JP2016160760A - Centrifugal compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a centrifugal compressor capable of suitably coping with both of small flow rate time and large flow rate time.SOLUTION: A centrifugal compressor 10 includes a housing 11 in which fluid is taken, and an impeller 22 which rotates and thereby compresses the fluid taken in the housing 11. The housing 11 includes an impeller chamber 27 storing the impeller 22, and a discharge chamber 41 to which the fluid compressed by the impeller 22 is discharged. The housing 11 has a first diffuser flow passage 30 and a second diffuser flow passage 50 having a flow passage cross section smaller than that of the first diffuser flow passage 30 so as to communicate the impeller chamber 27 with the discharge chamber 41.SELECTED DRAWING: Figure 2

Description

  The present invention relates to a centrifugal compressor.

  Conventionally, a centrifugal compressor including an impeller that compresses a fluid sucked into a housing by rotating is known (see, for example, Patent Document 1). The housing has, for example, an impeller chamber in which the impeller is accommodated, and a discharge chamber that communicates with the diffuser channel. The fluid compressed by the impeller is further compressed by passing through the diffuser flow path, and flows into the discharge chamber.

Japanese Patent Laid-Open No. 05-60097

  Here, for example, when the flow passage cross-sectional area of the diffuser flow path is set in correspondence with the required maximum discharge flow rate, it is possible to suitably cope with a large flow rate in which a relatively large discharge flow rate is required. On the other hand, when the flow rate is small, that is, when a relatively small discharge flow rate is required, a surge phenomenon may occur and normal operation may not be possible, or efficiency may be reduced.

  On the other hand, as shown in Patent Document 1, for example, it is also conceivable to employ a caging treatment that increases the flow rate sucked into the impeller by circulating the fluid. However, caging treatments do not improve efficiency due to their characteristics.

From the above, there is still room for improvement in the configuration for dealing with both the small flow rate and the large flow rate.
The present invention has been made in view of the above-described circumstances, and an object thereof is to provide a centrifugal compressor that can suitably cope with both a small flow rate and a large flow rate.

  A centrifugal compressor that achieves the above object includes a housing having a suction port through which fluid is sucked, and an impeller that rotates integrally with a rotary shaft and compresses the fluid by rotating. The housing communicates with the suction port, and includes an impeller chamber in which the impeller is accommodated, a discharge chamber in which fluid compressed by the impeller is discharged, the impeller chamber, and the discharge chamber. A first diffuser channel that communicates, and a second diffuser channel that communicates the impeller chamber and the discharge chamber and has a smaller channel cross-sectional area than the first diffuser channel, The impeller includes a first position where fluid flows preferentially in the first diffuser channel over the second diffuser channel, and the second diffuser over the first diffuser channel. Wherein the fluid chromatography The flow path is movable between a second position in which flow preferentially.

  According to this configuration, the diffuser flow channel that flows preferentially is switched according to the position of the impeller. Thus, for example, when the impeller is disposed at the first position at a large flow rate, the fluid can be preferentially flowed into the first diffuser flow path having a larger flow path cross-sectional area than the second diffuser flow path. It can cope with the flow rate suitably. On the other hand, for example, when the flow rate is small, by disposing the impeller at the second position, it is possible to preferentially flow the fluid through the second diffuser channel having a smaller channel cross-sectional area than the first diffuser channel. Sometimes it is possible to respond appropriately. Therefore, it is possible to suitably cope with both a large flow rate and a small flow rate.

  In the centrifugal compressor, the impeller has a shape whose diameter is reduced from a proximal end portion toward a distal end portion, the distal end portion is disposed closer to the suction port than the proximal end portion, and the rotating shaft The first diffuser flow path is a flow path surrounded by a first opposing wall surface and a second opposing wall surface that are arranged to face each other in the axial direction. And in the axial direction, the first opposing wall surface is disposed closer to the tip side of the impeller than the second opposing wall surface and the base end portion of the impeller, and the impeller chamber in the second diffuser flow path A second inlet that communicates with the impeller in the axial direction is disposed closer to a tip side of the impeller than a first inlet that communicates with the impeller chamber in the first diffuser flow path. When the impeller is disposed at the second position, the base end portion of the peller may be closer to the first opposing wall surface than when the impeller is disposed at the first position. . According to such a configuration, the fluid sucked from the suction port is compressed as it flows from the front end portion of the impeller toward the base end portion, and flows into the first inflow port or the second inflow port. In such a configuration, when the impeller is disposed at the second position, the base end portion of the impeller approaches the first opposing wall surface, so that the fluid compressed by the impeller does not easily flow into the first diffuser flow path. . Thereby, the fluid compressed by the impeller flows preferentially to the second diffuser flow path having the second inlet provided on the tip side of the impeller rather than the first inlet. Therefore, when the impeller is disposed at the second position, the fluid can be preferentially flowed to the second diffuser flow path rather than the first diffuser flow path.

  On the other hand, when the impeller is disposed at the first position, the base end portion of the impeller is separated from the first opposing wall surface in the axial direction, so that the fluid compressed by the impeller easily flows into the first diffuser flow path. It has become. Thereby, when the impeller is arrange | positioned in the 1st position, a fluid can be flowed preferentially to a 1st diffuser flow path rather than a 2nd diffuser flow path.

  In the configuration in which the second inlet is disposed closer to the tip side of the impeller than the first inlet, fluid may flow into the second inlet regardless of the position of the impeller. However, since the second diffuser channel has a smaller channel cross-sectional area than the first diffuser channel, the fluid flows into the second inlet in a situation where the impeller is disposed at the first position. Even if it exists, it is easy to flow a fluid preferentially to the 1st diffuser channel rather than the 2nd diffuser channel. Therefore, the diffuser flow path preferentially flowing can be switched by changing the positional relationship of the base end portion of the impeller with respect to the first opposing wall surface.

  About the said centrifugal compressor, it is good for the said base end part of the said impeller to have the opposing base end part which has opposed the said axial direction with respect to the said 1st opposing wall surface. According to such a configuration, the fluid compressed by the impeller flows through a gap formed by the opposed base end portion and the first opposed wall surface. And when the impeller is arrange | positioned in the 2nd position, the said clearance gap tends to become narrower than a 1st inflow port. Thereby, the fluid is restricted from flowing into the first diffuser flow path by the gap. Therefore, it is possible to suppress the fluid from flowing into the first diffuser flow path in the situation where the impeller is disposed at the second position.

  About the said centrifugal compressor, when the said impeller is arrange | positioned in the said 2nd position, it is good for the clearance gap formed by the said opposing base end part and the said 1st opposing wall surface to be narrower than the said 2nd inflow port. According to such a configuration, when the impeller is disposed at the second position, the gap formed by the opposed base end portion and the first opposed wall surface is narrower than the second inflow port. Thereby, the fluid compressed by the impeller is easier to flow into the second inlet than the gap. Therefore, the fluid can be preferentially flowed to the second diffuser flow path rather than the first diffuser flow path.

  In the centrifugal compressor, the impeller chamber includes a back region that is a region where a surface of the base end portion of the impeller opposite to the tip side of the impeller is exposed and communicates with a discharge side of the impeller. The housing includes a bypass passage that communicates the back region and the suction side of the impeller, and a control valve is provided on the bypass passage. The centrifugal compressor is in a state in which the control valve is open. A first positioning portion that positions the impeller at the first position, a second positioning portion that positions the impeller at the second position when the control valve is in a closed state, and the control And a controller that controls the position of the impeller by controlling the pressure in the back region by controlling the opening and closing of the valve. According to such a configuration, the impeller is given the first pressing force due to the pressure of the fluid compressed by the rotation of the impeller and the second pressing force due to the pressure in the back region.

  Here, when the control valve is in the open state, the pressure in the back region is the same as or corresponding to the pressure on the suction side of the impeller. In this case, since the first pressing force is larger than the second pressing force, the impeller moves in the pressing direction of the first pressing force. The impeller is positioned at the first position by the first positioning portion.

