Centrifugal compressor

Abstract

A radial compressor (1) comprising: an impeller (4) comprising a main body (41) having a front surface (41a) and a rear surface (41b) facing its opposite sides in an axial direction, and a side surface (41c) connected to the front surface (41a) and the rear surface (41b); a first wall portion (6) comprising a first wall surface (6c) opposite the front surface (41a) and which, together with the front surface (41a), forms a flow passage (P1) through which a working fluid flows; a second wall portion (8) comprising a second wall surface (8a) opposite the rear surface (41b) and the first wall surface (6c) and, together with the rear surface (41b), forms a first gap (C1); anda projecting wall portion (71) provided on an outer side in a radial direction with respect to the side surface (41c) of the impeller (4),to protrude from the second wall surface (8a) toward the first wall surface (6c), wherein the protruding wall portion (71) comprises a third wall surface (71a) extending from the second wall surface (8a) in the axial direction and facing the side surface (41c) of the impeller (4), wherein the third wall surface (71a) further extends toward the first wall surface (6c) in the axial direction from a connecting portion (41d) connecting the front surface (41a) and the side surface (41c), and the third wall surface (71a) and the side surface (41c) form a second gap (C2) between each other, wherein the second gap (C2) connects the flow passage (P1) to the first gap (C1), characterized in that the third wall surface (71a) has two or more inner edge surfaces (71c, 71e) and a step portion (71d) formed between the inner edge surfaces (71c, 71e),a first inner edge surface (71c) of the two or more inner edge surfaces (71c, 71e) extends in the axial direction, the step portion (71d) is connected to a side opposite to the second wall surface (8a) in the first inner edge surface (71c) and extends to the outside in the radial direction, and a second inner edge surface (71e) of the two or more inner edge surfaces (71c, 71e) is connected to a side opposite to the first inner edge surface (71c) in the step portion (71d) and extends in the axial direction.

Description

[0001] The present invention relates to a radial compressor.

[0002] JP S50 - 138 410 A discloses a radial compressor according to the preamble of claim 1.

[0003] WO 2016 / 129 039 A1 describes a centrifugal compressor comprising a rotating shaft, a compressor impeller fixed to one end of the rotating shaft, and a compressor housing that accommodates the compressor impeller. In such a centrifugal compressor, a working fluid is drawn into a flow passage in the compressor housing to be compressed as the compressor impeller rotates.

[0004] In the centrifugal compressor described above, a negative pressure may be generated in a gap on the rear surface side of the compressor impeller when the compressor impeller rotates. This creates a risk that, for example, oil on the rotating shaft side may be sucked in by the negative pressure and leak toward the gap.

[0005] It is the object of the present invention to provide a radial compressor in which oil leakage is reliably prevented.

[0006] The object of the invention is achieved with a radial compressor according to claim 1. Advantageous developments of the invention are the subject of the dependent claims.

[0007] According to the present invention, it is possible to provide a radial compressor in which oil leakage is prevented. Fig. 1 is a sectional view showing a radial compressor according to an embodiment not claimed but useful for understanding the invention. Fig. 2 is a partially enlarged view of the Fig. 1. Fig. 3 is a diagram showing a third wall surface of a centrifugal compressor of a modified example which is the subject of the claims.

[0008] A centrifugal compressor according to the present invention includes an impeller including a main body having a front surface and a rear surface facing its opposite sides in an axial direction, and a side surface connected to the front surface and the rear surface; a first wall portion including a first wall surface opposite to the front surface and forming, together with the front surface, a flow passage through which a working fluid flows; a second wall portion including a second wall surface opposite to the rear surface and the first wall surface and forming, together with the rear surface, a first gap; and a projecting wall portion provided on an outer side in a radial direction with respect to the side surface of the impeller to project from the second wall surface toward the first wall surface.The protruding wall portion includes a third wall surface extending from the second wall surface in the axial direction and facing the side surface of the impeller. The third wall surface further extends toward the first wall surface in the axial direction from a connecting portion connecting the front surface and the side surface, and the third wall surface and the side surface form a second gap between them. The second gap connects the flow passage to the first gap.

