KR101536061B1 - Shaft seal - Google Patents

Abstract

The bearing housing (30) of the turbomachine, between the empty space (50) in the bearing housing (30) and the wheel back space (15) of the operating wheel (11) of the turbomachine, The shaft seal of the shaft 20 installed in the bearing housing 30 and 31 and the mounting portion 81 is connected to the operating wheel side seal in the form of at least one piston ring 41 and 42, Side seal in the form of a sealing gap 43 between the mounting portion (31) and the mounting portion (81). An oil drainage chamber 53 is provided between the operating wheel side seal and the bearing side seal, wherein the oil drainage chamber 53 is provided between the bearing housing 30, 31 and the mounting portion 81, (44). ≪ / RTI > A gas discharge chamber (55) is disposed between the third seal and the operating wheel side seal. Wherein the attachment portion has an outline and the outline forms the oil drain chamber and the gas discharge chamber together with the bearing housing and the at least one piston ring And at least one groove for receiving the at least one groove. The attachment part (81) has two support areas (821, 822) with respect to the shaft, which are axially spaced and capable of radially transmitting force, wherein the support part (822) is disposed axially in the region of said at least one piston ring (41,42) of said operating wheel-side seal.
Through two short sheets at each end of the attachment (shaft seal bush) instead of one long continuous sheet, the contact surface between the shaft and the bearing attachment, and thereby the heat input from the operation wheel through the shaft Can be reduced.

Description

SHAFT SEAL {SHAFT SEAL}

The present invention relates to the field of exhaust turbochargers driven by exhaust gases from the field of turbo machines, in particular internal combustion engines.

The present invention relates to the shaft seal of such a turbomachine.

In order to improve the output of the internal combustion engine, an exhaust gas turbocharger with a turbine in the exhaust gas track of the internal combustion engine and with a compressor disposed upstream of the internal combustion engine is used today as a standard, And is connected to the turbine through a shaft. With the supercharging of the internal combustion engine using an exhaust gas turbocharger, the charge amount in the cylinders and thus the fuel mixture is increased, and thereby a significant power increase for the engine is obtained. Optionally, the energy contained in the exhaust gas of the internal combustion engine can be converted to electrical or mechanical energy using a power turbine. At this time, instead of a compressor such as an exhaust gas turbocharger, a generator or a mechanical consumer is connected to the turbine shaft.

Exhaust gas turbochargers are typically equipped with a rotor comprising a shaft, a compressor wheel and a turbine wheel, bearings for the shaft, housing components (compressor housing or turbine housing) and bearing housing for guiding the flow, Lt; / RTI >

Based on the high process pressure in the compressor side flow region as well as on the turbine side, the shaft of the exhaust gas turbocharger must be sealed using a suitable sealing concept for the clearance of the bearing housing. The internal pressure in the empty space of the bearing housing generally corresponds to the atmospheric pressure. On the other hand, the gas pressure in the flow channel on the compressor side or on the turbine side depends on the current operating point of the exhaust gas turbocharger and exceeds the pressure of the empty space in the bearing housing at most operating points. In certain cases, for example, a low pressure may be expected at partial load operation or at rest.

DE 20 25 125 discloses a turbine side shaft seal of an exhaust gas turbocharger which comprises a single oil collection chamber from the radial bearing at the turbine side and a piston ring with sealing action between the shaft and the bearing housing, (piston ring). The bearing oil exiting the radial bearing in the axial direction moves outward and is ejected onto a rotating shaft shoulder and centrifugally discharged into the oil collection chamber by centrifugal force. Then, the bearing oil thus centrifugally discharged flows downward from the inside of the oil collecting chamber along gravity, and then returns to the oil circulating portion for bearing lubrication again.

