JP2000213359A - Variable capacity turbocharger - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the desired supercharged pressure according to the engine operating state without increasing fuel consumption of the engine, by preventing exhaust gas from flowing from an inner peripheral scroll part to an outer peripheral scroll part. SOLUTION: Communication passages 30a are provided so that each vane part 34 of an involute partition wall 30 formed between the mutually adjacent communication passages 30a has a downstream first surface 34a extending in the tangential direction of the inner peripheral surface of the partition wall 30 and an upstream second surface 34b extending in parallel with the first surface. The peripheral length of each vane part 34 is set to the length in which the normal line passing the inner peripheral scroll part side end (a) in relation to a straight line linking the inner peripheral scroll part side end (a) and the outer peripheral scroll part side end (b) to each other intersects the vane part 34 arranged on the downstream side.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a variable capacity turbocharger for supercharging a vehicle engine.

[0002]

2. Description of the Related Art As a conventional variable capacity turbocharger, for example, there is one disclosed in Japanese Patent Application Laid-Open No. 10-8977. The variable-capacity turbocharger includes a shaft, a turbine rotor fixed to one end of the shaft, and an exhaust inlet, an exhaust outlet, and an exhaust inlet and an exhaust inlet and an exhaust outlet communicating with the turbine rotor through the turbine rotor. A turbine housing having a scroll portion whose sectional area gradually decreases, a compressor rotor fixed to the other end of the shaft and housed in the compressor housing, and a scroll portion radially extending into an inner peripheral scroll portion and an outer peripheral scroll portion. It is provided with a partition wall having a plurality of communication holes that are divided and communicate between the two scroll portions, and a control valve that can control opening and closing of communication between an exhaust inlet and the outer peripheral scroll portion.

Each of the communication holes of the partition wall has a first surface on the downstream side in which each vane formed between the communication holes adjacent to each other extends toward the inner peripheral scroll portion in a direction substantially tangential to the inner peripheral surface of the partition wall. And an upstream second surface extending toward the inner peripheral scroll portion toward the rotation center of the turbine rotor.

In this variable capacity turbocharger, in a low speed range of an engine having a small amount of exhaust gas, communication between an exhaust inlet and an outer scroll portion is cut off by a control valve.
Exhaust gas is caused to flow only into the inner peripheral scroll portion having a small capacity to obtain a small exhaust inflow angle with respect to the blades of the turbine rotor and a high exhaust flow velocity, thereby accelerating the turbine rotor and increasing the supercharging pressure. Further, after the middle speed range where a predetermined supercharging pressure is reached, the exhaust gas flows into the outer scroll portion via the control valve, and the exhaust gas flowing into the outer scroll portion flows through the communication hole of the partition wall into the inner circumferential portion. The exhaust gas flows into the scroll portion toward the rotation center of the turbine rotor and recombines with the exhaust gas flowing into the inner peripheral scroll portion, and the tangential flow of the exhaust gas in the inner peripheral scroll portion to the turbine rotor rotation center The speed of the turbine rotor is limited by reducing the flow velocity of the exhaust gas impinging on the turbine rotor and increasing the exhaust inflow angle, and the opening of the control valve is controlled so as to maintain a constant supercharging pressure. You.

[0005]

However, in the above-described conventional variable capacity turbocharger, the opening area of the communication hole on the inner circumferential scroll portion side becomes extremely small, so that the back pressure is prevented from increasing in the middle and higher speed regions of the engine. In each adjacent vane portion, the end of the first surface of the upstream vane portion on the inner peripheral scroll portion side and the end of the second surface of the downstream vane portion on the outer peripheral scroll portion side are separated in the circumferential direction. Therefore, when the exhaust gas flowing into the inner peripheral scroll portion flows along the inner peripheral surface of the partition wall due to the action of the centrifugal force, the exhaust gas flows out to the outer peripheral scroll portion through the communication hole by the centrifugal force. I will. Therefore, in the low-speed range of the engine described above, the desired exhaust pressure cannot be obtained due to a decrease in the exhaust flow velocity, and the flow from the inner circumferential scroll portion to the outer circumferential scroll portion through the communication hole after the middle speed range of the engine. This causes a problem in that the exhaust gas flowing becomes a resistance to the flow of the exhaust gas in the outer peripheral scroll portion, so that the back pressure of the engine increases and fuel efficiency increases.

