JPH0131938Y2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an electronic weight measuring device, and provides a novel device that has a relatively simple configuration and can easily perform digital signal processing.

In digital signal processing of conventional electronic weight measuring devices, weight-related information is detected as an analog signal, and this analog signal is converted to an A/D.
Conversion into a digital signal is performed using a converter. In this case, in order to improve the resolution, it is inevitable that the configuration of the A/D converter becomes complicated, and the cost also increases. To solve these drawbacks, for example, devices using vibrating strings have been put into practical use. This detects the natural frequency that changes depending on the tensile force applied to the vibrating string, and since a frequency signal can be obtained directly, signal processing becomes easy. However, such a vibrating string requires an initial force to enable the string to vibrate, and must be applied as a pulling force. In addition, the amount of displacement due to force becomes large, and various restrictions arise, such as the method of detecting vibrations being limited.

The present invention solves these drawbacks and will be described in detail below with reference to the drawings.

FIG. 1 is a structural explanatory diagram showing one embodiment of the present invention, in which 10 is a base, 20 is a lever, 30,
40 is a flexure, 50 is a vibrating body, 60 is a mounting piece, 70 is a plate, 80 is a plate support, 90 is a flexure, and 100 and 110 are stays.

The base 10 is to which predetermined components are attached, and in this embodiment, an example is shown in which the base 10 is formed so as to have a substantially H-shaped side profile. Studs 12 ₁ to 12 ₄ (12 ₄
(not shown) is provided.

The lever 20 is attached to the other vertical side 13 of the base 10.
flexure 30, facing the upper end of the
It is displaceably attached via 40. A counterweight 21 is provided at one end of this lever 20, and a rectangular penetrating portion 22 is provided at the other end.

The flexures 30 and 40 constitute the fulcrum of the lever 20 as described above, and a specific example thereof is shown in FIG.

The vibrating body 50 has a natural frequency that changes depending on the applied force, and in this embodiment, as shown in FIG. An example is shown in which two tuning fork-shaped vibrators are machined into a shape in which two vibrating pieces 51 and 52 are parallel and symmetrical with respect to the central axis are formed. By applying an axial force in the long axis direction of the vibrating body 50 having such a shape, the resonant frequency of the vibrating body 50 changes. By setting the vibration mode of the vibrating body 50 to be a symmetric mode that vibrates symmetrically with respect to the central axis in the long axis direction, the reaction force and moment generated at the joint portion of the vibrating pieces 51 and 52 have magnitudes in opposite directions. are equal and cancel each other out, so that the vibration energy acts as an excellent vibrating body that does not leak to the outside. One end of the vibrating body 50 configured in this way is located on the main plane 1 of the base 10.
4 through an attachment piece 60 as shown in FIG. 2, and the other end is attached to the lever 20 through an attachment piece (not shown) similar to attachment piece 60.

The plate 70 is for placing the object to be measured.

The pan support 80 is attached to the end 22 of the lever 20 via a flexure 90 so as to be substantially perpendicular to the lever 20. This dish support 80
Studs 81 ₁ and 81 ₂ are provided at both ends of the lever 20 , and one stud 81 ₂ is connected to the lever 20 .
It is inserted into the penetration part 22 so as to protrude from the surface of the. The plate 70 is fitted into and supported by a stud ₈₁₂ protruding from the surface of the lever 20.

Flexure 90 acts as a weighted flexure, as previously described.

The stays 100 and 110 constitute a Roberval mechanism. In this embodiment, a substantially triangular shape is used. Stays 100 and 110 are similarly formed. For example, the stay 100 has a flexure portion 1 at its apex.
A mounting hole 102 is formed through which the stud 81 ₁ of the dish support 80 is inserted, and flexure portions 103 and 10 are formed near both ends of the bottom portion, respectively.
Studs 12 ₂ , 12 ₄ of base 20 through 5
Mounting hole 10 for inserting (12 ₄ not shown)
4,106 are formed. The stays 100 and 110 configured in this manner have one end attached to the base 10 and the other end attached to the plate support 80 so as to sandwich the base 10, lever 20, plate support 80, etc. therebetween.

The operation of the device configured in this way will be explained.

