JP2013032745A - Internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To suppress the outflow of gas in the crankcase to the outside in a stop period of an internal combustion engine.SOLUTION: The internal combustion engine includes: a variable compression ratio mechanism moving a cylinder block relative to a crankcase; a blow-by gas reducing device ventilating the inside of the crankcase; and a pressure reduction means reducing a pressure of an engine intake passage. A seal member is disposed between the crankcase and the cylinder block. The internal combustion engine performs stop control for reducing the pressure of the engine intake passage on the basis of a state of gas inside the crankcase when a stop request is detected and for increasing a ventilation flow rate of the gas inside the crankcase.

Description

  The present invention relates to an internal combustion engine.

  In the combustion chamber of the internal combustion engine, the air-fuel mixture is burned in a compressed state. It is known that the compression ratio when compressing the air-fuel mixture affects the output torque and the fuel consumption. By increasing the compression ratio, the output torque can be increased or the fuel consumption can be reduced. On the other hand, it is known that if the compression ratio is too high, abnormal combustion such as knocking occurs. In the prior art, an internal combustion engine having a variable compression ratio mechanism capable of changing the compression ratio during an operation period is known.

  Japanese Patent Application Laid-Open No. 2009-114989 discloses a variable compression ratio engine that changes the compression ratio by relatively displacing a cylinder block with respect to a crankcase. In this variable compression ratio engine, a sealing material for sealing a gap between the crankcase and the cylinder block is provided between the inner surface of the crankcase and the side surface of the cylinder block. It is disclosed that a suction hole is formed in the lower part of the seal material in the cylinder block, and that the suction hole and the intake pipe (downstream part of the throttle) are connected by a suction pipe.

  In an internal combustion engine, it is known that gas in a cylinder leaks into a crankcase from between a piston ring arranged on a piston and a hole in a cylinder block. The blow-by gas leaking from the cylinder into the crankcase includes unburned gas remaining without being burned and burned gas that has already been burned. In a conventional internal combustion engine, it is known that the gas inside the crankcase is returned to the engine intake passage and supplied to the combustion chamber again.

  Japanese Patent Application Laid-Open No. 2004-285890 discloses a system for ventilating blow-by gas using a negative pressure of an intake system of an engine in a hybrid vehicle including an engine and a motor. Further, this publication discloses that when changing from running with an engine and a motor to running with a motor alone, the engine is idled for a predetermined time and then stopped to effectively ventilate the blow-by gas. Has been.

JP 2009-114989 A JP 2009-114947 A JP 2004-285890 A JP 2010-096033 A

  The blow-by gas that flows out from the cylinder into the crankcase contains a lot of gas. For this reason, it is preferable not to let the gas inside the crankcase flow out. In addition to storing the blow-by gas in the space inside the crankcase, the blow-by gas may be dissolved in the lubricating oil stored at the bottom of the crankcase. The blow-by gas dissolved in the lubricating oil may later evaporate from the lubricating oil and become a gas inside the crankcase.

  As disclosed in Japanese Patent Application Laid-Open No. 2009-114989, the compression ratio can be made variable by moving the cylinder block relative to the crankcase. In the compression ratio variable mechanism in which the cylinder block moves relative to the crankcase, there is a portion where the crankcase and the cylinder block slide.

  During the stop period of the internal combustion engine, the gas inside the crankcase may flow out to the outside through the sliding portion between the crankcase and the cylinder block. For this reason, a seal member is disposed between the crankcase and the cylinder block, but there is a problem that gas inside the crankcase flows out through the seal member.

  An object of the present invention is to suppress the gas inside the crankcase from flowing out to the outside during the stop period of the internal combustion engine.

  An internal combustion engine according to the present invention includes a crankcase, a cylinder block is formed to move relative to a support structure that supports a crankshaft, and a compression ratio variable mechanism capable of adjusting a compression ratio; It includes a supply passage for supplying the internal gas downstream from the throttle valve of the engine intake passage, and includes a ventilation means for ventilating the inside of the crankcase and a pressure reduction means for reducing the pressure of the engine intake passage. A seal member is arranged between the support structure and the cylinder block to prevent the gas inside the crankcase from flowing out. When the internal combustion engine detects a request to stop the internal combustion engine, the internal combustion engine reduces the pressure of the engine intake passage by the pressure reducing means based on the state of the gas inside the crankcase, and reduces the ventilation flow rate of the gas inside the crankcase. Perform stop-time control to increase.

  In the above-mentioned invention, the variable valve mechanism that can adjust the closing timing of the intake valve is provided, and the pressure reducing means controls the pressure of the engine intake passage in a state in which the intake air amount is maintained substantially constant during the stop time control. The opening degree of the throttle valve can be reduced and the valve closing timing of the intake valve can be advanced so as to decrease.

  In the above-mentioned invention, the variable valve mechanism that can adjust the closing timing of the intake valve is provided, and the pressure reducing means is configured to reduce the pressure of the engine intake passage while the intake air amount increases in the stop time control. It is possible to reduce the opening of the throttle valve, advance the closing timing of the intake valve, and further retard the ignition timing.

  In the above invention, when the stop request of the internal combustion engine is detected, the pressure reducing means advances the intake valve closing timing and stops the throttle valve opening after increasing the throttle valve opening. It can be made smaller than the opening when detecting the request.

  In the above invention, the duration of the control at the time of stop can be set based on the state of the gas inside the crankcase.

  ADVANTAGE OF THE INVENTION According to this invention, it can suppress that the gas inside a crankcase flows out outside during the stop period of an internal combustion engine.