[0009] In the centrifugal compressor, the working fluid flows through the flow passage to be compressed as the impeller rotates around the axis. The centrifugal compressor includes the protruding wall portion provided on the outer side in the radial direction with respect to the side surface of the impeller so as to protrude from the second wall surface toward the first wall surface. The protruding wall portion includes the third wall surface extending from the second wall surface in the axial direction and facing the side surface of the impeller. The third wall surface further extends toward the first wall surface in the axial direction from the connecting portion between the front surface and the side surface. The third wall surface and the side surface form the second gap between each other, connecting the flow passage to the first gap.For this reason, a portion of the working fluid flowing through the flow passage along the front surface collides with the third wall surface and flows to the first gap through the second gap. Accordingly, negative pressure is prevented from forming in the first gap on the rear surface side of the impeller, and oil is prevented from being sucked into the first gap due to the negative pressure. Thus, according to the centrifugal compressor, oil leakage is prevented.

[0010] According to the invention, the third wall surface includes two or more inner edge surfaces and a step portion formed between the inner edge surfaces. In this case, a degree of freedom regarding design of the protruding wall portion is improved.

[0011] Preferably, the radial compressor comprises a diffuser and a scroll communicating with the flow passage, wherein the protruding wall portion includes a fourth wall surface connected to the side opposite to the second wall surface in the third wall surface and facing the first wall surface, and wherein the fourth wall portion extends in the radial direction to form the diffuser together with the first wall surface and is continuously continuous with an inner wall surface forming the scroll. In this case, even in the radial compressor having the protruding wall portion, a desired compression efficiency can be achieved without deteriorating compression efficiency.

[0012] Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. Note that the same or corresponding parts of the drawings are denoted by the same reference numerals, and redundant descriptions are omitted. Furthermore, in this description, the "radial direction" and the "circumferential direction" are defined based on a rotational axis X, which will be described below.

[0013] Referring to Fig. 1, a turbocharger according to a non-claimed embodiment is described. A turbocharger (radial compressor) 1, which in Fig. 1 is mounted, for example, on an internal combustion engine for a motor vehicle. The turbocharger 1 comprises a shaft 2 extending along the rotation axis X and rotatable about the rotation axis X, a turbine impeller 3 provided at a first end 2a of the shaft 2, and a compressor impeller (runner) 4 provided at a second end 2b of the shaft 2. The turbocharger 1 further comprises a turbine housing 5 accommodating the turbine impeller 3, a compressor housing (first wall portion) 6 accommodating the compressor impeller 4, and a bearing housing 7 accommodating the shaft 2 between the turbine housing 5 and the compressor housing 6.

[0014] The turbine runner 3 includes a main body 31 and a plurality of blades 32. The main body 31 includes a front surface 31a and a rear surface 31b facing its opposite sides in the axial direction along the rotation axis X, and a side surface 31c connected to the front surface 31a and the rear surface 31b. The front surface 31a is a curved surface whose outer diameter decreases from the rear surface 31b toward the front surface 31a. The plurality of blades 32 are provided in the front surface 31a. The blade 32 is integrally formed with the main body 31. The turbine runner 3 is fixed to the first end 2a of the shaft 2 so that the rear surface 31b faces the shaft 2. The turbine housing 5 is provided with an inlet (not shown), a scroll 5a communicating with the inlet, and an outlet 5b communicating with the scroll 5a.The turbine runner 3 and the turbine housing 5 constitute a turbine 30.

