JP4577104B2 - Variable turbocharger - Google Patents

Description

  The present invention relates to a variable turbocharger that sufficiently and sufficiently secures a supercharging pressure in a turbocharged engine from a low speed range to a high speed range of an internal combustion engine.

  The variable turbocharger has a poor acceleration performance because it takes time to increase the rotational speed of the turbine when accelerating from a low speed. Therefore, conventionally, a method for sufficiently ensuring the efficiency of the variable turbocharger from the low speed range to the high speed range of the internal combustion engine is known. For example, in Patent Document 1, in order to ensure the efficiency of the variable turbocharger widely and sufficiently from the low speed range to the high speed range, a bypass passage that bypasses the compressor is provided, and a bypass valve is installed in the bypass passage. There is described a technique for controlling opening and closing of a bypass valve in different rotational ranges of an internal combustion engine.

JP 2004-324522 A

  However, the variable turbocharger described in Patent Document 1 controls the opening and closing of the bypass valve based on the rotation range of the internal combustion engine. On the other hand, the efficiency of the compressor depends on the flow rate of air passing through the compressor. Since the variable turbocharger described in Patent Document 1 does not control opening and closing of the bypass valve based on the air flow rate passing through the compressor, it cannot be said that the efficiency of the compressor is sufficiently good.

  The present invention has been made in view of the above points, and provides a variable turbocharger capable of improving the efficiency of a compressor and improving acceleration performance.

  In one aspect of the present invention, a variable turbocharger includes a compressor disposed in an intake passage of an internal combustion engine, a turbine disposed in an exhaust passage of the internal combustion engine, a shaft connecting the compressor and the turbine, In the intake passage, based on the bypass passage connecting the upstream side of the compressor and the downstream side of the compressor, the bypass valve for adjusting the flow rate of air flowing through the bypass passage, and the rotational speed of the turbine, Compressor optimal air flow rate calculation means for calculating an optimal air flow rate that is an air flow rate passing through the compressor when maximizing efficiency, and compressor passing air flow rate measurement that measures a passing air flow rate that is an air flow rate passing through the compressor Means, pressure upstream of the compressor and under the compressor Pressure measuring means for measuring the pressure on the side, and bypass valve adjusting means for adjusting the bypass valve based on the pressure on the upstream side of the compressor, the pressure on the downstream side of the compressor, the optimal air flow rate, and the passing air flow rate And comprising.

  The variable turbocharger includes a compressor, a turbine, and a shaft that connects the compressor and the turbine. The compressor is disposed in an intake passage of the internal combustion engine, and the turbine is disposed in an exhaust passage of the internal combustion engine. Further, the intake passage is provided with a bypass passage, and connects the upstream side of the compressor and the downstream side of the compressor. Further, the bypass passage is provided with a bypass valve for adjusting the air flow rate. The compressor optimum air flow rate calculation means calculates an optimum air flow rate that is an air flow rate that passes through the compressor when the efficiency of the compressor is maximized, based on the rotational speed of the turbine. The pressure measuring means measures the pressure on the upstream side of the compressor and the pressure on the downstream side of the compressor. The compressor passing air flow rate measuring means measures a passing air flow rate that is an air flow rate passing through the compressor. The bypass valve adjusting means adjusts the bypass valve based on the pressure on the upstream side of the compressor, the pressure on the downstream side of the compressor, the optimum air flow rate, and the passing air flow rate. As described above, the opening of the bypass valve is adjusted based on the pressure upstream of the compressor, the pressure downstream of the compressor, the optimum air flow rate, and the passing air flow rate, and air flows into the bypass passage. As a result, the flow rate of air passing through the compressor can be adjusted, and the compressor can be driven efficiently.

  In one aspect of the above variable turbocharger, the bypass valve adjusting means is configured such that the passing air flow rate is larger than the optimum air flow rate, and the pressure on the upstream side of the compressor is larger than the pressure on the downstream side of the compressor. Or when the passing air flow rate is smaller than the optimum air flow rate and the pressure on the upstream side of the compressor is smaller than the pressure on the downstream side of the compressor, the passing air flow rate becomes the optimum air flow rate. The bypass valve is adjusted until Thereby, the said passage air flow rate can be match | combined with the said optimal air flow rate, and the efficiency of a compressor can be improved to the maximum.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

(Configuration of variable turbocharger)
First, the configuration of the variable turbocharger according to the present embodiment will be described.