1 is a schematic view of an internal combustion engine in an embodiment. It is explanatory drawing of an effect | action of the variable valve mechanism in embodiment. In the internal combustion engine of the embodiment, it is a schematic cross-sectional view of a cylinder block and a crankcase portion when the mechanical compression ratio is a high compression ratio. In the internal combustion engine of the embodiment, it is a schematic cross-sectional view of a cylinder block and a crankcase portion when the mechanical compression ratio is a low compression ratio. It is explanatory drawing of the control at the time of the normal driving | operation of the internal combustion engine in embodiment. It is a flowchart of the operation control at the time of stopping the internal combustion engine in embodiment. It is a time chart of the 1st stop time control in an embodiment. It is a time chart of the 2nd stop time control in an embodiment. It is a time chart of the control at the time of the 3rd stop in an embodiment.

  The internal combustion engine in the embodiment will be described with reference to FIGS. In the present embodiment, an internal combustion engine disposed in a vehicle will be described as an example.

  FIG. 1 is a schematic view of an internal combustion engine in the present embodiment. The internal combustion engine in the present embodiment is a spark ignition type. The internal combustion engine includes an engine body 1. The engine body 1 includes a cylinder block 2 and a cylinder head 4. A piston 3 is disposed in a hole formed in the cylinder block 2. The piston 3 is connected to the crankshaft 24 via a connecting rod 23. As the piston 3 reciprocates inside the hole of the cylinder block 2, the crankshaft 24 rotates.

  In the present embodiment, the space in the cylinder surrounded by the crown surface of the piston 3, the hole of the cylinder block 2, and the cylinder head 4 when the piston 3 reaches the compression top dead center is referred to as a combustion chamber 5. An engine intake passage and an engine exhaust passage are connected to the combustion chamber 5. The engine intake passage is a passage for supplying air or a mixture of fuel and air to the combustion chamber 5. The engine exhaust passage is a passage for discharging exhaust gas generated by the combustion of fuel from the combustion chamber 5.

  An intake port 7 and an exhaust port 9 are formed in the cylinder head 4. The intake valve 6 is disposed at the end of the intake port 7 and is configured to be able to open and close the engine intake passage communicating with the combustion chamber 5. The exhaust valve 8 is disposed at the end of the exhaust port 9 and is configured to be able to open and close the engine exhaust passage communicating with the combustion chamber 5. A spark plug 10 as an ignition device is fixed to the cylinder head 4.

  The internal combustion engine in the present embodiment includes a fuel injection valve 11 for supplying fuel to the combustion chamber 5. The fuel injection valve 11 in the present embodiment is disposed so as to inject fuel into the intake branch pipe 13. The fuel injection valve 11 is not limited to this configuration, and may be arranged so that fuel can be supplied to the combustion chamber 5. For example, the fuel injection valve may be arranged to inject fuel directly into the combustion chamber. The fuel injection valve is connected to the fuel tank via an electronically controlled variable discharge amount fuel pump.

  The intake port 7 of each cylinder is connected to a surge tank 14 via a corresponding intake branch pipe 13. The surge tank 14 is connected to the air cleaner 12 via the intake duct 15. An air flow meter 16 for detecting the amount of intake air is disposed inside the intake duct 15. A throttle valve 18 driven by a step motor 17 is disposed inside the intake duct 15. On the other hand, the exhaust port 9 of each cylinder is connected to a corresponding exhaust branch pipe 19. The exhaust branch pipe 19 is connected to the three-way catalyst 20. The three-way catalyst 20 is connected to the exhaust pipe 22.

  The internal combustion engine in the present embodiment includes an electronic control unit 31. The electronic control unit 31 in the present embodiment includes a digital computer. The electronic control unit 31 includes a RAM (random access memory) 33, a ROM (read only memory) 34, a CPU (microprocessor) 35, an input port 36 and an output port 37 which are connected to each other via a bidirectional bus 32. .

  The output signal of the air flow meter 16 is input to the input port 36 via the corresponding AD converter 38. A load sensor 41 is connected to the accelerator pedal 40. The load sensor 41 generates an output voltage proportional to the depression amount of the accelerator pedal 40. This output voltage is input to the input port 36 via the corresponding AD converter 38. The required load can be detected from the output of the load sensor 41.

  The crank angle sensor 42 generates an output pulse each time the crankshaft 24 rotates, for example, a predetermined angle, and this output pulse is input to the input port 36. The engine speed can be detected from the output of the crank angle sensor 42. Further, the crank angle can be detected from the output of the crank angle sensor 42. An air-fuel ratio sensor 43 that detects the ratio of air to unburned fuel contained in the exhaust gas flowing into the three-way catalyst 20 (the air-fuel ratio of the exhaust gas) is disposed upstream of the three-way catalyst 20. The pressure sensor 65 detects the pressure in the engine intake passage downstream from the throttle valve 18. The output of the air-fuel ratio sensor 43 and the output of the pressure sensor 65 are input to the input port 36 via the corresponding AD converter 38.

  The output port 37 of the electronic control unit 31 is connected to the fuel injection valve 11 and the spark plug 10 via the corresponding drive circuits 39. The electronic control unit 31 in the present embodiment is formed to perform fuel injection control and ignition control. That is, the fuel injection timing and the fuel injection amount are controlled by the electronic control unit 31. Further, the ignition timing of the spark plug 10 is controlled by the electronic control unit 31. The output port 37 is connected to a step motor 17 that drives the throttle valve 18 via a corresponding drive circuit 39. The throttle valve 18 is controlled by the electronic control unit 31.

  The intake valve 6 is formed to open and close as the intake cam 51 rotates. The exhaust valve 8 is formed to open and close as the exhaust cam rotates. The internal combustion engine in the present embodiment includes a variable valve mechanism. The variable valve mechanism in the present embodiment includes a variable valve timing device 53 that changes the opening / closing timing of the intake valve 6. The variable valve timing device 53 in the present embodiment is connected to the rotation shaft of the intake cam 51. The variable valve timing device 53 is controlled by the electronic control unit 31.

