JP2000009051A - Gear pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a gear pump having sufficient lubrication in a side clearance between a driving gear and a side plate, regardless of largeness thereof, so as to smoothly operate for a long time. SOLUTION: At least one pair of a driving gear 9 and driven gears 5, 7 respectively engaging with the driving gear 9 are accommodated in a housing 4. A thrust load receiving mechanism 13 is provided on a driving shaft 10 which extends from the driving gear 9 and projects outward from the housing 4. Furthermore, a gap adjusting mechanism 14 for keeping a side clearance between a side face of the driving gear 9 and the housing 4 may be provided.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gear pump for high-viscosity liquids such as molten resin, and more particularly, to a lubrication deficiency in a side clearance between a drive gear and a side plate even when a pump capacity is increased. The present invention relates to a gear pump that enables long-term smooth operation.

[0002]

2. Description of the Related Art In a melt film forming machine for producing a film,
As a means for feeding and measuring the molten resin, a gear pump has conventionally been used. FIG. 4 shows an example of such a gear pump. The gear pump of FIG. 4 is configured as a three-gear type, and has two side plates 1 on both sides of a gear case 2.
3 is arranged to form a housing 4, in which a driving gear 9 and driven gears 5, 7 meshing with each other are housed, and a driving shaft 10 of the driving gear 9 and driven shafts 6, 8 and so on. When the drive gear 9 is driven, 2
The driven gears 5 and 7 rotate to suck the molten resin between the teeth and discharge the liquid to feed the liquid. In such an operation, the molten resin is drawn into the gap between the gear and the gear case (top clearance), the gap between the gear and the side plate (side clearance), and the gap between the shaft and the side plate (shaft clearance). The sliding portion of each gap is lubricated by the resin itself.

However, in recent years, as the capacity of a gear pump has been increased in order to improve the productivity of a resin film and the drive shaft has been designed to have a large shaft diameter, a lubricating portion formed by the molten resin itself has been developed. Many failures due to insufficient lubrication have been observed. In particular, the lubrication deterioration in the side clearance between the side surface of the drive gear 9 and the side plate 3 appears remarkably, and in the worst case, a trouble such as stopping the gear pump occurs.

In addition, since the wear pieces scraped from the gears and side plates are mixed into the molten resin before the gear pump stops, the filter clogging in the process is promoted to shorten the filter life, and the filter life is shortened. The wear pieces that are not caught in the film are mixed into the film, which causes the quality of the final product to deteriorate.

[0005]

SUMMARY OF THE INVENTION An object of the present invention is to solve the problem of insufficient lubrication in the side clearance between the drive gear and the side plate, regardless of the capacity of the gear pump, and to enable smooth operation for a long period of time. It is to provide a gear pump.

[0006]

A gear pump according to the present invention to achieve the above object has at least a pair of meshing drive gears and driven gears incorporated in a housing, and a drive shaft projecting from the drive gears to the outside of the housing. A thrust load receiving mechanism.

According to the results of a detailed study by the present inventors,
In the conventional gear pump as shown in FIG. 4, the drive shaft 10 moves toward the side plate 3 due to the pressure of the liquid 11 penetrating into the gap between the drive shaft 10 and the side plate 1. Side clearance (tens to hundreds of microns)
The drive gear 9 and the side plate 3 rotate without being in contact with each other due to the lubrication by the liquid material that has entered the liquid crystal. However, by increasing the diameter of the shaft with the increase in the size of the gear pump, the drive shaft
It has been found that the pressing force against the side plate 3 increases, and the lubricating film made of the liquid material between the drive gear 9 and the side plate 3 is broken, resulting in insufficient lubrication.

According to the present invention, by providing a thrust load receiving mechanism on the drive shaft as described above, the side clearance between the side surface of the drive gear and the housing is kept constant, and the liquid film is always applied to the side clearance. The lubricating property is maintained favorably by being formed, so that a long-term smooth operation becomes possible. In addition, when used for applications such as melt film forming machines, the wear pieces shaved from the drive gear and side plates do not mix into the liquid material, so the filter life can be extended and the final There is no possibility of lowering the product quality due to mixing in the molded product.

[0009]

1A and 1B show an embodiment of a gear pump according to the present invention, which is designed especially for a melt film forming machine. The illustrated gear pump is of a three-gear type. The side plates 1 and 3 and the gear case 2 constitute a housing 4 with the side plates 1 and 3 disposed on both sides of the gear case 2 respectively. The drive gear 9 and the driven gears 5 and 7 meshing with each other are housed inside the housing 4 and support the drive shaft 10 and the driven gears 5 and 7 of the drive gear 9 and the driven gears 5 and 7. ing. When the driving gear 9 is rotated, the driven gears 5 and 7 rotate, and the liquid is sucked between one tooth of one of the meshing portions and discharged from the other, and the liquid is sent.

