JP2007211717A - Centrifugal compressor - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a centrifugal compressor which suppresses the surging caused by a stall cell occurring in the vicinity of a vaneless diffuser. <P>SOLUTION: When a stall cell having locally high pressure in an operating region near a surge limit is formed in the vicinity of a vaneless diffuser plate 9, the stall cell passes through a plurality of bypass holes 9A formed on the entire circumference of the vaneless diffuser plate 9 and flows out to a scroll flow passage 3A. Accordingly, the surging caused by the stall cell occurring in the vicinity of the vaneless diffuser plate 9 is satisfactorily suppressed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a centrifugal compressor, and more particularly to a centrifugal compressor provided with a vaneless diffuser.

  In a centrifugal compressor that pumps intake gas toward a scroll passage formed around a compressor wheel by a compressor wheel (impeller) that rotates in the compressor housing, the outer periphery of the compressor wheel and the scroll passage around the compressor wheel An annular gas flow path is usually formed between them by a diffuser. This annular gas flow path reduces the flow rate of the suction gas pumped from the compressor wheel toward the scroll flow path by gradually increasing the cross-sectional area from the inner peripheral side toward the outer peripheral side. Increase pressure.

As a centrifugal compressor provided with this type of diffuser, a turbocharger compressor provided with a so-called vaneless diffuser having no vane plate is generally known (see, for example, Patent Documents 1 to 3).
JP 2000-257437 A JP 2002-266797 A Japanese Utility Model Publication No. 6-63897

  By the way, in the centrifugal compressor provided with the vaneless diffuser as described in Patent Documents 1 to 3, the flow rate of the suction gas is small, and the pressure ratio of the suction gas (pressure after compression / pressure before compression) is low. In the operating region near the high surge limit, a locally stalled cell with high pressure is generated near the vaneless diffuser, and as a result, the centrifugal compressor cannot operate due to surging (periodic pressure fluctuation or flow velocity fluctuation of the intake gas). There is a risk of becoming.

  Then, this invention makes it a subject to provide the centrifugal compressor which can suppress the surging resulting from the stall cell which generate | occur | produces near a vane less diffuser.

  A centrifugal compressor according to the present invention is a centrifugal compressor provided with a vaneless diffuser plate for forming an annular gas flow path between an outer periphery of a compressor wheel in a compressor housing and a scroll flow path around the compressor wheel. The vaneless diffuser plate is provided with a bypass hole that communicates the gas flow path and the scroll flow path.

  In the centrifugal compressor according to the present invention, when a stall cell with high pressure is generated in the vicinity of the vaneless diffuser plate in the operating region near the surge limit, the stalled cell is swirling along the vaneless diffuser plate. Since it passes through the bypass hole and flows out to the scroll flow path, surging due to the stall cell generated in the vicinity of the vaneless diffuser plate is suppressed.

  In the centrifugal compressor of the present invention, when a plurality of bypass holes are provided over the entire circumference of the vaneless diffuser plate, a plurality of stall cells generated near the vaneless diffuser plate are caused to flow out from the plurality of bypass holes to the scroll flow path. This is preferable because surging due to a stall cell generated in the vicinity of the vaneless diffuser plate can be sufficiently suppressed.

  Here, the centrifugal compressor of the present invention can have a structure provided with a bypass hole opening / closing means that opens the bypass hole only in the operation region near the surge limit and closes the bypass hole in the other operation region.

  According to the centrifugal compressor according to the present invention, when a stall cell having a high pressure is generated in the vicinity of the vaneless diffuser plate in the operation region near the surge limit, the stall cell passes through the bypass hole and is scrolled. Since it flows out to the road, it is possible to suppress surging caused by a stalled cell generated near the vaneless diffuser plate.

  DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, preferred embodiments of a centrifugal compressor according to the invention will be described with reference to the drawings. In this description, the same or similar components are denoted by the same reference numerals, and redundant description may be omitted. Here, in the drawings to be referred to, FIG. 1 is a cross-sectional view showing the structure of a turbocharger provided with the centrifugal compressor according to the first embodiment as a compressor, and FIG. 2 is a front view of the vaneless diffuser plate shown in FIG. is there.

  The centrifugal compressor according to the first embodiment is configured as a compressor of the turbocharger 1 shown in FIG. The turbocharger 1 connects a turbine housing 2 for a turbine interposed in the middle of an exhaust system of a vehicle engine (not shown) and a compressor housing 3 for a compressor interposed in the middle of an intake system. A center housing (bearing housing) 4 is provided.

  In the turbine housing 2, a scroll flow path 2 </ b> A for introducing exhaust gas flowing through the exhaust system of the vehicle engine is formed. A turbine wheel 5 that is rotationally driven by the passage of exhaust gas flowing in from the scroll flow path 2 </ b> A is accommodated in the turbine housing 2.

  On the other hand, the compressor housing 3 accommodates a compressor wheel 6 for supercharging the intake air of the vehicle engine to a pressure higher than the atmospheric pressure. Around the compressor wheel 6 is formed a scroll passage 3A for sending pressurized intake air to the intake system of the vehicle engine.

  The turbine wheel 5 in the turbine housing 2 and the compressor wheel 6 in the compressor housing 3 are connected to each other via a shaft 7 so as to rotate integrally. The shaft 7 is rotatably supported by the center housing 4 via a floating bearing 8.

  Here, in the compressor housing 3, a vane for forming an annular air flow path (gas flow path) 3 </ b> B between the outer periphery of the base end of the compressor wheel 6 and the scroll flow path 3 </ b> A around the compressor wheel 6. A less diffuser plate 9 (see FIG. 2) is installed. The vaneless diffuser plate 9 is formed in a flat ring shape facing the back plate 3 </ b> C of the compressor housing 3, and an inner periphery thereof is fitted to a circular support portion 3 </ b> D formed inside the compressor housing 3. Is fixed.

  Such an annular air flow path 3B formed between the vaneless diffuser plate 9 and the back plate 3C has a compressor wheel that gradually increases in cross-sectional area from the inner peripheral side toward the outer peripheral side. The flow rate of the intake air pumped from the outer periphery of the base end portion 6 toward the scroll flow path 3A is reduced to increase its pressure.

  Here, the vaneless diffuser plate 9 is formed with a bypass hole 9A that communicates the annular air passage 3B on one side with the scroll passage 3A on the opposite side. The bypass holes 9 </ b> A are formed as arc-shaped slit holes as shown in FIG. 2, for example, and a plurality of bypass holes 9 </ b> A are formed over the entire circumference of the vaneless diffuser plate 9. These bypass holes 9A may be changed to a plurality of circular holes as shown in FIG. 3, for example.

  In the turbocharger 1 configured as described above, exhaust gas discharged to the exhaust system in accordance with the operation of a vehicle engine (not shown) flows from the scroll passage 2A in the turbine housing 2 through the turbine wheel 5 and flows. By doing so, the turbine wheel 5 is rotationally driven. Then, the compressor wheel 6 in the compressor housing 3 is rotationally driven in conjunction with the rotation of the turbine wheel 5 so that the intake air of the intake system of the vehicle engine is pressurized to atmospheric pressure or higher and supercharged. .

  At that time, in the compressor of the turbocharger 1 configured as the centrifugal compressor of the first embodiment, the intake air pumped from the outer periphery of the base end portion of the compressor wheel 6 toward the scroll passage 3A is an annular air passage. In the process of passing 3B from the inner circumference side toward the outer circumference side, the flow velocity gradually decreases and the pressure rises, passes through the plurality of bypass holes 9A of the vaneless diffuser plate 9, and flows out to the scroll flow path 3A. There is little to do.

  Here, in the compressor of the turbocharger 1 (the centrifugal compressor of the first embodiment), the surge limit is low and the intake air flow rate is low and the intake air pressure ratio (pressure after compression / pressure before compression) is high. When a stall cell having a high pressure is generated in the vicinity of the vaneless diffuser plate 9 in the vicinity of the operation region, the stall cell having a high pressure is swung along the vaneless diffuser plate 9 while any of the plurality of bypass holes 9A. Flows out into the scroll flow path 3A. For this reason, surging caused by the stalled cell generated in the vicinity of the vaneless diffuser plate 9 is effectively suppressed.

  The suppression of surging in this way is indicated by the solid line from the position indicated by the two-dot chain line in the diagram of FIG. 4 showing the operating characteristics of the compressor of the turbocharger 1 (the centrifugal compressor of the first embodiment). It means moving toward the position shown in FIG. Therefore, the engine operating line in the region where the intake air amount is small can be moved from the position indicated by the dotted line toward the position indicated by the solid line toward the side where the intake air amount is less, and the engine operating region can be moved to the lower speed side. It is possible to expand to.

  Next, a centrifugal compressor according to the second embodiment will be described with reference to FIGS. The centrifugal compressor according to the second embodiment is configured as a compressor of the turbocharger 10 shown in FIG. 5, and includes a set of two fixed vaneless diffuser plates 11 instead of the vaneless diffuser plate 9 shown in FIG. A movable vaneless diffuser plate 12 is provided. Note that the turbocharger 10 shown in FIG. 5 is configured in substantially the same manner as the turbocharger 1 shown in FIG. 1, and therefore, the same components are denoted by the same reference numerals and description thereof is omitted.

  As shown in FIG. 5, the fixed vaneless diffuser plate 11 is formed in a flat ring shape, and its inner periphery is fitted and fixed to a circular support portion 3 </ b> D formed inside the compressor housing 3. ing. On the other hand, the movable vaneless diffuser plate 12 is formed in, for example, a ring shape with a key-shaped cross section that holds the outer periphery of the fixed vaneless diffuser plate 11, and is rotatable relative to the fixed vaneless diffuser plate 11. It is overlapped and faces the back plate 3 </ b> C of the compressor housing 3.

  As shown in FIG. 6, the fixed vaneless diffuser plate 11 has a plurality of arc-shaped long holes as the bypass holes 11 </ b> A arranged on the same circumference and formed intermittently. Similarly, in the movable vaneless diffuser plate 12, a plurality of arc-shaped long holes serving as bypass holes 12A are intermittently formed on the same circumference.

  Here, when the rotation position of the movable vaneless diffuser plate 12 with respect to the fixed vaneless diffuser plate 11 is at a predetermined first rotation position, each bypass hole 12A of the movable vaneless diffuser plate 12 is fixed to the fixed vaneless diffuser plate 11. When each of the bypass holes 11A is fully opened so as to overlap with each of the bypass holes 11A, and the rotational position of the movable vaneless diffuser plate 12 with respect to the fixed vaneless diffuser plate 11 is at a predetermined second rotational position, the movable vaneless diffuser Each bypass hole 12A of the plate 12 is displaced from each bypass hole 11A of the fixed vane-less diffuser plate 11, and each bypass hole 11A is fully closed.

  Therefore, each bypass hole 11A of the fixed vaneless diffuser plate 11 is opened and closed by rotating the movable vaneless diffuser plate 12 between the first rotating position and the second rotating position with respect to the fixed vaneless diffuser plate 11. A bypass hole opening / closing means is provided. This bypass hole opening / closing means opens each bypass hole 11A of the fixed vaneless diffuser plate 11 only in the operating region near the surge limit of the compressor (centrifugal compressor of the second embodiment) of the turbocharger 10 shown in FIG. In the other operation region, each bypass hole 11A is fully closed.

  The bypass hole opening / closing means 20 detects the flow rate Q of the intake air flowing through the compressor housing 3 as shown in FIG. 7 as a group of sensors for detecting the operating region of the turbocharger 10 shown in FIG. An air flow sensor 21, an inlet side air pressure sensor 22 that detects an inflow air pressure Pin on the inlet side of the compressor housing 3, and an outlet side air pressure sensor 23 that detects an outflow air pressure Pout on the outlet side of the compressor housing 3. .

  The bypass hole opening / closing means 20 is controlled by a control device 24 to which detection signals are input from the air flow sensor 21, the inlet side air pressure sensor 22 and the outlet side air pressure sensor 23, and a control signal output from the control device 24. And a drive motor 26 whose rotation is controlled via a motor drive circuit 25.

  The control device 24 is configured using the hardware and software of a microcomputer such as an ECU (Electric Control Unit) (not shown) mounted on the vehicle. The control device 24 receives an input / output interface I / O and an A / D converter between the air flow sensor 21, the inlet side air pressure sensor 22, the outlet side air pressure sensor 23, and the motor drive circuit 25, as well as programs and data. As a hardware, a ROM (Read Only Memory), a RAM (Random Access Memory) that temporarily stores input data, a CPU (Central Processing Unit) that executes a program, and the like are provided.

  Here, in the control device 24, a compressor pressure ratio calculation unit 24A, a bypass hole opening / closing unit 24B, a data map 24C, and a drive signal output unit 24D are configured as software. In the data map 24C, surge lines indicated by two-dot chain lines in FIG. 4 are stored as a two-dimensional map.

  The compressor pressure ratio calculation unit 24A is based on the detection signals of the inflow air pressure Pin and the outflow air pressure Pout input from the inlet side air pressure sensor 22 and the outlet side air pressure sensor 23, respectively. The pressure ratio of the centrifugal compressor of the second embodiment is calculated, and a signal of the pressure ratio (Pout / Pin) is output to the bypass hole opening / closing part 24B.

  The bypass hole opening / closing unit 24B performs data based on the compressor pressure ratio (Pout / Pin) signal input from the compressor pressure ratio calculation unit 24A and the compressor intake air flow rate Q signal input from the airflow sensor 21. By looking up the map 24C, whether the operating region corresponding to the intake air flow rate Q and the pressure ratio (Pout / Pin) of the compressor is near the surge limit near the right side of the surge line shown by the two-dot chain line in FIG. It is determined whether or not, and the determination signal is output to the drive signal output unit 24D.

  The drive signal output unit 24D is based on the determination signal input from the bypass hole opening / closing unit 24B, and when the operation region corresponding to the compressor intake air flow rate Q and the pressure ratio (Pout / Pin) is near the surge limit, The movable vaneless diffuser plate 12 is rotated to the first rotation position with respect to the fixed vaneless diffuser plate 11 to output a drive signal (fully opened) to the motor drive circuit 25 to fully open the bypass hole 11A. The drive signal output unit 24D bypasses the movable vaneless diffuser plate 12 to the second rotational position with respect to the fixed vaneless diffuser plate 11 when the operating region of the compressor is not near the surge limit. A drive signal (fully closed) for closing the hole 11A is output to the motor drive circuit 25.

  When a drive signal (fully opened) is input from the drive signal output unit 24D, the motor drive circuit 25 causes the drive motor 26 to rotate the movable vaneless diffuser plate 12 to the first rotation position via a link mechanism (not shown). Thus, the rotation direction and the rotation amount of the drive motor 26 are controlled. When a drive signal (fully closed) is input from the drive signal output unit 24D, the motor drive circuit 25 causes the drive motor 26 to move the movable vaneless diffuser plate 12 to the second rotational position via a link mechanism (not shown). The rotation direction and the rotation amount of the drive motor 26 are controlled so as to be rotated to the right.

  Hereinafter, the procedure of the bypass hole opening / closing process executed by the control device 24 of the bypass hole opening / closing means 20 will be described with reference to the flowchart shown in FIG. First, in step S1, the signal of the inflow air pressure Pin is input from the inlet side air pressure sensor 22 to the compressor pressure ratio calculation unit 24A of the control device 24, and in the subsequent step S2, the compressor pressure ratio calculation unit is output from the outlet side air pressure sensor 23. The signal of the outflow air pressure Pout is input to 24A. In the next step S3, the compressor pressure ratio calculator 24A calculates the compressor pressure ratio (Pout / Pin).

  In the subsequent step S4, a signal of the pressure ratio (Pout / Pin) calculated by the compressor pressure ratio calculation unit 24A is input to the bypass hole opening / closing unit 24B, and in the next step S5, the air flow sensor 21 supplies the bypass hole opening / closing unit 24B. A signal of the intake air flow rate Q is input.

  Then, the bypass hole opening / closing unit 24B looks up the data map 24C in step S6, and the operation region corresponding to the intake air flow rate Q and the pressure ratio (Pout / Pin) of the compressor is indicated by a two-dot chain line in FIG. It is determined whether it is near the surge limit near the right side of the surge line (S7), and the determination signal is output to the drive signal output unit 24D.

  If the decision result in the step S7 is YES, the drive signal output unit 24D outputs a drive signal (fully opened) to the motor drive circuit 25 in a subsequent step S8. As a result, the drive motor 26 rotates the movable vaneless diffuser plate 12 to the first rotation position via a link mechanism (not shown). As a result, each bypass hole 11A of the fixed vaneless diffuser plate 11 shown in FIGS. 5 and 6 is fully opened.

  On the other hand, if the decision result in the step S7 is NO, the drive signal output unit 24D outputs a drive signal (fully closed) to the motor drive circuit 25 in a step S9. As a result, the drive motor 26 rotates the movable vaneless diffuser plate 12 to the second rotation position via a link mechanism (not shown). As a result, the bypass holes 11A of the fixed vaneless diffuser plate 11 shown in FIGS. 5 and 6 are fully closed.

  Thus, in the compressor of the turbocharger 10 shown in FIG. 5 (centrifugal compressor of the first embodiment), the operating region is near the surge limit near the right side of the surge line indicated by the two-dot chain line in FIG. If not, each bypass hole 11A of the fixed vaneless diffuser plate 11 is fully closed. For this reason, the intake air pumped from the outer periphery of the base end portion of the compressor wheel 6 toward the scroll passage 3A may inadvertently flow out from the bypass holes 11A of the fixed vaneless diffuser plate 11 to the scroll passage 3A. Without passing through the annular air flow path 3B from the inner peripheral side toward the outer peripheral side, the flow rate gradually decreases and the pressure increases efficiently.

  On the other hand, when the operation region of the compressor (the centrifugal compressor of the first embodiment) of the turbocharger 10 shown in FIG. 5 is near the surge limit near the right side of the surge line shown by the two-dot chain line in FIG. Each bypass hole 11A of the fixed vaneless diffuser plate 11 is fully opened. For this reason, when a stall cell having a high pressure is generated in the vicinity of the movable vaneless diffuser plate 12, the stall cell having a high pressure rotates along the movable vaneless diffuser plate 12 and the plurality of bypass holes 12 </ b> A and The fixed vaneless diffuser plate 11 passes through the plurality of bypass holes 11A and flows out to the scroll passage 3A. Accordingly, surging caused by the stalled cell generated in the vicinity of the movable vaneless diffuser plate 12 is effectively suppressed.

  Since surging is suppressed in this way, in the compressor of the turbocharger 10 shown in FIG. 5 (the centrifugal compressor of the first embodiment), the surge line shown in FIG. 4 is indicated by a solid line from the position indicated by the two-dot chain line. Move toward the position with less intake air. Therefore, the engine operating line in the region where the intake air amount is small can be moved from the position indicated by the dotted line toward the position indicated by the solid line toward the side where the intake air amount is less, and the engine operating region can be moved to the lower speed side. It is possible to expand to.

  The centrifugal compressor according to the present invention is not limited to the above-described embodiments. For example, the shape of the bypass hole of the vane-less diffuser plate shown in FIG. 1 is not limited to the shape shown in FIGS. 2 and 3 and can be changed to an appropriate shape. Similarly, the shapes of the bypass hole of the fixed vaneless diffuser plate and the bypass hole of the movable vaneless diffuser plate shown in FIG. 5 are not limited to the shapes shown in FIG. 6 and can be changed to appropriate shapes.

It is sectional drawing which shows the structure of the turbocharger provided with the centrifugal compressor which concerns on 1st Embodiment of this invention as a compressor. It is a front view of the vane less diffuser plate shown in FIG. It is a front view which shows the modification of the vaneless diffuser plate shown in FIG. It is a diagram which shows the operating characteristic of the compressor of the turbocharger shown in FIG. It is sectional drawing which shows the structure of the turbocharger provided with the centrifugal compressor which concerns on 2nd Embodiment of this invention as a compressor. FIG. 6 is a front view of the fixed vaneless diffuser plate and the movable vaneless diffuser plate shown in FIG. 5. It is a block diagram which shows the structure of the bypass hole opening-and-closing means provided in the turbocharger shown in FIG. It is a flowchart which shows the process sequence of the bypass hole opening / closing means shown in FIG.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1 ... Turbocharger, 2 ... Turbine housing, 3 ... Compressor housing, 3A ... Scroll flow path, 3B ... Air flow path, 3C ... Back plate, 4 ... Center housing, 5 ... Turbine wheel, 6 ... Compressor wheel, 9 ... Vane Less diffuser plate, 9A ... Bypass hole, 10 ... Turbocharger, 11 ... Fixed vaneless diffuser plate, 11A ... Bypass hole, 12 ... Movable vaneless diffuser plate, 12A ... Bypass hole, 20 ... Bypass hole opening / closing means, 24 ... Control apparatus.

Claims (3)

A centrifugal compressor including a vaneless diffuser plate for forming an annular gas flow path between an outer periphery of a compressor wheel in a compressor housing and a scroll flow path around the compressor wheel,
The centrifugal compressor, wherein the vaneless diffuser plate is provided with a bypass hole that communicates the gas flow path and the scroll flow path.   The centrifugal compressor according to claim 1, wherein a plurality of the bypass holes are provided over the entire circumference of the vaneless diffuser plate.   The centrifugal compressor according to claim 1 or 2, wherein the bypass hole opening means is configured to open the bypass hole only in an operating region near the surge limit and close the bypass hole in the other operating region. A centrifugal compressor characterized by comprising:

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