Control device

Abstract

To provide a controller capable of suppressing damage to a supercharger.SOLUTION: A controller of a supercharger comprises a turbine arranged in an exhaust passage of an internal combustion engine, and a compressor arranged in an intake passage of the internal combustion engine and driven by the turbine. The controller has: a control unit that controls the turbine so that a boost pressure of the supercharger in the intake passage is equal to or lower than an allowable value; a first calculation unit that calculates an amount of decrease in compressor efficiency of the compressor; and a second calculation unit that calculates the allowable value from an intake volume of the intake passage in accordance with the amount of decrease.SELECTED DRAWING: Figure 4

Description

[Technical Field]

[0001] The present invention relates to a control device. [Background technology]

[0002] For example, Patent Document 1 describes that in a supercharger equipped with a compressor and a turbine disposed in the intake and exhaust passages of an engine, respectively, an actuator is controlled so that the supercharging pressure in the intake passage is equal to or lower than the allowable supercharging pressure corresponding to the allowable upper limit rotational speed of the turbine, in order to prevent damage caused by an excessively high turbine rotational speed. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2016-151254 Summary of the Invention [Problem to be solved by the invention]

[0004] However, if oil mist from the engine's exhaust system gets mixed into the intake air and adheres to the compressor housing, forming deposits, the compressor's operating characteristics will change over time, reducing the allowable boost pressure, which could result in the boost pressure exceeding the allowable boost pressure.

[0005] The present invention has been made in view of the above-mentioned problems, and has an object to provide a control device that can suppress damage to a turbocharger. [Means for solving the problem]

[0006] The control device of the present invention is a control device for a turbocharger including a turbine disposed in an exhaust passage of an internal combustion engine and a compressor disposed in an intake passage of the internal combustion engine and driven by the turbine, the control device including: a control unit that controls the turbine so that a supercharging pressure of the turbocharger in the intake passage becomes equal to or less than a tolerance value; and a first calculation unit that calculates a decrease amount of compressor efficiency of the compressor. When the intake air amount of the intake passage is constant, the allowable value decreases as the compressor efficiency decreases, based on a correlation: The amount of decrease The compressor efficiency is reduced by ,before Record Air volume In response to and a second calculation unit that calculates the tolerance.

[0007] In the above control device, the first calculation unit may calculate the compressor efficiency at time intervals and calculate the amount of decrease from a change in the compressor efficiency over time.

[0008] In the above control device, the first calculation unit may calculate the amount of decrease from pressure and temperature in the intake passage on the upstream side and downstream side of the compressor.

[0009] In the above control device, the first calculation unit may calculate the amount of decrease from a change in a control amount of the turbine.

[0010] In the control device, the second calculation unit The aforementioned Based on data showing the correlation, the amount of decrease The intake air at the compressor efficiency reduced by amount In response to The tolerance may be calculated. [Effects of the Invention]

[0011] According to the present invention, damage to the turbocharger can be suppressed. [Brief explanation of the drawings]

[0012] [Figure 1] FIG. 1 is a configuration diagram showing an example of a vehicle system. [Figure 2] FIG. 2 is a configuration diagram showing an example of an ECU (Electronic Control Unit). [Figure 3] FIG. 3 is a diagram showing an example of the operating characteristics of the supercharger. [Figure 4] FIG. 4 is a flowchart showing an example of a turbine control process. [Figure 5] FIG. 5 is a flowchart showing an example of a process for determining a decrease in compressor efficiency. DETAILED DESCRIPTION OF THE INVENTION

[0013] (Vehicle system configuration) 1 is a configuration diagram showing an example of a system of a vehicle 9. The vehicle 9 is, by way of example, a gasoline vehicle, but is not limited to this and may be a diesel vehicle, a hybrid vehicle, an electric vehicle, or the like.

[0014] The vehicle 9 has an ECU (Electronic Control Unit) 1, an engine 2, a turbocharger 3, an air cleaner 60, an intercooler 61, a throttle valve 62, a catalytic converter 63, an intake passage 20, an exhaust passage 21, a bypass passage 22, an EGR (Exhaust Gas Recirculation) passage 23, a wastegate valve (WG valve) 50, and an actuator 51. In Fig. 1, dashed arrows indicate control signals from the ECU 1 or detection signals from sensors.

[0015] The engine 2 is an example of an internal combustion engine. The engine 2 takes in air through an intake passage 20 and mixes it with gasoline. The engine 2 burns the mixture and discharges it through an exhaust passage 21. The EGR passage 23 connects the intake passage 20 and the exhaust passage 21, and recirculates a portion of the exhaust gas back into the intake passage 20. Note that the engine 2 is a gasoline engine, but it may also be a diesel engine.

[0016] The intake passage 20 is provided with, in this order from the upstream side, an air cleaner 60, an intercooler 61, and a throttle valve 62. The exhaust passage 21 is provided with a catalytic converter 63.

[0017] The supercharger 3 is, for example, a turbocharger, and includes a compressor 30 and a turbine 31 connected to each other via a turbine shaft 32. The compressor 30 is disposed downstream of an air cleaner 60 in the intake passage 20 and upstream of an intercooler 61. The turbine 31 is disposed upstream of a catalytic converter 63.

[0018] The turbine 31 is rotated by the exhaust air flowing through the exhaust passage 21. The compressor 30 is driven by the rotation of the turbine 31. As a result, the compressor 30 compresses the air.

[0019] A bypass passage 22 that bypasses the turbine 31 is connected to the exhaust passage 21. A WG valve 50 is provided in the bypass passage 22 to adjust the flow rate of exhaust gas flowing from the engine 2 into the bypass passage 22. An actuator 51 adjusts the opening of the WG valve 50. The flow rate of exhaust gas flowing into the bypass passage 22 changes depending on the opening of the WG valve 50, and therefore the exhaust gas flowing into the turbine 31 also changes accordingly. This controls the rotation speed of the turbine 31.

[0020] The vehicle 9 also has an inlet pressure sensor 40, an inlet temperature sensor 41, an air flow meter 42, an outlet pressure sensor 43, an outlet temperature sensor 44, an intake pressure sensor 45, an atmospheric pressure sensor 46, an accelerator opening sensor 47, and a crank position sensor 48. The ECU 1 collects the detected values ​​of the inlet pressure sensor 40, the inlet temperature sensor 41, the air flow meter 42, the outlet pressure sensor 43, the outlet temperature sensor 44, the intake pressure sensor 45, the atmospheric pressure sensor 46, the accelerator opening sensor 47, and the crank position sensor 48, for example, at regular intervals.

[0021] The inlet pressure sensor 40, the inlet temperature sensor 41, and the air flow meter 42 are provided in the intake passage 20 on the upstream side of the compressor 30. The inlet pressure sensor 40 detects the pressure of the air on the inlet side of the compressor 30, and the inlet temperature sensor 41 detects the temperature of the air on the inlet side of the compressor 30. The air flow meter 42 detects the flow rate per unit time of air flowing through the intake passage 20 on the upstream side of the compressor 30.

[0022] The outlet pressure sensor 43 and the outlet temperature sensor 44 are provided in the intake passage 20 downstream of the compressor 30. The outlet pressure sensor 43 detects the pressure of the air on the outlet side of the compressor 30, and the outlet temperature sensor 44 detects the temperature of the air on the outlet side of the compressor 30.

[0023] The intake pressure sensor 45 is provided in the intake passage 20 downstream of the throttle valve 62. The intake pressure sensor 45 detects the supercharging pressure of the air taken into the engine 2.

[0024] The atmospheric pressure sensor 46 detects the atmospheric pressure around the vehicle 9. The accelerator pedal position sensor 47 detects the position of an accelerator pedal (not shown). The crank position sensor 48 detects the rotation angle of a crankshaft (not shown) of the engine 2.

[0025] The ECU 1 is an example of a control device. The ECU 1 is a computer such as a microcontroller. The ECU 1 determines a target torque of the engine 2 in response to the accelerator position sensor 47 and the like, and controls the ignition timing and fuel injection amount of the engine 2, the opening of the throttle valve 62, and the like based on the target torque.

[0026] Furthermore, the ECU 1 controls the turbine 31 so that the supercharging pressure of the supercharger 3 is equal to or less than an allowable value, thereby preventing the rotation speed of the turbine 31 from becoming excessively high and damaging the supercharger 3.

[0027] (ECU configuration) 2 is a configuration diagram showing an example of the ECU 1. The ECU 1 has a CPU (Central Processing Unit) 10, a ROM (Read Only Memory) 11, a RAM (Random Access Memory) 12, a storage memory 13, and an input / output port 14. The CPU 10 is electrically connected to the ROM 11, the RAM 12, the storage memory 13, and the input / output port 14 via a bus 19 so as to be able to input and output signals among them.

[0028] The ROM 11 stores a program that drives the CPU 10. The RAM 12 functions as a working memory for the CPU 10. The input / output port 14 processes input and output of signals between the CPU 10 and an actuator 51, an inlet pressure sensor 40, an inlet temperature sensor 41, an air flow meter 42, an outlet pressure sensor 43, an outlet temperature sensor 44, an intake pressure sensor 45, an atmospheric pressure sensor 46, an accelerator opening sensor 47, a crank position sensor 48, and the like.

[0029] When the CPU 10 reads a program from the ROM 11, it functions as an operation control unit 100, a turbine control unit 101, a compressor efficiency calculation unit 102, and an allowable boost pressure calculation unit 103. The operation control unit 100 instructs the turbine control unit 101, the compressor efficiency calculation unit 102, and the allowable boost pressure calculation unit 103 to operate in accordance with a predetermined sequence. In addition, the storage memory 13 holds allowable boost pressure map data 130.

[0030] The turbine control unit 101 is an example of a control unit. The turbine control unit 101 controls the turbine 31 so that the boost pressure of the turbocharger 3 is equal to or lower than an allowable value. Specifically, the turbine control unit 101 calculates a required boost pressure according to the driving state of the engine 2, for example, based on the detected values ​​of the accelerator opening sensor 47 and the crank position sensor 48. The turbine control unit 101 compares the required boost pressure with an allowable boost pressure according to the allowable upper limit rotation speed of the turbine 31, and determines a target boost pressure to be used as a control target based on the comparison result. If the required boost pressure is greater than the allowable boost pressure, the target boost pressure is the allowable boost pressure, and if the required boost pressure is equal to or less than the allowable boost pressure, the target boost pressure is the required boost pressure. The turbine control unit 101 controls the actuator 51 based on the difference between the target boost pressure and the detected value of the intake pressure sensor.

[0031] In this way, the turbine control unit 101 controls the turbine 31 by determining the control amount of the actuator 51 based on the supercharging pressure of the supercharger 3. Therefore, a rotation speed sensor for detecting the rotation speed of the turbine 31 is not required.

[0032] The compressor efficiency calculation unit 102 is an example of a first calculation unit. The compressor efficiency calculation unit 102 calculates the amount of decrease in compressor efficiency of the compressor 30. For example, if oil mist contained in the exhaust gas of the engine 2 mixes with the intake air and adheres to the compressor 30 to form deposits, the compressor efficiency will decrease. Note that a means for calculating the amount of decrease in compressor efficiency will be described later.

[0033] The allowable boost pressure calculation unit 103 is an example of a second calculation unit. The allowable boost pressure calculation unit 103 calculates the allowable boost pressure from the corrected intake air amount of the intake passage 20 according to the amount of decrease in compressor efficiency. The allowable boost pressure is an example of an allowable value of the boost pressure according to the upper limit of the rotation speed of the turbine 31.

[0034] For example, the allowable boost pressure calculation unit 103 calculates the allowable boost pressure based on the allowable boost pressure map data 130. The allowable boost pressure map data 130 indicates, for example, the correlation between the corrected air flow rate (kg / s) and the allowable boost pressure (Pa) for each compressor efficiency. The allowable boost pressure calculation unit 103 calculates the allowable boost pressure according to the corrected air flow rate. Here, the corrected air flow rate is a value obtained by correcting the air flow rate detected by the air flow meter 42 based on the air temperature detected by the inlet temperature sensor 41 and the atmospheric pressure detected by the atmospheric pressure sensor 46.

[0035] As an example, symbol Ga indicates the change characteristic of the allowable boost pressure when the compressor efficiency is high ("high"), symbol Gb indicates the change characteristic of the allowable boost pressure when the compressor efficiency is medium ("medium"), and symbol Gc indicates the change characteristic of the allowable boost pressure when the compressor efficiency is low ("low"). As indicated by the dotted arrow, when the corrected air flow rate is constant, the allowable boost pressure decreases as the compressor efficiency decreases.

[0036] For this reason, if the allowable boost pressure calculation unit 103 calculates the allowable boost pressure according to the corrected air flow rate based only on the correlation corresponding to a "large" compressor efficiency, for example, when the compressor efficiency drops to "medium" or "small," it will calculate an inappropriate allowable boost pressure that exceeds the appropriate value. For this reason, the turbine control unit 101 controls the turbine 31 so that the boost pressure is equal to or lower than the inappropriate allowable boost pressure, which may cause the boost pressure to exceed the allowable boost pressure and damage the turbocharger 3.

[0037] Therefore, the allowable boost pressure calculation unit 103 calculates an appropriate allowable boost pressure based on a correlation corresponding to the reduced compressor efficiency, depending on the amount of reduction in compressor efficiency calculated by the compressor efficiency calculation unit 102. For example, if the compressor efficiency drops from "high" to "medium," the allowable boost pressure calculation unit 103 calculates the allowable boost pressure from the corrected air flow rate based on the correlation of symbol Gb. Therefore, the ECU 1 can prevent damage to the supercharger 3 by using an appropriate allowable boost pressure. The corrected intake air volume is an example of the intake air volume of the intake passage 20.

[0038] Furthermore, the allowable boost pressure calculation unit 103 calculates the allowable boost pressure according to the amount of decrease in compressor efficiency based on allowable boost pressure map data 130, which indicates the correlation between compressor efficiency and allowable boost pressure. Therefore, the load of the calculation process for the allowable boost pressure can be reduced compared to, for example, when the allowable boost pressure is calculated using a predetermined calculation formula from the amount of decrease in compressor efficiency.

[0039] (Calculation of the decrease in compressor efficiency) The compressor efficiency calculation unit 102 calculates the compressor efficiency at time intervals and calculates the amount of decrease in the compressor efficiency from the change in the compressor efficiency over time. Therefore, the compressor efficiency calculation unit 102 can calculate the amount of decrease in the compressor efficiency with higher accuracy than when calculating the compressor efficiency using map data, for example.

[0040] ηc=ψ / λ (1) λ=Cp(Tout-Tin) / U 2 ···(2) ψ=Cp{(Pout / Pin) (κ―1) / κ -1} / U 2 ···(3) U=Ncrr·D·π / 60 ···(4) ηc=Tin{(Pout / Pin) (κ―1) / κ -1} / (Tout-Tin) (5)

[0041] The compressor efficiency ηc (%) is calculated, for example, from the work coefficient λ and pressure coefficient ψ of the compressor 30 using the above formula (1). The work coefficient λ is calculated, for example, from the constant pressure specific heat Cp (J / Kg·K), the outlet temperature Tout (K) and inlet temperature Tin (K) in the intake passage 20, and the peripheral speed U (m / s) of the impeller of the compressor 30 using the above formula (2). The outlet temperature Tout and the inlet temperature Tin are obtained from the detection values ​​of the outlet temperature sensor 44 and the inlet temperature sensor 41, respectively. The constant pressure specific heat Cp is a constant. The outlet temperature Tout is the temperature downstream of the compressor 30, and the inlet temperature Tin is the temperature upstream of the compressor 30.

[0042] The pressure coefficient ψ is, for example, a constant pressure specific heat Cp and an outlet pressure Pout ( Pa ) and inlet pressure Pin( Pa ), the specific heat ratio κ, and the peripheral speed U of the impeller of the compressor 30, using the above formula (3). The outlet pressure Pout and the inlet pressure Pin are obtained from the detection values ​​of the outlet pressure sensor 43 and the inlet pressure sensor 40, respectively. The specific heat ratio κ is a constant. Note that the outlet pressure Pout is the pressure downstream of the compressor 30, and the inlet pressure Pin is the pressure upstream of the compressor 30.

[0043] The peripheral speed U is calculated, for example, from the corrected rotation speed Ncrr (rpm) of the compressor 30, the diameter D (m) of the impeller of the compressor 30, and pi (π) using the above formula (4). The corrected rotation speed Ncrr is, for example, a value (N×(Tref / Tin)) obtained by correcting the rotation speed N of the compressor 30 using the reference temperature Tref and the inlet temperature Tin. 1 / 2) where the reference temperature Tref is a constant determined by the design.

[0044] For example, if a turbo speed sensor is provided in the supercharger 3, the rotation speed N of the compressor 30 is acquired from the detected value of the turbo speed sensor. In this case, the compressor efficiency calculation unit 102 can calculate the compressor efficiency ηc using equations (1) to (4).

[0045] However, if the turbocharger 3 is not provided with a turbo speed sensor, the compressor efficiency calculation unit 102 cannot acquire the rotation speed N of the compressor 30. Therefore, the compressor efficiency calculation unit 102 calculates the compressor efficiency ηc using the outlet temperature Tout, inlet temperature Tin, outlet pressure Pout, and inlet pressure Pin in the intake passage 20, and the specific heat ratio κ, using the above formula (5). Here, formula (5) is obtained from formulas (1) to (3).

[0046] The compressor efficiency calculation unit 102 calculates the amount of decrease in the compressor efficiency ηc from the change in the compressor efficiency ηc when the operating point at which the supercharger 3 is operated is the same.

[0047] 3 is a diagram showing an example of the operating characteristics of the turbocharger 3. The horizontal axis indicates the corrected air flow rate (kg / s), and the vertical axis indicates the pressure ratio. The corrected air flow rate is a value obtained by correcting the air flow rate M detected by the air flow meter 42 using the inlet temperature Tin, the inlet pressure Pin, the reference temperature Tref, and the reference pressure Pref (M×(Pref / Pin)×(Tin / Tref) 1 / 2 ) where the reference temperature Tref and the reference pressure Pref are constants according to the design. The pressure ratio is the ratio of the outlet pressure Pout to the inlet pressure Pin (Pout / Pin).

[0048] The operating characteristics are determined for each corrected rotation speed Ncrr of the compressor 30. As an example, the operating characteristics when the corrected rotation speed Ncrr is N1 to N6 are shown. Here, of N1 to N6, N1 is the largest and N6 is the smallest. The larger the corrected rotation speed Ncrr, the higher the corrected air flow rate and pressure ratio.

[0049] Furthermore, the solid line indicates the operating characteristics before the compressor efficiency is reduced, and the dashed line indicates the operating characteristics after the compressor efficiency is reduced. When the compressor efficiency is reduced, the pressure ratio is reduced even if the corrected air flow rate is maintained. For example, when the turbocharger 3 is operating at an operating point P1 corresponding to the corrected rotational speed Ncrr=N2, if the compressor efficiency ηc is reduced, the turbocharger 3 will operate at an operating point P2 which has a lower pressure ratio than the operating point P1. Therefore, the turbine control unit 101 controls the actuator 51 to increase the rotational speed of the compressor 30 so as to compensate for the reduction in the compressor efficiency ηc.

[0050] The compressor efficiency calculation unit 102 calculates the amount of decrease in the compressor efficiency ηc from the outlet temperature Tout, inlet temperature Tin, outlet pressure Pout, and inlet pressure Pin in the intake passage 20. Specifically, the compressor efficiency calculation unit 102 calculates the amount of decrease as the change over time in the compressor efficiency ηc calculated at a certain operating point. This allows the compressor efficiency calculation unit 102 to calculate the amount of decrease in the compressor efficiency ηc with high accuracy in accordance with the state of the intake passage 20.

[0051] Lc=Cp×M×Tin×{(Pout / Pin) (κ―1) / κ -1} / ηc (6)

[0052] The energy Lc required to operate the compressor 30 at a certain operating point is expressed by the above formula (6) using, for example, the constant pressure specific heat Cp, the above-mentioned corrected air flow rate M, the inlet temperature Tin in the intake passage 20, the outlet pressure Pout and the inlet pressure Pin in the intake passage 20, the compressor efficiency ηc, and the specific heat ratio κ. Therefore, the larger the compressor efficiency ηc, the smaller the energy Lc, and vice versa.

[0053] This energy Lc is recovered from the exhaust gas that rotates the turbine 31. For this reason, when the compressor efficiency ηc decreases, the ECU 1 reduces the opening of the WG valve 50 so as to increase the amount of exhaust gas flowing to the turbine 31. For this reason, the control amount of the actuator 51 when operating the compressor 30 at a certain operating point changes according to the compressor efficiency ηc. In other words, the lower the compressor efficiency ηc, the greater the energy Lc required, and therefore the control amount of the actuator 51 changes so as to reduce the opening of the WG valve 50.

[0054] The compressor efficiency calculation unit 102 may calculate the amount of decrease in the compressor efficiency ηc from the control amount of the actuator 51 using the above. In this case, the compressor efficiency calculation unit 102 can calculate the amount of decrease in the compressor efficiency ηc from, for example, a correspondence relationship (map data or calculation formula) between the control amount of the actuator 51 (control amount of the turbine 31) and the compressor efficiency ηc for each operating point. In this way, when the compressor efficiency calculation unit 102 calculates the amount of decrease in the compressor efficiency ηc from a change in the control amount of the turbine 31, the load of the calculation process can be reduced compared to when the compressor efficiency calculation unit 102 calculates the amount of decrease in the compressor efficiency ηc from the inlet pressure Pin and the outlet pressure Pout, and the inlet temperature Tin and the outlet temperature Tout. Note that the means for calculating the compressor efficiency ηc is not limited to the above, and various methods can be used depending on the system of the vehicle 9.

[0055] (ECU operation) 4 is a flowchart showing an example of a control process for the turbine 31. This process is executed, for example, at a fixed interval. First, the turbine control unit 101 collects the detection values ​​of the accelerator opening sensor 47 and the crank position sensor 48 (step St1).

[0056] The turbine control unit 101 calculates a required boost pressure Pr according to the driving state of the engine 2 based on each detected value etc. (step St2). Next, the compressor efficiency calculation unit 102 determines whether the compressor efficiency ηc has decreased (step St3). The process of determining whether the compressor efficiency ηc has decreased will be described later.

[0057] If the compressor efficiency ηc has decreased (Yes in step St3), the allowable boost pressure calculation unit 103 changes the allowable boost pressure map data 130 in accordance with the amount of decrease in the compressor efficiency ηc calculated by the compressor efficiency calculation unit 102 (step St4). Specifically, as described with reference to FIG. 2, the allowable boost pressure calculation unit 103 selects a change characteristic corresponding to the amount of decrease in the compressor efficiency ηc from among the change characteristics of the allowable boost pressures indicated by the symbols Ga to Gc. Next, the allowable boost pressure calculation unit 103 calculates a corrected air flow rate and calculates the allowable boost pressure Pu corresponding to the corrected air flow rate from the allowable boost pressure map data 130 (step St5). On the other hand, if the compressor efficiency ηc has not decreased (No in step St3), the allowable boost pressure map data 130 is not changed, and the processing of step St5 is executed.

[0058] Next, the turbine control unit 101 compares the allowable boost pressure Pu with the required boost pressure Pr (step St6). If Pr>Pu holds (Yes in step St6), the turbine control unit 101 sets the allowable boost pressure Pu to the target boost pressure (step St7). If Pr≦Pu holds (No in step St6), the turbine control unit 101 sets the required boost pressure Pr to the target boost pressure (step St8). As a result, the target boost pressure is suppressed to be equal to or lower than the allowable boost pressure Pu.

[0059] Next, the turbine control unit 101 detects the boost pressure using the intake pressure sensor 45 (step St9). Next, the turbine control unit 101 adjusts the opening of the WG valve 50 by controlling the actuator 51 according to the difference between the detected boost pressure and the target boost pressure (step St10). As a result, exhaust gas according to the target boost pressure flows through the turbine 31. In this manner, the control process for the turbine 31 is executed.

[0060] 5 is a flowchart showing an example of a process for determining whether or not the compressor efficiency has decreased. This process is executed, for example, at regular intervals.

[0061] First, the compressor efficiency calculation unit 102 collects detection values ​​from the inlet pressure sensor 40, the inlet temperature sensor 41, the outlet pressure sensor 43, and the outlet temperature sensor 44 (step St21). Next, the compressor efficiency calculation unit 102 calculates two parameters from the corrected air flow rate, the pressure ratio, and the corrected rotation speed, thereby identifying the operating point in the operating characteristics of the compressor 30, and determines whether the operating point has changed since the previous execution of this process (step St22). If the operating point has changed (No in step St22), the process of step St21 is executed again.

[0062] Furthermore, if the operating point has not changed (Yes in step St22), the compressor efficiency calculation unit 102 calculates the compressor efficiency ηc from each detected value according to the above formula (5) (step St23). Note that, if a turbo speed sensor is provided in the supercharger 3, the compressor efficiency calculation unit 102 may calculate the compressor efficiency ηc from each detected value according to the above formulas (1) to (4). Alternatively, the compressor efficiency calculation unit 102 may calculate the compressor efficiency ηc from the control amount of the actuator 51, as described above. Next, the compressor efficiency calculation unit 102 calculates the amount of change in the compressor efficiency ηc from the calculated value when this process was previously executed (step St24). That is, the amount of change over time in the compressor efficiency ηc is calculated.

[0063] Next, the compressor efficiency calculation unit 102 compares the amount of change over time in the compressor efficiency ηc with a threshold value TH (step St25). If the amount of change over time≦TH holds (No in step St25), the compressor efficiency calculation unit 102 determines that the compressor efficiency ηc has not decreased (step St27). If the amount of change over time>TH holds (Yes in step St25), the compressor efficiency calculation unit 102 determines that the compressor efficiency ηc has decreased (step St26). In this case, the compressor efficiency calculation unit 102 outputs the amount of change over time in the compressor efficiency ηc as the amount of decrease to the allowable boost pressure calculation unit 103. In this manner, the compressor efficiency decrease determination process is executed.

[0064] The above-described embodiment is a preferred example of the present invention, but the present invention is not limited to this and can be modified in various ways without departing from the spirit of the present invention. [Explanation of symbols]

[0065] 1 ECU (control device), 2 engine (internal combustion engine), 3 turbocharger, 20 intake passage, 21 exhaust passage, 30 compressor, 31 turbine, 50 wastegate valve, 51 actuator, 101 turbine control unit (control unit), 102 compressor efficiency calculation unit (first calculation unit), 103 allowable boost pressure calculation unit (second calculation unit), 130 allowable boost pressure map data (data)

Claims

1. A control device for a turbocharger including a turbine disposed in an exhaust passage of an internal combustion engine and a compressor disposed in an intake passage of the internal combustion engine and driven by the turbine, a control unit that controls the turbine so that the supercharging pressure of the supercharger in the intake passage is equal to or less than a tolerable value; a first calculation unit that calculates a decrease in compressor efficiency of the compressor; and a second calculation unit that calculates the allowable value according to the intake air amount when the compressor efficiency is decreased by the amount of decrease, based on a correlation in which the allowable value decreases as the compressor efficiency decreases when the intake air amount of the intake passage is constant. Control device.

2. the first calculation unit calculates the compressor efficiency at time intervals and calculates the decrease amount from a change in the compressor efficiency over time. The control device according to claim 1 .

3. the first calculation unit calculates the decrease amount from pressures and temperatures upstream and downstream of the compressor in the intake passage, The control device according to claim 1 or 2.

4. the first calculation unit calculates the decrease amount from a change in a control amount of the turbine. The control device according to claim 1 or 2.

5. the second calculation unit calculates, based on data indicating the correlation, the allowable value corresponding to the intake air amount at the compressor efficiency decreased by the decrease amount. The control device according to claim 1 or 2.

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