JPS61164040A - Internal-combustion engine with turbo charger - Google Patents

Abstract

PURPOSE:To prevent torque drop in the operational range of a second turbo charger by operating a variable capacity type turbo charger to increase the capacity after supercharging pressure reaches a predetermined value through the turbo charger substantially initially operated. CONSTITUTION:Since a flap 29 of a variable capacity mechanism 24 in a second turbo charger 7 at the low rotational frequency and low load of an engine is fully closed, exhaust from an engine body 1 flows into a first turbine 9 of a first turbo charger 5 to operate only said charger 5. Thereafter, as the rotation and load of the engine are increased, when the discharge pressure of a first compressor 17 reaches a desired supercharging pressure, the supercharging pressure acts on an actuator 35 to open a flap 29 and increases the turbine capacity. Thus, the capacity of a second turbe charger 7 is increased to increase exhaust to the second turbo charger 7 while decreasing exhaust to the first turbo charger 5 to maintain the desired supercharging pressure.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a turbocharged internal combustion engine having a plurality of turbochargers.

[Prior art] Internal combustion with a turbocharger is generally used in automobiles, etc. Since the first engine is used in a wide rotation range and a wide load range, it is desirable for the turbocharger to operate effectively over a wide range. As a countermeasure to this problem, a method is proposed in which a plurality of turbochargers are installed and the number of turbochargers to be activated is changed depending on the operating conditions, for example, in Japanese Patent Laid-Open No. 59-685.
It is described in Publication No. 21.

In the system described in this publication, two turbochargers 1r are arranged in parallel, and the first turbocharger is operated in a low rotation range, and the second Open the control valve installed at the turbine inlet of the turbocharger to operate the second turbocharger.

However, in such a conventional internal combustion engine with a turbocharger, in the operation start region of the second turbocharger, that is, until the opening of the control valve at the turbine inlet of the second turbocharger V reaches the initial or half-open position. A pressure drop occurs in this control valve, resulting in a sudden change in turbine flow characteristics and a delay in the increase in rotation of the turbocharger, resulting in a drop in torque and deterioration in drivability.

[Objective of the Invention] The present invention was devised in view of the above conventional problems, and provides an internal combustion engine with a turbocharger that does not cause a drop in torque in the region where the second turbocharger starts operating after the first turbocharger operates. For the purpose of providing institutions.

[Structure of the Invention] In order to achieve this object, the present invention provides a plurality of turbochargers in an internal combustion engine, and at least one of the plurality of turbochargers is of a variable displacement type.

[Operation] In the above configuration, after the supercharging pressure reaches a predetermined value by the turbocharger that operates substantially first, the variable displacement turbocharger is operated to increase the capacity.

[Example] Hereinafter, an example of the present invention will be described in detail based on the drawings.

Figure 1 is a schematic overall configuration diagram of an internal combustion engine in which two turbochargers are arranged in parallel. The first turbocharger 5 operates, and the variable displacement second turbocharger 7 operates when the compressor discharge pressure of the cylinder 1 turbocharger 5 reaches a predetermined value after the first turbocharger 5 operates. Second
A turbine 9.11 is connected. And this first
．． The second turbine 9.11 has a first turbine. Second exhaust passage 10
．． 12 are connected to each other.

The intake pipe 13 connected to the upper side of the engine body 1 in the figure is
An intercooler 15 is disposed in the middle, and the first. Each of the first . The first and second intake passages 18 and 20 are located on the discharge side of the second compressors 17 and 19.
are connected via. This first. The suction sides 21, 23 of the second compressors 17, 19 are connected to an air cleaner side (not shown), respectively.

In the variable displacement mechanism 24 of the second turbocharger 7, as shown in FIG. 2, a flap 29 for opening and closing the turbine inlet portion 27 is attached to the turbine housing 25 so as to be rotatable about a shaft 31. The flap 29 is a link mechanism 33
It is opened and closed by an actuator 35 via. This actuator 35 is vertically divided into three control pressure chambers and an atmospheric pressure chamber 41 in FIG. 2 by a diaphragm 37, and the control pressure chamber 39 and the first... The intake pipe 13 between the confluence section 43 of the second intake passage 18.20 and the intercooler 15 communicates with each other through the first control passage 45, and the diaphragm 37 is placed in the atmospheric pressure chamber 41 upward in FIG. A spring 47 is loaded to bias it.

The flap 29 is fully opened (as shown by the two-dot chain line) until the discharge pressure of the first compressor 17 reaches a predetermined value (target supercharging pressure) due to the force of the spring 47 exceeding the supercharging pressure. It gradually opens as the pressure increases.

An intake control valve 49 is provided in the second intake passage 20 upstream of the merging portion 43 so as to be able to open and close the passage 20 .

One end of a second control passage 51 communicates with the second intake passage 20 between the intake control valve 49 and the second compressor 19, and the other end is an actuator that opens and closes the intake control valve 49 via a control valve 53 in the middle. It is connected to 55. This actuator 55 is approximately equivalent to the actuator 35, and the control valve 53 controls the pressure inside the second intake passage 20, that is, the second
The control pressure is not introduced into the actuator 55 until the discharge pressure of the compressor 19 reaches a predetermined value, for example, 90% of the target supercharging pressure.

That is, when the discharge pressure of the second compressor 19 reaches 90% of the target boost pressure, the intake control valve 49 is controlled to be fully open. This is to prevent the supercharged air on the discharge side of the first compressor 17 from flowing back to the second compressor 19 side via the intake control valve 49 when the intake control valve 49 is opened.

Next, the effect will be explained.

When the engine is running at low speed and under low load, the flap 29 of the variable displacement mechanism 24 is fully open, so the exhaust from the engine body 1 flows into the first turbine 9 of the first turbocharger 5.
Only the first turbocharger 5 is operated. At this time,
Since the second turbocharger 7 is not operating, the discharge pressure of the second compressor 19 does not increase, and the intake control valve 49 is not operated via the actuator 55 and remains closed.

After the first turbocharger 5 is activated, the discharge pressure (supercharging pressure) of the first humbpressor 17 increases as the engine rotates and the load increases.
When the target supercharging pressure is reached, this supercharging pressure acts on the actuator 35 to gradually open the flap 29 and gradually increase the turbine capacity.

In this way, by gradually increasing the capacity of the second turbocharger 7 as the supercharging pressure increases, the amount of exhaust gas to the second turbocharger 7 is increased while the first turbocharger 5
The aim is to maintain the target boost pressure by reducing exhaust gas to.

FIGS. 3 and 4 show changes in supercharging pressure and engine back pressure depending on the engine speed, with solid lines showing the embodiment of the present invention and broken lines showing the conventional example. According to this, in the conventional example, the second
Near the operation start point P of the turbocharger 7, both the supercharging pressure and the engine back pressure decrease rapidly. On the other hand, in the embodiment of the present invention, such a problem does not occur, and it can be seen that the target supercharging pressure reached by the operation of the first turbocharger 5 is maintained substantially unchanged even after the operation of the second turbocharger 7. That is, when the second turbocharger 7 is operated in addition to the first turbocharger 5, fluctuations in the engine torque, so-called stepping, do not occur. Note that point Q in FIGS. 3 and 4 is the position where the second turbine 11 has the maximum capacity.

FIG. 5 shows an embodiment of the present invention (shown by solid lines) and a conventional example (shown by solid lines).
This figure shows a comparison of turbine efficiency with that shown in the figure (dashed line shown). According to this, the efficiency of the embodiment of the present invention is generally higher than that of the conventional example, and in particular, the control valve (corresponding to the flap 29 in the embodiment of the present invention) provided at the turbine inlet of the second turbocharger in the conventional example. When the amount of inflowing exhaust gas is small and the opening degree of When a turbine capacity changing device is used, the efficiency is good even with a small flow rate, so the turbine rotational speed increases quickly from the early stage of operation, and the boost pressure reaches a predetermined value in a short time. In addition, the fifth
Point R in the figure is when the conventional control valve and flap 29 are fully open, point 8 is when this control valve is fully open, and point T is when flap 29 is fully open.
9 when fully opened.

FIG. 6 shows another embodiment. Incidentally, here, the same components as those in the above-described embodiment are given the same reference numerals to simplify the explanation. In this embodiment, pressure detectors 57 and 59 are provided in the intake pipe 13 between the intercooler 15 and the merging section 43, and in the second intake passage 20 between the intake control valve 49 and the second compressor 19, respectively. and each pressure sensor 5
The pressure signal from 7.59 is input to the controller 61.

On the other hand, a first solenoid valve 63 is provided near the actuator 35 of the 11th IJ control passage 45, and this first solenoid valve 63 receives a signal from the controller 61 to open and close the first control passage 45. Further, the actuator 55 and the first control passage 45 on the side of the intake pipe 13 from the first solenoid valve 63 communicate with each other through a first control passage 65 .
A second solenoid valve 67 is provided. The second solenoid valve 67 receives a signal from the controller 61 to open and close the second control passage 65 .

That is, when the discharge pressure (supercharging pressure) of the first compressor 7 reaches the target supercharging pressure, the pressure detector 57 detects this supercharging pressure, and then the first solenoid valve 63 opens the cylinder part 1 control passage 45. Actuator 3 operates to release X.
5 opens the flap 29, and the second turbo charge 1
Activate 77.

After the second turbocharger 7 is activated, when the discharge pressure of the second compressor 7 reaches 90% of the predetermined target supercharging pressure, the pressure detector 59 detects this and the second Activate the solenoid valve 67. As a result, the discharge pressure from the first compressor 7 is introduced into the actuator 55, the intake control valve 49 is opened, and supercharge air is supplied to the engine body 1 from the second turbocharger v7 in addition to the first turbocharger 5. .

Other configurations and operations are substantially the same as those of the previous embodiment.

Note that this invention is not limited to the above-described embodiments. For example, the flap 29 of the second turbocharger 7 may not be fully opened when the engine is running at low speeds and under low load, but may be slightly opened. A configuration may be adopted in which the intake control valve 49 is opened when the values are equal. Further, if necessary, one or both of the turbochargers 5.7 may be provided with an exhaust bypass mechanism.

[Effects of the Invention] As described above, according to the present invention, at least one of the plurality of turbochargers is of a variable capacity type, and when the supercharging pressure reaches a predetermined value by the turbocharger that operates substantially first, Since the capacity of the variable displacement turbocharger that is activated after that is increased, the turbocharger, which was idle at low speeds and low loads, can operate at high turbine efficiency immediately after starting operation, resulting in smooth operation with no drop in torque. characteristics, and the turbocharger can be operated efficiently over a wide operating range.

[Brief explanation of drawings]

FIG. 1 is a schematic overall configuration diagram of an internal combustion engine with a turbocharger according to an embodiment of the present invention, FIG. 2 is an enlarged sectional view of the variable displacement turbocharger variable displacement mechanism in FIG. 1, and FIG. Fig. 4 is an explanatory diagram showing the relationship between supercharging pressure and engine exhaust pressure according to engine speed, Fig. 5 is an explanatory diagram showing turbine efficiency, and Fig. 6 is an internal combustion engine with a turbocharger according to another embodiment. FIG. (Explanation of symbols representing main parts of the drawings) 5...First turbocharger 7...Second turbocharger (variable displacement turbocharger) Patent applicant Nissan Motor Co., Ltd. Figure 1 Figure 2 j/ 41 4/ 35

Claims (2)

[Claims] (1) A turbocharged internal combustion engine having a plurality of turbochargers, wherein at least one of the plurality of turbochargers is a variable displacement turbocharger. (2) When the supercharging pressure reaches a predetermined value by the turbocharger that operates substantially first, the capacity of the variable displacement turbocharger that operates thereafter is increased. Internal combustion engine with turbocharger.