JPH0473634B2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field to which the Invention Pertains] The present invention is directed to a method for detecting force such as a load applied to a pressure-receiving surface by decomposing it into component forces in three directions orthogonal to each other.
The present invention relates to a method of manufacturing a pressure sensor in which a component force detection pressure-sensitive module is used as a unit, and a large number of pressure-sensitive modules are arranged in an array so that distributed loads and the like can be detected.

[Prior art and its problems] The pressure-sensitive module is capable of decomposing forces such as the above-mentioned loads into a basic orthogonal coordinate system and detecting them separately as components of forces in three directions. By synthesizing it using an arithmetic expression, it is possible to determine the magnitude and direction of the force, and furthermore, it is possible to determine the force in any direction, so it is of course useful as a single load meter, etc. In particular, pressure sensors arranged in an array have relatively new uses because they can determine the distribution of force, the center of force (center of gravity), and the resultant force acting on it.

An example of this can be seen in the human body dynamics experiment shown in FIG. The figure shows the foot 2 of a person walking on the pressure sensor 1, and in the state on the right side of the figure, the heel of the foot is in contact with the load cell 1, which is indicated by the tip of the bag-shaped arrow. In the state on the left side of the figure, the toe is in contact with the pressure sensor 1. As the walking dynamics progress, the distribution of the load applied to the pressure sensor and the three component forces Fx, Fy, and Fz of the load naturally change over time. Measuring the load during walking dynamics using an ordinary weight scale does not provide very useful information, even if it is possible to measure temporal changes in the overall load. However, if it is possible to accurately measure the planar distribution of load and the transition of component forces during walking dynamics, it is known that very useful knowledge can be obtained regarding individual differences in walking dynamics and patterns of physical disorders. It is being Furthermore, by attaching this pressure sensor 1 to the back of the robot's foot, it becomes possible to provide the robot with a sophisticated walking control function.

The need to detect the distribution of such load components exists widely in the industrial field, and FIG. 2 shows an example of a pressure sensor for a robot. In the figure, one of the robot hands 4 attached to the tip of the multi-joint arm 3 is shown.
A state in which an object 6 is gripped by a pair of fingers 5, 5 is shown. If the object 6 has sufficient hardness and strength, such as many industrial parts, there will be no problem, but if the object 6 is soft or perishable, such as fruit, it may be difficult to use strong force. Gripping is not allowed. In order to handle this type of object with a robot without damaging it, the gripping force, that is, the component force of the load applied to the fingers 5 and its distribution, must be measured fairly accurately, and the gripping force must be measured with a moderate amount of force that will not damage the object or cause it to fall. must be grasped.

Also, in order to know whether the grip is being performed correctly, it is useful to know the planar distribution of the load component force. For example, when gripping a relatively elongated object 6 as shown in the figure, the distribution of the load component force differs depending on the part of the object to be gripped, so if the distribution is abnormal, the gripping may be performed inappropriately. I know that there is. Furthermore, when a soft object is being gripped with a relatively small gripping force, the risk of the object falling off can be predicted from the time course of the load component force.

FIG. 3 shows an outline of the configuration of such a pressure sensor. In the illustrated pressure sensor 1, a large number of pressure sensitive modules 10 are arranged in a plane array in both the x and y directions on a common substrate 30, and each pressure sensitive module 10
The pressure-sensitive cells 20 receive loads having component forces Fx, Fy, and Fz through the pressure-receiving plates 40, respectively, and the pressure-sensitive cells 20 detect not only the vertical force Fz that the pressure-receiving plates 40 receive, but also the lateral forces Fx and Fy. do. Through this, for example, as illustrated in FIG. 1, in addition to the distribution of the weight of the human body applied to the pressure sensor 1, it is possible to know the magnitude and distribution of the force Fy that is kicked backwards and the force Fy that is pushed out in the lateral direction with respect to the walking direction. be able to. Each pressure sensitive module 10
As shown surrounded by a dashed line in the figure, the pressure sensitive cell 20 is a pressure sensitive element, a common substrate 30, and an upper pressure receiving plate 40.

By the way, as shown in FIGS. 4 and 5, the conventional pressure-sensitive cells 20 that have already been proposed include separate and independent pressure-sensitive rings (ring-shaped pressure-sensitive members) 21, 21 for each pressure-sensitive cell 20. It was empty.
Therefore, in order to form the pressure sensor 1, a step of engaging one end side of the plurality of rings 21 with a plurality of parallel grooves 31 on the lower substrate 30 and standing up a predetermined number of rings in each groove; At least the steps of arranging the rings 21 distributed in the row direction along the grooves 31 in the column direction, and fixing one end side of each ring 21 engaged with the groove 31 to the substrate are performed. This has the drawback of increasing manufacturing and assembly man-hours.

Moreover, this type of pressure sensor is required to be as small as possible and to be highly integrated. For example, it is said that the size of the pressure receiving plate 40 is desirably several mm square, preferably 1 mm square or less. However, it is not easy to perform each of the above-mentioned steps accurately with these required dimensions because the ring 21 also becomes extremely small, which may lead to lower yields, lower reliability, and higher manufacturing costs. The problem was that it was difficult to fully automate manufacturing and assembly.

Therefore, we created multiple pressure-sensitive cells in the column direction using rectangular single-crystal silicon, and then arranged the created rectangular bodies on a substrate to form a pressure sensor, thereby reducing manufacturing and assembly man-hours. However, a pressure sensor as shown in FIGS. 6 and 7 has been proposed in order to facilitate the manufacture of the pressure sensor.

The pressure sensor shown in FIG. 6 has a plurality of small circular holes 52 and large circular holes 53 alternately opened at approximately equal intervals along the longitudinal direction in the vertical surface of a rectangular short crystal silicon 51, and further A diffusion type strain gauge group 54 is formed around each small circular hole 52 by a known diffusion technique, so that the resistance value of the strain gauge group 54 changes to cause the silicon 51
A plurality of pressure-sensitive cells 55 are integrally configured to detect the force applied to the pressure-receiving surface 51a via the pressure-receiving surface 40 by dividing it into three force components. Small circular hole 5 mentioned above
Reference numeral 2 denotes a circular hole that applies distortion constituting the cell 55, and the large circular hole 53 acts as a boundary separating each cell 55 from each other.

The pressure sensor shown in FIG. 7 has a plurality of small circular holes 56 added to the outer periphery of the strain gauge group 54 in order to make the shape of the cell 55 more similar to the basic ring shape.

The pressure sensor in FIG. 8 has the large circular hole 5 described above.
3, a large cut groove 58 which is open at the top is provided as a boundary between each cell 55, thereby reducing interference between adjacent cells.

After fitting the lower ends 51b of the silicon strips 51 constructed in this manner into the respective grooves 31 of the lower substrate 30 as shown in FIG. 4 or 5 and vertically fixing them at predetermined positions, each strip A pressure receiving plate 40 is fixed to the pressure receiving surface 51a on the upper part of the body silicon 51 for each pressure sensitive module to form one pressure sensor.

The pressure sensors in FIGS. 6 to 8 are cell 5 in the column direction.
5 are continuously formed on one silicon 51 for each column, so that the grooves 31 of the substrate 31 are formed for each cell.
The conventional manufacturing process of engaging, aligning and fixing the silicon strips at predetermined positions is no longer necessary, and a manufacturing process is performed for each silicon strip 51, which greatly reduces the number of manufacturing steps and, in turn, reduces manufacturing costs. moreover,
Since the size of the pressure-sensitive body to be handled increases in the longitudinal direction, work such as assembly and fixing into the groove of the lower substrate becomes easier, which in turn improves yield and reliability, and facilitates complete automation of manufacturing and assembly. becomes.

However, if a plurality of cells 55 are separated by only a circular hole 53 as shown in FIG. 6, the stress generated in the adjacent cells will interfere and cause distortion in the adjacent cells, which will affect the output of this cell. affect Furthermore, the seventh
Even if a plurality of small circular holes 56 are used to separate adjacent cells as shown in the figure, interference cannot be completely eliminated.

Furthermore, interference can be eliminated by separating adjacent cells by large cut grooves 57 as shown in FIG. It is extremely difficult to achieve this with current processing technology. For this reason, the accuracy of the distances l and l' from the outer periphery of the cell to the strain gauge 54 deteriorates, causing variations in the output from each cell.

[Object of the Invention] An object of the present invention is to provide a pressure sensor that is easy to manufacture and eliminates interference from adjacent cells.

[Summary of the Invention] The present invention is a method for manufacturing a pressure sensor in which positional accuracy and dimensional accuracy are ensured by circular holes, and interference from adjacent cells is blocked by small cut grooves. . That is, in order to achieve the above object, the present invention provides a plurality of diffused type components that decompose and detect the force applied to the pressure-receiving surface into force components in three directions along the longitudinal direction of a plane perpendicular to the pressure-receiving surface. A group of strain gauges is formed, and a plurality of circular holes for configuring cells corresponding to the group of strain gauges and at least one circular hole for separating cells provided between the circular holes for configuring a plurality of cells are formed. a step of manufacturing a rectangular single crystal silicon substrate, a step of supporting the rectangular single crystal silicon substrate on a lower substrate, and a step of supporting the rectangular single crystal silicon substrate in the circular hole for cell separation. The method is characterized by including a step of separating the cells into a plurality of independent cells arranged in an array.

[Embodiments of the Invention] The present invention will be described in detail below with reference to the drawings.

9A to 9D show an embodiment of the present invention. 9th
As shown in Figure A, a rectangular single crystal silicon 6
A circular hole 62 for cell configuration, a circular hole 63 for cell separation, and a semicircular hole 66 are alternately bored in 1,
A strain gauge 64 is formed around a circular hole 62 for forming a cell to form a cell. These circular holes 62, 63, and 66 can be made with high precision by laser and diamond drilling. Note that the strain gauges 64 may be formed in the rectangular single crystal silicon 61 and the holes 62, 63, and 66 may be opened therein.

Furthermore, as shown in FIG. 9B, the above-mentioned rectangular single crystal silicon 61 in which cells are formed are lined up and fixed in the groove of the lower substrate 30 with the pressure-receiving surface facing upward. After the pressure receiving plate 40 is mounted and fixed, as shown in FIGS. 9C and D, the cells 61S adjacent to the pressure receiving plate 40 are separated by cut grooves 67 passing through the cell separation holes 63 and 66. separate from each other. Here, the cut groove 67 may be created using a thin grindstone cutter, or may be created by laser machining.

In this way, the only machining that affects the strain gauge 64 is the machining of the circular holes 63 and 66, which can be machined with high precision, so that a high degree of positional accuracy and dimensional accuracy can be ensured. This solves the problem that the accuracy of the distance from the outer periphery of the cell to the strain gauge deteriorates, causing variations in the output from each cell. Furthermore, interference from the adjacent cells 61S is blocked by the small cut grooves 67.

10A-10D show other embodiments of the invention.
As shown in FIG. 10A, after circular holes 62 for cell configuration and large-diameter circular holes 68 for cell separation are alternately drilled in a rectangular single-crystal silicon 61, the large-diameter holes 68 are A rectangular cell separation notch groove 69 is formed in accordance with the position. Others are the above-mentioned Figure 9 A~
Since this embodiment is similar to the embodiment shown in FIG. D, detailed explanation thereof will be omitted. In this example, a slight error occurs in detecting the force perpendicular to the end face of the rectangular single crystal silicon 61, but the number of processing steps is smaller than in the embodiment shown in FIGS. 9A to 9D.

FIG. 11 shows a detailed arrangement example of each strain gauge in the strain gauge group 64 of FIG. 10. first,
Loads from three directions are applied to the pressure receiving surface 61a via the pressure receiving plate 40.
When Fx, Fy, and Fz are applied independently, the stress generated in the cell 61S is
0 and the pressure receiving plate 40, it is expressed by the following approximate equation.

σ=3/8 R/bt ³ Fxr/R+rcosα……(1) σ=1/4Rb/IFycosα……(2) σ=3/8 R ² /bt ³ Fz(2/π−sinα)r/
R+r...(3) However, σ: Circumferential stress, R: Average circle of the cell 61S, that is, the radius of the material mechanical neutral axis when the cell 61S is viewed as a beam, that is, the radius of the two adjacent circular holes 62. 2t: the width of the cell 61S, that is, the minimum width of the outer edges of the two adjacent circular holes 62 and 68; b: the thickness of the cell 61S; That is, silicon 61S
Thickness, I: Moment of inertia of cell 61S in the Fy direction, r: Cell 61 based on the average circle R of cell 61S
A variable in the radial direction of S, α: An angular variable taken from the upper end of the cell 61S.

In order to detect strain based on such stress, the 11th
A strain gauge is attached to a position around the circular hole 62 shown in the figure. First, considering the case when load Fx is applied, Fx measurement gauges 64xt, 64xc
is located at the location r=-t of the inner diameter part of the small hole 62,
Also, since it is provided at the position α = 39.6°, R
≫ As t, σ=0.29R/bt ² Fx ...(4), and at the point where the gauge is 64xt, the tensile strain is
Compressive strain occurs at gauge 64xc, but
Since α=90° at the load Fx measurement gauges 64zt and 64zc, as can be seen from equation (1), the strain is "0" and therefore no detection signal is generated from these gauges.

Next, when load Fz is applied independently, Fz
Since the measurement gauges 64zt and 64zc are located at the inner and outer circumferences of α=90° (r=-t or r=t),
Note that according to equation (3), similarly, assuming R≫t, σ=0.14R/bt ² Fz (5), and the gauge 64zt detects the tensile strain and the gauge 64zc detects the compressive strain. At this time, at the positions of the Fx detection gauges 64xt and 64xc, α=
At 39.6°, the term (2/π−sinα) in equation (3) becomes “0”, so the strain is “0” and no detection signal is generated from these gauges.

From the above, the separation FX measurement gauge 64xt,
64xc and component force Fz measurement gauges 64zt and 64zc, as seen from equations (4) and (5), there is a difference in output signal of about twice, but there is no mutual interference and the component forces are completely separated. It can be seen that it can be measured using

On the other hand, considering the age for measuring component force Fy,
Assuming that the load Fy is applied in a direction toward the front of the paper in FIG. 7, strain detection gauges 64yt and 64yc are provided as shown. At the positions of these gauges, similarly in equation (2), α = 39.6°, R≫t, σ = 0.19Rb/IFy ...(6) The strain based on stress is expressed as tensile strain at gauge 64yt. , by detecting compressive strain with gauge 64yc, α=90° at the positions of component force Fz measurement gauges 64zt and 64zc, so σ
= 0, so there is no interference signal, but the component force
At the position of Fx measurement gauge 64xt, 64xc, component force is applied.
As in the case of the Fy measurement gauge, the strain detection output will be based on the stress σ=0.19Rb/IFy...(7). If the detection signal from this distribution Fx measurement gauge is output as is, it will naturally become an erroneous signal, but as shown in Figures 12A to C, when the bridge circuit is in a normal state, it is designed to cancel the erroneous signal. Therefore, an erroneous detection signal will not be output from the bridge circuit for measuring component force Fx.

[Effects of the Invention] As described above, according to the present invention, as a result of employing the above method, a pressure sensor that has little variation in output from each cell and is easy to manufacture and assemble can be obtained.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing an example in which the pressure sensor to which the present invention is applied is used to measure the walking dynamics of a human body, and Fig. 2 is an explanatory diagram showing an example in which the pressure sensor is used as a sensor for controlling a robot hand. , Fig. 3 is a perspective view showing the basic structure of the pressure sensor, Figs. 4 and 5 are perspective views showing the manufacturing process and structure of the conventional pressure sensor, and Figs. 6 to 8 are the conventional rectangular pressure sensor. FIG. 9A is a front view showing an example of the main part configuration of a pressure sensor.
~C are plan views showing the main components and manufacturing process of one embodiment of the present invention, Figure 9D is a perspective view of Figure 9C, and Figures 10A~C are diagrams of other embodiments of the present invention. FIG. 10D is a perspective view of FIG. 10C, FIG. 11 is an explanatory diagram showing the arrangement of the strain gauge, and FIGS. 12A to C are diagrams of the strain gauge. FIG. 2 is a circuit diagram showing an example of a connection mode. 30... Lower common board, 31... Groove, 40...
Upper pressure receiving plate, 51, 61... Rectangular single crystal silicon, 51a, 61a... Pressure receiving surface, 52, 62...
Circular hole for cell configuration, 54, 64...Strain gauge group, 53, 56, 63, 66, 68... Circular hole for boundary, 55, 61S...Pressure sensitive cell, 57, 67
... cut groove, 69 ... cut groove for boundary.

Claims (1)

[Claims] 1. A plurality of diffusion strain gauge groups are formed along the longitudinal direction of a plane perpendicular to the pressure-receiving surface, and detect the force applied to the pressure-receiving surface by decomposing it into force components in three directions. , and a rectangular unit in which a plurality of cell-forming circular holes corresponding to the strain gauge group and at least one cell-separating circular hole provided between the plurality of cell-forming circular holes are formed. a step of producing a crystalline silicon substrate; a step of supporting the rectangular single crystal silicon substrate on a lower substrate; and a step of separating the rectangular single crystal silicon substrate at the circular hole for cell separation to form an array. A method for manufacturing a pressure sensor, comprising: forming a plurality of independent cells arranged in a row.