JPH0510486B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a turbine scroll for a turbocharger, and more particularly to a turbine scroll in which the exhaust capacity supplied to the exhaust turbine is made variable at the scroll inlet depending on the operating state of the engine.

Figure 1 shows an example of a conventional turbine scroll with variable capacity of this type.
This is disclosed in No. 11233. here,
A turbine rotor 1 is directly connected to a compressor impeller (not shown) by a rotor shaft 2. A turbine scroll 3 with a spiral passage is provided on the outer periphery of the turbine rotor 1. Exhaust gas from passage 4 is guided.

Further, in the turbine scroll 3 of this example, the housing 5 has a wall 5 projecting from an oblique direction with respect to the shaft 2.
The large exhaust passage section 3A and the small exhaust passage section 3B form a spiral chamber, and these passage sections 3A and 3B are opened toward the inlet section 1A of the rotor 1. I'm letting you do it.

Reference numeral 6 denotes an on-off valve provided on the large exhaust passage 3A side of the exhaust passage 4 connected to the inlet portion 3C of the scroll 3. This on-off valve 6 changes the volume of exhaust gas flowing into the large exhaust passage 3A. can be done. 7 is an exhaust gas outlet.

In the turbine scroll 3 configured in this way, when the engine is in a low speed rotation region,
In order to maintain compatibility between the turbocharger and the engine and obtain good supercharging characteristics at low speeds, it is necessary to reduce the gas passage area. (1) allows the on-off valve 6 to be operated to adjust the volume of gas passing through the large exhaust passage 3A. Furthermore, when the engine is in a high speed rotation region, the large exhaust passage 3
Gas is supplied to the rotor 1 from both A and the small exhaust passage 3B.

However, in the turbine scroll 3 in which the gas capacity supplied to the rotor 1 is made variable in this way, both the large exhaust passage 3A and the small exhaust passage 3B have a shape that opens toward the rotor inlet portion 1A, and furthermore, Since the gas flow rate of the large exhaust passage 3A is configured to be throttled by the valve 6, when the gas supply to the large exhaust passage 3A is suddenly cut off by the on-off valve 6 in the low speed rotation region of the engine, this A dead water area occurs in the large exhaust passage 3A.

In such a state, gas flows from the rotor inlet 1A to the rotor 1 via the small exhaust passage 3B.
At this time, a swirling flow 10 as shown in FIG. 2A is generated near the inlet portion 1A, so that the gas fluid forming the swirling flow 10 has a centrifugal force. A part of the gaseous fluid is then dissipated into the gas body which is a dead water region of the large exhaust passage 3A, thereby generating a circulating flow 11 as shown in FIG. 2B. Since this circulating flow 11 flows along the wall surface of the large exhaust passage 3A, it loses energy due to friction loss and joins the swirling flow 10 again, so the energy loss within the turbine scroll 3 is large and the turbine efficiency is reduced. This results in the effect of lowering the

Furthermore, FIG. 3 shows a commonly used double entry housing type scroll 3,
In this type of device, the housing 5 is divided in the axial direction by a wall 5A projecting from the outer periphery. However, even if such a double entry housing type scroll 3 is provided with an on-off valve (not shown) that opens and closes either one of the exhaust passages 3D, a similar phenomenon may occur. , the efficiency is lower than in the case of a single-entry turbine scroll, making it difficult to build up turbocharging pressure at low speeds.

An object of the present invention is to focus on the above-mentioned problems, and to make effective use of the exhaust engine from low speed to high speed engine speeds, reduce loss, maintain good turbine efficiency, and further reduce engine backlash. An object of the present invention is to provide a turbine scroll for a turbocharger that contributes to maintaining sufficient high-speed output through the effect of lowering pressure.

In order to achieve such an object, the present invention includes a spiral main exhaust passage having an opening toward the turbine rotor inlet, and a spiral main exhaust passage that is attached to the main exhaust passage and is separated from the turbine rotor inlet by a partition wall. The partition wall includes an auxiliary exhaust passage and a valve that makes the amount of exhaust gas supplied to the auxiliary exhaust passage variable depending on the operating condition of the engine, and the partition wall has an axis centered on the axis of the turbine rotor. A communication portion having a constant width bounded by two concentric circles extending from the main exhaust passage side to the auxiliary exhaust passage side is provided substantially over the entire circumference of the turbine rotor, and the cross-sectional shape including the axis of the communication portion is arranged from the main exhaust passage side to the auxiliary exhaust passage side. Exhaust gas moves directly between the main exhaust passage and the auxiliary exhaust passage in a direction parallel to the axis via the communication portion so as to be inclined in a direction closer to the axis of the turbine rotor. In the low speed rotation region of the engine, the auxiliary exhaust passage is closed by the valve to allow the exhaust gas to communicate only along the slope of the communication portion. It is characterized in that the exhaust gas is supplied to the turbine rotor only through a passage.

The present invention will be explained in detail below based on the drawings.

FIG. 4 shows one embodiment of the invention, where 13
is a turbine scroll, and 13A is a spiral main exhaust passage of the scroll 13. The main exhaust passage 13A has an opening 14 facing the inlet 1A of the rotor 1, and the main exhaust passage 13A
A communication portion 15 is provided between the exhaust gas and the auxiliary exhaust passage 13B provided in parallel with each other via the partition wall 5B.

Although this communication portion 15 is formed concentrically as described above, the slit is formed from the main exhaust passage 13A side as shown in this figure. It is inclined in a direction approaching the axis O of the rotor 1 toward the auxiliary exhaust passage 13B, and a constant width B is maintained.

Furthermore, although the communication portion 15 is formed with an inclination, at the same time, the main exhaust passage 13A and the auxiliary exhaust passage 13B side are separated by a partition wall 5B as shown in FIG.
It is desirable to obtain an overlapping amount (overlap amount) L. However, this communication part 15
Accordingly, the sharp edge portions 15A and 15B formed on the main exhaust passage 13A side and auxiliary exhaust passage 13B side surfaces of the partition wall 5B may be finished smoothly within a range where the overlap amount L can be obtained.

Further, as shown in FIG. 6, the communication portion 15 is provided in a concentric shape around the rotor axis O, but the wider the circumferential range, the more desirable the communication portion 15 is. By making the range where there is no fluid as short as possible, increase in fluid energy loss due to non-uniformity of flow at the inlet portion 1A of the turbine rotor 1 is suppressed.

In this example, the passage is formed from the smallest passage on the rotor 1 side in the tongue 16 of the scroll 13 to a position as close as possible to the constriction, that is, the throat 17 formed by the tongue 16 and the housing 5. .

Furthermore, in FIG. 6, 25 is the auxiliary exhaust passage 13.
This is an on-off valve (rotary valve in this example) provided on the upstream side of the throat portion 17 of B, and this on-off valve 25
The flow rate on the auxiliary exhaust passage 13B side is adjusted by. As shown in FIG. 7, the on-off valve 25 includes a cover 26 attached to the scroll 5 by means such as bolts, and a bush 2 press-fitted into the cover 26.
7, a valve body 25A having a shaft 28 rotatably supported by a bush 27, and a lever 29 for rotating the shaft 28, and is controlled to open and close by a control means (not shown). Note that FIG. 6 shows the on-off valve 25 in a closed state.

Further, in this example, the on-off valve 25 is provided in the housing 5 upstream from the throat portion 17, but instead, the on-off valve 25 is provided in an auxiliary exhaust passage (not shown) upstream from the inlet portion 13C of the scroll 13. You can do it like this. Thus, the on-off valve 25 is closed by the control means in the low speed rotation region of the engine.

Next, the setting of the width B of the communication portion 15 in the turbine scroll configured as described above will be described. When setting the width B, it is necessary to consider the influence on the supercharging characteristics, and the conditional expression that provides the best supercharging characteristics confirmed by the inventor is shown below.

B≧A _BT /R _B /A _AT /R _A +A _BT /R _B ×H... (1) However, in equation (1), A _AT : Area of main exhaust passage 13A at throat portion 17A B _BT : Auxiliary Throat portion 17B of exhaust passage 13B
area R _A : Distance from the rotor axis O to the center of gravity of the throat part 17A R _B : Distance from the rotor axis O to the center of gravity of the throat part 17B H : Blade width at the inlet part 1A of the turbine rotor 1 In other words, (1) It is desirable to set the width B of the communication portion 15 using the formula, but if the width B is to be made narrower than this due to design reasons, the above conditions should be kept in mind and consideration should be given to reduce loss as much as possible. It must be.

Next, the fluid behavior of the turbine scroll 13 configured as described above during engine operation will be described, and the effects of providing the communication portion 15 will also be described.

