JPH068310Y2 - Gear pump shaft seal mechanism - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial field of application] The present invention relates to a shaft seal mechanism of a gas pump which is particularly preferably used for transferring a high temperature, high viscosity fluid such as molten plastic.

[Prior Art] In the gas pump used for this type of application, it is important to provide a good sealability around the shaft of the drive gear connected to the external prime mover in order to reduce the waste of the transfer liquid. . Conventionally, various types of gear seals such as a gland packing, a clearance seal, or a mechanical seal have been applied to the shaft seal mechanism of the gas shaft.

Looking at the case where the mechanical seal is used, the mechanical seal will not operate if the high-viscosity transfer liquid fills the inside, so the mechanical seal will be reversed in the seal case that penetrates the gas shaft. Adopt a double mechanical seal system to be attached to
In addition, a seal liquid whose pressure is appropriately adjusted is injected from the outside between them. Then, the seal liquid pressure that is filled and filled in the seal case is adjusted to a certain constant pressure that is always higher than the leak pressure of the transfer liquid that is expected to be applied to the mechanical seal from the pump body side. It is customary. This is to ensure that the high-viscosity transfer liquid leaks between the mechanical seals by setting the seal liquid pressure of the mechanical seal to be absolutely higher than the transfer liquid pressure that tries to leak from the pump body side. This is to prevent and permanently ensure the normal operation of the mechanical seal.

[Problems to be solved by the invention] However, in such a conventional double mechanical seal type shaft sealing mechanism, conversely, a large amount of sealing liquid leaks out and is mixed into the transfer liquid in the gas pump. To be done.
The reason for this is that, while the seal liquid pressure is constant as described above, the transfer liquid leak pressure changes greatly depending on conditions such as transfer liquid viscosity, suction, discharge pressure, and operating speed.
It is considered that the pressure difference between the seal liquid pressure between the mechanical seals and the leak pressure of the transfer liquid becomes excessive depending on the pump operating conditions.

In this case, if the transfer liquid and the seal liquid are the same, there is no problem, but in the case where the reaction proceeds with the progress of time and temperature, such as a polymer, the seal liquid is a stable and dedicated exclusive liquid separately from the transfer liquid. Since it is usual to use the liquid, if the seal liquid is mixed in the gas pump, the purity of the transfer liquid is lowered, and the quality of the product using the transfer liquid as a raw material is adversely affected.

The present invention pays attention to such a problem, and particularly in the case of using the double mechanical seal, it is possible to minimize not only the leakage of the transfer liquid but also the leakage of the sealing liquid. The present invention provides a shaft seal mechanism for a gap pump.

[Means for Solving the Problems] In order to achieve such an object, the present invention provides a shaft sealing mechanism applied to a portion where a gear shaft of a gear pump for transferring a transfer liquid extends from a pump main body, wherein A seal case formed by penetrating the shaft, a pair of mechanical seals arranged in the seal case with a distance in the axial direction, and a seal case for opening the seal case and injecting a seal liquid between the mechanical seals. Equipped with an inlet, a pressure detector that measures the leak pressure of the transfer liquid applied to the mechanical seal from the pump body side, and a pressure detector that measures the liquid pressure of the seal liquid injected between both mechanical seals. Therefore, based on the detection values of both pressure detectors, the hydraulic pressure of the seal liquid can be kept relatively higher than the leak pressure of the transfer liquid by an amount corresponding to the optimum differential pressure. To do.

[Operation] When the pressure sensor is provided inside and outside the double mechanical seal as described above, the seal liquid pressure and the transfer liquid leak pressure are measured, and the differential pressure between the two is constantly detected during operation. Can be monitored. Therefore, if an abnormality occurs in the differential pressure value between the two due to changes in pump operating conditions (including both excessive and excessive pressure), control the amount of sealing liquid and sealing liquid injection pressure into the seal case. Then, it can be adjusted to maintain the optimum differential pressure condition (usually ² to 3 kg / cm ² ), which prevents leakage of the transfer liquid from the pump body side into the mechanical seal and at the same time It is possible to constantly minimize the amount of leaked into the pump body.