Piston rings made of metal, e.g., line iron, are typically used to reduce gas leakage from the flow channel through the rear space of the turbine into the empty space of the bearing housing. The piston ring under tension is tensioned in a radial groove by an axial stop shoulder in the bearing housing. As a corresponding part to the piston ring, a rotating shaft is provided with radial grooves, in which the piston ring is axially constrained within the groove and radially covers it. Due to the pressure difference between the exhaust gas pressure and the pressure in the interior of the bearing housing, the piston ring is displaced axially in the interior of the groove onto the stop in the direction of the pressure gradient present. The piston ring is seated through the axial bearing of the piston ring on one of the grooves, and the bearing housing plenum is sealed against the exhaust gas flow. In order to improve the sealing action, two or more piston rings may be used, for example as disclosed in CH 661 964 A5, US 3 180 568, US 4 196 910 or EP 1 860 299. These documents show how sealing action against hot exhaust gases can be improved through the additional use of sealed air or by ventilation of the space between the two piston rings and through which leakage of exhaust gas into the bearing housing can be prevented There is a sign.

DE 37 37 932 A1 discloses a turbine side shaft seal of an exhaust gas turbocharger in which oil drainage from a radial bearing between the bearing part and the two piston rings is carried out. At this time, in order to improve oil sealability, an additional centrifugal disc is used instead of a single axial shaft shoulder.

As a result, the amount of undesired bearing oil generated in the region of the piston ring groove can be significantly reduced. Similarly, in the shaft seals according to US 4 268 229 and DE 30 21 349, oil drainage occurs between the radial bearing and the neighboring piston rings, wherein the oil drainage section always consists of one chamber. Additionally, the empty space between the two piston rings is connected to the free space of the bearing housing by means of an additional connecting channel, and is vented to atmospheric pressure. This prevents the pressure difference caused by the left piston ring, so that the piston ring mostly functions to seal the oil, but not to seal the hot exhaust gas. Thereby, only the right piston ring seals between the flow channel under pressure and the empty space of the bearing housing. According to this, through these structural modifications, two separate drain pipes for the media, namely the oil (from the radial bearing) and the exhaust gas (from the flow channel), are generated and the drain pipes are separated do. The lubricating oil exiting the radial bearing is occasionally ejected axially into the piston ring region of the gas seal and, if undesirable, locks the entire piston ring groove. Generally, the gas pressure in the flow channel of the compressor or turbine is greater than the internal pressure in the bearing housing of the turbocharger. In this way, due to the positive pressure difference (the pressure in the flow channel is greater than in the empty space of the bearing housing), the resulting gas leakage penetrates the piston ring seal and, unintentionally, Transfer it back into the oil collection chamber of the bearing housing.

A sealing device for a lubricated bearing of a rotor shaft as described in DE 10 2004 055 429 B3 attempts to prevent this and the sealing device axially seals the bearing housing of the exhaust gas turbocharger against the supplied lubricant . On the rotor shaft there is provided a first seal in the form of a gap, a labyrinth or piston ring and a second seal in the form of a narrow gap or labyrinth, the seals having, between them, And the oil drainage channel is formed by using a housing side oil drain groove and a shaft side oil drain groove disposed coaxially with the oil drainage channel. In the oil drainage channel, there is provided an annular sealing web protruding into the annular oil drain channel at one end in the radial direction of the rotor shaft, and the sealing web is connected to the oil drainage channel Means a barrier acting in the axial direction with respect to the lubricant entering into the gap, and radially covers the gap of the second seal.

In all of the shaft sealing concepts described above, under certain circumstances, hot oil from the rear wheel space of the exhaust turbine leaks through the piston ring seal, and bearing oil remains in the region of the piston ring region and oil drain grooves There is a risk that it will burn locally, thereby causing strong caulking of the shaft seal, and associated wear. The risk of caulking is increased by an increase in exhaust gas temperature and an increase in gas leakage through the piston rings and bad part cooling. Thus, active cooling of the sealing portion is important for operational safety of the shaft seal.

EP 2375000 discloses a shaft seal between a bearing housing and a shaft of a turbomachine which includes an operating wheel side seal and a bearing side seal wherein an oil drain chamber is provided between the operating wheel side seal and the bearing side seal And the oil drainage chamber is defined by a third seal between the bearing housing and the shaft. A gas discharge chamber is disposed between the third seal and the operating wheel side seal wherein the structure is actively cooled through at least one oil spray bore in the region of the oil drain, Can be prevented from being caulked. At this time, the third seal separates the oil from the oil drain chamber and the gas from the gas discharge chamber. Optionally, the shaft-side part of the seal is formed by an attachment on the shaft.