[0015] The compressor impeller 4 includes a main body 41 and a plurality of blades 42. The main body 41 includes a front surface 41a and a rear surface 41b facing its opposite sides in the axial direction along the rotation axis X, and a side surface 41c connected to the front surface 41a and the rear surface 41b. The front surface 41a is a curved surface whose outer diameter decreases from the rear surface 41b toward the front surface 41a. The plurality of blades 42 are provided in the front surface 41a. The blade 42 is integrally formed with the main body 41. The compressor impeller 4 is fixed to the second end 2b of the shaft 2 so that the rear surface 41b faces the shaft 2. The compressor housing 6 is provided with an inlet 6a, a scroll 6b communicating with the inlet 6a, and an outlet (not shown) communicating with the scroll 6b.The compressor impeller 4 and the compressor housing 6 constitute a compressor 40.

[0016] The bearing housing 7 is connected to the turbine housing 5 and the compressor housing 6. The turbine housing 5 is connected to the first end of the bearing housing 7 in the axial direction. The compressor housing 6 is connected to the second end of the bearing housing 7 in the axial direction. The bearing housing 7 accommodates the shaft 2 and a bearing 21 fixed to the shaft 2. The shaft 2 is rotatably supported by the bearing housing 7 through the bearing 21.

[0017] The turbocharger 1 further includes a disc-shaped seal plate (second wall portion) 8 provided in the inner wall surface of the second end of the bearing housing 7. The seal plate 8 is, for example, inserted into the inner wall surface of the second end of the bearing housing 7. The seal plate 8 is provided to face the rear surface 41b of the main body 41 of the compressor impeller 4. The seal plate 8 is provided with a through hole into which the shaft 2 is inserted. The seal plate 8 surrounds the shaft 2 in the circumferential direction through a collar 22 fixed to the outer peripheral surface of the shaft 2. A space S in which an oil (lubricating oil) circulates is formed in the seal plate 8 on the side opposite the compressor impeller 4. Note that a ring member (not shown) is provided between the collar 22 and the seal plate 8.A space accommodating the compressor impeller 4 and a flow passage of a working fluid F, which will be described below, are formed by the compressor housing 6, the bearing housing 7 and the seal plate 8.

[0018] As in Fig. As shown in Figure 2, the compressor casing 6 includes a first wall surface 6c. The first wall surface 6c faces the front surface 41a of the main body 41 of the compressor impeller 4. The first wall surface 6c extends from the inlet 6a in the axial direction and extends toward the scroll 6b in the radial direction. The plurality of blades 42 are arranged between the front surface 41a and the first wall surface 6c. The first wall surface 6c faces the blade 42 with a small clearance relative to a tip 42a of the blade 42.

[0019] The seal plate 8 includes a second wall surface 8a, which faces the rear surface 41b of the main body 41 of the compressor impeller 4 and is formed along the rear surface 41b. The outer diameter of the seal plate 8 is larger than the outer diameter of the main body 41. The second wall surface 8a extends to the outside in the radial direction with respect to the side surface 41c of the main body 41. The second wall surface 8a faces the first wall surface 6c on the outside (outer peripheral edge) in the radial direction with respect to the side surface 41c. The second wall surface 8a forms a first gap C1 together with the rear surface 41b.

[0020] The bearing housing 7 includes a protruding wall portion 71 provided on the outer side in the radial direction relative to the side surface 41c of the main body 41 of the compressor impeller 4, so as to protrude from the second wall surface 8a toward the first wall surface 6c. The protruding wall portion 71 is, for example, a part of the bearing housing 7. The protruding wall portion 71 includes a third wall surface 71a and a fourth wall surface 71b connected to the third wall surface 71a.

