Vehicle

Abstract

To provide a vehicle that secures frequency of an abnormality determination of a waste gate valve.SOLUTION: A vehicle includes: an engine; a supercharger supercharging intake air to the engine; an exhaust passage that is connected to the engine and in which a turbine of the supercharger is disposed; a bypass passages that bypasses the turbine and is connected to the exhaust passage; a waste gate valve for opening / closing the bypass passage; and an abnormality determination device including a determination section that determines an abnormality of the waste gate valve when an operating state of the engine is in a supercharged state.SELECTED DRAWING: Figure 4

Description

Technical Field

[0001] The present invention relates to a vehicle.

Background Art

[0002] A technique for performing an abnormality determination of a wastegate valve when the operating state of an engine is in a low rotation and low load state is known (see Patent Document 1).

Prior Art Documents

Patent Documents

[0003]

Patent Document 1

Summary of the Invention

Problems to be Solved by the Invention

[0004] Depending on the driving characteristics of the driver and the vehicle type, the period during which the operating state of the engine is maintained in a low rotation and low load state may be short, or the frequency thereof may decrease, thereby possibly reducing the frequency of abnormality determination of the wastegate valve.

[0005] Therefore, an object of the present invention is to provide a vehicle that ensures the frequency of abnormality determination of a wastegate valve.

Means for Solving the Problems

[0006] The above object can be achieved by a vehicle including an engine, a supercharger that supercharges intake air to the engine, an exhaust passage connected to the engine and in which a turbine of the supercharger is disposed, a bypass passage that bypasses the turbine and is connected to the exhaust passage, a wastegate valve that opens and closes the bypass passage, and an abnormality determination device including a determination unit that determines an abnormality of the wastegate valve when the operating state of the engine is in a supercharged state. The supercharging state is a full load state where the accelerator opening is fully open. The vehicle can achieve this.

[0007] The abnormal determination device includes an acquisition unit that acquires the supercharging pressure and the intake air amount of the engine, and the determination unit may determine an abnormality of the waste gate valve based on the supercharging pressure and the intake air amount in the supercharged state.

[0008] The determination unit may determine an abnormality of the waste gate valve based on the supercharging pressure and the intake air amount in the supercharged state and the supercharging pressure and the intake air amount in the case where the operating state is an idle state.

[0009] When a determination value, which is a value obtained by dividing a difference in the supercharging pressure between the idle state and the supercharged state by a difference in the intake air amount between the idle state and the supercharged state, is less than a threshold value, the determination unit may determine that the waste gate valve is normal, and when the determination value is greater than or equal to the threshold value, the determination unit may determine that the waste gate valve is abnormal.

Advantages of the Invention

[0012] According to the present invention, it is possible to provide a vehicle that ensures the frequency of abnormal determination of a waste gate valve.

Brief Description of the Drawings

[0013]

Figure 1

Figure 2

Figure 3

Figure 4

Figure 5

Figure 6

Embodiments for Carrying Out the Invention

[0014] [Schematic Configuration of Vehicle] FIG. 1 is a schematic configuration diagram of a vehicle 100. The vehicle 100 is equipped with an engine 1, an intake passage 3, an exhaust passage 4, a supercharger 5, an intercooler 6, a catalyst 7, a bypass passage 8, a wastegate valve 9, a transmission 21, a differential 23, wheels 25, and an ECU (Electronic Control Unit) 30, etc. The engine 1 is a multi-cylinder engine having four cylinders 2 arranged in series, and is a gasoline engine, but the number of cylinders is not limited to this, and it may be a diesel engine. The driving force of the engine 1 is transmitted to the wheels 25 via the transmission 21 and the differential 23.

[0015] The intake passage 3 and the exhaust passage 4 are connected to the engine 1. In the middle of the intake passage 3, a compressor 5b of the supercharger 5 is arranged. In the middle of the exhaust passage 4, a turbine 5a of the supercharger 5 is arranged. The turbine 5a and the compressor 5b are coaxially connected by a shaft. The supercharger 5 supercharges the intake air to the engine 1.

