JPH03267525A - Engine with supercharger - Google Patents

Abstract

PURPOSE:To avoid collision of exhaust gas discharged from a main turbocharger and an exhaust by-pass passage by completely closing the exhaust by-pass valve in the case where both of the main and sub-turbochargers are operating. CONSTITUTION:Downstreams of outlets of turbines of a sub-turbocharger 8 and a main turbocharger 7 are communicated with each other through an exhaust by-pass passage 39. An exhaust by-pass valve 38 is provided in the exhaust by-pass passage 39 for speeding up the preparatory rotational speed of the sub-turbocharger 8 by supplying a part of the exhaust gas discharged from the sub-turbocharger 8 to the downstream of the exit of the turbine of the main turbocharger 7 through opening the exhaust by-pass valve 38 before opening an exhaust change-over valve 17. In this case, a computer 29 closes the exhaust by-pass valve 39 completely in the case where both of the turbochargers 7 and 8 operate together. Thus, collision of the exhaust gas discharged from the main turbocharger 7 and the exhaust by-pass passage 39 is avoided in the case of heavy load, and supercharging performance is improved.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention has a main turbocharger and a sub-turbocharger, and in a low speed range, only the main turbocharger performs supercharging, and in a high speed range, both turbochargers are operated. The present invention relates to a supercharged engine that is supercharged by both turbochargers, a so-called two-stage twin turbo engine.

[Conventional technology]

Two stage turbochargers are placed in parallel to the engine body, with only the main turbocharger operating in the low speed range to form a single turbocharger, and both turbochargers operating in the high speed range. Supercharged engines that employ turbo systems are known. The configuration of this type of supercharged engine is shown in FIG. 6, for example. A main turbocharger (T/C-1) 92 and a sub-turbocharger (T/C-2) 93 are provided in parallel to the engine body 91. An intake switching valve 94 and an exhaust switching valve 95 are provided in the intake and exhaust systems connected to the auxiliary turbocharger 93, respectively, and an intake bypass valve 96 is provided in the intake bypass passage that bypasses the compressor of the auxiliary turbocharger 93. It is being By fully closing both the intake switching valve 94 and the exhaust switching valve 95, only the main turbocharger 92 is operated for supercharging, and by fully opening both and closing the intake bypass valve 96, the auxiliary turbocharger 93 is also operated. It is possible to carry out supercharging operation and operate two turbochargers.

In addition, from 1 turbocharger operation (in other words, only the main turbocharger 92 is in supercharging operation) to 2 turbochargers in operation (in other words, both turbochargers 92 and 93 are in supercharging operation)
In order to more smoothly switch to JP-A-61-1
In the system disclosed in Japanese Patent No. 12734, the exhaust switching valve is gradually opened and slightly opened at a boost pressure lower than that at the time of switching the turbocharger, and the approach rotation speed of the sub-turbocharger is increased before switching.

However, in a supercharged engine like the one shown in Figure 6, a single exhaust switching valve controls boost pressure when using one turbocharger and switches from one turbocharger to two turbochargers. Therefore, the following problems arise.

In supercharging pressure control when a single turbocharger is used (the main turbocharger +92 is driven in the entire engine speed range, and the auxiliary turbocharger 93 is controlled by opening the exhaust switching valve 95 slightly in the medium speed range), the exhaust switching valve 95 is The bore diameter is large (approximately 50φ, the diameter necessary to ensure output performance at high speeds), and the controllability of boost pressure is poor.
In other words, a butterfly valve has the characteristic that it controls the flow in a large or small range up to a certain small opening, but the flow rate hardly changes beyond a certain opening, and when this is applied to a large diameter bore. Controlling boost pressure becomes difficult. Therefore, switching shock occurs when switching from one turbocharger to two turbochargers, resulting in poor controllability.

In addition, the exhaust switching valve 95 has a two-stage diaphragm consisting of one diaphragm for controlling boost pressure during turbocharging and one to two diaphragms for switching between turbochargers, so it is large and disadvantageous in mounting. be.

