JP2522422B2 - Supercharging control method for supercharged engine - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a supercharging control method for a supercharged engine in which main and sub turbochargers are arranged in parallel.

[Prior Art] An engine with a supercharger in which two main and two subcharger turbochargers are arranged in parallel with respect to the engine body is known (JP-A-60-169630 and JP-A-60-259722). etc).
The structure of this type of supercharged engine is as shown in FIG. 6, for example. For the engine body 91, the main turbocharger (T / C-1) 92 and the sub-turbocharger (T / C-1)
-2) 93 are provided in parallel. Deputy turbocharger
The intake switching valve 9 is connected to the intake and exhaust systems connected to 93.
4. An exhaust switching valve 95 is provided, and an intake bypass valve 96 is provided in a bypass passage that bypasses the compressor of the auxiliary turbocharger 93. By fully closing both the intake switching valve 94 and the exhaust switching valve 95, only the main turbocharger 92 is supercharged, both are fully opened, and the intake bypass valve 96 is also closed to supercharge the sub turbocharger 93. It is possible to operate the two turbochargers.

When switching from one turbocharger operation (that is, only the main turbocharger 92 is supercharged) to two turbocharger operation (that is, both turbochargers 92 and 93 are supercharged), the above-mentioned JP-A-60-169630 is disclosed. In this system, the intake bypass valve is closed at the same time when the exhaust switching valve is fully opened. In the system disclosed in Japanese Patent Laid-Open No. 60-259722, the difference between the compressor outlet pressure of the always operating turbocharger (main turbocharger) and the compressor outlet pressure of the turbocharger (sub-turbocharger) that has stopped the supercharging operation. When the pressure falls below a certain value (for example, 40 mbar: about 30 mmHg), the intake bypass valve is fully closed, and then the exhaust switching valve is fully opened to switch to two turbocharger operation.

[Problems to be Solved by the Invention] In a supercharged engine as shown in FIG.
By opening the exhaust gas switching valve 95 while keeping the intake gas switching valve 94 closed, the auxiliary turbocharger 93 can be run-up before the switching from the one turbocharger to the two turbocharger. At this time, the sub turbocharger 93 is
As shown in the figure, as the compressor outlet side is throttled and the compressor outlet pressure is increased relative to the compressor inlet pressure, the turbine speed increases. Therefore, when the stopped turbocharger (sub-turbocharger 93) is running, intake bypass is not executed (intake bypass valve 96
Closing) makes the run-up speed of the stopped turbocharger higher, smoothing the connection when switching from one turbocharger to two turbochargers, and suppressing the switching shock and torque decrease during switching. it can.

However, when the intake bypass is not executed, as shown in FIG. 8, when the compressor outlet pressure rises, the supercharged air flows back to the compressor inlet, and the action of supercharging the backflowed air is repeated. become. As a result, the intake air temperature becomes high and the compressor impeller also becomes hot. Generally, since the impeller is made of an aluminum alloy, its heat resistance is not so high, and it is a heat resistance problem to use the impeller in a state where the temperature rises. In order to prevent the impeller from reaching a high temperature, it is necessary to perform sufficient intake bypass during the stop turbocharger running, that is, to prevent the compressor outlet pressure from becoming too high. However, if the intake bypass is sufficiently performed, the running speed of the stopped turbocharger becomes low as described above, and the connection from one turbocharger to two turbochargers cannot be smoothly performed.

In the system disclosed in Japanese Unexamined Patent Publication No. 60-169630, when switching from one turbocharger to two turbochargers, intake bypass is performed until immediately before the exhaust switching valve is fully opened, so the intake temperature (impeller temperature) rises. However, since the running speed of the stopped turbocharger is low, the connection state when switching the number of operating turbochargers is poor, and the problems of switching shock and torque reduction during switching remain.

