JP7340296B1 - How to transfer low viscosity fluid - Google Patents

Abstract

【assignment】
Transfers low viscosity fluid at high pressure using a gear pump.
[Solution]
In a gear pump 10 that includes a drive gear 11 that is rotationally driven, a driven gear 12 that meshes with the drive gear 11 and rotates as a result of rotation, and a casing 13 that accommodates the drive gear 11 and the driven gear 12, the side surface of the drive gear 11 and the casing The side clearance C _S between the inner wall surface of the casing 13 and the side clearance C _S between the side surface of the driven gear and the inner wall surface of the casing 13 are set to 30 μm or less. This makes it possible to transfer the low-viscosity fluid M ₂ with a viscosity of 100 mPa·sec or less at a pressure (outlet pressure) of 5 MPa or more.
[Selection diagram] Figure 4

Description

The present invention relates to a low-viscosity fluid transfer method capable of transferring low-viscosity fluid at high pressure, and a gear pump used therefor.

As shown in FIG. 1, a separator film and the like in a lithium ion battery is produced by introducing raw material _M1 into an extruder 52 through a hopper 51, forming it into a film F with a die 53, and then passing the film F into a cooling device 54. The film is manufactured by cooling the film, stretching it in a predetermined direction using a longitudinal stretching device 55 and a transverse stretching device 56, and winding it up using a winding machine 57 (see, for example, Patent Document 1). The raw material _M1 is supplied to the extruder 52 in the form of a high viscosity fluid obtained by heating and melting a resin material such as polypropylene.

However, the film F such as a separator film is rarely manufactured using only one type of raw material, and is often manufactured by blending multiple types of raw materials. For example, a raw material M ₂ made of a low-viscosity fluid (such as an organic solvent) may be blended with a raw material M ₁ made of a high-viscosity fluid. In order to blend low viscosity raw material M ₂ with high viscosity raw material M ₁ , it is necessary to increase the pressure of raw material M ₂ and supply it. In this regard, conventionally, a plunger pump 59 is used to supply the raw material _M2 to the extruder 52.

However, the plunger pump 59 transfers the fluid (raw material M ₂ ) from inside the cylinder to outside the cylinder by reciprocating a piston within the cylinder. Therefore, when the operation of the piston is switched, the pressure of the fluid (raw material M ₂ ) fluctuates (pulsates), and the pulsations may appear as a striped pattern on the film F. Separator films and the like are required to be homogeneous regardless of location, but fluctuations (pulsations) in the pressure of the raw material _M2 often cause defects in the film F.

Further, a vane pump may be used instead of the plunger pump 59. A vane pump is equipped with a casing, a rotor housed in the casing, and a plurality of vanes provided on the outer periphery of the rotor so that they can move forward and backward.By rotating the rotor, each vane is The fluid in between is transferred (for example, see Patent Document 2). Each blade is biased in the centrifugal direction of the rotor so that its tip contacts the inner circumferential surface of the casing. A vane pump can transport even a low viscosity fluid (M ₂ ) at a constant pressure by rotating its impeller at a constant speed.

However, in a vane pump, in order to increase the pressure of the low-viscosity fluid (M ₂ ) being transferred, it is necessary to rotate the rotor at high speed. Therefore, there is a problem in that the device becomes high temperature due to frictional heat, and a mechanism for cooling it is required.

JP2020-095946A JP2021-102955A Japanese Patent Application Publication No. 2019-196760

Incidentally, in addition to the plunger pump and vane pump described above, gear pumps (see, for example, Patent Document 3) are known as devices for transferring fluid. A gear pump rotates a gear within a casing to transfer the fluid in the tooth grooves (between adjacent teeth) through the gap between the inner circumferential surface of the casing and the outer circumferential surface of the gear. There is. Therefore, like the vane pump, if the rotation speed of the gear is kept constant, the fluid (raw material M ₂ ) can be transferred at a constant pressure without pressure pulsations.

However, in gear pumps, a gap C _S (FIG. 4) called "side clearance" inevitably occurs between the inner wall surface of the casing and the side surface of the gear. Therefore, in the gear pump, there is a risk that fluid may flow backward through the side clearance. The lower the viscosity of the fluid to be transferred, the more likely this backflow will occur. A gear pump is not suitable for use in transferring a low-viscosity fluid (raw material M ₂ ) at high pressure, and cannot be used in place of the plunger pump 59 in the use shown in FIG.

