JP2008111369A - Centrifugal compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a centrifugal compressor capable of uniformly and accurately performing variable control of a passage width in a diffuser passage of the centrifugal compressor. <P>SOLUTION: The centrifugal compressor 10A is for adjusting the diffuser passage width W by varying the position of an annular movable part 20 provided in a vaneless diffuser. The movable part 20 is rotatable around an impeller rotating shaft with respect to a housing 11. A screw mechanism 21 is provided for moving the movable part 20 in the direction of the diffuser passage width W by rotating the movable part 20 in the peripheral direction of the impeller rotating shaft. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a centrifugal compressor such as a turbocharger.

Conventionally, for example, a centrifugal compressor such as a turbocharger used for an internal combustion engine for automobiles is known.
FIG. 12 is a cross-sectional view showing a main part of a conventional centrifugal compressor. The illustrated centrifugal compressor 10 compresses a fluid such as gas or air introduced from the outside of the housing 11 by rotating an impeller 13 having a large number of blades 12 in the housing 11. The fluid flow (air flow) formed in this way is sent to the outside through an impeller outlet (hereinafter also referred to as “diffuser inlet”) 14, a diffuser passage 15 and a scroll (not shown) which is an outer peripheral end of the impeller 13. The In addition, the code | symbol 16 in a figure is an axial centerline with which the impeller 13 rotates.

The above-described diffuser passage 15 is provided between the impeller outlet 14 and the scroll, and is a passage for recovering the dynamic pressure to a static pressure by decelerating the airflow discharged from the impeller outlet 14. The diffuser passage 15 is usually formed by a pair of opposed wall surfaces. In the following description, one of the pair of opposed wall surfaces is called a shroud side wall surface 15a, and the other is called a hub side wall surface 15b.
Incidentally, in a turbocharger for automobiles used in combination with an internal combustion engine, a wide compressor operating range is required, and therefore, a type of diffuser (vaneless diffuser) that does not normally have a vane is employed.

Since the operating range of the turbocharger is determined by the compressor, a compressor having a wide operating range is required. Further, as shown in FIG. 13, the minimum limit of the working flow rate is defined by an unstable phenomenon such as surging, and a flow range is defined between the surge flow rate Qs that defines the minimum flow rate and the choke flow rate Qc that defines the maximum flow rate. Become. For this reason, in order to widen the operating range of the compressor, a means for preventing surging is necessary.
The start of the surging described above is caused by the backflow in the diffuser passage 15 having no vane. In FIG. 12B, the reverse flow region of the shroud wall surface 15a at the time of surging is indicated by a broken line, and the reverse flow region of the shroud wall surface 15a at the start of the stall is indicated by a solid line.

As a conventional technique for preventing the surging of the centrifugal compressor, it has been proposed to provide a throttle portion that optimally adjusts the cross-sectional area of the diffuser in accordance with the discharge flow rate. The throttle portion is constituted by a disk-shaped diffuser side plate that forms one side portion of the diffuser. The diffuser side plate is provided in a recess formed in the diffuser, and can be reciprocated in the flow path cross section. (For example, see Patent Document 1)
Japanese Utility Model Publication No. 6-63897 (see FIG. 1)

By the way, in particular, in-vehicle turbochargers, it is desired to increase the supercharging pressure at the time of engine acceleration, and a compressor having a high pressure ratio is required even at a small flow rate and low rotation. It is known that the surge flow rate Qs can be controlled and the operating range can be greatly improved by making the passage width of the diffuser passage 15 that greatly affects the operating range of the compressor variable. In such a variable diffuser passage mechanism, it is necessary to uniformly and accurately carry out variable control of the passage width.
The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a centrifugal compressor capable of uniformly and accurately performing variable control of the passage width in the diffuser passage of the centrifugal compressor. Is to provide.

In order to solve the above problems, the present invention employs the following means.
A centrifugal compressor according to the present invention is a centrifugal compressor in which a vaneless diffuser is provided with an annular movable portion that constitutes one wall surface of the vaneless diffuser, and the diffuser passage width is adjusted by changing the position of the annular movable portion. A screw mechanism is provided that allows the movable portion to rotate about an impeller rotation shaft with respect to the housing, and moves the movable portion in the direction of the diffuser passage width by rotating the movable portion in the circumferential direction of the impeller rotation shaft. It is characterized by that.

