JP2008019711A - Supercharger system of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a supercharger system of an internal combustion engine, which both reduces heat capacity of a turbine housing and improves turbo efficiency, at the same time. <P>SOLUTION: The heat capacity of the turbine housing 2 is reduced by adopting an aluminum alloy as a constituting material of the turbine housing 2. The turbine housing 2 is cooled by engine cooling water so that the ratio of the temperature of the turbine housing 2 and the temperature of a turbine wheel 51, becomes the relationship of the reciprocal ratio, to the ratio of an expansion coefficient of the constituting material of the turbine housing 2 and an expansion coefficient of a constituting material of the turbine wheel 51. Thus, both early activation of a catalyst by reduction in the heat capacity of the turbine housing 2 and continuous security of high turbo efficiency by maintenance of a tip clearance, are made compatible. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a supercharger system mounted on an internal combustion engine such as an automobile engine. In particular, the present invention relates to measures for achieving both a reduction in the heat capacity of the turbine housing and an improvement in turbo efficiency.

  2. Description of the Related Art Conventionally, in an automobile engine, a turbocharger (hereinafter referred to as a turbocharger) that increases the air density by compressing intake air using the fluid energy of exhaust gas and thereby increasing the engine output is known. ing. In this turbocharger, a turbine shaft includes a turbine wheel provided in the turbine housing and disposed in the turbine housing, and a compressor wheel (also referred to as an impeller) disposed in the compressor housing and disposed in the intake passage. And a turbo rotor connected to each other. When the turbine wheel is rotated by the pressure of the exhaust gas, the rotational force is transmitted to the compressor wheel via the turbine shaft, and the intake air is supercharged toward the combustion chamber by the rotation of the compressor wheel.

  Incidentally, an exhaust system of an automobile engine or the like is provided with a catalytic converter for purifying exhaust gas. In general, the catalytic converter uses a heat of the exhaust gas to heat a catalyst (for example, a three-way catalyst) and raises the catalyst to a predetermined activation temperature so as to exhibit an exhaust gas purification function. It has become. Therefore, particularly when the engine is cold started, the exhaust gas purification function is not exhibited until the catalyst temperature reaches the activation temperature. Therefore, there is a demand for a structure for rapidly increasing the catalyst temperature.

  However, when the turbocharger as described above is mounted on an engine, the constituent material of the turbine housing is generally steel (heat-resistant cast steel), and since its heat capacity is large, the heat of the exhaust gas at the cold start is Most of it will be taken away by the turbine housing. For this reason, the temperature of the exhaust gas passing through the catalytic converter becomes low, and it becomes difficult to activate the catalyst at an early stage.

In view of this point, for example, in Patent Document 1 and Patent Document 2 described below, a turbine housing is formed of an aluminum alloy having a specific heat lower than that of steel, and the heat capacity thereof is reduced. As a result, the amount of heat taken away by the turbine housing at the time of cold start of the engine is reduced, and early activation of the catalyst accompanying rapid increase of the catalyst temperature is realized.
Japanese Utility Model Publication No. 64-34404 JP 2005-163786 A

  However, simply changing the constituent material of the turbine housing to an aluminum alloy causes a new problem as described below.

  That is, there is a difference between the expansion coefficient (linear expansion coefficient) of the material (aluminum alloy) constituting the turbine housing and the expansion coefficient (linear expansion coefficient) of the material (for example, heat-resistant steel) constituting the turbine wheel ( Since the aluminum alloy has a larger linear expansion coefficient, the distance between the two (the turbine wheel blade and the turbine housing inner surface) depends on the difference between the turbine wheel expansion rate and the turbine wheel expansion rate when the turbocharger is driven. (Hereinafter referred to as chip clearance). In general, it is preferable to set the tip clearance to a small dimension of about 0.5 mm. However, the tip clearance may be, for example, 0.8 mm or more due to the difference in expansion coefficient between the above materials.

  This significantly increases the amount of exhaust gas introduced into the turbocharger that passes through the tip clearance (exhaust gas that passes through without giving fluid energy to the turbine wheel), and deteriorates turbo efficiency. Will be invited. If the constituent material of the turbine housing and the constituent material of the turbine wheel are made the same material, that is, if the turbine wheel is made of an aluminum alloy, the above-mentioned problem is unlikely to occur, but it is not possible to apply an aluminum alloy as the constituent material of the turbine wheel. Difficult in terms of heat resistance.

  Thus, while adopting an aluminum alloy as the constituent material of the turbine housing so far, the heat capacity of the turbine housing is reduced to enable a rapid increase in the catalyst temperature, while the tip clearance is reduced to a small value (for example, 0. 0). The actual situation is that no effective technique has been proposed yet to maintain (at about 5 mm).

  The present invention has been made in view of such points, and an object of the present invention is to provide a supercharger system for an internal combustion engine that can achieve both a reduction in the heat capacity of a turbine housing and an improvement in turbo efficiency. It is to provide.

-Solving principle-
The solution principle of the present invention devised to achieve the above object is to reduce the heat capacity of the turbine housing by adopting an aluminum alloy as the constituent material of the turbine housing, and to reduce the heat capacity of the turbine housing and the turbine wheel. The turbine housing is cooled in accordance with the difference in expansion coefficient from the constituent material, so that the expansion amount of the turbine housing and the expansion amount of the turbine wheel are substantially matched, thereby preventing the tip clearance from changing.

-Solution-
Specifically, the present invention relates to an internal combustion engine that supercharges intake air by rotating a turbine wheel housed in a turbine housing by receiving fluid energy of exhaust gas and transmitting the rotational force to the compressor wheel. Assume a feeder system. For the turbocharger system of the internal combustion engine, the constituent material of the turbine housing is an aluminum alloy, and the constituent material of the turbine wheel is steel (carbon steel). When the ratio of the coefficient of expansion of the constituent material of the turbine housing to the coefficient of expansion of the constituent material of the turbine wheel is “N: 1” (N includes not only an integer but also a decimal number), the temperature of the turbine housing The turbine housing is provided with a cooling means for cooling the turbine housing with a cooling medium so that the ratio of the turbine wheel to the temperature is substantially the inverse ratio “1: N” of the ratio of the expansion coefficients.