When the on-off valve 25 is closed in the low speed rotation range of the engine, a dead water area is generated in the auxiliary exhaust passage 13B, but the auxiliary exhaust passage 13B is separated from the main exhaust passage 13A by the partition wall 5B, Since it is not opened toward the inlet section 1A, the second
Flows such as those described in FIGS. A and B do not occur.

In addition, the main exhaust passage 1 of the turbine scroll 13
The flow velocity distribution on the 3A side is a free vortex flow expressed by V x r = constant, where r is the distance from the axis O to the fluid position and V is the flow velocity at that position, so it is inversely proportional to the radius r. proportionally the flow velocity V
changes. That is, the flow velocity becomes slower closer to the outer circumference of the scroll 13, and the flow velocity becomes faster closer to the rotor 1. Therefore, the static pressure is low on the inlet 1A side of the rotor 1, and the static pressure is high on the outer circumference.

Therefore, it can be seen that in the case of the communicating portion 15 provided concentrically at positions equidistant from the axis O, the static pressure in this portion 15 is kept constant over the entire circumference. That is, this prevents the fluid from branching from the main exhaust passage 13A side to the auxiliary exhaust passage 13B side due to the pressure difference caused by the difference in radial position, and maintains a good flow condition. be able to. Next, the effect of the overlap formed in the communication portion 15 will be explained with reference to FIG. In this example, the edge portion 15A on the side of the main exhaust passage 13A is formed to protrude from the line of the main wall surface 5D on this side of the partition wall 5B, and the reason and effect thereof will be described later.

Now, as an example where no overlap is formed in the communication section 15, assume that the outer communication section wall 30A is located at the position indicated by the broken line. Auxiliary exhaust passage 13 in this case
Main exhaust passage 1 with the edge part on the B side set as 15B'
The radial position corresponding to this edge portion 15B' on the 3A side is A1, the radial position corresponding to the edge 15A is A2, and the radial position midway between positions A1 and A2 on the auxiliary exhaust passage 13B side is B1.
shall be.

Therefore, the positions A1, A2 and B in this case
When the static pressures at 1 are respectively P _A1 , P _A2 and P _B1 , a relationship of P _A1 > P _B1 > P _A2 holds between these static pressures.

Therefore, if we do not form such an overlap, we can move from A1 to B as shown by the dashed line.
1, and further from B1 to A2, a secondary flow 40 is generated in a direction parallel to the axis of the turbine rotor 1. That is, a swirling flow suddenly jumps out from the main exhaust passage 13A side to the auxiliary exhaust passage 13B side, and from the auxiliary exhaust passage 13B side, the fluid in the low energy dead water region is instead returned to the main exhaust passage 13A side. , their mixing results in a loss of fluid energy.

On the other hand, the outer communication wall 30B is positioned as shown by the solid line in FIG. If this is done (the amount of overlap is zero), the tendency of secondary flow in the direction parallel to the axis as described above is suppressed, and if the secondary flow from the main exhaust passage 13A side to the auxiliary exhaust passage 1
Even if a part of the swirl flow flows into the auxiliary exhaust passage 13B, the wall surface 5E of the partition wall 5B
The flow of fluid from the side to the main exhaust passage 13A side is blocked, and energy loss can be suppressed to a minimum.

The present inventor conducted an experiment to confirm the effect of the above-mentioned overlap formation, and found a tendency for the efficiency to decrease as shown in FIG. 9. Here, the horizontal axis shows the ratio of the overlap amount L to the communication portion slit width B, and the vertical axis shows the turbine efficiency in a low speed region with respect to L/B. As is clear from this figure, the overlap L is zero, that is, the set area marked with the mark to the left of L/B=0 (when the width B and the thickness of the partition wall 5B are constant, the slit of the communication portion 15 As the slope decreases toward the left on the horizontal axis), the efficiency η _T decreases rapidly.

As is clear from the results of this experiment, it is preferable to set the overlap amount L to at least zero, but even if such a setting is difficult due to design reasons, the negative overlap amount can be set to a width B. 25% of
In other words, it is desirable to keep L/B to about -0.25 in order to almost suppress the exhaust gas from flowing in a direction parallel to the axis.

Next, the control and fluid operation in the engine medium speed rotation region will be explained. In this state, the on-off valve 25
is controlled so that it is almost half open. Therefore, the exhaust gas flows outside the main exhaust passage 13A through the auxiliary exhaust passage 13B, which is in a half-open state, but the gas flowing through the passage 13B flows through the communication portion 1 according to the opening degree of the on-off valve 25.
The gas starts flowing along the slope from the communication part 15 at the most downstream position of No. 5, that is, the minimum passage position, and then the inflow range is gradually expanded upstream to guide the gas to the main exhaust passage 13A side.

Thus, by fully opening the on-off valve 25 in the high speed rotation region of the engine, the auxiliary exhaust passage 1
Gas efficiently flows into the main exhaust passage 13A side from the 3B side through the entire circumference of the communication portion 15 and is guided to the turbine rotor 1, so that the inlet pressure of the turbine, that is, the back pressure of the engine, is reduced compared to the conventional case. can contribute to improving output.

In addition, in FIG. 8, the wall surface 5C on the rotor 1 side, which is limited by the communication part 15 of the partition wall 5B, is made to protrude from the main wall surface 5D by a dimension C, and the partition wall 5B in this part
Although the edge portion 15A is formed in this example, the effect thereof will be supplementarily explained. As mentioned above, the auxiliary exhaust passage 1
When gas is also supplied to the 3B side, the fluid that has lost energy due to friction with the wall surface of the auxiliary exhaust passage 13B gathers on the inner circumference side of the passage 13B.
This secondary flow is about to be led directly to the rotor inlet 1A. The partition wall 5B on the rotor 1 side that forms the edge portion 15A not only acts as a barrier (boundary rare fence) that prevents such secondary flow from being guided to the rotor inlet 1A, but also
It serves to help mix the gas flow led from the communication part 15 to the main exhaust passage 13A side and the main flow flowing through the main exhaust passage 13A, and improves the flow around the turbine inlet 1A to improve the turbine efficiency and improve overall efficiency. Good turbine performance can be maintained over the operating range.

Furthermore, the fact that the partition wall 5B on the rotor 1 side protrudes by the dimension C reduces the boundary layer generated on the partition wall surface 5D on the main exhaust passage 13A side.
By conversely guiding the secondary flow toward the auxiliary exhaust passage 13B, it is possible to further prevent the above-mentioned secondary flow from being directly guided to the rotor inlet 1A.

Note that it is preferable to set the radial position of the communication portion 15 as large as the design allows, in order to improve efficiency in the medium and high speed range where exhaust gas is guided to the auxiliary exhaust passage 13B side.

FIG. 10 shows another embodiment of the invention. In this example, the valve is a slap valve 35, and 36 is its opening/closing shaft. In this case, a valve seat 37 is provided on the wall surface of the housing 5 forming the auxiliary exhaust passage 13B, and when the valve 35 is closed, the valve 35 body comes into contact with the stepped valve seat 37, thereby preventing leakage. This aims to prevent this and improve performance at low speeds.

FIG. 11 shows still another embodiment of the present invention, in which auxiliary exhaust passages are provided in multiple stages. Here, 13B and 13D are auxiliary exhaust passages, and 5G is a partition wall between auxiliary exhaust passages 13B and 13D. Therefore, the partition walls 5B and 5G
A communication portion 15 as shown in FIG. 4 or FIG. 8 is provided at a substantially relative position of the auxiliary exhaust passages 13B and 13D. The other configurations are the same as those shown in FIG. 4, and their explanation will be omitted. In the turbine scroll 13 configured in this manner, the flow rate range can be greatly changed by appropriately controlling the on-off valves provided in each of the auxiliary passages 13B and 13D, and control is easy.

Furthermore, in this example, although not shown, a generally known exhaust bypass valve may be provided in the auxiliary exhaust passage 13B or 13D, and the supercharging pressure of the engine may be controlled by this exhaust bypass valve. Needless to say.