  According to such a centrifugal compressor, the movable portion can be rotated around the impeller rotation shaft with respect to the housing, and the movable portion is moved in the direction of the diffuser passage width by rotating in the circumferential direction of the impeller rotation shaft. Since the screw mechanism is provided, the diffuser passage width is changed by the parallel translation of the movable portion without being inclined by the multiplication of the pitch of the screw and the number of rotations.

  In the above invention, it is preferable to provide a stopper for restricting the movement of the movable part at the maximum position of the diffuser width so that the diffuser passage width does not increase with respect to the impeller outlet width. Can be prevented from spreading.

In the above invention, the screw mechanism is preferably provided on the outer diameter side or the inner diameter side with respect to the pressing force canceling position so that the pressing force of the airflow acting on the movable portion is in the same direction. As a result, a sealing function is always generated at the meshing portion between the movable portion side and the fixed portion side, so that airflow leakage can be prevented or reduced.
In this case, it is preferable that the screw mechanism is provided at a radial position where a part of the pressing force of the airflow acting on the movable part is canceled out. Reduction is possible.

  According to the present invention described above, since the movable portion can be rotated with respect to the housing, and the screw mechanism for moving the movable portion in the direction of the diffuser passage width is provided, the passage width W of the diffuser passage is By multiplying the pitch and the number of rotations, the movable part uniformly translates and changes without tilting. Therefore, the passage width W of the diffuser passage can be uniformly and accurately controlled by the screw mechanism, and a centrifugal compressor having a wide operating range can be easily provided.

Hereinafter, one embodiment of a centrifugal compressor concerning the present invention is described based on a drawing.
In the centrifugal compressor 10 </ b> A shown in FIG. 1, an impeller 13 having a plurality of blades 12 rotates around an axial center line 16 in a housing 11 to compress a fluid such as gas or air introduced from the outside of the housing 11. To form an airflow. This airflow is introduced into the diffuser passage 15A from the impeller outlet (diffuser inlet) 14, is decelerated when passing through the diffuser passage 15A, recovers the static pressure, and then is sent to the outside through a scroll (not shown).

The diffuser passage 15A is a vaneless diffuser, and is formed by arranging a pair of shroud side wall surfaces 15a and a hub side wall surface 15b to face each other. Among these, the annular movable part 20 which forms a part of shroud side wall surface 15a is provided in one wall surface of the vaneless diffuser, for example, the shroud side wall surface 15a. The movable portion 20 can adjust the diffuser passage width W by changing its position.
In addition, although the movable part 20 is provided to the middle of the downstream side from the diffuser inlet 14, if the starting point of the movable part 20 is the diffuser inlet 14, the end point will not be specifically limited.

The movable portion 20 is a substantially ring-shaped plate-like member installed coaxially with the impeller 13, and is screwed into the housing 11 via a screw mechanism 21. As a result, the movable portion 20 can rotate with respect to the housing 11 about the axial center line 16, and the movable portion 20 reciprocally translates in the direction of the diffuser passage width W as indicated by the white arrow 17. .
In the illustrated example, a screw mechanism 21 is provided on the inner peripheral side of the movable portion 20 and is screwed into the housing 11. That is, the screw mechanism 21 is formed in which the concave portion 18 is formed in the shroud side wall surface 15a and the screw portion 21a provided on the inner peripheral surface of the ring of the movable portion 20 is screwed with the screw portion 11a provided in the concave portion 18 on the housing 11 side. Is provided.
Further, by subjecting the lower end corner portion 19 of the movable portion 20 located at the diffuser inlet 14 to R processing, even when the movable portion 20 moves to the diffuser passage 15A side, it is difficult to disturb the airflow.

Next, an example of the drive mechanism 30 that rotates the movable portion 20 will be described with reference to FIG.
The drive mechanism 30 is one in which one or a plurality of pinion gears 31 are rotatably supported at predetermined positions of the housing 11 and meshed with a drive gear portion 22 formed on the outer peripheral side of the movable portion 20. As a result, when the pinion gear 31 is rotated in a desired direction by a drive source such as an electric motor (not shown), the movable portion 20 in which the driving gear portion 22 meshes with the pinion gear 31 is moved in the opposite direction to the pinion gear 31. Rotate. In such a drive mechanism 30, since the rotation speed of the pinion gear 31 and the rotation speed of the movable portion 20 are determined by the gear ratio, the controllability of the diffuser passage width W that changes as the screw mechanism 21 rotates is high.

When the movable portion 20 is thus rotated, the movable portion 20 is translated in the direction of the white arrow 17 by the screw mechanism 21 according to the rotation direction, and the position thereof is changed. As a result, the diffuser passage width W is appropriately adjusted between the maximum Wa (see FIG. 1B) and the minimum Wi (see FIG. 1C).
At this time, a stopper for restricting the movement of the movable portion 20 at the maximum position Wa of the diffuser passage width W is provided so that the diffuser passage width W does not exceed the maximum Wa, and the diffuser passage width W is increased more than necessary. It is preferable to prevent this. That is, a stopper is provided so that the diffuser passage width W does not become larger than the impeller outlet width.

As a specific example of the stopper described above, for example, as shown in FIG. 1C, a stopper surface 11b is provided on the housing 11 side, and a restriction surface 20a on the movable portion 20 side is brought into contact with the stopper surface 11b. There is.
Alternatively, as shown in FIG. 2, by appropriately selecting the tooth width (thickness) of the pinion gear 31 described above, the regulation surface 20a on the movable part 20 side is brought into contact with the pinion gear 31 to limit the movable width. It is good also as a structure. The centrifugal compressors 10 having different operating flow rates also have different adjustment ranges of the diffuser passage 15A, so that the compatibility of the drive mechanism 30 and the like can be provided by changing the tooth width of the pinion gear 31.

  As described above, if the diffuser passage width W is variable by translating the movable portion 20 by the screw mechanism 21, the surge flow rate Qs is reduced by reducing the diffuser passage width W as shown in FIG. be able to. In other words, the surge flow rate Qs when the diffuser passage width W is the maximum Wa is reduced by the largest value ΔQ with the smallest Wi as the diffuser passage width W is reduced. Therefore, by appropriately adjusting the diffuser passage width W, the range of the flow rate Q at which the centrifugal compressor 10A operates is widened by ΔQ to the lower flow rate side than between the conventional Qs / Qc.

Therefore, when the centrifugal compressor 10A described above is applied to a turbocharger, for example, as shown in FIG. 4, the control unit creates and inputs a database regarding the engine operating state and the drive amount of the movable unit 20. The drive amount is determined based on the engine operating state data. Then, when the drive mechanism 30 is operated by outputting the drive amount signal determined here, the movable portion 20 rotates and translates to a desired position.
At this time, since the screw mechanism 21 is adopted, the parallel movement amount of the movable portion 20 is accurately calculated by multiplying the pitch length P of the screw by the rotation speed N (P × N).

By adopting the screw mechanism 21, as shown in FIG. 5 (b), the movable portion 20 is not inclined in the axial direction with the axial center line 16 interposed therebetween. Therefore, as shown in FIG. 5 (a). Thus, the diffuser passage 15 </ b> A having a uniform passage width can be formed by the uniform parallel movement along the axial center line 16. Further, the amount of movement in this case can be controlled to an accurate value by the pitch length P and the rotational speed N of the screw.
Further, in the screw mechanism 21, the screw portion 21a on the movable portion 20 side and the screw portion 11a on the housing 11 side receive the pressure of the air current, thereby bringing the screw surfaces into close contact with each other and exhibiting a sealing function. For this reason, the airflow leaks from the gap formed between the movable part 20 and the housing 11 on the fixed part side, and returns to the diffuser passage 15A through the back side of the movable part 20 (solid arrow in FIG. 8). F) can be prevented or suppressed. In the example shown in the figure, since the high pressure recovered from the static pressure acts on the back side of the movable portion 20, the movable portion 20 is pressed toward the diffuser passage 15A and the screw surfaces are in close contact with each other.

In the above-described embodiment, the configuration in which the screw portion 21 is provided on the inner peripheral side as shown in FIG. 6 has been described. However, for example, as shown in FIG. Good.
In the configuration shown in FIG. 6 (the threaded portion 21 is on the inner peripheral side), as shown in FIG. 8, the high-pressure outlet pressure P2 that has recovered the static pressure through the diffuser passage 15A passes through the gap S of the movable portion 20. Acts on the back side. On the other hand, in the vicinity of the diffuser inlet 14, the low-pressure inlet pressure P <b> 1 does not act on the back side of the movable portion 20 due to the sealing action of the screw mechanism 21 before the static pressure is restored. At this time, since the pressure P of the airflow flowing in the diffuser passage 15A increases from the inlet pressure P1 to the outlet pressure P2, the outlet pressure P2 acting on the back side is an average value of the pressure P flowing in the diffuser passage 15A. taller than. Accordingly, the force that presses the movable portion 20 due to the pressure difference is always in the direction of the white arrow 17a toward the diffuser passage 15A.