Therefore, the present applicant has previously proposed a technology that significantly alleviates the switching shock when switching from one turbocharger to two turbochargers and improves controllability (Patent application No. No. 273803).

FIG. 7 shows an example of a supercharged engine previously proposed by the present applicant. In FIG. A turbocharger 83 is provided in parallel. The intake and exhaust systems connected to the auxiliary turbocharger 83 are provided with an intake switching valve 84 and an exhaust switching valve 85, respectively, and an intake bypass passage that bypasses the compressor of the auxiliary turbocharger 83 is provided with an intake bypass valve 86. It is being An exhaust bypass passage 87 is provided downstream of the turbine exit of the sub-turbocharger 83 and opens into an exhaust passage downstream of the turbine exit of the main turbocharger 82 . An exhaust bypass valve 88 is provided in the exhaust bypass passage 87, and the exhaust bypass valve 88 is opened before the exhaust switching valve 85 is opened. In addition,
In the figure, 89 indicates wastegate pulp.

In this way, in a supercharged engine having the exhaust bypass valve 86, even if the exhaust switching valve 85 is left fully open,
By controlling the opening and closing of the exhaust bypass valve 88, the auxiliary turbocharger 83 can perform run-up rotation. Therefore, the exhaust bypass passage 87 only needs to have a small diameter, and the accuracy of approach rotation control can be improved compared to conventional control using an exhaust switching valve provided in a large diameter bore. The occurrence of switching shocks is significantly alleviated.

[Problem to be solved by the invention]

However, the supercharged engine shown in FIG. 7 still has some problems. In other words, in the case of high load when both the main turbocharger 82 and the auxiliary turbocharger 830 are operating, if the exhaust bypass valve 88 is in the open state, the main turbocharger 82 is activated as shown in FIG.
The exhaust gas G exiting from the auxiliary turbocharger 83 and the exhaust gas G exiting from the auxiliary turbocharger 83 via the exhaust bypass passage 87 collide near the downstream opening of the exhaust bypass passage 87, and the exhaust gas G exits from the auxiliary turbocharger 83 via the exhaust bypass passage 87 collides near the downstream opening of the exhaust bypass passage 87. The exhaust pressure will increase.

That is, since the downstream end of the exhaust bypass passage 87 opens into the exhaust passage downstream of the main turbocharger 82, the exhaust gas G1 that has passed through the main turbocharger 82 and the exhaust gas that has passed through the sub-turbocharger 83 are separated. G! They collide, causing pressure loss.

Therefore, the exhaust pressure on the turbine outlet side of the main turbocharger 82 increases, and supercharging performance decreases.

Furthermore, if the diameters of the downstream exhaust passages of both turbochargers are the same, the amount of exhaust gas flowing into the main turbocharger 82 side increases by the amount of exhaust gas bypassed via the exhaust bypass passage 87, and the amount of exhaust gas flowing into the main turbocharger 82 increases. Exhaust pressure on the side increases. This creates an exhaust pressure difference between both turbochargers, and the supercharging performance deteriorates due to the imbalance between both turbochargers.

The present invention has focused on the above-mentioned problem, and has developed a supercharger that can further improve supercharging performance by eliminating the collision between the exhaust gas from the main turbocharging and the exhaust gas from the exhaust bypass passage during high loads. The purpose is to provide an attached engine.

[Means to solve the problem]

A supercharged engine according to the present invention that meets this objective has a main turbocharger and a sub-turbocharger, and connects an exhaust passage downstream of a turbine outlet of the sub-turbocharger and an exhaust passage downstream of the turbine outlet of the main turbocharger to an exhaust bypass. A portion of the exhaust gas flowing out from the secondary turbocharger is transferred to the exhaust bypass passage through a valve that is opened before the exhaust switching valve located downstream of the exhaust bypass valve is opened. An engine equipped with a supercharger is provided with an exhaust bypass valve that increases the run-up rotation speed of a sub-turbocharger by allowing the flow to flow downstream of a turbine outlet, and in a state where both the main turbocharger and the sub-turbocharger are operating, the exhaust bypass valve It is equipped with a valve-closing command means for fully closing the valve.