On the other hand, in the system disclosed in Japanese Patent Laid-Open No. 60-259722, when the differential pressure between the compressor outlet pressure of the stopped turbocharger and the compressor outlet pressure of the always operating turbocharger falls within a certain value, the intake bypass valve is closed first. It becomes possible to raise the running speed of the stopped turbocharger before the exhaust switching valve is fully opened. However, in order to reach the condition of the intake bypass valve closing, when the intake bypass valve is opened (that is, at the time of intake bypass), the compressor outlet pressure of the stopped turbocharger is close to the compressor outlet pressure of the constantly operating turbocharger and is considerably high. It has to be pressure. Therefore, in this system, the intake bypass flow rate is suppressed to a small flow rate so as to reach the above pressure.
However, when continuously operated immediately before the switching from the one turbocharger to the two turbochargers and immediately before the intake bypass valve is fully closed, the intake bypass flow rate becomes insufficient, and therefore, as shown in FIG. The same backflow as that described above causes a problem of intake air temperature rise. Therefore, in a system that determines the opening and closing conditions of the intake bypass based on the differential pressure between the two compressor outlet pressures, in order to enable continuous operation under the above conditions, that is, even when continuously operated under the above conditions In order to keep the intake air temperature rise on the turbocharger compressor side low, the compressor outlet pressure (supercharging pressure) of the normally operating turbocharger, which is the comparison target of the differential pressure, should be kept low, and the compressor of the turbocharger stopped under the above conditions. It is a design essential condition that the intake air temperature does not become so high even if a backflow of supercharged air occurs on the side. Therefore, in the conventional system,
The turbocharging pressure cannot be set to a high value when the turbocharger is operating. Therefore, a so-called two-stage turbo system is used in which the degree of output torque improvement due to supercharging is low in the low speed range where one turbocharger operates, and the number of turbocharger operations is switched between the high speed range and the low speed range in two stages. The effect is small.

The present invention uses two turbochargers from one turbocharger to compensate for the drawbacks of the two types of prior art described above.
Stop before switching to individual turbocharger While suppressing the rise in intake air temperature on the turbocharger side, it is possible to set the supercharging pressure at the time of operating one turbocharger to be high, and from one turbocharger to operating two turbochargers. The purpose is to smooth the transition when switching.

[Means for Solving the Problem] A supercharging control method for a supercharged engine according to the present invention, which is directed to the above object, includes a main turbocharger and a sub turbocharger provided in parallel with an engine body, and a sub turbocharger. An intake switching valve and an exhaust switching valve that are respectively provided in the intake and exhaust systems of the connected engine and that cause the sub turbocharger to perform supercharging operation when both are fully opened, and stop supercharging operation when both are fully closed, In a supercharged engine having a bypass passage bypassing the compressor of the sub turbocharger and an intake bypass valve opening / closing the bypass passage, as shown in FIG. Supercharging operation status 82
Before the engine intake air intake valve is open 83, the exhaust switching valve is opened slightly to rotate the auxiliary turbocharger in the auxiliary run (step 84). When a predetermined intake air amount that is less than the switching valve fully open condition is reached (step 85)
Then, the intake bypass valve is closed (step 86), the exhaust bypass valve that has been slightly opened is fully opened (step 87) with a time delay from the closing of the intake bypass valve (step 87), and the intake bypass valve is opened (step 88). ) A method of starting the supercharging operation of the auxiliary turbocharger.

[Operation] In such a supercharging control method, the exhaust switching valve full-open condition may be one turbocharger operating or two turbocharger operating, with the intake air amount of the engine as a scale. Both are set as certain target values that can exhibit high turbine efficiency.

