JPS6270623A - Multiturbo supercharging device - Google Patents

Abstract

PURPOSE:To prevent the occurrence of hunting phenomenon to a supercharging pressure, by a method wherein a supercharger at a preceding stage is actuated in an engine low load region, and when a current supercharging pressure is increased to a given value, side pass valve is released, and when a supercharging pressure is further increased, actuation of a supercharger at a subsequent stage is started. CONSTITUTION:Air introduced from an air cleaner 21 is fed to compressors 11 and 17 of first and second turbo superchargers 3 and 6 through branch suction passages 13 and 14, and the air after boosted thereby is joined to feed it to combustion chamber 1 through a suction passage 15. Turbine 4 and 7 of the supercharger 3 and 6, respectively, are located in an exhaust passage 2 and a branch exhaust passage 27 branched from the passage 2, and a bypass passage 25 running around the turbine 4 is formed to the exhaust passage 27, and this constitution causes opening of the side pass valve 26 by means of a delivery air pressure from the supercharger 3 and causes opening of the on-off valve when the delivery air pressure is increased to a given supercharging pressure.

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to a multi-turbo supercharging device, and more specifically, a multi-turbo supercharging device that drives one or more turbo superchargers depending on the operating state of an engine. Regarding equipment.

[Prior art]

As a conventional multi-turbocharger of this type, there is one shown in FIG. 3, for example.

(Refer to Japanese Unexamined Patent Publication No. 59-F3B521). In this figure, the exhaust gas discharged from the combustion chamber 1 of the engine to the exhaust passage 2 is rotated by the exhaust turbine 4 of the first turbo supercharger 3. However, when the rotational speed of the internal combustion engine is low, the amount of exhaust gas discharged from the combustion chamber l is small, and the pressure inside the exhaust passage 2 is weak, so that the exhaust passage 2 and this exhaust passage are In the exhaust pressure control type wastegate valve 9 provided at the connection point between the exhaust gas passage 8 and the branch exhaust passage 8 that branches from the exhaust gas turbine 7 of the second turbocharger 6, the force of the spring 9A overcomes the exhaust gas pressure. , the valve body 9B keeps the inlet of the branch exhaust passage 8 open.

Thus, the rotation of the exhaust turbine 4 drives the compressor 11 via the drive shaft 10, but in this state, the check valve 12 is controlled to open the second branch intake passage 13 by the control described later.
Since the intake air is closed, the intake air supercharged by the compressor 11 is sent into the combustion chamber 1 from the intake passage 15 through the first branch intake passage 14 .

Next, when the rotational speed of the internal combustion engine increases and the amount of exhaust gas discharged from the combustion chamber 1 increases, and the pressure in the exhaust passage 2 upstream of the exhaust turbine 4 increases, the exhaust gas pressure increases to the exhaust pressure. Overcoming the spring force of the spring 9A provided in the control type waste gate valve 9, the valve body 9B
opens the entrance portion of the first branch exhaust passage 8. Therefore, part of the exhaust gas flows through the first branch exhaust passage 6.

The exhaust turbine 7 of the second turbocharger 6 is rotated, and the exhaust gas is discharged from the exhaust passage 5 to the outside. Thus, the rotation of the exhaust turbine 7 drives the compressor 17 via the drive shaft 16, and the compressor 17 starts supercharging intake air from the second branch intake passage 13.

Here, the supercharged air from the compressor 17 is configured to be guided through the intake passage 15, but upstream of the confluence point 15A of the intake passage 15 with the first branch intake passage, as described above, there is a A check valve 12 is interposed, and in this check valve 12, the supercharging pressure from the second turbo supercharger 6 guided to the first diaphragm chamber 12A is guided to the second diaphragm chamber 12B. 15A side, that is, when the supercharging pressure from the first turbo supercharger 3 and the spring force of the spring 12G incorporated in the check valve 12 are overcome, the valve is opened, and the second turbo supercharger 6 The supercharged air from the engine is supplied to the engine combustion chamber 1 via the intake passage 15.

Reference numeral 18 denotes a bypass passage provided between the inflow side of the second turbocharger turbine 7 and its exhaust passage 19, and a branch part of the bypass passage 18 with the branch exhaust passage 8 is connected to the intake pressure. A valve body 2OA of the second wastegate valve 20 of the controlled intake pressure adjustment type is provided, and when the intake pressure in the intake passage 15 exceeds a predetermined pressure, the valve is opened and the second wastegate valve 20 is supplied to the second turbo supercharger 6. Exhaust gas is discharged through passage 1.
Detour to the 9th side.

