JPH04311630A - Controller for engine with supercharger - Google Patents

Abstract

PURPOSE:To prevent surely a main and sub-supercharger from over-running in all driving conditions. CONSTITUTION:An engine 1 is provided with an exhaust bypass valve 32 and waste gate valve 42 for adjusting supercharging pressure. An ECU 71 controls the opening of both valves 32, 42 on the basis of supercharging pressure detected by an intake pressure sensor 62 to adjust the supercharging pressure in the operation of only a main turbo charger 10 and the supercharging pressure in the operations of both main and sub-turbo chargers 10, 11. Also, the ECU 71 allows the exhaust bypass valve 32 and waste gate valve 42 to control the supercharging pressure when the actual rotational frequencies of both turbo chargers 10, 11 detected by a second rotational frequency sensor 69 is lower that the rotational frequency of guard, and the ECU 71 applies the guard to the actual rotational frequency to provide the rotational frequency of the guard when the actual rotational frequency exceeds the rotational frequency of the guard.

Description

[Detailed description of the invention]

0001

[Industrial Application Field] The present invention arranges a main supercharger and an auxiliary supercharger in parallel in the intake system and exhaust system of an engine, and switches the number of operating superchargers depending on the operating state of the engine. The present invention relates to a control device for a supercharged engine as described above.

0002

[Prior Art] Conventionally, two main and auxiliary superchargers (turbochargers) are installed in parallel to the intake system and exhaust system of an engine, and the auxiliary turbocharger operates in a low engine intake air amount region. Equipped with a so-called ``2-stage twin turbo system'' supercharger, in which the main turbocharger only performs supercharging when the engine is stopped, and both the main and auxiliary turbochargers are supercharged in the engine high intake air volume region. The engine is known.

[0003] In this engine, the value of the intake air amount (switching point) when switching between the operating state of only the main turbocharger and the operating state of both the main and auxiliary turbochargers is usually the same regardless of the driving state of the vehicle. It is set constant. For this reason, for example, even if the switching point is set to an optimal value on flat ground, the following problem occurs when traveling on high ground with low air density. That is, at high altitudes, the degree of increase in the amount of intake air with respect to the increase in rotational speed of the turbocharger is low, so the rotational speed of the main turbocharger at the switching point is higher than that at flatlands. As a result, the rotation speed of the main turbocharger exceeds the permissible rotation speed (
There is a risk of damage due to overrun.

Therefore, for example, Japanese Patent Laid-Open No. 2-119625 discloses a supercharger in which the switching point of the turbocharger at high altitudes where the air density is low is shifted to the lower intake air amount side than the switching point at flatlands. A control device for an engine with an engine is disclosed.

[0005]

However, in the conventional supercharged engine, only the switching point when the operating state of the turbocharger is switched is corrected, so when only the main turbocharger is operating, Although it is possible to prevent the rotation of the main turbocharger from exceeding the permissible rotational speed, it is not possible to prevent the main and auxiliary turbochargers from overrunning, for example, in a high-speed, high-load range where both the main and auxiliary turbochargers operate. Therefore, a control device that can prevent turbocharger overrun under all operating conditions is desired.

The present invention has been made in view of the above-mentioned circumstances, and its purpose is to provide a control device for a supercharged engine that can reliably prevent a supercharger from overrunning under any operating condition. There is a particular thing.

[0007]

[Means for Solving the Problems] In order to achieve the above object, in the present invention, as shown in FIG.
A main supercharger M4 and a sub-supercharger M5 provided in parallel with the intake system M2 and exhaust system M3, and an intake switching valve provided in the intake system M2 and exhaust system M3 corresponding to the sub-supercharger M5. M
6 and exhaust switching valve M7, intake air amount detection means M8 for detecting the intake air amount to the engine M1, and when the intake air amount detected by the intake air amount detection means M8 is less than a predetermined value, Both the intake switching valve M6 and the exhaust switching valve M7 are closed to operate only the main supercharger M4, and when the intake air amount is larger than a predetermined value, the intake switching valve M6 and the exhaust switching valve M7 are closed. A control device for a supercharged engine comprising an opening/closing control means M9 that opens both to operate the main supercharger M4 and the auxiliary supercharger M5,
A supercharging pressure regulating valve M10 that is provided in the exhaust system M3 of the engine M1 and adjusts the supercharging pressure to the engine M1, and a supercharging pressure detection means M1 that detects the supercharging pressure to the engine M1.
1, the opening degree of the boost pressure regulating valve M10 is controlled based on the boost pressure detected by the boost pressure detection means M11, and the boost pressure when only the main supercharger M4 is in operation is determined. and sub-supercharger M5
a supercharging pressure control means M12 that adjusts the supercharging pressure during operation; a rotational speed detection means M13 that detects the actual rotational speed of the main supercharger M4 and the subsupercharger M5; and the rotational speed detection means M1
3, when the actual rotational speed of the main supercharger M4 and the sub-supercharger M5 is smaller than the predetermined rotational speed, the supercharging pressure control means M
12 to control the supercharging pressure regulating valve M10, and when the actual rotational speed is equal to or higher than the predetermined rotational speed, the supercharging pressure regulating valve M1
0 and adjusts the actual rotational speed to a predetermined rotational speed.

[0008]

[Operation] When the intake air amount is detected by the intake air amount detection means M8 during operation of the engine M1, the opening/closing control means M
9 compares the detected intake air amount with a predetermined value. If the detected value is below a predetermined value, the opening/closing control means M9 closes both the intake switching valve M6 and the exhaust switching valve M7 to switch the main supercharger M4 off.
Activate only. Further, when the intake air amount is larger than a predetermined value, the opening/closing control means M9 opens both the intake switching valve M6 and the exhaust switching valve M7 to operate the main supercharger M4 and the sub supercharger M5.

