JPS61164041A - Internal-combustion engine with turbo charger - Google Patents

Abstract

PURPOSE:To prevent torque drop in the range of starting the operation of a second turbo charger by substantially initially operating at least one variable capacity type of a plurality of turbo chargers. CONSTITUTION:An exhaust controlling valve 43 at the second turbo charger 9 side is closed in the low rotation and load of an engine, while the capacity of a first turbo charger 5 is minimized, i.e. the area of a turbine inlet path is minimized by a flap 39 of a variable capacity mechanism 33. Thus, exhaust is not flowed to a second turbine 11 and only the first turbo charger 5 is operated. And when discharge pressure, i.e. supercharging pressure reaches a predetermined value by a first compressor 21 as the engine load is increased, the flap 39 is opened to enlarge the capacity of the first turbo charger 5. Thereafter, when said capacity is maximized, an exhaust controlling valve 43 is opened and exhaust flows also into a second turbine 11, while the capacity of the first turbo charger 5 is lessened.

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] Generally, turbochargers used in automobiles etc.
Supercharging efficiency differs depending on the operating condition of the engine.

Therefore, if a turbocharger with good supercharging efficiency is used in a certain operating range, the supercharging efficiency will be poor in other operating ranges.

Therefore, in order to effectively operate the turbocharger over a wide rotation speed and a wide load range, multiple turbochargers are provided for one engine, and the number of turbochargers activated is varied depending on the operating status of the III engine. This is described, for example, in Japanese Patent Laid-Open No. 59-68521.

The system described in this publication has two turbochargers arranged in parallel, and the first turbocharger is operated in a low rotation range, and by increasing the compressor discharge pressure, that is, the supercharging pressure, of the first turbocharger, the second turbocharger is activated. The control valve provided at the turbine inlet of the engine is opened to operate the second turbocharger.

However, in such a conventional internal combustion engine with a turbocharger, this control cannot be performed until the operation start range of the second turbocharger, that is, the opening of the turbine inlet control valve of the second turbocharger reaches the initial or half-open position. A pressure drop occurs at the valve, resulting in a sudden change in turbine flow characteristics and a delay in the turbocharger speeding up, causing a drop in torque and deteriorating driveability.

[Object of the Invention] The present invention has been 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.

[Configuration of the Invention] In order to achieve this object, the present invention has a configuration in which at least one of the plurality of turbochargers is of a variable displacement type, and the variable displacement type turbocharger is operated substantially first.

[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 turbine 7 of the first turbocharger 5 and the second turbine 11 of the fixed capacity second turbocharger 9
are connected. The first and second turbines 7.11 include a first turbine. A second exhaust passage 13.15 is connected respectively.

The intake pipe 17 connected to the upper side of the engine body 1 in the figure is
There is an intercooler 19 in the middle, and a first . They are connected via second intake passages 25,27. This first. Suction side 29 of the second compressor 21.23
．． 31 are each communicated with an air cleaner side (not shown).

The first turbocharger 5 is USP2944786,
The variable capacity mechanism 33 described in Japanese Patent Application Laid-Open No. 54-71221 and the like is provided. This variable capacity mechanism 33 is
The actuator 35 connects the first
It has a flap 39 that opens and closes the exhaust gas inlet of the turbine 7 and changes the turbine capacity, and an actuator 35
is operated by the controller 41. Also,
The first turbocharger 5 operates before the second turbocharger 9 when the engine is running at low speeds and under low load.

The second turbocharger 9 is not a variable displacement type, but a second turbocharger 9.
An exhaust control valve 43 is provided upstream of the exhaust gas of the turbine 11, and the exhaust control valve 43 is provided after the first turbocharger 5 is operated.
The valve is opened to allow exhaust gas to flow to the second turbine 11, thereby operating when the engine is under medium or high load. The exhaust control valve 43 is operated by an actuator 45 via a link mechanism 47, and the actuator 45 is operated by a controller 49.

The exhaust pipe 51 where the first exhaust passage 13 and the second exhaust passage 15 join together and the exhaust manifold 3 communicate through an exhaust bypass passage 53, and an exhaust bypass valve 55 is provided on the exhaust manifold 3 side of the bypass passage 53. is installed so that it can be opened and closed. The exhaust bypass valve 55 opens to bypass exhaust gas when the engine is under high load in order to keep the supercharging pressure constant. Its operation is performed by an actuator 57 via a link mechanism 59, and the actuator 57 is operated by a controller 61. It is configured to operate by. The second intake passage 27 is provided with a known check valve (not shown) to prevent intake air from flowing backward through the passage 27 when only the first turbocharger 5 is operating.

Next, the operation will be explained with reference to FIGS. 2 and 3, which show changes in supercharging pressure and am back pressure.

In FIGS. 2 and 3, this embodiment is shown by solid lines, and the broken lines and dashed-dotted lines show the conventional example.

