JP3379112B2 - Supercharger for internal combustion engine - Google Patents

Description

BACKGROUND OF THE INVENTION [0001] Field of the Invention The present invention relates to a supercharging system for an internal combustion engine with multiple turbochargers. 2. Description of the Related Art In recent years, a sequential turbo system provided with a plurality of turbochargers has been proposed to improve the acceleration performance and the like of a supercharged engine. As shown in FIG. 7, a conventional turbocharger of this type has two turbochargers 1 and 2 arranged in parallel, and operates the exhaust switching valves 3 and 4 in a low-speed operation region where the exhaust gas flow rate is small. Thus, a desired supercharging pressure is obtained by supplying and driving the exhaust gas to the turbine 5 of the first turbocharger 1 having a small capacity. Then, the rotation speed increases and the exhaust gas flow rate increases, and the compressor 6 of the first turbocharger 1
When the discharge pressure is increased, the exhaust switching valves 3 and 4 are operated to supply the exhaust gas to the turbine 7 of the second turbocharger 2 so as to rotate the turbine, and the air supply switching valves 8 and 9 are operated to operate the exhaust gas. The compressed air from the compressor 10 is supplied to the engine. [0004] In addition, a system in which a turbocharger is provided in series is also known. A similar operation of an exhaust switching valve and an air supply switching valve enables a small-capacity turbocharger in a low rotation speed region and a large capacity in a high rotation speed region. Supercharging is performed by a turbocharger with a capacity. [0005] In the above-mentioned conventional sequential turbo system, the switching valves 3 and 4 are used.
It has been a problem that the step of the boost pressure (boost pressure) caused by the ON / OFF operation of the switches 8 and 9 deteriorates the running feeling. Further, since the exhaust gas switching valves 3 and 4 are used at a high temperature, there is a problem that durability (gas sealability, abrasion, sharpness) is poor. In view of the above circumstances, the present invention has been devised in order to provide a supercharging device for an internal combustion engine in which there is no step in the supercharging pressure when switching the turbocharger and the durability is good. is there. As a technique to be compared with the present invention, a bypass passage provided with a flow rate control valve is provided on the turbine side in series, and a variable capacity mechanism is provided on the downstream side of the turbine, and these are adapted to the operating conditions of the engine. ("Exhaust turbocharger", Japanese Patent Application Laid-Open No. 61-210223)
However, it is considered that the above-mentioned durability problem remains because the flow control valve is provided on the exhaust side. The present invention relates to a supercharging device for an internal combustion engine,
The first turbocharger with a relatively small capacity that is always driven
And a turbocharger installed in parallel with the first turbocharger
Relatively large capacity second turbo with variable bin capacity
The charger and the compressor of this second turbocharger
The air supply provided in the air supply passage connecting the
Air on-off valve and upstream and downstream air supply to this on-off valve
Pressure sensor and internal combustion engine rotation speed
When this happens, the operation of the variable turbine capacity mechanism
The second turbocharger is driven appropriately and the pressure
Control the air supply on-off valve based on the value detected by the sensor.
And a controller. With the above-described structure , appropriate supercharging is performed over the entire rotation range of the engine, and a step in the boost pressure is eliminated, so that the driving feeling is improved. [0012] With the above configuration, when the engine is running at a low speed, the first turbocharger is driven to perform appropriate supercharging. During high-speed operation, the controller controls the turbine capacity variable mechanism to drive the second turbocharger according to the rotation speed and the like, and at the time of this switching, the turbine capacity is adjusted so that the detection value of the pressure sensor becomes equal. After controlling the variable mechanism to increase the supercharging pressure, the air supply opening / closing valve is opened, and the compressed air from the second turbocharger is joined to the air supply port. An embodiment of the present invention will be described below with reference to the accompanying drawings. First, an embodiment of a supercharging device for an internal combustion engine according to the present invention will be described with reference to FIG. This supercharging device
The first turbocharger 11 having a relatively small capacity, the second turbocharger 12 having a relatively large capacity provided in parallel with the first turbocharger 11, and the air supply passage 13 of the second turbocharger 12 are provided. An air supply on-off valve 14 provided;
Pressure sensors 15 and 16 provided on the upstream and downstream sides of the air supply on / off valve 14 and the second turbocharger 12
And a controller (CPU) 17 for appropriately driving the air supply opening / closing valve 14. The first turbocharger 11 is a known turbocharger having a compressor 18 and a turbine 19 coaxially. A gas inlet 23 of the turbine 19 is attached to an exhaust pipe 22 connected to an exhaust manifold 21 of an engine 20. And an intake pipe 24 for taking in outside air is connected to an air inlet 25 of the compressor 18 and a discharge port 26
