JP2008064059A - Engine supercharging apparatus - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To prevent fuel from leaking into an internal crankcase upon starting an engine. <P>SOLUTION: This engine supercharging apparatus, equipped with an electric supercharger disposed on an intake passage and started by an electric starter, includes a pressurizing intake air supply unit which operates the electric supercharger upon completion of operating the electric starter and supplies pressurizing intake air by the electric supercharger into the crankcase of the engine. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to an engine supercharging device.

  As a method of improving the output characteristics of the engine, there is a method of supercharging the intake port by providing a supercharger. An example of such a supercharger is an exhaust turbocharger. However, a sufficient supercharging pressure cannot be obtained at a low engine speed. Therefore, for example, as described in Patent Document 1, it has been proposed that a supercharger is electrically operated so that a sufficient supercharging pressure can be obtained even at a low engine speed. Although different from the intake port supercharging technique, Patent Document 2 discloses a technique for restarting the engine without operating the starter by pressurizing the crankcase and sending air into the combustion chamber when the engine is restarted. Has been.

JP 2004-251240 A JP 2006-57529 A

  By the way, when the engine is started, unburned fuel is likely to be present in the combustion chamber, and this is likely to adhere to the inner wall surface of the cylinder due to the vertical movement of the piston due to cranking. In particular, when the engine is cold, the amount of fuel is increased at the time of starting, so that the fuel tends to adhere to the inner wall surface of the cylinder. When the air-fuel mixture ignites and the pressure in the combustion chamber becomes high, the fuel adhering to the cylinder inner wall surface may leak into the crankcase. The fuel flowing down into the crankcase leads to a reduction in fuel consumption and also to dilution of engine oil.

  Accordingly, an object of the present invention is to prevent fuel from leaking into the crankcase when the engine is started.

  According to the present invention, in an engine supercharger that includes an electric supercharger disposed in an intake passage and is started by an electric starter, the electric supercharger is operated after the operation of the electric starter is finished, There is provided an engine supercharging device comprising pressurized intake air supply means for supplying pressurized intake air from an electric supercharger into a crankcase of the engine.

  According to this configuration, when the engine is started, the inside of the crankcase is pressurized by the pressurized intake air supply means, so that fuel that is about to leak into the crankcase can be pushed back to the combustion chamber. Therefore, it is possible to prevent the fuel from leaking into the crankcase when the engine is started. Further, the supercharging of the intake port and the pressurization of the crankcase can be used together by the electric supercharger, and the number of parts can be reduced. Furthermore, by operating the electric supercharger after the operation of the electric starter is completed, the power consumption of the battery can be reduced as compared with the case where both are operated simultaneously.

  In the present invention, the pressurized intake air supply means supplies the pressurized intake air from the electric supercharger into the crankcase of the engine until the engine reaches a predetermined temperature after the operation of the electric starter is completed. A supply configuration can be employed.

  In general, during the warm-up operation of the engine, the amount of fuel is increased, and the amount of fuel attached to the inner wall surface of the cylinder increases. Further, since the startability is poor when the engine is cold, the amount of fuel attached to the inner wall surface of the cylinder increases. According to the above configuration, the inside of the crankcase is pressurized until the engine reaches a predetermined temperature, so that it is possible to prevent fuel from leaking into the crankcase in any of the above cases.

  In the present invention, it is possible to adopt a configuration in which the pressurized intake air is set to a pressure equal to or lower than the oil seal pressure resistance of the crankshaft of the engine.

  According to this configuration, it is possible to prevent the fuel from leaking into the crankcase by pressurizing the crankcase without impairing the sealing performance of the crankshaft.

  In the present invention, the intake passage is further branched to bypass the electric supercharger, the bypass passage control valve disposed in the bypass passage, and the bypass passage control valve. And a throttle valve disposed in the intake passage downstream from the bypass passage, and the pressurized intake air supply means is upstream from the throttle valve, and The pressurized intake air supply passage is branched from the intake passage downstream of the bypass passage and connected to the crankcase, and the control means is configured to supply the pressurized intake air. When supplying into the crankcase, it is possible to adopt a configuration in which the bypass passage control valve is controlled so that the electric supercharger does not generate surging.

  According to this configuration, it is possible to prevent the electric supercharger from generating surging when the inside of the crankcase is pressurized when the engine is started.

  Further, in the present invention, it is possible to employ a configuration provided with a suppression means that is disposed in the supply passage and suppresses the flow of gas from the crankcase to the intake passage.

