BACKGROUND OF THE INVENTION

1. Field of the Invention

[0001] The invention relates to a turbine housing of a turbosupercharger. To be specific, the invention relates to a turbine housing suitable to a case where abnormal air-fuel ratio variation between cylinders is diagnosed based on an output of an air-fuel ratio sensor arranged in an exhaust passage that is connected to an outlet of the turbine housing of a turbosupercharger.

2. Description of Related Art

[0002] An air-fuel ratio between cylinders sometimes varies (A/F imbalance) in a multicylinder type internal combustion engine (an engine) with a turbosupercharger. In a case where an extent of the air- fuel ratio variation between cylinders is small, it is possible to absorb the air-fuel ratio variation between cylinders by air-fuel ratio feedback control. However, when the extent of the air- fuel ratio variation between cylinders is large, exhaust emission is deteriorated.

[0003] For example, Japanese Patent Application Publication No. 2012-241545 A (JP 2012-241545 A) and Japanese Patent Application Publication No. 201 1 -185159 A (JP 201 1-185159 A) describe that it is possible to diagnose an abnormal air- fuel ratio variation between cylinders based on an output of an air-fuel ratio sensor (also referred to as an A/F , sensor) disposed in an exhaust passage. In JP 2012-241545 A and JP 2011-185159 A, the air-fuel ratio sensor is arranged on a downstream side of a turbine wheel of a

turbosupercharger in a structure including a bypass line that bypasses the turbine wheel, and a waste gate valve that opens and closes the bypass line.

[0004] The foregoing JP 2012-241545 A and JP 201 1-185159 A consider the fact that detection accuracy tends to decrease when the air-fuel ratio sensor is arranged on the downstream side of the turbine wheel of the turbosupercharger. In the above-mentioned JP 2012-241545 A, exhaust gas passing through the bypass line is caused to hit the air- fuel ratio sensor directly. In the above-mentioned JP 201 1 - 185159 A, abnormal air- fuel ratio variation between cylinders is diagnosed based on an output of the air- fuel ratio sensor when the waste gate valve is open.

SUMMARY OF THE INVENTION

[0005] Incidentally, in the foregoing JP 2012-241545 A and JP 201 1-185159 A, diagnosis of abnormal air-fuel ratio variation between cylinders is possible only when the waste gate valve is open. Therefore, diagnosis of abnormal air-fuel ratio variation between cylinders is not carried out so frequently, and it is thus required to diagnose abnormal air-fuel ratio variation between cylinders more accurately

[0006] In view of such a condition, the invention provides a turbine housing of a turbosupercharger, the turbine housing restrains that exhaust gas discharged while turning towards an exhaust pipe from an outlet of the turbosupercharger spreads, and the turbine housing of the turbosupercharger is connected to an exhaust passage in which an air-fuel ratio sensor of an internal combustion engine is arranged.

[0007] A first aspect of the invention relates to a turbine housing of a

turbosupercharger, which is provided in an exhaust passage of an internal combustion engine. The turbosupercharger has a turbine wheel provided in the exhaust passage, and an outlet of the turbine housing is connected with an exhaust pipe in which an air-fuel ratio sensor is provided. A protruding part is provided in the turbine housing. The protruding part is provided on an inner periphery surface of the turbine housing, and is provided in a given region in a circumferential direction at a position closer to the outlet of the turbine housing than the turbosupercharger. Further, the protruding part guides so that the exhaust gas is sent out from the outlet of the turbine housing towards the exhaust pipe while restraining spreading of the exhaust gas discharged from the outlet of the turbine housing towards the exhaust pipe. The exhaust gas is discharged wheel while turning by the turbine. [0008] In the foregoing aspect, it is possible to restrain spreading of exhaust gas discharged while turning from the outlet of the turbine housing to the exhaust pipe. Thus, it is possible to restrain a decrease in flow velocity of exhaust gas that is discharged while turning from the outlet of the turbine housing towards the exhaust pipe. Thus, exhaust gas at a high flow velocity hits the air-fuel ratio sensor continuously. As a result, an output value of the air-fuel ratio sensor is stabilized. Therefore, when the turbine housing according to the invention is used, abnormal air-fuel ratio variation between cylinders can be diagnosed accurately.