As described above, according to the present invention, there is provided a spiral main exhaust passage having an opening toward the turbine rotor inlet, and a partition wall that is provided along with the main exhaust passage and extends from the turbine rotor inlet. It has an isolated auxiliary exhaust passage and a valve that varies the amount of exhaust gas supplied to the auxiliary exhaust passage depending on the operating condition of the engine, and the partition wall has a wall with a central axis of the turbine rotor as the center. A communicating portion having a constant width bounded by two concentric circles is provided over the entire circumference of the turbine rotor, and a cross-sectional shape including the axis of the communicating portion extends from the main exhaust passage side to the auxiliary exhaust passage side. Exhaust gas moves directly between the main exhaust passage and the auxiliary exhaust passage in a direction parallel to the axis via the communication portion so as to be inclined in a direction closer to the axis of the turbine rotor. In the low speed rotation region of the engine, the auxiliary exhaust passage is closed by the valve, and the main exhaust Since the exhaust gas is supplied to the turbine rotor only through the passage, even when the engine is running at low speed, it is possible to prevent the exhaust gas in the dead water region generated in the auxiliary exhaust passage from being carried into the rotor in a state where energy has been lost. I can,
Appropriate boost pressure can be supplied and good turbine efficiency can be obtained.

Furthermore, even at medium-high speeds, the exhaust gas can be guided directly to the rotor for supercharging, so there is less loss of exhaust energy and the back pressure of the engine can be lowered, contributing to medium-high speed output. It goes without saying that it can be done.

In addition, in the above explanation, the partition wall is configured to be a surface perpendicular to the rotation axis, but depending on the spiral form of the scroll to be set, the partition wall does not necessarily have to be a surface perpendicular to the rotation axis. , the surface may be slightly inclined from this angle.

[Brief explanation of the drawing]

Fig. 1 is a sectional view showing an example of the configuration of a conventional variable displacement turbine scroll, and Figs. 2 A and B show the swirling flow generated around the turbine rotor and the large exhaust passage when the on-off valve is open and closed. An explanatory diagram showing the tendency of circulating flow that occurs in
FIG. 3 is a cross-sectional view showing an example of a conventional turbine scroll of the double entry housing type, FIG. 4 is a cross-sectional view showing an example of the structure of the turbine scroll of the turbocharger of the present invention, and FIG. 5 shows details of the communication portion thereof. 6 is a sectional view showing a state in which a rotary valve is provided in the auxiliary exhaust passage of the turbine scroll according to the present invention; FIG. 7 is a sectional view taken along Y-Y line of the rotary valve in FIG. 6; FIG. is a sectional view illustrating a state in which harmful secondary flow is blocked by the communication portion of the turbine scroll according to the present invention,
Fig. 9 is a characteristic curve diagram showing the state of decrease in turbine efficiency when the ratio between the width of the slit and the amount of overlap in the communication portion is changed, and Fig. 10 A and B are auxiliary examples of the present invention. A cross-sectional view showing a state in which a flap valve is provided in the exhaust passage, a cross-sectional view taken along the line X--X, and FIG. 11 are a cross-sectional view of a turbine scroll according to still another embodiment of the present invention. 1... Turbine rotor, 1A... Inlet section, 2...
...Shaft, 3,13...Turbine scroll, 3A,
3B, 4...Exhaust passage, 3C, 13C...Inlet, 5...Housing, 5A...Wall, 5B, 5G
...Partition wall, 5C, 5D, 5E...Wall surface, 6,2
5, 35... Valve, 7... Gas outlet, 10... Swirling flow, 11... Circulating flow, 13A, 13B, 13D...
...exhaust passage, 14...opening, 15...communication part,
15A, 15B, 15B'...Edge part, 16...
...Tongue, 17...Throat, 26...Cover,
27...butsuyu, 28...shaft, 29...
Lever, 30A, 30B...Wall, A1, A2, B
1...Position, 36...Opening/closing axis, 37...Valve seat part,
40...flow.

Claims (1)

[Claims] 1. A spiral main exhaust passage having an opening facing the turbine rotor inlet, an auxiliary exhaust passage provided alongside the main exhaust passage and separated from the turbine rotor inlet by a partition wall, and the auxiliary exhaust The partition wall has a valve with a constant width bounded by two concentric circles centered on the axis of the turbine rotor. A communication portion is provided over substantially the entire circumference of the turbine rotor, and a cross-sectional shape including the axis of the communication portion is inclined in a direction from the main exhaust passage side to the auxiliary exhaust passage side toward the axis of the turbine rotor. The exhaust gas is prevented from directly moving between the main exhaust passage and the auxiliary exhaust passage in a direction parallel to the axis via the communication portion, and the exhaust gas is directed to the communication portion. so that communication is possible only along the slope of the engine, and in a low speed rotation region of the engine, the auxiliary exhaust passage is closed by the valve and the exhaust gas is supplied to the turbine rotor only through the main exhaust passage. A turbine scroll for a turbocharger characterized by: