Patent Application
20090302546
The present invention relates generally to a contact, single type mechanical seal device for sealing a fluids particularly a fluid on the periphery of a rotary shaft of a pump for feeding a gas.
Conventional mechanical seal devices suffer from a leakage problem of a sealed fluid through the clearance gap formed at the periphery of the rotary shaft when providing a seal between parts of an apparatus using a chemical fluid, natural gas, hydrogen or the like, e.g., sealing a sealed fluid (operating fluid) which is present around the rotary shaft of a feeding apparatus of an automobile which feeds a combustion gas to the tank, a chemical apparatus or the like. The mechanical seal device further requires a complex construction for sealing the sealed fluid of evaporated gas within the apparatus. This creates another problem of increasing cost of the mechanical seal device. Moreover, in case of providing a seal to a sealed fluid such as chemical liquid, the mechanical seal device could be put in a danger that slide friction heat generated at the slide seal faces of seal rings thereof due to the reaction of the chemical fluid may cause an inflammation of the chemical fluid. In addition, there is a danger of malfunction of a combustion apparatus that impurities such as a lubricant or the like may get into the operating fluid (combustion gas). In recent years, the foresaid technical background has necessitated prevention of friction heat at the slide seal faces, improvement over the impurities getting into the sealed fluid through the seal faces as well as a structural simplification of the mechanical seal device.
Related prior art of the present invention is found as a mechanical seal device whose construction is shown in
The mechanical seal device 100 thus constructed is disposed within a chamber defined by the entire seal housing construction and forms a sealed fluid chamber C in the outer circumference of the rotary seal device 101. This sealed fluid chamber C allows the circulation of a lubrication fluid O which is supplied from a first passageway 121 by means of a pump, not shown, and discharged from a second passageway 122. This sealed fluid chamber C is filled with the lubrication fluid O supplied, for example a liquid lubricant. And a sealing contact formed between the first seal face 102A and the second seal face 112A separates the sealed fluid chamber C from the operating fluid chamber L. Likewise, a sealing contact formed between the third seal face 103A and the fourth seal face 113A separates the sealed fluid chamber C from the atmospheric side A.
In such a mechanical seal device 100, whether the sealed fluid chamber C may be pressurized higher or lower than the operating fluid chamber L, there is a possibility of leaking between the slide surfaces of the first seal face 102A and the second seal face 112A to the operating fluid chamber L side. When the lubrication fluid O leaks to the operating fluid chamber L, the performance as operating fluid may deteriorate. For example, in case of the lubrication fluid O getting into a combustion gas which is an operating fluid of automobile or the like, the lubricant burns together when the combustion gas burns, which causes a problem that burnt foreign matter is deposited in the operating fluid chamber L. Providing the sealed fluid chamber C with an operating fluid which is non-flammable and of the same type as the operating fluid of the operating fluid chamber L in order to circumvent the foresaid problem, will solve the combustion problem as well as the mixing problem because it is now the same fluid as the operating fluid of the operating fluid chamber L. However, it may lose a lubrication effect on the slide surfaces of the first seal face 102A and the second seal face 112A, which will in turn induce generation of frictional heat. If a malfunction or some sort further increases the frictional heat to an unexpected high temperature, a volatile operating fluid may catch fire. Also the operating fluid within the sealed fluid chamber C may leak out to the atmospheric side A from the slide surfaces of the third seal face 103A and the fourth seal face 113A. Leakage of the operating fluid to the atmospheric side A may cause an environmental damage, especially in case of combustion gas. As indicated in the patent reference 1 or patent reference 2 given below, having dynamic pressure inducing grooves decreases generation of frictional heat due to the non-contact state of the seal faces formed thereby. The operating fluid or lubrication fluid O, however, may leak to the other side from the interface of the seal faces.
Patent reference 1: Japanese Patent 2954125 Publication
Patent reference 2: Japanese Patent 3066367 Publication
Patent reference 3: U.S. Pat. No. 5,213,340, Description
The present invention is proposed for alleviating the above mentioned disadvantages, and the technical problem to be solved by the invention is to prevent a chemical fluid as a sealed fluid from leaking to a device outboard
section through a fit engagement gap between the seal housing and the rotary shaft. Another technical problem, at the same time, is to prevent a different fluid from mixing with the sealed fluid. Yet another problem is to prevent the sealed fluid from being inflamed by slide friction heat in the sliding seal faces. Yet another problem is to reduce cost of the mechanical seal device by simplifying construction thereof.
