JPH0861076A - Exhaust bypass structure of turbocharger - Google Patents

Abstract

(57) [Abstract] [Purpose] To provide an exhaust bypass structure of a turbocharger that can effectively use the energy of exhaust gas. A turbocharger exhaust bypass structure according to the present invention includes a turbine housing inner wall 16 of a turbine casing 1 that surrounds a turbine impeller 3 from the outside in a radial direction.
A bypass that faces the inside of an outlet region 22 whose axial range is defined by the throat portion 18 of the turbine impeller 3 and bypasses exhaust gas from the outlet region 22 to the exhaust passage 21 on the downstream side of the turbine impeller 3. One end of the passage 23 is opened.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an exhaust bypass structure for a turbocharger mounted on an automobile or the like.

[0002]

2. Description of the Related Art Generally, as shown in FIG. 5, a turbocharger a mounted on an automobile or the like uses a high temperature and high pressure energy of exhaust gas to rotate a turbine impeller b at a high speed and a compressor c coaxial with the turbine impeller. It is designed to rotate and supercharge.

Further, the turbocharger a usually has a supercharging pressure control means, and the illustrated example is an example of a typical exhaust bypass system.

The turbine impeller b is a turbine casing d.
An introduction passage f for accommodating the exhaust gas from the engine in the turbine housing chamber e inside the turbine casing d.
Is formed. The illustrated example shows a radial turbine, that is, a scroll chamber g is formed between the introduction passage f and the turbine housing chamber e, and the exhaust gas of this scroll chamber g is directed radially outward to the turbine impeller b. Was introduced from
After changing the direction at right angles between the turbine blades h, the exhaust passage i on the downstream side of the turbine blade wheel b toward the axial tip direction thereof.
Exhausted through.

In the turbine casing d, a bypass passage j that bypasses the turbine impeller b and connects the introduction passage f and the exhaust passage i is formed. The bypass passage j is partitioned from the introduction passage f by a partition wall k, and its inlet is formed by a bypass hole 1 provided in the partition wall k. A wastegate valve m for opening and closing the bypass hole 1 is provided in the bypass passage j, and the wastegate valve m is operated by an actuator n to which intake pressure or supercharging pressure from the compressor c is introduced. Therefore, when the supercharging pressure exceeds a predetermined value, the actuator n opens the valve m, thereby releasing a part of the exhaust gas to the bypass passage j, limiting the exhaust gas flow rate to the turbine impeller b, and controlling the supercharging pressure. ing.

As described above, when the exhaust gas is bypassed, a method of bypassing the upstream side of the turbine is generally used, and it is schematically shown in FIG.

[0007]

By the way, in such a system, since the exhaust gas is released on the upstream side of the turbine, the energy possessed by the exhaust gas is simply discarded, and the energy cannot be utilized. .

Therefore, the present invention has been devised in view of the above viewpoint, and an object thereof is to provide an exhaust bypass structure of a turbocharger which can effectively use the energy of exhaust gas.

[0009]

In order to achieve the above object, an exhaust bypass structure for a turbocharger according to the present invention is provided with a turbine casing inner wall of a turbine casing that surrounds a turbine impeller from the outside in the radial direction. By opening one end of a bypass passage, which faces the inside of an outlet area whose axial range is defined by the throat portion of the impeller and which bypasses exhaust gas from the outlet area to an exhaust passage on the downstream side of the turbine impeller. is there.

[0010]

The throat portion is a substantial exhaust gas outlet of the gas passage formed between the turbine blades. By opening one end of the bypass passage so as to face the outlet region where the axial range is defined by the throat portion, the exhaust gas can be used for rotation of the turbine impeller and then bypassed. Therefore, the energy of the exhaust gas can be effectively used.

[0011]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT A preferred embodiment of the present invention will be described in detail below with reference to the accompanying drawings.

FIG. 1 is an enlarged side sectional view showing a turbine peripheral portion of a turbocharger.

As shown in the figure, inside the turbine casing 1, a scroll chamber 2 into which exhaust gas from an engine is introduced, a turbine chamber 4 in which a turbine impeller 3 is rotatably accommodated, and these scroll chambers 2 And an intermediate zone 5 located in the middle of the turbine accommodating chamber 4. Since these are in communication with each other, their sections are shown by imaginary lines a and b.

The scroll chamber 2 is located in the radial direction of the turbine accommodating chamber 4. However, unlike the aspect of the radial turbine in this embodiment, the gas inlet portion 7 of the turbine blade 6 of the turbine impeller 3 is cut diagonally. Missing. That is, the turbine impeller 3 is of a mixed flow type, and particularly the leading edge portion (end edge portion) 8 of the turbine blade 6 is inclined much more than in the case of the conventional mixed flow type, that is, with respect to its turbine axis 9. The angle α is larger than the conventional one (up to 30 °) (35 ° -60 °).
°).

