JP2000034985A - Gear pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To prevent deterioration of quality of fluid due to heating of bearing lubrication, in a pump which is an inner bearing type and performs self- lubrication by the transferred fluid. SOLUTION: Reflux passages P1, P2 are communicated with lubrication grooves 7M, 8M of bearings 7, 8 for flowing fluid lubricating the bearings back to a suctioning port D of a pump. Cooling jackets 9, 10 are arranged on the reflux passages P1, P2. Coolant is charged into and circulated through the jackets 9, 10. After the lubrication, the fluid is cooled through the reflux passages P1, P2 to the same temperature as the suctioning port D.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gear pump used for conveying a fluid such as a high molecular weight polymer.

[0002]

2. Description of the Related Art In a gear pump used for conveying (pressurizing) a fluid such as a viscous liquid of a polymer or a molten plastic, or a fluid such as a chemical, the fluid itself is conveyed by a driving gear and a driven gear in a pump case. Therefore, a so-called self-lubrication system is adopted in which the bearings of the drive shaft of the drive gear and the driven shaft of the driven gear are lubricated. FIGS. 4 and 5 show the structure of a conventional self-lubricating gear pump. FIG.
FIG. 5 is a cross-sectional view of a part of the drive shaft 31S of the first drive shaft 31S and the driven shaft 32S of the driven gear 32, and FIG.
The cross section is shown enlarged.

This gear pump comprises a pump case 30, a drive gear 31 provided integrally with a drive shaft 31S, and a driven gear 32 provided integrally with a driven shaft 32S. The drive gear 31 and the driven gear 32 mesh with each other, and when the drive shaft 31S is driven to rotate in the direction of the arrow, the fluid on the suction port D side is extruded and conveyed to the discharge port E side. An example in which cooling jackets 34 and 35 are attached to the outside of the pump case 30 is shown. That is,
Reference numerals 36 and 37 denote covers forming a jacket, which are covered outside the pump case 30. Cooling medium is supplied to supply unit 3
It is injected from 8, 40 and discharged from the discharge units 39, 41. Normally, the fluid such as a high polymer is a high temperature, but it is necessary to keep the temperature of the entire pump within a certain range in order to prevent the fluid from being deteriorated due to a higher temperature due to rotation of the gears 31 and 32 or the like. The cooling jackets 34 and 35 are provided for this purpose.

In this gear pump, as shown in FIG. 5, a gear 31 is supported by a pump case 30 via a journal bearing 33. This bearing 33
A shaft sealing portion 42 is installed outside the shaft, and the drive shaft 31S penetrates the shaft sealing portion 42, and is connected to a rotation drive portion (not shown). As described above, in this type of gear pump, the bearing is self-lubricated by a fluid (such as a viscous liquid of a polymer or a molten plastic) that is conveyed. That is, a lubrication groove 33M is formed in the inner peripheral surface of the bearing 33 in the axial direction, and a part of the fluid to be conveyed flows into the lubrication groove 33M. The inflowing fluid enters the inner peripheral surface of the bearing 33 by the rotation of the drive shaft 31S to perform lubrication. The fluid after the lubrication is pushed outward and flows out into the space KP.

On the other hand, the pump case 30 is provided with a return passage R for returning the lubricated fluid to the suction port D side. Therefore, the fluid accumulated in the space KP is also returned to the suction port D side through the return path R under the action of the low pressure of the suction port D. This self-lubrication needs to be constantly performed with a new fluid, and the size of the lubrication groove is set so that the new fluid sequentially flows into the lubrication groove 33M.

[0006]

In the above-described self-lubrication, the liquid flowing into the lubrication groove 33M of the bearing 33 penetrates and diffuses into the inner peripheral surface of the bearing to lubricate between the bearing 33 and the drive shaft 31S. Heat is generated due to friction between the two, and the lubricating liquid (conveyed fluid) is thermally affected by the heat generation. Since the heat generation increases as the gear rotates at a higher speed, the amount of lubrication must be increased accordingly. Depending on the properties of the fluid to be conveyed, there is a case where the fluid is deteriorated or deteriorates drastically when affected by the heat generation. In particular, when the fluid has a low vapor pressure, the fluid is gasified by heat generation, cavitation occurs due to a reduction in volume, and the pump may be damaged.