When switching from the single turbocharger operation to the double turbocharger operation, first, the exhaust switching valve is controlled to a small open state while the intake bypass valve is opened, and the stopped sub-turbocharger is rotated for the run-up. At this time, the air pressurized by the sub turbocharger compressor is circulated to the compressor inlet side through the bypass passage, so that the compressor outlet pressure is suppressed to be low and the intake air temperature rise is also low. When the intake air amount of the engine reaches a predetermined constant value smaller than the exhaust switching valve full-open condition value, the intake bypass valve is closed. Since the intake bypass is stopped and the compressor outlet pressure is increased by closing the intake bypass valve, the auxiliary revolution speed of the auxiliary turbocharger that is already in advance is further increased. After that, with an appropriate short time delay, the exhaust switching valve, which was controlled to be small open, was fully opened.
Then, the intake switching valve is opened and the supercharge operation of the sub turbocharger is started. Shortly before the exhaust switching valve is fully opened, the intake bypass is stopped and the running speed is increased.
Smooth connection when switching from individual turbocharger to two turbocharger. This intake bypass stop time is short, so there is no problem of excessive intake temperature rise, and 1
It is not necessary to set the supercharging pressure at the time of individual turbocharger operation low. In addition, by appropriately setting the engine intake air amount to close the intake bypass valve and the time from closing the intake bypass valve to fully opening the exhaust switching valve according to the type of engine, acceleration After the intake bypass valve is closed, the actual intake air amount naturally becomes the optimum intake air amount during switching, that is, the highest turbine efficiency is obtained when switching from one turbocharger to two turbocharger operation. It is possible to reach the amount of intake air to be reached.

[Embodiment] A preferred embodiment of the present invention will be described below with reference to the drawings.

FIG. 2 shows an apparatus configuration for carrying out the method according to one embodiment of the present invention, and shows the case of a 6-cylinder engine.

In FIG. 2, 1 is an engine, 2 is a surge tank,
3 shows an exhaust manifold. The exhaust manifold 3 has two cylinder groups, # 1 to # 3 cylinder groups and # 4 to # 6 cylinder groups, which do not involve exhaust interference.
And the gathering portions are communicated with each other by the communication passage 3a. Reference numerals 7 and 8 denote a main turbocharger and a sub turbocharger arranged in parallel with each other. The turbines 7a and 8a of the turbochargers 7 and 8 are connected to the collecting portion of the exhaust manifold 3, and are connected to the compressors 7b and 8b, respectively.
8b is connected to the surge tank 2 via an intercooler 6 and a throttle valve 4. The main turbocharger 7 is operated from the engine low speed range to the high speed range, and the sub turbocharger 8 is stopped in the engine low speed range.

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 so that both turbochargers 7 and 8 can be operated and stopped. When both the intake and exhaust switching valves 18, 17 are fully opened, both turbochargers 7, 8 are operated.

In the intake passage of the auxiliary turbocharger 8 that is stopped in the low speed range, an intake bypass passage 13 that connects the upstream side and the downstream side of the compressor 8b is provided in order to facilitate the switching from one turbocharger to two turbochargers. An intake bypass valve 33 provided in the intake bypass passage 13 is provided. The intake bypass valve 33 is opened and closed by the actuator 10. The air flow downstream side of the intake bypass passage may be connected to the intake passage upstream of the compressor of the main turbocharger 7. Further, the check valve 12 is provided in the bypass passage that connects the upstream side and the downstream side of the intake switching valve 18, and the intake switching valve 18
Even when closed, when the compressor outlet pressure on the sub turbocharger 8 side becomes higher than that on the main turbocharger 7 side, air can flow from the upstream side to the downstream side (engine side). In FIG. 2, reference numeral 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 the air cleaner 23. A front pipe 20 forming an exhaust passage is connected to an exhaust muffler 22 via an exhaust gas catalyst 21.

The intake switching valve 18 is opened and closed by the actuator 11,
The exhaust switching valve 17 is opened and closed by a two-stage diaphragm type actuator 16. 9 is a waste gate valve 31
The actuator which opens and closes is shown. Actuator 10,
To turn on and off the supercharging pressure or negative pressure that operates 11 and 16 (selectively switch between supercharging pressure or negative pressure and atmospheric pressure), the first, second, third, and fourth directions Solenoid valves 25, 26, 27,
28 are provided. Switching of the three-way solenoid valves 25, 26, 27, 28 is performed according to a command from the engine control computer 29. ON / OFF of the three-way solenoid valves 25 and 28 is an exhaust switching valve 1
The actuators 11 and 16 are operated so that the valves 8 and 17 are fully opened, and when OFF, the actuators 11 and 16 are operated so that the intake and exhaust switching valves 18 and 17 are fully closed. Reference numeral 32 is a fifth three-way solenoid valve for controlling the small opening of the exhaust switching valve 17. 16a, 16b
Is a diaphragm chamber of the actuator 16, 16c is an adjusting screw, 10 is a diaphragm chamber of the actuator 10, 11a, 11b
Indicate the diaphragm chambers of the actuator 11, respectively.