A primary object of the present invention is to solve the above mentioned technical problems, and a solution to such problems is embodied as follows.
A mechanical seal device of the present invention is a mechanical seal device for sealing an operating fluid at a clearance gap formed between a seal housing and a rotary shaft. The mechanical seal device is comprised of a stationary seal ring which is attached to a seal cover of the seal housing in a sealing relation and has a seal face, a rotary seal ring which has an opposed seal face wherein the opposed seal face is able to oppose to the seal face in a sealing contact relation, a fixed portion which retains the rotary seal ring in a sealing relation and is retained by the rotary shaft in a sealing relation and rotates with the rotary shaft in an integral relation, a seal member which is disposed to a device outboard section side away from the seal-tight contact surfaces of the seal face and the opposed seal face and provides a seal between the seal cover and the rotary shaft, a fluid chamber which reserves the lubricant formed between the seal-tight contact surfaces of the seal face and the opposed seal face and the seal member, and a supply port which supplies the lubricant to the fluid chamber, wherein a lubrication region surface is disposed in the fluid chamber side of the seal face or the opposed seal face, wherein a self-lubrication region surface is disposed in the device inboard section side, wherein an introduction port is disposed in the lubrication region surface for inducting the lubricant, wherein stopper grooves in an annular form are disposed in the self-lubrication region surface, wherein the stopper grooves stop the lubricant from the lubrication region surface.
In the mechanical seal device of the present invention, a seal face of either rotary seal ring or stationary seal ring disposes a lubrication region surface and a self-lubrication region surface therein, retains introduction ports in the lubrication region surface so as to induct the lubricant thereinto, and retains stopper grooves in the self-lubrication region surface for stopping the lubricant thereat. Therefore, sliding faces of the seal face and the opposed seal face can be lubricated with the lubricant inducted from the introduction port, and the lubricant provides a seal so as to prevent the operating fluid from leaking to the device outboard section side. Furthermore the actions of the stopper groove and the seal face effectively prevent the lubricant from leaking from the seal faces into the device inboard section side and mixing with the operating fluid. Also the lubricant trapped in the stopper groove effectively prevents the operating fluid from leaking. In addition, as the stationary seal ring is securely retained by the seal cover while the rotary seal ring is securely retained in the rotary shaft side, it is advantageous that construction thereof is made simple and assembly thereof is also made straightforward.
Described below is the details of the figures of a preferred embodiment in accordance with the principles of the present invention. All the figures explained below are constructed according to actual design drawings with accurate dimensional relations.
Further details on the mechanical seal device 1 will be given below by referring to
Device outboard A side of the inner circumferential surface 70C defines a fit engagement surface 73 for mounting a seal element 45. This fit engagement surface 73 receives the seal element 45 which sealingly contains the lubrication fluid. This seal element 45, for instance, should preferably be an oil seal. The inner circumferential surface 70C of the seal cover 70 disposes a step shoulder surface to the device inboard L side of the seal element 45 which is for fittingly mating the fit surface 20B of the stationary seal ring 20. In addition, there is disposed a supply port 75 in the seal cover 70 in the mid point between the stationary seal ring 20 and the seal element 45 which communicates the external to the fluid chamber D. This supply port 75 enables the lubrication fluid to be fed to the fluid chamber D within the inner circumferential surface 70C by means of a tank, not shown (lubrication fluid only needs to be accumulated in the tank as there is no need of pressure feed by means of a pump). Instead of having a tank, the lubrication fluid can be accumulated within the fluid chamber D. The inner circumferential surface 70C retains a plurality of fixture pins 72 in equally spaced a manner along the circumference near the hind wall of the stationary seal ring 20.
