JPH0325152Y2 - - Google Patents

Description

[Detailed Description of the Invention] (Industrial Application Field) The present invention mainly relates to a load cell that is used by being incorporated into an electronic scale.

(Prior art) As shown in FIG. 1, two load cells that convert the magnitude of a load into an electric signal are provided in parallel between a fixed rigid body part 2 and a movable rigid body part 3 of a strain-generating body 1. There are two flexible parts 6...6 on each of the beam parts 4 and 5.
are provided, and the strain gauges 7...7 are attached to the flexible parts 6...6, respectively, and the strain gauges 7 are attached to the flexible parts 6...6, respectively.
. . 7 constitutes a bridge circuit as shown in FIG. 2, and an input/output conductor 8 for transmitting signals with external equipment is connected to the bridge circuit. When a load is applied to the movable rigid body part 3 with a voltage applied between the pair of opposing connection points A and B of the bridge circuit, each strain is caused by the strain generated in each flexible part 6...6. As the electrical resistance values of the gauges 7...7 change, the balance of the bridge circuit is broken and an electrical signal corresponding to the load is output between the other connection points C and D.

By the way, the wiring work during the manufacture of such a load cell involves bridge-coupling the strain gauges attached to the strain-generating body using lead wires such as enameled wires, and attaching input/output conductors to the bridge circuit. Wiring work is extremely troublesome work, especially since the strain gauge is a small component, and is prone to wiring mistakes. Furthermore, as shown in FIG. 1, each strain gauge 7...7 and the input/output conductor 8 are attached to different surfaces of the strain body 1, so that the wiring lead wires are attached to different surfaces of the strain body. Since the lead wires are connected across the wires, the coating of the lead wires may peel off at the corners of the flexure element, causing problems such as a short circuit between the lead wires and the flexure element.

In order to facilitate the wiring work of the load cell as described above, a printed wiring board has conventionally been used. For example, a relay board for strain gauge connection is pasted between two strain gauges pasted on each beam part, and an input/output board for connecting input/output conductors is attached to the side of the fixed rigid body part. By pasting it on, wiring around the gauge and connection of input/output conductors can be facilitated.

However, even in this case, each board is provided on a different surface of the strain body, so the lead wires connecting each board are wired across different surfaces of the strain body. Similarly, the problem arises that the lead wire coating is peeled off at the corners of the flexure element and short-circuited to the flexure element. It was a hassle to have to lay down cloth etc.

In order to solve this problem, the applicant proposed in an earlier application (Utility Application No. 58-162035) that the input/output board to which the input/output conductor is connected is attached with a strain gauge from the side of the fixed rigid body. We proposed an idea for an ``electrical wiring board'' that is characterized by being able to be pasted across the surfaces of both the upper and lower beam parts. According to this, the lead wire does not straddle the corner of the strain-generating body, and the problem of peeling off of the coating of the lead wire is solved.

(Purpose of the invention) The present invention further improves the invention related to the above application.
The purpose of the present invention is to realize a highly reliable load cell that is inexpensive and free from wiring errors by further improving the workability of wiring work during load cell manufacturing.

(Structure of the invention) That is, the present invention provides an upper surface of the upper beam part in a strain-generating body consisting of a fixed rigid body part and a movable rigid body part at both ends, and an upper beam part and a lower beam part provided between both the rigid body parts. and a load cell in which a plurality of strain gauges are attached to the lower surface of the lower beam part, and a bridge circuit is configured by these strain gauges and a printed wiring board attached to the strain body, the printed wiring board consists of an input/output part to which the input/output conductor is connected, and a pair of relay parts provided on both sides of the input/output part to which the strain gauge is connected, and each of these parts is integrally formed, and the input/output part is The flexure element is pasted from the side surface of the fixed rigid body section to the upper surface of the upper beam section and the lower surface of the lower beam section, and the pair of relay sections are attached to the upper surface of the upper beam section and the lower surface of the lower beam section, respectively. It is characterized by what it did. According to such a configuration, the required circuit is configured only by the connection between the relay part of the printed wiring board and the strain gauge, and the connection between the input/output part of the board and the input/output conductor, and the above objective is achieved. be done.

