Supercharger

Abstract

In the present invention, a supercharger includes: a compressor and a turbine connected via a rotary shaft; a first exhaust introduction passage and a second exhaust introduction passage for supplying exhaust gas to the turbine; a communication passage via which a middle part of the first exhaust introduction passage and a middle part of the second exhaust introduction passage communicate; a bypass passage via which the exhaust gas in the communication passage is discharged to an exhaust gas flow passage; and an opening / closing valve that is provided in a portion via which the communication passage and the bypass passage communicate, said opening / closing valve being capable of enabling and disabling communication with the communication passage, and capable of enabling and disabling communication between the communication passage and the bypass passage. The opening / closing valve is provided with a communication groove along a direction crossing the opening / closing direction of the opening / closing valve on an outer peripheral part.

Description

turbocharger

[0001] The present disclosure relates to a supercharger and method.

[0002] A turbocharger is a rotatable housing that houses a compressor and a turbine, which are integrally connected by a rotating shaft. The turbine is rotated by exhaust gas, and the rotational force of the turbine is transmitted to the compressor by the rotating shaft, which then rotates. The compressor pressurizes the air to produce compressed air, which supercharges the engine.

[0003] Among turbochargers, there is a turbocharger having a double scroll structure with two spiral-shaped exhaust inlet passages. This turbocharger has two exhaust inlet passages that supply exhaust gas to a turbine. The two exhaust inlet passages are connected to the turbine and communicate with each other at their midpoints through a communication passage, which is in turn communicated with an exhaust gas flow path via a bypass passage. An on-off valve is provided at the communication portion between the communication passage and the bypass passage. When the on-off valve is closed, communication between the two exhaust inlet passages is blocked, and communication between the exhaust inlet passage and the bypass passage is also blocked. On the other hand, when the on-off valve is open, the two exhaust inlet passages are communicated with each other through the communication passage, and the exhaust inlet passage is communicated with the bypass passage via the communication passage. An example of such a turbocharger is described in Patent Document 1.

[0004] DE 102013002894 A1

[0005] In a double-scroll turbocharger, when the on-off valve is in a low to medium opening range, the two exhaust inlet passages are connected to each other, allowing exhaust gas to circulate through the two exhaust inlet passages. However, at this time, part of the exhaust gas flowing through the two exhaust inlet passages flows into the bypass passage via the connecting passage. This reduces the flow rate of exhaust gas supplied to the turbine from the exhaust inlet passage, resulting in a problem of reduced turbocharger efficiency.

[0006] The present disclosure is devised to solve the above-described problems, and aims to provide a turbocharger that improves efficiency by reducing the flow rate of exhaust gas into a bypass passage in a range from low to medium opening of an on-off valve.

[0007] In order to achieve the above object, the turbocharger of the present disclosure includes a compressor and a turbine connected via a rotating shaft, a first exhaust inlet passage and a second exhaust inlet passage that supply exhaust gas to the turbine, a communication passage that connects a midpoint of the first exhaust inlet passage with a midpoint of the second exhaust inlet passage, a bypass passage that discharges exhaust gas in the communication passage to an exhaust gas flow path, and an on-off valve that is provided at a communication portion between the communication passage and the bypass passage and is capable of connecting and blocking the communication passage and connecting and blocking the communication passage and the bypass passage, and the on-off valve is provided with a communication groove on its outer periphery that runs along a direction that intersects with the opening and closing direction of the on-off valve.

[0008] According to the turbocharger of the present disclosure, the flow rate of exhaust gas into the bypass passage in the low to medium opening range of the on-off valve can be reduced, thereby improving efficiency.

[0009] FIG. 1 is a schematic diagram showing a turbocharger of this embodiment. FIG. 2 is a schematic diagram showing an exhaust gas path in the turbocharger. FIG. 3 is a front view of an on-off valve. FIG. 4 is a plan view of the on-off valve. FIG. 5 is a cross-sectional view showing the on-off valve in a closed state. FIG. 6 is a cross-sectional view taken along line VI-VI of FIG. 5 showing the on-off valve in a closed state. FIG. 7 is a cross-sectional view showing the on-off valve in a slightly open state. FIG. 8 is a graph showing the communication area versus the valve opening degree of the on-off valve. FIG. 9 is a graph showing the bypass area versus the valve opening degree of the on-off valve. FIG. 10 is a graph showing the communication direction flow rate versus the bypass flow rate. FIG. 11 is a graph showing turbine efficiency versus engine speed. FIG. 12 is a graph showing fuel consumption versus engine speed. FIG. 13 is a front view of a first modified on-off valve. FIG. 14 is a front view of a second modified on-off valve. FIG. 15 is a front view of a third modified on-off valve. FIG. 16 is a plan view of a fourth modified on-off valve.

[0010] Preferred embodiments of the present disclosure will be described in detail below with reference to the drawings. Note that the present disclosure is not limited to these embodiments, and when there are multiple embodiments, the present disclosure also includes configurations that combine the embodiments. Furthermore, the components in the embodiments include those that can be easily imagined by a person skilled in the art, those that are substantially identical, and those that are within the so-called equivalent range.

[0011] [First embodiment] <Turbocharger> Fig. 1 is a schematic diagram showing a turbocharger of this embodiment.

[0012] A supercharger is mounted on a vehicle such as an automobile that has a reciprocating engine (hereinafter simply referred to as an engine) as an internal combustion engine as a drive source. The supercharger is a so-called turbocharger that compresses intake air (air) using exhaust gas from the engine.

