JPH02119623A - Air intake device of engine - Google Patents

Abstract

PURPOSE:To recover power by providing at least one variable cycle type mechanical supercharger down the stream and operating it in compression cycle at low speed range and in expansion cycle at high speed range, in an engine with at least two supercharger provided in series. CONSTITUTION:Air intake passages 2 and 3 on each bank of a V-type engine 1 are connected to a common air intake passage 6 through manifolds 4 and 5, respectively, and a turbosupercharger 10 and a mechanical supercharger 11 are provided in series in the common air intake passage 6. The mechanical supercharger 11 down the stream is of byaxial screw type of Lysholm and the top end of the drive shaft of the supercharger 11 is provided with a variable pulley 24 that its diameter varies according to centrifugal force. The rotation of the pulley is transmitted to a crank shaft 29 through a belt 25, a second variable pulley 26, an electro-magnetic clutch 27, etc. In an area where the discharge pressure of the turbosupercharger is higher than that of the mechanical supercharger at high engine speed, the mechanical supercharger 11 is used as an expander for power recovery.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an intake system for an engine in which at least two superchargers are arranged in series.

(Prior Art) Engines in which at least two superchargers are arranged in series are conventionally known. For example, JP-A-61-14952
In the engine described in Publication No. 1, by placing the mechanical supercharger downstream of the turbo supercharger, the respective characteristics of the turbo supercharger and mechanical supercharger are effectively brought out, and the engine speed from low to high speed is improved. The aim is to increase boost pressure and improve response over a wide operating range.

By the way, when multiple turbochargers are arranged in series like this, especially when the downstream side is a mechanical turbocharger, the downstream turbocharger cannot provide sufficient supercharging with the upstream turbocharger alone. It is conceivable that the system not only compensates for the lack of supercharging pressure in operating ranges where pressure cannot be obtained, but also functions to recover power in operating ranges where the discharge pressure of the upstream supercharger is sufficiently high. However, mechanical superchargers are usually designed as compressors with the primary objective of increasing discharge pressure, so the effect of power recovery as described above is actually not that great. .

Additionally, in order to increase charging efficiency and reduce heat load, the intake air that has been pressurized by the supercharger and has reached a high temperature must be cooled as much as possible before entering the combustion chamber, but it is difficult to do this with just an intercooler. This inevitably increases the capacity and makes layout difficult.

(Object of the Invention) The present invention has been made in view of the above-mentioned problems, and it combines a plurality of superchargers to obtain high supercharging over a wide operating range from low engine speed to high engine speed. The objective is to obtain an engine intake system that can efficiently perform power recovery and intake air cooling by utilizing a part of the supercharger.

(Structure of the Invention) The present invention provides, for example, when using a screw type mechanical supercharger known as the Lysholm type, by making the opening/closing timing of the suction port and discharge port variable. , which focuses on the fact that a mechanical supercharger can be used either as a compressor that performs a compression cycle or as a refrigerator that performs an expansion cycle, and its configuration is as follows. That is, the engine intake system according to the present invention is an engine intake system in which at least two superchargers are arranged in series, in which at least one downstream supercharger is a variable cycle mechanical supercharger, and The mechanical supercharger is characterized by a compression cycle at low engine speeds and an expansion cycle at high engine speeds.

(Operation) The plurality of superchargers arranged in series each have their own supercharging characteristics, and by combining them, high supercharging is achieved over a wide engine rotation range.

The variable cycle mechanical turbocharger on the downstream side uses a compression cycle at low engine speeds to provide efficient supercharging.
Furthermore, at high engine speeds, the engine enters an expansion cycle to recover power, and its cooling action cools the intake air entering the engine combustion chamber.

(Example) Examples will be described below based on the drawings.