  FIG. 2 is an explanatory diagram of the function of the variable valve timing device in the present embodiment. The horizontal axis is the crank angle, and the vertical axis is the amount of movement of the valve. A solid line indicating the movement of the intake valve indicates a state in which the phase of the rotation shaft of the intake cam is advanced most by the variable valve timing device. On the other hand, the broken line indicating the movement of the intake valve indicates a state where the phase of the rotation axis of the intake cam is most retarded. The variable valve timing device 53 according to the present embodiment is configured such that the operating angle from when the intake valve 6 starts to open until it closes is substantially constant, and the phase of the center of the operating angle can be changed. In the present embodiment, the closing timing of the intake valve can be set to an arbitrary crank angle within the range indicated by the arrow C. The variable valve mechanism is not limited to this form, and may be configured so that the closing timing of the intake valve can be changed.

  The internal combustion engine in the present embodiment includes a variable compression ratio mechanism. The compression ratio of the internal combustion engine is determined depending on the volume of the combustion chamber when the piston reaches the compression top dead center. The variable compression ratio mechanism in the present embodiment is formed to change the compression ratio by changing the volume of the combustion chamber. The actual compression ratio, which is the actual compression ratio in the combustion chamber, is expressed by (actual compression ratio) = (combustion chamber volume + piston stroke volume when the intake valve is closed) / (combustion chamber volume).

  FIG. 3 shows a first schematic cross-sectional view of the compression ratio variable mechanism of the internal combustion engine in the present embodiment. FIG. 3 is a schematic diagram when a high compression ratio is obtained by the variable compression ratio mechanism. FIG. 4 shows a second schematic cross-sectional view of the compression ratio variable mechanism of the internal combustion engine in the present embodiment. FIG. 4 is a schematic diagram when a low compression ratio is achieved by the compression ratio variable mechanism.

  1, 3 and 4, in the internal combustion engine in the present embodiment, the support structure including crankcase 79 and cylinder block 2 arranged on the upper side of the support structure move relative to each other. To do. The support structure in the present embodiment supports the cylinder block 2 via a compression ratio variable mechanism. Further, the support structure in the present embodiment supports the crankshaft 24 so as to be rotatable on one rotating shaft.

  A plurality of protrusions 80 are formed below the side walls on both sides of the cylinder block 2. A cam insertion hole having a circular cross section is formed in the projecting portion 80, and a circular cam 86 is rotatably disposed inside the cam insertion hole. A plurality of protrusions 82 are formed on the crankcase 79. A cam insertion hole having a circular cross section is formed in the projecting portion 82, and a circular cam 88 is rotatably disposed inside the cam insertion hole. The protrusion 80 of the cylinder block 2 is fitted between the protrusions 82 of the crankcase 79.

  The circular cam 86 inserted into the protruding portion 80 of the cylinder block 2 and the circular cam 88 inserted into the protruding portion 82 of the crankcase 79 are connected to each other via an eccentric shaft 87. A plurality of circular cams 86 and a plurality of circular cams 88 are connected via an eccentric shaft 87 to form camshafts 84 and 85. In the present embodiment, a pair of camshafts 84 and 85 are formed. The compression ratio variable mechanism in the present embodiment includes a rotating device that rotates the pair of camshafts 84 and 85 in opposite directions. The circular cam 88 is arranged coaxially with the rotation axis of the cam shafts 84 and 85. The circular cam 86 is eccentric with respect to the rotation axis of the cam shafts 84 and 85. Further, the eccentric shaft 87 is eccentric with respect to the rotation axis of the camshafts 84 and 85.

  Referring to FIG. 3, when the circular cams 88 arranged on the respective camshafts 84 and 85 are rotated in opposite directions as indicated by arrows 97, the eccentric shaft 87 faces the upper end of the circular cam 88. Move. The circular cam 86 supporting the cylinder block 2 rotates in the opposite direction to the circular cam 88 as indicated by an arrow 96 inside the cam insertion hole. The cylinder block 2 moves in a direction away from the crankcase 79 as indicated by an arrow 98.

  As shown in FIG. 4, when the eccentric shaft 87 moves to the upper end of the circular cam 88, the central axis of the circular cam 88 moves below the eccentric shaft 87. Referring to FIGS. 3 and 4, the relative position between crankcase 79 and cylinder block 2 is determined by the distance between the central axis of circular cam 86 and the central axis of circular cam 88. As the distance between the central axis of the circular cam 86 and the central axis of the circular cam 88 increases, the cylinder block 2 moves away from the crankcase 79. The volume of the combustion chamber 5 increases as the cylinder block 2 moves away from the crankcase 79.

  In the variable compression ratio mechanism in the present embodiment, the volume of the combustion chamber is variably formed by moving the cylinder block relative to the crankcase. In the present embodiment, a compression ratio determined only from the stroke volume of the piston from the bottom dead center to the top dead center and the volume of the combustion chamber is referred to as a mechanical compression ratio. The mechanical compression ratio is represented by (mechanical compression ratio) = (combustion chamber volume + piston stroke volume) / (combustion chamber volume) without depending on the closing timing of the intake valve.

  In the state shown in FIG. 3, the volume of the combustion chamber 5 is small, and the compression ratio is high when the intake air amount is always constant. This state is a state where the mechanical compression ratio is high. On the other hand, in the state shown in FIG. 4, the volume of the combustion chamber 5 is large, and the compression ratio is low when the intake air amount is always constant. This state is a state where the mechanical compression ratio is low. Thus, the internal combustion engine in the present embodiment can change the compression ratio during the operation period. For example, the compression ratio can be changed by a variable compression ratio mechanism according to the operating state of the internal combustion engine.

  The variable compression ratio mechanism according to the present embodiment moves the cylinder block relative to the crankcase by rotating a circular cam whose eccentric shaft is eccentric. However, the present invention is not limited to this configuration. An arbitrary mechanism for moving the cylinder block relative to the cylinder block can be employed.

