JP2024075051A - Transfer method for low viscosity fluid - Google Patents

Abstract

To transfer low viscosity fluid with high pressure while using a gear pump.SOLUTION: A gear pump 10 includes: a driving gear 11 rotated and driven; a driven gear 12 engaging with the driving gear 11 and driven to rotate; and a casing 13 that accommodates the driving gear 11 and the driven gear 12. A side clearance CS between a side surface of the driving gear 11 and an inner wall surface of the casing 13 and a side clearance CS between a side surface of the driven gear and the inner wall surface of the casing 13 are set to 30 μm or smaller. This configuration enables transfer of low viscosity fluid M2 having 100 mPa s or less of viscosity with 5 MPa or greater of pressure (outlet pressure).SELECTED DRAWING: Figure 4

Description

The present invention relates to a method for transferring low-viscosity fluids at high pressure, and a gear pump used therefor.

As shown in Fig. 1, a separator film for a lithium ion battery is produced by introducing a raw material _M1 into an extruder 52 through a hopper 51, forming the raw material M1 into a film F through a die 53, cooling the film F in a cooling device 54, stretching the film in a predetermined direction through a longitudinal stretching device 55 and a transverse stretching device 56, and winding the film F up through a winder 57 (see, for example, Patent Document 1). The raw material _M1 is supplied to the extruder 52 in the state of a high-viscosity fluid obtained by heating and melting a resin material such as polypropylene.

However, a film F such as a separator film is rarely produced from only one type of raw material, but is often produced by blending multiple types of raw materials. For example, a raw material _M1 made of a high-viscosity fluid may be blended with a raw material _M2 (such as an organic solvent) made of a low-viscosity fluid. In order to blend a raw material _M2 having a low viscosity with a raw material _M1 having a high viscosity, it is necessary to supply the raw material _M2 at an increased pressure. In this regard, conventionally, the raw material _M2 is supplied to the extruder 52 using a plunger pump 59.

However, the plunger pump 59 transfers the fluid (raw material _M2 ) from inside the cylinder to outside the cylinder by reciprocating a piston within the cylinder. Therefore, when the action of the piston is switched, the pressure of the fluid (raw material _M2 ) fluctuates (pulsates), and the pulsations may appear as striped patterns on the film F. Although separator films and the like are required to be homogeneous regardless of location, the fluctuation (pulsation) of the pressure of the raw material _M2 often causes defects in the film F.

Also, a vane pump may be used instead of the plunger pump 59. The vane pump includes a casing, a rotor housed in the casing, and a plurality of vanes (vanes) provided on the outer periphery of the rotor in a state in which they can advance and retreat, and transfers the fluid between the vanes by rotating the rotor (see, for example, Patent Document 2). Each vane is urged in the centrifugal direction of the rotor so that its tip abuts against the inner periphery of the casing. If the vane pump rotates its impeller at a constant speed, it can transfer even a low-viscosity fluid (M ₂ ) at a constant pressure.

However, in order to increase the pressure of the low-viscosity fluid ( _M2 ) being transported in a vane pump, it is necessary to rotate the rotor at high speed, which causes a problem that the device becomes hot due to frictional heat, and a mechanism for cooling it is required.

JP 2020-095946 A JP 2021-102955 A JP 2019-196760 A

In addition to the above-mentioned plunger pumps and vane pumps, gear pumps (see, for example, Patent Document 3) are also known as devices for transporting fluids. Gear pumps rotate gears within a casing, and transport fluid in the tooth grooves (between adjacent teeth) of the gears through the gap between the inner circumferential surface of the casing and the outer circumferential surface of the gears. Therefore, similar to vane pumps, if the rotation speed of the gears is kept constant, the fluid (raw material _M2 ) can be transported at a constant pressure without pressure pulsation.

However, a gear pump inevitably generates a gap C _S (FIG. 4) called a "side clearance" between the inner wall surface of the casing and the side of the gear. For this reason, in a gear pump, there is a risk of fluid backflowing through the side clearance. The lower the viscosity of the fluid to be transported, the more likely this backflow will occur. A gear pump is not suitable for transporting a low-viscosity fluid (raw material M ₂ ) at high pressure, and cannot be used in place of the plunger pump 59 in the application shown in FIG. 1.

