There is provided a turbocharger whose constitution is compact, in which exhaust interference seldom occurs, and which can be applied also to an EGR type engine. In the turbocharger, an introduction part of an exhaust inflow passage possesses a partition part dividing a range from an inlet to a predetermined position in a downstream of the inlet into two exhaust inflow passages, a throttle part, whose sectional area becomes gradually small, from the inlet to a position where the partition part ceases, a joining part where exhaust gases passing through the left and right exhaust inflow passages are joined, and a diffuser part, whose sectional area becomes gradually large, from the joining part to a tongue part.

BACKGROUD OF THE INVENTION

1. Field of the Invention

The present invention relates to a turbocharger.

2. Description of the Related Art

From old times, as means increasing a charge amount of engine, there has been known a turbocharger compressing the air and charging it to the engine by rotating a turbine wheel by utilizing an energy of exhaust gas, and driving a compressor wheel of a centrifugal type through a shaft formed monolithically with the turbine wheel.

InFIG. 7, there is shown a piping system diagram of an engine using the turbocharger concerning the prior art. It is explained with a straight 6-cylinder engine62being taken as an example. The engine62possesses six cylinders64A,64B linearly arranged. The six cylinders64A,64B are classified into the upside three cylinders64A and the downside three cylinders64B. The upside cylinders64A are referred to as front cylinder group64A, and the downside cylinders64B are referred to as rear cylinder group64B.

Exhaust ports of the front cylinder group64A are connected to a front exhaust manifold65A, and exhaust gases63A exhausted from the exhaust ports of the front cylinder group64A join in the front exhaust manifold65A. Exhaust ports of the rear cylinder group64B are connected to a rear exhaust manifold65B, and exhaust gases63B exhausted from the exhaust ports of the rear cylinder group64B join in the rear exhaust manifold65B.

The exhaust gas63A emerging from the front exhaust manifold65A flows into a left exhaust inflow passage19A of a turbocharger11while passing through a front exhaust piping75A. The exhaust gas63B emerging from the rear exhaust manifold65B flows into a right exhaust inflow passage19B of the turbocharger11while passing through a rear exhaust piping75B.

In this manner, for the front/rear cylinder groups64A,64B, by providing respectively the front/rear exhaust manifolds65A,65B and the front/rear exhaust piping and it was going to use radio and minimum woman OK one does not as owner audio OK does not we do not those long as I did all that follow75A,75B, it is possible to reduce an exhaust interference. A turbine wheel14is rotated by flows of the exhaust gases63A,63B passing through the exhaust inflow passages19A,19B, and a compressor wheel16is rotated through a shaft23. By this, the air compressed is cooled while passing through an after-cooler67, and supplied to each of the cylinders64A,64B through a charge manifold71.

Next, it is explained in detail about the turbocharger11. InFIG. 8andFIG. 9, the turbocharger11possesses an exhaust side part12taking out a rotation energy from the exhaust gases63A,63B, and a charge side part13compressing the air by this rotation energy and feeding it to the engine.

The exhaust side part12possesses the turbine wheel14surrounded by a turbine housing15. The turbine housing15possesses an exhaust inflow passage19supplying the exhaust gases63A,63B to the turbine wheel14.

The exhaust inflow passage19is divided in its inside into the left exhaust inflow passage19A and the right exhaust inflow passage19B by a partition wall66. The front/rear exhaust piping75A,75B are respectively connected to the left and right exhaust inflow passages19A,19B. The exhaust inflow passage19comprises an approximately linear introduction part69connected to the front/rear exhaust piping75A,75B, and a scroll part68formed annularly so as to surround an outer periphery of the turbine wheel14.

The turbine housing15possesses an exhaust outflow port21discharging the exhaust gases63A,63B after having given an energy to the turbine wheel14. The exhaust outflow port21is approximately cylindrically formed so as to be approximately coaxial with a rotation center of the turbine wheel14. An opening part in a side opposite to the exhaust outflow port21is closed by an exhaust side inner plate22.

The turbine wheel14is rotated by being given the energy by the exhaust gases63A,63B flowing in from the exhaust inflow passages19A,19B. The shaft23is formed monolithically with the turbine wheel14. The shaft23penetrates through the exhaust side inner plate22, and is rotatably supported by a bearing24. The turbine wheel14and the shaft23are generally made of a nickel-based superalloy and a steel alloy.