  On the other hand, when the control valve is in a closed state, the pressure in the back region is the same as or corresponding to the pressure on the discharge side of the impeller. In this case, since the second pressing force is larger than the first pressing force, the impeller moves in the pressing direction of the second pressing force. The impeller is positioned at the second position by the second positioning portion. From the above, the position control of the impeller can be performed by the pressure control of the back surface region. Thereby, the position control of the impeller can be performed without providing an actuator or the like for moving the impeller.

  In particular, according to this configuration, the pressure in the back region becomes the pressure on the suction side of the impeller or the pressure on the discharge side of the impeller according to the state of the control valve, and accordingly, the first pressing force and the second pressing force are changed accordingly. The magnitude relationship with is reversed. This magnitude reversal phenomenon is not easily affected by the discharge flow rate. Thereby, malfunction due to the influence of the discharge flow rate or the like can be suppressed.

  In the centrifugal compressor, both of the first diffuser flow path and the second diffuser flow path are flow paths whose flow cross-sectional areas change according to positions, and the minimum flow path breakage of the second diffuser flow path. The area may be set smaller than the minimum channel cross-sectional area of the first diffuser channel. According to such a configuration, both diffuser channels are channels whose channel cross-sectional area changes depending on the position, and therefore, the degree of freedom in designing both diffuser channels can be improved. Even in this case, since the minimum flow path cross-sectional area of the second diffuser flow path is set smaller than the minimum flow path cross-sectional area of the first diffuser flow path, the above-described effects can be obtained. Therefore, it is possible to improve the degree of freedom in designing both diffuser channels while being able to cope with both high flow rate and low flow rate.

  In the centrifugal compressor, the flow length of the second diffuser flow path is preferably shorter than the flow length of the first diffuser flow path. According to such a configuration, it is possible to improve the efficiency when the flow rate is small.

  According to the present invention, it is possible to suitably cope with both a small flow rate and a large flow rate.

Sectional drawing which shows the principal part of a centrifugal compressor typically. The partially expanded view of FIG. The elements on larger scale which show the periphery of both diffuser flow paths in case the impeller is arrange | positioned in the 1st position. The elements on larger scale which show the periphery of both diffuser flow paths in case the impeller is arrange | positioned in the 2nd position. Sectional drawing in case the impeller is arrange | positioned in the 1st position. Sectional drawing in case the impeller is arrange | positioned in the 2nd position.

  Hereinafter, an embodiment of the centrifugal compressor will be described. In the present embodiment, the centrifugal compressor is mounted on a fuel cell vehicle having a fuel cell, and is used in an air supply device that supplies air to the fuel cell.

  As shown in FIG. 1, the centrifugal compressor 10 includes a housing 11 that constitutes an outline of the compressor 10 and has a suction port 11a through which fluid (for example, air) is sucked. The housing 11 has, for example, two parts 12 and 13 assembled to each other. The front part 12 includes a cylindrical front main body portion 12b having a front through hole 12a penetrating in the axial direction, for example. The rear part 13 has a substantially disk shape. The front part 12 and the rear part 13 are assembled in a state where the axis of the front main body 12b and the axis of the rear part 13 coincide.

  The front part 12 has a boss 12c that is formed so as to protrude from a surface 12ba on the opposite side to the rear part 13 side of the front main body 12b. The boss 12c is erected from the peripheral edge of the front through hole 12a of the front main body 12b. The suction port 11a is an opening formed by the boss 12c and communicates with the front through hole 12a. The fluid flows from the suction port 11a into the housing 11 (specifically, into the front through hole 12a).

For convenience of explanation, in the following explanation, the suction port 11a side is the front side, and the side opposite to the suction port 11a side, that is, the rear part 13 side is the rear side.
As shown in FIG. 1, the centrifugal compressor 10 includes a rotating shaft 21 and an impeller 22 attached to the rotating shaft 21. The rotating shaft 21 is supported by the housing 11 in a rotatable state. A rear through hole 13 a that is slightly larger than the rotating shaft 21 is formed at the center of the rear part 13. The rotary shaft 21 is inserted into the rear through hole 13a in a state where the axial direction Z thereof coincides with the axial direction of the rear part 13, and a part of the rotary shaft 21 is inserted into the front through hole 12a via the rear through hole 13a. It protrudes. Note that the axes of the parts 12 and 13 and the axes of the through holes 12a and 13a coincide with the axis of the rotary shaft 21. Further, the rotation axis of the impeller 22 and the axis of the rotation shaft 21 coincide with each other. For this reason, the axial direction Z of the rotating shaft 21 can also be said to be the rotating axis direction of the impeller 22.

  Between the rotation shaft 21 and the inner surface of the rear through hole 13a, a seal member S is provided that fills the space between the rotation shaft 21 and the rear through hole 13a in a state where the rotation shaft 21 is rotatable. The seal member S restricts the movement of fluid between the suction port 11a side of the rear part 13 and the side opposite to the suction port 11a side. Although not shown, a mechanism for supporting the rotating shaft 21 is provided on the opposite side of the rear part 13 from the suction port 11a side.

  The impeller 22 rotates with the rotation of the rotating shaft 21, and has a shape with a diameter reduced from the proximal end portion 22a toward the distal end portion 22b in the rotation axis direction. The impeller 22 has an insertion hole 22c that extends in the rotation axis direction of the impeller 22 and through which the rotation shaft 21 can be inserted. The impeller 22 is attached in a state where a portion of the rotating shaft 21 protruding into the front through hole 12a is inserted into the insertion hole 22c. In this case, the impeller 22 is movable in the axial direction Z of the rotating shaft 21.

  The rotating shaft 21 includes a protruding portion 21 a that protrudes to the front side of the tip end portion 22 b of the impeller 22. A thread groove is formed on the surface of the protruding portion 21a. A fixing bolt 23 as a fixing portion is screwed to the tip of the protruding portion 21a. The fixing bolt 23 has a larger outer diameter than the insertion hole 22 c of the impeller 22.

  Between the fixing bolt 23 and the tip 22b of the impeller 22, a spring 24 as an urging portion is provided. The spring 24 is larger than the protruding portion 21a and has an inner diameter equal to or smaller than the outer diameter of the distal end portion 22b, and is inserted through the protruding portion 21a. The spring 24 is sandwiched between the fixing bolt 23 and the tip 22b. The spring 24 applies an urging force from the front side to the rear side with respect to the impeller 22.

  The rear part 13 includes a base end facing surface 13 b that faces the base end portion 22 a of the impeller 22. A protrusion 25 as a first positioning portion is provided on the base end facing surface 13b. The protrusion 25 has, for example, an annular shape (specifically, an annular shape), and projects forward from the peripheral edge of the rear through hole 13a. In the initial state where the impeller 22 is not rotating, the impeller 22 is pressed rearward by an urging force and is positioned at a position where the base end portion 22a and the protrusion 25 are in contact with each other. A position where the base end portion 22a and the protrusion 25 are in contact with each other is defined as a first position. The first position can also be said to be the initial position.

  The spring 24 is contracted in the axial direction Z in a situation where the impeller 22 is disposed at the first position, and there is room for further contraction. The length in the axial direction Z of the spring 24 in the situation where the impeller 22 is disposed at the first position is defined as the initial length.

  The impeller 22 is disposed in the front through hole 12a and is accommodated in an impeller chamber 27 defined by an inner wall surface 26 of the front through hole 12a and a base end facing surface 13b. That is, the housing 11 has an impeller chamber 27 in which the impeller 22 is accommodated. The impeller chamber 27 and the suction port 11a communicate with each other, and the impeller 22 is accommodated in the impeller chamber 27 in a state where the tip end portion 22b is disposed on the front side (suction port 11a side) with respect to the base end portion 22a. .

  As shown in FIG. 2, the impeller 22 is, for example, a closed impeller. Side wall 22f covering from the outside in the radial direction R.