  FIG. 1 is a diagram showing a schematic configuration when a variable turbocharger 100 according to this embodiment is applied to an internal combustion engine.

  The variable turbocharger 100 mainly includes a compressor 4 provided in an intake passage 2 connected to the internal combustion engine 1, a turbine 7 provided in an exhaust passage 3 connected to the internal combustion engine 1, and a compressor 4. A shaft 8 for connecting the turbine 7, a bypass passage 5 installed in the intake passage 2, and an ECU (Engine Control Unit) 10 are provided.

  Air from the outside flows into a cylinder (not shown) of the internal combustion engine 1 through the intake circuit 2. Examples of the internal combustion engine 1 include a gasoline engine and a diesel engine. Exhaust gas generated by combustion in the cylinder is discharged to the exhaust passage 3. The exhaust gas discharged into the exhaust passage 3 rotates the turbine 7. The rotational torque of the turbine 7 is transmitted to the compressor 4 through the shaft 8. Due to the rotational torque transmitted from the turbine 7, the compressor 4 rotates and compresses the air flowing into the intake passage 2.

  A bypass passage 5 that directly connects the upstream side of the compressor 4 and the downstream side of the compressor 4 is installed in the intake passage 2. The air flowing into the bypass passage 5 can bypass (bypass) the compressor 4. A bypass valve 6 for adjusting the amount of air flowing through the bypass passage 5 is installed in the bypass passage 5. The bypass valve 6 can be installed at any location in the bypass passage 5.

  Further, in the intake passage 2, on the upstream side of the compressor 4, there are an air flow meter (AFM) 11 that measures the flow rate of air passing through the compressor 4 and a pressure gauge 12 that measures the pressure P 0 of the air upstream of the compressor 4. Installed. On the downstream side of the compressor 4, a pressure gauge 13 for measuring the air pressure P <b> 3 on the downstream side of the compressor 4 is installed. The AFM 11 supplies the measured air flow rate as the signal S1, the pressure gauge 12 supplies the measured pressure P0 as the signal S2, and the pressure gauge 13 supplies the measured pressure P3 as the signal S3 to the ECU 10, respectively. Accordingly, the AFM 11 functions as a compressor passing air flow rate measuring unit, and the pressure gauges 12 and 13 function as a pressure measuring unit.

  The ECU 10 includes a CPU, a ROM, a RAM, an A / D converter, an input / output interface, and the like (not shown). The ECU 10 controls the vehicle by output signals supplied from various sensors in the vehicle. In the present embodiment, the ECU 10 determines whether to open or close the bypass valve 6 based on the signal S1 supplied from the AFM 11, the signal S2 supplied from the pressure gauge 12, and the signal S3 supplied from the pressure gauge 13. To decide. When opening the bypass valve 6, the ECU 10 variably controls the bypass valve 6 from fully closed to fully opened by supplying the signal S <b> 4 to the bypass valve 6. Therefore, the ECU 10 functions as a bypass valve adjusting unit.

  FIG. 2 is a graph showing the relationship between the flow rate of air passing through the compressor and the efficiency of the compressor in a general variable turbocharger. The horizontal axis represents the air flow rate passing through the compressor, and the vertical axis represents the compressor efficiency. ing. FIG. 2 shows a plurality of convex graphs. Each convex graph (for example, graph 31 in FIG. 2) shows the relationship between the flow rate of air passing through the compressor and the efficiency of the compressor at the same turbine speed. From the viewpoint of the rotation speed of the same turbine, it can be seen that the efficiency of the compressor is maximized at a predetermined air flow rate indicated by a black dot (for example, point 32 in FIG. 2). Further, as shown in FIG. 2, it can be seen that the efficiency of the compressor increases overall as the rotational speed of the turbine increases.

