JP2002107212A - Electronic force balance - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enhance the stiffness of a Roberval mechanism and to easily change a spring constant. SOLUTION: The Roberval mechanism 2 has a moving part 14, a fixed part 12, Roberval parts 18, and spring parts 20 having the same width, and is formed by scooping out a single material lump having large width W1 to enhance the stiffness of the spring part 20. The Roberval mechanism 20 has the Roberval parts 18 in upper and lower parts, and spring parts 20 at both ends of the Roberval part. Adjusting opening parts 44 having a specified diameter L3, W3 are installed in the central position of the spring part 20. Therefore, while the stiffness is enhanced, the spring constant of the spring part 20 can be adjusted so as to conform to a measuring range of a mass of a weighing object.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electronic balance for measuring the mass of an object to be weighed, and more particularly to an electronic balance in which the spring constant can be easily changed without greatly changing the rigidity of a Roberval mechanism constituting the electronic balance. About.

[0002]

2. Description of the Related Art FIG. 10 shows a conventional electronic balance (Japanese Patent Publication No.
No. 29761), and FIG. 11 is a perspective view of the same. Another example is disclosed in Japanese Patent Application Laid-Open No. 11-51756. These electronic balances 80 are placed on the
0, a roberval mechanism 81 in which a movable portion 81b movable with respect to a fixed portion 81a, a lever 83 interlocked with the movement of the movable portion 81b, an electromagnetic coil 85 for controlling movement of the lever 83 to be in an equilibrium state, A position detection sensor (not shown) for detecting an equilibrium state of the electromagnetic coil 85;
And a control unit (not shown) for calculating and outputting the mass of the object to be weighed by controlling the energization of the object.

As shown in the figure, the roberval mechanism 81 has a pair of upper and lower parallel roberval portions 86 formed by cutting aluminum or the like in the shape of a rectangular parallelepiped from the side. A total of four thin spring portions 87 are formed in the roberval portion 86. When an object to be weighed is placed on the placing plate 90 of the movable portion 81b, the spring portion 87 is deformed by receiving this load. Then, the movable portion 81b moves downward while maintaining the horizontal state.

In conjunction with this, the free end 83b of the lever 83 is displaced upward from the equilibrium position. The control unit controls the energization of the electromagnetic coil 85 based on the output of the position detection sensor so that the lever 83 is in an equilibrium state, and calculates the mass of the object to be weighed based on the current value to the electromagnetic coil 85 when the lever 83 is in equilibrium. Calculation output.

The lever 83 in the configuration shown in the figure is
While the other electronic balance (Japanese Patent Laid-Open No. 11-51756) is formed separately from the above-mentioned electronic balance, it is different from the one formed integrally with the roberval mechanism 81. 81 is formed by hollowing out the above-mentioned integral lump.

[0006] Such a roberval mechanism 81 is formed with a predetermined measurement range of the mass of the object to be weighed. In particular, the rigidity of the entire roberval mechanism 81 and the spring constant of the spring portion 87 are suitable for this measurement. It is set appropriately. The stiffness of the roberval mechanism 81 and the spring constant of the spring portion 87 affect the time (response time) from the start of measurement, that is, the convergence of the vibration of the movable portion 81b from when the object to be weighed is placed on until it can be measured. .

[0007]

However, the conventional Roberval mechanism 81 cannot improve the overall rigidity and cannot arbitrarily change the spring constant of the spring portion 87. The mechanism 81 had to be used.

For example, when it is intended to measure a heavier mass than before, the rigidity of the roberval mechanism 81 itself and the spring portion 8
7, it is necessary to change the spring constant. In order to increase the spring constant in a case where the width W of the spring portion 87 is to be obtained by changing the width W, the roberval mechanism 8 is required.
1, the width W of the whole was increased, and the entire electronic balance was enlarged.
In particular, when the electronic balance is provided in the measuring device, problems such as the arrangement arise. Similarly, as a method of increasing the spring constant, there is a method of changing the thickness of the spring portion 87 itself. However, even if an attempt is made to reduce the thickness in order to reduce the spring constant, there is a limit in processing, which sometimes fails.

Further, the above-mentioned conventional electronic balance is applied to a static balance in which an object to be weighed is placed directly on a mounting plate on a movable part, and measurement is performed, and the object to be weighed is taken out after the measurement. It could not be applied to a weighing scale. The dynamic balance transports the object to be weighed on a conveyor or the like, and measures the mass of the object to be weighed by using the electronic balance during the transportation period. For this reason, it is necessary to take measures against impact when the object to be weighed is input and to shorten the response time, and it is necessary to easily change the spring constant of the spring portion 87 while further increasing the rigidity of the roberval mechanism 81.