The engine control computer 29 is electrically connected to various operating condition detection sensors of the engine, and receives signals from the various sensors. The engine operating condition detection sensor includes an intake pipe pressure sensor 30, a throttle opening sensor 5, and an air flow meter as an intake air amount measurement sensor.
24, O ₂ sensor 19, etc. are included.

The engine control computer 29 includes a central processor unit (CPU) for calculation, a read-only memory (ROM) that is a read-only memory, a random access memory (RAM) for temporary storage, and an input / output interface (I / D interface). ), It is equipped with an A / D converter that converts analog signals from various sensors into digital quantities. FIG. 3 shows a control program for opening / closing the switching valve, which is stored in the ROM and read by the CPU to execute the operation of opening / closing the valve.

The supercharging control method in the present embodiment will be described with reference to FIGS. 4 and 5 together with the control flow of FIG. Note that, in FIG. 3, the first to fifth three-way solenoid valves are represented as VSV No. 1 to VSV No. 5, respectively. Further, in FIGS. 3 to 5, the turbocharger is represented by T / C.

First, in FIG. 3, the valve control routine is entered in step 100, and the intake air amount Q of the engine is read in step 101. The intake air amount is a signal from the air flow meter 24. Next, at step 102, it is determined whether it is a high speed region or a low speed region, that is, whether it is a two turbocharger operating region or one turbocharger operating region. In the illustrated example, for example, Q is 5500
If it is larger than / min, it is judged that it should be switched to the operation of two turbochargers. However, as will be described later, there is a time delay before actually switching to the two turbocharger operation, so the switching will occur near 6000 / min.

When it is determined in step 102 that the operation should be switched to the operation of two turbochargers, the process proceeds to step 103, the third three-way solenoid valve 27 is turned on, and the intake pipe pressure (supercharging pressure) in the compressor downstream of the diaphragm chamber 10a of the actuator 10 is turned on. )
To close the intake bypass valve 33. However, at this time, as will be described later, the exhaust switching valve 17 is already in the small open control in the single turbocharger operating region, and the auxiliary turbocharger 8 is in the run-up rotation.

Next, after the third three-way solenoid valve 27 is turned ON, a predetermined time required for increasing the running speed of the turbocharger on the operation stop side, that is, the sub-turbocharger 8, for example, with a time delay of 1 second, is applied for 1 second. After the lapse of time, in step 104, the fourth three-way solenoid valve 28 is turned on, the intake pipe pressure (supercharging pressure) downstream of the compressor is introduced into the diaphragm chamber 16a of the actuator 16, and the exhaust switching valve 17 is fully opened. If the compressor pressure of the sub turbocharger 8 becomes higher than the compressor pressure of the main turbocharger 7, the supercharged air of the sub turbocharger 8 is supplied to the engine via the check valve 12. Then, after turning on the fourth three-way solenoid valve 28, a predetermined time,
For example, after 0.5 seconds has passed, in step 105, the first three-way solenoid valve 25
Is turned on to guide the intake pipe pressure (supercharging pressure) downstream of the compressor to the diaphragm chamber 11a of the actuator 11 to fully open the intake switching valve 18. In this state, the two turbochargers are activated (when the turbochargers are switched to the two turbochargers after the lapse of the predetermined time, the intake air amount is approximately 6000 / min, which is a target for good turbine efficiency). Then, it proceeds to step 113 and returns.

If it is determined in step 102 that the turbocharger operating range is one, the routine proceeds to step 106, where the intake pipe pressure PM is read. In step 107, it is determined whether the intake pipe pressure is higher or lower than a predetermined value. Intake pipe pressure PM is, for example, +500 mmHg
If it is smaller than the above, the routine proceeds to step 108, the fifth three-way solenoid valve 32 is turned off, and the diaphragm chamber 1 of the actuator 16 is turned off.
Guide atmospheric pressure to 6b. In this state, proceed to step 109,
Determine whether the load is light or heavy. Although the figure shows the case where the load signal and the intake pipe pressure are taken as an example, the throttle opening, intake air amount / engine speed may be substituted instead of the intake pipe pressure. For example, if the intake pipe pressure PM is less than -100 mmHg, it is judged as a light load, and if it is -100 mmHg or more, it is judged as a high load.

When it is determined that the load is high in step 109, step 112
Then, the first to fourth three-way solenoid valves 25 to 28 are turned off.
That is, the first and second three-way solenoid valves 25 and 26 are OF
Actuator 11 diaphragm chambers 11a and 11 as F
The atmospheric pressure is introduced to b to fully close the intake switching valve 18, the third three-way solenoid valve 27 is turned off, and atmospheric pressure is introduced to the diaphragm chamber 10a of the actuator 10 to fully open the intake bypass valve 33, and the fourth three-way valve is opened. Actuator 1 with solenoid valve 28 OFF
Exhaust gas switching valve 17 by introducing atmospheric pressure to the diaphragm chamber 16a of 6
Is fully closed, and the routine proceeds to step 113 and returns. 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 is activated when the intake air amount is small, and supercharging pressure and torque response are good. Becomes

If the load is judged to be light in step 109, step 1
Go to 10 and turn on the second three-way solenoid valve 26 to turn on the actuator.
The negative pressure in the surge tank 2 is introduced to the diaphragm 11b of 11 to open the intake switching valve 18. In this state, since the exhaust switching valve 17 is closed, the sub turbocharger 8 does not operate, and only the main turbocharger 7 operates. However, the intake passage 14
Since the intake switching valve 18 is open, the intake passages for two turbochargers are open. That is, air is taken in through the compressors 7b and 8b of both turbochargers. As a result, a large amount of supercharged air can be supplied to the engine 1, and the acceleration characteristic from a low load is improved. continue,
The process proceeds to step 113 and returns.

If it is determined in step 107 that the intake pressure PM is not less than +500 mmHg, the fifth three-way solenoid valve 32 is turned on and the diaphragm chamber 16b of the actuator 16 is connected to the intake pipe pressure (supercharging pressure) of the compressor downstream of the main turbocharger 7. ) Lead. Next, the routine proceeds to step 112, where the first to fourth three-way solenoid valves 25 to 28 are turned off as described above. That is, the actuators 1 and 2 are turned off by turning off the first and second three-way solenoid valves 25 and 26.
Atmospheric pressure is introduced to the diaphragm chambers 11a and 11b of 1 to fully close the intake switching valve 18, and the third three-way solenoid valve 27 is turned off to introduce atmospheric pressure to the diaphragm chamber 10a of the actuator 10 to fully open the intake bypass valve 33. And the fourth three-way solenoid valve
28 is turned off to introduce atmospheric pressure to the diaphragm chamber 16a of the actuator 16. In this case, a two-stage actuator
Since the intake pipe pressure (supercharging pressure) downstream of the compressor of the main turbocharger 7 is introduced into the 16 diaphragm chambers 16b, the exhaust switching valve 17 is controlled to a small opening. This small opening control is performed by partially opening the exhaust switching valve 17 so that the intake pipe pressure does not exceed +500 mmHg.
In other words, the opening degree of the exhaust gas switching valve 17 is controlled so that the boost pressure is maintained at +500 mmHg in the single turbocharger operating range. Normally, in supercharging pressure control of a turbocharger, when the pressure exceeds a set pressure (for example, +500 mmHg), the wastegate valve 31 is opened to control the rotation speed of the main turbocharger 7. In the turbocharger, instead of opening the wastegate valve 31, the exhaust switching valve 17 is controlled to a small opening to control the rotation speed of the main turbocharger 7, that is, the supercharging pressure by the main turbocharger 7. Then, the exhaust switching valve 17 is partially opened and a part of the exhaust gas is guided to the turbine 8a of the sub-turbocharger 8 on the operation stop side, so that the sub-turbocharger 8 is rotated to run. As the running speed of the auxiliary turbocharger 8 is higher, the torque reduction (torque shock) at the time of switching from the one turbocharger to the two turbocharger is alleviated, and the switching is smoothly performed. continue,
Proceed to step 113 and return.

