Engine system

Abstract

To provide an engine system suppressing deterioration of supercharging efficiency.SOLUTION: An engine system includes an engine, a supercharger including a compressor arranged in an intake passage of the engine, a throttle valve arranged in the intake passage in the downstream side of the compressor, a PCV passage which allows blow-by gas generated in the engine to flow in the intake passage in the upstream side of the compressor when an operation point of the engine is in a supercharging zone, an electromagnetic valve for opening and closing the PCV passage, a temperature sensor for detecting a temperature of supercharged air supercharged by the compressor, a communication passage which communicates the engine with the intake passage in the downstream side of the compressor and in the upstream side of the throttle valve, a pump for pressure-feeding the blow-by gas in the engine into the intake passage through the communication passage, and a control device which closes the electromagnetic valve and operates the pump when the temperature of the supercharged air is equal to or higher than a threshold.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an engine system. [Background technology]

[0002] Blow-by gas generated in the engine is introduced into an intake passage upstream of the compressor, thereby allowing the blow-by gas to be burned (see, for example, Patent Document 1). [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Publication No. 2020-128724 Summary of the Invention [Problem to be solved by the invention]

[0004] If the blow-by gas is introduced upstream of the compressor when the compressor is hot, the insoluble components in the oil in the blow-by gas may change in quality, causing deposits to form on the compressor surface, which may reduce turbocharging efficiency.

[0005] SUMMARY OF THE INVENTION It is therefore an object of the present invention to provide an engine system that suppresses a decrease in supercharging efficiency. [Means for solving the problem]

[0006] The above object can be achieved by an engine system including an engine, a turbocharger including a compressor arranged in an intake passage of the engine, a throttle valve arranged in the intake passage downstream of the compressor, a PCV passage through which blow-by gas generated in the engine flows to the intake passage upstream of the compressor when an operating point of the engine is in a supercharging region, a solenoid valve that opens and closes the PCV passage, a temperature sensor that detects the temperature of supercharged air supercharged by the compressor, a communication passage that communicates the engine with the intake passage downstream of the compressor and upstream of the throttle valve, a pump that pressurizes and feeds blow-by gas from within the engine to the intake passage via the communication passage, and a control device that closes the solenoid valve and operates the pump when the temperature of the supercharged air is equal to or higher than a threshold value. [Effects of the Invention]

[0007] According to the present invention, it is possible to provide an engine system in which a decrease in supercharging efficiency is suppressed. [Brief explanation of the drawings]

[0008] [Figure 1] FIG. 1 is a schematic configuration diagram of an engine system. [Figure 2] 4 is a flowchart illustrating control of the solenoid valve and the scavenge pump executed by the ECU. DETAILED DESCRIPTION OF THE INVENTION

[0009] [Engine system overview] FIG. 1 is a schematic diagram of an engine system. The engine system is mounted on, for example, a vehicle. The engine system includes an engine 1 and an ECU (Electronic Control Unit) 20. The engine 1 functions, for example, as a power source for driving the vehicle. The engine 1 includes a cylinder block 3a, a cylinder head 3b, and a crankcase 3c. The engine 1 is a gasoline engine, but may also be a diesel engine. A plurality of cylinders are provided within the cylinder block 3a. Combustion chambers communicating with the cylinders are formed within the cylinder head 3b. A crankshaft (not shown) is rotatably provided within the crankcase 3c.

[0010] An intake passage 4 is connected to the cylinder head 3b via an intake manifold 9. The intake passage 4 is provided with, from upstream, an air cleaner 5, a compressor 6a, an intercooler 7, and a throttle valve 8. The compressor 6a of the turbocharger 6 compresses the intake air. The compressor 6a is integrally connected to a turbine 6b arranged in the exhaust passage via a connecting shaft. The intercooler 7 cools the supercharged air supercharged by the compressor 6a. The opening of the throttle valve 8 is controlled by the ECU 20 to adjust the amount of intake air to the engine 1. An exhaust passage is connected to the cylinder head 3b via an exhaust manifold.

[0011] A blow-by gas introduction chamber 11 is provided in the cylinder block 3a. A blow-by gas guide passage 12 is in communication with the blow-by gas introduction chamber 11. The blow-by gas guide passage 12 is formed to penetrate the cylinder block 3a and the cylinder head 3b. The blow-by gas guide passage 12 communicates with the crankcase 3c and the oil separator 13 via the blow-by gas introduction chamber 11, and guides the blow-by gas present in the crankcase 3c to the oil separator 13.

[0012] In the oil separator 13, oil mist is separated from the blow-by gas and returned to the intake manifold 9 via a PCV (Positive Crankcase Ventilation) passage 15. A differential pressure operated valve 14 is installed at the end of the PCV passage 15 on the oil separator 13 side. The differential pressure operated valve 14 operates in response to the differential pressure between the cylinder head 3b side on the upstream side and the intake manifold 9 on the downstream side. The differential pressure operated valve 14 adjusts the flow rate of the blow-by gas returned to the intake manifold 9 and prevents the blow-by gas from flowing back.

