JP2009243277A - Turbine housing cooling system - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a turbine housing cooling system suited for a turbo-charger of an engine for a vehicle. <P>SOLUTION: A turbo-charger 18 of an engine 10 for a vehicle equipped with a turbine housing 34 having a cooling passage 36 includes a flow rate changing means 42 for changing a flow rate of a cooling medium circulating in the cooling passage 36, and a cooling medium flow rate control means 60 for controlling the flow rate of the cooling medium by the flow rate changing means 42, so that a chip clearance 35 falls within a predetermined range based on the temperature of the cooling medium and the operating state of the engine. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a turbine housing cooling system, and more particularly, to a turbine housing cooling system for a turbocharger provided in a vehicle engine.

  In general, in a gas turbine, the gap between the tip of a moving blade constituting the turbine, that is, a tip, and an inner wall surface of the turbine housing (this is generally called a tip clearance) is an important factor that determines the efficiency of the turbine. It is known that The tip clearance is preferably as small as possible in order to increase the efficiency of the turbine.

  Therefore, in Patent Document 1, a cooling passage is provided in a blade ring facing the tip of a moving blade of a gas turbine, and an auxiliary boiler and a steam supply source from a bottoming system of the steam turbine are connected to the cooling passage. A technique has been proposed in which the tip clearance between the blade tip and the blade ring opposite to the tip of the blade is reduced by cooling the blade ring by collecting the steam and collecting the steam after cooling.

  Patent Document 2 proposes a technique in which the turbine tip clearance is controlled within a predetermined range by cooling the turbine blade and casing with cooling air and controlling the amount of cooling air in accordance with the metal temperature. Has been.

  Furthermore, Patent Document 3 discloses that the housing of the exhaust turbine has a double wall in order to prevent the heat from the turbocharger in the vehicle engine from being consumed by a peripheral device such as a motor generator. A technique has been proposed in which a cooling medium is allowed to flow through the space when the engine is stopped.

JP 2001-248406 A JP 2004-19549 A JP 2004-84480 A

  However, the tip clearance control technology proposed in Patent Document 1 or 2 is for a stationary gas turbine for power generation, and only the turbine efficiency is pursued so that the tip clearance is always minimized. Therefore, it is difficult to apply this as it is to a turbocharger of a vehicle engine. This is because in a vehicular engine, an output request required for the engine greatly changes in accordance with a change in traveling state including acceleration / deceleration of the vehicle. Therefore, the tip clearance is controlled in response to the output request. It is because it is preferable.

  Further, if the turbine housing is cooled and controlled so as to reduce the tip clearance as much as possible by pursuing the turbine efficiency, the tip of the turbine rotor blade and the inner wall of the turbine housing may come into contact due to overcooling of the turbine housing. Once such contact occurs, the turbine rotating at high speed will be immediately damaged, so this situation must be reliably avoided.

  Accordingly, an object of the present invention is to provide a turbine housing cooling system suitable for a turbocharger of a vehicle engine that solves the conventional problems.

  A turbine housing cooling system according to an aspect of the present invention that achieves the above object is a turbocharger for a vehicle engine including a turbine housing provided with a cooling passage, and a flow rate for changing a flow rate of a cooling medium circulating in the cooling passage. Changing means, and cooling medium flow rate control means for controlling the flow rate of the cooling medium by the flow rate changing means so that the tip clearance is within a predetermined range based on the temperature of the cooling medium and the operating state of the engine. It is characterized by providing.

  According to the turbine housing cooling system according to one aspect of the present invention, the flow rate of the cooling medium circulating in the cooling passage of the turbine housing by the flow rate changing means is determined based on the temperature of the cooling medium and the operating state of the engine, and the tip clearance is predetermined It is controlled by the cooling medium flow rate control means so as to be within the range. Thus, since the flow rate of the coolant at a predetermined temperature is controlled so that the tip clearance is within the predetermined range in accordance with the temperature of the turbine housing that changes according to the operating state of the engine, the turbine efficiency is high. Maintained. Therefore, a turbine housing cooling system suitable for a turbocharger of a vehicle engine can be obtained.