  FIG. 3 is a graph showing the relationship between the rotational speed of the turbine and the flow rate of air passing through the compressor corresponding to the black spot in FIG. FIG. 3 shows the air flow rate (hereinafter simply referred to as “optimum air flow rate”) passing through the compressor when the efficiency of the compressor is maximum with respect to the turbine rotation speed, and the horizontal axis represents the turbine rotation speed. And the vertical axis represents the optimum air flow rate. As shown in the graph 41 of FIG. 3, the optimum air flow rate is small when the turbine speed is low, and the optimum air flow rate is large when the turbine speed is high. If the optimum air flow rate is obtained from the rotational speed of the turbine using the graph 41 of FIG. 3 and the air flow rate passing through the compressor can be brought close to the obtained optimum air flow rate, the compressor can be driven more efficiently. . Furthermore, if the air flow rate passing through the compressor can be matched with the optimum air flow rate, the compressor can be driven with maximum efficiency. Thus, the acceleration performance of the variable turbocharger can be improved by adjusting the flow rate of air passing through the compressor. The ECU 10 calculates the optimum air flow rate using the graph 41 of FIG. Therefore, the ECU 10 also functions as a compressor optimum air flow rate calculation unit.

  After calculating the optimal air flow rate, the ECU 10 adjusts the air flow rate passing through the compressor 4 to the calculated optimal air flow rate by adjusting the opening degree of the bypass valve 6. Specifically, the ECU 10 supplies the signal S4 to the bypass valve 6 and adjusts the opening degree of the bypass valve 6 so that air flows into the bypass passage 5 and the air flow rate passing through the compressor 4 is set to the optimum air flow. Adjust to flow rate. Thereby, the compressor 4 can be driven with the maximum efficiency.

(Bypass valve control processing)
Next, the bypass valve control process in the variable turbocharger 100 according to the present embodiment will be specifically described with reference to the flowchart of FIG. First, the ECU 10 measures the rotational speed of the turbine 7 (step S11). As a method for measuring the rotational speed of the turbine 7, for example, a magnet is attached to the tip of the blade of the turbine 7, and the periodic change of the magnetic field of the turbine 7 can be obtained by using a sensor or the like (not shown).

  The ECU 10 calculates the optimum air flow rate using the relationship of the graph 41 of FIG. 3 described above based on the measured rotation speed of the turbine 7 (step S12), and then obtains the signal S1 supplied from the AFM 11 as a result. Based on this, the flow rate of air passing through the compressor 4 is measured (step S13). Further, the ECU 10 adjusts the bypass valve 6 in order to match the air flow rate passing through the compressor 4 with the calculated optimum air flow rate (step S14).

  Next, the adjustment method of the bypass valve in step S14 will be specifically described with reference to FIG. FIG. 5 is a chart showing the relationship between the flow rate condition, the pressure condition, and the bypass valve operation. Here, the flow rate condition indicates a condition of the magnitude relationship between the air flow rate passing through the compressor 4 and the optimum air flow rate, and the pressure condition indicates the magnitude of the pressure P0 on the upstream side of the compressor 4 and the pressure P3 on the downstream side. Indicates the size relationship. In FIG. 5, regarding the bypass valve operation, when the bypass valve is opened (including the intermediate opening degree) is indicated by “open”, and when the bypass valve is completely closed is indicated by “closed”. The bypass valve operation is determined by two conditions, a flow rate condition and a pressure condition.

  When the measured air flow rate through the compressor 4 is larger than the optimum air flow rate, it is necessary to reduce the air flow rate through the compressor 4 to approach the optimum air flow rate. Therefore, the magnitude of the pressure P0 on the upstream side of the compressor 4 is compared with the pressure P3 on the downstream side. If the pressure P0 is larger, the opening degree of the bypass valve 6 is adjusted so that air is also supplied to the bypass passage 5. Shed. At this time, the air flow direction is the direction of the arrow A1 shown in FIG. Thereby, the air flow rate which flows into the compressor 4 can be brought close to the optimal air flow rate. The ECU 10 adjusts the opening degree of the bypass valve 6 until the air flow rate flowing through the compressor 4 becomes the same as the optimum air flow rate.

