turbocharger

Abstract

Turbocharger (C), which includes: a turbocharger body (1); a turbine shaft (7) rotatably mounted in the turbocharger body (1), with a turbine impeller (8) provided at one end of the turbine shaft (7) and a compressor impeller (9) provided at the opposite end of the turbine shaft (7); a bearing (20) provided in the turbocharger body (1) and configured to rotatably support the turbine shaft (7) in an insertion hole (21) formed in the bearing (20); and an opposite section (25a, 25b) which faces an end surface (26, 27) of the bearing (20) in an axial direction of the turbine shaft (7), wherein an end-surface guide section (28) designed as a groove, configured to cause the insertion hole (21) and an outer circumferential edge (26b) of the end surface (26) of the bearing (20) to be in contact with each other in radial directions of the turbine shaft (7), is provided on an opposite surface of the bearing (20) facing the opposite section (25a, 25b), or on an opposite surface of the opposite section (25a, 25b) facing the bearing (20), the end surface guide section (28) extends forward in a direction of rotation of the turbine shaft (7) from a part of the end surface (26, 27) of the bearing (20) which is connected with the insertion hole (21), and the end surface guide section (28) forms a passage configured to discharge a foreign substance (a) together with lubricant from the opposite surface provided with the end surface guide section (28) to the outside of the opposite surface in the radial directions, characterized in that the end surface guide section (28) extends along a path defined by the equation given below: r = r 1 exp [ ( θ − θ 1 ) 2 2 ] where r represents the distance of an oil droplet of the lubricant, which absorbs part of the rotational force of the turbine shaft (7), from the center of rotation and θ represents the phase angle of the oil droplet and where r=r1 and θ=θ1 at time t=0.

Description

[0001] The present invention relates to a turbocharger with a bearing designed to absorb an axial load.

[0002] Traditional turbochargers consisted of a turbine shaft rotatably supported by a bearing housing, with a turbine impeller at one end and a compressor impeller at the other. This turbocharger was connected to an engine. The turbine impeller was rotated by exhaust gases from the engine. This rotation was then transferred to the compressor impeller via the turbine shaft, causing it to rotate as well. The turbocharger thus compressed the air, boosting the engine with this compressed air.

[0003] A bearing configured to rotatably support the turbine shaft is provided within the bearing housing. While supporting the turbine shaft, the bearing accepts both a radial and an axial load. Lubricant is supplied to the space between an end surface of the bearing in an axial direction of the turbine shaft and, for example, a thrust ring opposite the end surface. However, it is not easy for the lubricant to reach the space without some arrangement, as the axial load causes the bearing and thrust ring to collide. In a turbocharger described in PTL 1, several grooves through which the lubricant flows are provided on an end surface of a bearing, such that they come into contact with a thrust ring, in such a way that they extend in radial directions of the bearing.

[0004] A turbocharger with the features described in claims 1 and 6 is known from JP 2008 - 190 498 A. [List of prior art][Patent literature]

[0005] [PTL 1] Japanese Patent Publication JP 2007 - 023 858 A [Summary of the invention][Technical problem]

[0006] When a foreign substance enters the lubricant, it moves along the inner circumferential surface of the bearing and reaches the bearing's end surface. Subsequently, due to a centrifugal force associated with the rotation of the turbine shaft, the foreign substance, along with the lubricant, is expelled radially from the bearing and forward in the direction of rotation of the turbine shaft. Consequently, in the turbocharger described in PTL 1, the foreign substance can leak out of the grooves in a circumferential direction and become trapped between the thrust ring and the bearing, damaging the bearing or blocking the grooves, thus preventing the lubricant from flowing through them.

[0007] One object of the present invention is to create a turbocharger that is able to remove foreign matter that may enter the lubricant by improving the performance of the bearing, reducing damage to its bearing and improving its lubrication performance. [Solution to the problem]

[0008] A first aspect of the present invention provides a turbocharger comprising: a turbocharger body; a turbine shaft rotatably mounted in the turbocharger body, with a turbine impeller provided at one end of the turbine shaft and a compressor impeller provided at the opposite end of the turbine shaft; a bearing provided in the turbocharger body and configured to rotatably support the turbine shaft in an insertion hole formed in the bearing; and an opposing section facing an end surface of the bearing in an axial direction of the turbine shaft.Here, an end-surface guide section is provided, configured to cause the insertion hole and an outer circumferential edge of the bearing end surface to communicate with each other in radial directions of the turbine shaft, at any of an opposing surface of the bearing facing the opposite section and an opposing surface of the opposing section facing the bearing. The end-surface guide section further extends forward in a direction of rotation of the turbine shaft from a portion of the bearing end surface communicating with the insertion hole.

