CN105386972A - Screw vacuum pump of motive seal structure - Google Patents

Abstract

The invention discloses a screw vacuum pump of a motive seal structure. The screw vacuum pump comprises a pump body, a front end cap, a rear end cap, a shaft and a rotor. A sealing mechanism is arranged between the shaft and the front end cap. The sealing mechanism further comprises a cooling casing pipe. A cooling channel is arranged in the cooling casing pipe. The cooling channel is filled with a cooling medium so as to prevent heat from transferring along an axial shaft seal part from the rotor, and thus the working temperature of a mechanical sealing assembly is lowered. The friction pair surface of a sealing static ring of the sealing mechanism is subjected to surface texture treatment so as to effectively reduce the surface abrasion of a friction pair and reduce temperature rise of the end face of the friction pair; meanwhile, a heat insulating layer, formed between the shaft and the rotor, of the cooling casing pipe is used for preventing the heat from transferring to an exhaust end shaft seal, and the working environment of a shaft seal component is improved, so that the service life of the seal assembly is prolonged.

Description

A kind of screw vacuum pump with movable sealing structure

Technical field

The invention belongs to technical field of vacuum, be specifically related to a kind of screw vacuum pump.

Background technique

Screw vacuum pump belongs to non-contact type dry pump, it is a kind of desirable vacuum pump occurred phase early 1990s, with its pumping speed wide ranges, simple and compact for structure, pumping chamber element without friction, the life-span is long, energy consumption is low, be used widely in industries such as microelectronic, semiconductor, pharmacy, precision machining without advantages such as oil pollutions.Domestic screw vacuum pump is through vicennial fast development, and its main performance index (as pumping speed, ultimate pressure, energy consumption, zero delivery compression ratio, pressure reduction) all reaches or close to Foreign Advanced Lerel; But pump operation stability, operational safety and external advanced pump still gap are comparatively large, and its dynamic sealing technology is one of major influence factors, become the key issue that current domestic screw pump market faces in working life of the reliability and Sealing that how to improve sealing.Screw vacuum pump working procedure be divided into air-breathing, etc. hold conveying, compression, exhaust Four processes, gas temperature can be made sharply to raise in the process of compression and exhaust, cause the temperature of exhaust end rotor and axle higher, under black box is in the bad working environments of high temperature and high speed, and traditional mechanical seal dynamic and static ring directly contacts, make black box rapid wear, working life reduces greatly.

Summary of the invention

In order to solve the mechanical sealing assembly Problems existing of the screw vacuum pump that high temperature and high speed runs, improving the working life of screw vacuum pump, the invention provides a kind of screw vacuum pump with movable sealing structure.

A kind of screw vacuum pump with movable sealing structure comprises the pump housing 21, front cover 3, rear end cover, axle 1 and rotor 2; The side radial direction of the described pump housing 21 is provided with air inlet port, and described front cover 3 and rear end cover are fixed at the axial two ends of the pump housing 21 respectively; The side radial direction of described front cover 3 is respectively equipped with exhaust port and cooling medium entrance; The side radial direction of described rear end cover is provided with cooling medium outlet; Described rotor 2 is sheathed to be fixed on axle 1, and rotor 2 is positioned at the pump housing 21; One end of described axle 1 is fixed in rear end cover, and it is outside that the other end extends front cover 3, is provided with sealing mechanism between axle 1 and front cover 3; Described sealing mechanism comprises stationary seal ring 6 and moving sealing ring 7, and described moving sealing ring 7 is arranged with spring, and moving sealing ring 7 is fixed on axle 1 by Cock screw;

Described sealing mechanism also comprises cooling collar 4; Axial one end of the rotor 2 corresponding with sealing mechanism is sleeve pipe step hole, and making has toroidal cavity between rotor 2 and axle 1;