The surface of the main body portion 22d is curved toward the outside in the radial direction R of the rotating shaft 21 as it goes from the distal end portion 22b to the proximal end portion 22a.
The plurality of blades 22e connect the surface of the main body portion 22d and the inner surface of the side wall 22f. The blade 22e extends from the main body portion 22d in the radial direction R of the rotary shaft 21 and is spiral with respect to the axial direction Z. For convenience of illustration, the blades 22e are simplified in each drawing.

  The side wall 22f is disposed on the outer side in the radial direction R of the rotation shaft 21 from the main body 22d. Side wall 22f is cylindrical as a whole. The side wall 22f has a diameter that is slightly smaller than the suction port 11a from the front end 22fa to the midway position of the side wall 22f, and has a shape that gradually increases in diameter from the midway position toward the rear end 22fb. The side wall 22f is curved toward the outer side in the radial direction R of the rotating shaft 21 from the middle position toward the rear side.

  Here, an opening formed by the main body 22d and the front end 22fa of the side wall 22f is an impeller inlet 28, and an opening formed by the rear end 22fb and the base end 22a of the side wall 22f is an impeller outlet 29. To do. Since both the main body portion 22 d and the side wall 22 f are curved, the impeller inlet 28 opens in the axial direction Z, and the impeller outlet 29 opens in the radial direction R of the rotating shaft 21. The impeller outlet 29 is narrower than the impeller inlet 28. The fluid sucked from the suction port 11 a flows from the impeller inlet 28 and is discharged from the impeller outlet 29.

The impeller 22 is accommodated in the impeller chamber 27 in a state in which the inner wall surface 26 and the side wall 22f of the front through hole 12a are arranged to face each other in the radial direction R of the rotary shaft 21.
The front through hole 12a is formed corresponding to the shape of the impeller 22 (specifically, the side wall 22f). Specifically, the front through hole 12a has a diameter that is the same as that of the suction port 11a from the front side to the rear side and is slightly larger than the front end 22fa of the side wall 22f, and gradually from the front side to the rear side. And a portion that is wider in the radial direction R of the rotating shaft 21 than the rear end 22fb of the side wall 22f.

  Specifically, the inner wall surface 26 of the front through hole 12a is disposed on the suction port 11a side, and is a first cylindrical surface 26a that is slightly larger than the front end 22fa of the side wall 22f, and the first cylindrical surface. 26a, and a second cylindrical surface 26b disposed on the outer side in the radial direction R of the rotating shaft 21 with respect to the rear end 22fb of the side wall 22f. Further, the inner wall surface 26 is continuous with both cylindrical surfaces 26a and 26b, and is curved toward the outer side in the radial direction R of the rotary shaft 21 from the first cylindrical surface 26a toward the second cylindrical surface 26b. Surface 26c.

  Here, the bending mode of the curved surface 26c is different from the bending mode of the side wall 22f. Specifically, the curved surface 26c has a space between the curved surface 26c and the side wall 22f so that the impeller 22 can move forward from the first position in a situation where the impeller 22 is disposed at the first position. Further, it is curved more tightly than the side wall 22f.

  As shown in FIGS. 2 to 4, a diffuser flow path 30 through which fluid compressed by rotation of the impeller 22 flows is defined in the housing 11. The diffuser flow path 30 is annular (specifically, annular) as a whole, and is provided outside the radial direction R of the rotating shaft 21 (in other words, the impeller 22) with respect to the impeller chamber 27.

  The diffuser flow path 30 is partitioned by the front part 12 and the rear part 13. Specifically, the parts 12 and 13 have opposing wall surfaces 31 and 32 that are arranged to face each other in the axial direction Z as a part that defines the diffuser flow path 30. The diffuser channel 30 is a channel surrounded by both opposing wall surfaces 31 and 32. In the present embodiment, the facing distance H <b> 1 between the opposing wall surfaces 31 and 32 is constant regardless of the position in the radial direction R of the rotating shaft 21 in the diffuser flow path 30.

  The first opposing wall surface 31 of the front part 12 is disposed in the front end side (that is, the front side) of the impeller 22 relative to the second opposing wall surface 32 of the rear part 13 and the base end portion 22a of the impeller 22 in the axial direction Z. The first opposing wall surface 31 is continuous in a state orthogonal to the inner wall surface 26 (specifically, the second cylindrical surface 26 b) of the front through hole 12 a that defines the impeller chamber 27, and extends in the radial direction R of the rotating shaft 21. ing. In the situation where the impeller 22 is disposed at the first position, the rear end 22fb of the side wall 22f is disposed so as not to protrude rearward from the first opposing wall surface 31 (that is, the second opposing wall surface 32 side). Yes.

  The second opposing wall surface 32 of the rear part 13 protrudes toward the first opposing wall surface 31 in the axial direction Z from the proximal opposing surface 13b, and there is a step between the second opposing wall surface 32 and the proximal opposing surface 13b. A surface 33 is formed. The step surface 33 is disposed outside the second cylindrical surface 26b in the radial direction R of the rotary shaft 21.

  The base end portion 22 a of the impeller 22 includes a counter base end portion 34 that opposes the first counter wall surface 31 in the axial direction Z. The opposed base end portion 34 protrudes outward in the radial direction R of the rotating shaft 21 from the rear end portion 22fb and the blade 22e of the side wall 22f. In the situation where the impeller 22 is disposed at the first position, the opposed base end portion 34 is opposed to the step surface 33 in the radial direction R of the rotation shaft 21, and the opposed base end portion 34, the step surface 33, A gap 35 is formed between them.

  Incidentally, the inflow port 36 communicating with the impeller chamber 27 in the diffuser flow path 30 is the position of the inner end in the radial direction R of the rotating shaft 21 in the second opposing wall surface 32. The inflow port 36 is formed wider than the gap 35. The inflow port 36 (the diffuser flow path 30) is arranged at a position facing the impeller outlet 29 and the radial direction R of the rotary shaft 21 in a situation where the impeller 22 is arranged at the first position. The inlet 36 can also be said to be the inlet of the diffuser channel 30.

  In a situation where the impeller 22 is disposed at the first position, the base end portion 22a of the impeller 22 is opposed to the step surface 33 and the base end so that the base end portion 22a does not protrude forward from the second opposing wall surface 32. It enters into a recess defined by the surface 13b. Specifically, the opposed base end portion 34 has an opposed surface 34 a that faces the first opposed wall surface 31. The protrusion 25 has a protruding dimension such that the facing surface 34a is flush with the second facing wall surface 32 or behind the second facing wall surface 32 in a situation where the impeller 22 is disposed at the first position. The thickness is set in accordance with the thickness dimension of the opposing base end portion 34 (base end portion 22a).

  Here, as shown in FIG. 3, a gap formed by the opposed base end portion 34 (opposed surface 34 a) and the first opposed wall surface 31 is defined as an outlet gap 37. The width of the exit gap 37, specifically, the facing distance between the facing base end portion 34 (facing surface 34a) and the first facing wall surface 31 is defined as the exit distance Ha. The exit distance Ha when the impeller 22 is disposed at the first position is defined as a first exit distance Ha1. The first outlet distance Ha <b> 1 is equal to or greater than the opposing distance H <b> 1 between the opposing wall surfaces 31 and 32 that define the diffuser flow path 30. In other words, the outlet gap 37 is wider than the inlet 36 when the impeller 22 is disposed at the first position. For this reason, when the impeller 22 is disposed at the first position, the fluid discharged from the impeller outlet 29 flows into the diffuser flow path 30 without being blocked by the outlet gap 37. The exit gap 37 corresponds to “a gap formed by the opposed base end portion and the first opposed wall surface”.

  Since the protrusion 25 and the gap 35 are provided as described above, a back surface region 38 through which fluid can flow in via the gap 35 is formed on the rear side of the impeller 22. In other words, the impeller chamber 27 has a back region 38 that is disposed on the opposite side of the impeller 22 from the suction port 11 a and communicates with the discharge side of the impeller 22. The back surface region 38 is a region where the surface 22aa on the side opposite to the tip side of the impeller 22 at the base end portion 22a of the impeller 22 is exposed.