[Effect]

In the supercharged engine configured in this manner, the exhaust bypass valve is closed by the valve closing command means during high load when both the main turbocharger and the auxiliary turbocharger operate. Therefore, the exhaust gas from the exhaust bypass passage does not flow into the exhaust passage downstream of the turbine outlet of the main turbocharger, and an increase in exhaust pressure due to collision between exhaust gases is prevented.

Furthermore, since the run-up rotation of the sub-turbocharger has been completed during high load, no problem will occur in terms of performance even if the exhaust bypass valve is closed.

〔Example〕

Preferred embodiments of the supercharged engine according to the present invention will be described below with reference to the drawings.

First Embodiment FIGS. 1 to 4 show a first embodiment of the present invention, particularly when applied to a six-cylinder engine.

In Figure 1, 1 is the engine, 2 is the surge tank, 3
indicates an exhaust manifold. Exhaust manifold 3 is used for two cylinder groups, #1 to #3 cylinder group and #4 to #6 cylinder group, which do not cause exhaust interference.
The assembled parts are communicated with each other by a communication path 3a. 7.8 is a main turbocharger and a sub-turbocharger arranged in parallel with each other. Each of the turbines 7a and 8a of the turbocharger 7.8 is connected to a gathering part of the exhaust manifold 3, and each of the combination leaves 7b and 8b is connected to the surge tank 2 via an intercooler 6 and a throttle valve 4.

The main turbocharger 7 is operated from a low engine speed range to a high engine speed range, and the auxiliary turbocharger 8 is stopped in a low engine speed range.

In order to enable operation and stop of both turbochargers 7.8, an exhaust switching valve 17 is provided downstream of the turbine 8a of the auxiliary turbocharger 8, and an intake switching valve 18 is provided downstream of the compressor 8b. Suction/exhaust switching valve 18.17
When both turbochargers are fully open, both turbochargers 7.
8 is activated.

In order to smoothly switch from one turbocharger to two turbochargers, the intake passage of the auxiliary turbocharger 8 that is stopped in a low speed range is provided with an intake bypass passage 13 that communicates between the upstream and downstream of the compressor 8b. , an intake bypass valve 33 disposed midway through the intake bypass passage 13 is provided. The intake bypass valve 33 is opened and closed by the actuator 10.

Note that the air flow downstream side of the intake bypass passage may be communicated with the intake passage upstream of the main turbocharging compressor 7. In addition, a check valve 12 is provided in the bypass passage that communicates the upstream and downstream sides of the intake switching valve 18, so that even when the intake switching valve 18 is closed, the compressor outlet pressure on the auxiliary turbocharger 8 side is lower than that on the main turbocharger 7 side. This allows air to flow from the upstream side to the downstream side when it becomes large.

In FIG. 1, 14 indicates an intake passage on the compressor outlet side, and 15 indicates an intake passage on the compressor inlet side.

The intake passage 15 is connected to an air cleaner 23 via an air flow meter 24. A front pipe 20 forming an exhaust passage is connected to an exhaust muffler 2 via an exhaust gas catalyst 21.
Connected to 2.

The intake switching valve 18 is opened and closed by the actuator 11, and the exhaust switching valve 17 is opened and closed by the diaphragm type actuator 16.
It is opened and closed by Note that 9 indicates an actuator that opens and closes the waste gate pulp 31.

The first, second, third,
A fourth three-way solenoid valve 25, 26, 27, 28 is provided. Switching of the three-way magnetic valves 25, 26, 27, and 28 is performed according to commands from the engine control computer 29. When the three-way solenoid valve 25.28 is turned on, the actuator 11.1 is turned on to fully open the intake and exhaust switching valve 18.17.
6 is activated, and when it is OFF, the actuator 11.16 is activated so that the intake/exhaust switching valve 18.17 is fully closed. Note that 32 is a fifth three-way solenoid valve for controlling the exhaust gas switching valve 17 to open slightly. 16a is a diaphragm chamber of the actuator 16, 10a is a diaphragm chamber of the actuator 10, and lla and llb are diaphragm chambers of the actuator 11, respectively.

