Exhaust gas turbocharger

Abstract

Exhaust gas turbocharger (1) with a compressor (2) comprising a compressor wheel (3) in a compressor housing (4); with a turbine (5) comprising a turbine wheel (6) in a turbine housing (7); and with a bearing housing (8) which accommodates a fixed bearing bushing (9) for a rotor shaft (10) and has a bearing housing cover (11) on the compressor side, characterized in that the bearing bushing (9) is provided with axial bearing surfaces (12, 13) and is force-fitted in the bearing housing (8), and that the bearing housing (8) has a housing shoulder (20, 21) for axial support of the bearing bushing (9).

Description

[0001] The invention relates to an exhaust gas turbocharger according to the preamble of claim 1.

[0002] DE1400440A1 discloses a bearing assembly, wherein a housing has a bore for receiving a shaft. A floating bearing is arranged in the bore, and means are provided for securing the bearing against rotational movement. Furthermore, fluid films are provided between the bearing and housing, as well as between the bearing and shaft, to dampen vibrations. Furthermore, means are provided for circulating a fluid between the bearing and shaft, and between the housing and bearing.

[0003] US3993370A discloses a bearing structure for use in machines in which certain components operate at high speeds. The structure comprises a shaft mounted for rotation within a stationary housing member. A pair of longitudinally spaced bearings is disposed between the shaft and the adjacent surface of the housing member. The housing member is provided with a passage for high-pressure oil terminating at the bearings. Each bearing is sleeve-like and is provided with a plurality of radial bores communicating with the oil passage of the housing member. A plurality of longitudinal openings are formed in each bearing, interconnecting the end faces of the bearing. The openings communicate with the bores of the bearing, allowing oil to flow to the end faces.

[0004] US4355850A relates to a turbomachine with an axial air bearing for axially supporting the rotating shaft of the turbomachine. The axial air bearing comprises a disk-shaped hollow impeller mounted on the rotating shaft and a pair of stationary bearing disks mounted on each side of the impeller on the housing of a turbocharger. The impeller has a thin wall defining an inner chamber. A plurality of air inlet holes are formed on the side wall of the impeller to direct ambient air into the inner chamber. Furthermore, a plurality of air outlet holes are formed on the circumferential outer wall of the impeller to discharge the air within the inner chamber to the atmosphere.

[0005] US4838711A discloses a bearing for an exhaust gas turbocharger with a sleeve arranged in a bore of a bearing housing and secured against rotation. The sleeve contains an inner and an outer bearing surface at each of its two axial end regions and at least two openings between the end regions. The sleeve is secured against rotation in a functionally reliable manner and with minimal design effort by a preferably annular, circumferentially elastic spring element, which engages with an axially bent first end in a groove in the sleeve. The bearing housing has a recess that opens radially toward the shaft into the bore of the bearing housing and into which the radially outwardly bent second end of the spring element engages.

[0006] Reference is also made to US3058787A, which deals with the lubrication of high-speed shaft bearings.

[0007] US6499884B1 also describes a turbocharger comprising a housing and a rotor arranged in the housing and rotatable about an axis. A bearing and seal assembly are mounted in an axial bore in the housing. The bearing has an inner bearing surface for supporting the rotor. The bearing and seal are secured to each other.

[0008] Furthermore, US5967762A describes a turbocharger with a shaft, a turbine wheel, and an impeller. The shaft is supported in the housing by means of a floating bearing and a ball bearing. A preload spring, arranged between a stationary race of the ball bearing and a thrust plate attached to the housing, provides a force that presses the ball bearing against a shoulder on the main shaft. This can counteract thrust forces that tend to move the shaft toward the turbine wheel.

[0009] Since the generic exhaust gas turbocharger is equipped with a fixed radial bearing bush and an additional axial bearing, this results in a relatively high number of parts to be assembled and thus longer assembly times.

[0010] It is therefore an object of the present invention to provide an exhaust gas turbocharger of the type specified in the preamble of claim 1, the technical structure of which is simplified.

[0011] This problem is solved by the features of claim 1.

[0012] According to the invention, it is therefore possible to provide a single fixed bearing bush in the bearing housing, which enables both the radial bearing and the axial bearing of the rotor shaft.

[0013] A force-locking fixation of the bearing bush in the bearing housing also results in the advantage that no further securing elements are required for the axial stop of the bearing bush, which results in a further reduction in parts and thus a reduction in costs.

[0014] A further cost reduction results from the reduction in assembly time.

[0015] Furthermore, the axial dimensions of the exhaust gas turbocharger according to the invention can be reduced since the bearing bush comprises both the radial bearing points and the axial bearing points, so that a separate axial bearing can be omitted.

[0016] The fact that the bearing bush is held in the seat by force, for example by spring force, results in a further simplification compared to known techniques, such as positive locking by means of locking pins, whereby the bearing bush retains sufficient radial play despite the fixation.

[0017] The subclaims contain advantageous developments of the invention.

[0018] If a preloading device is used to create the frictional fixation, it can, for example, rest with one end on the bearing housing cover and with the other end on a contact collar of the bearing bush. This makes it possible to arrange an oil collection chamber between the preloading device and the bearing cover, which in turn reduces oil leakage, as oil thrown outwards can be collected in this oil collection chamber and drained away through oil drain holes provided, for example, in the preloading device.

[0019] The bearing housing cover can be connected to the bearing housing by screwing, clamping, using a snap ring, or a bayonet lock, although screwless connections are preferred. The bearing housing cover itself can form the preload device without any additional components.

[0020] The axial bearing surfaces of the bearing bush are supported on the turbine side via the rotor shaft and on the compressor side via a sealing bush.

[0021] Overall, the design according to the invention, in addition to the advantages already explained, provides the possibility of greater degrees of freedom in the divisibility of the bearing housing.