A drive gear 9 and a drive shaft 10, and driven gears 5, 7
The gears and the driven shafts 6 and 8 may be configured such that the gear and the shaft are formed of different members and fixed to each other, or may be formed as a single body. Drive shaft 1
Reference numeral 0 protrudes outside the housing 4, and casings 12 a, 12 b and a lid 15 are attached to the housing 4 so as to cover the protruding portion. The casing 12a is fixed to the housing 4 with a port, and a sliding portion of the casing 12a is provided with a shaft seal portion 16. Further casing 1
A casing 12b is connected and fixed to the outer side of 2a with another bolt, and a thrust bearing 13 is attached to an outer end of the casing 12b, and a lid 15 is attached.

Although the outer ring of the thrust bearing 13 is movable in the axial direction without being restricted by the casing 12b, the thrust bearing 13 is axially locked to the drive shaft 10 by the stepped portion 10a. I have. The locking means of the thrust bearing 13 to the drive shaft 10 may be performed by a retaining ring fixed to the drive shaft 10 without using the stepped portion 10a as shown.

The thrust bearing 13 must move relative to the casing 12b and the lid 15, so that the thrust bearing 13
b so that the casing 1
2b and the inner diameter of the lid 15 need to be determined. In the illustrated example, the casing 12a is fixed to the side plate 3 and the casing 12b is fixed to the casing 12a. However, these casings 12a and 12b may be a structure integrated with the side plate 3.

Between the lid 15 and the thrust bearing 13,
As means for adjusting the side clearance between the drive gear 9 and the side plate 3, a gap adjusting plate 14 is incorporated.
A plurality of gap adjusting plates 14 having different thicknesses are prepared in advance, and one or several sheets are appropriately selected and assembled from these to adjust the side clearance between the driving gear 9 and the side plate 3. Can be adjusted.

In the present invention, the size of the gap adjusted by the gap adjusting plate 14 is determined by the amount by which the thrust bearing 13 (thrust load receiving mechanism) undergoes compressive strain deformation due to the maximum thrust load predicted for the gear pump. 9 and the side plates 1 and 3 on both sides are set to be smaller than the total amount of the side clearances. An opening 17 is provided between the shaft seal 16 and the thrust bearing 13. The opening 17 is provided in the casing 12b in the example shown in the drawing, and the discharge discharged from the shaft seal portion 16 is taken out from the opening 17 so that the discharge does not enter the thrust bearing 13 side.

The casing 12b has a supply port 18 and a discharge port 19 for lubricating oil. The thrust bearing 13 becomes high temperature (about 100 ° C.) during operation,
The lubricating oil and fats are thermally degraded by the heat. By providing such a lubricating oil supply port 18 and a discharge port 19, new lubricating oil and fat are supplied from the supply port 18 and used lubricating oil and fat are discharged. By discharging from the outlet 19, a good lubrication state can always be maintained.

FIG. 2 shows a gear pump according to another embodiment of the present invention. In this embodiment, as a mechanism for receiving a thrust load, a hydraulic mechanism is provided instead of the thrust bearing used in the embodiment of FIG. A partition plate 20 is fixed to a protruding portion of the drive shaft 10 extending from the housing 4 at a position corresponding to the casing 12b on the shaft, and the partition plate 20 forms two hydraulic chambers 21a and 21b in the casing 12b. , Its hydraulic chamber 2
It is a double-acting hydraulic mechanism in which hydraulic oil is supplied to and discharged from 1a and 21b, respectively. Alternatively, a single-acting hydraulic mechanism in which the hydraulic chamber 21b is formed only on one side by the partition plate 20 and hydraulic oil is supplied and discharged to the hydraulic chamber 21b may be used.

As a method of controlling the hydraulic mechanism, for example, the pressure of a liquid material applied in the shaft clearance 11 between the drive shaft 10 and the side plate 1 is detected, and a pressure larger than the pressure of the liquid material is applied to the hydraulic chamber 21b. , The thrust load due to the liquid pressure of the shaft clearance 11 can be canceled. Alternatively, the amount of movement of the drive shaft 10 in the thrust direction during operation may be detected, and the pressure of the hydraulic oil applied to both the hydraulic chambers 21a and 21b may be controlled such that the amount of movement is kept within a certain range.

As a mechanism for adjusting the side clearance between the drive gear 9 and the side plate 3, a gap adjusting plate 14 as shown in FIG. 1 may be used. Alternatively, as in the embodiment shown in FIG. The screw mechanism 22 is provided on the lid 15, and the screw mechanism 22 is tightened or loosened to thereby drive the drive shaft 1.
The movement position of 0 may be restricted. The gear pump of the present invention described above is applicable regardless of the size of the pump capacity. Particularly, when the gear pump is applied to a large-capacity gear pump of 500 cc / rev or more, the lubricating effect of the liquid film described above is remarkable. Can be demonstrated.