When the engine is at low speed and load, the second turbocharger 9
The side exhaust control valve 43 is closed, and the capacity of the first turbocharger 5 is minimized, that is, the flap 39 of the variable displacement mechanism 33 minimizes the turbine inlet passage area. Therefore, the exhaust gas does not flow to the second turbine 11, and only the first turbocharger 5 operates. When the discharge pressure, that is, the supercharging pressure, reaches a predetermined value by the first compressor 21 as the engine load increases (point A in the figure), the flap 39 is gradually opened to increase the capacity of the first turbocharger 5. Open. After this capacity reaches its maximum (point B in the diagram), the exhaust control valve 43 is opened to allow exhaust to flow into the second turbine 11, and at the same time, the distance between each of the first turbochargers 5 is reduced to provide supercharging. Keep the pressure almost constant (point C in the diagram)
Thereafter, when the engine load further increases, the capacity of the first turbocharger 5 is again maximized (point in the figure). When the capacity of the first turbocharger 5 reaches its maximum, the exhaust bypass valve 55 is opened to bypass the exhaust gas to prevent excessive rise in supercharging pressure.

As a result, as shown in FIGS. 2 and 3, the supercharging pressure is kept constant, and the engine back pressure has fewer steps than in the past. In contrast, conventionally, when exhaust gas is flowed to the second turbocharger side in order to operate the second turbocharger after operating only the first turbocharger, the engine back pressure suddenly increases as shown by the dashed line in Figure 3. As a result of this, the rotation of the turbocharger decreases, resulting in a decrease in supercharging pressure as shown by the dashed line in FIG. Also, if you try to keep the supercharging pressure constant, only the first turbocharger will operate the engine until the second turbocharger's supercharging pressure (compressor discharge pressure) reaches a predetermined supercharging pressure (compressor discharge pressure) from the first turbocharger. Air must be supplied to the main body, and the first turbocharger must be rotated at an extremely high rotational speed, resulting in a significant increase in engine back pressure as shown by the broken line in FIG. FIG. 4 shows another embodiment. In addition, here, the same reference numerals are attached to the same components as in the above-described embodiment to simplify the explanation. In this embodiment, in addition to the first turbocharger 5, the second turbocharger 1763 is also of variable capacity type. This second turbocharger 63 has a variable displacement mechanism 67 equipped with a flap 65 similar to that of the first turbocharger 5, and the flap 65 is operated to open and close the exhaust gas inflow portion of the second turbine 11 by an actuator 71 via a link mechanism 69. . The actuator 71 is operated by a controller 73.
is configured to also operate the actuator 35 on the first turbocharger V-jar 5 side.

Next, the effect of the above configuration will be explained. Incidentally, the engine back pressure in this embodiment is shown by a two-dot chain line in FIG. That is, when the engine is running at low speed and under low load, the capacity of the second turbocharger 63 remains small, and as the rotational speed, load, etc. increase, the capacity of the first turbocharger 5 is gradually increased to reach the maximum capacity (see Fig. 3). Middle A1). Thereafter, as the engine load increases, the capacity of the first turbocharger 5 is reduced to a medium level, and at the same time, the capacity of the second turbocharger 63 is increased to a medium level (point 81 in FIG. 3). When the engine load further increases, the capacity of the first turbocharger 175 is maximized and the capacity of the second turbocharger 63 is also maximized (81 in FIG. 3).

By operating the turbochargers 5 and 63 in this manner, the difference in engine back pressure is further reduced as shown by the two-dot chain line in FIG. 3, and the drivability is further improved.

Note that this invention is not limited to the above-mentioned embodiments. For example, in the embodiment shown in FIG. 4, the capacity of the second turbocharger 63 may be set to zero during low rotation and low load, that is, the exhaust gas may not flow to the second turbine 11 during this operation.

[Effect of the Invention 1 As described above, according to the present invention, at least one of the plurality of turbochargers is a variable capacity type, and this variable capacity type turbocharger is operated substantially first, and its capacity is increased to approximately the maximum. Because we reduced the capacity and effectively operated other turbochargers,
To operate the turbocharger efficiently over a wide operating range, with no drop in torque and smooth operating characteristics, even immediately after the turbocharger starts operating, which was essentially at rest at low speeds and low loads. I can do it.

[Brief explanation of the drawing]

Fig. 1 is a schematic overall configuration diagram of an internal combustion engine with a turbocharger according to an embodiment of the present invention, and Figs. 2 and 3 show supercharging pressure and engine back pressure comparing the embodiment of the present invention and a conventional example. FIG. 4 is a schematic overall configuration diagram of an internal combustion engine with a turbocharger according to another embodiment. (Explanation of symbols representing main parts of the drawing) 5...First turbocharger 9...Second turbocharger (variable displacement type) 33...
・Variable capacity mechanism patent applicant Nissan Motor Co., Ltd. Fig. 1 5 Near 1 turbo chain Sef Niya 1 turbine Fig. 2 Fig. 3 PAm rotary shear Fig. 4

Claims (2)

[Claims] (1) In an internal combustion engine having a plurality of turbochargers, at least one of which is a variable displacement turbocharger, the variable displacement turbocharger operates substantially first. Internal combustion engine. (2) The turbocharger according to claim 1, wherein after the variable capacity turbocharger reaches a substantially maximum capacity, the capacity is reduced and other turbochargers are substantially operated. Internal combustion engine with charger.