  On the other hand, when the pressure P0 is smaller than the pressure P3, when the bypass valve 6 is opened, air flows in the direction of the arrow A2 shown in FIG. 1, and the flow rate of air passing through the compressor 4 increases. Therefore, when the pressure P0 is smaller, the bypass valve 6 is completely closed. Actually, in this state, due to the pressure difference between the pressures P0 and P3, the air flow rate passing through the compressor 4 is already almost the same as the optimum air flow rate.

  When the measured air flow rate through the compressor 4 is smaller than the optimum air flow rate, it is necessary to increase the air flow rate through the compressor 4 to approach the optimum air flow rate. Therefore, the magnitude of the pressure P0 on the upstream side of the compressor 4 is compared with the pressure P3 on the downstream side. If the pressure P3 is larger, the opening degree of the bypass valve 6 is adjusted to allow air to flow into the bypass passage 5 as well. Shed. At this time, the air flow direction is the direction of the arrow A2 shown in FIG. 1, so that the flow rate of air passing through the compressor 4 can be increased. Thereby, the air flow rate which flows into the compressor 4 can be brought close to the optimal air flow rate. The ECU 10 adjusts the opening degree of the bypass valve 6 until the air flow rate flowing through the compressor 4 becomes the same as the optimum air flow rate.

  On the other hand, when the pressure P3 is smaller than the pressure P0, when the bypass valve 6 is opened, air flows in the direction of the arrow A1 shown in FIG. 1, and the flow rate of air passing through the compressor 4 decreases. Therefore, when the pressure P3 is smaller, the bypass valve 6 is completely closed. Actually, in this state, due to the pressure difference between the pressures P0 and P3, the air flow rate passing through the compressor 4 is already almost the same as the optimum air flow rate.

  By controlling the opening and closing of the bypass valve 6 as described above, the air flow rate passing through the compressor 4 can be matched with the optimum air flow rate, and the efficiency of the compressor 4 can be maximized.

It is a figure which shows schematic structure of the variable turbocharger which concerns on this embodiment. It is a figure which shows the relationship between the air flow rate which passes a compressor, and the efficiency of a compressor. It is a figure which shows the relationship between the rotation speed of a turbine, and the optimal air flow rate. It is a flowchart of a bypass valve control process according to the present embodiment. It is a graph which shows the relationship between flow volume conditions and pressure conditions, and bypass valve operation | movement.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Intake passage 3 Exhaust passage 4 Compressor 7 Turbine 8 Shaft 5 Bypass passage 6 Bypass valve 10 ECU
100 variable turbocharger

Claims (2)

A compressor disposed in the intake passage of the internal combustion engine;
A turbine disposed in an exhaust passage of the internal combustion engine;
A shaft connecting the compressor and the turbine;
A bypass passage connecting the upstream side of the compressor and the downstream side of the compressor in the intake passage;
A bypass valve for adjusting the flow rate of air flowing through the bypass passage;
A compressor optimum air flow rate calculation means for calculating an optimum air flow rate that is an air flow rate passing through the compressor when maximizing the efficiency of the compressor based on the rotational speed of the turbine;
A compressor passing air flow rate measuring means for measuring a passing air flow rate which is an air flow rate passing through the compressor;
Pressure measuring means for measuring the pressure on the upstream side of the compressor and the pressure on the downstream side of the compressor;
A variable turbo comprising: a bypass valve adjusting means for adjusting the bypass valve based on a pressure upstream of the compressor, a pressure downstream of the compressor, the optimum air flow rate, and the passing air flow rate. Charger.   The bypass valve adjusting means is configured such that when the passing air flow rate is larger than the optimum air flow rate and the pressure on the upstream side of the compressor is larger than the pressure on the downstream side of the compressor, or the passing air flow rate is Adjusting the bypass valve until the passing air flow rate becomes the optimum air flow rate when the pressure is smaller than the optimum air flow rate and the pressure on the upstream side of the compressor is smaller than the pressure on the downstream side of the compressor; The variable turbocharger according to claim 1.

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