KR20080039256A - Centrifugal compressor - Google Patents

Abstract

A centrifugal compressor is provided to uniformly and precisely perform variable control of the width of a diffuser path using a screw mechanism to readily provide a centrifugal compressor having a wide operation range. A centrifugal compressor includes a housing(11), and an impeller(13). The impeller having a plurality of blades(12) is installed in the housing and rotates about its axial center line to compress fluid such as gas or air introduced from the outside of the housing to form an air stream. The air stream is introduced into a diffuser path(15A) through an impeller outlet(14), and then decelerated when passing through the diffuser path to recover a constant pressure.

Description

Centrifugal Compressor {CENTRIFUGAL COMPRESSOR}

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

Conventionally, centrifugal compressors, such as a turbocharger used for the internal combustion engine for automobiles, are known, for example.

17 and 18 are cross-sectional views showing the main parts 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 the impeller 13 including the plurality of blades 12 in the housing 11. . The flow (flow) of the fluid thus formed passes through an impeller outlet (hereinafter also referred to as a "diffuser inlet") 14, a diffuser passage 15, and a scroll (not shown) that serve as the outer circumferential end of the impeller 13. Is sent out. In addition, the code | symbol 16 in a figure is an axial center line which the impeller 13 rotates.

The diffuser passage 15 described above is formed between the impeller outlet 14 and the scroll, and is a passage for restoring dynamic pressure to a constant pressure by decelerating the airflow discharged from the impeller outlet 14. This diffuser passage | path 15 is normally formed with a pair of opposing wall surface, In the following description, one of a pair of opposing wall surfaces is called the shroud side wall surface 15a, and the other is a hub side wall surface ( 15b).

In addition, in the turbocharger for automobiles used in combination with an internal combustion engine, since a wide compressor operating range is required, a diffuser (vaneless diffuser) of a type having no vane is usually employed.

Since the operating range of the turbocharger is determined by the compressor, a compressor having a wide operating range is required. In addition, as shown in FIG. 19, the minimum limit of the operating flow rate is defined by an unstable phenomenon such as surging, and the flow rate is between the surge flow rate Qs that defines the minimum flow rate and the choke flow rate Qc that defines the maximum flow rate. Range. For this reason, in order to expand the operation range of a compressor, the means for preventing surging is needed.

The above-mentioned start of surging is caused by the backflow in the diffuser passage 15 which does not have a vane. 18, the reverse flow region of the shroud wall surface 15a at the time of surging is shown by the broken line, and the reverse flow region of the shroud wall surface 15a at the time of stall start is shown by the solid line.

As a conventional technique for preventing surging of the centrifugal compressor, it is proposed to form a fastening portion for optimally adjusting the flow passage cross-sectional area of the diffuser in accordance with the discharge flow rate. This fastening part is comprised by the disk-shaped diffuser side plate which forms one side part of a diffuser. This diffuser side plate is provided in the recessed part formed in the diffuser, and can freely reciprocate to the flow path end surface side. (See, for example, Japanese Unexamined Utility Model Publication No. Hei 6-63897. FIG. 1)

By the way, especially in the turbocharger for vehicle use, it is desired to raise the boost pressure at the time of engine acceleration, and the compressor with a high pressure ratio is required even at a low flow rate and low rotation. It is known that by controlling the passage width of the diffuser passage 15 which greatly affects the operating range of the compressor, it is possible to control the surge flow rate Qs and to significantly improve the operating range. In such a variable mechanism of the diffuser passage, it is necessary to uniformly and accurately perform variable control of the passage width.

SUMMARY OF THE INVENTION The present invention has been made in view of the above circumstances, and an object thereof is to provide a centrifugal compressor capable of uniformly and accurately performing variable control of a passage width in a diffuser passage of a centrifugal compressor. .

MEANS TO SOLVE THE PROBLEM In order to solve the said subject, this invention employ | adopted the following means.

In the centrifugal compressor according to the present invention, a vaneless diffuser is provided with a annular movable portion constituting one wall surface of the vaneless diffuser, and the centrifugal compressor for varying the diffuser passage width by changing the position of the annular movable portion. The screw mechanism is provided so that the movable part can be rotated about the impeller rotating shaft with respect to the housing, and the movable part is rotated in the circumferential direction of the impeller rotating shaft to move in the direction of the diffuser passage width.

