is narrower than a width of the strain sensor.

3. The torque detector of claim 1,

the recess is narrower than an interval in the axial direction of the two flange portions.

4. The torque detector according to any one of claims 1 to 3,

the recess is formed in a semicircular shape or a shape having an R shape at a corner.

5. The torque detector according to any one of claims 1 to 4,

the strain sensor is a semiconductor strain gauge.

6. The torque detector according to any one of claims 1 to 4,

the strain sensor includes: a substrate layer that generates strain according to an external force; and a resistance meter formed by forming a film on the substrate layer.

7. The torque detector of claim 5,

the base plate comprises kovar.