Is connected to an air supply manifold 27 of the engine 20. The second turbocharger 12 has a gas inlet 29 of a turbine 28 attached downstream of the exhaust pipe 26 and a compressor 30 connected to an intake pipe 31 separate from the first turbocharger 11. The second air supply pipe 32 that defines the air supply path 13 extends in parallel with the first air supply pipe 26 and is connected to the air supply manifold 27. The turbine 28 is provided with a turbine capacity variable mechanism 33 for adjusting the gas flow rate. As shown in FIGS. 2 and 3, the turbine capacity variable mechanism 33 includes a plurality of nozzle vanes 36 provided in a nozzle throat portion 35 of a turbine wheel 34 as a turbine 28, and a nozzle link plate 37 And a rotation ring 39 connected via a slide joint 38 and a drive lever 41 connected to the rotation ring 39 via a drive link plate 40. When the drive lever 41 is steplessly driven by the step motor 42 as an actuator, the rotary ring 39 rotates around the turbine shaft 43, and the nozzle vanes 36 rotate around their respective axes simultaneously by this rotation. By changing the inclination angle, the nozzle opening is changed. In particular, in the present embodiment, as shown by a two-dot chain line (36a) in the drawing, a state where the nozzle vanes 36 are rotated so as to appropriately overlap each other and the nozzles are fully closed is formed. . The air supply on-off valve 14 is connected between the discharge port 44 of the compressor 30 of the second turbocharger 12 and the engine 20.
And between the fully closed state where the air supply path 13 is opened and the fully open state where the air supply path 13 is opened by the drive of the step motor 45. Has become. The pressure sensors 15 and 16 are for detecting a supercharging pressure in the second air supply pipe 32, and input a detection signal to the controller 17. The controller 17 includes a pressure sensor 15,
The engine rotation speed and the load are input in addition to the supercharging pressure detection value by the controller 16, and an operation signal to the step motors 42 and 45 is output based on the information. That is, the controller 17, the optimum supercharging pressure determined by the load and the engine speed is integrated in the form of advance in the control map (see FIG. 6), more than a predetermined value R _A of the engine speed R is set In other words, when a state where a supercharging pressure higher than the supercharging pressure by the first turbocharger 11 is required, the optimum supercharging pressure P is extracted from the control map and the optimum supercharging pressure is extracted. The opening degree of the nozzle vane 36 is changed so as to make the pressure P. When the supercharging by the second turbocharger 12 is started by the operation of the nozzle vane 36, the pressures P ₁ and P ₂ on both sides of the closed air supply opening / closing valve 14 become equal, and then the air supply opening / closing valve 14 is closed. Is opened. Next, an embodiment of a method for supercharging an internal combustion engine according to the present invention will be described as an operation of the above-mentioned structure (see FIG. 4). At the time of supercharging control by the supercharging device, when the engine 20 is started, the nozzle vanes 36 of the variable turbine capacity mechanism 33 of the second turbocharger 12 are fully closed, and the second air supply pipe is provided. Also, the air supply on-off valve 14 of 32 is fully closed (ST1). That is, only the first turbocharger 11 supercharges the engine 20 by the turbine drive according to the exhaust gas. And while the engine is running, the controller 17 is constantly input rotation speed and load (ST 2), the engine speed R ₁ and the predetermined value R
Comparing the _A (ST 3). If the engine speed R ₁ does not exceed the predetermined value R _A (R ₁ ≦ R _A ), the drive of only the first turbocharger 11 is continued. When the engine speed R ₁ exceeds the predetermined value R _A (R ₁ > R _A ), the controller 17 outputs an operation signal to the step motor 42 and opens the nozzle vane 36 (ST 4). The turbine 28 of the second turbocharger 12 is driven to rotate by the exhaust energy in accordance with the nozzle opening, and pressurized air flows into the second air supply pipe 32. The controller 17 inputs the detection values from the pressure sensors 15 and 16 to the downstream side of the closed air supply on-off valve 14,
That the pressure P ₁ of the supply manifold 27 side gas is supplied by the first turbocharger 11, by a second turbocharger 12 compares the pressure P ₂ of the air supply upstream (ST 5), these When the values become equal, the air supply opening / closing valve 14 is opened (ST6). Thus, the compressed air from the second turbocharger 12 flows into the air supply manifold 27. The controller 17 controls the opening degree of the vane so that the desired supercharging pressure P is obtained according to the control map shown in FIG. 6 (ST7). That is, as shown in FIG. 5, after the engine speed R reaches the predetermined value _RA , in addition to the supercharging pressure of the first turbocharger 11, the second turbocharger controlled by the turbine capacity variable mechanism 33 The supercharging pressure of the charger 12 is added. [0025] The controller 17 compares the second even after the turbocharger 12 starts driving by inputting the rotational speed R ₂ (ST 8) a predetermined value R _A, if more than a predetermined value R _A is maintained The control is performed as it is (ST 9), and the predetermined value R
If it falls below _A , narrow the vane opening (ST10). Then, when the vane opening reaches the predetermined value B shown in FIG.