1st, 3rd, 4th, 5th three sides magnetic valve 25.27.28
．． 32 selectively switches between atmospheric pressure and the intake pipe pressure downstream of the compressor and upstream of the throttle valve 4. A check valve 35 is provided in this intake pipe pressure introduction path, and the compressor outlet pressure (normal The maximum value of pressure) can be held. Therefore, the compressor outlet pressure can be held in each diaphragm chamber even in a light load range, and the operating state of the two turbochargers can be maintained in a high speed range.

The engine control computer 29 is electrically connected to sensors for detecting various operating conditions of the engine, and receives signals from the various sensors. Engine operating condition detection sensors include an intake pipe pressure sensor 30, a throttle opening sensor 5, and an air flow meter 2 as an intake air amount measurement sensor.
4, an O2 sensor 19, an engine rotation speed sensor 34, and the like.

The engine control computer 29 includes a central processor unit (CPU) for calculations, a read-only memory (ROM), and a read-only memory (ROM).
), -Random access memory (RAM) for time storage
), an input/output interface (I/D interface), and an A/D converter that converts analog signals from various sensors into digital quantities. A control program for opening and closing the switching valve is stored in the ROM, and is read out by the CPU to execute calculations for opening and closing the valve.

The turbines of the main and auxiliary turbochargers 7.8 and the structures downstream thereof are as follows. For example, as shown in FIG.
．． The outlets of 41 are opposite, and the outlets of turbine housing 40
．． 41 each have a turbine outlet elbow 42.
．． 43 is connected. This turbine outlet elbow 42.43 extends in the same direction after being bent with a moderate R, and the zero passage 44.45 connected to the exhaust switching valve housing 46 having mutually independent exhaust passages 44.45 is a front exhaust pipe. 47 and merges at the front exhaust pipe.

The exhaust switching valve 17 is housed in an exhaust passage 45 on the auxiliary turbocharger side in the exhaust switching valve housing 46 so as to be openable and closable, and is opened and closed by the actuator 16 via a rond. The actuator 16 has a single-stage diaphragm and is smaller than a conventional two-stage diaphragm actuator.

The downstream side of the turbine outlet of the main turbocharger 7 and the downstream side of the turbine outlet of the auxiliary turbocharger 8 can communicate with each other via an exhaust bypass passage 39 .

As shown in the figure, the inlet 39a of the exhaust bypass passage 39 is provided at a downstream portion of the turbine housing 41 of the sub-turbocharger 8 near the turbine blades.

This exhaust bypass passage 39 can be opened and closed by an exhaust bypass valve 38. The exhaust bypass valve 38 is housed in a bypass passage portion 39b formed in the wall of the turbine housing 31 of the sub-turbocharger so as to be able to open and close the inlet 39a. The exhaust bypass valve 38 is driven by a small single-stage diaphragm actuator 37 via a rond. Supercharging pressure is introduced into a diaphragm chamber of the actuator 37, and a spring is housed in a chamber separated from the pressure chamber by the diaphragm. The actuator 37 is placed in the same position as the wastegate pulp. The arrangement position of the actuator 37 and the arrangement of the exhaust bypass valve 38 within the turbine housing wall reduce the installation space of the exhaust bypass valve assembly.

In this embodiment, the exhaust bypass passage 39 is formed of a pipe formed separately from the turbine outlet elbow 43, or a casting that is integrated with the elbows 43, 42 and has a passage. The exhaust bypass passage 39 extends toward the turbine outlet elbow 42 on the main turbocharger 7 side, and the downstream end of the exhaust bypass passage 39 opens into the exhaust passage 44 of the seven main turbochargers at the turbine outleft elbow 42. There is. The upstream end of the exhaust bypass passage 39 is connected to a passage portion 39 formed in the wall of the turbine housing 41 of the auxiliary turbocharger 8 . By forming the exhaust bypass passage 39 from a pipe and connecting it to the turbine outlet elbow 42 of the main turbocharger 7, the installed pipe can be made more compact, preventing interference with other equipment, and improving catalyst warm-up. You can make improvements.