In the multi-turbo supercharger configured in this way,
First, the first turbo supercharger 3 is driven, and the supercharged air from the compressor 11 is transferred to the branched intake passage 14 and the intake passage 15.
However, when the exhaust gas pressure increases as the engine load increases, the waste gate valve 9 is opened and the second turbo supercharger 6 is driven, and both superchargers are supplied to the engine. Boost pressure is supplied to.

Note that since the first turbo supercharger 3 is of a relatively small capacity, it operates satisfactorily even in the low load and low rotation range of an internal combustion engine with a small amount of exhaust gas, and its supercharging efficiency is high. It is maintained. In addition, when the operating state of the internal combustion engine enters the high-load, high-speed range and the amount of exhaust gas increases, the flow of exhaust gas will change to 2.
It is divided into two parts and used to operate the first and second turbochargers 3 and 6. Therefore, the amount of exhaust gas that operates the first turbocharger 3 does not change much from before, and its supercharging efficiency is still maintained high. Furthermore, if the capacity of the second turbocharger 6 is set in advance to an appropriate value depending on the amount of exhaust gas, the supercharging efficiency of the second turbocharger 6 can also be maintained high. In this way, supercharging efficiency is maintained high over substantially the entire operating range of the engine.

[Problem that the invention seeks to solve]

However, in such a conventional multi-turbo supercharging device, when the discharge air pressure generated by the compressor 11 of the first turbo supercharger 3 reaches a specified pressure, the waste gate valve 9 closes. When the branch exhaust passage 8 is opened, exhaust gas is introduced from the branch exhaust passage 8 to the turbine 7 of the second turbocharging Ja 6.If the cross-sectional area of the branch exhaust passage 8 is set large for a relatively large capacity, Even if the waste gate valve 8 opens slightly, the amount of exhaust gas supplied from the branch exhaust passage 8 increases, causing the exhaust pressure in the exhaust passage 2 to drop rapidly.

Therefore, the waste gate valve 9 closes due to this drop in exhaust pressure, and the branch passage 8 is cut off.
The exhaust pressure rises again, but this repetition causes the supercharging pressure to hunt, which significantly impairs the ride comfort of a car.

Furthermore, if the cross-sectional area of the branch exhaust passage 8 is set to be small, sufficient output cannot be expected because the high-speed region of the engine becomes high. - [Object of the Invention] The object of the present invention is to eliminate the above-mentioned drawbacks, and to first drain exhaust gas through a bypass passage with a small flow rate when the supercharging pressure obtained from the front-stage turbocharger reaches a predetermined pressure. When the bypass passage causes the supercharging pressure to still exceed a predetermined pressure, the exhaust gas is switched to a branch passage with a relatively large flow rate to supply the exhaust gas to the subsequent turbo supercharger. To provide a multi-turbo supercharging device that does not cause supercharging pressure hunting in the process of driving a rear-stage turbo supercharger and maintains appropriate engine output from a low speed range to a high speed range.

[Structure of the invention]

In order to achieve such an object, the present invention has a plurality of turbo superchargers and sequentially connects the engine from the front turbo supercharger to the rear turbo supercharger via an exhaust passage depending on the engine load condition. In a multi-turbo supercharging device configured to supply and drive exhaust gas, an exhaust passage is branched into a first exhaust passage for a turbo supercharger in the previous stage and a second exhaust passage for a turbo supercharger in the next stage. The cross-sectional area of the second exhaust passage is made almost equal to that of the exhaust passage before branching, a bypass passage is provided in the first exhaust passage for bypassing the turbocharger in the previous stage, and a bypass valve is arranged in the bypass passage. , an on-off valve is disposed in the second exhaust passage, the side passage valve is controlled by the discharge air pressure from the turbo supercharger in the previous stage, and the on-off valve is controlled by the side passage valve when the side passage valve is opened;
Moreover, the valve is opened when the discharge air pressure from the front-stage turbocharger reaches a predetermined supercharging pressure.

