JP4860430B2 - Load measuring device - Google Patents

Description

  The present invention relates to a sheet-like load measuring device that does not depend on load distribution and a rehabilitation walking device using the same.

  In order to expedite recovery after treatment of fractures of the lower limbs, unloaded walking training is performed as part of rehabilitation. This uses crutches and parallel bars to start from about 1/3 of the total weight and gradually increase the load on the lower limbs to 1/2, 2/3. The specific method is that the patient steps on the weight-free foot and memorizes the sense when the indicated value reaches the target load. The way of walking is exclusively.

  However, with such a method that relies only on sensory memory, the patient has a strong psychology of fear of overweight, and his anxiety must be compelling. As a result, it is usual to walk with a lighter weight than the target value. In addition, this suppresses the effects of rehabilitation that accelerates recovery, leading to prolonged hospitalization and hospitalization.

  In order for a patient to perform effective gait training with peace of mind psychologically, a means to immediately notify when a load exceeding the target value is applied to the lower limb is necessary, but it has not been put into practical use. It is. In view of such a situation, a load measuring device that assembles a plurality of load sensors composed of strain gauges into shoes and uses a load signal from these sensors to sound a notification buzzer when a preset target value is reached. This is disclosed in Japanese Patent Laid-Open No. 7-204236.

However, this method has the following problems. First, since individual strain gauges are used, it is necessary to concentrate the load distributed over the entire sole on the strain gauge portion, which complicates the structure and must be incorporated into footwear (shoes). Second, since a part of the load is shared by the load sensor case and does not contribute to the strain, it is difficult to obtain linearity of the sensor output with respect to the load amount. Third, it is necessary to adjust the sensor interval according to the foot size. Fourth, although the method of measuring the total load from a plurality of outputs of a plurality of load sensors is not specified, it is usually considered that the output of each individual sensor is individually converted into an electrical signal and then added. A number of electrical signal conversion means equal to the number of sensors is required.
JP-A-7-204236

  The problem to be solved is to provide a sheet-like load measuring device that does not depend on the load distribution, and to apply it to a walking implement for load-free walking training.

  The main feature of the present invention is that the total amount of vertical load applied in an arbitrarily distributed manner to the sheet-like elastic body is performed by electrically detecting a change in the capacitance of the sheet-like elastic body. To do.

  The load measuring device of the present invention uses a sheet-like elastic body provided with a number of voids or depressions periodically as a dielectric, and a sheet-like conductive elastic body as an electrode, so that the thickness of the dielectric is proportional to the load. As a result, the total amount of the vertical load that is arbitrarily distributed and applied can be performed by electrically detecting the change in the capacitance of the generally sheet-like elastic body. There is an advantage that a practical walking aid for load-free walking can be provided. By making the thickness change due to the load 30% or less with respect to the maximum load pressure to be measured, the total load can be measured with an error accuracy of 30% or less.

  The change in capacitance is electrically measured by proportionally changing the total amount of vertical load applied in a distributed manner to the sheet-like elastic body and the change in capacitance of the roughly sheet-like elastic body with good accuracy. By doing so, the purpose of measuring the total amount of vertical load was realized with the minimum number of parts and without sacrificing the thickness of the entire sensor section.

  FIG. 1 shows an embodiment of the sensor unit 6 of the device of the present invention. (A) shows the structure of a member, (b) and (c) are two types of enlarged sectional views, and (d) is an enlarged plan view of a central member. In the present embodiment, a sheet-like elastic body 2 provided with a large number of voids or depressions and two sheet-like conductive elastic bodies 1 and 3 sandwiching the sheet-like elastic body are made of an elastic adhesive or an adhesive material. It is used and laminated. The sheet-like elastic body 2 is periodically provided with a large number of voids 11 or depressions 12 as shown in FIG. An enlarged cross section of the sensor section 6 when the gap 11 is provided is shown in FIG. 5B, and an enlarged cross section of the sensor section 6 when the recess 12 is provided is shown in FIG. The gap 11 or the depression 12 has a cross section perpendicular to the surface. More specifically, the sheet-like elastic body 2 is provided with a gap 11 having the dimensions shown in FIG. 4D in a rubber sheet having a hardness of 50 ° and a thickness of 2 mm. The sheet-like conductive elastic bodies 1 and 3 are conductive rubber sheets having a volume resistivity of 5 Ωcm, a hardness of 60 °, and a thickness of 0.5 mm. As the elastic adhesive, a commercially available one-component moisture-curing elastic adhesive is used. The sensor unit 6 has a thickness of 3 mm, and the outer shape is an insole shape such as a shoe.

  When the sensor unit 6 having such a configuration is stepped on with a foot, the thickness of the sensor unit 6 changes according to the pressure of the part. The deformation of the rubber material due to the external pressure is performed while keeping the volume constant, but the sheet-like elastic body 2 is provided with a number of voids or depressions periodically, so that the volume commensurate with the decrease in thickness is in this portion. Can be compressed and deformed corresponding to the Young's modulus of the elastic body. That is, in a range where the thickness change is relatively small, the thickness decreases in proportion to the pressure.

