JPS6222028B2 - - Google Patents

Description

[Detailed description of the invention]

The present invention provides a mechanical seal in which a stationary sealing ring and a rotating sealing ring are brought into sliding contact with each other at their sealing end surfaces.
The present invention particularly relates to a mechanical seal suitable for sealing high-load sealing fluids. The load limit acting on the sealed end face of a mechanical seal is determined as the product of the load force P acting on the sealed end face and the circumferential speed V at the sealed end face, the so-called PV value. Generally, the peripheral speed V takes a predetermined value, so the load force P acting on the sealed end face cannot exceed a certain value depending on the load limit PV value. In other words, in conventional mechanical seals,
The pressure relationship acting on the sealed end surface S without the spring force is schematically shown in FIG. 1. That is, the force P _p that opens the sealed end surface S and the pressing force P _c are approximately expressed by equations (1) and (2), respectively. P _p = 1/2 _{A p1} ...(1) P _c = B _p1 ...(2) Here, p ₁ is the sealing fluid pressure, A is the area of the sealed end surface S, A = π/4 (D ₂ ² −D ₁ ² ) B is the pressing area due to p ₁ acting on the sealed end surface S, B = π/4 (D ₂ ² −D ₃ ² ) And, in order to maintain the sealing function, normally, in the case of a mechanical seal, P The configuration is such that _c > P _p . Therefore, the load force P generated on the sealed end surface S
is expressed by equation (3). P=P _c -P _p =B _P1 -1/2A _p1 = (K-1/2)A _p1 ...(3) Here, K is called the balance ratio, and K=B/A It is indicated by. This equation (3) was the basic theory and way of thinking of conventional mechanical seals. Therefore, in the conventional mechanical seal, the load force P shown in equation (3)
is fixedly determined by the balance ratio K=B/A, and as the pressure of the fluid increases, the load force P applied to the sealed end surface S increases accordingly.
As described above, conventional mechanical seals are determined by the load limit PV value acting on the sealing end surface S, and are therefore unsuitable for sealing the sealing fluid under high load conditions. The present invention was made in view of the above-mentioned circumstances, and
The purpose of this is to reduce the load force acting on the sealed end face without being affected by the pressure of the sealing fluid, thereby significantly expanding the usable limit range based on the PV value. It is intended to provide a seal. In order to achieve the above object, the present invention provides a mechanical seal in which a stationary sealing ring and a rotating sealing ring are brought into sliding contact with each other at annular sealing end surfaces having an inner diameter D ₁ and an outer diameter _{D 2 .} is formed facing the sealed end surface, and faces the back side of one of the sealing rings that applies a load force to the sealed end surface,
A pressure that is independent of the main sealed chamber and has a maximum pressure receiving diameter D ₄ toward the main sealed chamber side that is larger than the outer diameter D ₂ of the sealed end surface and a minimum pressure receiving diameter D ₃ that is smaller than the outer diameter D ₂ of the sealed end surface. A sub-sealed chamber of p ₂ is formed, the pressure p ₂ is lower than the pressure p ₁ , and the load force P' acting on the sealed end face due to the pressures p ₁ and p ₂ is P'=π/ 4(D ₂ ² −D ₃ ² )p ₂ −1/2・π/4(D ₂ ² −
The gist is a mechanical seal characterized by being expressed by the following formula: D ₁ ² )p ₁ −π/4(D ₄ ² −D ₂ ² )(p ₁ −p ₂ ). Hereinafter, the present invention will be explained based on FIGS. 2 to 4. FIG. 2 shows an embodiment of a mechanical seal to which the present invention is applied, and in FIG. 2, X indicates the atmosphere side and Y indicates the sealing liquid side sealed by the mechanical seal of the present invention. ing. And 1 in the same figure
is a seal housing, a rotary shaft 2 is inserted through the center of the seal housing 1, and the mechanical seal of the present invention is installed in an annular space 3 between the rotary shaft 2 and the seal housing 1. Below, this mechanical seal will be explained in detail.
5 is a stationary sealing ring, and 5 is a rotating sealing ring.
A and 5a are in sliding contact. And stationary sealing ring 4
is held by a seal ring retainer 6 which is attached by shrink fitting, for example, so as to cover its outer periphery and back surface, and is interposed between a flange portion 6b of this seal ring retainer 6 and a fixing member 7. A predetermined pressing force is applied between the sealed end surfaces 4a and 5a by the coil spring 8 in a compressed state, and the cylindrical shaft portion 6a of the seal ring retainer 6
The inner cylindrical portion 7a of the fixed member 7 is interposed with an O-ring packing 9 and a back-up spring 10 to allow movement in the axial direction, but is held so as not to wobble in the radial direction. 7 is fixed to the seal housing 1 by bolts 11 with O-ring gaskets 12 and 13 interposed therebetween. Further, the rotary sealing ring 5 includes a small diameter portion 2a of the rotary shaft 2.
The rotating sealing ring 5 is fitted and fixed on the outer periphery with a key 14 interposed therebetween, and includes a sleeve 16 fitted onto the outer periphery of the small diameter portion 2a of the rotating shaft 2 with an O-ring gasket 15 interposed therebetween; By tightening the nut 17, which is located outside the sleeve 16 and is threaded onto the threaded portion 2c of the rotating shaft 2, between the sleeve 16 and the stepped portion 2b formed by the portion 2a, it is prevented from coming off in the axial direction. ing. A main sealed chamber 18 is formed in the seal housing 1 facing the sealed end surfaces 4a and 5a, and a main sealed chamber 18 is formed in the seal housing 1.