  The housing 11 has a discharge chamber 41 into which the fluid compressed by the impeller 22 is discharged. The discharge chamber 41 is disposed outside the diffuser flow path 30 in the radial direction R of the rotation shaft 21. The discharge chamber 41 and the impeller chamber 27 communicate with each other through the diffuser flow path 30. In other words, it can be said that the diffuser flow path 30 allows the impeller chamber 27 and the discharge chamber 41 to communicate with each other. The fluid from the diffuser flow path 30 flows into the discharge chamber 41. The fluid in the discharge chamber 41 is discharged through a discharge port (not shown) provided in the housing 11.

  Here, in the present embodiment, because the diffuser flow path 30 has an annular shape, the cross-sectional area of the diffuser flow path 30 is an impeller on the inner diameter side rather than the discharge chamber 41 side on the outer diameter side. The chamber 27 side is smaller. That is, the diffuser flow path 30 of the present embodiment is a flow path whose flow path cross-sectional area changes according to its position. In this case, the minimum flow path cross-sectional area of the diffuser flow path 30 is the cross-sectional area of the inflow port 36.

  As shown in FIG. 1, the centrifugal compressor 10 includes an electric motor 42 that rotates the rotary shaft 21 and a control unit 43 that controls the electric motor 42 and the like. The control unit 43 controls the rotation of the rotary shaft 21 by controlling the electric motor 42 based on a command from the vehicle controller 100 mounted on the vehicle. Thereby, the rotation of the impeller 22 can be controlled, and the flow rate of fluid discharged from the centrifugal compressor 10 (specifically, the discharge chamber 41 in detail) (hereinafter simply referred to as discharge flow rate) can be controlled.

Although illustration is omitted, the housing 11 has a motor housing in which the electric motor 42 is accommodated. The motor housing and the housing 11 are unitized.
Further, the rotary shaft 21 and the electric motor 42 may be configured such that the rotational force of the electric motor 42 is directly transmitted to the rotary shaft 21, or the speed increasing device provided with the centrifugal force in the centrifugal compressor 10. The structure transmitted to the rotating shaft 21 may be sufficient.

  Here, the maximum discharge flow rate that is the maximum value of the flow rate that can be discharged by the centrifugal compressor 10 is determined by the shape of the impeller 22 and the minimum flow path cross-sectional area of the diffuser flow path 30. For example, the maximum discharge flow rate is a flow rate that is a threshold value for occurrence of a choke phenomenon in which the speed at the impeller 22 (specifically, the throat portion of the blade 22e) reaches the speed of sound.

  For this reason, the shape of the impeller 22 and the minimum flow path cross-sectional area of the diffuser flow path 30 are set corresponding to the required maximum discharge flow rate. Specifically, the length in the axial direction Z of the impeller 22 and the opposing distance H1 between the opposing wall surfaces 31 and 32 of the diffuser flow path 30 can discharge a fluid having a required maximum discharge flow rate. The length is set to correspond to the maximum discharge flow rate. Accordingly, the centrifugal compressor 10 can discharge a fluid having a required maximum discharge flow rate, and can be normally operated with relatively high efficiency when the discharge flow rate is a large flow rate close to the maximum discharge flow rate, for example.

  On the other hand, in the configuration in which the shape of the impeller 22 and the minimum flow path cross-sectional area of the diffuser flow path 30 are set corresponding to the required maximum discharge flow rate, when the discharge flow rate is small, the flow is self-excited. There may be inconveniences such as occurrence of a certain surge phenomenon that hinders operation or decreases efficiency.

  On the other hand, the centrifugal compressor 10 of the present embodiment has a configuration that can suitably cope with a small flow rate. The configuration will be described in detail below. For convenience of explanation, in the following explanation, the diffuser flow path 30 is referred to as a first diffuser flow path 30, and the inlet 36 of the first diffuser flow path 30 is referred to as a first inlet 36.

  As shown in FIGS. 2 to 4, the housing 11 of the centrifugal compressor 10 includes a second diffuser channel 50 that communicates the impeller chamber 27 and the discharge chamber 41 separately from the first diffuser channel 30. . The second diffuser flow channel 50 is, for example, annular (specifically, annular) when viewed from the axial direction Z. The second diffuser flow path 50 is a flow path surrounded by a third facing wall surface 51 and a fourth facing wall surface 52 that are disposed to face each other in the axial direction Z.

  In addition, the 2nd diffuser flow path 50 is not the perfect cyclic | annular form formed over the perimeter, but the shape where a part of circumferential direction was notched. For this reason, the part having the third opposing wall surface 51 in the front main body portion 12b and the part having the fourth opposing wall surface 52 in the front main body portion 12b are the front main body portion 12b corresponding to the notch portion of the second diffuser flow path 50. It is connected (integrated) by a part of.

  Both diffuser flow paths 30 and 50 are flow paths provided between the impeller chamber 27 and the discharge chamber 41 disposed outside the impeller chamber 27 in the radial direction R of the rotation shaft 21. The shaft 21 extends in the radial direction R. The second diffuser flow path 50 is disposed in front of the first diffuser flow path 30 in the axial direction Z, and both the diffuser flow paths 30 and 50 are disposed to face each other in the axial direction Z. In the present embodiment, the second diffuser flow path 50 is curved forward as it goes from the impeller chamber 27 side to the discharge chamber 41 side. As shown in FIGS. 3 and 4, the channel length L <b> 2 of the second diffuser channel 50 is shorter than the channel length L <b> 1 of the first diffuser channel 30.

  The second inflow port 53 communicating with the impeller chamber 27 in the second diffuser flow path 50 is disposed in front of the first inflow port 36 (the front end side of the impeller 22) in the axial direction Z. Specifically, the second inflow port 53 is provided on the second cylindrical surface 26 b of the inner wall surface 26 of the front through hole 12 a that partitions the impeller chamber 27. The second inflow port 53 is disposed on the front side of the rear end 22fb of the side wall 22f in a situation where the impeller 22 is disposed at the first position. In this case, the second inlet 53 and the impeller outlet 29 are not opposed to each other.

  Incidentally, the discharge chamber 41 is disposed outside the impeller chamber 27 in the radial direction R of the rotating shaft 21, and attention is paid to the fact that the diffuser flow paths 30 and 50 that connect the impeller chamber 27 and the discharge chamber 41 are annular. In this case, the inlets 36 and 53 communicating with the impeller chamber 27 can be said to be the inner peripheral ends of the diffuser flow paths 30 and 50. The second inflow port 53 is disposed at a position closer to the axis of the rotation shaft 21 than the first inflow port 36.

  As shown in FIGS. 3 and 4, the second diffuser channel 50 is opposed to both opposing wall surfaces 51, 52 that define the second diffuser channel 50 from the second inlet 53 toward the discharge chamber 41. The aperture region 54 has a gradually shortened distance H2, and the constant width region 55 that is continuous with the aperture region 54 and has a constant opposing distance H2 between the opposing wall surfaces 51 and 52. The opposing distance H2 between the opposing wall surfaces 51 and 52 in the constant width region 55 is the minimum distance of the opposing distance H2, and is shorter than the opposing distance H1 between the opposing wall surfaces 31 and 32 that define the first diffuser flow path 30. The constricted region 54 can also be said to be a widened region in which the opposing distance H2 between the opposing wall surfaces 51 and 52 gradually increases from the discharge chamber 41 side toward the second inlet 53.

  Here, since the second diffuser flow path 50 has an annular shape when viewed from the axial direction Z, the second diffuser flow path 50 is separated from the axis of the rotary shaft 21 according to the position in the radial direction R of the rotary shaft 21. The distance varies. Further, in the throttle region 54 of the second diffuser flow path 50, the facing distance H <b> 2 between the facing wall surfaces 51 and 52 varies according to the position in the radial direction R of the rotating shaft 21. For this reason, the channel cross-sectional area of the second diffuser channel 50 changes depending on the position. In such a configuration, the minimum channel cross-sectional area of the second diffuser channel 50 is set smaller than the minimum channel cross-sectional area of the first diffuser channel 30.