Accordingly, the present invention provides a variable displacement turbocharger in which exhaust gas is prevented from flowing from the inner scroll portion to the outer scroll portion, and the variable capacity turbocharger is adapted to the engine operating state without increasing the fuel efficiency of the engine. It is an object to obtain a desired supercharging pressure.

[0007]

Means for Solving the Problems The technical means of the present invention taken to solve the above-mentioned problems includes a shaft, a turbine rotor fixed to one end of the shaft, an exhaust inlet for accommodating the turbine rotor and an exhaust inlet. A turbine housing having a scroll portion that communicates the exhaust outlet and the exhaust inlet with the exhaust outlet through the turbine rotor, the cross-sectional area of which is gradually reduced; and a turbine housing fixed to the other end of the shaft. The accommodated compressor rotor, a partition wall dividing the scroll portion radially into an inner scroll portion and an outer scroll portion, and a plurality of the inner circumferential scroll portions provided on the partition wall at predetermined circumferential intervals. A communication passage communicating between the outer peripheral scroll portions;
In a variable capacity turbocharger including at least opening / closing means capable of opening / closing communication between the exhaust inlet and the outer peripheral scroll portion, each vane portion of the partition wall formed between the communication passages adjacent to each other is formed by the partition. The communication path is provided so as to have a downstream first surface extending substantially tangentially to the inner peripheral surface of the wall and an upstream second surface extending substantially parallel to the first surface. The circumferential length of the vane portion is set such that a normal passing through the inner peripheral scroll portion side end is located on the downstream side with respect to a straight line connecting the inner peripheral scroll portion side end and the outer peripheral scroll portion side end. And the length intersects with the vane portion.

According to this means, since the shape and the circumferential length of each vane are determined as described above, the inner circumferential scroll portion of the first surface of the upstream vane in each adjacent vane is provided. The side end portion and the end portion of the second surface of the downstream side vane portion on the outer peripheral scroll portion side are not separated in the circumferential direction,
The opening area on the inner peripheral scroll portion side of the communication passage is ensured. As a result, when the exhaust gas flows along the inner peripheral surface of the partition wall in the inner peripheral scroll portion, the exhaust gas is accurately prevented from flowing out to the outer peripheral scroll portion through the communication path due to the centrifugal force. Thus, a desired supercharging pressure can be efficiently obtained in a low-speed region of the engine in which exhaust gas flows only into the inner peripheral scroll portion. Further, after the middle speed region of the engine in which the exhaust gas flows into the inner and outer scroll portions by the opening / closing means, the exhaust gas in the outer scroll portion due to the exhaust gas flowing from the inner scroll portion to the outer scroll portion through the communication path. The gas flow is maintained smoothly without being disturbed, and the back pressure of the engine is reduced, thereby reducing fuel consumption.

In the above-mentioned means, it is preferable that the first surface and the second surface of each vane portion are each a convex arc surface.

[0010]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment of a variable capacity turbocharger according to the present invention will be described below with reference to the drawings.

In FIG. 1, the variable displacement turbocharger has a cylindrical bearing housing 10 having a shaft hole 10a formed therein, and a radial bearing 21 in the shaft hole 10a. A shaft 20 is rotatably supported via 22. The radial bearings 21 and 22 are rotatably fitted in the shaft hole 10a, and the movement in the axial direction to the sides facing each other is restricted by the snap ring. The radial bearing 22 is restricted from moving rightward in the figure by a step formed on the shaft 20. A small diameter portion is formed on the left side of the shaft 20 fitted in the radial bearing 21 in the drawing, and a flange portion is formed on the right end portion of the small diameter portion in contact with one end surface of the radial bearing 21. A cylindrical bush 23 is fitted. The bush 2
A bush 29 having a flange formed at the right end in the figure is fitted on the left side of the figure 3. Bush 2
An oil seal is fitted in an annular groove formed on the outer periphery of the bearing housing 9.
The inner peripheral cylindrical portion of the plate seal 25 fitted in the large-diameter hole formed on the left side of the 0 shaft hole 10a in the drawing slides in a liquid-tight manner. The compressor rotor 19 is fitted to a small diameter portion of the shaft 20 on the left side of the bush 29 in the drawing, and is fixed by a bolt 27 screwed to an end of the small diameter portion. Thus, the bushes 23 and 29 are sandwiched between the illustrated right end surface of the compressor rotor 19 and the step portion of the small diameter portion of the shaft 20, and rotate integrally with the shaft 20 together with the compressor rotor 19. A thrust bearing 24 fixed to the right side of the large-diameter hole of the bearing housing 10 in the drawing is interposed between the flange portions of the bushes 23 and 29. The thrust bearing 24 includes the bearing housing 10
, And are communicated with oil passages for supplying oil to the radial bearings 21 and 22, and the bushes 23 and 29
An oil supply hole for supplying oil between the sliding portion and the flange portion is formed. In addition, the plate seal 25 includes
An oil shielding plate 26 having a hole through which the cylindrical portion of the bush 29 penetrates is fixed. A compressor housing 18 having an intake port 18a and an intake port 18b is hermetically fixed to the bearing housing 10, and a compressor rotor 19 is accommodated in the compressor housing 18.

