JP2009030474A - Bearing structure for turbocharger - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a bearing structure for a turbocharger capable of inhibiting generation of noise caused by whirl vibration of a rotary shaft in the turbocharger of which rotary shaft connecting a turbine wheel and a compressor wheel is rotatably supported by a hydraulic bearing. <P>SOLUTION: The hydraulic bearings 50a, 50b form hydraulic layers of lubricating oil between a rotary shaft 41 of an impeller and inner circumference surfaces 52a, 52b of floating metals 51a, 51b, and rotatably supports the rotary shaft 41 via the hydraulic layer. The inner circumference surfaces 52a, 52b of the floating metals 51a, 51b are formed in tapered surfaces to guide inclination of the rotary shaft 41 due to precession of the rotary shaft 41 generated by an influence of turning flow formed in the hydraulic layer. Inertia moment of the impeller in precession is increased by increasing distance between a support of precession and a center of gravity of the impeller. <P>COPYRIGHT: (C)2009,JPO&INPIT

Description

  The present invention relates to a turbocharger bearing structure in which an impeller in which a turbine wheel and a compressor wheel are connected by a rotary shaft is supported by a fluid bearing.

  A turbocharger is widely known as a supercharger that increases the intake efficiency of an internal combustion engine. In a turbocharger, exhaust gas discharged from an internal combustion engine is blown onto a turbine wheel, whereby the turbine wheel is rotated using the energy of the exhaust gas. As a result, the compressor wheel connected to the turbine wheel via the rotary shaft rotates, and the intake air is forcibly fed into the combustion chamber of the internal combustion engine.

  Conventionally, as a bearing structure for rotatably supporting the rotary shaft of such a turbocharger, as described in Patent Document 1, a fluid layer is formed by lubricating oil discharged from a housing, as described in Patent Document 1. And those using a fluid bearing that supports the rotary shaft through the fluid layer.

  As shown in FIG. 11, in the bearing structure using such a fluid bearing, the rotary shaft 3 that connects the turbine wheel and the compressor wheel is inserted into the two support holes 2 formed in the housing 1, and A cylindrical floating metal 4 is interposed between the rotary shaft 3 and each support hole 2. Each support hole 2 is provided with a lubricating oil supply port 5 that discharges the lubricating oil. By the lubricating oil discharged from the lubricating oil supply port 5, between the inner periphery of the support hole 2 and the outer periphery of the floating metal 4. A fluid layer is formed. Further, the lubricating oil is introduced into the inner peripheral side of the floating metal 4 through the lubricating oil introduction hole 6 provided in the floating metal 4, so that the lubricating oil is also formed between the inner periphery of the floating metal 4 and the rotary shaft 3. A fluid layer is formed. The rotary shaft 3 is rotatably supported in the housing 1 through these fluid layers.

According to such a bearing structure, the rotational force of the rotary shaft 3 is transmitted to the floating metal 4 via the fluid layer formed between the inner periphery of the floating metal 4 and the rotary shaft 3, and the floating metal 4 is Rotate around 3. As a result, the rotational resistance of the rotary shaft 3 can be greatly reduced, and cooling by the lubricating oil is performed on both the inner and outer circumferences of the floating metal 4, so that seizure of the bearing portion is effective. Can be suppressed.
JP-A-56-138423

  However, as the rotational speed of the rotary shaft 3 increases, a swirling flow is generated in the fluid layer of the lubricating oil as shown by broken line arrows in FIGS. 12 (a) and 12 (c), the rotary shaft 3 is rotated about the axis L in the direction indicated by the broken arrow. Then, due to the influence of the swirling flow, the rotary shaft 3 turns in the floating metal 4 as shown by arrows in FIGS. 12A and 12C. As a result, FIG. It is known that the rotary shaft 3 comes to precess as shown in FIG.

  Such vibration of the rotary shaft 3 due to precession is also called whirl vibration, and although it is minute vibration, it generates sound in a certain frequency range regardless of the change in the rotational speed of the rotary shaft 3. This sound, unlike the turbo sound whose frequency changes as the rotational speed of the rotary shaft 3 increases, has little correlation with the running state of the vehicle, so it is easy to give the driver a sense of discomfort and is recognized as noise. Easy to be.

  The generation of noise due to such whirl vibration is caused by interposing the floating metal 4 between the housing 1 and the rotary shaft 3 as described above, and forming a fluid layer of lubricating oil on both the inner and outer circumferences. Fluid bearings such as those that support the rotary shaft 3 through a fluid layer formed between the support hole 2 and the rotary shaft 3 without providing the floating metal 4 are used in addition to the bearing structure. The turbocharger having the conventional bearing structure is generally common.

  As shown in FIG. 12 (b), the inventor of the present application has a precession fulcrum P determined by the inner diameter of the floating metal 4 and the shape of the rotary shaft 3 and the center of gravity G of the entire impeller including the turbine wheel and the compressor wheel. Paying attention to the fact that the moment of inertia when the rotary shaft 3 swings around due to precession increases and the energy required for precession increases, the greater the distance D from the It was confirmed by experiments that the generation of precession can be suppressed by increasing the distance D to the fulcrum P of the differential movement.

  The present invention has been made on the basis of the above knowledge, and an object of the present invention is a turbocharger in which a rotary shaft that connects a turbine wheel and a compressor wheel is rotatably supported by a fluid bearing. An object of the present invention is to provide a turbocharger bearing structure capable of suppressing the generation of noise due to the whirling vibration of the turbocharger.

