JP2000055720A - Weight detecting equipment - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide weight detecting equipment at a low cost which is not affected by humidity in the air and has a simple structure. SOLUTION: When a load is applied to a retainer 6 in the case of weight detection, the retainer changes in the up and down direction, and a signal width converting means 10 interlocking with the retainer 6 also changes in the up and down direction. In the signal width converting means 10, a triangular or trapezoidal protruding body 11 is formed in the vertical (up and down) direction on a circumference whose center is the retainer 6. The protruding body 11 rotates at a constant speed at a constant height from a reference surface. By using a signal detecting means 13 like an optical sensor, the width of the protruding body 11 is measured. The signal width of the protruding body 11 measured in accordance with the vertical movement of the protruding body 11 (signal width converting means 10) also changes. By making the measured signal width of the protruding body 11 correspond to the weight, the weight can be accurately detected irrespective of humidity in the air.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a weight detecting device which can measure the weight of an object to be measured while the object is placed on a mounting table and rotated.

[0002]

2. Description of the Related Art A conventional weight detector of this type is disclosed in, for example, Japanese Patent Application Laid-Open No. 62-168364. FIG. 6 shows an outline of this configuration. In FIG. 1, a support bar of a mounting table 1 is connected to a motor mounting plate 2 together with a rotary drive motor, and the motor mounting plate 2 is connected to one common end of a leaf spring 3 which is two parallel metal plates. The other common end of the leaf spring 3 is fixed to the Roberval mounting plate 4. A movable electrode plate 5 a is connected to a connection between the motor mounting plate 2 and the leaf spring 3 so as to be parallel to the leaf spring 3. Further, the fixed electrode plate 5b is fixed to the roberval mounting plate 4 so as to face the movable electrode plate 5a.
When the object to be measured is placed on the mounting table 1, the leaf spring 3 is deformed downward according to its weight, and accordingly, the movable electrode plate 5a fixed to one end of the leaf spring 3 is also displaced downward. Therefore, when the object to be measured is placed on the mounting table 1, the movable electrode plate 5a moves downward, and the distance between the movable electrode plate 5a and the fixed electrode plate 5b increases according to the weight. The weight can be determined by measuring the capacitance between the two electrodes.

[0003]

However, the conventional weight detecting device has a problem that the dielectric constant between the parallel metal plates changes due to the humidity in the air, so that the capacitance changes and an error occurs in the measured weight. Was. In addition, it is necessary to finely adjust the parallelism and the distance between the metal plates in order to increase the measurement accuracy, and the entire apparatus becomes precise and complicated, which causes a high cost.

[0004]

SUMMARY OF THE INVENTION It is an object of the present invention to provide a weight detecting device which is not affected by humidity in the air, has a simple structure and is inexpensive.

According to the structure of the weight detecting device of the present invention, when a load is applied to the support in detecting the weight, the support changes vertically in accordance with the load, and the signal width conversion linked to the support is performed. The means also changes in the vertical direction according to the load. The signal width conversion means is vertically (up and down) on the circumference around the support
Since the projections having different widths in the direction are formed, for example, by utilizing the fact that the projections rotate at a constant height from the reference plane at a constant height by a signal width detecting means such as an optical sensor, the projections are formed. When the width in the circumferential direction is measured, the circumferential width of the protrusion measured as the protrusion (signal width converter) moves up and down also changes. If the measured width of the protrusion corresponds to the weight, the weight can be accurately detected. According to this configuration, the magnitude of the load is measured as the circumferential width of the protrusion on the circumference, so that the weight can be accurately detected regardless of the humidity in the air. Furthermore, if the projection (signal width conversion means) is formed integrally with the rotational force transmission means, a simple and inexpensive configuration with a smaller number of parts can be obtained.

