Supercharger

Abstract

To provide a supercharger capable of preventing any of a rotational shaft, a turbine wheel and a compressor impeller from contacting peripheral members (for example, an inside surface of a housing constituting the supercharger) even when performance deterioration of a bearing for rotatably holding the rotational shaft provided with the turbine wheel and the compressor impeller occurs.SOLUTION: A supercharger has: a main bearing that contacts an oil region where lubricant is held in a rotational shaft, and rotatably holds the rotational shaft; and an auxiliary bearing that contacts the oil region and rotatably holds the rotational shaft when the main bearing cannot hold the rotational shaft.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to a turbocharger, and more particularly to a turbocharger having a rotating shaft on which a turbine wheel and a compressor impeller are provided. [Background technology]

[0002] Patent Document 1 discloses a lubrication structure for a rolling bearing that rotatably holds this type of rotating shaft. According to this structure, an oil reservoir that stores lubricating oil supplied through an oil passage is formed around the rolling bearing. Therefore, at start-up, when the flow rate of lubricating oil flowing through the oil passage is low, lubricating oil is supplied from the oil reservoir to the rolling bearing. As a result, the rolling bearing is suitably lubricated even at start-up. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2023-167847 Summary of the Invention [Problem to be solved by the invention]

[0004] However, if the performance of the rolling bearing deteriorates, it may become difficult to stably hold the rotating shaft. In this case, the whirling of the rotating shaft increases, which may result in the rotating shaft, turbine wheel, or compressor impeller (hereinafter also referred to as "rotating body") coming into contact with a surrounding component (for example, the inner surface of the housing that constitutes the turbocharger).

[0005] The present invention was devised in consideration of these points, and aims to provide a turbocharger that can prevent the rotating body from coming into contact with surrounding components even when performance degradation of the bearing occurs. [Means for solving the problem]

[0006] In order to solve the above problems, a turbocharger according to a first aspect of the present invention includes a rotating shaft provided with a turbine wheel and a compressor impeller, a main bearing that comes into contact with an oil region of the rotating shaft in which lubricating oil is retained and rotatably holds the rotating shaft, and an auxiliary bearing that comes into contact with the oil region and rotatably holds the rotating shaft when the main bearing cannot retain the rotating shaft.

[0007] A second aspect of the present invention is the turbocharger according to the first aspect of the present invention, further comprising a shaft seal for partitioning the oil region, and the sub-bearing is disposed between the main bearing and the shaft seal.

[0008] A third aspect of the present invention is the turbocharger according to the first or second aspect of the present invention, wherein the rotating shaft is formed with an annular convex portion for separating the lubricating oil from the rotating shaft, and the sub-bearing is disposed between the main bearing and the annular convex portion.

[0009] A fourth aspect of the present invention is the turbocharger according to the first aspect, wherein at least one of an area of the rotating shaft that contacts the auxiliary bearing and an area of the auxiliary bearing that contacts the rotating shaft is made of a wear-resistant material. [Effects of the Invention]

[0010] In the first aspect of the present invention, if the performance of the main bearing deteriorates, the rotating shaft is rotatably held by the secondary bearing. This prevents the rotating body from coming into contact with surrounding components. In this case, the secondary bearing, like the main bearing, contacts the area of the rotating shaft where lubricating oil is held (i.e., the area where an oil film is formed), thereby preventing wear of the secondary bearing. This makes it possible to maintain the state in which the rotating shaft is rotatably held by the secondary bearing for a relatively long period of time. In addition, the formation of an oil film on the area of the rotating shaft facing the secondary bearing contributes to reducing frictional resistance between the rotating shaft and the secondary bearing.

[0011] In the second aspect of the present invention, the sub-bearing is disposed between the main bearing and a shaft seal that defines an area on the rotating shaft where lubricating oil supplied to the main bearing is retained (i.e., an oil area where an oil film is formed). This increases the likelihood that an oil film sufficient to reduce wear of the sub-bearing will be formed in the area of the rotating shaft that comes into contact with the sub-bearing.