In the following, means for achieving the above object and its effects are described.
The invention according to claim 1 is a bearing structure of a turbocharger that rotatably supports an impeller in which a turbine wheel and a compressor wheel are connected by a rotary shaft, and is discharged into a support hole through which the rotary shaft is inserted. In the turbocharger bearing structure in which a fluid layer is formed between the support hole and the rotary shaft by the lubricant, and the rotary shaft is rotatably supported via the fluid layer. A moment of inertia increasing means for increasing the moment of inertia of the impeller in the precession by increasing the distance between the fulcrum of the precession of the impeller generated by the influence of the swirling flow generated in the layer and the center of gravity of the impeller; The gist is to provide it.

  According to the above configuration, the rotary shaft is precessed by increasing the distance between the fulcrum of the impeller precession generated by the swirling flow of the fluid layer and the center of gravity of the entire impeller including the turbine wheel and the compressor wheel. Can increase the moment of inertia when swinging. As a result, the energy required for causing precession increases, and the occurrence of precession is suppressed. As a result, generation of noise due to whirl vibration can be suppressed.

The position of the fulcrum of the precession can be estimated based on the support mode of the rotary shaft, such as the inner diameter of the support hole and the shape of the rotary shaft.
According to a second aspect of the present invention, in the turbocharger bearing structure according to the first aspect, the fulcrum of the precession is separated from the center of gravity of the impeller on the inner peripheral surface of the support hole as the inertia moment increasing means. Thus, the gist is that a tapered surface for guiding the inclination of the rotary shaft in the precession is formed.

  Specifically, as in the invention described in claim 2, the inclination of the rotary shaft in the precession movement is set so that the fulcrum of the precession movement is separated from the center of gravity of the impeller on the inner peripheral surface of the support hole for supporting the rotary shaft. By forming the tapered surface to be guided, the position of this fulcrum can be moved so that the distance between the fulcrum of precession and the center of gravity of the impeller is increased.

  According to a third aspect of the present invention, in the turbocharger bearing structure according to the second aspect, the inner diameter of the support hole gradually increases as the tapered surface approaches a wheel closer to the center of gravity of the impeller among the wheels. The gist is that it is formed in a larger form.

  According to the above configuration, since the tapered surface is formed so that the inner diameter of the support hole gradually increases as the wheel closer to the center of gravity of the impeller approaches, the fulcrum of precession motion guided by the tapered surface. Is located on the wheel side farther from the center of gravity of the impeller. Therefore, the moment of inertia when the rotary shaft swings around due to precession can be increased, and the generation of noise due to whirl vibration can be more suitably suppressed.

  According to a fourth aspect of the present invention, in the turbocharger bearing structure according to the first aspect, the rotary shaft inserted through the cylindrical floating metal is inserted into the support hole together with the floating metal, and the support hole and A fluid layer made of the lubricating oil is formed between the outer peripheral surface of the floating metal and between the inner peripheral surface of the floating metal and the rotary shaft, and the rotary shaft can be rotated through the fluid layer. A bearing structure of a turbocharger that supports the rotary in the precession so that the fulcrum of the precession moves away from the center of gravity of the impeller on the inner peripheral surface of the floating metal as the inertia moment increasing means The gist that a tapered surface is formed to guide the tilt of the shaft. To.

  In the bearing structure in which a cylindrical floating metal is interposed between the support hole and the rotary shaft, the rotary shaft in the precession motion is formed on the inner peripheral surface of the floating metal. By forming a tapered surface for guiding the inclination, the position of this fulcrum can be shifted so that the distance between the fulcrum of precession and the center of gravity of the impeller is increased. Thereby, like the invention of the said Claim 2, generation | occurrence | production of precession can be suppressed and generation | occurrence | production of the noise resulting from a whirl vibration can be suppressed now.

  According to a fifth aspect of the present invention, in the turbocharger bearing structure according to the fourth aspect, the inner diameter of the floating metal gradually increases as the tapered surface approaches a wheel closer to the center of gravity of the impeller among the wheels. The gist is that it is formed in a larger form.

  According to the above configuration, the tapered surface is formed so that the inner diameter of the floating metal gradually increases as the wheel closer to the center of gravity of the impeller approaches, so the fulcrum of precession motion guided by this tapered surface. Is located on the wheel side farther from the center of gravity of the impeller. Therefore, the moment of inertia when the rotary shaft swings around due to precession can be increased, and the generation of noise due to whirl vibration can be more suitably suppressed.

  According to a sixth aspect of the present invention, there is provided the turbocharger bearing structure according to the fifth aspect, wherein the rotary shaft is supported by a plurality of floating metals. The gist is that the tapered surfaces are respectively formed so that the angles are set to be equal and located on the same conical surface.

  In the bearing structure that supports the rotary shaft by a plurality of floating metals, the inclination angle of the tapered surface formed on the inner peripheral surface of each floating metal is set to be equal as in the invention of claim 6 above, By forming them so that they lie on the same conical surface, the tapered surfaces cooperate to guide the inclination of the rotary shaft in the precession, and the fulcrum of the precession is more preferably the impeller. It can be moved to the wheel side farther from the center of gravity.

  According to a seventh aspect of the present invention, in the turbocharger bearing structure according to any one of the second to sixth aspects, the taper surface has an inclination angle of the rotary shaft guided by the taper surface. The gist is that the tilt angle is set to be smaller than the maximum tilt angle at which the shaft can tilt.

  The smaller the moving amount of the center of gravity of the impeller due to the precession, in other words, the smaller the inclination angle of the rotary shaft in the precession, the smaller the vibration energy of the whirl vibration and the accompanying noise.

  In addition, when a tapered surface is formed on the inner peripheral surface of the support hole or the inner peripheral surface of the floating metal, and the taper surface guides the inclination of the rotary shaft in the precession of the impeller, The inclination of the rotary shaft is limited by the inclination of the tapered surface. Here, as in the seventh aspect of the invention, the maximum inclination angle of the rotary shaft determined based on the shape of the rotary shaft, the support hole, the inner diameter of the floating metal, etc. By setting it smaller than this, the inclination angle of the rotary shaft in the precession can be made smaller, and the noise accompanying the whirl vibration can be more suitably suppressed.