[For production]

In a multi-turbo supercharging device configured in this way, when the engine is in a low load region, exhaust gas is supplied to the turbo supercharger in the previous stage to perform supercharging, and when the supercharging pressure reaches a predetermined pressure, In order to maintain a predetermined pressure, the bypass valve is first opened and the exhaust gas is diverted, increasing the engine load.
When the supercharging pressure is about to exceed the predetermined pressure, the branch passage to the turbocharger in the later stage is opened, and the exhaust gas is switched from the side passage to the branch passage to charge the turbocharger in the later stage. It continues to operate to maintain the boost pressure at a predetermined pressure.

〔Example〕

Embodiments of the present invention will be described in detail and specifically below based on the drawings.

FIG. 1 shows an embodiment of the present invention. First, the intake system will be described. Air is passed through an air cleaner 21 and an air flow meter 22 to the compressor 11 of the first turbocharger 3 and the second turbocharger 6. However, the discharge outputs in the branch intake passages 14 and 13 on the discharge side of the compressors 11 and 17 are detected by the control circuit 23. The air flow meter 22 also supplies the detected air flow rate to the control circuit 23 as an output signal. Furthermore, in this example, a check valve 24 is disposed on the upstream side of the discharge-side branch intake passage 13 immediately before the junction with the branch intake passage 14 .

Next, let's talk about the exhaust system. Reference numeral 25 denotes a bypass passage of the first turbocharger (relatively small capacity), and in the case of this example, exhaust gas can be diverted to the exhaust passage and discharged by this bypass passage 25. 26 is a side valve provided in the bypass passage 25, and 26A is a side valve 2.
8 actuators. The actuator 28A is driven by the discharge pressure from the first turbocharger 3, and when the discharge pressure, that is, the supercharging pressure, reaches a predetermined pressure or more, it starts opening the side passage valve 26, can be maintained.

27 is a branch exhaust passage to the second turbine 7 which is branched from the exhaust passage 2 so as to further bypass the first turbocharger turbine 4;
The membrane area should be maintained approximately equal to that of . 2 is a branch passage on-off valve provided in the branch exhaust passage 27;
The actuator 28A of No. 8 is driven by a control signal from the control circuit 23 mentioned above.

Furthermore, the turbine 7 of the second turbocharger B is also provided with a bypass passage 29 and a bypass valve 30 that bypass the turbine 7, and the bypass valve 30 is controlled by an actuator 30A controlled by the discharge pressure from the compressor 17. It is equipped with

Describing the control operations in the multi-turbo supercharging system configured as described above, first, the control operation is performed so that the supercharging pressure obtained from the first turbo supercharging fi3 does not reach a predetermined pressure in the low load region of the engine. In this state, the actuator 28A keeps the branch passage opening/closing valve 28 open in response to a signal from the control circuit 23, so that supercharging pressure is supplied to the engine only from the compressor 11 of the first turbocharger 3. be done.

In this way, high torque can be obtained even in a low load region, but when the operating region moves from such a state to a region where the boost pressure is further increased, the bypass valve 28 begins to open via the actuator 2EiA, and the compressor The discharge pressure from 11 is controlled to be maintained at a predetermined supercharging pressure. In this case, the bypass passage 25 is formed with a cross section with a relatively small flow rate, and the exhaust gas bypassed from the bypass passage 25 is directly discharged to the outside from the discharge passage 5.

Then, the load on the engine increases further, and the bypass passage 2
Even in the open state of 5, when the discharge pressure from the compressor 11 exceeds the predetermined supercharging pressure, the control circuit 23 opens the on-off valve 28 via the actuator 28A based on the signal from the air flow meter 22 and the detection signal of the discharge pressure. Let me speak.

As a result, the exhaust pressure decreases due to the opening of the on-off valve 28, but on the other hand, if the discharge pressure from the compressor 11 attempts to decrease below a predetermined pressure, the bypass passage 25 is closed. The bypassed exhaust gas supplements this, and the discharge pressure from the compressor 11 is maintained at a predetermined pressure without hunting. That is, the side valve 2e provided in the bypass passage 25 is in charge of fine adjustment of the flow rate to the branch exhaust passage 27 having a large flow cross section.

Furthermore, even if the engine load increases, the branch exhaust passage 27 has a sufficient cross-sectional area so that the second turbocharger 6 can be appropriately driven, resulting in high-speed operation. It can provide high output power. Note that if the discharge pressure from the second compressor 17 still exceeds the predetermined supercharging pressure, the actuator 30A controls the bypass valve 30 to release excess exhaust gas from the bypass passage 29. can.