  Due to this specific matter, the temperature of the turbine housing and the turbine wheel both rise due to the heat of the exhaust gas as the turbocharger is driven during the operation of the internal combustion engine. At this time, since the turbine housing is made of an aluminum alloy having a specific heat smaller than that of heat-resistant cast steel that is generally used, the heat capacity of the turbine housing as a whole is greatly reduced. For this reason, it is possible to significantly reduce the amount of heat taken away by the turbine housing, particularly when the engine is cold started. Therefore, the catalyst temperature of the catalytic converter can be raised to the activation temperature within a short time after the engine is started, and early activation of the catalyst can be realized. Moreover, weight reduction as the whole supercharger can be achieved by making the turbine housing into an aluminum alloy.

  In the state where the temperature of both the turbine housing and the turbine wheel has risen, the turbine housing is cooled by the cooling means using the cooling medium, and the temperature of the turbine housing is set lower than the temperature of the turbine wheel. When the turbine housing is cooled, when the ratio of the expansion coefficient of the constituent material (aluminum alloy) of the turbine housing to the expansion coefficient of the constituent material (steel) of the turbine wheel is “N: 1”, the turbine housing The ratio between the temperature of the turbine and the temperature of the turbine wheel is set to be substantially the reverse ratio “1: N” of the ratio between the expansion coefficients. That is, the turbine housing is cooled by the cooling medium so that the temperature of the turbine housing becomes “1 / N” of the temperature of the turbine wheel. Thereby, the expansion amount of the turbine housing due to heat and the expansion amount of the turbine wheel substantially coincide with each other, and the tip clearance between them does not vary. That is, the inner diameter dimension of the turbine housing is increased by the increase of the outer diameter dimension (blade outer diameter dimension) due to the expansion of the turbine wheel, and the tip clearance between the two is maintained at a predetermined dimension. For this reason, even when the tip clearance is set to a very small value (for example, 0.5 mm) in advance, the value is continuously maintained.

  As described above, according to this solution, it is possible to achieve both early activation of the catalyst by reducing the heat capacity of the turbine housing and continuous securing of high turbo efficiency by maintaining the tip clearance.

  Specifically, the cooling means is a cooling water passage formed inside the turbine housing, and the cooling water passage for cooling the internal combustion engine (engine cooling water) as a cooling medium is allowed to flow through the cooling water passage. It is configured to cool.

  According to this, the turbine housing can be cooled using the existing cooling water for cooling the internal combustion engine, and a cooling structure for the turbine housing can be realized with a simple design change. Further, according to this configuration, heat exchange between the cooling water and the exhaust gas is performed inside the supercharger, so that the heat in the exhaust gas can be given to the cooling water, and the temperature of the cooling water is increased. It can be performed rapidly and the warm-up operation of the internal combustion engine can be completed early. As a result, the temperature of the lubricating oil (engine oil) of the internal combustion engine is rapidly increased, and the time until the oil obtains a desired viscosity (the time until the oil viscosity decreases to a predetermined value) is shortened. In addition, the effect of reducing the friction caused by the oil after starting the internal combustion engine can be obtained at an early stage, which can contribute to the improvement of the fuel consumption of the internal combustion engine.

  The temperature of the turbine housing and the turbine wheel varies depending on the operating condition of the internal combustion engine. For this reason, in order to maintain the above-mentioned tip clearance with high accuracy, it is preferable to change the cooling state with respect to the turbine housing corresponding to these fluctuating temperatures. The following are mentioned as a configuration in view of this point. That is, the cooling medium adjusting means is provided for adjusting the temperature or flow rate of the cooling medium so that the ratio between the temperature of the turbine housing and the temperature of the turbine wheel approaches the inverse ratio of the expansion coefficients.

  In this case, specific examples of the adjusting operation by the cooling medium adjusting means include the following. First, a wheel temperature estimating means for estimating the temperature of the turbine wheel based on the operating state of the internal combustion engine is provided. The cooling medium adjusting means adjusts the temperature or flow rate of the cooling medium according to the temperature of the turbine wheel estimated by the wheel temperature estimating means so that the lower the turbine wheel temperature, the higher the ability to cool the turbine housing. It is configured to do.

  According to this configuration, the temperature of the turbine housing can be changed so as to follow the change in the temperature of the turbine wheel. That is, for example, when the exhaust gas temperature is low and the temperature of the turbine wheel is low, such as when the internal combustion engine is running at a low speed, the cooling capacity for the turbine housing is set high. For example, the temperature of the cooling medium supplied to the turbine housing is set low, or the flow rate of the cooling medium is set high. On the other hand, for example, when the exhaust gas temperature is high and the temperature of the turbine wheel is also high, such as when the internal combustion engine is rotating at high speed, the cooling capacity for the turbine housing is set low. For example, the temperature of the cooling medium supplied to the turbine housing is set high, or the flow rate of the cooling medium is set low. By such an operation, control is performed so that the ratio between the temperature of the turbine housing and the temperature of the turbine wheel approaches the inverse ratio of the ratios of the expansion coefficients. As a result, the tip clearance can be maintained with high accuracy, and high turbo efficiency can be continuously maintained.

  The present invention also includes the following technical idea. That is, it is based on a supercharger system for an internal combustion engine in which a turbine wheel housed in a turbine housing rotates by receiving fluid energy of exhaust gas and supercharges intake air by transmitting the rotational force to the compressor wheel. To do. For the turbocharger system of the internal combustion engine, the exhaust gas passage area in the plane orthogonal to the exhaust gas flow line in the turbine housing is the Mach coefficient (exhaust gas flow velocity / sound velocity) at the maximum exhaust gas flow rate. Is set to be substantially “1”.

  When the flow passage area in the turbine housing is set in this way, the flow passage in the turbine wheel (for example, the maximum flow rate of the exhaust gas discharged to the exhaust system, which is the highest temperature) In the scroll chamber, the gas flow rate is high in the central portion of the flow path cross section, and the exhaust gas having a relatively high temperature flows through this portion. On the other hand, the gas flow rate in the outer peripheral portion of the flow path cross section is low, and the exhaust gas having a relatively low temperature flows through this portion. For this reason, the amount of heat in the exhaust gas transmitted to the turbine housing and the turbine wheel is also kept low. Therefore, the amount of heat taken away by the turbine housing and the turbine wheel can be greatly reduced, particularly during cold start of the engine, and the catalyst temperature of the catalytic converter can be raised to the activation temperature within a short time after the engine is started. And early activation of the catalyst can be realized.