  Note that the vibration energy of the whirl vibration can be reduced as the inclination angle of the taper surface is reduced, but the moment of inertia when the rotary shaft swings around due to precession is also reduced accordingly, and the whirl vibration itself is suppressed. The effect will be reduced. Therefore, the inclination angle of the taper surface is set to a size that can suitably suppress the generation of noise due to the whirl vibration in consideration of the balance between the distance between the fulcrum of precession and the center of gravity of the impeller. desirable.

  The invention according to claim 8 is the turbocharger bearing structure according to claim 1, wherein the rotary shaft inserted through a pair of floating metals is inserted into the support holes together with the floating metals, A fluid layer of lubricating oil is formed between the outer peripheral surface of each floating metal and between the inner peripheral surface of each floating metal and the rotary shaft, and the rotary shaft can be rotated via the fluid layer. The gist of the invention is that the floating metal closer to the center of gravity of the impeller of the pair of floating metals is formed of a material having a larger coefficient of thermal expansion than the other floating metal.

  As the temperature of the lubricating oil rises as the rotary shaft rotates, the floating metal rises in temperature and thermally expands. According to the configuration described in claim 8, the floating metal closer to the center of gravity of the impeller formed of a material having a large thermal expansion coefficient is more thermally expanded than the other floating metal. Therefore, the gap between the floating metal and the rotary shaft is larger than the gap between the other floating metal and the rotary shaft. Thereby, when the rotary shaft swivels along the inner peripheral surface of the floating metal, the swing of the rotary shaft in the floating metal becomes larger than the swing of the other floating metal. Therefore, the fulcrum of the precession is positioned near the other floating metal, and the fulcrum of the precession can be moved to a position farther from the center of gravity of the impeller. That is, according to the above configuration, it is possible to suppress generation of noise due to whirl vibration by causing a pair of floating metals having different thermal expansion coefficients to function as inertia moment increasing means.

  According to a ninth aspect of the present invention, in the turbocharger bearing structure according to the first aspect, the inertia moment increasing means is configured to increase the distance between the precession fulcrum and the center of gravity of the impeller. The gist is to move the center of gravity.

  As in the above configuration, the distance between the fulcrum of the precession and the center of gravity of the impeller can be increased by moving the center of gravity of the impeller, thereby increasing the moment of inertia when the rotary shaft swings around due to the precession. Therefore, it is possible to suppress the generation of noise due to whirl vibration.

  According to a tenth aspect of the present invention, in the turbocharger bearing structure according to the ninth aspect, the hollow portion extending along the rotation axis of the rotary shaft from the rotation center of one end portion in the axial direction of the rotary shaft. The gist is to move the center of gravity of the impeller by forming.

  In general, the lighter the turbocharger impeller, the better the response when raising the boost pressure. Therefore, in the invention described in claim 10, the center of gravity of the impeller is moved by forming a hollow portion extending along the axial direction of the rotary shaft from the rotation center of one end portion in the axial direction of the rotary shaft. I have to. By moving the center of gravity of the impeller with such a configuration, it is possible to suppress the generation of noise due to the whirl vibration, reduce the weight of the entire impeller, and improve the response when the boost pressure is increased. Further, by forming a hollow portion extending along the rotation axis of the rotary shaft, which is the rotation center of the impeller, the center of gravity can be moved without breaking the rotation balance of the impeller.

(First embodiment)
A first embodiment in which the present invention is embodied in a bearing structure for a turbocharger will be described below with reference to FIGS. FIG. 1 shows a schematic configuration of the turbocharger of the present embodiment. As shown in FIG. 1, the turbocharger is formed by integrating a center housing 10, a turbine housing 20, and a compressor housing 30.

  The center housing 10 supports an impeller 40 in which a turbine wheel 42 and a compressor wheel 43 are connected by a rotary shaft 41. The impeller 40 is rotatable with respect to the center housing 10 by the rotary shaft 41 being supported by a fluid bearing 50a disposed on the turbine wheel 42 side and a fluid bearing 50b disposed on the compressor wheel 43 side. It is supported. Further, a lubricating oil supply passage 11 is formed in the center housing 10, and lubricating oil having a predetermined pressure is supplied to the fluid bearings 50a and 50b by an oil pump (not shown).

  A turbine wheel 42 fixed to the left end of the rotary shaft 41 in FIG. 1 is provided with a plurality of blades 42 a extending radially about the axis L of the rotary shaft 41. On the other hand, the compressor wheel 43 fixed to the right end of the rotary shaft 41 in FIG. 1 is provided with a plurality of blades 43 a extending radially about the axis L of the rotary shaft 41.

  In the impeller 40, the turbine wheel 42 is formed of a material such as an alloy having high heat resistance in order to secure the strength of the turbine wheel 42 that is directly exposed to high-temperature exhaust gas and to reduce the weight of the impeller 40 as a whole. On the other hand, the compressor wheel 43 is made of a lightweight material such as aluminum while being reinforced. Therefore, as shown in FIG. 1, the center of gravity G of the impeller 40 is unevenly distributed on the turbine wheel 42 side.

  In the turbine housing 20 assembled to the left end of the center housing 10 in FIG. 1, a scroll passage 21 extending so as to surround the outer periphery of the turbine wheel 42 and a discharge port 22 extending in the direction of the axis L of the rotary shaft 41 are formed. Has been. The scroll passage 21 communicates with an exhaust passage of an internal combustion engine (not shown), and exhaust gas from the combustion chamber of the internal combustion engine is sent to the scroll passage 21 through the exhaust passage.