A sealing liquid flow path 19 is formed which communicates with 8. Also, of the sealing rings 4 and 5, the sealing end face 4
A sub-sealed chamber 20, which is independent of the main sealed chamber 18, is formed facing the back side of one of the sealing rings, that is, the stationary sealing ring 4, which applies a load force to a and 5a. That is, this sub-sealed chamber 20 is
By interposing the O-ring packing 21 between the inner surface of the outer cylinder portion 7b that is fitted to the inner surface of the seal housing 1 with the O-ring gasket 13 interposed therebetween and the outer surface of the flange portion 6b of the seal ring retainer 6, It is surrounded by O-ring gaskets 9 and 21, a seal ring retainer 6, and a fixing member 7. A pressure regulating fluid passage 22 communicating with the auxiliary sealed chamber 20 is formed through the seal housing 1 and the outer cylindrical portion 7b of the fixing member 7, and the pressure p ₂ in the auxiliary sealed chamber 20 is adjusted through this pressure regulating fluid passage 22. , the pressure of the sealing fluid in the main sealed chamber 18 is controlled to be lower than the pressure _p1 by a predetermined amount. In addition, in FIG. 1 showing the pressure distribution acting on the sealed end surface S of a conventional mechanical seal, and FIGS. 2 and 3 showing an embodiment of the present invention,
D ₁ and D ₂ are the inner and outer diameters of the sealed end surface 4a, D ₃ is the pressure receiving diameter of the O-ring packing 9 portion which is the minimum pressure receiving diameter toward the main sealed chamber 18 side in the sub sealed chamber 20, and D ₄ is the pressure receiving diameter of the sub sealed chamber 20. This is the pressure receiving diameter of the O-ring packing 21 portion which is the maximum pressure receiving diameter toward the main sealed chamber 18 side at 20. The pressure relationship acting on the sealed end faces 4a, 5a of the mechanical seal according to the present invention shown in FIG. 2 is schematically shown as shown by the solid line in FIG. 3. The two-dot chain line portion in FIG. 3 is the pressure relationship in FIG. 1, and is shown for comparison. Based on this FIG. 3, the opening force P _p ', pressing force P _c ', and load force P' acting on the sealed end faces 4a, 5a of the mechanical seal according to the present invention are expressed by equations (4) and (5), respectively. , as shown in equation (6). P _p ′=1/2A _p1 +C _p1 ...(4) P _c ′=B _p2 +C _p2 ...(5) P′=P _c ′−P _p ′=B _P2 −1/2A _p1 −C _{(p1 -p2)} ...(6) (However, A = π/4 (D ₂ ² - D ₁ ² ), B = π/4 (D ₂ ² - D ₃ ² ), C = π/4 (D ₄ ² -D ₂ ² )) In the mechanical seal according to the present invention configured as described above, first, the rotating sealing ring 5 rotates due to the rotation of the rotating shaft 2, and the stationary sealing ring 4 is connected to the seal ring retainer. The stationary seal ring 4 and the rotary seal ring 5 are fixed to the seal housing 1 through the seal housing 1 through the seal housing 1 and the fixed member 7.
A and 5a are in sliding contact and perform a sealing action, thereby preventing liquid leakage from the main sealed chamber 18 on the sealing liquid side Y to the atmosphere side X. As described above, the present invention provides a stationary seal that faces the sealed end faces 4a, 5a to form the main sealed chamber 18, and that applies a load force to the sealed end faces 4a, 5a of both the seal rings 4, 5. A sub-sealed chamber 20 facing the back side of the ring 4 and independent of the main sealed chamber 18
, and the pressure p ₂ in the sub-sealed chamber 20 is lower than the sealing liquid pressure p ₁ in the main sealed chamber 18 by a predetermined amount, so that the first and second terms of equation (6) above are satisfied. p 1 = p _{2 by the rate by which the pressure p 2} decreases in the term p ₁ = p ₂
Load force is reduced compared to conventional mechanical seals. In addition, the main sealed chamber 18 of the sub sealed chamber 20
The maximum pressure receiving diameter D ₄ on the side is the sealed end surface 4a, 5a.
Since the outer diameter D ₂ of the main sealed chamber 18 and the pressure of the sub-sealed chamber _{20 are larger than the outer diameter D 2} of the main sealed chamber 18 and the minimum pressure receiving diameter D ₃ is larger than the outer diameter D ₂ of the sealed end surfaces 4a and 5a.
An area expressed by C = π/4 (D ₄ ² - D ₂ ² ) is formed which is subjected to a differential pressure of p ₂ , and as a result, the third term of equation (6) representing the load force P' mentioned above is , −C(p ₁ −
p ₂ ) can be generated. Due to the existence of such a load adjustment term, the pressure _p1 in the main sealed chamber 18, that is, the load force P' when the sealed fluid pressure is the same, is significantly reduced compared to the case where the load adjustment term does not exist. be able to. Conversely, in equation (6) above, the load force is the same as the load force when there is no load adjustment term.
The pressure p ₁ when obtaining P' can be made significantly larger than the pressure p ₁ when no load adjustment term exists. For this reason, the mechanical seal of the present invention can significantly expand the usable limit range based on the PV value, which has been considered a limit up to now, and can be applied to sealing liquids with high p ₁ pressures to improve their reliability (stability). ) can be significantly improved. Next, the effects of the mechanical seal of the present invention will be explained using examples. The conditions of the mechanical seal of the present invention in this example are as shown in Table 1.