The present invention was made to solve the above problems, and aims to transport low-viscosity fluids at high pressure using a gear pump.

The above issues are:
A drive gear that is driven to rotate;
A driven gear that meshes with the drive gear and rotates in response to the drive gear;
A gear pump having a casing that houses a drive gear and a driven gear,
The side clearance between the side surface of the drive 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,
The problem is solved by providing a gear pump that is characterized in that it is capable of transferring a low-viscosity fluid having a viscosity of 100 mPa·sec or less at a pressure (outlet pressure) of 5 MPa or more.

In this way, by reducing the side clearance of the drive gear and driven gear, even low-viscosity fluids can be transported 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 transport of low-viscosity fluids, so it is quite surprising that high-pressure transport of low-viscosity fluids is possible simply by reducing the side clearance. In addition, by rotating the drive gear and driven gear at a constant speed, the gear pump can also reduce pressure pulsation of the transported fluid. For this reason, the gear pump of the present invention can be suitably employed in the above-mentioned applications (blend low-viscosity fluids into high-viscosity fluids in manufacturing equipment for separator films, etc.).

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

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

FIG. 1 is a diagram illustrating a conventional film production facility. FIG. 1 is a diagram illustrating a film production facility using a gear pump according to an embodiment of the present invention. 1 is a cross-sectional view showing a gear pump of the present embodiment cut along a plane perpendicular to rotation center lines _L1 and _L2 of a drive gear and a driven gear. 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 .

An embodiment of the gear pump of the present invention will be specifically described with reference to 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 within the scope of the invention.

1. Uses of the Gear Pump The gear pump of the present invention can be used for various applications for transferring low-viscosity fluids at high pressure. For example, in a hydraulic cylinder that hydraulically drives a piston housed in the cylinder, it is necessary to transfer oil into the cylinder at high pressure, and the gear pump of the present invention can be used for the application of supplying oil into the cylinder of the hydraulic cylinder. Also, as already mentioned, when producing a film (such as a separator film in a lithium ion battery), a low-viscosity fluid may be blended with a high-viscosity fluid in an extruder, and the gear pump of the present invention can also be used for the application of supplying a low-viscosity fluid into the extruder. In the following, for the convenience of explanation, the gear pump of the present invention will be explained by taking the case of producing a film as an example.

2. Film manufacturing equipment FIG. 2 is a diagram for explaining a film manufacturing equipment using a 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 transverse stretching device 56, a winding machine 57, a hopper 58 for raw material _M2 , and a gear pump 10. Raw material _M1 is a high-viscosity fluid obtained by heating and melting a resin material (pellets, etc.) such as polypropylene or polyethylene, which is the main raw material of the film F, and raw material _M2 is a low-viscosity fluid, such as an organic solvent, that is added to raw material _M1 . Raw material _M1 is introduced into the extruder 52 through the hopper 51, and raw material _M2 is introduced into the gear pump 10 through the hopper 58, and the pressure is increased by the gear pump 10 before being introduced into the extruder 52.

The extruder 52 extrudes the raw materials _M1 and _M2 into a downstream die 53 while mixing them with a screw or the like. In this embodiment, a twin-screw extruder (twin-screw mixer) equipped with two screws is used as the extruder 52.

The die 53 is a device for forming the raw materials _M1 , _M2 (a mixture of raw materials _M1 and _M2 ; the same applies below) extruded from the extruder 52 into a film by leading them out through a slit. In this embodiment, a T-shaped die called a "T die" is used as the die 53. If the raw materials _M1 , _M2 are difficult to form into a film and lead out of the die 53 only by the pressure of the extruder 52, a fluid transfer means (not shown) for transferring the raw materials _M1 , _M2 to the die 53 can be provided in the piping connecting the extruder 52 and the die 53. As the fluid transfer means, a gear pump (not necessarily the gear pump 10 of the present invention, but may be a general gear pump) and the like can be mentioned.

The cooling device 54 is for cooling the film F that is led out from the die 53. In this embodiment, the cooling device 53 is composed of a drive roller that is driven to rotate, and multiple guide rollers that are arranged in parallel to the drive roller. The film F that is led out from the die 53 is dropped onto the outer circumferential surface of the drive roller of the cooling device 54, and is placed in a state in which it is wrapped around the multiple guide rollers. The film F is naturally cooled while being transported from the drive roller to the multiple guide rollers. The cooling device 54 can also be provided with a means for actively cooling the film F, such as a cold air fan.

