WO2012140509A2

WO2012140509A2 - Compressor

Info

Publication number: WO2012140509A2
Application number: PCT/IB2012/000841
Authority: WO
Inventors: Minoru Ishino; Masayoshi Otsuka; Masakasu TABATA
Original assignee: Toyota Jidosha Kabushiki Kaisha
Priority date: 2011-04-12
Filing date: 2012-04-12
Publication date: 2012-10-18
Also published as: JP2012219756A; WO2012140509A3; JP5192060B2

Abstract

A compressor portion (30) has a diffuser chamber (54), a scroll chamber (56) and a diffuser vane unit (38). The diffuser vane unit (38) is made up of a single vane, and is disposed so that the angle θ that represents the front end position thereof to the impeller-housing chamber (52) side is in the range of 0°≤θ≤180°.

Description

COMPRESSOR

BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The invention relates to a compressor for use in a turbocharger.

2. Description of Related Art

[0002] Japanese Patent No. 4389442 describes a compressor constructed so as to project a guide vane into a diffuser or withdraw the guide vane from the inside of the diffuser.

[0003] Journal of the Gas Turbine Society of Japan, vol.33, No.4 (July, 2005), pp. 288-294, describes a compressor that employs a diffuser that has a plurality (six) of vanes.

[0004] "Garrett Electric Boosting Systems Program" in Federal Grant DE-FC05-000R22809, US DOE report (June, 2005), pp. 57-58, describes a variable-vane-equipped diffuser that makes it possible to change the degree of opening of a flow path of air in the diffuser.

[0005] However, in a diffuser in which a plurality of vanes are circumferentially disposed as in Japanese Patent No. 4389442, Journal of the Gas Turbine Society of Japan, vol.33, No.4 (July, 2005), p.288-294, and "Garrett Electric Boosting Systems Program" in Federal Grant DE-FC05-OOOR22809, US DOE report (June, 2005), pp. 57-58, the amount of flow is restricted by the smallest area of a flow path formed between adjacent vanes, and therefore it is difficult to restrain the decline in the compressor efficiency that occurs when the amount of flow is increased from an optimum amount of flow.

[0006] Besides, in the case where a vaneless diffuser is used, when the amount of flow is decreased from the optimum amount of flow, the flow path lengthens in the diffuser due to the small angle of outflow from the impeller, so that the friction loss increases. This makes it difficult to increase the compressor efficiency. -

SUMMARY OF THE INVENTION [0007] The invention provides a compressor capable of increasing the compressor efficiency obtained when the amount of flow of air that flows into an impeller-housing chamber is small, and of restraining the decline in the compressor efficiency that occurs when the foregoing amount of flow is large.

[0008] A compressor in accordance with a first aspect of the invention includes: an impeller-housing chamber that houses an impeller that rotates so as to accelerate air that has flown in; a diffuser chamber that is formed along an outer periphery of the impeller-housing chamber, and that communicates with an inside of the impeller-housing chamber, and that decelerates and pressurizes the air accelerated by rotation of the impeller; a scroll chamber that is formed in a spiral shape outside the diffuser chamber, and that communicates with an inside of the diffuser chamber, and that allows the air pressurized in the diffuser chamber to flow to an outside of the scroll chamber; and a diffuser vane unit that is provided in the diffuser chamber and that guides the air flowing in from the impeller-housing chamber to the scroll chamber. The diffuser vane unit is constructed of a single vane or a vane row made up of a plurality of vanes juxtaposed in an air flow direction in which the air flows. Each vane of the vane row or the single vane that has a linear or curved camber line. The diffuser vane unit is disposed so that an angle Θ formed between a first line segment and a second line segment is a range of 0°<θ<180° from a reference position, at which a sectional area of the scroll chamber that is orthogonal to the air flow direction is maximum, toward an upstream side in the air flow direction. The first line segment is defined as being a line segment connecting a rotation center position of the impeller and a front end position, on an impeller housing chamber side, of the single vane or of a most upstream vane of the vane row in the air flow direction. The second line segment is defined as being a line segment connecting the rotation center position of the impeller and the reference position.

[0009] According to the foregoing construction, the diffuser chamber is formed along the outer periphery of the impeller-housing chamber, and the impeller-housing chamber and the diffuser chamber communicate with each other, so that air can move therebetween. Furthermore, the scroll chamber is formed outside the diffuser chamber, and the diffuser chamber and the scroll chamber communicate with each other, so that air can move therebetween. Therefore, the air that flows into the impeller-housing chamber is accelerated by rotation of the impeller, so that the air flows into the diffuser chamber after being given added kinetic energy. Then, the air is decelerated and therefore pressurized in the diffuser chamber, with kinetic energy being converted into pressure energy. The air pressurized in the diffuser chamber is collected in the scroll chamber, and is allowed to flow to the outside of the scroll chamber.

[0010] It is to be noted herein that the diffuser vane unit is a single vane (one vane) or a vane row made up of a plurality of vanes juxtaposed in a direction (the vane row operates in the same manner as the single vane), and the impeller-housing chamber-side front end position of the diffuser vane unit is prescribed. Therefore, in the case where an amount of flow of air that is smaller than a pre-set amount flows into the impeller-housing chamber, the flow of air out of the impeller is deflected from the tangential directions to the radial directions of the impeller by the single vane (or the vane row) of the diffuser vane unit within the diffuser chamber, so that the pressure of air rises. Therefore, this compressor is able to raise the compressor efficiency at the side of small flow in comparison with a compressor that is not provided with a diffuser vane unit.