  Further, the sensor unit 6 having such a configuration can be regarded as a capacitor in which the two sheet-like conductive elastic bodies 1 and 3 are electrodes and the sheet-like elastic body 2 is a dielectric. If the above-described deformation condition, that is, the thickness decreases in proportion to the pressure in the range where the change in thickness is relatively small, the change in the capacitance of the capacitor is detected by the sensor unit 6. The following consideration shows that it is proportional to a good approximation to the total load applied to and does not depend on the load distribution.

  As is clear from the above consideration, the total load can be measured by measuring the change in capacitance, and the error rate is equal to the compression rate. When the load is distributed, the compression rate of the portion with the highest load pressure becomes the upper limit of the error. In the case of load-free walking training, an error of up to about 30% is allowed, so the compression amount with respect to the maximum load pressure needs to be 30% or less. The amount of compression with respect to the load can be adjusted by the hardness of the sheet-like elastic body 2 and the size of the gap or dent in FIG. It should be noted that the sheet used as the electrode must have sufficient elasticity like the rubber sheet of this example, and if an inelastic film or the like is used, permanent deformation occurs due to surface stress when a load is applied, and the sheet is used repeatedly. I can't stand it. The volume specific resistance of the sheet-like conductive elastic body used as the electrode is a resistance connected in series to the capacitance of the sensor unit 6, but the resistance value change depending on the load distribution and the load value change is not Since it becomes an error factor of a measured value, it is necessary to make it small. In this example, the error cannot be ignored if it exceeds 100 Ωcm.

  Various methods are well known for the electric circuit unit 7 that measures the electrostatic capacity of the sensor unit and outputs an alarm when a predetermined load is exceeded. An example is shown in FIG. In the figure, a 10 kHz, 5 V sine wave voltage generated by a sine wave voltage generation circuit is applied to one of the two electrodes of the sheet-like conductive elastic bodies 1, 3 of the sensor unit 6, and the other electrode is applied. Connect to current-voltage converter. When the sine wave voltage is applied to the dielectric of the sensor unit 6, a sine wave current flows. The magnitude of this current is proportional to the capacitance of the sensor unit 6 when the sine wave voltage is constant. When this sine wave current is input to the current-voltage conversion circuit, the circuit outputs a sine wave voltage proportional to the current value. When this sine wave voltage is passed through a narrow band filter tuned to the same 10 kHz frequency as the applied sine wave voltage, noise such as DC offset voltage and commercial frequency of the circuit is removed, and a highly accurate measurement signal voltage is obtained. can get. This voltage is compared with a voltage set in accordance with the load for which an alarm should be issued by a comparison circuit, and an alarm is output when the voltage exceeds the set voltage. Alternatively, it is possible to use a method in which the capacitance of the sensor unit 6 is made a part of the oscillation circuit and a change in capacitance is detected by a change in oscillation frequency, but this is well known and will not be described in detail.

  In the load measuring device of this embodiment, the configuration of the sensor unit 6 is a simple one in which three sheets are laminated, the shape is a thin sheet, and the total amount of arbitrarily distributed loads can be measured with good accuracy. By installing this on footwear such as commercially available shoes or sandals, a practical rehabilitation walking tool for load-free walking training that does not depend on the size of the foot or how to apply the load can be realized.

  FIG. 2 shows another embodiment of the sensor unit 8 of the device of the present invention. (A) is a structure of a member, (b) is an expanded sectional view. In this embodiment, a sheet-like elastic body 2 provided with a large number of gaps or depressions periodically, a flat sheet-like elastic body 4, and three sheet-like conductive materials sandwiching these sheet-like elastic bodies in a sandwich shape. The elastic bodies 1, 3, and 5 are laminated using an elastic adhesive material or an adhesive material. The sheet-like elastic body 2 is periodically provided with a large number of voids 11 or depressions as in FIG. On the other hand, the flat sheet-like elastic body 4 does not have voids or depressions. An enlarged cross section of the sensor unit 8 when the air gap 11 is provided is shown in FIG. The members will be described in detail. The sheet-like elastic body 2 is a rubber sheet similar to that of the first embodiment. The sheet-like conductive elastic bodies 1, 3 and 5 are the same conductive rubber sheets as in the first embodiment. As the elastic adhesive, the same elastic adhesive as in Example 1 is used. The thickness of the sensor is 4 mm, and the outer shape is an insole shape such as shoes.

  The sensor unit 8 having such a configuration can be compressed and deformed in the same manner as in the first embodiment when stepped on with a foot. That is, in a range where the thickness change is relatively small, the thickness decreases in proportion to the pressure. On the other hand, since the sheet-like elastic body 4 cannot move in the surface direction, the change in thickness is so small that it can be ignored.