The present invention was made in order to solve the above problems, and its object is to transfer a low viscosity fluid at high pressure while using a gear pump.

The above issues are
a rotationally driven drive gear;
a driven gear that meshes with the driving gear and rotates as a result;
A gear pump comprising a driving gear and a casing housing a driven gear,
By setting the side clearance between the side surface of the driving gear and the inner wall surface of the casing and the side clearance between the side surface of the driven gear and the inner wall surface of the casing to be 30 μm or less,
The problem is solved by providing a gear pump characterized by being able to transfer a low-viscosity fluid with a viscosity of 100 mPa·sec or less at a pressure (outlet pressure) of 5 MPa or more.

By suppressing the side clearance of the driving gear and the driven gear in this way, even a low viscosity fluid can be transferred at a high pressure of 5 MPa or more. As already mentioned, it is common technical knowledge that gear pumps are not suitable for high-pressure transfer of low-viscosity fluids, but it is possible to transfer low-viscosity fluids at high pressures simply by reducing the side clearance. , which is very surprising. In addition, in a gear pump, if the driving gear and the driven gear are rotated at a constant speed, pulsations in the pressure of the fluid to be transferred can be suppressed. Therefore, the gear pump of the present invention can also be suitably employed in the above-mentioned applications (in the manufacturing equipment for separator films, etc., applications in which low-viscosity fluid is blended with high-viscosity fluid).

In the gear pump of the present invention, it is preferable that the top clearance between the tip of the driving gear and the inner circumferential surface of the casing and the top clearance between the tip of the driven gear and the inner circumferential surface of the casing are also set to 30 μm or less. . This is because backflow of the fluid to be transferred (low viscosity fluid) can occur not only through the side clearance of the driving gear and driven gear, but also through the top clearance of the driving gear and driven gear. This is because by keeping the top clearance small, it becomes easier to further increase the pressure of the fluid to be transferred (low viscosity fluid).

As described above, the present invention makes it possible to transfer low-viscosity fluid at high pressure while using a gear pump.

FIG. 2 is a diagram illustrating conventional film manufacturing equipment. It is a figure explaining the film manufacturing equipment using the gear pump of this embodiment. FIG. 2 is a cross-sectional view showing the gear pump of the present embodiment taken along a plane perpendicular to rotation center lines L ₁ and L ₂ of the driving gear and the driven gear. FIG. 4 is a cross-sectional view showing the gear pump of the present embodiment taken along the X ₁ -X ₁ plane in FIG. 3. FIG.

Embodiments of the gear pump of the present invention will be specifically described using the drawings. However, the configuration described below is merely a preferred embodiment, and the technical scope of the gear pump of the present invention is not limited to the configuration described below. The gear pump of the present invention can be modified as appropriate without departing from the spirit of the invention.

1. Applications of Gear Pump The gear pump of the present invention can be used in various applications for transferring low-viscosity fluids at high pressure. For example, in a hydraulic cylinder that uses hydraulic pressure to drive a piston housed in the cylinder, it is necessary to transfer oil into the cylinder at high pressure. can be used. Additionally, as mentioned above, when producing films (such as separator films for lithium-ion batteries), a low viscosity fluid may be blended with a high viscosity fluid in an extruder. The gear pump of the present invention can also be used in applications that supply low viscosity fluids. In the following, for convenience of explanation, the gear pump of the present invention will be explained using an example in which a film is manufactured.

2. Film Manufacturing Equipment FIG. 2 is a diagram illustrating a film manufacturing equipment using the gear pump 10. As shown in FIG. 2, this film manufacturing equipment includes a hopper 51 for raw material _M1 , an extruder 52, a die 53, a cooling device 54, a longitudinal stretching device 55, a horizontal stretching device 56, and a winding device. In addition to the machine 57, a hopper 58 for the raw material _M2 and a gear pump 10 are provided. The raw material _M1 is a high viscosity fluid made by heating and melting a resin material (pellet, etc.) such as polypropylene or polyethylene, which is the main raw material of the film F, and the raw material M2 is a high-viscosity fluid made by heating and melting a resin material (pellet, etc.), which is the main raw material of the film F, and the raw material _M2 is an organic solvent or the like added to the raw material _M1 . It is a low viscosity fluid. The raw material M ₁ is introduced into the extruder 52 through the hopper 51 , and the raw material M ₂ is introduced into the gear pump 10 through the hopper 58 , the pressure of which is increased by the gear pump 10 , and the raw material M 2 is introduced into the extruder 52 .