  In the present invention, the heat capacity of the turbine housing is reduced by adopting an aluminum alloy as a constituent material of the turbine housing. Further, the turbine housing is configured such that the ratio of the temperature of the turbine housing and the temperature of the turbine wheel has a substantially inverse relationship with respect to the ratio of the expansion coefficient of the constituent material of the turbine housing and the expansion coefficient of the constituent material of the turbine wheel. Is cooling. For this reason, the catalyst temperature of the catalytic converter can be raised to the activation temperature within a short time after the internal combustion engine is started, the catalyst can be activated early, and the chip clearance can be reduced to a very small value. Even if it is set, the value can be continuously maintained, and high turbo efficiency can be continuously secured.

  Hereinafter, embodiments of the present invention will be described with reference to the drawings. In the present embodiment, a case where the present invention is applied to a single turbo turbocharger mounted on an automobile diesel engine will be described. The present invention is not limited to this, and the present invention can also be applied to a hybrid turbocharging system provided with a twin turbo turbocharger, a sequential turbo turbocharger, and a supercharger.

(First embodiment)
-Configuration explanation of turbocharger-
FIG. 1 is a longitudinal sectional view of a turbocharger 1 according to this embodiment. The turbocharger 1 is accommodated in a turbine housing 2 provided in an exhaust passage of the engine and is rotated by exhaust gas fed into the turbine housing 2, and a compressor housing provided in an intake passage of the engine. 3 and a compressor wheel 52 that receives the rotational force of the turbine wheel 51 and forcibly feeds air (intake air) into the combustion chamber.

  The turbine wheel 51 and the compressor wheel 52 are connected to each other by a metal (for example, cast iron) turbine shaft 53 so as to be integrally rotatable. That is, the turbine wheel 51, the compressor wheel 52, and the turbine shaft 53 are arranged on the same axis, and are integrally assembled to constitute the turbo rotor 5. As the turbine wheel 51 rotates, the turbine shaft 53 and the compressor The wheel 52 is configured to rotate around this axis.

  The turbine wheel 51 includes a large number of turbine blades 51a, 51a,. The turbine wheel 51 is made of heat-resistant steel (carbon steel) because it is exposed to high-temperature (for example, 600 to 800 ° C.) exhaust gas. In addition, a scroll chamber 21 having a spiral shape is formed in the turbine housing 2 so as to surround the turbine wheel 51. The scroll chamber 21 has an exhaust gas intake port that opens in the tangential direction of the turbo rotor 5 and an exhaust gas discharge port 22 that opens in the axial direction of the turbo rotor 5. The exhaust gas intake port is connected to an exhaust manifold of the internal combustion engine, and the exhaust gas discharge port 22 is connected to an exhaust pipe that guides the exhaust gas to the catalytic converter.

  On the other hand, the compressor wheel 52 includes a large number of compressor blades 52a, 52a,. The compressor wheel 52 is made of a lightweight aluminum alloy or synthetic resin in order to suppress turbo lag. A spiral diffuser 31 is formed in the compressor housing 3 so as to surround the compressor wheel 52. The diffuser 31 has an intake air inlet 32 that opens in the axial direction of the turbo rotor 5 and a supercharged air outlet that opens in the tangential direction of the turbo rotor 5. The air supply intake 32 is connected to an air cleaner, and the supercharged air discharge is connected to an intake manifold of the internal combustion engine.

  The shape of the turbine wheel 51 is not particularly limited, and an impact type, a reflection type, a mixed flow type, or the like can be adopted. Similarly, the shape of the compressor wheel 52 is not particularly limited, and a radial type, a backward type, a backward lake type, or the like can be adopted. In the turbo rotor 5 of the present embodiment, the turbine wheel 51, the compressor wheel 52, and the turbine shaft 53 are formed as separate bodies, and these are integrally assembled. However, even if these are integrally formed, Good.

  The turbine shaft 53 is inserted through a bearing member 41 formed in the bearing housing 4. The bearing member 41 has a cylindrical space formed therein, and a bearing metal 42 as a bearing is loosely fitted on the inner peripheral surface thereof. Further, the inner peripheral surface of the bearing metal 42 is loosely fitted to the turbine shaft 53. That is, the bearing metal 42 is disposed in a sliding portion between the turbine shaft 53 and the bearing member 41. Further, lubricating oil is supplied to the bearing metal 42 from a lubricating oil supply passage 43 formed in the bearing housing 4. By supplying the lubricating oil, an oil film is formed between the inner peripheral surface of the bearing member 41 and the outer peripheral surface of the bearing metal 42. On the other hand, in the bearing metal 42, oil supply holes 42a penetrating from the outer peripheral surface to the inner peripheral surface are formed at a plurality of locations. Therefore, the lubricating oil supplied to the outer peripheral surface of the bearing metal 42 is also supplied to the inner peripheral surface of the bearing metal 42 through the plurality of oil supply holes 42 a, and the inner peripheral surface of the bearing metal 42 and the turbine shaft 53. An oil film is also formed between the outer peripheral surface. Thus, the bearing system of the turbine shaft 53 in the present embodiment is a so-called floating bearing system, and the bearing metal 42 can freely rotate between the turbine shaft 53 and the bearing member 41. ing. The bearing metal 42 is restricted from moving in the axial direction by the snap rings 44 and 44. The bearing structure having such a configuration is provided at both ends in the longitudinal direction of the turbine shaft 53 (two locations, a location close to the turbine wheel 51 and a location close to the compressor wheel 52).

  The bearing housing 4 is made of the same material as the turbine shaft 53 (for example, cast iron). Thereby, the amount of expansion of the bearing housing 4 due to heat and the amount of expansion of the turbine shaft 53 are made substantially equal, and a good bearing state is continuously maintained. Moreover, it is preferable that the constituent material of the said compressor wheel 52 and the compressor housing 3 is also the same material.

  The feature of the present embodiment is the constituent material of the turbine housing 2 and the structure for cooling the turbine housing 2. This will be specifically described below.

  The turbine housing 2 in the present embodiment is formed of an aluminum alloy (an alloy containing aluminum, silicon, copper, or the like). This aluminum alloy has a smaller specific heat than heat-resistant cast steel that has been generally used as a constituent material of the turbine housing 2 until now. For this reason, the heat capacity of the turbine housing 2 as a whole can be significantly smaller than that of the conventional one, and the amount of heat taken away by the turbine housing 2 when the engine is cold started can be reduced. As a result, after the engine is started, the catalyst temperature of the catalytic converter can be raised to the activation temperature within a short time, and early activation of the catalyst can be realized. Further, the overall weight of the turbocharger 1 can be reduced.