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

The transverse stretching device 56 stretches the film F in the transverse direction by applying tension in the transverse direction (perpendicular to the direction of transport of the film F) to the film F sent from the longitudinal stretching device 55. In this embodiment, the transverse stretching device 56 uses clips (not shown) installed on both sides of the film F to pull the film F in the transverse direction.

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

In this film production equipment, it is necessary to supply raw material _M2 consisting of a low viscosity fluid at high pressure into extruder 52. Because raw material _M1 , which is a high viscosity fluid, has already been supplied into extruder 52, if the pressure of raw material _M2 is low, raw material _M2 will not enter extruder 52. In addition, in this film production equipment, it is also necessary to supply raw material _M2 consisting of a low viscosity fluid into extruder 52 while suppressing pressure fluctuation (pulsation) of raw material _M2 . If the pressure of raw material _M2 supplied into extruder 52 pulsates, a striped pattern will appear on film F, and the density of raw material _M2 will be different from other parts at the patterned parts, making film F non-uniform.

In this embodiment, a gear pump 10 is used to supply the raw material _M2 at a high and constant pressure into the extruder 52. As already mentioned, a gear pump is generally not suitable for transferring low viscosity fluids at high pressure, but in this embodiment, this is made possible by applying the following innovation to the gear pump 10. Another advantage of using the gear pump 10 is 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 showing the gear pump 10 of this embodiment cut along a plane perpendicular to the rotation center lines _L1 , _L2 of the drive gear 11 and the driven gear 12. Fig. 4 is a cross-sectional view showing the gear pump 10 of this embodiment cut along the _X1 - _X1 plane in Fig. 3. As shown in Figs. 3 and 4, the gear pump 10 of this embodiment includes the drive gear 11, the driven gear 12, and a casing 13.

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, the intermediate portion 13a of the casing 13 is provided with a fluid introduction chamber _α0 , a driving gear accommodating chamber _α1 , a driven gear accommodating chamber _α2 , and a fluid discharge chamber _α1 in a state of communication. The fluid introduction chamber _α0 is provided with a fluid introduction portion IN, and the fluid discharge chamber _α3 is provided with a fluid discharge portion OUT. The fluid introduction portion IN is connected to a hopper 58 (Fig. 2), and the raw material _M2 introduced into the hopper 58 is introduced into the fluid introduction chamber _α0 through the fluid introduction portion IN. On the other hand, the fluid discharge portion OUT is connected to an extruder 52 (Fig. 2), and the fluid (raw material _M2 ) in the fluid discharge chamber _α3 is sent to the extruder 52 through the fluid discharge portion OUT. The fluid introduction chamber _α0 and the fluid discharge chamber _α1 are arranged on opposite sides of a boundary portion (communicating portion) between the drive gear accommodating chamber _α1 and the driven gear accommodating chamber _α2 .

The driving gear 11 is accommodated in the driving gear accommodating chamber _α1 , and the driven gear 12 is accommodated in the driven gear accommodating chamber _α2 . The driving gear 11 and the driven gear 12 are provided with a plurality of teeth 11a, 12a on their outer peripheries, respectively. As the driving gear 11 and the driven gear 12, a spur gear (a gear with a plurality of teeth provided in parallel on the outer periphery of a cylindrical member) or a helical gear (a gear having a shape of a twisted spur gear) 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 accommodating chamber _α1 and the driven gear accommodating chamber _α2 are both circular in cross section, and the outer diameters of the driving gear 11 and the driven gear 12 are set to be slightly smaller than the diameters of the driving gear accommodating chamber _α1 and the driven gear accommodating chamber _α2 , respectively.

Of the driving gear 11 and the driven gear 12, the driving gear 11 is fixed integrally to the outer periphery of a cylindrical shaft 14. The shaft 14 is rotatably supported by the casing 13, and a rotary 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 by the outer periphery of a cylindrical shaft 15. The shaft 15 is fixed immovably to the casing 13. Therefore, when the rotary drive means is driven, the rotary shaft 14 and the driving gear 11 rotate about the rotation center line _L1 (see arrow _A1 in FIG. 3), and the driven gear 12 rotates about the rotation center line _L2 (see arrow _A2 in FIG. 3) following the rotation of the driving gear 11. The rotation direction _A1 of the driving gear 11 and the rotation direction _A2 of the driven gear 12 are opposite to each other.