  Note that the position of the minimum flow path cross-sectional area in the second diffuser flow path 50 is determined based on the above two parameters that vary depending on the position. That is, the position of the minimum flow path cross-sectional area in the second diffuser flow path 50 is the distance from the axis of the rotating shaft 21 (the distance in the radial direction R of the rotating shaft 21) and the facing distance H2 of both facing wall surfaces 51 and 52. It depends on.

  Here, the minimum flow path cross-sectional area of the second diffuser flow path 50 is set in correspondence with the minimum discharge flow rate that is the minimum value of the required discharge flow rate. Specifically, the minimum channel cross-sectional area is set so that no surge phenomenon occurs when the discharge flow rate is the minimum discharge flow rate required.

  Here, as already described, since a space is provided between the side wall 22f and the curved surface 26c of the inner wall surface 26, the impeller 22 is movable forward from the first position. Specifically, the impeller 22 can move to a position where the spring 24 has a minimum length. The position of the impeller 22 where the spring 24 has the minimum length is defined as the second position. That is, the spring 24 and the fixing bolt 23 function as a second positioning portion that positions the impeller 22 at the second position.

  As shown in FIG. 4, in the situation where the impeller 22 is disposed at the second position, the inner wall surface 26 and the side wall 22f of the front through hole 12a are separated from each other. Further, the movable distance of the impeller 22 is a distance obtained by subtracting the minimum length from the initial length of the spring 24.

In such a configuration, as shown in FIG. 4, the second inflow port 53 is provided at a position facing the impeller outlet 29 in a situation where the impeller 22 is disposed at the second position.
As shown in FIG. 4, the base end portion 22 a of the impeller 22 is directed toward the first opposing wall surface 31 rather than the second opposing wall surface 32 when the impeller 22 is disposed at the second position. It protrudes (in other words, forward). And in the axial direction Z, the base end part 22a of the impeller 22 is closer to the first opposing wall surface 31 when the impeller 22 is disposed at the second position than when it is disposed at the first position. ing.

  Specifically, as shown in FIGS. 3 and 4, the second outlet distance Ha2, which is the outlet distance Ha when the impeller 22 is disposed at the second position, is shorter than the first outlet distance Ha1. . The second outlet distance Ha2 is shorter than the facing distance H1 between the first facing wall surface 31 and the second facing wall surface 32, and the facing between the third facing wall surface 51 and the fourth facing wall surface 52 at the second inflow port 53. It is set shorter than the distance H2. That is, the outlet gap 37 is narrower than both the first inlet port 36 and the second inlet port 53 when the impeller 22 is disposed at the second position.

  As shown in FIG. 2, the housing 11 includes a bypass passage 60 that allows the back surface region 38 and the suction side of the impeller 22 to communicate with each other. The bypass channel 60 communicates the back region 38 and the space upstream of the impeller inlet 28 in the front through hole 12a.

  The bypass flow path 60 includes a first bypass hole 61 provided in the rear part 13 and a second bypass hole 62 provided in the front part 12. The first bypass hole 61 opens at the base end facing surface 13b. The second bypass hole 62 opens at a portion upstream (front side) of the inner wall surface 26 of the front through hole 12a from the impeller inlet 28. The first bypass hole 61 and the second bypass hole 62 communicate with each other.

  An electromagnetic valve 63 as a control valve is provided on the bypass flow path 60. The electromagnetic valve 63 is in an open state in which the back region 38 and the space upstream of the impeller inlet 28 in the front through hole 12a communicate with each other via the bypass flow path 60, or in the back region 38 and the front through hole 12a. It switches to the shut-off state in which the space upstream of the impeller inlet 28 is shut off.

  The impeller 22 moves according to the state of the electromagnetic valve 63. More specifically, a plurality of types of forces are applied to the rotating impeller 22 in the axial direction Z. Specifically, the impeller 22 is given a first pressing force from the front to the rear by the rotation of the impeller 22. The first pressing force is a pressing force generated by the pressure of the fluid flowing from the impeller inlet 28 toward the impeller outlet 29. Further, the impeller 22 is given a second pressing force directed forward by the pressure in the back surface region 38.

  In such a configuration, when the electromagnetic valve 63 is in an open state, the pressure in the back region 38 becomes the pressure on the suction side of the impeller 22. In this case, the first pressing force is larger than the second pressing force. Accordingly, the impeller 22 moves rearward and is positioned at the first position where it comes into contact with the protrusion 25. That is, the protrusion 25 functions as a first positioning portion that positions the impeller 22 at the first position when the electromagnetic valve 63 is in the open state.

  On the other hand, when the electromagnetic valve 63 is closed, a part of the high-pressure fluid in the discharge chamber 41 flows into the back surface region 38 via the first diffuser flow path 30 and the gap 35. For this reason, the pressure in the back region 38 becomes the pressure on the discharge side of the impeller 22, specifically the pressure in the discharge chamber 41. For this reason, the second pressing force is larger than the first pressing force. Accordingly, the impeller 22 moves forward and is positioned at the second position where the spring 24 has the minimum length. That is, the fixing bolt 23 and the spring 24 function as a second positioning portion that positions the impeller 22 at the second position when the electromagnetic valve 63 is in the closed state.

  For convenience of explanation, only the first pressing force and the second pressing force have been described as the force applied to the impeller 22, but actually, the urging force of the spring 24 or the impeller 22 rotates on the impeller 22. Other forces such as a thrust force generated by this are applied. Regardless of these other forces, the difference between the first pressing force and the second pressing force is that the impeller 22 is disposed in the first position when the solenoid valve 63 is in the open state, and the solenoid valve 63 is in the closed state. In this case, the impeller 22 is arranged at the second position.

  Also, to be sure, the spring constant of the spring 24 is such that when the solenoid valve 63 is in a closed state, the impeller 22 does not depend on the pressure on the discharge side of the impeller 22 (the rotation speed of the impeller 22). It is set to be arranged at the second position.

  The controller 43 controls the position of the impeller 22 by controlling the pressure in the back region 38 by controlling the opening and closing of the electromagnetic valve 63. Specifically, the control unit 43 sets the impeller 22 at the first position at a large flow rate, which is a case where the required discharge flow rate is relatively large, and a small size, which is a case where the required discharge flow rate is relatively small. At the time of flow, opening / closing control of the electromagnetic valve 63 is performed so that the impeller 22 is disposed at the second position.

  For example, the control unit 43 is configured to be able to grasp the driving situation of the vehicle by acquiring information related to the driving situation of the vehicle from the vehicle controller 100. And the control part 43 performs position control of the impeller 22 based on the driving | running state of a vehicle. Specifically, it is generally assumed that the required discharge flow rate is large at high loads such as when the vehicle is accelerating or driving on an uphill road. For this reason, the control part 43 makes the electromagnetic valve 63 an open state so that the impeller 22 is arrange | positioned in a 1st position, when the driving | running state of a vehicle is at the time of the above high loads.

  On the other hand, the required discharge flow rate may be small at low loads such as when the vehicle is in idle operation or when the vehicle operation mode is a fuel consumption mode that can improve fuel consumption more than the normal mode. is assumed. For this reason, the control part 43 makes the electromagnetic valve 63 a closed state so that the impeller 22 is arrange | positioned in a 2nd position, when the driving | running state of a vehicle is the above time of low load.

Next, the operation of this embodiment will be described.
When the flow rate is large, the impeller 22 is arranged at the first position as shown in FIG. In this case, the fluid compressed by the rotation of the impeller 22 passes through the outlet gap 37 and preferentially flows through the first diffuser flow path 30.

  Actually, when the impeller 22 is disposed at the first position, the high-pressure fluid in the discharge chamber 41 flows into the impeller chamber 27 via the second diffuser flow path 50, but the flow rate is very small. The effect is small.