  According to this configuration, the gas in the crankcase can be prevented from flowing back into the intake passage.

  The present invention further includes an exhaust turbocharger including a compressor disposed in the intake passage and a turbine disposed in the exhaust passage on a downstream side of the electric supercharger, and The pressurized intake air supply means may employ a configuration including the pressurized intake air supply passage branched from the intake passage downstream of the compressor and connected to the crankcase.

  According to this configuration, the reduction of the supercharging pressure in the intake passage due to the intake air flowing into the supply passage does not reach the periphery of the compressor, and the lubricating oil of the exhaust turbocharger is transferred from the compressor to the intake passage. Can be prevented from leaking into

  As described above, according to the present invention, fuel can be prevented from leaking into the crankcase when the engine is started.

  FIG. 1 is a block diagram of a gasoline engine system 1 including a supercharging device according to an embodiment of the present invention. Although this embodiment illustrates an example in which the present invention is applied to a system using a gasoline engine, the present invention can also be applied to a system using a diesel engine. Further, in this document, the terms “upstream” and “downstream” of a passage follow the direction of the flow of fluid flowing through the passage.

  The gasoline engine system 1 includes a gasoline engine 10, an intake passage 20, an exhaust passage 30, an electric supercharger 50, and an exhaust turbocharger 60. The electric supercharger 50 includes a compressor (compressor wheel) 50b disposed in the intake passage 20 and an electric motor 50a that rotationally drives the compressor 50b. The exhaust turbocharger 60 is configured by coaxially fixing a compressor (compressor wheel) 61 disposed in the intake passage 20 and a turbine (turbine wheel) 62 disposed in the exhaust passage 30.

  The gasoline engine 10 is, for example, an in-line four-cylinder engine, and includes a cylinder head 11, a cylinder block 12, and a crankcase 13. The cylinder head 11 includes a combustion chamber 11a, an ignition unit 16 that ignites an air-fuel mixture in the combustion chamber 11a, and an intake port 14 and an exhaust port 15 that communicate with the combustion chamber 11a.

  The cylinder head 11 also includes an electronically controlled fuel injection valve 14 b that injects fuel into the intake port 14. The fuel injected from the fuel injection valve 14b is mixed with the intake air supplied to the intake port 14 to form an air-fuel mixture.

  The intake port 14 communicates with the intake passage 20 and the exhaust port 15 communicates with the exhaust passage 30. The intake port 14 is opened and closed by an intake valve 14 a provided in the cylinder head 11, and the exhaust port 15 is opened and closed by an exhaust valve 15 a provided in the cylinder head 11.

  A piston 12a is housed in the cylinder block 12 (cylinder) so as to be slidable in the vertical direction. A crankshaft 13a for converting the vertical movement of the piston 12a into a rotational movement is disposed in the crankcase 13. The crankcase 13 and the crankshaft 13a are sealed with an oil seal (not shown) according to a known method. When the gasoline engine 10 is started, the crankshaft 13a is rotationally driven (cranked) by an electric starter (not shown) in FIG. 1 (electric starter 205 in FIG. 2).

  From the upstream side of the intake passage 20, an air filter 21, an air flow meter (intake amount sensor) 22, a compressor 50 b of the electric supercharger 50, a compressor 61 of the exhaust turbocharger 60, an intercooler 23, an electronically controlled type An independent intake pipe 27 is provided for each cylinder connecting the throttle valve 24, the surge tank 25, and the surge tank 25 to the intake port 14 of each cylinder. The surge tank 25 is provided with an intake pressure sensor 26 that detects the intake pressure in the surge tank 25. In addition, the arrow shown to the intake passage 20 in FIG. 1 shows the direction of the flow of intake air.

  The intake passage 20 is provided with a bypass passage 20 a that is branched in the middle of the intake passage 20 and bypasses the electric supercharger 50. The bypass passage 20a is connected to the intake passage 20 on the upstream side and the downstream side of the electric supercharger 50, and on the downstream side of the bypass passage 20a, the compressor 61, the intercooler 23, and the electronic device of the exhaust turbocharger 60 described above are connected. A control type throttle valve 24, a surge tank 25, an intake pressure sensor 26, and an intake pipe 27 are located.

  The bypass passage 20a is provided with an electronically controlled bypass passage control valve 70 whose opening degree can be adjusted. The bypass passage control valve 70 is basically closed when the electric supercharger 50 is operated, and is opened when the electric supercharger 50 is stopped, and intake air flows in the direction indicated by the solid line arrow. However, when surging occurs in the operating electric supercharger 50, for example, the valve is opened halfway and the intake air is released in the direction indicated by the broken-line arrow to eliminate the surging.

