JPH08303356A - Gear pump - Google Patents

Abstract

PURPOSE: To provide a gear pump having a shaft seal mechanism which has simple structure and durability, and surely prevents atmosphere from entering even in such a using condition that a suction side is vacuum. CONSTITUTION: Liquid apt to leak is pushed back in a pump inside by the first screw groove 53 provided around the outer circumference of a rotary shaft 11 and at the same time a force pushing the liquid toward the outside of the pump is acted by the second screw groove 54. An antigonism point (D) of the force acted by both screw grooves 53, 54 is ordinary raised more than an atmospheric pressure so that the atmosphere is prevented from mixing into the case main body 5 by exceeding the antagonism point (D), even when the suction port 8 side is vacuum.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a gear pump that is particularly suitable for handling high-viscosity fluids such as high molecular polymers and chemicals.

[0002]

2. Description of the Related Art A gear pump has a rotating shaft which penetrates a casing and extends from the inside to the outside. However, fluid leaks from the inside of the casing to the outside through a gap between the inside and the outside of the casing and the rotating shaft. There is a fear. For this reason, a double mechanical seal, a gland packing, a labyrinth seal, or a shaft sealing mechanism in which these are combined has been conventionally configured in this portion.

By the way, this type of gear pump is often used in a situation where the suction side is in a vacuum state. In such a case, with the exception of the double mechanical seal, the atmosphere may enter the inside of the pump through the shaft penetrating portion, and the quality may deteriorate. As a countermeasure against this, as shown in FIG. 6, a part of the high-pressure fluid existing at the discharge port 101 is guided to the atmospheric approach system path 102, and the pressure adjusting mechanism 103 is configured to maintain this portion at atmospheric pressure or higher. Is being developed. More specifically, in a general gear pump, in order to lubricate the bearing 104, a part of the fluid flowing out to the discharge port 101 is provided between the bearing 104 and the rotary shaft 105 in order to lubricate the bearing 104. After passing through the suction port 109 through the reflux groove 108 opened in the mating surface of the stuffing box 106 that forms a part of the casing and the case body 107 and the reflux hole 112 formed in the case body 107. It has a configuration of refluxing to the side. Therefore, the pressure adjusting mechanism 103 supplies the high-pressure fluid collected from the discharge port 101 through the separate flow passage 110 to the above-mentioned atmosphere entry system passage 102.
After being guided to the upper side, it is configured to return to the suction port 109 side by utilizing the reflux groove 108 and the reflux hole 112,
A pressure adjusting spool valve 111 is interposed in the flow passage 110, so that the pressure is adjusted so that the atmospheric pressure on the admission passage 102 is higher than atmospheric pressure. Since the double mechanical seal has a complete sealing portion and is not likely to enter the atmosphere, it is vulnerable to a high-viscosity fluid and is excluded here.

[0004]

By the way, the inlet of the return groove 108 is open at the mating surface of the case body 107 and the stuffing box 106, and the pressure adjusting mechanism 1 is provided.
The fluid whose pressure is adjusted by 03 flows into the reflux groove 108 after flowing on the outer periphery of the rotating shaft 105 as shown by the arrow in FIG. 7. In this case, on the circumference of the rotating shaft 105, the starting end position A of the recirculating fluid communicates with the discharge port 101 and has a positive pressure, but the end position F communicates with the recirculating groove 108 on the suction port 109 side and has a negative pressure. Often pressure. Therefore, in such a case, it is necessary to adjust the pressure of the pressure adjusting mechanism 103 to increase the amount of recirculation and adjust the pressure of the mating surfaces so that all the parts are at atmospheric pressure or higher. However, if the amount of reflux is increased indiscriminately, there are various problems that are directly related to the deterioration of pump performance, such as a decrease in volumetric efficiency, an increase in pump internal temperature, a poor lubrication of the bearing 104, and a decrease in strength of the stuffing box 106. It will cause adverse factors. For this reason, such pressure adjustment method is, in fact, extremely difficult to adjust,
There is a drawback that it is structurally complicated. In particular, the pressure at the mating surface, that is, the pressure at the point F is subtly changed depending on the pressure conditions of the suction port 109 and the discharge port 101, the viscosity of the fluid to be handled, and the like, so that the above adjustment becomes more difficult and sometimes appropriate. In many cases, it becomes impossible to set.