The extruder 52 uses a screw or the like to extrude the raw material M ₁ and the raw material M ₂ to a die 53 at a subsequent stage while mixing the raw materials M 1 and M 2 . In this embodiment, a twin-screw extruder (twin-screw mixer) equipped with two screws is used as the extruder 52.

The die 53 molds the raw materials M ₁ and M ₂ (a mixture of the raw materials M ₁ and the raw materials M ₂ ; the same applies hereinafter) extruded from the extruder 52 into a film by drawing them out from the slit. There is. In this embodiment, a T-shaped die called a "T die" is used as the die 53. If the raw materials M ₁ and M ₂ become film-like and are difficult to be extracted from the die 53 with only the pressure of the extruder 52, the raw materials M ₁ and M ₂ are inserted into the pipe connecting the extruder 52 and the die 53. A fluid transfer means (not shown) for transferring the fluid to 53 may also be provided. Examples of this fluid transfer means include a gear pump (not necessarily the gear pump 10 of the present invention, but may be a general gear pump).

The cooling device 54 is for cooling the film F drawn out from the die 53. In this embodiment, the cooling device 53 includes a rotationally driven drive roller and a plurality of guide rollers arranged in parallel to the drive roller. The film F drawn out from the die 53 is dropped onto the outer peripheral surface of the drive roller of the cooling device 54, and is wound around a plurality of guide rollers. The film F is naturally cooled while being transported from the drive roller to the plurality of guide rollers. The cooling device 54 can also be provided with a means for actively cooling the film F, such as a cooling fan.

The longitudinal stretching device 55 stretches the film F in the longitudinal direction by applying tension in the longitudinal direction (transfer direction of the film F) to the film F sent from the cooling device 54 . In this embodiment, the longitudinal stretching device 55 is composed of a plurality of guide rollers arranged in parallel with each other.

The lateral stretching device 56 stretches the film F sent from the longitudinal stretching device 55 in the lateral direction by applying tension in the lateral direction (direction perpendicular to the transport direction of the film F). It becomes. In this embodiment, the lateral stretching device 56 is one that stretches the film F in the lateral direction using clips (not shown) installed on both sides of the film F.

The winder 57 winds up the film F sent from the lateral stretching device 56 into a roll. In this embodiment, the winder 57 is constituted by a drive roller that is rotationally driven. This drive roller (winding machine 57) is rotationally driven by an electric motor or the like (not shown). The film F wound up by the winder 57 is a blend of raw material _M1 and raw material _M2 .

In this film manufacturing equipment, it is necessary to feed raw material M ₂ made of a low viscosity fluid into the extruder 52 at high pressure. This is because the raw material M ₁ , which is a highly viscous fluid, has already been supplied into the extruder 52, so if the pressure of the raw material _M2 is low, the raw material _M2 will not enter the extruder 52. Furthermore, in this film manufacturing equipment, it is necessary to feed the raw material M ₂ into the extruder 52 while suppressing pressure fluctuations (pulsations) of the raw material M ₂ made of a low-viscosity fluid. When the pressure of the raw material _M2 supplied into the extruder 52 pulsates, a striped pattern appears on the film F, and the density of the raw material _M2 changes in the part of the pattern from that in other parts, making the film F homogeneous. This is because it does not become.

In this embodiment, the raw material M₂A gear pump 10 is used to supply the extruder 52 at high and constant pressure. As already mentioned, gear pumps are generally not suitable for use in transferring low-viscosity fluids at high pressures, but in this embodiment, this is made possible by applying a device to the gear pump 10 that will be described later. Further, by employing the gear pump 10, there is an advantage that heat generation can be suppressed.