The compressor wheel16of the centrifugal type compressing the air is attached to a side opposite to the turbine wheel14of the shaft23(hereafter, referred to as tip part side of the shaft23). The compressor wheel16possesses plural blade parts18, and in its center part there is penetrated an attaching hole25. The shaft23is inserted into the attaching hole25in a degree of slight clearance fit or shrink fit. The compressor wheel16is fixed to the shaft23by driving an attaching nut26to a male screw part40formed in the tip part of the shaft23.

The compressor wheel16is accommodated inside the compressor housing17. The compressor housing17possesses an intake inflow port27sucking the air into the compressor wheel16. The intake inflow port27is approximately cylindrically formed so as to be approximately coaxial with a rotation center of the compressor wheel16. The air compressed by the compressor wheel16is centrifugally discharged while passing through a charge discharging passage28formed annularly so as to surround an outer peripheral part of the compressor wheel16. And, as shown inFIG. 7, it is cooled while passing through the after-cooler67, and supplied to each of the cylinders654A,64B through the charge manifold71.

However, in the above prior art, there is such a problem as mentioned below. That is, the exhaust inflow passage19is divided into the left and right exhaust inflow passages19A,19B by the partition wall66not only in the introduction part69but also in the scroll part68. For this reason, especially in the turbine housing15, whose passage sectional area is small, for a small flow rate, flow passages for the exhaust gases63A,63bare narrow, so that a loss of the energy is large.

Further, in recent years, it is demanded as a countermeasure to reduce nitrogen oxide (NOx) contained in the exhaust gases63A,63B of the diesel engine62.

One of effective measures solving this problem is a technique referred to as EGR (Exhaust Gas Recirculation) system. This is one in which one part of the exhaust gases63A,63B discharged from the engine62is returned to a charge system of the engine62and recirculated.

InFIG. 10, front/rear EGR passages73A,73B are respectively connected to the front/rear exhaust manifolds65A,65B respectively connected to the front/rear cylinder groups64A,64B. The front/rear EGR passages73A,73B are connected to the charge manifold71for the cylinders64A,64B. By this, one part (these are referred to as EGR gases74A,74B) of the exhaust gases63A,63B entering into the exhaust manifolds65A,65B is returned from the EGR passages73A,73B to the cylinders64A,64B while passing through the charge manifold71, and recirculated.

However, if the EGR passages73A,73B are respectively connected to the front/rear exhaust manifolds65A,65B in this manner, there is a problem that the apparatus becomes a large size because the two EGR passages73A,73B are necessary and a management of them is required. Moreover, there arises a necessity to connect various components, such as EGR coolers72A,72B cooling the EGR gases74a,74B, respectively to midways of the EGR passages73A,73B. Further, two sets of piping for cooling water to the EGR cooler72A,72B, and so forth are necessary, so that a constitution of the apparatus becomes complex.

Further, as shown inFIG. 11, there has been considered a constitution in which the EGR passage73B is connected only to one exhaust manifold65B, and the EGR gas74B is returned to the charge manifold71. However, if made in this manner, a difference occurs between a piping resistance of the front exhaust manifold65A and that of the rear exhaust manifold65B. For this reason, a flow rate of the exhaust gas63A exhausted from the front cylinder group64A becomes different from that of the exhaust gas63B exhausted from the rear cylinder group64B. As a result, there is a problem that a combustion in each of the cylinders64A,64B becomes not uniform and thus an unbalance occurs in an operation.

Further, as shown inFIG. 12, the front/rear exhaust piping75A,75B are joined somewhere short of the exhaust inflow passage19without providing the partition wall66in the exhaust inflow passage19. And, there has been considered also a constitution in which an EGR passage73is connected to a joined exhaust piping75, and the EGR gas74is returned to the charge manifold71while passing through an EGR cooler72.

However, if made in this manner, there is the fact that, for example under a state that the exhaust gas63A exhausted from the front cylinder group64A is remaining, the exhaust gas63B enters from the rear cylinder group64B into the exhaust piping75. As a result, the exhaust interference occurs, and a flow of the exhaust gas63B from the rear cylinder group64B is hindered by a flow of the exhaust gas63A from the front cylinder group64A, so that an engine pumping work increases and thus fuel consumption is deteriorated.

