JPH08303353A - Control device, control method, shaping device, and shaping method for fixed displacement pump - Google Patents

Abstract

PURPOSE: To reduce delivery pressure changes of a fixed displacement pump despite of a simple and inexpensive structure, by amplifying output signals of a filter circuit which passes only frequency signal components of the delivery pressure changes originated from the fixed displacement pump, converting the amplified output signals into binary values, and selecting a voltage value according to the binary signals. CONSTITUTION: A pressure gage 3 is provided downstream from the delivery opening of a fixed displacement pump 2 which is driven by a motor 1 and only frequency signal components of delivery pressure changes originated from the fixed displacement pump 2 out of its output signals are made to pass through a filter circuit 4. The signals passed through the filter circuit are amplified 5 and then compared with a prescribed reference voltage in a comparison circuit 6 so as to be converted into binary values and voltage values (b), (c) (b>c), which are set in an additional value set circuit 8, are selected and output according to the binary signals by a selector 9. Next, the output voltage of the selector 9 and the output voltage (a) of a rotation speed set circuit 7 are added 10, and the output after addition is output 11 to a motor 1 by converted into a voltage value or a current value drivable of the motor.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a discharge pressure fluctuation reducing device for a metering pump that discharges a fixed amount of fluid, a method of using the same, a shaping device for an organic polymer, and a shaping method thereof.

[0002]

2. Description of the Related Art Considering, for example, a gear-type metering pump as a metering pump, the principle of pumping is that the fluid is filled at the inlets of the tooth spaces of two gears that rotate while meshing with each other, The fluid is trapped between the tooth space and the casing and moves circumferentially toward the outlet,
When the teeth of the gear mesh with each other at the outlet, they are pushed out and discharged. Generally, spur gears are used as the gear teeth, so the meshing of the teeth is intermittent,
Causes fluctuations in fluid discharge pressure. When manufacturing a shaped object continuously by supplying raw materials using such a gear type metering pump, fluctuations in the fluid discharge pressure cause fluctuations in the fluid discharge amount, causing the shape irregularity of the shaped object. Becomes Therefore, in the production of shaped objects that require particularly high dimensional accuracy,
It is necessary to reduce the fluctuation of the discharge amount of the gear type metering pump.

A well-known method for reducing the variation in the discharge amount of fluid due to such a gear type metering pump is to alleviate the pressure variation by an accumulator. This is to reduce the fluctuation of the fluid discharge amount by mechanically changing the internal volume of the pipe from the gear type metering pump to the discharge part of the shaping device by the changed discharge volume. .

Further, there is a triple gear type metering pump in which the fluctuation of the discharge amount of the gear type metering pump itself is small. This three-gear type metering pump has a structure in which three gears are arranged in parallel and fluid is pressure-fed from two meshing parts to cancel out the phase of fluctuation of the discharge amount, and exhibits high discharge stability.

[0005]

However, the accumulator has a complicated structure and needs a power source for operating the accumulator in addition to the operation of the gear type metering pump.
The device itself becomes large and expensive. Further, the three-gear type metering pump is also more complicated and expensive than the ordinary gear type metering pump.

Further, when the molded product manufactured in the existing device requires higher dimensional accuracy, a large-scale modification of the device is required in order to incorporate an accumulator or a triple gear type metering pump in the shaping device. Will be needed.

In view of the above problems, it is an object of the present invention to provide a device which can reduce the discharge pressure fluctuation of the metering pump, that is, the discharge amount fluctuation, with a simple structure and a low cost, and a method of using the same. is there.

[0008]

The gist of the first invention of the present application is to provide a motor (1) whose rotation speed is controlled by a DC voltage value or a DC current value, and a constant quantity which is driven by the motor (1) to pump a fluid. With respect to the output signal of the pump (2), the pressure gauge (3) provided on the downstream side of the discharge port of the metering pump (2), and the output signal of the pressure gauge (3), the frequency of the discharge pressure fluctuation caused by the metering pump. A filter circuit (4) that passes only the signal component, an amplifier circuit (5) that amplifies the output signal of the filter circuit (4), and an output signal of the amplifier circuit (5) are compared with a predetermined reference voltage, A comparison circuit (6) that performs binarization, a rotation speed setting circuit (7) that sets a predetermined voltage value a, and an addition value setting circuit (8) that sets the two voltage values b and c as b> c. And b or c depending on the binary signal of the comparison circuit (6). The selector (9) for selecting the pressure value, the adder circuit (10) for adding the output voltage of the rotation speed setting circuit (7) and the output voltage of the selector (9), and the output of the adder circuit (10) are connected to the motor (1 Circuit for converting () to a drivable voltage value or current value and outputting it
It is a constant pump discharge pressure fluctuation reducing device.

The gist of the second invention is, in the above-mentioned device, the predetermined voltage value a set by the rotation speed setting circuit (7) is a digital value a'of a predetermined number of bits, and the addition circuit (10 ) And the output circuit (11) between D (digital)
A / A (analog) conversion circuit (12) is provided, and the voltage value b and the voltage value c set by the addition value setting circuit (8) are further provided.
Is a digital value b ′ and a digital value c ′ of a predetermined number of bits, in a constant pump discharge pressure fluctuation reducing device.

The gist of a third invention is that, in the first device, a second rotation speed setting circuit (16) for setting a voltage value d satisfying a> d is arranged instead of the addition value setting circuit (8). However, the addition circuit (10) is omitted and the rotation speed setting circuit (7)
Connected to the selector (9) to configure a circuit for selecting the voltage value a or the voltage value d according to the binarized signal of the comparison circuit (6), and the output of the selector (9) is output to the output circuit (11). The constant pressure pump discharge pressure fluctuation reducing device is characterized in that it is configured to send.

The gist of a fourth invention is, in the second device, a second value for setting a digital value d'having a predetermined number of bits such that a '>d', in place of the addition value setting circuit (8).
The rotation speed setting circuit (16) is arranged, the addition circuit (10) is omitted, the rotation speed setting circuit (7) is connected to the selector (9), and digital signals are output in accordance with the binary signal of the comparison circuit (6). A metering pump discharge characterized in that a circuit for selecting the value a'or the digital value d'is configured to send the output of the selector (9) to the D (digital) / A (analog) conversion circuit (12). It is in the pressure fluctuation reducing device.

The gist of the fifth and sixth inventions is to use the device according to the first or second invention to obtain a voltage value b or a digital value when the discharge pressure due to the metering pump (2) becomes low. There is a constant pump discharge pressure fluctuation reducing method in which the voltage value c or the digital value c ′ is selected by the selector (9) when b ′ becomes high.

The gist of the seventh and eighth inventions is to use the device according to the third or fourth invention to obtain a voltage value a or a digital value when the discharge pressure due to the metering pump (2) becomes low. There is a constant pump discharge pressure fluctuation reducing method in which a selector 9 selects a voltage value d or a digital value d ′ when a ′ becomes high.

A ninth aspect of the present invention is to provide an organic polymer or a mixture containing an organic polymer on the upstream side of the metering pump (2) of the metering pump discharge pressure fluctuation reducing device according to any one of the first to fourth aspects. The shaping apparatus comprises a melt-kneading supply device (17) and a shaping device (18) disposed downstream of the pressure gauge (3).

The tenth aspect of the invention is to melt-knead an organic polymer or a mixture containing an organic polymer by a melt-kneading supply device (17) using the shaping apparatus according to any of the ninth invention. The molten kneaded material is supplied to the shaping device (18) while the discharge pressure is controlled to be constant by using the method for reducing the fluctuation of the discharge pressure of the metering pump according to the fifth, sixth, seventh or eighth invention. It is a method of shaping a mixture containing a polymer or an organic polymer into a predetermined shape.