A turbine rotor 13 is fixed to the right end of the shaft 20 in the figure. The turbine rotor 13 is housed in a second turbine housing 12 which is airtightly fixed via a gasket to a first turbine housing 11 fixed to the right end of the bearing housing 10 in the figure. The second turbine housing 12 has an exhaust inlet 12a
(See FIG. 2) and an exhaust outlet 12b are formed. An exhaust manifold of an engine (not shown) is connected to the exhaust inlet 12a, and an exhaust outlet pipe (not shown) is airtightly connected to the exhaust outlet 12b. . Incidentally, in FIG.
Is a shielding plate whose outer peripheral end is sandwiched and fixed between the first turbine housing 11 and the bearing housing 10 and whose inner peripheral end extends to the back of the turbine rotor 13.

As shown in FIGS. 1 and 2, the second turbine housing 12 is provided with a scroll portion for guiding the exhaust gas introduced into the exhaust inlet 12 a to the outer periphery of the turbine rotor 13. The scroll portion includes an involute partition wall 30 provided in the second turbine housing 12.
An inner peripheral scroll groove 12d and an outer peripheral scroll groove 12c radially partitioned by are formed.
By closing the opening of 12c by the first turbine housing 11, the inner peripheral scroll part 31 and the outer peripheral scroll part 32 having a larger volume than the inner peripheral scroll part 31 are provided.
Are formed in a compartment. The inner and outer scroll portions 31 and 32 have a sectional area of the turbine rotor 1.
3 is provided so as to gradually decrease in the rotation direction (counterclockwise direction in FIG. 2), and communicates with the downstream end portion of the involute partition wall 30.

As shown in FIG. 2, a downstream portion of the involute partition wall 30 (the inner periphery of which is
A plurality of communication holes 30a which communicate the inner and outer scroll portions 31 and 32 are formed in the outer peripheral portion of the inner peripheral scroll portion 31 which is open to the outer peripheral portion of the third blade, and thereby are adjacent to each other. Vane portions 3 between communication holes 30a
4 are formed. In the present embodiment, each of the vane portions 34 includes a first surface 34a on the downstream side extending substantially tangentially to a portion of the inner peripheral surface of the involute partition wall 30 located on the downstream side by a predetermined angle, and the first surface 34a. And each of the communication holes 3 has an upstream second surface 34 b extending substantially in parallel with the communication hole 3.
0a is formed, and as described later, when the exhaust gas flowing through the outer peripheral scroll portion 32 flows toward the inner peripheral scroll portion 31 in the rotation direction of the turbine rotor 13 through the communication hole 30a, the inner peripheral scroll portion 31 The flow of the exhaust gas flowing in the tangential direction of the turbine rotor is changed to the flow toward the rotation center of the turbine rotor 13. The circumferential length of each vane portion 34 is determined by its inner scroll portion side end point a and its outer scroll portion side end point b.
The length of a normal passing through the end point a on the inner peripheral scroll portion side with respect to the straight line connecting to the vane portion 34 adjacent to the downstream side is set to a length. In the present embodiment, the first surface 3
Both 4a and the second surface 34b are formed as convex arc surfaces.

The exhaust inlet 12 of the involute partition wall 30
As shown in FIG. 2, an opening 33 communicating between the outer peripheral scroll portion 32 and the exhaust inlet 12a is provided at the a-side end (upstream end).
Are formed. A flow control valve 40 that opens and closes the opening 33 by being seated on and separated from a valve seat formed on the outer edge of the opening 33 on the outer scroll portion 32 side is provided in the outer scroll portion 32. A hinge portion is fixed to the flow control valve 40 by a pin, and a rotation shaft fixed to the hinge portion is rotatably supported by the second turbine housing 12. A known negative pressure type actuator 42 is connected to one end of the rotation shaft of the flow control valve 40 through a link mechanism 41.
Are connected to one end of the output rod. The negative pressure actuator 42 rotates the rotary shaft via a link mechanism by applying a negative pressure from a negative pressure source (not shown) by a well-known proportional flow control valve (not shown) according to the running state of the vehicle as described later. Then, the opening and closing of the opening 33 by the flow control valve 40 is controlled.