When the object to be measured is placed on the plate 70, the plate support 8
A force acts on 0. This plate support 80 is
Since it is supported by a Roberval mechanism consisting of 00 and 110, true gravity will act in the vertical direction no matter where on the plate 70 the object to be measured is placed. The force acting on the dish support mechanism 80 is applied via the flexure 90 to the end 22 of the lever 20 as a downward force. As a result, a tensile force that is l ₁ /l ₂ times the weight applied to the plate 70 acts on the vibrating body 50 . Therefore, the vibrating body 50
By measuring the resonance frequency of the object, the weight of the object to be measured can be detected. The conversion formula for the quadratic approximation of these weights and resonance frequencies is expressed as follows.

W=A(f/fo-1)+B(f/fo-1) ² (1) W: Weight of the object to be measured A, B: Constant fo: Resonant frequency when W=0 f: When W≠0 FIG. 3 is a block diagram showing an example of a circuit configuration for signal processing in the device shown in FIG.
It is composed of two parts: an oscillation circuit section A and an arithmetic circuit section B. The oscillation circuit section A includes an exciter EX for vibrating the vibrating body 50, an oscillation circuit OSC including a detector PT, a temperature measuring circuit TMP for detecting the temperature near the vibrating body 50 as an analog voltage, and an output of the temperature measuring circuit TMP. It consists of a modulation circuit PWM that pulse-width modulates the output signal of the oscillation circuit OSC using a signal. Arithmetic circuit section B includes a counting circuit CAL, an arithmetic circuit DSP,
It consists of a display device DSP, etc. With this configuration, the oscillation circuit section A sends out a pulse width modulated signal as shown in FIG. In FIG. 4, times T ₁ and T ₂ are respectively expressed as follows.

T ₁ = f(W) (2) T ₂ /T ₁ = K・T (3) K: Constant T: Temperature In other words, find the weight W of the object to be measured by measuring the period T ₁ of the output signal. is possible,
The temperature T can be determined by measuring T ₂ /T ₁ . Thereby, temperature compensation can be applied to the measurement results as necessary. Also, using a pulse width modulation signal as an output signal in this way
This is extremely advantageous for performing various processes using a microprocessor or the like.

Note that in FIG. 1, a damping mechanism may be added in order to quickly stabilize the measurement state. FIG. 5 is a configuration explanatory diagram showing an example of such a damping mechanism, where CP is a cup made of copper, and M is a permanent magnet formed into a cylindrical shape so as to be included in the cup CP. . The cup CP is suspended from the lower surface of the free end 21 of the lever 20,
The permanent magnet M is attached to the base 10 so as to face the cup CP. Here, when the free end 21 of the lever 20 is displaced up and down, the cup CP is also displaced in the magnetic flux biased by the permanent magnet M. As a result, an induced current is generated in the cup CP and a reaction force is generated, resulting in a damping effect.

In the above embodiment, an example is shown in which the vibrating body 50 is formed in the shape of two tuning fork-shaped vibrators brought together, but the present invention is not limited to this.

Alternatively, the plate 70 may be suspended.

As explained above, according to the present invention, a weight measuring device with a relatively simple configuration, easy to perform digital signal processing, and excellent stability can be realized at low cost, and its practical effects are great.

[Brief explanation of the drawing]

FIG. 1 is a configuration explanatory diagram showing an embodiment of the present invention;
FIG. 2 is a perspective view showing some of the components shown in FIG. 1;
Fig. 3 is a block diagram showing an example of the signal processing circuit of the device shown in Fig. 1, Fig. 4 is a waveform diagram for explaining the operation of Fig. 3, and Fig. 5 is a configuration explanatory diagram showing an example of the damping mechanism. It is. 10...base, 20...lever, 30,40
...Flexia, 50... Vibrating body, 60... Mounting piece, 70... Dish, 80... Dish support, 90... Flexia, 100, 110... Stay.

Claims (1)

[Scope of utility model registration request] A base to which a given component is attached, a lever rotatably supported by a portion of the base via a flexure, and one end attached to the base and the other end attached to the lever depending on the applied force. A vibrating body whose frequency changes, a plate on which the object to be measured is placed, a plate support that is attached to the lever via a flexure so as to be almost perpendicular to the lever and the plate is attached to one end, a base, and a lever. and a roberbal mechanism constituted by a pair of stays arranged in parallel so as to sandwich a dish support, etc., each one end of which is attached to a base, and each other end of which is attached to a dish support.