[0016]

BEST MODE FOR CARRYING OUT THE INVENTION In the present invention, the fluid is exemplified by an organic polymer or a mixture containing an organic polymer.
The mixture containing an organic polymer, a mixture of an organic polymer and a polymerizable monomer, a mixture of an organic polymer and a non-polymerizable compound, an organic polymer and a polymerizable monomer and a non-polymerizable compound A mixture etc. are illustrated. Fiber by the shaping apparatus of the present invention,
Various shaped objects such as optical fibers, films, and resin plates can be manufactured. As the organic polymer and the monomer, known compounds known as these raw materials can be used. That is, as the organic polymer, cellulose, natural rubber, synthetic resin, synthetic rubber or the like can be used. As the polymerizable monomer, it is possible to use a material which is a raw material of the organic polymer or a material which produces a polymer having physical properties different from the organic polymer such as solubility, heat resistance, transparency and refractive index. Further, as the non-polymerizable compound, for example, an organic polymer or a compound having a refractive index different from that of the monomer can be used. The device of the present invention and the method of using the same will be described below with reference to the drawings.

[0017]

【Example】

Embodiment 1 FIG. 1 is a block diagram showing an embodiment of the first device of the present invention. The rotation speed setting circuit (7) adjusts the voltage value a so that the motor (1) has a predetermined rotation speed, and the addition circuit (1
0). The addition value setting circuit (8) sets predetermined voltage values b and c (where b> c) as addition values, and outputs them to the selector (9).

On the other hand, the pressure gauge (3) provided on the downstream side of the metering pump (2) detects the discharge pressure signal of the metering pump (2) and outputs it to the filter circuit (4). In the filter circuit (4), only the frequency of the discharge pressure fluctuation component of the discharge pressure signal of the metering pump (2) caused by the inner metering pump (2) is passed and output to the amplifier circuit (5). The amplifier circuit (5) amplifies the output from the filter circuit (4) to a discriminable level and outputs it to the comparison circuit (6). Here, although the filter circuit (4) and the amplifier circuit (5) are separately configured, the amplifier circuit (5) may be provided with the function of the filter circuit (4) and may be integrally configured.

In the comparison circuit (6), the output from the amplification circuit (5) is compared with the voltage of a predetermined level set in the reference voltage generation circuit (15). For example, when the pressure becomes higher than the predetermined level. A high level (hereinafter abbreviated as H) and a low level (hereinafter abbreviated as L) are output to the selector (9) when the level becomes low. The selector (9) selects the voltage value b when the output signal from the comparison circuit (6) is L, and selects the voltage value c when it is H and outputs it to the addition circuit (10).

The adder circuit (10) adds the voltage value a and the voltage value b or the voltage value c output from the selector (9) and outputs the result to the output circuit (11). The output circuit (11) outputs to the motor (1) as a voltage or current value capable of driving the motor (1) according to the output value from the adding circuit (10). The motor (1) drives the metering pump (2) according to the output from the output circuit (11).

With the above operation, when the discharge pressure is about to increase with respect to the discharge pressure fluctuation caused by the metering pump (2), the output of the addition circuit (10) is a +.
c (this value is smaller than a + b) and the motor (1) rotates at low rotation, and when the discharge pressure is about to decrease, the output of the addition circuit (10) becomes a + b and the motor (1) rotates at high rotation, It is possible to reduce the fluctuation of the discharge pressure.

Embodiment 2 FIG. 2 is a block diagram showing an embodiment of the second device of the present invention. Compared with the device of the first invention of FIG. 1, the predetermined voltage value a set by the rotation speed setting circuit (7) is a digital value a ′, and the addition circuit (10) and the output circuit (1
The difference is that a D (digital) / A (analog) conversion circuit (12) is provided between the first and second types.

The rotation speed setting circuit (7) is constructed as shown in the block diagram of FIG. 5, so that the motor (1) is set to a predetermined rotation speed by the volume (hereinafter referred to as VR) (13). Adjust to. Voltage value a set by VR (13)
Is converted into, for example, an 8-bit digital value a ′ by the A / D conversion circuit (14) and output to the addition circuit (10). The addition value setting circuit (8) sets, for example, b '= 10 and c' =-10 as an addition value with an 8-bit digital value, and outputs it to the selector (9). The values of b'and c'are set appropriately according to the degree of reduction in pressure fluctuation.

