JPH03105018A - Controller for engine equipped with supercharger - Google Patents

Abstract

PURPOSE:To improve the reliability in trouble by carrying out change from the operation of only a primary supercharger to the operation with the added secondary supercharger under a specific condition and fixing the selection condition in a low intake region side when a specific condition detecting means is in trouble. CONSTITUTION:Exhaust passages 2 and 3 in which the turbines 5 and 7 of the primary and secondary turbosuperchargers 4 and 6 are arranged are allowed to communicate through a communication passage 22 on the upstream of superchargers 4 and 6, and an exhaust cut valve 23 is installed on an exhaust passage 3 side. Further, in a branched passage in which the blower 13 of the supercharger 6 is arranged, an intake cut valve 32 is arranged, and an intake relief valve 35 is arranged midway in a relief passage 34 which makes a detour around the blower 13. Though the operation of only the supercharger 4 and the operation of the both superchargers 4 and 6 are selected by opening/closing- controlling the valves 23, 32, 35, etc., the selection condition is changed freely when a specific condition is satisfied, and when a specific condition detecting means is in trouble, the above-described selection condition is fixed to a low intake region side.

Description

Detailed Description of the Invention (Industrial Application Field) The present invention relates to a control device for a supercharged engine, and more particularly, to a control device for a supercharged engine in which a plurality of superchargers are arranged in parallel. It is related to.

(Prior Art) Conventionally, as disclosed in, for example, Japanese Utility Model Application Publication No. 60-178329, two turbo superchargers, a primary and a secondary turbo supercharger, are installed in parallel, and the turbine inlet measurement and blower exit measurement of the secondary supercharger are performed. An exhaust cut valve and an intake cut valve are provided on each side, and by opening and closing these cut valves, only the primary supercharger performs supercharging in low flow areas, and not only the primary supercharger provides supercharging in high flow areas. A supercharger called a twin-turbo type or sequential turbo type that also operates a secondary supercharger is known.

In addition, in order to ensure the reliability of the primary turbocharger in the above-mentioned types of turbochargers, we have changed the operation of the primary turbocharger only to a secondary turbocharger in addition to the primary turbocharger. In order to prevent a drop in boost pressure when switching to the operation of It is also known that the third speed is changed to the low intake region side in order, and the above-mentioned switching is performed under desirable conditions.

(Problem to be Solved by the Invention) However, as described above, when changing the switching condition, that is, the switching line in the control map, based on the gear ratio of the transmission, the sensor that detects this gear ratio may be malfunctioning. For example, even though the gear ratio is currently 3rd gear, it may be detected as 1st gear, and as a result, the switching line may be set to the high intake region side.

In this way, if the switching line is incorrectly set to the high intake region side, the primary turbo supercharger will continue to operate, and the load on the primary turbo supercharger will become too large, causing the primary turbo supercharging to become too large. There is a problem that the reliability of the machine decreases.

SUMMARY OF THE INVENTION Therefore, an object of the present invention is to provide a control device for a supercharged engine that can ensure the reliability of a primary turbocharger in the event of a sensor failure.

(Means for Solving the Problems) The present invention provides a control device for a supercharged engine in which a primary supercharger that operates all the time and a secondary supercharger that operates in a high intake region are arranged side by side. a change means for changing the conditions for switching from the operation of only the primary supercharger to the operation of the secondary supercharger in addition to the primary supercharger when a specific condition is met; and a detection means for detecting the specific condition to determine a failure. and determining means, and when the determining means determines that the detecting means has failed, the switching condition by the changing means is fixed to a low intake region side.

(Operations and Effects of the Invention) In the supercharged engine control device of the present invention, the conditions for switching from the operation of only the primary supercharger to the operation of the secondary supercharger in addition to the primary supercharger are set. When it is determined that there is a failure in the detection means that detects the specific conditions for changing, the above switching conditions are fixed to the low intake region side, so as mentioned above, the primary turbocharger is overloaded and the Reliability is prevented from decreasing.

(Embodiment) Hereinafter, a control device for a supercharged engine according to a preferred embodiment of the present invention will be described with reference to the accompanying drawings.

FIG. 1 is an overall system diagram of a supercharged engine incorporating a control device according to an embodiment of the present invention.

