JP2013124544A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To accurately remove blowby gas in an internal combustion engine including a PCV passage and an ejector passage.SOLUTION: The PCV passage (first blowby gas passage) 21 makes the blowby gas in a crank chamber 2a flow back to a suction passage 10 by a negative pressure action. The ejector passage (second blowby gas passage) 25 sucks the blowby gas from the crank chamber 2a while an exhaust turbo supercharger 18 is driven. When intake pressure P reaches a preset value, a wastegate valve 20 is closed to pre-drive the exhaust turbo supercharger 18. Thereby, the blowby gas can be sucked and removed from the crank chamber 2a by making the ejector passage 25 function while suction of the blowby gas by the PCV passage 21 is incomplete. When supercharging pressure reaches an upper limit value, the amount of supercharging by the exhaust turbo supercharger 18 is decreased for prevention of excessive suction.

Description

  The present invention relates to an internal combustion engine for a vehicle in which a blow-by gas in a crank chamber is recirculated to intake air through a PCV passage and an ejector passage.

  In a vehicle internal combustion engine equipped with an exhaust turbocharger, the crank chamber and the intake passage are connected by a PCV passage as ventilation means for the crank chamber, and blow-by gas is supplied to the intake passage so that the crank chamber pressure does not become higher than atmospheric pressure. Refluxing is performed. On the other hand, pressure fluctuation occurs in the crank chamber due to the reciprocating motion of the piston. In particular, in the case of a four-cycle two-cylinder internal combustion engine, the pressure fluctuation in the crank chamber is large because the two pistons reciprocate in the same phase, and therefore the inside of the crank chamber becomes higher than the atmospheric pressure even if the PCV passage is provided If the phenomenon easily occurs, there is a problem that oil leaks from the crank chamber to the outside of the engine. Further, in the supercharging operation region, there is a problem that recirculation due to blow-by gas intake negative pressure cannot be performed.

  Therefore, paying attention to the exhaust turbocharger, the upstream side and the downstream side of the exhaust turbocharger are connected by a bypass passage, and an ejector-type suction portion is provided in the bypass passage so that the ejector-type suction portion and the crank chamber Are connected to each other through an ejector passage to reduce the pressure in the crank chamber and return the blow-by gas to the intake passage (for example, Patent Document 1).

JP 2009-299645 A

  Now, since the exhaust turbocharger acts as a resistance against the flow of the exhaust gas, the fuel consumption is deteriorated if it is always driven. Therefore, the exhaust turbocharger is provided with a wastegate valve that controls the amount of exhaust gas entering the turbine chamber, and the exhaustgate turbocharger is closed only when a load exceeding a certain level is required for the engine. Driving the feeder is done.

  When the exhaust turbocharger is provided with a wastegate valve in this way, for example, the ejector type suction part provided in the bypass passage cannot function because it is not supercharged in the low / medium load region, and the crank chamber ventilation means However, if the intake passage is at a pressure close to the atmospheric pressure, the blow-by gas is not sucked from the PCV passage due to the negative pressure. There is a situation where oil cannot be prevented from leaking to the outside. Further, since the crank chamber cannot be accurately ventilated, there is a risk of causing a situation in which deterioration of the oil stored in the crank chamber is advanced.

  For example, when the vehicle is accelerated moderately from steady running, the exhaust turbocharger operates (supercharging) even though the blow-by gas increases and the internal pressure of the crank chamber increases due to the increase in engine load and rotation speed. Otherwise, the pressure in the intake passage remains at atmospheric pressure and the ejector suction unit does not function, and as a result, phenomena such as oil leakage and oil deterioration may occur.

  The same thing occurs in a supercharger driven by an electric motor or a supercharger driven by an output shaft of an engine. This is because regardless of the type of turbocharger, if the turbocharger is driven in an operation region where the throttle valve is not fully open, the supercharged intake air is limited by the throttle valve, and the work of the supercharger is wasted. This is because the turbocharger is driven only when a load of a certain level or more is required for the engine.