[0012] In the third aspect of the present invention, an auxiliary bearing is disposed between the main bearing and an annular protrusion for removing lubricating oil supplied to the main bearing from the rotating shaft. For example, if the turbocharger also has a shaft seal, the annular protrusion is disposed between the auxiliary bearing and the shaft seal. According to the third aspect of the present invention, there is a high possibility that an oil film sufficient to reduce wear of the auxiliary bearing will be formed in the area of the rotating shaft that contacts the auxiliary bearing.

[0013] According to the fourth aspect of the present invention, wear of the auxiliary bearing and / or the area of the rotating shaft that comes into contact with the auxiliary bearing is reduced, so that the rotating shaft can be maintained in a state in which it is rotatably held by the auxiliary bearing for an even longer period of time. [Brief explanation of the drawings]

[0014] [Figure 1] 1 is a schematic diagram (cross-sectional view) of a turbocharger according to an embodiment. [Figure 2] FIG. 2 is a partially enlarged cross-sectional view of the turbocharger. [Figure 3] FIG. 2 is a cross-sectional perspective view of an auxiliary bearing of the turbocharger. DETAILED DESCRIPTION OF THE INVENTION

[0015] An embodiment of the present invention will be described with reference to Figures 1 to 3. The same symbols (reference numerals) used in the description refer to the same elements having the same functions, although duplicated descriptions will not be given. A supercharger 1 according to this embodiment is disposed in an internal combustion engine (not shown) mounted on a vehicle as a driving force source. The supercharger 1 is operated by exhaust gas from the internal combustion engine and pressurizes and feeds intake air to the internal combustion engine.

[0016] As shown in Figures 1 and 2, the turbocharger 1 includes a main body case 10, a main bearing 21 housed in the main body case 10, a rotating shaft 41, a turbine wheel 42, a compressor impeller 43, a pair of shaft seals 44, and a pair of auxiliary bearings 45.

[0017] The main bearing 21 rotatably holds the rotating shaft 41. A turbine wheel 42 is fixed to one end of the rotating shaft 41. A compressor impeller 43 is fixed to the other end of the rotating shaft 41. That is, the turbine wheel 42 and the compressor impeller 43 rotate integrally with the rotating shaft 41 held (supported) by the main bearing 21. The rotating shaft 41, the turbine wheel 42, and the compressor impeller 43 are also collectively referred to as a "rotating body."

[0018] 1 and 2 represents the axis of the rotating shaft 41 (i.e., the central axis of rotation of the rotating shaft 41 held by the main bearing 21). Hereinafter, the extending direction of the dashed dotted line Lc is also referred to as the axial direction A. The turbocharger 1 according to this embodiment is mounted on the vehicle described above so that the axial direction A is approximately horizontal. In addition, the direction perpendicular to the axial direction A and extending approximately vertically up and down is also referred to as the vertical direction B. The vertical direction B is also one of the radial directions of the rotating shaft 41.

[0019] The main body case 10 is formed with an exhaust passage 11, an intake passage 12, a bearing space 13, a pair of shaft housings 14, a supply passage 15, and a discharge passage 16. A turbine wheel 42 is housed in the exhaust passage 11. A compressor impeller 43 is housed in the intake passage 12.

[0020] The turbine wheel 42 rotates due to the pressure of the exhaust gas discharged from the internal combustion engine and flowing into the exhaust passage 11. That is, the turbine wheel 42 rotates due to the exhaust pressure of the internal combustion engine. The exhaust gas that rotates the turbine wheel 42 flows out from the exhaust passage 11. The compressor impeller 43, which rotates together with the turbine wheel 42, compresses the intake air that has flowed into the intake passage 12 and causes it to flow toward the internal combustion engine. That is, high-pressure intake air is discharged from the intake passage 12.

[0021] 1 and 2, the turbine wheel 42 and the compressor impeller 43 are indicated by two-dot chain lines (outer shell lines). More specifically, the sets of positions (points) on the turbine wheel 42 and the compressor impeller 43 that are farthest from the one-dot chain line Lc are indicated by the two-dot chain lines.

