JPH079377B2 - Weight measuring device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is to mount an object to be weighed on a mounting portion and to provide a stable vibration state before a DC steady state (stationary state) is achieved. The present invention relates to a weight weighing device (also simply referred to as a weighing device in the present specification) capable of detecting an accurate weight of an object to be weighed.

(Prior Art) Generally, in a weighing device such as a scale, as shown in FIG. 7, a detection unit having an elastic body 1 such as a spring is used, and the lower end of the elastic body 1 is fixed to a machine base 2 or the like. It is supported on the side, and is configured to place the object to be weighed 4 on the upper end of the tray 3 via the tray 3. By the way, in the weighing device configured as described above, when the object to be weighed is placed on the pan and the weight of the object to be weighed is freely vibrated, as shown by the solid line in FIG. At that time, the peak of the impact occurs and vibration is superimposed, and the center displacement of vibration reaches a constant value (stable vibration state) only after the placement is completed, but the vibration continues. Amplify the detected value that exhibits such a vibration state,
Even with A / D conversion, the obtained value has an oscillatory component and is not stable, so an accurate weight could not be obtained.

For this reason, conventionally, in the above-described weighing device, a damper for damping is attached between the tray on which the object to be weighed is placed and the machine base side, and a signal circuit or an amplifier for removing low-frequency harmful vibrations is added. It was common to have a filter in series with the circuit.

As described above, when a damper or a filter is provided in the weighing device and a filter is provided in series with the signal circuit or the amplification circuit, a detection value having a time response as shown by the alternate long and short dash line in FIG. After a lapse of time, the detected value becomes a DC steady state, and an accurate weight can be obtained.

(Problems to be Solved by the Invention) However, even if the weighing device is provided with the damper and the filter as described above, in general, there is a relatively long response delay until the detected value reaches a DC steady state. , For example,
Even if a strong damper and a filter effective against low-frequency harmful vibration are provided in order to obtain a highly accurate and highly sensitive weighing device, it is generally 0.
It took about 6 to 1 second. In addition, in such a case, since a damper having a large capacity is required, there is a drawback that the cost is increased and the apparatus is correspondingly increased in size.

The present invention has been made in view of the above-described current situation, and the vibration is stable after the object to be weighed is placed on the tray and the object to be weighed is relatively stationary with respect to the tray (after the placement is completed). An object of the present invention is to provide a weight weighing device capable of detecting the weight of an object to be weighed in an extremely short time by using the vibration data under the above-mentioned state (under the state after T _{1 in} FIG. 9).

(Means for Solving the Problem) A weight weighing device according to the present invention is a weight weighing device configured to detect the weight of an object to be weighed when a detected value is in a vibrating state. , At least a light source for irradiating photoelectrically convertible light, an elastic body whose one end is fixed to the machine base side and deforms according to the weight of the object to be weighed, and an object to be weighed attached to the free end side of this elastic body. A supporting frame having a mounting portion for mounting, a displacement magnifying lens system that bends light parallel to the optical axis according to the change of the elastic body, and light emitted from the light source passes through the displacement magnifying lens system. A plurality of electric charges, which are arranged in the scanning direction at the irradiation front position, are accumulated in an integrated manner every time the light emitted from the light source scans the surface of each light receiving element. Charge storage consisting of multiple elements Type photoelectric converter, a conversion unit connected to the charge storage type photoelectric converter for A / D converting the stored value of the charge of each element of the charge storage type photoelectric converter, and the conversion unit connected to this conversion unit The element having the minimum value of the accumulated charge in the predetermined measurement time range is determined from among the elements of the charge storage type photoelectric converter based on the output value from, and the object to be weighed is determined from the arrangement position of the element having the minimum value. Of the light source or the displacement magnifying lens system is fixed to the machine side, and the other one is arranged on the support frame. It is characterized by being installed.

