JPH01285619A - Engine with supercharger - Google Patents

Abstract

PURPOSE:To enable execution of smooth supercharging operation by providing an exhaust valve device with variable lift function which gradually opens and exhaust valve with a low speed area rest function to drive a supercharger for a high speed from a point of time at when the pressure of supercharge by a working supercharger driven through operation of a working exhaust valve is increased to a maximum value. CONSTITUTION:Each cylinder 1 is provided with working suction and exhaust valves 2 and 4 actuated in a whole operation area and suction and exhaust valves 3 and 5 with low speed area rest function operated only in a high speed area. Turbines 11t and 12t of a working supercharger 11 and a supercharger 12 for a high speed are mounted in exhaust flow passages 8 and 9, respectively. In an engine with a supercharger so constituted, a variable lift mechanism 35 is additionally mounted to an exhaust valve 5 with low sped rest function. The variable lift mechanism 35 is formed such that by means of a command from a control device, the exhaust valve 5 is gradually opened from a point of time when the pressure of supercharge by the working supercharger 11 is increased to a maximum value. This constitution enables smooth connection of supercharge by the working supercharger 11 to supercharge by the supercharger 12 for a high speed.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a supercharged engine equipped with an exhaust valve device with a shutdown function and two exhaust type superchargers, and particularly to the exhaust valve device thereof. .

[Prior art] In order to obtain stable torque characteristics over a wide operating range in a supercharged engine equipped with two exhaust-type superchargers, a regular exhaust valve for each cylinder is operated over the entire operating range, except in the low speed range. An exhaust valve with a pause function that operates in the operating range is provided, and a regular supercharger is driven by the exhaust flow from the regular exhaust valve, and a high-speed supercharger is driven by the exhaust flow from the exhaust valve with a pause function. It is known from Japanese Unexamined Patent Application Publication No. 174537/1989 proposed by the present applicant.

[Problems to be Solved by the Invention] In a supercharged engine equipped with such an exhaust valve device with a shutdown function and two exhaust type superchargers, supercharging by the regular supercharger reaches the maximum supercharging pressure. After that, the exhaust valve with a pause function is activated and the high-speed supercharger starts to drive, but there is a time lag from when the high-speed supercharger reaches the maximum boost pressure from the stopped state, and there is a pause. There is a problem in that the supercharging pressure from the regular supercharger temporarily drops when exhaust gas is supplied to the high-speed supercharger by fully opening the functional exhaust valve.

As a countermeasure, the high-speed turbocharger starts driving in advance from the time when the regular turbocharger reaches the maximum boost pressure, and the regular turbocharger continues to drive while maintaining the maximum boost pressure. In addition, in order to smoothly connect the supercharging from the high-speed supercharger, for example, before the exhaust valve with a pause function is activated, a passage and a flow control valve are installed to bypass the exhaust flow to the regular supercharger and lead it to the high-speed supercharger. It is possible to consider setting up a

However, if such a bypass passage and a flow control valve are provided, the structure becomes complicated, and in addition to controlling the exhaust valve, it is also necessary to control the flow control valve provided in the bypass passage.

Therefore, an object of the present invention is to gradually open an exhaust valve with a pause function from the time when the maximum supercharging pressure is reached or from the point where the maximum supercharging pressure is reached, without the need to separately add a bypass passage or a control valve. can start driving.

To provide a supercharged engine capable of smoothly connecting supercharging by a regular supercharger and supercharging by a high-speed supercharger while maintaining maximum supercharging pressure.

[Means for Solving the Problems] In order to achieve the above problems, the present invention includes a first exhaust valve 4 that operates in all operating ranges and a second exhaust valve 5 that operates in operating ranges excluding low speed ranges. An Ml exhaust type supercharger 11 is provided in each cylinder 1 and driven by the exhaust flow from the first exhaust valve 4, and a second exhaust gas is driven by the exhaust flow from the second exhaust valve 5. In a supercharged engine equipped with a supercharger 12, the second exhaust valve 5 is gradually opened from the point in time when supercharging by the first exhaust supercharger 11 reaches the maximum supercharging pressure.
The variable lift function starts driving the exhaust type supercharger 12 (
35) An exhaust valve device is provided.

[Operation] When the second exhaust valve 5 is in a rest state, when the supercharging by the first exhaust type supercharger 11 reaches the maximum supercharging pressure, the second exhaust valve device with the variable lift machine t@(35) The exhaust valve 5 gradually opens and the second exhaust type supercharger 12 starts to be driven, so when the second exhaust valve 5 is fully opened, the second exhaust type turbocharger 12 starts overheating with almost no time lag. The charge can be increased to the maximum boost pressure.

