JP4833793B2 - Lubricating device for atmospheric turbine - Google Patents

Description

  The present invention relates to an atmospheric turbine engine including a portion that operates under negative pressure, and more particularly to a bearing lubrication device for such an engine.

  In a conventional gas turbine engine, air at atmospheric pressure is boosted by a compressor, guided to a combustor, mixed with fuel and burned, and then the turbine recovers power, so the fuel pressure is the compressor outlet air pressure. It is difficult to use gasified fuel, solid fuel, unused high-temperature gas, etc. because normal pressure combustion and normal pressure exhaust heat cannot be used.

  On the other hand, in recent years, as a turbine device that can use normal pressure and high temperature gas, normal pressure high temperature gas obtained by normal pressure combustion is expanded in a turbine, and after recovering heat with a heat exchanger or the like in a negative pressure state, There is known an atmospheric combustion turbine engine in which a pressure is returned to atmospheric pressure by a compressor and exhausted into the atmosphere. Since this normal pressure combustion turbine engine can use normal pressure combustion and normal pressure waste heat, it can use various gasified fuels, solid fuel, unused high-temperature gas, etc., and circulate exhaust gas to the outside of the system. There is an advantage that the amount of heat released can be reduced.

The conventional lubrication structure of the rotor shaft bearing of a gas turbine engine or the crankshaft bearing of a piston engine has a lubricating oil sucked from an oil reservoir placed under atmospheric pressure, and is pressurized by an oil pump. Then, the oil is returned to the atmospheric oil reservoir and circulated (see Patent Document 1).
JP 2000-87754 A

  However, when the conventional bearing lubrication structure used in an engine operating under normal pressure is applied directly to an engine having a portion operating under negative pressure in the system, such as a normal pressure combustion turbine engine, Due to the differential pressure between the pressure part and the negative pressure part, the lubricating oil in the lubricating oil path under normal pressure flows out. Alternatively, in order to prevent this, it is necessary to provide a highly airtight oil seal between the lubricating oil path under normal pressure and the negative pressure generating portion.

  In view of this, the present invention provides a simple structure that does not require high airtightness in the normal pressure turbine by maintaining the portion of the lubrication line that returns from the bearing to the oil pump at a negative pressure. Another object of the present invention is to provide a lubrication device that reduces the outflow of lubricating oil into the engine.

  In order to achieve the above object, a lubricating apparatus according to the present invention comprises a normal pressure combustion turbine engine including a turbine that expands a normal pressure and high temperature working gas to a negative pressure, and a compressor that boosts the exhaust gas from the turbine. An oil pump that supplies the bearing with lubricating oil that lubricates a bearing that supports a rotating shaft of the engine, and a lubrication line through which the lubricating oil circulates between the bearing and the oil pump. The oil return path of the lubrication line returning from the bearing to the oil pump is maintained at a negative pressure. Here, the normal pressure refers to the pressure in the installation environment of the apparatus or the like, and the negative pressure refers to a pressure lower than that. In the present specification, the engine operating between normal pressure and negative pressure refers to an engine including a portion that operates under negative pressure.

  According to this configuration, the oil return path returning from the bearing to the oil pump in the lubrication line is held at a negative pressure, so that other negative pressure parts in the engine are compared to when the path is under normal pressure. The pressure difference between the bearing and the lubrication part of the bearing and the other negative pressure part in the engine has a simple structure with low airtightness, and the lubricating oil flows into the engine. Can be suppressed.

  The pressure in the oil return path is preferably maintained substantially equal to the lowest pressure in the engine. In this way, the lubricating oil flow out due to the differential pressure is almost eliminated, so the seal structure of the bearing lubrication part is the same as that used in a conventional engine operating under normal pressure, while the lubricating oil inside the engine Outflow to can be greatly suppressed.