[0009] In the above aspect, the turbine housing of the turbosupercharger may be formed of a straight passage, and a cylinder part provided on a downstream side of the straight passage. The straight passage may be provided on the downstream side of the turbine wheel and goes along a rotation center axis of the turbine wheel. The cylinder part may have a cylindrical shape, and a diameter of the cylinder part may be larger than a diameter of the straight passage, and a center axis of the cylinder part may offset parallel to a center axis of the straight passage. The protruding part may be provided in a region of the cylinder part, the region being closer to the straight passage than the outlet of the turbine housing.

[0010] Here, a forming position of the protruding part is specified. The following is the reason why the protruding part is able to restrain spreading of exhaust gas that flows while turning, by specifying the forming position of the protruding part.

[0011] In a process that exhaust gas proceeds in the straight passage, the exhaust gas flows while turning without an increase of a turning radius of the exhaust gas. Unless the protruding part is provided, the turning radius of the exhaust gas is likely to spread when the exhaust gas proceeds from the straight passage to the cylinder part.

[0012] However, in a case where the protruding part is provided like the foregoing aspect, exhaust gas collides with the protruding part when the exhaust gas proceeds from the straight passage to the large diameter cylinder part. Since the exhaust gas collides with the protruding part, the turning radius of the exhaust gas is unlikely to expand. [0013] In the foregoing aspect, the turbine housing may have a straight passage, a cylinder part provided on a downstream side of the straight passage, and a protruding part provided in the cylinder part. The straight passage may be provided on the downstream side of the turbine wheel, and goes along a rotation center axis of the turbine wheel. The straight passage may be set so that exhaust gas discharged while turning by the turbine wheel flows straight and hit a detection part of the air- fuel ratio sensor. The cylinder part may be have a cylindrical shape. A diameter of the cylinder part may be larger than a diameter of the straight passage. A center axis of the cylinder part may be offset to parallel to a center axis of the straight passage. The protruding part may be connected with the straight passage in succession. And the protruding part may be made of a part that goes along a direction of the center avis find a part thnt goes nlong a r.i ir.nm f til iyrt direction in the cylinder part.

[0014] In the foregoing aspect, a flow velocity of exhaust gas discharged from the turbine housing to the exhaust pipe is Unlikely to drop. Therefore, exhaust gas at a high flow velocity hits the air-fuel ratio sensor continuously, and an output value of the air-fuel ratio sensor is stabilized.

[0015] In the foregoing aspect, the protruding part may prevent a radius of the exhaust gas spreading in direction to go ahead of the exhaust gas. The exhaust gas may be discharged while turning by the turbine wheel.

[0016] When exhaust gas sent out by the turbine wheel to the straight passage proceeds from the straight passage to the cylinder part, the exhaust gas hits the protruding part, thus spreading of the turning radius of the exhaust gas unlikely. Therefore, the exhaust gas hits the air-fuel ratio sensor continuously, and an output value of the air-fuel ratio sensor is stabilized.

[0017] According to the foregoing aspect of the invention, in the turbine housing of the turbosupercharger, which is connected to the exhaust pipe in which the air-fuel ratio sensor of the internal combustion engine . is arranged, it is possible to restrain spreading of exhaust gas that is discharged while turning from the outlet of the turbosupercharger to the exhaust pipe. [0018] Therefore, it is possible to restrain a decrease in flow velocity of exhaust gas that is discharged while turning from the outlet to the exhaust pipe. Thus, exhaust gas at high flow velocity hits the air-fuel ratio sensor, and an output value of the air-fuel ratio sensor is stabilized. As a result, in a case where the turbine housing according to the ^' foregoing aspect of the invention is used, it is possible to accurately diagnose abnormal air-fuel ratio variation between cylinders. In short, the present invention is able to contribute to an improvement of reliability of diagnosis of abnormal air-fuel ratio variation between cylinders.

