JP7329190B2 - Control device for turbocharged engine - Google Patents

Description

The present invention relates to a control device for a turbocharged engine that controls a bypass valve that opens and closes a bypass passage that communicates upstream and downstream sides of a compressor.

Conventionally, in an engine equipped with a turbocharger, when the throttle valve is closed during deceleration, surging occurs downstream of the compressor due to an increase in intake pressure between the compressor and the throttle valve. It is known to generate vibration and noise.
Therefore, a bypass passage that communicates the upstream side and the downstream side of the compressor, and an air bypass valve (hereinafter referred to as ABV) that opens and closes this bypass passage are provided, and during deceleration, the ABV is opened to supercharge. Intake air is returned to the upstream side of the compressor.

In addition, in a turbocharged engine, the compressor, throttle valve, intercooler, etc. are arranged in the intake passage, and the passage length becomes long. In addition to this, a boost pressure rise time is required in the intake passage.
In particular, as the volume of the intake passage from the combustion chamber to the throttle valve becomes larger than the volume of the intake passage from the throttle valve to the compressor, response delay, so-called turbo lag, increases, resulting in a decrease in acceleration response.

A control device for a turbocharged engine disclosed in Patent Document 1 includes a turbocharger having a compressor disposed in an intake passage and a turbine connected to the compressor and disposed in an exhaust passage, and a compressor. A throttle valve disposed on the downstream side, a bypass passage that communicates the upstream side and the downstream side of the compressor, an ABV that opens and closes the bypass passage, and a pressure sensor that detects the intake pressure between the compressor and the throttle valve. and control means for controlling the opening and closing of the ABV, the control means opening the ABV when the intake pressure is lower than the boost pressure determination threshold during acceleration of the engine.

Japanese Patent No. 6191526

The control device for an engine with a turbocharger disclosed in Patent Document 1 allows intake air to bypass the compressor by opening the ABV when the intake pressure detected by the pressure sensor downstream of the compressor is lower than the boost pressure determination threshold. , the intake pressure loss caused by passage through the intake passage is reduced.
However, with the technique disclosed in Patent Document 1, there is a concern that the rotation speed of the compressor may excessively increase when the ABV valve opening period is prolonged.

The turbine and compressor are connected by a connecting shaft including a turbine-side shaft and a compressor-side shaft, and this connecting shaft is rotatably supported by the housing, ensuring structural reliability of the turbocharger. The upper speed limit is set as a possible permissible value.
When the engine is accelerated, for example, when the engine is accelerated again after decelerating while the supercharging pressure is high, the ABV valve opening operation for deceleration and the acceleration valve opening operation are continuous, so the ABV valve opening period is is prolonged.

Especially in the case of an engine with a large intake passage volume from the combustion chamber to the throttle valve, when the engine accelerates, the ABV is opened for a long period of time, and the load (work) of the compressor decreases. Due to the increase, the rotation speed of the compressor (connecting shaft) increases rapidly, and there is a possibility that the rotation speed of the compressor may exceed the upper limit rotation speed of the turbocharger.
That is, it is not easy to avoid excessive rotation of the compressor while improving the acceleration response of the engine.

SUMMARY OF THE INVENTION It is an object of the present invention to provide a control device for a turbocharged engine that can ensure the reliability of the turbocharger while improving the acceleration response of the engine.

A control device for a turbocharged engine according to claim 1, comprising: a turbocharger having a compressor disposed in an intake passage; a turbine connected to the compressor and disposed in an exhaust passage; a throttle valve disposed on the downstream side of the compressor, a bypass passage that communicates the upstream side and the downstream side of the compressor, a bypass valve that opens and closes the bypass passage, and a control means that controls opening and closing of the bypass valve. In the control device for a turbocharged engine comprising and closing the bypass valve or reducing the degree of opening of the bypass valve .

