JPS6234273Y2 - - Google Patents

Description

[Detailed Description of the Invention] The present invention relates to a load cell used for measuring load.

Compared to known load cells, which are constructed by bonding a metal foil resistor pattern to an insulating film, and then bonding this film to the strain-generating region of the beam body where the load to be measured acts, the number of manufacturing steps is reduced. A new load cell that can be easily and inexpensively manufactured with a small number of loads and that can perform highly accurate measurements has been proposed by the inventors of the present invention and has already been filed. This load cell is made by directly forming an insulating coating on one surface of the beam body, and directly laminating a metal material on this coating by vapor deposition, sputtering, or masking.
It is constructed by providing necessary resistor patterns and terminal lead patterns.

By the way, in this type of load cell, the four strain gauge resistor patterns are divided into two pieces facing a pair of parallel strain-generating parts, and four circuits formed by a part of the terminal lead pattern are arranged. The wires are connected at the internal wiring part to form a Wheatstone bridge circuit. On the other hand, since the four in-circuit wiring parts are directly laminated on the insulating film, it is impossible to cross them. Therefore, when forming the four in-circuit wiring sections, it is necessary to take measures such as detouring the strain gauge resistor patterns so that they do not cross each other. As a result, it is inevitable that the lengths of the four internal wiring sections will be different.
Since this difference in length affects the bridge balance, it is not suitable for cases where higher precision measurement is required.

The present invention was proposed under the above circumstances, and its purpose is to provide a load cell that can perform measurements with higher accuracy by eliminating the influence of internal circuit wiring on bridge balance. It is in.

That is, the present invention includes two strain gauge resistor patterns provided between a pair of mutually parallel strain-generating parts, one strain-gauge resistor pattern facing each other, and the other strain-gauge resistor patterns facing each other. Three wiring portions out of the four circuit wiring portions that are connected to the other two strain gauge resistor patterns to form a Wheatstone bridge circuit are formed from part of the terminal lead pattern, This is a load cell characterized in that these are made to have the same length and width, and the remaining in-circuit wiring part is formed of a lead wire having the same resistance value as the wiring part.

Hereinafter, the present invention will be described with reference to an embodiment shown in the drawings.

In the figure, 1 is a beam body, which is formed by machining metal materials such as stainless steel (SUS630) and high-strength aluminum alloy (A2218). This beam body 1 has mounting holes 2, 2 provided at one end.
It is used by being cantilevered by a fixed part 4 by a bolt 3 passing through it. A pair of mutually parallel circular holes 5, 5 and a gap 6 connecting these circular holes 5, 5 are provided in the intermediate part of the beam body 1, passing through the circular holes 5, 5, respectively in the width direction. The upper and lower parts of the upper and lower parts are made thinner, and the upper thinner part in particular is formed to be used as the strain-generating parts 7A and 7B. A locking hole 8 is provided at the free end of this beam body 1, and this hole 8
For example, a hanging metal fitting 9 is attached to it, and the load W to be measured is applied as shown by the arrow (see FIG. 2).

An insulating coating 10 is directly formed on at least the pattern forming surface of the beam body 1 to cover it. In this example, the moisture resistance of the beam body 1,
The figure shows the case where the insulating coating 10 is directly formed to cover all surfaces of the beam body 1 in order to further improve the corrosion resistance, prevent mechanical damage, and further prevent the insulating coating 10 from peeling off. . This insulating coating 10 is made of a polymeric material such as polyimide resin.

Four strain gauge resistor patterns 11 to 14 and a terminal lead pattern 15 are formed by directly laminating metal materials on a portion of the insulating coating 10 that covers the upper surface of the beam body 1. A lead wire 16 is provided.

The strain gauge resistor patterns 11 to 14 are
Two of them are arranged opposite to the strain-generating portions 7A and 7B of the beam body 1, and are made of, for example, a Ni-Cr alloy. And each of these patterns 1
1 to 14 form a zigzag shape as shown in FIG.

The terminal lead pattern 15 is formed of a metal layer A that forms the resistor patterns 11 to 14, and a metal layer B such as Au or Al that is directly laminated thereon. This terminal lead pattern 15 has input terminal portions 15A, 15B and output terminal portions 15C, 15D. It is located. Further, the terminal lead pattern 15 includes two strain gauge resistor patterns 11 and 13 placed opposite to one strain generating part 7A, and two other strain gauge resistor patterns 11 and 13 placed facing to the other strain generating part 7B. It has three in-circuit wiring parts 17, 18, and 19 that connect the resistor patterns 12 and 14. These wiring portions 17 to 19 have the same length and width, and therefore have the same resistance value. Note that, for example, the in-circuit wiring section 17 connects the resistor patterns 11 and 12 with each other, and the in-circuit wiring section 18 connects the resistor patterns 11 and 14 with each other.
The in-circuit wiring portion 19 connects the resistor patterns 13 and 14 to each other and is provided in parallel to each other.

Further, the lead wire 16 is used as the remaining one wiring part in the circuit, and is provided by wire bonding, and the resistor pattern 12,
13 are connected to each other by intersecting with the in-circuit wiring parts 17 to 19 without touching them. This lead wire 1
Reference numeral 6 is made of Au or the like and has the same resistance value as the wiring parts 17 to 19. And these wiring parts 17
19 and lead wires 16, the resistor patterns 11 to 14 are connected to form a Wheatstone bridge circuit as shown in FIG.

Note that the load cell having the above configuration is manufactured, for example, as follows.

First, as shown in FIG. 6A, after forming the insulating coating 10 on all surfaces of the beam body 1, two types of metal layers A and B are applied to the insulating coating portion covering the upper surface of the beam body 1. Laminated layers are formed in sequence. To form the insulating coating 10, all surfaces of the beam body obtained by cutting are degreased and cleaned, then immersed in a varnish-like insulating resin (for example, polyimide) liquid whose viscosity is adjusted to about 1000 cp, taken out, and placed in a spinner. support. The spinner is supported using the mounting holes 2, 2 and the locking hole 8, and is supported in a floating state. Then, the beam body 1 is rotated by the spinner.
By rotating at a speed of about 1600rpm,
4 to 5 μm of insulation coating material is applied to all surfaces of the beam body 1.
Adjust and apply to a thickness of about m. Next, this beam body 1 is first heat-treated at 100°C for about 1 hour to remove the solvent in the insulation coating material, and then
A hard insulating film 10 is formed by heat treatment at 250° C. with an opening time of about 5 o'clock. Further, each of the metal layers A and B is directly laminated by vapor deposition, sputtering, etc., and of course the thickness of each is appropriately determined to be several μm or less.

Next, as shown in FIG. 6B, the metal layer B is removed by photo-etching using an etchant suitable for the metal material, leaving the terminal lead pattern 15 behind.

After this, as shown in FIG. 6C, the metal layer A
, using an etchant appropriate for the metal material,
Terminal lead pattern 15 by photo etching
and strain gauge resistor patterns 11 to 14
The metal layers are then removed with only a few remaining, and then heat treated to stabilize each metal layer.

Finally, as shown in FIG. 6D, the strain gauge resistor pattern 1 is bonded by wire bonding.
2 and 13 are connected via lead wire 16, and the load cell shown in FIG. 1 is completed.

Although the above-mentioned embodiment is constructed as described above, in the present invention, a span adjustment resistor pattern, a temperature compensation resistor pattern, etc. may be added as necessary. In addition, when implementing the present invention, the specific structure, shape, position and The materials etc. are not limited to those of the above embodiment unless it goes against the gist of the invention.
Of course, it can be configured and implemented in various ways.

The gist of the present invention described above is the configuration described in the claims of the above-mentioned utility model registration. Therefore,
According to the present invention, regardless of the lengths of the four in-circuit wiring parts that connect the four strain gauge resistor patterns to the Wheatstone bridge circuit, the respective resistance values can be formed to be the same. This eliminates the influence on bridge balance due to differences in the lengths of the four internal circuit wiring sections, and has the effect of realizing more accurate measurements.

[Brief explanation of the drawing]

The drawings show an embodiment of the present invention, with FIG. 1 being a perspective view and FIG.
3 is a sectional view taken along the line in FIG. 1, FIG. 3 is a sectional view taken along the line in FIG. 1, and FIG. 4 is an enlarged view of the strain gauge resistor pattern. FIG. 5 is an electric circuit diagram, and FIGS. 6A to 6D are explanatory diagrams sequentially showing the manufacturing method. 1... Beam body, 7A, 7B... Strain generating part, 10
...Insulating coating, 11 to 14...Strain gauge resistor pattern, 15...Terminal lead pattern, 1
6...Lead wire (circuit wiring part), 17-19...
...Wiring section inside the circuit.

Claims (1)

[Scope of utility model registration request] An insulating film is directly formed on one surface of a beam body having a pair of parallel strain generating portions formed along the width direction,
A load cell in which a metal material is directly laminated on the coating to form four strain gauge resistor patterns, two of which are arranged facing each strain-generating portion, and a terminal lead pattern, the load cell being characterized in that three of the four in-circuit wiring portions which are provided between the pair of strain-generating portions and connect the two strain gauge resistor patterns arranged facing one strain-generating portion with the other two strain gauge resistor patterns arranged facing the other strain-generating portion to form a Wheatstone bridge circuit are formed from parts of the terminal lead patterns and have the same length and width, and the remaining in-circuit wiring portion is formed from a lead wire having the same resistance as the wiring portions.