  Further, an introduction passage 23 that extends along the circumferential direction of the turbine wheel 42 and communicates with the scroll passage 21 is formed in the turbine housing 20 so as to surround the outer periphery of the turbine wheel 42. The exhaust from the scroll passage 21 is blown toward the turbine wheel 42 through the introduction passage 23. As a result, the turbine wheel 42 rotates about the axis L. Thereafter, the exhaust is discharged to the discharge port 22 and returned to the exhaust passage.

  On the other hand, the compressor housing 30 assembled to the right end of the center housing 10 in FIG. 1 has an intake port 31 extending in the direction of the axis L of the rotary shaft 41 and an internal combustion engine (not shown) extending so as to surround the outer periphery of the compressor wheel 43. A compressor passage 32 communicating with the intake passage of the engine is formed. Further, the compressor housing 30 is provided with a delivery passage 33 for sending out the air introduced into the compressor housing 30 through the suction port 31 to the compressor passage 32. Thus, when the turbine wheel 42 is rotated by blowing exhaust gas, the compressor wheel 43 connected to the turbine wheel 42 via the rotary shaft 41 rotates about the axis L, and the air is supplied to the suction port 31 and the delivery passage. It is forcibly sent to the intake passage of the internal combustion engine through the compressor passage 33 and the compressor passage 32.

  In such a turbocharger, the rotary shaft 41 connecting the turbine wheel 42 and the compressor wheel 43 rotates at a very high speed. In the turbocharger according to the present embodiment, the rotary shaft 41 is supported by the fluid bearings 50a and 50b in which fluid layers are formed by lubricating oil in order to suppress seizure of the journal portion of the rotary shaft 41. Yes.

Next, the bearing structure will be described in more detail with reference to FIG. 2 is an enlarged view of a portion X surrounded by a two-dot chain line in FIG.
As shown in FIG. 2, the fluid bearing 50a is provided on the support portion 12a formed on the turbine wheel 42 side of the center housing 10, and the fluid bearing 50b is provided on the support portion 12b formed on the compressor wheel 43 side. . The support portions 12a and 12b are respectively formed with support holes 13a and 13b having a circular cross section. The support hole 13a has a cylindrical floating metal 51a, and the support hole 13b has a cylindrical floating metal 51b. Each is interpolated. Further, as shown in FIG. 2, a rotary shaft 41 is inserted into the support holes 13a and 13b while being inserted through the floating metals 51a and 51b. The floating metal 51a of the fluid bearing 50a is restricted in movement in the axial direction by a pair of snap rings 53, and the floating metal 51b of the fluid bearing 50b is restricted by the snap ring 53 and thrust bearing 54.

  When the floating metals 51a and 51b are arranged in the center housing 10 as described above, the inner peripheral surfaces 52a and 52b are tapered so that the inner diameter gradually increases toward the turbine wheel 42 as shown in FIG. Is formed. Further, these inner peripheral surfaces 52a and 52b are formed so as to be located on the same conical surface as shown by a two-dot broken line in FIG. 2, and the inclination angle θ, that is, the inclination with respect to the horizontal direction in FIG. The angle θ is set to be smaller than the maximum inclination angle θmax with which the rotary shaft 41 can be inclined.

  Note that the maximum inclination angle θmax of the rotary shaft 41 is, specifically, when the rotary shaft 41 is inclined most greatly with respect to the horizontal direction in FIG. 2, specifically, the point Y on the floating metal 51a and the point on the floating metal 51b. The tilt angle when tilted until it contacts Z, and the angle can be estimated based on the inner diameters of the floating metals 51a and 51b, the shape of the rotary shaft 41, and the like.

  As shown in FIG. 2, the supply passage 11 formed in the center housing 10 includes discharge passages 11a and 11b for discharging lubricating oil to the support holes 13a and 13b. Each of the floating metals 51a and 51b is formed with a plurality of (six in this embodiment) through-holes 55 extending radially from the inner peripheral surfaces 52a and 52b and communicating with the outer periphery. As described above, the lubricating oil supplied through the supply passage 11 is discharged into the support holes 13a and 13b through the discharge passages 11a and 11b, and is introduced to the inner peripheral surfaces 52a and 52b through the through holes 55. As a result, lubricating oil is used between the inner peripheral surfaces of the support holes 13a and 13b and the outer peripheral surfaces of the floating metals 51a and 51b and between the inner peripheral surfaces 52a and 52b of the floating metals 51a and 51b and the rotary shaft 41. Each fluid layer is formed.

  As described above, when exhaust is blown onto the turbine wheel 42, the rotary shaft 41 rotates together with the turbine wheel 42. The rotational force of the rotary shaft 41 is transmitted to the floating metals 51a and 51b through a fluid layer formed between the inner peripheral surfaces 52a and 52b of the floating metals 51a and 51b and the rotary shaft 41, and the floating metals 51a and 51b. Rotates about the axis L of the rotary shaft 41. As a result, the rotational resistance of the rotary shaft 41 can be greatly reduced, and cooling by the lubricating oil is performed on both the inner peripheral surfaces 52a and 52b of the floating metals 51a and 51b and the outer peripheral surfaces. The seizure of the portion can be effectively suppressed.

  However, as the rotational speed of the rotary shaft 41 increases, a swirling flow is generated in the fluid layer formed between the rotary shaft 41 and the inner peripheral surfaces 52a and 52b of the floating metals 51a and 51b. Due to the influence of the swirling flow, the rotary shaft 41 revolves along the inner peripheral surfaces 52a and 52b of the floating metals 51a and 51b. As a result, the rotary shaft 41 precesses in the center housing 10. It becomes like this.

  Next, the precession movement of the rotary shaft 41 will be described with reference to FIG. FIG. 3A is a schematic diagram showing a precession mode of the rotary shaft 41 in the bearing structure of the present embodiment, and FIG. 3B is a precession mode of the rotary shaft 41 in a general bearing structure. It is a schematic diagram which shows. 3A and 3B, the distance between the inner peripheral surfaces 52a and 52b of the floating metals 51a and 51b and the rotary shaft 41, the inclination of the rotary shaft 41, and the like are exaggerated. As shown.