  Further, as a structure for cooling the turbine housing 2, a cooling water passage (cooling in the housing) is provided in the turbine housing 2 at a position close to the scroll chamber 21 and around the exhaust gas discharge port 22. Means) 23 is formed. The cooling water passage 23 in the housing has an upstream end connected to the discharge side of the water pump 63 via an introduction pipe H3, which will be described later, while a downstream end thereof is connected to the discharge side of the water pump 63, via an outlet pipe H6, which will be described later. It is connected to the suction side (details will be described later using FIG. 2). Therefore, as the water pump 63 is driven, engine cooling water (cooling medium) is introduced into the in-housing cooling water passage 23 via the introduction pipe H3, and the turbine housing 2 is cooled by this cooling water. Is returned to the water pump 63 via the outlet pipe H6. The cooling water is cooled by the radiator 61 as necessary.

  As another feature of the present embodiment, the flow passage area in a plane orthogonal to the exhaust gas stream line in the space in the turbine housing 2 (for example, the scroll chamber 21) is the exhaust gas. The Mach coefficient at the maximum flow rate is set to be substantially “1”. Parameters for setting the Mach coefficient at the maximum exhaust gas flow rate include engine displacement, engine output, exhaust gas temperature, turbine scroll area, and the like. That is, by appropriately setting these parameters, the turbocharger 1 is designed so that the Mach coefficient at the maximum exhaust gas flow rate is substantially “1”.

  When the flow passage area in the turbine housing 2 is set in this way, the exhaust gas temperature exhausted to the exhaust system is at the highest temperature at the maximum exhaust gas flow rate. In the flow path (such as the scroll chamber 21), the gas flow rate in the central portion of the cross section of the flow path is high, and exhaust gas having a relatively high temperature flows through this portion. The exhaust gas having a low temperature and a relatively low temperature flows through this portion. For this reason, the high temperature region of the exhaust gas is not exposed to the turbine housing 2 and the turbine wheel 51, and the amount of heat in the exhaust gas transmitted to the turbine housing 2 and the turbine wheel 51 can be kept low. it can. For this reason, the amount of heat taken away by the turbine housing 2 and the turbine wheel 51 can be greatly reduced, particularly at the time of cold start of the engine. Also with this configuration, the catalyst of the catalytic converter can be obtained within a short time after the engine is started. The temperature can be raised to the activation temperature, and early activation of the catalyst can be realized.

-Explanation of cooling water circulation path-
Hereinafter, the cooling water circulation path of the engine according to the present embodiment will be described. FIG. 2 is a circuit diagram showing an outline of a cooling water circulation path according to the present embodiment. As shown in FIG. 2, the cooling water circulation path includes a radiator 61, a thermostat 62, a water pump 63, the turbocharger 1, the devices 61, 62, 63, 1, and a water jacket 64 formed in the engine body E. Piping and hoses H1, H2, H3, H4, H5, and H6 are provided.

  Specifically, the lower tank 61a of the radiator 61 and the thermostat 62 are connected by the lower hose H1, and the discharge port of the water pump 63 communicates with the water jacket 64 of the engine body E. In the water jacket 64, the cooling water from the water pump 63 passes through the water jacket 64a on the cylinder block side, is introduced into the water jacket 64b on the cylinder head side, and is then taken out from the engine body E by the take-out pipe H2. This take-out pipe H2 is branched, one is connected to the in-housing cooling water passage 23 of the turbocharger 1 by the introduction pipe H3, and the other is connected to the upper tank 61b of the radiator 61 by the upper hose H4. The upper hose H4 and the suction side of the water pump 63 are connected by a cold bypass hose H5.

  The in-housing cooling water passage 23 of the turbocharger 1 is connected to the suction side of the water pump 63 by a lead-out pipe H6. That is, after a part of the cooling water taken out from the engine main body E by the take-out pipe H2 is introduced into the in-housing cooling water passage 23 of the turbocharger 1 by the introduction pipe H3, this cooling water is sent by the outlet pipe H6 to the water pump 63. It is configured to be returned to the suction side.

  The introduction pipe H3 is provided with a solenoid valve 24 that can be freely opened and closed. That is, when the electromagnetic valve 24 is in the open state, cooling water is introduced into the in-housing cooling water passage 23 of the turbocharger 1 and the turbine housing 2 is cooled. On the other hand, when the electromagnetic valve 24 is in the closed state, The cooling water is not introduced into the in-housing cooling water passage 23 of the charger 1 and the cooling operation of the turbine housing 2 is not performed. The opening / closing control of the electromagnetic valve 24 will be described later.

  Hereinafter, the configuration and function of each device constituting the cooling water circulation path will be briefly described.

  The radiator 61 in the present embodiment is of a down flow type, and a radiator core 61c is provided between the upper tank 61b and the lower tank 61a. As a result, when the cooling water collected from the engine body E through the take-out pipe H2 and the upper hose H4 flows down to the lower tank 61a through the inside of the radiator core 61c, the outside air (air flow by driving air or a cooling fan is driven). The cooling water is cooled by exchanging heat with the air and radiating heat to the outside air.

  The thermostat 62 adjusts the temperature of the cooling water by switching the water channel of the cooling water circulation path. For example, the thermostat 62 uses the thermal expansion of wax sealed inside, and the valve provided in accordance with the temperature of the cooling water. A mechanism to be opened and closed is provided. When the engine body E is cold, that is, when the cooling water temperature is relatively low, the valve of the thermostat 62 is closed and the water path between the lower tank 61a of the radiator 61 and the water pump 63 is shut off, and the radiator By not supplying cooling water to 61, the warm-up operation of the engine body E can be completed early. On the other hand, after the engine body E has been warmed up, that is, when the coolant temperature is relatively high, the valve of the thermostat 62 is opened, and the water path between the lower tank 61a of the radiator 61 and the water pump 63 is opened. By flowing a part of the cooling water through the radiator 61, the heat recovered by the cooling water is released to the atmosphere by the radiator 61.

  The water pump 63 is for generating a water flow in the cooling water circulation path, and a transmission belt is stretched between a water pump pulley and a crankshaft pulley provided on the drive shaft. It is driven by the rotational force of the crankshaft.

-Cooling water circulation operation and cooling operation of the turbine housing 2-
Next, the cooling water circulation operation in the above-described cooling water circulation path will be described.

  First, the cooling water circulation operation at the time of cold start of the engine will be described. At the time of the cold start, the thermostat 62 is in a closed state and the electromagnetic valve 24 provided in the introduction pipe H3 is in an open state. As the cooling water circulation operation, the cooling water flows in the order of the water pump 63, the water jacket 64, and the take-out pipe H2, as indicated by solid arrows in FIG. And the cooling water taken out from the engine main body E by this taking-out pipe H2 is shunted to the introduction pipe H3 and the cold time bypass hose H5. The cooling water divided into the introduction pipe H3 is introduced into the in-housing cooling water passage 23 of the turbocharger 1, and after cooling the turbine housing 2, it is sucked into the water pump 63 through the outlet pipe H6. Further, the cooling water diverted to the cold time bypass hose H <b> 5 is also returned to the suction side of the water pump 63. Thus, a relatively small amount of cooling water is circulated by bypassing the radiator 61, and the heat dissipation operation in the radiator 61 is not performed, so that the engine warm-up is completed at an early stage.

  As described above, the turbine housing 2 is formed of an aluminum alloy, and the heat capacity of the turbine housing 2 as a whole is small. Therefore, at the time of such cold start, the turbine housing 2 takes away the heat in the exhaust gas. The amount of heat generated is small, so that a relatively high temperature exhaust gas can be passed through the catalytic converter. For this reason, the catalyst temperature of the catalytic converter can be raised to the activation temperature within a short time after the engine is started, and early activation of the catalyst can be realized.

  Further, according to such a cooling water circulation operation, heat exchange between the cooling water and the exhaust gas (heat exchange between the turbine housing 2 and the cooling water) is performed inside the turbocharger 1. The cooling water receives not only the heat received from the engine body E but also the heat of the exhaust gas, so that the temperature can be rapidly increased. For this reason, the engine warm-up operation can be completed at an early stage, and the temperature of the engine oil can be increased quickly, so that the effect of reducing the friction caused by the oil after starting the engine can be obtained at an early stage. It can contribute to improvement.

  Next, the cooling water circulation operation after the engine warm-up operation is completed will be described. In this case, the thermostat 62 is opened, and the opening / closing operation of the electromagnetic valve 24 provided in the introduction pipe H3 is controlled.

  The opening / closing operation of the electromagnetic valve 24 will be described. The ROM in the engine controller stores a wheel temperature estimation map for estimating the temperature of the turbine wheel 51 on the basis of the engine speed, the engine load, and the coolant temperature, and the estimation of the turbine wheel 51 from the wheel temperature estimation map. The temperature is read out (turbine wheel temperature estimation operation by the wheel temperature estimation means in the present invention). When the temperature of the turbine wheel 51 is equal to or higher than a predetermined temperature, the solenoid valve 24 is closed to lower the cooling capacity for the turbine housing 2 so that the temperature of the turbine wheel 51 can be quickly followed (described later). As described above, the temperature of the turbine housing 2 is allowed to rise (so that the temperature of the turbine housing 2 does not fall below a half value of the temperature of the turbine wheel 51). On the other hand, when the temperature of the turbine wheel 51 is lower than the predetermined temperature, the solenoid valve 24 is opened so that the temperature of the turbine housing 2 is sufficiently lower than the temperature of the turbine wheel 51 (as described later, the turbine housing 2 The cooling capacity for the turbine housing 2 is increased so that the temperature of the turbine housing 51 does not exceed half the temperature of the turbine wheel 51.

  By adjusting the cooling capacity for the turbine housing 2 in this manner, the ratio between the expansion coefficient of the aluminum alloy that is the constituent material of the turbine housing 2 and the expansion coefficient of the steel that is the constituent material of the turbine wheel 51 is “N: 1. ”, The ratio of the temperature of the turbine housing 2 and the temperature of the turbine wheel 51 is set to be substantially the reverse ratio“ 1: N ”of the ratio of the expansion coefficients. That is, the turbine housing 2 is cooled by the cooling water so that the temperature of the turbine housing 2 becomes “1 / N” of the temperature of the turbine wheel 51.

More specifically, for example, the linear expansion coefficient of an aluminum alloy that is a constituent material of the turbine housing 2 is about 20 × 10 ⁻⁶ , and the expansion coefficient of steel that is a constituent material of the turbine wheel 51 is about 10 × 10 ^−6. In this case, the ratio between the expansion coefficient of the aluminum alloy and the expansion coefficient of the steel is “2: 1”. At this time, when the temperature of the turbine wheel 51 is 600 ° C., which is a value close to the exhaust gas temperature, the temperature of the turbine housing 2 is ½ of the temperature of the turbine wheel 51, that is, 300 ° C. Thus, the cooling capacity for the turbine housing 2 is changed by opening / closing control of the electromagnetic valve 24. These values are not limited to this, and can be set arbitrarily.

  In other words, the ratio between the temperature of the turbine housing 2 and the temperature of the turbine wheel 51 so as to have an inverse relationship with respect to the ratio between the expansion coefficient of the constituent material of the turbine housing 2 and the expansion coefficient of the constituent material of the turbine wheel 51. Is adjusted so that the expansion coefficient of the aluminum alloy that is the constituent material of the turbine housing 2, the expansion coefficient of the steel that is the constituent material of the turbine wheel 51, and the opening / closing operation of the electromagnetic valve 24 are switched. Is set appropriately.

  Hereinafter, a specific cooling water circulation operation will be described. As indicated by the dashed arrows in FIG. 2, the cooling water flows in the order of the water pump 63, the water jacket 64, and the take-out pipe H2. And the cooling water taken out from the engine main body E by this taking-out pipe H2 is divided into the introduction piping H3 and the upper hose H4. When the estimated temperature of the turbine wheel 51 is relatively low and the solenoid valve 24 is in an open state, the cooling water divided into the introduction pipe H3 is introduced into the in-housing cooling water passage 23 of the turbocharger 1, After the turbine housing 2 is cooled, it is sucked into the water pump 63 through the outlet pipe H6. Further, the cooling water divided into the upper hose H4 is returned to the radiator 61.

  On the other hand, when the estimated temperature of the turbine wheel 51 is relatively high and the solenoid valve 24 is in a closed state, cooling water is not introduced into the introduction pipe H3, and the turbine housing 2 is not cooled. . For this reason, all the cooling water flowing through the take-out pipe H2 is returned to the radiator 61 through the upper hose H4.

  By the above cooling water circulation operation, the heat of the cooling water is discharged to the atmosphere by the radiator 61 to cool the cooling water, the engine body E is maintained at an appropriate temperature, and the temperature of the turbine wheel 51 is less than a predetermined temperature so that the solenoid valve When 24 is in an open state, a cooling operation for the turbine housing 2 is performed.

  In this way, the cooling capacity for the turbine housing 2 is adjusted according to the temperature of the turbine wheel 51, and the expansion coefficient of the constituent material (aluminum alloy) of the turbine housing 2 and the expansion coefficient of the constituent material (steel) of the turbine wheel 51 are When the ratio is “N: 1”, the ratio between the temperature of the turbine housing 2 and the temperature of the turbine wheel 51 is set to be substantially the reverse ratio “1: N” of the ratio between the expansion coefficients. For this reason, the expansion amount of the turbine housing 2 due to heat and the expansion amount of the turbine wheel 51 substantially coincide with each other, and the tip clearance between them does not fluctuate. That is, the inner diameter dimension of the turbine housing 2 is increased by the increase in the outer diameter dimension (the outer diameter dimension of the turbine blade 51a) due to the expansion of the turbine wheel 51, and the tip clearance between the two is maintained at a predetermined dimension. . For this reason, even if the tip clearance is set to a very small value (for example, 0.5 mm) in advance, the value is continuously maintained, and high turbo efficiency is continuously secured. be able to.

  In the opening / closing control of the electromagnetic valve 24 in the above-described embodiment, the opening / closing of the electromagnetic valve 24 is switched depending on whether or not the estimated temperature of the turbine wheel 51 is equal to or higher than a predetermined temperature. According to this, the relationship between the expansion coefficient of the constituent material of the turbine housing 2 and the expansion coefficient of the constituent material of the turbine wheel 51 is substantially opposite without particularly recognizing the temperature of the turbine housing 2. It is possible to adjust the ratio of the temperature of the turbine housing 2 and the temperature of the turbine wheel 51 so that

  On the other hand, in order to perform the cooling operation of the turbine housing 2 with higher accuracy, a housing temperature sensor for detecting the temperature of the turbine housing 2 is provided, which is detected by the estimated temperature of the turbine wheel 51 and the housing temperature sensor. The temperature of the turbine housing 2 is compared with the estimated temperature of the turbine wheel 51, and the temperature of the turbine housing 2 is “½” (the expansion coefficient of the constituent material of the turbine housing 2 and the expansion of the constituent material of the turbine wheel 51). It is preferable to perform the opening / closing control of the solenoid valve 24 so that the ratio to the coefficient is “2: 1”.

(Second Embodiment)
Next, a second embodiment will be described. The configuration of the turbocharger 1 in the present embodiment is the same as that of the turbocharger 1 in the first embodiment described above. Accordingly, the description of the configuration of the turbocharger 1 is omitted here, and only the cooling water circulation path, the cooling water circulation operation, and the cooling operation of the turbine housing 2 will be described. Moreover, in FIG. 3 which shows the outline of the cooling water circulation path | route which concerns on this embodiment, the same code | symbol is attached | subjected about the member same as the thing of 1st Embodiment mentioned above.

-Explanation of cooling water circulation path-
Hereinafter, the cooling water circulation path of the engine according to the present embodiment will be described. FIG. 3 is a circuit diagram showing an outline of a cooling water circulation path according to the present embodiment. As shown in FIG. 3, the cooling water circulation path includes a radiator 61, a thermostat 62, a water pump 63, a turbocharger 1, and each of these devices 61, 62, 63, 1 and the like as in the first embodiment. Pipes and hoses H1, H2, H4, and H5 for connecting a water jacket 64 formed on the engine body E are provided.

  The difference of the cooling water circulation path according to the present embodiment from the first embodiment is in the cooling water path for cooling the turbine housing 2 of the turbocharger 1. That is, in the present embodiment, a dedicated cooling water path for cooling the turbine housing 2 of the turbocharger 1 is provided. As this cooling water path, the upstream end is connected to the lower hose H1, the downstream end is connected to the in-housing cooling water passage 23 of the turbocharger 1, and the upstream end is the in-housing cooling water passage 23 of the turbocharger 1. , And a downstream end is provided with a lead-out pipe H8 connected to the upper hose H4. The introduction pipe H7 is provided with a housing cooling pump 25. In other words, as the housing cooling pump 25 is driven, the cooling water taken out from the lower tank 61a of the radiator 61 is introduced into the in-housing cooling water passage 23 of the turbocharger 1 via the lower hose H1 and the introduction pipe H7, and the turbine housing. 2 is cooled and then returned to the upper tank 61b of the radiator 61 through the outlet pipe H8 and the upper hose H4. That is, the turbine housing 2 is cooled only when the housing cooling pump 25 is driven. The control of the housing cooling pump 25 will be described later.

  Other configurations of the cooling water circulation path are the same as those of the first embodiment described above.

-Cooling water circulation operation and turbine housing 2 cooling operation-
Next, the cooling water circulation operation in this embodiment will be described.

  First, the cooling water circulation operation at the time of cold start of the engine will be described. During this cold start, the thermostat 62 is closed and the housing cooling pump 25 is driven. As the cooling water circulation operation, as shown by the solid line arrow in FIG. 3, the circulation operation in which the cooling water flows in the order of the water pump 63, the water jacket 64, the take-out pipe H 2, the cold bypass hose H 5, and the water pump 63. Is done. As the housing cooling pump 25 is driven, the cooling water taken out from the lower tank 61a of the radiator 61 is introduced into the in-housing cooling water passage 23 of the turbocharger 1 through the lower hose H1 and the introduction pipe H7. After cooling, it is returned to the upper tank 61b of the radiator 61 through the outlet pipe H8 and the upper hose H4.

  Also in the present embodiment, the turbine housing 2 is formed of an aluminum alloy, and the heat capacity of the turbine housing 2 as a whole is small. For this reason, at the time of the cold start, the amount of heat taken away by the turbine housing 2 out of the heat in the exhaust gas is small, and as a result, a relatively high temperature exhaust gas can be passed through the catalytic converter. The catalyst temperature of the catalytic converter can be raised to the activation temperature within a short time, and the early activation of the catalyst can be realized.