Further, when the engine M1 is operating, the supercharging pressure to the engine M1 is detected by the supercharging pressure detection means M11, and the actual rotational speeds of the main supercharger M4 and the sub supercharger M5 are detected. It is detected by the number detection means M13. Then, when the rotational speed of the main supercharger M4 and the sub-supercharger M5 determined by the rotational speed detection means M13 is smaller than a predetermined rotational speed, the supercharging pressure control means M12 activates the supercharging pressure regulating valve M1.
By controlling the opening degree of 0, the supercharging pressure when only the main supercharger M4 is operated by the supercharging pressure detection means M11 and the supercharging pressure when the main supercharger M4 and the auxiliary supercharger M5 are operating. and adjust. Also,
When the rotational speed determined by the rotational speed detection means M13 is equal to or higher than the predetermined rotational speed, the rotational speed adjustment means M14 controls the supercharging pressure regulating valve M10 to make the actual rotational speed the predetermined rotational speed.

As described above, in the present invention, in addition to controlling the supercharging pressure, the rotational speed of the superchargers M4 and M5 is controlled, so even in the operating range of only the main supercharger M4, the main supercharger M4 Also in the operating range of the auxiliary supercharger M5, the rotational speed thereof is prevented from becoming larger than the predetermined rotational speed.

[0011]

[Example] Hereinafter, an example embodying the present invention is shown in FIGS.
This will be explained according to FIG. 2, 4, and 5 are schematic configuration diagrams illustrating an in-line six-cylinder supercharged gasoline engine system mounted on a vehicle in this embodiment. The intake system of the engine 1 is provided with a surge tank 2 for preventing intake pulsation or intake interference. Further, a throttle body 3 is provided upstream of the surge tank 2. A throttle valve 4 is provided inside the throttle body 3 and is opened and closed in conjunction with the operation of an accelerator pedal (not shown). By opening and closing the throttle valve 4, the intake air flow rate to the surge tank 2 is adjusted. Further, downstream of the surge tank 2 is an intake manifold 5 that is branched to each cylinder #1, #2, #3, #4, #5, and #6 of the engine 1. This intake manifold 5 includes fuel injection valves (injectors) 6A, which inject and supply fuel to each cylinder #1 to #6 of the engine 1.
6B, 6C, 6D, 6E, and 6F are provided, respectively. Each of the injectors 6A to 6F is supplied with fuel at a predetermined pressure from a fuel tank by the operation of a fuel pump (not shown). Furthermore, corresponding to each cylinder #1 to #6 of the engine 1, spark plugs 7A, 7B,
7C, 7D, 7E, and 7F are provided, respectively.

On the other hand, the exhaust system of the engine 1 is provided with an exhaust manifold 8. This exhaust manifold 8 connects cylinder groups #1 to #3 without exhaust interference and cylinder groups #4 to ##.
6, and the assembled portions 8a and 8b are communicated with each other by a communication path 9. A main turbocharger 10 as a main supercharger and a sub-turbocharger 11 as a sub-supercharger are provided in parallel in the intake system and exhaust system of the engine 1, respectively. That is, each turbine 10a that constitutes each main and sub-turbocharger 10, 11
, 11a have their upstream sides communicated with the collecting portions 8a, 8b of the exhaust manifold 8, respectively. In other words, cylinder groups #1 to #1 of the engine 1 correspond to the main turbocharger 10.
#3 is in communication with the cylinder group #4 to #6 of the engine 1 corresponding to the sub-turbocharger 11. Also,
The downstream side of each turbine 10a, 11a is communicated with separate main and sub exhaust passages 12, 13. The main and auxiliary exhaust passages 12 and 13 merge on the downstream side thereof and are communicated with the outside via a catalytic converter 14 having a built-in three-way catalyst.

On the other hand, the main and sub turbochargers 10,
The upstream sides of the compressors 10b and 11b constituting the compressor 11 are communicated with separate main and sub intake passages 15 and 16, respectively. The upstream sides of each of the main and auxiliary intake passages 15 and 16 merge into one common intake passage 17 and communicate with the outside via an air cleaner 18. In addition, each compressor 10b, 1
The downstream side of 1b is communicated with separate main and sub intake passages 19 and 20. The downstream sides of each of the main and auxiliary intake passages 19 and 20 merge and communicate with one common intake passage 21, and are connected to an intercooler 22 for cooling intake air, and further to a throttle body 3.
It is connected to the surge tank 2 via.

In this embodiment, the main turbocharger 1
0 is one that is operated from a low intake air amount region to a high intake air amount region of the engine 1, and the auxiliary turbocharger 11 is stopped in the low intake air amount region of the engine 1, and is operated only in the high intake air amount region of the engine 1. Both the main and sub turbochargers 10 and 11 constitute a so-called "two-stage twin turbo system."

In order to enable both the main and sub turbochargers 10 and 11 to operate and stop, the sub turbocharger 1
An exhaust switching valve 23 is provided in the middle of the auxiliary exhaust passage 13 communicating with the first turbine 11a. Further, an intake switching valve 24 is provided in the middle of the auxiliary intake passage 20 that communicates with the compressor 11b of the auxiliary turbocharger 11. The exhaust switching valve 23 and the intake switching valve 24 are driven by diaphragm actuators 27 and 28 that are driven by opening and closing of three types of first and second vacuum switching valves (hereinafter simply referred to as "VSV") 25 and 26, respectively. They are opened and closed respectively. Atmospheric air is introduced into the atmospheric ports of the first and second VSVs 25 and 26 via an air filter 29, and required high-pressure air is introduced from the pressure tank 30 into the pressure ports.