Next, another embodiment of the present invention will be described with reference to FIG.

In this example, instead of the bypass passage 25 shown in FIG.
A bypass passage 35 is provided downstream of the on-off valve 28, and 38 is the bypass valve, and 3e is its actuator.

If configured as in this example, when the supercharging pressure obtained from the first turbo supercharger 3 reaches a predetermined pressure, exhaust gas is directly supplied from the bypass passage 35 to the branch exhaust passage 27, thereby reducing waste. It is possible to start rotating the turbine 7 of the second turbocharger B from this point without discharging gas, and the rotation can be rapidly increased when the on-off valve 28 is opened and closed.

〔Effect of the invention〕

As described above, the present invention has a plurality of turbo superchargers, and the exhaust passage is sequentially connected from the front turbo supercharger to the rear turbo supercharger depending on the load condition of the engine. In a multi-turbo supercharging device that supplies and drives engine exhaust through While branching, the second exhaust passage maintains a membrane area that is almost the same as that of the exhaust passage before branching, and the first exhaust passage is provided with a bypass passage that bypasses the turbo supercharger in the previous stage. A bypass valve is provided in the second exhaust passage, and an on-off valve is provided in the second exhaust passage. Since the valve is opened when the front-stage turbocharger is opened and the discharge air pressure from the front-stage turbocharger reaches a predetermined supercharging pressure, the valve is opened and the rear-stage turbocharger is opened. During the driving stage, the bypass valve acts to compensate for the amount of exhaust gas supplied to the second exhaust passage, thereby preventing the hunting phenomenon from occurring in the boost pressure.
Furthermore, it is possible to supply sufficient high output over the entire driving range from low speeds to high speeds.

Yet again. In the second embodiment, in addition to the above-mentioned effects, it is possible to assist the rotation increase of the rear-stage turbocharger and rapidly increase the rotation to cope with a high load.

[Brief explanation of drawings]

FIG. 1 is a schematic diagram showing an example of the configuration of a multi-turbo supercharger according to the present invention, and FIG. 2 is a schematic diagram showing a configuration near a first turbo supercharger as another embodiment of the present invention. FIG. 3 is a schematic diagram showing an example of the configuration of a conventional multi-turbo supercharging device. ■... Combustion chamber, 2... Exhaust passage, 3... First turbo supercharger, 4.7... Exhaust turbine, 5... Exhaust passage, 6... Second turbo supercharging Machine, 8... Branch exhaust passage, 9... Waste gate valve, 9A... Spring, 9B... Valve body, 10.113... Drive shaft. 11.17... Compressor, 12... Check valve, 12A, 12B... Diaphragm chamber, 12C...
・Spring, 13...Second branch intake passage, 14,...Ca χ14) City υ0 to π passes through 15...Intake passage, 15A...Confluence point, 18...Bypass passage, ■9... - Discharge passage, 20... Waste gate valve, 2OA... Valve body, 21... Air cleaner, 22... Air flow meter, 23... Control circuit, 24... Check valve. 25.29.35 River bypass passage, 2B, 30.38... Side passage valve, - 28A, 28A, 30A, 38A... Actuator, 27... Branch exhaust passage, 28... Branch passage opening/closing valve . Patent applicant Nissan Motor Co., Ltd.

Claims (1)

[Scope of Claims] It has a plurality of turbo superchargers, and drives the engine by supplying engine exhaust gas from the front turbo supercharger to the subsequent turbo supercharger through an exhaust passage in order according to the load condition of the engine. In the multi-turbo supercharging device, the exhaust passage is branched into a first exhaust passage for the previous stage turbo supercharger and a second exhaust passage for the next stage turbo supercharger, and the second exhaust passage The cross-sectional area of the passage is made almost equal to the exhaust passage before branching, a bypass passage is provided in the first exhaust passage for bypassing the turbo supercharger in the previous stage, and a bypass valve is disposed in the bypass passage. , an on-off valve is disposed in the second exhaust passage, the side passage valve is controlled by the discharge air pressure from the preceding turbo supercharger, and the on-off valve is configured to:
A multi-turbo supercharging device characterized in that the bypass valve is opened and the valve is opened when the discharge air pressure from the front-stage turbo supercharger reaches a predetermined supercharging pressure.