JP2016183651A - Variable compression ratio internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a variable compression ratio internal combustion engine capable of achieving both an oil separation performance when the engine operates at a high load and a blow-by gas scavenging performance when the engine operates at a low load.SOLUTION: A variable compression ratio internal combustion engine comprises an oil separator 70. The oil separator comprises: a first inlet hole 73 and a second inlet hole 74; an outlet hole 75; an oil separation plate 76; and a regulation plate 78 that moves relatively to the first inlet hole and the second inlet hole when a cylinder block 2 moves relatively to a crankcase 1, and that is configured such that a pressure loss when a blow-by gas passes through the oil separator is smaller when the blow-by gas enters from the second inlet hole than when the blow-by gas enters from the first inlet hole, and the regulation plate is configured such that an opening area of the second inlet hole is reduced and an opening area of the first inlet hole is increased or kept at a largest area when the cylinder block moves relatively to the crankcase so as to reduce a mechanical compression ratio.SELECTED DRAWING: Figure 5

Description

  The present invention relates to a variable compression ratio internal combustion engine.

  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 and output performance of the internal combustion engine. As such a technique, for example, a cylinder block and a crankcase are connected so as to be relatively movable, a camshaft is provided at the connecting portion, and the camshaft is rotated to connect the cylinder block and the crankcase in the cylinder axial direction. There is a technique in which the volume of the combustion chamber is changed by relatively moving the internal combustion engine to change the compression ratio of the internal combustion engine (for example, Patent Documents 1 and 2).

  Also in such a variable compression ratio internal combustion engine, a part of the air-fuel mixture in the combustion chamber leaks into the crankcase through the gap between the cylinder wall surface and the piston and becomes blow-by gas. Since blow-by gas deteriorates oil stored in the crankcase, for example, in an internal combustion engine described in Patent Document 1, an exhaust pipe and a circulation pipe are provided between the crankcase and the engine intake passage. By scavenging blow-by gas from the crankcase through these exhaust pipes and flow pipes, deterioration of oil in the crankcase can be suppressed.

  Further, oil is present as fine particles in the blow-by gas (oil mist). When a large amount of oil flows into the engine intake passage, deposits are likely to adhere to the combustion chamber or the like, and the air-fuel mixture may self-ignite before ignition by the spark plug. For this reason, it is known to use an oil separator that separates oil from blow-by gas when returning blow-by gas to the engine intake passage (for example, Patent Document 1).

JP 2013-238117 A JP 2011-149280 A

  By the way, at the time of engine high load operation, the amount of intake air supplied to the combustion chamber increases, and the amount of blow-by gas leaking from the combustion chamber, and hence the amount of oil mist in the blow-by gas, also increases. For this reason, at the time of engine high load operation, it is required to improve the oil separation performance of the oil separator. However, if the oil separation performance of the oil separator is increased, the pressure loss when blow-by gas passes through the oil separator increases, and the scavenging performance of the blow-by gas decreases.

  Further, in a variable compression ratio internal combustion engine, in order to improve the fuel efficiency of the internal combustion engine, the engine compression ratio is increased and the intake valve closing timing is increased in order to increase the expansion ratio while maintaining the actual compression ratio during engine low load operation. It is also known to retard or advance the angle away from the intake bottom dead center. In this case, since the intake air amount is reduced by the delay or advance of the closing timing of the intake valve, the opening of the throttle valve is increased despite the low engine load. As a result, the pressure difference between the crankcase and the engine intake passage is reduced, and the scavenging performance of blow-by gas is reduced. Also, during engine low load operation, unlike the engine high load operation such as a supercharging region, the blow-by gas in the crankcase cannot be scavenged using the ejector. Therefore, during engine low load operation, it is required to improve the scavenging performance of blow-by gas rather than the oil separation performance.

  Accordingly, in view of the above problems, an object of the present invention is to provide a variable compression ratio internal combustion engine that can achieve both oil separation performance during engine high load operation and blow-by gas scavenging performance during engine low load operation. There is.

  In order to solve the above-mentioned problem, in the first aspect of the invention, in the variable compression ratio internal combustion engine in which the mechanical compression ratio can be changed by moving the cylinder block relative to the crankcase, it is included in the blow-by gas in the crankcase. An oil separator capable of separating oil is provided. The oil separator has a first inlet hole and a second inlet hole through which blow-by gas flows into the oil separator, and blow-by gas flowing into the oil separator flows out from the oil separator. When the cylinder block moves relative to the crankcase, and the oil separation plate disposed in the blow-by gas passage between the first inlet hole and the outlet hole. 2 and an adjustment plate that moves relative to the inlet hole, and blow-by gas passes through the oil separator. The pressure loss is reduced when the blow-by gas flows from the second inlet hole than when the blow-by gas flows from the first inlet hole, and the variable compression ratio internal combustion engine has a maximum mechanical compression ratio of the mechanical compression ratio. Until the ratio is reached, the mechanical compression ratio is changed so that the mechanical compression ratio increases as the engine load decreases, and the adjustment plate moves when the cylinder block moves relative to the crankcase so that the mechanical compression ratio decreases. A variable compression ratio internal combustion engine is provided that is configured such that the opening area of the second inlet hole is reduced and the opening area of the first inlet hole is increased or maintained at a maximum.

  ADVANTAGE OF THE INVENTION According to this invention, the variable compression ratio internal combustion engine which can make the oil separation performance at the time of engine high load operation and the scavenging performance of blow-by gas at the time of engine low load operation compatible is provided.

FIG. 1 is a side sectional view schematically showing a spark ignition type internal combustion engine according to the present invention. FIG. 2 shows an exploded perspective view of the variable compression ratio mechanism A shown in FIG. FIG. 3 shows a schematic side sectional view of the internal combustion engine. FIG. 4 is a diagram showing changes in the mechanical compression ratio and the like according to the engine load. FIG. 5 is a schematic cross-sectional view showing a region X of FIG. 1 in an enlarged manner. FIG. 6 is a schematic cross-sectional view of the oil separator taken along line CC in FIG. FIG. 7 shows the state of the oil separator when the mechanical compression ratio is maximum. FIG. 8 shows the state of the oil separator when the mechanical compression ratio is minimum.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same reference numerals are assigned to similar components.

<Configuration of internal combustion engine>
FIG. 1 is a side sectional view of a spark ignition type internal combustion engine. Referring to FIG. 1, 1 is a crankcase, 2 is a cylinder block, 3 is a cylinder head, 4 is a piston, 5 is a combustion chamber, 6 is a spark plug disposed at the center of the top surface of the combustion chamber 5, and 7 is an intake air 8 is an intake port, 9 is an exhaust valve, and 10 is an exhaust port. The intake port 8 is connected to a surge tank 12 via an intake branch pipe 11, and a fuel injection valve 13 for injecting fuel into the corresponding intake port 8 is arranged in each intake branch pipe 11. Note that the fuel injection valve 13 may be disposed in each combustion chamber 5 instead of being attached to each intake branch pipe 11.

  The surge tank 12 is connected to an air cleaner 15 via an intake duct 14, and a throttle valve 17 driven by an actuator 16 and an air flow meter 18 using, for example, heat rays are arranged in the intake duct 14. The intake port 8, the intake branch pipe 11, the surge tank 12, and the intake duct 14 form an engine intake passage. On the other hand, the exhaust port 10 is connected to a catalytic converter 20 containing, for example, a three-way catalyst via an exhaust manifold 19, and an air-fuel ratio sensor 21 is disposed in the exhaust manifold 19.

  On the other hand, in the embodiment shown in FIG. 1, the piston 4 is compression dead by changing the relative distance in the axial direction of the cylinder 25 between the crankcase 1 and the cylinder block 2 at the connecting portion between the crankcase 1 and the cylinder block 2. A variable compression ratio mechanism A capable of changing the volume of the combustion chamber 5 when located at a point is provided. Furthermore, in the embodiment shown in FIG. 1, a variable valve timing mechanism B that can change the valve closing timing of the intake valve 7 is provided.

  The internal combustion engine of the present embodiment also includes a flow pipe 22 that can supply air into the crankcase 1 from the engine intake passage, and a return pipe 23 that returns the blowby gas in the crankcase 1 to the engine intake passage. The flow pipe 22 communicates with the crankcase 1 at one end and communicates with the air cleaner 15 at the other end. Note that the flow pipe 22 may communicate with a place other than the air cleaner 15 as long as it is upstream of the throttle valve 17. On the other hand, the return pipe 23 communicates with the crankcase 1 at one end and communicates with the surge tank 12 at the other end. Note that the return pipe 23 may communicate with a place other than the surge tank as long as it is downstream of the throttle valve 17. Further, a check valve may be provided in the return pipe 23 that permits the flow of fluid from the internal combustion engine body to the engine intake passage but prohibits the reverse flow.

  The electronic control unit 30 is composed of a digital computer, and is connected to each other by a bidirectional bus 31. A ROM (read only memory) 32, a RAM (random access memory) 33, a CPU (microprocessor) 34, an input port 35 and an output port 36. It comprises. Output signals of the air flow meter 18 and the air-fuel ratio sensor 21 are input to the input port 35 via the corresponding AD converters 37. A load sensor 41 that generates an output voltage proportional to the amount of depression of the accelerator pedal 40 is connected to the accelerator pedal 40, and the output voltage of the load sensor 41 is input to the input port 35 via the corresponding AD converter 37. The Further, the input port 35 is connected with a crank angle sensor 42 that generates an output pulse every time the crankshaft rotates by a predetermined angle. On the other hand, the output port 36 is connected to the spark plug 6, the fuel injection valve 13, the throttle valve drive actuator 16, the variable compression ratio mechanism A, and the variable valve timing mechanism B through corresponding drive circuits 38.

<Configuration of variable compression ratio mechanism>
Next, the configuration of the variable compression ratio mechanism A of the present embodiment will be described with reference to FIGS. 2 is an exploded perspective view of the variable compression ratio mechanism A shown in FIG. 1, and FIG. 3 is a side sectional view of the internal combustion engine schematically shown. Referring to FIG. 2, a plurality of block-side shaft holding portions 50 are formed below the both side walls of the cylinder block 2 so as to be spaced apart from each other. Each block side shaft holding part 50 is formed of an inner part 50a and an outer part 50b. A block-side cam insertion hole 51 having a circular cross section is formed in each block-side shaft holding portion 50. These block side cam insertion holes 51 are formed on the same axis so as to be parallel to the arrangement direction of the cylinders 25. In particular, the block-side cam insertion hole 51 is formed between the inner portion 50a and the outer portion 50b of the block-side shaft holding portion 50. The block-side shaft holding portion 50 is thus divided into the inner portion 50a and the outer portion 50b, so that camshafts 54 and 55 described later can be attached to the block-side cam insertion hole 51. The block side shaft holder 50 holds the camshafts 54 and 55 in a rotatable manner.

  On the other hand, on the upper wall surface of the crankcase 1, a plurality of case-side shaft holding portions 52 are formed which are fitted between the corresponding block-side shaft holding portions 50 at intervals. Each case-side shaft holding part 52 is formed of an inner part 52a and an outer part 52b. The outer portions 52b are connected to each other by a connecting plate 52c. The plurality of outer portions 52b and the plurality of connecting plates 52c of the case side shaft holding portion 52 are integrally formed so as to become one member. A case-side cam insertion hole 53 having a circular cross section is also formed in each case-side shaft holding portion 52. The case side cam insertion holes 53 are also formed on the same axis line so as to be parallel to the arrangement direction of the cylinders 25, similarly to the block side cam insertion holes 51. The case side cam insertion hole 53 is also formed between the inner side portion 52a and the outer side portion 52b of the case side shaft holding portion 52. Since the case side shaft holding portion 52 is thus divided into the inner portion 52 a and the outer portion 52 b, camshafts 54 and 55 described later can be attached in the case side cam insertion hole 53. The case side shaft holding portion 52 holds the camshafts 54 and 55 rotatably.

  In addition, the variable compression ratio mechanism A includes a pair of camshafts 54 and 55 that function as operating axes as shown in FIG. On each of the cam shafts 54 and 55, case-side circular cams 58 that are rotatably inserted into the case-side cam insertion holes 53 are fixed. These case-side circular cams 58 are coaxial with the rotational axes of the camshafts 54 and 55. On the other hand, as shown in FIG. 3, eccentric shafts 57 arranged eccentrically with respect to the rotation axes of the camshafts 54 and 55 extend on both sides of each case-side circular cam 58. The block-side circular cam 56 is eccentrically attached to be rotatable. As shown in FIG. 2, these block-side circular cams 56 are arranged on both sides of each case-side circular cam 58, and these block-side circular cams 56 are rotatably inserted into the corresponding block-side cam insertion holes 51. Has been. As can be seen from FIGS. 2 and 3, the cylinder block 2 is connected to the crankcase via the camshafts 54 and 55 so as to move relative to the crankcase 1 by the rotation of the camshafts 54 and 55 having the eccentric shaft 57. 1 is supported.

  The variable compression ratio mechanism A includes a drive device that rotates the camshafts 54 and 55. In the present embodiment, the drive source of the drive device is a drive motor 59. As shown in FIG. 2, a pair of worm gears 61, 62 having opposite spiral directions are attached to the rotation shaft 60 of the drive motor 59 in order to rotate the camshafts 54, 55 in opposite directions, respectively. Worm wheels 63 and 64 meshing with the worm gears 61 and 62 are fixed to end portions of the camshafts 54 and 55, respectively. In this embodiment, by driving the drive motor 59, the volume of the combustion chamber 5 when the piston 4 is located at the compression top dead center can be changed over a wide range.

<Method of changing mechanical compression ratio by variable compression ratio mechanism>
When the case-side circular cams 58 fixed on the camshafts 54 and 55 are rotated in opposite directions as indicated by arrows in FIG. 3A from the state shown in FIG. Move away from each other. For this reason, the block-side circular cam 56 rotates in the block-side cam insertion hole 51 in the opposite direction to the case-side circular cam 58, and as shown in FIG. It becomes the height position. Next, when the case-side circular cam 58 is further rotated in the direction indicated by the arrow, the eccentric shaft 57 is at the lowest position as shown in FIG.

  3A, 3B, and 3C show the center a of the case-side circular cam 58, the center b of the eccentric shaft 57, and the center c of the block-side circular cam 56 in each state. The positional relationship is shown.

  As can be seen by comparing FIGS. 3A to 3C, the relative distance between the crankcase 1 and the cylinder block 2 depends on the distance between the center a of the case-side circular cam 58 and the center c of the block-side circular cam 56. Determined. The cylinder block 2 moves away from the crankcase 1 as the distance between the center a of the case side circular cam 58 and the center c of the block side circular cam 56 increases. That is, the variable compression ratio mechanism A changes the relative distance between the crankcase 1 and the cylinder block 2 by a crank mechanism using a rotating cam. And if the cylinder block 2 leaves | separates from the crankcase 1, the volume of the combustion chamber 5 when piston 4 is located in a compression top dead center will increase. Therefore, the volume of the combustion chamber 5 (hereinafter referred to as “combustion chamber volume”) when the piston 4 is located at the compression top dead center can be changed by rotating the camshafts 54 and 55.

In particular, in the example shown in FIG. 3, the cylinder block 2 is moved relative to the crankcase 1 by D ₁ between the state shown in FIG. 3 (A) and the state shown in FIG. 3 (B). The cylinder block 2 is moved relative to the crankcase 1 by D ₂ between the state shown in FIG. 3B and the state shown in FIG.

  Even if the volume of the combustion chamber 5 when the piston 4 is located at the compression top dead center is changed by rotating the camshafts 54 and 55 in this way, the stroke volume of the piston 4 during the compression stroke (the piston 4 The volume of the combustion chamber 5 that changes when moving from the intake bottom dead center to the compression top dead center does not change. Therefore, the mechanical compression ratio represented by (combustion chamber volume + stroke volume) / combustion chamber volume changes as the combustion chamber volume is changed as described above. That is, according to the variable compression ratio mechanism A of the present embodiment, the mechanical compression ratio of the internal combustion engine can be changed by rotating the camshafts 54 and 55 by the drive motor 59.

<Control according to engine load>
Next, overall operation control will be described with reference to FIG.
FIG. 4 shows changes in the required intake air amount, the closing timing of the intake valve 7, the mechanical compression ratio, the expansion ratio, the actual compression ratio, and the opening degree of the throttle valve 17 according to the engine load. In the present embodiment, the average air-fuel ratio in the combustion chamber 5 is usually the air-fuel ratio sensor 21 so that unburned HC, CO and NO _x in the exhaust gas can be simultaneously reduced by the three-way catalyst in the catalytic converter 20. Feedback control to the stoichiometric air-fuel ratio based on the output signal.

  As shown in FIG. 4, the mechanical compression ratio is lowered during engine high load operation. For this reason, the expansion ratio is low, and the valve closing timing of the intake valve 7 is set near the intake bottom dead center as shown by the solid line in FIG. At this time, the amount of intake air is large, and at this time, the opening degree of the throttle valve 17 is kept fully open or almost fully open, so that the pumping loss is zero.

  On the other hand, as shown by the solid line in FIG. 4, when the engine load becomes low, the closing timing of the intake valve 7 is retarded so as to be away from the intake bottom dead center in order to reduce the intake air amount. Further, at this time, as shown in FIG. 4, the mechanical compression ratio is increased as the engine load is lowered so that the actual compression ratio is kept substantially constant. Therefore, the expansion ratio is also increased as the engine load is lowered. At this time, the throttle valve 17 is kept fully open, and therefore the amount of intake air supplied into the combustion chamber 5 is controlled by changing the closing timing of the intake valve 7 without depending on the throttle valve 17. Has been. Also at this time, the pumping loss becomes zero.

  As described above, when the engine load is reduced from the engine 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 5 when the piston 4 reaches the compression top dead center is reduced in proportion to the reduction in the intake air amount.

When the engine load is further reduced, the mechanical compression ratio is further increased, and when the engine load is lowered to the medium load L ₁ slightly close to the low load, the mechanical compression ratio reaches the maximum critical mechanical compression ratio that is the structural limit of the combustion chamber 5. . When the mechanical compression ratio reaches the maximum critical mechanical compression ratio, the mechanical compression ratio is maintained at the maximum critical mechanical compression ratio in a region where the load is lower than the engine load L ₁ when the mechanical compression ratio reaches the maximum critical mechanical compression ratio. The Therefore, the mechanical compression ratio is maximized and the expansion ratio is maximized at the time of low engine load operation and low engine load operation, that is, on the engine low load operation side. In other words, the mechanical compression ratio is maximized so that the maximum expansion ratio is obtained on the engine low load operation side. Therefore, the variable compression ratio internal combustion engine of the present embodiment changes the mechanical compression ratio so that the mechanical compression ratio increases as the engine load decreases until the mechanical compression ratio reaches the maximum limit mechanical compression ratio.

On the other hand, in the embodiment shown in FIG. 4, when the engine load decreases to L ₁ , the closing timing of the intake valve 7 becomes the limit closing timing that can control the amount of intake air supplied into the combustion chamber 5. When the closing timing of the intake valve 7 reaches the limit closing timing, the closing timing of the intake valve 7 in a region where the load is lower than the engine load L ₁ when the closing timing of the intake valve 7 reaches the closing timing. Is held at the limit valve closing timing.

When the closing timing of the intake valve 7 is held at the limit closing timing, the amount of intake air can no longer be controlled by changing the closing timing of the intake valve 7. In the embodiment shown in FIG. 4, at this time, that is, in a region where the load is lower than the engine load L ₁ when the closing timing of the intake valve 7 reaches the limit closing timing, the throttle valve 17 causes the combustion chamber 5 to enter the combustion chamber 5. The amount of intake air to be supplied is controlled, and the opening degree of the throttle valve 17 is made smaller as the engine load becomes lower.

  In addition, as shown by the broken line in FIG. 4, the intake air amount is controlled without depending on the throttle valve 17 by advancing the closing timing of the intake valve 7 away from the intake bottom dead center as the engine load decreases. May be. In the following description, the case where the closing timing of the intake valve 7 is retarded as the engine load decreases will be described as an example. However, the present invention can be similarly applied to the case where the closing timing of the intake valve 7 is advanced. .

By the way, when the mechanical compression ratio and the closing timing of the intake valve 7 are not changed, the opening degree of the throttle valve 17 becomes smaller as the engine load is smaller as shown by the broken line in FIG. On the other hand, in the variable compression ratio internal combustion engine, until the engine load is reduced to L _1, together with the mechanical compression ratio is increased, the closing timing of the intake valve 7 is retarded. In this case, since the required intake air amount is controlled by the closing timing of the intake valve 7, until the engine load is reduced to L _1, the opening degree of the throttle valve 17 is fully opened. Further, as described above, in the region where the load is lower than the engine load L ₁ when the closing timing of the intake valve 7 reaches the limit closing timing, the intake air amount is reduced by reducing the opening of the throttle valve 17. Be controlled. However, even in a region where the load is lower than the engine load L _1, the opening degree of the throttle valve 17 in the variable compression ratio internal combustion engine becomes larger than when the mechanical compression ratio and the closing timing of the intake valve 7 are not changed. Therefore, in the variable compression ratio internal combustion engine, the pressure difference between the crankcase 1 and the engine intake passage is reduced during engine low load operation, so that the scavenging performance of blow-by gas is deteriorated.

<Configuration of slider>
Further, the variable compression ratio internal combustion engine of the present embodiment includes a slider 90 that urges the cylinder block 2 toward the inside of the crankcase 1. In the present specification, the inside means the center side of the cylinder 25 in the direction perpendicular to the axial direction and the arrangement direction of the cylinders 25 (hereinafter referred to as “left-right direction”), and the outside means the cylinder 25 in the left-right direction. It means the side away from the center. Below, the slider 90 of this embodiment is demonstrated with reference to FIG. In FIG. 1, the slider 90 is omitted.

  FIG. 5 is a schematic cross-sectional view showing a region X of FIG. 1 in an enlarged manner. In particular, FIG. 5 is a cross-sectional view in a cross section perpendicular to the axis of the camshaft 54 at a position where the block side shaft holding portion 50 is provided. As can be seen from FIG. 5, the connection plate 52 c of the case side shaft holding portion 52 is disposed outside the block side shaft holding portion 50. As described above, the rotation of the camshafts 54 and 55 causes the cylinder block 2 to move relative to the crankcase 1 in the direction of the arrow in the figure, so that the block side shaft holding portion 50 also holds the case side shaft. It moves relative to the connecting plate 52c of the part 52 in the direction of the arrow in the figure.

  The slider 90 includes a fixing portion 91 fixed to the connecting plate 52c of the case side shaft holding portion 52, and a sliding portion 92 slidably engaged with the fixing portion 91 and the block side shaft holding portion 50. The fixing portion 91 is fixed to the connecting plate 52c by a fixing tool (not shown) such as a bolt. The sliding portion 92 is partially accommodated in the fixed portion 91.

  The slider 90 further includes urging means disposed between the fixed portion 91 and the sliding portion 92. In the present embodiment, the urging means is the first spring 93. The first spring 93 biases the cylinder block 2 inward via the sliding portion 92. As a result, vibration in the left-right direction of the cylinder block 2 that occurs when the cylinder block 2 is moved relative to the crankcase 1 can be suppressed.

  The slider 90 is disposed on both sides of the cylinder block 2 in the left-right direction. A plurality of sliders 90 may be disposed on each side of the cylinder block 2.

<Configuration of oil separator>
Further, the variable compression ratio internal combustion engine of the present embodiment includes an oil separator 70 that can separate oil contained in blow-by gas in the crankcase 1. Below, the oil separator 70 of this embodiment is demonstrated with reference to FIG.5 and FIG.6. FIG. 6 is a schematic cross-sectional view of the oil separator 70 taken along line CC in FIG. In FIG. 1, the oil separator 70 is omitted.

  As shown in FIG. 5, the crankcase 1 includes a cover 80 disposed on the outside of the case side shaft holding portion 52. The cover 80 is disposed so as to close an opening in which the camshafts 54 and 55, the block-side shaft holding portion 50, the case-side shaft holding portion 52, and the slider 90 that constitute the variable compression ratio mechanism A are arranged. The oil separator 70 is formed inside the cover 80. The oil separator 70 is formed below the slider 90 in the axial direction of the cylinder 25. The positions of the oil separator 70 and the slider 90 may be upside down. The oil separator 70 may be separated from the slider 90 in the arrangement direction of the cylinders 25.

  The oil separator 70 includes a surrounding plate 71 and a gasket 72. The surrounding plate 71 extends from the cover 80 toward the connection plate 52c of the case-side shaft holding portion 52. In the present embodiment, the surrounding plate 71 is formed integrally with the cover 80. Note that the surrounding plate 71 is separate from the cover 80 and may be fixed to the cover 80 by a fixing tool such as a bolt. The gasket 72 is disposed between the connecting plate 52c and the surrounding plate 71, and seals the space between the connecting plate 52c and the surrounding plate 71. For example, the gasket 72 has a rectangular shape and is made of an elastic body such as rubber. As shown in FIG. 5, the space in the oil separator 70 is defined by the connecting plate 52 c, the cover 80, the surrounding plate 71, and the gasket 72.

  In the present embodiment, the oil separator 70 has a first inlet hole 73 and a second inlet hole 74 through which blow-by gas flows into the oil separator 70, and blow-by gas that has flowed into the oil separator 70 flows out from the oil separator 70. And an oil separator plate 76 disposed in the blow-by gas flow path between the first inlet hole 73 and the outlet hole 75. In the cross-sectional view of FIG. 6, the outlet hole 75 that does not actually appear is indicated by a broken line for reference.

  As shown in FIGS. 5 and 6, the first inlet hole 73 and the second inlet hole 74 have a circular cross section and extend in the left-right direction so as to penetrate the connecting plate 52c. Accordingly, the first inlet hole 73 and the second inlet hole 74 are formed in the connecting plate 52c. The first inlet hole 73 and the second inlet hole 74 are separated from each other in the axial direction of the cylinder 25, and the second inlet hole 74 is closer to the outlet hole 75 than the first inlet hole 73. On the other hand, the outlet hole 75 has a circular cross section and extends through the cover 80. Accordingly, the outlet hole 75 is formed in the cover 80. The outlet hole 75 is separated from the first inlet hole 73 and the second inlet hole 74 in the left-right direction. The outlet hole 75 is connected to the return pipe 23.

  In the present embodiment, the number of oil separation plates 76 is five. As shown in FIG. 6, the oil separating plate 76 alternately extends in the arrangement direction of the cylinder 25 from the front portion 71a and the rear portion 71b of the surrounding plate 71 spaced in the arrangement direction of the cylinder 25, and in the left-right direction. The connecting plate 52c extends to the cover 80.

  The blow-by gas flowing in from the first inlet hole 73 changes its direction many times in the oil separator 70 and then flows out from the outlet hole 75 as shown by the solid line arrow in FIG. At this time, the blow-by gas collides with the cover 80, the surrounding plate 71, and the oil separation plate 76, so that the oil contained in the blow-by gas is separated. On the other hand, the blow-by gas that has flowed in from the second inlet hole 74 flows out from the outlet hole 75 without passing through the flow path between the oil separation plates 76, as indicated by the dashed arrows in FIG. Therefore, in the oil separator 70, the pressure loss when the blow-by gas passes through the oil separator 70 is smaller when the blow-by gas flows from the second inlet hole 74 than when the blow-by gas flows from the first inlet hole 73. It is configured.

  The oil separated from the blow-by gas in the oil separator 70 is returned to the oil pan disposed below the crankcase 1 through the oil dropping hole 77 formed in the lower portion 71 c of the surrounding plate 71. On the other hand, the blow-by gas from which the oil has been separated flows into the engine intake passage through the return pipe 23.

  The oil separator 70 further includes an adjustment plate 78 disposed inside the first inlet hole 73 and the second inlet hole 74 (that is, upstream in the flow direction of blow-by gas) so as to contact the connecting plate 52c. A groove 50c is provided on the surface facing the block side shaft holding portion 50, more specifically, the connecting plate 52c of the outer portion 50b. The adjustment plate 78 is partially accommodated in the groove 50c. A second spring 79 is provided in the groove 50c and biases the adjustment plate 78 toward the connecting plate 52c. For this reason, the adjusting plate 78 always abuts on the connecting plate 52 c by the urging force of the second spring 79.

  As described above, the adjustment plate 78 is partially accommodated in the groove 50 c provided in the block side shaft holding portion 50. For this reason, when the cylinder block 2 moves relative to the crankcase 1, the adjustment plate 78, together with the block-side shaft holding portion 50, includes the first inlet hole 73 and the first holes formed in the connecting plate 52 c of the crankcase 1. It moves relative to the two inlet holes 74. At this time, the adjusting plate 78 slides on the connecting plate 52c. In particular, the adjusting plate 78 slides on the connecting plate 52c in a region where the first inlet hole 73 and the second inlet hole 74 are provided. Therefore, the adjustment plate 78 can change the opening area of the first inlet hole 73 and the second inlet hole 74 when the cylinder block 2 moves relative to the crankcase 1.

<Operation of adjusting plate>
Hereinafter, the operation of the adjustment plate 78 will be described with reference to FIGS. 7 and 8. FIG. 7 shows the state of the oil separator when the distance between the cylinder block 2 and the crankcase 1 is minimum, that is, when the mechanical compression ratio is maximum. On the other hand, FIG. 8 is a diagram schematically showing the state of the oil separator when the distance between the cylinder block 2 and the crankcase 1 is maximum, that is, when the mechanical compression ratio is minimum. 7 and 8 are cross-sectional views taken along the line CC of FIG. 5 similar to FIG. In the cross-sectional views of FIGS. 7 and 8, the outlet hole 75 and the adjustment plate 78 that do not actually appear are indicated by broken lines for reference. Moreover, the arrow in a figure has shown the flow of blow-by gas.

  As described above, the variable compression ratio internal combustion engine of the present embodiment changes the mechanical compression ratio so that the mechanical compression ratio increases as the engine load decreases until the mechanical compression ratio reaches the maximum limit mechanical compression ratio. Therefore, FIG. 7 showing the state where the mechanical compression ratio is maximum shows the state of the oil separator during engine low load operation. On the other hand, FIG. 8 showing a state where the mechanical compression ratio is minimum shows a state of the oil separator during the engine high load operation.

  As shown in FIG. 7, when the distance between the cylinder block 2 and the crankcase 1 is minimum, the adjustment plate 78 is located on the first inlet hole 73 side, closes the first inlet hole 73 and 2 The inlet hole 74 is opened. Therefore, at this time, the opening area of the first inlet hole 73 is zero, and the opening area of the second inlet hole 74 is maximum. In this case, the blow-by gas flows into the oil separator 70 from the second inlet hole 74. As a result, the blow-by gas hardly collides with the oil separation plate 76 during the engine low load operation, so that the pressure loss when the blow-by gas passes through the oil separator 70 is reduced, and the scavenging performance of the blow-by gas is enhanced.

  As the cylinder block 2 moves away from the crankcase 1, the adjustment plate 78 moves from the first inlet hole 73 side to the second inlet hole 74 side. Therefore, the adjustment plate 78 has a smaller opening area of the second inlet hole 74 and an opening area of the first inlet hole when the cylinder block 2 moves relative to the crankcase 1 so that the mechanical compression ratio is lowered. It is configured to be large. As the opening area of the second inlet hole 74 decreases and the opening area of the first inlet hole increases, the amount of blow-by gas flowing from the second inlet hole 74 decreases, and the blow-by gas flowing from the first inlet hole 73 is reduced. The amount of increases.

  As shown in FIG. 8, when the distance between the cylinder block 2 and the crankcase 1 is the maximum, the adjustment plate 78 is located on the second inlet hole 74 side, opens the first inlet hole 73 and 2 The inlet hole 74 is closed. Therefore, at this time, the opening area of the first inlet hole 73 is the maximum, and the opening area of the second inlet hole 74 is zero. In this case, blow-by gas flows into the oil separator 70 from the first inlet hole 73. As a result, during the engine high load operation, the oil in the blow-by gas is effectively separated by the oil separation plate 76 and the like, so that the oil separation performance is improved. Therefore, the variable compression ratio internal combustion engine of the present embodiment can achieve both oil separation performance during engine high load operation and blow-by gas scavenging performance during engine low load operation.

  When both the first inlet hole 73 and the second inlet hole 74 are opened, most of the blow-by gas flows from the second inlet hole 74 with a small pressure loss when passing through the oil separator 70. For this reason, the adjustment plate 78 may be configured to change only the opening area of the second inlet hole 74 when the cylinder block 2 moves relative to the crankcase 1. Specifically, the adjusting plate 78 has a smaller opening area of the second inlet hole 74 and the first inlet hole when the cylinder block 2 moves relative to the crankcase 1 so that the mechanical compression ratio is lowered. The opening area of 73 may be configured to be maintained at a maximum. In this case, at the time of engine low load operation, both the first inlet hole 73 and the second inlet hole 74 are opened. As a result, most of the blow-by gas flows from the second inlet hole 74, and the scavenging performance of the blow-by gas is enhanced during engine low load operation. On the other hand, at the time of engine high load operation, the first inlet hole 73 is opened and the second inlet hole 74 is closed by the adjustment plate 78. As a result, the blow-by gas flows from the first inlet hole 73, and the oil separation performance is enhanced during engine high load operation.

  The preferred embodiments according to the present invention have been described above, but the present invention is not limited to these embodiments, and various modifications and changes can be made within the scope of the claims. For example, the first inlet hole 73, the second inlet hole 74, and the outlet hole 75 may have a cross section other than a circle, for example, a cross section such as a rectangle, an ellipse, or a triangle. Further, the oil separator 70 is configured such that the pressure loss when the blow-by gas passes through the oil separator 70 is smaller when the blow-by gas flows from the second inlet hole 74 than when the blow-by gas flows from the first inlet hole 73. If so, the number and extending direction of the oil separating plates 76, the positions of the first inlet hole 73, the second inlet hole 74, and the outlet hole 75 may be different from those of the present embodiment.

DESCRIPTION OF SYMBOLS 1 Crankcase 2 Cylinder block 3 Cylinder head 6 Spark plug 13 Fuel injection valve 30 Electronic control unit (ECU)
50 Block-side shaft holding portion 52 Case-side shaft holding portion 54, 55 Cam shaft 70 Oil separator 71 Enclosure plate 72 Gasket 73 First inlet hole 74 Second inlet hole 75 Outlet hole 76 Oil separation plate 78 Adjustment plate 80 Cover A Variable compression Ratio mechanism B Variable valve timing mechanism

Claims (1)

In a variable compression ratio internal combustion engine in which the mechanical compression ratio can be changed by moving the cylinder block relative to the crankcase,
Comprising an oil separator capable of separating oil contained in the blow-by gas in the crankcase;
The oil separator has a first inlet hole and a second inlet hole for the blow-by gas to flow into the oil separator, and an outlet hole for the blow-by gas that has flowed into the oil separator to flow out of the oil separator; An oil separation plate disposed in the blow-by gas flow path between the first inlet hole and the outlet hole, and the first inlet hole and the oil inlet when the cylinder block moves relative to the crankcase; And an adjustment plate that moves relative to the second inlet hole, and the pressure loss when the blow-by gas passes through the oil separator is greater than that when the blow-by gas flows from the first inlet hole. It is configured to be small when flowing from the second inlet hole,
The variable compression ratio internal combustion engine changes the mechanical compression ratio so that the mechanical compression ratio increases as the engine load decreases until the mechanical compression ratio reaches the maximum limit mechanical compression ratio.
The adjustment plate has a smaller opening area of the second inlet hole and a larger opening area of the first inlet hole when the cylinder block moves relative to the crankcase so that the mechanical compression ratio decreases. A variable compression ratio internal combustion engine configured to be or be maintained at a maximum.

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