[0016] Therefore, the first and second VSVs 25, 26
The air pressure introduced into the diaphragm chambers 27a, 28a of each actuator 27, 28 is adjusted by switching the opening/closing of , thereby operating each actuator 27, 28, and opening/closing the exhaust switching valve 23 and the intake switching valve 24, respectively. . That is, when the first VSV 25 is turned on, it operates the actuator 27 to fully open the exhaust switching valve 23, and when it is turned off, the actuator 27 is operated to fully open the exhaust switching valve 23.
The actuator 27 is operated to fully close the door. When the second VSV 26 is turned on, it operates the actuator 28 to fully open the intake switching valve 24, and when it is turned off, it operates the actuator 28 to fully close the intake switching valve 24. let When both the exhaust switching valve 23 and the intake switching valve 24 are fully open, a "double supercharging stage" occurs in which both the main and auxiliary turbochargers 10, 11 operate, and both the switching valves 23,
24 are fully closed, the main turbocharger 10
This is a "single supercharging stage" in which only one supercharger is activated.

Turbine 11a of sub-turbocharger 11
An exhaust bypass passage 31 that bypasses the exhaust switching valve 23 and communicates with the main exhaust passage 12 is provided in the auxiliary exhaust passage 13 that communicates with the main exhaust passage 12 . Further, this exhaust bypass passage 31 is provided with an exhaust bypass valve 32 that constitutes a part of the supercharging pressure regulating valve. This exhaust bypass valve 32 is opened and closed by a diaphragm type actuator 33. The diaphragm chamber 33a of this actuator 33 is located in the sub-intake passage 2 downstream of the intake switching valve 24.
0, and the auxiliary intake passage 1 on the upstream side of the compressor 10b via the third VSV 34 of two types.
It is connected to 6. By opening and closing this third VSV 34, the compressor 10 is placed in the diaphragm chamber 33a.
By adjusting the introduction of supercharging pressure by b, the actuator 33 is operated and the exhaust bypass valve 32 is opened and closed. That is, by controlling the duty of the third VSV 34, it adjusts the amount of supercharging pressure bled into the atmosphere by the compressor 10b of the main turbocharger 10, adjusts the operating pressure to the diaphragm chamber 33a, and operates the exhaust bypass valve 32. The degree of opening (opening amount) is variable.

Furthermore, both passages 20 and 15 are communicated between the auxiliary intake passage 20 upstream of the intake switching valve 24 and the main intake passage 15 upstream of the compressor 10b of the main turbocharger 10. First intake bypass passage 35
is provided. In addition, the first intake bypass passage 35
A first intake bypass valve 37 driven by a diaphragm actuator 36 is provided at one end to open and close the passage 35 . This actuator 36 is driven by opening/closing switching of the fourth VSV 38 of three types. Atmospheric air is introduced into the atmospheric port of this fourth VSV 38 via an air filter 29, and required high pressure air is introduced from the pressure tank 30 into the pressure port.

Accordingly, based on the opening/closing switching of the fourth VSV 38, the introduction of air pressure into the diaphragm chamber 36a of the actuator 36 is adjusted, thereby operating the actuator 36 and opening/closing the first intake bypass valve 37. . That is, when the fourth VSV 38 is turned on, it operates the actuator 36 to fully close the first intake bypass valve 37, and when it is turned off, it operates the actuator 36 to fully open the first intake bypass valve 37. The actuator 36 is operated as follows. This first intake bypass passage 3
Reference numeral 5 denotes a passage that is opened to smoothly switch from the operation of only the main turbocharger 10 to the operation of both the main and auxiliary turbochargers 10 and 11.

Note that the pressure port of the pressure tank 30 is connected to the common intake passage 2 upstream of the intercooler 22.
1, and supercharging pressure from the main turbocharger 10 is supplied to the pressure tank 30. Further, a reed valve 40 is provided in a bypass passage 39 that communicates the upstream side and the downstream side of the intake switching valve 24 in the auxiliary intake passage 20 . When the outlet pressure of the compressor 11b of the auxiliary turbocharger 11 becomes higher than that of the main turbocharger 10, air is transferred from the upstream side of the intake switching valve 24 to the downstream side via the bypass passage 39 and the reed valve 40. is now bypassed.

On the other hand, in the main turbocharger 10,
A wastegate passage 41 is provided between the upstream side and the downstream side of the turbine 10a. Further, this wastegate passage 41 is provided with a wastegate valve 42 that constitutes a supercharging pressure regulating valve together with the exhaust bypass valve 32. In order to prevent the supercharging pressure by the main turbocharger 10 from exceeding a preset pressure, the wastegate valve 42 bypasses exhaust gas flowing into the turbine 10a to the outlet side of the turbine 10a.
This is for adjusting the output of the main turbocharger 10 and controlling the supercharging pressure by the main turbocharger 10. The waste gate valve 42 is operated by a diaphragm type actuator 4.
3 to open and close. The diaphragm chamber 43a of this actuator 43 is connected to the compressor 1.
It is connected to the main intake passage 19 on the downstream side of 0b, and the compressor 1
It communicates with the main intake passage 15 on the upstream side of 0b. By opening and closing the fifth VSV 44, the introduction of supercharging pressure by the compressor 10b into the diaphragm chamber 43a is adjusted, thereby operating the actuator 43 and opening and closing the wastegate valve 42. In other words, the duty of the fifth VSV 44 is controlled to adjust the amount of supercharging pressure bled into the atmosphere, and the diaphragm chamber 4
The opening degree (opening amount) of the wastegate valve 42 is made variable by adjusting the operating pressure of the wastegate valve 3a.