In the above control, the boost pressure characteristic in the case of operating one turbocharger and in the case of operating two turbochargers is the fourth
It becomes like the figure.

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. 2 by this
The individual turbochargers 7 and 8 are supercharged, a sufficient amount of supercharged air is obtained, and the output is improved. At this time, the boost pressure is
Waste gate valve 31 not to exceed +500 mmHg
Controlled by.

Both the intake switching valve 18 and the exhaust switching valve 17 are closed and the intake bypass valve 33 is opened in the low speed range and at the time of high load.
As a result, only one turbocharger 7 is driven. The reason why one turbocharger is used in the low rotation speed region is that the one turbocharger supercharging characteristic is superior to the two turbocharger supercharging characteristic in the low rotation speed region as shown in FIG. By using one turbocharger, the boost pressure and the rise of torque are accelerated, and the response is prompt.

In the low speed range and when the load is light, the intake switching valve 18 is opened while the exhaust switching valve 17 is closed. As a result, the two intake passages for the turbocharger are opened while the single turbocharger is driven, and the increase in intake resistance due to the single turbocharger can be eliminated. As a result, the boost pressure rising characteristics and response in the initial stage of acceleration from a low load can be further improved.

When shifting from the low speed range to the high speed range, that is, when switching from the one turbocharger operation to the two turbocharger operation, the intake air amount Q reaches 5500 / min after the small opening control of the exhaust switching valve 17 is started. Sometimes intake bypass valve
33 is closed, and after that, with a time delay (after 1 second has elapsed in this embodiment), the exhaust gas switching valve 17 is fully opened, then the intake air switching valve 18 is fully opened, and the two turbocharger supercharging operation is started. To be done.

The operation sequence in the control of the present invention will be described with reference to FIG.

First, in a region where the intake air amount Q is less than 5500 / min, when the supercharging pressure (intake pipe pressure (PM)) by the main turbocharger 7 increases and reaches +500 mmHg, the fifth three-way solenoid valve 32 (VSV The small opening control of the exhaust switching valve 17 by No. 5) starts, and the auxiliary turbocharger 8 is rotated to run. At this time, the intake bypass valve 33 is open, and the compressed air on the outlet side of the compressor 8b of the sub turbocharger 8 is circulated to the compressor inlet side through the bypass passage 13, so that the excessive rise of the compressor outlet pressure is prevented. In addition, the intake air temperature is prevented from rising excessively in this portion. The passage diameter of the bypass passage 13 is set to be relatively large so that the compressor outlet pressure does not become so high even when continuously operated under this condition.

When the intake air amount Q reaches 5500 / min after the start-up rotation of the auxiliary turbocharger 8 is started, the intake bypass valve 33 is closed. Since the outlet pressure of the compressor 8b is increased by closing the intake bypass valve 33, the running speed of the auxiliary turbocharger 8 is increased as shown in FIG. If it is continuously operated for a long time in this state, the same problem as the intake air temperature rise will occur, but in the method of the present invention, after the intake bypass valve 33 is closed for a predetermined time (1 second in this embodiment). After a lapse of time), the exhaust switching valve 17, which has been controlled to be small open, is fully opened. At this time, the intake air amount Q naturally reaches a value of 6000 / min, which has the best turbine efficiency as a switching condition, or a value in the vicinity thereof, under acceleration conditions. Then, the intake switching valve 18 is fully opened (in this embodiment, 0.5 seconds has elapsed after the exhaust switching valve 17 was fully opened), and two turbocharger supercharging operations are switched.

In this switching, the intake bypass valve 33 is closed slightly before the exhaust switching valve 17 is fully opened, and the running speed of the auxiliary turbocharger 8 is increased. Therefore, switching from one turbocharger to two turbocharger operation is performed. The connection becomes smooth, and the shock and torque drop at the time of switching are reduced. Further, since the intake bypass valve 33 is closed for a short time until the exhaust switching valve 17 is fully opened, the intake air temperature does not rise excessively. Since there is no fear that the intake air temperature will rise excessively, it is possible to set a high boost pressure when one turbocharger is operating.