In order to solve such a situation, it is necessary to reduce the heat generated in the bearing portion. However, it is directly required to reduce the speed of the rotation of the gear and thereby reduce the pressure.
However, lowering the speed and lowering the pressure necessitates carrying a predetermined volume, so that the pump must be increased in size, resulting in an increase in weight. The lowering of the pressure also requires a lowering of the pressure of the system of the entire plant, and has various problems such as various restrictions on the production of the polymer. Although it is conceivable to reduce heat generation as an external bearing method in which a bearing is provided outside the pump case 30, there is a problem that the external bearing method has a complicated structure and is expensive. An object of the present invention is to solve such a problem and to provide a gear pump which is less affected by the thermal influence of a fluid.

[0008]

SUMMARY OF THE INVENTION In order to solve the above-mentioned problems, a gear pump provided by the present invention has a recirculation passage communicating with a lubrication groove of a bearing and returning a fluid lubricated to a bearing portion to a suction port side of the pump. And cooling means for cooling the lubricated fluid. Specific examples of the cooling means include a forced cooling method in which a refrigerant is brought into contact with the periphery of the return path, and a natural cooling method in which the return path is long interposed in the atmosphere and air-cooled. The fluid lubricated by the cooling means is cooled immediately afterward, and the influence of heat generation is reduced.

[0009]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The gear pump provided by the present invention is:
FIG. 1 shows the configuration. The embodiment shown in FIG. 1 is an example of a form in which a coolant or the like is caused to flow around a return path of a lubricating fluid and is forcibly cooled, and a longitudinal section thereof is shown in the drawing. In FIG. 1, reference numeral 1 denotes a pump case, and a driving gear 2 and a driven gear 3 (not shown) meshing with each other are closely fitted inside the hollow of the pump case. D is a suction port for receiving the fluid to be conveyed, and E is a discharge port. Reference numeral 2S denotes a drive shaft to which the drive gear 2 is integrally attached, which extends through the front cover 4 and the shaft seal 6, and is connected to a rotary drive (not shown).
5 is a rear cover that seals the left side of the pump case 1,
The combination of the pump case 1, the front cover 4, and the rear cover 5 forms the appearance of the pump. The drive shaft 2S (and a driven shaft (not shown)) is supported at both ends by journal bearings 7, 8 inserted into the through hole 1K of the pump case 1, and is supported by the shaft. 7M and 8M
Are lubrication grooves formed on the inner peripheral surfaces of both bearings 7 and 8. As shown, the lubrication grooves 7M and 8M are open on the inner side to the end face of the gear 2, so that when the fluid is pushed out and conveyed by the pump action due to the rotation of the gear 2, a part of the lubrication groove is formed. It flows into 7M and 8M. Then, lubrication between the bearings 7, 8 and the drive shaft 2S is performed by this fluid. The above configuration is the same as the conventional one.

In the above construction, according to the present invention, the front cover 4 and the rear cover 5 connected to the outer sides of the two lubrication grooves 7M and 8M respectively have flow passages 4T and 4H for guiding the lubricated fluid. And 5H are drilled. The flow path 4T is formed so as to surround the drive shaft 2S, and communicates with the flow path 4H functioning as a relay path. On the other hand, the flow path 5H has a left end opening to the left end of the bearing 8, and a left end opening to the outer surface of the rear cover 5. When the pump operation is performed by the above-described configuration, the newly lubricated fluid sequentially flows inward from the inside of the lubricating fluid, so that the flow paths 4T, 4H of the front cover 4 and the flow path 5H of the rear cover 5 are formed. Will be leaked to The fluid flowing out to the flow paths 4T, 4H, and 5H is returned to the suction port D through the return paths R1 and R2 formed in the pump case 1. In the present invention, these flow paths are used. 4T, 4H, and 5H and reflux path R
1 and R2 are provided with cooling recirculation paths P1 and P2.