In this control device for a turbocharged engine, the control means opens the bypass valve when the engine is accelerating, so that the compressor is bypassed and the intake pressure loss due to passage through the intake passage can be reduced. , the reduction in torque caused by turbo lag can be eliminated.
When the rotational speed of the compressor exceeds a rotational speed threshold associated with the upper limit rotational speed, the bypass valve is closed or the degree of opening of the bypass valve is reduced , thereby suppressing intake air recirculation to the upstream side of the compressor through the bypass passage. Thus, the load on the compressor can be increased, and overspeed of the compressor exceeding the upper limit speed of the turbocharger can be avoided by considering the closing operation time of the bypass valve.

According to a second aspect of the invention, there is provided an intake pressure detecting means for detecting an intake pressure between the compressor and the throttle valve in the invention according to the first aspect, and the control means controls the pressure between the compressor and the throttle valve. The bypass valve is opened when the intake pressure during the intake is lower than a predetermined pressure threshold.
According to this configuration, when the engine is accelerating, it is possible to reliably determine the situation in which the load on the compressor is reduced, and it is possible to avoid unnecessary opening of the bypass valve.

The invention of claim 3 is the invention of claim 1 or 2, wherein the control means reduces the degree of opening of the bypass valve when the rotation speed of the compressor exceeds a rotation threshold associated with the upper limit rotation speed. is characterized by
According to this configuration, the load on the compressor can be reliably increased.

The invention of claim 4 is characterized in that, in the invention of claim 3, the control means closes the bypass valve.
According to this configuration, the load on the compressor can be increased early.

The invention of claim 5 is the invention of any one of claims 1 to 4, wherein the control means closes the bypass valve when the rotation speed of the compressor exceeds a set rotation speed, which is the rotation threshold. It is characterized in that the degree of opening of the valve or the bypass valve is reduced .
According to this configuration, it is possible to reliably determine the possibility of the compressor exceeding the upper limit rotation speed by using the rotation speed of the compressor.

The invention of claim 6 is the invention of any one of claims 1 to 5 , wherein the control means estimates the rotation speed of the compressor based on the pressure ratio before and after the compressor and the flow rate of intake air passing through the compressor. is characterized by
According to this configuration, the rotation speed of the compressor can be estimated without providing a dedicated compressor rotation speed detection means.

According to the control device for a turbocharged engine of the present invention, by avoiding over-rotation of the compressor exceeding the upper limit rotation speed of the turbocharger, the acceleration response of the engine is improved and the reliability of the turbocharger is improved. can ensure the integrity of the

1 is a configuration diagram schematically showing a supercharging system for a turbosupercharged engine according to Embodiment 1. FIG. 2 is a block diagram showing the control system of FIG. 1; FIG. 4 is a map showing the relationship between intake volumetric flow rate and pressure ratio; 4 is a graph showing the relationship between engine speed, throttle opening, accelerator opening, and ABV opening during acceleration. 4 is a flow chart showing processing by a control system; It is the analysis result regarding the first intake passage pressure of the present embodiment model and the comparative model. It is an analysis result about the engine output of a present Example model and a comparative model. Analysis results of the embodiment model and the comparison model in a situation of deceleration and then re-acceleration, where (a) is the change in supercharging pressure, (b) is the change in the turbine speed, and (c) is the engine It shows the change in rotation speed.

EMBODIMENT OF THE INVENTION Hereinafter, the form for implementing this invention is demonstrated based on drawing. The following description of preferred embodiments is merely exemplary in nature and is not intended to limit the invention, its applications or uses.

Embodiment 1 of the present invention will be described below with reference to FIGS. 1 to 8. FIG.
A supercharging system for an engine with a turbocharger according to the first embodiment includes a bypass passage that bypasses a compressor in an intake passage, and an air bypass valve that opens and closes the bypass passage. Surging in the intake passage associated with this is suppressed by opening the air bypass valve.

As shown in FIG. 1, the supercharging system S includes an intake passage 2 through which intake air (air) introduced from the outside passes; An engine 1 (for example, an in-line 6-cylinder gasoline engine) that generates power for a vehicle by burning an air-fuel mixture, an exhaust passage 3 that discharges exhaust gas generated by combustion in the engine 1, and a turbocharger 4 , and a control unit 5 (control means, see FIG. 2), etc., as main components.