According to such a centrifugal compressor, a screw mechanism for moving the movable part in the direction of the diffuser passage width by allowing the movable portion to be rotatable about the impeller rotary shaft and rotating the movable portion in the circumferential direction of the impeller rotary shaft is provided. The change of? Is represented by the multiplication of the pitch of the screw and the rotational speed, and the diffuser passage width is changed while the movable part is uniformly moved in parallel without being inclined.

In the above invention, it is preferable to provide a stopper that regulates the movement of the movable portion at the maximum position of the diffuser width such that the width of the diffuser passage does not become larger than the width of the impeller outlet. As a result, the passage width can be prevented from being widened more than necessary.

In the above invention, it is preferable that the screw mechanism is provided on the outer diameter side or the inner diameter side with respect to the offset position of the pressing force so that the pressing force of the air flow acting on the movable portion is in the same direction. Since the sealing function always occurs in the engaging portion on the government side, leakage of airflow can be prevented or reduced.

In this case, it is preferable that the said screw mechanism is provided in the radial position which part of the pressurization force of the airflow acting on the said movable part cancels, and the direction of a pressurization force does not change. By adopting such a configuration, it is possible to reduce the driving force for rotating the movable portion, and since the direction of the pressing force does not change, it is preferable because there is no rattling at the engaging portion.

According to this invention mentioned above, since the screw mechanism which makes the movable part rotatable with respect to a housing | casing, and moves this movable part in the direction of the diffuser passage width was provided, the passage width W of the diffuser passage | path is the pitch of a screw | thread. It is indicated by the multiplication of and the rotation speed, and the passage width of the diffuser is changed in such a manner that the movable portion is uniformly moved in parallel without being inclined. Therefore, the passage width W of the diffuser passage can be uniformly and precisely variable controlled by the screw mechanism, and can easily provide a centrifugal compressor having a wide operating range.

EMBODIMENT OF THE INVENTION Hereinafter, one Embodiment of the centrifugal compressor which concerns on this invention is described based on drawing.

In the centrifugal compressor 10A shown in FIGS. 1 to 3, an impeller 13 having a plurality of blades 12 rotates about an axis centerline 16 in the housing 11, and the housing 11 is rotated. A gas such as air or air introduced from the outside is compressed to form an air stream. This airflow is introduced into the diffuser passageway 15A from the impeller outlet (diffuser inlet) 14, decelerated when passing through the diffuser passageway 15A, and restored the static pressure, and then sent out through a scroll (not shown) to the outside. do.

The diffuser passage 15A is a vaneless diffuser and is formed by opposing the pair of shroud side wall surfaces 15a and the hub side wall surfaces 15b. Among these, the annular movable part 20 which forms a part of the shroud side wall surface 15a is formed in one wall surface of the vaneless diffuser, for example, the shroud side wall surface 15a. This movable part 20 can adjust the diffuser path width W by changing the position.

In addition, the movable part 20 is formed to the middle of the downstream side from the diffuser inlet 14 as a starting point. However, if the starting point of the movable part 20 is the diffuser inlet 14, the end point is not specifically limited.

The movable part 20 is a substantially ring-shaped plate-shaped member formed on the same axis as the impeller 13, and is screwed with the housing 11 via the screw mechanism 21. As a result, the movable part 20 becomes rotatable about the axial center line 16 with respect to the housing 11, and the movable part 20 makes a white arrow 17 in the direction of the diffuser passage width W. As shown in FIG. Reciprocating parallel movement

In the example shown in figure, the screw mechanism 21 is provided in the inner peripheral side of the movable part 20, and the movable part 20 is screwed with the housing 11 via this screw mechanism 21. As shown in FIG. That is, the recessed part 18 is formed in the shroud side wall surface 15a, the threaded part 21a is formed in the ring inner peripheral surface of the movable part 20, and the threaded part 21a is formed in the recessed part 18 of the housing 11 side. The screw part 11a which is screwed together with the screw is formed, and the movable part 20 is screwed with the housing 11 via the screw mechanism 21 comprised by the screw part 21a and the screw part 11a.

Moreover, a movable part is performed by performing R processing to the lower edge part 19 of the movable part 20 located in the diffuser inlet 14 (corner part of the hub side wall surface 15b side of the ring inner peripheral part of the movable part 20). Even when 20 moves to the diffuser passage 15A side, it becomes difficult to cause confusion in the flow of airflow.

Next, an example of the drive mechanism 30 which rotates the movable part 20 is shown and demonstrated in FIG. 4 and FIG.