The selector (9) selects the digital value b'when the output signal from the comparison circuit (6) is L and the digital value c'when it is H and outputs it to the addition circuit (10). The adder circuit (10) adds the digital value a'to the digital value b'or the digital value c'which is the output of the selector (9), and the result is added to the D / A conversion circuit (1
Output to 2). The D / A conversion circuit (12) converts the output signal from the addition circuit (10) from a digital value to an analog value and outputs it to the output circuit (11). The output circuit (11) outputs to the motor (1) as a voltage or current value capable of driving the motor (1) according to the output value from the D / A conversion circuit (12). The motor (1) drives the metering pump (2) according to the output from the output circuit (11).

With the above operation, when the discharge pressure is about to increase with respect to the discharge pressure fluctuation caused by the metering pump (2), the output of the addition circuit (10) is a '.
+ C '(here, c' =-10), the motor (1) rotates at a low speed, and when the discharge pressure is about to decrease, the output of the addition circuit (10) is a '+ b' (here, b '.
= + 10), the motor (1) rotates at high rotation, and the fluctuation of the discharge pressure can be reduced.

Embodiment 3 FIG. 3 is a block diagram showing an embodiment of the third device of the present invention. Compared with the device of the first invention of FIG. 1, a second rotation speed setting circuit (16) for setting a voltage value d satisfying a> d is provided instead of the addition value setting circuit (8), and the addition circuit is added. (10) is omitted, the rotation speed setting circuit (7) is connected to the selector (9), and a circuit for selecting the voltage value a or the voltage value d according to the binarized signal of the comparison circuit (6) is configured. The difference is that the output of the selector (9) is sent to the output circuit (11).

The rotation speed setting circuit (7) includes a motor (1).
Adjusts the voltage value a so that the rotation speed is slightly higher than the desired rotation speed, and outputs it to the selector (9). The second rotation speed setting circuit (16) sets a predetermined voltage value d such that a> d and outputs it to the selector (9). The voltage value d can be set in association with the voltage value a set by the rotation speed setting circuit (7).

The selector (9) selects the voltage value a when the output signal from the comparison circuit (6) is L, and selects the voltage value d when it is H and outputs it to the output circuit (11). Output circuit (1
In 1), the motor (1) is output to the motor (1) as a voltage or current value capable of driving the motor (1) according to the output value from the selector (9). The motor (1) has an output circuit (1
The metering pump (2) is driven according to the output from (1).

By the above operation, when the discharge pressure is about to increase with respect to the discharge pressure fluctuation caused by the metering pump (2), the output of the selector (9) becomes d and the motor (1) rotates at a low speed. When the output pressure of the selector (9) rotates and the discharge pressure is about to decrease, the output of the selector (9) becomes a and the motor (1) rotates at high rotation, and the fluctuation of the discharge pressure can be reduced.

Embodiment 4 FIG. 4 is a block diagram showing an embodiment of the fourth device of the present invention. As compared with the device of the second aspect of the invention shown in FIG. 2, instead of the additional value setting circuit (8), a second rotational speed setting circuit (16) for setting a digital value d'where a '>d' is arranged. Then, the adder circuit (10) is omitted, the rotation speed setting circuit (7) is connected to the selector (9), and the comparator circuit (6)
A circuit for selecting the digital value a ′ or the digital value d ′ according to the binarized signal is configured to send the output of the selector (9) to the D (digital) / A (analog) conversion circuit (12). Is different.

The rotation speed setting circuit (7) includes a motor (1)
Outputs the digital value a ′ to the selector (9) so that the rotation speed becomes a predetermined rotation speed. In the second rotation speed setting circuit (16), a digital value d'where a> d 'is set and sent to the selector (9). The digital value d'can be set in association with the digital value a'set by the rotation speed setting circuit (7).

The selector (9) selects the digital value a'when the output signal from the comparison circuit (6) is L and the digital value d'when it is H and outputs it to the D / A conversion circuit (12). The D / A conversion circuit (12) converts the output signal from the selector (9) from a digital value to an analog value and outputs it to the output circuit (11). Output circuit (1
In 1), the motor (1) is output to the motor (1) as a voltage or current value capable of driving the motor (1) according to the output value from the D / A conversion circuit (12). The motor (1) drives the metering pump (2) according to the output from the output circuit (11).