[Embodiment] An embodiment shown in FIGS. 1 to 3 will be described below.

First, the main body of the gear pump will be briefly described. The pump main body I includes a drive gear 1 and a driven gear 2 in which the shaft portions on both sides of the pump body I are rotatably supported by bearings 5a, 5b, 6a, 6b. It is configured to be meshed with each other, a suction port 7 is opened on the tooth tip separating side, and a discharge port 8 is opened on the mating side, and both open ends are covered with a front cover 3a and a rear cover 3b.

The drive gear 1 includes a gear shaft 4 connected to the front cover 3a side.
Is penetrated through the front cover 3a and extended to the outside, and is driven by an input torque transmitted to the shaft 4 from an external prime mover (not shown). Further, in the front cover 3a, double mechanical seals 10A and 10B are mounted on the gear shaft 4 in order to seal the transfer liquid which is about to leak from the pump body I side through the gap between the gear shaft 4 and the bearing 5a. The seal case 9 is continuously provided. In this gear pump, in order to prevent the high pressure of the pump body I from being applied to the end portion of each gear shaft and the seal case 9, as shown in FIG. 1, the front cover 3a and the rear cover 3b are respectively circulated. Grooves 11a and 11b are provided, and the case 13 has a circulation hole 12 for communicating the circulation grooves 11a and 11b with the suction port 7.
a and 12b are provided.

The seal case 9 penetrates the gas shaft 4 inside and seals the outer opening of the gas shaft 4 with a case lid 9a. The seal case 9 has two mechanical seals 10A and 10B arranged on the gas shaft 4 in opposite directions. I wear it heavily. Both mechanical seals 10A and 10B have a common structure that is known per se, and the mechanical seal 10B on the inner end side prevents the transfer liquid from leaking from the pump body I side and the mechanical seal on the outer end side. The mechanical seal 10A plays a role of preventing the seal liquid from leaking to the outside. Referring to FIG. 1, one mechanical seal 10B will be described more specifically. A floating sheet 10a supported by a seal case 9 via an O-ring and a seal ring 10b abutting on the floating sheet 10a.
An O-ring 10c wound around the gas shaft 4, a compression ring 10d sandwiching the O-ring 10c between the seal ring 10b, and a coil spring 10e for urging the compression ring 10d toward the floating seat 10a. It is equipped with the elements of.

The outer mechanical seal 1 is attached to the seal case 9 that houses the double mechanical seals 10A and 10B.
A sealing liquid inlet 13A is opened in the vicinity of 0A, and a sealing liquid extraction port 13B is opened in the vicinity of the inner mechanical seal 10B, and the sealing liquid is injected from a supply source (not shown) as shown by an arrow a to seal. The space between the mechanical seals 10A and 10B in the case 9 is filled with the seal liquid, and is extracted and circulated as indicated by an arrow b.

Therefore, in such a double mechanical seal type shaft sealing mechanism, the front cover 3a and the seal case 9 are
The pressure detectors 14 and 18 for measuring the liquid pressure are respectively provided at two positions of the portion. In the pressure detector 14, the pressure guiding pipe 16 is inserted into the pressure outlet port 15 provided in the front cover 3a to face the gap 17 between the gas shaft 4 and the front cover 3a, and the inner mechanical seal 10B from the pump body I side.
The leak pressure P _out of the transfer liquid applied to the pipe is measured. Also,
The pressure detector 18 is a pressure lead-out port 19 provided in the seal case 9 at an intermediate position between the mechanical seals 10A and 10B.
Similarly, the pressure guide tube 20 is inserted and attached, and the seal fluid pressure P _in injected between the mechanical seals 10A and 10B of the seal case 9 is measured.

The pressure detectors 14 and 18 may be integrally mounted on the front cover 3a or the seal case 9 as shown in FIG.

As described above, the two pressure detectors 14 and 18 are provided, and the leak pressure P _out of the transfer liquid and the seal liquid pressure P _in can be measured. Therefore, the pressure on both sides of the seal portion of the inner mechanical seal 10B is sandwiched. The gap pump can be operated while constantly detecting and monitoring the differential pressure ΔP (P _in −P _out ).