[Table] The conditions in Table 1 above are sealing conditions that cannot be achieved with the current technical level of mechanical seals, and the current market level is a p ₁ V value of 1500 kgf/cm ² m/sec. However, in the mechanical seal of the present invention, pressures p ₁ and p ₂ act as shown by the solid line in FIG. 3, and by setting p ₁ > p ₂ , the intended purpose can be fully satisfied. The implementation results were obtained. Fourth
The figure shows a plot of the actual measurement results. In this Fig. 4, the horizontal axis is the differential pressure △p (=p ₁ −
p ₂ ) is displayed on an equally spaced scale, and the vertical axis is the actual measured value of the leakage amount on a logarithmic scale. In the same figure,
The broken line F is the value at which the load force P' becomes zero at △ _p = 0.74 kgf/cm ² , that is, the theoretical leakage point, and the broken line E shows the value at which the load force P' becomes p ₁ V of the conventional mechanical seal.
It shows the differential pressure Δp value 0.48 kgf/cm ² when it becomes equal to the value 1500 kgf/cm ² m/sec, and therefore p ₁ V
When the value is 3080kgf/ ^cm2・m/sec, △p=
0.48kgf/cm ² , that is, p ₁ = 40kgf/cm ² , so p ₂
= 39.52kgf/cm ² , p ₁ V value 1500kgf/
This means that the load can be reduced to the same load condition as cm ² m/sec. In this case, if the specifications allow a large amount of leakage, Δp may be gradually increased in the direction of arrow _G2 , and if leakage is desired to be reduced, Δp may be decreased in the direction of arrow _G1 . In addition, in the above embodiment, the O-ring packing 9,
Although the sub-sealed chamber 20 is formed with 21, the present invention is not limited thereto, and the present invention can be practiced even if the sub-sealed chamber is formed with, for example, a metal bellows or the like. Furthermore, in the above embodiments, it goes without saying that the present invention can also be applied to a mechanical seal in which one sealing ring 4 is rotated and the other sealing ring 5 is stationary.

[Brief explanation of the drawing]

Fig. 1 is an explanatory diagram showing the pressure relationship acting on the sealed end face of a conventional mechanical seal, Fig. 2 is a longitudinal sectional view showing an embodiment of the present invention, and Fig. 3 is an explanatory diagram showing the pressure relationship acting on the sealed end face in Fig. 2. An explanatory diagram showing the pressure relationship,
FIG. 4 is a diagram showing the results of implementing the present invention. 1... Seal housing, 2... Rotating shaft, 4...
...Stationary sealing ring (one sealing ring), 4a... Sealing end face of stationary sealing ring, 5... Rotating sealing ring, 5a... Sealing end face of rotating sealing ring, 6... Seal ring retainer, 7... Fixed member , 9... O-ring packing,
18... Main sealed room, 20... Secondary sealed room, 21...
O-ring seal, p ₁ ... Sealing fluid pressure in the main sealed chamber, p ₂ ... Pressure in the sub-sealed chamber, X... Atmospheric side, Y
...Sealing liquid side.

Claims (1)

[Claims] 1. The stationary sealing ring and the rotating sealing ring have an inner diameter D ₁ and an outer diameter.
In a mechanical seal formed by sliding contact between annular sealed end faces of D ₂ , a main sealed chamber with a pressure p ₁ is formed facing the sealed end faces, and a load force is applied to the sealed end faces of both seal rings. Facing the back side of one sealing ring, it is independent from the main sealed chamber, and the maximum pressure receiving diameter D ₄ to this main sealed chamber side is the outer diameter D ₂ of the sealed end face.
A sub-sealed chamber with a pressure p 2 larger than the above and a minimum pressure receiving diameter D ₃ smaller than the outer diameter _{D 2} of the sealed end surface is formed, and the pressure p 2 is lower than the pressure p ₁ , so that a The load force P' exerted by the pressures p ₁ and p ₂ is P' = π/4 (D ₂ ² - D ₃ ² ) p ₂ -1/2・π/4 (D ₂ ² - D ₁ ² ) A mechanical seal characterized in that it is expressed by the following formula: p ₁ −π/4(D ₄ ² −D ₂ ² )(p ₁ −p ₂ ).