Also related to the main turbocharger 10,
Main intake passage 15 upstream of the compressor 10b
and the common intake passage 2 downstream of the same compressor 10b.
1, a second intake bypass passage 45 is provided. A second intake bypass valve 47 is provided at one end of the second intake bypass passage 45 and is driven by a diaphragm actuator 46 to open and close the passage 45 . A diaphragm chamber 46a of this actuator 46 is communicated with the surge tank 2. Therefore, only when the inside of the surge tank 2 becomes negative pressure,
The actuator 46 is operated so that the second intake bypass valve 47 is opened, and at other times, the actuator 46 is operated so that the second intake bypass valve 47 is closed.

The engine 1 receives outside air introduced through the air cleaner 18 through the common intake passage 17, the main and auxiliary intake passages 15 and 16, and the main and auxiliary turbochargers 1.
The air is taken in through compressors 10b and 11b, intercooler 22, surge tank 2, intake manifold 5, etc. Further, at the same time as taking in the outside air, the engine 1 takes in fuel injected from each of the injectors 6A to 6F. Further, the engine 1 explodes and burns the mixture of the taken in fuel and outside air in the combustion chambers of each cylinder #1 to #6 to obtain driving force, and then sends the exhaust gas to the exhaust manifold 8, the main Turbines 10a and 11a of each of the auxiliary turbochargers 10 and 11, and each of the main and auxiliary exhaust passages 12 and 13
and discharged to the outside via the catalytic converter 14.

Each sensor constituting the operating state detection means for detecting the operating state of the engine 1 detects the opening degree of the throttle valve 4 (throttle opening degree) in the throttle body 3.
A throttle opening sensor 61 is provided to detect the throttle opening. The surge tank 2 is provided with an intake pressure sensor 62 as a boost pressure detection means, and the sensor 62 detects the boost pressure PM.
As a result, the intake pipe pressure in the surge tank 2 is detected. On the downstream side of the air cleaner 18, a movable vane air flow meter 63 is provided as an intake air amount detection means for measuring the amount of intake air Q passing through the common intake passage 17. The engine 1 is provided with a water temperature sensor 64 that detects the temperature of its cooling water (cooling water temperature). Furthermore, an oxygen sensor 65 for detecting the oxygen concentration in the exhaust gas is provided near the confluence of the main and auxiliary exhaust passages 12 and 13. This oxygen sensor 65 is arranged at a position offset from the main exhaust passage 12. Further, each of the main and auxiliary turbochargers 10 and 11 is provided with a second rotation speed sensor 69 as a rotation speed detection means for detecting their actual rotation speed NTR, and an atmospheric pressure sensor 69 is provided outside the engine 1. An atmospheric pressure sensor 70 is provided to detect P0.

An ignition signal distributed by a distributor 48 is applied to each of the spark plugs 7A to 7F provided for each cylinder #1 to #6 of the engine 1. The distributor 48 synchronizes the high voltage output from the igniter 49 with the crank angle of the engine 1 to each spark plug 7A~
This is for distribution to the 7th floor. The ignition timing of each spark plug 7A to 7F is determined by the high voltage output timing from the igniter 49.

The distributor 48 has a built-in rotor (not shown) that rotates in conjunction with the rotation of the engine 1. The distributor 48 is provided with a first rotation speed sensor 66 that detects the engine rotation speed NE from the rotation of the rotor. Similarly, cylinder discrimination sensors 67 are respectively attached to the distributors 48 to detect changes in the crank angle of the engine 1 at a predetermined rate according to the rotation of the rotor. In this embodiment, assuming that the engine 1 rotates twice per stroke, the cylinder discrimination sensor 67 detects the crank angle at a rate of 360° CA. Further, a transmission (not shown) drivingly connected to the engine 1 is provided with a vehicle speed sensor 68 for detecting vehicle speed.

[0027] Each injector 6A to 6F, igniter 49, and first to fifth VSVs 25, 26, 34,
38 and 44 are electrically connected to an electronic control unit (hereinafter simply referred to as "ECU") 71, and their drive timings are controlled by the operation of the ECU 71. Next, the configuration of the ECU 71 will be explained according to the block diagram of FIG. The ECU 71 includes a central processing unit (CPU) 72 that constitutes opening/closing control means, boost pressure control means, and rotation speed adjustment means, a read-only memory (ROM) 73 that stores predetermined control programs, etc., and calculation results of the CPU 72, etc. Random access memory (R
AM) 74, a backup RAM 75 for storing pre-stored data, these parts and an external input circuit 76,
It is configured as a logic operation circuit connected to an external output circuit 77 and the like via a bus 78.

The external input circuit 76 includes the aforementioned throttle opening sensor 61, intake pressure sensor 62, air flow meter 63, water temperature sensor 64, oxygen sensor 65, first rotation speed sensor 66, cylinder discrimination sensor 67, and vehicle speed sensor. 68,
A second rotation speed sensor 69 and an atmospheric pressure sensor 70 are each connected. Then, the CPU 72 inputs the air flow meter 63 and each sensor 61 through the external input circuit 76.
The output signals from 62, 64 to 70 are read as input values.

