JP5594271B2 - Variable compression ratio internal combustion engine - Google Patents

Description

  The present invention relates to a variable compression ratio internal combustion engine, and more particularly to a variable compression ratio internal combustion engine in which a cylinder block and a crankcase can move relative to each other.

  2. Description of the Related Art In recent years, techniques for changing the compression ratio of an internal combustion engine have been proposed for the purpose of improving the fuel efficiency performance and output performance of the internal combustion engine. As this type of technology, there is provided a compression ratio variable mechanism that connects the cylinder block and the crankcase relatively close to and away from each other in the vertical direction or the cylinder axis direction, and operates or controls the compression ratio variable mechanism. A technique for changing the compression ratio has been proposed (see, for example, Patent Document 1).

JP2011-149285A

  By the way, in such a variable compression ratio internal combustion engine, a cylinder block is generally fitted inside a crankcase so as to be movable in the cylinder axial direction. In this case, a part of the cylinder block is covered with the crankcase and is not exposed to the outside, and a cooling effect due to heat radiation to the outside cannot be expected at that part.

  Accordingly, the present invention has been made in view of the above circumstances, and an object thereof is to provide a variable compression ratio internal combustion engine capable of enhancing the heat dissipation and cooling performance of a cylinder block.

According to one aspect of the invention,
A variable compression ratio internal combustion engine in which a cylinder block is fitted inside a crankcase so as to be movable in the cylinder axial direction.
A fresh air discharge passage for discharging fresh air is provided in the internal combustion engine so as to be directed to the cylinder block, a fresh air extraction passage for extracting fresh air from the intake passage is provided, and locations other than the intake passage A fresh air introduction path for introducing fresh air is provided, and valve means for adjusting the communication state of the fresh air discharge path and the fresh air extraction path and the communication state of the fresh air discharge path and the fresh air introduction path are provided. A variable compression ratio internal combustion engine is provided.

  Preferably, the internal combustion engine is mounted on a vehicle, and an inlet of the fresh air introduction path is directed so as to face a traveling wind during traveling of the vehicle.

  Preferably, the inlet of the fresh air introduction path is directed toward the front of the vehicle.

  Preferably, the inlet of the fresh air introduction path is located at the front end of the vehicle.

  Preferably, at least one of a load of the internal combustion engine and a temperature of the cylinder block is detected, and the valve means is controlled in accordance with the detected at least one.

  Preferably, when at least one of the load and the temperature is equal to or higher than a predetermined value, the communication state of the fresh air discharge path and the fresh air extraction path is a fully closed state and the communication of the fresh air discharge path and the fresh air introduction path The valve means is controlled so that the state is fully open.

  Preferably, another fresh air discharge path directed to a crank journal portion in the crankcase is provided to discharge fresh air into the internal combustion engine, and an upstream end of the new fresh air discharge path is a new air discharge path. The fresh air discharge path is connected downstream of the valve means in the air flow direction.

  Preferably, the another fresh air discharge path is defined inside the crankcase.

  According to this invention, the outstanding effect that the heat dissipation and cooling property of a cylinder block can be improved is exhibited.

1 is an exploded perspective view showing a schematic configuration of an internal combustion engine according to a first embodiment of the present invention. It is sectional drawing which shows a mode that a cylinder block moves relatively with respect to a crankcase. 1 is a diagram showing a schematic configuration of an internal combustion engine mounted on a vehicle. It is a figure which shows schematic structure of the internal combustion engine which concerns on 2nd Embodiment of this invention. It is a figure which shows schematic structure of the internal combustion engine which concerns on 3rd Embodiment of this invention.

Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.
[First Embodiment]
FIG. 1 shows a schematic configuration of a variable compression ratio multi-cylinder internal combustion engine according to the first embodiment. The internal combustion engine (engine) 1 changes the compression ratio by moving the cylinder block 3 formed with the cylinder 2 relative to the crankcase 4 to which the crankshaft 20 (see FIG. 3) is assembled in the cylinder axial direction. To do. The crankcase 4 and the cylinder block 3 are connected by a variable compression ratio mechanism 21 so as to be able to move close to and away from each other in the vertical direction or the cylinder axis direction. The internal combustion engine 1 of the present embodiment is a gasoline engine (spark ignition internal combustion engine), but the present invention is also applicable to a diesel engine (compression ignition internal combustion engine).