[0022] The minimum value of the length (gap, clearance) from the inner surface of the main body case 10 that forms the exhaust flow path 11 to the turbine wheel 42 is length t1 (see FIG. 1). Similarly, the minimum value of the length from the inner surface of the main body case 10 that forms the intake flow path 12 to the compressor impeller 43 is length t2. Because gaps are formed between the turbine wheel 42 and the compressor impeller 43 and the inner surface of the main body case 10, contact (interference) between the turbine wheel 42 and the compressor impeller 43 and the inner surface of the main body case 10 is avoided when the rotating body rotates.

[0023] The bearing space 13 accommodates a main bearing 21. The main bearing 21 has a substantially cylindrical shape, and a rotating shaft 41 is inserted through the main bearing 21. The main bearing 21 is a semi-floating type sliding bearing, and is disposed between the inner wall surface of the main body case 10, which forms the bearing space 13, and the outer peripheral surface of the rotating shaft 41, to rotatably hold (support) the rotating shaft 41.

[0024] (oil road) 2, an example of the distribution of lubricating oil in the turbocharger 1 is shown by a pattern. Lubricating oil is supplied to the supply passage 15 from an oil pump (not shown). The lubricating oil supplied to the supply passage 15 flows into the bearing space 13, and an oil film is formed between the inner wall surface of the bearing space 13 and the outer peripheral surface of the main bearing 21. In addition, an oil film is also formed between the inner peripheral surface of the main bearing 21 and the outer peripheral surface of the rotating shaft 41. In other words, the main bearing 21 is in contact with an area of the rotating shaft 41 where the lubricating oil is held. More specifically, a plurality of bearing oil holes 21a are formed in approximately the center of the main bearing 21 in the axial direction A. Each of the bearing oil holes 21a extends radially (i.e., in a direction perpendicular to the axial direction A). Some of the lubricating oil that flows into the bearing space 13 passes through the bearing oil holes 21a (particularly the bearing oil holes 21a that are above the rotating shaft 41) and the outside of both ends of the main bearing 21 (i.e., the left and right ends of the main bearing 21 shown in Figure 2), and flows between the inner surface of the main bearing 21 and the outer surface of the rotating shaft 41.

[0025] The lubricating oil that has flowed into the bearing space 13 is discharged from the turbocharger 1 through the discharge passage 16. The lubricating oil that has formed an oil film between the inner peripheral surface of the main bearing 21 and the outer peripheral surface of the rotating shaft 41 reaches the discharge passage 16 through the bearing oil holes 21a (particularly the bearing oil holes 21a that are located below the rotating shaft 41). Note that the lubricating oil supplied to the turbocharger 1 does not need to be specialized for lubrication (i.e., friction reduction), and may be an oil type that also has functions such as sealing and cooling.

[0026] (lubricating oil shaft seal) In order to prevent the lubricating oil in the oil passage 51 from reaching the turbine wheel 42 and / or the compressor impeller 43, each shaft accommodating portion 14 is formed with a labyrinth structure including a shaft seal 44. More specifically, the shaft seal 44 is fixed to the inner surface of the main body case 10 that forms the shaft accommodating portion 14. The shaft seal 44 has an annular shape, and the rotating shaft 41 is inserted through the shaft seal 44.

[0027] The inner peripheral surface of the shaft seal 44 protrudes toward the rotating shaft 41. Meanwhile, the rotating shaft 41 is formed with an annular recess 41a corresponding to the shaft seal 44 (see FIG. 2). The combination of the annular recess 41a of the rotating shaft 41 and the shaft seal 44 (i.e., a labyrinth structure) prevents the fluid from moving in the axial direction A.