Based on these input values, the CPU 72 controls each of the injectors 6A to 6F, the igniter 49, and the first to fifth VSVs connected to the external output circuit 77.
25, 26, 34, 38, 44, etc. are suitably controlled. Note that fuel injection is independent injection for each cylinder #1 to #6, and each injector 6A to 6F is individually driven and controlled when the injection timing for each cylinder #1 to #6 arrives. ing. In the engine 1 of this embodiment, fuel injection in each cylinder #1 to #6 is performed in the order of cylinder #1, cylinder #5, cylinder #3, cylinder #6, cylinder #2, and cylinder #4. It has become.

The ROM 73 stores information about the exhaust bypass valve 32 and the waste gate valve 4 when the vehicle runs on flat ground.
The boost pressure adjusted by opening and closing 2 is the set boost pressure PM.
It is stored as a. In addition, the ROM73 also contains
A map as shown in is stored in advance. This map is for correcting the set supercharging pressure PMa when the vehicle travels on highlands with low air density, and defines a corrected supercharging pressure PMb according to the atmospheric pressure P0. In this embodiment, the corrected supercharging pressure PMb is set to decrease linearly as the atmospheric pressure P0 becomes lower (at a higher altitude).

In the supercharged gasoline engine system configured as described above, the CPU 72 judges the current operating state based on the input values from the air flow meter 63 and each sensor 61, 62, 64-70, and The operation of the main turbocharger 10 and the sub-turbocharger 11 is controlled as follows depending on the operating state. First, when the operating state of the engine 1 is in a low speed range and a high load range, the CPU 72 switches the first and second VSVs 25 and 26 so that both the exhaust switching valve 23 and the intake switching valve 24 are closed. Control. This allows the main turbocharger 1
This is a "single supercharging stage" in which only stage 0 is activated. In this "single supercharging stage", exhaust gas from the engine 1 flows only through the main turbocharger 10, as shown by the arrow in FIG. 4, and rotationally drives the turbine 10a. Further, the exhaust gas that has passed through the turbine 10a passes through the main exhaust passage 12, reaches the confluence of the main and auxiliary exhaust passages 12 and 13, and then passes through the catalytic converter 14 downstream. It passes through and is discharged to the outside. In this way, the reason for using a "single supercharging stage" in the low intake air amount range is that in the low speed range, the supercharging characteristics with only the main turbocharger 10 are better than those with both the main and sub turbochargers 10 and 11. Because it is better than. By using such a "single supercharging stage", the torque of the engine 1 increases quickly, and the response in the low speed range can be significantly improved.

Furthermore, in this embodiment, the oxygen sensor 65
The installation position is the turbine 1 of the main turbocharger 10.
Since it is offset from the main exhaust passage 12 communicating with the main turbocharger 10, the exhaust gas flow from the main turbocharger 10 efficiently hits the oxygen sensor 65 and its oxygen concentration is detected. Therefore, the oxygen sensor 65 is rapidly warmed by the exhaust gas flow, and can quickly reach a stable output temperature characteristic range for air-fuel ratio control. In this "single supercharging stage", the entire amount of the exhaust gas flow always hits the oxygen sensor 65, and even in the "double supercharging stage", which will be explained later, the main turbocharger 10 is always operated.
Since the exhaust gas flow from the exhaust gas always hits the oxygen sensor 65, the oxygen concentration of the exhaust gas can be detected with high accuracy by the oxygen sensor 65. Therefore, oxygen sensor 6
By feeding back the detection signal in 5,
It becomes possible to always perform accurate air-fuel ratio control.

Furthermore, when the operating state of the engine 1 is in a low speed range and a low load range, the CPU 72 controls the first and second switching valves so that only the intake switching valve 24 is opened while the exhaust switching valve 23 remains closed. 2 VSVs 25 and 26 are switched and controlled. As a result, both the main and auxiliary intake passages 15 and 16 are opened while the "single supercharging stage" remains, and an increase in intake resistance due to the operation of only the main turbocharger 10 can be suppressed. By doing so, it is possible to improve the boost pressure rise characteristics and operational response at the beginning of acceleration from a low load range.

Furthermore, when the operating state of the engine 1 shifts from a low intake air amount region to a high intake air amount region, that is, when switching from a "single supercharging stage" to a "double supercharging stage," the CPU 72 The first and second V so that both the exhaust switching valve 23 and the intake switching valve 24 are opened
Controls switching between SV25 and 26. At this time, the CPU 72 switches and controls the third VSV 34 so that the exhaust bypass valve 32 is opened when the exhaust switching valve 23 is closed. In other words, part of the exhaust gas is transferred to the sub-turbocharger 1.
1, the run-up rotation speed of the sub-turbocharger 11 can be increased and stage switching can be performed more smoothly. In addition, the CPU 72 switches and controls the fourth VSV 38 so as to open the first intake bypass valve 37, so that the stage switching can be performed even more smoothly.

On the other hand, when the operating state of the engine 1 is in a high intake air amount region, the CPU 72 operates so that the exhaust switching valve 23 and the intake switching valve 24 both remain open and the exhaust bypass valve 32 is closed. 1st to 3rd VSV25,2
6 and 34 are switched and controlled. As a result, a "double supercharging stage" state in which supercharging is performed by both the main and sub turbochargers 10 and 11 is maintained. In this "double supercharging stage", exhaust gas from the engine 1 flows through both the main and auxiliary turbochargers 10, 11, as shown by arrows in FIG. 5, and rotationally drives each turbine 10a, 11a. Furthermore, the exhaust gas that has passed through each of the turbines 10a and 11a passes through both the main and auxiliary exhaust passages 12 and 13 to reach their confluence, as shown by the arrows in FIG. 5, and further passes through the catalytic converter 14 downstream. and flows to the outside. In this way, by using the "double supercharging stage", sufficient supercharging pressure can be obtained by both the compressors 10b and 11b of both the main and auxiliary turbochargers 10 and 11,
The output of the engine 1 in the high speed range is improved. Then, the CPU 72 drives and controls the fifth VSV 44 (duty control) to open and close the waste gate valve 42 so that the supercharging pressure at this time does not exceed, for example, "+500 mmHg".