Particularly, in order to increase the processing speed per time, it is necessary to increase the conveyor speed, so that the rigidity and the spring constant must be improved. Conventionally, the improvement of the rigidity and the increase of the spring constant have been integrated, and it has not been possible to form them independently.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above problems, and has as its object to provide an electronic balance that can increase the rigidity of a roberval mechanism and easily change a spring constant.

[0012]

In order to achieve the above object, an electronic balance according to the present invention comprises a movable portion which moves under the load of an object to be weighed, and a movable portion which moves between a fixed portion and the movable portion. The free end 4b is shifted from the equilibrium state by interlocking with the movement of the movable section 14 and the roberval mechanism 2 including a pair of roberval sections 18 having a predetermined length and moving the movable section 14 in a horizontal state. Lever 4 displaced by a predetermined amount
A balance driving means 6 for controlling the movement of the lever 4 so as to be in an equilibrium state; a plurality of spring portions 20 formed at both ends of the roberval portion 18; and a spring constant required for each of the spring portions 20. And an adjustment opening 44 formed at a center position of each spring portion 20 with a predetermined opening diameter.

The movable part 14, the fixed part 12, the roberval part 18, and the spring part 20 have the same predetermined width W1 even in electronic balances having different measurement ranges by hollowing out a single piece of material. It is also possible to adopt a configuration integrally formed.

The roberval mechanism 2 has a lever housing 2b formed by hollowing out from one end 2a in the longitudinal direction. The lever housing 2b has a predetermined length and has a lever housing 2b. The lever 4 having a width smaller than the opening diameter of the lever 4 is accommodated, and the fixed portion 30 and the movable portion 32 of the lever 4 are respectively attached to the fixed portion 12 and the movable portion 14 of the roberval mechanism 2.
a may be configured to be connected and fixed.

According to the above configuration, the adjustment opening 44 is formed at the center position of the spring portion 20 provided at both ends of the roberval portion 18 of the roberval mechanism 2. Thereby, the spring constant of the spring portion 20 can be adjusted so as to match the measurement range of the mass of the object to be weighed. The roberval mechanism 2 includes a movable unit 1
4. The rigidity of the spring portion 20 can be increased by hollowing out a single material lump having a large width W1 of the fixing portion 12, the roberval portion 18 and the spring portion 20. Then, while the rigidity of the spring portion 20 is improved and the rigidity of the entire Roberval mechanism 2 is increased, the spring constant can be varied by the adjustment opening portion 44. Further, the lever 4 is formed separately from the roberval mechanism 2 to have a width smaller than the opening diameter of the lever accommodating portion 2b, and is accommodated and fixed in the lever accommodating portion 2b.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Hereinafter, an embodiment of an electronic balance according to the present invention will be described. FIG. 1 is a perspective view showing a schematic configuration of the electronic balance. The electronic balance 1 includes a roberval mechanism 2, a lever 4, an equilibrium driving unit 6 including an electromagnetic coil for controlling the lever 4 to be in an equilibrium state, a position detecting unit (not shown),
It has a control unit (not shown).

A load receiving member (not shown) is fixed on the movable portion 14 of the roberval mechanism 2, and a dynamic balance having a conveyor mounted on the load receiving member can be constructed. Then, the mass of the object is measured while the object is conveyed by the conveyor. In addition, it is also possible to provide a placing plate on the movable portion 14 and use the object to be weighed on the placing plate as a static balance for measuring the mass.

FIG. 2 is a front view showing the roberval mechanism 2.
FIG. 3 is a plan view, and FIG. 4 is a side view. The roberval mechanism 2 has a fixed part 12 and a movable part 14 that moves vertically with respect to the fixed part 12. The upper surface of the movable part 14 is formed slightly higher than the fixed part 12. The roberval mechanism 2 is formed by hollowing out a rectangular parallelepiped aluminum lump having a length L and a width W1 from the front side and penetrating a hollow portion 16 therein. Further, in the roberval mechanism 2, the hollow portion 16 may be formed by extrusion molding or the like. At this time, a pair of parallel roberval portions 18 having a predetermined thickness are provided above and below. The pair of roberval portions 18 have the same length in the length direction L, and have thin spring portions 20 at both ends.
Are formed. The spring portions 20 are provided at two locations on the upper and lower surfaces, for a total of four locations. Each of the spring portions 20 has an arc shape when viewed from the upper and lower surfaces, and is formed in a linear shape that is continuous in the width W1 direction.