[0009] Here, the end-surface guide section can form a passage configured to carry away foreign matter along with lubricant from the opposite surface, which is equipped with the end-surface guide section, to the outside of the opposite surface in radial directions. Furthermore, the orientation of the end-surface guide section can be aligned with the direction of movement of oil droplets of lubricant that absorb a rotational force from the turbine shaft.

[0010] The bearing can be formed from a bushing with a running surface configured to accept a radial load from the turbine shaft, with an oil film being maintained between the running surface and the turbine shaft.

[0011] The running surface or an outer circumferential surface of the turbine shaft facing the running surface can be provided with a running surface guide section formed by a groove extending from one end to the opposite end in the axial direction of the turbine shaft. Here, one end of the running surface guide section in the axial direction of the turbine shaft can be in contact with the end surface guide section, and this one end of the running surface guide section in the axial direction of the turbine shaft can be positioned further forward in the direction of rotation of the turbine shaft than the opposite end of the running surface guide section.

[0012] The running surface guide section can form a passage configured to carry away foreign matter along with the lubricant from the running surface to the end surface guide section. Furthermore, the running surface guide section can be oriented along the direction of movement of the lubricant droplets that absorb the rotational force of the turbine shaft.

[0013] The bearing can be formed from a semi-floating bearing, the movement of which in its rotational and axial direction is restricted by a pin provided on the turbocharger body.

[0014] A second aspect of the present invention provides a turbocharger comprising: a turbocharger body; a turbine shaft rotatably mounted in the turbocharger body, with a turbine impeller provided at one end of the turbine shaft and a compressor impeller provided at the opposite end of the turbine shaft; a thrust ring configured to rotate integrally with the turbine shaft; and a thrust bearing arranged facing the thrust ring in an axial direction of the turbine shaft, the turbine shaft being inserted into an insertion hole formed in the thrust bearing, and the thrust bearing being configured to absorb an axial load of the turbine shaft via the thrust ring.Here, an end-surface guide section is provided, configured to cause the insertion hole and an outer circumferential edge of the thrust ring to communicate with each other in radial directions of the turbine shaft, at any opposite surface of the thrust bearing facing the thrust ring and an opposite surface of the thrust ring facing the thrust ring. The end-surface guide section further extends forward in a direction of rotation of the turbine shaft from a portion of an end surface of the thrust bearing communicating with the insertion hole.

[0015] Here, the end-surface guide section can form a passage configured to carry away foreign matter along with lubricant from the opposite surface, which is equipped with the end-surface guide section, to the outside of the opposite surface in radial directions. Furthermore, the orientation of the end-surface guide section can be aligned with the direction of movement of oil droplets of lubricant that absorb a rotational force from the turbine shaft. [Advantageous effects of the invention]

[0016] The present invention can reduce damage to the bearing and improve lubrication performance by improving the bearing's performance in removing foreign substances. [Brief description of the drawings] [ Fig. 1] Fig. Figure 1 is a schematic cross-sectional view of a turbocharger of an embodiment of the present invention. [ Fig. 2] Fig. 2 is a partially enlarged view of the interior of a Fig. 1 bearing housing shown. [ Fig. 3] Fig. 3(a) is a view of an end surface of a bearing of the embodiment of the present invention, which is from the front of the turbocharger body, and Fig. Figure 3(b) is a front view of a bearing contained in a conventional turbocharger shown for comparison. [ Fig. 4] Fig. Figure 4 is a cross-sectional view of the bearing of the embodiment of the present invention, which is along a plane parallel to the axial direction of the bearing. [ Fig. 5] Fig. Figure 5 is a schematic cross-sectional view of the interior of a bearing housing of a modified example of the embodiment of the present invention. [Description of the embodiments]

[0017] With reference to the accompanying drawings, detailed descriptions of one embodiment of the present invention are provided below. Dimensions, materials, specific numerical values, and the like in this embodiment are shown as examples only to facilitate understanding of the present invention and do not limit it unless otherwise stated. In the patent description and the drawings, components with theoretically the same functions and configurations are designated with the same reference numerals, and redundant explanations are avoided. Components not directly related to the present invention are omitted from the drawings.