(Operation) Then, when the object to be weighed is placed on the weight measuring apparatus configured as described above, the following operations are performed. That is, when the object to be weighed is placed on the weight measuring device, either the light source or the displacement magnifying lens system, which is attached to the free end side of the elastic body through the support frame, is relatively displaced (vibrated). ), And a stable vibration state is exhibited after a predetermined time. On the other hand, the light emitted from the light source is bent by the displacement magnifying lens system which is relatively displaced under such a stable vibration state,
Irradiation is performed on the element of the charge storage type photoelectric converter arranged in front of the element in a state where the displacement is enlarged. Then, each element irradiated with light accumulates as an electric charge, and the accumulated amount of this electric charge in a predetermined time range is converted by the A / D conversion unit and processed by the arithmetic unit as data regarding the accumulated amount of electric charge of each element. To be done. That is, the extreme value determiner of the arithmetic unit determines the element having the smallest amount of electric charge from these data. This is because the velocity of light irradiating each of the above-mentioned elements is measured at a displacement point (light-receiving element), which is the true value of the object to be measured, when the measurement is performed for a predetermined time in a stable vibration state. This is because it passes at the fastest speed than the relationship. By thus determining the element having the smallest amount of electric charge, the true value of the object to be measured can be easily obtained from the position of the element based on the elastic coefficient of the elastic body used.

(Example) Hereinafter, a weight detection method which is a basic concept used in the weight measuring apparatus of the present invention will be described, and then the weight measuring apparatus according to the present invention will be described.

As shown in FIG. 7, assuming that the x-coordinate having the positive direction of the weight is given and the time from the weighing start time is t, in the weighing device having the modeled elastic body 1, the object to be weighed is placed on the tray 3. 4 is placed and the displacement X (t) of vibration when the elastic body 1 is loaded is expressed by the following equation (1).

X (t) = Acos ωt + Bsin ωt + P (1) In the equation (1), Here, A and B are integration constants, K is the equivalent spring constant of the load cell 1, M is the equivalent mass of the pan 3, m is the equivalent mass of the object 4, and g is the gravitational acceleration.

By the way, the above P is a direct current component which is a value obtained in a steady state, "Acos ωt + Bsin ωt" is a harmonic vibration component, and ω is a natural frequency of the vibration system.

Now, in the vibration state shown by the solid line in FIG. 9, when the measurement is performed for a predetermined time range [T1, T2] and a predetermined displacement range [X1, X2] as shown in FIG. The vibration X (t) represented by is a certain displacement point x ₁ (x ₁ ∈ [X1, X2])
Through multiple times. Now, suppose that the vibration passes the displacement point x in [T1, T2] n times and passes the displacement point x ₁ at the i-th time t (x ₁ , i), i = 1, ..., If n (x ₁ ), it is expressed as the following equation (2).

xi = X (t (xi, 1)) = X (t (xi, 2)) = ... = X (t (xi, i)) = ...
= X (t (xi, n (xi))) (2) Further, the vibration speed at the displacement point x ₁ is expressed by the following equation (3).

Therefore, (here Is a monotonic function that depends on the system. ) Vi represented by the above equation (4) is taken as a function of x, and Vi is integrated at each displacement point as shown in FIG.
The following expression (5) is obtained.

When X (t) = P in the above formula (1), the integrated value (V _{1 to} Vn ₍ x ₎ ) of the displacement velocity Vi is an extreme value (Fig. 8 (b) from the relationship between elastic energy and displacement velocity). ) Maximum value; F
Since it has (x) _MAX ), the value of x (= xp) that satisfies the following equation (6) for finding the extreme value becomes the DC component (see FIG. 8 (b)).

From this DC component xp, weigh the object Is required.

The extreme value may be obtained by differentiating the function F (x) representing the integrated value of the displacement velocity with x as described above, or by simply comparing the integrated values of the respective displacement points. You may ask.

The weight measuring device according to the present invention utilizes the above-described weight detecting method, and the weighing device will be described below.

FIG. 1 is a configuration diagram showing the overall configuration of the weighing device according to this embodiment, and FIG. 2 is a configuration diagram showing an amplification mechanism and an integration storage mechanism of this device.