It is an object of the present invention to provide an improved shaft seal of a shaft installed in a bearing housing of a turbomachine, wherein the risk of caulking of the piston ring seal can be minimized through improved heat dissipation from the sealing portion.

An equivalent shaft seal of the shaft installed in the bearing housing of the turbomachine between an empty space in a bearing housing and a wheel back space of an operating wheel of a turbomachine having an attachment on the shaft, And a bearing seal in the form of a sealing gap between the bearing housing and the mounting portion, wherein the bearing wheel seal is in the form of at least one piston ring between the operating wheel side seal and the bearing seal Wherein the oil drain chamber is defined by a third seal in the form of a sealing gap between the bearing housing and the mounting portion and between the third seal and the operating wheel side seal, Wherein a discharge chamber is disposed, the attachment having an outline, The shaft seal includes at least one groove for receiving the at least one piston ring and the oil drain chamber and the gas discharge chamber together with the bearing housing. According to the present invention, And two bearing areas for said shaft, axially spaced and capable of transmitting radial forces, said support areas being formed such that they allow force transmission in the radial direction , Wherein one of the two support regions disposed on the operating wheel side is disposed axially in the region of the at least one piston ring of the operating wheel side seal.

Instead of one long continuous seat, through two short sheets at each end of the attachment (shaft seal bush), the contact surface between the shaft and the bearing attachment, and thereby the shaft The heat input from the operating wheel through it can be reduced and there is preferably an empty space filled with air between the two support regions which can transmit radial force spaced axially in the axial direction of the shaft, Respectively.

Deformation due to centrifugal force can be kept small through the arrangement of the operating wheel side sheet within the area of the piston ring.

Optionally, an oil draining passage is radially outside the oil drain chamber into the bearing housing, and at least one oil injecting bore is disposed in the bearing housing, the oil draining passage having the oil injecting bore, Wherein the oil drains extend axially beyond the at least one piston ring of the operating wheel side seal.

Whereby most of the heat in the bearing housing can be radially radially discharged from the outside of the piston rings through the lubricating oil.

Preferably, the oil draining passage is inclined with respect to the shaft toward the operating-wheel-side seal in the axial direction, so that the oil guided in the oil drainage at the bearing side is moved toward the operating wheel in the axial direction due to gravity Flows.

Optionally, the piston rings of the operating wheel-side seal are directly subjected to a cooling medium (sealing air). This prevents hot gases from entering the bearing clearance from the rear space of the operating wheel.

Alternatively, the attachment portion (shaft seal bush) may be provided with the function of a torsion damper, which can be achieved by a weak pressing on the bearing side seat and a strong pressing on the operating wheel side seat. At this time, the pressing in the front seat must be designed corresponding to the damping requirement. Additionally or alternatively, friction elements, such as Teflon tape, can be introduced into the seat, through which relative movements in the shaft can be used to further increase the degree of damping in torsional vibration.

Alternatively, the area of the bearing housing that is part of the shaft seal formed in accordance with the present invention may be formed as a liner. The liner can be easily replaced upon wear due to actuation or can be disassembled from the bearing housing in the short term for example for cleaning purposes. Further, as a material for this liner, a material having a heat conductive property as high as possible can be selected.

Hereinafter, a shaft seal according to the present invention will be described in detail based on the drawings.

1 is a partially cutaway view of a prior art exhaust gas turbocharger with a centrifugal compressor and an axial turbine,
Fig. 2 is a cross-sectional view of a turbine-side shaft seal of an exhaust gas turbocharger according to the prior art,
3 is a cross-sectional view of a turbine side shaft seal of an exhaust gas turbocharger according to the prior art having an attachment on the shaft,
4 shows a section of the turbine side shaft seal according to the invention of the exhaust gas turbocharger, which is guided along the shaft.

Figure 1 shows a prior art exhaust gas turbocharger with a centrifugal compressor (70) and an axial turbine (10). In order to be able to see the rotor with the compressor wheel 71, the shaft 20 and the turbine wheel 11, the housing of the exhaust turbocharger shown is shown partially cut away. Air guidance from the air inlet 72 to the compressor wheel 71 is indicated by a thick arrow. On the turbine side, hot exhaust gas is conducted through the gas inlet 12 to the gas outlet 13 via the turbine wheel 11. Shaft 20 is generally rotatably mounted within bearing housing 30 using two radial bearings and at least one axial bearing.