[0006]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS A weight detecting device according to the present invention is a weight detecting device, wherein a support for supporting and rotating a load, and the support for supporting the load of the support and moving up and down depending on the magnitude of the load. An elastic body that supports the rotation of the support, a rotation drive unit for rotating the support, a rotation force transmission unit that transmits a rotation force from the rotation drive unit to the support, and a vertical movement and rotation of the support. Signal width conversion means in which projections having different widths in the upper side and the lower side are provided in the vertical direction on the circumference centered on the support in conjunction with each other, and the signal width conversion means fixed at a certain height from the reference plane. Signal width detection means for detecting the circumferential width of the protrusion using rotation of the means,
Weight is detected by changing the signal width of the signal width detecting means according to the height position of the signal width converting means from the reference plane. According to this configuration, the magnitude of the load is measured as the circumferential width of the protrusion on the circumference, so that the weight can be accurately detected regardless of the humidity in the air. Furthermore, if the projection (signal width conversion means) is formed integrally with the rotational force transmission means, a simple configuration with a smaller number of parts can be obtained. In addition, if a reference width projection that generates a reference width signal of a fixed width is provided separately from the projection, and the signal width detected by the projection is corrected by the reference width detected by the reference width projection, temperature-dependent It is possible to obtain a weight detecting device having excellent accuracy without any problem.

[0007]

(Embodiment 1) An embodiment of the present invention will be described below with reference to the drawings. 1 to 4 show a configuration of a weight detecting device according to an embodiment of the present invention.

FIG. 1A is a cross-sectional view of a main part as viewed from the side of the present invention. FIG. 1B is an external view as viewed from below.
FIG. 1C is a view taken in the direction of the arrow A shown in FIG.
In FIGS. 1 (a) and 1 (b), reference numeral 6 denotes a rotatable support that supports a load, mounts a pan (not shown) on the upper part, and mounts an object on the pan. Reference numeral 7 denotes an elastic body that supports the load of the support 6 and supports the support 6 so that it can move up and down depending on the magnitude of the load. The elastic body 7 is formed of a leaf spring having excellent elasticity. Note that the elastic body 7 may be a coil spring and is not limited to a leaf spring. Reference numeral 8 denotes a rotation drive unit for rotating the support 6, and the rotation force generated by the rotation drive unit 8 is transmitted to the support 6 by rotation force transmission means (9a, 9b) composed of two gears. The rotational force transmitting means 9b and the support 6 are fixed by, for example, connection pins. Reference numeral 10 denotes a support 6 in a concave portion formed in a cylindrical hole by a signal width converting means.
Is press-fitted and fixed. The signal width conversion means 10 extends vertically downward at the end of the circumferential surface around the support 6 as shown in FIG.
A trapezoidal projection 11 and a rectangular parallelepiped reference width projection 12 shown in (c) are formed. Reference numeral 13 denotes a signal width detecting means comprising a light emitting element and a light receiving element, which is commercially available as a photo interrupter. The signal width detecting means 13 is positioned at a certain height from the reference plane so that the projection 11 and the reference width projection 12 block the optical axis of the concave portion of the signal width detecting means 13 when the signal width converting means 10 rotates. Will be installed. Note that the signal width detecting means 13 may have a configuration in which the light emitting element and the light receiving element are separated, and the effect of the present invention can be obtained by a configuration in which the light receiving element is fixed on the optical axis of the light emitting element with the projection 11 and the reference width projection 12 interposed therebetween. can get. The support 6 and the signal width converter 10 are fixed by a first housing 15 and a second housing 16 provided with through holes.

Next, the operation principle will be described. When an object to be measured is placed on a tray installed above the support 6, the support 6 receives a load in the vertical direction according to the weight of the object to be measured.
Since the support 6 is supported by the elastic body 7 via the signal width conversion means 10, the support 6 keeps an equilibrium at a certain amount of descending distance according to the load. Since the signal width conversion means 10, the projection 11, and the reference width projection 12 also move in the same manner as the support 6, they also descend by a certain amount. Naturally, as the weight of the measured object increases, the descending amount also increases. On the other hand, since the signal width detecting means 13 is fixed at a fixed height from the reference plane, the optical axis of the built-in light emitting element is also maintained at a fixed height from the reference plane. (The optical axis is indicated by the dashed line 14). As the weight of the device under test increases, the signal width converter 10 descends more. Therefore, as shown in FIG. 1 (c), the trajectory of the optical axis 14 has a heavy weight 14a and a light weight 14b.
Becomes Since the protrusion 11 has a trapezoidal shape as shown in FIG. 1C, the width of the protrusion 11 on the optical axis 14 increases as the weight increases. If the width of the projection 11 is measured, an output corresponding to the weight can be obtained.