3. Gear Pump The structure of the gear pump 10 of this embodiment will be described in detail. FIG. 3 is a cross-sectional view of the gear pump 10 of this embodiment taken along a plane perpendicular to the rotation center lines L ₁ and L ₂ of the drive gear 11 and the driven gear 12. FIG. 4 is a cross-sectional view of the gear pump 10 of this embodiment taken along the X ₁ -X ₁ plane in FIG. 3. As shown in FIG. The gear pump 10 of this embodiment includes a drive gear 11, a driven gear 12, and a casing 13, as shown in FIGS. 3 and 4.

As shown in FIG. 4, the casing 13 has a structure in which both sides of a plate-shaped intermediate portion 13a are sandwiched between a pair of plate-shaped cover portions 13b and 13c. As shown in FIG. 3, in the intermediate portion 13a of the casing 13, a fluid introduction chamber _α0 , a drive gear housing chamber _α1 , a driven gear housing chamber _α2 , and a fluid outlet chamber _α1 are in communication with each other. It is provided. The fluid introduction chamber α ₀ is provided with a fluid introduction part IN, and the fluid delivery chamber α ₃ is provided with a fluid delivery part OUT. The fluid introduction part IN is connected to the hopper 58 (FIG. 2), and the raw material _M2 put into the hopper 58 is introduced into the fluid introduction chamber _α0 through the fluid introduction part IN. On the other hand, the fluid outlet OUT is connected to the extruder 52 (FIG. 2), and the fluid (raw material M ₂ ) in the fluid outlet chamber α ₃ is sent out to the extruder 52 through the fluid outlet OUT. ing. The fluid introduction chamber α ₀ and the fluid discharge chamber α ₁ are arranged on opposite sides of the boundary portion (communicating portion) between the drive gear storage chamber α ₁ and the driven gear storage chamber α ₂ .

A drive gear 11 is housed in the drive gear housing chamber _α1 , and a driven gear 12 is housed in the driven gear housing chamber _α2 . A plurality of teeth 11a and 12a are provided on the outer peripheries of the driving gear 11 and the driven gear 12, respectively. As the driving gear 11 and the driven gear 12, a spur gear (a gear in which a plurality of teeth are provided in parallel on the outer periphery of a cylindrical member) or a helical gear (a gear having a twisted shape of a spur gear) can be used. Can be used. In this embodiment, a spur gear is used. The driving gear 11 and the driven gear 12 are arranged in a state of circumscribing each other so that the teeth 11a and the teeth 12a mesh with each other. The driving gear housing chamber α ₁ and the driven gear housing chamber α ₂ both have a circular cross section, and the outer diameters of the driving gear 11 and the driven gear 12 are the same as the driving gear housing chamber α ₁ and the driven gear housing chamber α 2, respectively. It is set slightly smaller than the diameter of chamber _α2 .

Of the driving gear 11 and the driven gear 12, the driving gear 11 is integrally fixed to the outer circumference of the shaft 14 having a cylindrical shape. The shaft 14 is rotatably supported by the casing 13, and a rotational drive means (not shown) such as an electric motor is connected to the shaft 14. On the other hand, the driven gear 12 is rotatably supported on the outer circumference of a cylindrical shaft 15. The shaft 15 is immovably fixed to the casing 13. Therefore, when the above-described rotation drive means is driven, the rotation shaft 14 and the drive gear 11 rotate around the rotation center line _L1 (see arrow _A1 in FIG. 3), and the drive gear 11 rotates. The driven gear 12 rotates around the rotation center line _L2 (see arrow _A2 in FIG. 3). The rotational direction _A1 of the drive gear 11 and the rotational direction _A2 of the driven gear 12 are opposite.

When the driving gear 11 and the driven gear 12 rotate in the directions of arrows A ₁ and A ₂ , the fluid (raw material M ₂ ) in the fluid introduction chamber α ₀ flows into the tooth grooves of the driving gear 11 and the driven gear 12. The fluid is held and transferred to the fluid outlet chamber α 3 through between the inner circumferential surface of the drive gear housing chamber α ₁ and the outer circumferential surface of the drive gear 11 (see arrow A ₃ in FIG. 3), and the _driven gear The fluid passes between the inner peripheral surface of the gear storage chamber α ₂ and the outer peripheral surface of the driven gear 12 and is transferred to the fluid outlet chamber α ₃ (see arrow A ₄ in FIG. 3). The fluid (raw material M ₂ ) that has reached the fluid outlet chamber α ₃ is led out from the fluid outlet section OUT and supplied to the extruder 52 . The pressure (outlet pressure) of the fluid (raw material M ₂ ) drawn out from the fluid outlet portion OUT can be increased by increasing the rotational speed of the driving gear 11 and the driven gear 12.