[0013] As shown in Figure 1, the engine 10 is a multi-cylinder internal combustion engine. An engine body 11 is provided with a plurality of cylinder bores 12, and pistons 13 are supported in the cylinder bores 12 via cylinder liners (not shown) so as to be vertically movable. A crankshaft (not shown) is rotatably supported at the bottom of the engine body 11, and each piston 13 is connected to the crankshaft via a connecting rod 14.

[0014] The combustion chamber 15 is defined by the wall and bottom surfaces of the cylinder bore 12 and the top surface of the piston 13. An intake port 16 and an exhaust port 17 are formed in the upper part of the combustion chamber 15, and an intake valve 18 and an exhaust valve 19 are provided in the intake port 16 and the exhaust port 17, respectively. The intake valve 18 and the exhaust valve 19 are supported so as to be freely movable along the axial direction and are supported so as to be biased in a direction to close the intake port 16 and the exhaust port 17 (upward in FIG. 1 ). The intake valve 18 and the exhaust valve 19 open and close the intake port 16 and the exhaust port 17 by the action of intake cams and exhaust cams of an intake camshaft and an exhaust camshaft (not shown). A fuel injection valve 20 is also provided in the upper part of the combustion chamber 15. The fuel injection valve 20 is capable of injecting high-pressure fuel into the combustion chamber 15.

[0015] Therefore, the engine 10 performs four strokes (intake stroke, compression stroke, expansion stroke, and exhaust stroke) during two revolutions of the crankshaft. At this time, the intake camshaft and the exhaust camshaft rotate once, and the intake valve 18 and the exhaust valve 19 open and close the intake port 16 and the exhaust port 17.

[0016] In the engine body 11, an intake passage 21 is connected to the intake port 16, and an exhaust passage 22 is connected to the exhaust port 17. A supercharger 23 is disposed between the intake passage 21 and the exhaust passage 22. The supercharger 23 has a compressor section 24, a turbine section 25, a bearing section 26, and an exhaust bypass device 27.

[0017] The compressor unit 24 compresses intake air (air) introduced from an air cleaner (not shown) and sends it into the combustion chamber 15. The compressor unit 24 has a compressor wheel (compressor) 31 and a compressor housing 32. The compressor wheel 31 is housed in the compressor housing 32 and supported so as to be rotatable about the axis O. The compressor wheel 31 compresses intake air A, which flows in from one side of the axis O by centrifugal force, from the inside to the outside in the radial direction about the axis O. Compressed air B compressed by the compressor wheel 31 is discharged radially outward about the axis O and supplied to the intake passage 21.

[0018] The compressor housing 32 has a wheel accommodating portion 33, an intake air introduction passage 34, and an intake air discharge passage 35. The compressor wheel 31 is rotatably supported and housed in the wheel accommodating portion 33. The intake air introduction passage 34 is connected to one side of the axis O of the compressor wheel 31 with respect to the wheel accommodating portion 33. The intake air discharge passage 35 is connected to the wheel accommodating portion 33 on the radially outer side centered on the axis O of the compressor wheel 31. The intake air discharge passage 35 is connected to the intake passage 21. The intake air discharge passage 35 introduces compressed air B from the intake passage 21 to the combustion chamber 15.

[0019] The turbine section 25 obtains rotational force from the exhaust gas C discharged from the combustion chamber 15. The turbine section 25 has a turbine wheel (turbine) 41 and a turbine housing 42. The turbine wheel 41 is housed in the turbine housing 42 and supported so as to be rotatable about the axis O. The turbine wheel 41 is rotated by the exhaust gas C discharged from the exhaust passage 22 toward the inside in the radial direction centered on the axis O. The exhaust gas C that rotates the turbine wheel 41 flows from the other side of the axis O toward the outside.

[0020] The turbine housing 42 has a wheel accommodating portion 43, an exhaust inlet passage 44, and an exhaust discharge passage 45. The turbine wheel 41 is rotatably supported and accommodated in the wheel accommodating portion 43. The exhaust inlet passage 44 is connected to the exhaust passage 22. The exhaust inlet passage 44 is connected to the wheel accommodating portion 43 on the radially outer side thereof, centered on the axis O of the turbine wheel 41. The exhaust discharge passage 45 is connected to the wheel accommodating portion 43 on the other side of the axis O of the turbine wheel 41. The exhaust discharge passage 45 discharges exhaust gas C.

[0021] The bearing unit 26 has a rotating shaft 51 and a bearing housing (not shown). The compressor wheel 31 is fixed to one side of the axis O of the rotating shaft 51, and the turbine wheel 41 is fixed to the other side of the axis O. The compressor wheel 31 and the turbine wheel 41 can rotate integrally by the rotating shaft 51. The bearing housing rotatably accommodates the rotating shaft 51. For example, a plain bearing or a rolling bearing is used as the bearing. The compressor housing 32 and the turbine housing 42 are connected to the bearing housing.

[0022] The exhaust bypass device 27 adjusts the flow rate of the exhaust gas C bypassing the turbine section 25, i.e., the flow rate of the exhaust gas C supplied to the turbine wheel 41, in accordance with the intake pressure in the intake passage 21. In other words, the exhaust bypass device 27 allows excess exhaust gas to flow directly into the exhaust discharge path 45 without supplying it to the turbine section 25.

[0023] Therefore, when intake air (air) is supplied from the intake passage 21 to the combustion chamber 15 of the engine body 11, the air is compressed by the rising of the piston 13, generating compressed air, and high-pressure fuel is injected from the fuel injection valve 20 into the compressed air. The high-pressure air and high-pressure fuel then mix, ignite, and burn. The generated combustion gas is discharged into the exhaust passage 22 as exhaust gas C. At this time, the exhaust gas C discharged from the combustion chamber 15 rotates the turbine wheel 41 of the supercharger 23. The rotational force of the turbine wheel 41 is transmitted to the compressor wheel 31 via the rotary shaft 51, causing it to rotate, thereby pressurizing the intake air and supercharging the combustion chamber 15. The exhaust bypass device 27 directs the exhaust gas C to the exhaust discharge path 45 instead of supplying it to the turbine section 25, depending on the intake pressure in the intake passage 21.