Next, supercharging control in this embodiment will be explained with reference to the control flow shown in FIG. 3. In addition, in FIG. 3, the first to fifth three-way solenoid valves are respectively VSVThl to
It is expressed as VSV11kt5.

Further, in FIG. 3, the turbocharger is expressed as T/C.

In FIG. 3, a pulp control routine is entered at step 100, and at step 101, the engine rotation speed (NE) is read based on a signal from the engine rotation speed sensor 34.

Next, the process proceeds to step 102, where it is determined whether or not the first three-way magnetic valve 25 is ON.

Here, if the first three-way aT61 valve 25 is OFF,
Proceeding to step 104, in step 102, the first
If it is determined that the three-way IL solenoid valve 5 is ON,
Proceed to step 103, and the engine speed (NE) is 30.
It is determined whether or not it is lower than 00rp-. Here, if it is determined that the engine speed is higher than 3000 rpm (2 T/Cs), the process proceeds to step 122 and the above-described process is repeated.

In step 103, the engine speed is 3000 r.
If it is determined that the engine speed is lower than p-, the process proceeds to step 104, where it is determined whether the engine speed is higher than 400 rpm. Here, the engine speed is 4000r
If it is determined that the intake air amount (Q) is higher than o-, the process proceeds to step 105, and the intake air amount (Q) is read based on the signal from the air flow meter 24. When the intake air amount is read, the process proceeds to step 106, where the intake air amount is 40001/
It is determined whether or not it is greater than sin. Step 1
If it is determined in step 04 that the engine speed is lower than 400 rpm, the process proceeds to step 108, where the intake pipe pressure (
PM) is read. When the intake pipe pressure is read, the process proceeds to step 109, and the intake pipe pressure is +500 mHg.
It is determined whether or not it is higher than .

In step 106, the intake air amount is 400017w.
If it is determined that it is larger than 1n, the process proceeds to step 107, and the fifth three-way solenoid valve 32 is turned on. Also, in step 106, the amount of intake air is 4000 j! If it is determined that the value is smaller than /sin, the process proceeds to step 110, and the fifth three-way magnetic valve 32 is turned off. Step 1
If it is determined in step 09 that the intake pipe pressure is greater than +500 mHg, the process proceeds to step 107, where the fifth three-way II solenoid valve 2 is turned on, and in step 109, the intake pipe pressure is reversed. If it is determined that it is less than +500 mHg, the process proceeds to step 110, and the fifth three-way solenoid valve 32 is turned off.

When the fifth three-way solenoid valve 32 is turned on, the exhaust bypass valve 38 is opened and exhaust gas small opening control is started.

As a result, the sub-turbocharger 8 is rotated during the run-up.

When the fifth three-way II solenoid valve 2 is turned off, the exhaust bypass valve 38 is closed, and the small opening control ends.

When the exhaust small opening control is started, the process proceeds to step 111,
In the illustrated example, which determines whether it is a high speed range or a low speed range, that is, a two-turbocharger operating range or a one-turbocharger operating range, it is determined that if Q is greater than 5500//sin, it should be switched to two-turbocharger operation. If it is less than 55001/■in, it is considered to be in the operating range during one turbo charge.

However, as described below, there is a time delay before the two turbochargers actually operate, so 60001
It will switch around /win.

If it is determined in step 111 that it is necessary to switch to two-turbocharger operation, the process advances to step 112, and the second
Mikata i! OFF if solenoid valve 6 is ON
Then, the opening of the intake switching valve 18 (partial loading) is stopped. After the second three-way solenoid valve 26 is turned OFF, or if it is originally OFF, the process proceeds to step 113, where the third three-way solenoid valve 27 is turned ON, and the intake pipe pressure downstream of the compressor ( (supercharging pressure) and closes the 1-atm bypass valve 33. Before the intake bypass valve 33 is closed, the exhaust switching valve 17 is fully open, but since the engine exhaust pressure is also applied to the turbine 8a of the auxiliary turbocharger 8, the auxiliary turbocharger +8 is in the run-up rotation (preliminary idling) as described above. ) has been done.