However, when the viscosity of the fluid to be transferred (raw material M ₂ ) is low (when the raw material M ₂ is a low viscosity fluid), even if the rotational speed of the driving gear 11 and the driven gear 12 is increased, the driving gear 11 The gap between the side surface of the driven gear 12 and the inner wall surface of the casing 13 (the inner wall surface of the drive gear accommodating chamber _α1 ) (the side clearance C _S on the drive gear 11 side in FIG. 4), and the gap between the side surface of the driven gear 12 and the inner wall surface of the casing 13 ( The fluid (raw material M ₂ ) flows back from the fluid outlet chamber α ₃ to the fluid introduction chamber α ₀ through the gap (side clearance C _S on the driven gear 12 side in FIG. 4) with the inner wall surface of the driven gear storage chamber α ₂ . As a result, the pressure of the fluid (raw material M ₂ ) drawn out from the fluid outlet portion OUT may not increase as expected.

The low viscosity fluid (raw material M ₂ ) flows from a high-pressure location to a low-pressure location, and when the driving gear 11 and the driven gear 12 are driven to rotate, the pressure in the fluid outlet chamber α ₃ becomes lower than that in the fluid outlet chamber α ₀ . This is because it becomes expensive. For the same reason, the gap between the tip of the tooth of the drive gear 11 (the apex P _T of the tooth 11a) and the inner circumferential surface of the casing 13 (the inner circumferential surface of the drive gear housing chamber α ₁ ) (the gap on the drive gear 11 side in FIG. top clearance C _T ) and the gap between the tip of the tooth of the driven gear 12 (the apex P _T of the tooth 12a) and the inner peripheral surface of the casing 13 (the inner peripheral surface of the driven gear housing chamber α ₂ ) (the driven gear 12 in FIG. A backflow of the fluid (raw material M ₂ ) can also occur through the side top clearance C _T (see dashed arrows A ₅ and A ₆ in FIG. 3). In addition, the backflow from the fluid outlet chamber α ₃ to the fluid outlet chamber α ₀ can also occur at the boundary between the driving gear 11 and the driven gear 12 (see broken line arrow A ₇ in FIG. 3). Backflow of the low-viscosity fluid (raw material M ₂ ) is likely to occur when the viscosity of the fluid (raw material M ₂ ) is 100 mPa·sec or less. The backflow of the low-viscosity fluid (raw material M ₂ ) increases as the viscosity of the fluid (raw material M ₂ ) becomes lower than 50 mPa·sec, below 40 mPa·sec, below 30 mPa·sec, below 20 mPa·sec, and below 10 mPa·sec. , more likely to occur.

In this regard, in this embodiment, the side clearance C _S (FIG. 4) and the top clearance C _T (FIG. 3) are both suppressed to 30 μm or less to prevent the backflow of the fluid (raw material M ₂ ). ing. By making the side clearance C _S and the top clearance C _T even smaller, such as 20 μm or less, 10 μm or less, or 5 μm, it is possible to further prevent backflow from occurring. The lower limits of the side clearance C _S and the top clearance C _T are not particularly limited, but considering the manufacturing of the drive gear 11, driven gear 12, and casing 13, they are thought to be about 0.1 to 1 μm.

As described above, by keeping the side clearance C _S and top clearance C _T small, even when the raw material M ₂ is a low viscosity fluid with a viscosity of 100 mPa・sec or less, the raw material M ₂ can be kept at a pressure of 5 MPa or more (at the outlet). can be transferred by pressure). It was also confirmed that by increasing the rotational speed of the driving gear 11 and the driven gear 12, the outlet pressure of the raw material _M2 could be further increased to 10 MPa or more, 15 MPa or more. The upper limit of the outlet pressure of the raw material M ₂ is not particularly limited, but it is thought to be about 50 to 100 MPa.