[0011 j On the other hand, in the case where an amount of flow of air larger than a pre-set amount flows into the impeller-housing chamber, there is on choking of the flow of air (no occurrence of a choking phenomenon in which flow of air is choked between vanes) since the diffuser vane unit is a single vane without any adjacent vane (or a vane row in which spaces between the vanes are nanow) and therefore no throat diameter exists. Hence, it is possible to restrain decline in the compressor efficiency at the side where the amount of flow is large, in comparison with a compressor that has a plurality of diffuser vanes that are disposed in different directions.

[0012] In the above-described compressor of the invention, a portion, of each vane of the vane row or of the single vane, that is closer to the impeller-housing chamber side is located more upstream in the air flow direction. [0013] In the foregoing compressor, the diffuser vane unit may be constructed of the vane row, and a line segment connecting the front end position of a downstream vane of the vane row in the air flow direction and the rotation center position of the impeller may be longer than a line segment connecting the front end position of an upstream vane of the vane row in the air flow direction and the rotation center position of the impeller.

[0014] According to the foregoing construction, in the vane row, the line segment connecting the impeller-housing chamber-side front end position of a relatively downstream-side located vane and the rotation center position of the impeller is longer than the line segment connecting the impeller-housing chamber-side front end position of. a relatively upstream-side located vane and the rotation center position of the impeller. Therefore, flow of air is deflected further to the radial directions of the impeller from the tangential directions of the impeller, and therefore is further decelerated. Due to this, the pressure further rises, so that the compressor efficiency at the side of small flow can be raised.

[0015] In the foregoing compressor, the diffuser vane unit may be configured to be projected and withdrawn relative to the inside of the diffuser chamber, and the compressor may further include a move device that moves the diffuser vane unit so that the diffuser vane unit is projected and withdrawn relative to the inside of the diffuser chamber.

[0016] According to the foregoing construction, when the amount of flow of air into the iifipeller-housing chamber is large, as for example, the diffuser vane unit is withdrawn from the inside of the diffuser chamber by the move device. This restrains the pressure loss caused by the boundary layer separation on the diffuser vane unit, and therefore restrains decline in the compressor efficiency.

[0017] In the foregoing compressor, the diffuser vane unit may have a rotating shaft that is along a rotation axis of the impeller, and the compressor may further include an alteration device that alters an angle formed between the camber line of a leading edge portion, of each vane of the vane row or the single vane, and a tangent line to an outer periphery of the impeller by turning the rotating shaft. [0018] According to the foregoing construction, the alteration device turns the rotating shaft of the diffuser vane unit to alter the angle of the diffuser vane unit (e.g., equalize the angles) in accordance with the angle of inflow air to the diffuser vane unit which changes depending on the amount of flow. Due to this, the angle of incidence of the leading edge portion of the diffuser vane unit resides in a proper range, and the energy loss caused by the boundary layer separation or collision at the leading edge portion is restrained, so that decline in the compressor efficiency can be restrained.

[0019] Due to the foregoing constructions, the invention is able to raise the compressor efficiency obtained when the amount of flow of air into the impeller-housing chamber is small, and to restrain the decline in the compressor efficiency that occurs when the amount of flow of air into the chamber is large.

BRIEF DESCRIPTION OF THE DRAWINGS

[0020] Features, advantages, and technical and industrial significance of exemplary embodiments of the invention will be described below with reference to the accompanying drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is an overall diagram showing a general construction of a turbocharger in accordance with a first embodiment of the invention;

FIG. 2A is an illustrative diagram showing a general construction of a compressor portion in accordance with the first embodiment of the invention;

FIG. 2B is a partial sectional view of the compressor portion in accordance with the first embodiment of the invention;

FIG. 3 A is a schematic diagram of a diffuser vane in accordance with the first embodiment of the invention;

FIG. 3B is a schematic diagram of another example of the diffuser vane in accordance with the first embodiment of the invention;

FIG. 4A is a schematic diagram of the compressor portion in which the angle of disposition of the diffuser vane in accordance with the first embodiment of the invention is 0°; FIG. 4B is a schematic diagram of the compressor portion in which the angle of disposition of the diffuser vane in accordance with the first embodiment of the invention is 45°;

FIG. 4C is a schematic diagram of the compressor portion in which the angle of disposition of the dififuser vane in accordance with the first embodiment of the invention is 90°;

FIG. 4D is a schematic diagram of the compressor portion in which the angle of disposition of the diffuser vane in accordance with the first embodiment of the invention is 180°;

FIG. 5 is a schematic diagram showing regions of increased pressure in a compressor housing caused by a single-piece diffuser vane in accordance with the first embodiment of the invention;

FIG. 6A is a schematic diagram showing a pressure distribution in a compressor portion not provided with a diffuser vane as a comparative example;

FIG. 6B is a schematic diagram showing a pressure distribution in a compressor portion in accordance with the first embodiment of the invention;

FIG. 7A is a graph showing relations between the amount of flow of air into the compressor portion and the compressor efficiency which were found by calculation with regard to the compressor portion of the first embodiment of the invention and compressor portions of comparative examples (one without a diffuser vane, and one with seven diffuser vanes);