The engine 1 includes an intake valve 11 that introduces the intake air supplied from the intake passage 2 into the combustion chamber 13, a fuel injection valve 16 that injects fuel toward the combustion chamber 13, and the intake air supplied into the combustion chamber 13. A spark plug 17 that ignites an air-fuel mixture, a piston 14 that reciprocates vertically due to combustion of the air-fuel mixture in the combustion chamber 13, a crankshaft 15 that rotates by the reciprocating motion of the piston 14, and a combustion chamber 13 It has an exhaust valve 12 and the like for discharging the exhaust gas generated by the combustion of the air-fuel mixture inside to the exhaust passage 3 .

As shown in FIG. 1, the intake passage 2 includes, in order from the upstream side, an air cleaner 21 that cleans the intake air introduced from the outside, a compressor 41 that compresses the passing intake air to increase the intake pressure, and an amount of the passing intake air. , an intercooler 23 for cooling the passing intake air, a surge tank 24 for temporarily storing the intake air to be supplied to the engine 1 (combustion chamber 13), and the like. Hereinafter, for convenience of explanation, the passage from the air cleaner 21 to the compressor 41 is the upstream intake passage 25, the passage from the compressor 41 to the throttle valve 22 is the first intake passage 26, and the passage from the throttle valve 22 to the engine 1 is the second intake passage. 27.

A bypass passage 28 is formed in the intake passage 2 so that intake air bypasses the compressor 41 . The bypass passage 28 communicates the upstream side of the compressor 41 (the downstream end portion of the upstream intake passage 25) and the downstream side of the compressor 41 (the upstream end portion of the first intake passage 26). An air bypass valve (hereinafter referred to as ABV) 29 for controlling the flow rate of intake air flowing through the bypass passage 28 is provided in the middle of the bypass passage 28 .

As shown in FIG. 1, the exhaust passage 3 is provided with, in order from the upstream side, a turbine 42 that is rotationally driven by the passing exhaust gas, an exhaust silencer 31 that processes abnormal noise of the passing exhaust gas, and the like. An exhaust bypass passage 32 is formed in the exhaust passage 3 to bypass the turbine 42 and allow the exhaust gas to flow. The exhaust bypass passage 32 communicates the upstream side of the turbine 42 with the downstream side of the turbine 42 . A waste gate valve 33 that controls the flow rate of exhaust gas flowing through the exhaust bypass passage 32 is provided in the middle of the exhaust bypass passage 32 .

The turbocharger 4 accommodates a compressor 41 arranged in the intake passage 2, a turbine 42 arranged in the exhaust passage 3, a connecting shaft 43 connecting the compressor 41 and the turbine 42, and the compressor 41 and the turbine 42. It has a housing 44 and the like. The housing 44 is formed with a compressor housing portion, a turbine housing portion, and a bearing housing portion. The connecting shaft 43 is rotatably supported by a cylindrical bearing housing via a predetermined bearing (not shown).

Next, the controller 5 will be explained.
The control unit 5 is configured to control the opening and closing of the ABV 29 and the waste gate valve 33 . As shown in FIG. 2, the control unit 5 includes an ABV 29, a waste gate valve 33, an accelerator opening sensor 61, a first intake pressure sensor 62 (intake pressure detection means), an air flow sensor 63, and an outside air temperature sensor. 64 are electrically connected.

The accelerator opening sensor 61 detects the opening of an accelerator pedal (not shown) operated by the driver and outputs it to the controller 5 . The degree of opening of the throttle valve 22 is electronically controlled according to the amount of depression of the accelerator pedal. The first intake pressure sensor 62 is installed in the first intake passage 26, and detects and controls the intake pressure (first intake passage pressure p) of the first intake passage 26 corresponding to the boost pressure of the turbocharger 4. Output to part 5. The airflow sensor 63 detects the amount of intake air and outputs it to the control unit 5 , and the outside air temperature sensor 64 detects the outside air temperature of the external environment and outputs it to the control unit 5 .

As shown in FIG. 2, the control unit 5 includes a WG control unit 51 that controls the operation of the wastegate valve 33, a rotation speed estimation unit 52 that estimates the rotation speed of the compressor 41, and an ABV control unit that controls the operation of the ABV 29. It has a portion 53 .