  Here, the configuration of the variable compression ratio mechanism 21 will be described. As shown in the drawing, a plurality of raised portions are formed at the lower portions on both sides of the cylinder block 3, and bearing housing holes 5 are formed in the raised portions. The bearing housing holes 5 are circular and formed so as to be perpendicular to the axial direction of the cylinders 2 and parallel to the arrangement direction of the plurality of cylinders 2. The bearing housing holes 5 on one side of the cylinder block 3 are all located on the same axis. A pair of central axes of the bearing housing holes 5 on both sides of the cylinder block 3 are parallel to each other.

  A plurality of standing wall portions are formed in the crankcase 4 so as to be positioned between the plurality of raised portions in which the bearing housing holes 5 described above are formed. A semicircular recess is formed on the surface of each standing wall portion facing the outside of the crankcase 4. Moreover, the cap 7 attached with the volt | bolt 6 is prepared for each standing wall part, and the cap 7 also has a semicircle recessed part. When the cap 7 is attached to each standing wall portion, a circular cam housing hole 8 is formed. The shape of the cam storage hole 8 is the same as that of the bearing storage hole 5 described above.

  The plurality of cam storage holes 8, like the bearing storage holes 5, are perpendicular to the axial direction of the cylinders 2 when the cylinder block 3 is attached to the crankcase 4 and parallel to the arrangement direction of the plurality of cylinders 2. Each is formed to be. The plurality of cam storage holes 8 are also arranged on both sides of the cylinder block 3, and the plurality of cam storage holes 8 on one side are all located coaxially. A pair of central axes of the cam housing holes 8 arranged on both sides of the cylinder block 3 are parallel to each other. Further, the distance between the bearing housing holes 5 on both sides and the distance between the cam housing holes 8 on both sides are the same.

  Cam shafts 9 are respectively inserted into the bearing storage holes 5 and the cam storage holes 8 in two rows on both sides. Thereby, the cylinder block 3 and the crankcase 4 are connected to each other. The cam shaft 9 is fixed to the shaft portion 9a in a state of being eccentric with respect to the shaft portion 9a and the central axis of the shaft portion 9a, and has the same outer shape as the cam portion 9b having a regular circular cam profile. And a movable bearing portion 9c that is rotatably attached to the shaft portion 9a. The cam portions 9b and the movable bearing portions 9c are alternately arranged. The pair of cam shafts 9 have a mirror image relationship. Further, an attachment portion 9 d for attaching the gear 10 is formed at the end portion of the cam shaft 9. The center of the shaft portion 9a and the center of the attachment portion 9d are eccentric, and the center of the cam portion 9b and the center of the attachment portion 9d coincide with each other.

  The movable bearing portion 9c is also eccentric with respect to the shaft portion 9a, and the amount of eccentricity is the same as that of the cam portion 9b. In each camshaft 9, the eccentric directions of the plurality of cam portions 9b are the same. The outer shape of the movable bearing portion 9c is a perfect circle having the same diameter as the cam portion 9b. By rotating the movable bearing portion 9c with respect to the shaft portion 9a, the outer peripheral surface of the cam portion 9b and the outer peripheral surface of the movable bearing portion 9c can be made to coincide with each other.

  A gear 10 is attached to the attachment portion 9d of each camshaft 9. Worm gears 11a and 11b are meshed with the pair of gears 10 fixed to the ends of the pair of cam shafts 9, respectively. The worm gears 11 a and 11 b are attached to one output shaft of the single motor 12. The worm gears 11a and 11b have spiral grooves that rotate in opposite directions. For this reason, when the motor 12 is rotated in one direction, the pair of cam shafts 9 and 9 rotate in the opposite directions via the worm gears 11 a and 11 b and the gears 10 and 10. The motor 12 is fixed to the cylinder block 3.

  Next, the operation of the compression ratio variable mechanism 21 will be described. 2A to 2C are cross-sectional views showing the relationship between the cylinder block 3, the crankcase 4, and the camshaft 9 disposed therebetween. The center axis of the shaft portion 9a is indicated by a, the center of the cam portion 9b is indicated by b, and the center of the movable bearing portion 9c is indicated by c. FIG. 2A shows a state in which the outer peripheral surfaces of all the cam portions 9b and the movable bearing portion 9c coincide with each other when viewed from the extension line of the shaft portion 9a. At this time, the pair of shaft portions 9 a are located outside the bearing housing hole 5 and the cam housing hole 8.