[0021] The third wall surface 71a is a part of the inner peripheral surface of the bearing housing 7, which is provided with the seal plate 8. The third wall surface 71a extends from the second wall surface 8a in the axial direction and faces the side surface 41c. The third wall surface 71a faces the side surface 41c over the entire circumference of the side surface 41c. The third wall surface 71a is formed by an inner peripheral surface. That is, the third wall surface 71a extends continuously from the second wall surface 8a in the axial direction. The third wall surface 71a further extends toward the first wall surface 6c in the axial direction from a connecting portion 41d connecting the front surface 41a and the side surface 41c. That is, the third wall surface 71a is opposed to the side surface 41c of the main body 41 and the rear edge (trailing edge) 42b of the blade 42 in the radial direction.The third wall surface 71a forms a second gap C2 together with the side surface 41c.

[0022] The fourth wall surface 71b is connected to the side opposite to the second wall surface 8a in the third wall surface 71a. The fourth wall surface 71b extends in the radial direction. The fourth wall surface 71b is opposite to the first wall surface 6c. The fourth wall surface 71b is continuously continuous with the inner wall surface of the compressor housing 6, which forms the scroll 6b (see Fig. 1). That is, a connecting portion between the fourth wall surface 71b and the inner wall surface forming the spiral 6b is flush. Note that a connecting portion between the third wall surface 71a and the fourth wall surface 71b may be chamfered or deburred.

[0023] The axial distance (step amount) between the fourth wall surface 71b and the connecting portion 41d, that is, the axial height of the third wall surface 71a with respect to the connecting portion 41d (the height of the portion extending from the connecting portion 41d further toward the first wall surface 6c) is, for example, 1 / 20 or more of the length of the trailing edge 42b of the blade 42. The step amount is preferably about 1 / 10 of the length of the trailing edge 42b of the blade 42. The step amount can be freely set in accordance with the specifications and requirements of the turbocharger 1.

[0024] As described above, the flow passage through which the working fluid (e.g., air) F flows is formed by the first wall surface 6c of the compressor housing 6, the front surface 41a of the main body 41, the second wall surface 8a of the seal plate 8, and the fourth wall surface 71b of the projecting wall portion 71. That is, the first wall surface 6c forms a suction flow passage (flow passage) P1 together with the front surface 41a of the main body 41, through which the working fluid F flows. The first wall surface 6c, together with the second wall surface 8a of the seal plate 8, forms an intermediate flow passage P2 that communicates with the downstream side of the suction flow passage P1 in the flow direction of the working fluid F.The first wall surface 6c, together with the fourth wall surface 71b of the projecting wall portion 71, forms a diffuser P3 which communicates with the downstream side of the intermediate flow passage P2 in the flow direction of the working fluid F.

[0025] The volute 6b is connected to the downstream side of the diffuser P3 in the flow direction of the working fluid F. In other words, the turbocharger 1 includes the diffuser P3 and the volute 6b, which communicate with the suction flow passage P1. Note that the intermediate flow passage P2 includes the second gap C2. Further, the suction flow passage P1 and the first gap C1 are connected to each other by the intermediate flow passage P2, which includes the second gap C2. In other words, the second gap C2 connects the suction flow passage P1 to the first gap C1.

[0026] The compressor housing 6 includes an annular protruding wall portion 61. The diffuser P3 is a flow passage formed between the surface of the protruding wall portion 61 (a portion extending in the radial direction of the first wall surface 6c) and the fourth wall surface 71b. The surface of the protruding wall portion 61 and the fourth wall surface 71b extend in the radial direction and the circumferential direction, respectively, and are substantially perpendicular to the rotation axis X. The diffuser P3 is formed on the edge (i.e., the downstream side) of the compressor impeller 4 and extends in the radial direction and the circumferential direction. The starting end (inlet) of the diffuser P3 is the third wall surface 71a. The terminal end (outlet) of the diffuser P3 is a front end of the protruding wall portion 61.