  As a countermeasure against this phenomenon, it is conceivable to increase the flow rate of the bypass passage so that the ejector-type suction section operates even at a low pressure. However, in this countermeasure, a high supercharging operation such as maximum torque operation (WOT) is performed. In this case, there is a problem that the amount of suction from the ejector-type suction portion increases so much that the amount of oil mist taken out from the crank chamber increases.

  The present invention has been made in view of such a current situation, and an object thereof is to accurately process blow-by gas without increasing oil consumption.

  The internal combustion engine of the present invention basically includes an engine body having a combustion chamber and a crank chamber, an intake passage and an exhaust passage connected to the combustion chamber of the engine body, and a compressor interposed in the intake passage. Equipped with a supercharger.

  In the first aspect of the present invention, in the basic configuration, a throttle valve is provided on the downstream side of the turbocharger in the intake passage, and the downstream side of the throttle valve in the intake passage. And the crank chamber are connected by a first blow-by gas recirculation passage, and a bypass passage is connected to the intake passage to return the air downstream of the supercharger to the upstream side. The ejector-type suction part provided in the bypass passage and the crank chamber are connected by a second blow-by gas recirculation passage, and provided in the bypass passage when the supercharger is driven and the intake air is supercharged. In addition, the ejector type suction part functions.

  Furthermore, in the invention of claim 1, the supercharger is provided with a supercharging pressure adjusting means, and is based on an actual generation amount or an estimated generation amount of blow-by gas, or an actually measured value or an estimated value of a crank chamber pressure. The supercharging pressure adjusting means is controlled so that the supercharging pressure by the supercharger becomes a target value.

  According to a second aspect of the present invention, in the first aspect, the load applied to the main shaft, the rotational speed of the main shaft and the engine temperature are used as variables, and the amount of blow-by gas increases as the load and the rotational speed increase and as the engine temperature decreases. As a result, the target value of the supercharging pressure is set.

  According to the present invention, by pre-driving the turbocharger by predicting an increase in the pressure in the crank chamber and an increase in blow-by gas, the ejector-type suction portion provided in the bypass passage can function properly, and the blow-by gas in the crank chamber Can be accurately eliminated and recirculated to the intake passage. Further, since the supercharger is not always driven but is driven only when necessary, the supercharger is not wasted and the fuel consumption is not deteriorated, and there is no need to increase the flow of the bypass passage. Therefore, the oil consumption does not increase due to excessive suction of the crank chamber in the high load operation region.

  Now, when the engine load increases or the engine speed increases, the amount of blow-by gas generated tends to increase due to an increase in fuel consumption and an increase in combustion pressure. On the other hand, when the engine temperature is high, the gap between the piston and the cylinder bore becomes small and blow-by gas decreases. However, when the engine temperature is low, the gap between the piston and the cylinder bore increases and the amount of blow-by gas increases. Therefore, the load and the rotational speed are in a positive proportional relationship with the amount of blow-by gas generated, and the height of the engine temperature is in a negative proportional relationship with the amount of blow-by gas. Therefore, if the structure of claim 2 is adopted as a basis for controlling the load, the rotational speed, and the engine temperature, the amount of blow-by gas generated can be accurately predicted and processed accurately.

It is a schematic diagram (conceptual diagram) of an embodiment of the present invention. It is a graph for explanation of a control example. It is a flowchart of a control example.

(1). Configuration of Internal Combustion Engine Next, a description will be given based on an embodiment of the present invention. This embodiment is applied to an internal combustion engine using gasoline as fuel. The internal combustion engine is a two-cylinder vertical type, and has an engine body 1 having a cylinder block 2 and a cylinder head 3 as main elements, and a piston 4 is slidably fitted into the cylinder block 2 2. Two cylinder bores 5 are arranged side by side in a direction perpendicular to the paper surface. The combustion chamber is a space surrounded by the cylinder head 3, the cylinder bore 2 and the piston 4. An oil pan 6 is fixed to the lower surface of the cylinder block 2, and a cylinder head cover 7 covering the valve chamber is fixed to the cylinder head 3.

  An intake manifold 8 is attached to one surface of the cylinder head 3 constituting the engine body 1, and an exhaust manifold 9 is attached to the other surface of the cylinder head 3. An intake passage 10 is connected to the intake manifold 8, an air cleaner 11 is disposed upstream of the intake passage 10, an intercooler 12 is inserted downstream thereof, and a throttle valve is further disposed downstream thereof. 14 is inserted. A surge tank 13 is provided on the downstream side of the throttle valve 14.