The jacket pipe that described cooling collar 4 is closed for the open at one end the other end, the cavity between the inner tubal wall of described jacket pipe and outer tube wall is the cooling channel 9 of ring-type; The open-mouth end of cooling collar 4 is fixedly connected the axial inner ends face of front cover 3, and the close mouth end of cooling collar 4 is positioned at the sleeve pipe step hole of rotor 2;

Described cooling channel 9 is communicated with the cooling chamber 10 in front cover 3, is provided with cooling medium in cooling chamber 10, realizes forming heat insulation layer between axle and rotor, and blocking temperature axially stationary seal ring 6 and moving sealing ring 7 place transmits;

Uniformly on the surface of friction pair 14 of the stationary seal ring 6 corresponding with moving sealing ring 7 offer micropore 15, described micropore 15 is blind hole, and micropore 15 provides lubricant oil as micro-oil storage pool to surface of friction pair.

The structure of further optimization is as follows:

The surface of the axle 1 adjacent with described sealing mechanism is provided with labyrinth seal groove 19.

The second seal ring 18 and the 3rd seal ring 20 is respectively equipped with between the open-mouth end of cooling collar 4 and the axial inner ends face of front cover 3.

The external cylindrical surface of described cooling collar 4 is provided with outside thread 13, forms spiral seal between described outside thread 13 and the collar aperture of rotor 2.The rotation direction of described outside thread 13 is contrary with the rotation direction of rotor 2.

The inner cylindrical surface of described cooling collar 4 is provided with internal thread 12, forms spiral seal between described internal thread 12 and axle 1; The rotation direction of described internal thread 12 is identical with the rotation direction of rotor 2.

Described micropore 15 is square hole, and radially uniform, and the density of radial uniform micropore 15 on surface of friction pair 14 surface is 20% ~ 25%.The hole depth of described micropore 15 is 0.2 ~ 0.25 with the ratio of the length of side.

Cavity in front cover 3 is cooling chamber 10, the end face of the front cover 3 corresponding with the pump housing 21 is provided with the through hole 11 of more than two that are communicated with cooling chamber 10 and the return port 22 of more than two, and the through hole 11 of more than two is communicated with cooling channel 9 respectively with the return port 22 of more than two.

Advantageous Effects of the present invention embodies in the following areas:

1. present invention improves the movable sealing structure of screw vacuum pump exhaust end, by setting up cooling collar, having completely cut off the transmission of temperature from rotor shaft seal position vertically, having reduced the operating temperature of mechanical sealing assembly; The screw thread on cooling collar surface, can realize the effect of spiral seal, wherein internal thread rotation is to identical with rotor rotation direction, thus stops mechanical seal side sealing medium to bleed in pump chamber, external thread rotary to rotor rotation direction, thus stop the impurity in pump intracavity gas and dust to bleed mechanical seal.

2., by offering micropore on the end face of stationary seal ring, improve lubrication and the abrasion condition of mechanical seal under high temperature and high speed operating mode, the existence of micropore can increase hydrodynamic pressure between dynamic and static ring, and then reduces dynamic and static ring end wear and the temperature rise of mechanical seal.Under Starved Lubrication conditioned disjunction or even dry friction situation, micropore can be used as micro-oil storage pool and provides lubricant oil to surface of friction pair.Meanwhile, micro-hole or very low power also can hold abrasive particle, to reduce the height wearing and tearing because abrasive particle produces.

Square surface micro-pores mechanical seal structure of the present invention, by the parameter of the Surface Textures such as the ratio of selected pore density, micropore hole depth and the length of side, the processing methods such as laser are used to process micron-sized square micropore 15 at the surface of friction pair 14 of mechanical sealing static ring, radially be distributed on stationary ring surface, moving sealing ring 6 opposing seal stationary ring 7 under the drive of axle 1 rotates, due to the existence of hydrodynamic pressure, moving sealing ring 6 axial end corresponding with stationary seal ring 7 does not contact.Ensureing under the prerequisite that leakage rate meets the demands, in order to obtain less friction torque, pore density is tried to achieve by following method with the ratio of micropore hole depth with the length of side:

When pore density and hole depth and ratio one timing of the length of side, friction pair end face hydrodynamic pressure can be obtained according to formula (1):

$\frac{\∂}{\∂x}\left(h^3\frac{\∂p}{\∂x}\right)+\frac{\∂}{\∂y}\left(h^3\frac{\∂p}{\∂y}\right)=6\mathrm{\μ}U\frac{\∂h}{\∂x}---\left(1\right)$

Unseal power can be obtained by formula (2):

$F_0=\frac{(r_a+r_b)}{2r_c}{\mathrm{\Σ}}_{i=1}^{M-1}{\mathrm{\Σ}}_{j=1}^{N-1}{P}_{i,j}\·\mathrm{\Δ}X\·\mathrm{\Δ}Z---\left(2\right)$

Seal closure power can be tried to achieve by formula (3):

$F_c=\mathrm{\π}(r_b^2-r_a^2)(P_s+\mathrm{\Δ}P\·B)---\left(3\right)$

Work as F ₀with F _cwhen balancing each other, thickness h now can be obtained ₀.Friction torque can be tried to achieve by formula (4):

$T=\frac{\mathrm{\μ}U({r_b}^2-{r_a}^2)(r_a+r_b)}{2}\[\frac{\mathrm{\π}(1-S_p)}{h_c}+\frac{4S_p}{h_c+h_p}\]---\left(4\right)$

Leakage rate can be tried to achieve by formula (5):

$Q=\frac{{{\mathrm{\πh}}_c}^3{r}_m}{6\mathrm{\μ}}\·\frac{P_0-P_i}{r_b-r_a}---\left(5\right)$

In formula: μ is the dynamic viscosity of sealing medium; U is the average tangential velocity of rotating ring; r _a, r _bbe respectively the internal-and external diameter of stationary seal ring 6, r _mfor the two mean value; h _cfor the non-porose area liquid film thickness of dynamic and static interannular; h _pfor the micropore degree of depth; r _pfor pore radius; P ₀, P _ibe respectively the pressure of friction pair end face external diameter and inner radius, Δ P is the two difference; Ps is spring pressure; B is sealing and balancing ratio; S _pfor pore density.The ratio of different micropore hole depth and the length of side and the friction torque of pore density lower sealing surface and the size of leakage rate easily can be obtained by above formula.Under ensureing that leakage rate meets the prerequisite of seal request, select the ratio of suitable micropore hole depth and the length of side and pore density to obtain minimum friction torque, obtain optimum sealability.

Accompanying drawing explanation

Fig. 1 is structural representation of the present invention;

Fig. 2 is the partial enlarged drawing of Fig. 1;

Fig. 3 is cooling collar schematic diagram;

Fig. 4 is the end-face structure schematic diagram of stationary seal ring;

Fig. 5 is the schematic diagram between stationary seal ring and moving sealing ring axis;

Sequence number in upper figure: axle 1, rotor 2, front cover 3, cooling collar 4, spring 5, stationary seal ring 6, moving sealing ring 7, Cock screw 8, cooling channel 9, cooling chamber 10, through hole 11, internal thread 12, outside thread 13, surface of friction pair 14, micropore 15, first seal ring 16, bearing 17, second seal ring 18, labyrinth seal groove 19, the 3rd seal ring 20, the pump housing 21, return port 22.

Embodiment

Below in conjunction with accompanying drawing, by embodiment, the present invention is further described.

See Fig. 1, a kind of screw vacuum pump with movable sealing structure comprises the pump housing 21, front cover 3, rear end cover, axle 1 and rotor 2.The side radial direction of the pump housing 21 is provided with air inlet port, and front cover 3 and rear end cover are fixedly installed in the axial two ends of the pump housing 21 respectively.The side radial direction of front cover 3 is respectively equipped with exhaust port and cooling medium entrance.The side radial direction of rear end cover is provided with cooling medium outlet.Rotor 2 suit is fixed on axle 1, and rotor 2 is positioned at the pump housing 21; One end of axle 1 is fixed in rear end cover, and it is outside that the other end extends front cover 3, is provided with sealing mechanism between axle 1 and front cover 3; Sealing mechanism comprises stationary seal ring 6 and moving sealing ring 7, and moving sealing ring 7 is set with spring, and moving sealing ring 7 is fixed on axle 1 by Cock screw; Axle 1 surface Machining corresponding with sealing mechanism has labyrinth seal groove 19.

See Fig. 2, sealing mechanism also comprises cooling collar 4; Axial one end of the rotor 2 corresponding with sealing mechanism is sleeve pipe step hole, and making has toroidal cavity between rotor 2 and axle 1.

The jacket pipe that cooling collar 4 is closed for the open at one end the other end, the cavity between the inner tubal wall of jacket pipe and outer tube wall is the cooling channel 9 of ring-type; The open-mouth end of cooling collar 4 is fixedly connected the axial inner ends face of front cover 3, is separately installed with the second seal ring 18 and the 3rd seal ring 20, prevents cooling medium from entering in the pump housing 21 between the open-mouth end of cooling collar 4 and the axial inner ends face of front cover 3.The close mouth end of cooling collar 4 is positioned at the sleeve pipe step hole of rotor 2, and cooling collar 4 does not rotate with rotor 2.

See Fig. 3, the external cylindrical surface of cooling collar 4 is provided with outside thread 13, forms spiral seal between the collar aperture of outside thread 13 and rotor 2; The rotation direction of outside thread 13 is contrary with the rotation direction of rotor 2, and the dust in the stop pump housing 21 and particle enter sealing mechanism.

The inner cylindrical surface of cooling collar 4 is provided with internal thread 12, forms spiral seal between internal thread 12 and axle 1; The rotation direction of internal thread 12 is identical with the rotation direction of rotor 2, and the lubricant medium of baffle seal mechanism side enters in the pump housing 21.

Cavity in front cover 3 is cooling chamber 10, cooling medium is provided with in cooling chamber 10, the end face of the front cover 3 corresponding with the pump housing 21 is provided with four through holes 11 and four return ports 22 that are communicated with cooling chamber 10, and four through holes 11 are communicated with cooling channel 9 respectively with four return ports 22; Realize forming heat insulation layer between axle and rotor, blocking temperature axially stationary seal ring 6 and moving sealing ring 7 place transmits.

See Fig. 4, uniformly on the surface of friction pair 14 of the stationary seal ring 6 corresponding with moving sealing ring 7 offer radial micropore 15, micropore 15 is blind hole, and is square hole, and the density of radial uniform micropore 15 on surface of friction pair 14 surface is 20%.The hole depth of micropore 15 is 0.2 with the ratio of the length of side.Micropore 15 provides lubricant oil as micro-oil storage pool to surface of friction pair.Stationary seal ring 6 is fixed on front cover 3, does not rotate with axle 1; Moving sealing ring 7 is fixed on axle 1 by Cock screw 8, rotates with axle; Stationary seal ring 6 and moving sealing ring 7 are compressed by spring 5, do relative rotary motion, thus realize seal action under axle 1 drives.Between stationary seal ring 6 and front cover 3, the first seal ring 16 is all installed between rotating ring 7 and axle 1, the sealing between the chamber at guarantee sealing mechanism, bearing 17 place and the pump housing 21.

Working principle of the present invention is described as follows: see Fig. 1 and Fig. 2, after cooling medium enters screw vacuum pump, is entered the cooling channel 9 of cooling collar 4 from the cooling chamber 10 front cover 3 by through hole 11, then flows back to the cooling chamber 10 in front cover 3 by return port 22.

Owing to carrying out compressed action to gas when rotor 2 works near exhaust end, produce very high heat, thus the temperature of the exhaust end of rotor 2 is higher, from Fig. 2 and Fig. 3, the exhaust end that cooling collar 4 extend into rotor 2 is inner, by cooling medium circulating in inside, cooling channel 9, between rotor 2 and axle 1, forms heat insulation layer, thus block the transmission of temperature stationary seal ring and moving sealing ring vertically, reduce the operating temperature of black box.

See Fig. 4 and Fig. 5, Surface Texture process is carried out to described stationary seal ring 6, namely adopt the technology such as laser in the friction pair end face of stationary ring, process equally distributed micropore, pore size is micron level, radially be distributed on stationary ring surface, micro-pore shape is optional multiple: square, ellipse, parabola shaped etc.And moving sealing ring 7 the same with conventional machinery moving sealing ring be still planar end surface, make to produce larger hydrodynamic when stationary seal ring 6 is relative with moving sealing ring 7 to be rotated, avoiding dynamic and static ring directly contacts, thus reduces its friction power loss and End Face Temperature Rise.Under ensureing that leakage rate meets the prerequisite of seal request, in order to obtain less friction torque, need to select suitable pore density and the ratio of micropore hole depth with the length of side, when pore density and hole depth and ratio one timing of the length of side, friction pair end face hydrodynamic pressure can be obtained according to formula (1):

$\frac{\∂}{\∂x}\left(h^3\frac{\∂p}{\∂x}\right)+\frac{\∂}{\∂y}\left(h^3\frac{\∂p}{\∂y}\right)=6\mathrm{\μ}U\frac{\∂h}{\∂x}---\left(1\right)$

Unseal power can be obtained by formula (2):

$F_0=\frac{(r_a+r_b)}{2r_c}{\mathrm{\Σ}}_{i=1}^{M-1}{\mathrm{\Σ}}_{j=1}^{N-1}{P}_{i,j}\·\mathrm{\Δ}X\·\mathrm{\Δ}Z---\left(2\right)$

Seal closure power can be tried to achieve by formula (3):

$F_c=\mathrm{\π}({r_b}^2-{r_a}^2)(P_s+\mathrm{\Δ}P\·B)---\left(3\right)$

Work as F ₀with F _cwhen balancing each other, thickness h now can be obtained ₀.Friction torque can be tried to achieve by formula (4):

$T=\frac{\mathrm{\μ}U({r_b}^2-{r_a}^2)(r_a+r_b)}{2}\[\frac{\mathrm{\π}(1-S_p)}{h_c}+\frac{4S_p}{h_c+h_p}\]---\left(4\right)$

Leakage rate can be tried to achieve by formula (5):

$Q=\frac{{{\mathrm{\πh}}_c}^3{r}_m}{6\mathrm{\μ}}\·\frac{P_0-P_i}{r_b-r_a}---\left(5\right)$

In formula: μ is the dynamic viscosity of sealing medium; U is the average tangential velocity of rotating ring; r _a, r _bfor the internal-and external diameter of mechanical sealing static ring, r _mfor the two mean value; h _cfor the non-porose area liquid film thickness of dynamic and static interannular; h _pfor the micropore degree of depth; r _pfor pore radius; P ₀, P _ibe respectively the pressure of friction pair end face external diameter and inner radius, Δ P is the two difference; Ps is spring pressure; B is sealing and balancing ratio; S _pfor pore density.The ratio of different micropore hole depth and the length of side and the friction torque of pore density lower sealing surface and the size of leakage rate easily can be obtained by above formula.When ensureing favorable sealing property, the ratio of suitable micropore hole depth and the length of side and pore density is selected to obtain minimum friction torque, obtain optimum sealability, through above-mentioned calculating, for square micropore, pore density is chosen to be 20% ~ 25%, and hole depth is chosen to be 0.2 ~ 0.25 with the ratio of the length of side.