Then, when the intake bypass valve 33 is closed, the outlet pressure of the compressor 8b increases, so the number of run-ups increases.

Next, after the magnetic valve 27 is turned on, the third three-way 1 is provided with a predetermined time delay, for example, 1 second, necessary to amplify the run-up rotation speed of the turbocharger on the inactive side, that is, the sub-turbocharger 8, After one second has elapsed, the fourth three-way solenoid valve 28 is turned on in step 114, and the intake pipe pressure (supercharging pressure) downstream of the compressor is guided to the diaphragm chamber 16a of the actuator 16, and the exhaust switching valve 17 is fully opened. If the compressor pressure of the auxiliary turbocharger 8 becomes larger than the compressor pressure of the main turbocharger 7,
Supercharging air from the sub-turbocharger 8 is supplied to the engine via the check valve 12. Subsequently, after turning on the fourth three-way solenoid valve 28, the first three-way solenoid valve 25 is turned on in step 115 after a predetermined period of time, for example, 0.5 seconds, and the intake pipe downstream of the compressor is connected to the diaphragm chamber 11a of the actuator 11. The pressure (supercharging pressure) is guided to fully open the intake switching valve 18. In this state, two turbochargers operate (note that when switching to two turbochargers after the predetermined time has elapsed, the intake air amount is approximately 600012/win, which is the target for good turbine efficiency).

In step 115, the intake switching valve 18 is fully opened,
When the main turbocharger 7 and the sub-turbocharger 8 are both in operation, the process proceeds to step 116, where the fifth three-way NTa valve 32 is turned off and the exhaust bypass valve 38 is closed. Therefore, exhaust gas does not flow into the exhaust passage 44 downstream of the main turbocharger 7 via the exhaust bypass valve 38, and collisions between the exhaust gases are avoided. The function of turning off the fifth three-way tM1 valve 32 in step 116 is stored in the ROM of the engine control computer 29. That is, the process I! of the engine control computer 29 in step 116! This function constitutes valve closing command means for the exhaust bypass valve 38.

When the fifth three-way II solenoid valve 2 is turned off, step 1
The process advances to step 22 and returns.

If it is determined in step 111 that one turbocharger is in the operating range, the process proceeds to step 117, where the first three-way solenoid valve 25 is turned off and the intake switching valve 18 is fully closed. When the intake switching valve 18 is fully closed, step 118
The fourth three-way solenoid valve 28 is turned off, and the exhaust switching valve 17 is turned off.
is considered to be fully closed. Next, in step 119, the magnetic valve 27 of the third three-way 1 is turned off, and the intake bypass valve 33 is fully opened. Stay in this state.

The process advances to block 120, where it is determined whether the load is light or high.

Although the figure shows a case where the intake pipe pressure is used as an example of the load signal, the intake pipe pressure may be replaced by the throttle opening degree or the intake air amount/engine speed. For example, if the intake pipe pressure PM is less than 1100 m8g, it is determined to be a light load, and if it is 100 m8g or more, it is determined to be a high load.

If it is determined that the load is high in step 120, step 1
22, the second three-way solenoid valve 26 is turned off. In this state, the first and second three-way solenoid valves 25 and 2
6 is turned OFF and atmospheric pressure is introduced into both the diaphragm chambers 11a and llb of the actuator 11, the intake switching valve 18 is fully closed, and the process proceeds to step 117 and returns. In addition, in this state, the intake switching valve 18
is fully closed, the exhaust switching valve 17 is fully closed, and the intake bypass valve 33 is fully open, so one turbocharger operates in a state where the amount of intake air is small, resulting in good boost pressure and torque response.