  An exhaust passage 16 is connected to the exhaust manifold 9, and a catalyst-type exhaust purification device 17 is inserted into the exhaust passage 16. A silencer (not shown) is connected to the downstream end of the exhaust passage 8, and the exhaust gas is finally released to the atmosphere. The internal combustion engine has an exhaust turbocharger 18, a portion of the exhaust passage 16 upstream of the exhaust purification device 17 is connected to the turbine chamber 18 a of the exhaust turbocharger 18, and the exhaust turbocharger is connected. A portion of the intake passage 10 between the air cleaner 11 and the intercooler 12 is connected to the 18 compressor chambers 18b. Inside the compressor chamber 18b, a compressor impeller connected by a shaft to a turbine impeller provided in the turbine chamber 18a is disposed, and the compressor impeller and the casing form a compressor.

  A waste gate valve 20 driven by an electric motor 19 is provided as a supercharging pressure adjusting means in front of the turbine chamber 18a in the exhaust turbocharger 18. The wastegate valve 20 is a valve for releasing the exhaust gas upstream of the turbine chamber (exhaust pressure of the exhaust gas). By controlling the opening degree of the wastegate valve 20, the work efficiency of the exhaust turbocharger 18 can be reduced. Control from 0 to 100 is possible.

  The crank chamber 2 a of the cylinder block 2 and the surge tank 13 are connected by a first blow-by gas passage (PCV passage) 21. The first blow-by gas passage 21 is provided with a PCV valve 21a having a check valve. Therefore, if a pressure difference occurs between the crank chamber 2a and the surge tank 13 so that the surge tank 13 side (the intake passage 10 side) is negative, the blow-by gas accumulated in the crank chamber 2a It is discharged to be used for combustion.

  In the intake passage 10, the upstream portion and the downstream portion of the exhaust turbocharger 18 are connected by a bypass passage 23. In the present embodiment, the start end of the bypass passage 23 is connected to a portion between the intercooler 12 and the throttle valve 14. The bypass passage 23 has an ejector-type suction portion 24 having a horizontal hole facing an orifice having a narrow flow passage. The ejector-type suction portion 24 and the crank chamber 2a are connected to a second blow-by gas passage (ejector). (Path) 25.

  In order for the intake air to flow into the bypass passage 23, the intake passage 10 must be at a positive pressure higher than the atmospheric pressure, and for this purpose, the exhaust turbocharger 18 must be driven. Therefore, the ejector-type suction unit 24 functions only when the exhaust turbocharger 18 is driven, and the suction of the blowby gas by the second blowby gas passage 25 can be performed only when the exhaust turbocharger 18 is driven. Not done. In FIG. 1, the flow of blow-by gas is indicated by dotted arrows.

  Note that clean air is supplied to the valve operating chamber 27 through the ventilation pipe 26 from a portion of the intake passage 10 between the air cleaner 11 and the exhaust turbocharger 18. The internal combustion engine includes an EGR device that recirculates a part of the exhaust gas to the intake system, but a description thereof is omitted.

  The internal combustion engine is provided with a control device (ECU) 29 equipped with a CPU and memories, and the control device 29 detects a throttle sensor 30 for detecting the opening degree of the throttle valve 14 and a pressure inside the surge tank 13. An intake pressure sensor 31, a crank chamber pressure sensor 32 for detecting the pressure inside the crank chamber 2a, a rotation sensor 34 for detecting the rotation speed of the main shaft (crank shaft) 33, and a load sensor 35 for detecting a load applied to the main shaft 33. An engine temperature sensor 36 for detecting the temperature of the engine, an accelerator sensor (potentiometer) 38 for detecting the depression amount of the accelerator pedal 37, and an excessive pressure for detecting the pressure in the intake passage between the exhaust turbocharger and the throttle valve 14. A supply pressure sensor 39 and the like are connected. The rotation of the motor 19 that drives the waste gate valve 20 is controlled based on an instruction signal from the control device 29. The engine temperature sensor 36 can be replaced with a coolant temperature sensor.