At a position directly below the upper roberval portion 18,
A lever fixing portion 22 for fixing the lever 4 is formed in parallel with the roberval portion 18. The lever fixing part 22 is composed of the fixing part 12 of the roberval part 18 and the movable part 14.
Has a cutting portion 22s in the middle of the length L direction corresponding to
There is a gap that does not hinder the movement of the movable part 14 with respect to the fixed part 12. By this cutting, the lever fixing part 22
It has a fixed side 22a and a movable side 22b.

A protruding piece 24 of a predetermined length is formed on an upper end of one end 2a of the roberval mechanism 2 in the longitudinal direction L, and a balance driving means 6 is mounted on a lower surface thereof.
An approximately rectangular parallelepiped lever housing 2b is formed by opening from the center of one side surface of the roberval mechanism 2 located at the one end 2a toward the inside of the roberval mechanism 2. The lever accommodating portion 2b is
2, and is hollowed out to a position on the side of the movable portion 14 as viewed from the front side in FIG. 2 (until it reaches a position beyond the spring portion 20 of the roberval portion 18).

FIG. 5 is a front view of the lever 4, FIG. 6 is a plan view thereof, and FIG. 7 is a side view thereof. The lever 4 has a width W2 smaller than the width W1 of the roberval mechanism 2 and is reduced in size and weight. On the base end portion 4a side, the fixed portions 3 fixed to the fixed portion 12 and the movable portion 14 of the roberval portion 18 respectively.
0, a movable portion 32a is formed. The other end is a free end 4b. The free end 4b extends to a position outside the roberval mechanism 2 after the lever is fixed, and is located immediately below the protruding piece 24.

The movable portion 32a of the lever 4 moves in conjunction with the movement of the movable portion 14 of the roberval mechanism 2, and the free end 4b moves up and down. The lever 4 has two fulcrums A and B
And a function of attenuating the mass (load load) of the object to be weighed applied to the movable portion 14 by a predetermined amount by the two fulcrums A and B, and shortening the length L2 of the lever 4. I have.

The lever 4 is also formed by hollowing out an aluminum lump or the like. In particular, the cutting portion 28 (28a, 28b, 28c) is formed in a substantially U-shape when viewed from the front. The fixed portion 30 is provided at the substantially central portion by the cut portion 28,
The movable portions 32 (32
a, 32b, 32c) are formed. The fixed portion 30 and the movable portion 32 of the lever 4 are connected to each other by two thin spring portions 34 located at fulcrums A and B. The spring part 34 is formed in substantially the same shape as the spring part 20 of the roberval mechanism 2, and the description is omitted.

The load applied to the base portion 4a is efficiently transmitted to the free end 4b side via the fulcrums A and B of the spring portion 34 on the movable portion 32 side. In order to maintain the strength, a plurality of spring parts 3
6 is formed similarly to the spring portion 34.

FIG. 8 is a partially cut front view showing an assembled state of the electronic balance. In this drawing, for convenience, the lever 4 is not cut, and only the robarbal mechanism 2 is cut. The electronic balance 1 is configured by inserting and fixing a lever 4 inside the roberval mechanism 2. In the roberval mechanism 2, the fixing part 12 is fixed on the base plate 10 with screws 11. Lever housing 2
The lever 4 is inserted into “b”, and the proximal end 4 a is fixed to the lever fixing portion 22 with the screw 25. A step portion 22d for guiding one side surface of the lever 4 along the length direction L is formed on the lower surface of the lever fixing portion 22 forming the lever housing portion 2b. Thereby, positioning at the time of insertion of the lever 4 can be easily performed and assembly can be easily performed.

The fixed part 30 of the lever 4 is fixed to the fixed side 22a of the lever fixed part 22, and the movable part 32 of the lever 4 is fixed to the movable side 22b of the lever fixed part 22.
In this fixed state, the free end 4 b of the lever 4 protrudes from the one end 2 a of the roberval mechanism 2 and is located immediately below the protruding piece 24. As described above, by providing the lever 4 inside the roberval mechanism 2, the overall size can be reduced.

On the free end 4b side of the lever 4, a weight mounting piece 3
8 is formed so as to protrude downward, and a substantially horizontal screw hole 38b is formed.
The balance weight 40 is attached to the part so as to be slidable in the horizontal direction. Thereby, the movable part 14 of the roberval mechanism 2
The lever 4 can be balanced by adjusting the balance weight 40 when the load receiving member or the like is under a heavy load. The equilibrium state of the lever 4 is detected by a slit provided at the free end 4b and a position detection sensor (not shown) fixed to the protruding piece 24 side, and the moving direction of the lever 4 is also detected. Has become.

