JPS63297733A - Supercharging device for engine - Google Patents

Abstract

PURPOSE:To enhance the scavenging effect and improve the output by dividing a plurality of cylinders into two cylinder groups, supercharging the first cylinder group and the second cylinder group by a mechanical supercharger and an exhaust turbocharger, respectively, and differentiating a suction/exhaust overlap period of the first cylinder group from that of the second cylinder group. CONSTITUTION:In a 6-cylinder engine, six cylinders 1 are divided into first and second cylinder groups 2 and 3. First and second suction passages 4 and 5 are connected to the cylinders 1 of the first and second cylinder groups 2 and 3, respectively. A mechanical supercharger 12 to be driven by the engine is provided in the first suction passage 4 at a position upstream of a throttle valve 1, and a compressor 17a of an exhaust turbocharger 17 is provided in the second suction passage 5 at a position upstream of a throttle valve 16. An exhaust turbine 17b of the exhaust turbocharger 17 is provided in an exhaust passage 7 of the first cylinder group 2. A suction/exhaust overlap period of the second cylinder group 3 is set to be longer than that of the first cylinder group 2. Accordingly, a scavenging effect of the second cylinder group 3 may be accelerated to thereby improve the output.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to an engine supercharging device, and particularly to an improvement in a system that uses a mechanical supercharger and an exhaust turbo supercharger in combination.

(Prior Art) Conventionally, engines equipped with this type of supercharging device have been equipped with an exhaust turbo supercharger and a mechanical supercharger in the intake passage, for example, as disclosed in Japanese Utility Model Application Publication No. 60-28215. A bypass passage is provided to bypass the mechanical supercharger, and for example, in the low rotation range of the engine, the bypass passage is closed by a control valve etc. and the mechanical supercharger is operated. While improving the acceleration response of the engine, in other rotation ranges the control valve is opened to stop the mechanical supercharger, and supercharging is performed only by the exhaust turbo supercharger, effectively recovering exhaust energy and boosting the engine. There are known devices that increase the output.

(Problems to be Solved by the Invention) By the way, when aiming to improve fuel efficiency by increasing the compression ratio in an engine equipped with such a supercharging device, for example, in order to prevent knocking, it is necessary to increase the intake/exhaust overlap period. It is necessary to take measures such as increasing the length to promote the scavenging effect, or setting the intake valve closing timing later to substantially reduce the displacement. However, in the conventional system described above, since the exhaust pressure increases due to the provision of the exhaust turbine, no scavenging effect can be expected even if the intake/exhaust overlap period is lengthened. Moreover, if the closing timing of the intake valve is set later, the exhaust energy will be reduced and the supercharging effect will be reduced. However, if supercharging is performed only by a mechanical supercharger, the exhaust energy cannot be effectively recovered, resulting in poor fuel efficiency.

The present invention has been made in view of these points, and its purpose is to use an exhaust turbo supercharger and a mechanical supercharger in parallel, and to achieve supercharging by the exhaust turbo supercharger. There is no exhaust turbine installed on the exhaust side of the cylinder to be supercharged by a mechanical supercharger, and the exhaust pressure is reduced to lengthen the intake/exhaust overlap period and allow the intake valve to close later. An exhaust turbine is provided on the exhaust side of the exhaust gas to effectively recover exhaust energy while preventing exhaust gas from blowing back.

(Means for Solving the Problem) In order to achieve the above object, the solving means of the present invention includes two cylinder groups, a first and a second cylinder group, which are divided into a plurality of cylinders of an engine, and a first cylinder group and a second cylinder group. It includes a mechanical supercharger that supercharges intake air, and an exhaust turbo supercharger that supercharges intake air to the second cylinder group. The exhaust turbine of the exhaust turbo supercharger is disposed in the exhaust passage of the first cylinder group so as to be driven by the exhaust energy of the first cylinder group.

Furthermore, the intake/exhaust overlap period of the second cylinder group is set to be longer than the intake/exhaust overlap period of the first cylinder group. In other words, when comparing an exhaust turbo supercharger and a mechanical supercharger, the mechanical supercharger has a wide range in which the boost pressure exceeds the exhaust pressure, and takes advantage of this difference in characteristics to achieve efficient combined supercharging. This is the configuration of the device.

(Function) With the above configuration, in the present invention, the exhaust turbo supercharger is not driven by the exhaust energy of the second cylinder group supercharged by the supercharger, so the exhaust pressure of the second cylinder group becomes low. . As a result, the scavenging effect obtained by prolonging the intake and exhaust overlap period of the second cylinder group is effectively exhibited, and the intake valve can be closed late without reducing the exhaust energy to the exhaust turbine, and the compression ratio Knocking is suppressed and prevented when the engine is raised.

Further, since the exhaust turbo supercharger is driven by the exhaust energy of the first cylinder group supercharged by the mechanical supercharger, the exhaust energy is effectively recovered. In this case, the exhaust pressure on the first cylinder group side increases, but the difference between the boost pressure and the exhaust pressure is relatively small, and the intake and exhaust overlap period of the '7J first cylinder group is set short, so the exhaust gas Blowback is prevented.

(Example) Embodiments of the present invention will be described below based on the drawings.