In this embodiment, the engine 1 is a two-cylinder engine made by Resopro, and exhaust passages 2 and 3 are provided independently corresponding to each other. A turbine 5 of a primary turbocharger 4 is disposed in one of the two exhaust passages 2 and 3, and a turbine 7 of a secondary turbocharger 6 is disposed in the other. The two exhaust passages 2 and 3 merge into one downstream of both the turbines 5 and 7, and are connected to a silencer (not shown).

Further, the intake passage 9 is divided into two downstream of an air cleaner (not shown), and the blower 1l of the primary turbocharger 4 is located in the middle of the first branch passage 10, and the second branch passage 12 is located in the middle of the first branch passage 10. A blower 13 of the secondary turbocharger 6 is disposed in the middle. These branch passages IO, 12 are shaped so as to face each other at the branch part and extend substantially in a straight line on both sides. In addition, the two branch passages 10 and 2 meet again downstream of the respective blowers 11 and 13. Then, an intercooler 14 is disposed in the intake passage 9, which has become one again, and a surge tank 15 is disposed downstream of the intercooler 14, and a throttle valve 16 is disposed between the intercooler 14 and the surge tank 15. ing. In addition, the downstream end of the intake vent branches out to become two independent intake passages 17 and 18 corresponding to each air passage of the engine l,
It is connected to each intake boat (not shown). Fuel injection valves 19 and 20 are disposed in each of these independent intake passages l7 and 18, respectively.

Upstream of the intake passage 9, an air flow meter 21 is provided upstream of the branch of the first and second branch passages 10 and 12 to detect the amount of intake air.

The two exhaust passages 2 and 3 are communicated with each other by a relatively small diameter communication passage 22 upstream of the primary turbocharger 4 and the secondary turbocharger 6. The exhaust passage 3 in which the turbine 7 of the secondary turbocharger 6 is disposed is provided with an exhaust force/isolation valve 23 immediately downstream of the opening position of the communication passage 22. Further, a bypass passage 25 is formed that extends from the middle of the communication passage 22 and communicates with the combined air wandering device 24 downstream of the turbines 5 and 7. A diaphragm type actuator 26 is linked to the bypass passage 25. A waste gate valve 27 is provided. Then, a leak passage 28 is formed which communicates the upstream part of the waste gate valve 27 of the Ibus passage 25 with the downstream part of the exhaust cut valve 23 of the exhaust passage 3 connected to the turbine 7 of the secondary turbo supercharger 6,
The leakage passage v828 is provided with an exhaust leakage valve 30 linked to a diaphragm type actuator 29.

The exhaust cut valve 23 is linked to a diaphragm type actuator 3l. On the other hand, an intake cut valve 32 is disposed downstream of the blower 13 in the branch passage 12 in which the blower l3 of the secondary turbocharger 6 is disposed. This intake cut valve 32 is composed of a butterfly valve,
It is also linked to a diaphragm type actuator 33. In addition, this secondary side branch passage l2
In this case, the relief passage 3 is installed so as to bypass the blower l3.
4, and a diaphragm type intake relief valve 35 is discharged into the relief passage 34.

The pressure chamber of the diaphragm actuator 29 that operates the exhaust leak valve 30 is communicated via a conduit 36 with the downstream side of the blower 1l of the branch passage 10 from which the blower 11 of the primary turbocharger 4 is discharged. ing. When the pressure downstream of the blower 1l exceeds a predetermined level, the actuator 29 is actuated to open the exhaust leakage valve 30, thereby allowing a small amount of exhaust gas to pass through the bypass passage 28 while the exhaust cut valve 23 is closed. It flows and is supplied to the turbine 7 of the secondary turbocharger 6. Therefore, the secondary turbo supercharger 6 starts rotating before the exhaust cut valve 23 opens. During this time, since the intake relief valve is open as will be described later, the rotation of the secondary turbo supercharger 6 increases, the transient response when the exhaust cut valve opens is improved, and the torque shock is alleviated.

The pressure chamber of the actuator 33 that operates the intake cut valve 32 is connected to an electromagnetic solenoid type three-way valve 38 via a conduit 37.
connected to the output boat.

The actuator 361 that operates the exhaust cut valve 23 is connected to the electromagnetic solenoid type three-way valve 40 through a conduit 39.
connected to the output port of the Further, a pressure chamber of an actuator 41 that operates the intake relief valve 35 is connected to an output port of an electromagnetic solenoid type three-way valve 43 through a conduit 42 .

