JPS61210223A - Exhaust turbosupercharging device - Google Patents

Abstract

PURPOSE:To obtain good turbocharging response by causing the rotation of a downstream turbine preliminarily on an exhaust after its actuation of an upstream turbine, and increasing the turbine speed through throttling an exhaust introduced to the downstream turbine at the start of acceleration. CONSTITUTION:Turbines 9a and 10a each for two turbochargers 9 and 10 are arranged in series in the exhaust passage 11 of an engine. And a passage 12 is branched from the exhaust passage 11 at the upstream of a primary turbine 9a, continuously to the upstream of a secondary turbine 10a, and a flow control valve 13 is provided in way of the said passage 12. On the other hand, a variable capacity mechanism 18 is provided for the secondary turbine 10a and so made that a variable vane 20 will throttle the throat of a scroll housing 19, depending upon pressure working on a diaphragm device 21 via a pressure regulating valve 22. And pressure regulating valves 17 and 22 are actuated by a control circuit 29, according to detected signals from a speed sensor 27 and a turbocharged pressure sensor 28, thereby controlling the opening of the flow control valve 13 and the variable vane 20.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an exhaust turbocharging device including a plurality of turbochargers.

(Prior Art) A turbocharger is provided in order to improve engine output and fuel efficiency, but some engines are equipped with a plurality of turbochargers in order to improve the acceleration performance of the VA system. In such a device, the rise of the supercharging pressure of the first turbocharger is important, so the first turbocharger V is downsized, and in the low speed range, the first turbocharger first increases the supercharging pressure to the set supercharging pressure. After increasing the pressure in a responsive manner and reaching the set supercharging pressure, a relatively large second turbocharger is operated to ensure supercharging effect in the medium and high speed range (Japanese Patent Laid-Open No. 59-134327). (see publication).

This is shown in FIG. 6. In the figure, the first turbocharger 2 includes a first turbine 2a installed in an exhaust passage 3 communicating with the combustion chamber of the engine body 1, and a first turbine 2a installed in a first intake passage 4a. 1 compressor 2b and a rotating shaft 2C that directly connects them.

A bypass passage 5 is branched from the exhaust passage 3 upstream of the first turbine 2a, through which exhaust gas flows bypassing the first turbine 2a.
An exhaust switching valve 6 is installed in this branch portion.

The second turbocharger 7 includes a second turbine 7a installed in the bypass passage 5, a second compressor 7b installed in the second intake passage 4b, and a rotating shaft 7C directly connecting these.

The first and second intake passages 4a and 4b merge upstream of the intake passage 4, and an intake switching valve 8 is interposed at the junction.

When the discharge pressure of the first compressor 2b reaches a specified value, the exhaust switching valve 6 opens the bypass passage 5 and introduces 1 air into the second turbine 7a. Further, the intake switching valve 8 opens the second intake passage 4b when the discharge pressure of the second compressor 7b reaches a specified value.

Therefore, in the low speed operating range where the engine exhaust flow m is small,
Exhaust from the combustion chamber passes through the exhaust passage 3 to the first turbine 2.
This exhaust energy is supplied to the first turbine 2
a is rotationally driven. The first compressor 2b is driven by the rotational force of the turbine 2a, whereby the air in the first intake passage 4a is pressurized and sent under pressure to the combustion chamber via the intake passage 4.

In this state, the discharge pressure of the first compressor 2b is low and the exhaust switching valve 6 closes the bypass passage 5.
Exhaust gas is not supplied to the turbine 7a: 2nd turbo
Ja7 is out of operation.

Further, when the operating body of the second turbocharger 7 is stopped, the discharge pressure of the second compressor 7b is ◯, and the intake switching valve 8 closes the second intake passage 4b.

From this state, when the exhaust flow rate increases due to an increase in the engine speed, the discharge pressure increases due to the increase in the rotation speed of the first compressor 2b, and when this reaches a specified value, the exhaust switching valve 6 opens and a part of the exhaust gas is transferred to the bypass passage. Start running at 5. This exhaust gas is supplied to the second turbine 7a, the second turbine 7a, the second
The compressor 7b is driven to rotate. Therefore, the second compressor 7b increases the discharge pressure.

When the discharge pressure of the second compressor 7b reaches the specified value, the intake switching valve 8 opens the second intake passage 4b, and the air pressurized by the second compressor 7b is supplied to the combustion chamber.

In this way, the first turbocharger 2, which exhibits high efficiency with a relatively small exhaust flow rate in the low speed rotation range, is operated,
By operating the second turbocharger 7, which has a relatively large capacity, in the medium to high speed rotation range, a sufficient supercharging effect is ensured in the entire operating range.

(Problems to be Solved by the Invention) However, in such a device, the first turbine 2a and the second turbine 7a are connected in parallel, and after the discharge pressure of the first compressor 2b reaches a specified value, Since the exhaust gas is guided to the second turbine 7a and drives the second compressor 7b, if the exhaust flow rate of the engine does not increase considerably after the discharge pressure of the first compressor 2b reaches a specified value, the second compressor 7b will be activated. The discharge pressure does not increase.

For this reason, there is a problem in that it takes time for the discharge pressure of the second compressor 7b to rise to the specified value, and the acceleration responsiveness deteriorates accordingly.

In addition, if the capacity of the second turbocharger 7 is lowered in order to improve acceleration response, the overall amount of discharged air may be insufficient, and as shown in [A] in Fig. 5, the medium speed region where supercharging is switched There was a problem that the engine torque decreased and the maximum output also decreased.

(Means for Solving the Problems) This invention provides a branch passageway in which a turbine that drives a compressor is arranged in series in an exhaust passage of an engine, and a branch passage bypasses the turbine on the upstream side and introduces exhaust gas into the turbine on the downstream side. A flow control valve is installed in this passage, a variable capacity mechanism is provided in the turbine on the downstream side, and a means is provided for controlling the drive of the variable capacity mechanism and the control valve according to the operating conditions of the engine. [Puru.

(Operation) The downstream turbine is rotated in advance by the exhaust gas that drives the upstream turbine, and the downstream turbine is equipped with a variable capacity mechanism, so the rise in the discharge pressure of the downstream compressor is sufficiently accelerated during acceleration. .

Therefore, good responsiveness can be obtained without reducing the turbo capacity, and it is possible to improve the maximum output while ensuring high engine acceleration.

(Example) Figures 1 and 2 are block diagrams including a plot diagram and a control system showing practical examples of the present invention, where 1 is the engine body, 9 is the small-capacity first turbocharger, and 10 is a comparison diagram. This is a second turbo bench for large customers.

Turbine (first turbine) 9 of first turbocharger 9
a and the turbine (second turbine) 10a of the second turbo digital engine 1710 are arranged in series in the exhaust passage 11 of the engine.

A branch passage 12 is formed from the exhaust passage 11 upstream of the first turbine 9a to bypass the first turbine 9a and connect to the upstream side of the second turbine 10a, and a flow control valve 13 is formed in the middle of the branch passage 12.
is interposed.

In this case, the branch passage 12 may be directly connected to the exhaust manifold 14 as shown in FIG.

The flow ffi ill tit valve 13 has a butterfly type valve body 15 connected to a diaphragm device 16, and a pressure regulating valve 1.
The opening degree is changed according to the operating pressure supplied to the diaphragm device 16 via the diaphragm device 7.

The second turbine 10a is equipped with a variable displacement mechanism 18.

Each variable tooth mechanism 18 may have a variable nozzle disposed on the outer circumference of the blade of the turbine 10a, but in this case, a variable vane 2 that narrows the throat portion is installed in the scroll housing 19.
0 is attached, and the variable vane 20 is connected to the diaphragm device 2.
1. The variable vane 20 throttles the throat portion of the housing 19 in accordance with the operating pressure supplied to the diaphragm device 21 via the pressure regulating valve 22.

Note that the pressure within the intake passage 23 is used as the operating pressure of the diaphragm device 16.21.

A compressor (first
A compressor (compressor) 9b is installed in the first intake passage 23a, and a compressor (second compressor) 10b driven by the second turbine 10a is installed in the second intake passage 23b.

The first and second intake passages 23a and 23b merge in the middle and are connected to the intake passage 23, and one-way valves 24 and 25 are interposed in front of the junction to prevent backflow, respectively. 26 is an intercooler.

On the other hand, a rotation speed sensor 27 for detecting the rotation speed of the engine and a pressure sensor 28 for detecting the pressure in the intake passage 23, that is, the supercharging pressure, are provided as means for detecting the operating conditions of the engine.
These detection signals are sent to a control circuit 29 as a control means.

The two control circuits drive the pressure regulating valves 17 and 22 based on these detection signals, and the supercharging pressure increases as shown in FIGS. 3(a) and 3(a).
The drift control valve 13 and the variable vane 20 are controlled to the opening degrees shown in FIG. 4 according to the engine speed so that the values shown in [a] of b) are obtained.

However, in (a) and (b) of FIG. 3, [port] is the discharge pressure of the first compressor 9b, and [c] is the discharge pressure of the second compressor 10.
The discharge pressure of b, [1], and [I[] each represent the characteristics of a single unit. Also, in the figure, the corrected flow rate is shown instead of the engine speed.

Note that 30 in Fig. 1 is a waste gate valve that releases part of the exhaust gas to the relief passage 31 (not shown in Fig. 2).
, is opened by the control circuit 29 when the boost pressure exceeds the upper limit value.

Next, the effect will be explained.

When the throttle is opened from a low-speed engine rotation state, the exhaust gas introduced through the exhaust passage 11 first accelerates the rotation of the first turbine 9a in a responsive manner, and the discharge pressure of the compressor 9b quickly rises. Figure 3 (a), (b)
) of A-+8).

At this time, the variable vane 20 of the second turbine 10a is fully opened (see FIG. 4), and the second turbine 10a starts rotating due to the exhaust gas that has driven the first turbine 9a.

The exhaust flow history increases with the progress of acceleration, and when the discharge pressure of the first compressor 9b reaches the set value P, the variable vane 2
0 is gradually closed (from C to D in Figure 4).