BRIEF DESCRIPTION OF THE DRAWINGS

[00JL9] Features,— advantages,— and— technical— and— industrial— significance of ^" exemplary embodiments of the invention will be described below with reference to the accompanying. drawings, in which like numerals denote like elements, and wherein:

FIG. 1 is a view showing a rough structure of an embodiment of a multicylinder type internal combustion engine with a turbosupercharger, to which the invention is applied;

FIG. 2 is an enlarged sectional view schematically showing a turbine housing and its periphery in FIG. 1 ;

FIG. 3 is an enlarged view schematically showing how exhaust gas passes through the turbine housing in FIG. 2;

FIG. 4 is a perspective view showing a state where a lower side of the turbine housing in FIG. 2 is shown as a fracture section;

FIG. 5 is an arrow view taken along the X - X section in FIG. 2;

FIG. 6 is an internal perspective view schematically showing a flow of exhaust gas in a view from a direction of an arrow Y in FIG. 5; and

FIG. 7 is a view of a comparative example of the embodiment. The view

corresponds to FIG. 6.

DETAILED DESCRIPTION OF EMBODIMENTS [0020] A best embodiment for carrying out the invention is explained in detail with reference to the drawings.

[0021] FIG. 1 to FIG. 6 show an embodiment of the invention. An internal combustion engine (an engine 1 ) shown as an example in this embodiment is an inline-four engine. The number of cylinders and a type of the engine are not particularly limited to the inline-four engine.

[0022] An intake manifold 2 for distributing and supplying intake air to respective cylinders #1 to #4 is attached to the engine 1. Further, exhaust manifolds 3 A, 3B for gathering exhaust gas discharged form the respective cylinders #1 to #4 is attached to the engine 1.

[0023] An intake pipe 4 for taking in air from the atmosphere is connected to the intake manifold 2. An air cleaner 5 is attached to an inlet of the intake pipe 4. A part where the intake manifold 2 and the intake pipe 4 are combined corresponds to an "intake air passage".

[0024] On an upstream side of the intake manifold 2 in an intake air flow direction, a throttle valve 6 for adjusting an amount of intake air into the engine 1 is provided. The throttle valve 6 is operated by a throttle motor 6a and an electronic control unit (ECU) 50. Also, injectors (fuel injecting valves) 7 that inject fuel directly to the respective cylinders #1 to #4, spark plugs 8, and so on are attached to the engine 1.

[0025] The first exhaust manifold 3 A is connected to respective exhaust ports of, for example, the first cylinder #1 and the fourth cylinder #4 of the engine 1. The second exhaust manifold 3B is connected to respective exhaust ports of, for example, the second cylinder #2 and the third cylinder #3 of the engine 1. Each of the exhaust manifolds 3 A, 3B is formed to be forked on the upstream side, and has a shape to be united into one on the downstream side. In short, the shape of the exhaust manifolds of the engine 1 is a 2 in 1 shape.

[0026] Further, a turbosupercharger 20 is attached to the downstream side of the two exhaust manifolds 3A, 3B. [0027] The turbosupercharger 20 is a supercharger that supercharges intake air (fresh air) and supplies the intake air to the engine 1 by using exhaust pressure. The turbosupercharger 20 is provided with at least a turbine wheel 21, a compressor impeller 22, and so on.

[0028] As a basic operation of the turbosupercharger 20, the turbine wheel 21 is rotated by energy of exhaust gas discharged to the exhaust manifolds 3 A, 3B from the engine 1. As the compressor impeller 22 is rotated integrally with the above-mentioned rotated turbine wheel 21 , air inhaled into the intake pipe 4 is supercharged. Then, the above-mentioned air is forced into combustion chambers of the respective cylinders #1 to #4 of the engine 1. Air supercharged by the compressor impeller 22 is cooled by an inter cooler 9. The inter cooler 9 is disposed in the intake, pipe 4 on the downr.trnnm nidn nf th compressor impeller 22 in the intake air flow direction.

[0029] The turbine wheel 21 is provided to be able to rotate inside the turbine housing 24. An exhaust gas introduction port of the turbine housing 24 is sectioned into two inside. The downstream sides of the two exhaust manifolds 3A, 3B are

communicated and connected with the respective sectioned exhaust gas introduction ports, respectively. The turbosupercharger 20 that uses the turbine housing 24 having the exhaust gas introduction port sectioned into two is referred to as a so-called "twin scroll types turbosupercharger".

[0030] The compressor impeller 22 is provided inside a compressor housing 25 disposed in a middle of the intake pipe 4. The compressor impeller 22 is attached to a turbine shaft 23 that is integral with the turbine wheel 21. Thus, the turbine wheel 21 and the compressor impeller 22 rotate integrally with each other.