The electromagnetic coils constituting the balance driving means 6 are as follows:
An annular magnet 6a is fixed to the lower surface of the protruding piece 24, and a wound coil 6b is fixed to the inside of the ring of the magnet 6a on the upper surface of the free end 4b of the lever 4. As described above, since the electromagnetic coil can be provided outside the roberval mechanism 2, assembly and maintenance during manufacturing can be easily performed. The equilibrium drive unit 6 receives current control of the control unit when measuring the object to be weighed, changes the magnetic force between the magnet 6a and the current supplied to the coil 6b, and returns the lever 4 to the equilibrium state.

Next, an operation of measuring the mass of an object to be weighed by the electronic balance 1 having the above-described configuration will be described. By adjusting the balance weight 40, the balance of the lever 4 in the heavy load state of the load receiving portion (including the conveyor weight) is obtained. The equilibrium state of the lever is detected by a position detection sensor.

Next, the objects to be weighed are placed on the conveyor and conveyed on the conveyor. In the roberval mechanism 2, the movable portion 14 descends in the Z1 direction in FIG. At this time, the roberval portion 18 has a total of four spring portions 2.
By the deformation of 0, the movable part 14 is lowered while maintaining the horizontal state.

In conjunction with the lowering of the movable section 14, the movable section 32 of the lever 4 similarly moves down. When the movable part 32a moves down, the movable part 32b moves in the Z2 direction around the spring part 34 (fulcrum A), and the free end 4b of the lever 4 (the movable part 32) moves.
c) rises in the Z3 direction around the spring portion 34 (fulcrum B).

The free end 4b of the lever 4 is displaced (rises) by a predetermined amount with respect to the equilibrium state, and this displacement is detected by a position detecting sensor. The control section controls the energization of the electromagnetic coil of the balancing means 6 so that the lever 4 returns to the balanced state again. At this time, the current direction of the electromagnetic coil to the coil 6b and the amount of current to be supplied are controlled, and the lever 4 is detected by the position detection sensor.
Obtains a current value to the electromagnetic coil 6b when it is detected that the balance has reached the equilibrium state again, and calculates and outputs the mass of the object to be weighed based on this current value.

As described above, the fulcrum of the lever 4 is set at two points A,
By providing B, the mass (load load) of the object to be weighed applied to the movable portion 32 can be attenuated and transmitted to the free end 4b side, and at the same time, the displacement of the free end 4b side with respect to the movement amount of the movable portion 32 side It can be obtained in increasing amounts. This allows
The weighing accuracy can be improved. In addition, the length L2 of the lever 4 can be reduced and the configuration having a predetermined amount of attenuation can be achieved. By reducing the size and weight of the lever 4, the response of the movement to the load can be made more sensitive, and the measurement accuracy can be improved. If a force is applied from the free end 4b of the lever 4, the force can be increased and transmitted to the movable portion 32 (the movable portion 14 of the roberval mechanism 2), so that the lever 4 can be braked with a small force at the free end 4b. Become like

The electronic balance 1 can withstand a use as a dynamic balance in which a heavy object such as a conveyor is provided on a load receiving portion. This rigidity is obtained because the roberval mechanism 2 has a relatively wide width W1. Due to the improvement of the rigidity, the electronic balance 1 can withstand an impact or the like when the object to be weighed is placed on the conveyor.

On the other hand, the configuration is such that the spring constant of the spring portion 20 can be easily changed according to the measurement range of the mass of the object to be measured. FIG. 9 is a plan view for explaining a variable state of the spring constant of the spring section 20. As shown in the figure, the spring portions 20 are provided on the upper and lower surfaces of the roberval mechanism 2, and have a predetermined length L3 and a width W3 at the center of each of the four spring portions 20 and have an adjustment opening. 44 is formed. The length L3 is larger than the length direction of the spring portion 20, and the width W3 is set to an arbitrary width according to a desired spring constant. The spring constant of the spring section 20 can be changed by the size of the opening diameter of the adjustment opening section 44.

The mass measurement range of the roberval mechanism 2 without the adjustment opening 44 shown in FIGS. 1 to 8 is centered on 3 kg. On the other hand, the measurement range of the mass in the case where the adjustment opening 44 is formed in the spring portion 20 of the Roberval mechanism 2 having the same size as shown in FIG. 9 is around 60 g or 600 g. As described above, only the spring constant of the spring portion 20 can be changed without changing the size and rigidity of the entire Roberval mechanism 2. By changing the spring constant of the spring portion 20, the measurement range of the mass can be easily changed, and a spring constant suitable for the measurement range of the mass to be measured can be obtained.
The convergence time (response time) of vibration and the like from the time when the object to be weighed is placed on the conveyor until the measurement can be performed can be adjusted optimally, and the measurement can be speeded up.

Since the spring portion 20 is formed on the upper and lower surfaces of the roberval mechanism 2, the adjustment opening 44 can be easily formed after the roberval mechanism 2 is formed. Further, by adjusting the opening diameters of the respective adjustment openings 44, the spring constants of the respective spring portions 20 can be adjusted so as to be the same. By making the spring constants of the respective spring portions 20 the same, the moving operation of the movable portions 14 connected by the roberval portion 18 can be performed smoothly, and the measurement accuracy can be improved. Regardless of the presence or absence of the adjustment opening 44, the overall size of the roberval mechanism 2 is unchanged, and the lever 4 is configured to be housed inside the roberval mechanism 2. The size of the electronic balance 1 itself can be made the same, and the arrangement layout of the electronic balance 1 can be shared by the applicable devices (such as a conveyor-type weighing machine and a sorting machine).

[0038]

According to the electronic balance of the present invention, an adjustment opening having a predetermined diameter is formed at the center of the spring portion so that the spring constant can be varied. Can be adjusted to fit the measurement range of the mass, and the response speed at the time of measurement can be improved to enable high-speed and high-precision measurement.
Further, the rigidity of the spring portion can be increased by forming the movable portion, the fixed portion, the roberval portion, and the spring portion of the roberval mechanism to have the same width and forming the lump of a single material having a large width W. . Since the spring constant can be varied by adjusting the opening while increasing the rigidity of the spring part and the rigidity of the Roberval mechanism, the vibration resistance against the load load on the object to be measured is improved and the reliability is improved. At the same time, the response speed can be improved. In addition, the arm is formed separately from the roberval mechanism and has a width smaller than the opening diameter of the lever housing, and is housed and fixed in the lever housing, enabling more accurate mass measurement using a small and lightweight lever. .

[Brief description of the drawings]

FIG. 1 is a perspective view showing an embodiment of an electronic balance of the present invention.

FIG. 2 is a front view showing a roberval mechanism.

FIG. 3 is a plan view of a roberval mechanism.

FIG. 4 is a side view of the roberval mechanism.

FIG. 5 is a front view showing a lever.

FIG. 6 is a plan view of a lever.

FIG. 7 is a side view of a lever.

FIG. 8 is a cutaway front view showing a state in which a lever is incorporated in the roberval mechanism.

FIG. 9 is a view showing an adjustment opening for changing a spring constant.

FIG. 10 is a front sectional view showing a conventional electronic balance.

FIG. 11 is a perspective view of the conventional electronic balance.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 ... Electronic balance, 2 ... Robarbal mechanism, 2b ... Lever accommodation part, 4 ... Lever, 4a ... Base end part, 4b ... Free end, 6 ... Balance drive means (electromagnetic coil), 12 ... Fixed part, 14 ... Movable part , 18 ... Robarbal part, 20 ... Spring part, 22 ... Lever fixing part, 22s ... Cutting part, 30 ... Fixing part, 32 (32
a, 32b, 32c) movable part, 34 spring part (support points A, B), 40 balance weight, 44 adjustment opening.

Claims (3)

[Claims] 1. A movable part (14) which moves under a load of an object to be weighed, and a pair having a predetermined length provided between a fixed part (12) and the movable part, and the movable part is placed in a horizontal state. A free end (4) by interlocking with the movement of the movable part,
b) a lever (4) displaced by a predetermined amount from the equilibrium state; equilibrium drive means (6) for controlling movement of the lever so as to be in an equilibrium state; and a plurality of spring sections (2) formed at both ends of the roberval section.
0), and an adjusting opening (44) which is formed with a predetermined opening diameter at a center position of each spring in accordance with a spring constant required for each spring. Electronic balance. 2. The movable part (14), the fixed part (12),
The electronic balance according to claim 1, wherein the roberval portion (18) and the spring portion (20) are integrally formed by hollowing out a lump of a single material. 3. A lever accommodation portion (2b) is formed in the roberval mechanism (2) by hollowing out from one end (2a) in the longitudinal direction, and the lever accommodation portion has a predetermined length. The lever (4) having a width smaller than the opening diameter of the lever housing portion is housed, and the fixed portion (30) and the movable portion (32a) of the lever are connected to the fixed portion (12) and the movable portion (14) of the roberval mechanism, respectively. The electronic balance according to claim 1, which is fixed.