[0024] <Exhaust Gas Path> FIG. 2 is a schematic diagram showing an exhaust gas path in the turbocharger.

[0025] As shown in FIG. 2 , the turbine section 25 of the turbocharger 23 is configured such that a turbine wheel 41 is housed in a turbine housing 42 and supported for free rotation. The turbine housing 42 has a wheel housing portion 43, an exhaust inlet passage 44, and an exhaust discharge passage 45. The turbocharger 23 has a double-scroll structure. That is, the exhaust inlet passage 44 has two spiral-shaped exhaust inlet passages 61, 62. The first exhaust inlet passage 61 introduces exhaust gas from, for example, a first cylinder and a fourth cylinder (not shown) of the four cylinders (combustion chambers 15) of the engine 10. The second exhaust inlet passage 62 introduces exhaust gas from, for example, a second cylinder and a third cylinder (not shown) of the four cylinders of the engine.

[0026] The first exhaust introduction passage 61 and the second exhaust introduction passage 62 are arranged side by side. The upstream sides of the first exhaust introduction passage 61 and the second exhaust introduction passage 62 in the flow direction of the exhaust gases C1 and C2 are connected to the exhaust passage 22 (see FIG. 1 ). The downstream side of the first exhaust introduction passage 61 in the flow direction of the exhaust gas C1 is connected to one radial side of the wheel accommodating portion 43, and the downstream side of the second exhaust introduction passage 62 in the flow direction of the exhaust gas C2 is connected to the other radial side of the wheel accommodating portion 43.

[0027] The first exhaust introduction passage 61 and the second exhaust introduction passage 62 are connected by a communication passage 63. The communication passage 63 has a first branch passage 64, a second branch passage 65, and a communication portion 66. The first branch passage 64 branches off from a midpoint of the first exhaust introduction passage 61, and the second branch passage 65 branches off from a midpoint of the second exhaust introduction passage 62. The communication portion 66 communicates the downstream ends of the first branch passage 64 and the second branch passage 65 in the flow direction of the exhaust gas C1.

[0028] The communication passage 63 is connected to the exhaust discharge passage (exhaust gas flow path) 45 by a bypass passage 67. The bypass passage 67 has an upstream end in the flow direction of the exhaust gas C1 that communicates with the communication part 66 and a downstream end in the flow direction of the exhaust gas C1 that communicates with the exhaust discharge passage 45. The bypass passage 67 can allow part or all of the exhaust gas C1 flowing through the first exhaust introduction passage 61 and the exhaust gas C2 flowing through the second exhaust introduction passage 62 to bypass the turbine wheel 41 and flow into the exhaust discharge passage 45 without supplying them to the turbine wheel 41.

[0029] The communication passage 63 is provided with an on-off valve 68. The on-off valve 68 is disposed in a communication portion 66 of the communication passage 63. The on-off valve 68 is disposed in the communication portion 66 between the communication passage 63 and the bypass passage 67, and is capable of connecting and disconnecting the communication passage 63, as well as connecting and disconnecting the communication passage 63 and the bypass passage 67. That is, when the on-off valve 68 is closed, it blocks communication between the first branch passage 64 and the second branch passage 65 that constitute the communication passage 63, and also blocks communication between the first branch passage 64 and the second branch passage 65 and the bypass passage 67. On the other hand, when the on-off valve 68 is open, it connects the first branch passage 64 and the second branch passage 65 that constitute the communication passage 63, and also connects the first branch passage 64 and the second branch passage 65 and the bypass passage 67.

[0030] The exhaust bypass device 27 is composed of a bypass passage 67 and an on-off valve 68 .

[0031] Therefore, when the on-off valve 68 is closed, communication between the first branch passage 64 and the second branch passage 65 is blocked, so that the exhaust gas C1 is supplied from the first exhaust introduction passage 61 to the turbine wheel 41, and the exhaust gas C2 is supplied from the second exhaust introduction passage 62 to the turbine wheel 41. On the other hand, when the on-off valve 68 is open, the first branch passage 64 is connected to the second branch passage 65 and the bypass passage 67 is connected, so that the pressure of the exhaust gas C1 flowing through the first exhaust introduction passage 61 and the exhaust gas C2 flowing through the second exhaust introduction passage 62 is equalized by the communication part 66, and the flow rates of the exhaust gases C1 and C2 in the exhaust introduction passages 61 and 62 are equalized. In addition, the exhaust gas C1 flowing through the first exhaust introduction passage 61 and the exhaust gas C2 flowing through the second exhaust introduction passage 62 flow from the bypass passage 67 to the exhaust discharge passage 45. As a result, the flow rate of the exhaust gas C1 supplied from the first exhaust introduction passage 61 to the turbine wheel 41 and the flow rate of the exhaust gas C2 supplied from the second exhaust introduction passage 62 to the turbine wheel 41 decrease.

[0032] <Configuration of the On-Off Valve> FIG. 3 is a front view showing the on-off valve, and FIG. 4 is a plan view showing the on-off valve.

[0033] As shown in FIGS. 3 and 4 , the on-off valve 68 has a flange portion 71 , a valve element 72 , a support portion 73 , and a cylindrical portion 74 .