FIG. 7B is a graph showing relations between the amount of flow of air into the compression portion and the compressor efficiency which were found by actual measurement with regard to the compressor portion of the first embodiment of the invention and the compressor portion of the comparative example not provided with a diffuser vane;

FIG. 8 is a graph showing relations between the angle of disposition of the diffuser vane and the compressor efficiency which were found by calculation with regard to the compressor portion of the first embodiment of the invention and the compressor portion of the comparative example (without a diffuser vane);

FIG. 9 A is an illustrative diagram showing a state in which a diffuser vane of a compressor portion in accordance with a first other example of the first embodiment of the invention is projected into a diffuser chamber;

FIG 9B is an illustrative diagram showing a state in which the diffuser vane of the compressor portion in accordance with the first other example of the first embodiment of the invention is withdrawn from the inside of the diffuser chamber;

FIG. 10 is an illustrative diagram showing a diffuser vane capable of angle alteration that is provided in a compressor portion in accordance with a second other example of the first embodiment of the invention;

FIG. 11 is an illustrative diagram showing a general construction of a compressor portion in accordance with a second embodiment of the invention; and

FIG. 12 is a schematic diagram showing the disposition of a diffuser vane row in accordance with the second embodiment of the invention.

DETAILED DESCRIPTION OF EMBODIMENTS

[0021] An example of a compressor in accordance with a first embodiment of the invention will be described.

[0022] FIG. 1 shows a general construction of a turbocharger 10 according to the first embodiment. The turbocharger 10, as an example, has a turbine portion 20 that is provided in an exhaust passageway 12 of an engine (not shown) of a vehicle, a compressor portion 30 as an example of a compressor provided in an intake passageway 14 of the internal combustion engine, and a link portion 40 that links the turbine portion 20 and the compressor portion 30. In the link portion 40, a rotating shaft 42 is rotatably provided. A turbine 22 is linked to an end side of the rotating shaft 42 (a turbine portion 20 side thereof), and an impeller 32 is linked to another end side of the rotating shaft 42 (a compressor portion 30 side thereof).

[0023] The turbine 22 has a plurality of turbine blades 23. On the turbine 22 having a circular disc shape in a plan view, the turbine blades 23 stand with predetermined intervals left therebetween in a circumferential direction. The turbine 22 is housed rotatably in a turbine housing 24. The turbine housing 24 has an exhaust gas inlet opening 26 through which high-temperature exhaust gas Gl discharged from the internal combustion engine flows in, and an exhaust gas outlet opening 28 through which the exhaust gas G2 is discharged after performing a work of turning the turbine 22 in the turbine housing 24.

[0024] On the other hand, an impeller 32 has a plurality of impeller blades 33. On the impeller blades 33 having a circular disc shape in a plan view, the impeller blades 33 stand with predetermined intervals left therebetween in the circumferential direction. The impeller 32 is housed rotatably in the compressor housing 50. The compressor housing 50 has an air inlet opening portion 34 for taking in air Al from the atmosphere, and an air outlet opening 36 from which compressed air A2 compressed by the impeller 32 turning at high speed is jetted out. The compressed air A2 jetted out from the air outlet opening 36 is supplied to the engine as a supercharge gas for combustion.

[0025] It is to be noted herein that the exhaust gas G2 jetted at high speed from the exhaust gas inlet opening 26 collides with the turbine blades 23, so that the turbine 22 rotates at high speed and therefore the impeller 32 linked thereto via the rotating shaft 42 rotates at high speed. Therefore, air flows into the compressor portion 30, and the inflow air is compressed by rotation of the impeller 32, and the compressed air is sent out from the air outlet opening 36 to the engine.

[0026] As shown in FIG. 2A, the compressor housing 50 includes: an impeller-housing chamber 52 in which the impeller 32 is housed; a diffuser chamber 54 that is formed along an outer periphery of the impeller-housing chamber 52 and that communicates with an inside of the impeller-housing chamber 52; a scroll chamber 56 that is formed outside the diffuser chamber 54 and that communicates with an inside of the diffuser chamber 54; and one (single-piece) diffuser vane 38 that is provided in the diffuser chamber 54.

[0027] As shown in FIG. 2B, in the impeller-housing chamber 52, an opening portion 58 is formed at a side opposite to the rotating shaft 42 in the direction of an axis of the impeller 32 (hereinafter, termed the arrow-Z direction). The opening portion 58 is connected to the air inlet opening portion 34 (see FIG 1). Therefore, air flows from the air inlet opening portion 34 into the impeller-housing chamber 52 through the opening portion 58. Besides, the impeller 32 rotates due to rotation of the turbine 22 (see FIG. 1), and sends the air that has flown in into the diffuser chamber 54 while accelerating it.

[0028] As shown in FIG 2A, the diffuser chamber 54 is formed outside the impeller-housing chamber 52 so as to have a generally annular shape in a view in the arrow-Z direction. Besides, the diffuser chamber 54 is lower in the height in the arrow-Z direction than that of the impeller-housing chamber 52, so that the accelerated air that flows from the impeller-housing chamber 52 into the diffuser 54 is decelerated and pressurized. Furthermore, the diffuser chamber 54 has a generally annular bottom wall 55 in a view in the arrow-Z direction. Although in the embodiment, the bottom wall 55 and the diffuser vane 38 are integrally formed, they may also be separately provided.