[0016] In the middle of the exhaust passage 4, there are provided a bypass passage 8 that bypasses the turbine 5a and a wastegate valve 9 that opens and closes the bypass passage 8. The wastegate valve 9 is connected to a diaphragm-type negative pressure actuator 9a, and the ECU 30 controls the opening degree of the wastegate valve 9 by controlling the negative pressure actuator 9a. By adjusting the opening degree of the wastegate valve 9, the distribution ratio between the flow rate of the exhaust gas flowing through the bypass passage 8 and the flow rate of the exhaust gas flowing through the turbine 5a is adjusted. Thereby, the rotational driving force of the turbine 5a is adjusted, the amount of compressed air by the compressor 5b is adjusted, and the supercharging pressure of the engine 1 is adjusted. Here, specifically, the smaller the opening degree of the wastegate valve 9, the smaller the flow rate of the exhaust gas flowing through the bypass passage 8 and the larger the flow rate of the exhaust gas flowing through the turbine 5a. Incidentally, when the wastegate valve 9 is fully open, the engine 1 can operate in the same manner as a naturally aspirated engine without a supercharger. Also, instead of the negative pressure actuator 9a, an electric actuator that electrically drives the wastegate valve 9 may be used.

[0017] An intercooler 6 is disposed downstream of the compressor 5b in the intake passage 3. The intercooler 6 has a refrigerant for the engine 1 flowing inside. Thereby, heat exchange is performed between the refrigerant flowing through the intercooler 6 and the air passing through the intercooler 6, and the intake air is cooled. A throttle valve 3a is disposed downstream of the intercooler 6 in the intake passage 3. By adjusting the opening degree of the throttle valve 3a, the intake air amount of the engine 1 is adjusted. The opening degree of the throttle valve 3a is controlled by the ECU 30 based on the accelerator opening degree.

[0018] A catalyst 7 for purifying the exhaust gas is provided on the downstream side of the turbine 5a in the exhaust passage 4. An air-fuel ratio sensor 14 is provided on the upstream side of the catalyst 7 in the exhaust passage 4. An oxygen sensor 15 for detecting the oxygen concentration of the exhaust gas is provided on the downstream side of the catalyst 7 in the exhaust passage 4.

[0019] The ECU 30 includes a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory). The ECU 30 executes the abnormality determination control described below based on information from sensors and information stored in the ROM in advance, according to a control program stored in the ROM in advance. The ECU 30 is an example of an abnormality determination device. The abnormality determination control is executed by a determination unit and an acquisition unit that are functionally realized by the CPU, the ROM, and the RAM. Details will be described later.

[0020] The ECU 30 controls the operating state of the engine 1 based on detection signals from various sensors such as a crank angle sensor 11, an air flow meter 12, a supercharging pressure sensor 13, an air-fuel ratio sensor 14, an oxygen sensor 15, and an accelerator opening sensor 16. The crank angle sensor 11 detects the rotational angle of the crankshaft of the engine 1. The air flow meter 12 detects the amount of intake air inhaled into the intake passage 3. The supercharging pressure sensor 13 detects the pressure in the intake passage 3 on the downstream side of the compressor 5b and on the upstream side of the throttle valve 3a. The air-fuel ratio sensor 14 detects the air-fuel ratio of the exhaust gas flowing into the catalyst 7. The oxygen sensor 15 detects the oxygen concentration of the exhaust gas discharged from the catalyst 7. The accelerator opening sensor 16 detects the opening of the accelerator pedal operated by the driver.

[0021] The ECU 30 outputs an instructed negative pressure value to the negative pressure actuator 9a so that the waste gate valve 9 has an opening degree corresponding to the operating state of the engine 1. The instructed negative pressure value indicates the instructed value of the pressure in the negative pressure chamber of the diaphragm type negative pressure actuator 9a. The negative pressure instructed value in this embodiment is the absolute value of the pressure based on the atmospheric pressure and is shown as a positive value. Here, as the pressure in the negative pressure chamber decreases from the atmospheric pressure, the opening degree of the waste gate valve 9 decreases, and as the pressure in the negative pressure chamber increases approaching the atmospheric pressure, the opening degree of the waste gate valve 9 increases. That is, the larger the required opening degree of the waste gate valve 9, the smaller the instructed negative pressure value is adjusted, and the smaller the required opening degree of the waste gate valve 9, the larger the instructed negative pressure value is adjusted. For example, when the required opening degree of the waste gate valve 9 is fully open, the instructed negative pressure value is controlled to be less than the pressure value n1 as described later. In addition, when the operating state of the engine 1 is an idle state or a naturally aspirated state, the required opening degree of the waste gate valve 9 is fully open, and when the operating state of the engine 1 is a supercharged state, the required opening degree of the waste gate valve 9 is other than fully open.

[0022] As described above, when the waste gate valve 9 is in a normal state, its opening degree is controlled according to the instructed negative pressure value from the ECU 30 to the negative pressure actuator 9a, and thereby the supercharging pressure is controlled. However, there is a possibility that the waste gate valve 9 may enter an abnormal state where it is fixed in the fully closed state (hereinafter referred to as fully closed fixation). In this case, since the opening degree of the waste gate valve 9 is maintained in the fully closed state regardless of the instructed negative pressure value to the negative pressure actuator 9a, it may affect drivability. Therefore, the ECU 30 executes an abnormality determination control for determining such full closed fixation of the waste gate valve 9.

[0023] [Abnormality Determination Control] Figure 2 is a timing chart showing an example of abnormality determination control when vehicle 100 starts low-speed driving from a temporary stop. In Figure 2, the transitions of the intake air amount, vehicle speed, supercharging pressure, and indicated negative pressure value are shown. When the first monitor condition is satisfied during the temporary stop of vehicle 100 (time t1), ECU 30 acquires the intake air amount I1 and the supercharging pressure P1 (time t2). The first monitor condition is a case where the intake air amount and the supercharging pressure are stable, the intake air amount < g1, and the indicated negative pressure value < n1. That the indicated negative pressure value is less than the pressure value n1 indicates that the required opening degree of the waste gate valve 9 is fully open. In other words, the first monitor condition indicates that the operating state of engine 1 is an idle state.

[0024] Next, the driver operates the accelerator pedal with a relatively small opening degree, and temporarily, the indicated negative pressure value to the negative pressure actuator 9a increases, the required opening degree of the waste gate valve 9 becomes the closed side, the intake air amount and the supercharging pressure increase, and vehicle 100 accelerates (time t3). After that, the indicated negative pressure value decreases again to less than the pressure value n1, the required opening degree of the waste gate valve 9 becomes fully open, the vehicle speed is maintained at a low speed (time t4), and the intake air amount and the supercharging pressure become stable.

[0025] Next, when the second monitor condition is satisfied (time t5), ECU 30 acquires the intake air amount I2 and the supercharging pressure P2 (time t6). The second monitor condition is a case where the intake air amount and the supercharging pressure are stable, the intake air amount > g2, and the indicated negative pressure value < n1 (hereinafter referred to as condition (a)). Also in this case, that the indicated negative pressure value is less than the pressure value n1 indicates that the required opening degree of the waste gate valve 9 is fully open. In other words, condition (a) indicates that the operating state of engine 1 is a natural intake state other than the idle state.

[0026] When the wastegate valve 9 is normal here, during acceleration, the required opening degree of the wastegate valve 9 temporarily becomes fully closed, and after the vehicle speed becomes constant, it becomes fully open again, and the supercharging pressure decreases. Therefore, the supercharging pressure P2 is almost the same as the supercharging pressure P1. However, when the wastegate valve 9 is stuck in the fully closed position, the exhaust gas discharged from the engine 1 passes through the turbine 5a without passing through the bypass passage 8, and the supercharging pressure remains high without decreasing even after the vehicle speed becomes constant. Therefore, as shown in FIG. 2, the supercharging pressure P2x in the abnormal state at time t6 becomes higher than the supercharging pressure P2 in the normal state.

[0027] The ECU 30 performs an abnormality determination as follows. The difference in the supercharging pressure acquired when the first and second monitoring conditions are satisfied is divided by the difference in the intake air amount acquired when the first and second monitoring conditions are satisfied. This division value is referred to as the determination value. Therefore, when the wastegate valve 9 shown in FIG. 2 is in the normal state, the determination value = (P2 - P1) / (I2 - I1). When the wastegate valve 9 shown in FIG. 2 is in the abnormal state, the determination value = (P2x - P1) / (I2 - I1).

[0028] FIG. 3 is a graph showing the relationship between the supercharging pressure and the intake air amount. The vertical axis represents the supercharging pressure, and the horizontal axis represents the intake air amount. The determination value corresponds to the slope of the line segment in the graph of FIG. 3. When the determination value is less than the threshold value T1, it is determined to be normal, and when the determination value is greater than or equal to the threshold value T1, it is determined to be abnormal.

[0029] In this way, when the vehicle 100 starts low-speed driving from a temporary stop, the above-described abnormality determination control can be executed. However, for example, when the vehicle 100 is a sports car and the driver frequently depresses the accelerator deeply, the frequency of the above-described low-speed driving may decrease, and the execution frequency of the abnormality determination control may also decrease. Therefore, the ECU 30 in this embodiment executes the abnormality determination control also when the vehicle 100 starts high-speed driving from a temporary stop as described below.

[0030] FIG. 4 is a timing chart showing an example of abnormality determination control when the vehicle 100 starts high-speed driving from a temporary stop. FIG. 4 corresponds to FIG. 2. When the first monitor condition is satisfied (time t1), the ECU 30 acquires the intake air amount I1 and the supercharging pressure P1 (time t2). Next, the driver operates so that the accelerator opening becomes full open, and the intake air amount and the supercharging pressure increase, and the vehicle 100 accelerates (time t3). Thereafter, the vehicle speed is maintained at a high speed (time t4), and the indicated negative pressure value is controlled to a value larger than the pressure value n1 so that the intake air amount and the supercharging pressure are stabilized.

[0031] Thereafter, when the second monitor condition is satisfied (time t5), the ECU 30 acquires the intake air amount I3 and the supercharging pressure P3 (time t6). Here, the second monitor condition is that the intake air amount and the supercharging pressure are stable, and when g3 < intake air amount < g4 and the indicated negative pressure value < n2 (hereinafter referred to as condition (b)). The fact that the indicated negative pressure value is less than the pressure value n2 indicates a case where the required opening degree of the wastegate valve 9 is other than fully closed. In other words, condition (b) indicates that the operating state of the engine 1 is in a supercharged state. The supercharged state required by condition (b) is a full load state where the accelerator opening is full open and the required opening degree of the throttle valve 3a is full open. Therefore, when either one of the above-described conditions (a) and (b) is satisfied, it is regarded that the second monitor condition is satisfied. Note that with respect to the intake air amount, the relationship of g2 < g3 < g4 holds. With respect to the negative pressure indicated value, the relationship of atmospheric pressure = 0 < n1 < n2 holds.

[0032] Here, when the wastegate valve 9 is normal, the required opening degree of the wastegate valve 9 is maintained at half open during acceleration, and the supercharging pressure increases and is maintained at a predetermined value. However, when the wastegate valve 9 is stuck fully closed, all the exhaust from the engine 1 passes through the turbine 5a and the supercharging pressure increases excessively. Therefore, as shown in FIG. 4, the supercharging pressure P3x in the abnormal state at time t6 becomes higher than the supercharging pressure P3 in the normal state. Therefore, when the wastegate valve 9 shown in FIG. 4 is in a normal state, the determination value = (P3 - P1) / (I3 - I1). When the wastegate valve 9 shown in FIG. 4 is in an abnormal state, the determination value = (P3x - P1) / (I3 - I1).

[0033] FIG. 5 is a graph showing the relationship between the supercharging pressure and the intake air amount. FIG. 5 corresponds to FIG. 3. When the determination value is less than the threshold value T2, it is determined as normal, and when the determination value is greater than or equal to the threshold value T2, it is determined as abnormal. The threshold value T2 is a value larger than the threshold value T1 shown in FIG. 3.

[0034] By including the condition (b) in the second monitoring condition in this way, even when the frequency of low-speed driving is low, the execution frequency of the abnormality determination control can be ensured.

[0035] For example, if the second monitoring condition is only the condition (a), it may be considered to limit the transition to the supercharged state until the wastegate valve 9 is determined to be normal in consideration of safety. In this case, the drivability decreases until the second monitoring condition is satisfied. By including the condition (b) in the second monitoring condition as described above, since the abnormality determination can be executed even in the supercharged state, the above-described limitation is unnecessary, and the decrease in drivability can be suppressed.

[0036] Also, as described above, in the condition (b), it is limited to g3 < intake air amount < g4, and this range of the intake air amount is set in a range where the difference between the supercharging pressure during normal operation and the supercharging pressure during full-closed sticking is large. That is, when the intake air amount belongs to this range, the difference between the supercharging pressure during normal operation and the supercharging pressure during full-closed sticking is large. Therefore, the abnormality determination can be performed with high accuracy.

[0037] FIG. 6 is a flowchart showing an example of the abnormality determination control executed by the ECU 30. The ECU 30 determines whether or not the first monitoring condition is satisfied (step S1). If No in step S1, this control is terminated. If Yes in step S1, the ECU 30 acquires the supercharging pressure and the intake air amount based on the detection values of the supercharging pressure sensor 13 and the air flow meter 12 (step S2). Step S2 is an example of the process executed by the acquisition unit.

[0038] Next, the ECU 30 determines whether or not the second monitoring condition is satisfied (step S3). The second monitoring condition is considered to be satisfied when either of the above-described conditions (a) and (b) is met. If the result in step S3 is No, this control ends. If the result in step S3 is Yes, the ECU 30 acquires the supercharging pressure and the intake air amount (step S4). Step S4 is an example of the process executed by the acquisition unit. Next, the ECU 30 calculates a determination value by the above-described method based on the supercharging pressure and the intake air amount acquired in steps S2 and S4 (step S5).

[0039] Next, the ECU 30 determines whether or not the determination value is less than the threshold value (step S6). As described above, the threshold value T1 is used when condition (a) is satisfied in the second monitoring condition, and the threshold value T2 is used when condition (b) is satisfied in the second monitoring condition. The threshold value T1 is the lower limit value of the difference in the supercharging pressure with respect to the difference in the intake air amount when shifting from the idle state to the naturally aspirated state and the wastegate valve 9 is fully closed and fixed. The threshold value T2 is the lower limit value of the difference in the supercharging pressure with respect to the difference in the intake air amount when shifting from the idle state to the supercharged state and the wastegate valve 9 is fully closed and fixed. The threshold value T2 is not limited to a fixed value and may be variably set according to the intake air amount.

[0040] If the result in step S6 is Yes, the ECU 30 determines that the wastegate valve 9 is in a normal state (step S7). If the result in step S6 is No, the ECU 30 determines that the wastegate valve 9 is in an abnormal state where it is fully closed and fixed (step S8). Steps S7 and S8 are examples of the processes executed by the determination unit. Incidentally, when an abnormality determination is made, the ECU 30 may notify the driver that an abnormality has occurred in the wastegate valve 9, for example, by turning on the MIL (Malfunction Indicator Light).

[0041] In the above-described embodiment, the abnormality determination is performed based on the supercharging pressure and the intake air amount in the idle state and the supercharged state, but it is not limited thereto. For example, when the value obtained by dividing the supercharging pressure by the intake air amount in the supercharged state is less than a predetermined threshold value, the wastegate valve 9 may be determined to be normal, and when this value is equal to or greater than the threshold value, the wastegate valve 9 may be determined to be abnormal.

[0042] In the above-described embodiment, the full load state is described as an example of the supercharged state in which the condition (b) of the second monitor condition is satisfied, but it is not limited thereto. For example, the supercharged state may be a case where the accelerator opening is equal to or greater than a predetermined opening.

[0043] The vehicle 100 is an engine vehicle equipped with only the engine 1 as a drive source, but it is not limited thereto, and it may be a hybrid vehicle equipped with a motor in addition to the engine as a drive source.

[0044] As described above in detail with respect to the embodiments of the present invention, the present invention is not limited to such specific embodiments, and various modifications and changes are possible within the scope of the gist of the present invention described in the claims.

Explanation of Reference Numerals

[0045] 1 Engine 3 Intake passage 3a Throttle valve 4 Exhaust passage 5 Supercharger 5a Turbine 8 Bypass passage 9 Wastegate valve 12 Airflow meter 13 Supercharging pressure sensor 30 ECU (Abnormality determination device) 100 Vehicle

Claims

1. An engine, a supercharger for supercharging the intake air to the engine, an exhaust passage connected to the engine and having a turbine of the supercharger disposed therein, a bypass passage bypassing the turbine and connected to the exhaust passage, a wastegate valve for opening and closing the bypass passage, an abnormality determination device including a determination unit for determining an abnormality of the wastegate valve when the operating state of the engine is a supercharged state, and the supercharged state is a full load state where the accelerator opening is fully open, a vehicle.

2. The abnormality determination device includes an acquisition unit for acquiring the supercharging pressure and the intake air amount of the engine, and the determination unit determines an abnormality of the wastegate valve based on the supercharging pressure and the intake air amount in the supercharged state. The vehicle according to claim 1.

3. The determination unit determines an abnormality of the wastegate valve based on the supercharging pressure and the intake air amount in the supercharged state and the supercharging pressure and the intake air amount in the idle state of the operating state. The vehicle according to claim 2.

4. When the determination value, which is a value obtained by dividing the difference in the supercharging pressure between the idle state and the supercharged state by the difference in the intake air amount between the idle state and the supercharged state, is less than a threshold value, the determination unit determines that the wastegate valve is normal, and when the determination value is greater than or equal to the threshold value, the determination unit determines that the wastegate valve is abnormal. The vehicle according to claim 3.

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