[0022] When dimensioning the pre-tensioning device, it must be designed so that the pre-tensioning force is greater than the maximum axial force in the direction of the compressor that occurs during operation of the exhaust gas turbocharger.

[0023] Further details, advantages, and features of the present invention will become apparent from the following description of an exemplary embodiment with reference to the drawing. The sole figure of the drawing shows a simplified schematic representation of an exhaust gas turbocharger 1 according to the invention with a compressor 2 and a turbine 5.

[0024] The compressor 2 has a compressor wheel 3 arranged in a compressor housing 4. The turbine 5 has a turbine wheel 6 arranged in a turbine housing 7.

[0025] A bearing housing 8 is arranged between the compressor housing 4 and the turbine housing 7. The bearing housing 8 has a stationary bearing bush 9 for a rotor shaft 10 and has a bearing housing cover 11 on the compressor side.

[0026] According to the invention, the bearing bush 9 is provided with axial bearing surfaces 12 and 13 which are arranged on the end face, wherein the axial bearing surface 12 is the compressor-side bearing surface, while the axial bearing surface 13 represents the turbine-side bearing surface.

[0027] Furthermore, the bearing bush 9 has radial bearing surfaces 24 and 25, which can be supplied with oil via oil inlet bores 26 and 27. The bearing bush 9 is not clamped in the bearing housing 8, but is dimensioned such that a gap remains between the outer circumference of the bearing bush 9 and the inner bore of the bearing housing 8, into which oil can be supplied.

[0028] The bearing bush 9 is fixed in the bearing housing 8 by a force connection, for which purpose a preloading device 14 is provided in the example shown, which applies the required preload force for the force-locking connection so that the bearing bush (9) can be arranged in the bearing housing 8 in a rotationally fixed manner.

[0029] In the illustrated embodiment, the preloading device 14 is designed as a disc spring. One end region 15 of the preloading device 14 rests on the bearing housing cover 11, and the other end region 16 of the preloading device 14 rests on a contact collar 17 that is larger in diameter than the main body of the bearing bush 9 and is integrally connected to the main body of the bearing bush 9.

[0030] In the axial direction, the bearing bush 9 can be supported either on a housing shoulder 20 or a housing shoulder 21, wherein the housing shoulder 20 is oriented on the compressor side, while the housing shoulder 21 is oriented on the turbine side, as is immediately apparent from the graphic representation.

[0031] As the figure further illustrates, the rotor shaft 10 has a shaft shoulder 18, which represents a counter surface for the turbine-side axial bearing surface 13 of the bearing bushes 9.

[0032] The compressor-side axial bearing surface 12 of the bearing bushes 9 is supported on a sealing bush 19 which is arranged on the rotor shaft 10.

[0033] In the illustrated embodiment, the preloading device 14 defines an oil collection chamber 22 with the bearing housing cover 11, in which oil radially thrown off the rotor shaft 10 can be collected. To facilitate oil return, the oil collection chamber 22 has at least one oil drain opening 23, which in the example is formed in the preloading device 14.

[0034] In addition to the above written disclosure of the invention, reference is hereby explicitly made to the graphic representation of the invention in the single figure. List of reference symbols 1 exhaust gas turbocharger 2 compressors 3 Compressor wheel 4 Compressor housing 5 turbines 6 Turbine wheel 7 Turbine housing 8 bearing housings 9 Bearing bush 10 Rotor shaft on which the compressor wheel 3 and the turbine wheel 6 are arranged 11 Bearing housing cover 12, 13 Axial bearing surfaces 14 Pre-tensioning device 15, 16 end areas 17 Investment Association 18 wave heel 19 Sealing bushing 20, 21 Case shoulder 22 Oil collection chamber 23 Oil drain opening 24, 25 radial bearing positions 26,27 Oil inlet holes

Claims

[1] Exhaust gas turbocharger (1) with a compressor (2) having a compressor wheel (3) in a compressor housing (4); with a turbine (5) having a turbine wheel (6) in a turbine housing (7); and with a bearing housing (8) which accommodates a fixed bearing bush (9) for a rotor shaft (10) and has a bearing housing cover (11) on the compressor side, characterized by that the bearing bush (9) is provided with axial bearing surfaces (12, 13) and is fixed in the bearing housing (8) by force, and that the bearing housing (8) has a housing shoulder (20, 21) for axially supporting the bearing bush (9). [2] Exhaust gas turbocharger according to claim 1, characterized by a preloading device (14) for generating a fixing force for the bearing bush (9). [3] Exhaust gas turbocharger according to claim 2, characterized bythat the pretensioning device (14) is supported at one end region (15) on the bearing housing cover (11) and at the other end region (16) on a contact collar (17) of the bearing bush (9). [4] Exhaust gas turbocharger according to claim 2 or 3, characterized by that the pretensioning device (14) is designed as a disc spring. [5] Exhaust gas turbocharger according to one of claims 1 to 4, characterized by that the axial bearing surfaces (12, 13) are arranged on the end faces of the bearing bush (9). [6] Exhaust gas turbocharger according to one of claims 1 to 5, characterized by that the rotor shaft (10) has a shaft shoulder (18) as a counter surface for the turbine-side axial bearing surface (13). [7] Exhaust gas turbocharger according to one of claims 1 to 6, characterized by that the compressor-side axial bearing surface (12) is supported on a sealing bush (19) arranged on the rotor shaft (10). [8] Exhaust gas turbocharger according to one of claims 2 to 7, characterized bythat the pretensioning device (14) and the bearing housing cover (11) delimit an oil collecting chamber (22). [9] Exhaust gas turbocharger according to claim 8, characterized by that the oil collection chamber (22) has at least one oil drain opening (23).

Images