  Here, an acceleration / deceleration request detecting means for detecting an acceleration / deceleration request to the engine, and a target coolant flow rate by the coolant flow control means according to the acceleration request or the deceleration request detected by the acceleration / deceleration request detecting means. It is preferable to further include correction means for correcting the value.

  According to this aspect, the target coolant flow rate value is corrected in accordance with the acceleration request or deceleration request to the engine detected by the acceleration / deceleration request detection means. Thus, in the case of an acceleration request to the engine, the target coolant flow rate value is corrected so as to increase, and conversely, in the case of a deceleration request to the engine, the target coolant flow rate value is corrected to decrease. Can be. Therefore, at the time of acceleration request at which engine output is required, the target coolant flow rate value is increased. As a result, the coolant flow rate is increased and the thermal expansion of the turbine housing is suppressed, so that the tip clearance is further reduced. Thus, the turbine efficiency can be improved and the engine output corresponding to the acceleration request can be obtained quickly.

  The cooling medium is cooling water and may be stored in a livestock heat tank.

  According to this form, it can also be shared with engine cooling water, and can be configured at low cost. Moreover, the warm water stored in the livestock heat tank can be used when the engine is cold-started, and the warm-up of the engine can be promoted.

  Further, the acceleration / deceleration request detecting means may detect an accelerator opening.

  According to this aspect, it is possible to easily detect an acceleration / deceleration request to the engine.

  Embodiments of the present invention will be described below with reference to the accompanying drawings. FIG. 1 is a system diagram showing an outline of a turbine housing cooling system of an engine equipped with a turbocharger to which the present invention is applied, and 10 is an engine body.

  As an intake system of the engine 10, an intake manifold 12 is communicated with an intake port, and a throttle chamber 16 having a throttle valve interposed is communicated with the intake manifold 12 via a surge tank 14 in which intake passages of the respective cylinders are gathered. Yes. The throttle valve is driven by a throttle motor (not shown). A compressor 20 of the turbocharger 18 is provided in the intake passage upstream of the throttle chamber 16. Further, an air cleaner is provided at the upstream end of the intake passage, and an air flow meter 19 for measuring the intake air flow rate is provided downstream thereof. An unillustrated fuel injection valve is disposed immediately upstream of the intake port of each cylinder, and an unillustrated spark plug is disposed for each cylinder of the cylinder head.

  On the other hand, as an exhaust system of the engine 10, exhaust is joined by an exhaust manifold 22 communicating with an exhaust port, and an exhaust passage is connected to the exhaust manifold 22. A turbine 30 of the turbocharger 18 is interposed in the exhaust passage. The turbocharger 18 rotationally drives the compressor 20 with the energy of the exhaust gas flowing into the turbine 30 and sucks and pressurizes air to supercharge the turbocharger 18. As a supercharging pressure control device, for example, an inlet side of the turbine 30 A waste gate valve is provided in a bypass passage that communicates with the outlet side. The wastegate valve is driven by a wastegate valve actuator that is an electric actuator such as a DC motor, for example, and can take its “fully closed”, “fully open”, and intermediate positions therebetween.

  Here, the turbine 30 according to the present embodiment will be further described with reference to FIG. In the turbine 30 according to the present embodiment, a turbine rotor blade 33 is formed on a turbine rotor 32 connected to an impeller of the compressor 20 via a shaft 31 and is rotatably accommodated in a turbine housing 34. A tip clearance 35 is formed between the tip of the turbine rotor blade 33 and the inner wall surface of the turbine housing 34. Further, an annular cooling passage 36 is formed in the wall of the turbine housing 34 that forms the tip clearance 35. In the illustrated embodiment, two annular cooling passages 36A and 36B are formed along the inner wall surface of the turbine housing 34. The annular cooling passages 36A and 36B are independent of each other. It may be two passages or one passage that is spirally continuous. The reason for providing the plurality of cooling passages 36 along the inner wall surface is to uniformly control the tip clearance 35 formed along the tip of the turbine rotor blade 33 over the entire surface. Is not limited.

  Here, referring again to FIG. 1, the cooling medium circulation path 40 is communicated with the cooling path 36. The cooling medium circulation path 40 is also communicated with a storage heat tank 41 that stores the cooling medium by storing it. Further, the cooling medium circulation path 40 sucks the cooling medium stored in the storage heat tank 41. A pump 42 for supplying the cooling passage 36 while controlling the flow rate is provided. Reference numeral 43 denotes a coolant temperature sensor that detects the temperature of the coolant in the coolant circulation path 40.

  Further, the engine 10 is provided with a crank angle sensor 50 for obtaining the rotational speed of the engine 10 and an accelerator opening sensor 51 for detecting a load (accelerator opening). Further, a water temperature sensor (not shown) for detecting the cooling water temperature of the engine 10, a pressure sensor (not shown) used for controlling the supercharging pressure, and the air-fuel ratio of the air-fuel mixture in the combustion chamber are detected based on the oxygen concentration in the exhaust gas. An air-fuel ratio sensor (not shown) or the like is provided, and the output of these various sensors is sent to an electronic control unit (ECU) 60 constituted by a microcomputer or the like together with the above-described sensor.

  The ECU 60 controls the fuel injection amount, the ignition timing, the supercharging pressure, etc. according to the output value sent from each sensor. The control values used for controlling the fuel injection amount, the ignition timing, the supercharging pressure, etc. are, for example, the operating state of the engine 10 with the engine load on the vertical axis and the engine speed on the horizontal axis. In the map to be represented, optimum values experimentally obtained in accordance with required characteristics of the engine 10 are set as control values, and these maps are stored in a table of the ECU 60.

  Here, an example of the tip clearance control executed in the vehicle engine 10 with the turbocharger 18 having the turbine housing 34 provided with the cooling passage 36 having the above-described configuration is shown in the flowchart of FIG. 3 and FIGS. This will be described with reference to the graph of FIG. The tip clearance control is executed at a predetermined cycle while the engine 10 is operating.

  First, before describing the actual tip clearance control, the relationship between the output PS of the engine 10 that greatly affects the exhaust gas temperature that changes according to the operating state of the engine 10 and the temperature Tht of the turbine housing 34 of the turbocharger 18. The relationship between the output PS of the engine 10 and the flow rate Gc of the coolant at the temperature Tw for obtaining the turbine housing temperature Tht will be described with reference to the graphs of FIGS.

  Here, in order to explain the relationship between the engine output PS and the temperature Tht of the turbine housing 34, the graph of FIG. 4 takes the engine output PS (exhaust gas temperature) on the horizontal axis and the turbine housing temperature Tht on the vertical axis. It is shown that the temperature Tht of the turbine housing increases as the engine output PS increases. Here, the upper curve a represents the target turbine housing temperature Thttgt for setting the tip clearance 35 to a predetermined value d in order to obtain a predetermined turbine efficiency. On the other hand, the lower curve b represents the minimum value Thtmin of the turbine housing temperature Tht, that is, when the tip clearance 35 is zero, and the temperature Tht of the turbine housing is decreased beyond this, the tip contacts. ing. From this graph, when the engine output PS (exhaust gas temperature) changes, the turbine housing temperature Tht also changes, and when the turbine housing temperature Tht is lowered below its minimum value Thtmin, tip contact can occur. It is understood.

  Next, the graph of FIG. 5 is obtained by taking the engine output PS (exhaust gas temperature) on the horizontal axis and the flow rate Gc of the cooling medium on the vertical axis. In order to obtain the turbine housing temperature Tht shown in FIG. The relationship between the coolant flow rate Gc to be passed through the coolant circulation path 40 and the coolant passage 36 of the turbine housing 34 and the engine output PS is shown. Here, the lower curve aa represents the target coolant flow rate Gctgt for obtaining the target turbine housing temperature Thttgt that sets the above-described tip clearance 35 to the predetermined value d. On the other hand, the upper curve bb indicates that if the flow rate Gc of the cooling medium is increased beyond this, the turbine housing 34 is supercooled, the tip clearance 35 becomes zero, and the tip comes into contact. The maximum value Gcmax is represented.

  The specific control value of the target coolant flow rate Gctgt for obtaining the target turbine housing temperature Thttgt with respect to the engine output PS described above is obtained in advance by experiments or the like in correspondence with the coolant temperature Tw described later, and is obtained from the ECU 60. Is stored as a map.

  Therefore, first, in step S301 where the control is started as the engine 10 is started, the tip clearance control is stopped (OFF), and the flow rate Gc of the cooling medium is maintained at the minimum flow rate Gcmin. That is, the pump 42 is controlled by the command from the ECU 60 so that the discharge amount from the pump 42 becomes the minimum flow rate Gcmin. Then, the process proceeds to the next step S302, and it is determined whether or not the tip clearance control is possible. Specifically, it is determined by detection of the cooling medium temperature sensor 43 whether or not the temperature Tw of the cooling medium in the cooling medium circulation path 40 exceeds the minimum cooling medium temperature Tws at which chip clearance control is possible. When the cooling medium temperature Tw does not exceed the minimum cooling medium temperature Tws, that is, when “No”, the process returns to step S301 again. This is because if the cooling medium temperature Tw does not exceed the minimum cooling medium temperature Tws, the turbine housing 34 may be overcooled and the chips may come into contact as described above.

  On the other hand, when it is determined in step S302 that the cooling medium temperature Tw exceeds the minimum cooling medium temperature Tws, that is, "Yes", the process proceeds to step S303, and the tip clearance control is started (ON).

  In this tip clearance control, the flow rate Gc of the cooling medium is controlled so that the target cooling medium flow rate Gctgt is set as Gc = f (PS) according to the current engine output PS. That is, as described above, the control value of the target coolant flow rate Gctgt stored as a map corresponding to the engine output PS and the coolant temperature Tw is set, and the pump 42 is controlled accordingly. is there. The current engine output PS is obtained by calculation in the ECU 60 based on the intake air amount Ga obtained from the detection signal from the air flow meter 19 and the engine speed Ne obtained from the detection signal from the crank angle sensor 50. Here, in the present embodiment, the flow rate Gc of the cooling medium is corrected as Gc = f (PS, To) using the atmospheric temperature To as an increasing / decreasing element. That is, when the atmospheric temperature To is higher than the reference temperature, it is considered that the heat radiation from the turbine housing 34 is also reduced. In this case, the coolant flow rate Gc is increased and corrected based on the target coolant flow rate Gctgt. When To is lower than the reference temperature, the amount of weight is corrected.

  Next, in step S304, it is determined whether there has been an acceleration request for the engine 10 that exceeds a predetermined value. Specifically, based on a signal from the accelerator opening sensor 51, it is determined whether or not the accelerator pedal depression amount exceeds a predetermined amount. When the acceleration request does not exceed the predetermined value, the process returns to step S303, and the tip clearance control according to the current engine output PS is continued. On the other hand, when the acceleration request exceeds a predetermined value, the process proceeds to step S305, and acceleration request correction is performed. Specifically, the target coolant flow rate value is corrected so as to increase. In other words, the flow rate Gc of the cooling medium is controlled so that its target value is increased to (target cooling medium flow rate Gctgt + α) and becomes the target cooling medium flow rate Gctgt + α as Gc = f (PS) + α. This state will be described with reference to FIG. 5. From the state in which the tip clearance 35 is controlled along the target coolant flow rate Gctgt represented by the lower curve aa so as to have a predetermined value d, the coolant flow rate Gc. Is increased by α (shown as ↑ + α in FIG. 5).

  In this way, at the time of an acceleration request that requires an increase in the output of the engine 10, the target coolant flow rate value is increased. As a result, the coolant flow rate Gc is increased, and thermal expansion of the turbine housing 34 is suppressed. Further, the tip clearance 35 can be further reduced to increase the turbine efficiency, and the output of the engine 10 according to the acceleration request can be obtained quickly.

  In step S306, it is determined whether or not there has been a deceleration request for the engine 10 that exceeds a predetermined value. Specifically, based on the signal from the accelerator opening sensor 51, it is determined whether or not the accelerator pedal is released. When the deceleration request does not exceed the predetermined value, the process returns to step S303, and the tip clearance control according to the current engine output PS is continued. On the other hand, when the deceleration request exceeds a predetermined value, the process proceeds to step S307, and deceleration request correction is performed. Specifically, the target coolant flow rate value is corrected so as to decrease. In other words, the flow rate Gc of the cooling medium is corrected so that the target value is reduced to (target cooling medium flow rate Gctgt−β), and Gc = f (PS) −β is set to the target cooling medium flow rate Gctgt−β. It is done. This state will be described with reference to FIG. 5. From the state in which the tip clearance 35 is controlled along the target coolant flow rate Gctgt represented by the lower curve aa so as to be the predetermined value d, the coolant flow rate is changed. Gc is decreased by β (indicated as ↓ −β in FIG. 5).

  In this way, when the deceleration request is not required for the output of the engine 10, the coolant flow rate Gc is reduced as a result of the target coolant flow rate value being decreased, and the thermal expansion of the turbine housing 34 is not suppressed. 35 is larger than usual. Therefore, since the turbine efficiency is lowered, the engine brake can be operated effectively.

  Note that the tip clearance 35 of the turbine 30 may have variations due to the manufacturing accuracy of individual components. As a result, the target turbine housing temperature Thttgt at which the above-described tip clearance 35 is set to the predetermined value d may differ individually. Therefore, the chip clearance at the time of manufacturing is determined as an initial chip clearance df by a measuring means or an estimating means such as a gap sensor or a gap gauge, and by taking into account the difference between the determined initial chip clearance df and a predetermined value d, The target coolant flow rate Gctgt described above may be corrected. For example, by correcting the target coolant flow rate Gctgt to be increased so that the coolant flow rate Gc is increased when the difference is large, high-precision control can be performed regardless of manufacturing variations of individual components. .

It is a system diagram showing an outline of a turbine housing cooling system of an engine equipped with a turbocharger to which the present invention is applied. 1 is a partial cross-sectional view of a turbine housing according to an embodiment of the present invention. It is a flowchart which shows an example of the tip clearance control of embodiment of this invention. It is a graph for demonstrating the relationship between engine output PS and the temperature Tht of the metal which comprises the turbine housing. 6 is a graph showing a relationship between a coolant flow rate Gc to be flowed to obtain a turbine housing temperature Tht shown in FIG. 4 and an engine output PS.

Explanation of symbols

DESCRIPTION OF SYMBOLS 10 Engine 18 Turbocharger 20 Compressor 30 Turbine 32 Turbine rotor 33 Turbine rotor blade 34 Turbine housing 35 Chip clearance 36 Cooling passage 40 Cooling medium circulation passage 41 Livestock heat tank 42 Pump 43 Cooling medium temperature sensor 50 Crank angle sensor 51 Accelerator opening sensor 60 Electronic control unit (ECU)
PS Engine output Tht Turbine housing temperature Thtmin Minimum turbine housing temperature Thhtgt Target turbine housing temperature Gc Coolant flow rate Gcmax Maximum coolant flow rate Gctgt Target coolant flow rate Tw Coolant temperature Tws Minimum coolant temperature To Atmosphere temperature

Claims (4)

In a turbocharger for a vehicle engine comprising a turbine housing provided with a cooling passage,
Flow rate changing means for changing the flow rate of the cooling medium circulating in the cooling passage;
Cooling medium flow rate control means for controlling the flow rate of the cooling medium by the flow rate changing means based on the temperature of the cooling medium and the operating state of the engine so that the tip clearance is within a predetermined range;
A turbine housing cooling system comprising: Acceleration / deceleration request detection means for detecting an acceleration / deceleration request to the engine;
Correction means for correcting a target coolant flow rate value by the coolant flow rate control means in response to an acceleration request or a deceleration request detected by the acceleration / deceleration request detection means;
The turbine housing cooling system according to claim 1, further comprising: The turbine housing cooling system according to claim 1 or 2, wherein the cooling medium is cooling water and is stored in a livestock heat tank. The turbine housing cooling system according to any one of claims 1 to 3, wherein the acceleration / deceleration request detecting means detects an accelerator opening.

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