  As shown in FIG. 3B, in the general bearing structure, the floating metal 51 on the turbine wheel 42 side and the compressor wheel 43 side has the same specifications. Moreover, the inner peripheral surface 52 of each floating metal 51 is not formed with a tapered surface, and the inner diameter thereof is constant. Therefore, as the rotational speed of the rotary shaft 41 increases, a swirling flow is generated in the fluid layer formed between the rotary shaft 41 and the inner peripheral surface 52 of the floating metal 51. When the rotary shaft 41 starts to turn along the inner peripheral surface 52, the rotary shaft 41 performs a precession with the middle of each floating metal 51 as a fulcrum Px as shown in FIG. 3B. Become.

  On the other hand, as shown in FIG. 3A, in the bearing structure of the present embodiment, as described above, the inner peripheral surfaces 52a and 52b of the floating metals 51a and 51b gradually become closer to the turbine wheel 42 side. It is formed by a tapered surface that becomes larger. Therefore, when the rotary shaft 41 comes to swivel along the inner peripheral surfaces 52a and 52b of the floating metals 51a and 51b, the fluid in the portion where the inner peripheral surfaces 52a and 52b and the rotary shaft 41 are close to each other. The inclination of the rotary shaft 41 is guided so that the layer thickness is constant. Thereby, in the precession, the rotary shaft 41 is inclined so that the rotary shaft 41 and the inner peripheral surfaces 52a and 52b are parallel to each other, and the fulcrum P of the precession of the rotary shaft 41 as shown in FIG. Is located closer to the compressor wheel 43 than the fulcrum Px of the precession in a general bearing structure. That is, in the bearing structure of this embodiment, the distance D between the precession fulcrum P and the center of gravity G of the impeller 40 is further greater than the distance Dx between the precession fulcrum Px and the center of gravity G in the general bearing structure. growing.

According to the first embodiment described above, the following effects can be obtained.
(1) In the first embodiment, the inner peripheral surfaces 52a and 52b of the floating metals 51a and 51b are formed in a tapered shape, and the inclination of the rotary shaft 41 in the precession motion is guided by this tapered surface. The position of the fulcrum P is moved so that the distance D between the fulcrum P of the differential motion and the center of gravity G of the impeller 40 is increased. Thus, by increasing the distance D between the fulcrum P of the precession motion of the impeller 40 generated due to the swirling flow of the fluid layer and the center of gravity G of the impeller 40 including the turbine wheel 42 and the compressor wheel 43, the rotary shaft 41 is The moment of inertia when swinging around due to precession can be increased. As a result, the energy required for causing precession increases, and the occurrence of precession is suppressed. As a result, generation of noise due to whirl vibration can be suppressed.

  (2) Since the inner peripheral surfaces 52a and 52b are inclined so that the inner diameters of the floating metals 51a and 51b gradually increase toward the turbine wheel 42 close to the center of gravity G of the impeller 40, the inner peripheral surface 52a. , 52b, the fulcrum P of the precession motion is located on the compressor wheel 43 side far from the center of gravity G of the impeller 40. Therefore, the moment of inertia when the rotary shaft 41 swings around due to precession can be increased, and the generation of noise due to whirl vibration can be more suitably suppressed.

  (3) Since the inclination angles θ of the inner peripheral surfaces 52a and 52b of the floating metals 51a and 51b are set to be equal and are formed so as to be positioned on the same conical surface, the inner peripheral surfaces 52a and 52b 52b cooperates and guides the inclination of the rotary shaft 41 in the precession. Therefore, the precession fulcrum P can be moved to the compressor wheel 43 side far from the center of gravity G of the impeller 40 more reliably.

  (4) The smaller the amount of movement of the center of gravity of the impeller 40 due to the precession, in other words, the smaller the inclination angle of the rotary shaft 41 in the precession, the smaller the vibration energy of the whirl vibration and the accompanying noise. . Further, as in the first embodiment, when the inclination of the rotary shaft 41 in the precession movement of the impeller 40 is guided by the inner peripheral surfaces 52a and 52b of the floating metals 51a and 51b, the rotary shaft in the precession movement 41 is limited by the inclination of the inner peripheral surfaces 52a and 52b. In the first embodiment, the inclination angle θ of the inner peripheral surfaces 52a and 52b is set to be smaller than the maximum inclination angle θmax of the rotary shaft 41. Therefore, the inclination angle of the rotary shaft 41 in the precession exercise is further increased. It is possible to reduce the noise, and the noise accompanying the whirl vibration can be more suitably suppressed.

  As the tilt angle θ of the floating metals 51a and 51b is reduced, the vibration energy of the whirl vibration can be reduced. In accordance with this, the moment of inertia when the rotary shaft 41 swings around due to precession is also reduced. The effect of suppressing vibration itself is reduced. Therefore, the inclination angle θ of the inner peripheral surfaces 52a and 52b preferably generates noise due to the whirl vibration in consideration of the balance between the distance D between the precession fulcrum P and the center of gravity G of the impeller 40. It is desirable to set it to a size that can be suppressed.

The first embodiment can also be implemented in the following forms that are appropriately modified.
In the first embodiment, the configuration in which the inclination angle θ of the floating metals 51a and 51b is set to be smaller than the maximum inclination angle θmax of the rotary shaft 41 is shown. However, the inclination angle θ of the inner peripheral surfaces 52a and 52b is It does not necessarily have to be smaller than the maximum inclination angle θmax of the rotary shaft 41. That is, even when the inclination angle θ is set to be larger than the maximum inclination angle θmax of the rotary shaft 41, the moment of inertia when the rotary shaft 41 swings around due to precession is increased, resulting in the whirl vibration. It suffices if noise generation can be suppressed.