The gear pump of the present invention is particularly effective when used for a melt film-forming machine, but can also be applied to other extrusion molding machines such as a melt spinning machine.

[0020]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the gear pump for a melt film forming machine shown in FIGS. 1A and 1B, the shaft diameter of the drive shaft 10 was set to 95 mm. Since the predicted maximum pressure generated by the shaft diameter of 95 mm is 100 kg / cm ² , the maximum load applied to the drive shaft 10 is 7 ton. A single type thrust ball bearing was used for the thrust bearing 13. The axial displacement of the single type thrust ball bearing in the single axial direction with respect to the predicted maximum thrust load of 7 ton is about 50 microns.

By setting the total amount of side clearance between the drive gear 9 and the side plates 1 and 3 to about 110 microns, the side clearance between the drive gear 9 and the side plates 3 is maintained at least several tens of microns during operation. The thickness of the gap adjusting plate 14 was determined as follows.

In the cold state, the drive shaft 10 was pulled with a load of 2 tons, and the actual movement of the drive shaft 10 with respect to the housing 4 was measured. As a result, a movement of about 50 microns was confirmed. Since it is known that the axial deformation of the thrust bearing carrier with respect to the thrust load of 2 ton is about 22 microns, even if the load is applied up to 7 tons, the distance between the drive gear 9 and the side plate 3 is about 30 microns. It was confirmed that the gap could be maintained and no contact occurred during operation.

Actually, for example, the temperature of a gear pump for melt-spinning a polyester resin is about 300 ° C., so that the gear pump is heated to 300 ° C. in consideration of thermal expansion.
When a gap was confirmed by applying a load in the same manner as described above, it was confirmed that there was no contact between the drive gear 9 and the side plate 3. When the gear pump was continuously used in a polyester resin melt spinning machine, and disassembled and checked after about two years had passed, the side face and the side plate 3 of the drive gear 10 were not damaged at all.

[0024]

As described above, according to the gear pump of the present invention, the thrust load receiving mechanism is provided on the drive shaft, and the side clearance between the side surface of the drive gear and the housing is maintained constant, so that the capacity of the gear pump can be increased. Regardless of the method, a liquid film of a liquid material is always formed on the side clearance to maintain good lubricity, and a long-term smooth operation can be performed.

Further, since the worn pieces scraped off from the drive gear and the side plate do not mix into the liquid material, the filter life is extended when used in applications such as a melt film forming machine, and the final wear of the worn pieces is reduced. There is no possibility of lowering the product quality due to mixing in the molded product.

[Brief description of the drawings]

1A is a longitudinal sectional view showing a gear pump according to an embodiment of the present invention, and FIG.
FIG.

FIG. 2 is a longitudinal sectional view of a gear pump according to another embodiment of the present invention.

FIG. 3 is a longitudinal sectional view showing another embodiment of the gap adjusting mechanism used in the present invention.

FIG. 4 is a sectional view of a conventional gear pump.

[Explanation of symbols]

1, 3 side plate 2 gear case 4 housing 5, 7 driven gear 6, 8 driven shaft 9 drive gear 10 drive shaft 11 shaft clearance (gap) 12, 12a, 12b casing 13 thrust bearing (thrust load receiving mechanism) 14 gap adjustment plate 15 Lid 16 Shaft seal 17 Opening 20 Partition plate (Thrust load receiving mechanism) 21a, 21b Hydraulic chamber (Thrust load receiving mechanism) 22 Screw mechanism

Claims (8)

[Claims] 1. A gear pump in which at least a pair of meshing drive gears and driven gears are housed in a housing, and a thrust load receiving mechanism is provided on a drive shaft protruding outside the housing from the drive gears. 2. The gear pump according to claim 1, further comprising a gap adjusting mechanism for maintaining a constant side clearance between a side surface of the drive gear and the housing together with the thrust load receiving mechanism. 3. The device according to claim 1, wherein the amount of compressive strain deformation of the thrust load receiving mechanism based on the predicted maximum thrust load is smaller than the total amount of side clearance between the side surface of the drive gear and the housing. Gear pump. 4. The gear pump according to claim 1, wherein the thrust load receiving mechanism is a thrust bearing. 5. The gear pump according to claim 1, wherein the thrust load receiving mechanism is a hydraulic mechanism that supplies and discharges hydraulic oil to and from a hydraulic chamber divided into a partition plate fixed to the drive shaft. 6. A shaft seal portion is provided on a sliding portion of a drive shaft protruding from the housing, and an opening for taking out discharged matter is provided between the shaft seal portion and the thrust load receiving mechanism. 5. The gear pump according to any one of 5. 7. The gear pump according to claim 1, wherein the capacity of the gear pump is 500 cc / rev or more. 8. The gear pump according to claim 1, which is provided for feeding a molten resin in a melt film forming machine.