  When the motor 12 is driven from the state of FIG. 2A to rotate the shaft portion 9a in the direction of the arrow, the state of FIG. At this time, since the cam portion 9b and the movable bearing portion 9c are displaced in the eccentric direction with respect to the shaft portion 9a, the cylinder block 3 is slid relative to the crankcase 4 to the upper or top dead center side, It can be moved in the direction of separation. The sliding amount is maximized when the cam shaft 9 is rotated until the state shown in FIG. 2C is reached, and is twice the eccentric amount of the cam portion 9b and the movable bearing portion 9c. The cam portion 9b and the movable bearing portion 9c rotate inside the cam storage hole 8 and the bearing storage hole 5, respectively, and allow the position of the shaft portion 9a to move inside the cam storage hole 8 and the bearing storage hole 5, respectively. doing.

  Although not shown, when the motor 12 is driven from the state of FIG. 2 (c) to rotate the shaft portion 9a in the direction opposite to the arrow direction, the crank is moved to the state of FIG. 2 (b) or FIG. 2 (a). The cylinder block 3 can be slid relative to the case 4 downward or at the bottom dead center, and moved in the proximity direction.

  By using this mechanism, the cylinder block 3 can be moved relative to the crankcase 4 in the cylinder axial direction, and the compression ratio can be changed.

  Next, the above-described internal combustion engine 1 mounted on a vehicle (not shown) will be described with reference to FIG. In FIG. 3, the direction indicated by the arrow F is the front of the vehicle. Although not shown, in the present embodiment, the crankcase 4 of the internal combustion engine 1 is fixed to the vehicle via an engine mount. Therefore, the cylinder block 3 moves up and down with respect to the fixed crankcase 4. However, the mounting method may be reversed to fix the cylinder block 3 to the vehicle. The illustrated example is an example of a front engine vehicle, and the internal combustion engine 1 is stored in an engine room on the front side of the vehicle.

  The internal combustion engine 1 includes a piston 24 that can be moved up and down in the cylinder 2, a cylinder head 25 that is attached to the top of the cylinder block 2, and a head cover 26 that is attached to the top of the cylinder head 25 and covers it from above. The oil pan 27 is attached to the bottom of the crankcase 4 and covers it from below. The piston 24 is connected to the crankshaft 20 via a connecting rod 19.

  A valve operating chamber 28 is defined inside the head cover 26 and the cylinder head 25. In the valve operating chamber 28, an intake valve Vi and an exhaust valve Ve that open and close the intake port Pi and the exhaust port Pe, respectively, and a valve spring (not shown) that urges the intake valve Vi and the exhaust valve Ve in a valve closing direction, respectively. And an intake camshaft Ci and an exhaust camshaft Ce that drive the intake valve Vi and the exhaust valve Ve in the valve opening direction, respectively. The valve operating chamber 28 is supplied with oil for valve operating lubrication from an oil supply port (not shown). An injector 29 for injecting fuel and a spark plug 30 for igniting the air-fuel mixture are attached to the cylinder head 25.

  A combustion chamber 31 is defined above the piston 24, and a crank chamber 32 is defined below the piston 24. A crankshaft 20 is provided in the crank chamber 32, and oil (not shown) is stored at the bottom thereof.

  A surge tank 34 is connected to the intake port Pi via an intake manifold 33 for each cylinder, and intake air is distributed from the surge tank 34 to the intake port Pi of each cylinder via the intake manifold 33. An intake pipe 35 is connected to the upstream side of the surge tank 34, and an electronically controlled throttle valve 36 and an air filter 37 are provided in the intake pipe 35. An intake passage is defined by the intake port Pi, the intake manifold 33, the surge tank 34, and the intake pipe 35.

  An exhaust pipe (not shown) is connected to the exhaust port Pe of each cylinder via an exhaust manifold 38, and an exhaust passage is defined by the exhaust port Pe, the exhaust manifold 38 and the exhaust pipe.

  The internal combustion engine 1 is equipped with a device for processing blow-by gas leaked from the combustion chamber 31 through the gap between the piston 24 and the cylinder 2 and leaking into the crank chamber 32. That is, the blow-by gas leaking into the crank chamber 32 rises through an oil drop hole (not shown) provided in the cylinder block 2 and the crankcase 4 and reaches the valve operating chamber 28. In order to circulate this blow-by gas through the intake passage, the valve operating chamber 28 is connected to the surge tank 34 via the blow-by gas passage 38. A PCV (Positive Crankcase Ventilation) valve 39 whose opening degree is adjusted according to the intake negative pressure or load is provided at the inlet of the blowby gas passage 38, and the PCV valve 39 is attached to the head cover 26.

  On the other hand, the internal combustion engine 1 is also equipped with a device for introducing fresh air or external air for ventilation. This will be described in detail later.

