JP4888791B2 - Unburned fuel recirculation system - Google Patents

Description

  The present invention relates to an unburned fuel recirculation system that recirculates unburned fuel in a crankcase of an internal combustion engine to an intake system of the internal combustion engine.

  It is known that so-called blow-by gas containing unburned fuel leaking into the crankcase from the gap between the piston and the cylinder significantly accelerates the deterioration of the oil when diluted with oil in the crankcase.

  For this reason, there is known a PCV (Positive Crankcase Ventilation) device that introduces blow-by gas in a crankcase into an intake system and burns unburned fuel contained in the blow-by gas (see, for example, Patent Document 1).

  Further, in Patent Document 2, in order to stabilize the fuel concentration returned to the intake system, an oil separator and a canister are provided in a return path for returning the gas in the crankcase to the intake system. A technology is disclosed in which an oil component and a fuel component contained are separated by an oil separator, and then the separated fuel component is temporarily adsorbed by a canister and returned to an intake system.

  Further, Patent Document 3 discloses a technique in which gas in a crankcase is sucked with a negative pressure pump and directly returned to the intake system.

Japanese Patent Laid-Open No. 2003-332052 JP 2005-315172 A JP 2001-164918 A

  By the way, if the unburned fuel in the crankcase is recirculated to the intake system, the air-fuel ratio of the air-fuel mixture may be disturbed, and combustion of the air-fuel mixture in the combustion chamber may become unstable. As a result, problems such as a decrease in drivability due to the occurrence of torque fluctuation and an increase in harmful pollutants contained in the exhaust gas may occur.

  The present invention has been made in view of the above circumstances, and an object thereof is an unburned fuel recirculation system for recirculating unburned fuel in a crankcase of an internal combustion engine to an intake system of the internal combustion engine. An object of the present invention is to provide an unburned fuel recirculation system that can efficiently remove unburned fuel in a crankcase while stabilizing the fuel concentration in an intake system.

  An unburned fuel recirculation system according to the present invention is an unburned fuel recirculation system that recirculates unburned fuel in a crankcase of an internal combustion engine to an intake system of the internal combustion engine, and derives the gas in the crankcase to the outside. And fuel primary storage means for temporarily storing the evaporated fuel contained in the gas derived from the crankcase before returning it to the intake system.

  The said structure WHEREIN: The structure which further has the adjustment valve which adjusts the quantity returned from the said fuel primary storage means to the intake system of an internal combustion engine, and the adjustment valve control means which controls the said adjustment valve is employable.

  In the above-described configuration, the derivation unit may include a pump that sucks the gas in the crankcase and depressurizes the crankcase, and a pump control unit that controls the operation of the pump.

  In the above configuration, the internal combustion engine has air-fuel ratio feedback control means for causing the detected air-fuel ratio of the air-fuel mixture to follow the target air-fuel ratio, and the adjustment valve control means is configured to detect the detected air-fuel ratio and the target in the air-fuel ratio feedback control means. A configuration in which the opening degree of the regulating valve is controlled according to the magnitude of the deviation from the air-fuel ratio can be employed.

  The adjusting valve control means can adopt a configuration in which fuel is recirculated from the primary fuel storage means when the detected air-fuel ratio is in the vicinity of stoichiometry, and an air-fuel ratio sensor that detects the air-fuel ratio of the air-fuel mixture is activated. Thereafter, the fuel can be recirculated from the fuel primary storage means, and further, the fuel primary storage means can prevent the deviation between the detected air-fuel ratio and the target air-fuel ratio from deviating from a predetermined range. It is possible to adopt a configuration for controlling the amount of fuel recirculation.

  In the above configuration, the adjustment valve control means limits the recirculation of fuel from the fuel primary storage means when the magnitude of the deviation between the detected air-fuel ratio and the target air-fuel ratio is outside a predetermined range. Can be adopted.

  The said structure WHEREIN: The said adjustment valve control means can employ | adopt the structure which interrupts | blocks the said adjustment valve, when the pressure of the said intake system is higher than the discharge pressure of the said pump.

  In the above configuration, the pump control means may employ a configuration that operates the pump when the internal combustion engine is decelerated.

  The said structure WHEREIN: The said pump control means can employ | adopt the structure which controls operation | movement of the said pump based on the temperature of the engine oil in the said crankcase.

  According to the present invention, the unburned fuel in the crankcase can be efficiently removed and returned to the intake system while stabilizing the fuel concentration in the intake system.

DESCRIPTION OF EXEMPLARY EMBODIMENTS Hereinafter, exemplary embodiments of the invention will be described with reference to the accompanying drawings.
FIG. 1 is a configuration diagram of an internal combustion engine to which an unburned fuel recirculation system according to an embodiment of the present invention is applied.