With the above operation, when the discharge pressure is about to increase with respect to the discharge pressure fluctuation caused by the metering pump (2), the output of the adding circuit (10) is d '.
When the motor (1) rotates at a low speed and the discharge pressure is about to decrease, the output of the selector (9) becomes a'and the motor (1) rotates at a high speed to reduce the fluctuation of the discharge pressure. it can.

Example 5 FIG. 6 is a block diagram showing an example of a shaping apparatus for an organic polymer or a mixture containing an organic polymer according to the present invention.
The control device (21) is a first to a first device of the discharge pressure fluctuation reducing device.
The part of the embodiment of the fourth device excluding the motor (1), the metering pump (2) and the pressure gauge (3) is shown. The organic polymer is melted and kneaded by the melt-kneading supply device (17), sent to the metering pump (2), and discharged from the metering pump (2) at a constant rate. The discharge pressure is measured by the pressure gauge (3), the fluctuation of the measured value is determined by the control device (21) in the same manner as in Examples 1 to 4, and the rotation speed of the motor (1) is increased / decreased. The motor (1) is controlled so that a constant amount of the organic polymer is always discharged from 2). The organic polymer whose discharge amount is controlled to be constant is shaped into a predetermined shape by a shaping device (18).

FIG. 7 is a view showing a first embodiment of the shaping apparatus (18) of FIG. The shaping device is provided with a die (31) for shaping the organic polymer into a predetermined shape. As the metering pump (2), for example, a gear type metering pump of 0.6 cc / revolution is used, and the motor (1) is AC.
It uses a servo motor and is equipped with a 1/100 speed reducer. The device of the first embodiment is used as the discharge pressure fluctuation reducing device (22). As the base (31), for example, a cylindrical one having a diameter of 5 mm is used, and the diameter is 1 m.
Thus, a thread-shaped shaped product of m was obtained.

As a comparative example, a discharge pressure fluctuation reducing device (22)
Without using the motor (1), for example, about 1500r
When the discharge pressure of the metering pump (2) is measured by the pressure gauge (3) rotating at pm, the pressure fluctuation corresponding to the meshing of gear teeth, and the shaft of the motor (1) and the shaft of the metering pump (2) A fluctuation of an amplitude of about 0.5 kg / cm ² was observed as a pressure fluctuation of a cycle proportional to the rotation speed due to the mounting accuracy or the processing accuracy of the metering pump (2). At this time, when the variation of the diameter of the shaped object was measured by a laser outer diameter measuring instrument, a variation of about 10 μm was observed with respect to the center value of the diameter.

On the other hand, the discharge pressure fluctuation reducing device (22)
And the signal a set by the rotation speed setting circuit (7) is
As an example, the value when the motor (1) is rotated at about 1500 rpm is set, and the signal b set by the addition value setting circuit (8) is set to the value when the motor (1) is rotated at 750 rpm, and the addition is performed. The signal c set by the value setting circuit (8) was set to the value when the motor (1) was rotated at -750 rpm. The fluctuation frequency band of the discharge pressure that passes through the filter circuit (4) was set between about 0.1 Hz and about 10 Hz.

When shaping is performed with this configuration, when the discharge pressure of the metering pump (2) is measured by the pressure gauge (3), the fluctuation of the discharge pressure is 1 with respect to the fluctuation frequency to be reduced.
/ 10 or less. At this time, the variation of the diameter of the shaped object was about 2 μm with respect to the center value of the diameter, and the variation of the diameter was reduced to about ⅕.

In the present embodiment, the shape formed by the die (31) is one, but in order to obtain a shape having a multi-layer structure, the fluid forming each layer is pumped. By applying this device to the metering pump (2), it is possible to manufacture a highly accurate shaped object.
The device shown in FIG. 7 can also be used when a mixture of an organic polymer and a non-polymerizable compound is used as the fluid.

Embodiment 6 FIG. 8 is a block diagram showing a second embodiment of the shaping apparatus (18) of FIG. This example is a shaping device for a mixture containing an organic polymer and a polymerizable monomer, and the shaping device (18)
Is provided with a die (31) for shaping the kneaded product of the organic polymer and the polymerizable monomer into a predetermined shape, and a polymerization device (32) for polymerizing the polymerizable monomer.