That is, in the figure, 9 and 10 are pipe-shaped cooling jackets, each of which has a cooling return passage P
1, P2 is inserted. Pipe-shaped cooling jacket 9
The lower end is connected to the upper surface of the front cover 4, and the upper end is connected to the opening of the return path R <b> 1 formed in the pump case 1. On the other hand, the lower part of the pipe-shaped cooling jacket 10 is connected to the left side of the rear cover 5, and the upper end is connected to the opening of the return path R <b> 2 of the pump case 1. Further, inside the two pipe-shaped cooling jackets 9, 10, the cooling return paths P1, P2 are connected to the flow path 4H and the return path R1, and the flow path 5H and the return path R2. Reference numeral 11 denotes a supply port for injecting a refrigerant into the pipe-shaped cooling jacket 9;
Is its outlet. Reference numeral 13 denotes a supply port for injecting refrigerant into the pipe-shaped cooling jacket 10, and reference numeral 14 denotes a discharge port thereof.

Since the gear pump of the present invention is constructed as described above, the fluid is conveyed by the pump operation, and at the same time, a part of the fluid flows into the lubrication grooves 7M, 8M, and the flow paths 4T, 4H and 5H to the cooling reflux path P1,
The fluid is returned to the suction port D via the return paths R1 and R2 via P2.

Therefore, in the course of flowing through the cooling return passages P1, P2, cooling is performed by the refrigerant in the pipe-shaped cooling jackets 9, 10. Of course, since the refrigerant in the pipe-shaped cooling jackets 9 and 10 is also in contact with the pump case 1, the front cover 4 and the rear cover 5, the cooling function of the entire gear pump, such as cooling these members, is also provided. The lubricated fluid having the lubrication is returned to the suction port D immediately after the lubrication. Such a forced cooling method is applied to a gear pump when the polymer temperature is high or when the solidification is performed at a certain temperature or lower. In this case, a refrigerant having a temperature slightly lower than the jacket temperature is used.

Although the present invention has been described with reference to the forced cooling system based on FIG. 1, the present invention is not limited to the forced cooling system, but also includes natural cooling, for example, an air cooling system. 2 and 3 are views showing an embodiment using the air cooling system, FIG. 2 is a view showing the gear pump in a longitudinal section, and FIG. 3 is a side view of a partial cross section viewed from AA in FIG. is there. In these drawings, the components denoted by the same reference numerals as those in FIG. 1 are the same components as those in FIG. 1 or members performing the same functions, and detailed descriptions of the functions of these components will be omitted. FIG. 2 is a longitudinal sectional view showing both the drive shaft 2S and the driven shaft 3S.
S and 3S are provided with lubrication grooves 7M and 8M, respectively. In addition, flow paths 4H and 5H for receiving the lubricated fluid are provided corresponding to the respective lubrication grooves 7M and 8M (four). 15 is a cooling jacket.

Air-cooled recirculation paths F1 to F4 for recirculating the fluids of the flow paths 4H and 5H to the suction port D side of the gear pump are provided. Since each of the air-cooled recirculation paths F1 to F4 has the same configuration, the configuration of the air-cooled recirculation path F1 will be described as a representative example.

As shown in FIG. 2, a pipe 16 is screwed into the outer opening of the flow passage 4H, and the other end thereof is connected to a pipe 17 via an L-shaped elbow 22. Further, a pipe 18 is connected to the other end of the pipe 17 via a connecting flange 23. The other end of the pipe 18 is connected to the pipe 19 via an L-shaped elbow 24.
Are connected, and the pipe 20 is further connected through an L-shaped elbow 25.
The connecting flange 26 is attached to the other end of the pipe 20. The pipe 21 further extends to the connection flange portion 26. This pipe 2
Although not explicitly shown in the drawing, the other end of 1 is connected to a return passage R3 opened to the suction port D side as shown in FIG.

As described above, the air-cooled recirculation passage F1 is formed in a bent channel shape by connecting a plurality of pipes, and the area in contact with air is increased. The two connecting flanges 2
The intervention of 3 and 26 is for maintenance and for adjusting the length of the recirculation path (additional connection of pipes between the flanges of each flange portion), and has a function of further increasing the cooling surface. . The last-stage pipe 21 of the other air-cooled return path F2 is connected to the return path R4, the last-stage pipe 21 of the air-cooled return path F3 is connected to the return path R3, and the last-stage pipe of the air-cooled return path F4. 21 is connected to the return path R4.