  The internal combustion engine includes a head cover 16, a cylinder block 17, and an oil pan 74, and includes an intake passage 11 for introducing intake air into the head cover 16 and an exhaust passage 13 for exhausting air from the head cover 16.

  The internal combustion engine has a rotational speed sensor 43 that detects the rotational speed of the crankshaft of the internal combustion engine, a water temperature sensor 45 that detects the temperature of cooling water that cools the cylinder block, and the level of lubricating oil that is held in the oil pan 74. An oil level sensor 47 for detecting, an intake air amount sensor 42 for detecting the intake air amount provided in the intake passage 11, an accelerator sensor 44 for detecting a depression amount (accelerator opening) provided in the vicinity of the accelerator pedal 60, and the exhaust passage 13 And an air-fuel ratio sensor 46 for detecting the air-fuel ratio.

  The internal combustion engine is provided in the middle of the intake passage 11 and adjusts the amount of intake air introduced into the combustion chamber 12, a fuel injection valve 20 provided downstream thereof, and an ignition provided in a cylinder described later. Plug 22 etc. are included. An electronic control unit (ECU) 50 receives the outputs of various sensors and controls the opening degree of the throttle valve 26, the ignition timing of the spark plug 22, the fuel injection amount injected from the fuel injection valve 20, the injection timing, and the like. Further, the ECU 50 executes air-fuel ratio feedback control for controlling the fuel injection amount so that the detected air-fuel ratio detected by the air-fuel ratio sensor 46 becomes the target air-fuel ratio.

  The cylinder block 17 includes a cylinder (cylinder) 17A and a crankcase 17B. A piston 14 is provided inside the cylinder 17A so as to be able to reciprocate. A combustion chamber 12 is formed by the upper portion of the piston 14 and the cylinder inner peripheral surface 18. In the head cover 16, the combustion chamber 12 is connected to the intake passage 11 and the exhaust passage 13.

  The intake air introduced from the intake passage 11 is mixed with the fuel injected from the fuel injection valve 20 to become an air-fuel mixture, and is introduced into the combustion chamber 12 when the intake valve 21 is open. The air-fuel mixture is explosively burned by ignition of the spark plug 22 and then discharged from the combustion chamber 12 to the exhaust passage 13 when the exhaust valve 23 is opened. The exhaust passage 13 is provided with a catalyst device 27 having an exhaust purification function.

  An oil pan 74 is attached to the lower portion of the crankcase 17B, and a predetermined amount of engine oil (lubricating oil) is held in the oil pan 74. The retained engine oil OL is supplied to each part of the internal combustion engine by a lubricating oil supply device (not shown).

  The lubricating oil supply device includes an oil pump, a filter, an oil jet mechanism, and the like. The oil OL in the oil pan 74 is sucked by the oil pump through the filter and supplied to the oil jet mechanism. In order to lubricate between the piston 14 and the cylinder inner peripheral surface 18, lubricating oil is supplied to the cylinder inner peripheral surface by an oil jet mechanism.

In the internal combustion engine, the intake passage 11 on the upstream side of the throttle valve 26 and the inside of the head cover 16 are communicated with each other by an atmospheric passage 76.
The cylinder block 17 is formed with an oil dropping passage 15 that communicates the inside of the head cover 16 and the inside of the crankcase 17B. The oil dropping passage 15 is a passage for dropping oil accumulated on the cylinder head after the valve system lubrication toward the oil pan 74, and fresh air (atmospheric air) into the crankcase 17B through the air passage 76. ) To serve as a supply passage.

The unburned fuel recirculation system according to this embodiment includes a pump 110, a canister 120 as a primary fuel storage means, an adjustment valve 150, an ECU 50, and the like.
The pump 110 is connected to the crankcase 17 </ b> B through a gas passage 111, and the pump 110 is connected to the canister 120 through a gas passage 121. The pump 110 and the gas passages 111 and 121 constitute the derivation means of the present invention.

  The pump 110 is configured by, for example, an electric pump, and sucks the gas G in the crankcase 17B to depressurize the crankcase 17B and supplies the sucked gas G to the canister 120. A driver 130 is connected to the pump 110, and the driver 130 receives a control command from the ECU 50 and controls the operation of the pump 110. By using an electric pump as the pump 110, the pump 110 can be driven regardless of the driving state of the engine 1, and the inside of the crankcase 17B can be decompressed. The driver 130 and the ECU 50 constitute pump control means.