Next, the functions and effects of this embodiment will be explained. FIG. 7 is a flowchart showing supercharging pressure control by the exhaust bypass valve 32 in the "single supercharging stage" among various processes executed by the CPU 72, and FIG. It is a flowchart which shows rotation speed control by guard of both turbochargers 10 and 11.

In FIG. 7, the CPU 72 first determines the operating states of the main and sub turbochargers 10 and 11 in step 101. That is, the CPU 72 uses the first VSV 25
is turned on, and if the first VSV 25 is turned off, the exhaust switching valve 23 is fully closed and only the main turbocharger 10 operates, a "single supercharging stage".
It is determined that Then, if the CPU 72 is in the "single supercharging stage", the following step 10
After the atmospheric pressure P0 at that time is taken in by the atmospheric pressure sensor 70 in step 2, the process moves to step 103, and the corrected supercharging pressure PMb corresponding to the atmospheric pressure P0 is determined based on the map in FIG.
seek. The corrected supercharging pressure PMb at this time has a lower value as the altitude increases. Next, in step 104, the CPU 72 takes in the supercharging pressure PM detected by the intake pressure sensor 62 at that time.

Then, the CPU 72 performs processing to match the corrected supercharging pressure PMb calculated in step 103 with the supercharging pressure PM taken in in step 104. That is, the CPU 72 compares the supercharging pressure PM and the corrected supercharging pressure PMb in step 105, and if the supercharging pressure PM is higher than the corrected supercharging pressure PMb, the CPU 72 moves to step 106, and changes the duty to the coil of the third VSV 34. Increase the ratio. As a result, the actuator 33 operates and the opening degree of the exhaust bypass valve 32 becomes larger, so that the main turbocharger 10
The amount of exhaust gas flowing from the side to the sub-turbocharger 11 side increases, and as a result, the supercharging pressure P measured by the intake pressure sensor 62 increases.
M decreases.

Further, in step 105, if the supercharging pressure PM at that time is equal to or less than the corrected supercharging pressure PMb, CP
U72 moves to step 107 and reduces the duty ratio to the coil of the third VSV 34. As a result, the opening degree of the exhaust bypass valve 32 becomes smaller and the supercharging pressure PM increases. By controlling the opening degree of the exhaust bypass valve 32 in this manner, the supercharging pressure PM is adjusted to the corrected supercharging pressure PMb.

Therefore, the supercharging pressure PM at the timing from t1 to t2 in FIG. 10 becomes the set supercharging pressure PMa defined with reference to the flat ground when the control shown in FIG. 7 is not performed (comparative example indicated by the broken line). However, in this embodiment, as shown by the solid line, the corrected supercharging pressure PMb is lower than the set supercharging pressure PMa. In addition, in accordance with this, the actual rotation speed NTR of the main turbocharger 10 measured by the second rotation speed sensor 69 is as shown in FIG.
The state decreases from the broken line state at 0 to the solid line state. As a result, the actual rotational speed NTR is regulated to be less than or equal to the guard rotational speed A, that is, the actual rotational speed NTR is prevented from exceeding the allowable rotational speed of the main turbocharger 10. As described above, according to this embodiment, it is possible to prevent overrun of the main turbocharger 10 in the "single supercharging stage" when traveling at high altitudes.

Note that when the first VSV 25 is turned on in step 101, the CPU 72 enters a "double supercharging stage" in which the exhaust switching valve 23 is fully opened and both the main and auxiliary turbochargers 10 and 11 are activated. It is determined that there is, and this routine is ended without performing the processing of steps 102 to 107. Next, the processing in FIG. 8 will be explained. First, in step 201, the CPU 72 determines the operating states of the main and sub turbochargers 10 and 11. That is, C.P.
U72 determines whether or not the first VSV 25 is turned on. If the first VSV 25 is turned on, the exhaust switching valve 23 is fully opened and both the main and auxiliary turbochargers 10 and 11 are activated. It is determined that the company is in the “pay stage”. Then, if the CPU 72 is in the "double supercharging stage", in the following step 202, the second rotation speed sensor 69 detects the current state of both the main and sub turbochargers 10 at that time.
, 11's actual rotational speed NTR is taken in.

[0042] Subsequently, the CPU 72 calculates the actual rotation speed NTR.
Processing is performed to prevent the higher value of these from exceeding the guard rotation speed A. This guard rotational speed A is a value used to prevent both the main and auxiliary turbochargers 10 and 11 from overrunning, and is stored in the ROM 73 in advance. This guard rotation speed A is the allowable rotation speed (
For example, the rotation speed is set to a value lower by a predetermined value (for example, 130,000 rpm) than 140,000 rpm (for example, 140,000 rpm).

[0043] In order to control the actual rotation speed NTR, CP
U72 compares this actual rotation speed NTR and guard rotation speed A in step 203. If the actual rotation speed NTR is less than the guard rotation speed A, the CPU 72 moves to step 204 and sets the fifth duty ratio according to the normal supercharging pressure PM.
The VSV 44 of the controller is controlled. Further, when the actual rotation speed NTR increases and is determined to be equal to or higher than the guard rotation speed A in step 203, the CPU 72 moves to step 205 and increases the duty ratio to the coil of the fifth VSV 44. As a result, the opening degree of the wastegate valve 42 increases, and the turbine 1 passes through the wastegate passage 41.
The amount of exhaust gas bypassed to the exit side of 0a increases, and the actual rotation speed NTR decreases.