The WG control unit 51 holds in advance a target supercharging pressure according to the operating state, and suppresses overspeeding of the turbine 42 . The WG control unit 51 compares the first intake passage pressure p detected by the first intake pressure sensor 62 with the target boost pressure, and when the first intake passage pressure p is higher than the target boost pressure, The rotational speed of the turbine 42 is reduced by opening the wastegate valve 33 . In addition, the WG control unit 51 feedback-controls the operation of the waste gate valve 33 in order to promote short-term convergence of the supercharging pressure.

The rotational speed estimator 52 holds a compressor map M in advance and estimates the rotational speed Nc of the compressor 41 currently rotating.
As shown in FIG. 3, in the compressor map M, the horizontal axis represents the intake air volumetric flow rate Qa (m3/sec) and the vertical axis represents the pressure ratio p/po. It is The pressure ratio is a value obtained by dividing the first intake passage pressure p of the first intake passage 26, which corresponds to the downstream pressure of the compressor 41, by the upstream intake passage pressure po of the upstream intake passage 25, which corresponds to the upstream pressure of the compressor 41. be. The upstream intake passage pressure po is obtained using the detection value of the airflow sensor 63 and the detection value of the outside air temperature sensor 64 . A curve indicated by a dashed line is the Qa-p/po characteristic at the upper limit rotation speed (for example, 170000 rpm) at which the reliability of the compressor 41 can be ensured. The rotational speed estimator 52 obtains the rotational speed Nc of the compressor 41 using the compressor map M and the detection values of the respective sensors.

The ABV control unit 53 is configured to be capable of executing deceleration control for opening the ABV 29 during deceleration of the engine 1 and acceleration control for opening the ABV 29 during acceleration of the engine 1 .
The ABV control unit 53 has an acceleration control flag f1, a deceleration control flag f2, and a timer corresponding to each control (all not shown). 0 is normally assigned to these flags f1 and f2, and 1 is assigned only when each execution condition is satisfied.
Each timer continues counting while it is assigned a 1 and is reset when it is assigned a 0.

During deceleration when the accelerator pedal is released, the ABV control unit 53 opens the ABV 29 for a predetermined time (for example, 0.5 sec) to relieve supercharged intake air to the upstream side of the compressor 41 . This suppresses an increase in intake pressure between the throttle valve 22 and the compressor 41, thereby avoiding surging. The deceleration state is determined by comparing the output of the accelerator opening sensor 61 and the deceleration determination threshold, and the acceleration state is determined by comparing the output of the accelerator opening sensor 61 and the acceleration determination threshold.

FIG. 4 is a graph showing the relationship between engine speed (chain line), throttle opening (dotted line), accelerator opening (broken line), and ABV opening (solid line) during acceleration. The unit of the ABV opening is millimeters (mm).
As shown in FIG. 4, the ABV control unit 53 is controlled when the accelerator pedal is depressed and the first intake passage pressure p is lower than the atmospheric pressure. When accelerating from this state, the ABV 29 is opened for a predetermined time (for example, 0.5 sec) to introduce intake air from the upstream side of the compressor 41 to the downstream side of the compressor 41 .

When the ABV 29 is opened, there is a delay from the receipt of the valve closing command signal to the completion of closing the valve. It is output after 4 seconds have passed. As a result, the intake air can bypass the compressor 41, thereby reducing the intake pressure loss that accompanies passing through the intake passage. Even during acceleration, when the first intake passage pressure p is equal to or higher than the atmospheric pressure, such as during acceleration from a medium-to-high vehicle speed state, almost no intake pressure loss occurs, so the ABV 29 maintains the valve closed state. ing.

When the decrease in the first intake passage pressure p during acceleration is large and the acceleration control by the ABV control unit 53 continues for a long period of time, the load applied to the compressor 41 is reduced. The rotation speed Nc of the compressor 41 increases rapidly, and there is a possibility that the rotation speed Nc of the compressor 41 exceeds the upper limit rotation speed of the turbocharger 4 .
Therefore, considering the operation time until the ABV 29 is closed, a set rotation speed Nd (for example, 30000 rpm) lower than the upper limit rotation speed is set, and when the rotation speed Nc of the compressor 41 exceeds the set rotation speed Nd forcibly closes the ABV 29 even during acceleration control. As a result, the load applied to the compressor 41 can be increased immediately, and the rotation speed Nc of the compressor 41 does not exceed the upper limit rotation speed regardless of the increase in the engine rotation speed.

