JPS60158327A - Load cell array for detecting three components - Google Patents

Abstract

PURPOSE:To detect the distribution of a load and the time change of distribution, by arranging unit load cells, which can decompose the load into three perpendicular directions and can detect the load, in a matrix pattern. CONSTITUTION:Control scanners 20 are switched to 3Xm pieces of switching elements and a base voltage is applied. At the same time, an output scanners 21 is switched from the first to the mth rows. The output data is extracted out of the bridge of each cell and sent to a CPU22. The columns for flowing currents are switched from the first column to the nth column by the control scanners 20. Thus the output voltages of all the unit load cells can be taken out. In this circuit constitution, the number of output wirings from each unit load cell becomes three. Therefore, the number of the output wirings from the unit load cells of mn pieces becomes 3Xm. Even though the number of the unit load cells is increased, the number increases in proportion to (m), and the wiring density does not become so high as before.

Description

[Detailed description of the invention] [Technical field to which the invention pertains] This invention is a method of arranging unit load meters in a matrix, which can separate and detect loads into three directions orthogonal to each other, to determine the state of load distribution and load. This invention relates to a three-component force sensing load meter array that detects temporal changes in distribution.

[Prior art and its problems]

This type of load cell array has been proposed by the applicant and is capable of decomposing the load in three directions and measuring its distribution, and can be used to measure surface pressure distribution on contact surfaces and as a pressure sensor for robots. Figure 1J shows the configuration.

Here, the unit load cell 1 is composed of an upper pressure receiving plate ia and a load cell lb made of two silicon single crystal wafers, and a plurality of stress gauges 1c are arranged on the surface of at least one of the load cells 1b, which will be explained later. This structure is formed on the surface of a silicon wafer by a diffusion method. A plurality of unit load cells 1 are fitted into grooves 2a provided on the multilayer lower substrate 2 and fixed by adhesive as shown in the figure, and are arranged in a matrix on the multilayer lower substrate 2. 1st
The figure shows a case where 2x2 = 4 unit load cells are arranged in a matrix, but this can be any number and is generally mx
n pieces (hereinafter referred to as mn pieces) are arranged in a matrix.

The load signals output from each unit load cell are taken into the scanner 3 incorporating a differential amplifier and switching elements through wiring (not shown) formed by etching technology, and then sent to a subsequent signal processing device. Also, for ease of explanation below, the direction perpendicular to the upper pressure receiving plate 1a is referred to as the Z direction, the direction parallel to the load cell 1b in a plane parallel to the upper pressure receiving plate 1a is referred to as the X direction, and the perpendicular direction is referred to as the X direction. put.

FIG. 2 shows a state in which a load cell 1b constituting the unit load cell 1 has a load cell 1b mounted on the surface thereof. Attach the force Fx detection strain gauges a to 4d in the X direction to the positions shown in the figure. If a load is applied in the X direction by attaching a strain gauge at this position, a tensile stress proportional to the load will be applied to the strain gauge 4a and 4c, and a tensile stress will be applied to the strain gauge 4a and 4c.
Compressive stresses proportional to the load are generated at positions b and 4d, and the absolute values of these stresses are all equal. Therefore, if a voltage is applied between the power supply (+) terminal 7a and the power supply (-) terminal 7b, the bridge's Fxx force terminal 8a and Fxx
A voltage signal proportional to the X-direction load is generated between the force terminals 8b.

If a load is applied in the X direction here, the stress gauge 4
A compressive stress proportional to the load occurs at the positions a and 4b, and a tensile stress proportional to the load occurs at the positions of the stress gauges 4c and 4d, and the absolute values of these stresses are all equal.

Therefore, in the bridge circuit shown in the figure, Fxx force terminal 8
Since the potential of a and the potential of the Fxx force terminal 8b are equal, no voltage signal is generated between them.