[0013] The PCV passage 16 connects the oil separator 13 to a portion of the intake passage 4 downstream of the air cleaner 5 and upstream of the compressor 6a. A solenoid valve 17 is provided in the PCV passage 16. The solenoid valve 17 is, for example, of a normally open type that maintains an open state when de-energized. When a predetermined condition is met, the ECU 20 closes the solenoid valve 17. A communication passage 19 connects the blow-by gas introduction chamber 11 to a portion of the intake passage 4 downstream of the intercooler 7 and upstream of the throttle valve 8. A scavenge pump 18 is provided in the communication passage 19. The scavenge pump 18 is an electric pump. When a predetermined condition is met, the ECU 20 drives the scavenge pump 18. The solenoid valve 17 and the scavenge pump 18 will be described in detail later.

[0014] The ECU 20 is mainly configured with a computer including a CPU (Central Processing Unit) and volatile and non-volatile memories such as RAM (Random Access Memory) and ROM (Read Only Memory). The ECU 20 is an example of a control device. A sensor group 22 is connected to the ECU 20. The sensor group 22 includes a crank angle sensor and an air flow meter. The crank angle sensor detects the rotation speed of the engine 1. The air flow meter calculates the amount of intake air of the engine 1. A temperature sensor 24 is also connected to the ECU 20. The temperature sensor 24 is provided in the intake passage 4 downstream of the compressor 6a and upstream of the intercooler 7 and the throttle valve 8. The temperature sensor 24 detects the temperature of the supercharged air supercharged by the compressor 6a. The ECU 20 also controls the solenoid valve 17 and the scavenge pump 18.

[0015] When the operating point of the engine 1 is in the natural aspiration (NA) region, the pressure inside the intake manifold 9 downstream of the throttle valve 8 becomes negative, and the pressure inside the intake passage 4 upstream of the compressor 6a becomes atmospheric. Therefore, in the NA region, blow-by gas is returned to the intake manifold 9 via the oil separator 13 and the PCV passage 15. In this way, the blow-by gas is burned.

[0016] When the operating point of the engine 1 is in the supercharging region, the downstream side of the compressor 6a is under positive pressure, and the inside of the intake passage 4 upstream of the compressor 6a is under negative pressure. Therefore, in the supercharging region, blow-by gas is returned to the intake passage 4 upstream of the compressor 6a via the oil separator 13 and the PCV passage 16. In this way, the blow-by gas is burned.

[0017] [Control of solenoid valve 17 and scavenge pump 18] The ECU 20 controls the solenoid valve 17 and the scavenge pump 18 as follows. Figure 2 is a flowchart illustrating the control of the solenoid valve 17 and the scavenge pump 18 executed by the ECU 20. The ECU 20 determines whether the operating point of the engine 1 is in the supercharging region based on the engine speed and the intake air amount (step S1). If the answer is No in step S1, this control ends.

[0018] If the answer is Yes in step S1, the ECU 20 determines whether the temperature of the supercharged air is equal to or higher than a threshold value based on the detection value of the temperature sensor 24 (step S2). The threshold value is set to the minimum temperature of the supercharged air at which deposits may occur in the compressor 6a when air containing blow-by gas is introduced into the compressor 6a. If the answer is No in step S2, this control ends.

[0019] If the answer to step S2 is Yes, the ECU 20 closes the solenoid valve 17 (step S3). This prevents blow-by gas from being introduced to the compressor 6a via the PCV passage 16 when the operating point of the engine 1 is in the supercharging region and the supercharging air is at a high temperature. This prevents deposits from forming in the compressor 6a and reduces the decrease in supercharging efficiency.

[0020] Here, if the solenoid valve 17 is closed, the blow-by gas in the engine 1 will not be discharged to the outside, which could cause the pressure inside the engine 1 to rise. Therefore, the ECU 20 drives the scavenge pump 18 (step S4). As a result, the blow-by gas in the engine 1 is pressure-fed to the intake passage 4 downstream of the compressor 6a via the communication passage 19. This makes it possible to burn the blow-by gas while preventing the pressure inside the engine 1 from rising. Note that, as described above, when the operating point of the engine 1 is in the supercharging region, the pressure downstream of the compressor 6a becomes positive due to the pressure of the supercharged air. Therefore, it is preferable that the pressure of the blow-by gas supplied by the scavenge pump 18 to the downstream side of the compressor 6a be higher than the pressure of the supercharged air.

[0021] Although the embodiments of the present invention have been described in detail above, the present invention is not limited to such specific embodiments, and various modifications and variations are possible within the scope of the gist of the present invention as defined in the claims. [Explanation of symbols]

[0022] 1 engine 4 Intake passage 6a Compressor 8 Throttle valve 16 PCV passage 17 Solenoid valve 18 Scavenge Pump 19 Communication path 20 ECU (control unit) 24 Temperature Sensor

Claims

[Claim 1] The engine and a supercharger including a compressor disposed in an intake passage of the engine; a throttle valve disposed in the intake passage downstream of the compressor; a PCV passage through which blow-by gas generated by the engine flows into the intake passage upstream of the compressor when the engine is operating in a supercharging region; a solenoid valve that opens and closes the PCV passage; a temperature sensor that detects the temperature of the supercharged air supercharged by the compressor; a communication passage that communicates the engine with the intake passage downstream of the compressor and upstream of the throttle valve; a pump that pumps blow-by gas from within the engine into the intake passage through the communication passage; a control device that closes the solenoid valve and operates the pump when the temperature of the supercharged air is equal to or higher than a threshold value.

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