  -Although the bearing structure which supports the rotary shaft 41 by a pair of fluid bearing 50a, 50b was illustrated, this invention is not limited to such a structure. For example, the present invention can be applied to a bearing structure in which the rotary shaft 41 is supported by a single fluid bearing. Specifically, as shown in FIG. 4, the inner peripheral surface 152 of the floating metal 151 is formed in a taper shape in which the inner diameter gradually increases toward the turbine wheel 42 side, so that the precession fulcrum P and the center of gravity of the impeller 40 are obtained. The distance D with G can be increased, and the generation of noise due to whirl vibration can be suppressed.

  -The present invention is also applied to a bearing structure in which a rotary shaft is inserted into a support hole without using a floating metal and the rotary shaft is supported through a fluid layer formed between the support hole and the rotary shaft. can do. Specifically, as shown in FIG. 5, the inner peripheral surface of the support hole 113 of the center housing 10 is tapered so that the inner diameter gradually increases as it approaches the turbine wheel 42 side. The distance D between the fulcrum P and the center of gravity G of the impeller 40 can be increased.

  In the above-described embodiment, the configuration in which the inner peripheral surface of the floating metal or the support hole is inclined so that the inner diameter gradually increases as it approaches the turbine wheel 42 side. On the other hand, the inclination of the rotary shaft 41 in the precession is guided by the inclination of the inner peripheral surface, and the distance D between the center of gravity G of the impeller 40 and the fulcrum P of the precession can be increased. If so, the inclination direction and the inclination angle of the inner peripheral surface can be appropriately changed and employed. For example, as shown in FIG. 6A, in the case of the floating metal 251a on the turbine wheel 42 side, the inner peripheral surface 252a is formed in a tapered shape whose inner diameter gradually increases as it approaches the turbine wheel 42 side. In the floating metal 251b on the compressor wheel 43 side, it is also possible to adopt a configuration in which the inner peripheral surface 252b is formed in a tapered shape whose inner diameter gradually increases as it approaches the compressor wheel 43 side. Even when such a configuration is adopted, by adjusting the inclination angles of the inner peripheral surfaces 252a and 252b, the fulcrum P when the rotary shaft 41 precesses as shown in FIG. The distance D between the impeller 40 and the center of gravity G can be made larger than the distance Dx between the precession fulcrum Px and the center of gravity G of the impeller 40 in the general bearing structure shown in FIG. It is possible to suppress the occurrence of noise.

-In addition, a configuration in which a tapered surface is formed only on some floating metals among a plurality of floating metals, a part of the inner peripheral surface of the floating metal, or a part of the inner peripheral surface of the support hole of the center housing is tapered. Even when the configuration is adopted, the distance D between the fulcrum P of the precession and the center of gravity G of the impeller 40 can be made larger than the distance Dx in the general bearing structure by appropriately adjusting the inclination angle. it can.
(Second Embodiment)
Hereinafter, the second embodiment will be described with reference to FIGS. 7 and 8. Since the present embodiment is different from the first embodiment in the configuration of the floating metal, the description of the same members will be omitted only by assigning the same reference numerals, and the differences will be mainly described. FIG. 7 is an enlarged cross-sectional view showing the vicinity of the fluid bearings 50a and 50b in the bearing structure according to the present embodiment.

  In the bearing structure of the present embodiment, of the pair of fluid bearings 50a and 50b, the floating metal 351a in the fluid bearing 50a on the turbine wheel 42 side near the center of gravity G of the impeller 40 is replaced with the fluid bearing 50b on the compressor wheel 43 side. It is made of a material having a larger thermal expansion coefficient than that of the floating metal 351b.

  Specifically, as shown in FIG. 7, a floating metal 351b made of steel is disposed in the support hole 13b on the compressor wheel 43 side, while a floating metal made of brass having a larger thermal expansion coefficient than this steel. 351a is arranged in the support hole 13a on the turbine wheel 42 side. As shown in FIG. 7, in this embodiment, the floating metals 351a and 351b have the same shape.

  Next, the operation of the bearing structure of this embodiment will be described with reference to FIG. FIG. 8 is a schematic view showing a precession mode of the rotary shaft 41 in the bearing structure of the present embodiment. For convenience of explanation, FIG. 8 exaggerates the interval between the inner peripheral surfaces 352a and 352b of the floating metals 351a and 351b and the rotary shaft 41, the inclination of the rotary shaft 41, and the like.

  As shown in FIG. 8, the floating metals 351 a and 351 b increase in temperature and thermally expand as the temperature of the lubricating oil increases as the rotary shaft 41 rotates. At this time, the floating metal 351a on the turbine wheel 42 side close to the center of gravity G of the impeller 40 is made of brass having a larger thermal expansion coefficient than steel, and thus is larger in thermal expansion than the floating metal 351b made of steel. It becomes like this. Therefore, the inner diameter d1 of the floating metal 351a is larger than the inner diameter d2 of the floating metal 351b on the compressor wheel 43 side, and the gap between the floating metal 351a and the rotary shaft 41 is the gap between the floating metal 351b and the rotary shaft 41. Bigger than. As a result, when the rotary shaft 41 swings along the inner peripheral surfaces 352a and 352b of the floating metals 351a and 351b, the swing of the rotary shaft 41 in the floating metal 351a is caused in the floating metal 351b. It becomes larger than the swing. Accordingly, the precession fulcrum P of the rotary shaft 41 is positioned near the floating metal 351b, and the precession fulcrum P is located farther from the center of gravity G of the impeller 40 than the general bearing structure. To move.

According to the second embodiment described above, the following effects can be obtained.
(1) According to the second embodiment, the moment of inertia that increases the distance D between the fulcrum P and the center of gravity G of the impeller 40 in the precession of the rotary shaft 41 for the floating metals 351a and 351b having different thermal expansion coefficients. By functioning as an increasing means, it is possible to suppress the generation of noise due to whirl vibration.