In the first embodiment, the width of the projection 11 is detected as the sensor output time of the signal width detecting means 13 by utilizing the fact that the signal width converting means 10 rotates at a constant speed. FIG. 2 shows the detection circuit. In FIG. 2, the signal width detecting means 13
Is composed of a light emitting element 13a and a light receiving element 13b. The output of the light receiving element 13b is taken out from the connector number 4 as a signal. FIG. 3 shows an output signal waveform from the light receiving element 13b. In the circuit shown in FIG. 2, the output signal becomes High (5 V) when the light is applied to the light receiving element 13b, and is not blocked by the projection 11 and the reference width projection 12 so that the light is not applied to the light receiving element 13b. At this time, the output becomes Low (0 V). FIG. 3A shows a case where the object to be measured is light in weight.
(B) shows the waveform of the output signal when the object to be measured is heavy. When the object to be measured is light, the width (time) in which the projection 11 blocks the optical axis 14 is small, so that the time (t1) when the output signal is low as shown in FIG. Is shorter than the output signal (t2). (T1 <t
2). As described above, since the digital output signal time from the light receiving element 13b changes according to the weight of the measured object, if the digital output signal time is processed as a function of the weight, the weight of the measured object can be accurately determined.

According to this configuration, the magnitude of the load is measured as a digital signal corresponding to the circumferential width of the trapezoidal projection formed on the vertical surface on the circumference centered on the support. The weight can be detected accurately regardless of the humidity inside. In addition, the apparatus has a simple configuration, has a small number of parts, and is economically advantageous.

Next, correction using the reference width projection 12 will be described. FIG. 4 shows a digital signal waveform according to a difference in ambient temperature when the object to be measured has a constant weight. FIG. 4A shows a digital output waveform of the light receiving element 13b at the ambient temperature Ta ° C., and FIG. 4B shows an output waveform at the ambient temperature Tb ° C., where Ta ° <Tb ° C. holds. At this time, the ambient temperature T
If the output Low time at a ° C. (shielding of the optical axis 14 by the projection 11) is t1, the same time at the ambient temperature Tb ° C. is t1.
+ Th1 + th2. This is understood as follows. In general, when the ambient temperature rises, the light-emitting element (light-emitting diode or the like) emits less light, so that the output of the light-receiving element is easily turned off and conversely hard to be turned on. Conversely, when the projection 11 passes by, the output return timing is delayed by th2. Next, considering the output waveform due to the shielding of the reference width projection 12, the output Low at Ta ° C.
Assuming that the time is ts, T is the same as in the case of the projection 11.
The output Low time at b ° C. is ts + th1 + th2. Therefore, if the output Low time by the reference width projection 12 is subtracted from the output Low time by the projection 11, Ta ° C.
Time and at Tb ° C., both times are equal to t1−ts. As described above, by subtracting the output Low time from the reference width projection 12 from the output Low time from the projection 11 and setting this value as a new digital output signal value, an accurate weight value independent of the ambient temperature can be calculated. . The usable range of the device is greatly expanded.

(Embodiment 2) FIG. 5 is a sectional view of a main part of Embodiment 2. The difference from the first embodiment is that the projection 11 and the reference width projection 12 which are signal width conversion means are connected to the rotational force transmission means 9.
In this configuration, the signal width conversion means does not need to be configured as a separate component, and the number of components is reduced, so that an apparatus which is advantageous in cost can be provided.