  Preferably, an oil tank for storing the lubricating oil is provided in the middle of the oil return path, and a tank space above the oil level in the oil tank communicates with the turbine outlet or the compressor inlet. By configuring in this way, the tank space can be reduced from normal pressure to negative pressure in a very short time from the startup of the normal pressure combustion turbine engine, so that the outflow of lubricating oil immediately after startup can be suppressed. it can.

  Preferably, the oil return path communicates with an outlet of the turbine or an inlet of the compressor. According to this configuration, the bearing is communicated with the turbine outlet or the compressor inlet, which is the negative pressure part of the normal pressure combustion turbine engine, and the return part from the bearing to the oil pump can be connected to the negative pressure or inside the engine. As a minimum pressure, the outflow of the lubricating oil can be suppressed. Furthermore, the seal structure between the bearing and the turbine outlet and the compressor inlet can be as simple as a labyrinth seal.

  Preferably, a gas-permeable seal is interposed between the oil return path and the turbine outlet or the compressor inlet, the rotating shaft is a hollow shaft, and passes through an inner space of the hollow shaft. By providing a communication path that communicates between the engine exterior and the seal portion, the seal portion is held at a pressure higher than that of the oil return path. According to this configuration, the air outside the engine introduced into the seal portion pushes the lubricating oil back to the oil return path communicating with the negative pressure oil tank, so that the lubricating oil can be prevented from flowing out more reliably. it can.

  Alternatively, the oil return path may communicate with an inner diameter part on the inlet side of the turbine or an inner diameter part on the outlet side of the compressor. According to this configuration, since the oil return path communicates with the compressor outlet at normal pressure, the oil at the compressor outlet communicates the lubricating oil with the negative pressure oil tank through the seal portion. Since it pushes back to the return path, it is possible to prevent the lubricant from flowing out more reliably.

  When the oil tank upper space and the turbine outlet or the compressor inlet are communicated as described above, it is preferable to provide an oil mist trap for capturing the oil mist of the lubricating oil therebetween. By providing the oil mist trap in this way, when the normal pressure combustion turbine engine is started, that is, when the upper space of the oil tank is reduced from normal pressure to negative pressure, a part of the lubricating oil in the tank becomes mist-like. Thus, it is possible to prevent the oil from flowing out of the lubrication line. Therefore, it is possible to reduce the load of maintenance and inspection of the engine by suppressing the decrease of the lubricating oil in the lubrication line.

  The oil tank is preferably located below the bearing. According to this configuration, since the lubricating oil can be returned to the oil tank by gravity, the structure of the lubricating line can be simplified.

  As described above, according to the lubrication apparatus of the present invention, in the atmospheric combustion turbine engine, the portion of the lubrication line through which the lubricating oil circulates is returned to the oil pump from the bearing, so the portion is maintained at a negative pressure. Compared to when the pressure is under normal pressure, the differential pressure with other negative pressure parts in the engine is greatly reduced, so the seal between the bearing lubrication part and the other negative pressure parts in the engine While having a simple structure with low airtightness, the outflow of lubricating oil into the engine can be suppressed.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic view of an atmospheric combustion turbine engine including a lubricating device according to a first embodiment of the present invention. In this embodiment, an atmospheric combustion turbine engine APT is used as an engine including a negative pressure portion. The normal pressure combustion turbine engine APT generates a combustor 1 that combusts fuel F together with air A, a turbine 2 that expands the combustion gas G1 that is the combustion gas to a negative pressure, and the turbine 2. The compressor 4 is driven by power to boost the working gas G2 exhausted from the turbine 2, and is supplied to a cooler, for example, the combustor 1, for cooling the hot working gas G2 entering the compressor 4 from the turbine 2. A heat exchanger 8 that exchanges heat with the air A is provided. Instead of the combustor 1, a high-temperature exhaust gas from an industrial heat treatment furnace such as a carburizing treatment furnace, or a water-cooled cooler may be provided instead of or in addition to the heat exchanger 8. . The turbine 2 and the compressor 4 are connected by a rotating shaft 23, and the rotating shaft is rotatably supported on the casing 20 by first and second bearings 25 and 26 which are ball bearings which are a kind of mechanical bearings. Has been. The rotating shaft 23 is connected to a generator GE that is a load.