If it is determined that the load is light in step 120, the process proceeds to step 121, where the second three-way magnetic valve 26 is turned on, the negative pressure in the surge tank 2 is guided to the diaphragm llb of the actuator 11, and the intake switching valve 18 is opened. , at this time, the intake negative pressure is transferred from the second three-way solenoid valve 26 to the actuator 11.
is introduced into the diaphragm chamber 11b, and the intake switching valve 18 becomes open. In this state, the exhaust switching valve 17a is closed, so the auxiliary turbocharger 8 does not operate, and only the main turbocharger 7 operates. However, intake passage 1
4, the intake switching valve 18 is open, so the intake passages for two turbochargers are open. Therefore, air is sucked in through the compressors 7b, 8b of both turbochargers. As a result, a large amount of supercharging air can be supplied to the engine l, and acceleration characteristics from low loads are improved. Subsequently, the process advances to step 117 and returns.

In the above control, the boost pressure characteristics when one turbocharger is operated and when two turbochargers are operated are as shown in FIG.

In the high speed range, both the intake switching valve 18 and the exhaust switching valve 17 are opened, and the intake bypass valve 33 is closed. As a result, the two turbochargers 7.8 operate for supercharging, a sufficient amount of supercharging air is obtained, and the output is improved. At this time, the supercharging pressure is set at the waste gate pulp 3 so as not to exceed the set pressure.
Controlled by 1.

In a low speed range and under high load, both the intake switching valve 18 and the exhaust switching valve 17 are closed, and the intake bypass valve 33 is opened. As a result, only one turbocharger 7 is driven. The reason why one turbocharger is used in the low speed range is that the supercharging characteristics of a single turbocharger are superior to the supercharging characteristics of a two turbocharger in the low speed range. 1
By performing individual turbocharging, boost pressure and torque rise faster, resulting in faster response. Also at this time, the supercharging pressure is controlled by the waste gate valve 31 so as not to exceed the set pressure.

In a low speed range and under light load, the aeration switching valve 18 is opened while the exhaust switching valve 17a is kept closed. As a result, the intake passages for two turbochargers are opened while one turbocharger remains driven, and an increase in intake resistance caused by one turbocharger can be eliminated.

This makes it possible to further improve the boost pressure rise characteristics and response at the beginning of acceleration from a low load.

When moving from a low speed range to a high speed range, that is, when switching from one turbocharger to two turbochargers, the intake bypass valve 33 is closed when the intake air amount Q reaches 5500 i 71n, and the auxiliary turbocharger is activated. After the run-up rotation of 8 is increased, there is a time delay (
In this embodiment, after 1 second has elapsed, the exhaust switching valve 17 is fully opened,
Subsequently, the intake switching valve 18 is fully opened and two turbocharger supercharging operations are started.

In addition, when switching to a two-turbocharger, the exhaust bypass valve 38 is opened in advance and the run-up rotation speed of the auxiliary turbocharger 8 is increased, so that the shock when switching from a one-turbocharger to a two-turbocharger is reduced. significantly alleviated.

In this embodiment, when two turbochargers are used, the exhaust bypass valve 38 is fully closed by a command from the valve closing command means (engine control combinator 29), so that the exhaust gas flowing out from the sub-turbocharger 8 is fully closed. Gas no longer flows into the exhaust passage 44 downstream of the outlet of the main turbocharger 7 via the exhaust bypass passage 39 . As a result, the exhaust resistance (exhaust pressure) of both turbochargers 7.8 becomes uniform, improving supercharging performance.

Second Embodiment FIG. 5 shows a second embodiment of the supercharged engine according to the present invention. The configuration of this embodiment is similar to the configuration of FIG. 7 shown in the prior art, so the same applies. By assigning the same reference numerals to the parts as in FIG. 7, a description of the corresponding parts will be omitted, and only the different parts will be described.