(2). Control Mode Next, a control mode will be described. The intake pressure described here is the pressure in the intake pipe downstream from the throttle valve, and is specifically a value detected by the intake pressure sensor 31 provided in the surge tank. The supercharging pressure is the pressure in the intake passage between the exhaust turbocharger and the throttle valve 14, and is specifically a value detected by the supercharging pressure sensor 39.

  First, the outline will be described with reference to FIG. FIG. 2 is a graph showing the relationship between the PCV passage flow rate (flow rate of the first blow-by gas passage 21) and the intake pressure, and the relationship between the suction amount in the ejector passage (second blow-by gas passage 25) and the intake pressure. . Since the PCV passage 21 sucks blow-by gas using the differential pressure between the intake passage 10 and the crank chamber 2a, the suction amount is negatively proportional to the intake pressure, and the intake pressure becomes equal to the atmospheric pressure. (To be exact, when the pressure difference becomes zero), the suction amount becomes zero.

  On the other hand, since suction in the ejector passage 25 utilizes the flow in the bypass passage 23, suction is not performed unless the supercharging pressure is positive. When the load applied to the engine becomes large to some extent due to depression of the accelerator pedal 37 or the like, the exhaust turbocharger 18 is driven and supercharged. Conventionally, as shown by the curve A, the suction by the PCV passage 21 is performed. Since the supercharging was started after the engine stopped, there was a region where the blow-by gas could not be sufficiently removed by the PCV passage 21 alone.

  Therefore, in the present embodiment, as indicated by curve B, the exhaust turbocharger 18 is actively driven even when the intake pressure is negative, whereby fresh air is supplied to the bypass passage 23 and blow-by gas is discharged from the ejector passage 25. This causes the blow-by gas to be accurately sucked and refluxed. This control is based on, for example, the detection value of the intake pressure sensor 31, and when this exceeds the drive target value, the wastegate valve 20 of the exhaust turbocharger 18 is closed, and when the boost pressure reaches the target set value, the waist is reached. This is realized by a system that maintains the opening of the gate valve 20.

  If the crank chamber 2a is ventilated excessively, the amount of oil consumption increases, so when the supercharging pressure exceeds the target set value, the wastegate valve 20 is driven in the opening direction to reduce the efficiency of the exhaust turbocharger 18. .

  Next, a flowchart of a control example will be described based on FIG. In the figure, the step is indicated by S, YES is simplified as Y, and NO is simplified as N below S2. The control system starts with the engine operation, and the exhaust turbocharger 18 is not driven in this state.

  Therefore, it is determined in S1 whether or not the intake pressure P of the surge tank 13 has reached the supercharging start target value P1, and if YES, the wastegate valve 20 is driven in the closing direction to start supercharging ( S2), the supercharging amount increases with time. If NO in S1, return.

  The exhaust turbo supercharger 18 increases the driving efficiency. In the course of this, it is determined at an appropriate time interval whether or not the supercharging pressure P ′ is larger than the supercharging target value P2 (S3). When the supercharging pressure P ′ is larger than the supercharging target value P2, the wastegate valve 20 is driven in the opening direction to reduce the supercharging amount by the exhaust turbocharger 18 (S4). When P ′ is smaller than the supercharging target value P2, the wastegate valve 20 is driven in the closing direction to increase the supercharging amount by the exhaust turbocharger 18 (S5).

  Next, it is determined whether or not the supercharging pressure P ′ and the supercharging target value P2 coincide with each other (S6). If they coincide with each other, the driving of the wastegate valve 20 is stopped and the supercharging amount becomes a constant state. (S7). In this case, the wastegate valve 20 may be in a steady state when fully closed, or may be in a steady state before being fully closed. The supercharging target value P2 only needs to be such that the ejector-type suction unit 24 functions to suck the blow-by gas in the crank chamber 2a. When the intake pressure is equal to or lower than the atmospheric pressure, at least the engine speed and the suction target value P2. If the intake pressure is greater than the atmospheric pressure, it is determined from at least the engine speed, the intake pressure, and the amount of depression of the accelerator pedal.