[0029] The scroll chamber 56 is formed in a spiral shape outside the diffuser chamber 54 in a view in the arrow-Z direction. The scroll chamber 56 collects the air pressurized by the diffuser chamber 54, and allows the air to flow to an external device (to a downstream side). The position which is near a scroll start point (starting point of spiral) of the scroll chamber 56 in a view in the arrow-Z direction and at which the scroll area is a maximum area SI is termed the point PA (reference position). Besides, the scroll area is a sectional area orthogonal to the direction in which the air (fluid) flows (to the air flow direction) in the scroll chamber 56.

[0030] As shown in FIG 3 A, the diffuser vane 38, when viewed in the arrow-Z direction, has an outwardly convex outline LI (convex to a side opposite to the impeller 32) and an inwardly convex outline L2 (convex to the impeller 32 side) at opposite sides of a linear camber line (center line) Ml . An impeller 32-side front end position on the diffuser vane 38 is termed the point PB, and a rear end position thereon at an opposite side to the impeller 32 is termed the point PC.

[0031] Besides, a radial direction of the impeller 32 is termed the arrow-X direction, a tangent direction of the impeller 32 is termed the arrow-Y direction, and an angle between the arrow-Y direction and the camber line Ml of a leading edge portion of the diffuser vane 38 (a front end-side portion thereof) is termed the angel a. The angle a is set in the range of 0°<a<30°. The disposition of the diffuser vane 38 is determined by determining an angle Θ that represents the front end position and the angle a that represents the angle of disposition. The camber line is obtained by connecting the centers of circles inscribed between the outlines LI and L2.

[0032] It is to be noted herein that in FIG. 2A, the position of the rotation center of the impeller 32 is termed the point O, and the angle formed between a line segment connecting the point PA and the point O and a line segment connecting the point O and the point PB is termed the angle Θ. This angle Θ is an angle set in a direction from the point PA, that is, a reference position, toward the upstream side (a direction opposite to the direction in which the air flows, that is, a counterclockwise direction shown in FIG. 2A). That is, the angle Θ represents the impeller 32-side front end position of the diffuser vane 38. Although FIG. 2 A shows the disposition of the diffuser vane 38 in the case of O^BS⁰, the diffuser vane 38 may also be disposed so that 6=0°, 45°, 90° and 180° as shown as examples in FIGS. 4A, 4B, 4C and 4D. Besides, FIGS. 3 A and 3B show the case of 9=90°.

[0033] As another example of the diffuser vane 38 (see FIG. 3 A) in this embodiment, a diffuser vane 62 having a curved camber line M2 as shown in FIG. 3B may also be used. The diffuser vane 62, when viewed in the arrow-Z direction, has an outwardly convex outline L3 (convex to the side opposite to the impeller 32) and another outwardly convex outline L4 at opposite sides of the camber line M2. Besides, the angle between the arrow-Y direction and the camber line M2 of a leading edge portion (a front end-side portion) of the diffuser vane 62 is an angle β. The angle β is also set in the range of 0°<β<30°.

[0034] Next, operation of the first embodiment will be described.

[0035] As shown in FIG. 1, in the turbocharger 10, as the exhaust gas G2 jetted at high speed from the exhaust gas inlet opening 26 collides with the turbine blades 23, the turbine 22 rotates at high speed, so that the impeller 32 linked thereto via the rotating shaft 42 rotates at high speed.

[0036] Subsequently, as shown in FIG. 2A, the air that flows into the impeller-housing chamber 52 is accelerated by rotation of the impeller 32, and then flows in the accelerated state into the diffuser chamber 54, and is decelerated in the diffuser chamber 54, so that the air is pressurized (compressed). Then, the air pressurized in the diffuser chamber 54 is collected in the scroll chamber 56, and is sent out from the air outlet opening 36 to the engine (not shown) that is provided outside the compressor housing 50.

[0037] As shown in FIG. 5, in the compressor portion 30, when air flows from the impeller-housing chamber 52 into the diffuser chamber 54 as the impeller 32 rotates in an arrow-R direction (clockwise direction indicated in FIG. 5), the flow of the air is deflected by the diffuser vane 38 to the direction to the outlet of the scroll chamber 56, and becomes a flow shown by a flow line Qa in FIG. 5. Then, as a result of deceleration of the deflected flow of air, energy of speed is converted into energy of pressure in a region SA shown in FIG. 5, the pressure in the outlet opening of the diffuser chamber 54 heightens.

[0038] Subsequently, as a result of deceleration of the flow of air in the region SA, the flow in a region SB contiguous to the region SA also decelerates, so that the pressure rises. Then, as a result of deceleration of the flow in the region SA and the region SB, the flow decelerates and the pressure rises in a region SC in the scroll chamber 56 as well. Furthermore, as a result of deceleration of the flow in the region SC, the flow decelerates and the pressure rises in a region SD present at an upstream side of the region SC as well In this manner, the pressure rises in the compressor portion 30.

[0039] In the case where air in a rate (or an amount) of flow smaller than a pre-set rate (or a pre-set amount) flows into the impeller-housing chamber 52, the flow from the impeller 32 is deflected from the tangential directions of the impeller 32 to the radial directions thereof and is therefore decelerated by the single-piece diffuser vane 38 provided in the diffuser chamber 54, so that the pressure rises. Hence, in this embodiment, the compressor efficiency on the side of small flow can be raised in comparison with a compressor not provided with a diffuser vane 38.