A joint surface 22 is formed in the fit surface 20B of the stationary seal ring 20 fitting the aforementioned inner circumferential surface 70C of the seal cover 70. The joint surface 22 defines a cavity portion for receiving an O-ring 41 between itself and the step shoulder surface of the inner circumferential surface 70C. Front end surface of the stationary seal ring 20 to the device inboard L side defines a seal face 24. On the opposite side of the seal face 24, the stationary seal ring 20 disposes U-shaped pin insertion bore 20A along the circumferential surface which respectively engage a plurality of the fixture pins 72. The inner circumference of the stationary seal ring 20 also defines a passageway surface 20C. The inner circumferential side of the passageway surface 20C in conjunction with the outer circumferential surface 30A of the sleeve 30 defines a portion of fluid chamber D for lubricant as well. This stationary seal ring 20 is made of a material such as silicon carbide, super hard steel, ceramics or the like.
The inner circumferential surface 30B of the sleeve 30 comes to a fit engagement with the outer circumferential surface of the rotary shaft 50. This sleeve 30 is fixed at fixture portion thereof, not shown, against the rotary shaft 50 by means of a set screw. This sleeve 30 forms a step shoulder surface on the outer circumferential surface 30A, defining a large diameter portion and a small diameter portion. Between the outer circumferential surface 30A of the sleeve 30 and inner surface 60C of the seal housing 60 there is formed an operating fluid passageway C which communicates with the device inboard section L. The sleeve 30 is made of a material such as stainless steel, brass, ferrum or the like.
Back portion of the rotary seal ring 3 opposite the opposed seal face 4 fittingly joins the step shouldered fixing surface 10A1 of the first fixed ring 10A. The first fixed ring 10A is disposed at the free end portion of the fixed portion 10 which retains the rotary seal ring 3 toward the rotary shaft 50 side. On the opposite side of the first fixed ring 10A in the fixed portion 10 is disposed a second fixed ring 10D. The first fixed ring 10A and the second fixed ring 10D are sealingly connected with each other by means of bellows 10B being made of metal. This bellows 10B has a wave-form cross-section and a resilient spring force of the bellows resiliently urges the rotary seal ring 3 to the stationary seal ring 20. The inner circumferential engagement surface 10C of the second fixed ring 10D fittingly engages the outer circumferential surface 30A of the sleeve 30. A seal between the engagement surface 10C and the sleeve 30 is provided by O-ring 42. Furthermore, the second fixed ring 10D disposes a female thread 10N which radially runs through between inner and outer diameter surfaces. A set screw 11 fastens this female thread 10N for fixing the second fixed ring 10D to the sleeve 30. The fixed portion 10 is made of material such as stainless steel, brass or the like. The O-rings 41, 42 are made of rubber-like elastic resin or rubber material with chemical liquid resistivity, for example, Nitrile Rubber (NBR), Hydrogenated Nitrile Rubber (HNBR), Polytetrafluoroethylene (PTFE), Fluoride Rubber (FKM) or the like.
The rotary seal ring 3 disposed in the fixed portion 10 can be resiliently urged by means of a coiled spring, not shown, instead of being urged by the bellows 10B. In this case, the first fixed ring 10A should form a fit engagement with the sleeve 30 in a freely slidable relation while the fit clearance should be sealed by O-ring or the like.
This mechanical seal device 1 is meant to secure respective members as described below after engaging the sleeve 30 with the rotary shaft 50. Namely, O-ring 42 is installed in the O-ring groove of the second fixed ring 10D, and the second fixed ring 10D fittingly engages the outer circumferential surface 30A of the sleeve 30. The sleeve 30 is then secured against the rotary shaft 50 by means of a set screw 11. Assembling as described installs the fixed portion 10 disposed with the rotary seal ring 3 to the sleeve 30. The stationary seal ring 20, on the other hand, fittingly engages the step shoulder surface in the inner circumferential surface 70C of the seal cover 70 after fitting the O-ring 41 to the joint surface 22. In doing so, inserting the fixture pins 72 in the pin insertion bore 20A secures the stationary seal ring 20 so as not to rotate together during the relative rotation of the rotary seal ring 3. And the seal cover 70 is assembled to the outer end surface 60A of the seal housing 60 via nut 31. The seal face 24 of the stationary seal ring 20 and the opposed seal face 4 of the rotary seal ring 3 form a seal-tight contact accordingly. As a result, not only that leakage of the operating fluid to the atmospheric region is prevented from causing pollution but also that the lubricant is effectively prevented from getting into the operating fluid and causing malfunction during the operation.