  In this way, the supercharging start target value P1 is set for the intake pressure P1, and the target value P2 is set for the supercharging pressure, and the exhaust turbocharger 18 is driven based on this (controlling the wastegate valve 20). Therefore, pre-supercharging can be performed in a state where the PCV passage 21 is not functioning, and blow-by gas can be appropriately sucked and refluxed, and an increase in oil take-out due to excessive supercharging can be prevented.

  Furthermore, it is also possible to control the opening and closing of the wastegate valve 20 based on a target value set in advance by using the pressure in the crank chamber 2a, the load acting on the main shaft 33, or the temperature of the engine as a control value. In this case, the pressure and load of the crank chamber 2a may be a main control element at the same level as the intake pressure P and the rotation speed R, or an auxiliary element (correction element) that complements the control by the intake pressure P and the rotation speed R. It is good. It is also possible to calculate the control element of the independent concept which packaged each element, and to control the wastegate valve 20 based on this.

  Further, the target set value does not need to be unchanged, and can be changed according to the driving situation. Further, the opening degree of the throttle valve 14 can be adopted as a control element of the wastegate valve 20.

  The ejector-type suction part provided in the bypass passage and the crank chamber do not need to be directly connected by the second blow-by gas recirculation passage, for example, via the blow-by passage provided in the valve operating chamber or the cylinder block. You may connect.

  In the above embodiment, the crank chamber pressure sensor 32 that detects the pressure inside the crank chamber 2a is provided. However, the amount of blow-by gas may be estimated from the engine speed and the intake pressure to derive the crank chamber pressure. In the above embodiment, the load sensor 35 for detecting the load applied to the main shaft 33 is provided. However, the load applied to the main shaft 33 may be estimated from the engine speed and the intake pressure. Further, in the above embodiment, the supercharging pressure sensor 39 is provided in the portion of the intake passage 10 between the exhaust turbocharger 18 and the throttle valve 14 as the supercharging pressure detection means. The supercharging pressure may be estimated from the atmospheric pressure and the throttle valve opening.

  The present invention is actually applicable to an internal combustion engine. Therefore, it can be used industrially.

DESCRIPTION OF SYMBOLS 1 Engine body 2 Cylinder block 3 Cylinder head 4 Exhaust manifold 10 Intake passage 12 Intercooler 13 Surge tank 14 Throttle valve 16 Exhaust passage 18 Exhaust turbocharger as an example of supercharger 19 Motor for driving a wastegate valve 20 Excess Wastegate valve 21 as an example of supply pressure adjusting means 21 First blow-by gas passage (PCV passage)
23 Bypass passage 24 Ejector type suction part 25 Second blow-by gas passage (ejector passage)
29 Control device 30 Throttle sensor 31 Intake pressure sensor 32 Crank chamber pressure sensor 34 Rotation sensor 35 Load sensor
39 Supercharging pressure sensor

Claims (2)

An engine body having a combustion chamber and a crank chamber, an intake passage and an exhaust passage connected to the combustion chamber of the engine body, and a supercharger in which a compressor is inserted in the intake passage,
A throttle valve is provided downstream of the supercharger in the intake passage, and a portion of the intake passage downstream of the throttle valve and the crank chamber are connected by a first blow-by gas recirculation passage. In addition, a bypass passage that can return the air on the downstream side of the supercharger to the upstream side is connected to the intake passage, and an ejector-type suction portion provided in the bypass passage and the crank chamber are connected to each other. 2 connected by a blow-by gas recirculation passage,
When the supercharger is driven and the intake air is supercharged, the ejector-type suction part provided in the bypass passage is configured to function,
The supercharger is provided with a supercharging pressure adjusting means, and the supercharging pressure by the supercharger is determined based on the actual generation amount or the predicted generation amount of blow-by gas, or the measured value or predicted value of the pressure in the crank chamber. The supercharging pressure adjusting means is controlled so that becomes a target value,
Internal combustion engine. Using the load applied to the main shaft, the rotational speed of the main shaft, and the engine temperature as variables, the target value of the supercharging pressure is predicted by increasing the amount of blow-by gas as the load and the rotational speed are higher and as the engine temperature is lower. Is set,
The internal combustion engine according to claim 1.

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