The present invention has been made in view of the above problems, and can reliably prevent atmospheric invasion without deteriorating the performance of the pump, and it can be used regularly such as gland packing or mechanical seal. An object of the present invention is to provide a gear pump having a shaft sealing mechanism that does not require maintenance and replacement of various consumable parts.

[0006]

In order to achieve such an object, the present invention provides a gear pump having a rotary shaft which penetrates a casing and extends from the inside to the outside, wherein a casing is provided on the outer periphery of the rotary shaft. A first for biasing the fluid existing in the gap between the inner and outer circumferences of the rotating shaft toward the inside of the casing
The screw groove and the second screw groove for urging the fluid toward the outside of the casing are formed so that the urging forces of them antagonize each other on the shaft.

[0007]

With this structure, the first screw groove on the outer circumference of the rotary shaft rotates to push the fluid in the gap between the inner and outer circumferences of the casing and the outer circumference of the rotary shaft back into the casing. At the same time, the second screw groove exerts the action of pushing the fluid in the gap between the inner and outer peripheries to the outside of the casing from the direction opposite to the pushing back direction. Then, since the competition point is set on the rotation axis, the competition point is maximized for the fluid pressure of the fluid existing in the gap between the inner circumference and the outer circumference of the casing and the rotation axis,
From here, a pressure gradient that gradually decreases toward the outside of the casing and the inside of the casing occurs. Therefore, not only can the fluid that leaks to the outside of the casing be appropriately sealed by the action of the first screw groove, but also by setting the fluid pressure at the antagonistic point to be larger than the atmospheric pressure, The atmosphere that is about to enter can be reliably prevented by the action of the second screw groove. In addition, the antagonistic point exists at a position far from the mating surface of the casing and the stuffing box, and there is no local fluid lead-in / out point in the surroundings, so this point is set along the circumferential direction of the rotation axis. A uniform pressure can be maintained.

[0008]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of the present invention will be described below with reference to FIGS.

This gear pump is used, for example, for transferring a polymer in the process of manufacturing a polymer melt such as polyester or polystyrene. As shown in FIGS. 1 to 3, the gear pump 1 includes a casing 2 and a pair of fluid feeding gears 3 and 4 that mesh with each other in the casing 2.

The casing 2 includes a cylindrical case body 5 and
The case body 5 is formed of a side plate 6 connected to one end side with a bolt not shown and a stuffing box 7 connected to the other end side with a bolt not shown. Further, a fluid suction passage 8 and a fluid discharge passage 9 are formed in the case body 5.

One gear 3 is on the drive side and has a drive gear body 10 having teeth formed on the outer periphery thereof, and the drive gear body 1
And a drive shaft portion 11 extending in both axial directions from 0. The drive shaft portion 11 is supported by a bearing 14.

The other gear 4 is on the driven side and has a driven gear body 12 having teeth formed on the outer periphery thereof, and the driven gear body 1
2 and a driven shaft portion 13 projecting from both in the axial direction. The driven shaft portion 13 is supported by a bearing 14.

A bearing 14 for supporting the drive shaft 11;
The bearings 14 that support the driven shaft portion 13 are each cylindrical and are fitted to the case body 5 and the shaft portions 11 and 13, and are joined together.

The space surrounded by the outer peripheral surfaces of the teeth of the gears 3 and 4, the inner peripheral surface of the case body 5, and the bearing 14 forms a fluid feed passage, and the gear 3 on the drive side is shown in FIG. By being driven to rotate in the direction of the arrow, the fluid is sucked from the suction port 8 and discharged from the discharge port 9 through the fluid feed passage.