  Below the second bearing 26, an oil pump 12 for supplying the lubricating oil LO to the first and second bearings 25, 26 and an oil tank 14 for storing the lubricating oil LO are installed. The outlet side of the oil pump 12 is connected to the oil supply passage 30. The oil supply passage 30 branches in two directions in the middle and extends to the vicinity of the bearings 25 and 26, and guides the lubricating oil LO toward the first and second bearings 25 and 26 at respective tip portions thereof. An oil supply nozzle 31 is attached.

  The first and second bearings 25 and 26 and the oil tank 14 communicate with each other via the first return passage 33a. The oil tank 14 communicates with the suction side of the oil pump 12 via the second return passage 33b. The first return path 33a, the oil tank 14, and the second return path 33b form an oil return path 33 that is a path for returning the lubricating oil LO from the bearings 25 and 26 to the oil pump 12. Furthermore, the oil return path 33, the oil pump 12, the oil supply path 30, and the first and second bearings 25 and 26 constitute a lubrication line 35 that is a circulation path of the lubrication oil LO.

  Between the first and second bearings 25, 26 and the turbine 2 and the compressor 4, a gas-permeable, liquid-tight first seal 28 and a second seal 29 are interposed, respectively. The structure near the first and second bearings 25 and 26 will be described in detail later. The tank upper space 14a, which is a tank space above the oil level, in the oil tank 14 communicates with the inlet of the compressor 4 via the oil tank communication path 32, whereby the oil tank 14 is compressed. The inlet pressure of the machine 4 is maintained. In the middle of the oil tank communication path 32, an oil mist trap 16 for capturing the oil mist of the lubricating oil LO is provided. The oil mist captured by the oil mist trap 16 returns to the tank upper space 14a from the return passage 34 as a liquid. Note that the tank upper space 14 a may communicate with the outlet of the turbine 2. The oil mist trap 16 may be disposed anywhere in the middle of the oil tank communication path 32, but it is preferable in terms of space to be disposed above the oil tank 14 as in this embodiment.

  FIG. 2 is a longitudinal sectional view showing the vicinity of the second bearing 26, which is a main part of this embodiment. The vicinity of the first bearing 25 on the turbine 2 side in FIG. 1 has substantially the same structure as the vicinity of the second bearing 26 on the compressor 4 side, so here the vicinity of the second bearing 26 on the compressor 4 side is here. Will be described as a representative. In this embodiment, the compressor 4 shown in FIG. 2 is a centrifugal type, and the compressor inlet 4b which is the negative pressure portion faces the bearing side.

  The second bearing 26 is a ball bearing composed of an inner ring 26a, an outer ring 26c, and a rolling element 26b that is a ball interposed between the two, but any ball bearing that can rotatably support the rotating shaft 23 is used. Not only a bearing but other types of mechanical bearings such as a roller bearing and a needle bearing may be used. The turbine 2 side (left side in FIG. 2) end surface of the inner ring 26 a is in contact with the end surface on the compressor 4 side of the cylindrical first spacer 42 attached to the central portion in the axial direction of the rotating shaft 23. The other end face of the first spacer 42 is in contact with the inner ring of the first bearing 25 in FIG. On the other hand, the end surface of the inner ring 26 a on the compressor 4 side (left side in FIG. 2) is in contact with a second spacer 43 fitted into the outer peripheral surface of the rotating shaft 23. Further, the end surface of the outer ring 26c on the compressor 4 side is in contact with a stop ring 44 fitted to the inner peripheral surface of the bearing housing portion of the casing 20 forming the outer wall surface of the atmospheric combustion engine APT. The axial position of the second bearing 26 is regulated by the first spacer 42, the second spacer 43, and the retaining ring 44.