The drive mechanism 30 supports one or a plurality of pinion gears 31 so as to be rotatable in a predetermined position of the housing 11, and the drive gear portion 22 formed on the outer circumferential side of the movable portion 20. And interlock with each other. 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 connected to the pinion gear. Rotate in the opposite direction to (31). Since the drive mechanism 30 is determined by the gear ratio, the rotation speed of the pinion gear 31 and the rotation speed of the movable part 20 are such that the diffuser passage width W varies by the rotational movement of the screw mechanism 21. Controllability is high.

When the movable portion 20 rotates in this way, the movable portion 20 is moved in parallel in the direction of the white arrow 17 by the screw mechanism 21 to change its position in accordance with the rotational movement direction thereof. As a result, the diffuser passage width W is appropriately adjusted between the maximum Wa (see FIG. 2) and the minimum Wi (see FIG. 3).

At this time, a stopper for restricting the movement of the movable portion 20 to 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. It is preferable to prevent it from becoming wider than necessary. That is, a stopper is provided so that the diffuser passage width W does not become large with respect to the impeller exit width.

As a specific example of the above-mentioned stopper, for example, as shown in FIG. 3, a stopper face 11b is formed on the housing 11 side, and the stopper face 11b is regulated on the movable part 20 side. There exists a structure which regulates the movement of the movable part 20 by making the surface 20a abut.

Or as shown to FIG. 4 and FIG. 5, the restricting surface 20a which opposes the pinion gear 31 is formed in the movable part 20, and the gear width (thickness) of the pinion gear 31 mentioned above is suitably. In this case, the pinion gear 31 may be brought into contact with the restricting surface 20a on the movable part 20 side to restrict the movement of the movable part 20 to limit the movable width of the movable part 20. In addition, the centrifugal compressor 10A having different operating flow rates also has a different adjustment range of the diffuser passage 15A, so that the drive mechanism 30 or the like can be provided by changing the gear width of the pinion gear 31.

As described above, when the movable portion 20 is moved in parallel by the screw mechanism 21 to vary the diffuser passage width W, as shown in FIG. 6, the surge flow rate is reduced by making the diffuser passage width W small. (Qs) can be reduced. 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 at the minimum Wi with the decrease in the diffuser passage width W. 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 from the conventional Qs / Qc to the storage amount side.

For this reason, when the above-mentioned centrifugal compressor 10A is applied to a turbocharger, for example, as shown in FIG. 7, the control unit creates a database relating to the engine operating state and the driving amount of the movable unit 20. The driving amount is determined based on the input data of the engine operating state. And when the drive mechanism 30 is operated by outputting the signal of the drive amount determined here, the movable part 20 rotates and moves to a desired position in parallel.

Since the screw mechanism 21 is employ | adopted at this time, the parallel movement amount of the movable part 20 is computed correctly by the product (PxN) of the pitch length P of the screw, and rotation speed N. FIG.

And by employ | adopting the screw mechanism 21, as shown in FIG. 9, the movable part 20 does not incline in the axial direction across the axis centerline 16, Therefore, as shown in FIG. Similarly, the diffuser passage 15A of uniform passage width can be formed by the uniform parallel movement along the axial center line 16. In addition, the movement amount in this case can be controlled to an accurate value by the pitch length P and rotation speed N of a screw.

Moreover, in the screw mechanism 21, the screw part 21a by the side of the movable part 20, and the screw part 11a by the side of the housing 11 receive the pressure of an airflow, and mutually contact | connect the screw surfaces, and provide the sealing function. Exert. For this reason, airflow leaks from the clearance gap formed between the movable part 20 and the housing 11 of the fixed part side, and passes through the back side of the movable part 20, and returns to 15 A of diffuser passages (refer FIG. 12). Formation of a solid arrow F) can be prevented or suppressed. In the example shown in figure, since the high pressure which restored | restored the positive pressure acts on the back side of the movable part 20, the movable part 20 is pressed to the diffuser channel | path 15A side, and screw surfaces are in close contact.

By the way, in embodiment mentioned above, the structure which formed the screw part 21a in the inner peripheral side of the movable part 20 was demonstrated as shown in FIG. 10, For example, as shown in FIG. 11, the screw part 21a is shown. May be formed on the outer circumferential side of the movable portion 20.

In the structure shown in FIG. 10 (the structure in which the screw part 21a was formed in the inner peripheral side of the movable part 20), as shown in FIG. 12, the high pressure | pressure outlet pressure P2 which passed | restored the positive pressure through 15 A of diffuser passages is restored. It passes through this gap S and acts on the back side of the movable part 20. On the other hand, in the vicinity of the diffuser inlet 14, the low pressure inlet pressure P1 does not act on the back side of the movable part 20 by the sealing action of the screw mechanism 21 before restoring the static pressure. At this time, since the pressure P of the air flow flowing in the diffuser passage 15A rises from the inlet pressure P1 to the outlet pressure P2, the outlet pressure P2 acting on the back side is the diffuser passage. It is higher than the average value of the pressure P which flows in 15A. Therefore, the force which presses the movable part 20 by a pressure difference always becomes the direction of the white arrow 17a toward 15 A of diffuser passages.

In the structure shown in FIG. 11 (the structure in which the screw part 21a was formed in the outer peripheral side of the movable part 20), as shown in FIG. 13, before the positive pressure is restored in the diffuser passage 15A, the low pressure inlet pressure P1 is It acts on the back side of the movable part 20 through the clearance S. On the other hand, in the vicinity of the diffuser outlet, the high pressure outlet pressure P2 which restored the positive pressure does not act on the back side of the movable part 20 by the sealing action of the screw mechanism 21. At this time, since the pressure P of the airflow flowing in the diffuser passage 15A rises from the inlet pressure P1 to the outlet pressure P2, the inlet pressure P1 acting on the back side is the pressure difference. The force which presses the movable part 20 by this always becomes the direction of the white arrow 17b toward the housing 11.

Thus, since the force which pressurizes the movable part 20 by a pressure difference always becomes the same direction, and a pressurization direction may not be changed by an operating condition, the leak prevention which always maintains the sealing function of the screw mechanism 21 is performed. Effect is obtained. In other words, since the screw mechanism 21 is provided on the outer diameter side or the inner diameter side with respect to the offset position of the pressing force so that the pressing force of the airflow acting on the movable part 20 is in the same direction, the sealing function of the screw mechanism 21 is provided. The effect of preventing leakage is always obtained. Therefore, when there is a leak in the sealing mechanism of the screw mechanism 21, as shown by the solid arrow F in the figure, airflow leaks and generates the circulation flow which flows from the high pressure side to the low pressure side, and the efficiency of the centrifugal compressor 10A is reduced. Although the force which pressurizes the movable part 20 by a pressure difference always becomes the same direction, this efficiency fall can be suppressed or eliminated.

In another embodiment shown in FIGS. 14-16, 21 A of screw mechanisms are arrange | positioned in the middle of the inner and outer peripheries of the movable part 20. In this case, the screw 40 on the fixed side may be one in which a screw part is formed in one of them shown in FIG. 15, or may be a screw 40A in which both of the screws are formed in both parts of FIG. 16.

In the structure shown in FIG. 14, the screw 40 is arrange | positioned at the diffuser inlet 14 side from the middle in the airflow flow direction of the movable part 20. As shown in FIG. For this reason, the low pressure inlet pressure P1 and the high pressure outlet pressure P2 act on the back side of the movable part 20.

Among these, the inlet pressure P1 acts on the back side lower than the screw 40, and the outlet pressure P2 acts on the back side higher than the screw 40. As shown in FIG. Therefore, above the screw 40, the movable part 20 has a white arrow by the pressure difference between the outlet pressure P2 and the average value of the pressure P which flows upwards rather than the screw 40 in the diffuser passage 15A. It is pressurized to the diffuser passage 15A side shown by 17c.

However, below the screw 40, the movable part 20 has a white arrow by the pressure difference between the inlet pressure P1 and the average value of the pressure P which flows below the screw 40 in the diffuser passage 15A below. It is pressed toward the housing 11 side shown by 17d.

In addition, airflow does not leak between the top and bottom of the screw 40 by the sealing function of 21 A of screw mechanisms mentioned later.

At this time, due to the difference in the hydraulic pressure area and the pressure, the force in the reverse direction acting on the movable portion 20 becomes a different value, so that the absolute values of the forces remaining to cancel each other decrease. The force acting on the movable part 20 is directed toward the larger direction, that is, the force acting in the direction of the diffuser passage 15A indicated by the white arrow 17c in the illustrated example, so that the diffuser passage 15A Towards the direction, there is always a pressing force. For this reason, between the screw surfaces of 21 A of screw mechanisms, a sealing function is exhibited by always making close contact in the same direction. In addition, the direction in which the pressing force always acts can be set in a desired direction by changing the position of the screw 40 in the flow direction of the airflow.