  As shown in the drawing, the lower side of the cylinder block 3 is fitted inside the upper side of the crankcase 4 so as to be movable in the cylinder axial direction. In particular, in the fitting portion, the lower side of the cylinder block 3 protrudes laterally and outward with respect to the upper side, and the cylinder block 3 can slide with respect to the crankcase 4 at the protruding portion. In the fitting portion, the cylinder block 3 is covered from the outside by the crankcase 4, and in particular, the heat dissipation and cooling properties of the cylinder block 3 are lowered at this portion. It is one of the objects of the present invention to suppress this decrease in heat dissipation and cooling properties. A water jacket W is defined in the cylinder block 3 so as to surround the cylinder 2.

  A seal member 40 is provided to seal a fitting portion or a sliding portion between the cylinder block 2 and the crankcase 4. The seal member 40 is formed in an annular shape so that the whole of the seal member 40 makes one round around the outer peripheral side surface of the cylinder block 2 and is made of an elastic body whose cross section is formed in a bellows shape as shown in the drawing. The upper end edge of the seal member 40 is sandwiched and fixed between the cylinder block 2 and the cylinder head 25, and the lower end edge of the seal member 40 is fixed to the crankcase 4.

  When the cylinder block 3 descends and approaches the crankcase 4 (when the compression ratio becomes high), the seal member 40 contracts. When the cylinder block 2 rises and moves away from the crankcase 4 (when the compression ratio becomes low), the seal member 40 extends. Thus, even if the relative position between the cylinder block 2 and the crankcase 3 changes, the sealing member 40 can be expanded and contracted to maintain the airtightness of the fitting portion or the sliding portion.

  As illustrated, a space 41 surrounded by the cylinder block 3, the crankcase 4, and the seal member 40 is formed. The space 41 includes an upper space 41A sandwiched between the cylinder block 3 and the seal member 40 and a lower space 41B sandwiched between the cylinder block 3 and the crankcase 4.

  Since the cylinder block 3 is also covered from the outside by the seal member 40, the heat dissipation and cooling performance of the cylinder block 3 are deteriorated. Therefore, in order to improve heat dissipation and cooling performance, the present embodiment employs the following configuration.

  That is, a fresh air discharge passage 42 for discharging fresh air into the internal combustion engine 1 is provided so as to face the cylinder block 3. In the present embodiment, the fresh air discharge passage 42 includes a discharge port 43 formed through the portion of the crankcase 4 that defines the lower side space 41B, and a discharge passage 44 that is connected to the discharge port 43 and extends to the outside. . That is, the fresh air discharge path 42 communicates with the lower space 41B. The outlet of the fresh air discharge passage 42 or the discharge port 43 is directed to the portion of the cylinder block 3 that similarly defines the lower space 41B, and the fresh air discharged from the discharge port 43 as shown by the arrow F3 It is supposed to be applied to.

  The discharge port 43 may be formed from a through hole or a pipe embedded in the crankcase 4. The outlet of the fresh air discharge path 42 may be directed toward the sliding portion of the cylinder block 3 so that fresh air is applied to the sliding portion. The position to apply freshness is arbitrary. A fresh air discharge passage 42 may be provided through the seal member 40.

  Fresh air discharged from the fresh air discharge passage 42 passes through a gap (not shown) between the cylinder block 3 and the crankcase 4 or a fresh air passage formed in at least one of the cylinder block 3 and the crankcase 4 to Sent to chamber 32. Thus, fresh air is sent to the inside of the internal combustion engine 1 or to the crank chamber 32, and ventilation is realized.

  On the other hand, a fresh air extraction passage 45 for extracting fresh air from the intake passage is provided. The inlet or upstream end of the fresh air extraction path 45 is connected to the intake pipe 35 upstream of the throttle valve 36, and the fresh air extraction path 45 extracts fresh air from the intake passage at this position.

  Furthermore, a fresh air introduction path 46 for introducing fresh air from a place other than the intake passage is provided. The upstream end of the fresh air introduction path 46 is a free end opened in the engine room.

  In particular, as a preferred embodiment, the inlet 46A of the fresh air introduction path 46 is positioned and oriented so as to face the traveling wind during vehicle traveling. Specifically, the inlet 46A is directed toward the front F of the vehicle, faces the traveling wind flowing backward with respect to the vehicle, and collects the traveling wind directly and efficiently.

  The inlet 46A is located at the front end of the vehicle, and is offset from the radiator R disposed at the front end of the vehicle, as viewed from the front side of the vehicle. The inlet 46A is preferably located above the radiator R, more preferably above and ahead of the radiator R. As a result, hot air discharged rearward from the radiator is not introduced into the inlet 46A, and only sufficiently low temperature fresh air can be introduced.