When the driving gear 11 and the driven gear 12 rotate in the directions of the arrows _A1 and _A2 , respectively, the fluid (raw material _M2 ) in the fluid introduction chamber _α0 is held in the tooth grooves of the driving gear 11 and the tooth grooves of the driven gear 12, and is transferred to the fluid discharge chamber _α3 through the gap between the inner peripheral surface of the driving gear storage chamber _α1 and the outer peripheral surface of the driving gear 11 (see arrow _A3 in FIG. 3), and is transferred to the fluid discharge chamber _α3 through the gap between the inner peripheral surface of the driven gear storage chamber _α2 and the outer peripheral surface of the driven gear 12 (see arrow _A4 in FIG. 3). The fluid (raw material _M2 ) that reaches the fluid discharge chamber _α3 is discharged from the fluid discharge portion OUT and supplied to the extruder 52. The pressure (outlet pressure) of the fluid (raw material _M2 ) discharged from the fluid discharge portion OUT can be increased by increasing the rotation speed of the driving gear 11 and the driven gear 12.

However, when the viscosity of the fluid to be transported (raw material _M2 ) is low (when raw material _M2 is a low-viscosity fluid), even if the rotational speed of the drive gear 11 and the driven gear 12 is increased, the fluid (raw material _M2 ) may flow back from the fluid discharge chamber α3 to the fluid introduction chamber _α0 through the gap between the side of the drive gear 11 and the inner wall surface of the casing 13 (the inner wall surface of the drive gear accommodating chamber α1) (side clearance Cs on the drive gear 11 side in Figure 4) or the gap between the side of the driven gear 12 and the inner wall surface of the casing ₁₃ (the inner wall surface of the driven gear accommodating chamber _α2 ) (side clearance _Cs on the driven gear ₁₂ side in Figure 4) _, and the pressure of the fluid (raw material _M2 ) discharged from the fluid discharge section OUT may not increase as expected.

This is because a low-viscosity fluid (raw material _M2 ) flows from a place of high pressure to a place of low pressure, and when the drive gear 11 and the driven gear 12 are rotated, the pressure in the fluid outlet chamber _α3 becomes higher than that in the fluid outlet chamber _α0 . For the same reason, backflow of the fluid (raw material M2) can also occur through the gap between the tooth tip (apex P _T of the tooth 11a) of the drive gear 11 and the inner peripheral surface of the casing 13 (inner peripheral surface of the drive gear accommodating chamber _α1 ) (top clearance C _T on the drive gear 11 side in FIG. 3) and the gap between the tooth tip (apex P _T of the tooth 12a) of the driven gear 12 and the inner peripheral surface of the casing ₁₃ (inner peripheral surface of the driven gear accommodating chamber α2) (top clearance C _T on the driven gear ₁₂ side in FIG. 3) (see dashed arrows _A5 and _A6 in FIG. 3). In addition, backflow from the fluid outlet chamber _α3 to the fluid outlet chamber _α0 can also occur at the boundary between the drive gear 11 and the driven gear 12 (see dashed arrow _A7 in FIG. 3). Backflow of the low-viscosity fluid (raw material _M2 ) is likely to occur when the viscosity of the fluid (raw material _M2 ) is 100 mPa·sec or less. Backflow of the low-viscosity fluid (raw material _M2 ) is more likely to occur as the viscosity of the fluid (raw material _M2 ) becomes lower, such as 50 mPa·sec or less, 40 mPa·sec or less, 30 mPa·sec or less, 20 mPa·sec or less, and 10 mPa·sec or less.

In this embodiment, the side clearance C _S (FIG. 4) and top clearance C _T (FIG. 3) are both kept to 30 μm or less to prevent backflow of the fluid (raw material M ₂ ). By reducing the side clearance C _S and top clearance C _T to 20 μm or less, 10 μm or less, or 5 μm, backflow can be made even less likely to occur. There are no particular restrictions on the lower limits of the side clearance C _S and top clearance C _T , but considering the manufacture of the drive gear 11, driven gear 12, and casing 13, it is thought that they should be around 0.1 to 1 μm.