2 shows a prior art shaft seal separating the wheel rear space 15 of the turbine wheel 11 and the hollow space 50 in the bearing housing. At this time, the bearing housing includes a liner 31 (seal bush) in the region of the shaft seal, and the liner is realized as a separate component. The liner 31 is formed in an annular shape and includes a radially outer oil drain 52 for radially outwardly centrifugally ejected and laterally centrifugally ejected oil from the radial bearing 34. The liner is sprayed directly or indirectly with injection oil and is thereby actively cooled. The injection oil is guided to the parts to be cooled through the oil injection bore 61. The supply of the injection oil is performed through the oil channel 60 in the bearing housing 30. [ The oil injection bore 61 is designed and arranged so that the injection oil in the region of the bearing housing 30 strikes the inner contour 63 and the liner is wetted in the region of the oil drain 52. Through the injection oil and the oil from the bearing 34 and the oil drain 51, the liner and the piston rings, seals and drain chambers therein are all cooled and the caulking is mostly blocked. In order to increase the cooling action on the piston rings and the drainage chambers, the liner 31 is preferably made of a material with as high a thermal conductivity as possible. The oil drain 52 is defined by the radially positioned sealing plate 32 in the axial direction and the sealing plate itself is cooled through the oil in the drain channel 51. The liner also includes recesses for receiving the two piston rings 41, 42 arranged in series. The liner also includes an oil drain chamber 53 in an area located radially inwardly, a separate gas discharge chamber 55 for gas leakage from the two piston rings 41, 42, and a sealing web 33 And the sealing web separates the oil drainage chamber 53 and the gas discharge chamber 55 from each other.

An oil drain path 51 between the radial bearing 34 and the sealing plate 32 forms the first main drainage channel of the bearing oil exiting the radial bearing. The sealing plate 32 forms a first radial sealing gap 43 with the radially facing first web 21 of the shaft 20 and the bearing oil is introduced into the oil drain 51 into the oil drain chamber 53 is minimized. The rotating shaft contour of the oil drain chamber 53 is provided with a radially inwardly offset drain groove through which two jetting edges are formed inside the oil drain chamber 53, Are formed on the left and right sides of the groove. The oil centrifugally ejected into the radially outward region of the oil drain chamber 53 formed through the grooves in the liner 31 through the injection edges causes the contour of the liner 31 inside the oil drain chamber 53 due to gravity, Lt; / RTI > The oil drainage chamber 53 has at least one oil drainage channel 54 in the lower region so that the bearing oil can be returned from the oil drainage chamber 53 into the oil circulation portion of the bearing lubrication portion.

The liner 31 of the shaft seal formed in accordance with the present invention is characterized by a gas discharge chamber 55 disposed next to the oil drain chamber 53 and the gas discharge chamber is sealed by an enclosed sealing web 33, And is separated from the chamber 53. The annularly shaped gas discharge chamber 55 is used to collect the hot gas passing through the piston rings 41,42. The sealing web 33 forms a second radial sealing gap 44 with the second web 22 of the radially facing shaft 20. The sealing gap 44, according to the present invention, clears the oil from the two media, the gas discharge chamber 55 and the oil drain chamber 53. The gas collected in the gas discharge chamber 55 is again passed through the at least one separate gas drain channel 56 within the liner 31 and from the oil drain channel 54 into the empty space (50). Through the specific separation of the two divisions, the mixing of the two media in the region of the oil drain chamber 53 has to be blocked and thereby the risk of caulking in the sealing engagement has to be reduced. In addition, through the large oil drainage passage 51 and the first sealing portion 43, most of the bearing oil leaving the radial bearing 34 is discharged to the outside and is removed from the piston ring portion through the oil drain passage 52 All.

Fig. 3 shows the shaft seal according to Fig. 2 (only the additional features are marked with reference to Fig. 2 for better recognition); in the shaft seal, the diameter of the turbine in the region of the shaft seal The rotating shaft contour is designed by a sleeve-shaped attachment portion 81. At this time, the attachment portion 81 is shrink-fitted on the long sheet 82 on the shaft, and the edge formed on the shaft is used as the attachment portion 81 as an axial stop 83 .