In such a configuration, the force for pressing the movable part 20 toward the diffuser passage 15A side and the force for pressing the movable part 20 toward the housing 11 side cancel each other depending on the position where the screw 40 is installed. The driving force necessary for rotating the movable part 20 can be reduced. That is, when the installation position of the screw mechanism 21A is a radial position that cancels a part of the pressing force of the airflow acting on the movable portion 20, and the position where the pressing force does not change, the movable portion 20 is rotated with a small driving force. It is possible to move and prevent rattling due to a change in the pressing force direction at the engaging portion, thereby facilitating control of the passage width of the diffuser passage 15A, and occurring in sliding portions such as the screw mechanism 21A. Wear is reduced.

In the present invention described above, the screw mechanism (21, 21A) which makes the movable part 20 rotatable with respect to the housing 11, and also moves this movable part 20 in the direction of the diffuser passage width W is provided. Since the width | variety (W) is provided, the passage width (W) is represented by the multiplication of the pitch (P) of the screw and the rotation speed (N), and the movable part 20 does not incline and changes in parallel parallel movement. Therefore, the passage width W of the diffuser passage 15A can be uniformly and precisely variable controlled by the screw mechanisms 21 and 21A, and can easily provide a centrifugal compressor having a wide operating range.

By the way, in this embodiment mentioned above, 15 A of diffuser passages were demonstrated as the vaneless diffuser, For example, as shown to an imaginary line in FIG. 2, FIG. 3, wing height h is low and a hub side wall surface is shown. The present invention is also applicable to a vane diffuser having vanes 23 in a range not reaching 15b.

In addition, this invention is not limited to embodiment mentioned above, It can change suitably within the range which does not deviate from the summary of this invention.

BRIEF DESCRIPTION OF THE DRAWINGS It is a figure which shows one Embodiment of the centrifugal compressor which concerns on this invention, and is sectional drawing which shows the principal part around the diffuser.

Fig. 2 is a diagram showing one embodiment of the centrifugal compressor according to the present invention, and is an enlarged view of a main portion showing a state where the flow path width W of the diffuser passage is maximum.

Fig. 3 is a diagram showing one embodiment of the centrifugal compressor according to the present invention, and is an enlarged view of a main portion showing a state in which the flow path width W of the diffuser passage is minimum.

4 is a cross-sectional view showing a configuration example of a drive mechanism for rotating the movable portion shown in FIG. 1.

FIG. 5: is a figure which shows the structural example of the drive mechanism which rotates the movable part shown in FIG. 1, and is a left side view of FIG.

6 is a performance curve showing the flow rate Q-pressure ratio for the centrifugal compressor according to the present invention.

7 is a block diagram showing a process of driving amount determination.

8 is a view showing the operation of the present invention, showing a state in which the movable portion is moved in parallel.

9 is a view showing a state in which the movable portion is inclined.

10 is an enlarged view of the main portion of the diffuser passage showing a state where a screw mechanism is provided on the inner circumferential side of the movable portion.

11 is an enlarged view of a main portion of the diffuser passage showing a state where a screw mechanism is provided on the outer peripheral side of the movable portion.

12 is an explanatory diagram showing the operation of FIG. 10.

FIG. 13 is an explanatory diagram showing the operation of FIG. 11.

It is explanatory drawing which shows other embodiment of this invention.

FIG. 15 is a view showing the screw portion of FIG. 14, in which a screw is provided on one side. FIG.

FIG. 16 is a view showing the screw portion of FIG. 14, in which screws are provided on both sides.

It is a figure which shows the conventional example of a centrifugal compressor, and is sectional drawing which shows the principal part around the diffuser.

It is a figure which shows the conventional example of a centrifugal compressor, and is a figure which shows the airflow of a diffuser channel | path.

19 is a performance curve showing a flow rate Q-pressure ratio for a conventional centrifugal compressor.

Claims (4)

In the centrifugal compressor which forms the annular movable part which comprises one wall surface of the vaneless diffuser in a vaneless diffuser, and changes the position of this diffuser passage | path by changing the position of this annular movable part, A centrifugal compressor comprising: a screw mechanism for allowing the movable portion to rotate in a circumferential direction of the impeller rotating shaft with respect to the housing and for moving the movable portion in a circumferential direction of the impeller rotating shaft. The method of claim 1, A centrifugal compressor 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 become larger than the impeller exit width. The method according to claim 1 or 2, The screw mechanism is provided on the outer diameter side or the inner diameter side with respect to the offset position of the pressing force so that the pressing force of the air flow acting on the movable portion is in the same direction. The method of claim 3, wherein The said screw mechanism is provided in the radial position in which a part of the pressing force of the airflow which acts on the said movable part cancels, and the direction of a pressing force does not change, The centrifugal compressor characterized by the above-mentioned.

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