  In the configuration shown in FIG. 7 (the screw portion 21 is on the outer peripheral side), as shown in FIG. 9, the low pressure inlet pressure P1 passes through the gap S before the static pressure is restored in the diffuser passage 15A, and the back side of the movable portion 20 Act on. On the other hand, in the vicinity of the diffuser outlet, the high-pressure outlet pressure P <b> 2 that has recovered the static pressure does not act on the back side of the movable portion 20 due to the sealing action of the screw mechanism 21. At this time, since the pressure P of the airflow flowing in the diffuser passage 15A increases from the inlet pressure P1 to the outlet pressure P2, the inlet pressure P1 acting on the back side is an average value of the pressure P flowing in the diffuser passage 15A. Lower. Accordingly, the force that presses the movable portion 20 due to the pressure difference is always in the direction of the white arrow 17 b toward the housing 11.

  In this way, the force that presses the movable portion 20 due to the pressure difference is always in the same direction, and the pressing direction does not change depending on the operating conditions, so that the effect of preventing leakage that always maintains the sealing function of the screw mechanism 21 can be obtained. In other words, the screw mechanism 21 is provided on the outer diameter side or the inner diameter side with respect to the pressing force canceling position so that the pressing force of the airflow acting on the movable portion 20 is in the same direction. The effect of preventing leakage that always maintains the sealing function 21 can be obtained. Therefore, when there is a leak in the sealing mechanism of the screw mechanism 21, as shown by a solid line arrow F in the figure, an air flow leaks to generate a circulating flow that flows from the high pressure side to the low pressure side, thereby reducing the efficiency of the centrifugal compressor 10A. However, if the force that presses the movable portion 20 by the pressure difference is always in the same direction, such a decrease in efficiency can be suppressed or eliminated.

In other embodiments shown in FIGS. 10 and 11, the screw mechanism 21 </ b> A is disposed at a midway position on the inner and outer periphery of the movable portion 20. In this case, the screw 40 on the fixed side may be a screw provided with a screw portion on either one shown in FIG. 11 (a), or a screw provided with a screw portion on both sides shown in FIG. 11 (b). 40A may be sufficient.
In the configuration shown in FIG. 10, the screw 40 is arranged on the diffuser inlet 14 side from the middle in the airflow direction of the movable portion 20. For this reason, the low pressure inlet pressure P1 and the high pressure outlet pressure P2 act on the back side of the movable portion 20.

Among these, the inlet pressure P1 acts on the back side below the screw 40, and the outlet pressure P2 acts on the back side above the screw 40. Therefore, above the screw 40, the movable portion 20 is located on the side of the diffuser passage 15A indicated by the white arrow 17c due to the pressure difference between the outlet pressure P2 and the average value of the pressure P flowing above the screw 40 in the diffuser passage 15A. Pressed.
However, below the screw 40, due to the pressure difference between the inlet pressure P1 and the average value of the pressure P flowing below the screw 40 in the diffuser passage 15A, the movable portion 20 moves toward the housing 11 indicated by the white arrow 17d. Pressed.
In addition, air current does not leak between the upper and lower sides of the screw 40 by the sealing function of the screw mechanism 21A described later.

  At this time, the reverse forces acting on the movable portion 20 have different values due to the difference between the pressure receiving area and the pressure, so that the absolute values of the remaining forces that are offset from each other are reduced. And, since the force acting in the direction of the diffuser passage 15A indicated by the white arrow 17c in the illustrated example is large toward the direction in which the force acting on the movable portion 20 is large, in the direction of the diffuser passage 15A, A pressing force always acts. For this reason, between the screw surfaces of the screw mechanism 21A, the sealing function is exhibited by always closely contacting in the same direction. The direction in which the pressing force always acts can be set to a desired direction by changing the position of the screw 40 to the airflow direction.

  With such a configuration, the force that presses the movable portion 20 toward the diffuser passage 15A and the force that presses the movable portion 20 toward the housing 11 are offset according to the position where the screw 40 is provided. The driving force required to rotate the unit 20 can be reduced. That is, if the installation position of the screw mechanism 21A is at a radial position that cancels a part of the pressing force of the airflow acting on the movable part 20, the movable part 20 can be rotated with a small driving force. Control of the width of the diffuser passage 15A is facilitated, and wear generated in sliding portions such as the screw mechanism 21A is reduced.

In the present invention described above, the movable portion 20 is rotatable with respect to the housing 11, and the screw mechanisms 21, 21A for moving the movable portion 20 in the direction of the diffuser passage width W are provided. By the multiplication of the screw pitch P and the rotational speed N, the movable portion 20 is translated and changed uniformly without being inclined. Accordingly, the passage width W of the diffuser passage 15A can be uniformly and accurately controlled by the screw mechanisms 21 and 21A, and a centrifugal compressor having a wide operation range can be easily provided.
In the above-described embodiment, the diffuser passage 15A has been described as a vaneless diffuser. However, for example, as indicated by phantom lines in FIGS. 1B and 1C, the blade height h is low and the hub side wall surface 15b The present invention is also applicable to a vaned diffuser having a vane 23 in a range that does not hit.
In addition, this invention is not limited to embodiment mentioned above, In the range which does not deviate from the summary of this invention, it can change suitably.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows one Embodiment of the centrifugal compressor which concerns on this invention, (a) is sectional drawing which shows the principal part periphery of a diffuser, (b) is a principal part expansion which shows the flow path width W of a diffuser channel | path in the maximum. FIG. 4C is an enlarged view of a main part showing a state where the flow path width W of the diffuser passage is the smallest. FIGS. 2A and 2B are diagrams illustrating a configuration example of a drive mechanism that rotates a movable portion illustrated in FIG. 1, in which FIG. 1A is a cross-sectional view and FIG. 2B is a left side view of FIG. It is a performance curve which shows flow volume (Q) -pressure ratio about the centrifugal compressor concerning the present invention. It is a block diagram which shows the process of drive amount determination. It is a figure which shows the effect | action of this invention, (a) is the state in which a movable part moves in parallel, (b) has shown the state in which the movable part inclined. It is a principal part enlarged view of the diffuser channel | path which shows the state which provided the screw mechanism in the inner peripheral side of the movable part. It is a principal part enlarged view of the diffuser channel | path which shows the state which provided the screw mechanism in the outer peripheral side of the movable part. It is explanatory drawing which shows the effect | action of FIG. It is explanatory drawing which shows the effect | action of FIG. It is description which shows other embodiment of this invention. FIGS. 11A and 11B are diagrams illustrating a screw portion of FIG. 11, in which FIG. 11A illustrates an example in which a screw is provided on one side, and FIG. 11B illustrates an example in which a screw is provided on both sides. It is a figure which shows the prior art example of a centrifugal compressor, (a) is sectional drawing which shows the principal part around a diffuser, (b) is a figure which shows the airflow of a diffuser channel | path. It is a performance curve which shows flow volume (Q) -pressure ratio about the conventional centrifugal compressor.

Explanation of symbols

10A Centrifugal compressor 11 Housing 12 Blade 13 Impeller 14 Impeller outlet (diffuser inlet)
15A Diffuser passage 15a Shroud side wall surface 18 Recessed portion 20 Movable portion 21, 21A Screw mechanism 22 Drive gear portion 30 Drive mechanism 31 Pinion gear 40, 40A Screw

Claims (4)

In the centrifugal compressor for adjusting the width of the diffuser passage by changing the position of the annular movable portion by providing the annular movable portion constituting one wall surface of the vaneless diffuser to the vanless diffuser,
A screw mechanism is provided that allows the movable portion to rotate about an impeller rotation shaft with respect to the housing, and moves the movable portion in the direction of the diffuser passage width by rotating the movable portion in the circumferential direction of the impeller rotation shaft. Centrifugal compressor characterized by.   The centrifugal compressor according to claim 1, further comprising a stopper for restricting movement of the movable portion at a maximum position of the diffuser width so that the diffuser passage width does not increase with respect to an impeller outlet width.   The screw mechanism is provided on an outer diameter side or an inner diameter side with respect to a pressing force canceling position so that a pressing force of an airflow acting on the movable portion is in the same direction. Or the centrifugal compressor of 2.   4. The centrifugal compressor according to claim 3, wherein the screw mechanism is provided at a radial position where a part of the pressing force of the airflow acting on the movable portion is canceled out.

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