Therefore, while maintaining the maximum boost pressure, the first exhaust type supercharger 1
In addition to the supercharging by the second exhaust type supercharger 12, it is possible to smoothly connect the supercharging by the second exhaust type supercharger 12.

[Example] Examples will be described below based on the accompanying drawings.

In FIG. 1 showing an example of an intake and exhaust system of an engine to which the present invention is applied, - each cylinder (not shown) is provided with a pair of intake valves 2, 3 and an exhaust valve 4, 5, respectively;
Among them, the intake valve 2 and exhaust valve 4 of the set are regular intake and exhaust valves that operate in the entire operating range from low speed range to high speed range, and the other set of intake valve 3 and exhaust valve 5 operates only in the high speed range. There is a low speed range pause Ja I hit the intake and exhaust valves. The low-speed range rest and high-speed range operation of the intake valve 3 and exhaust valve 5 are switched off by a control device (not shown), for example, by a sliding operation of each camshaft 6.7. It is designed to be manipulated.

Exhaust passages 8 and 9 are provided in the exhaust boats opened and closed by the exhaust valves 4 and 5, respectively, and a first exhaust type supercharging m (in the following embodiments) is provided in the exhaust passage 8 on the side of the regular exhaust valve 4. 11 turbines (denoted as regular turbochargers) are arranged,
Furthermore, a second
12 exhaust type supercharging m (referred to as a high speed turbocharger in the following examples) 12 turbines 12t are arranged.

On the downstream side of each turbine lit, 12t, both exhaust passages 8
．． 9 merges, an 02 sensor 14 is installed in the merge part 13, and a catalyzer 15 is installed downstream of this merge part 13.
It is then exposed to the atmosphere via a muffler (not shown).

Further, on the upstream side of each turbine lit, 12t, bypass passages 16.17 from both exhaust passages 8.9 to the merging section 13 are provided, respectively, and a waste gate valve 18 is further provided to open and close both bypass passages 16.17 at the same time. 19 is its actuator.

On the other hand, intake passages 22 and 23 are provided that branch from the downstream side of the air cleaner 21 that sucks and purifies outside air.
The compressor 12c of the high-speed turbocharger 12 is arranged in the intake passage 23. Both intake passages 22 and 23 connect to the intercooler 24 on the downstream side.
A backflow prevention control valve 25 is provided in the intake passage 23 on the upstream side of the intercooler 24, and the -
A surge prevention valve 27 is provided in a bypass passage 26 that connects the intake passage 23 and the confluence part on the downstream side of the air cleaner 21 in the L flow.

A throttle valve 29 is provided in the merging passage 28 downstream of the intercooler 24, and a chamber-shaped surge tank 31 and branch passages 32 and 33 are provided downstream of the merging passage 28.
The branch passages 32 and 33 are connected to each of the intake boats which are opened and closed by the intake valves 2 and 3, respectively. Further, a supercharging pressure take-out boat 34 is provided upstream of the throttle valve 29 on the second day of the merging passage, and this supercharging pressure take-out boat 34 is connected to the actuator 19 of the waste gate valve 18 .

In the above, each of the exhaust valves 5 with a low-speed range stop function is further provided with a variable lift mechanism 35.

This variable lift machine 4I35 is in the low speed operating range.

The regular turbocharger 11 is activated by a command from the control device.
The exhaust valve 5 with a low-speed range stop function is gradually opened (stepwise or steplessly) from the point in time when the supercharging reaches the maximum supercharging pressure.

Next, the supercharging function of the above twin turbocharged engine will be explained.

First, in the low-speed, low-load operating range of the engine, only the regular intake and exhaust valves 2 and 4 operate, and the exhaust flow from the regular exhaust valve 4 rotationally drives the turbine lit of the regular turbocharger 11 installed in the exhaust passage 8. . The outside air sucked in from the air cleaner 21 is pressurized in the intake passage 22 by the compressor lie which rotates integrally with the turbine lit, and is then compressed into the intercooler 24, the merging passage 28, the surge tank 31 and the branch passage 3.
Intake air is pumped to each cylinder 1 via 2. At this time, the backflow prevention control valve 25 and the surge prevention valve 27 are closed as shown.