  The internal combustion engine in the present embodiment has a portion in which the crankcase 79 and the cylinder block 2 slide in contact with each other. The crankcase 79 in the present embodiment includes a cover 61 formed so as to cover the protrusion 82 of the crankcase 79 and the protrusion 80 of the cylinder block 2. Further, the cover 61 is formed so as to surround the side surface of the cylinder block 2. The cover 61 is in contact with the side surface of the cylinder block 2.

  In the internal combustion engine in the present embodiment, the cover portion 61 of the crankcase 79 and the cylinder block 2 slide. The cover 61 has a function of sealing the inside of the crankcase 79 even during a period in which the cylinder block 2 is moving relative to the crankcase 79. A seal member 60 is disposed in a portion where the cover portion 61 and the cylinder block 2 slide relative to each other. The seal member 60 in the present embodiment is disposed inside a recess formed on the side surface of the cylinder block 2. By disposing the seal member 60 between the support structure including the crankcase 79 and the cylinder block 2, it is possible to suppress the gas inside the crankcase 79 from flowing out of the internal combustion engine.

  The seal member 60 in the present embodiment is formed in an annular shape so as to surround the side surface of the cylinder block 2. The seal member in the present embodiment is formed of rubber or resin. As a sealing member, it is not restricted to this form, The arbitrary members which have a sealing function are employable. Further, the seal member in the present embodiment is arranged on the side surface of the cylinder block, but is not limited to this form, and includes the crankcase so as to suppress the gas inside the crankcase from flowing out. It can be arranged between the support structure and the cylinder block.

  Referring to FIG. 1, the internal combustion engine in the present embodiment includes ventilation means for ventilating the inside of crankcase 79. The ventilation means in the present embodiment includes a blow-by gas reduction device. In the space inside the crankcase 79, blow-by gas flows out from the inside of the cylinder including the combustion chamber 5. In addition, lubricating oil is stored at the bottom of the crankcase 79, and part of the blow-by gas may melt into the lubricating oil. Thus, the gas containing blow-by gas exists in the crankcase 79.

  The blow-by gas reduction device in the present embodiment supplies the gas inside the crankcase 79 to the combustion chamber 5. The blow-by gas reduction device includes a return pipe 63 as a supply passage that connects the space inside the crankcase 79 and the engine intake passage. The return pipe 63 in the present embodiment is connected downstream of the throttle valve 18 in the intake duct 15. A PCV valve 64 is disposed in the middle of the return pipe 63. The PCV valve 64 is formed to open when the difference between the pressure inside the crankcase 79 and the pressure inside the intake duct 15 becomes larger than a predetermined pressure difference.

  By making the opening degree of the throttle valve 18 smaller than fully open during the operation of the internal combustion engine, the pressure becomes smaller than the atmospheric pressure in the engine intake passage downstream of the throttle valve 18. That is, it becomes a negative pressure. For this reason, the gas inside the crankcase 79 can be sucked into the engine intake passage via the return pipe 63. In the present embodiment, the gas including the blow-by gas inside the crankcase 79 is sucked into the engine intake passage through the return pipe 63 as indicated by an arrow 66. The gas supplied to the engine intake passage is supplied again to the combustion chamber 5 through the engine intake passage. Unburned gas contained in the blow-by gas burns in the combustion chamber 5. The gas contained in the blow-by gas that has flowed into the crankcase can be burned and sent to the exhaust purification device. Further, the burned gas contained in the blow-by gas can also be sent to the exhaust purification device via the combustion chamber 5.

  The blow-by gas reduction device in the present embodiment includes an air introduction pipe 62 for supplying unburned gas and air containing no burned gas into the crankcase 79. The air introduction pipe 62 in the present embodiment is connected to the upstream side of the throttle valve 18 in the intake duct 15. The air introduction pipe 62 is connected to the crankcase 79 so as to supply air into the crankcase 79. Air is supplied from the intake duct 15 into the crankcase 79 as indicated by an arrow 67.

  When the air inside the crankcase 79 is sucked into the engine intake passage, the inside of the crankcase 79 becomes negative pressure. As the pressure inside the crankcase 79 decreases, air is introduced into the crankcase 79 through the air introduction pipe 62 as indicated by an arrow 67. In this way, the inside of the crankcase 79 can be ventilated. The blow-by gas reduction device in the present embodiment can supply the gas inside the crankcase to the combustion chamber again.

  The ventilation means is not limited to the blow-by gas reduction device described above, and any device that supplies the gas inside the crankcase to the engine intake passage and ventilates the inside of the crankcase can be employed.

  Next, an example of operation control in the present embodiment will be described with reference to FIG. FIG. 5 is a graph schematically illustrating the general operation control of the ultra-high expansion ratio control. FIG. 5 shows changes in required intake air amount, intake valve closing timing, expansion ratio (mechanical compression ratio), actual compression ratio, and throttle valve opening according to the load at a certain engine speed. Yes.

  During high load operation of the internal combustion engine, the mechanical compression ratio is controlled to be low. Further, the opening degree of the throttle valve is kept fully open, and the intake air amount is increased by advancing the closing timing of the intake valve. Since the opening of the throttle valve is kept fully open, pumping loss can be suppressed.

  The amount of intake air supplied into the combustion chamber is controlled by changing the closing timing of the intake valve. When the load of the internal combustion engine decreases, the closing timing of the intake valve is delayed in order to reduce the intake air amount. At this time, the mechanical compression ratio is increased as the load is lowered so that the actual compression ratio is maintained substantially constant. Therefore, the expansion ratio increases as the load decreases. Also at this time, the throttle valve is held in a fully opened state.