Fig. 4 shows a further effect of the shaft seal according to Fig. 3 according to the invention. At this time, the bearing housing, the attachment and the shaft seat are formed such that heat dissipation is minimized through oil cooling, and heat inflow is maximized through the support region for the shaft. The attachment portion should preferably be made of a material that conducts heat well.

According to the present invention, two short sheets are placed on the shaft 20 in the attachment portion 81. [ An empty space 85 filled with air extends between the bearing side seat 821 and the operating wheel side seat 822, and the empty space is used as an insulating layer between the mounting portion and the shaft. An axial stop 83 is abutted against the shaft in the axial direction. In the illustrated embodiment, the annular attachment portion 81 has four outer grooves. The two bearing side grooves together with the corresponding grooves in the liner 31 of the bearing housing form the oil drain chamber 53 and the gas discharge chamber 55, which are known from the prior art, as described above. The two operating wheel side grooves of the attachment portion are used to receive two piston rings 41 and 42, which form the working wheel side seal of the shaft seal. The two piston rings contact the liner (31) of the bearing housing. The liner 31 of the bearing housing has an oil drainage passage 52 which enables the supply of lubricating oil radially into the area outside the attachment section. According to the present invention, the oil drain passage extends in the axial direction to at least one piston ring (41, 42), so that cooling of the operating wheel side seal can be ensured by using lubricating oil. The oil drain 52 has an inclination to the axis, so that the lubricating oil introduced into the oil drain can flow toward the operating wheel side along the oil drain due to gravity. At this time, the bearing housing 30 and the liner 31 are formed so as to be provided in a lower region capable of draining the lubricant in relation to gravity. In the figure, the oil flow is shown as a thin, dark arrow. Preferably, lubricating oil is used to cool the shaft seal, from the bearing area, in a specific example, from a supply line to a radial bearing.

In the embodiment shown, the shaft seal has a sealed air supply. At this time, compressed air, shown by small white arrows, is guided into the bearing clearance on the operating wheel side of the piston ring seal on the operating wheel side through the sealed air channel in the bearing housing 30 from the compressor side (or externally supplied) . At this time, the sealed air is used for direct cooling of the seal on the one hand, and on the other hand the possibility of hot gas entering the sealing gap from the wheel rear space 15 of the operating wheel is blocked.

Optionally, the attachment (shaft seal bush) is provided with the function of a torsional damper, which can be achieved through a weak pressure in the bearing side seat 821 and a strong pressure in the operating wheel side seat 822. At this time, the pressure in the bearing side seat must be designed corresponding to the damping requirement. In addition, or in the alternative, a friction element 86 for damping vibration, such as Teflon tape, for example, may be introduced into the seat. Thereby, relative movements in the shaft can be used to increase the degree of damping during torsional vibration.

Optionally, the bearing housing may be formed without a separate liner in the region of the shaft seal formed in accordance with the present invention. In this case, corresponding grooves, sealing plates and sealing webs are introduced directly into the bearing housing. The exemplary embodiment described above with a separate liner 31, in contrast to the variant in which the liner 31 is integrally formed without a separate liner, is characterized in that the liner 31 has a good thermal conductivity Material (e.g., Ck45), and is not dependent on the bearing housing material (e.g., GGG-40) used thereby. In addition to this, the liner can be easily replaced when worn according to operating conditions or can be disassembled from the bearing housing in the short term, for example for cleaning.

In the embodiment shown, the shaft seal includes two piston rings 41,42. Alternatively, only one piston ring may be provided, or other piston rings may be provided in the region of the shaft seal or at other locations.

The above-described and illustrated embodiments illustrate shaft seals formed in accordance with the present invention on the turbine side of an exhaust gas turbocharger or power turbine. Of course, the shaft seal formed in accordance with the present invention may be used in any other turbo machine.