The second embodiment can also be carried out in the following forms that are appropriately modified.
In the second embodiment, the structure in which the floating metal 351a on the turbine wheel 42 side is made of brass and the floating metal 351b on the compressor wheel 43 side is made of steel is shown, but this embodies the present invention. This is an example of the configuration. That is, if the floating metal closer to the center of gravity of the impeller 40 is made of a material having a larger thermal expansion coefficient than the other floating metal, the combination of materials forming each floating metal is It can be changed as appropriate.
(Third embodiment)
Hereinafter, the third embodiment will be described with reference to FIGS. 9 and 10. Since the present embodiment is different from the first embodiment in the configuration of the impeller and the floating metal, the same members are only given the same reference numerals and the description thereof is omitted, and the differences between the two are mainly described. . 9 is a cross-sectional view of the impeller 40 of the present embodiment, and FIG. 10 is an enlarged cross-sectional view of the vicinity of the fluid bearings 50a and 50b in the bearing structure of the present embodiment.

  As shown in FIG. 9, in the impeller 40 of this embodiment, a hollow portion 41 a extending along the axis L from the rotation center of the end portion of the rotary shaft 41 on the compressor wheel 43 side is formed. . The hollow portion 41a can be easily formed by forming a hole having a predetermined depth in the rotary shaft 41 with a drill or the like. By forming the hollow portion 41a in this way, the compressor wheel 43 side becomes lighter, so that the center of gravity G of the impeller 40 is the position of the center of gravity Gx of the impeller when the hollow portion 41a is not formed as shown in FIG. It moves further to the turbine wheel 42 side.

  Further, as shown in FIG. 10, in the bearing structure of the present embodiment, the same floating is performed in both the fluid bearing 50a on the turbine wheel 42 side and the fluid bearing 50b on the compressor wheel 43 side, as in the general bearing structure. Metal 51 is used. Therefore, the fulcrum P when the rotary shaft 41 precesses is positioned between the floating metals 51 as shown in FIG. Here, in the present embodiment, by forming the hollow portion 41a in the impeller 40, the position of the center of gravity G of the impeller 40 is moved further to the turbine wheel 42 side than the position of the center of gravity Gx of the general impeller. As shown in FIG. 10, the distance D between the fulcrum P of the precession of the rotary shaft 41 and the center of gravity G of the impeller 40 is further larger than these distances in a general bearing structure.

According to the third embodiment described above, the following effects can be obtained.
(1) Since the distance D between the fulcrum P of the precession motion and the gravity center G of the impeller 40 is increased by moving the center of gravity G of the impeller 40, the rotary shaft 41 swings around due to the precession motion. The inertia moment can be increased, and the generation of noise due to whirl vibration can be suppressed.

  (2) The response when raising the supercharging pressure can be improved as the impeller 40 of the turbocharger becomes lighter. In the third embodiment, the center of gravity G of the impeller 40 is formed by forming the hollow portion 41a extending along the axis L of the rotary shaft 41 from the rotation center of the end portion on the turbine wheel 42 side in the axial direction of the rotary shaft 41. To move. By moving the center of gravity G of the impeller 40 with such a configuration, it is possible to suppress the generation of noise due to the whirl vibration, reduce the weight of the impeller 40 as a whole, and improve the response when the boost pressure is increased. it can. Further, by forming the hollow portion 41a extending along the axis L of the rotary shaft 41 that is the rotation center of the impeller 40, the center of gravity of the impeller 40 can be moved without breaking the rotation balance.

The third embodiment can also be implemented in the following forms that are appropriately modified.
-Although the structure which forms the hollow part 41a extended along the axis line L from the edge part by the side of the compressor wheel 43 of the rotary shaft 41 was shown, the air introduced into the compressor housing 30 via the suction port 31 is this hollow part 41a. If it enters, it may be considered that the flow of the intake air is disturbed. Therefore, such disturbance of the intake air can be suppressed by plugging the opening of the hollow portion 41a.

  In the third embodiment, the configuration in which the compressor wheel 43 side is lightened by forming the hollow portion 41a in the impeller 40 has been shown, but in addition, the impeller 40 has a configuration in which the turbine wheel 42 side is heavy. The specific method of moving the center of gravity G of the can be changed as appropriate.

  The configurations of the first to third embodiments can be applied in combination. For example, a configuration in which a tapered surface is formed on the inner peripheral surface of the floating metal and the fulcrum P of the precession is moved, and a configuration in which the center of gravity G of the impeller 40 is moved by reducing one of the impellers is reduced. It is also possible to adopt a configuration in which the distance D between the fulcrum P and the center of gravity G is further increased.

  In the first to third embodiments, the center of gravity G of the impeller 40 is unevenly distributed on the turbine wheel 42 side. However, in the present invention, the center of gravity G is unevenly distributed on the turbine wheel 42 side. The bearing structure of the turbocharger provided with the impeller 40 is not limited. According to the position of the center of gravity G of the impeller, the direction of inclination of the tapered surface, the inclination angle thereof, and the arrangement of the floating metal having different thermal expansion coefficients are changed, so that the fulcrum P of the rotary shaft precession and the impeller The distance D from the center of gravity G can be further increased. In addition, the direction of moving the center of gravity of the impeller is changed as appropriate according to the position of the fulcrum P in the precession of the floating metal estimated by the inner diameter of the support hole of the floating metal or center housing, the shape of the rotary shaft, etc. By doing so, the distance D between the fulcrum P of the precession of the rotary shaft and the center of gravity G of the impeller can be further increased.