The melt-kneading supply device (17) melt-kneads the mixture of the organic polymer and the polymerizable monomer and supplies the mixture to the metering pump (2). As the metering pump (2), for example, a gear type metering pump of 0.15 cc / revolution is used, an AC servomotor is used as the motor (1), and a reduction gear of 1/100 is equipped. The discharge pressure fluctuation reducing device (22) may be any of the first to fourth discharge pressure fluctuation reducing devices shown in FIGS. 1 to 4, but the device of the first embodiment is used here. There is. As the die (31), for example, a cylindrical one having a diameter of 2 mm was used. The monomer was polymerized by the polymerization device (32) arranged on the downstream side of the die (31) to obtain a thread-shaped shaped product having a diameter of 1 mm.

As a comparative example, the motor (1) is about 400r.
It was rotated at pm, and the other conditions were the same as in Example 5 except that the discharge pressure fluctuation reducing device (22) was not used.
An amplitude variation of about 0.5 kg / cm ² was observed, and the variation of the diameter of the shaped object was about 10 μm with respect to the center value of the diameter.

Further, the discharge pressure fluctuation reducing device (2) is set under the same conditions as in the fifth embodiment except that the signal a is set to about 400 rpm, the signal b is set to 200 rpm, and the signal c is set to -200 rpm.
When it was carried out using 2), the fluctuation of the discharge pressure was reduced to 1/10 or less with respect to the frequency of the fluctuation to be reduced.
The variation in the diameter of the shaped object was about 2 μm with respect to the center value of the diameter, and the variation in the diameter was reduced to about 1/5.

In the case of manufacturing a shaped object having a multi-layered structure, it is possible to manufacture a shaped object with high accuracy by applying the present apparatus to the metering pump (2) for pressure-feeding the fluid forming each layer. You can The device of FIG. 8 can also be used when an organic polymer or a mixture of a polymerizable monomer and a non-polymerizable compound is used as the fluid.

[0045]

The metering pump discharge pressure fluctuation reducing device of the present invention has a simple structure and is inexpensive. In addition, since this device has a filter circuit that passes only the fluctuation component caused by the metering pump in the input pressure signal waveform,
For example, even if the viscosity of the fluid changes due to a temperature change or the like and the pressure changes, no reaction occurs if the change is outside the frequency band of the filter circuit, and only the fluctuation component caused by the metering pump can be reduced. When a raw material is supplied using this apparatus to produce a shaped article, a shaped article having a small shape spot and high dimensional stability can be obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing a configuration of a first embodiment of a discharge pressure fluctuation reducing device of the present invention.

FIG. 2 is a block diagram showing the configuration of a second embodiment of the discharge pressure fluctuation reducing device of the present invention.

FIG. 3 is a block diagram showing the configuration of a third embodiment of the discharge pressure fluctuation reducing device of the present invention.

FIG. 4 is a block diagram showing the configuration of a fourth embodiment of the discharge pressure fluctuation reducing device of the present invention.

5 is a block diagram showing a configuration example of a rotation speed setting circuit 7 in FIG.

FIG. 6 is a block diagram showing an example of a shaping apparatus for an organic polymer or a mixture containing an organic polymer according to the present invention.

FIG. 7 is a block diagram showing a first embodiment of the shaping apparatus 18 of FIG.

FIG. 8 is a block diagram showing a second embodiment of the shaping apparatus 18 of FIG.

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Kazumi Nakamura 20-1 Miyuki-cho, Otake-shi, Hiroshima Mitsubishi Rayon Co., Ltd. Central Research Laboratory (72) Makoto Muro 20-1 Miyuki-cho, Otake-shi, Hiroshima Central Research Laboratory, Mitsubishi Rayon Co., Ltd.

Claims (10)

[Claims] 1. A motor (1) whose rotation speed is controlled by a DC voltage value or a DC current value, a metering pump (2) driven by the motor (1) to pump a fluid, and a metering pump (2). Pressure gauge (3) provided on the downstream side of the discharge port
A filter circuit (4) for passing only the frequency signal component of the discharge pressure fluctuation caused by the metering pump with respect to the output signal of the pressure gauge (3), and an amplification for amplifying the output signal of the filter circuit (4). A circuit (5), a comparison circuit (6) for comparing the output signal of the amplifier circuit (5) with a predetermined reference voltage to perform binarization, and a rotation speed setting circuit (7) for setting a predetermined voltage value a. ), And a selector (8) for setting the two voltage values b and c as b> c, and a selector (b) for selecting the voltage value of b or c according to the binarized signal of the comparison circuit (6). 9), and an adder circuit (10) for adding the output voltage of the rotation speed setting circuit (7) and the output voltage of the selector (9).
And a constant pump discharge pressure fluctuation reducing device comprising an output circuit (11) for converting the output of the adding circuit (10) into a voltage value or a current value capable of driving the motor (1) and outputting the voltage value or current value. 2. The device according to claim 1, wherein the predetermined voltage value a set by the rotation speed setting circuit (7) is a digital value a ′ of a predetermined number of bits, and the addition circuit (10) and the output are provided. A D (digital) / A (analog) conversion circuit (12) is provided between the circuit (11) and the voltage value b and the voltage value c set by the addition value setting circuit (8) have a predetermined number of bits. A constant pump discharge pressure fluctuation reducing device characterized in that it is a digital value b ′ and a digital value c ′. 3. The apparatus according to claim 1, further comprising a second rotation speed setting circuit (16) for setting a voltage value d satisfying a> d, instead of the addition value setting circuit (8). (10) is omitted, the rotation speed setting circuit (7) is connected to the selector (9), and a circuit for selecting the voltage value a or the voltage value d according to the binarized signal of the comparison circuit (6) is configured. A constant pump discharge pressure fluctuation reducing device characterized in that the output of the selector (9) is sent to the output circuit (11). 4. The apparatus according to claim 2, wherein instead of the addition value setting circuit (8), a second rotation speed setting circuit for setting a digital value d ′ of a predetermined number of bits such that a ′> d ′. (16) is arranged, the adder circuit (10) is omitted, the rotation speed setting circuit (7) is connected to the selector (9), and the digital value a ′ or the digital value a ′ depending on the binary signal of the comparison circuit (6). A constant pump discharge pressure fluctuation reducing device characterized in that a circuit for selecting a digital value d'is configured to send the output of the selector (9) to a D (digital) / A (analog) conversion circuit (12). . 5. A selector using the device according to claim 1 for selecting a voltage value b when the discharge pressure due to the metering pump (2) becomes low and a voltage value c when the discharge pressure becomes high. The method for reducing fluctuations in the delivery pressure of the constant pump selected in (9). 6. The apparatus according to claim 2, wherein a digital value b ′ is obtained when the discharge pressure due to the metering pump (2) is low, and a digital value c ′ is obtained when the discharge pressure is high. A method for reducing fluctuations in the delivery pressure of the constant-rate pump, in which the selector (9) is selected. 7. A selector according to claim 3, wherein the voltage value a is selected when the discharge pressure due to the metering pump (2) is low, and the voltage value d is selected when the discharge pressure is high. A method for reducing fluctuations in the delivery pressure of the metering pump selected in (9). 8. The apparatus according to claim 4, wherein a digital value a ′ is obtained when the discharge pressure resulting from the metering pump (2) is low, and a digital value d ′ is obtained when the discharge pressure is high. A method for reducing fluctuations in the delivery pressure of the constant-rate pump, in which the selector (9) is selected. 9. A melt-kneading supply device for an organic polymer or a mixture containing an organic polymer upstream of the metering pump (2) of the metering pump discharge pressure fluctuation reducing device according to any one of claims 1 to 4. (17) is arrange | positioned, and the shaping device which arrange | positions the shaping device (18) downstream of the pressure gauge (3). 10. The molding apparatus according to claim 9, wherein an organic polymer or a mixture containing an organic polymer is melt-kneaded by a melt-kneading supply device (17), and The molten kneaded product is supplied to the shaping device (18) while the discharge pressure is controlled to be constant by using the method for reducing the discharge pressure fluctuation of the metering pump according to claim 6, 6, or 8, and the organic polymer or A method of shaping a mixture containing an organic polymer into a predetermined shape.