[0028] In the labyrinth structure, the length (i.e., the gap) from the inner surface of the main body case 10 that forms the shaft accommodating portion 14 to the outer surface of the rotating shaft 41 is relatively small. In the shaft accommodating portion 14 on the turbine wheel 42 side, the minimum value of the gap with the rotating shaft 41 is length t3 (see FIG. 2). Similarly, in the shaft accommodating portion 14 on the compressor impeller 43 side, the minimum value of the gap with the rotating shaft 41 is length t4. In this embodiment, length t3 and length t4 are approximately equal to each other. In addition, length t3 and length t4 are shorter than length t1 and length t2, respectively.

[0029] Furthermore, in order to remove the lubricating oil on the rotating shaft 41 before it reaches the shaft seal 44, an annular protrusion 41b is formed in each section of the rotating shaft 41 between the main bearing 21 and the shaft seal 44 (see FIG. 2). On the other hand, the section of the shaft accommodating portion 14 facing the annular protrusion 41b has a larger inner diameter. That is, a recess corresponding to the annular protrusion 41b is formed on the inner surface of the main case 10. The shaft accommodating portion 14 is connected to a discharge passage 16. In other words, the shaft accommodating portion 14 connected to the discharge passage 16 forms a discharge path (i.e., an oil drain) for the lubricating oil.

[0030] When the turbocharger 1 is operating (i.e., when the rotating shaft 41 is rotating), most of the lubricating oil flowing on the surface of the rotating shaft 41 from the oil passage 51 toward the shaft seal 44 is separated from the rotating shaft 41 at the top of the annular protrusion 41b by centrifugal force and flows into the shaft accommodating portion 14. That is, the lubricating oil on the rotating shaft 41 is separated at the position where the radius of the rotating shaft 41 is maximum in the section where the annular protrusion 41b is formed, and flows into the shaft accommodating portion 14. The lubricating oil that has flowed into the shaft accommodating portion 14 is discharged via the discharge passage 16.

[0031] (auxiliary bearing) Each of the sub-bearings 45 is fixed to the inner surface of the main case 10, which forms the shaft accommodating portion 14, at a position between the main bearing 21 and the annular protrusion 41b. The sub-bearings 45 have an annular shape, and the rotating shaft 41 is inserted through each of the sub-bearings 45. The gap between the outer surface of the rotating shaft 41 held by the main bearing 21 and the inner surface of the sub-bearing 45 has a length t5 (see FIG. 2). That is, the radius of the cylindrical through hole formed by the inner surface of the sub-bearing 45 is larger by the length t5 than the radius of the section of the rotating shaft 41 that faces the sub-bearing 45. The length t5 is smaller than each of the lengths t1 to t4.

[0032] More specifically, the runout deviation of the main bearing 21 is smaller than the length t5. In other words, the whirling of the rotating shaft 41 rotatably held by the main bearing 21 is smaller than the length t5, and therefore, the rotating shaft 41 does not come into contact (interfere) with the sub-bearing 45. In other words, a gap (space) is formed between the outer circumferential surface of the rotating shaft 41 and the inner circumferential surface of the sub-bearing 45.

[0033] However, as the runout deviation of the main bearing 21 increases due to breakage, damage, etc., the gap between the rotating shaft 41 and the sub-bearing 45 decreases. When the runout deviation of the main bearing 21 becomes relatively large (i.e., when performance degradation of the main bearing 21 occurs), the rotating shaft 41 comes into contact with one or both of the sub-bearings 45. In other words, when the main bearing 21 cannot rotatably hold the rotating shaft 41, the sub-bearing 45 rotatably holds the rotating shaft 41.

[0034] When the rotating shaft 41 is rotatably held by the sub-bearing 45, the whirling of the rotating shaft 41 (i.e., the runout deviation of the rotating shaft 41 held by the sub-bearing 45) is smaller than each of the lengths t1 to t4. In other words, when the rotating shaft 41 is rotatably held by the sub-bearing 45, the whirling of the rotating shaft 41 is greater than when the rotating shaft 41 is held by the main bearing 21. However, even when the rotating shaft 41 is rotatably held by the sub-bearing 45, the length t5 is adjusted so that the rotating body does not come into contact with peripheral members (specifically, the main body case 10 and the shaft seal 44).