1 is a cross-sectional view showing a schematic configuration of a turbocharger according to a first embodiment of the present invention. Sectional drawing which expands and shows the part X of the turbocharger concerning the embodiment. (A) is a schematic diagram which shows the aspect of the precession of the rotary shaft in the bearing structure of the embodiment, (b) is a schematic diagram which shows the aspect of the precession of the rotary shaft in a general bearing structure. The schematic diagram which shows the aspect of the precession of the rotary shaft in the bearing structure concerning the example of a change of the embodiment. The schematic diagram which shows the aspect of the precession of the rotary shaft in the bearing structure concerning the example of a change of the embodiment. (A) is a schematic diagram which shows the aspect of the precession of the rotary shaft in the bearing structure concerning the modification of the embodiment, (b) is the schematic diagram which shows the aspect of the precession of the rotary shaft in a general bearing structure. Sectional drawing which expands and shows the bearing structure of the turbocharger concerning 2nd Embodiment of this invention. The schematic diagram which shows the aspect of the precession of the rotary shaft in the bearing structure of the embodiment. Sectional drawing of the impeller of the turbocharger concerning 3rd Embodiment of this invention. Sectional drawing which expands and shows the bearing structure concerning the embodiment. Sectional drawing which expands and shows the bearing structure of a general turbocharger. (A), (b), (c) is a schematic diagram which shows the aspect of the precession of the rotary shaft in a general turbocharger.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 ... Center housing, 11 ... Supply passage, 11a, 11b ... Discharge passage, 12a, 12b ... Support part, 13a, 13b ... Support hole, 20 ... Turbine housing, 21 ... Scroll passage, 22 ... Discharge port, 23 ... Introduction passage , 30 ... Compressor housing, 31 ... Suction port, 32 ... Compressor passage, 33 ... Delivery passage, 40 ... Impeller, 41 ... Rotary shaft, 41a ... Hollow portion, 42 ... Turbine wheel, 42a ... Blade, 43 ... Compressor wheel, 43a ... Blade, 50a, 50b ... Fluid bearing, 51a, 51b ... Floating metal, 52a, 52b ... Inner peripheral surface, 53 ... Snap ring, 54 ... Thrust bearing, 55 ... Through hole, 113 ... Support hole, 151 ... Floating metal, 152 ... inner peripheral surface, 251a, 251b ... Computing metal, 252a, 252b ... the inner circumferential surface, 351a, 351b ... floating metal, 352a, 352b ... the inner circumferential surface.

Claims (10)

A turbocharger bearing structure that rotatably supports an impeller in which a turbine wheel and a compressor wheel are connected by a rotary shaft, wherein the support hole is formed by lubricating oil discharged into a support hole through which the rotary shaft is inserted. In a turbocharger bearing structure in which a fluid layer is formed by lubricating oil between the rotary shaft and the rotary shaft is rotatably supported via the fluid layer.
Increasing the moment of inertia that increases the moment of inertia of the impeller in the precession by increasing the distance between the fulcrum of the precession of the impeller generated by the swirl flow generated in the fluid layer and the center of gravity of the impeller A turbocharger bearing structure comprising: means. The turbocharger bearing structure according to claim 1,
As the inertia moment increasing means, a tapered surface for guiding the inclination of the rotary shaft in the precession is formed on the inner peripheral surface of the support hole so that the fulcrum of the precession is separated from the center of gravity of the impeller. A turbocharger bearing structure characterized by The turbocharger bearing structure according to claim 2,
The taper surface is formed in such a manner that the inner diameter of the support hole gradually increases as it approaches a wheel closer to the center of gravity of the impeller among the wheels. A rotary shaft inserted through a cylindrical floating metal is inserted into the support hole together with the floating metal, between the support hole and the outer peripheral surface of the floating metal, and an inner peripheral surface of the floating metal and the rotary shaft. Each of which forms a fluid layer of the lubricating oil, and supports the rotary shaft through the fluid layer so as to be rotatable. The bearing structure of the floating metal is used as the moment of inertia increasing means. 2. The turbocharger bearing according to claim 1, wherein a taper surface that guides an inclination of the rotary shaft during the precession is formed on an inner peripheral surface so that a fulcrum of the precession is separated from a center of gravity of the impeller. Construction. The turbocharger bearing structure according to claim 4,
The taper surface is formed in such a manner that the inner diameter of the floating metal gradually increases as it approaches a wheel closer to the center of gravity of the impeller among the wheels. The rotary shaft is supported by a plurality of floating metals, and the tapered surfaces are respectively set on the inner peripheral surface of each floating metal so that the inclination angles thereof are set to be equal and on the same conical surface. The turbocharger bearing structure according to claim 5 formed. In the turbocharger bearing structure according to any one of claims 2 to 6,
The turbocharger is characterized in that the inclination angle of the rotary shaft guided by the taper surface is set so that the inclination angle of the rotary shaft is smaller than a maximum inclination angle at which the rotary shaft can be inclined. Bearing structure. The rotary shaft inserted through a pair of floating metals is inserted into the support hole together with the floating metal, and between the support hole and the outer peripheral surface of each floating metal, and the inner peripheral surface of each floating metal and the rotary shaft Each of which forms a fluid layer made of lubricating oil and rotatably supports the rotary shaft via the fluid layer. Of the pair of floating metals, the one closer to the center of gravity of the impeller The turbocharger bearing structure according to claim 1, wherein the floating metal is made of a material having a larger thermal expansion coefficient than the other floating metal. The turbocharger bearing structure according to claim 1,
The turbocharger bearing structure, wherein the inertia moment increasing means moves the center of gravity of the impeller so that a distance between a fulcrum of the precession and the center of gravity of the impeller is increased. The turbocharger bearing structure according to claim 9,
A turbocharger bearing structure, wherein the center of gravity of the impeller is moved by forming a hollow portion extending along the rotation axis of the rotary shaft from the rotation center of one end portion in the axial direction of the rotary shaft.

Images