[0031] An exhaust pipe 10 for releasing exhaust gas into the atmosphere is connected to the downstream side of the turbine housing 24. The exhaust pipe 10 is a component called an "elbow". The exhaust pipe 10 is an exhaust pipe having a shape that goes straight along a discharge direction of exhaust gas sent out from the turbine wheel 21 , and then bent at about 90 degrees and extends almost downwardly in a vertical direction. In short, the exhaust pipe 10 explained above is an exhaust pipe formed into, for example, a "reverse upside down L shape".

[0032] A catalyst 1 1 for purifying exhaust gas is provided in a downward part of the exhaust pipe 10. Further, an air- fuel ratio sensor 66 is provided in the exhaust pipe 1 Oon the upstream of the catalyst 1 1.

[0033] A diameter of the catalyst 1 1 is set to be larger than a diameter of the downward part of the exhaust pipe 10. Therefore, the downward part of the exhaust pipe 10 is formed to have a cone shape that expands gradually towdrds the catalyst 1 1. A part where the two exhaust manifolds 3 A, 3B, the turbine housing 24, and the exhaust pipe 10 are combined corresponds to an "exhaust passage".

[0034] Incidentally, the FCT I 0 is provided with a micrnmmpntp.r itnH nf n - CPU, a ROM, a RAM, and so on, and an input-output interface. The ECU 50 is a publicly known ECU, and detailed illustration is omitted. The ECU 50 executes various types of control of the engine 1 by referring to various maps stored in the ROM as necessary, based on outputs from various sensors, and a computed value obtained from a computing equation using the output values.

[0035] Examples of the above-mentioned control include various types of control of the engine 1 such as fuel injection control (control of an injection quantity and injection timing) by the injector 7, ignition timing control of the spark plugs 8, and opening control of the throttle valve 6. Other examples of the control include at least processing for diagnosing abnormal air-fuel ratio variation between cylinders (A/F imbalance).

Moreover, examples of the foregoing various types of sensors include a crank position sensor 61 , a water temperature sensor 62, an air flowmeter 63, an intake air temperature sensor 64, a throttle opening sensor 65, and the air-fuel ratio sensor 66. Other examples of the various types of sensors include at least a cam position sensor and an accelerator opening sensor. Illustration of the cam position sensor and the accelerator opening sensor - is omitted. Abnormality diagnostic processing of air- fuel ratio variation between cylinders is executed based on an output of the air-fuel ratio sensor 66. [0036] In the turbosupercharger 20 of this embodiment, a bypass passage 26, and a waste gate valve (WGV) 27 are provided.

[0037] The bypass passage 26 is provided in the turbine housing 24. Exhaust gas discharged from the engine 1 passes through the bypass passage 26, thus bypassing the turbine wheel 21 , and is lead to the exhaust pipe 10. In short, the bypass passage 26 is disposed so as to short-circuit an introduction side and a discharge side of exhaust gas in the turbine housing 24.

[0038] The waste gate valve 27 is disposed so as to be able to open and close on a side of a discharge port of the bypass passage 26. By opening and closing the waste gate valve 27 to adjust opening of the bypass passage 26, a bypass amount of exhaust gas is adjusted. Ry adjusting the hypass amount of exhaust gas, it become possibl to eontrol - for example, supercharging pressure. In addition, when swiftly activating the catalyst 1 1 after cold start of the engine 1 , it is possible to use adjustment of the bypass amount of exhaust gas.

[0039] The waste gate valve 27 is formed as, for example, a circular and plate-shaped member. A given position of an outer periphery of the waste gate valve 27 is attached to a support shaft 28 and the waste gate valve 27 is able to rotate integrally with the support shaft 28. The support shaft 28 is driven to rotate by an appropriate driving device. As the support shaft 28 is driven to rotate, the waste gate valve 27 adjusts opening of the bypass passage 26.

[0040] Incidentally, as shown in FIG. 2, a straight passage 24a, which goes along a rotation center axis 100 of the turbine wheel 21 , is provided in the turbine housing 24 on the downstream side of the turbine wheel 21. With the straight passage 24a, a cylinder part 24b having a large diameter is provided on the downstream side of the straight passage 24a. The cylinder part 24b is formed into a cylindrical shape in this embodiment.