  The rotary shaft 23 and the impeller 4a of the compressor 4 are relatively rotated by press-fitting the large-diameter press-fit portion 23a of the rotary shaft 23 into the front portion of the shaft hole of the impeller 4a (the portion near the second bearing 26). Linked impossible. The outer side in the radial direction of the compressor 4 is covered with a shroud 5 a of the compressor casing 5, and one end of the oil tank communication passage 32 is opened near the compressor inlet 4 b in the compressor casing 5. The back surface of the impeller 4 a is covered with a back plate 5 b of the compressor casing 5 that extends in a direction perpendicular to the axis. A gap between the rear boss 4aa of the impeller 4a that is a rotating body and the inner diameter surface of the back plate 5b that is a fixed side is sealed by a third seal 4e such as a labyrinth seal provided on the boss 4aa. Yes. In this embodiment, the rotary shaft 23 is a solid shaft, but a hollow shaft may be used.

  A second seal 29 having a breathable seal structure is formed in the vicinity of the inlet side end of the impeller 4a on the outer peripheral surface of the rotating shaft 23. As the second seal 29, any type can be applied, and the second seal 29 may be separate from the rotary shaft 23 and the casing 20, but in this embodiment, it is integrally formed on the outer peripheral surface of the rotary shaft 23. Use a labyrinth seal. There is a slight gap 27 between the inlet side end of the rotating impeller 4a and the casing 20 which is the fixed side covering this, and the second bearing 26 and the compressor are interposed via the second seal 29 and the gap 27. The inlet 4a which is the negative pressure portion 4 is communicated so as to have substantially the same pressure.

  In the vicinity of the second bearing 26 on the inner peripheral surface of the casing 20, on the turbine 2 side (left side in FIG. 2), an oil supply that guides the lubricating oil LO from the oil supply passage 30 to the space between the inner ring 26a and the outer ring 26c. A nozzle 31 is provided. In the vicinity of the second bearing 26, one end of the first return passage 33 a is opened in the compressor 4 side (the right side in FIG. 2), that is, in the space between the second bearing 26 and the second seal 29.

  Next, the operation of the atmospheric combustion turbine engine provided with the lubricating device according to the above configuration will be described. In FIG. 1, normal pressure / high temperature gas G1 discharged from a combustor 1 that mixes and burns air A and fuel F is sent to a turbine 2 to drive the turbine 2, and the compressor 4 is driven by the generated power. Then, the generator GE arranged outside the atmospheric combustion turbine engine APT is driven. The normal pressure / high temperature gas G1 is expanded to a negative pressure by passing through the turbine 2, and the expanded negative pressure / medium temperature working gas G2 is sent to the compressor 4 through the suction passage 3, where The pressure is increased to atmospheric pressure (normal pressure) and released into the atmosphere as normal temperature exhaust gas G3. A heat exchanger 8 is provided in the middle of the suction passage 3 to exchange heat between the air A sent to the combustor 1 and the working gas G2 sent to the compressor 4 to heat and burn the air A. The combustion efficiency in the compressor 1 is increased, and the working gas G2 is cooled to reduce the compressor work in the compressor 4, thereby increasing the engine efficiency.

  Lubricating oil LO in the oil tank 14 is sucked into the oil pump 12 through the second return passage 33b, discharged from the oil pump 12, and passed through the oil supply passage 30 to the first oil supply nozzle 31 at the tip thereof. And supplied to the second bearings 25 and 26. The lubricating oil LO that has lubricated the bearing is collected in the oil tank 14 through the first return passage 33a.