  On the other hand, when the flow rate is small, the impeller 22 is arranged at the second position as shown in FIG. In this case, the second inlet 53 and the impeller outlet 29 face each other, and the outlet gap 37 is narrower than both the first inlet 36 and the second inlet 53 (see FIG. 4). The fluid compressed by the rotation preferentially flows through the second diffuser flow path 50. That is, the impeller 22 preferentially flows to the first diffuser flow path 30 rather than the second diffuser flow path 50 and the second diffuser flow path 50 preferentially to the first diffuser flow path 30. It is movable between the second position where the fluid flows.

According to the embodiment described above in detail, the following effects are obtained.
(1) The centrifugal compressor 10 includes a housing 11 in which a suction port 11a through which fluid is sucked is formed, and an impeller 22 that compresses the fluid sucked from the suction port 11a by rotating. The housing 11 has an impeller chamber 27 in which the impeller 22 is accommodated, and a discharge chamber 41 into which fluid compressed by the impeller 22 flows.

  In this configuration, the housing 11 communicates the impeller chamber 27 and the discharge chamber 41, and the first diffuser channel 30 and the second diffuser channel having a smaller channel cross-sectional area than the first diffuser channel 30. 50. The impeller 22 preferentially flows to the first diffuser flow path 30 rather than the second diffuser flow path 50 and the second diffuser flow path 50 preferentially to the first diffuser flow path 30. It can move between the second position where the fluid flows.

  According to this configuration, the diffuser flow channel that flows preferentially is switched according to the position of the impeller 22. Thereby, for example, when the flow rate is large, the impeller 22 is arranged at the first position, so that the fluid can be preferentially flowed into the first diffuser flow path 30 having a larger flow path cross-sectional area than the second diffuser flow path 50. Therefore, it can cope with a large flow rate suitably. On the other hand, for example, when the impeller 22 is disposed at the second position at a small flow rate, the fluid can be preferentially flowed into the second diffuser flow path 50 having a smaller flow path cross-sectional area than the first diffuser flow path 30. Therefore, the occurrence of a surge phenomenon can be suppressed and it is possible to cope with a small flow rate. Therefore, it is possible to suitably cope with both a large flow rate and a small flow rate, and an operable range can be expanded.

  In particular, in this embodiment, two diffuser channels 30 and 50 having different channel cross-sectional areas are formed in the housing 11 in advance. Thereby, by switching the diffuser flow path used at the time of the small flow rate and at the time of the large flow rate, it is possible to improve the efficiency both at the time of the small flow rate and at the time of the large flow rate.

  Furthermore, since the two diffuser channels 30 and 50 having different channel cross-sectional areas are formed in advance, the channel cross-sectional area does not vary. Thereby, compared with the structure which provides the proportional control valve etc. which change a flow-path cross-sectional area linearly on a diffuser flow path, the stable flow-path cross-sectional area can be ensured by simple control, for example.

  (2) The impeller 22 has a shape that is reduced in diameter from the base end portion 22a toward the tip end portion 22b, the tip end portion 22b is disposed on the front side of the base end portion 22a, and is movable in the axial direction Z. It is attached to the rotating shaft 21 in a state. The first diffuser flow path 30 is a flow path surrounded by a first facing wall surface 31 and a second facing wall surface 32 that are arranged to face each other in the axial direction Z. The first facing wall surface 31 includes the second facing wall surface 32 and the second facing wall surface 32. The impeller 22 is disposed in front of the base end portion 22a. The second inflow port 53 communicating with the impeller chamber 27 in the second diffuser flow path 50 is disposed in front of the first inflow port 36 communicating with the impeller chamber 27 in the first diffuser flow path 30 in the axial direction Z. Has been. In such a configuration, the base end portion 22a of the impeller 22 is closer to the first facing wall surface 31 when the impeller 22 is disposed at the second position than when the impeller 22 is disposed at the first position. Yes.

  According to such a configuration, the fluid sucked from the suction port 11 a is compressed as it flows from the tip end portion 22 b of the impeller 22 toward the base end portion 22 a and flows into the first inflow port 36 or the second inflow port 53. In this case, when the impeller 22 is disposed at the second position, the base end portion 22a of the impeller 22 is approaching the first opposing wall surface 31, so that the fluid compressed by the impeller 22 enters the first diffuser flow path 30. It becomes difficult to flow in. Thereby, the fluid compressed by the impeller 22 preferentially flows into the second diffuser flow path 50 having the second inlet 53 provided on the front side of the first inlet 36. Therefore, when the impeller 22 is disposed at the second position, the fluid can be preferentially flowed to the second diffuser flow path 50 rather than the first diffuser flow path 30.

  On the other hand, when the impeller 22 is disposed at the first position, the base end portion 22a of the impeller 22 is separated from the first opposing wall surface 31 in the axial direction Z, so that the fluid compressed by the impeller 22 is the first. It is easy to flow into the diffuser flow path 30. Thereby, when the impeller 22 is arrange | positioned in the 1st position, a fluid can be flowed preferentially to the 1st diffuser flow path 30 rather than the 2nd diffuser flow path 50. FIG.

  In the configuration in which the second inflow port 53 is disposed in front of the first inflow port 36, the fluid can flow into the second inflow port 53 when the impeller 22 is in the first position. However, since the second diffuser flow path 50 has a smaller flow path cross-sectional area than the first diffuser flow path 30, it is assumed that the fluid flows into the second inlet 53 in a situation where the impeller 22 is disposed at the first position. Even if it flows through the first diffuser flow path 30, the fluid flows more preferentially than the second diffuser flow path 50.

  (3) The base end portion 22 a of the impeller 22 has an opposing base end portion 34 that faces the first opposing wall surface 31 in the axial direction Z. As a result, when viewed from the axial direction Z, the base end portion 22a of the impeller 22 and the first opposing wall surface 31 partially overlap, so that the fluid compressed by the impeller 22 It will flow through the exit gap 37 which is a gap between the opposing wall surface 31. And since the base end part 22a of the impeller 22 including the opposing base end part 34 protrudes to the 1st opposing wall surface 31 side rather than the 2nd opposing wall surface 32, when the impeller 22 is arrange | positioned in the 2nd position, The exit gap 37 is narrower than the first inflow port 36. Thereby, the flow of the fluid to the first diffuser flow path 30 is restricted by the outlet gap 37. Therefore, it is possible to suppress the fluid from flowing into the first diffuser flow path 30 in a situation where the impeller 22 is disposed at the second position. In addition, even when the impeller 22 is disposed at the second position, the exit gap 37 is formed, so that sliding between the opposed base end portion 34 and the first opposed wall surface 31 can be suppressed.

  (4) The outlet gap 37 when the impeller 22 is disposed at the second position is narrower than the second inlet 53. According to such a configuration, the outlet gap 37 when the impeller 22 is arranged at the second position is narrower than the second inlet 53, so that the fluid compressed by the impeller 22 is more than the outlet gap 37. Is easy to flow into the second inlet 53. Therefore, it is possible to further suppress the fluid from flowing into the first diffuser flow path 30 via the outlet gap 37.

  (5) The impeller chamber 27 is a region where the surface 22aa of the base end portion 22a of the impeller 22 opposite to the tip end portion 22b of the impeller 22 is exposed, and a back region 38 communicating with the discharge side of the impeller 22 is provided. Including. The housing 11 includes a bypass passage 60 that communicates the back region 38 and the suction side of the impeller 22, and the bypass passage 60 is provided with an electromagnetic valve 63 as a control valve. The centrifugal compressor 10 includes a control unit 43 that controls the position of the impeller 22 by controlling the pressure in the back region 38 by controlling the opening and closing of the electromagnetic valve 63. Specifically, the control unit 43 sets the pressure of the back surface region 38 to the pressure on the suction side of the impeller 22 by opening the electromagnetic valve 63, while setting the electromagnetic valve 63 to the closed state. The pressure of 38 is set to the pressure on the discharge side of the impeller 22. The centrifugal compressor 10 is configured such that when the electromagnetic valve 63 is in an open state, the impeller 22 is positioned in the first position. The projection 25 serving as a first positioning portion and the electromagnetic valve 63 are in a closed state. A spring 24 and a fixing bolt 23 are provided as a second positioning portion for positioning 22 at the second position. Thereby, the impeller 22 can be disposed at the first position or the second position by the pressure control of the back surface region 38 by the opening / closing control of the electromagnetic valve 63. Therefore, the position control of the impeller 22 can be performed without providing a dedicated actuator or the like for moving the impeller 22.