[0041] A center axis 300 of the cylinder part 24b is eccentric from a center axis 200 of the straight passage 24a in a parallel or generally parallel fashion. In other word, the center axis 300 of the cylinder part 24b offsets parallel to a center axis 200 of the straight passage 24a. Opening of the cylinder part 24b is an outlet 24c of the turbine housing 24. The discharge port of the foregoing bypass passage 26 is provided in a wall part 24d that goes along a radius direction between the straight passage 24a and the cylinder part 24b.

[0042] Exhaust gas discharged from the straight passage 24a is flown straight in a discharge direction while turning, and the exhaust gas is set to hit a detection part of the air-fuel ratio sensor 66. The air-fuel ratio sensor 66 is provided so as to be stuck into a depressed region in a corner part of the exhaust pipe 10.

[0043] Incidentally, exhaust gas sent out by the turbine wheel 21 of the turbo supercharger 20 flows while turning when passing through the straight passage 24a. When the cylinder part 24b is provided on the downstream side of the straight passage 24a in the turbine housing 24 as shown in FIG. 7, a turning radius of exhaust gas expands as the exhaust gas flowing while turning in the, straight passage 24a enter , the cylinder pnr† 24b. A turning radius of the exhaust gas with the expanded turning radius gradually expands towards the outlet 24c.

[0044] Thus, the exhaust gas is guided so as to be sent out to the outlet 24c while restraining spreading of the turning radius of the exhaust gas that flows while turning from the outlet 24c of the turbine housing 24 to the exhaust pipe 10. To do so, a protruding part 24e is provided in a given region of the cylinder part 24b of the turbine housing 24. < . [0045] Specifically, as shown in FIG. 3 to FIG. 5, the protruding part 24e is provided in the cylinder part 24b of the turbine housing 24, in a region close to the straight passage 24a, and also in a given region in a circumferential direction. The protruding part 24e is provided so as to protrude inwardly in the radius direction from an inner periphery surface of the cylinder part 24b.

[0046] In the large-diameter cylinder part 24b, the protruding part 24e has a part 24f that goes along an axis direction to be continuous from the straight passage 24a, and a part 24g that goes along the circumferential direction. In short, the protruding part 24e is like a wall extending the straight passage 24a to the large-diameter cylinder part 24b.

[0047] As explained so far, the embodiment, to which the invention is applied, obtains the following peculiar and excellent actions and effects. [0048] . Exhaust gas sent out by the turbine wheel 21 to the straight passage 24a heads to the outlet 24c while turning with a generally constant turning radius as

schematically shown in FIG. 3. Once the exhaust gas proceeds from the straight passage 24a to the cylinder part 24b, the exhaust gas hits the protruding part 24e. Therefore, as schematically shown in FIG. 3 and FIG. 6, it is unlikely that the turning radius of the exhaust gas expands.

[0049] Due to this, it becomes possible to send out exhaust gas to the outlet 24c while restraining spreading of the turning radius (diffusion) of the exhaust gas that flows while turning from the outlet 24c of the turbine housing 24 to the exhaust pipe 10. In short, a decrease in flow velocity of exhaust gas discharged from the turbine housing 24 to the exhaust pipe 10 is

air- fuel ratio sensor 66 continuously. As a result, an output value of the air-fuel ratio sensor 66 is stabilized. Hence, in a case where the turbine housing 24 is used, diagnosis of abnormal air-fuel ratio variation between cylinders can be done by the ECU 50 accurately.

[0050] The invention is not limited to the above-mentioned embodiment, and changes can be made as appropriate without departing from the scope of the claims or a scope equal to the scope of the claims.

[0051] The engine 1 , to which an exhaust system explained in the foregoing embodiment is applied, is not limited to a gasoline engine, but may be a diesel engine.

[0052] An example was stated in the foregoing embodiment that the

turbosupercharger 20, to which the turbine housing 24 according to the invention is applied, is provided with the bypass passage 26 and the waste gate valve 27, but the invention is not limited to this. For example, the turbosupercharger 20, to which the turbine housing 24 according to the invention is applied, may have a structure without the bypass passage 26 and the waste gate valve 27.

[0053] It is possible to suitably use the invention for a turbine housing of a turbosupercharger connected with an exhaust passage in which an air-fuel ratio sensor of an internal combustion engine is arranged.