[0035] As shown in Fig. 3, oil grooves 45a are formed in the sub-bearing 45. More specifically, the oil grooves 45a are recesses extending in the axial direction A on the inner peripheral surface of the sub-bearing 45 (i.e., the surface facing the outer peripheral surface of the rotating shaft 41). The oil grooves 45a are provided at 120° intervals around the center of the annular sub-bearing 45. That is, three oil grooves 45a are formed in the sub-bearing 45. Two of these oil grooves 45a are shown in Fig. 3.

[0036] The sub-bearings 45 in this embodiment are made of phosphor bronze, a type of wear-resistant material. Therefore, the sub-bearings 45 have excellent wear resistance, and even when the rotating shaft 41 held by each of the sub-bearings 45 rotates, wear of the sub-bearings 45 (i.e., change in shape and, ultimately, increase in whirling of the rotating shaft 41 held by the sub-bearings 45) is suppressed. The wear-resistant material constituting the sub-bearings 45 may be a copper-based alloy (e.g., a copper-lead alloy) or an aluminum alloy (e.g., an aluminum-tin alloy). As one example, the sub-bearings 45 are formed so that their inner diameter (i.e., the diameter of the through hole through which the rotating shaft 41 is inserted) is approximately 10 mm and their thickness (i.e., the length in the axial direction A) is 3 to 5 mm.

[0037] As described above, according to the turbocharger 1, when the main bearing 21 is unable to rotatably hold the rotating shaft 41, the rotating shaft 41 is rotatably held by the sub-bearing 45. In other words, even if performance degradation occurs in the main bearing 21, the rotating bodies (i.e., the rotating shaft 41, the turbine wheel 42, and the compressor impeller 43) are rotatably held (supported) without interfering with surrounding members, and thus the turbocharger 1 can continue to operate.

[0038] As described above, the lengths t3 and t4 are shorter than the lengths t1 and t2, respectively. Therefore, if the sub-bearing 45 were not provided in the turbocharger 1 and the main bearing 21 could not rotatably hold the rotating shaft 41, the rotating body would come into contact with the shaft seal 44 and an area near the shaft seal 44 on the inner surface of the main body case 10 (rather than the inner surfaces of the exhaust passage 11 and the intake passage 12). That is, in this case, the rotation of the rotating body would be hindered, making it difficult for the turbocharger 1 to continue operating.

[0039] In addition, when the sub-bearing 45 holds the rotating shaft 41, the sub-bearing 45 abuts against an area of the rotating shaft 41 where an oil film is formed (i.e., an area where lubricating oil is held, also referred to as an "oil area"). This makes it possible to prevent wear on the sub-bearing 45 and / or the rotating shaft 41. In other words, it becomes possible to maintain the state in which the sub-bearing 45 rotatably holds the rotating shaft 41 for a relatively long period of time. In addition, the fact that an oil film is formed in an area of the rotating shaft 41 facing the sub-bearing 45 contributes to reducing frictional resistance between the rotating shaft 41 and the sub-bearing 45.

[0040] More specifically, since the lubricating oil is supplied to the bearing space 13 via the supply passage 15, an oil film is formed between the main bearing 21 and the rotating shaft 41. Even if the lubricating oil supplied to the rotating shaft 41 flows toward the turbine wheel 42 and / or the compressor impeller 43, most of the lubricating oil is removed from the rotating shaft 41 by the annular protrusion 41b. Furthermore, the shaft seal 44 prevents the lubricating oil from reaching the turbine wheel 42 and / or the compressor impeller 43. That is, the shaft seal 44 defines an oil region. Therefore, it is highly likely that an oil film sufficient to reduce wear of the sub-bearing 45 is formed in the region of the rotating shaft 41 between the main bearing 21 and the annular protrusion 41b. In other words, the lubricating oil that flows into the turbocharger 1 via the supply passage 15 is sufficiently supplied to the main bearing 21 and the sub-bearing 45.