The intake relief valve 35 keeps the relief passage 34 open until a predetermined time before the exhaust cut valve 23 and the intake cut valve 32 open, as will be described later. And, thereby,
When the secondary turbo supercharger 6 is pre-rotated by the exhaust gas flowing through the leak passage 28, the pressure upstream of the intake cut valve 32 is prevented from rising and entering the surging region, and the rotation of the blower 13 is increased. .

Further, the actuator 26 that operates the waste gate valve 27 is connected to an output port of an electromagnetic solenoid type three-way valve 45 through a conduit 44 .

The four electromagnetic solenoid type three-way valves 38, 40, 43,
45 is controlled by a control unit 46 configured using a microcomputer. In addition to the engine speed R1 and intake air fiQ, detection signals such as throttle opening TV○, boost pressure P1 downstream of the blower 11 of the primary turbocharger 4, and overall boost pressure P3 are input to the control unit 46. Based on these, control as described below is performed.

One input port of the electromagnetic solenoid type three-way valve 38 for controlling the intake cut valve 32 is connected to a negative pressure tank 48 via a conduit 47, and the other input port is connected to a differential pressure detection valve (described later) via a dedicated pipe 49. 50 output ports 70. Intake negative pressure downstream of the throttle valve 16 is introduced into the negative pressure tank 48 via a check valve 5l. Further, one input port of the electromagnetic solenoid three-way valve 40 for controlling the exhaust cut valve 23 is open to the atmosphere, and the other input port is connected to the negative pressure tank 48 via a conduit 52. It is connected to the conduit 47 mentioned above. On the other hand, one input port of the electromagnetic solenoid three-way valve 43 for controlling the intake IJ IJ-F valve 35 is connected to the negative pressure tank 48 via a conduit 53, and the other input port is open to the atmosphere. There is. Also, waste gate valve 27
One input port of the electromagnetic solenoid type three-way valve 45 for control is open to the atmosphere, and the other input port is connected via a conduit 54 to the conduit 36 that communicates with the downstream side of the primary blower 11. .

As shown in FIG. 2, the differential pressure detection valve 150 has three chambers 64, 65, 66 formed within its casing 61 by two first and second diaphragms 62, 63.
It is divided into. A first chamber 64 on one end side thereof
A first input port 67 is opened therein, and a compression spring 68 is disposed between the inner surface of the end portion of the casing 61 and the first diaphragm 62 . Also, the second
A second input boat 69 is opened in the chamber 65, and the third chamber 66 at the other end has an output port 70 in the center of the end wall of the casing 6l, and an atmosphere release port 7l in the side wall. It is opened. A valve body 72 is fixed to the diaphragm 62 and extends through the second diaphragm 63 and toward the output port 70 of the third chamber 66 .

The l-th input port 67 is connected to the downstream side of the intake cut valve 32 by a conduit 73, as shown in FIG. is introduced into the first chamber 64. Also, the second
The input port 69 of the intake cut valve 3 is connected to the intake cut valve 3 by a conduit 74.
Therefore, when the intake cut valve 32 is closed, the pressure P2 on the upstream side of the intake cut valve 32 is introduced. Both input ports 67, 6
When the difference between the pressures Pi and P2 introduced from 9 is equal to or greater than a predetermined value, the valve body 72 opens the output port 7o. This output port 70 is connected via a conduit 49 to one of the input ports of the electromagnetic solenoid type three-way valve 38 for controlling the intake force 71 and the valve 32. Therefore, with the three-way valve 38 communicating the conduit 37 connected to the pressure chamber of the actuator 33 for operating the intake valve 32 with the conduit 49 connected to the output port of the differential pressure detection valve 50, the differential pressure P2P1 is maintained at a predetermined level. When the value becomes larger than this value, the atmosphere is introduced into the actuator 33 and the intake cut valve 32 is opened. Also,
When the three-way valve 38 connects the conduit 37 on the actuator 33 side to the conduit 47 connecting the negative pressure tank 48, negative pressure is supplied to the actuator 33 and the intake cut valve 32 is closed.