Based on the flowchart of FIG. 5, the operation processing procedure of ABV29 by the control part 5 is demonstrated. In the figure, Si (i=1, 2, . . . ) indicates each step.

First, various information such as the output values of the sensors 61 to 64 and the set rotational speed Nd are read (S1).
Next, it is determined whether or not the engine 1 is accelerating based on the output of the accelerator opening sensor 61 (S2). As a result of the determination in S2, if the engine 1 is in the acceleration state, the process proceeds to S3, and if the engine 1 is not in the acceleration state, the process proceeds to S13.

In S3, it is determined whether or not the first intake passage pressure p is lower than the atmospheric pressure.
If the result of the determination in S3 is that the first intake passage pressure p is lower than the atmospheric pressure, it is during acceleration from a stopped state or a low vehicle speed state, so the process proceeds to S4. If the result of determination in S3 is that the first intake passage pressure p is equal to or higher than the atmospheric pressure, it means that the vehicle is accelerating from a middle-to-high vehicle speed state, so the process proceeds to S9.
In S4, it is determined whether the flag f1 is 0 or not. As a result of the determination in S4, if the flag f1 is 0, the conditions for execution of acceleration control are satisfied from the running state in which no acceleration control is currently being performed, so the ABV 29 is fully opened (S5). As a result of the determination in S4, if the flag f1 is 1, the acceleration control has already started, so the process proceeds to S7.

After S5, the acceleration control timer starts counting (S6), the compressor map M is used to estimate the rotation speed Nc of the compressor 41 (S7), and the process proceeds to S8.
In S8, it is determined whether or not the acceleration control timer has finished counting (0.5 sec).
If the acceleration control timer has finished counting as a result of the determination in S8, the risk of intake pressure loss has been eliminated, so the ABV 29 is fully closed in order to increase the supercharging efficiency (S9). . If the result of determination in S8 is that the acceleration control timer has not finished counting, the process proceeds to S11. After S9, 0 is substituted for each of the flags f1 and f2 (S10), and the process returns.

In S11, it is determined whether or not the rotation speed Nc of the compressor 41 is higher than the set rotation speed Nd. If the result of determination in S11 is that the rotation speed Nc of the compressor 41 is higher than the set rotation speed Nd, the process proceeds to S9. This is to avoid the risk of damage or the like that occurs due to the rotation speed Nc of the compressor 41 exceeding the upper limit rotation speed, although the risk of intake pressure loss is not eliminated. In addition, even if the rotation speed Nc of the compressor 41 increases until the valve closing operation of the ABV 29 is completed, in order to keep the rotation speed Nc of the compressor 41 below the upper limit rotation speed, the set rotation speed Nd lower than the upper limit rotation speed is set. Judging. When the rotational speed Nc of the compressor 41 is less than the set rotational speed Nd as a result of the determination in S11, the ABV 29 is kept open and the process proceeds to S12. In S12, 1 is substituted for the flag f1 and 0 for the flag f2, and the process returns.

In S13, based on the output of the accelerator opening sensor 61, it is determined whether the engine 1 is in a deceleration state. If the result of determination in S13 is that the vehicle is decelerating, the process proceeds to S14. If the result of determination in S13 is that the vehicle is not decelerating, the vehicle is in a running state other than acceleration/deceleration running, so the process proceeds to S9.
In S14, it is determined whether the flag f2 is 0 or not. As a result of the determination in S14, if the flag f2 is 0, the deceleration control execution condition is satisfied from the running state in which deceleration control is not currently being performed, so the ABV 29 is fully opened to eliminate surging (S15). . If the flag f2 is 1 as a result of the determination in S14, the deceleration control has already started, so the process proceeds to S17.
After S15, the acceleration control timer starts counting (S16).