Therefore, when the differential pressure ΔP deviates from the above-mentioned optimum condition due to the pump operating conditions, the optimum differential pressure condition can be adjusted by the control means such as controlling the injection condition of the seal liquid as described above. Is too large to leak the seal liquid to the pump main body I side, and conversely, too small to leak the transfer liquid between the mechanical seals, which can be effectively prevented. At that time, not only the necessary differential pressure detection mechanism and the variable seal liquid injection mechanism, but also both can be systematically controlled automatically. In addition, as the pressure difference between the seal liquid pressure and the transfer liquid leak pressure is converged to a constant value in this way, the adverse effect resulting from the previous setting of the internal pressure of the seal case to an unexpectedly high value is expected. Is also canceled. Specifically, the design pressure of the mechanical seal can be lowered, so that a more compact one can be used, and since the minimum necessary pressure is applied to the seal portion, the service life is extended.

Next, an improved embodiment of the present invention will be described. For example, when the transfer liquid of the gas pump is a high molecular weight polymer, it is recognized that the viscosity change with respect to the temperature change is considerably large. Therefore, if a temperature detector is attached to the seal part of the mechanical seal and a liquid temperature control means for the seal liquid is provided at the seal part so as to develop the optimum liquid viscosity and temperature, it is even more effective in enhancing the sealing effect. It will be a measure.

In addition, in order to maintain the purity of the transfer liquid and thoroughly implement quality control,
It is effective to install a system that monitors the amount of returned liquid relative to the amount of seal liquid supplied. That is, if this system is added, the leak amount of the seal liquid into the pump body can be directly grasped from the value.

[Advantage of the Invention] As described above, according to the present invention, the pressure detector is provided so that the differential pressure inside and outside the mechanical seal can be detected, so that the optimum differential pressure condition can be satisfied. In addition, it is possible to prevent the transfer liquid from entering the mechanical seal, and at the same time, to minimize the inconvenient leakage of the seal liquid to the pump body side. As a result, the deterioration of the purity of the transfer liquid sent by the gas pump is reduced, and at the same time, the mechanical seal used in the shaft sealing mechanism is made compact and the life is extended.

[Brief description of drawings]

1 to 3 show an embodiment of the present invention. 1 is a cross-sectional view showing the main body of the pump and its shaft-sealing mechanism, which corresponds to a cross-section taken along the line BB of FIG. 2 (for convenience, the shaft-sealing mechanism is shown with a 90 ° phase shift in the illustrated direction). is doing. FIG. 2 is a front view of the gap pump. FIG. 3 is a cross-sectional view of the gap pump main body and corresponds to a cross section taken along the line AA of FIG. FIG. 4 is a partial cross-sectional view of a seal case and the like showing a modification of the mounting mode of the pressure detector. I ... Pump main body, 1 ... Drive gear 3 ... Gear case, 4 ... Gas shaft 3a ... Front cover, 3b ... Rear cover 5a, 5b, 6a, 6b ... Bearing 7 ... Suction port, 8 ... Discharge port 9 ... Seal case, 9a ... Case lid 10A, 10B ... Mechanical seal 13A ... Injection port, 13B ... Extraction port 14,18 ... Pressure detector, 17 ... Gap 15,19 ... Pressure derivation port 16,20 ... Pressure pipe

Claims (1)

[Scope of utility model registration request] 1. A shaft sealing mechanism applied to a portion where a gas shaft of a gas pump for transferring a transfer liquid extends from a pump body, wherein a seal case is formed by penetrating the gas shaft, and a seal case is provided in the seal case. A pair of mechanical seals arranged at a distance in the axial direction, an inlet for opening the seal case to inject a seal liquid between both mechanical seals, and a transfer liquid added to the mechanical seal from the pump body side. It is equipped with a pressure detector that measures the leak pressure and a pressure detector that measures the liquid pressure of the seal liquid injected between both mechanical seals. A shaft seal mechanism for a gear pump, characterized in that the liquid pressure can be kept relatively higher than the leak pressure of the transfer liquid by an amount corresponding to an optimum differential pressure.