The passageway C is filled with operating fluid (sealed fluid). Then the lubricant is supplied from the supply port 75 into the fluid chamber D. Atmospheric pressure can be used as the lubricant is aimed for a lubrication effect. Therefore, unlike in conventional techniques, there is no need to pressure-feed the lubricant, which omits the necessity of having a feed facility such as a pump or the like for pressure-feeding the lubricant. Therefore a facility cost of the feed facility can be reduced. Furthermore, in case of pressure-feeding the lubricant in a conventional manner, pressure control or flow control of the lubricant becomes necessary in conjunction with the seal faces. The present invention, however, does not require a pressure monitoring and the running cost can significantly be reduced. The operating fluid inside the passageway C, on the other hand, is for process use and kept under a higher pressure than the lubricant in the fluid chamber D which is meant for lubrication purpose alone.
For example, in case of CNG booster compressor which supplies natural gas or hydrogen fuel to an automobile, since the fuel pressure becomes about 10 kg/cm.sup.2, the operating fluid (sealed fluid) as a fuel needs to be prevented from leaking outside and causing pollution. With a conventional non-contact type mechanical seal device which disposes dynamic pressure slits on seal face thereof and tolerates leakage of the sealed fluid to some extent, it is impossible to securely seal the high-pressure operating fluid. However, with the contact-type mechanical seal device 1 of the present invention, as the opposing respective seal faces 4, 24 are always kept in contact relation, it is possible to securely seal the sealed fluid (operating fluid). A problem seen in the contact type mechanical seal device 1 which is caused by a particular chemical operating fluid can be solved, for instance, by combination of introduction port 5B and stopper groove 5A which are disposed on the seal face 4 of the rotary seal ring 3. Furthermore, since the self-lubrication region surface 4A is the surface which exhibits a self-lubricating function under a sliding motion and also is disposed with the stopper groove 5A, it can prevent the lubricant from leaking and mixing with the operating fluid in the device inboard section L. Therefore an occurrence of an engine malfunction can be prevented as the result of prevention of a mixing of the lubricant with natural gas or hydrogen and a formation of carbide due to combustion of the lubricant with natural gas or hydrogen.
The mechanical seal device 1 constructed as described above operates as follows. Lubricant supplied from the supply port 75 fills the fluid chamber D. Pressure of the lubricant in the fluid chamber D is arranged lower than the pressure of the operating fluid in the passageway C. The low pressure of the lubricant may be an atmospheric pressure. And the lubricant remains on the lubrication region surface 4B between the seal face 24 and the opposed seal face 4 for providing lubrication to the sliding surfaces in order to prevent friction and abrasion of the sliding surfaces. The lubricant staying between the seal face 24 and the opposed seal face 4 comes in via fluid chamber D from the introduction port 5B which is disposed in the opposed seal face 4. In addition, when the seal face 24 and the opposed seal face 4 undergo a relative rotation, a lubricant is sucked in between the two sliding surfaces, being inducted from the introduction port 5B into the lubrication region surface 4B. This lubricant prevents heat generation at the sliding surfaces by providing lubrication to the seal face 24 and the opposed seal face 4. The lubricant, however, is stopped from leaking along the lubrication region surface 4B into the self-lubrication region surface 4A during the rotation of the seal face 24 and the opposed seal face 4 by means of stopper grooves 5A (5A1, 5A2) which are disposed on the self-lubrication region surface 4A. And as the self-lubrication region surface 4A exhibits a self-lubrication function owing to high-strength dense carbon (NC-6Mi) regardless of absence of lubricant, induction of heat generation under a sliding movement is prevented. Therefore, occurrence of a blistering phenomenon in which a sliding heat carbonizes and solidifies the lubricant oil and the like remaining on the self-lubrication region surface 4A and the carbide formed rips off the respective seal faces 4, 24, can effectively be prevented.