[0034] The flange portion 71 has a disk shape centered on the axis O1. The valve element 72 is integrally connected to one flat portion of the flange portion 71. The valve element 72 has a cylindrical shape centered on the axis O1. The valve element 72 has a tapered shape with its outer diameter decreasing toward one side of the axis O1. The valve element 72 has an outer peripheral surface 72a and a bottom surface 72b. The outer peripheral surface 72a has a shape that bulges outward in the axial direction. The bottom surface 72b has a flat shape and is smoothly connected to the outer peripheral surface 72a via a curved portion 72c. In other words, the valve element 72 has a convex shape with its outer diameter decreasing from the flange portion 71 side toward the bottom surface 72b side, forming a tapered shape.

[0035] The flange portion 71 is integrally connected to a cylindrical portion 74 via a support portion 73. The cylindrical portion 74 has a cylindrical shape centered on an axis O2. The axis O2 is perpendicular to the axis O1 and is offset from the axis O1 in the radial direction of the flange portion 71 and the valve body 72. One end of the cylindrical portion 74 along the axis O2 is connected to the other flat portion of the flange portion 71 via the support portion 73. A shaft portion 75 is fitted into the cylindrical portion 74, and the cylindrical portion 74 is rotatably supported via a bearing (not shown). That is, the on-off valve 68 has a valve body 72 extending along the axis O1 and is supported rotatably about the axis O2.

[0036] The on-off valve 68 is provided with a communication groove 76 on its outer periphery, which extends in a direction intersecting the opening / closing direction (direction along the axis O1) of the on-off valve 68. The communication groove 76 is provided on the outer periphery of the valve element 72 on the side opposite the axis O2 with respect to the axis O1. In other words, the communication groove 76 is provided on the outer periphery of the valve element 72 of the valve element that is farthest from the axis O2, which is the rotation center of the on-off valve 68. The communication groove 76 is provided on the outer periphery of the valve element 72 of the on-off valve 68 along the circumferential direction, but the groove bottom 76a is linear. In other words, the communication groove 76 is provided on part of the outer periphery of the valve element 72 of the on-off valve 68. As shown in Figures 2 and 3, when the on-off valve 68 blocks the communication passage 63 and also blocks the communication passage 63 from the bypass passage 67, the communication groove 76 connects a portion of the communication passage 63, that is, connects only a portion of the first branch passage 64 and the second branch passage 65.

[0037] In this case, the length La from the top surface 72d of the on-off valve 68 to the center of the communicating groove 76 is preferably at least 0.3 times the length L in the opening and closing direction (direction along the axis O1) of the on-off valve 68. Furthermore, the length Lb from the bottom surface 72b of the on-off valve 68 to the communicating groove 76 is preferably in the range of 1.0 to 1.2 times the length L from the bottom surface 72b of the on-off valve 68 to the inner surface of the communicating passage 63 on the opening direction side of the on-off valve 68. Furthermore, the width of the communicating groove 76 is preferably in the range of 0.1 to 0.3 times the length L in the opening and closing direction (direction along the axis O1) of the on-off valve 68.

[0038] <Operation of On-Off Valve> FIG. 5 is a cross-sectional view showing the on-off valve in a closed state, FIG. 6 is a cross-sectional view taken along line VI-VI of FIG. 5 showing the on-off valve in a closed state, and FIG. 7 is a cross-sectional view showing the on-off valve in a slightly open state.

[0039] 5 and 6 , the on-off valve 68 is supported by a housing 81. That is, the on-off valve 68 is supported relative to the housing 81 so as to be rotatable about an axis O2. The on-off valve 68 has a convex shape that can be fitted into an opening 82 that communicates the communication passage 63 with the bypass passage 67 from the bypass passage 67 side. The axis O1 of the on-off valve 68 and the axis O3 that is the center of the opening 82 substantially coincide with each other. The on-off valve 68 is rotatable about an axis O2 that is perpendicular to the opening direction of the opening 82 (the direction along the axis O3) and that is shifted radially from the center of the opening 82 (axis O3).

[0040] The communicating groove 76 is provided on the outer periphery of the on-off valve 68 (valve element 72) offset in the other radial direction from the center (axis O3) of the opening 82. The communicating groove 76 is provided along the circumferential direction on the outer periphery of the valve element 72 of the on-off valve 68. The communicating passage 63 has a recess 83 provided on an inner surface 63a that faces the opening 82 in the radial direction. When the on-off valve 68 is closed, the bottom (bottom surface 72b) of the valve element 72 fits into the recess 83. In other words, when the on-off valve 68 is closed, the bottom surface 72b of the valve element 72 is located below the inner surface 63a of the communicating passage 63. The communicating groove 76 is also provided along the opening / closing direction of the on-off valve 68, i.e., along a direction perpendicular to the exhaust gas C that flows from the communicating passage 63 to the bypass passage 67 when the on-off valve 68 is open.

[0041] When the on-off valve 68 is open, the exhaust gas C flowing from the communication passage 63 to the bypass passage 67 flows along the outer peripheral surface of the valve body 72 of the on-off valve 68. At this time, the exhaust gas C interferes with a communication groove 76 formed in a recessed shape on the outer peripheral portion of the on-off valve 68. This obstructs the flow of the exhaust gas C from the communication passage 63 to the bypass passage 67, reducing the flow rate of the exhaust gas C flowing from the communication passage 63 to the bypass passage 67.

[0042] Fig. 6 is a cross-sectional view of the communication passage 63 showing the on-off valve 68 in a closed state, and Fig. 7 is a cross-sectional view of the communication passage 63 showing the on-off valve 68 in a slightly open state. However, the cross-sectional views of Fig. 6 and Fig. 7 are projections of the communication passage 63 and the on-off valve 68 when the second branch passage 65 is viewed from the first branch passage 64 side. Therefore, in the explanation of Fig. 6 and Fig. 7, the projection state is considered to be communication.