As described above, by keeping the side clearance C _S and the top clearance C _T small, even if the raw material _M2 is a low-viscosity fluid with a viscosity of 100 mPa·sec or less, the raw material _M2 can be transferred at a pressure (outlet pressure) of 5 MPa or more. It was also confirmed that the outlet pressure of the raw material _M2 can be further increased to 10 MPa or more, 15 MPa or more, by increasing the rotation speed of the driving gear 11 and the driven gear 12. The upper limit of the outlet pressure of the raw material _M2 is not particularly limited, but 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 high (for example, when it is set to 5 MPa), it is possible to achieve high volumetric efficiency (for example, 85% or more). It has also been confirmed that the volumetric efficiency of the gear pump 10 can be further increased to 90% or more, or 95% or more. However, even if the volumetric efficiency of the gear pump 10 is not very high, the outlet pressure of the raw material _M2 can be increased by increasing the rotation speed of the drive gear 11 and the driven gear 12.

Furthermore, it was confirmed that the gear pump 10 of this embodiment generates 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 _M2 can be made 5% or less (for example, when the target pressure is 5 MPa, the pulsation can be made 0.25 MPa or less). The ratio of pulsation to the outlet pressure (target pressure) of the raw material _M2 can be made even smaller, such as 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, it can be adopted for a gear pump with a discharge flow rate of 1 cc/rev class (greater than 0.1 cc/rev and equal to or less than 1 cc/rev), a gear pump with a discharge flow rate of 10 cc/rev class (greater than 1 cc/rev and equal to or less than 10 cc/rev), or a gear pump with a discharge flow rate of 100 cc/rev class (greater than 10 cc/rev and equal to or less than 100 cc/rev).

REFERENCE SIGNS LIST 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 Transverse stretching device 57 Winder 58 Hopper (for raw material _M2 )
59 Plunger pump A ₁ Rotation direction of the drive gear A ₂ Rotation direction of the driven gear A ₃ Direction of transport of raw material _M2 by the drive gear A ₄ Direction of transport of raw material _M2 by the driven gear A ₅ Direction of backflow through the top clearance on the drive gear side A ₆ Direction of backflow through the top clearance on the drive gear side A ₇ Direction of backflow through the boundary part (mesh part) between the drive gear and the driven gear L ₁ Rotation center line of the drive gear L ₂ Rotation center line of the driven gear M ₁ Raw material (high viscosity fluid)
_M2 raw material (low viscosity fluid)
C _T Top clearance between the tooth tip of the driving gear or driven gear and the inner peripheral surface of the casing C _S Side clearance between the side surface of the driving gear or driven gear and the inner wall surface of the casing IN Fluid inlet OUT Fluid outlet α ₀ Fluid inlet chamber α ₁ Driving gear accommodating chamber α ₂ Driven gear accommodating chamber α ₃ Fluid outlet chamber

Claims (3)

A drive gear that is driven to rotate;
A driven gear that meshes with the drive gear and rotates in response to the drive gear;
a casing that houses a drive gear and a driven gear;
By using a gear pump in which the side clearance between the side of the drive gear and the inner wall surface of the casing and the side clearance between the side of the driven gear and the inner wall surface of the casing are set to 30 μm or less,
A method for transferring a low-viscosity fluid, comprising transferring a low-viscosity fluid having a viscosity of 100 mPa·sec or less at a pressure of 5 MPa or more.
2. A method for transferring a low viscosity fluid according to claim 1, wherein a top clearance between the tip of the teeth of the drive gear and the inner peripheral surface of the casing, and a top clearance between the tip of the teeth of the driven gear and the inner peripheral surface of the casing are set to 30 μm or less.
A drive gear that is driven to rotate;
A driven gear that meshes with the drive gear and rotates in response to the drive gear;
A gear pump having a casing that houses a drive gear and a driven gear,
The side clearance between the side surface of the drive 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,
A gear pump capable of transporting a low-viscosity fluid having a viscosity of 100 mPa·sec or less at a pressure of 5 MPa or more.

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