By the way, this structure has the same structure as that previously proposed by the present applicant (see "Turbine for Supercharger" filed on August 19, 1994, Japanese Patent Application No. 6-194469).
According to this, the centrifugal force to the exhaust gas introduced into the gas inlet portion 7 of the turbine blade 6 is removed, and the exhaust gas entering the intermediate zone 5 from the radial direction is smoothly directed toward the gas inlet portion 7. Therefore, the introduction of the exhaust gas is made smooth and the characteristics and efficiency of the turbine are significantly improved.

A plurality of turbine blades 6 are erected on the outer peripheral surface of the disk 10. The disk 10 has a simple substantially conical shape, whereas the turbine blade 6 has a three-dimensional and complicated shape. ing. Therefore, for convenience, the illustrated turbine impeller 3 is represented by a meridional surface shape in which the turbine impeller 3 is cut along a vertical plane including the turbine axis 11, that is, a vertical plane. And usually
The outermost peripheral edge 12 of the turbine blade 6 is called a shroud, and its connecting edge 13 with the disk 10 is called a hub. Further, the leading edge 8 is different from the edge at the gas outlet 14 of the turbine blade 6. Reference numeral 15 is referred to as a trailing edge portion. Here, the shroud 12 is slightly separated from the inner wall 16 of the turbine housing chamber 4, in other words,
The inner wall 16 surrounds the turbine impeller 3 from the outside in the radial direction.

FIG. 2 shows the shroud 12 of the turbine blade 6.
It is a figure which shows the shape in a position. Turbine blade 6
The center portion is smoothly bent, and the distance between the turbine blades 6 adjacent to each other is maximum between the leading edge portions 8 and thereafter, is gradually reduced along the gas flow direction. The portion sandwiched by these turbine blades 6 is the gas flow path 1
7 is formed, but the flow passage cross-sectional area is the smallest in the throat portion 18 which is substantially the outlet of the exhaust gas.

Returning to FIG. 1, an exhaust manifold 20 is connected to the outlet portion 19 of the turbine casing 1, and an exhaust passage 21 is formed on the downstream side of the turbine impeller 3 by these.

Further, the turbine casing 1 is formed with a bypass passage 23 for bypassing the exhaust gas from the inside of the outlet region 22 whose axial range is defined by the throat portion 18 to the exhaust passage 21. Exit area 2 here
2 is the region shown between the dotted lines c and d in FIGS. 1 and 2, and the position of the dotted line c is particularly the position of the shroud 12 at the axially proximal end side of the throat portion 18, and the position of the dotted line d. Also coincides with the position on the tip side in the axial direction. Specifically, the bypass passage 23 is formed in a ring shape around the entire circumference of the inner wall 16 and is open to face the outlet region 22 and open.
And a communicating passage 25 provided so as to communicate the groove portion 24 and the inside of the outlet portion 19. The groove 24 has a rectangular cross section, and the opening thereof has a width h that fits in the outlet region 22.
And the communication passage 25 is substantially formed by a hole 26 bored axially from the side wall of the groove portion 24 into the outlet portion 19.

In addition, the outlet 19 has a bypass passage 2
An on-off valve for opening and closing 3, that is, a waste gate valve 27 is provided. Also referring to FIG. 3, the waste gate valve 27 is specifically a swing valve,
That is, this includes a valve shaft 28 rotatably provided through the outlet portion 19, a valve body portion 29 provided at one end of the valve shaft 28 located inside the outlet portion 19, and a valve shaft 28 It is mainly configured by the action portion 30 provided at the end. A dashpot 31, which is an actuator, is connected to the action portion 30 via a rod 31a, and an intake pressure or a supercharging pressure p from a compressor (not shown) is introduced into the dashpot 31. Therefore, when the supercharging pressure p exceeds a predetermined value, the dashpot 31 acts on the action portion 30 to rotate the valve shaft 28, open the valve body 32 of the valve body portion 29, and open the communication passage 25, that is, the bypass passage 23. Open.

The above structure is schematically shown in FIG.

Next, the operation of the above embodiment will be described.

When the normal wastegate valve 27 is closed, the exhaust gas from the engine is introduced into the turbine casing 1 through an introduction passage (shown by f in FIG. 5).
It is introduced into the scroll chamber 2 while the flow velocity is increased inside.
Then, the exhaust gas flows through the intermediate zone 5 through the gas flow path 17 of the turbine impeller 3 and is discharged to the outside through the exhaust passage 21.