[0043] As shown in Figure 6, when the on-off valve 68 closes the communication passage 63, the flange portion 71 comes into close contact with the flat surface of the housing 81 on the bypass passage 67 side, the valve body 72 fits into the opening 82 to close it, and the bottom portion (bottom surface 72b) fits into the recess 83 of the communication passage 63. As a result, communication between the first branch passage 64 and the second branch passage 65 is blocked, and communication between the first branch passage 64 and the second branch passage 65 and the bypass passage 67 is also blocked. However, since the on-off valve 68 has a communication groove 76 in the valve body 72, the communication passage 63 is connected, that is, the first branch passage 64 and the second branch passage 65 are connected. The area indicated by diagonal lines in Figure 6 is the communication area S1.

[0044] On the other hand, as shown in FIG. 7 , when the on-off valve 68 slightly opens the communication passage 63, the flange portion 71 is slightly spaced from the flat portion of the housing 81 on the bypass passage 67 side, the valve body 72 is fitted into the opening 82 to nearly close it, and the bottom portion (bottom surface 72b) is slightly spaced from the recess 83 of the communication passage 63. However, since the recess 83 is provided in the communication passage 63, the first branch passage 64 and the second branch passage 65 remain blocked. At this time, since the communication groove 76 is provided in the valve body 72 of the on-off valve 68, the communication passage 63 is connected, that is, the first branch passage 64 and the second branch passage 65 are connected. The shaded area in FIG. 7 is the communication area S2. The communication area S2 when the on-off valve 68 is slightly open is smaller than the communication area S1 when the on-off valve 68 is open or closed.

[0045] <Function and Effect of On-Off Valve> Figure 8 is a graph showing the communication area versus the valve opening degree of the on-off valve. Here, the communication area refers to the communication areas S1 and S2 of the communication passage 63 due to the communication groove 76 described using the projection views of Figures 6 and 7. In Figure 8, the dotted line represents a conventional on-off valve without the communication groove 76, and the solid line represents the on-off valve 68 of this embodiment with the communication groove 76.

[0046] As shown by the dotted line in Fig. 8, in the turbocharger having a conventional on-off valve, the communication area increases uniformly as the valve opening increases from when the on-off valve is closed (valve opening degree 0). On the other hand, as shown by the solid line in Fig. 8, in the turbocharger 23 having the on-off valve 68 of this embodiment, the communication area decreases once and then increases as the valve opening increases from when the on-off valve 68 is closed (valve opening degree 0). Therefore, the amount of exhaust gas C passing through the first branch path 64 and the second branch path 65 when the on-off valve 68 is slightly open is limited.

[0047] 9 is a graph showing the bypass area versus the valve opening degree of the on-off valve. Here, the bypass area is the communication area between the communication passage 63 and the bypass path 67. In FIG. 9, the dotted line represents a conventional on-off valve without the communication groove 76, and the solid line represents the on-off valve 68 of this embodiment with the communication groove 76.

[0048] As shown by the dotted line in Fig. 9, in the turbocharger having the conventional on-off valve, the bypass area increases uniformly as the valve opening increases from when the on-off valve is closed (valve opening 0). On the other hand, as shown by the solid line in Fig. 9, in the turbocharger 23 having the on-off valve 68 of this embodiment, the bypass area increases uniformly as the valve opening increases from when the on-off valve 68 is closed (valve opening 0), but when the valve opening is large, the bypass area becomes smaller than that of the conventional on-off valve.

[0049] 10 is a graph showing the bypass flow rate versus the communication direction flow rate. Here, the bypass flow rate is the flow rate of the exhaust gas C flowing from the communication passage 63 to the bypass passage 67, and the communication direction flow rate is the flow rate of the exhaust gas C flowing between the first branch passage 64 and the second branch passage 65. In addition, in FIG. 10, the dotted line represents a conventional on-off valve without the communication groove 76, and the solid line represents the on-off valve 68 of this embodiment with the communication groove 76.

[0050] As shown by the dotted line in Fig. 10, in a turbocharger having a conventional on-off valve, when the bypass amount of exhaust gas C increases as the opening amount of the on-off valve increases, the communication direction flow rate increases as the bypass amount increases. At this time, in the region from the low opening degree to the medium opening degree of the on-off valve, the bypass amount of exhaust gas C increases and the communication direction flow rate does not increase sufficiently. On the other hand, as shown by the solid line in Fig. 10, in the turbocharger 23 having the on-off valve 68 of this embodiment, when the bypass amount of exhaust gas C increases as the opening degree of the on-off valve 68 increases, the communication direction flow rate increases as the bypass amount increases. At this time, in the region from the low opening degree to the medium opening degree of the on-off valve 68, the rate of increase in the bypass amount of exhaust gas C is slower than in the conventional on-off valve, and the communication direction flow rate increases significantly.

[0051] When the on-off valve 68 is in the low to medium opening range, the exhaust gas C flowing from the communication passage 63 to the bypass passage 67 interferes with the communication groove 76 formed on the outer periphery of the on-off valve 68, reducing the flow rate of the exhaust gas C flowing from the communication passage 63 to the bypass passage 67. As a result, the flow rate of the exhaust gas C flowing between the first branch passage 64 and the second branch passage 65, i.e., the flow rate in the communication direction, increases.

[0052] 11 is a graph showing turbine efficiency versus engine speed. In FIG. 11, the dotted line indicates a conventional on-off valve without the communicating groove 76, and the solid line indicates the on-off valve 68 of this embodiment with the communicating groove 76.