When the supercharging by the regular turbocharger 11 reaches the maximum supercharging pressure, the variable lift mechanism 35 is activated to gradually open the exhaust valve 5 with a low speed range stop function, and the exhaust gas is gradually discharged from the exhaust valve 5. Due to the flow, the turbine 12t of the high-speed turbocharger 12 installed in the exhaust passage 9 begins to rotate. This starts driving the high-speed turbocharger 12 in the low-speed, low-load operating range, and pressurizes the intake passage 23 by the compressor 12c.

At this time, since the backflow prevention control valve 25 is closed, there is a possibility that the compressor llc of the regular turbocharger 11 enters the surge zone due to the rotation of the high-speed turbocharger 12, and in that case, the surge prevention valve 27 is opened.

When the engine speed further increases and enters a high-speed, high-load operating range, both the intake and exhaust valves 3 and 5 with a low-speed range stop function are fully opened, and at the same time, the backflow prevention control valve 25 is opened. When the exhaust valve 5 is fully opened, the turbine 12t, whose rotation has been increased by −L in advance as described above, immediately rotates at high speed, that is, the high-speed turbocharger 12 is quickly driven, and the compressor 12C causes the intake passage 23 to rotate. Pressurized intake air is sent from the intercooler 24 to the merging passage 28, and supercharged intake air combined with that from the regular turbocharger 11 is sent to each cylinder l via the surge tank 31 and both branch passages 32 and 33. becomes. At this time, the surge prevention valve 27 is closed, and the backflow prevention control valve 25 opens while compensating for a slight time lag of the high-speed turbocharger 12.

In this way, the maximum boost pressure from the twin turbochargers 11 and 12 can be obtained with almost no time lag in the high-speed, high-load operating range of the engine. In other words, the rotation speed (P2) - supercharging pressure (Ne) characteristic is shown in Fig. 2, and after the supercharging by the regular turbocharger 11, which is shown by the solid line, reaches the maximum supercharging pressure, the broken line shows the characteristic. Conventionally, there was a drop in the boost pressure until the supercharging by the high-speed turbocharger 12 reached the maximum boost pressure, but as shown in the lift control zone A of the exhaust valve 5 according to the present invention, While supercharging by the regular turbocharger 11 is maintained at the maximum supercharging pressure, supercharging by the high-speed turbocharger 12 is connected with almost no time lag, and the maximum supercharging pressure can be increased.

In addition, in the case of supercharging in a high-speed, high-load operation range, each exhaust bypass passage is operated by the actuator 19, which responds to the boost pressure from the boost pressure take-off boat 34 provided in the intake merging passage 28. Since the common waste gate valve 18 provided at 16 and 17 opens, the high exhaust pressure is released and the supercharging pressure is maintained below a predetermined pressure.

[Effects of the Invention] As described above, according to the present invention, from the time point when the supercharging by the regular supercharger driven by the operation of the regular exhaust valve reaches the maximum boost pressure, the low speed range stop that drives the high speed supercharger is started. Exhaust valve with variable lift function that gradually opens the exhaust valve with function? Because the engine is equipped with a low-speed stop function, when the exhaust valve is fully open, the high-speed supercharger can increase the supercharging pressure to the maximum with almost no time lag, thus maintaining the maximum supercharging pressure. At the same time, it is possible to smoothly connect supercharging with a high-speed supercharger in addition to supercharging with a regular supercharger.

[Brief explanation of the drawing]

FIG. 1 is a configuration diagram of an intake and exhaust system of a supercharged engine showing an embodiment of the present invention, and FIG. 2 is a rotation speed-supercharging pressure characteristic diagram. In one drawing, 1 is a cylinder, 4 is a first exhaust valve, 5 is a second exhaust valve, 11 is a first supercharger, 12 is a second supercharger, and 35 is a variable lift mechanism.

Claims (1)

[Scope of Claims] Each cylinder is provided with a first exhaust valve that operates in the entire operating range and a second exhaust valve that operates in the operating range excluding the low speed range, and is driven by the exhaust flow from the first exhaust valve. In a supercharged engine provided with a first exhaust type supercharger that is driven by an exhaust flow from a second exhaust valve, and a second exhaust type supercharger that is driven by an exhaust flow from a second exhaust valve, the first exhaust type providing an exhaust valve device with a variable lift function that gradually opens the second exhaust valve and starts driving the second exhaust type supercharger from the point at which supercharging by the supercharger reaches the maximum supercharging pressure; A supercharged engine featuring