The pressure of the lubricant in the fluid chamber D being lower than the pressure of the operating fluid and stopper groove 5A (5A1, 5A2) disposed can securely prevent induction of impurities. And when the lubricant is trapped in the stopper groove 5A (5A1, 5A2) of the self-lubrication region surface 4A, a multiplicative effect of the lubricant and the stopper groove 5A (5A1, 5A2) not only prevents the operating fluid from leaking out to the device outboard section A but also prevents the lubricant from leaking into the device inboard section L. Furthermore, as the counterpart self-lubrication region surface 4A enjoys a self-lubrication ability, occurrence of generation of sliding frictional heat at the respective seal faces 4, 24 as well as friction and wear under a sliding motion relative to the seal face 4 can be prevented. Therefore solidifying of chemical liquid on the seal faces 4, 24 due to frictional heat generation and giving damage to the seal faces 4, 24 are effectively prevented. The above described introduction port 5B and the stopper groove 5A disposed in the rotary seal ring 3 can be disposed instead in the seal face 4 of the stationary seal ring 20, which achieves a similar effect when having a relative sliding motion to the rotary seal ring 3.
Construction and operational effect of a mechanical seal device as other embodiment related to the present invention will be described below.
In a mechanical seal device of the first invention relative to the present invention, the rotary seal ring or the stationary seal ring is made of high-strength dense carbon.
According to the mechanical seal device of the first invention, as the rotary seal ring or the stationary seal ring is made of high-strength dense carbon, the self-lubrication region is capable of self-lubricating under a sliding motion and effectively preventing a frictional heat generation despite the absence of a lubricant on the self-lubrication region. Therefore it is possible to prevent frictional heat from igniting the operating fluid for catching fire. In addition, since there is only a small amount of lubricant needed, management of the lubricant is made easier and a facility cost and running cost of the feeding facility to supply the lubricant can be reduced.
In a mechanical seal device of the second invention relative to the present invention, pressure of the lubricant in the fluid chamber is kept lower than the pressure of operating fluid.
According to the mechanical seal device of the second invention, as the pressure of the lubricant in the fluid chamber is kept lower than the pressure of operating fluid, it effectively prevents the fluid pressure from forcing the lubricant to leak to the device inboard. The lubricant also can be reserved in the fluid chamber by means of self-weight pressure and does not require a pump or the like for feeding the lubricant, thereby reducing the feeding facility cost. It also does not require pressure or flow control of the lubricant, thereby simplifying management thereof and reducing running cost thereof.
In a mechanical seal device of the third invention relative to the present invention, the lubricant in the fluid chamber is kept under atmospheric pressure.
According to the mechanical seal device of the third invention, as the lubricant in the fluid chamber is kept under atmospheric pressure, reserving the lubricant in the fluid chamber alone enables lubrication of the seal faces. Therefore a feeding facility cost for supplying the lubricant can be reduced.
In a mechanical seal device of the fourth invention relative to the present invention, the fixed portion disposes a bellows which exerts a resilient urging force to the rotary seal ring and provides a seal at the joint portion with the rotary seal ring, and the fixed portion is secured to a sleeve which securely engages a rotary shaft.
According to the mechanical seal device of the fourth invention, as the fixed portion disposing the bellows is secured to the sleeve which securely engages the rotary shaft, the mechanical seal device can be installed simply by joining the seal cover with the seal housing and securely engaging the sleeve with the rotary shaft. At the same time it also prevents a chemical liquid from causing a malfunction of the resilient urging means such as a spring disposed in the mechanical seal device. It also brings a merit of simplifying stock management and assembly of the mechanical seal device. Furthermore, for storage purpose the stationary seal ring is attached to the seal cover while the rotary seal ring is fittingly engaged with the sleeve, thus the seal face and the opposed seal face in storage being protected from damaging.
As described so far a mechanical seal device of the present invention is advantageous in that the mechanical seal device prevents impurities in the fluid chamber from mixing with the operating fluid like a chemical liquid in process and that the chemical liquid is prevented from leaking to device outboard section and causing a pollution. The mechanical seal device is also advantageous in that fabrication cost and running cost thereof is reduced.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2005-133371 | Apr 2005 | JP | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/JP2006/308520 | 4/24/2006 | WO | 00 | 10/26/2007 |