[0053] As shown by the dotted line in Fig. 11, the turbine efficiency of a turbocharger having a conventional on-off valve increases as the engine speed increases. On the other hand, as shown by the solid line in Fig. 11, the turbine efficiency of the turbocharger 23 having the on-off valve 68 of this embodiment increases as the engine speed increases. At this time, the turbine efficiency is improved (increased) compared to a turbocharger having a conventional on-off valve in the range of low to medium engine speeds.

[0054] 12 is a graph showing fuel consumption versus engine speed. In FIG. 11, the dotted line indicates a conventional on-off valve without the communicating groove 76, and the solid line indicates the on-off valve 68 of this embodiment with the communicating groove 76.

[0055] As shown in Fig. 12, the fuel economy versus increase in engine speed of an engine equipped with a turbocharger having a conventional on-off valve is represented by the dotted line in Fig. 12. On the other hand, the fuel economy versus increase in engine speed of an engine 10 equipped with a turbocharger 23 having an on-off valve 68 of this embodiment is represented by the solid line in Fig. 12. Here, the fuel economy of the engine 10 of this embodiment is improved (reduced) compared to the conventional engine.

[0056] <Modifications> In the above-described embodiment, the communication groove 76 is provided along the circumferential direction on the outer periphery of the valve body 72 of the on-off valve 68, but the present invention is not limited to this configuration.

[0057] FIG. 13 is a front view showing a first modified example of the on-off valve.

[0058] 13 , the on-off valve 68A has a flange portion 71, a valve element 72, a support portion 73, and a cylindrical portion 74. A communication groove 76A is provided on the outer periphery of the on-off valve 68A along a direction intersecting the opening and closing direction of the on-off valve 68A (the direction along the axis O1). The communication groove 76A is provided along the circumferential direction on the outer periphery of the valve element 72 of the on-off valve 68A. In other words, the communication groove 76A is provided around the entire outer periphery of the valve element 72 of the on-off valve 68A.

[0059] 5 and 13 , when the on-off valve 68A is open, the exhaust gas C flowing from the communication passage 63 to the bypass passage 67 flows along the outer circumferential surface of the valve body 72 of the on-off valve 68A. At this time, the exhaust gas C passes through the communication groove 76A formed as a recess around the entire outer periphery of the on-off valve 68A. As a result, the flow of the exhaust gas C flowing from the communication passage 63 to the bypass passage 67 is obstructed by the communication groove 76A, and the flow rate of the exhaust gas C flowing from the communication passage 63 to the bypass passage 67 is reduced. Furthermore, by providing the communication groove 76A around the entire outer periphery of the valve body 72 of the on-off valve 68A, it is possible to improve processing performance and reduce processing costs.

[0060] FIG. 14 is a front view showing a second modified example of the on-off valve.

[0061] As shown in FIG. 14 , the on-off valve 68B includes a flange portion 71, a valve element 72, a support portion 73, and a cylindrical portion 74. The on-off valve 68B includes a communication groove 76B on its outer periphery, which extends in a direction intersecting the opening / closing direction (direction along the axis O1) of the on-off valve 68B. The communication groove 76B includes a first communication groove 91 and a second communication groove 92. The first communication groove 91 and the second communication groove 92 are spaced apart in the direction of the axis O1 and parallel to each other. The first communication groove 91 is wider in the direction of the axis O1 and longer in the circumferential direction than the second communication groove 92. The communication grooves 76B (first communication groove 91, second communication groove 92) are provided on the outer periphery of the valve element 72 on the side opposite the axis O2 from the axis O1.

[0062] 5 and 14 , when the on-off valve 68B is open, the exhaust gas C flowing from the communication passage 63 to the bypass passage 67 flows along the outer peripheral surface of the valve body 72 of the on-off valve 68B. At this time, the exhaust gas C interferes with the communication groove 76B, which is formed in two stages and has a recessed shape on the outer peripheral portion of the on-off valve 68B, that is, the first communication groove 91 and the second communication groove 92. As a result, the flow of the exhaust gas C from the communication passage 63 to the bypass passage 67 is obstructed by the communication groove 76B, and the flow rate of the exhaust gas C flowing from the communication passage 63 to the bypass passage 67 is reduced.

[0063] FIG. 15 is a front view showing a third modified example of the on-off valve.

[0064] As shown in FIG. 15 , the on-off valve 68C includes a flange portion 71, a valve element 72, a support portion 73, and a cylindrical portion 74. The on-off valve 68C has a communication groove 76C formed on its outer periphery along a direction intersecting the opening / closing direction (direction along the axis O1) of the on-off valve 68C. The communication groove 76C is formed on the outer periphery of the valve element 72 on the opposite side of the axis O2 from the axis O1. The communication groove 76C is formed along the circumferential direction on the outer periphery of the valve element 72 of the on-off valve 68C. In other words, the communication groove 76C is formed on a portion of the outer periphery of the valve element 72 of the on-off valve 68C. The communication groove 76C opens toward the flange portion 71 in a plane perpendicular to the axis O1. However, the communication groove 76C may also open toward the opposite side of the flange portion 71 (toward the bottom surface 72b) in a plane perpendicular to the axis O1.

[0065] 5 and 15 , when the on-off valve 68C is open, the exhaust gas C flowing from the communication passage 63 to the bypass passage 67 flows along the outer peripheral surface of the valve body 72 of the on-off valve 68C. At this time, the exhaust gas C interferes with the communication groove 76C that is formed as a recess around the entire outer periphery of the on-off valve 68C. As a result, the flow of the exhaust gas C from the communication passage 63 to the bypass passage 67 is obstructed by the communication groove 76C, and the flow rate of the exhaust gas C flowing from the communication passage 63 to the bypass passage 67 is reduced.