In order to avoid such an exhaust interference, for example in FIG. 1 and FIG. 3 of Patent Document 1 (JP-A-8-28286), there is disclosed a technique avoiding the exhaust interference by providing the two turbine wheels14although it is not an example using the EGR. However, if the two turbine wheels14are provided, there is a problem that a volume occupied by the turbocharger11is increased and it becomes expensive.

Further, as shown in FIG. 2 of Patent Document 2 (JP-A-57-124028), there is a known technique where the exhaust interference is prevented by providing a scroll chamber inside the exhaust manifolds65A,65B. However, according to such a technique, the exhaust manifolds65A,65B become very large sizes. Accordingly, it is possible to use this technique in a large size engine such as for a ship, but it is difficult to apply it to an apparatus, such as construction machinery, limited in its installation area.

SUMMARY OF THE INVENTION

The invention is one made in view of the above problems, and its object is to provide a turbocharger whose constitution is compact, so that the exhaust interference seldom occurs, and which can be applied also to an EGR type engine.

In order to achieve the above object, in a turbocharger concerning the invention, an exhaust inflow passage has an introduction part formed approximately linearly from an inlet through which an exhaust gas is introduced, a scroll part annularly surrounding a circumference of a turbine wheel, and a tongue part provided in a rear end part of a roll of the scroll part annularly surrounding a circumference of a turbine wheel and forms a boundary against the introduction part formed approximately linearly from an inlet through which an exhaust gas is introduced. The introduction part of the exhaust inflow passage possesses a partition part dividing a range from an inlet to a predetermined position in a downstream of the inlet into two exhaust inflow passages, a throttle part, whose sectional area becomes gradually small, from the inlet to a throttle outlet where the partition part ceases, a joining part where exhaust gases passing through the left and right exhaust inflow passages are joined, and a diffuser part, whose sectional area becomes gradually large, from the joining part to the tongue part.

By this, since a pulse converter is provided in the exhaust inflow passage inside the turbocharger, a compact constitution is obtained. Further, by the pulse converter, an interference between the exhaust gases introduced from the inlets in two places can be reduced. Additionally, since a dynamic pressure can be effectively converted into a static pressure, a loss of energy for rotating the turbine wheel becomes small.

In the turbocharger concerning the invention, a sum of sectional areas of the exhaust inflow passages at the throttle outlet may be made 50–80% of a sectional area of the exhaust inflow passage at the tongue part, or in the diffuser part a minimum sectional area of the exhaust inflow passages may be made 50–80% of a maximum sectional areas of the exhaust inflow passages. By this, the loss of the energy when recovering the dynamic pressure as the static pressure becomes small.

In the turbocharger concerning the invention, a distance between the throttle inlet to the throttle outlet may be made 20–40% of a distance from the throttle inlet to a rear end of the tongue part. By this, it is possible to prevent the exhaust interference by sufficiently increasing flow velocities of the exhaust gases and, since the diffuser part is long, the dynamic pressure can be effectively converted into the static pressure.

In the turbocharger concerning the invention, an EGR passage taking out one part of the exhaust gas flowing through the exhaust inflow passage and recovering it to a charge side of an engine may be connected to a downstream of the joining part. By this, it is possible to take out one part of the exhaust gas by only one EGR passage without destroying a balance between the exhaust gases exhausted from the front/rear cylinder groups. Accordingly, the number of components of the EGR cooler and so forth becomes small.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereunder, embodiments concerning the invention are explained in detail while referring to the drawings.

First, a 1st embodiment is explained. It is an example of an engine that does not use an EGR system. As shown inFIG. 1toFIG. 4, the exhaust piping75A,75B are respectively connected to the front/rear exhaust manifolds65A,65B. The introduction part69of the exhaust inflow passage19is bisected from its inlets81A,81B to its approximately halfway part into the two exhaust inflow passages19A,19B by a partition part79. And, the exhaust piping75A,75B are respectively connected to inlets81A,81B of the exhaust inflow passages19A,19B.

The exhaust gases63A,63B exhausted from the front/rear cylinder groups64A,64B respectively flow into the inlets81A,81B of the two exhaust inflow passages19A,19B while passing through the front/rear exhaust manifolds65A,65B and the front/rear exhaust piping75A,75B. And, the exhaust gases63A,63B are joined at a joining part82in a halfway part, of the introduction part69, where the partition part79ceases.