In S17, it is determined whether or not the deceleration control timer has finished counting (0.5 sec). If the deceleration control timer has finished counting as a result of the determination in S17, the risk of surging has been eliminated, so the ABV 29 is closed (S9). If the deceleration control timer has not finished counting as a result of the determination in S17, the process proceeds to S18. In S18, 0 is substituted for the flag f1 and 1 for the flag f2, and the process returns.

Next, the operation and effects of the supercharging system S will be described.
A simulation analysis by CAE (Computer Aided Engineering) was performed to explain the action and effect. Model A without acceleration control by the control unit 5, Model B with acceleration control in which the opening operation time of the ABV 29 is 0.3 sec, and Model C with acceleration control in which the opening operation time of the ABV 29 is 0.5 sec. , and calculated the first intake passage pressure p and the drive torque of the engine 1 for the models A to C for acceleration scenes from a stopped state. Other specifications including deceleration control are set to the same specifications, and the waste gate valve 33 is operated to open 70%.

FIG. 6 shows the analysis result of the first intake passage pressure p. The horizontal axis indicates time (sec), and the vertical axis indicates pressure (kPa).
As shown in FIG. 6, in the model A, the first intake passage pressure p of the first intake passage 26 is greatly reduced due to the negative pressure of the second intake passage 27 immediately after acceleration. In the model B, the intake air supplied to the first intake passage 26 via the bypass passage 28 suppresses the decrease in the first intake passage pressure p in the first intake passage 26 more than in the model A. It was confirmed that the model C had the smallest decrease in the first intake passage pressure p.

FIG. 7 shows analysis results of the driving torque of the engine 1. As shown in FIG. The horizontal axis indicates time (sec), and the vertical axis indicates torque (Nm).
As shown in FIG. 7, immediately after acceleration, model A experiences a large torque reduction due to turbo lag due to intake pressure loss. Model B shows an improvement over model A, but torque reduction still occurs due to a decrease in the first intake passage pressure p. Model C did not show any torque down.

FIGS. 8(a) to 8(c) show the boost pressure, turbine speed, and engine speed of model A and model C, which are decelerated with high boost pressure and then accelerated again. The horizontal axis indicates time (sec), and the wastegate valve 33 is fully closed. Models A and B start decelerating at 2.48 sec after the start of analysis, and start re-accelerating at 2.65 sec.
As shown in FIGS. 8(a) and 8(c), in Model A, the ABV 29 is kept fully open from deceleration control to acceleration control, so both boost pressure and engine speed decrease. ing. Further, as shown in FIG. 8(b), although the model A exceeds the upper limit rotation speed of the turbocharger 4 in a short period of time, the model C has a longer period until the upper limit rotation speed is exceeded compared to the model A. long.
Therefore, in model C, both the boost pressure and the engine speed rise faster than model A.

According to the supercharging system S according to the first embodiment, since the control unit 5 opens the ABV 29 when the engine 1 is accelerating, the compressor 41 is bypassed to reduce the intake pressure loss caused by passing through the intake passage 2. It is possible to eliminate the decrease in torque caused by turbo lag. When the rotation speed Nc of the compressor 41 exceeds the rotation threshold value (set rotation speed Nd) associated with the upper limit rotation speed, the ABV 29 is closed , so that intake air recirculation to the upstream side of the compressor 41 via the bypass passage 28 is suppressed. Thus, the load on the compressor 41 can be increased, and overspeed of the compressor 41 exceeding the upper limit speed of the turbocharger 4 can be avoided in consideration of the valve closing operation time of the ABV 29 .

It has a first intake pressure sensor 62 for detecting a first intake passage pressure p of the first intake passage 26, and the control unit 5 detects that the first intake passage pressure p of the first intake passage 26 is a predetermined pressure threshold (atmospheric pressure). ), the ABV 29 is opened. Therefore, when the engine 1 is accelerated, the situation in which the load of the compressor 41 is reduced can be reliably determined, and unnecessary opening operation of the ABV 29 can be avoided.

When the rotation speed Nc of the compressor 41 exceeds the rotation threshold value (set rotation speed Nd) associated with the upper limit rotation speed, the control unit 5 decreases the opening of the ABV 29, thereby reliably increasing the load applied to the compressor 41. be able to.