The operation of this embodiment having the above configuration will be described.

When an engine (not shown) is started, supercharging by the variable displacement turbocharger is started. That is,
The exhaust gas flowing from the exhaust manifold into the exhaust inlet 12a drives the turbine rotor 13 to rotate, and the compressor rotor 19 rotates together with the shaft 20 to supercharge an engine (not shown).

In the low speed range of the engine having a small amount of exhaust gas, a negative pressure type actuator 4 is controlled by a control device (not shown).
2, a negative pressure is supplied from a negative pressure source (not shown), and the flow control valve 40 is in a closed state shown in FIG. Therefore, the exhaust gas flowing from the exhaust manifold into the exhaust inlet 12a is supplied to the turbine rotor 13 only through the inner peripheral scroll portion 31, and the turbine rotor 13 is driven to rotate. As a result, it functions as a turbocharger having a small A / R (small scroll capacity) to obtain a high exhaust flow velocity, and exhaust gas flows in a tangential direction of the turbine rotor 13 via the inner peripheral scroll portion 31 (turbine rotor). Thirteen blades at a small angle of inflow),
The turbine rotor 13 is efficiently rotated, the turbine rotor 13 is accelerated, and the boost pressure is increased.

In the present embodiment, the shape and the circumferential length of each vane portion 34 are determined as described above, so that the upstream vane portion 3 in each adjacent vane portion 34 is formed.
4 and the end of the downstream surface of the second surface 34b of the vane portion 34b on the outer peripheral scroll portion side of the communication hole 30a without being separated in the circumferential direction. The opening area on the peripheral scroll portion side is secured. Therefore, when the exhaust gas flows along the inner peripheral surface of the involute partition wall 30 in the inner peripheral scroll portion 31, the exhaust gas is prevented from flowing out to the outer peripheral scroll portion 32 through the communication hole 30 a due to centrifugal force. Is done. When the exhaust gas flows through the inner peripheral scroll portion 31 along the inner peripheral surface of the involute partition wall 30, the exhaust gas is applied to the second surface 34 of each vane portion 34.
However, since the second surface 34b is formed of a convex arc surface, the exhaust gas does not flow out to the outer peripheral scroll portion 32 along the second surface 34b. As a result, the inner scroll part 31 moves to the outer scroll part 3
Exhaust gas is prevented from flowing out through the communication hole 30a to the engine 2 properly, and a desired supercharging pressure can be efficiently obtained in the above-described low-speed range of the engine.

After the middle speed range of the engine where the amount of exhaust gas increases, the negative pressure is not supplied from the negative pressure source (not shown) to the negative pressure type actuator 42, and the flow rate is increased by the urging force of the spring (not shown) in the negative pressure type actuator 42. The control valve 40 swings around the drive shaft 42 to open the opening 33. Therefore, the exhaust gas flowing from the exhaust manifold to the exhaust inlet 12 a flows into the inner peripheral scroll part 31 and also flows into the outer peripheral scroll part 32 through the opening 33. The exhaust gas flowing into the outer scroll portion 31 flows into the inner scroll portion 31 through the communication hole 30 a of the involute partition wall 30 toward the rotation center side of the turbine rotor 13, and the exhaust gas flows into the inner scroll portion 31. The gas rejoins with the gas and changes the flow of the exhaust gas in the inner peripheral scroll portion 31 in the tangential direction of the turbine rotor 13 to the flow toward the rotation center of the turbine rotor 13, and the flow velocity of the exhaust gas impinging on the turbine rotor 13 decreases. As a result, the exhaust gas hits the blades of the turbine rotor 13 at a small inflow angle, the efficiency of rotating the turbine rotor 13 is reduced, the rotation of the turbine rotor 13 is suppressed from rising, and the supercharging pressure is kept constant. Will be kept.