Further, the gap between the side surfaces of the gear bodies 10 and 12 and the side surfaces of the bearings 14 and the gap between the outer peripheral surfaces of the shaft portions 11 and 13 and the inner peripheral surfaces of the bearings 14 are equal to each other. It is supposed to be lubricated by fluid. Therefore, each bearing 1
A lubricating groove 45 extending from the side surface facing the gear bodies 10 and 12 to the inner peripheral surface is formed in the gear 4.

The lubrication groove 45 is formed in each gear body 10, 12
The radially outer end of the portion 45a formed on the side surface opposed to is opened to the discharge port 9. (Note that Figure 2
In the above, although the lubricating groove 45 is not originally shown in the drawing according to the accurate drawing method, it is shown for convenience of description).

As a result, since the discharge side fluid has a higher pressure than the suction side fluid, a part of the feed fluid reaching the discharge port 9 passes through the lubrication groove 45 and the bearing 14 and each gear body 10,
12 flows into the gap between the side surfaces facing each other, and from there, each bearing 14
And flows into the gap between the inner and outer peripheral surfaces of the shaft portions 11 and 13 and ensures reliable lubrication. In order to recirculate the lubricating fluid to the suction side, the side plate 6 and the stuffing box 7 are formed with a groove 51 that communicates with the inside of the bearing 14, and a communication hole 52 that communicates the groove 51 and the suction port 8 is formed in the case body. 5 is formed.

One side of the drive shaft portion 11 in the axial direction is extended, penetrates through a through hole 15 formed in the stuffing box 7, and is projected to the outside of the casing 2.
This protrusion is interlocked with a drive source such as a motor (not shown).

In such a structure, the present embodiment further forms the first screw groove 53 and the second screw groove 54 on the outer periphery of the drive shaft portion 11 inside the through hole 15 of the stuffing box 7. ing. The first screw groove 53 is set at a position closer to the case main body 5 side than an intermediate point that bisects the through hole 15 of the stuffing box 7 in the longitudinal direction. It is formed on the outer circumference of the shaft located on the outer end side,
The twisting direction is the rotation of the drive shaft portion 11 (first in the present embodiment,
The direction toward the inside of the case main body 5 with respect to the fluid that is about to leak to the outside of the case main body 5 through the gap between the inner and outer peripheries of the stuffing box 7 and the drive shaft portion 11 (in the direction of arrow X in the drawing) ( This is the direction in which the force in the left direction in FIG. 1) acts. Further, the second screw groove 54 is formed on the outer circumference of the shaft portion located on the inner end side of the antagonistic point D, and the twisting direction is changed by the rotation of the drive shaft portion 11 in the X direction. Fing box 7 and drive shaft 11
The direction of exerting a force for pushing the fluid existing in the gap between the inner and outer peripheries of the fluid toward the outside of the case body 5.