Claims (10)

1. there is a screw vacuum pump for movable sealing structure, comprise the pump housing (21), front cover (3), rear end cover, axle (1) and rotor (2); The side radial direction of the described pump housing (21) is provided with air inlet port, and described front cover (3) and rear end cover are fixed at the axial two ends of the pump housing (21) respectively; The side radial direction of described front cover (3) is respectively equipped with exhaust port and cooling medium entrance; The side radial direction of described rear end cover is provided with cooling medium outlet; Described rotor (2) is sheathed to be fixed on axle (1), and rotor (2) is positioned at the pump housing (21); One end of described axle (1) is fixed in rear end cover, and it is outside that the other end extends front cover (3), is provided with sealing mechanism between axle (1) and front cover (3); Described sealing mechanism comprises stationary seal ring (6) and moving sealing ring (7), and (7) are arranged with spring to described moving sealing ring, and moving sealing ring (7) is fixed on axle (1) by Cock screw, it is characterized in that:

Described sealing mechanism also comprises cooling collar (4); Axial one end of the rotor (2) corresponding with sealing mechanism is sleeve pipe step hole, and making has toroidal cavity between rotor (2) and axle (1);

The jacket pipe that described cooling collar (4) is closed for the open at one end the other end, the cavity between the inner tubal wall of described jacket pipe and outer tube wall is the cooling channel (9) of ring-type; The open-mouth end of cooling collar (4) is fixedly connected the axial inner ends face of front cover (3), and the close mouth end of cooling collar (4) is positioned at the sleeve pipe step hole of rotor (2);

Described cooling channel (9) is communicated with the cooling chamber (10) in front cover (3), and cooling chamber is provided with cooling medium in (10), realizes forming heat insulation layer between axle and rotor, and blocking temperature axially stationary seal ring (6) and moving sealing ring (7) place transmits;

The surface of friction pair (14) of the stationary seal ring (6) corresponding with moving sealing ring (7) is above uniform offers micropore (15), and described micropore (15) is blind hole, and micropore (15) provides lubricant oil as micro-oil storage pool to surface of friction pair.

2. a kind of screw vacuum pump with movable sealing structure according to claim 1, is characterized in that: the surface of the axle (1) adjacent with described sealing mechanism is provided with labyrinth seal groove (19).

3. a kind of screw vacuum pump with movable sealing structure according to claim 1, is characterized in that: be respectively equipped with the second seal ring (18) and the 3rd seal ring (20) between the open-mouth end of cooling collar (4) and the axial inner ends face of front cover (3).

4. a kind of screw vacuum pump with movable sealing structure according to claim 1, it is characterized in that: the external cylindrical surface of described cooling collar (4) is provided with outside thread (13), forms spiral seal between the collar aperture of described outside thread (13) and rotor (2).

5. a kind of screw vacuum pump with movable sealing structure according to claim 4, is characterized in that: the rotation direction of described outside thread (13) is contrary with the rotation direction of rotor (2).

6. a kind of screw vacuum pump with movable sealing structure according to claim 1, is characterized in that: the inner cylindrical surface of described cooling collar (4) is provided with internal thread (12), forms spiral seal between described internal thread (12) and axle (1).

7. a kind of screw vacuum pump with movable sealing structure according to claim 6, is characterized in that: the rotation direction of described internal thread (12) is identical with the rotation direction of rotor (2).

8. a kind of screw vacuum pump with movable sealing structure according to claim 1, it is characterized in that: described micropore (15) is square hole, and radially uniform, the density of radial uniform micropore (15) on surface of friction pair (14) surface is 20% ~ 25%.

9. a kind of screw vacuum pump with movable sealing structure according to claim 1 and 8, is characterized in that: the hole depth of described micropore (15) is 0.2 ~ 0.25 with the ratio of the length of side.

10. a kind of screw vacuum pump with movable sealing structure according to claim 1, it is characterized in that: the cavity in front cover (3) is cooling chamber (10), the end face of the front cover (3) corresponding with the pump housing (21) is provided with the through hole (11) of more than two that are communicated with cooling chamber (10) and the return port (22) of more than two, and the through hole of more than two (11) is communicated with cooling channel (9) respectively with the return port (22) of more than two.