[0027] In the turbocharger 1 having the above-described configuration, the working fluid F is compressed as described below. Exhaust gas discharged from an internal combustion engine flows from an inlet of the turbine 30 into the volute 5a to rotate the turbine impeller 3, and then flows out of the outlet 5b to the outside. As the compressor impeller 4 rotates with the rotation of the turbine impeller 3 and the shaft 2, the working fluid F is sucked from the inlet 6a of the compressor 40 into the compressor housing 6 and sequentially passes through the suction flow passage P1, the intermediate flow passage P2, the diffuser P3, and the volute 6b to be compressed. The compressed working fluid F is supplied to an intake side of the internal combustion engine.

[0028] As described above, in the turbocharger 1, when the compressor impeller 4 rotates about the rotation axis X, the working fluid F flows through the suction flow passage P1 to be compressed. At this time, a negative pressure is formed in the first gap C1 in some cases. Accordingly, oil circulating in the space S leaks from a gap between the seal plate 8 and the collar 22 to the first gap C1 due to the suction force generated by the negative pressure, so that a so-called oil leakage occurs. The turbocharger 1 includes the protruding wall portion 71 provided on the outer side in the radial direction with respect to the side surface 41c of the compressor impeller 4 so as to protrude from the second wall surface 8a toward the first wall surface 6c. The projecting wall portion 71 includes the third wall surface 71a extending from the second wall surface 8a in the axial direction and facing the side surface 41c of the compressor impeller 4.The third wall surface 71a further extends toward the first wall surface 6c in the axial direction from the connecting portion 41d connecting the front surface 41a and the side surface 41c. The third wall surface 71a forms the second gap C2 together with the side surface 21c, which connects the suction flow passage P1 to the first gap C1. For this reason, a part of the working fluid F flowing through the suction flow passage P1 along the front surface 41a and passing through the intermediate flow passage P2 collides with the third wall surface 71a and flows into the first gap C1 through the second gap C2. Accordingly, negative pressure is prevented from being formed in the first gap C1 on the rear surface 41b side of the compressor impeller 4, and oil is prevented from being sucked into the first gap C1 due to the negative pressure. Thus, according to the turbocharger 1, oil leakage is prevented.

[0029] The third wall surface 71a is formed by an inner peripheral surface. According to this configuration, because the third wall surface 71a is formed by an inner peripheral surface, a portion of the working fluid F flowing through the suction flow passage P1 along the front surface 41a and passing through the intermediate flow passage P2 collides with the third wall surface 71a and flows unhindered to the first gap C1 through the second gap C2. Accordingly, negative pressure is reliably prevented from forming in the first gap C1.

[0030] The turbocharger 1 includes the diffuser P3 and the scroll 6b, which communicate with the suction flow passage P1. The protruding wall portion 71 includes the fourth wall surface 71b, which is connected to the side opposite to the second wall surface 8a in the third wall surface 71a, and faces the first wall surface 6c. The fourth wall surface 71b extends in the radial direction to form the diffuser P3 together with the first wall surface 6c, and is continuously continuous with the inner wall surface forming the scroll 6b. According to this configuration, even in the turbocharger 1 having the protruding wall portion 71, a desired compression efficiency can be achieved without deteriorating compression efficiency.

[0031] Although one embodiment has been described above, the present disclosure is not limited to the above-described embodiment.

[0032] The inner diameter of the third wall surface 71a can be constant or changed in the axial direction. For example, if the connecting portion between the third wall surface 71a and the fourth wall surface 71b is chamfered or deburred, the inner diameter of the third wall surface 71a can be changed.

[0033] An example has been described such that the protruding wall portion 71 is a part of the bearing housing 7, however, the protruding wall portion 71 may be provided separately from the bearing housing 7. The protruding wall portion 71 is, for example, an annular plate and may be connected to the bearing housing 7. Furthermore, the protruding wall portion 71 may be integrally formed with the seal plate 8. That is, the protruding wall portion 71 may be a part of the seal plate 8.

[0034] As in Fig.3, the third wall surface 71a may include two or more inner peripheral surfaces and a step portion formed between the inner peripheral surfaces. More specifically, the third wall surface 71a may include, for example, a first inner peripheral surface 71c extending from the second wall surface 8a toward the first wall surface 6c, a step portion 71d connected to the side opposite to the second wall surface 8a in the first inner peripheral surface 71c and extending in the radial direction, and a second inner peripheral surface 71e connected to the side opposite to the first inner peripheral surface 71c in the step portion 71d and extending toward the first wall surface 6c. The inner diameter of the second inner peripheral surface 71e is larger than the inner diameter of the first inner peripheral surface 71c. That is, the third wall surface 71a may have a step.According to this configuration, the degree of freedom in designing the protruding wall portion 71 is improved.

[0035] An example has been described such that the fourth wall surface 71b is continuously continuous with the inner wall surface forming the spiral 6b, but the fourth wall surface 71b does not have to be continuously continuous with the inner wall surface forming the spiral 6b.

[0036] According to the present invention, it is possible to provide a radial compressor in which oil leakage is prevented. List of reference symbols

[0037] 1: Turbocharger (Centrifugal compressor), 4: Compressor impeller (wheel), 6: Compressor casing (first wall section), 6b: Volute, 6c: First wall surface, 8: Seal plate (second wall section), 8a: Second wall surface, 41: Main body, 41a: Front surface, 41b: Rear surface, 41c: Side surface, 41d: Connecting section, 71: Projecting wall section, 71a: Third wall surface, 71b: Fourth wall surface, C1: First gap, C2: Second gap, F: Working fluid, P1: Suction flow passage (flow passage), P3: Diffuser, X: Rotation axis (axis).

Claims

[1] Radial compressor (1) with: an impeller (4) comprising a main body (41) having a front surface (41a) and a rear surface (41b) facing its opposite sides in an axial direction, and a side surface (41c) connected to the front surface (41a) and the rear surface (41b); a first wall portion (6) comprising a first wall surface (6c) opposite the front surface (41a) and forming, together with the front surface (41a), a flow passage (P1) through which a working fluid flows; a second wall section (8) comprising a second wall surface (8a) opposite the rear surface (41b) and the first wall surface (6c) and forming a first gap (C1) together with the rear surface (41b); and a projecting wall portion (71) provided on an outer side in a radial direction with respect to the side surface (41c) of the impeller (4) to project from the second wall surface (8a) toward the first wall surface (6c), wherein the projecting wall portion (71) comprises a third wall surface (71a) extending from the second wall surface (8a) in the axial direction and facing the side surface (41c) of the impeller (4), wherein the third wall surface (71a) extends further toward the first wall surface (6c) in the axial direction from a connecting portion (41d) connecting the front surface (41a) and the side surface (41c), and the third wall surface (71a) and the side surface (41c) form a second gap (C2) between each other, the second gap (C2) connecting the flow passage (P1) to the first gap (C1), characterized by , that the third wall surface (71a) comprises two or more inner edge surfaces (71c, 71e) and a step portion (71d) formed between the inner edge surfaces (71c, 71e), a first inner edge surface (71c) of the two or more inner edge surfaces (71c, 71e) extends in the axial direction, the step portion (71d) is connected to a side opposite to the second wall surface (8a) in the first inner edge surface (71c) and extends to the outside in the radial direction, and a second inner edge surface (71e) of the two or more inner edge surfaces (71c, 71e) is connected to a side opposite to the first inner edge surface (71c) in the step portion (71d) and extends in the axial direction. [2] Radial compressor (1) according to claim 1, further comprising: a diffuser (P3) and a spiral (6b) connected to the flow passage (P1), wherein the projecting wall portion (71) comprises a fourth wall surface (71b) connected to the side opposite to the second wall surface (8a) in the third wall surface (71a) and opposite to the first wall surface (6c), and wherein the fourth wall surface (71b) extends in the radial direction to form the diffuser (P3) together with the first wall surface (6c), and is continuously continuous with an inner wall surface forming the spiral (6b).

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