On the other hand, in the exhaust cut valve 23, a three-way valve 40 for controlling the exhaust cut valve 23 connects a conduit 39 connected to a pressure chamber of an actuator 3l for operating the exhaust cut valve 23 to a negative pressure tank 48.
When connected to the conduit 52 on the side, it is closed by supplying negative pressure to the actuator. Further, when the three-way valve 40 opens the conduit 39 on the output side to the atmosphere,
The exhaust cut valve 23 is opened and the secondary turbo supercharger 6
Supercharging is performed by

FIG. 3 is a control map showing the open/close states of the intake cut valve 32, the exhaust cut valve 23, the intake relief valve 35, and the waste gate valve 27, together with the open/close state of the exhaust leak valve 3o. This map is stored in advance in the control unit 46, and the four electromagnetic solenoid type three-way valves 38, 40, 43, and 45 are controlled based on this.

In a region where the engine speed R is low or the intake air amount Q is small, the intake relief valve 35 is open, and the secondary turbocharger 60 is pre-rotated by opening the exhaust leakage valve 30. Then, when the engine speed reaches R2 or the intake air amount reaches the line Q2, the intake relief valve 35 is closed, and after that, until the exhaust cut valve 23 is opened, the downstream side of the blower l3 of the secondary turbo supercharger 6 is Pressure increases. When the line Q4-R4 is reached, the exhaust cut valve 23 opens, and then the Q4-R4 line is reached.
When the 6-R6 line is reached and the intake cut valve 32 opens, supercharging by the secondary turbo supercharger 6 starts.
Primary turbo supercharger 4 is connected to this Q6-R6 line.
and the secondary turbo supercharger 6 enter the supercharging region.

Intake cut valve 32, exhaust cut valve 23, and intake IJ
The IJ-F valve 35 has a slight hysteresis from the high flow rate side to the low flow rate side, that is, the Q
It is switched on each line of 5-R5, Q3-R3, and Ql-R1.

Note that the bent portions of each of these lines are on the so-called no-load line or low-load line.

The waste gate valve 27 is opened when the engine speed R and the throttle opening TVO are at least a predetermined value, and when the supercharging pressure P1 downstream of the blower 11 of the primary turbocharger 4 is at least a predetermined value.

This waste gate valve 27 is also outside the control of the map shown in FIG. Even if the conditions are met, it can be closed. The closing control of the waste gate valve 27 at the time of switching the operation of the supercharger is canceled when the total supercharging pressure P3 exceeds a predetermined value that is larger than the above-mentioned predetermined value for the supercharging pressure P1. This prevents the supercharging pressure from decreasing when switching the operation of the supercharger.

Furthermore, during acceleration, as shown in FIG. 4, by shifting the opening timing of the exhaust cut valve 23 and intake cut valve 32 to the high flow rate and high rotation side compared to the steady state, the operation of the secondary turbo supercharger 6 is controlled. Switching to supercharging region is delayed. This prevents the boost pressure from decreasing, which might occur if the timing is not changed. However, the closing timing of the intake relief valve 35 remains unchanged.

The above-mentioned judgment as to whether it is accelerating is made based on whether the rate of change of the throttle opening TVO is greater than or equal to a predetermined value, but if the throttle opening sensor is malfunctioning, the engine may be constantly accelerating even in a steady state of operation. As a result, as described above, the secondary turbo supercharger 6
By delaying the switching to the supercharging region of operation, the primary turbocharger 4 may become overloaded, which may reduce the reliability of the primary turbocharger 4.

Therefore, in this embodiment, when the control unit 46 that receives the signal indicating the throttle opening TVO determines that the throttle opening sensor is malfunctioning based on the signal, the exhaust cut valve 23 and the intake cut valve 32
Opening timing, i.e. primary turbo supercharger 4
The timing of activation is set to steady state. Fix it to that of the state. That is, when the sensor is out of service, the switching line for operating the secondary turbo supercharger 6 is fixed to the switching line on the low intake region side among the switching lines used, and the primary turbo supercharger 4 is switched on. The reliability of the primary turbocharger 4 is ensured by preventing overload.

Next, a specific example of the control of the intake cut valve 32, the exhaust cut valve 23, the intake relief valve 35, and the waste gate valve 27 by the control unit 46 will be explained with reference to the flowcharts of FIGS. 5 and 6. do. Note that in the flowcharts of FIGS. 5 and 6 above, S indicates each step. Also, F
is a flag, and the shape of this flag! ! ! (F-■~6
〉 means as shown in Fig. 3, and the previous transition is a transition from the high flow rate side to the low flow rate side of the Ql-Rl line (F = 1) and the Q2-R2 line, respectively. is the transition from the low flow rate side to the high flow rate side (F = 2),
This is the transition from the high flow rate side to the low flow rate side of the Q3-R3 line (F = 3), the transition from the low flow side to the high flow rate side of the Q4R4 line (F = 4), and the high flow rate of the Q5-R5 line. It is a transition from the flow rate side to the low flow rate side (F=5), Q6
- This is the transition from the low flow rate side to the high flow rate side of the R6 line (
F=6). The steps will be explained below.

First, in FIG. 5, the process starts and initialization is performed in S1. At this time, flag F is set to 1.

Next, in S2, the intake air amount Q and the engine speed R are input. Then, in S3, the Masop values Q1 to Q6, Rl. −
Read R6.

Next, in S4, it is determined whether the throttle sensor is normal, and only when this determination is YES, in S5, the acceleration is determined depending on whether the rate of change dTVO/dt of the throttle opening TV Make a judgment. If dTV○/dt is greater than 8 and it is during acceleration, then in step 86, Q4, Q6, R4, and R6 corresponding to the opening timings of the exhaust cut valve 23 and the intake cut valve 32 are set to predetermined values ΔQ4, respectively.
Increase correction is made by ΔQ6, ΔR4, and ΔR6. If it is not during acceleration, the process moves to S7.

If the judgment in S4 is NO and the throttle sensor is out of order, or if the judgment in S5 is NO and the state is not in an acceleration state but in a steady state, in S7, Q4, Q6, R4, R
6 are set to Q4, Q6, R4, and R6, respectively.

Next, in S8, it is determined whether the flag F is 1, that is, whether the previous transition was from the high flow rate side to the low flow rate side of the Ql-Rl line. Note that initially F=
1, and therefore, this determination is YES.

If F=1, then in S9 it is determined whether the current intake air amount Q is larger than Q2, and if NO, then in SIO it is determined whether the current engine speed R is larger than R2. judge. Then, the judgment of S9 is YES or 31
If the determination of 0 is YES, the flag F is set to 2 in Sll, and the intake relief valve 35 is controlled to be closed in S12 (positive pressure is introduced into the actuator). Also, S9
If both of the determinations in 310 and 310 are NO, the process directly returns.

When the determination in S8 is NO, in S13 it is checked whether the flag F is set to an even number, that is, whether the previous transition in the line was from a low flow rate side to a high flow rate side, or from a high flow rate side to a low flow rate side. Determine whether there is a transition.

When this determination is YES, it is determined in 314 whether F=2, that is, whether the previous transition was from the low flow rate side to the high flow rate side of the Q2-R2 line, and if F=2, Moving on to 315.

In 315, it is determined whether the current intake air fiQ is larger than Q4, and if NO, then in 316 it is determined whether the current engine rotation speed R is larger than R4. And S
If either the determination in S15 or S16 is YES, the flag F is set to 4 in 317, and the exhaust cut valve 23 is controlled to be opened in S18 (negative pressure is introduced into the actuator).

Further, when both the determinations in 315 and 316 are NO, it is determined in Sl9 whether the current intake air amount Q is smaller than Ql.

If the determination at Sl9 is YES, it is determined at S20 whether the current engine rotation speed R is smaller than R1. and,
If this determination is YES, the flag F is set to 1 in S22, and the intake/air relief valve 35 is controlled to be opened in S22 (negative pressure is introduced into the actuator). Also, S19
If the determinations at 320 and 320 are both No, the process directly returns.

When the determination in step 314 is NO, it is checked in S23 whether the flag F is 4, that is, if the previous transition was 04-R.
4, it is determined whether the transition was from the low flow rate side to the high flow rate side. If this determination is YES, it is determined at 324 whether the current intake air amount Q is greater than Q6, and if this determination is NO, then it is determined at 825 whether the current engine rotation speed R is greater than R6. do. And S24 or S25
If any of the above is YES, the flag F is set to 6 in 326, and the intake cut valve 32 is controlled to be opened in 327 (the actuator is communicated with the differential pressure detection valve side). Further, when the determination in S25 is NO, it is determined in 328 whether the intake air amount Q is smaller than Q3, and if YES, S2
In step 9, it is determined whether R is smaller than R3. And S29
If the determination is YES, the flag F is set to 3 in S30, and the exhaust cut valve 23 is controlled to be closed in S31 (atmospheric air is introduced into the actuator).