When the engine speed or the supercharging pressure rises, the exhaust gas flow rate also gradually increases, but when the flow rate value reaches a certain value, the scroll chamber 2 and the turbine impeller 3 are moved.
Since the exhaust gas is smoothly introduced into the turbine impeller 3, the throat portion 18 of the turbine impeller 3 is closed or choked, that is, the exhaust gas pressure is increased and the flow thereof is rapidly deteriorated.

However, when the supercharging pressure reaches a predetermined value, the waste gate valve 27 is opened.
A part of the exhaust gas is bypassed from the outlet region 22 including 8 to the bypass passage 23. In this case, the pressure of the throat portion 18 is lowered and the flow of the exhaust gas is also smoothed, while the rotation increase of the turbine impeller 3 is suppressed and the supercharging pressure can be controlled.

As is apparent here, even when the exhaust gas is bypassed, all the exhaust gas can be used for the rotation of the turbine impeller 3. Therefore, it is possible to recover more high-temperature and high-pressure energy of exhaust gas, and it is possible to effectively use it.

Further, since a large amount of energy of exhaust gas is recovered, energy efficiency can be improved and the turbine inlet pressure can be set lower than in the conventional case. Further, the exhaust pressure of the engine can be lowered, and the engine output can be improved.

By the way, the inside of the exhaust passage 21 is almost atmospheric pressure, and therefore the position immediately after the throat portion 18 is also atmospheric pressure. On the other hand, the exhaust gas in the position immediately before the throat portion 18 has a higher pressure than that, and even if the wastegate valve 27 is closed, the exhaust gas may escape to the exhaust passage 21 through the groove 24. However, at this time, the bypass passage 23 is a closed space, and the exhaust gas that has entered the bypass passage 23 is subjected to centrifugal force, so that the escape amount is extremely small. Also, at this position, there is no problem because the exhaust gas has been sufficiently worked.

When the waste gate valve 27 is opened, exhaust gas can escape from the entire circumference through the groove 24. Then, the high-pressure exhaust gas immediately before the throat portion 18 and the exhaust gas in the depressurization process from the high pressure immediately after the throat portion 18 to the atmospheric pressure in the outlet region 22 can be released. Furthermore, since only one communication passage 25 that connects the groove 24 and the exhaust passage 21 is provided, only one wastegate valve 27 is required and downsizing can be achieved. Further, the structure is simple, and it can be put to practical use at low cost.

In this way, by allowing one end of the bypass passage 23 to face the outlet area 22, normal operation is performed when bypass is not performed, and choke of the throat portion 18 is prevented during bypass, and the turbine is maximized. It is possible to control the supercharging pressure while working. The above configuration is applicable to a general radial type turbine, but is particularly effective for a mixed flow type turbine that is less affected by centrifugal force when introducing exhaust gas.

[0031]

The present invention exhibits the following excellent effects.

(1) The high temperature and high pressure energy of exhaust gas can be recovered more and can be effectively utilized.

(2) The energy efficiency can be improved and the turbine inlet pressure can be set low.

[Brief description of drawings]

FIG. 1 is a side sectional view showing an exhaust bypass structure of a turbocharger according to the present invention.

FIG. 2 is a diagram showing a shape of a turbine blade at a shroud position.

FIG. 3 is a schematic plan sectional view showing a supercharging pressure control portion including a waste gate valve.

FIG. 4 is a schematic view showing a turbocharger according to the present invention.

FIG. 5 is a schematic sectional view showing a conventional turbocharger.

FIG. 6 is a schematic view showing a conventional turbocharger.

[Explanation of symbols]

 1 Turbine casing 3 Turbine impeller 4 Turbine accommodation chamber 16 Inner wall 18 Throat portion 21 Exhaust passage 22 Outlet area 23 Bypass passage 24 Groove 25 Communication passage

Claims (2)

[Claims] 1. An exhaust gas is exposed to an inner wall of a turbine housing of a turbine casing that surrounds a turbine impeller from the outside in a radial direction so as to face an outlet area whose axial range is defined by a throat portion of the turbine impeller. An exhaust bypass structure for a turbocharger, characterized in that one end of a bypass passage for bypassing from the outlet region to an exhaust passage on the downstream side of the turbine impeller is opened. 2. The bypass passage is formed in a ring shape over the entire circumference of the turbine accommodating chamber inner wall and is open to face the outlet region, the groove portion formed in the turbine casing and the exhaust gas. The exhaust bypass structure for a turbocharger according to claim 1, wherein the exhaust bypass structure is formed by a communication passage communicating with the passage.