  The intake passage 20 also branches from the intake passage 20 upstream of the throttle valve 24 and downstream of the bypass passage 20 a and the compressor 61 of the exhaust turbocharger 60 and is connected to the crankcase 13. A supply passage 40 is also provided. In the present embodiment, the crankcase 13 can be supercharged by supplying pressurized intake air from the electric supercharger 50 into the crankcase 13 via the supply passage 40.

  In the present embodiment, as will be described later, when the gasoline engine 10 is started, the electric supercharger 50 is operated after the operation of the electric starter (not shown) is completed, and the pressurized intake air from the electric supercharger 50 is supplied into the crankcase 13. To do. This prevents the fuel adhering to the cylinder inner wall of the cylinder block 12 from leaking into the crankcase 13 when the gasoline engine 10 is started. FIG. 4B is a schematic diagram showing the fuel F adhering to the cylinder inner wall of the cylinder block 12.

  When the gasoline engine 10 is started, unburned fuel is generated, and the fuel F adheres to the inner wall of the cylinder as shown in FIG. When the air-fuel mixture is ignited in the combustion chamber 11a and the pressure in the combustion chamber 11a becomes high, the fuel F adhering to the cylinder inner wall surface may leak into the crankcase 13. Therefore, as in the present embodiment, the inside of the crankcase 13 is supercharged and the internal pressure is increased, whereby the fuel F that is about to leak into the crankcase 13 can be pushed back into the combustion chamber 11a.

  Returning to FIG. 1, an electronically controlled switching valve 41 and a check valve 42 that suppresses the flow of gas from the crankcase 13 to the intake passage 20 are disposed in the supply passage 40. The switching valve 41 is opened when the supply passage 40 and the intake passage 20 are communicated, and is closed when both are shut off. The check valve 42 is disposed to prevent the gas in the crankcase 13 from flowing back into the intake passage 20 when the switching valve 41 is opened.

  A turbine 62 of the exhaust turbocharger 60 is disposed in the exhaust passage 30. In FIG. 1, the arrows shown in the exhaust passage 30 indicate the direction of the exhaust flow.

  Next, FIG. 2 is a block diagram of a control system of the gasoline engine system 1. The ECU (engine control unit) 200 includes, for example, a CPU, storage means such as a RAM and an EEPROM, and an interface. The CPU executes a control program stored in an EEPROM or the like. The control program includes an electric supercharging control program described later.

  The ECU 200 is connected to a rotational speed sensor 201, an accelerator opening sensor 202, the air flow meter 22, the water temperature sensor 203, the intake pressure sensor 26, and an IG / SW (ignition switch) 204. The rotation speed sensor 201 is, for example, a sensor that detects the rotation speed of the crankshaft 13 a and is used to detect the rotation speed of the gasoline engine 10.

  The accelerator opening sensor 202 detects the opening degree of the accelerator operation by the driver. The air flow meter 22 detects the amount of intake air (fresh air). The water temperature sensor 203 is a sensor that detects the temperature of the cooling water that cools the gasoline engine 10. In this embodiment, the water temperature sensor 203 controls the temperature detected by the water temperature sensor 203 as the temperature of the gasoline engine 10. 10 function as temperature detection means.

  The intake pressure sensor 26 is a sensor that detects the intake pressure in the surge tank 25 as described above. The IG / SW 204 detects the start operation of the gasoline engine 10 by the driver.

  Based on the detection results of these sensors, the ECU 200 controls the throttle valve 24, the fuel injection valve 14b, the ignition unit 16, the electric motor 50a of the electric supercharger 50, the bypass passage control valve 70, the switching valve 41, and the electric starter 205. Do. The ECU 200 operates the electric starter 205 to crank the crankshaft 13a while the IG / SW 204 is ON.

  Next, an example of electric supercharging control by the ECU 200 using the electric supercharger 50 will be described. FIG. 3 is a flowchart of electric supercharging control executed by the ECU 200. The ECU 200 repeatedly executes the process shown in FIG. In S1, the detection result of each sensor is acquired.

  In S2, it is determined based on the detection result of the sensor acquired in S1 whether the electric starter 205 is operating (whether the IG / SW 204 is ON). If applicable, the process proceeds to S3 if applicable, and the process proceeds to S6 if not applicable. The process proceeds to S3 when the crankshaft 13a is being cranked by the electric starter 205, and the process proceeds to S6 when the gasoline engine 10 is started and the operation of the electric starter 205 is finished.

  In S3, the electric supercharger 50 is stopped. In S4, the switching valve 41 is closed. As a result, the supply passage 40 is blocked and intake air is not supplied from the intake passage 20 into the crankcase 13. In S5, the bypass passage control valve 70 is opened. As a result, the intake air passes through the bypass passage 20a and bypasses the electric supercharger 50. Thereafter, one unit of processing is completed.

  In S6, based on the detection result of the water temperature sensor 203, it is determined whether or not the temperature of the gasoline engine 10 is equal to or lower than the threshold temperature α. If yes, go to S7, otherwise go to S12. The threshold temperature α is a reference for determining whether or not the gasoline engine 10 is cold, and is set to about 80 to 90 degrees Celsius, for example. In the present embodiment, when the gasoline engine 10 is cold (when the temperature detected by the water temperature sensor 203 is equal to or lower than the threshold temperature α), control for increasing the amount of fuel injected by the fuel injection valve 14b (warming-up increase) Control).

  In S7, the electric supercharger 50 is operated, and in S8, the switching valve 41 is opened. Thereby, the pressurized intake air by the electric supercharger 50 is supplied not only to the intake port 14 but also to the crankcase 13, and the crankcase 13 is supercharged. Therefore, the ECU 200, the supply passage 40, and the switching valve 41 operate the electric supercharger 50 after the operation of the electric starter 205 is finished, and add the pressurized intake air from the electric supercharger 50 into the crankcase 13 of the gasoline engine 10. It functions as a pressure intake supply means.

  In this case, the output of the electric motor 50a is adjusted so that the supercharging pressure of the electric supercharger 50 is equal to or lower than the pressure resistance of the oil seal of the crankshaft 13a. For example, it is 0.3 bar or less. By doing so, it is possible to prevent the fuel from leaking into the crankcase 13 by pressurizing the inside of the crankcase 13 without impairing the sealing performance of the crankshaft 13a.

  In S9, based on the detection result of each sensor acquired in S1, it is determined whether surging has occurred in the electric supercharger 50 or not. If yes, go to S10, otherwise go to S11.

  In S10, the opening degree of the bypass passage control valve 70 is controlled so that the electric supercharger 50 does not generate surging (surging prevention control). For example, the bypass passage control valve 70 is set half open. Surging generally occurs when the intake air amount is small and the pressure difference before and after the electric supercharger 50 is high (when the downstream side is higher than the electric supercharger 50).

  By making the bypass passage control valve 70 half open, the intake air recirculates through the bypass passage 20a as shown by the broken line arrow in FIG. 1, the pressure difference before and after the electric supercharger 50 becomes smaller, and surging can be eliminated. . In this embodiment, in order to pressurize the inside of the crankcase 13, surcharge may occur because the electric supercharger 50 is operated when the gasoline engine 10 is started and the gasoline engine 10 is started. Can be eliminated.

  After the processing of S10, one unit of processing ends. In S11, the bypass passage control valve 70 is closed. Thereafter, one unit of processing is completed.

  In S12, it is determined whether or not the operation state of the gasoline engine 10 is in the electric supercharging region. If yes, go to S13, otherwise go to S15. The electric supercharging region is an operating state in which the electric supercharger 50 is operated to perform supercharging. As shown in FIG. 4A, the exhaust turbocharger 60 has a low supercharging pressure at a low rotation speed. At high demand torque (accelerator opening: large).

  In S13, the electric supercharger 50 is operated, and in S14, the switching valve 41 is closed. Thereby, only the intake port 14 is supercharged by the electric supercharger 50, and the inside of the crankcase 13 is not supercharged. When the gasoline engine 10 is warm, even if it is restarted, there is little unburned fuel and there is almost no fuel adhering to the inner wall of the cylinder so that the crankcase 13 is not supercharged. It is a thing. After the process of S14, the above-described processes after S9 are executed.

  In S15, the electric supercharger 50 is stopped, and in S16, the switching valve 41 is closed. Further, in S17, the bypass passage control valve 70 is opened. As a result, the intake air passes through the bypass passage 20 a and is supplied to the intake port 14, and is not supplied into the crankcase 13. Thereafter, one unit of processing is completed.

  As described above, according to the present embodiment, when the gasoline engine 10 is started, the inside of the crankcase 13 is pressurized, so that the fuel that is about to leak into the crankcase 13 can be pushed back to the combustion chamber 11a. Therefore, it is possible to prevent fuel from leaking into the crankcase 13 when the gasoline engine 10 is started.

  Further, the supercharging of the intake port 14 and the pressurization of the crankcase 13 can be used together by the electric supercharger 50, and the number of parts can be reduced. Furthermore, by operating the electric supercharger 50 after the operation of the electric starter 205 is completed, the power consumption of the battery can be reduced as compared with the case where both are operated simultaneously.

  In the present embodiment, the pressurized intake air supplied by the electric supercharger 50 is supplied into the crankcase 13 until the temperature of the gasoline engine 10 reaches a predetermined temperature (threshold temperature α) by the determination process of S6. is doing. During the warm-up operation of the gasoline engine 10, the amount of fuel is increased, so that the fuel adheres to the inner wall surface of the cylinder, and the startability is poor when the gasoline engine 10 is cold. According to this configuration, the inside of the crankcase 13 is pressurized until the gasoline engine 10 reaches the threshold temperature α. Therefore, in any of the above cases, the fuel is contained in the crankcase 13. Can be prevented from leaking out.

  In the present embodiment, the electric supercharger 50 is disposed upstream of the compressor 61 of the exhaust turbocharger 60, and the supply passage 40 is connected to the intake passage 20 downstream of the compressor 61. Since a part of the intake air flows into the supply passage 40 at the branch point between the intake passage 20 and the supply passage 40, the supercharging pressure in the intake passage 20 by the electric supercharger 50 slightly decreases downstream from the branch point. However, since the compressor 61 is located on the upstream side of the branch point, it is not affected. For this reason, the periphery of the compressor 61 is maintained at a higher pressure, and the lubricating oil that lubricates the shaft portion of the exhaust turbocharger 60 can be prevented from leaking from the compressor 61 to the intake passage 20.

It is a block diagram of gasoline engine system 1 provided with the supercharging device concerning one embodiment of the present invention. 2 is a block diagram of a control system of the gasoline engine system 1. FIG. It is a flowchart which shows the example of electric supercharging control. (A) is explanatory drawing of an electric supercharging area | region, (b) is a schematic diagram which shows the fuel F adhering to the cylinder inner wall of the cylinder block 12. FIG.

Explanation of symbols

10 Engine 13 Crankcase 20 Intake passage 20a Bypass passage 30 Exhaust passage 40 Supply passage 50 Electric supercharger 70 Bypass passage control valve 205 Electric starter

Claims (6)

In an engine supercharger comprising an electric supercharger disposed in an intake passage and started by an electric starter,
An engine comprising: a pressurized intake air supply means for operating the electric supercharger after the operation of the electric starter is completed and supplying pressurized intake air from the electric supercharger into a crankcase of the engine. Supercharger.   The pressurized intake air supply means supplies pressurized intake air from the electric supercharger into the crankcase of the engine until the engine reaches a predetermined temperature after the operation of the electric starter is completed. The supercharger for an engine according to claim 1.   2. The engine supercharging device according to claim 1, wherein the pressurized intake air is set to a pressure equal to or lower than an oil seal pressure resistance of a crankshaft of the engine. Furthermore,
A bypass passage that branches off the intake passage and bypasses the electric supercharger;
A bypass passage control valve disposed in the bypass passage;
Control means for controlling the bypass passage control valve;
A throttle valve disposed in the intake passage on the downstream side of the bypass passage,
The pressurized intake air supply means includes
The pressurized intake air supply passage, which is upstream of the throttle valve and branched from the intake passage downstream of the bypass passage and connected to the crankcase,
The control means includes
2. The bypass passage control valve according to claim 1, wherein the pressurized suction supply means controls the bypass passage control valve so that the electric supercharger does not generate surging when the pressurized intake air is supplied into the crankcase. The engine supercharger described in 1. Furthermore,
The supercharger for an engine according to claim 4, further comprising a suppressor disposed in the supply passage and configured to suppress a gas flow from the crankcase to the intake passage. Furthermore,
An exhaust turbocharger including a compressor disposed in the intake passage and a turbine disposed in the exhaust passage on the downstream side of the electric supercharger;
The pressurized intake air supply means includes
2. The engine supercharging device according to claim 1, further comprising a supply passage for the pressurized intake air that is branched from the intake passage downstream of the compressor and connected to the crankcase.

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