FIG. 1 is an overall system diagram of an embodiment of the present invention. In this embodiment, the engine 1 is a V-type cross-flow type, and the intake passages 2.3 of each bank rise upward between the banks and are connected to the upstream common intake passage 6 via each gathering portion 45. . Further, exhaust passages 7 and 8 extend from the outside of each bank and are connected to a common exhaust passage 9.

In the common intake passage 6, a turbo supercharger IO is provided on the upstream side, and a mechanical supercharger 11 is provided in series with the turbo supercharger IO on the downstream side. This mechanical supercharger 11 uses a so-called Lysholm twin-screw type which is made up of a combination of male and female rotors. The throttle valve 12 is provided between the turbocharger IO and the mechanical supercharger 11, and a bypass passage 13 that bypasses the mechanical supercharger 11 is formed downstream of the throttle valve 12. This bypass passage 13 is provided with a negative pressure operated bypass valve 14 . A negative pressure passage 15 is connected to the bypass valve 14, and a negative pressure passage 15 is connected to the negative pressure passage 15, which guides the operating negative pressure from the collecting portion 5 on one side of the intake passage. ing. In addition, mechanical supercharger 1
! Upstream of the bypass passage 13, there is a second opening downstream of the bypass passage 13.
A throttle valve 17 is provided. This second throttle valve 17 is connected to the throttle valve 12 by a link mechanism (not shown) so that it begins to open when the throttle valve 12 opens to a predetermined opening degree.

An intercooler I8 is disposed downstream of the mechanical supercharger 11. Further, a second intercooler 20 is disposed downstream of the blower 19 of the turbocharger IO. The downstream side of the blower 19 is connected to an air cleaner 21, and an air flow meter 22 is provided immediately downstream of the air cleaner 2I.

The turbine 23 of the turbocharger IO is disposed in the common exhaust passage 9, and is rotated by exhaust energy to connect the connected blower 1.
Drive 9.

A variable pulley 24 whose diameter changes depending on centrifugal force is provided at the tip of the drive shaft of the mechanical supercharger 11.
The belt 25 causes a second belt whose diameter also changes due to centrifugal force.
The variable pulley 26 is connected to the variable pulley 26. And this second
An electromagnetic clutch 27 is coaxially connected to the variable pulley 26 , and a part of the outer part of the electromagnetic clutch 27 constitutes a pulley, which is connected to a drive pulley 30 at the tip of the crankshaft 29 by a second belt 28 .

The drive mechanism for the intake valve 31 and the exhaust valve 32 is provided with valve timing changing means (not shown), whereby the overlap between intake and exhaust is large at high loads and small at low loads.

The boost pressure characteristics of the turbo supercharger IO and the mechanical supercharger 11 are as shown in FIG. The turbo supercharger IO does not rotate much when the engine speed (NE) is low, and as the engine speed increases, the speed gradually increases, and the speed increases sharply as the engine speed increases. Further, the discharge pressure (P,) increases accordingly on the high engine rotation side. On the other hand, with the mechanical supercharger 11, the rotation is increased by increasing the boolean ratio on the low engine speed side, and the supercharger is maintained even if the engine speed increases by lowering the pulley ratio on the high speed side. Since the rotation speed is kept unchanged, the discharge pressure (P,) increases on the low engine rotation side.

Since the turbo supercharger 10 and the mechanical supercharger 11 are installed in series, the discharge pressure (P,) of the turbo supercharger IO becomes equal to the discharge pressure (P,) of the mechanical supercharger 11 on the high engine speed side. In the region where the pressure is higher than P, ) (shaded region in FIG. 2), power can be recovered by the mechanical supercharger 11. In this embodiment, the Lysholm type supercharger as described above is used as the mechanical supercharger, and the discharge pressure (Pl
) is higher than the discharge pressure (P, ) of the mechanical supercharger II, it functions as a blower and contributes to supercharging to some extent, while mainly recovering power. When used as a blower, the opening timing of the discharge port is advanced so that there is almost no compression stroke.