(Example) Hereinafter, an example of the present invention will be described based on the drawings.

In FIG. 3, 10 is a load cell installed via brackets C and D between the scale body A and the weighing pan B provided on the top thereof, and as shown in FIG. The strain body 11 has a fixed rigid body part 12 at one end fixed to the scale body A via the bracket C, and a fixed rigid body part 13 at the other end to which the weighing pan B is fixed via the bracket D.
The upper beam section 14 and the lower beam section 15 provided between the upper and lower ends of the rigid body sections 12 and 13 form a hollow quadrilateral shape. The upper beam part 14 and the lower beam part 15 have flexible parts 1 whose walls are thinned by semicircular cuts.
4a and 15a are formed at two locations each, and first to fourth strain gauges 16 are formed on the surface of each flexible portion.
a to 16d (third and fourth strain gauges 16c,
16d (shown in FIG. 5) are attached respectively.

In addition to the strain gauges 16a to 16d, a printed wiring board 17 for bridge-coupling these strain gauges is attached to the strain body 11. As shown in FIG. 5, this substrate 17 is attached to the upper surface of the upper beam part 14, and
A first relay section 17a to which the second strain gauges 16a and 16b are connected, and a third and fourth strain gauge 16 attached to the lower surface of the lower beam section 15.
c, 16d are connected to the second relay part 17d, and the input/output part 17c is attached to the side surface or upper or lower surface of the fixed rigid body part 12 and is connected to the input/output conductors 18a, 18a, 18b, 18b. It has a U-shaped integral structure.

The first relay part 17a has terminals a, a to which the first strain gauge 16a is connected, and terminals b, b to which the second strain gauge 16b is connected,
Terminals c and c to which the output sensitivity temperature compensation element Rx is connected are provided, and similarly, the second relay section 17b is provided with terminals d and d to which the third strain gauge 16c is connected, and 4 strain gauges 16
Terminals e and e to which d is connected and terminals f and f to which an output sensitivity temperature compensation element Ry is connected are provided. Here, a total of four protrusions 17d...17d in both relay parts 17a, 17b prevent the lead wires of each strain gauge 16a to 16d attached to both beam parts 14, 15 from coming into contact with strain body 11. This is to prevent this.

The input/output section 17c also includes input terminals g, g to which voltages to be applied to the bridge circuit are input.
and the output terminals h, which output a signal corresponding to the load applied to the load cell 10, are normally short-circuited with a short-circuit lead wire, and when the bridge balance shifts or the zero point shifts due to temperature change. Two sets of adjustment terminals i, j, k to which constantan wires or thin copper wires for compensation are connected as necessary.
and l, m, n are provided.

The terminals a to n are connected by wiring lines 17e, . . . , 17e to form a bridge circuit as shown in FIG.

Note that when attaching the printed wiring board 17 to the flexural body 11, the portion indicated by the symbol L in FIG. has been done. In addition, each protrusion 17d
. . . The portion 17d is also not attached to the strain-generating body 11 and is in a floating state.

According to such a configuration, the load cell 10 is manufactured as follows.

First, each flexible portion 14a, 14a,
The first to fourth strain gauges 16a to 16d are attached to the surfaces of the strain gauges 15a and 15a, respectively, and after that, the printed wiring board 17 is placed across the fixed rigid body part 12 of the strain body 11 and both the upper and lower beam parts 14 and 15. Paste it. At this time, the first and second relay parts 17a and 17b of the substrate 17 are connected to both the upper and lower beam parts 14,
15, the input/output section 17c is bent along the bending lines x-x and y-y so that the input/output section 17c is bent on the side surface or above the fixed rigid body section 12,
It is pasted across the bottom surface. In addition, both relay parts 17
A temperature compensation resistor Rx for output sensitivity is installed between terminals c and c and between terminals f and f provided in a and 17b, respectively.
Ry is installed in advance, and the input/output section 17
The two sets of adjustment terminals i, j, k and l, m, n provided in c are short-circuited by lead wires, respectively.

Next, the leads of the first to fourth strain gauges 16a to 16d are connected between the terminals a, a, b, b, d, d, e, and e provided on both the relay parts 17a and 17b, respectively, and Two input and output conductive wires 18a, 18a, 18b, and 18b are connected to terminals g, g, h, and h in the input/output section 17c, respectively.

After that, bridge balance, sensitivity, temperature characteristic tests, etc. are conducted, but at this time, the two sets of adjustment terminals i, j,
Constantan wires or thin copper wires are inserted between k, l, m, and n instead of the lead wires as required.

After the above work, load cell 1
0 is subjected to coating treatments such as waterproofing and rustproofing, thereby completing the load cell. However, as is clear from the above explanation, the wiring work in the manufacturing process involves connecting the strain gauges 16a to 1 to the printed wiring board 17.
6d, input/output conductors 18a, 18a, 19b, 1
8b and the adjustment member soldering work,
There is no need to use lead wires to connect each strain gauge or between a plurality of substrates, and therefore, there is no need for lead wires to be wired across the corners of the strain body 11.

(Effects of the invention) As described above, according to the invention, in a load cell in which a plurality of strain gauges are attached to the surface of a strain-generating body and connected to form a bridge circuit, the bridge circuit and The input/output circuit is formed by simply connecting each strain gauge and the input/output conductor to the printed wiring board. This eliminates the need to connect each strain gauge or between a plurality of boards using lead wires, making wiring work easier and preventing wiring errors. In particular, since there is no need for wiring across different surfaces of the flexural element, there is no longer a problem of the lead wire sheathing peeling off and a short circuit to the flexural element as in the past, or to prevent this. This eliminates the need for insulating cloth, etc. As a result, the manufacturing cost of this type of load cell will be reduced, and the quality and reliability will be improved.

[Brief explanation of the drawing]

Fig. 1 is an external view of a conventional load cell, Fig. 2 is a bridge circuit diagram of the load cell, Fig. 3 is a schematic diagram of an electronic scale showing one usage state of the load cell according to the present invention, and Fig. 4 is the present invention. An external view of a load cell showing an embodiment of the invention, FIG. 5 is a developed plan view of a printed wiring board in the load cell, and FIG. 6 is a circuit diagram of a bridge circuit. 10...Load cell, 11...Strain element, 12...
...Fixed rigid body part, 13...Movable rigid body part, 14...Upper beam part, 15...Lower beam part, 16a-1
6d...Strain gauge, 17...Printed wiring board, 17a, 17b...Relay part, 17c...
Input/output section, 18a, 18b...Input/output conductor.

Claims (1)

[Scope of Claim for Utility Model Registration] (1) The upper surface of the upper beam part of a strain-generating body consisting of a fixed rigid body part and a movable rigid body part at both ends, and an upper beam part and a lower beam part provided between both rigid body parts. and a plurality of strain gauges are attached to the lower surface of the lower beam part, respectively, and a bridge circuit is constituted by these strain gauges and a printed wiring board attached to the above-mentioned strain-generating body. The wiring board is
It has an input/output part to which input/output conductors are connected, and a pair of relay parts provided on both sides of the input/output part to which the strain gauge is connected, and each of these parts is integrally formed so that the input/output part does not cause strain. A pair of relay parts are attached to the upper surface of the upper beam part and the lower surface of the lower beam part, respectively, extending from the side surface of the fixed rigid body part to the upper surface of the upper beam part and the lower surface of the lower beam part. load cell. (2) A portion attached across the upper surface of the upper beam section and lower surface of the lower beam section of the input/output section of the printed wiring board, and a pair attached to the upper surface of the upper beam section and the lower surface of the lower beam section. 2. The load cell according to claim 1, wherein a portion between the load cell and the relay portion is not attached to the upper surface and the lower surface.