With such a structure, the rotation of the first screw groove 53 on the outer periphery of the drive shaft 11 causes the fluid in the gap between the inner and outer peripheries of the through hole 15 and the drive shaft 11 to flow. The second screw groove 54 has a function of pushing back to the inside of the case body 5, and at the same time, has a function of pushing the fluid in the gap between the inner and outer circumferences to the outside of the case body 5 from a direction that opposes the pushing direction. Then, since the competitive point D is set on the drive shaft portion 11, the through hole 15
As shown in FIGS. 4 and 5 (imaginary line), the fluid pressure of the fluid existing in the gap between the inner and outer peripheries of the drive shaft 11 and the drive shaft portion 11 maximizes the competition point D, and from here, the case body A pressure gradient that gradually decreases toward the outside of 5 and the inside of the case body 5 is generated. That is, the fluid attempting to leak to the outside of the case main body 5 is prevented from flowing into the first screw groove 53.
Not only can it be properly sealed by the action of, but even if the fluid pressure at the point C located on the mating surface between the stuffing box 7 and the case body 5 becomes below atmospheric pressure as shown by the solid line in FIG. , The antagonistic point D is pressurized above the atmospheric pressure by the second screw groove 54 provided between the points C and D, so that the atmosphere trying to enter the inside of the case body 5 acts on the second screw groove 54. Can be surely prevented. Moreover, since the antagonistic point D is set at a position distant from the mating surface between the case body 5 and the stuffing box 7, at that portion, it is locally localized only at a specific phase position on the outer circumference of the drive shaft 11. The high-pressure fluid is not introduced into the device, and the return hole is not opened only at a specific transfer position. Therefore, this portion can be maintained at a uniform pressure along the circumferential direction. Further, since the mating surface between the case body 5 and the stuffing box 7 may have a negative pressure, it is not necessary to supply a large amount of high-pressure fluid to the mating surface, and the fluid from the discharge port 9 side to the suction port 8 side does not need to be supplied. It is possible to improve the volumetric efficiency and prevent the temperature rise of the pump by suppressing the amount of reflux to the minimum amount necessary only for bearing lubrication.

It is particularly desirable to make the leak flow rate slightly larger than the feed flow rate by the screw groove 53 so that the leak flow rate is as small as possible. Further, a pressure pool may be provided at the competition point D. By doing so, the operation of the present invention can be made stable.
Further, the specific configuration of each part is not limited to the above-described embodiment, and various modifications can be made without departing from the spirit of the present invention.

[0022]

As described above, the gear pump of the present invention, in order to seal the casing penetrating portion of the rotary shaft,
The first and second screw grooves are provided on the rotating shaft, and the first screw groove urges the fluid existing in the gap between the inner and outer circumferences of the casing and the rotating shaft toward the inside of the casing, and the urging force is applied. The fluid existing in the gap between the inner and outer circumferences of the casing and the rotating shaft is urged toward the outside of the casing by the second screw groove from the direction opposite to the above. Therefore, it is possible to reliably seal the casing penetration part of the rotating shaft, and even if it is used under conditions where the suction side is in a vacuum, it is possible to reliably prevent the invasion of the atmosphere through the gap at the counterpoint. can do. Therefore, according to the present invention, a labyrinth system having a structurally simple structure can be adopted as the shaft sealing mechanism to have high durability, and at the same time, a conventional fluid passage for preventing atmospheric intrusion and this By completely eliminating the need for a pressure adjusting mechanism interposed in the fluid passage, further simplification of the structure and cost reduction can be achieved, and at the same time, pressure adjusting work and manufacturing man-hours associated therewith can be eliminated. Further, there is an excellent effect that the volume efficiency can be surely improved. Further, as the volumetric efficiency is improved, the rise in pump temperature, which is harmful to polymers and the like, is reduced.

[Brief description of drawings]

FIG. 1 is an overall plan sectional view showing an embodiment of the present invention.

FIG. 2 is an overall vertical sectional view of the same.

FIG. 3 is a sectional view taken along line III-III in FIG. 2;

FIG. 4 is a sectional view of a main part of the embodiment.

FIG. 5 is an operation explanatory view corresponding to FIG.

FIG. 6 is a longitudinal sectional view of a main part showing a conventional example.

7 is a sectional view taken along line VII-VII in FIG.

FIG. 8 is an operation explanatory view corresponding to FIG. 7.

[Explanation of symbols]

 2 ... Casing 11 ... Rotating shaft (driving shaft part) 53 ... 1st screw groove 54 ... 2nd screw groove

Claims (1)

[Claims] 1. A gear pump having a rotating shaft which penetrates a casing and extends from the inside to the outside, wherein a fluid existing in a gap between an inside and an outside of the casing is provided on the outer periphery of the rotating shaft. A first screw groove for urging the fluid toward the outside of the casing, and a second screw groove for urging the fluid toward the outside of the casing are formed so that the urging forces of them antagonize each other on the shaft. Characteristic gear pump.