At this time, as shown inFIG. 4, the two exhaust inflow passages19A,19B are constituted such that their sectional areas are largest in the inlets81A,81B, and their sectional areas become gradually small until reaching to throttle outlets80A,80B where the partition part79ceases. That is, throttle parts77A,77B are formed between the inlets81A,81B and the throttle outlets80A,80B. As a result, the exhaust gases63A,63B having entered into the inlets81A,81B gradually increase their flow velocities, and reach to the joining part82.

Incidentally, as structures of the throttle parts77A,77B, inFIG. 4, an outer wall and an inner wall of the turbine housing15are depicted so as to be concaved inward, but it is not limited to this. For example, the throttle parts77A,77B may be formed with the outer wall being flat and the inner wall being protruded inward.

The exhaust inflow passage19is constituted such that, in a downstream of the joining part82, its sectional area becomes gradually large. By this, a diffuser part78is formed. Incidentally, in a case where a direction is expressed by words “from an upstream to a downstream”, it is made one on the basis of a direction of a flow of the exhaust gas shown by an arrow mark63A,63binFIG. 3.

By such a diffuser part78, the exhaust gases63A,63B emerging from the throttle parts77a,77bat high speeds gradually regain the static pressure. And, they flow into the scroll part68without losing the energy so much, thereby driving the turbine wheel14. At this time, as shown inFIG. 3, a part provided in a rear end part of a roll of the scroll part annularly surrounding a circumference of a turbine wheel and forms a boundary against the introduction part formed approximately linearly from an inlet through which an exhaust gas is introduced is referred to a tongue part76.

As explained above, according to this embodiment, in the exhaust inflow passage19of the turbine housing15, there are provided the throttle parts77A,77B and, following these, the diffuser part78. By this, it is possible to compactly constitute the pulse converter and efficiently transmit the energies of the exhaust gases63A,63B to the turbine wheel14.

The exhaust gas63A emerging from the front exhaust manifold65A and the exhaust gas63B emerging from the rear exhaust manifold65B are joined after having been increased in their flow velocities respectively in the throttle parts77A,77B. Accordingly, the exhaust interference becomes difficult to occur.

Incidentally, it is suitable that a distance between the throttle inlet81A,81B to the throttle outlet80A,80B is 20–40% of a distance from the throttle inlet81A,81B to a rear end of the tongue part76.

By this, since the exhaust interference can be prevented by sufficiently increasing the flow velocity of the exhaust gas and the diffuser part78of a sufficient length can be obtained, it is possible to efficiently convert the dynamic pressure into the static pressure.

It is appropriate that a sum of the sectional areas of the two exhaust inflow passages19A,19B at the throttle outlets80A,80B is made 50–80% of a sectional area of the exhaust inflow passage19at the tongue part76, or in the diffuser part a minimum sectional area of the exhaust inflow passages is 50–80% of a maximum sectional areas of the exhaust inflow passages. By doing so, when the exhaust gases63A,63B pass through the diffuser part78, it is possible to convert the dynamic pressure into the static pressure while reducing the loss of the energy.

Next, it is explained about a 2nd embodiment. As shown inFIG. 5andFIG. 6, the EGR passage73is connected to an outside of the scroll part68of the exhaust inflow passage19. A EGR gas74taken out through the EGR passage73is supplied to each of the cylinders64A,64B through the charge manifold71, and recirculated.

Like this, according to the 2nd embodiment, it is adapted such that the exhaust gases63A,63B enter, after having been joined, into the EGR passage73as the EGR gas74. By this, since the exhaust gases63A,63B emerging from the front/rear exhaust manifolds65A,65B equally enter into the EGR passage73, an unbalance of combustion between the front/rear cylinder groups64A,64B does not occur. Accordingly, in addition to the advantage of the 1st embodiment, also in the EGR system, a good operation of the engine62is made possible.

Further, after the static pressures of the exhaust gases63A,63B have been regained through the diffuser part78, one part of them is taken out as the EGR gas74through the EGR passage73. Accordingly, at a taking-out time, pressure loses of the exhaust gases63A,63B are difficult to occur, so that the loss of the energy is small.

Incidentally, inFIG. 6, the EGR passage73is connected to the downstream of the tongue part76, but it may be connected to substantially the same position as the tongue part76or to slightly upstream of the tongue part76. That is, it suffices if it is adapted such that the pressure loss becomes as small as possible when taking out the EGR gas74.