  In the illustrated example, the inlet 46A is enlarged in diameter so as to efficiently collect the traveling wind. Further, a fresh air filter 47 for filtering the introduced fresh air or running wind is provided in the middle of the fresh air introduction path 46.

  Further, valve means for adjusting the communication state of the fresh air discharge path 42 and the fresh air extraction path 45 and the communication state of the fresh air discharge path 42 and the fresh air introduction path 46 are provided. Specifically, the valve means comprises a single switching valve 48 as shown. The switching valve 48 is connected to the upstream end of the discharge passage 44, the downstream end of the fresh air extraction passage 45, and the downstream end of the fresh air introduction passage 46. The switching valve 48 is an electromagnetic three-way valve, and selectively connects one of the fresh air extraction path 45 and the fresh air introduction path 46 to the fresh air discharge path 42. However, not only such alternative switching but also intermediate switching operation is performed, and the ratio of the amount of fresh air sent from the fresh air extraction path 45 and the fresh air introduction path 46 to the fresh air discharge path 42 is determined. It may be changed.

  In the present embodiment, the fresh air extraction path 45 and the fresh air introduction path 46 are switched by a single switching valve 48, but the present invention is not limited to this, and the valve means may be configured by a plurality of valves. For example, valves may be provided individually for the fresh air extraction path 45 and the fresh air introduction path 46. Also, the passage configuration can be variously modified.

  The internal combustion engine 1 includes an electronic control unit (ECU) as a control means for electrically controlling various devices such as the injector 29, the spark plug 30, the throttle valve 36, the motor 12 of the variable compression ratio mechanism 21, and the switching valve 48. ) 100 is attached. The ECU 100 is a unit that includes a CPU, a ROM, a RAM, a backup RAM, and the like.

  The ECU 100 receives electrical signals from various sensors such as a crank position sensor 51, an accelerator position sensor 52, an air flow meter 53, and a water temperature sensor 54. The crank position sensor 51 outputs a pulse signal correlated with the rotational position of the crankshaft 20. The accelerator position sensor 52 outputs a signal correlated with the operation amount (accelerator opening) of the accelerator pedal. The air flow meter 53 outputs a signal correlated with the intake air amount per unit time. The water temperature sensor 54 outputs a signal correlated with the temperature of the cooling water of the internal combustion engine 1.

  The ECU 100 detects the operating state (engine operating state) of the internal combustion engine 1 according to the electrical signals of the various sensors described above, and controls the various devices described above according to the detection results. For example, ECU 100 is based on the rotational speed of the internal combustion engine (engine rotational speed) detected from the output signal of crank position sensor 51 and the load of the internal combustion engine (engine load) detected from the output signal of accelerator position sensor 52. Thus, the compression ratio variable mechanism 21 is controlled.

  At this time, when the engine speed and the engine load are in a predetermined low rotation / low load operation region, the ECU 100 causes the compression ratio of the internal combustion engine 1 to increase, in other words, the cylinder block 3 approaches the crankcase 4. Thus, the variable compression ratio mechanism 21 is controlled.

  Further, when the engine speed and the engine load deviate from the low rotation / low load operation region, the ECU 100 compresses the internal combustion engine 1 so that the compression ratio is lowered, in other words, the cylinder block 3 is moved away from the crankcase 4. The ratio variable mechanism 21 is controlled.

  The compression ratio may be switched in two steps as described above, but may be switched in a stepless manner according to the engine speed and the engine load.

  Thus, when the compression ratio of the internal combustion engine 1 is changed, it is possible to achieve both improvement in combustion efficiency in the low rotation / low load operation region and suppression of knocking in the high rotation or high load operation region outside the region. it can.

  By the way, the ECU 100 controls the switching valve 48 according to the detected engine load. Specifically, when the detected engine load is less than a predetermined value corresponding to a low load, the ECU 100 connects only the fresh air extraction path 45 to the fresh air discharge path 42 and the fresh air introduction path 46 serves as the fresh air discharge path. The switching valve 48 is switched to the first position so that it is not connected to 42. That is, the switching valve 48 is controlled so that the communication state of the fresh air discharge path 42 and the fresh air extraction path 45 is fully opened and the communication state of the fresh air discharge path 42 and the fresh air introduction path 46 is fully closed. Note that the predetermined value of the engine load here may be equal to or different from the load that defines the boundary of the low rotation / low load operation region where the high compression ratio and the low compression ratio are switched. If they are equal, the switching of the high compression ratio and the low compression ratio and the switching of the passages occur simultaneously.

  As a result, only fresh air extracted from the intake passage to the fresh air extraction passage 45 is applied to the cylinder block 3 through the switching valve 48 and the fresh air discharge passage 42 in this order, as indicated by an arrow F1 in FIG.

  On the other hand, when the detected engine load is equal to or higher than a predetermined value corresponding to a high load, the ECU 100 connects only the fresh air introduction path 46 to the fresh air discharge path 42 and the fresh air extraction path 45 to the fresh air discharge path 42. On the other hand, the switching valve 48 is switched to the second position so as not to be connected. That is, the switching valve 48 is controlled so that the communication state of the fresh air discharge path 42 and the fresh air extraction path 45 is fully closed and the communication state of the fresh air discharge path 42 and the fresh air introduction path 46 is fully open.

  Thereby, only the fresh air introduced into the fresh air introduction path 46 is applied to the cylinder block 3 through the switching valve 48 and the fresh air discharge path 42 in this order, as indicated by an arrow F2 in FIG.

  Thus, according to this embodiment, since the fresh air for ventilation can be always applied to the cylinder block 3, the heat dissipation and cooling performance of the cylinder block 3 can be improved. In addition, fresh air is introduced from a portion other than the intake passage through the fresh air introduction path 46 so that the fresh air can be applied to the cylinder block 3, so that fresh air having a lower temperature than the fresh air extracted from the intake passage is supplied to the cylinder block. 3 and the heat dissipation and cooling properties can be further enhanced.

  Further, the switching valve 48 allows the fresh air applied to the cylinder block 3 between the relatively hot fresh air extracted by the fresh air extraction passage 45 and the relatively cool fresh air introduced by the fresh air introduction passage 46. Switched with. Therefore, in the case where it is not desired to promote the heat radiation of the cylinder block 3, that is, during the low load operation or when the engine is warmed up, the relatively high temperature fresh air extracted by the fresh air extraction passage 45 as in a normal internal combustion engine. Can be applied to the cylinder block 3 to ensure the heat retention of the cylinder block 3 and to ensure warm-up.

  On the other hand, when it is desired to promote heat dissipation of the cylinder block 3, that is, during the above-described high load operation in which the cylinder block temperature becomes high, the relatively low temperature fresh air introduced by the fresh air introduction passage 46 is applied to the cylinder block 3, The heat dissipation and cooling performance of the cylinder block 3 can be improved. At this time, since the inlet 46A of the fresh air introduction path 46 is positioned and oriented as described above, low-temperature traveling wind or fresh air can be introduced smoothly and efficiently and applied to the cylinder block 3. In particular, the internal pressure of the crank chamber 32 tends to increase during high-load operation. Even at this time, a relatively large amount of fresh air can be introduced into the engine by using the wind force and inertia. For this reason, it is very advantageous for improvement of heat dissipation and cooling performance of the cylinder block 3.

  Thus, the optimum fresh air according to the engine operating state can be applied to the cylinder block 3 and introduced into the engine.

  In the above, the switching valve 48 is selectively switched, and the fresh air extraction path 45 and the fresh air introduction path 46 are selectively switched between a low load and a high load. However, it is also possible to control the switching valve 48 to an intermediate opening so that the mixing ratio of the fresh air from the fresh air extraction passage 45 and the fresh air from the fresh air introduction passage 46 is continuously variable according to the engine load. Is possible. For example, it is also preferable to control such that the latter fresh air ratio is increased with respect to the former fresh air ratio as the engine load increases.

  The inlet 46A of the fresh air introduction path 46 does not necessarily have to be directed toward the front of the vehicle. For example, when the traveling wind flows into the engine room from below the floor of the vehicle, the inlet 46A of the fresh air introduction path 46 can be directed downward so as to face the traveling wind. In any case, the inlet 46A of the fresh air introduction path 46 is directed to face the traveling wind so that the flow direction of the traveling wind coincides with the axial direction of the inlet 46A, and the traveling wind is directly introduced. Is preferred.

  Further, the inlet 46A of the fresh air introduction path 46 does not necessarily need to be positioned at the vehicle front end. For example, in the case of a rear engine vehicle or a midship engine vehicle, the inlet 46A of the fresh air introduction path 46 can be positioned at the center or rear end of the vehicle close to the internal combustion engine 1. This is because the cooler fresh air can be introduced into the engine when the distance from the inlet 46A of the fresh air introduction path 46 to the outlet (exhaust port 43) of the fresh air discharge path 42 is as short as possible.

[Second Embodiment]
Next, a second embodiment of the present invention will be described. The description of the same parts as in the first embodiment will be omitted, and the differences will be mainly described below.

  As shown in FIG. 4, in the present embodiment, a temperature sensor 55 that directly detects the temperature of the cylinder block 3 is provided. The temperature sensor 55 outputs a signal correlated with the temperature of the cylinder block 3 to the ECU 100. Note that the temperature of the cylinder block 3 can be indirectly detected by the water temperature sensor 54.

  In the present embodiment, the switching valve 48 is controlled according to the cylinder block temperature detected by the temperature sensor 55 instead of the engine load. That is, when the detected cylinder block temperature is less than the relatively low predetermined value, the ECU 100 connects only the fresh air extraction path 45 to the fresh air discharge path 42 and the fresh air introduction path 46 serves as the fresh air discharge path 42. The switching valve 48 is switched to the first position so as to be disconnected. That is, the switching valve 48 is controlled so that the communication state of the fresh air discharge path 42 and the fresh air extraction path 45 is fully opened and the communication state of the fresh air discharge path 42 and the fresh air introduction path 46 is fully closed.

  Thereby, only the fresh air extracted from the intake passage to the fresh air extraction passage 45 is applied to the cylinder block 3 through the switching valve 48 and the fresh air discharge passage 42 in this order, as indicated by an arrow F1 in FIG.

  On the other hand, when the detected cylinder block temperature is equal to or higher than a relatively high predetermined value, the ECU 100 connects only the fresh air introduction path 46 to the fresh air discharge path 42 and the fresh air extraction path 45 serves as the fresh air discharge path. The switching valve 48 is switched to the second position so that it is not connected to 42. That is, the switching valve 48 is controlled so that the communication state of the fresh air discharge path 42 and the fresh air extraction path 45 is fully closed and the communication state of the fresh air discharge path 42 and the fresh air introduction path 46 is fully open.

  Thereby, only the fresh air introduced into the fresh air introduction path 46 is applied to the cylinder block 3 through the switching valve 48 and the fresh air discharge path 42 in this order, as indicated by an arrow F2 in FIG.

  According to the present embodiment, when the cylinder block temperature is high during low load operation, for example, during steady running after uphill running, low temperature fresh air from the fresh air introduction path 46 is removed. It can be applied to the cylinder block 3, and the heat dissipation and cooling performance of the cylinder block 3 can be improved. And the cylinder block temperature can be lowered immediately. In the first embodiment, in this case, the fresh air extraction path 45 is connected to the fresh air discharge path 42, which is relatively disadvantageous compared to the first embodiment.

  Alternatively, the switching valve 48 can be controlled according to both the detected engine load and the cylinder block temperature. In this case, for example, when both the detected engine load and cylinder block temperature are lower than the predetermined threshold values corresponding to each of them, ECU 100 connects only fresh air extraction path 45 to fresh air discharge path 42 and The switching valve 48 is switched to the first position so that the air introduction path 46 is not connected to the fresh air discharge path 42. As a result, only fresh air extracted from the intake passage is applied to the cylinder block 3.

  On the other hand, when at least one of the detected engine load and cylinder block temperature is equal to or higher than a predetermined threshold value corresponding thereto, the ECU 100 connects only the fresh air introduction path 46 to the fresh air discharge path 42 and The switching valve 48 is switched to the second position so that the air extraction path 45 is not connected to the fresh air discharge path 42. As a result, only fresh air introduced into the fresh air introduction path 46 is applied to the cylinder block 3.

[Third Embodiment]
Next, a third embodiment of the present invention will be described. The description of the same parts as those in the first and second embodiments will be omitted, and the differences will be mainly described below.

  In the third embodiment, the following features are added to the first embodiment. That is, as shown in FIG. 5, another fresh air discharge passage directed to the crank journal portion 20 </ b> A in the crankcase 4 is provided to discharge fresh air into the internal combustion engine 1. The upstream end of the other fresh air discharge passage is connected to the fresh air discharge passage 42 on the downstream side of the switching valve 48 in the fresh air flow direction.

  In the case of this embodiment, another fresh air discharge path includes a branch passage 56 defined in the crankcase 4. The upstream end of the branch passage 56 is connected to the discharge port 43, and the branch passage 56 is branched from the discharge port 43. The branch passage 56 extends downward from the discharge port 43, and a downstream end or outlet thereof is opened toward the crank journal portion 20 </ b> A in the crank chamber 32 at a position close to the crankshaft 20. Here, the crank journal portion 20A refers to a portion of the crankshaft 20 that is rotatably supported by a bearing (not shown).

  According to the present embodiment, fresh air that has flowed into the discharge port 43 can be branched into the branch passage 56 as indicated by the arrow F4 and discharged toward the crank journal portion 20A as indicated by the arrow F5. Thereby, the heat dissipation of the crank journal part 20A is also improved, and the seizure of the crank journal part 20A can be avoided in advance.

  In particular, in the case of the variable compression ratio internal combustion engine as in the present embodiment, the cylinder block 3 and the crankcase 4 are separated from each other, so that the crankcase 4 by the cooling water in the cylinder block 3 and its Heat dissipation and cooling of the mounting parts (that is, heat sink to cooling water) cannot be expected. Therefore, the temperature of the crank journal portion 20A rises and seizure is likely to occur. The present embodiment can cope with such a problem. In particular, during high load operation, the surface pressure of the crank journal portion 20A increases and the temperature tends to rise, but even in such a case, the crank journal portion 20A is moved by the relatively low temperature fresh air introduced from the fresh air introduction passage 46. Since it can cool, the temperature rise of 20 A of crank journal parts can be suppressed reliably.

  Furthermore, since the branch passage 56 is defined inside the crankcase 4, the crankcase 4 can be cooled directly and indirectly by its fresh air flowing through the branch passage 56. This is advantageous for suppressing the temperature rise of the crank journal portion 20A.

  Note that the features of this embodiment may be added to the second embodiment. Further, another fresh air discharge path is not limited to the branch passage 56 defined in the crankcase 4 as in the present embodiment, and may be formed by a pipe branched from the middle of the discharge passage 44, for example.

  The preferred embodiment of the present invention has been described in detail above, but various other embodiments of the present invention are conceivable.

  The embodiment of the present invention is not limited to the above-described embodiment, and includes all modifications, applications, and equivalents included in the concept of the present invention defined by the claims. Therefore, the present invention should not be construed as being limited, and can be applied to any other technique belonging to the scope of the idea of the present invention. The above embodiments and components can be combined as much as possible.

DESCRIPTION OF SYMBOLS 1 Internal combustion engine 2 Cylinder 3 Cylinder block 4 Crankcase 9 Cam shaft 10 Gear 11a, 11b Worm gear 12 Motor 20 Crankshaft 20A Crank journal part 21 Compression ratio variable mechanism 42 Fresh air discharge path 45 Fresh air extraction path 46 Fresh air introduction path 46A Inlet 48 Switching valve 51 Crank position sensor 52 Accelerator position sensor 56 Branch passage 100 Electronic control unit (ECU)

Claims (8)

A variable compression ratio internal combustion engine in which a cylinder block is fitted inside a crankcase so as to be movable in the cylinder axial direction.
A fresh air discharge passage for discharging fresh air is provided in the internal combustion engine so as to be directed to the cylinder block, a fresh air extraction passage for extracting fresh air from the intake passage is provided, and locations other than the intake passage A fresh air introduction path for introducing fresh air is provided, and valve means for adjusting the communication state of the fresh air discharge path and the fresh air extraction path and the communication state of the fresh air discharge path and the fresh air introduction path are provided. A variable compression ratio internal combustion engine. 2. The variable compression ratio internal combustion engine according to claim 1, wherein the internal combustion engine is mounted on a vehicle, and an inlet of the fresh air introduction path is directed so as to face running wind when the vehicle is running. The variable compression ratio internal combustion engine according to claim 1 or 2, wherein an inlet of the fresh air introduction path is directed toward the front of the vehicle. The variable compression ratio internal combustion engine according to any one of claims 1 to 3, wherein an inlet of the fresh air introduction path is located at a vehicle front end. The valve means is controlled according to at least one of the load of the internal combustion engine and the temperature of the cylinder block, and the detected valve means is controlled according to any one of claims 1 to 4. The variable compression ratio internal combustion engine described. When at least one of the load and temperature is equal to or greater than a predetermined value, the communication state of the fresh air discharge path and the fresh air extraction path is fully closed, and the communication state of the fresh air discharge path and the fresh air introduction path is fully open. The variable compression ratio internal combustion engine according to claim 5, wherein the valve means is controlled so as to be in a state. Another fresh air discharge passage directed to the crank journal portion in the crankcase is provided to discharge fresh air inside the internal combustion engine, and the upstream end of the another fresh air discharge passage is in the fresh air flow direction. The variable compression ratio internal combustion engine according to any one of Claims 1 to 6, wherein the variable compression ratio internal combustion engine is connected to the fresh air discharge path downstream of the valve means. The variable compression ratio internal combustion engine according to claim 7, wherein the another fresh air discharge path is defined in the crankcase.

Images