JPS62291531A - Load detector - Google Patents

Abstract

PURPOSE:To detect load with high accuracy by preventing the variation in detection output due to humidity, by supplying dry air into a case having a load detection part fixed thereto. CONSTITUTION:A bush 11 is provided to the appropriate place of the wall part of a case 1 and a pipe 12 is connected to the wall part of the case 1 through the bush 11 to communicate with the interior of the case 1. When a pump 13 is driven, dried air is supplied into the case 1 through the pipe 12 and passes through the case 1 to be discharged to the outside from a gap 6. By this method, the load detection part 2 fixed to the case 1 is placed in a dried atmosphere and the output variation thereof due to humidity is prevented to make it possible to perform highly accurate detection. Since dry air is discharged to the outside through the gap 6, the dust in the case 1 is also discharge and the invasion of the dust from the outside through the gap 6 can be prevented.

Description

[Detailed Description of the Invention] 3. Detailed Description of the Invention [Field of Industrial Application] The present invention relates to a load (force, moment) acting on a certain object.
The present invention relates to a load detection device for detecting.

[Conventional technology]

Load detection devices are used in a wide range of fields.

In particular, the machine, based on the load detected by the load detection device,
In the field of controlling devices, extremely high detection accuracy is required. Therefore, if the surrounding environment of the installation part where the load detection device is installed is not good, the detection part is housed under the internal pressure of the case and the case opening is covered with a cover to protect the detection part from dust and impact, resulting in a high detection I try to maintain accuracy. Such a load detection device will be explained with reference to the drawings.

FIG. 2 is a sectional view of a conventional load detection device.

In the figure, 1 is a case, and 2 is a load detection section housed and fixed within the case l. The load detection section 2 includes a movable section 2a to which an external load acts, a fixed section 2b that fixes the load detection section 2 to the case, x, and l, and is mounted between the movable section 2a and the fixed section 2b. It is composed of a strain-generating portion 2C. The strain-generating portion 2C deforms according to the load acting on the movable portion 2a.

Reference numeral 3 denotes a strain gauge attached to a predetermined location of the strain generating section 2C, which generates strain according to the deformation of the strain generating section 2C, and the load is detected by the strain output.

The strain gauge 3 is connected to an appropriate external circuit by wiring (not shown), and the detected load is taken out as an electrical signal from the external circuit. A load input section 4 is connected to the movable section 2a, and transmits an external load to the movable section 2a. A cover 5 covers the opening of the case 1, and is provided with a through hole 5a through which the load input section 4 is inserted. 6 indicates a gap between the load input part 4 and the cover 5 in the through hole 5a. The load is transmitted to the load detection section 2 by the load input section 4, and the load is detected based on the deformation of the strain generating section 2C and the strain output of the strain gauge 3 due to this deformation.

[Problem that the invention seeks to solve]

In the load detection device described above, the presence of one gap 6 is essential. That is, in order to make the accuracy of the load detector high, f is such that all the load applied to the load input section 4 is transferred to the load detection section 2.
It is necessary that the information be communicated to the public. For this reason, it is undesirable to have a portion that provides resistance, such as sliding, to the load input section 4, and therefore the presence of the load input section 4 cannot be avoided.

By the way, if this gap 6 exists, the inside of the case 1 will be in communication with the outside, and the strain gauge 3 will be directly exposed to the outside air. The strain gauge 3 is particularly susceptible to humidity, and there is a problem in that the humidity of the outside air that enters causes fluctuations in the output of the load detection device, making highly accurate load detection impossible.

Furthermore, one gap 6 is provided to prevent dust from entering.

The dimensions are set to be as small as possible. For this reason, once the humid air enters the case 1, it becomes difficult for this air to escape to the outside, and there is a problem that depending on the temperature, there is a risk that a bond may occur and a short circuit may occur between the wires of the strain gauge 3. .

In order to avoid these problems, measures as shown in FIGS. 3 and 4 have been considered, but none of them are satisfactory. That is, FIG. 3 is a cross-sectional view of the load detection device, and 1
By covering the gap 6 with a thin diaphragm 8, case 1
is sealed. Other parts are the same as those shown in FIG. Inside the sealed case 1, nitrogen gas (Nt
), which completely eliminates the influence of humidity.

However, with this means, although the restraining force of the diaphragm 8 restraining the load input section 4 can be ignored in response to a force acting in the direction of the arrow F, the restraining force of the diaphragm 8 is negligible when a load in any other direction is applied. becomes large, and the applied load cannot be entirely transmitted to the load detection section, making highly accurate load detection in directions other than the direction of arrow F impossible.

Also, Fig. 4 shows the cross-section 1 of the load detection section and strain gauge.
A coating material 9 is applied on the strain gauge 3. The movable part 2a and the strain-generating part 2c are the same as those shown in FIG. Since the strain gauge 3 is not covered by the coating material 9, the influence of humidity is eliminated. However, by applying such a coating material, there is a creep phenomenon in which the output changes even when the same load is maintained.

A hysteresis phenomenon occurs in which the detected value for the same load differs when the load increases and decreases, making highly accurate load detection impossible.

SUMMARY OF THE INVENTION An object of the present invention is to provide a load detection device that can solve the problems of the prior art described above, can prevent fluctuations in detection output due to humidity, and can perform highly accurate load detection.

[Means for solving problems]

In order to achieve the above object, the present invention fixes the load detection section in a case, covers the opening of the case with a lid, provides an opening in the lid, and has a gap in the opening. A load input means is inserted into the tube, and the load input means is connected to a load detection section.One end of the tube is communicated with the inside of the case, and the other end is connected to the dry air supply means.

[Effect]

When the dry air supply means is driven and dry air is supplied into the case through the pipe, the inside of the case is filled with dry air and has low humidity. , the supplied dry air is discharged to the outside through the gap 6.

〔Example〕

The present invention will be explained below based on the illustrated embodiments.

FIG. 1 is a sectional view of a load detection device according to an embodiment of the present invention. In the figure, the same parts as those shown in No. 27 are given the same reference numerals, and the description thereof will be omitted. Reference numeral 11 denotes a bushing provided at an appropriate location on the wall of the case 1 (in the figure, on the side wall). ,1
A tube 2 is attached to the wall of the case 1 via a bush 11 and communicates with the inside of the case 1. A pump 13 is connected to the other end of the pipe 12 to send out air that has been dried in advance by a drying means (not shown).

When the pump 13 is driven, dry air is supplied into the case 1 through the pipe 12 and flows through the case 1 between 15 and 15.
! 6 and is discharged to the outside. Due to this.

The inside of case 1 is filled with dry air and maintains low humidity.
It is not affected by external humidity. or.

Because the gap 6 exists, all loads in any direction are transmitted, and there is no need to apply coating material, so
There are no disadvantages in the devices shown in FIGS. 3 and 4.

In this way, in the sixth embodiment, dry air is supplied from the pump into the case, and this dry air is discharged from the gap between the load input section and the cover.

The load detection unit fixed in the case is placed in a dry atmosphere, which prevents output fluctuations due to humidity and allows highly accurate detection.

In addition, since the dry air is exhausted to the outside through the gap, dust inside the case is also exhausted, and external dust can be prevented from entering through the gap, making it ideal for environments with a lot of dust. is effective for use. Furthermore, since the dry air is flowing, the inside of the case can be cooled, and in particular, if an electronic circuit or the like is built in the case, it can also be cooled.

Note that there are various types of load detection sections.

Regardless of the type, there is no change in the connection relationship between the load input section and the load detection section, and the present invention can be applied to any type of load detection device.

〔Effect of the invention〕

As described above, in the present invention, dry air is supplied into the case in which the load detection section is fixed, so that the inside of the case can be maintained at low humidity regardless of the external humidity. It is possible to prevent fluctuations in the detection output and perform highly accurate load detection.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a load detection device according to an embodiment of the present invention;
2 and 3 are cross-sectional views of a conventional load detection device, and FIG. 4 is a cross-sectional view of a conventional load detection section. l...Case, 2...Load detection section, 3
...Strain gauge, 4...Load input section, 5...Cover, 6...Gap, 12.
...Pipe, 13...Pump. Figure 1 Figure 2

Claims (1)

[Claims] a case, a lid body covering an opening of the case, a load detection section fixed in the case, an opening made in the lid body, and a part passing through the opening and leaving a gap therebetween. and a load input means inserted into the case and connected to the load detection section, the dryer comprising a tube having one end communicating with the inside of the case, and a drying device connected to the other end of the tube and supplying dry air to the tube. A load detection device characterized by being provided with an air supply means.