Then, as the back pressure of the first turbine 9a increases, the second
Since the speed of the exhaust gas introduced into the turbine 10a is increased, the rotation of the second turbine 10a gradually increases while the discharge pressure of the first compressor 9b is maintained at approximately P (BE)'.

When the variable vane 20 is fully opened (minimum area state), the flow control valve 13 of the branch passage 12 is gradually opened (F-
+G), the exhaust gas that has bypassed the first turbine 9a is introduced into the second turbine 10a.

Therefore, the discharge pressure of the first couplet li 9 b is the same <
P, and (E→1''), the second turbine 10
The rotation of a is quickly increased. As a result, the discharge pressure of the second compressor 10b also increases rapidly (r-
J) During this upward movement, the discharge pressure of the second compressor 10b is lower than the discharge pressure of the first compressor 9b, so that the discharge air of the second compressor 10b is not supplied to the engine.

Then, when the flow rate control valve 13 is opened to a certain extent and the discharge pressure of the second compressor 10b reaches the set value P2, the variable vane 20 is gradually opened from the minimum opening degree (after L), and the flow rate control valve 13 is fully opened. (G→K).

Then, since the resistance in the branch passage 12 is eliminated, almost no exhaust gas from the engine flows toward the first turbine 9a, and almost all of the exhaust gas is introduced into the second turbine 10a.

Therefore, the discharge pressure of the first compressor 9b decreases, and at the same time as the decrease, the discharge air of the second compressor 10b comes to be supplied to the engine.

After that, when the rotation of the second turbine 10a increases, the variable vane 2o is further opened so that the discharge pressure of the second compressor 10b does not exceed P.
Decrease the flow rate of exhaust gas introduced into 0a. Incidentally, at this time, the waste gate valve 30 may be opened to release the exhaust gas, or P2 may be arbitrarily set by these.

In this way, the first and second turbo V-jars 9.10
The exhaust gas that drove the first turbine 9a is guided to the second turbine 10a, and the
The flow velocity of the exhaust gas introduced into the turbine 10a is variable by the vane 2.
Since the speed is increased by 0, the second turbo charge tr
10 is sufficiently accelerated, and therefore, after the supercharging pressure by the first turbocharger v9 reaches the set pressure, supercharging by the second turbocharger 1o can begin immediately.

As a result, good responsiveness is ensured without reducing the capacity of the second turbocharger 10, high acceleration performance of the engine can be obtained, and since the capacity of the second turbocharger 10 can be increased, a sufficient amount of supercharging can be achieved. As shown in Figure 5, the maximum output can be improved over the entire operating range of the engine. However, [C] in FIG. 5 shows the output characteristics of a single turbocharger.

Δ3, when supercharging by the second turbocharger 10, the first
Since the turbo engine V-di ty9 almost stops, there is no exhaust pressure and the output is further improved.

Moreover, if the branch passage 12 is formed as shown in FIG. 2, the degree of freedom in arranging the turbochargers 9 and 10 is increased, flow path loss is reduced, and better acceleration performance can be obtained.

(Effects of the Invention) As described above, according to the present invention, the exhaust gas that drives the upstream turbine is used to pre-rotate the downstream turbine, and at the same time, the exhaust gas introduced into the downstream turbine at the time of acceleration is throttled. Since the engine speed is increased, an excessively good supercharging response can be obtained, and the acceleration performance and maximum output of the engine can be improved.

[Brief explanation of drawings]

Figures 1 and 2 are block diagrams showing embodiments of the present invention and configuration diagrams including the control system, Figures 3 (a) and (b) are graphs showing examples of supercharging pressure control, and Figure 4 5 is a graph showing an example of the operation of a flow control valve and a variable vane, FIG. 5 is an output characteristic diagram, and FIG. 6 is a configuration diagram of a conventional example. 9a, 10a...Turbine, 9b, 10b...
- Compressor, 11... Exhaust passage, 12... Branch passage, 13... Flow ffiυ1n valve, 18... Variable housing mechanism, 20... Variable vane, 23... Intake passage,
24.25... One-way valve, 27... Rotation speed sensor,
28...Pressure sensor, 29...Control circuit. Fig. 1 9σ, 10σ-1-9-gon 9b, 10h-1-Cosidem Vpu 11--Ichigoki 1 word 12-branch passage 13--Ichibara amount JFIJ Mii 18-11 Fraud amount f7 The mechanism Figure 2 2/Z1 Fishing J! mgJ bath 3rd figure 3 friends 1 4th figure 4th figure 5th figure 5 [mouth] Rotary wealth χ

Claims (1)

[Claims] A turbine that drives a compressor is arranged in series in the exhaust passage of the engine, and a branch passage is formed that bypasses the turbine on the upstream side and introduces exhaust gas into the turbine on the downstream side, and a flow control valve is installed in this passage. An exhaust turbo supercharging device, characterized in that a downstream turbine is provided with a variable capacity mechanism, and means for controlling the drive of the variable capacity mechanism and the flow rate control valve according to engine operating conditions.