[0040] In the case of the compressor of the comparative example not provided with a diffuser vane 38, the flow line is a flow line Qb represented by an interrupted line, and the flow path in the diffuser chamber 54 is longer and the friction loss is greater, and furthermore deceleration can be less easily accomplished. This results in a lower rate of conversion from energy of speed into energy of pressure and a lower compressor efficiency.

[0041] FIG. 6A shows a pressure distribution (results of calculation) at the time of rotation of the impeller 32 in a compressor portion 200 in a comparative example that is not provided with a diffuser vane 38. FIG. 6B shows a pressure distribution (results of calculation) at the time of rotation of the impeller 32 in the compressor portion 30 of the embodiment. In FIGS. 6A and 6B, the magnitudes of pressures PI, P2, P3 and P4 are P1<P2<P3<P4, indicating that as the region of the pressure P4 is larger, the pressure in the compressor portion is higher. Besides, in FIG. 6B, the position of the diffuser vane 38 is 9=90° (see FIG. 4C).

[0042] As shown in FIG. 6A, in the compressor portion 200 of the comparative example not provided with a diffuser vane 38, the pressure distribution from the impeller-housing chamber 52 (inner side) to the scroll chamber 56 (outer side) is made up of the region of the pressure PI, the region of the pressure P2 and the region of the pressure P3, with the pressure P3 being the maximum pressure.

[0043] On the other hand, in the compressor portion 30 in the first embodiment, as shown in FIG. 6B, the pressure distribution from the impeller-housing chamber 52 (inner side) to the scroll chamber 56 (outer side) is made up of the region of the pressure P2, the region of the pressure P3 and the region of the pressure P4, with the pressure P4 being the maximum pressure. From this, too, it can be understood that the compressor portion 30 of the embodiment provided with one diffuser vane 38 has a higher outlet opening pressure than the compressor portion 200 of the comparative example not provided with a diffuser vane 38, that is, is higher in compressor efficiency than the compressor portion 200.

(0044] FIG. 7A shows relations (results of calculation) between the rate (or the amount) of flow of air and the compressor efficiency in the case of the first embodiment where one diffuser vane 38 is provided (graph A), the case of the comparative example where a diffuser vane 38 is not provided (graph B) and the case of another comparative example where seven diffuser vanes 38 are disposed at equal intervals in the circumferential direction of the diffuser chamber 54 (graph C). The compressor efficiency is found, for example, on the basis of the temperature and pressure at the inlet opening side of the compressor portion 30, the temperature and pressure at the outlet opening side thereof, and the ratio of specific heat of the air that flows into the compressor portion 30. Besides, the disposition of the diffuser vane 38 in the first embodiment is set with 0=90°.

[0045] In FIG. 7A, an amount of flow of air that is smaller than a pre-set amount of flow of air (not shown) is termed the amount Tl , and an amount of flow of air that is larger than the pre-set amount is termed the amount V2. When the amount of flow air is V] , the compressor efficiency of the compressor portion 30 (see FIG 2A) of the first embodiment is K3, which is larger than¹ a compressor efficiency K2 of the compressor portion of the comparative example not provided with a diffuser bane 38 (see FIG. 2A). That is, it can be understood that in the compressor portion 30 of the first embodiment, the compressor efficiency on the small flow side is relatively high.

[0046] On the other hand, when the amount of flow of air is V2, the compressor efficiency of the compressor portion 30 of the first embodiment is K3, which is larger than a compressor efficiency Kl of the compressor portion of the comparative example provided with the seven diffuser vanes 38 (see FIG. 2A). That is, it can be understood that in the compressor portion 30 of the first embodiment, decline of the compressor efficiency on the side where the amount of flow is large is restrained.

[0047] A reason for the decline of the compressor efficiency in the case of the comparative example of many vanes in which the seven diffusion vanes 38 are provided is considered to be that because throat areas are present between adjacent vanes, the flow becomes choked and the efficiency deteriorates when the amount of flow increases. Besides, a reason for the high compressor efficiency of the compressor portion 30 of the first embodiment is considered to be that the diffuser vane 38 is of a single vane construction and therefore no throat diameter is present and therefore there is no choking, and that the pressure loss resulting from boundary layer separation on the diffuser vane 38 is smaller with the single-vane construction than the multiple-vane construction.

[0048] FIG. 7B shows relations (results of experiments) between the rate (or the amount) of flow of air and the compressor efficiency in the case of the first embodiment in which one diffuser vane 38 is provided (graph D) and the case of the comparative example where no diffuser vane 38 is provided (graph E). The disposition of the diffuser vane 38 in the first embodiment is set with θ=90°. From the comparison between the graph D and the graph E, it has been found that a difference ΔΚ in the compressor efficiency is about three points.

[0049] Next, an optimum range of the disposition of the diffuser vane 38 will be described.

[0050] FIG. 8 shows a graph F representing changes in the compressor efficiency that occur with alteration of the disposition (the angle Θ oriented to the upstream side in the direction of flow of air) of the diffuser vane 38 (see FIG. 2 A). A graph G represents an average efficiency obtained from the graph F, and a graph H represents the compressor efficiency of the comparative example not provided with a diffuser vane 38.

[0051] In FIG. 8, while the compressor efficiency of the comparative example is as low as Ka, the compressor efficiency of the first embodiment is higher than the compressor efficiency Ka of the comparative example (Ka<Kb<Kc<Kd) regardless of changes in the angle Θ. The average compressor efficiency of the first embodiment is Kc.

[0052] It is apparent from FIG. 8 that the graph F of the first embodiment is above the average efficiency Kc in the range of the angle Θ from 0° to 180°, and is below the average efficiency Kc in the range of the angle Θ from 180° to 360°. That is, it can be understood that the magnitude of the compressor efficiency changes depending on the angle Θ of disposition of the diffuser vane 38, and that the angle Θ is preferred to be set in the range of 0° θ<180°. In the first embodiment, the compressor efficiency reaches a maximum value ( d) when 0=90°.

[0053] Next, other examples of the compressor portion 30 of the first embodiment will be described.

[0054] The diffuser vane 38 in the first embodiment does not necessarily need to be fixed integrally with the bottom wall 55 of the diffuser chamber 54, but may also be constructed so as to be projected into the difruser chamber 54 or withdrawn from the inside of the diffuser chamber 54 as shown in FIGS. 9A and 9B.

[0055] As shown in FIG. 9A, a compressor portion 70 as a first other example of the compressor portion 30 of the first embodiment includes a compressor housing 74 provided with a movable diffuser vane 72, and an eccentric cam 76 as an example of move means for moving the diffuser vane 72. The interior of the compressor housing 74 is constructed in the same manner as the compressor housing 50 (see FIG. 1), except for the site where the diffuser vane 72 is moved. That is, the compressor housing 74 has an impeller-housing chamber 52, a diffuser chamber 54, and a scroll chamber 56.

[0056] As for the diffuser vane 72, a portion that is projected into the diffuser chamber 54 is substantially the same in size and shape as the above-described diffuser vane 38 (see FIG. 2A). Besides, the eccentric cam 76 is pivoted in the direction of an arrow +R (clockwise direction indicated in FIG. 9A) by an electric motor (not shown) to project the diffuser vane 72 into the diffuser chamber 54. An end of a tensile spring 78 is attached to an eccentric cam 76-side surface of the diffuser vane 72 so as to urge a returning force to the diffuser vane 72. Due to this, as the eccentric cam 76 is pivoted in the direction of an arrow -R (counterclockwise direction shown in FIG. 9B) by the electric motor, the diffuser vane 72 is withdrawn from the diffuser chamber 54 to the outer side.

[0057] When the amount of flow of air that flows into the compressor portion 70 is, for example, larger than the amount of flow of air V3 shown in FIG. 7A, the diffuser vane 72 is withdrawn from the diffuser chamber 54 by actuating the eccentric cam 76 as shown in FIG. FIG. 9B. That is, the diffuser vane is withdrawn by actuating the eccentric cam 76 when the amount of flow of air into the compressor portion 70 is equal to a pre-set amount of flow at which the withdrawal of the diffuser vane 72 increases the efficiency of the compressor portion 70 (the compressor), the eccentric can 76 is actuated so as to withdraw the diffuser vane 72. As a result of this, the diffuser vane disappears from inside the diffuser chamber 54, so that the graph of compressor efficiency becomes the graph B shown in FIG. 7A, instead of the graph A that represents the compressor efficiency with the single-piece diffuser vane 38. That is, during the state shown in FIG. 9B, there is no pressure loss caused by boundary layer separation on the diffuser vane 38, so that decline in the compressor efficiency is restrained.

[0058] As an example of a method for acquiring data of the amount of flow of air that flows into the compressor portion 70, a data table in which the amount of flow of air corresponds to the engine rotation speed and the accelerator operation amount may be set beforehand, and then, by using this data table, the amount of flow of air may be determined on the basis of obtained values of the engine rotation speed and the accelerator operation amount. Besides the indirect acquisition of data of the amount of flow, data of the amount of flow may also be directly acquired by using a flow sensor that is provided in the intake passageway 14 (see FIG. 1).

[0059] The diffuser vane 38 may also be provided in the diffuser chamber 54 so that the angle of disposition thereof can be changed, instead of being fixed in the diffuser chamber 54.

[0060] As shown in FIG. 10, a compressor portion 80 as a second other example of the compressor portion 30 of the first embodiment is similar to that of the above-described compressor portion 30 (see FIG. 2A), but has a construction in which the diffuser vane 38 is replaced with a diffuser vane 82. The diffuser vane 82 is basically the same in size as the diffuser vane 38, but is different therefrom in that the diffuser vane 82 is provided with a rotating shaft 84 whose axis direction is parallel to the rotation axis direction of the impeller 32 (the arrow-Z direction). The rotating' shaft 84 is rotated (pivoted) by an angle alteration portion 86 as an example of alteration means that includes an electric motor and a link mechanism (neither of which is shown), so that the aforementioned angle a (see FIG. 3A) can be altered.

[0061] It is to be noted herein that in the compressor portion 80, if the amount of flow of air that flows in changes, the angle of inflow to a leading edge portion of the diffuser vane 82 changes, and that the angle alteration portion 86 can acquire data of the inflow angle can by finding the amount of inflow air on the basis of a pre-set relation between the amount of flow and the inflow angle according to the above-described method (that includes measurement of the engine rotation speed, the acceleration operation amount, or the amount of flow). Then, the angle alteration portion 86 alters the angle a of the diffuser vane 82 in the range of 0°≤a<30°, corresponding to the inflow angle, so as to restrain the energy loss due to boundary layer separation or collision at the leading edge portion. Thus, decline of the compressor efficiency can be restrained.

[0062] Next, an example of a compressor in accordance with a second embodiment of the invention will be described. Basically the same members of the compressor as those of the first embodiment are denoted by the same reference characters as used in the first embodiment, and the description of such members may be omitted.

[0063] FIG. 11 shows a compressor portion 90 as an example of the compressor of the second embodiment. The compressor portion 90 is similar to the compressor portion 30 (see FIG. 2 A) of the first embodiment, but includes a row of diffuser vanes 92 as an example of a vane row in place of the single-piece diffuser vane 38, and also includes an impeller 32, an impeller-housing chamber 52, a diffuser chamber 54 and a scroll chamber 56.

[0064] As shown in FIG. 12, the diffuser vane row 92 is constructed of a first diffuser vane 92A as an example of an upstream-side vane and a second diffuser vane 92B as an example of a downstream-side vane that are juxtaposed in a direction in which air flows (the direction of an arrow T shown in FIG. 11). The first diffuser vane 92 A and the second diffuser vane 92B have the same shape (the same camber line shape) and the same size as an example. The the first diffuser vane 92A as a whole is disposed at an upstream side of the second diffuser vane 92B in the arrow-R direction that is the rotation direction of the impeller 32 (see FIG. 2A). Besides, a rear end portion of the first diffuser vane 92A and a front end portion of the second diffuser vane 92B are disposed so as to overlap each other when viewed in the direction of an arrow W orthogonal to the direction of an arrow T.

[0065] Herein, the front end position on the first diffuser vane 92A that is at the impeller 32 side (the upstream side in the arrow-T direction) is termed the point PD, and the rear end position on the first diffuser vane 92 A at a side opposite to the impeller 32 (the downstream side in the arrow-T direction) is termed the point PE. Besides, the front end position on the second diffuser vane 92B that is at the upstream side in the arrow-T direction is termed point PF, and the rear end position thereon at the downstream side in the arrow-T direction is termed the point PG. The arrow-T direction is, as an example, a direction from the diffuser chamber 54 to the scroll chamber 56 side (the outside) along a line passing through the point PD and the point PG. Besides, in FIG. 12, illustration of the impeller 32 (see FIG. 2 A) is omitted, and the compressor housing 50 is illustrated only partially by a two-dot chain line.

[0066] In the compressor portion 90, an angle ΘΑ formed between a line segment of a length R0 connecting a point PA and a point O and a line segment of a length Rl connecting the point O and the point PD (the angle from the point PA to the upstream side) is set as ΘΑ=135°, as an example. Besides, an angle ΘΒ formed between the line segment of the length R0 connecting the point PA and the point O and a line segment of a length R2 connecting the point O and the point PF (the angle from the point PA to the upstream side) is set as ΘΒ=112.5° (i.e., ΘΑ>ΘΒ). The distance R2 from the point O to the second diffuser vane 92B located at downstream side in the arrow-T direction is longer than the length Rl from the point O to the first diffuser vane 92 A located at the upstream side.

[0067] Furthermore, in the compressor portion 90, the line that is parallel to the line segment connecting the point PA and the point O and that passes through the point PD is termed the line Nl , and the angle formed between the line Nl and the camber line (not shown) of the first diffuser vane 92A at its front end side (point PD side) is termed the angle 0a. Likewise, the line that is parallel to the ling segment connecting the point PA and the point O and that passes through the point PF is termed the line N2, and the angle formed between the line N2 and the camber line (not shown) of the second diffuser vane 92B at its front end side (point PF side) is termed the angle Gb. It is to be noted herein that the first diffuser vane 92A and the second diffuser vane 92B are disposed so that the angles 9a and Ob have a relation of 0a>9b.

[0068] Between a rear end portion (point PE-side portion) of the first diffuser vane 92A and a front end portion (point PF-side portion) of the second diffuser vane 92B, a clearance 94 is formed. The size of the clearance 94 is set beforehand by experiments so that the first diffuser vane 92A and the second diffuser vane 92B allow air to flow in the same manner as one (single-piece) diffuser vane.

[0069] Next, operation of the second embodiment will be described.

[0070] As shown in FIG. 11 , in the compressor portion 90, when air flows from the impeller-housing chamber 52 into the diffuser chamber 54 as the impeller 32 rotates in the arrow-R direction, the flow of the air is deflected by the diffuser vane row 92 to the direction to the outlet of the scroll chamber 56, and becomes a flow shown by a flow line Qc in FIG. 11. As a result of the deflection decelerating the flow of air, energy of speed is converted into energy of pressure, so that the pressure in the outlet opening of the diffuser chamber 54 heightens, and the pressure inside the compressor portion 90 rises.

[0071] It is to be noted herein that in the diffuser vane row 92, the front end position of the first diffuser vane 92A on an impeller housing chamber 52 side is prescribed, and the first diffuser vane 92A and the second diffuser vane 92B juxtaposed in the arrow-T direction (see FIG. 12) operate to allow air to flow in the same manner as a single vane. Due to this, when an amount of air smaller than a pre-set amount flows into the impeller-housing chamber 52, the flow of air that flows out of the impeller 32 is deflected from the tangential directions of the impeller 32 to the radial directions thereof and is therefore decelerated by the diffuser vane row 92 in the diffuser chamber 54, so that the pressure in the outlet opening of the diffuser chamber 54 rises. Therefore, the compressor portion 90 is able to raise the compressor efficiency on the side of small flow, in comparison with a compressor that is not provided with either the diffuser vane row 92 or a single-piece diffuser vane.