Therefore, the rotation speeds of the main and sub turbochargers 10 and 11 after timing t3 in FIG. 10 are as follows:
If the control shown in FIG. 8 is not carried out, the rotation speed will be equal to or higher than the guard rotation speed A as shown in the comparative example indicated by the broken line in FIG. A guard is applied to the NTR, preventing it from exceeding the guard rotation speed A. In this way, in this embodiment, it is possible to prevent overrun of both the main and auxiliary turbochargers 10 and 11 in the "double supercharging stage" when traveling at high altitudes. Furthermore, when the actual rotational speed NTR is guarded after the t3 timing as described above, the supercharging pressure PM measured by the intake pressure sensor 62 becomes slightly lower than the set supercharging pressure PMa as shown by the solid line in FIG.

Note that if the first VSV 25 is turned off in step 201, the CPU 72 determines that the exhaust switching valve 23 is fully closed and the "single supercharging stage" is reached, in which only the main turbocharger 10 operates. However, this routine is ended without performing the processing in steps 202 to 205. According to this embodiment, in the "single supercharging stage", the opening degree of the exhaust bypass valve 32 is controlled and the supercharging pressure PM is set to the corrected supercharging pressure PMb corresponding to the atmospheric pressure P0 at that time. , the rotation speed of the main turbocharger 10 is lowered, and in the "double supercharging stage", the opening degree of the waste gate valve 42 is controlled, and the actual rotation speed NTR of both the main and auxiliary turbochargers 10 and 11 is changed to the guard rotation speed A. It has been regulated as follows. Therefore, unlike the conventional technology that only corrects the switching point of the operating state of the turbocharger, in this embodiment, regardless of the level of atmospheric pressure P0, it can be used in both the "single supercharging stage" and "double supercharging stage" Overrun of both the main and auxiliary turbochargers 10 and 11 can be reliably prevented.

By the way, FIG. 9 shows the relationship between engine speed NE, supercharging pressure PM, and turbocharger speed. In this figure, the boost pressure PM is set to the boost pressure PMa
If the engine speed NE is controlled so that Then, the rotation speed of the turbocharger is the guard rotation speed A (in this case, 1
30,000 rpm). In contrast, in this embodiment, as described above, when the actual rotation speed NTR of the main turbocharger 10 is equal to or higher than the guard rotation speed A in the "single supercharging stage", the exhaust bypass valve 32 is activated, and the "double supercharging stage" is activated. The actual rotational speed N of both the main and auxiliary turbochargers 10 and 11 is
When TR is equal to or higher than the guard rotation speed A, the opening degree of the waste gate valve 42 is controlled to be large, so that the actual rotation speed NTR becomes equal to or lower than the guard rotation speed A.
The supercharging pressure PM becomes equal to or lower than the characteristic line L shown by the solid line in FIG. Therefore, it can be seen from this fact that overrun of both the main and auxiliary turbochargers 10 and 11 can be prevented.

It should be noted that the present invention is not limited to the above-mentioned embodiments, and may be modified and embodied as desired without departing from the spirit of the invention, for example, as described below. (1) In the above embodiment, in the "single supercharging stage", the supercharging pressure PM is controlled to the corrected supercharging pressure PMb, which is lower than the set supercharging pressure PMa, and in the "double supercharging stage", both the main and sub-turbo Although a guard is applied to the actual rotational speed NTR of chargers 10 and 11, in addition to this, it is also possible to apply a guard to the actual rotational speed NTR in the "single supercharging stage", or to guard the actual rotational speed NTR in the "double supercharging stage". The supply pressure PM may be controlled to a value lower than the set supercharging pressure PMa.

For example, as shown in FIG. 11, in both the "single supercharging stage" and the "double supercharging stage", the actual rotational speed N of both the main and auxiliary turbochargers 10, 11 is
When guarding TR at guard rotation speed A, t2 ~
At timing t3 and timing after t4, the actual rotational speed NTR decreases from the state shown by the broken line to the state shown by the solid line, and the supercharging pressure PM decreases from the state shown by the broken line to the state shown by the solid line. In this case, the supercharging pressure PM is "single supercharging stage"
It decreases in the second half (timing t2 to t3) and rises again after the stage change, so there is room for improvement in terms of acceleration feeling.

Therefore, as shown in FIG. 12, the supercharging pressure PM in the "single supercharging stage" is set to
B in FIG. 12 in order to reduce the boost pressure PM from
As shown in the figure, the rise of supercharging pressure PM is made smooth. In this case, the supercharging pressure PM in the "double supercharging stage" may be controlled using a map. (2) In the embodiment described above, overrun of the main turbocharger 10 is prevented by controlling the supercharging pressure PM in the "single supercharging stage" to a corrected supercharging pressure PMb lower than the set supercharging pressure PMa. However, as shown by the solid line in FIG. 13, t1 to t2 at the same stage
The actual rotational speed NTR may be controlled using a map so that the boost pressure PM at the timing becomes the corrected boost pressure PMb. (3) In the above embodiment, the supercharging pressure PM was controlled to the corrected supercharging pressure PMb lower than the set supercharging pressure PMa only in the "single supercharging stage", but as shown in FIG. It may also be executed over both stages. (4) In the above embodiments, the present invention was embodied in a 6-cylinder in-line gasoline engine system with a supercharger, but it may also be embodied in a V-type engine instead of an in-line engine, or in a V-type engine instead of a 6-cylinder engine. It can be embodied in a 4-cylinder engine, an 8-cylinder engine, or the like.