  As described above, when the load is reduced from the high load operation state, the mechanical compression ratio is increased as the intake air amount is decreased while the actual compression ratio is substantially constant. That is, the volume of the combustion chamber decreases in proportion to the decrease in the intake air amount.

  As the load on the internal combustion engine is further reduced, the mechanical compression ratio further increases. When the load of the internal combustion engine decreases to a medium load L1 that is slightly closer to the low load, the mechanical compression ratio reaches a limit mechanical compression ratio (upper limit mechanical compression ratio) that becomes a structural limit of the combustion chamber. In the region where the load is lower than the load L1 when the mechanical compression ratio reaches the limit mechanical compression ratio, the mechanical compression ratio is held at the limit mechanical compression ratio. Therefore, at the time of medium load operation and low load operation on the low load side, that is, on the low load operation side, the mechanical compression ratio is maximized and the expansion ratio is also maximized. In other words, the mechanical compression ratio is maximized so that the maximum expansion ratio is obtained on the low load operation side.

  On the other hand, in the embodiment shown in FIG. 5, when the load decreases to L1, the closing timing of the intake valve becomes the limit closing timing that can control the amount of intake air supplied into the combustion chamber. In a region where the load is lower than the load L1 when the intake valve closing timing reaches the limit closing timing, the intake valve closing timing is held at the limit closing timing. In the region where the load is lower than the load L1 when the intake valve closing timing reaches the limit closing timing, the amount of intake air supplied into the combustion chamber is controlled by the throttle valve, and the throttle valve opening increases as the load decreases. Is made smaller. As described above, the closing timing of the intake valve in the present embodiment is from the intake bottom dead center BDC until the limit closing timing at which the amount of intake air supplied into the combustion chamber can be controlled as the load decreases from a high load. It will be moved away.

  In the internal combustion engine of the present embodiment, the closing timing of the intake valve is set late in an operation state with a small load. For this reason, even in the region of a load smaller than the load L1, the opening degree of the throttle valve can be made larger than that of the internal combustion engine that does not perform the control for delaying the closing timing of the intake valve. That is, the pumping loss can be reduced.

  However, in an operation state in which the load of the internal combustion engine in the present embodiment is small, the pressure downstream of the throttle valve 18 in the engine intake passage is not sufficiently lowered, and the gas inside the crankcase 79 is caused to flow by the blow-by gas reduction device. There may be cases where sufficient suction is not possible. For example, in the idling operation state before the internal combustion engine is stopped, the ventilation flow rate of the gas inside the crankcase 79 may be small. If the internal combustion engine is stopped with a large amount of blow-by gas remaining in the crankcase 79, the gas inside the crankcase 79 may permeate the seal member 60 and flow out of the internal combustion engine during the stop period. is there. Further, in the present embodiment, since the seal member is disposed at a portion where the support structure and the cylinder block slide, the seal member cannot be strongly compressed, and the support structure and the cylinder block are not compressed. In some cases, gas flows out from the portion where the and slide.

  The internal combustion engine of the present embodiment is formed so that, when a stop request is detected, the control at the time of stopping can be performed by reducing the pressure of the engine intake passage by the pressure reducing means and increasing the ventilation flow rate of the gas inside the crankcase. Has been. The internal combustion engine in the present embodiment includes pressure reducing means for reducing the pressure in the engine intake passage. The pressure reducing means in the present embodiment includes a throttle valve 18 and a variable valve timing device 53. The pressure reducing means is not limited to this form, and any device or control capable of reducing the pressure in the engine intake passage can be employed.

  FIG. 6 shows a flowchart of the operation control of the internal combustion engine in the present embodiment. The operation control shown in FIG. 6 can be repeatedly performed at predetermined time intervals, for example. In the operation control of the present embodiment, the state of the gas inside the crankcase is estimated, and the stop time control is performed based on the state of the gas inside the crankcase. In the present embodiment, the required ventilation amount, which is the ventilation amount required in the crankcase, is estimated as the state of the gas inside the crankcase. In the present embodiment, when the required ventilation becomes larger than the allowable value, the stop control according to the required ventilation is performed.

  For example, the required ventilation amount increases as the amount of blow-by gas stored in the crankcase increases, and the control during stop can be performed so that the ventilation flow rate inside the crankcase increases. Note that the return gas, which is the gas supplied from the crankcase to the engine intake passage, includes blow-by gas. The return gas includes the gas stored in the space inside the crankcase and the gas evaporated from the lubricating oil inside the crankcase.

  In step 101, the operating state of the internal combustion engine is detected during the operation period of the internal combustion engine. Referring to FIG. 1, in the present embodiment, a load sensor 41 detects a required load of the internal combustion engine. The crank angle sensor 42 detects the engine speed. Further, the pressure sensor 65 detects the pressure in the engine intake passage.

  Next, in step 102, the required ventilation volume is calculated. In the present embodiment, a map of the amount of blow-by gas generated with the required load and the engine speed as a function is stored in the electronic control unit 31 in advance. The amount of blow-by gas generated can be estimated based on the detected required load and the engine speed.

  Next, the ventilation amount ventilated inside the crankcase is estimated by the blow-by gas reduction device. In the present embodiment, a map of the ventilation amount inside the crankcase as a function of the pressure in the engine intake passage and the engine speed is stored in advance in the electronic control unit. Based on the detected pressure in the engine intake passage and the engine speed, the ventilation amount inside the crankcase can be estimated.

  Next, the required ventilation amount is estimated based on the estimated generation amount of blow-by gas and the estimated ventilation amount inside the crankcase. In the present embodiment, the electronic control unit 31 stores in advance a map of the required ventilation volume that is a function of the amount of blow-by gas generated and the ventilation volume inside the crankcase. The required ventilation amount can be set based on the estimated amount of blow-by gas generated and the estimated ventilation amount inside the crankcase.

  Next, in step 103, a request for stopping the internal combustion engine is detected. In the present embodiment, it is detected that the driver has performed an operation to stop the internal combustion engine. For example, it detects that the start switch has changed from an on state to an off state. In step 103, when the stop request for the internal combustion engine is not detected, this control is finished. If a stop request for the internal combustion engine is detected in step 103, the routine proceeds to step 104.

  In step 104, it is determined whether or not the required ventilation volume set in step 102 is equal to or less than a predetermined allowable value. In step 104, it is determined whether or not the stop-time control in this embodiment is to be performed. In step 104, if the required ventilation is below the allowable value, the routine proceeds to step 105. In this case, the amount of blow-by gas stored in the crankcase is extremely small, and it can be determined that the stop-time control in this embodiment is unnecessary.

  In step 105, normal internal control is performed to stop the internal combustion engine. As the normal stop control, for example, a fuel cut signal can be immediately transmitted to stop the fuel supply, and then the engine speed can be controlled to zero. Further, for example, it is possible to perform control to make the opening degree of the throttle valve substantially zero and advance the closing timing of the intake valve.

  In step 104, when the required ventilation volume exceeds the allowable value, the routine proceeds to step 106. It can be determined that the amount of blow-by gas contained in the gas inside the crankcase is larger than the amount to be controlled at the time of stop in the present embodiment. In this case, the stop time control in the present embodiment is performed.

  The internal combustion engine in the present embodiment is formed so as to be able to perform a plurality of stop-time controls. Moreover, the 1st determination value and the 2nd determination value for selecting the kind of control at the time of a stop are predetermined. The first determination value is set larger than the allowable value. The second determination value is set larger than the first determination value. In the present embodiment, the type of control at the time of stop is changed according to the required ventilation amount.

  In step 106, it is determined whether or not the required ventilation is less than a first determination value. In step 106, when the required ventilation volume is less than the first determination value, the routine proceeds to step 107. In step 107, the first stop control is performed among the stop controls in the present embodiment.

  In FIG. 7, the time chart of the 1st stop time control in this Embodiment is shown. In the first stop control according to the present embodiment, control is performed to reduce the opening of the throttle valve and advance the closing timing of the intake valve. In the first stop control, control is performed such that the pressure in the engine intake passage decreases while maintaining the intake air amount substantially constant.

  Until the time t1, the engine is idling. At time t1, the start switch is shifted from the on state to the off state. That is, the stop request for the internal combustion engine is detected at time t1. Although a stop request is detected at time t1, the operation of the internal combustion engine is continued for a predetermined time. A predetermined delay is caused from the request to stop the internal combustion engine to the transmission of the fuel cut signal.

  In the first stop control according to the present embodiment, control is performed to reduce the opening (TA) of the throttle valve at time t1. With reference to FIG. 1, by reducing the opening of throttle valve 18, the pressure in the engine intake passage downstream of throttle valve 18 can be reduced. At time t1, the pressure (PM) in the engine intake passage decreases. For this reason, more gas inside the crankcase 79 can be sucked. The flow rate of the return gas flowing from the crankcase 79 into the engine intake passage can be increased. For this reason, the ventilation flow rate of the gas inside the crankcase 79 can be increased.

  At time t1, control is performed to advance the valve closing timing (IVC) of the intake valve. Referring to FIG. 5, by advancing the closing timing of the intake valve, it is possible to compensate for a reduction in the intake air amount accompanying a decrease in the opening of the throttle valve. In the present embodiment, the closing timing of the intake valve is advanced so that the intake air amount remains substantially constant even when the throttle valve opening is reduced.

  The fuel cut signal (FC) for stopping the fuel injection from the fuel injection valve is transmitted at time t2 after elapse of a predetermined time from time t1. That is, the fuel injection from the fuel injection valve is continued until time t2, and the fuel supply is stopped at time t2. The engine speed becomes zero after the elapse of a predetermined time after the transmission of the fuel cut signal, and the internal combustion engine stops.

  In this way, during the period from time t1 to time t2, the operation in the state where the pressure in the engine intake passage is lowered continues, whereby ventilation in the crankcase can be promoted. Blow-by gas stored in the crankcase 79 can be supplied to the engine intake passage and burned in the combustion chamber 5. The amount of blow-by gas stored in the crankcase when the internal combustion engine is stopped can be reduced. For this reason, it is possible to suppress the unburned gas and burned gas contained in the blow-by gas from flowing out of the crankcase to the outside of the internal combustion engine during the stop period of the internal combustion engine.

  Further, by controlling the closing timing of the intake valve and the opening degree of the throttle valve so that the intake air amount becomes substantially constant, fluctuations in the output of the internal combustion engine at time t1 can be suppressed. In the first stop control in the present embodiment, ventilation inside the crankcase can be promoted while suppressing fluctuations in the output of the internal combustion engine.

  Referring to FIG. 6, when the required ventilation volume is equal to or greater than the first determination value in step 106, the process proceeds to step 108. In step 108, it is determined whether or not the required ventilation volume is less than the second determination value. In step 108, if the required ventilation volume is less than the second determination value, the routine proceeds to step 109. In step 109, the second stop time control in the present embodiment is performed.

  FIG. 8 shows a time chart of the second stop time control in the present embodiment. In FIG. 8, the second stop time control is indicated by a solid line. Further, the first stop control in the present embodiment is indicated by a broken line. The detection of a stop request of the internal combustion engine at time t1 and continuing the operation of the internal combustion engine for a predetermined time, and then sending the fuel cut signal at time t2 to stop the fuel supply is the first stop It is the same as the control.

  In the second stop time control, during the period from the time t3 to the time t2, the throttle valve opening is made smaller than when the stop request is detected, and the valve closing timing of the intake valve is advanced. Control is performed to increase the intake air amount more than when a stop request is detected.

  For example, when the first stop control is performed in the idling operation state before the internal combustion engine is stopped, the influence of the return gas in the gas flowing into the combustion chamber may increase. The amount of fuel injected from the fuel injection valve 11 is controlled based on, for example, the air flow rate detected by the air flow meter 16 and a predetermined air-fuel ratio. In an operating state such as idling, the amount of gas flowing into the combustion chamber is reduced. When the pressure in the engine intake passage decreases in this state, the return supplied from the crankcase to the engine intake passage for the amount of fresh air constituted by the air supplied through the air cleaner and the fuel injected from the fuel injection valve. The proportion of the amount of gas increases. For this reason, the influence of the ratio of unburned gas and air contained in the return gas becomes large, and the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber may become unstable. For example, when the concentration of blow-by gas in the crankcase is high, the amount of blow-by gas contained in the gas supplied to the combustion chamber may increase. For this reason, the air-fuel ratio (A / F) of the air-fuel mixture supplied to the combustion chamber may become unstable.

  The throttle valve opening from the time t3 to the time t2 of the second stop control is controlled to be larger than the throttle valve opening from the time t1 to the time t2 of the first stop control. The stop-time control is performed in a state where the intake air amount is larger than that in the first stop-time control. Further, the control at the time of stop is performed by increasing the intake air amount than when the stop request is detected.

  In the second stop time control, the influence of the gas contained in the return gas supplied from the crankcase to the engine intake passage can be reduced by increasing the amount of air supplied from the outside air to the combustion chamber. That is, in the air-fuel mixture flowing into the combustion chamber, the ratio of the amount of return gas to the amount of fresh air including outside air can be reduced to reduce the influence of return gas. As a result, the air-fuel ratio of the air-fuel mixture supplied to the combustion chamber can be stabilized.

  However, in the second stop time control, the amount of the air-fuel mixture flowing into the combustion chamber increases, so that the engine speed may increase rapidly. For this reason, in the second stop time control, a control for retarding the ignition timing is performed. In the second stop time control of the present embodiment, the ignition timing is retarded at time t1. By performing control to retard the ignition timing, it is possible to suppress the intake air amount from increasing and the engine speed from rising.

  The retard amount of the ignition timing in the present embodiment is set based on the increase amount of the intake air amount. In the internal combustion engine of the present embodiment, control is performed to increase the retard amount of the ignition timing as the amount of increase in the intake air amount increases. By performing this control, it is possible to suppress the output of the internal combustion engine from fluctuating greatly. The control of the retard amount of the ignition timing is not limited to this form, and for example, a predetermined retard amount can be adopted.

  In the second stop control, ventilation inside the crankcase can be promoted while maintaining a stable operating state even when the required ventilation amount inside the crankcase is large.

  Further, in the second stop time control of the present embodiment, the opening degree of the throttle valve is temporarily increased and then made smaller than the opening degree when the stop request is detected. During the period from time t1 to time t3 after elapse of a predetermined time, the throttle valve opening is increased. During the period from time t1 to time t3, the intake valve closing timing is controlled to maintain the intake valve closing timing at time t1. For this reason, the intake air amount increases at time t1.

  At time t3, control is performed to make the opening of the throttle valve smaller than the opening at time t1. The pressure in the engine intake passage is lower than the pressure when the stop request is detected. At time t3, control is performed to advance the closing timing of the intake valve. The intake air amount decreases at time t3. However, the intake air amount during the period from time t3 to time t2 is larger than the intake air amount when the stop request is detected. In the present embodiment, when the intake air amount decreases at time t3, control is performed to decrease the retard amount of the ignition timing.

  Thus, in the second stop time control in the present embodiment, when the stop request for the internal combustion engine is detected, the throttle valve opening is temporarily increased after the throttle valve opening is temporarily increased. Control is performed to make it smaller than the opening at the time of detection. By performing this control, a large amount of air can be supplied to the engine intake passage before the closing timing of the intake valve is advanced. When the opening degree of the throttle valve is reduced and the closing timing of the intake valve is advanced, the influence of the return gas can be suppressed more reliably.

  In the second stop time control of the present embodiment, the opening degree of the throttle valve is increased, then the closing timing of the intake valve is advanced, and the opening degree of the throttle valve is opened when the stop request is detected. However, the present invention is not limited to this mode, and the throttle valve opening is set to increase at time t1 so that the intake air amount increases without temporarily increasing the throttle valve opening. You may make it small and advance the valve closing timing of an intake valve.

  In addition, when the stop request of the internal combustion engine is detected, after the throttle valve opening is increased, the closing timing of the intake valve is advanced, and the throttle valve opening is determined from the opening when the stop request is detected. Can be applied to the first stop-time control in the present embodiment.

  Referring to FIG. 6, when the required ventilation volume is equal to or greater than the second determination value in step 108, the process proceeds to step 110. In step 110, the third stop time control is performed. In the third stop-time control of the present embodiment, control is performed to lengthen the second stop-time control period. Further, control is performed to notify the driver that the stoppage of the internal combustion engine is delayed.

  FIG. 9 shows a time chart of the third stop time control in the present embodiment. In FIG. 9, the third stop time control is indicated by a solid line. Moreover, the 2nd stop time control in this Embodiment is described with the broken line.

  The control from time t1 to time t2 in the third stop time control is the same as the second stop time control in the present embodiment. In the third stop time control, the fuel supply is extended to time t4 without transmitting the fuel cut signal at time t2. The operating state at time t2 is maintained until time t4. At time t4, the fuel cut signal has shifted from an off state to an on state. That is, control for stopping the supply of fuel is performed.

  When the required ventilation volume is large, ventilation may be insufficient even if the second stop control is performed. For example, when a large amount of blow-by gas is contained in the gas inside the crankcase, ventilation may be insufficient even if the first stop time control or the second stop time control is performed. In such a case, control for extending the operation period of the control at the time of stop is performed.

  In the third stop-time control of the present embodiment, the duration of the third stop-time control is set based on the required ventilation amount of the gas inside the crankcase. The longer the required ventilation, the longer the duration of control during stop. The time t4 at which the fuel cut signal is transmitted can be set based on the set duration time. For example, the duration of the third stop time control using the required ventilation volume as a function can be stored in advance in the electronic control unit. Based on the required ventilation volume set in step 102, the duration of the third stop time control can be set.

  In the third stop-time control of the present embodiment, the duration of the stop-time control is set based on the state of the gas inside the crankcase. By performing this control, the crankcase can be sufficiently ventilated even when the amount of blow-by gas stored in the crankcase is large. It is possible to more reliably suppress the outflow of gas and burned gas from the inside of the crankcase during the stop period of the internal combustion engine.

  In the third stop time control of the present embodiment, the duration of the stop time control is determined with respect to the second stop time control. You may set the duration of

  Further, in the third stop time control of the present embodiment, there is a case where it takes a long time to continue the operation of the internal combustion engine for the stop time control after the driver operates the start switch in the OFF state. For this reason, the driver may feel that the internal combustion engine is not stopped. That is, the driver may feel uncomfortable with the stopping operation of the internal combustion engine. For this reason, in the third stop-time control of the present embodiment, control is performed to notify the driver that the stop of the internal combustion engine is delayed.

  In the third stop time control of the present embodiment, the driver is notified at time t2. For example, the driver can be notified by arranging a notification lamp on the dashboard in front of the driver's seat and turning on the notification lamp.

  In the operation control of the present embodiment, the required ventilation is set as the state of the gas inside the crankcase. The state of the gas inside the crankcase is not limited to the required ventilation amount, and an amount related to blow-by gas such as the amount of blow-by gas, the amount of unburned gas, or the amount of burned gas can be employed. For example, the amount of gas stored in the crankcase may be estimated.

  Referring to FIG. 6, in the present embodiment, the state of gas inside the crankcase is estimated when a stop request for the internal combustion engine is detected. You may employ | adopt the integrated value which integrated | accumulated the state of the gas inside a crankcase over the period until it detects. Further, in the present embodiment, the operation state is detected by performing step 101 and step 102 continuously during the normal operation period. However, the present invention is not limited to this mode, and after the stop request is detected, the operation state is detected. The required ventilation amount may be calculated based on the detected operating state by detecting the state.

  In the stop control according to the present embodiment, the mechanical compression ratio is maintained substantially constant before and after the detection of the stop request of the internal combustion engine. However, the present invention is not limited to this form, and the mechanical compression ratio is determined by closing the intake valve. You may change according to the time. For example, in the first stop time control, the intake valve closing timing may be advanced and the mechanical compression ratio may be reduced.

  The order of the steps of the stop-time control flowchart of the present embodiment can be changed as appropriate within a range in which the function can be maintained. Each of the above embodiments can be combined as appropriate. In addition, the amount of each gas includes the amount of gas at a predetermined time. That is, the amount of gas includes the flow rate in addition to the absolute amount of gas, and can be selected as appropriate.

  In the respective drawings described above, the same or corresponding parts are denoted by the same reference numerals. In addition, said embodiment is an illustration and does not limit invention. In the embodiment, the change shown in a claim is included.

1 Engine Body 2 Cylinder Block 3 Piston 4 Cylinder Head 5 Combustion Chamber 6 Intake Valve 10 Spark Plug 11 Fuel Injection Valve 15 Intake Duct 16 Air Flow Meter 18 Throttle Valve 24 Crankshaft 31 Electronic Control Unit 41 Load Sensor 42 Crank Angle Sensor 51 Intake Cam 53 Variable Valve Timing Device 60 Seal Member 61 Cover 62 Air Introducing Pipe 63 Return Pipe 65 Pressure Sensor 79 Crankcase 84, 85 Camshaft 86 Circular Cam 87 Eccentric Shaft 88 Circular Cam

Claims (5)

A variable compression ratio mechanism that includes a crankcase and is formed such that the cylinder block moves relative to a support structure that supports the crankshaft, and the compression ratio can be adjusted;
A ventilation means for ventilating the inside of the crankcase, including a supply passage for supplying gas inside the crankcase downstream of the throttle valve of the engine intake passage;
Pressure reducing means for reducing the pressure in the engine intake passage,
Between the support structure and the cylinder block, a seal member is arranged to suppress the gas inside the crankcase from flowing out,
When a stop request for an internal combustion engine is detected, the pressure reduction means reduces the pressure in the engine intake passage based on the state of the gas inside the crankcase, and increases the ventilation flow rate of the gas inside the crankcase An internal combustion engine characterized by performing control. Equipped with a variable valve mechanism that can adjust the closing timing of the intake valve,
The pressure lowering means reduces the opening of the throttle valve and advances the closing timing of the intake valve so as to reduce the pressure in the engine intake passage while the intake air amount is maintained substantially constant in the control at the time of stop. The internal combustion engine according to claim 1, wherein the internal combustion engine is angled. Equipped with a variable valve mechanism that can adjust the closing timing of the intake valve,
The pressure lowering means reduces the throttle valve opening and advances the closing timing of the intake valve so that the intake air amount increases and the pressure in the engine intake passage decreases in the control at the time of stop. The internal combustion engine according to claim 1, wherein the timing is retarded.   The pressure reducing means, when detecting the stop request of the internal combustion engine, advances the closing timing of the intake valve after increasing the opening degree of the throttle valve, and also sets the opening degree of the throttle valve at the time of detecting the stop request. The internal combustion engine according to claim 2, wherein the internal combustion engine is smaller than the opening degree.   The internal combustion engine according to any one of claims 1 to 4, wherein a duration of the control at the time of stop is set based on a state of gas inside the crankcase.

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