[0018] Fig. Figure 1 is a schematic cross-sectional view of a turbocharger C according to the embodiment. The following descriptions are indicated by the direction of the arrow F in the Fig. 1, which points towards the front of the turbocharger C, and with a direction of arrow R in Fig. 1, which points towards the rear of turbocharger C, is given. As in Fig. As shown in Figure 1, the turbocharger C comprises a turbocharger body 1. The turbocharger body 1 includes: a bearing housing 2; a turbine housing 4, which is connected to the front of the bearing housing 2 by means of a fastening screw 3; and a compressor housing 6, which is connected to the rear of the bearing housing 2 by means of a fastening screw 5. These housings are integrated into the turbocharger body 1.

[0019] A bearing bore 2a is formed in the bearing housing 2. The bearing bore 2a penetrates the bearing housing 2 in the front-to-rear direction of the turbocharger C. A turbine shaft 7 is rotatably supported by a bearing 20, which will be described later and is provided at the bearing bore 2a. A turbine impeller 8 is integrally attached to the front end section (one end) of the turbine shaft 7. The turbine impeller 8 is rotatably mounted in the turbine housing 4. A compressor impeller 9 is also integrally attached to the rear end section (the other end) of the turbine shaft 7. The compressor impeller 9 is rotatably mounted in the compressor housing 6.

[0020] An inlet channel 10 is formed in the compressor housing 6. The inlet channel 10 opens towards the rear of the turbocharger C and is connected to an air filter, although not shown. Furthermore, when the bearing housing 2 and the compressor housing 6 are connected to each other using the fastening screw 5, the opposing surfaces of the two housings 2, 6 form a diffuser passage 11 configured to compress and charge air. The diffuser passage 11 is ring-shaped, extending from its inner to its outer side in the radial directions of the turbine shaft 7 (the compressor impeller 9). The inner side of the diffuser passage 11, in the radial directions, communicates with the inlet channel 10 via the compressor impeller 9.

[0021] Furthermore, the compressor housing 6 is provided with a compressor screw passage 12. The compressor screw passage 12 is ring-shaped and lies outside the diffuser passage 11 in the radial directions of the turbine shaft 7 (of the compressor impeller 9). The compressor screw passage 12 is connected to an inlet port of a power engine, although not shown, and is also connected to the diffuser passage 11. Therefore, as soon as the compressor impeller 9 rotates, fluid is introduced into the compressor housing 6 from the inlet port 10; the pressure of the introduced fluid is increased by the diffuser passage 11 and the compressor screw passage 12; and the resulting fluid is directed to the inlet port of the power engine.

[0022] An outlet channel 13 is formed in the turbine housing 4. The outlet channel 13 opens towards the front of the turbocharger C and is connected to an exhaust gas cleaning system (not shown). Furthermore, the turbine housing 4 is provided with a passage 14 and a turbine screw passage 15. The turbine screw passage 15 is ring-shaped and lies outside the passage 14 in the radial directions of the turbine shaft 7 (of the turbine impeller 8). The turbine screw passage 15 is connected to a gas inlet channel (not shown), to which exhaust gas emitted from an exhaust manifold of the engine (not shown) is directed. The turbine screw passage 15 is also connected to the passage 14. The exhaust gas is directed from the gas inlet channel to the turbine screw passage 15 and is then directed to the outlet channel 13 via the passage 14 and the turbine impeller 8.For this reason, during its flow process, the exhaust gas rotates the turbine impeller 8. The torque of the turbine impeller 8 is then transmitted to the compressor impeller 9 via the turbine shaft 7. The torque of the compressor impeller 9 increases the pressure of the fluid, as described above, and the resulting fluid is directed to the intake port of the engine.

[0023] Fig. Figure 2 is a partially enlarged view of the interior of the bearing housing 2, which is located in Fig. 1 is shown. With reference to Fig. 2. Descriptions are provided below for a support structure in which the bearing 20, which is housed in the turbocharger body 1, supports the turbine shaft 7.

[0024] In this embodiment, the bearing 20 is formed from a simple bearing (bushing) that allows sliding movement of the turbine shaft 7 within it and generates an oil film pressure between itself and the turbine shaft 7. The bearing 20 is provided with an insertion hole 21 that penetrates the bearing 20 in the axial direction. The bearing 20 is inserted into the bearing bore 2a in the bearing housing 2.

[0025] The bearing 20 is provided with a through hole 20a that penetrates the bearing 20 in a direction perpendicular to the axial direction. A pin 22 is inserted into the through hole 20a. The pin 22 is also inserted into a positioning hole 2b, which is provided inside the bearing bore 2a in the bearing housing 2. The insertion of the pin 22 into these holes causes the pin 22 to restrict the movement of the bearing 20 in the rotational and axial directions.