  In particular, the magnitude relationship between the first pressing force and the second pressing force is switched according to the state of the electromagnetic valve 63, but is hardly affected by the discharge flow rate. Thereby, it is possible to suppress malfunction caused by the fluctuation of the discharge flow rate.

  (6) Here, when the impeller 22 rotates, a thrust force from the rear toward the front is generated. In this regard, in the present embodiment, when the electromagnetic valve 63 is in the open state, the first pressing force in the direction opposite to the thrust force is dominant, so the first pressing force and the thrust force cancel each other. Thereby, the influence of thrust force can be reduced.

  On the other hand, when the solenoid valve 63 is in the closed state, the second pressing force in the same direction as the thrust force is dominant, and there is a concern that an excessive pressing force directed forward is applied to the impeller 22. Is done. However, the thrust force depends on the rotational speed of the impeller 22. For this reason, the thrust force tends to be small when the rotational speed of the impeller 22 is low and the flow rate is low. Therefore, the above inconvenience hardly occurs.

  (7) The spring 24 as the second positioning portion rotates the impeller 22 and the rotating shaft 21 integrally by applying a biasing force to the impeller 22. Thereby, the multifunction of the spring 24 can be achieved. Therefore, the configuration can be simplified as compared with the configuration in which the impeller 22 and the rotation shaft 21 are integrally rotated and the configuration in which the second positioning portion is provided separately.

  (8) Both of the diffuser channels 30 and 50 are channels whose channel cross-sectional areas change according to their positions. Specifically, the diffuser flow paths 30 and 50 are annularly disposed between the impeller chamber 27 and the discharge chamber 41 disposed outside the impeller chamber 27 in the radial direction R of the rotating shaft 21. It is a flow path. In such a configuration, the minimum channel cross-sectional area of the second diffuser channel 50 is set smaller than the minimum channel cross-sectional area of the first diffuser channel 30. Thereby, the effect (1) can be obtained. That is, the performance of the diffuser channel whose channel cross-sectional area changes according to the position is limited by the minimum channel cross-sectional area.

  (9) The channel length L2 of the second diffuser channel 50 is shorter than the channel length L1 of the first diffuser channel 30. Thereby, the efficiency at the time of a small flow volume can be aimed at. More specifically, since the occurrence of the surge phenomenon can be suppressed by shortening the channel length L2 of the second diffuser channel 50, the minimum channel cross-sectional area of the second diffuser channel 50 can be increased accordingly. it can. Therefore, the efficiency at the time of a small flow rate can be improved.

  In particular, when various designs such as the shape of the impeller 22 are made corresponding to a large flow rate, the efficiency at a small flow rate tends to be low. On the other hand, as described above, by making the flow length L2 of the second diffuser flow path 50 used at the time of the small flow rate shorter than the flow length L1 of the first diffuser flow path 30 used at the time of the high flow rate, It is possible to suitably cope with a small flow rate at which efficiency tends to be low.

  Further, the discharge chamber 41 has a shape projecting from the rotating shaft 21 as it goes from the base end portion 22a of the impeller 22 to the tip end portion 22b. For this reason, the second inflow port 53 of the second diffuser flow path 50 is provided on the inner wall surface 26 (in other words, in the middle of the impeller chamber 27 in the axial direction Z), so that the flow of the second diffuser flow path 50 is increased. It is easy to shorten the road length L2. Therefore, the efficiency at the time of a small flow rate can be improved more suitably.

  (10) The impeller 22 includes a main body portion 22d constituting the base end portion 22a and the front end portion 22b, a side wall 22f disposed outside the main body portion 22d in the radial direction R of the rotation shaft 21, and the main body portion 22d and the side wall 22f. Is a closed impeller provided with a plurality of blades 22e. An impeller outlet 29 is formed by the rear end 22fb and the base end 22a of the side wall 22f. When the impeller 22 is disposed at the first position, the impeller outlet 29 faces the first diffuser flow path 30 (first inflow port 36), while the impeller 22 is disposed at the second position. In this case, it faces the second diffuser channel 50 (second inlet 53). Thereby, the fluid discharged from the impeller outlet 29 can be guided to a desired diffuser flow path.

  (11) Particularly, the second inflow port 53 is provided at a position (specifically, the second cylindrical surface 26b) facing the impeller outlet 29 in a situation where the impeller 22 is disposed at the second position. Thereby, the fluid discharged from the impeller outlet 29 flows through the second diffuser flow path 50. The fluid discharged from the impeller outlet 29 has a higher pressure than the fluid at an intermediate position between the impeller inlet 28 and the impeller outlet 29. Therefore, it is possible to further suppress the surge phenomenon at a low flow rate.

In addition, you may change the said embodiment as follows.
The urging unit is not limited to the spring 24 and is arbitrary. Further, the spring 24 may be omitted. In this case, it is preferable to provide a convex portion on one of the surface of the rotating shaft 21 and the inner surface of the insertion hole 22c of the impeller 22 and provide a concave portion that fits the convex portion on the other. Thereby, even if the urging | biasing force is not provided, the rotating shaft 21 and the impeller 22 rotate integrally. Further, the fixing portion is not limited to the fixing bolt 23 and is arbitrary.

  O The opposing base end 34 may be omitted. Even in this case, when the impeller 22 is arranged at the second position, the base end portion 22a of the impeller 22 approaches the first opposing wall surface 31 in the axial direction Z, so that the fluid from the impeller outlet 29 is It is difficult to flow into the one diffuser flow path 30.

  O The configuration for moving the impeller 22 is arbitrary. For example, a dedicated drive device that moves the impeller 22 may be provided. The drive device may be an actuator that moves mechanically, or may use a magnetic force or the like.

The specific configuration of the first positioning unit and the second positioning unit is not limited to that of the embodiment and is arbitrary.
(Circle) the 2nd inflow port 53 may be wider than the 1st inflow port 36, and may be narrow. Moreover, both may be the same area.

  The specific configuration of the impeller 22 is arbitrary, and may be, for example, an open impeller without the side wall 22f. In this case, when the impeller 22 rotates, the side surface of the impeller 22 that virtually extends in the circumferential direction is formed by the tip surface of the blade 22e on the outer side in the radial direction R of the rotating shaft 21. That is, the outer end surface of the blade 22e in the radial direction R of the rotating shaft 21 constitutes the side surface of the impeller 22. Further, the centrifugal compressor 10 may have a configuration having two impellers arranged to face each other.

  The position of the 2nd inflow port 53 is not restricted to the 2nd cylindrical surface 26b, The curved surface 26c and the 1st cylindrical surface 26a may be sufficient. In short, the second inlet 53 may be provided at a position on the inner wall surface 26 of the front through-hole 12a that faces the side of the intermediate portion between the distal end portion 22b and the proximal end portion 22a of the impeller 22. In this case, a slit may be formed at a position facing the second inlet 53 when the impeller 22 is disposed at the second position on the side wall 22f. Thereby, the efficiency of the impeller 22 at the time of a low flow rate can be improved. However, from the viewpoint of suppressing the occurrence of a surge phenomenon when a high-pressure fluid flows through the second diffuser channel 50 at a low flow rate, the second inlet 53 is provided in the second cylindrical surface 26b. It is good to have.

The flow path length L2 of the second diffuser flow path 50 may be the same as or longer than the flow path length L1 of the first diffuser flow path 30.
○ At least one of the both diffuser channels may be a channel having a constant channel cross-sectional area regardless of the position. For example, the first diffuser channel may be a channel having a constant channel cross-sectional area regardless of the position, and the second diffuser channel may be a channel whose channel cross-sectional area changes depending on the position. . In this case, the minimum channel cross-sectional area of the second diffuser channel may be smaller than the channel cross-sectional area of the first diffuser channel.