  At the time of the steady operation of the normal pressure turbine engine APT, the outlet of the turbine 2 and the inlet 4b of the compressor 4 have negative pressure and are almost the lowest pressure in the normal pressure turbine engine APT. The first and second bearings 25 and 26 and the return passage 33 communicating with each other through the breathable first seals 28 and 29 also operate under the minimum pressure in the engine APT. In this embodiment, the range indicated by fine dots in FIG. 1 is a portion that operates under negative pressure and the lowest pressure in the engine APT, and the other portion is a portion that operates under atmospheric pressure. Therefore, the lubricating oil LO supplied to the first and second bearings 25 and 26 does not flow outward from the outlet of the turbine 2 or the inlet 4b of the compressor 4 due to the differential pressure. That is, regarding the compressor 4 side in FIG. 2, the lubricating oil LO supplied to the second bearing 26 is suppressed from leaking to the compressor inlet 4 b through the second seal 29 and the gap 27. Further, it is not necessary to use a particularly high airtight structure as the first seals 28 and 29 in FIG. 1, and the first seals 28 and 29 having a simple structure such as a labyrinth can be used.

  Further, since the tank upper space 14a of the oil tank 14 communicates directly with the inlet of the compressor 4 via the oil tank communication passage 32, the inlet of the compressor 4 is depressurized when the normal pressure combustion turbine engine APT is started. Almost simultaneously, the pressure in the oil tank 14 is reduced. Therefore, substantially no differential pressure is generated even at the time of start-up, and the outflow of the lubricating oil LO to the turbine 2 and the compressor 4 can be prevented.

  Furthermore, since the oil mist trap 16 is provided in the middle of the oil tank communication path 32, the lubricating oil LO generated by rapidly depressurizing the oil tank 14 in a short time when the normal pressure combustion turbine engine APT is started. The oil mist is prevented from being sucked into the compressor 4. Since the oil mist trap 16 is disposed above the oil tank 14, the captured oil mist returns from the return passage 34 into the oil tank 14 due to gravity. Therefore, the reduction of the lubricating oil LO in the lubricating line 35 is suppressed, and the burden of maintenance and inspection is reduced.

  Since the oil tank 14 is disposed below the first and second bearings 25 and 26, the lubricating oil LO after lubricating these bearings returns to the oil tank 14 due to a pressure difference and gravity. Therefore, the lubricating oil LO can be recovered in the oil tank 14 without using a driving device such as a pump.

  In this embodiment, in order to keep the oil return path 33 of the lubrication line 35 at a negative pressure or the lowest pressure in the engine, the inlet 4b of the compressor 4, which is a negative pressure portion, the bearings 25 and 26, and the tank top Although the space 14a is communicated with each other, only the other part of the oil return path 33, for example, the first return path 33a may be communicated with the outlet of the turbine 2 or the inlet 4b of the compressor 4 which is a negative pressure part. .

  FIG. 3 is a longitudinal sectional view showing a main part of an atmospheric combustion turbine engine provided with a lubricating device according to a second embodiment of the present invention. In this embodiment, the rotary shaft 23 is a hollow shaft, and the central portion 23b in the axial direction and the shaft end portion 23c on the compressor 4 side are connected via a fitting rod 47 that fits these inner diameter surfaces. Thus, the rotary shaft 23 is configured. Further, an annular gap 50 exists between the shaft hole of the impeller 4a and the shaft end portion 23c of the rotating shaft 23 in order to make this portion a non-pressure contact portion. In this embodiment, by making the rotary shaft 23 hollow in this way, a seal air path 59 that communicates with the second seal 29 through the inner space 23a of the rotary shaft 23 from the outside of the engine at normal pressure is provided. Forming. Specifically, the radial direction between the outer side in the axial direction (the right side in FIG. 3) and the boss 4aa of the impeller 4a than the portion facing the third seal 4e on the inner diameter surface of the back plate 5b of the compressor casing 5. 4f, an external air introduction hole 51 penetrating from the outer peripheral surface of the impeller 4a to the shaft hole at an axial position slightly inward (left side in FIG. 3) from the gap 4f, and an output portion 23c of the hollow rotating shaft 23 A seal air suction hole 53 penetrating from the outer peripheral surface of the rotary shaft 23 to the inner peripheral surface, a seal air supply hole 57 penetrating from the inner peripheral surface of the rotary shaft 23 to the outer peripheral surface and positioned substantially in the center of the second seal 29 Is additionally provided. Furthermore, the fitting rod 47 has a bottomed cylindrical shape that opens only on the compressor 4 side, and a recess 47a that communicates with the seal air supply hole 57 is formed in the axially central portion of the outer peripheral surface thereof. A through hole 55 penetrating from the inner peripheral surface to the outer peripheral surface is provided in the peripheral wall of the recess 47a. Therefore, the outside of the engine and the central portion of the second seal 29 in the axial direction are the gap 4f, the external air introduction hole 51, the gap 50, the seal air suction hole 53, the inner space 23a of the rotating shaft 23, the through hole 55, the recess. The point 47a and the seal air supply hole 57 communicate with each other.