  The gas G in the crankcase 17B is a so-called blow-by gas BG containing unburned fuel that blows out from the gap between the piston 14 and the cylinder inner peripheral surface 18, evaporated fuel that has been diluted again to engine oil OL, and evaporated again, oil mist Etc.

  The canister 120 is connected to the intake passage 11 on the downstream side of the throttle valve 26 via the gas passage 122, the adjustment valve 150, and the gas passage 151.

  The canister 120 incorporates activated carbon, and this activated carbon adsorbs and holds the evaporated fuel contained in the gas G in the crankcase 17B. The evaporated fuel is temporarily stored in the canister 120 and then purged to the intake passage 11 as an intake system through the gas passage 122, the adjustment valve 150, and the gas passage 151. As a result, unburned fuel returns from the crankcase 17B to the intake system. Although not shown, a so-called evaporation purge system having a known configuration can be applied between the canister 120 and the intake passage 11.

  The adjustment valve 150 is configured by a control valve, and adjusts the amount of gas recirculated from the canister 120 to the intake passage 11 in accordance with a control command from the ECU 50. The ECU 50 constitutes a regulating valve control means.

  Next, an example of a processing procedure in the unburned fuel recirculation system will be described with reference to FIGS.

  FIG. 2 is a flowchart showing an example of the control procedure of the regulating valve, and FIG. 3 is a flowchart showing an example of the control procedure of the pump operation.

  The adjustment valve control routine and the pump operation control routine shown in FIGS. 2 and 3 are executed in the ECU 50, for example, every predetermined period.

  As shown in FIG. 2, first, it is determined whether the air-fuel ratio sensor 46 is activated (step S1). This is because if the air-fuel ratio sensor 46 is not activated, the air-fuel ratio (A / F) cannot be detected, and the air-fuel ratio feedback control cannot be executed. In order to determine whether or not the air-fuel ratio sensor 46 is activated, for example, the temperature of the sensor is detected or estimated, or whether or not the internal combustion engine has been warmed up is determined.

  Next, when the air-fuel ratio sensor 46 is activated, it is determined whether the air-fuel ratio deviation between the air-fuel ratio detected by the air-fuel ratio sensor 46 and the target air-fuel ratio is smaller than a predetermined value (step S2). The magnitude of the air-fuel ratio deviation is determined when the air-fuel ratio deviation is large for some reason in the air-fuel ratio feedback control, and if the fuel is further purged from the canister 120, the air-fuel ratio deviation becomes larger and the air-fuel ratio may be disturbed. Because there is sex.

  If the air-fuel ratio sensor 46 is not activated, the discharge pressure of the pump 110 and the pressure in the intake passage 11 (intake pipe pressure) are compared (step S8). If the discharge pressure of the pump 110 is high Then, the adjustment valve 150 is shut off (step S7). This is to prevent the gas from flowing backward from the intake passage 11 side to the canister 120 side when the discharge pressure of the pump 110 is lower than the intake pipe pressure.

  Next, in step S2, if the magnitude of the air-fuel ratio deviation is smaller than a predetermined value, whether the current air-fuel ratio is in the vicinity of the stoichiometric air-fuel ratio (stoichiometric), that is, is in a predetermined range from the stoichiometric air-fuel ratio. Is determined (step S3). The reason why the current air-fuel ratio is in the vicinity of stoichiometry is that the vicinity of stoichiometry is in a range where the air-fuel ratio is stable. In other words, if the current air-fuel ratio is in the vicinity of stoichiometry, even if the air-fuel ratio fluctuates somewhat due to the purge of fuel from the canister 120, it is not significantly affected.

  When the magnitude of the air-fuel ratio deviation is smaller than the predetermined value in step S2, as described above, the discharge pressure of the pump 110 and the pressure in the intake passage 11 (intake pipe pressure) are compared (step S8). When the discharge pressure of the pump 110 is high, the adjustment valve 150 is shut off (step S7).

  When the air-fuel ratio sensor 46 is activated, the air-fuel ratio deviation is smaller than a predetermined value, and the current air-fuel ratio is close to the stoichiometry, the opening degree of the adjustment valve is determined according to the current air-fuel ratio deviation. (Step S4). The opening of the adjustment valve 150 is determined so that the air-fuel ratio deviation falls within a predetermined range when the fuel is purged into the intake passage 11. This is to minimize the disturbance of the air-fuel ratio. That is, the recirculation amount (purge amount) of fuel from the canister 120 to the intake passage 11 is determined so that the air-fuel ratio deviation falls within a range that can be compensated by the air-fuel ratio feedback control. This is because if the air-fuel ratio deviation becomes excessive, it takes a long time for the deviation to converge in the air-fuel ratio feedback control system.

  Next, the adjustment valve 150 is controlled to the determined opening, and the fuel is purged into the intake passage 11 (step S5).

  Next, it is determined whether the air-fuel ratio deviation is larger than a predetermined value (step S6). If the air-fuel ratio deviation is larger than a predetermined value, the disturbance of the air-fuel ratio increases, and this is prevented. Therefore, when the air-fuel ratio deviation is larger than the predetermined value, the adjustment valve 150 is shut off (step S7). Instead of shutting off the regulating valve 150, the opening of the regulating valve 150 may be controlled to be small.

  In step S6, it may be determined whether the operating condition of the internal combustion engine is high and the basic air-fuel ratio is high. Even when the operating condition of the internal combustion engine is high, the adjustment valve 150 is shut off. When the operating condition of the internal combustion engine is high, the air-fuel ratio is rich. Therefore, if the fuel is purged from the canister 120 in this state, the air-fuel ratio further becomes rich and the disturbance of the air-fuel ratio expands. Is to prevent.

  Next, the pump operation control routine will be described with reference to FIG. 3. First, it is determined whether the temperature of the engine oil OL in the oil pan 74 is equal to or higher than a predetermined value (step S11), and the temperature of the engine oil OL is predetermined. If it is above, the pump 110 is operated with a predetermined output (step S12). Even if the pressure in the crankcase 17B is reduced by the pump 110, if the temperature of the engine oil OL is too low, the fuel dissolved in the engine oil OL is difficult to evaporate, and the fuel removal efficiency is poor. For this reason, when the temperature of the engine oil OL rises to some extent, the unburnt fuel can be efficiently removed from the crankcase 17B by operating the pump 110.

  On the other hand, in step S11, when the temperature of the engine oil OL is not equal to or higher than the predetermined temperature, the pump 110 is stopped in consideration of poor fuel removal efficiency (step S13). For example, immediately after the cold start of the internal combustion engine, the temperature of the engine oil OL is low, so the pump 110 is not operated.

  Next, it is determined whether the operating state of the internal combustion engine shifts from cold low load to high rotation or high load, that is, whether the accelerator pedal is depressed and the throttle valve opening is increased (step S14). . If this is the case, the output of the pump 110 is increased (step S15). Preferably, the output of the pump 110 is fully opened. When shifting from a cold low load to a high rotation or high load, the fuel diluted in the engine oil OL starts to evaporate at once with a rapid temperature rise. At this time, the fuel can be efficiently recovered by increasing the output of the pump 110 and actively reducing the pressure in the crankcase 17B and recovering the unburned fuel.

  FIG. 4 is a configuration diagram of an internal combustion engine to which an unburned fuel recirculation system according to another embodiment of the present invention is applied.

  The difference between the unburned fuel recirculation system shown in FIG. 4 and the unburned fuel recirculation system shown in FIG. 1 is that a PCV (Positive Crankcase Ventilation) valve 160 comprising a one-way valve is connected to the pump 110 in parallel. . The PCV valve 160 is connected to the crankcase 17 </ b> B through a gas passage 161 and connected to the gas passage 121 through a gas passage 162.

  The PCV valve 160 is opened by an amount corresponding to the differential pressure only when the pressure on the crankcase 17B side is higher than the pressure in the intake passage 11. Accordingly, the gas G in the crankcase 17B is led out to the intake passage 11. When the pressure on the crankcase 17B side is lower than the pressure in the intake passage 11, the PCV valve 160 does not open, and no backflow of gas from the intake passage 11 to the crankcase 17B side occurs.

  In the configuration shown in FIG. 4, the operation time of the pump 110 can be, for example, only the time when the PCV valve 160 is not opened. For example, during WOT (Wide Open Throttle), since the throttle valve 26 is fully opened, the intake passage 11 is almost the same as the atmospheric pressure, and gas cannot be sucked from the crankcase 17B. In such a case, by operating the pump 110, the gas can be forcibly derived from the crankcase 17B and guided to the canister 120. According to this configuration, energy consumption of the pump 110 can be suppressed.

  In the above embodiment, the canister is described as an example of the primary fuel storage means, but in addition to the canister, evaporative fuel is provided by, for example, providing a labyrinth mechanism with gas in the crankcase and forcibly cooling it. Can be liquefied and temporarily stored.

  In the above embodiment, the adjustment valve 150 is simply provided between the intake system and the canister. However, a known evaporation purge system can be applied between the intake system and the canister.

  In the above embodiment, as the derivation means, the case where the pump 110 is used alone or the case where the pump 110 and the PCV valve 160 are used together has been described as an example, but the pump 110 is not used and only the PCV valve 160 is used. It is also possible to adopt a configuration to be used.