When the determination in S23 is NO, the flag F=6, which means that the previous transition was from the low flow rate side to the high flow rate side of the Q6-R6 line, and in this case, in S32, the current intake air is Determine whether the quantity Q is smaller than Q5, YES
If so, then it is determined in S32 whether R is smaller than R5 this time. If YES, the flag F is set to 5 in S34, and the intake cut valve 32 is controlled to be closed in S335 (negative pressure is introduced into the actuator).

Further, if the determination in either 332 or S33 is N○, the process directly returns.

Next, the control when the determination at Sl3 is NO will be explained with reference to the flowchart of FIG.

When the determination in S13 is NO, it is determined in S41 whether the flag is F3, that is, whether the previous transition was from the high flow rate side to the low flow rate side of the Q3R3 line.

If YES, then 342 and Q this time are Q.
It is determined whether R is larger than 1, and if YES, it is determined in S43 whether R is smaller than Rl this time. If YES, flag F is set to 1 in S44, and then 34
5, the exhaust cut valve 23 is controlled to open.

If either of the determinations in S42 or S43 above is NO, it is determined whether Q is larger than Q4, and if NO,
In S47, it is determined whether R is greater than R7. If the determination in either S46 or 347 is YES, 7 lag F is set to 4 in 348, and then S4
If NO at 9, return directly.

When the judgment in S41 is NO, it means that the flag F=5, so in this case, it is judged in 350 whether Q is smaller than Q3, and if YES, in S51, R is smaller than R3.
Determine whether it is smaller.

If the determination in 351 is YES, the flag F is set to 3 in S52, and then the exhaust cut valve 23 is set in S53.
Control closing.

If the determination in either 550 or 551 is N○, it is determined in 354 whether Q is greater than Q6, and if this determination is NO, then it is determined in S55 whether R is greater than R6. If the determination in either 354 or S55 is YES, the flag F is set to 6 in S56, and then, in 357, control is performed to open the intake cut valve 32.

On the other hand, when the determination at 355 is NO, the process returns directly.

In the embodiments described above, the conditions for starting the operation of the secondary turbocharger 6 are switched between a steady state and an acceleration state. However, as shown in FIG.
The gear ratio is detected by a gear position sensor, and the switching line corresponding to the detected gear ratio is used to switch between the secondary and secondary gears. The start of operation of the turbocharger 6 may also be controlled. In this case, when it is determined that the gear position sensor is malfunctioning,
The switching line is fixed to the switching line for the third speed, which is the lowest suction region side, and the start of operation of the secondary turbo supercharger 6 is controlled.

Furthermore, in the above embodiment, the switching line for switching the operation of the secondary turbocharger 6 was explained as being determined substantially by the intake air amount and the engine speed, but A value determined by a number may also be used.

As described above, according to the present invention, failure of the detection means for detecting a specific condition for changing the switching condition from the operation of only the primary supercharger to the operation of the secondary supercharger in addition to the primary supercharger is detected. When it is determined, the switching condition is fixed to the low intake region side, so that overloading the primary turbocharger and lowering its reliability as described above is prevented.

[Brief explanation of drawings]

FIG. 1 is an overall system diagram of a supercharged engine incorporating a control device according to an embodiment of the present invention, FIG. 2 is a sectional view of a differential pressure detection valve in the above embodiment, and FIGS. 3 and 4. are control characteristic diagrams for the above embodiment, respectively. Figures 5 and 6 are flowcharts for executing the control of the above embodiment. Figure 7 is for switching the operation of the secondary turbo supercharger. It is a map diagram showing other conditions. 1 Engine 4 Primary turbo supercharger 6 Secondary turbo supercharger 23 Exhaust cut valve 3 1, 32 34 35 38, 46 3 3, 41 Intake cut relief valve Intake relief valve 40, 43 Electromagnetic solenoid control unit actuated three-way valve

Claims (1)

[Claims] In a control system for a supercharged engine that has a primary supercharger that operates all the time and a secondary supercharger that operates in a high intake region, it is possible to
comprising a changing means for changing a condition for switching to operation of a secondary supercharger in addition to the primary supercharger when a specific condition is satisfied, and a determining means for determining a failure of the detection means for detecting the specific condition, A control device for a supercharged engine, characterized in that when the determining means determines that the detecting means has failed, the switching condition by the changing means is fixed to a low intake region side.