[0026] In this embodiment, the bearing 20 rotatably supports the turbine shaft 7, which is inserted into the mounting hole 21. It should be noted that the movement of the bearing 20 is restricted by the pin 22. The bearing 20 therefore functions as a so-called semi-floating bearing.

[0027] Running surfaces 23, 24 are provided in a section of the side of the turbine impeller 8 and a section of the side of the compressor impeller 9 of the inner circumferential surface of the bearing 20. The running surfaces 23, 24 accept a radial load from the turbine shaft 7 while maintaining oil films of lubricant supplied to the interior of the bearing 20 between themselves and the turbine shaft 7. It should be noted that the lubricant is supplied via an oil passage 2c formed in the bearing housing 2 and via an oil passage 20b formed in the bearing 20 and positioned facing oil passage 2c.

[0028] A pressure ring 25a (an opposing section) is attached near an end section of the side of the turbine impeller 8 of the turbine shaft 7 and rotates as a unit with the turbine shaft 7. The pressure ring 25a is opposite an end surface 26 of the bearing 20 in the axial direction of the turbine shaft 7 and causes an axial load of the turbine shaft 7 to act on the end surface 26.

[0029] An oil spray element 25b (the other opposite section) is mounted near an end section of the side of the compressor impeller 9 of the turbine shaft 7 and rotates as a unit with the turbine shaft 7. The oil spray element 25b is configured to prevent lubricant leaking from the bearing housing 2 from reaching the rear surface of the compressor impeller 9 by spraying the lubricant in radial directions using a centrifugal force associated with the rotation of the turbine shaft 7. The oil spray element 25b faces an end surface 27 of the bearing 20 in the axial direction of the turbine shaft 7. The oil spray element 25b further acts as a thrust ring configured to cause the axial load of the turbine shaft 7 to act on the end surface 27.

[0030] Brief descriptions of the process for mounting the bearing 20 and the turbine shaft 7 are provided here. In the assembly process, the bearing 20 is first secured in the bearing bore 2a in the bearing housing 2. While this position is maintained, the turbine shaft 7 is inserted into the insertion hole 21 in the bearing 20, starting with its rear end section, and the turbine impeller 8 is attached to the front end section of the turbine shaft 7.

[0031] The oil spray element 25b is then inserted into the bearing bore 2a in such a way that it comes into contact with the rear end of the turbine shaft 7, which projects towards the compressor impeller 9 in the bearing bore 2a, and is fastened to the turbine shaft 7. The oil spray element 25b is fastened to the turbine shaft 7 in a state of contact with stepped sections formed in the turbine shaft 7. At this point, the distance between the pressure ring 25a and the oil spray element 25b is designed to be slightly longer than the axial length of the bearing 20.

[0032] When the turbine shaft 7 moves in its axial direction, the pressure ring 25a comes into surface contact with the end surface 26 of the bearing 20, and the oil spray element 25b comes into surface contact with the end surface 27 of the bearing 20. In other words, the bearing 20 absorbs the axial load of the turbine shaft 7 through the pressure ring 25a and the oil spray element 25b.

[0033] Fig. Figure 3(a) is a view of the end surface 26 of the bearing 20 from the front of the turbocharger body 1. Fig. Figure 3(b) shows a bearing B intended for a conventional turbocharger as a comparative example. In the comparative example, an end surface B1 of the bearing B is provided with several grooves D in which lubricant flows. The grooves D extend radially in radial directions of the bearing B. A turbine shaft S (with a dashed line in Fig. 3(b) indicates) rotates in bearing B in a direction indicated by a white arrow. Therefore, if a foreign substance a enters a groove D provided in bearing B, the foreign substance a will be expelled radially from bearing B and forward in the direction of rotation of the turbine shaft S due to the centrifugal force associated with the rotation of the turbine shaft S, as indicated by a dashed-dotted arrow. Subsequently, the foreign substance a is less likely to engage a boundary region L of the groove D, which is oriented forward in the direction of rotation of the turbine shaft S, or to become trapped between the thrust ring and the bearing B after coming into contact with the boundary region L and be expelled by the thrust ring.

[0034] As in Fig. As shown in Figure 3(a), end-surface guide sections (first guide sections) 28 are provided on the opposing surfaces of the bearing 20 and the pressure ring 25a. In this embodiment, the end-surface guide sections 28 are provided on the end surface 26 of the bearing 20. The end-surface guide section 28 is designed as a groove (a recessed section) configured to cause the outer circumferential edge 26b and the inner circumferential edge 26a (the insertion hole 21) of the end surface 26 of the bearing 20 to align in a radial direction with the turbine shaft 7 (indicated by a dashed line in Fig. 3(a) are connected to each other. Furthermore, each end surface guide section 28 forms a passage configured to carry away a foreign substance a together with lubricant from the opposing surfaces of the pressure ring 25a and the end surface 26 to the outside in the radial direction.