Furthermore, in the gear pump 10 of this embodiment, even when the outlet pressure of the raw material _M2 is increased (eg, 5 MPa), it is possible to achieve high volumetric efficiency (eg, 85% or more). It was also confirmed that the volumetric efficiency of the gear pump 10 could be increased to 90% or more, 95% or more. However, even if the volumetric efficiency of the gear pump 10 is not increased too much, the outlet pressure of the raw material _M2 can be increased by increasing the rotational speed of the driving gear 11 and the driven gear 12.

Furthermore, it was also confirmed that in the gear pump 10 of this embodiment, there was almost no pulsation in the outlet pressure of the raw material _M2 . Specifically, it was confirmed that the ratio of pulsation to the outlet pressure (target pressure) of the raw material M ₂ could be reduced to 5% or less (for example, when the target pressure was 5 MPa, the pulsation could be reduced to 0.25 MPa or less). The ratio of pulsation to the outlet pressure (target pressure) of the raw material _M2 can be further reduced to 4% or less, 3% or less, or 2% or less.

The configuration of the gear pump 10 of this embodiment described above can be adopted regardless of the capacity of the gear pump. For example, a gear pump with a discharge flow rate of 1 cc/rev class (greater than 0.1 cc/rev and less than 1 cc/rev), a gear pump with a discharge flow rate of 10 cc/rev class (greater than 1 cc/rev and less than 10 cc/rev), Any gear pump with a discharge flow rate of 100 cc/rev class (greater than 10 cc/rev and less than 100 cc/rev) can be used.

10 Gear pump 11 Drive gear 11a Teeth 12 Driven gear 12a Teeth 13 Casing 13a Intermediate portion 13b Cover portion 13c Cover portion 14 Shaft 15 Shaft 16 Flange portion 51 Hopper (for raw material _M1 )
52 Extruder 53 Die 54 Cooling device 55 Longitudinal stretching device 56 Lateral stretching device 57 Winder 58 Hopper (for raw material _M2 )
59 Plunger pump _A1 Direction of rotation of driving gear _A2 Direction of rotation of driven gear _A3 Direction of transfer of raw material _M2 by driving gear _A4 Direction of transfer of raw material _M2 by driven gear _A5 Through the top clearance on the driving gear side Direction of reverse flow A ₆ Direction of reverse flow through the top clearance on the drive gear side A ₇ Direction of reverse flow through the boundary (meshing part) between the drive gear and driven gear L ₁ Center of rotation of drive gear L ₂ Center of rotation of driven gear Line _M1 raw material (high viscosity fluid)
_M2 raw material (low viscosity fluid)
C Top clearance between the tips of the teeth of the _T drive gear or driven gear and the inner peripheral surface of the casing C Side clearance between the side surfaces of the _S drive gear or driven gear and the inner wall surface of the casing IN Fluid introduction part OUT Fluid outlet part α ₀ Fluid introduction Chamber α ₁ Drive gear storage chamber α ₂ Driven gear storage chamber α ₃ Fluid outlet chamber

Claims (3)

a rotationally driven drive gear;
a driven gear that meshes with the driving gear and rotates as a result;
A casing that accommodates a driving gear and a driven gear,
The side clearance between the side surface of the driving gear and the inner wall surface of the casing and the side clearance between the side surface of the driven gear and the inner wall surface of the casing are set to 30 μm or less , and
Using a gear pump in which the top clearance between the tips of the driving gear teeth and the inner circumferential surface of the casing and the top clearance between the tips of the driven gear teeth and the inner circumferential surface of the casing are set to 30 μm or less ,
Transferring a low viscosity fluid with a viscosity of 100 mPa/sec or less to a high viscosity fluid in an extruder connected to the gear pump at a pressure of 5 MPa or more ,
A method for transferring a low viscosity fluid, comprising blending a low viscosity fluid and a high viscosity fluid in an extruder .
2. The method for transferring a low-viscosity fluid according to claim 1, wherein the gear pump has a volumetric efficiency of 90% or more when the outlet pressure is 5 MPa.
3. The method for transferring a low-viscosity fluid according to claim 2, wherein the gear pump has a discharge flow rate of 100 cc/rev or less.

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