As shown in FIG. 1, the optical measuring device according to the present embodiment is a light source having a wavelength component that can be detected by an image sensor (charge storage photoelectric converter with multiple elements) 22 (in the case of the present embodiment). , A semiconductor laser oscillator) 15, and an image sensor 22 that is configured integrally with the light source 15 and that emits light from the light source 15.
Collimator 16 that makes a parallel light flux that is sufficiently thinner than the light receiving area (light receiving width l ₀ ) of the light receiving bit 22a of the elastic body that bends the light flux parallel to the optical axis of the lens so that it passes through the focal point of the lens.
A displacement magnifying lens system that magnifies the amount of displacement of 11 (a convex lens that is an image forming optical system is used in this embodiment).
The displacement magnifying lens system 17 is mounted on a support frame 18 that supports the tray 13. The support frame 18 is attached to the free end side of the elastic body 11, the fixed end side of the elastic body 11 is attached to the support base 12 protruding from the machine base side, and the free end side of the elastic body 11 is a tray. It is configured to be displaced by the weight of the object 14 to be weighed on the item 13. A line L connecting the collimator 16 through which the light emitted from the light source 15 passes and the displacement magnifying lens system 17.
An optical path correcting cylinder lens 21 that corrects the optical path of the parallel light flux so as to irradiate the parallel light flux on the surface of the image sensor 22 is disposed in the front area above, and the parallel light flux is sensed in the front area thereof. An image sensor 22 having a photodiode array is provided as a sensor (light receiving element 22a) for storing the integrated light amount via a space. As shown in FIG. 2, the distance G · f from principal point O ₁ of the displacement magnifying lens system 17 to the light receiving surface 22b of the image sensor 22, the image space focal point F from the main point O ₁ of the displacement magnifying lens system 17 is set to G times the distance to ₁ (image space focal length) f. This is a configuration for amplifying the displacement like the amplifier in the load cell type weighing device. Further, the image sensor 22 is formed by a light-receiving element array in which m light-receiving elements 22a are arranged in the scanning direction (vibration direction), and each light-receiving element 22a constituting this light-receiving element array has an end (an upper end in this embodiment).
Positioning is performed by sequentially attaching numbers (called light receiving bit numbers), and as shown in FIG. 3, the displacement to be measured (X1 ≦ X ≦ X2) and the light receiving bit number j (j = 0,1,2). ,
..., m-1) are configured to correspond. For this reason, in this configuration, the received light bit number is immediately quantized displacement. Therefore, in order to obtain a sufficient resolution must be wide 1 ₀ is sufficiently small dimensions of the vibration direction of the light receiving element 22a.

Further, the image sensor 22 is connected to the extreme value determiner 24 of the arithmetic unit 25 via the A / D converter 23, as shown in FIG. In this embodiment, the arithmetic unit 25 is composed of a one-chip microcomputer, and the extreme value determiner 24 is realized in this microcomputer as shown in the flow chart of FIG.

Thus, the present weighing device weighs an object to be weighed in a stable vibration state as follows. That is, the light emitted from the light source 15 is converted into a sufficiently thin parallel light flux by the collimator 16, passes through the focal point F ₁ thereof by passing through the displacement magnifying lens system 17, and the front of the image sensor 22 of the cylinder lens 21. The light path is corrected so that the light is received on the light receiving surface, and the light receiving surface of the image sensor 22 is illuminated. In this state,
When the object to be weighed 14 is placed on the pan 13 and the elastic body 11 is in a vibrating state, the displacement magnifying lens system 17 is vertically displaced (vibrated), and the passing light is vertically moved by the light receiving surface of the image sensor 22. Shake. Here, an elastic body in a stable vibration state
Displacement of 11 free end side (in other words, displacement magnifying lens system 17)
X _S (t) is a displacement magnifying lens system 17 as shown in FIG.
The light receiving surface 22 of the image sensor 22
Amplification at b, displacement X (t) at the point of arrival of the parallel light flux
Will be transmitted. Therefore, in this device, P in the above equation (1) is Is used. Here, G is a gain.

The light-receiving point of each light-receiving surface 22b of the image sensor 22 to which the amplified displacement is transmitted as described above has an elastic body 1
Since it constantly moves due to the vibration of 1, it receives light in an amount that is inversely proportional to its moving speed (in other words, proportional to the time during which the light-receiving point of the parallel light beam remains on each light-receiving element).

That is, when these are expressed by mathematical expressions, now, when the light-arriving point of the parallel light flux passes through the light receiving element 22a (light receiving bit number j) for the Sth time, a minute time for passing the width l ₀ in the vibration direction of the light receiving element [ t (j, s), t (j, s) + Δt]
Within Therefore, when passing through the Sth time, the light receiving amount Is (j) of this light receiving element is expressed by the following equation (8).

However, in the equation (8), E is a proportional constant. Therefore, within the predetermined time range [T1, T2] to be measured, the light-receiving point of the parallel light flux is n
(J) Total amount of received light I of the light receiving element 22a when passing the number of times I
(J) is expressed by the following equation (9).

The above equation (8) corresponds to the above equation (4), and the equation (9) corresponds to the above equation (5).

Therefore, each light receiving bit 22 that constitutes the image sensor 22
a receives a parallel light flux of an amount represented by the above formula (9) within a predetermined time range [T1, T2], and accumulates it instead of an electric charge.

Light receiving amount (irradiation amount) I (j) (j = 0,1,2, ..., m) stored in the form of electric charge in each light receiving element in this image sensor
-1) is converted into a digital quantity I _D (j) by the A / D converter 23 and transmitted to the extreme value determiner 24 formed in the arithmetic unit 25.

The extreme value determiner 24 determines the light receiving element having the lowest light receiving amount from the light receiving amount (charge amount) of each light receiving element 22a of the image sensor 22, and determines the light receiving bit number jp of this light receiving element.
The displacement point Xp corresponding to is the DC component. Then, from the value Xp of this DC component, the weight value of the object to be weighed Can be detected. This is because the speed at which the DC component passes through the light receiving bit where the DC component is located becomes the highest due to the relationship between the elastic energy and the speed.

In addition, in the present weighing device, the calculation of each of the above equations is optically processed except for the extreme value determination / output. That is, in the optical measuring device, as shown in FIG. 3, each light receiving element of the light receiving element array arranged in the vibration direction becomes each displacement point as it is, and each light receiving element receives a light receiving amount inversely proportional to the speed. The total amount is stored (stored) in the form of electric charge. Then, only the extreme value determination is performed by the extreme value determiner 24 in the arithmetic unit 25 composed of a microcomputer, as shown in the flowchart of FIG.

Therefore, the configuration is extremely simple, and high-speed processing (measurement) can be performed by an arithmetic unit having a small capacity. For example, if the vibration frequency of the weighing device is 20 to 40 cycles, 10 times of vibration will occur in 0.25 seconds to 0.5 seconds, and about 20 times of data can be collected during this time, so accurate measurement can be performed in a short time. You can

Further, in the case of the optical type, the weight detection method described above can be implemented with a simple configuration, and thus high reliability can be expected.

In the case of this optical metering device, the location where the amount of received light is the minimum is the true value, so the predetermined time range for measurement [T1, T2] and the predetermined displacement range [X1, X2] , It is necessary to set it appropriately in consideration of the weighing device and the object to be weighed or the state rate of weighing.

For example, in the measurement showing the vibration state as shown in FIG.
It is necessary to set the range as shown in FIG. 8A as the predetermined time range and the predetermined displacement range.

Further, in the above embodiment, the displacement magnifying lens system using the convex lens is used as the displacement magnifying lens system, but as shown in FIG. 5, the displacement magnifying lens system is constructed by using the concave mirror 17 '. Alternatively, as shown in FIG. 6, the prism 17a ″ and the convex lens 17b ″ may be used together. Alternatively, instead of these, other well-known ones may be used.

(Effects of the Invention) According to the weight weighing device of the present invention, accurate weighing can be performed even under a stable vibration state, which has been impossible in the past. Moreover, a short time (2 to 3 of the conventional
Double speed). Therefore, unlike the conventional case, it is not necessary to wait until the elastic body reaches a steady state, so that a large amount of objects on a line transferred by a conveyor or the like can be measured accurately and quickly. That is, when it is necessary to measure the object being transferred in the transfer step, it takes a considerable amount of time in the measuring step in the related art, and the transfer speed is restricted by the measuring time, but the weight measuring apparatus according to the present invention. With, the transfer speed can be significantly improved.

Moreover, since the information obtained from the displacement signal is integrated to detect the mass of the object to be measured, a measurement error is unlikely to occur with respect to a disturbance having an average value of 0. Further, in particular, since the optical type according to the present invention has a simple structure, it is easy to implement, and the time required for the weight detection process can be dramatically shortened and high reliability can be expected. Further, since the capacity of the arithmetic unit may be small, it can be implemented at low cost.

Further, according to the weight measuring device according to the present invention, a damper for damping, which is required in the conventional weight measuring device, is not required at the time of implementation, so that the production cost can be significantly reduced.
In addition, since the viscous resistance element is eliminated, the impact generated when the objects to be weighed are suddenly loaded does not remain as a weighing error, and the size of the device can be reduced.

[Brief description of drawings]

FIG. 1 is a side view showing the overall structure of the optical weighing device according to the present embodiment, FIG. 2 is a view showing the amplifying mechanism and integration storage mechanism, and FIG. FIG. 4 is an enlarged view of a light receiving bit portion of the image sensor, FIG. 4 is a flowchart showing a processing process in the arithmetic unit, FIG. FIG. 7 is a side view of a main part showing another embodiment in which the magnifying lens system is different, FIG. 7 is a schematic view of the schematic structure of the detection part of the weighing device modeled, and FIGS. 8 (a) and 8 (b) are FIG. FIG. 9 is a diagram showing the relationship between displacement and time, and displacement and displacement speed in the weighing device having the structure, and FIG. 9 is a diagram showing various vibration states when a loose object is dropped. 11: Elastic body, 15: Light source, 16: Collimator, 17,1
7 ′, 17a ″, 17b ″ …… Displacement magnifying lens system, 18 …… Support frame, 22 …… Image sensor (multi-element charge storage photoelectric converter), 23 …… A / D converter, 24 …… Pole Value judge, 25 ……
Arithmetic unit.

Claims (1)

[Claims] 1. A weight measuring device configured to detect the weight of an object to be weighed when a detected value is in a vibrating state, wherein the weight measuring device includes at least a light source that emits light capable of photoelectric conversion. An elastic body whose one end is fixed to the machine base side and deforms according to the weight of the object to be weighed, and a support frame having a mounting portion mounted on the free end side of the elastic body for mounting the object to be weighed , A displacement magnifying lens system that bends light parallel to the optical axis according to the change of the elastic body, and is positioned and arranged in the scanning direction at a front position where the light emitted from the light source is irradiated through the displacement magnifying lens system. Each time the surface of each light receiving element is scanned by the light emitted from the light source, a charge accumulating photoelectric converter composed of a plurality of elements in which an amount of electric charge proportional to the exposure time is accumulated cumulatively, It is connected to a charge storage type photoelectric converter A conversion unit for A / D converting the charge accumulation value of each element of the load accumulation type photoelectric converter, and among each element of the charge accumulation type photoelectric converter based on the output value from the conversion unit connected to this conversion section. From the above, an arithmetic unit having an extreme value determiner for determining the element having the minimum value of the accumulated charge in the predetermined measurement time range and calculating and outputting the true value of the object to be measured from the arrangement position of the element having the minimum value. One of the light source and the displacement magnifying lens system is fixed to the machine base side, and the other one is disposed on the support frame.