[0035] It should be noted that, like the end surface 26, the end surface 27 of the bearing 20 is provided with end surface guide sections 28. The configurations of the end surface guide sections 28 provided on the end surface 26 and the end surface 27 are theoretically identical. For this reason, the following descriptions are given for the end surface guide sections 28 provided on the end surface 26.

[0036] As in Fig. As shown in 3(a), the turbine shaft 7 rotates in a clockwise direction (with a white arrow pointing inwards). Fig. 3(a)). Each end surface guide section 28 is directed radially from the inner circumferential edge 26a to the outer circumferential edge 26b of the end surface 26 of the bearing 20 and extends forward in the direction of rotation of the turbine shaft 7.

[0037] When the turbine shaft 7 rotates, the foreign substance a moves together with the lubricant in a direction indicated by a dashed-dotted arrow due to the centrifugal force associated with the rotation of the turbine shaft 7. In other words, the foreign substance a is expelled radially from the bearing 20 and forward in the direction of rotation of the turbine shaft 7. On the other hand, the end-surface guide section 28 is provided, which extends in the direction in which the lubricant and the foreign substance a are expelled. For this reason, the foreign substance a is less likely to be trapped between the pressure ring 25a and a boundary region 28a, which is arranged forward in the direction of rotation of the turbine shaft 7. Furthermore, the foreign substance a, in a state where it is in contact with the boundary region 28a, is less likely to be expelled by the pressure ring 25a.In other words, the foreign substance a is less likely to be trapped between the pressure ring 25a and the bearing 20.

[0038] Specifically, the direction of travel of each end-surface guide section 28 is the same as the direction of movement of oil droplets of the lubricant that absorbs the rotational force of the turbine shaft 7. The foreign substance a moves together with the lubricant. The direction of movement of the foreign substance a is almost the same as the direction of movement of the lubricant (the oil droplets).

[0039] The direction of motion of an oil droplet can be found on the basis of equations 1 to 5 given below. A polar coordinate system is assumed here, in which: the origin is the center of bearing 20 in the radial directions; θ denotes a phase angle, which is positive when moving counterclockwise from the horizontal direction (the left-right direction in the Fig. 3(a)) is measured; and r denotes the distance from the origin. As an initial condition, it is assumed that at time t=0 an oil droplet is located on an inner circumferential edge 26a of the end surface 26; and the phase angle of the oil droplet in the circumferential direction is represented by θ1, while the distance of the oil droplet from the origin is represented by r1. Furthermore, it is assumed that an angular velocity ω of the oil droplet is what is measured when the number of revolutions of the turbine shaft 7 is at an assumed maximum value.

[0040] Initially, the velocity of the oil droplet in a radial direction is expressed as ur=drdt=rω2 t where: r represents the distance of the oil droplet from the origin; ω represents the angular velocity of the oil droplet; and t represents time.

[0041] Furthermore, at time t, the phase angle θ of the oil droplet in the circumferential direction and the velocity uθ of the oil droplet in the circumferential direction are each expressed by θ=ωt+θl and u0=rω

[0042] In this respect, equation 4 is obtained by transforming the above equation 1. drr=ω2t dt

[0043] Equation 5 is derived by integrating equation 4 on the basis of the aforementioned initial condition (with regard to the distance of the oil droplet from the origin, r=r1 at time t=0). ∫r1rdrr=∫0tω2t dt

[0044] By expanding the integral expressions on both sides, equation 5 is transformed into equation 6, equation 7 and equation 8: [In r]r1r=[12ω2t2]01 In r−In r1=12ω2t2−0 and In(rr1)=12(ωt)2

[0045] Equation 9 is derived by substituting ωt = θ - θ1, which is obtained by solving equation 2 for ωt, into the right-hand side of equation 8. In(rr1)=(θ−θ1)22

[0046] The following equation 10 is then derived by transforming equation 9. r=r1 exp[(θ−θ1)22]

[0047] With reference to equation 10, it is learned that the distance r of the oil droplet from the origin is determined by the initial position of the oil droplet (the position at time t=0) and the phase angle θ of the oil droplet in the circumferential direction.

[0048] Each end-surface guide section 28 extends in the direction of oil droplet movement as specified by Equation 5. Therefore, as oil droplets move, the foreign substance a moves along with the oil droplets along the end-surface guide section 28 from the inner circumferential edge 26a to the outer circumferential edge 26b and is eventually carried away. Consequently, the turbocharger C of the embodiment is able to significantly reduce the probability that the foreign substance will be expelled from the end-surface guide section 28 in the circumferential direction and become trapped between the pressure ring 25 and the bearing 20.

[0049] Fig. Figure 4 is a cross-sectional view of the bearing 20 along a plane parallel to the axial direction of the bearing 20. As in Fig. As shown in Figure 4, the running surfaces 23, 24 are provided with running surface guide sections (secondary guide sections) 29. The running surface guide sections 29 are grooves that extend outwards in the radial directions of the turbine shaft 7. The running surface guide sections 29 form passages configured to remove foreign matter a together with the lubricant from the running surfaces 23, 24 towards the end surface guide sections 28.

[0050] The running surface guide sections 29 in the running surface 23 extend from one end 23a to the opposite end 23b of the running surface 23 in the axial direction of the turbine shaft 7. Likewise, the running surface guide sections 29 in the running surface 24 extend from one end 24a to the opposite end 24b of the running surface 24 in the axial direction of the turbine shaft 7. Furthermore, on the side of one end 23a in the axial direction of the turbine shaft 7, the running surface guide sections 29 in the running surface 23 are connected to the end surface guide sections 28 in the end surface 26. Likewise, on the side of one end 24a in the axial direction of the turbine shaft 7, the running surface guide sections 29 in the running surface 24 are connected to the end surface guide sections 28 in the end surface 27.Of all the guide sections 29, one end 23a, 24a is arranged further forward in the axial direction of the turbine shaft 7 in the direction of rotation (indicated by an arrow in the drawing) of the turbine shaft 7 than the opposite ends 23b, 24b. In other words, all guide sections 29 extend in the direction in which the foreign matter a is expelled from the running surfaces 23, 24 due to the rotation of the turbine shaft 7.

[0051] The running surface guide sections 29 with the preceding configuration act on the foreign matter a as in the case of the end surface guide sections 28. In other words, even if the foreign matter a is driven forward by the turbine shaft 7 in the direction of rotation of the turbine shaft 7, the foreign matter a is less likely to be trapped between the running surfaces 23, 24 and the bearing 20, since the running surface guide sections 29 are designed to extend in the direction in which the foreign matter a is driven out.

[0052] The directions of the running surface guide sections 29 are aligned with the directions of movement of the oil droplets of the lubricant that absorbs the rotational force of the turbine shaft 7. Like the end surface guide sections 28 described above, the running surface guide sections 29 are able to significantly reduce the probability that foreign substances a will be driven out of the running surface guide sections 29 in the circumferential direction and become trapped between the running surfaces 23, 24 and the bearing 20. (Modified examples)

[0053] Fig. Figure 5 is a schematic cross-sectional view of the interior of a bearing housing 2 of a modified example of the embodiment. As shown in Fig. As shown in Figure 5, in addition to the semi-floating metal (the bearing 20), axial bearings 30, 32 and a pressure ring 34 are arranged in the modified example. As in Fig. As shown in Figure 5, the pressure ring 34 is arranged on a section of the side of the compressor impeller 9 of the turbine shaft 7. The axial bearings 30, 32 are each located on one side of the axial direction (the left side of the pressure ring 34). Fig. 5) and an opposite side of the axial direction (the right side of the pressure ring 34 in Fig. 5) of the pressure ring 34 (of the opposite section).

[0054] The pressure ring 34 is attached to the turbine shaft 7 and rotates as a single unit with the turbine shaft 7. The pressure ring 34 comprises: an opposing surface 34b facing the axial bearing 30; and an opposing surface 34a facing the axial bearing 32.

[0055] The axial bearing 30 comprises: a through-hole 30a that penetrates the axial bearing 30 in the axial direction of the turbine shaft 7; and an opposing surface 30b that faces the opposing surface 34b of the pressure ring 34. The axial bearing 32 comprises: a through-hole 32a that penetrates the axial bearing 32 in the axial direction of the turbine shaft 7; and an opposing surface 32b that faces the opposing surface 34a of the pressure ring 34. The turbine shaft 7 is inserted into the through-holes 30a and 32a. Consequently, the axial bearings 30 and 32 absorb the load exerted by the turbine shaft 7 in the axial direction. Furthermore, the turbine shaft 7 and the axial bearings 30 and 32 exhibit a relative rotational relationship.