  In the embodiment of FIG. 3, the axial position of the external air introduction hole 51 is substantially the same as that of the gap 4f, but it may be arranged inside or outside of the gap 4f.

  In this embodiment, air flows from the outside of the engine, which is a normal pressure part, through the seal air path 59 to the second seal 29 that communicates with the compressor inlet 4b, which is a negative pressure part. However, since each of the holes forming the seal air path 59 is a small-diameter hole and the amount of air flowing in through the external air introduction hole 51 is limited by the influence of centrifugal force, the second seal Since the amount of air flowing into the engine 29 is small, the second seal 29 has a slightly negative pressure than the normal pressure and a positive pressure state (hereinafter referred to as the maximum negative pressure in the normal pressure combustion turbine APT). It is called “small negative pressure”).

  On the other hand, the first return passage 33 a is maintained at a large negative pressure (hereinafter referred to as “large negative pressure”) at the inlet 4 b of the compressor 4 via the oil tank 14. Therefore, the small negative pressure air introduced into the axially central portion of the air permeable second seal 29 communicates the lubricating oil LO with the negative pressure oil tank 14 through the bearing-side half 29a of the second seal 29. Therefore, the lubricating oil LO can be prevented from leaking to the inlet 4b of the compressor 4 more reliably as compared with the embodiment shown in FIG. On the other hand, the amount of leakage of small negative pressure air from the second seal 29 to the inlet 4 b of the compressor 4 is suppressed by the compressor-side half 29 b of the second seal 29.

  FIG. 4 is a longitudinal sectional view showing a main part of an atmospheric combustion turbine engine provided with a lubricating device according to a third embodiment of the present invention. In this embodiment, the outlet side inner diameter portion, which is the normal pressure portion of the compressor 4, is disposed so as to face the bearing side, and communicates with the first return passage 33 a via the second seal 29. is there. The rotary shaft 23 has a shape in which the axial end portion on the compressor side becomes a large-diameter press-fit portion 23a, and the press-fit portion 23a is press-fitted into the compressor inlet side portion of the shaft hole of the impeller 4a. Thereby, the rotating shaft 23 and the impeller 4a are connected so that relative rotation is impossible. An annular gap 50B is formed between the outlet side portion of the shaft hole of the impeller 4a and the outer peripheral surface of the rotary shaft 23. A labyrinth seal formed on the inner diameter surface of the back plate 5a of the compressor casing 5 that covers the back surface of the impeller 4a at an axial position between the first return passage 33a on the outer peripheral surface of the rotary shaft 23 and the impeller 4a. The 2nd seal | sticker 29 which is is facing. In this embodiment, the generator GE is connected to the rotating shaft 23 outside the turbine 2 (on the left side in FIG. 1). The structure of portions other than those described above in the present embodiment is the same as that of the embodiment shown in FIGS. In this embodiment, the rotating shaft 23 may be a solid shaft.

  The inner diameter portion of the back surface of the impeller 4a is slightly negative pressure than the normal pressure that is the pressure of the outlet 4c due to the action of centrifugal force, and this small negative pressure is applied to the end of the second seal 29 on the compressor side. Works. On the other hand, since the first return passage 33a has a large negative pressure, the air having the low negative pressure passes through the second seal 29 and pushes the lubricating oil LO back to the first return passage 33a. Therefore, it is possible to prevent the lubricating oil LO from leaking out to the compressor 4 more reliably as compared with the embodiment of FIG.

  Although not shown, the turbine 2 of FIG. 1 used in the above embodiments is a radial type. Therefore, the turbine 2 and the first seal 28 can be sealed with the same structure as in the centrifugal compressor shown in FIGS.

1 is a schematic view showing an atmospheric combustion turbine engine including a lubricating device according to a first embodiment of the present invention. It is a longitudinal cross-sectional view which shows the principal part of the engine which concerns on embodiment of FIG. It is a longitudinal cross-sectional view which shows the principal part of a normal pressure combustion turbine engine provided with the lubricating device which concerns on 2nd Embodiment of this invention. It is a longitudinal cross-sectional view which shows the principal part of a normal pressure combustion turbine engine provided with the lubricating device which concerns on 3rd Embodiment of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Combustor 2 Turbine 4 Compressor 4b Compressor inlet 4c Compressor outlet 4f Clearance 12 Oil pump 14 Oil tank 14a Oil tank upper space 16 Oil mist trap 23 Rotating shaft 23a Inner space of rotating shaft 25 First bearing 26 Second Bearing 28 First seal 29 Second seal 30 Oil supply passage 31 Oil supply nozzle 32 Oil tank communication passage 33 Oil return passage 33a First return passage 33b Second return passage 35 Lubrication line 47 Fitting rod 47a Fitting rod small diameter portion 50 Clearance 51 External air introduction hole 53 Seal air intake hole 55 Pass hole 57 Seal air supply hole 59 Seal air path APT Atmospheric pressure combustion turbine engine LO Lubricating oil

Claims (8)

A lubrication device in a normal pressure combustion turbine engine comprising a turbine for expanding a normal pressure and high temperature working gas to a negative pressure, and a compressor for boosting the exhaust from the turbine,
An oil pump that supplies the bearing with lubricating oil that lubricates a bearing that supports the rotating shaft of the engine, and a lubrication line through which the lubricating oil circulates between the bearing and the oil pump.
A lubrication apparatus in which an oil return path of the lubrication line returning from the bearing to the oil pump is maintained at a negative pressure.   2. The lubricating device according to claim 1, wherein the oil return path is maintained at a pressure substantially equal to the lowest pressure in the engine.   The oil tank for storing the lubricating oil is provided in the middle of the oil return path, and a tank space above the oil level in the oil tank communicates with the turbine outlet or the compressor inlet. Lubrication equipment.   4. The lubrication apparatus according to claim 1, wherein the oil return path communicates with an outlet of the turbine or an inlet of the compressor.   5. The air-permeable seal is interposed between the oil return path and the outlet of the turbine or the inlet of the compressor, and the rotating shaft is a hollow shaft, and an inner space of the hollow shaft according to claim 4. A lubricating device in which the seal portion is held at a pressure higher than that of the oil return path by providing a communication passage that communicates the engine exterior with the seal portion.   6. The lubrication apparatus according to claim 5, wherein the oil return path communicates with an inner diameter portion on an inlet side of the turbine or an inner diameter portion on an outlet side of the compressor. 7. The oil mist of the lubricating oil is trapped between the oil tank and the turbine outlet or the compressor inlet, according to claim 4 depending on claim 3. Lubricating device with an oil mist trap. The lubrication device according to any one of claims 4 to 7, wherein the oil tank is positioned below the bearing.