[0050]

[Effects of the Invention] As detailed above, according to the present invention,
By controlling the opening degree of the boost pressure regulating valve, the boost pressure is adjusted between the boost pressure when only the main supercharger is operating and the boost pressure when the main supercharger and sub-supercharger are operating. In addition to providing control means,
When the actual rotational speed of the main supercharger and the sub-supercharger is smaller than the predetermined rotational speed, control of the supercharging pressure regulating valve by the boost pressure control means is allowed, and the actual rotational speed is set to the predetermined rotational speed. In the above case, since a rotation speed adjustment means is provided to control the supercharging pressure regulating valve and adjust the actual rotation speed to a predetermined rotation speed, the main turbocharger and sub-supercharger can be reliably operated under all operating conditions. This has the excellent effect of preventing overruns.

[Brief explanation of drawings]

FIG. 1 is a diagram showing the basic configuration of the present invention.

FIG. 2 is a schematic configuration diagram showing a supercharged gasoline engine system in an embodiment embodying the present invention.

FIG. 3 is a block diagram showing the configuration of an ECU in one embodiment.

FIG. 4 is a schematic configuration diagram illustrating a supercharging operation in a "single supercharging stage" of a gasoline engine system with a supercharger according to an embodiment.

FIG. 5 is a schematic configuration diagram illustrating a supercharging operation in a "double supercharging stage" of a gasoline engine system with a supercharger according to an embodiment.

FIG. 6 is a diagram showing a map in which corrected supercharging pressure is determined with respect to atmospheric pressure in one embodiment.

FIG. 7 is a flowchart showing supercharging pressure control in a "single supercharging stage" executed by a CPU in one embodiment.

FIG. 8 is a flowchart showing rotation speed control by guard in a "double supercharging stage" executed by the CPU in one embodiment.

FIG. 9 is a diagram showing the relationship between engine speed, turbocharger speed, and supercharging pressure in one embodiment.

FIG. 10 is a diagram showing the relationship between turbocharger rotational speed and supercharging pressure with respect to time in one embodiment.

FIG. 11 is a diagram showing characteristics of the turbocharger rotational speed and supercharging pressure in another example in which the rotational speed of the turbocharger is guarded in a "single supercharging stage" and a "double supercharging stage."

[Fig. 12] Another example of a turbocharger in which the set supercharging pressure in the "single supercharging stage" is lowered to the corrected supercharging pressure from the state shown in Fig. 11, and the rise in supercharging pressure after stage switching is smoothed. FIG. 3 is a diagram showing characteristics of rotation speed and supercharging pressure.

FIG. 13 is a diagram showing characteristics of the turbocharger rotation speed and supercharging pressure in another example in which the turbocharger rotation speed in a "single supercharging stage" is controlled using a map.

FIG. 14 is a diagram showing characteristics of supercharging pressure in another example in which the set supercharging pressure is lowered to the corrected supercharging pressure across both the "single supercharging stage" and the "double supercharging stage".

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1... Engine, 10... Main turbocharger as a main supercharger, 11... Sub-turbocharger as a sub-supercharger, 1
2... Main exhaust passage forming part of the exhaust system, 13... Sub-exhaust passage forming part of the exhaust system, 15, 19... Main intake passage forming part of the intake system, 16, 20... Intake system 17, 21... common intake passage forming part of the intake system, 23... exhaust switching valve, 24... intake switching valve, 32... forming part of the supercharging pressure adjustment valve. 42...waste gate valve forming a part of the supercharging pressure regulating valve, 62...intake pressure sensor as supercharging pressure detection means,
63...Air flow meter as intake air amount detection means,
69...Second rotation speed sensor as rotation speed detection means, 7
2...CPU constituting the opening/closing control means, boost pressure control means, and rotation speed adjustment means, NTR...actual rotation speed of the turbocharger, PM...supercharging pressure, Q...intake air amount.

Claims (1)

[Claims] Claim 1: A main supercharger and a sub-supercharger provided in parallel to an intake system and an exhaust system of an engine; an intake switching valve and an intake switching valve provided in the intake system and exhaust system corresponding to the sub-supercharger; an exhaust switching valve; an intake air amount detection means for detecting the intake air amount to the engine; and when the intake air amount detected by the intake air amount detection means is less than or equal to a predetermined value, the intake switching valve and the Both exhaust switching valves are closed to operate only the main supercharger, and if the intake air amount is larger than a predetermined value, both the intake switching valve and the exhaust switching valve are opened to operate the main supercharger and the subsupercharger. A control device for a supercharged engine comprising an opening/closing control means for operating a charger, a supercharging pressure regulating valve provided in an exhaust system of the engine and regulating supercharging pressure to the engine; A supercharging pressure detection means detects the supercharging pressure of the main supercharger, and the opening degree of the supercharging pressure regulating valve is controlled based on the supercharging pressure detected by the supercharging pressure detecting means, to prevent overcharging when only the main supercharger is operated. A boost pressure control means for adjusting the boost pressure and the boost pressure during operation of the main supercharger and the sub-supercharger, and a rotation speed for detecting the actual rotation speed of the main supercharger and the sub-supercharger. detection means;
When the actual rotational speeds of the main supercharger and the sub-supercharger determined by the rotational speed detection means are smaller than the predetermined rotational speed, the supercharging pressure control means is allowed to control the supercharging pressure regulating valve; A supercharged engine characterized by comprising: a rotation speed adjusting means which controls a supercharging pressure regulating valve to adjust the actual rotation speed to a predetermined rotation speed when the rotation speed is equal to or higher than a predetermined rotation speed. Control device.