If a load is applied in the Z direction, the load is applied to the center gauge 4a~4.
Since the position of d is determined to be exactly on the neutral line of the Z direction load, each of the stress gauges 4a to 4d
No stress is generated at the position of Fxx force terminal 8.
No voltage signal is generated between a and 8b.

To summarize the above, between the Fxx force terminals 8a and 8b,
Voltage signal force 1 is generated only when a load is applied in the X direction, and
When a load is applied in one direction or two directions, no voltage signal is generated. In other words, when a load in an arbitrary direction is applied to the load cell 1b, a voltage signal proportional to the load F(II) x-direction component force F''xζ is generated between the F''x output terminals 8a and 8b. Similarly, if the Fy detection strain gauges 5a to 5d are installed in the positions shown in the figure, a voltage signal proportional to the y-direction component force Fy of the load F will be generated between the Fyy force terminals 9a and 9b. Then, if the Fz test detection stone range shields a to 6d are installed in the positions shown in the figure, the Fzz force terminal 1
A voltage signal proportional to the Z-direction component force Fz of the load JiF is generated between 0a and 10b. In this way, if a bridge circuit is constructed with the strain gauge position as shown in g2 [dl], the load F in any direction can be converted into a three-component force Fx which is orthogonal to each other.
, Fy, and Fz.

A unit load cell is constructed using a plurality of such load cells, and at least one load cell in which the three detection bridges are formed is sufficient for one unit load cell. Of course, all the load cells that make up the unit load cell are 3.
It is preferable to have two detection bridges; in this case, wire the bridge circuit in each load cell, and connect the corresponding bridge circuits of each load cell in series near the load cell on the board. Bye.

In measuring surface pressure distribution on contact surfaces and in pressure sensors for robots, mn unit load cells are arranged in mxnx rows, but conventional circuits apply bridge voltage to mn unit load cells and extract output. is shown in Figure 3.

In this example, a case will be described in which three detection bridges are formed in only one load cell among the load cells forming a unit load cell. That is, the load cell 11 constituting the first unit load cell has a Flx detection bridge lla, a Fly detection bridge llb, and an Fsz detection bridge llc, and there are mn load cells of the unit load cell having exactly the same configuration. .

That is, the load cell 12 of the mnth unit load cell is Fmn
Bridge 12a for xmn, bridge 1 for Fmnymn
2b, and a bridge 12c for Fmnzmn. The output of each bridge is differentially amplified by a differential amplifier 13 (hereinafter referred to as a differential amplifier), and then sent to a scanner 14.
CPL via multiplexer 15 scanned by
It is taken into l+16.

However, such a signal extraction circuit has the following drawbacks. In other words, it is necessary to wire from the output terminal of each unit load cell to the scanner with a built-in differential amplifier, but the number of wires required is two from the L bridge, and one load cell has three bridges. Since there are mn unit load cells with cells, a total of 6x until reaching the scanner
The number of wires is mn. If the number of unit load cells increases, the number of output wires on the board will increase according to mn, but with current wiring technology, the wiring pitch is limited to 100μ, so the integrated circuit where the output wires of each unit load cell gather Wiring becomes impossible in the surrounding area.

[Purpose of the invention]

In view of the above, an object of the present invention is to provide a 3-minute force sensing load meter array for realizing a signal extraction circuit with a reduced number of output wirings on a board.

[Key points of the invention]

According to the present invention, this purpose is to incorporate a differential amplifier and a switching element conventionally incorporated into an integrated circuit forming a scanner into a unit load cell5, and connect the output wiring of this switching element to n units in the same unit. It is common to the output wiring of each corresponding switching element of the load cell and leads to an output scanner provided outside the load cell array, and the control wiring of the switching element is connected to the m
This is achieved by connecting the control wiring of the switching elements of each unit load cell to a control scanner provided outside the load cell array.

[Embodiments of the invention]

FIG. 4 shows a signal extraction circuit according to an embodiment of the present invention. Note that in this example, like the previous conventional example, a case will be described in which three detection bridges are formed in only one load cell among the load cells forming a unit load cell.

That is, %mn unit load cells constitute mxnx rows, and the load cells 17 constituting the (1°1)th unit load needle are Fl, 1, X detection bridge 17a, F
J, 1. Y detection 7' IJ edge 17b, Fx, t,
In addition to the z-detection bridge 17c, it includes three differential amplifiers 17d for amplifying the outputs of the respective bridges, and three analog switches 17e for controlling whether or not to take out the outputs of the differential amplifiers. Such a unit load cell is M(
The load cell 18 of the 1, n)th unit load needle and the (m, n)th unit load needle
) constitutes an mxnx column including the load cell 19 of the unit load needle. Furthermore, the analog switch outputs of the Fxx output bridges of the n unit load cells constituting one row are input to the output scanner 21 in common. Fy
The same applies to the detection bridge and the Fz detection bridge.

In such a configuration, the control scanner 21 is switched to the 3xm switching elements in the first column to control the pace voltage, and the output scanner 21 is switched from the first row to the m-th row to control each load cell. The output data is taken out from the bridge and sent to the CPU 22. Furthermore, by switching the rows through which current flows from the first row to the nth row by applying a control scanner, the output voltages of all unit load meters can be obtained.

With this circuit configuration, the number of output wires from each unit load cell will be 3, so the number of output wires from mn unit load cells will be 3Xm, which is due to the increase in the number of unit load cells. The wiring density only increases in proportion to m, and the wiring density does not increase as high as before.

In addition, by incorporating the switching element 17e into the load cell, a new control wiring is added between the unit load cell and the control scanner to control conduction and interruption of the switching element, but this control wiring is connected to each unit load tr. Since the number of wires is commonly connected, the total number of wires increases only by n, and there is no risk of increasing the wire density.Next, the configuration of the load cell to realize such a circuit is shown in Fig. show. In the figure, Fx detection strain gauges 4a to 4aFymm strain gauges 5a to 5
d, the positions of the Fz detection strain gauges a to 6d, and the wiring and power supply terminals 7a that form a bridge with them;
7b are the same as shown in FIG. In this example, on the surface of the same silicon single crystal wafer, Fx, Fy
, differential amplifiers 23a to 23c for amplifying the output of the Fzz output bridge.

Analog switches 248 to 24G for controlling whether or not to output the output of the differential amplifier to the outside are formed by a diffusion process. And Fxx power terminal 25 for those outputs. F) r output terminal 26. F”z output terminal n
and a control signal terminal array for analog switch control. If a unit load cell is assembled using such a load cell,
Since the signal extraction circuit shown in FIG. 4 can be configured, the number of output wirings can be reduced to a large IJ as described above.

FIG. 6 shows another configuration of the load cell. In the configuration shown in FIG. 5, when the load cell receives a load, there is a risk that the differential amplifiers 23a to 23c and analog switches 24a to 24c formed on the surface of the silicon single crystal wafer will receive stress caused by the load l. There is. Further, the diffusion process for forming the Stosen gauge and the diffusion process for forming the differential amplifier and analog switch may be different processes, and the manufacturing process becomes complicated because the two processes are performed in series. In this configuration, Fx detection strain gauges 4a to 4dFy detection strain gauges 5a to
5dFzz output strain gauges a to 6d, wiring constituting a bridge, and power supply terminals 7a to 7b
is formed on the surface of the ring-shaped cell in the same manner as shown in FIG. A differential amplifier 23a- for amplifying the output of the bridge is placed on the surface of another silicon single crystal wafer.
23c, an analog switch 24a-24c for controlling whether or not to output the output of the differential amplifier to the outside is formed by a diffusion process, and a chip having the above elements is cut out from a silicon crystal wafer. is placed in the center hole of the ring-shaped cell, and the ring-shaped cell and the chip are connected by an array of ultrafine metal wires that also serves as a buffer means. In this way, the differential amplifiers 23a-Z
3c.