[0056] An oil passage 2c branches off from an oil passage 20b into another channel and is therefore also connected to the axial bearing 32 on the side of the compressor impeller 9. Lubricant is supplied to the opposite surface 32b of the axial bearing 32 and to the opposite surface 34a of the pressure ring 34 to lubricate the axial bearing 32 and the pressure ring 34.

[0057] Furthermore, the lubricant is supplied to the bearing 20 via the oil passage 20b and then flows to the axial bearing 30 and the pressure ring 34. Consequently, the lubricant is supplied to the opposite surface 30b of the axial bearing 30 and to the opposite surface 34b of the pressure ring 34 in order to lubricate the axial bearing 30 and the pressure ring.

[0058] After it has been used for lubrication, the lubricant is discharged via an oil drain passage 36, which is provided in the bearing housing 2.

[0059] End surface guide sections are provided on the opposite surface 30b, which is formed in the axial bearing 30. The end surface guide sections have a shape similar to that of the one in Fig. 3(a) end surface guide sections 28 and cause the through hole 30a and the outer circumferential edge of the pressure ring 34 to be in contact with each other in the radial directions of the turbine shaft 7.

[0060] Starting at their portions connected to the through-hole 30a, the end-surface guide sections of the modified example extend forward in the direction of rotation of the turbine shaft 7. The end-surface guide sections form passages configured to discharge foreign matter a, along with the lubricant, from the opposing surfaces 30b, 34b of the axial bearing 30 and the pressure ring 34 to the outside in the radial directions. This improves the discharge capability of the foreign matter a.

[0061] Furthermore, the directions of the end-surface guide sections provided on the opposite surface 30b are the same as the directions of movement of the oil droplets of the lubricant that absorbs the rotational force of the turbine shaft 7. This makes it possible to further improve the ability to remove foreign matter a.

[0062] The preceding descriptions were intended for the case in which the end-surface guide sections are provided on the opposite surface 30b of the axial bearing 30. However, the end-surface guide sections can instead be provided on the opposite surface 34b of the pressure ring 34.

[0063] The preceding embodiment described the case in which the bearing 20 is formed from the semi-floating bearing. However, the bearing 20 can instead be formed from the fully floating metal. In this case, the fully floating metal rotates relative to the turbine shaft 7 at a smaller number of revolutions than the turbine shaft 7 rotates. For this reason, the provision of the end-surface guide sections 28, which extend forward in the direction of rotation of the turbine shaft 7, makes it possible to improve the removal of foreign matter a.

[0064] The preceding embodiment described the case in which the end-surface guide sections 28 are provided on the end surfaces 26, 27 of the bearing 20, which face the pressure ring 25a and the oil spray element 25b, respectively. However, the end-surface guide sections 28 can also be provided separately on the end surfaces of the pressure ring 25a and the oil spray element 25b.

[0065] Furthermore, the preceding embodiment described the case in which the running surface guide sections 29 are provided on the running surfaces 23, 24 of the bearing 20. However, the running surface guide sections 29 can instead be provided on outer circumferential surfaces of the turbine shaft 7 that face the running surfaces 23, 24.

[0066] As with dashed lines in Fig.As specified in Figure 3(a), each end-surface guide section 28 can also extend linearly in a direction tangential to the inner circumferential edge 26a and forward in the direction of rotation of the turbine shaft 7. A foreign substance in each end-surface guide section 28 is subject to the rotational force (centrifugal force) of the turbine shaft 7, which the end-surface guide section 28 absorbs through the lubricant. This influence decreases as the depth (groove depth) of the end-surface guide section 28 increases. For this reason, the path of any foreign substance usually lies in a straight line extending in the direction tangential to the inner circumferential edge 26a. Consequently, even if the end-surface guide sections 28 are linearly extended parallel to the tangential directions, the same foreign substance removal capability, as described above, can be maintained.

[0067] Although the preceding descriptions of the preferred embodiment of the present invention were provided with reference to the accompanying drawings, the present invention is, of course, not limited to such an embodiment. It is clear that a person skilled in the art could arrive at various modified or revised examples within the scope of the claims. Naturally, such modified and revised examples are also covered by the technical scope of protection of the present invention. [Industrial applicability]

[0068] The present invention can be used for turbochargers that include a bearing configured to accept an axial load.