[0066] FIG. 16 is a plan view showing a fourth modified example of the on-off valve.

[0067] As shown in FIG. 16 , the on-off valve 68D has a flange portion 71, a valve element 72, a support portion 73, and a cylindrical portion 74. The on-off valve 68D is provided with a communication groove 76D on its outer periphery, extending along a direction intersecting the opening / closing direction (direction along the axis O1) of the on-off valve 68D. The communication groove 76D is provided on the outer periphery of the valve element 72 on the opposite side of the axis O1 from the axis O2. The communication groove 76D is provided on the outer periphery of the valve element 72 of the on-off valve 68D along the circumferential direction, but the groove bottom 76a is curved. In other words, the communication groove 76D is provided on a portion of the outer periphery of the valve element 72 of the on-off valve 68D.

[0068] 5 and 16 , when the on-off valve 68D is open, the exhaust gas C flowing from the communication passage 63 to the bypass passage 67 flows along the outer peripheral surface of the valve body 72 of the on-off valve 68D. At this time, the exhaust gas C interferes with the communication groove 76D that is formed as a recess around the entire outer periphery of the on-off valve 68D. As a result, the flow of the exhaust gas C from the communication passage 63 to the bypass passage 67 is obstructed by the communication groove 76D, and the flow rate of the exhaust gas C flowing from the communication passage 63 to the bypass passage 67 is reduced.

[0069] [Effects of the present embodiment] The turbocharger according to the first aspect includes a compressor wheel 31 and a turbine wheel 41 connected via a rotating shaft 51, a first exhaust inlet passage 61 and a second exhaust inlet passage 62 that supply exhaust gas C to the turbine wheel 41, a communication passage 63 that connects a midpoint of the first exhaust inlet passage 61 with a midpoint of the second exhaust inlet passage 62, a bypass passage 67 that discharges the exhaust gas C in the communication passage 63 to the exhaust discharge passage (exhaust gas flow path) 45, and on-off valves 68, 68A, 68B, 68C, 68D that are provided at a communication portion 66 between the communication passage 63 and the bypass passage 67 and are capable of connecting and disconnecting the communication passage 63 and connecting and disconnecting the communication passage 63 and the bypass passage 67, and the on-off valve 68 has communication grooves 76, 76A, 76B, 76C, 76D provided on its outer periphery along a direction intersecting the opening and closing direction of the on-off valve 68.

[0070] According to the turbocharger of the first aspect, when the on-off valves 68, 68A, 68B, 68C, 68D are in the low to medium opening range, the exhaust gas C flowing from the communication passage 63 to the bypass passage 67 flows along the outer circumferential surfaces of the valve bodies 72 of the on-off valves 68, 68A, 68B, 68C, 68D. At this time, the exhaust gas C interferes with the communication grooves 76, 76A, 76B, 76C, 76D provided on the outer circumferential portions of the on-off valves 68, 68A, 68B, 68C, 68D, and the flow of the exhaust gas C into the bypass passage 67 is obstructed. Therefore, by reducing the flow rate of the exhaust gas C flowing from the communication passage 63 to the bypass passage 67, it is possible to improve efficiency.

[0071] The turbocharger according to the second aspect is the turbocharger according to the first aspect, and further, the communication grooves 76, 76A, 76B, 76C, 76D communicate a part of the communication passage 63 when the on-off valves 68, 68A, 68B, 68C, 68D block the communication passage 63 and block the communication passage 63 from the bypass passage 67. This promotes the flow of the exhaust gas C1 in the first exhaust introduction passage 61 and the exhaust gas C2 in the second exhaust introduction passage 62, thereby improving efficiency.

[0072] A turbocharger according to a third aspect is the turbocharger according to the first or second aspect, further comprising: on-off valves (68, 68A, 68B, 68C, 68D) each having a convex shape that can be fitted from the bypass passage (67) side into an opening (82) that communicates between the communication passage (63) and the bypass passage (67), and having an axis O2 that is a rotation axis that is perpendicular to the opening direction of the opening (82) and that is shifted in one radial direction from the center (axis O3) of the opening (82), and communication grooves (76, 76A, 76B, 76C, 76D) are provided on outer peripheries of the on-off valves (68, 68A, 68B, 68C, 68D) that are shifted in the other radial direction from the center of the opening (82). This allows the exhaust gas C flowing from the communication passage (63) to the bypass passage (67) to appropriately interfere with the communication grooves (76, 76A, 76B, 76C, 76D), and reduces the flow rate of the exhaust gas C flowing from the communication passage (63) to the bypass passage (67).

[0073] A turbocharger according to a fourth aspect is the turbocharger according to any one of the first to third aspects, and further, the communication grooves 76, 76A, 76B, 76C, 76D are provided along the circumferential direction on the outer peripheries of the on-off valves 68, 68A, 68B, 68C, 68D. This allows the exhaust gas C flowing from the communication passage 63 to the bypass passage 67 to appropriately interact with the communication grooves 76, 76A, 76B, 76C, 76D.

[0074] A turbocharger according to a fifth aspect is the turbocharger according to any one of the first to fourth aspects, and further, the communication passage 63 is provided, on an inner surface radially facing the opening 82, with a recess 83 into which the bottom of the on-off valves 68, 68A, 68B, 68C, 68D fits when the on-off valves 68, 68A, 68B, 68C, 68D are closed. This makes it possible to restrict the flow of the exhaust gas C1 in the first exhaust introduction passage 61 and the exhaust gas C2 in the second exhaust introduction passage 62 when the on-off valves 68, 68A, 68B, 68C, 68D are closed.