Analog switches 24a-24C are no longer subject to stress caused by loads, providing advantage A of improved reliability. Furthermore, since the diffusion process for forming the Stosen gauge and the diffusion process for forming the differential amplifier/analog switch can be performed in parallel, the manufacturing process can be flexibly organized.

〔Effect of the invention〕

According to this invention, in addition to a load cell constituting a unit load cell and a load cell and three bridge circuits formed from the load cell, there is also a differential amplifier for amplifying the output of the bridge circuit, and whether or not the output of the differential amplifier is taken out. □ Incorporating an analog switch to control - and making the output wiring common for each row of multiple unit load cells, the number of output wiring on the board can be reduced from 6xmn to 3xm. Wiring between the meter and the scanner becomes possible.

[Brief explanation of the drawing]

Figure 1 is a perspective view showing a load cell array used for measuring surface pressure distribution and force sensing in robots, etc. Figure 2 is a front view showing the electrical connections on the surface of a conventional load cell, and Figure 8g3 shows each load cell array. Conventional circuit for processing output from unit load cell,
FIG. 4 is a circuit showing an embodiment of the present invention for processing the output from each unit load cell, and FIGS. 5 and 6 are front views showing the configuration of a load cell for implementing the present invention. It is. 1... Unit load cell, la... Upper pressure receiving plate, 1b...
・Load cell, 1c...Stosen gauge, 2...Multilayer lower substrate, 2a...Groove, 3...Scanner, 4a-4
d...Fx detection strain gauge s 5a to 5d...
・Fyy appearance stref) J-shi, 6a~6d...
Fz detection strain gauges 7a-7b...Power supply terminals, 8a-8b...Fx output terminals 9.a-9b.
...Fyy force terminal, 10-a to 10b...Fzz force terminal, 11...Load cell of the 1st unit load meter, 1
1a~llc...F! 3-component force detection bridge, 12
...Load cells of the mnth unit load cell, 12a to 12
c...Fmn 3-component force detection bridge, 13...Differential amplifier, 14...Scanner, 15...Multiplexer, 16...CP u s17...Jll, 1
Load cells of the th unit load cell, 17a to 17c...F
! , 1 3-component force detection bridge, 17d...differential amplifier, 17e...analog switch, 18...first,
Load cell of 4th unit load cell, 19...Load cell of m-th and n-th unit load cell, addition...'am scanner, 21...output scanner, 22...CP u 1
23a~23C...Differential amplifier, 24a~24C・
...Analog switch, 25...F'x output terminal,
Visit...Terminal for Fy output, Go...Terminal for Fz output, Public...terminal for control signal, Fourth...Superfine metal wire. 4'2 Diagram E Pj;', 32,
Name of the invention 3 TII 7 Diarrhea) Shioyakumu 4'f I V no 3, Person making the amendment 114 Relationship to the petitioner's case 4, Agent Address 1-1 Kozu, Tanabeshinden, Kawasaki-ku, Kawasaki City.

Claims (1)

[Scope of Claims] 1) In a three-component force sensing load cell array formed by arranging unit load cells in a matrix, each having three bridge circuits that convert stress in three orthogonal directions into electrical signals, the bridge circuit a differential amplifier that differentially amplifies the outputs of the
A switching element that conducts and cuts off the output of this differential amplifier is incorporated into the load cell, and the output wiring of the switching element is shared with the output wiring of the switching element corresponding to each of the plurality of unit load cells in the same unit. The load cell array is guided to an output scanner provided outside the load cell array, and the control wiring of the switching element is shared with the control wiring of the switching elements of a plurality of unit load cells in the same row. A 3-component force sensing load cell array that leads to an external control scanner. 2. The device according to claim 1, characterized in that the differential amplifier and the switching element are formed on a substrate separate from the load cell, and this substrate is incorporated into a part of the load cell via a buffer means. A three-component force sensing load cell array.