1) The air supply on-off valve 14 is fully closed and the nozzle vane 36 is fully closed. That is, the first turbocharger 1 is returned to the state at the time of engine start (RETURN, ST 1).
Supercharge only by one. As described above, the first turbocharger 11 which is constantly driven and the second turbocharger 12 having the variable turbine capacity mechanism 33 are provided in parallel and provided in the second intake pipe 32. Pressure sensors 15 and 16 are provided on the upstream and downstream sides of the air supply opening / closing valve 14 to drive the nozzle vanes 33 according to the rotation speed and load of the internal combustion engine and to open and close the air supply opening / closing valve 14 at the time of switching.
During low-speed low-load operation, only the first turbocharger 11 is driven, and during high-speed, high-load operation, the second turbocharger 12 is controlled and driven.
Since the supercharging pressure is sufficiently increased before merging with the air supply manifold 27, optimal supercharging is achieved over the entire rotation range, and switching of driving start or driving stop of the second turbocharger 12 is performed. In this case, the traveling feeling does not deteriorate due to the supercharging pressure step. That is, when the second turbocharger 12 is driven to reach the predetermined rotation speed _RA , the air supply manifold 27 is already supplied with the compressed air from the first turbocharger 11, and the closed air supply opening and closing is performed. The downstream side of the air supply of the valve 14 is in a high pressure state. Therefore, when the nozzle vane 33 is opened to drive the second turbocharger 12 and the air supply opening / closing valve 14 is opened at the same time, a reverse flow of air supply occurs in the air supply path 13, and the present invention prevents this from happening. It is something that is. With such a configuration, the flow control valve conventionally required on the exhaust side can be eliminated, and the durability can be improved. FIG. 2 shows a variable turbine capacity mechanism.
The configuration is not limited to the configuration illustrated in FIG. 3 and may be any configuration as long as the nozzle opening can be appropriately increased or decreased. In addition, a diesel engine or a gasoline engine can be applied as the internal combustion engine. In summary, according to the present invention, the following excellent effects are exhibited. (1) It is possible to prevent a step of the supercharging pressure from occurring at the time of switching, and to achieve an improvement in running feeling. (2) The flow rate control valve is not required on the exhaust side, and the durability is improved.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a front view showing an embodiment of a supercharging device for an internal combustion engine according to the present invention. FIG. 2 is a side sectional view showing a second turbocharger in FIG. 1; FIG. 3 is a front view of a main part of FIG. 2; FIG. 4 is a flowchart showing one embodiment of a method for supercharging an internal combustion engine according to the present invention. FIG. 5 is a diagram illustrating the relationship between the engine speed, the supercharging pressure, the vane opening, and the air supply on-off valve for explaining the operation of the present invention. FIG. 6 is a control map provided in the controller in FIG. 1; FIG. 7 is a configuration diagram showing a conventional supercharging device for an internal combustion engine. [Description of Signs] 11 First turbocharger (other turbocharger) 12 Second turbocharger (one turbocharger) 13 Air supply path 14 Air supply opening / closing valves 15, 16 Pressure sensor 17 Controller 20 Engine 27 Air supply Manifold (air supply port of internal combustion engine) 33 Turbine capacity variable mechanism

Claims (1)

(57) [Claim 1] A relatively small-capacity first terminal which is constantly driven.
-In parallel with the turbocharger and the first turbocharger
Relatively large capacity with a variable turbine capacity mechanism
A second turbocharger and the second turbocharger
Installed in the air supply passage connecting the compressor
And the supply air upstream and downstream of the supply air
Pressure sensor provided on the side and the rotational speed of the internal combustion engine, etc.
The turbine capacity variable mechanism when the pressure exceeds a predetermined value.
Operation of the second turbocharger as appropriate
And based on the value detected by the pressure sensor
And a controller for controlling the air supply on-off valve.
A supercharging device for an internal combustion engine.