  In addition, the sensor unit 8 having such a configuration is electrically connected to a capacitor having two sheet-like conductive elastic bodies 1 and 3 as electrodes and a sheet-like elastic body 2 as a dielectric, and two sheet-like conductive bodies. It can be considered that the elastic elastic bodies 3 and 5 are electrodes and the sheet-like elastic body 4 is a capacitor. In the capacitor using the sheet-like elastic body 2 as a dielectric, the change in the capacitance of the capacitor is proportional to the total load applied to the sensor unit 8 in a good approximation as in the first embodiment. Independent of distribution. In addition, when the outer dimension of the sheet-like conductive elastic body 3 is reduced by several mm as compared with the sheet-like conductive elastic bodies 1 and 5, the sheet-like conductive elastic body 3 is moved by the sheet-like conductive elastic bodies 1 and 5. There is an advantage that it can be electrically guarded, and as a result, the effects of stray capacitance can be eliminated.

  FIG. 4 shows an electric circuit unit 9 connected to the sensor unit 8 of this example. In the figure, a sine wave voltage generated by a sine wave voltage generation circuit is applied to an electrode made of the sheet-like conductive elastic body 1 of the sensor unit 9. Further, the voltage and phase of this sine wave voltage are adjusted to the following values by a gain & phase adjustment circuit and applied to the electrode made of the sheet-like conductive elastic body 5. An electrode made of the sheet-like conductive elastic body 3 is connected to a current-voltage conversion circuit, and the gain and phase adjustment is performed so that the output of the current-voltage conversion circuit becomes zero when no load is applied to the sensor unit 8. By doing in this way, the sum of the currents flowing through the two capacitors of the sensor unit 8 is canceled by 0 when there is no load. When the rubber of the same material is used for the two dielectrics, the gain is approximately equal to the inverse ratio of the thickness and is about 1/4 and the phase difference is about 180 °, but the series resistance of the electrode and the dielectric It is necessary to shift from 180 ° by the resistance equivalent to the dielectric loss.

  When a load is applied to the sensor unit 8, the capacitance of the capacitor using the sheet-like elastic body 2 as a dielectric increases in proportion to the total load as described above, whereas the sheet-like elastic body 4 is used as a dielectric. As described above, the capacitor has no change in thickness and the capacitance is unchanged. As a result, a current proportional to the total load flows through the current-voltage conversion circuit. By passing this output voltage through a narrow band filter tuned to the frequency of the applied sine wave voltage, the DC offset voltage of the circuit and the commercial frequency noise are removed, and a highly accurate measurement signal voltage can be obtained. This voltage is compared with a voltage set in accordance with the load for which an alarm should be issued by a comparison circuit, and an alarm is output when the voltage exceeds the set voltage.

  In addition to the same features as in the first embodiment, the load measuring device of the present embodiment measures the differential current between the two capacitors, and therefore changes the environmental conditions such as temperature by using the same material for the two types of dielectrics. In addition, since a current proportional to a change in capacitance due to a load is measured, highly accurate measurement can be performed even for a smaller load.

  Since the configuration is simple, the shape is thin, and the total amount of distributed load can be measured, it can be applied to load measurement in a narrow place, and in particular, it can be applied to commercially available footwear and a practical rehabilitation walking implement can be realized.

It is explanatory drawing which showed the implementation method of the sensor part of a load measuring device. Example 1 It is explanatory drawing which showed the implementation method of the sensor part of a load measuring device. (Example 2) It is explanatory drawing which showed the implementation method of the electric circuit part of a load measuring device. Example 1 It is explanatory drawing which showed the implementation method of the electric circuit part of a load measuring device. Example 24

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Sheet-like electroconductive elastic body 2 Sheet-like elastic body which provided many space | gap or hollow periodically 3 Sheet-like electroconductive elastic body 4 Flat sheet-like elastic body 5 Sheet-like electroconductive elastic body 6 Sensor part (Example) 1)
7 Electrical circuit section (Example 1)
8 Sensor unit (Example 2)
9 Electrical circuit section (Example 2)
11 void 12 dimple

Claims (4)

A sheet-like elastic body in which a large number of voids or depressions are periodically provided, and a flat sheet-like elasticity that is the same material as the sheet-like elastic body and does not have the voids or depressions and cannot move in the surface direction. and body, was a dielectric, a sensor unit formed by forming two capacitors these dielectrics as electrodes 3 sheet-like conductive elastic body sandwiched sandwich,
And the electric circuit portion that operates by measuring the change in the difference in capacitance of these capacitors consist,
The sensor part is compressed and deformed when stepped on with a foot,
The thickness of the gap or indentation provided a sheet-like elastic body, the load thus load measuring apparatus characterized by varying the range of 30% or less of the maximum load pressure to be measured. The load measuring device according to claim 1,
A load measuring device characterized in that an outer dimension of a central one of the three sheet-like conductive elastic bodies is reduced as compared with two sheets on both sides.   3. A walking tool for rehabilitation characterized in that the load measuring device according to claim 1 or 2 is applied to a shoe or the like, whereby a warning is issued when a load during walking exceeds a preset load. The volume resistivity of the sheet-like conductive elastic body is 100 Ωcm or less, and the load measuring device and rehabilitation walking device according to any one of claims 1 to 3 .

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