The gear pump employing such an air-cooled reflux passage is applied as a pump for polycarbonate by a catalyst manufacturing method. It uses methylene chloride as the solvent,
Reaction temperature around 80 °, estimated temperature rise in bearings 7 and 8 is 1
This is because the cooling purpose is about 5 °, and the purpose of cooling is to prevent cavitation due to gasification and to prevent polymer deterioration due to temperature rise.

The features of the gear pump provided by the present invention are as described above, but are not limited to the above and illustrated examples. That is, FIGS. 1, 2 and 3 are disclosed as embodiments of the present invention, but the configurations of the gear pumps in these are different from each other. In particular, the configuration of the shaft sealing device for the drive shaft 2 is different. This shaft sealing device is also different from the case of FIGS. The present invention does not depend on such a partial difference in configuration, and it can be applied to any gear pump that can be used for conveying polymer polymers, chemicals, and the like.

The cooling system according to the main part of the present invention also includes various structures other than those shown in the drawings for the forced system and the air cooling system. Certainly, the forced cooling system using the jacket is simplified and effective, but for example, forced cooling can be performed by blowing air. The blowing method has an advantage that cooling control is easy. In the case of the air cooling system, the example shown is a connection between a pipe and an elbow, etc., which has the advantage of being simple and inexpensive using a simple material.However, a modification in which cooling fins are attached to the pipe to increase the cooling efficiency Can also be considered. In this case, the length of the return path can be reduced. The present invention covers all of these modifications.

[0021]

The gear pump provided by the present invention is as described in detail above, so that it can be rotated at a high speed when conveying the same volume of fluid (polymer, etc.), so that it can be downsized compared to a conventional gear pump. Can be achieved. This provides a low cost and economical gear pump.
In addition, fluids (polymers) that could only be sent by a centrifugal pump or a gear pump of an external bearing type in order to avoid heat generation can be sent by a gear pump of an inner bearing type, thus expanding the applications. There is no possibility that the bearing may be damaged due to heat generation or the like, and the reliability is improved. Further, the problem that the polymer becomes high temperature due to the heat generated by the bearing and the viscosity is reduced to easily cause a leak is solved, and there is an advantage that the volume efficiency of the gear pump can be improved.

[Brief description of the drawings]

FIG. 1 is a diagram showing a configuration of a gear pump according to the present invention.

FIG. 2 is a diagram showing a configuration of a gear pump according to the present invention.

FIG. 3 is a diagram showing a configuration of a gear pump according to the present invention.

FIG. 4 is a diagram showing a conventional configuration.

FIG. 5 is a diagram showing a conventional configuration.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Pump case 2 ... Driving gear 2S ... Driving shaft 3 ... Driving gear 3S ... Driving shaft 4 ... Front cover 5 ... Rear cover 4T, TH, 5H ... Flow path 6 ... Shaft sealing part 7, 8 bearing 7M, 8M lubrication groove 9, 10 pipe cooling jacket 11, 13 supply port 12, 14 discharge port 15 cooling jacket 16, 17, 18, 19, 20 , 21 pipes 22, 24, 25 L-shaped elbows 23, 26 connecting flange 30 pump case 31 drive gear 31S drive shaft 32 driven gear 32S driven shaft 33 ... bearings 33M ... lubrication grooves 34, 35 ... cooling jackets 36, 37 ... covers 38, 40 ... supply parts 39, 41 ... discharge parts 42 ... shaft sealing parts D ... suction ports E ... discharge ports R, R1, R2, R3, R4 ... reflux path P , P2 ... cooling return path F1, F2, F1, F2 ... air-cooled reflux passage

Claims (1)

[Claims] A drive gear and a driven gear rotate while meshing with each other inside a pump case to convey fluid, and the conveyed fluid causes a drive shaft of the drive gear and a driven shaft of a driven gear to rotate. In a pump in which a bearing portion is self-lubricated, a lubrication groove formed in an inner peripheral surface of the bearing portion, and a return passage communicating with the lubrication groove and returning a fluid lubricated to the bearing portion to a suction port side of the pump. And a cooling means for cooling the fluid flowing through the return passage, wherein the fluid that has lubricated each bearing portion is returned to the suction port side while being cooled.