Claims

[1] Turbocharger (C), which includes: a turbocharger body (1); a turbine shaft (7) rotatably received in the turbocharger body (1), with a turbine impeller (8) provided at one end of the turbine shaft (7) and a compressor impeller (9) provided at an opposite end of the turbine shaft (7); a bearing (20) provided in the turbocharger body (1) and configured to rotatably support the turbine shaft (7) in an insertion hole (21) formed in the bearing (20); and an opposite portion (25a, 25b) facing an end surface (26, 27) of the bearing (20) in an axial direction of the turbine shaft (7), wherein an end surface guide portion (28) formed as a groove, which is configured to cause the insertion hole (21) and an outer peripheral edge (26b) of the end surface (26) of the bearing (20) to communicate with each other in radial directions of the turbine shaft (7), is provided on an opposite surface of the bearing (20) facing the opposite portion (25a, 25b) or an opposite surface of the opposite portion (25a, 25b) facing the bearing (20), the end surface guide portion (28) extends forward in a rotational direction of the turbine shaft (7) from a part of the end surface (26, 27) of the bearing (20) communicating with the insertion hole (21), and the end surface guide portion (28) forms a passage configured to discharge a foreign matter (a) together with lubricant from the opposite surface provided with the end surface guide portion (28) to the outside of the opposite surface in the radial directions, characterized by , that the end surface guide section (28) extends along a path defined by the equation given below: r=r1 exp[(θ−θ1)22] where r represents the distance of an oil droplet of the lubricant, which absorbs part of the rotational force of the turbine shaft (7), from the center of rotation and θ represents the phase angle of the oil droplet and where r=r1 and θ=θ1 at time t=0. [2] Turbocharger according to claim 1, wherein the bearing is formed from a bushing having a running surface (23, 24) configured to receive a radial load of the turbine shaft (7), wherein an oil film is maintained between the running surface (23, 24) and the turbine shaft (7). [3] Turbocharger according to claim 2, wherein the running surface (23, 24) or an outer peripheral surface of the turbine shaft (7) facing the running surface (23, 24) is provided with a running surface guide portion (29) formed from a groove extending from one end to an opposite end in the axial direction of the turbine shaft (7), one end of the running surface guide portion (29) in the axial direction of the turbine shaft (7) is connected to the end surface guide portion (28), and one end of the running surface guide portion (29) in the axial direction of the turbine shaft is arranged further forward in the rotational direction of the turbine shaft (7) than the opposite end of the running surface guide portion (29). [4] Turbocharger according to claim 3, wherein the running surface guide portion (29) forms a passage configured to discharge the foreign matter (a) together with the lubricant from the running surface (23, 24) to the end surface guide portion (28), and the running surface guide portion (29) extends along the direction of movement of the oil droplets of the lubricant which absorbs part of the rotational force of the turbine shaft. [5] Turbocharger according to one of claims 2 to 4, wherein the bearing (20) is formed of a semi-floating bearing whose movement in its rotational and axial direction is restricted by a pin (22) provided on the turbocharger body (1). [6] Turbocharger (C), which includes: a turbocharger body (1); a turbine shaft (7) rotatably received in the turbocharger body (1), with a turbine impeller (8) provided at one end of the turbine shaft (7) and a compressor impeller (9) provided at an opposite end of the turbine shaft (7); a thrust ring (25a, 25b) configured to rotate integrally with the turbine shaft (7); and a thrust bearing (20) arranged facing the thrust ring (25a, 25b) in an axial direction of the turbine shaft (7), wherein the turbine shaft (7) is inserted into an insertion hole (21) formed in the thrust bearing (20), and the thrust bearing (20) is configured to receive an axial load of the turbine shaft (7) via the thrust ring (25a, 25b), wherein an end surface guide portion (28) formed as a groove, which is configured to cause the insertion hole (21) and an outer peripheral edge (26b) of the thrust ring (26) to communicate with each other in radial directions of the turbine shaft (7), is provided on an opposite surface of the thrust bearing (20) facing the thrust ring (26) or an opposite surface of the thrust ring (26) facing the thrust bearing (20), the end surface guide portion (28) extends forward in a rotational direction of the turbine shaft (7) from a part of the end surface (26, 27) of the thrust bearing (20) which communicates with the insertion hole (21), and the end surface guide portion (28) forms a passage configured to discharge a foreign matter (a) together with lubricant from the opposite surface provided with the end surface guide portion (28) to the outside of the opposite surface in the radial directions, characterized by , that the end surface guide section (28) extends along a path defined by the equation given below: r=r1 exp[(θ−θ1)22] where r represents the distance of an oil droplet of the lubricant, which absorbs part of the rotational force of the turbine shaft (7), from the center of rotation and θ represents the phase angle of the oil droplet and where r=r1 and θ=θ1 at time t=0.

Images