In the above embodiment, the case where the shape of the projection 11 is trapezoidal, that is, the case where the projection on the surface perpendicular to the optical axis is trapezoidal, has been described. Is not limited to a trapezoidal shape. The width of the upper and lower parts of the projected figure is different, and the change in width from the upper part to the lower part can be expressed by a linear function, or the rate of change of the width (differential value) is first order Any shape that can be represented by a function may be used. That is, the shape of the projection may be triangular. In addition, a curved line may be used, but in this case, the configuration of the detecting unit may be complicated.

[0015]

As described above, the weight detecting device of the present invention
In the weight detection device, a support for supporting and rotating the load, an elastic body for supporting the load of the support and supporting the support to move up and down according to the magnitude of the load, and for rotating the support A rotational drive unit, a rotational force transmitting means for transmitting a rotational force from the rotational drive unit to the support, and a vertical movement and rotation on a circumference centered on the support in conjunction with the vertical movement and rotation of the support. A signal width converting means provided with protrusions having different widths in the vertical direction, and a circumferential width of the protrusion detected by using the rotation of the signal width converting means fixed at a fixed height from a reference plane. The signal width detecting means is provided, and the weight is detected by changing the signal width of the signal width detecting means depending on the height position of the signal width converting means from a reference plane. According to this configuration, the magnitude of the load is measured as the circumferential width of the protrusion on the circumference, so that the weight can be accurately detected regardless of the humidity in the air.

Furthermore, if the projection (signal width conversion means) is formed integrally with the torque transmission means, a simple configuration with a smaller number of parts can be obtained. In addition, if a reference width projection that generates a reference width signal of a fixed width is provided separately from the projection, and the signal width detected by the projection is corrected by the reference width detected by the reference width projection, temperature-dependent It is possible to obtain a weight detecting device having excellent accuracy without any problem.

[Brief description of the drawings]

FIG. 1A is a cross-sectional view of a main part of a weight detection device according to a first embodiment of the present invention, as viewed from the side. FIG. 1B is an external view of the weight detection device.

FIG. 2 is a signal processing circuit diagram of signal width detection means of the weight detection device.

FIG. 3A is a diagram showing a signal width of the same weight detector due to a small weight; FIG. 3B is a diagram showing a signal width of the same weight detector due to a large weight;

FIG. 4A is a diagram showing a signal width when the ambient temperature of the weight detection device is Ta ° C. FIG. 4B is a diagram showing a signal width when the ambient temperature of the weight detection device is Tb ° C.

FIG. 5 is a cross-sectional view of a main part of the weight detection device according to the second embodiment of the present invention, as viewed from a side.

FIG. 6 is an external view showing a conventional weight detection device.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 6 Support body 7 Elastic body 8 Rotation drive part 9 Rotational force transmission means 10 Signal width conversion means 11 Projection 12 Reference width projection 13 Signal width detection means

Claims (4)

[Claims] 1. A support for supporting and rotating a load, an elastic body for supporting the load of the support and supporting the support to move up and down according to the magnitude of the load, and for rotating the support A rotational drive unit, a rotational force transmitting means for transmitting a rotational force from the rotational drive unit to the support, and an upper part on a circumference centered on the support in conjunction with the vertical movement and rotation of the support. And a signal width conversion means having a projection having a shape with a different width on the lower side, and a circumferential width of the projection is fixed using a rotation of the signal width conversion means fixed at a fixed height from a reference plane. A weight detecting device comprising a signal width detecting means for detecting, and detecting a weight by changing a signal width of the signal width detecting means depending on a height position of the signal width converting means from a reference plane. 2. The weight detecting device according to claim 1, wherein the shape of the protrusion is a triangle or a trapezoid. 3. The weight detecting device according to claim 1, wherein the protrusion is provided on the rotational force transmitting means of the support. 4. A structure wherein a reference width projection for generating a reference width signal having a constant width is provided separately from the projection, and a signal width detected by the projection is corrected by the reference width detected by the reference width projection. Item 5. The weight detection device according to any one of Items 2 to 4.