[0072] On the other hand, when an amount of air larger than a pre-set amount flows into the impeller-housing chamber 52, the flow of air does not choke (a choke phenomenon in which flow of air chokes does not occur), because in the diffuser vane row 92, the clearance between the first diffuser vane 92A and the second diffuser vane 92B is narrow, and there is no other diffuser vane adjacent to the diffuser vane row 92, and there is no throat diameter. Due to this, the compressor portion 90 is able to restrain decline in the compressor efficiency on the side where the amount of flow is large, in comparison with a compressor in which a plurality of diffuser vanes are provided in individually different directions.

[0073] Furthermore, as shown in FIG. 11 and FIG. 12, with regard to the first diffuser vane 92A and the second diffuser vane 92B of the compressor portion 90, the length of the line segment connecting the front end position (the point PF), on an impeller housing chamber 52 side, of the downstream-side disposed second diffuser vane 92B (length R2) is longer than the length of the line segment connecting the front end position (the point PD) of the upstream-side disposed first diffuser vane 92A (length Rl), so that the flow of air is deflected further to the radial directions of the impeller 32 from the tangential directions thereof, and therefore is further decelerated. Therefore, the pressure in the outlet opening of the diffuser chamber 54 rises, so that the compressor efficiency on the side of small flow can be further raised.

[0074] It is to be noted herein that it is known that if the shape, the size of the first diffuser vane 92A and the second diffuser vane 92B and the clearance 94 therebetween are set so that the diffuser vane row 92 operates in the same manner as a single vane, substantially the same results (operation) as the results shown in FIGS. 6 and 8 that are obtained in the case where the diffuser vane 38 (see FIG. 2 A) of the first embodiment is used. That is, if the disposition of the diffuser vane row 92 is set in the same range of the angle Θ as for the disposition of the single-piece diffuser vane 38 shown in FIGS. 4 A to 4D, there is achieved an effect of raising the compressor efficiency obtained when the amount of flow of air flowing into the impeller-housing chamber 52 is small and restraining the decline in the compressor efficiency that occurs when the amount of flow of air is large.

[0075] The invention is not limited to the foregoing embodiments.

[0076] The diffuser vane row 92 is not limited to a vane row made up of two vanes (the first diffuser vane 92A and the second diffuser vane 92B), but may also be a row made up of three or more vanes, as long as the vane row operates in the same manner as a single vane. Besides, the diffuser vane row 92 may also be constructed so as to be moved into and out of the diffuser chamber 54 by move means such as the eccentric cam 76 as shown in FIGS. 9A and 9B. Furthermore, the angles of disposition of the first diffuser vane 92A and of the second diffuser vane 92B may be altered by using the angle alteration portion 86 shown in FIG. 10.

Claims

1. A compressor comprising:

an impeller-housing chamber that houses an impeller that rotates so as to accelerate air that has flown in;

a diffuser chamber that is formed along an outer periphery of the impeller-housing chamber, and that communicates with an inside of the impeller-housing chamber, and that decelerates and pressurizes the air accelerated by rotation of the impeller;

a scroll chamber that is formed in a spiral shape outside the diffuser chamber, and that communicates with an inside of the diffuser chamber, and that allows the air pressurized in the diffuser chamber to flow to an outside of the scroll chamber; and

a diffuser vane unit that is provided in the diffuser chamber and that guides the air flowing in from the impeller-housing chamber to the scroll chamber,

wherein the diffuser vane unit is constructed of a single vane or a vane row made up of a plurality of vanes juxtaposed in an air flow direction in which the air flows,

wherein each vane of the vane row or the single vane that has a linear or curved camber line,

wherein the diffuser vane unit is disposed so that an angle Θ formed between a first line segment and a second line segment is a range of 0°<θ<180° from a reference position, at which a sectional area of the scroll chamber that is orthogonal to the air flow direction is maximum, toward an upstream side in the air flow direction, and

wherein the first line segment is defined as being a line segment connecting a rotation center position of the impeller and a front end position, on an impeller housing chamber side, of the single vane or of a most upstream vane of the vane row in the air flow direction, and the second line segment is defined as being a line segment connecting the rotation center position of the impeller and the reference position.

2. The compressor according to claim 1 , wherein

a portion, of each vane of the vane row or of the single vane, that is closer to the impeller-housing chamber side is located more upstream in the air flow direction.

3. The compressor according to claim 1 or 2, wherein:

the diffuser vane unit is constructed of the vane row; and

a line segment connecting the front end position of a downstream vane of the vane row in the air flow direction and the rotation center position of the impeller is longer than a line segment connecting the front end position of an upstream vane of the vane row in the air flow direction and the rotation center position of the impeller.

4. The compressor according to any one of claims 1 to 3, wherein

the diffuser vane unit is configured to be projected and withdrawn relative to the inside of the diffuser chamber,

the compressor further comprising

a move device that moves the diffuser vane unit so that the diffuser vane unit is projected and withdrawn relative to the inside of the diffuser chamber.

5. The compressor according to any one of claims 1 to 3, wherein

the diffuser vane unit has a rotating shaft that is along a rotation axis of the impeller, the compressor further comprising

an alteration device that alters an angle formed between the camber line of a leading edge portion, of each vane of the vane row or the single vane, and a tangent line to an outer periphery of the impeller by turning the rotating shaft.