Also, when the difference between P+ and P2 increases, the mechanical supercharger 1
1 is used as an expander to efficiently recover power and lower the discharge temperature by the cooling effect of expansion.

In order to make the mechanical supercharger 11 function as an expander, an expansion stroke is created by interrupting the suction stroke when the mechanical supercharger 11 functions as an air blower. Note that by functioning as an expander in this way, it is possible to eliminate the noise that would be generated in the case of a blower.

In a region where the discharge pressure of the turbocharger IO is not high, the mechanical supercharger If performs supercharging efficiently as a normal compression cycle.

Figure 3 shows the engine load (intake pressure T,) and rotation speed (N
6) is an operating range diagram of the mechanical supercharger 11 shown in FIG. The mechanical supercharger 11 is used as a compressor in the low rotation and high load region indicated by A. In the high rotation and medium load region indicated by B, it is used as a blower. It is also used as an expander in region C, where thermal problems occur at high speeds and high loads.

The low load region indicated by D in FIG. 3 is an operating region that generally does not require supercharging, and in this region, the electromagnetic clutch 27 is turned off, the three-way solenoid valve 16 is switched at the same time, the bypass valve 14 is opened, and the bypass passage is opened. 13 to allow natural intake.

Furthermore, since the boost ratio of the mechanical supercharger II is reduced in the high engine speed range, the electromagnetic clutch 27 can be turned off in all ranges without gear shock. Note that in this region where the electromagnetic clutch 27 is off, the discharge pressure of the turbocharger IO is low, and therefore supercharging is not substantially performed.

In this embodiment, since the throttle valve 12 is provided between the turbocharger 10 and the mechanical supercharger 11 as described above, the intake sound generated by the mechanical supercharger 12 is directed to the upstream side. In addition, it is possible to prevent air from leaking from the shaft portion of the turbocharger IO due to the negative pressure generated downstream of the throttle valve I2 at low load.

In addition, the electromagnetic clutch 27 can be disengaged in all areas where supercharging is not required, and intake air can be supplied via the bypass passage 13, thereby reducing power loss caused by driving the mechanical supercharger II.

Further, since the intercooler I8 is provided downstream of the mechanical supercharger II, it is possible to more effectively reduce the combustion chamber temperature.

In the above embodiment, an electromagnetic clutch is provided to stop the operation of the mechanical supercharger in a predetermined low load range, but it is also possible to carry out the invention without providing such an electromagnetic clutch. It is.

In that case, in a predetermined low load area, as shown in Figure 3 (B
) On the high load side shown in (C), a mechanical supercharger is used as a blower to perform a certain amount of supercharging and power recovery, and on the low load side shown in (C), sufficient power recovery is performed as an expansion cycle. Good.

The mechanical supercharger is not limited to the Beam-Sholm type, and various other types can be used. Further, the supercharger provided on the upstream side may be a mechanical supercharger in addition to a turbo supercharger, and the number of superchargers can be two or more. There may also be a plurality of downstream superchargers with variable cycles.

The present invention can be implemented in various other ways.

(Effects of the Invention) Since the present invention is configured as described above, efficient supercharging can be performed in a wide operating range from engine low speed to high engine speed using a plurality of superchargers. By having the mechanical supercharger on the downstream side, which receives supercharging at low engine speeds, function as an expander in the high engine speed range, it is possible to recover power and reduce heat load.

[Brief explanation of the drawing]

FIG. 1 is an overall system diagram of an embodiment of the present invention, and FIGS. 2 and 3 are characteristic diagrams of the same embodiment. l: Engine, IO; Turbo supercharger, ■1: Mechanical supercharger, 19: Turbine.

Claims (1)

[Claims] (1) In an engine intake system in which at least two superchargers are arranged in series, at least one of the downstream superchargers is a variable cycle mechanical supercharger, and the mechanical supercharger is used to lower the engine temperature. An engine intake system characterized by a compression cycle in the rotation range and an expansion cycle in high rotations.