[0075] A turbocharger according to a sixth aspect is the turbocharger according to any one of the first to fifth aspects, further comprising: a communication passage (63) formed by connecting a first branch passage (64) branching from the first exhaust introduction passage (61) and a second branch passage (65) branching from the second exhaust introduction passage (62); on-off valves (68, 68A, 68B, 68C, 68D) are capable of connecting and blocking the first branch passage (64) and the second branch passage (65); and a communication area between the first branch passage (64) and the second branch passage (65) decreases and then increases as the valve openings of the on-off valves (68, 68A, 68B, 68C, 68D) increase from when they are closed. This makes it possible to restrict the flow of exhaust gas (C1) through the first exhaust introduction passage (61) and exhaust gas (C2) through the second exhaust introduction passage (62) when the on-off valves (68, 68A, 68B, 68C, 68D) are slightly open.

[0076] A turbocharger according to a seventh aspect is the turbocharger according to any one of the first to sixth aspects, and further, the length from the bottom surface of the on-off valve 68, 68A, 68B, 68C, 68D to the center of the communication groove 76, 76A, 76B, 76C, 76D is set to be 0.3 times or more the length in the opening and closing direction of the on-off valve 68, 68A, 68B, 68C, 68D. This makes it possible to provide the communication groove 76, 76A, 76B, 76C, 76D at an appropriate position of the on-off valve 68, 68A, 68B, 68C, 68D.

[0077] A turbocharger according to an eighth aspect is the turbocharger according to any one of the first to seventh aspects, and further, the length from the bottom surface of the on-off valve 68, 68A, 68B, 68C, 68D to the communicating groove 76, 76A, 76B, 76C, 76D is set in the range of 1.0 to 1.2 times the length from the bottom surface of the on-off valve 68, 68A, 68B, 68C, 68D to the inner surface of the communicating passage 63 on the opening direction side of the on-off valve 68, 68A, 68B, 68C, 68D. This makes it possible to provide the communicating groove 76, 76A, 76B, 76C, 76D at an appropriate position of the on-off valve 68, 68A, 68B, 68C, 68D.

[0078] REFERENCE SIGNS LIST 10 Engine 11 Engine body 15 Combustion chamber 21 Intake passage 22 Exhaust passage 23 Turbocharger 24 Compressor section 25 Turbine section 26 Bearing section 27 Exhaust bypass device 31 Compressor wheel (compressor) 32 Compressor housing 33 Wheel accommodating section 34 Intake introduction passage 35 Intake discharge passage 41 Turbine wheel (turbine) 42 Turbine housing 43 Wheel accommodating section 44 Exhaust introduction passage 45 Exhaust discharge passage 51 Rotating shaft 61 First exhaust introduction passage 62 Second exhaust introduction passage 63 Communication passage 64 First branch passage 65 Second branch passage 66 Communication section 67 Bypass passage 68, 68A, 68B, 68C, 68D Opening / closing valve 71 Flange section 72 Valve body 76, 76A, 76B, 76C, 76D Communication groove 81 Housing 82 Opening 83 Recess 91 First communication groove 92 Second communication groove A Intake B Compressed air C, C1, C2 Exhaust gas S1, S2 Communication area O, O1, O2 Axis

Claims

1. A turbocharger comprising: a compressor and a turbine connected via a rotating shaft; a first exhaust inlet passage and a second exhaust inlet passage for supplying exhaust gas to the turbine; a communication passage connecting a middle portion of the first exhaust inlet passage with a middle portion of the second exhaust inlet passage; a bypass passage for discharging exhaust gas in the communication passage to an exhaust gas flow path; and an on-off valve provided at the communication portion between the communication passage and the bypass passage and capable of connecting and blocking the communication passage and connecting and blocking the communication passage and between the communication passage and the bypass passage, wherein the on-off valve has a communication groove provided on its outer periphery along a direction intersecting the opening and closing direction of the on-off valve.

2. A turbocharger as set forth in claim 1, wherein said communication groove communicates with a part of said communication passage when an on-off valve blocks said communication passage and blocks said communication passage and said bypass passage.

3. A turbocharger as claimed in claim 1 or claim 2, wherein the on-off valve has a convex shape that can be fitted from the bypass passage side into an opening that communicates between the communication passage and the bypass passage, and has a rotation axis that is perpendicular to the opening direction of the opening and shifted in one radial direction from the center of the opening, and the communication groove is provided on the outer periphery of the on-off valve shifted in the other radial direction from the center of the opening.

4. The turbocharger according to claim 3, wherein the communication groove is provided along a circumferential direction on an outer periphery of the on-off valve.

5. A turbocharger as set forth in claim 3, wherein the communication passage has an inner surface radially opposed to the opening, the inner surface being provided with a recess into which the bottom of the on-off valve fits when the on-off valve is closed.

6. A turbocharger as claimed in claim 4, wherein the communication passage is constituted by communication between a first branch passage branching off from the first exhaust inlet passage and a second branch passage branching off from the second exhaust inlet passage, the on-off valve is capable of connecting and blocking communication between the first branch passage and the second branch passage, and a communication area between the first branch passage and the second branch passage decreases and then increases as a valve opening degree increases from the time the on-off valve is closed.

7. A turbocharger as set forth in claim 1, wherein the length from the bottom surface of the on-off valve to the center of the communication groove is set to be 0.3 times or more the length of the on-off valve in the opening and closing direction.

8. A turbocharger as set forth in claim 1, wherein the length from the bottom surface of the on-off valve to the communicating groove is set in the range of 1.0 to 1.2 times the length from the bottom surface of the on-off valve to the inner surface of the communicating passage on the opening direction side of the on-off valve.

Images