  In the above embodiment, the adjustment valve 150 is provided between the canister 120 and the intake passage 11. However, when the amount of fuel purged from the canister 120 to the intake passage 11 is almost constant at all times (air-fuel ratio If the disturbance is within an acceptable range), the regulating valve 150 can be omitted.

  In the above embodiment, the oil temperature has been described as an example of the conditions for operating the pump 110 (step S11 in FIG. 3). For example, when the operating state of the internal combustion engine is during deceleration, the pump 110 Can also be activated. If the pump 110 is used at the time of acceleration, energy is wasted. Therefore, if the operation is performed at the time of deceleration, more efficient traveling becomes possible.

  In the above embodiment, the case where an electric pump is used as the pump 110 is illustrated, but an oil pump connected to the crankshaft can also be used in addition to this.

1 is a configuration diagram of an internal combustion engine to which an unburned fuel recirculation system according to an embodiment of the present invention is applied. It is a flowchart which shows an example of the control procedure of an adjustment valve. It is a flowchart which shows an example of the control procedure of the operation | movement of a pump. It is a block diagram of the internal combustion engine to which the unburned fuel recirculation system which concerns on other embodiment of this invention was applied.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Intake passage 13 ... Exhaust passage 16 ... Head cover 17 ... Cylinder block 17B ... Crankcase 42 ... Intake air amount sensor 43 ... Rotational speed sensor 44 ... Accelerator sensor 45 ... Water temperature sensor 46 ... Air fuel ratio sensor 47 ... Oil level sensor 50 ... ECU
60 ... accelerator pedal 60
74 ... Oil pan 110 ... Pump 120 ... Canister 150 ... Adjustment valve BG ... Blow-by gas G ... Gas in crankcase

Claims (11)

An unburned fuel recirculation system for recirculating unburned fuel in a crankcase of an internal combustion engine to an intake system of the internal combustion engine,
Deriving means for deriving the gas in the crankcase to the outside;
Fuel primary storage means for temporarily storing the evaporated fuel contained in the gas derived from the crankcase before recirculating to the intake system;
Have
The derivation means includes a first passage connecting the crankcase and the fuel primary storage means;
A second passage connecting the crankcase and the fuel primary storage means;
A pump that is provided in the first passage and sucks the gas in the crankcase to depressurize the crankcase while supplying the sucked gas to the primary fuel storage means;
And a PCV valve provided in the second passage and opened only when the pressure in the crankcase is higher than the pressure in the passage of the intake system. An adjustment valve for adjusting the amount of recirculation from the primary fuel storage means to the intake system of the internal combustion engine;
Adjusting valve control means for controlling the adjusting valve;
The unburned fuel recirculation system according to claim 1, further comprising: It said deriving means, unburned fuel reflux system according to claim 1 or 2, characterized in that it comprises a pump control means to control the operation of the previous SL pump. The internal combustion engine has air-fuel ratio feedback control means for causing the detected air-fuel ratio of the air-fuel mixture to follow the target air-fuel ratio,
The adjusting valve control means controls the opening degree of the adjusting valve according to the magnitude of the deviation between the detected air-fuel ratio and the target air-fuel ratio in the air-fuel ratio feedback control means;
The unburned fuel recirculation system according to claim 3.   5. The unburned fuel recirculation system according to claim 4, wherein the adjustment valve control means recirculates fuel from the fuel primary storage means when the detected air-fuel ratio is in the vicinity of stoichiometric. The adjusting valve control means recirculates fuel from the fuel primary storage means after the air-fuel ratio sensor that detects the air-fuel ratio of the air-fuel mixture is activated.
The unburned fuel recirculation system according to claim 4 or 5. The regulating valve control means controls the recirculation amount of the fuel from the fuel primary storage means so that the magnitude of the deviation between the detected air-fuel ratio and the target air-fuel ratio does not deviate from a predetermined range;
The unburned fuel recirculation system according to any one of claims 4 to 6. The regulating valve control means restricts the recirculation of fuel from the fuel primary storage means when the magnitude of the deviation between the detected air-fuel ratio and the target air-fuel ratio is out of a predetermined range;
The unburned fuel recirculation system according to any one of claims 4 to 7. The regulating valve control means shuts off the regulating valve when the pressure of the intake system is higher than the discharge pressure of the pump;
The unburned fuel recirculation system according to any one of claims 3 to 8.   The unburned fuel recirculation system according to claim 3, wherein the pump control means operates the pump when the internal combustion engine is decelerated.   The unburned fuel recirculation system according to claim 3, wherein the pump control means controls the operation of the pump based on the temperature of engine oil in the crankcase.

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