FIG. 1 shows a six-cylinder engine equipped with a supercharging device according to an embodiment of the present invention. 1, 1, . . . are cylinders of the engine, and each cylinder 1, 1, . A first intake passage 4 is connected to each cylinder 1 of the first cylinder group 2, a second intake passage 5 is connected to each cylinder 1 of the second cylinder group 3, and the first and second intake passages 4, 5 are both communicated with the atmosphere via an air cleaner 6. Further, a first exhaust passage 7 is connected to each cylinder 1 of the first cylinder group 2, a second exhaust passage 8 is connected to each cylinder 1 of the second cylinder group 3, and the first and second exhaust passages are connected to each other. 7 and 8 are both communicated with the atmosphere via the exhaust gas purification device 30. Each of the above-mentioned intake passages 4
.

A throttle valve 11 is disposed in the first intake passage 4,
A roots-type mechanical supercharger 12 driven by the engine is provided upstream thereof, and supercharges the first cylinder group 2. A bypass passage 13 that bypasses the mechanical supercharger 12 is provided in the first intake passage 4, and a bypass valve 14 is provided in the bypass passage 13, and the bypass valve 14 is driven by an actuator 15. Further, a throttle valve 16 is provided in the second intake passage 5.
A compressor 17a of an exhaust turbo supercharger 17 driven by exhaust energy is provided upstream of the compressor 17a to supercharge the second cylinder group 3.

Further, an exhaust turbo supercharger 17 is provided in the first exhaust passage 7.
An exhaust turbine 17b is provided, and the exhaust turbo supercharger 17 is driven by the exhaust energy of the first cylinder group 2. The first exhaust passage 7 is provided with a bypass passage 18 that bypasses the exhaust turbine 17b, and the bypass passage 18 is provided with a bypass valve 19.
The bypass valve 19 is driven by an actuator 20.

Furthermore, a mechanical supercharger 12 is provided in the first intake passage 4.
An air flow sensor 21 is disposed upstream of the throttle valve 11, and a boost sensor 23 is disposed downstream of the throttle valve 11.

Further, a compressor 17 is provided in the second intake passage 5.
An air flow sensor 22 is disposed upstream of a, and a boost sensor 24 is disposed downstream of the throttle valve 16.

Each of these sensors 21 to 24 is connected to a controller 25 along with the output of a rotation speed sensor that detects the engine rotation speed.
The controller 25 controls each actuator 15, 20 so that the boost pressure becomes an appropriate pressure.

As shown in FIG. 2, the intake/exhaust overlap period T1 of the second cylinder group 3 is set longer than the intake/exhaust overlap period T2 of the TS1 cylinder group 2.

Therefore, in the above embodiment, since the exhaust turbo supercharger 17 and the mechanical supercharger 112 are used together, the engine output can be increased while improving the acceleration response of the engine.

Furthermore, since the exhaust turbine 17b is not disposed in the second exhaust passage 8, the exhaust pressure of the second cylinder group 3 is lowered. . Due to this, the scavenging effect obtained by setting the long intake and exhaust overlap period of the second cylinder group 3 is effectively exhibited, and the intake valve 9 is closed late without reducing the exhaust energy to the exhaust turbine 17b. This makes it possible to reliably prevent knocking when increasing the compression ratio, thereby effectively improving fuel efficiency.

Furthermore, since the exhaust turbine 17b is disposed in the first exhaust passage 7, the exhaust turbo supercharger 17 is driven by the exhaust energy of the first cylinder group 2 supercharged by the mechanical supercharger 12. , exhaust energy is effectively recovered. In this case, the exhaust pressure in the first exhaust passage 7 increases, but since the intake/exhaust overlap period of the first cylinder group 2 is set short, blowback of exhaust gas can be effectively prevented.

Note that, as shown by diagonal lines in FIG. 3, due to the characteristics of the supercharging characteristics of the mechanical supercharger 12, there is a region where the supercharging pressure is higher than the exhaust pressure in the low rotation range. In such a region, the intake/exhaust overlap period of the first cylinder group 2 may be made wider than the normal period. (Effects of the Invention) As explained above, according to the engine supercharging device of the present invention, the cylinders of the engine are divided into two cylinder groups, and the first cylinder group is connected to the second cylinder group by the mechanical supercharger. The cylinder groups are supercharged by an exhaust turbo supercharger, and the exhaust turbo supercharger is driven by the exhaust energy of the first cylinder group, and the intake and exhaust overlap period of the second cylinder group is set to a second cylinder group. Since it is set longer than the intake and exhaust overlap period of the first cylinder group, it is possible to promote the scavenging effect of the second cylinder group and prevent knocking while increasing the compression ratio and improving fuel efficiency. It is possible to recover exhaust energy and increase output while preventing blowback of exhaust gas in the cylinder group.

[Brief explanation of the drawing]

The drawings illustrate an embodiment of the present invention, with FIG. 1 being a general schematic diagram, FIG. 2 being an explanatory diagram showing an intake/exhaust overlap period, and FIG. 3 being a characteristic diagram showing supercharging characteristics. 1... Cylinder, 2... First cylinder group, 3... Second cylinder group, 12... Mechanical supercharger, 17... Exhaust turbo supercharger. 11i11 Drawing 2

Claims (1)

[Claims] (1) First and second cylinders that divide multiple cylinders of the engine
two cylinder groups, a mechanical supercharger that supercharges intake air to the first cylinder group, and an exhaust turbo supercharger that supercharges intake air to the second cylinder group, and the exhaust turbo supercharger supercharges intake air to the second cylinder group. The exhaust turbine of the supercharger is arranged in the exhaust passage of the first cylinder group so as to be driven by the exhaust energy of the first cylinder group, and the exhaust turbine of the supercharger is disposed in the exhaust passage of the first cylinder group.
A supercharging device for an engine, characterized in that an intake/exhaust overlap period of a cylinder group is set longer than an intake/exhaust overlap period of a first cylinder group.