At this time, since the exhaust gas from the inner scroll portion 31 to the outer scroll portion 32 does not flow out through the communication hole 30a as described above, the exhaust gas flowing into the outer scroll portion 32 flows Flows smoothly into the inner peripheral scroll portion 31 through the communication hole 30a without being disturbed. Further, in the present embodiment, as described above, in each of the adjacent vanes 34, the end of the first surface 34 a of the upstream vane 34 on the inner circumferential scroll portion side and the second end of the downstream vane portion 34. The surface of the surface 34b is not separated from the end on the outer peripheral scroll portion side in the circumferential direction, and the communication hole 30a
Because the inner peripheral scroll part side opening area of is secured,
The cross-sectional area (passage area) of the communication hole 30a can be increased, and the exhaust gas flowing into the outer scroll portion 32 smoothly flows into the inner scroll portion 31 through the communication hole 30a without resistance. Therefore, the flow of the exhaust gas in the inner peripheral scroll portion 31 in the tangential direction of the turbine rotor 13 can be reliably changed to the flow toward the rotation center side of the turbine rotor 13, and the pressure rise at the exhaust inlet 12a (engine Back pressure increase), and fuel efficiency can be reduced.

[0022]

As described above, according to the first aspect of the present invention, when the exhaust gas flows along the inner peripheral surface of the partition wall in the inner peripheral scroll portion, the exhaust gas is exhausted through the communication passage by centrifugal force. It is possible to accurately prevent the gas from flowing out to the outer scroll portion. This makes it possible to efficiently obtain a desired supercharging pressure in a low-speed range of the engine in which the exhaust gas flows only into the inner peripheral scroll portion by the opening / closing means, and to exhaust air to the inner peripheral and outer peripheral scroll portions by the opening / closing device. After the middle speed range of the engine into which gas flows,
Exhaust gas flowing from the inner scroll portion to the outer scroll portion through the communication passage is smoothly maintained without disturbing the flow of the exhaust gas in the outer scroll portion, and the back pressure of the engine is reduced to reduce fuel consumption. be able to.

According to the second aspect of the present invention, when the exhaust gas flows along the inner peripheral surface of the partition wall in the inner peripheral scroll portion, the exhaust gas that collides with the second surface of each vane portion is discharged. 2
And it can be prevented from flowing out to the outer peripheral scroll portion along the surface, and a desired supercharging pressure according to the operating state of the engine can be more reliably obtained.

[Brief description of the drawings]

FIG. 1 is a sectional view showing one embodiment of a variable capacity turbocharger according to the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

[Explanation of symbols]

 Reference Signs List 10 bearing housing 11 first turbine housing (turbine housing) 12 second turbine housing (turbine housing) 12a exhaust inlet 12b exhaust outlet 13 turbine rotor 18 compressor housing 19 compressor rotor 20 shaft 30 involute partition wall (partition wall) 30a communication hole ( (Communication passage) 31 inner peripheral scroll part 32 outer peripheral scroll part 33 opening 34 vane part 34a first surface 34b second surface 40 flow control valve (opening / closing means)

 ────────────────────────────────────────────────── ─── Continuing on the front page (72) Inventor Shinji Kono 2-1-1 Asahi-cho, Kariya-shi, Aichi F-term in Aisin Seiki Co., Ltd. 3G005 EA04 EA14 FA05 FA37 FA45 GA03 GA07 GB02 GB09 GB87 GC05 GD17 3G071 AA02 AB06 BA00 BA07 DA01 EA00 FA02 HA03

Claims (2)

[Claims] 1. A shaft, a turbine rotor fixed to one end of the shaft, an exhaust inlet, an exhaust outlet, and a communication between the exhaust inlet and the exhaust outlet via the turbine rotor while accommodating the turbine rotor. A turbine housing having a scroll portion whose cross-sectional area gradually decreases; a compressor rotor fixed to the other end of the shaft and housed in a compressor housing; and a radially inner scroll portion and an outer scroll scrolling the scroll portion. Partition wall, a plurality of communication passages provided on the partition wall at predetermined circumferential intervals and communicating between the inner scroll portion and the outer scroll portion, at least the exhaust inlet and the outer scroll portion A variable capacity turbocharger comprising opening and closing means capable of opening and closing communication between Each vane portion of the partition wall formed between the communication passages has a downstream first surface that extends substantially in a tangential direction of an inner peripheral surface of the partition wall and an upstream side surface that extends substantially parallel to the first surface. The communication path is provided so as to have the second surface, and the circumferential length of each of the vanes is set with respect to a straight line connecting the inner scroll side end and the outer scroll side end. A variable-capacity turbocharger, wherein a length of a normal passing through an end of the inner peripheral scroll portion side intersects the vane portion provided adjacently on the downstream side. 2. The variable-capacity turbocharger according to claim 1, wherein the first surface and the second surface of each vane portion are each a convex arc surface.