When the rotation speed Nc of the compressor 41 exceeds the rotation threshold value (set rotation speed Nd) associated with the upper limit rotation speed, the control unit 5 closes the ABV 29 so as to be fully closed. Can be increased early.

When the rotation speed Nc of the compressor 41 exceeds the set rotation speed Nd, which is the rotation threshold, the control unit 5 closes the ABV 29 or decreases the opening of the ABV 29 , so that the compressor 41 may exceed the upper limit rotation speed. It can be reliably determined using the rotational speed Nc of the compressor 41 .

Since the controller 5 estimates the rotation speed Nc of the compressor 41 based on the pressure ratio p/po before and after the compressor 41 and the intake flow rate Qa passing through the compressor 41, the compressor 41 can be operated without providing a dedicated compressor rotation speed detection means. The rotation speed Nc can be estimated.

Next, a modified example in which the above embodiment is partially changed will be described.
1) In the above-described embodiment, when the rotation speed Nc of the compressor 41 exceeds the set rotation speed Nd during acceleration of the engine 1, the ABV 29 is fully closed. The final opening may be smaller than the operated initial opening, and the final opening may be 60% or 80% of the initial opening. Also, when the ABV 29 is closed, an example has been described in which a command signal is generated to perform a full-close operation at once as a command signal. , the opening may be intermittently decreased step by step.

2) In the above-described embodiment, an example of comparing the rotation speed Nc of the compressor 41 and the set rotation speed Nd has been described. You can compare. Specifically, when the rate of increase in the rotational speed Nc of the compressor 41 exceeds the set rate of increase, the control unit 5 closes the ABV 29 or reduces the opening of the ABV 29 , thereby increasing the upper limit rotational speed of the compressor 41. can be reliably determined by using the rate of increase of the rotation speed Nc of the compressor 41.

3) In the above embodiment, an example of the in-line 6-cylinder engine 1 was explained, but if the engine has a large volume of the second intake passage 27 from the engine 1 to the throttle valve 22, the same effect can be obtained regardless of the number of cylinders. can be played.

4) In addition, without departing from the spirit of the present invention, a person skilled in the art can implement the above-described embodiment in a form in which various modifications are added or in a form in which each embodiment is combined. Any modifications are also included.

1 engine 2 intake passage 3 exhaust passage 4 turbocharger 5 control unit 22 throttle valve 28 bypass passage 29 ABV
41 Compressor 42 Turbine 52 Rotation speed estimation unit 53 ABV control unit 62 First intake pressure sensor S Supercharging system

Claims (6)

A turbocharger having a compressor disposed in an intake passage and a turbine connected to the compressor and disposed in an exhaust passage; a throttle valve disposed downstream of the compressor; A control device for a turbocharged engine comprising: a bypass passage that communicates between an upstream side and a downstream side; a bypass valve that opens and closes the bypass passage; and control means that controls opening and closing of the bypass valve,
The control means opens the bypass valve during acceleration of the engine, and closes or opens the bypass valve when the rotation speed of the compressor exceeds a rotation threshold associated with an upper limit rotation speed. A control device for a turbocharged engine, characterized in that the engine speed is reduced . an intake pressure detection means for detecting an intake pressure between the compressor and the throttle valve;
2. The turbocharger-equipped turbocharger according to claim 1, wherein said control means opens said bypass valve when an intake pressure between said compressor and said throttle valve is lower than a predetermined pressure threshold. Engine controller. 3. The turbosupercharger according to claim 1, wherein the control means reduces the degree of opening of the bypass valve when the rotational speed of the compressor exceeds a rotational speed threshold associated with the upper limit rotational speed. with engine control unit. 4. A control device for a turbocharged engine according to claim 3, wherein said control means closes said bypass valve. 5. The controller closes the bypass valve or reduces the degree of opening of the bypass valve when the rotation speed of the compressor exceeds a set rotation speed, which is the rotation threshold. A control device for a turbocharged engine according to any one of Claims 1 to 1. The turbocharger according to any one of claims 1 to 5, wherein the control means estimates the rotation speed of the compressor based on the pressure ratio before and after the compressor and the flow rate of intake air passing through the compressor. with engine control unit.