[0041] Furthermore, the fact that the rotating shaft 41 is made of a wear-resistant material further contributes to reducing wear on the sub-bearing 45. On the other hand, even when the rotating shaft 41 is rotatably held by the sub-bearing 45, the rotating shaft 41 does not come into contact with the shaft seal 44, so the shaft seal 44 does not need to be made of a wear-resistant material.

[0042] Furthermore, the formation of oil groove 45a in sub-bearing 45 promotes the even distribution of the oil film formed in the area of rotating shaft 41 facing sub-bearing 45. In other words, oil groove 45a contributes to reducing wear on sub-bearing 45 and reducing frictional resistance between rotating shaft 41 and sub-bearing 45.

[0043] Although the embodiments of the present invention have been described above with reference to the above structures, many modifications, improvements, and variations are possible without departing from the scope of the present invention. Therefore, the present invention includes all modifications, improvements, and variations that do not depart from the spirit and scope of the appended claims. The present invention is not limited to the specific structures described above, and modifications such as those described below are possible.

[0044] The main bearing 21 was a sliding bearing. Alternatively, the main bearing 21 may be configured as a rolling bearing (i.e., a ball bearing including rolling elements) that rotatably holds the rotating shaft 41. Even in this case, the main bearing 21 rotatably holds the rotating shaft 41, and if the main bearing 21 cannot rotatably hold the rotating shaft 41, the rotating shaft 41 is rotatably held by the sub-bearing 45. In addition, the rolling bearing (particularly the rolling elements included in the rolling bearing) comes into contact with the rotating shaft 41 via an oil film (i.e., lubricating oil supplied via the oil passage 51 and held on the rotating shaft 41).

[0045] The sub-bearing 45 was made of a wear-resistant material. Alternatively, the sub-bearing 45 may be made of a known iron-based material, and the inner circumferential surface of the sub-bearing 45 (i.e., the area that contacts the rotating shaft 41) may be plated with a wear-resistant material. In other words, the entire sub-bearing 45 does not have to be made of a wear-resistant material. Alternatively, the area of the rotating shaft 41 that faces the sub-bearing 45 may be plated with a wear-resistant material. At least the section of the rotating shaft 41 that faces the sub-bearing 45 may be made of a wear-resistant material.

[0046] The turbine wheel 42 and the compressor impeller 43 are fixed to the rotary shaft 41. Alternatively, the turbine wheel 42, the compressor impeller 43, and the rotary shaft 41 (i.e., the rotary body) may be integrally formed. [Explanation of symbols]

[0047] 1...Turbocharger 10...Main body case, 11...Exhaust passage, 12...Intake passage, 13...Bearing space 14...shaft receiving portion, 15...supply passage, 16...discharge passage 21...Main bearing, 21a...Bearing oil hole 41...rotating shaft, 41a...annular recess, 41b...annular protrusion 42...Turbine wheel, 43...Compressor impeller, 44...Shaft seal 45... Sub-bearing, 45a... Oil groove 51...Oil road A...Axis direction, B...Vertical direction t1~t5...length (gap)

Claims

1. A turbocharger, a rotating shaft provided with a turbine wheel and a compressor impeller; a main bearing that contacts an oil region of the rotating shaft in which lubricating oil is retained and rotatably holds the rotating shaft; an auxiliary bearing that comes into contact with the oil region and rotatably holds the rotating shaft when the main bearing cannot hold the rotating shaft.

2. The turbocharger according to claim 1, a shaft seal for partitioning the oil region; The auxiliary bearing is disposed between the main bearing and the shaft seal.

3. The turbocharger according to claim 1 or 2, The rotating shaft is formed with an annular protrusion for separating the lubricating oil from the rotating shaft, The auxiliary bearing is disposed between the main bearing and the annular protrusion.

4. The turbocharger according to claim 1, a region of the rotating shaft that contacts the auxiliary bearing and / or a region of the auxiliary bearing that contacts the rotating shaft, the region being made of a wear-resistant material;

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