In the above embodiment, a very short time delay (0.5 seconds) was provided between the exhaust switching valve 17 fully opening and the intake switching valve 18 fully opening, but this time may be set shorter or may be substantially shorter. It is also possible to eliminate both valves and open both valves at the same time. However, if the intake switching valve 18 is fully opened after the exhaust switching valve 17 is fully opened, the supercharged air can be sent to the engine after guiding the desired boost pressure until just before the intake switching valve 18. Switching from one turbocharger to two turbochargers is performed more smoothly.

[Effects of the Invention] As described above, according to the supercharging control method for an engine with a supercharger of the present invention, after the exhaust switching valve is controlled to a small opening and the auxiliary turbocharger is rotated in the forward direction, the engine intake air is rotated. When the amount reaches a predetermined value, the intake bypass valve is closed to increase the running speed, and the exhaust switching valve is fully opened after a relatively short predetermined time has elapsed since the intake bypass valve was closed, and then the intake switching valve is fully opened. Since we switched from one turbocharger to two turbochargers, we were able to secure a sufficient amount of intake bypass after the start of the sub-turbocharger approach that had been stopped, and there was concern about trouble such as compressor impeller due to intake air temperature rise. It is possible to achieve high supercharging at the time of one turbocharger and efficiently increase the run-up speed of the sub-turbocharger immediately before switching, The effect that the connection from the one turbocharger to the two turbocharger supercharging operation can be made smooth is obtained.

[Brief description of drawings]

FIG. 1 is a block diagram showing control steps of a supercharging control method for an engine with a supercharger according to the present invention, FIG. 2 is a system diagram of an apparatus used for carrying out the method according to an embodiment of the present invention, and FIG. FIG. 4 is a control flow chart when the method of the present invention is implemented using the apparatus of FIG. 2, FIG. 4 is an engine speed-supercharging pressure characteristic chart by the control flow of FIG. 3, and FIG. Fig. 6 is a characteristic diagram of turbine efficiency and operation of each valve during operation, Fig. 6 is a schematic system diagram of a conventional parallel turbocharged engine, and Fig. 7 is a general relationship between the compressor outlet pressure of the auxiliary turbocharger and the compressor discharge air amount. FIG. 8 and FIG. 8 are enlarged schematic configuration diagrams of the sub-turbocharger of the apparatus of FIG. 6 and its vicinity. 1 ... Engine 2 ... Surge tank 3 ... Exhaust manifold 4 ... Throttle valve 5 ... Throttle opening sensor 6 ... Intercooler 7 ... Main turbocharger 8 ... Sub turbocharger 10 ... Intake bypass valve actuator 11 …… Intake switching valve actuator 13 …… Intake bypass passage 14 …… Intake passage (downstream of compressor) 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 30 …… Intake pipe pressure sensor 31 …… Wastegate valve 32 …… Fifth three-way solenoid valve 33 …… Intake bypass valve

Claims (1)

(57) [Claims] 1. A main turbocharger and an auxiliary turbocharger provided in parallel with an engine body, and an intake and exhaust system of an engine connected to the auxiliary turbocharger, respectively. When both are fully opened, the auxiliary turbocharger is provided. An intake switching valve and an exhaust switching valve that perform a supercharging operation and that stop the supercharging operation when both are fully closed; a bypass passage that bypasses the compressor of the auxiliary turbocharger and an intake bypass valve that opens and closes the bypass passage. In a supercharged engine having, before the sub turbocharger changes from a supercharging operation stop state to a supercharging operation state, the intake switching valve is opened and the exhaust gas switching valve is slightly opened to open the sub turbocharger. Preliminary rotation is performed, and after the start of rotation, the intake air amount of the engine is less than the exhaust switching valve fully open condition. Upon reaching the intake air amount, closing the intake bypass valve, and remembering the time lag from the closed intake bypass valve, fully open the exhaust switching valve is small opened,
A supercharging control method for an engine with a supercharger, comprising: opening the intake switching valve to start a supercharging operation of a sub turbocharger.