  Further, according to such a cooling water circulation operation, heat exchange between the cooling water and the exhaust gas (heat exchange between the turbine housing 2 and the cooling water) is performed inside the turbocharger 1. The cooling water receives not only the heat received from the engine body E but also the heat of the exhaust gas, so that the temperature can be rapidly increased. Therefore, warm-up operation of the engine can be completed at an early stage, and the temperature of the engine oil rises quickly, so that the effect of reducing friction due to oil after the engine is started can be obtained early and the fuel efficiency of the engine can be improved. Can contribute.

  Next, the cooling water circulation operation after the engine warm-up operation is completed will be described. In this case, the thermostat 62 is opened and the driving state of the housing cooling pump 25 (the amount of cooling water discharged from the pump) is controlled.

  The control operation of the housing cooling pump 25 will be described. The ROM in the engine controller stores a wheel temperature estimation map for estimating the temperature of the turbine wheel 51 on the basis of the engine speed, the engine load, and the coolant temperature, and the estimation of the turbine wheel 51 from the wheel temperature estimation map. The temperature is read out (turbine wheel temperature estimation operation by the wheel temperature estimation means in the present invention). Then, the higher the temperature of the turbine wheel 51, the lower the cooling capacity for the turbine housing 2 by controlling the pump rotation speed so that the amount of cooling water discharged from the housing cooling pump 25 is reduced. The temperature of the turbine housing 2 is allowed to rise so as to quickly follow the rise (as described above, so that the temperature of the turbine housing 2 does not fall below a half value of the temperature of the turbine wheel 51). On the other hand, the temperature of the turbine housing 2 is sufficiently higher than the temperature of the turbine wheel 51 by controlling the pump rotation speed so that the cooling water discharge amount from the housing cooling pump 25 increases as the temperature of the turbine wheel 51 decreases. The cooling capacity for the turbine housing 2 is increased so as to be lower (so that the temperature of the turbine housing 2 does not exceed half the temperature of the turbine wheel 51 as described above).

  By adjusting the cooling capacity for the turbine housing 2 in this manner, the ratio between the expansion coefficient of the aluminum alloy that is the constituent material of the turbine housing 2 and the expansion coefficient of the steel that is the constituent material of the turbine wheel 51 is “N: 1. ”, The ratio of the temperature of the turbine housing 2 and the temperature of the turbine wheel 51 is set to be substantially the reverse ratio“ 1: N ”of the ratio of the expansion coefficients. That is, the turbine housing 2 is cooled by the cooling water so that the temperature of the turbine housing 2 becomes “1 / N” of the temperature of the turbine wheel 51.

  More specific numerical values are the same as those in the case of the first embodiment described above, and a description thereof will be omitted here.

  Hereinafter, a specific cooling water circulation operation will be described. As indicated by broken arrows in FIG. 3, the cooling water flows in the order of the radiator 61, the lower hose H 1, the thermostat 62, the water pump 63, the water jacket 64, the take-out pipe H 2, the upper hose H 4, and the radiator 61. Thereby, the heat of the cooling water is released to the atmosphere by the radiator 61 to cool the cooling water, and the engine body E is maintained at an appropriate temperature.

  When the estimated temperature of the turbine wheel 51 is relatively low and the discharge amount of the cooling water from the housing cooling pump 25 is controlled to be increased, the cooling water taken out from the lower tank 61a of the radiator 61 is cooled. Is introduced into the in-housing cooling water passage 23 of the turbocharger 1 through the lower hose H1 and the inlet pipe H7, and after cooling the turbine housing 2 with a high cooling capacity, the radiator 61 passes through the outlet pipe H8 and the upper hose H4. Is returned to the upper tank 61b. On the other hand, when the estimated temperature of the turbine wheel 51 is relatively high and the discharge amount of the cooling water from the housing cooling pump 25 is controlled to be small, or when the housing cooling pump 25 is stopped. The flow rate of the cooling water in the introduction pipe H7 is slight or “0”, and the cooling capacity of the turbine housing 2 is lowered.

  Thus, also in this embodiment, the cooling capacity with respect to the turbine housing 2 is adjusted according to the temperature of the turbine wheel 51, the expansion coefficient of the constituent material (aluminum alloy) of the turbine housing 2, and the constituent material (steel) of the turbine wheel 51. So that the ratio of the temperature of the turbine housing 2 and the temperature of the turbine wheel 51 is substantially the reverse ratio “1: N” of the ratio of the expansion coefficients. I have to. For this reason, the expansion amount of the turbine housing 2 due to heat and the expansion amount of the turbine wheel 51 substantially coincide with each other, and the tip clearance between them does not fluctuate. That is, the inner diameter dimension of the turbine housing 2 is increased by the increase in the outer diameter dimension (the outer diameter dimension of the turbine blade 51a) due to the expansion of the turbine wheel 51, and the tip clearance between the two is maintained at a predetermined dimension. . As a result, even if the tip clearance is set to a very small value (for example, 0.5 mm) in advance, the value is continuously maintained, and high turbo efficiency is continuously secured. be able to.

  The cooling water circulation path of the present embodiment also includes a housing temperature sensor for detecting the temperature of the turbine housing 2 as described above, and controls the rotational speed of the housing cooling pump 25 based on this sensing value. You may do it. That is, the estimated temperature of the turbine wheel 51 is compared with the temperature of the turbine housing 2 detected by the housing temperature sensor, and the temperature of the turbine housing 2 is “½” with respect to the estimated temperature of the turbine wheel 51 (turbine housing 2 The number of revolutions of the housing cooling pump 25 is controlled so that the ratio of the expansion coefficient of the constituent material of the above and the expansion coefficient of the constituent material of the turbine wheel 51 is “2: 1”.

(Modification 1)
Next, Modification 1 of the cooling water circulation path according to the first embodiment described above will be described. Here, only differences from the first embodiment will be described.

  FIG. 4 is a circuit diagram showing an outline of a cooling water circulation path according to this example. As shown in FIG. 4, in the cooling water circulation path of the present example, in addition to the cooling water circulation path of the first embodiment described above, a lead-out that is a piping on the cooling water discharge side of the in-housing cooling water passage 23 of the turbocharger 1. A reservoir tank 26 is provided in the pipe H6. The reservoir tank 26 is disposed below the position where the turbocharger 1 is disposed. The outlet pipe H6a extending from the in-housing cooling water passage 23 is connected to the upper part of the reservoir tank 26, and the outlet pipe H6b extending toward the suction side of the water pump 63 is connected to the lower part of the reservoir tank 26.

  Therefore, after the cooling water circulation operation as described in the first embodiment is performed, when the engine stops and the water pump 63 also stops, the cooling water in the in-housing cooling water passage 23 It is collected in the reservoir tank 26 via the lead-out pipe H6a, so that no cooling water exists in the in-housing cooling water passage 23. That is, the cooling water is extracted from the turbocharger 1 after the cooling water circulation operation is completed.

  Therefore, even when the engine is next started, there is no cooling water in the in-housing cooling water passage 23, and the heat in the exhaust gas flowing in the turbine housing 2 is transferred into the in-housing cooling water passage 23. It is never taken away by existing cooling water. For this reason, a synergistic effect with the formation of the turbine housing 2 made of an aluminum alloy allows the exhaust gas having a relatively high temperature to pass through the catalytic converter. The temperature can be raised to the activation temperature, and early activation of the catalyst can be realized.

  The configuration in which the reservoir tank 26 is disposed below the turbocharger 1 and the cooling water is extracted from the turbocharger 1 after the cooling water circulation operation is completed is compared with the cooling water circulation path in the second embodiment. Is also applicable.

(Modification 2)
Next, a modified example of the arrangement state of the turbocharger 1 will be described. Here, only differences from the first embodiment will be described.

  FIG. 5 is a longitudinal sectional view of the turbocharger 1 and its peripheral portion according to this example. In FIG. 5, the same members as those in the first embodiment described above are denoted by the same reference numerals.

  As shown in FIG. 5, in this example, the turbine housing 2 is integrally formed inside the cylinder head 7. That is, the space which becomes the scroll chamber 21 is formed continuously to the exhaust port 71 of the cylinder head 7, thereby the cylinder head 7 and the turbine housing 2 are integrated. Other configurations are the same as those of the turbocharger 1 described in the first embodiment.

  According to the configuration of this example, the turbine housing 2 is disposed inside the cylinder head 7, so that the engine can be reduced in size and weight.

-Other embodiments-
In each of the embodiments and modifications described above, the case where the present invention is applied to the turbocharger 1 mounted on the automobile diesel engine has been described. The present invention is not limited to this and can be applied to other internal combustion engines such as a gasoline engine. The engine to which the present invention is applicable is not limited to an automobile engine.

  In the first embodiment, the cooling capacity of the turbine housing 2 is adjusted by the opening / closing operation of the electromagnetic valve 24 and in the second embodiment by the discharge amount control of the housing cooling pump 25. The cooling capacity for the turbine housing 2 may be adjusted by controlling the temperature of the cooling water introduced into the passage 23. Specifically, it is desired to adjust the mixing ratio of the relatively low temperature cooling water derived from the lower tank 61a of the radiator 61 and the relatively high temperature cooling water derived from the water jacket 64 of the engine body E. The cooling water of the temperature is generated, and this cooling water is introduced into the in-housing cooling water passage 23 to adjust the cooling capacity for the turbine housing 2.

  Further, the cooling medium for cooling the turbine housing 2 is not limited to engine cooling water, and engine oil, fuel, and the like can be used.

  Further, in each of the above-described embodiments and modifications, the temperature of the turbine wheel 51 is estimated based on the engine speed, the engine load, and the cooling water temperature, and on the basis of the estimated value, the opening / closing control of the electromagnetic valve 24 and the housing cooling are performed. The rotational speed of the pump 25 was controlled. The present invention is not limited to this. Assuming that the temperature of the turbine wheel 51 is approximately approximate to the temperature of the exhaust gas, the opening / closing control of the electromagnetic valve 24 and the housing cooling pump 25 are based only on the temperature of the exhaust gas. The rotational speed control may be performed.

It is a longitudinal cross-sectional view of the turbocharger which concerns on embodiment. It is a circuit diagram which shows the outline of the cooling water circulation path | route which concerns on 1st Embodiment. It is a circuit diagram which shows the outline of the cooling water circulation path | route which concerns on 2nd Embodiment. FIG. 6 is a circuit diagram illustrating an outline of a cooling water circulation path according to Modification 1; It is a longitudinal cross-sectional view of the turbocharger which concerns on the modification 2, and its peripheral part.

Explanation of symbols

1 Turbocharger (supercharger)
2 Turbine housing 23 Cooling water passage in housing (cooling means)
24 Solenoid valve (cooling medium adjusting means)
25 Housing cooling pump (cooling medium adjusting means)
51 Turbine wheel 52 Compressor wheel

Claims (5)

In a supercharger system for an internal combustion engine in which a turbine wheel accommodated in a turbine housing rotates by receiving fluid energy of exhaust gas and supercharges intake air by transmitting the rotational force to a compressor wheel.
The constituent material of the turbine housing is an aluminum alloy, while the constituent material of the turbine wheel is steel,
When the ratio of the coefficient of expansion of the constituent material of the turbine housing to the coefficient of expansion of the constituent material of the turbine wheel is “N: 1”, the ratio of the temperature of the turbine housing and the temperature of the turbine wheel A supercharger system for an internal combustion engine, characterized by comprising cooling means for cooling the turbine housing with a cooling medium so as to have a substantially inverse ratio. In the internal combustion engine supercharger system according to claim 1,
The cooling means is a cooling water passage formed inside the turbine housing, and is configured to cool the turbine housing by flowing cooling water for cooling the internal combustion engine as a cooling medium through the cooling water passage. An internal combustion engine supercharger system. In the internal combustion engine supercharger system according to claim 1 or 2,
An internal combustion engine comprising cooling medium adjusting means for adjusting a temperature or a flow rate of the cooling medium so that a ratio between the temperature of the turbine housing and the temperature of the turbine wheel approaches an inverse ratio of the expansion coefficients. Turbocharger system. In the internal combustion engine supercharger system according to claim 3,
Wheel temperature estimating means for estimating the temperature of the turbine wheel based on the operating state of the internal combustion engine is provided, and the cooling medium adjusting means has a low temperature of the turbine wheel according to the temperature of the turbine wheel estimated by the wheel temperature estimating means. A supercharger system for an internal combustion engine, characterized in that the temperature or flow rate of the cooling medium is adjusted so as to increase the ability to cool the turbine housing. In a supercharger system for an internal combustion engine in which a turbine wheel accommodated in a turbine housing rotates by receiving fluid energy of exhaust gas and supercharges intake air by transmitting the rotational force to a compressor wheel.
The exhaust gas passage area in a plane orthogonal to the exhaust gas flow line in the turbine housing is set so that the Mach coefficient at the maximum exhaust gas flow rate is substantially “1”. Internal combustion engine supercharger system.

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