10: Turbine 11: Turbine wheel
12: gas inlet 13: gas outlet
15: Wheel rear space of the operating wheel 20: Shaft
21, 22: sealing web 30: bearing housing
31: liner of bearing housing 32: sealing plate
33: Sealing web 34: Radial bearing
35: Supply line for cooling medium (sealed air) 39: Bonnet cover
41, 42: piston ring 43, 44: radial sealing gap
50: empty space in the bearing housing 51, 52: oil drain
53: Oil drainage chamber 54: Oil drainage channel
55: gas discharge chamber 56: gas discharge channel
60: Oil channel 61: Oil injection bore
62: bearing flange 63: inner contour
70: compressor 71: compressor wheel
72: air inlet part 81: attachment part rotating with the shaft
821, 822: shaft seat 83:
85: empty space 86: element for damping vibration

Claims (10)

Between the empty space 50 in the bearing housing 30 and the wheel rear space 15 of the operating wheel 11 of the turbomachine with an attachment 81 on which the seat is placed on the shaft, As the shaft seal of the shaft (20) provided in the housing (30)
The shaft seal includes an operating wheel side seal in the form of at least one piston ring (41, 42) between the bearing housing (30, 31) and the mounting portion (81) And an oil drain chamber (53) is provided between the operating wheel side seal and the bearing side seal, and the oil drain chamber (53) is provided between the operating wheel side seal and the bearing side seal in the form of a sealing gap (43) Is defined by a third seal in the form of a sealing gap (44) between the bearing housing (30, 31) and the attachment portion (81), and between the third seal and the operating wheel side seal, a gas discharge chamber , Wherein the attachment portion (81) has an outline and the outline forms the oil drain chamber (53) and the gas discharge chamber (55) together with the bearing housing, and the at least one piston The rings 41, And at least one groove for the groove,
The seat of the attachment portion (81) on the shaft is axially spaced and has two support areas (821, 822) for the shaft, capable of transmitting radial forces, and one of the two support areas And a support region (822) disposed on the wheel side is disposed axially in the region of the at least one piston ring (41,42) of the operating wheel side seal. 3. A shaft seal according to claim 1, characterized in that a shaft seal (2) is provided between said two support areas (821, 822) in the axial direction, in which an empty space (85) defined by said shaft (20) . 2. The bearing housing according to claim 1, wherein an oil drainage path (52) is radially introduced into the bearing housing (30, 31) radially outside the oil drainage chamber (53) Wherein the bore (61) is arranged to allow oil to be moved in the oil drain passage by the oil injection bore and the oil drain passage extends in the axial direction to the at least one piston ring (41, 42) Shaft seal. The oil drainage passage (52) according to claim 3, wherein the oil drain passage (52) is formed to be inclined with respect to an axis toward the operating wheel side seal in the axial direction, so that the oil guided in the oil drainage at the bearing side, Shaft seal. The shaft seal of claim 1, wherein a vibration damping element (86) is disposed in a bearing side support area (821) of said two support areas between said shaft (20) and said attachment part (81). 2. The bearing assembly of claim 1, wherein the bearing housing comprises a liner (31) in the region of the shaft seal, wherein recesses are led into the liner and the recesses are connected to the oil drain chamber (53) And a shaft seal forming said gas discharge chamber (55). The shaft seal of claim 1, wherein the attachment portion (81) is made of a material having a higher thermal conductivity than the material of the shaft. 2. The apparatus according to claim 1, wherein a feed line for introducing a gaseous cooling medium into the gap region between the bearing housing (30, 31) and the attachment portion (81) And the supply line extends into the clearance between the bearing housing (30, 31) and the mounting portion (81) on the operating wheel side of the operating wheel side seal. A turbomachine including at least one working wheel (11) and a bearing housing (30) disposed on a shaft (20)
The shaft 20 is rotatably installed in the bearing housing 30 and the shaft seal according to any one of claims 1 to 8 is inserted between the bearing housing 30 and the shaft 20. [ A turbo machine being deployed. An exhaust gas turbocharger or power turbine comprising at least one turbine-actuated wheel (11) and a bearing housing (30) disposed on a shaft (20)
The shaft 20 is rotatably installed in the bearing housing 30 and the shaft seal according to any one of claims 1 to 8 is inserted between the bearing housing 30 and the shaft 20. [ Exhaust gas turbocharger or power turbine placed.

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