  Note that the first diffuser channel having a constant channel cross-sectional area regardless of the position is, for example, opposite of both opposing wall surfaces toward the outer side in the radial direction R of the rotating shaft 21 so that the channel cross-sectional area is constant. A flow path or the like formed so that the distance is gradually shortened can be considered. However, from the viewpoint of the degree of freedom in design of both diffuser channels, both diffuser channels may be channels whose channel cross-sectional area changes depending on the position.

  The shape of both diffuser flow paths 30 and 50 is not limited to an annular shape and is arbitrary. For example, the second diffuser flow path may be configured by a through-hole having a certain diameter extending radially from the impeller chamber 27. A plurality of the through holes may be provided in the circumferential direction. In this case, the cross-sectional area of the through hole is preferably smaller than the minimum flow path cross-sectional area of the first diffuser flow path 30. In addition, in a configuration in which a plurality of the through holes constituting the second diffuser flow path are provided, the sum of the cross-sectional areas of all the through holes may be smaller than the minimum flow path cross-sectional area of the first diffuser flow path 30.

  Further, the through hole may have a constricted region that gradually tapers from the inlet communicating with the impeller chamber 27 toward the discharge chamber 41. In this case, the aperture region may have a configuration in which the distance in the axial direction Z gradually decreases, or may have a configuration in which the distance in the direction orthogonal to the axial direction Z gradually decreases.

  ○ The positions of both diffuser channels are arbitrary. For example, the second diffuser channel with a relatively small channel cross-sectional area is arranged on the rear side, and the first diffuser channel with a relatively large channel cross-sectional area is on the front side May be arranged.

  The parameter for controlling the position of the impeller 22 is not limited to the driving situation of the vehicle and is arbitrary. For example, the centrifugal compressor 10 includes a flow rate sensor that detects the discharge flow rate, and the control unit 43 determines that the impeller 22 is in the first position when the detected flow rate detected by the flow rate sensor is equal to or higher than a predetermined threshold flow rate. On the other hand, when the detected flow rate is less than the threshold flow rate, the electromagnetic valve 63 may be controlled so that the impeller 22 is disposed at the second position.

  Further, for example, when the rotational speed of the impeller 22 is equal to or higher than a predetermined threshold rotational speed, the control unit 43 arranges the impeller 22 at the first position, while the rotational speed of the impeller 22 is less than the threshold flow rate. In some cases, the electromagnetic valve 63 may be controlled so that the impeller 22 is disposed at the second position. In this case, the rotational speed of the impeller 22 may be an actual rotational speed or a target rotational speed. For example, the target rotational speed may be determined by the vehicle controller 100 and notified from the vehicle controller 100 to the control unit 43.

  ○ The application target of the centrifugal compressor 10 and the fluid to be compressed are arbitrary. For example, the centrifugal compressor 10 may be used in an air conditioner, and the fluid to be compressed may be a refrigerant. Moreover, the mounting object of the centrifugal compressor 10 is not limited to the vehicle and is arbitrary.

Next, a preferable example that can be grasped from the embodiment and another example will be described below.
(A) The impeller includes both a main body part constituting the base end part and the front end part, a side wall disposed on the outer side in the radial direction of the rotation shaft from the main body part, and both the main body part and the side wall A closed impeller having a blade connected thereto, and an end of the side wall on the base end side and the base end form an impeller outlet through which fluid compressed by the impeller is discharged. The first inlet is disposed at a position facing the impeller outlet when the impeller is disposed at the first position, and the second inlet is configured such that the impeller is the second The centrifugal compressor according to claim 2, wherein the centrifugal compressor is disposed at a position facing the impeller outlet when disposed at a position.

  (B) The second positioning portion is provided between a fixed portion fixed to the distal end of the rotating shaft and the fixed portion and the impeller, and is proximal to the impeller from the distal end side of the impeller The centrifugal compressor according to claim 5, further comprising: an urging unit that imparts an urging force toward

  DESCRIPTION OF SYMBOLS 10 ... Centrifugal compressor, 11 ... Housing, 11a ... Inlet, 13b ... Base end opposing surface, 21 ... Rotating shaft, 22 ... Impeller, 22a ... Base end part, 22b ... Tip part, 22c ... Insertion hole, 22d ... Main body Part, 22e ... blade, 22f ... side wall, 23 ... fixing bolt (fixing part), 24 ... spring (biasing part), 25 ... protrusion (first positioning part), 26 ... inner wall surface of front through hole, 27 ... impeller Chamber 30... First diffuser channel 31. First counter wall surface 32. Second counter wall surface 34. Opposite base end 36. First inlet (inlet) 37. Outlet gap (gap) 38 ... Back region, 41 ... Discharge chamber, 43 ... Control unit, 50 ... Second diffuser flow path, 53 ... Second inlet, 60 ... Bypass flow path, 63 ... Solenoid valve (control valve), L1 ... First diffuser The channel length of the channel, L2... The channel length of the second diffuser channel.

Claims (7)

A housing formed with an inlet through which fluid is sucked;
An impeller that rotates integrally with a rotating shaft, and compresses the fluid by rotating;
In a centrifugal compressor with
The housing is
An impeller chamber that communicates with the suction port and that houses the impeller;
A discharge chamber into which the fluid compressed by the impeller is discharged;
A first diffuser flow path communicating the impeller chamber and the discharge chamber;
A second diffuser flow path for communicating the impeller chamber and the discharge chamber, the flow path cross-sectional area being smaller than the first diffuser flow path;
Have
The impeller has a first position where fluid flows preferentially in the first diffuser flow path over the second diffuser flow path, and fluid preferentially flows in the second diffuser flow path over the first diffuser flow path. A centrifugal compressor characterized by being movable between a flowing second position. The impeller has a shape that is reduced in diameter from the base end portion toward the tip end portion, and the tip end portion is disposed closer to the suction port than the base end portion, and is movable in the axial direction of the rotation shaft Is attached to the rotating shaft in a state,
The first diffuser flow path is a flow path surrounded by a first facing wall surface and a second facing wall surface that are arranged to face each other in the axial direction,
In the axial direction, the first opposing wall surface is disposed closer to the tip side of the impeller than the second opposing wall surface and the base end portion of the impeller,
The second inflow port that communicates with the impeller chamber in the second diffuser flow path is disposed closer to the tip side of the impeller than the first inflow port that communicates with the impeller chamber in the first diffuser flow path in the axial direction. Has been
The base end portion of the impeller is closer to the first opposing wall surface when the impeller is disposed at the second position than when the impeller is disposed at the first position. Item 2. The centrifugal compressor according to Item 1.   The centrifugal compressor according to claim 2, wherein the base end portion of the impeller has an opposing base end portion facing the first opposing wall surface in the axial direction.   4. The centrifugal compressor according to claim 3, wherein a gap formed by the opposed base end portion and the first opposed wall surface when the impeller is disposed at the second position is narrower than the second inflow port. . The impeller chamber is a region where a surface of the base end portion of the impeller opposite to the tip side of the impeller is exposed and includes a back region communicating with the discharge side of the impeller,
The housing includes a bypass channel that communicates the back region and the suction side of the impeller,
A control valve is provided on the bypass flow path,
The centrifugal compressor is
A first positioning portion for positioning the impeller at the first position when the control valve is in an open state;
A second positioning portion for positioning the impeller at the second position when the control valve is in a closed state;
A control unit for controlling the position of the impeller by controlling the pressure in the back region by opening and closing control of the control valve;
The centrifugal compressor as described in any one of Claims 1-4 provided with these. Both the first diffuser flow path and the second diffuser flow path are flow paths whose flow path cross-sectional areas change according to positions,
The centrifugal compressor according to any one of claims 1 to 5, wherein a minimum channel cross-sectional area of the second diffuser channel is set smaller than a minimum channel cross-sectional area of the first diffuser channel.   The centrifugal compressor according to any one of claims 1 to 6, wherein a channel length of the second diffuser channel is shorter than a channel length of the first diffuser channel.