JPH0131937Y2 - - 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 measure weight.

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 configuration explanatory diagram showing one embodiment of the present invention, in which 10 is a base, 20 and 30 are levers,
40 is a connecting body, 50 is a vibrating body, and 60 is a saucer.

The base 10 is formed into a substantially U-shape.

The levers 20 and 30 are each formed symmetrically and are arranged symmetrically at the open end of the base 10. That is, the first lever 20 is connected to one end 11 of the base 10.
via the flexure FL ₁ , and the second lever 30 is attached to the other end 12 of the base 10 via the flexure FL 1.
Attached via FL ₂ .

The connecting body 40 is attached via a flexure so as to connect the opposing ends of the first lever 20 and the second lever 30. FIG. 2 is a configuration explanatory diagram showing the state of these connections, in which a is an enlarged plan view of the main parts, b is a cross-sectional view along the line A-A',
c is a sectional view taken along line B-B'. In FIG. 2, one end 21 of the first lever 20 is formed so that the central portion thereof protrudes in a U-shape, and one end 31 of the second lever 30 has both side portions similar to the first lever 2.
The connecting body 40 is formed so as to protrude in a U-shape wider than the protruding part 21 of the first end 21 of the connecting body 40.
The protruding end surface of the one end 21 of the second lever 20 and the protruding end surface of the one end of the second lever 30 are arranged symmetrically on the same line. That is, one surface 41 of the connecting body 40 is formed with grooves 41a and 41b into which the protrusion of the one end 21 of the first lever 20 fits, and the other surface 42 is formed with one end 3 of the second lever 30.
Stepped portions 42a and 42b are formed opposite to the first protrusion. Moreover, the main plane 4 of this connecting body 40
3 is provided with a through hole 43a for attaching one end of the vibrating body 50. The portions facing the first lever 20, the second lever 30, and the connecting body 40 have flexures FL ₃ to _{FL 6 ,} respectively.
are connected via. These first levers 2
0, by the second lever 30 and the connecting body 40,
A platform scale mechanism will be constructed.

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 so that they meet, and two vibrating pieces 51 and 52 are formed that are symmetrical and parallel to the central axis. By applying an axial force S in the longitudinal 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 driving direction, the reaction force and moment generated at the joint of the vibrating pieces 51 and 52 are in opposite directions and have different magnitudes. They become equal and cancel each other out, and act as an excellent vibrating body that prevents vibration energy from leaking to the outside. In addition, in FIG. 3, EX is an exciter for vibrating the vibrating body 50, and DT is a detector for detecting vibration, and these are used to constitute an oscillation circuit. One end of the vibrating body 50 configured in this way is fitted into the through hole 43a of the connecting body 40, and the other end is fixed to the base 10.
is attached to a through hole (not shown) in the main plane 13 of.

The tray 60 is for placing an object to be measured (not shown), and is a fulcrum between the upper free ends 22 and 32 of the first lever 20 and the second lever 30.
It is attached via SP ₁ and SP ₂ .

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

As shown in FIG. 1, it is assumed that the levers 20 and 30 are attached to the base 10 and support the saucer 60 in a ratio of a:b. In this state, when the load W of the object to be measured is applied, a force F expressed by the following equation is applied to the vibrating body 50.

F=b/aW (1) Therefore, by measuring the resonance frequency of the vibrating body 50, the load on the object to be measured can be detected. The relationship between the resonant frequency f of the vibrating body 50 and the load W can be expressed by equation (2).

K: Constant fo: Resonant frequency when W=0 f: Resonant frequency when W≠0 FIG. 4 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 DT, a temperature measuring circuit TMP for detecting the temperature near the vibrating body 50 as an analog voltage, and a temperature measuring circuit TMP.
It consists of a modulation circuit PWM that pulse width modulates the output signal of the oscillation circuit OSC using the output signal of the oscillation circuit OSC.
Arithmetic circuit section B includes a counting circuit CTR, an arithmetic circuit CAL,
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. 5, times T ₁ and T ₂ are 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.

In the device according to the present invention, in order to protect against overload, it is necessary to install a vibrating body 5 between the levers 20, 30 and the saucer 60, as shown in FIG. 6a, for example.
It is sufficient to provide a stopper ST that forms a gap g corresponding to an effective displacement length of 0. Furthermore, as shown in FIG. 6b, a stopper ST may be provided at the bottom of at least one of the levers 20 and 30 to form a gap g corresponding to the effective displacement length of the vibrating body 50. In this case, by extending the lever facing the stopper, the gap can be widened, making the work easier. Furthermore, Figure 6c
Transducer 5 via Sprisig SG as shown in
By using a mechanism for attaching the end portion of the base 10 to the base 10, these gaps can be made wider. In this case, the spring SG is
It is sufficient to use one having a spring constant such that the set gap length is displaced when the maximum measurement load is applied.
Moreover, a magnetic support means may be used as a support mechanism for such a vibrating body.

BACKGROUND ART Conventionally, as this type of platform scale type weight measuring device, devices that detect displacement using a spring or devices that detect displacement using a strain gauge are often used. However, according to the former configuration, when measuring a heavy object, the fulcrum of the platform scale mechanism may be displaced in the horizontal direction due to the large displacement, which may cause an error. Also, according to the latter configuration,
Although it does not have the disadvantages of springs because the amount of displacement is small, it has low detection sensitivity.
A high performance amplifier must be used. Furthermore, both output signals are analog signals, and digital processing of the signals requires means for converting them into digital signals.

According to the device of the present invention, such conventional drawbacks can also be solved.

In the above embodiment, an example in which a flat plate-shaped flexure is used has been described, but a cross-shaped flexure can also be used. Thereby, stability against lateral vibrations can be improved.

As explained above, according to the present invention, it is possible to realize a weight measuring device having a platform scale structure with a relatively simple configuration, which can easily perform digital signal processing, and has excellent stability, and has great practical effects.

[Brief explanation of the drawing]

FIG. 1 is a configuration explanatory diagram showing an embodiment of the present invention;
2 is an explanatory diagram of the configuration showing the connection state of the main parts in FIG. 1, FIG. 3 is an explanatory diagram of the configuration of an example of the vibrating body used in the present invention, and FIG. FIG. 5 is a waveform diagram for explaining the operation of FIG. 4, and FIG. 6 is a configuration explanatory diagram showing a specific example of the overload protection mechanism. 10... Base, 20, 30... Lever, 40
... Connecting body, 50 ... Vibrating body, 60 ... Receiver,
FL...flexure, SP...fulcrum, ST...stopper, SG...spring.

Claims (1)

[Scope of utility model registration request] A base formed into a substantially U-shape, a first lever attached to one end of the opening of the base via a flexure, and a second lever attached to the other end of the opening of the base via a flexure. and,
A connecting body is attached via a flexure to connect the opposite ends of the first lever and the second lever, and one end is attached to the connecting body and the other end is attached to the main plane of the base. A vibrating body whose natural frequency changes depending on the force,
A weight measuring device including a tray attached via a fulcrum between the upper free ends of a first lever and a second lever and on which an object to be measured is placed.