In the figure, an exhaust bypass valve 88 is provided in the exhaust bypass passage 87. The exhaust bypass valve 88 is opened by an actuator 87'. When the engine is under high load, the actuator 87' that drives the exhaust bypass valve 88 is actuated by a signal from the valve closing command means (the path shown in the figure), and the exhaust bypass passage 87 is connected to the exhaust bypass valve 88 as shown in FIG. will definitely be blocked by

Other operations are similar to those in the first embodiment.

〔Effect of the invention〕

As explained above, in the supercharged engine according to the present invention, when both the main turbocharger and the auxiliary turbocharger are operating, valve closing command means for fully closing the exhaust bypass valve is provided. Therefore, when using two turbochargers, an exhaust bypass i! is installed in the exhaust passage downstream of the turbine outlet of the main turbocharger. There is no inflow of exhaust gas from the road, and collisions between exhaust gases can be prevented. Therefore, the exhaust resistance (exhaust pressure) of both turbochargers becomes uniform, and supercharging performance is improved.

In addition, if the capacity of the main turbocharger and the sub-turbocharger are the same, conventionally it is necessary to change the diameter of the exhaust pipe to compensate for the bypass of exhaust gas, but as in the present invention, two turbochargers can be used. By closing the exhaust bypass valve during charging, there is no need to change the exhaust pipe diameter. Therefore, the design becomes easy and the mountability on a vehicle is also advantageous.

[Brief explanation of drawings]

FIG. 1 is a system diagram of a supercharged engine according to a first embodiment of the present invention, FIG. 2 is a front view of the turbine downstream structure of the main and auxiliary turbochargers in the engine of FIG. 1, and FIG. A flowchart showing the supercharging control procedure in the device shown in FIG. 1, FIG. 4 a characteristic diagram showing the relationship between engine speed and intake pipe pressure in the device shown in FIG. 1, and FIG. 5 a second diagram of the present invention. A system diagram of a supercharged engine according to an embodiment; FIG. 6 is a schematic system diagram of a conventional supercharged engine; FIG. 7 is a system diagram showing an example of a supercharged engine having an exhaust bypass valve; FIG. 8 is a cross-sectional view showing the state of exhaust interference in the apparatus of FIG. 7. 1... Engine 2... Surge tank 3... Exhaust manifold 4... Throttle valve 5... Throttle opening sensor 6... ...Intercooler 7.82...Main turbocharger 7a...
・・Main turbocharger turbine 8.83・・・・
・Sub-turbocharger 8a...Sub-turbocharger turbine 10...Intake bypass valve actuator 11...Intake switching valve actuator I3...Intake bypass passage 14... Intake passage (compressor upstream) 15.
...Intake passage (compressor upstream) 16...
...Exhaust switching valve actuator 17...Exhaust switching valve 18...Intake switching valve 24...Air flow meter 25...First three-way solenoid valve 26 ......Second three-way solenoid valve 27...Third three-way solenoid valve 28...Fourth three-way solenoid valve 29...Engine control computer (
valve closing command means) 30... Intake pipe pressure sensor 31... Waste gate valve 32...
・Fifth three-way solenoid valve 33...Intake bypass valve 38.88...Exhaust bypass valve 39.87...
...Exhaust bypass passage 44...Exhaust passage 45 on the main turbocharger side...Exhaust passage on the sub-turbocharger side Applicant Toyota Motor Corporation Fig. 2 83 Akira Rita

Claims (1)

[Claims] 1. It has a main turbocharger and a sub-turbocharger, and communicates the downstream of the turbine outlet of the sub-turbocharger with the exhaust passage downstream of the turbine outlet of the main turbocharger via an exhaust bypass passage, and the exhaust bypass passage has a The valve is opened before the exhaust switching valve located downstream of the exhaust bypass valve is opened, and a part of the exhaust gas flowing out from the auxiliary turbocharger is allowed to flow into the downstream of the turbine outlet of the main turbocharger to run up to the auxiliary turbocharger. The supercharged engine is equipped with an exhaust bypass valve that increases the rotational speed, and is provided with valve closing command means for fully closing the exhaust bypass valve when both the main turbocharger and the auxiliary turbocharger are operating. A supercharged engine characterized by: