JP2013100754A - Variable compression ratio internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To optimize the rotation range of a camshaft when the camshaft is rotated for holding an oil film.SOLUTION: A variable compression ratio internal combustion engine includes a cylinder block and a crankcase coupled with each other for relative movement, and a camshaft rotatably provided at a coupling part, and rotates the camshaft to allow the cylinder block and the crankcase to move relative to each other to thereby change a compression ratio. The internal combustion engine is provided with a rotating means for regularly and forcibly rotating the camshaft not in operation, allowing an oil film to be retained between the camshaft and a bearing. The rotating means at least either rotates the camshaft within a first predetermined angle range ΔθL2 close to the minimum compression ratio, or rotates the camshaft within a second predetermined angle range ΔθH2 close to the maximum compression ratio.

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, the cylinder block and the crankcase are connected so as to be relatively close to and away from each other in the vertical direction or the cylinder axis direction, and the cam shaft is rotatably provided at the connecting portion, and the cam shaft is rotated. It has been proposed to change the compression ratio by relatively moving the cylinder block and the crankcase.

  Further, a load resulting from the combustion pressure, the weight of the cylinder block, or the like acts on the cam shaft and the bearing that supports the cam shaft. For this reason, it is important to hold the oil film of the lubricating oil between the bearing portion or the interface between the two. In particular, the camshaft is not always rotating at a high speed like a crankshaft or a valve-operated camshaft, so it is difficult to supply lubricating oil to the bearing portion and it is relatively difficult to form an oil film. .

  For this reason, for example, in the technique described in Patent Document 1, when the camshaft is continuously stopped for a predetermined time or longer, the camshaft is reciprocated to form an oil film between the camshaft and the bearing. ing.

JP 2008-45561 A

  However, when such reciprocating rotation of the camshaft is performed, the compression ratio also changes at the same time, which may deteriorate fuel consumption and drivability. Thus, when the reciprocating rotation of the cam shaft is performed, consideration must be given so as not to cause deterioration in fuel consumption and drivability, but the technique described in Patent Document 1 is insufficient.

  For example, in Patent Document 1, the angle at which the cam shaft is reciprocally rotated is described as a rotation angle obtained experimentally in advance so that oil film breakage can be resolved by reciprocating rotation, for example, 180 degrees. Has been. However, such an angle usually results in a large compression ratio change and is not necessarily optimal.

  Therefore, the present invention has been made in view of the above circumstances, and one object of the present invention is to optimize the rotation range of the cam shaft when the cam shaft is rotated for retaining the oil film, thereby improving fuel consumption and drivability. An object of the present invention is to provide a variable compression ratio internal combustion engine capable of suppressing deterioration.

According to one aspect of the invention,
A cylinder block and a crankcase are connected so as to be relatively movable, and a camshaft is rotatably provided at the connecting portion. By rotating the camshaft, the cylinder block and the crankcase are moved relative to each other to increase a compression ratio. A variable compression ratio internal combustion engine to be changed,
In order to maintain an oil film between the cam shaft and a bearing that supports the cam shaft, a rotation unit that periodically and forcibly rotates the cam shaft while the cam shaft is stopped is provided.
The rotating means rotates the cam shaft within a predetermined first angle range near the lowest compression ratio, and rotates the cam shaft within a second angle range near the highest compression ratio. There is provided a variable compression ratio internal combustion engine characterized by performing at least one of the above.

Preferably, the first angle range is located on the high compression ratio side with respect to the first angle from the third angle located on the anti-high compression ratio side with respect to the first angle corresponding to the lowest compression ratio. An angle range up to an angle,
The second angle range is from a fifth angle located on the anti-low compression ratio side relative to the second angle corresponding to the highest compression ratio to a sixth angle located on the low compression ratio side relative to the second angle. Angle range.

Preferably, the first angle range is an angle range from a first angle corresponding to the lowest compression ratio to a seventh angle located on the high compression ratio side with respect to the first angle,
The second angle range is an angle range from a second angle corresponding to the highest compression ratio to an eighth angle located on the low compression ratio side with respect to the second angle.

  Preferably, the rotating means rotates the cam shaft within the first angle range when the cam shaft has been stopped for a predetermined first time within the first angle range; and The camshaft is both rotated within the second angle range when the camshaft has been stopped within the second angle range for a predetermined second time, and the second The time is longer than the first time.

  Preferably, the cam shaft rotates 180 ° from a first angle corresponding to the lowest compression ratio to a second angle corresponding to the highest compression ratio.

  Preferably, during basic control other than cam shaft rotation control by the rotation means, the cam shaft is controlled such that the compression ratio decreases as the load of the internal combustion engine increases.

  According to the present invention, it is possible to optimize the cam shaft rotation range when performing cam shaft rotation for retaining an oil film, and to exhibit an excellent effect of being able to suppress deterioration of fuel consumption and drivability. Is done.

1 is a diagram showing a schematic configuration of an internal combustion engine according to an embodiment of the present invention. It is a disassembled perspective view which shows the structure of a compression ratio variable mechanism. It is sectional drawing which shows the action | operation of a compression ratio variable mechanism. It is a map which shows the relationship between the load and compression ratio in basic control. It is a graph which shows the relationship between the rotation angle of the cam shaft which concerns on a 1st example, and a compression ratio. It is a graph which shows the rotation angle of the cam shaft which concerns on a 1st example. It is a graph which shows the relationship between the rotation angle of the cam shaft which concerns on a 2nd example, and a compression ratio. It is a graph which shows the rotation angle of the cam shaft which concerns on a 2nd example. It is a flowchart of rotation control.

  Hereinafter, preferred embodiments of the present invention will be described with reference to the drawings.

  FIG. 1 shows a schematic configuration of a variable compression ratio internal combustion engine according to the present 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 is assembled in the cylinder axial direction. The crankcase 4 and the cylinder block 3 are connected by a compression ratio variable mechanism 21 described in detail later so that the crankcase 4 and the cylinder block 3 can 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 multi-cylinder (4-cylinder) gasoline engine (spark ignition type internal combustion engine) mounted on a vehicle, but the type, use, etc. of the internal combustion engine are not limited. For example, a diesel engine (Compression ignition type internal combustion engine) may be sufficient.

  In the present embodiment, the crankcase 4 is fixed to the vehicle via the 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 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 3, 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. The valve chamber 28 includes an intake valve Vi and an exhaust valve Ve that open and close the intake port Pi and the exhaust port Pe, respectively, and valve springs Si and Se that urge the intake valve Vi and the exhaust valve Ve in the valve closing direction, respectively. An intake camshaft Ci and an exhaust camshaft Ce are provided for driving 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). The cylinder head 25 is provided with an injector 29 for injecting fuel into the intake port Pi, and an ignition plug 30 for igniting the air-fuel mixture.

  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 common 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.

  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 and slidable in the cylinder axial direction. A water jacket W is defined in the cylinder block 3 so as to surround the cylinder 2.

  An annular seal member (or seal boot) 40 is provided between the cylinder block 3 and the crankcase 4 so as to cover the gap between the cylinder block 3 and the crankcase 4 over the entire circumference of the internal combustion engine 1. . The seal member 40 extends generally in the height direction of the internal combustion engine 1 as shown in the figure, and seals the gap in the fitting portion between the cylinder block 3 and the crankcase 4 from the outside.

  The seal member 40 is formed of a deformable elastic body having a cross section formed in a bellows shape as illustrated. One end edge of the seal member 40 is fixed to the crankcase 4, and the other end edge of the seal member 40 is sandwiched between the cylinder block 3 and the cylinder head 25. Fixed.

  When the cylinder block 3 descends and approaches the crankcase 4, the seal member 40 is deformed in the contraction direction. When the cylinder block 3 rises and moves away from the crankcase 4, the seal member 40 is deformed in the extending direction. Thus, even if the relative position between the cylinder block 3 and the crankcase 4 changes, the airtightness of the fitting portion can be maintained by the expansion / contraction operation of the seal member 40.

  The internal combustion engine 1 is provided with an electronic control unit (ECU) 100 as a control means for electrically controlling various devices such as an injector 29, a spark plug 30, a throttle valve 36, and a motor of the compression ratio variable mechanism 21. ing. 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, and an air flow meter 53. 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 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.

  Next, the configuration of the compression ratio variable mechanism 21 will be described with reference to FIG. A plurality of raised portions 5A forming a part of the bearing are formed at both lower portions of the cylinder block 3, and a bearing hole 5 is formed in each raised portion 5A. The bearing holes 5 are circular and are formed so as to be perpendicular to the axial direction of the cylinders 2 and parallel to the arrangement direction of the plurality (four) of cylinders 2. The bearing 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 holes 5 on both sides of the cylinder block 3 are parallel to each other.

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

  Similar to the bearing hole 5, the plurality of cam housing holes 8 are perpendicular to the axial direction of the cylinder 2 and parallel to the arrangement direction of the plurality of cylinders 2 when the cylinder block 3 is attached to the crankcase 4. Are formed respectively. 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. The distance between the bearing holes 5 on both sides and the distance between the cam storage holes 8 on both sides are the same.

  Cam shafts 9 are rotatably inserted into the bearing holes 5 and the cam accommodation holes 8 in two rows on both sides that are alternately arranged. As a result, the cam shaft 9 is rotatably provided at the connecting portion between the cylinder block 3 and the crankcase 4, and by rotating the cam shaft 9, the cylinder block 3 and the crankcase 4 are relatively moved to change the compression ratio. The The raised portion 5A, the standing wall portion 8A and the cap 7 assembled to each other form a bearing that rotatably supports the cam shaft 9. The inner surfaces of the bearing hole 5 and the cam housing hole 8 form bearing surfaces.

  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 fixed cam 9c having a regular circular cam profile. And a movable cam 9b rotatably attached to the shaft portion 9a. The fixed cam 9c and the movable cam 9b are alternately arranged. The pair of cam shafts 9 on both sides 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.

  The center of the fixed cam 9c and the center of the attachment portion 9d coincide with each other. On the other hand, the movable cam 9b is eccentric with respect to the shaft portion 9a, and the amount of eccentricity is the same as that of the fixed cam 9c. In each camshaft 9, the eccentric directions of the plurality of fixed cams 9c are the same. The outer shape of the movable cam 9b is a perfect circle having the same diameter as that of the fixed cam 9c. By rotating the movable cam 9b with respect to the shaft portion 9a, the outer peripheral surface of the fixed cam 9c and the outer peripheral surface of the movable cam 9b 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 with reference to FIG. 3A to 3C are cross-sectional views showing the relationship between the cylinder block 3, the crankcase 4, and the camshaft 9 disposed therebetween. The center of the shaft portion 9a is indicated by a, the center of the movable cam 9b is indicated by b, and the center of the fixed cam 9c is indicated by c. FIG. 3A shows a state in which the outer peripheral surfaces of all the fixed cams 9c and the movable cams 9b 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 on the lower side in the bearing hole 5 and the cam housing hole 8.

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

  Although not shown, when the motor 12 is driven from the state shown in FIG. 3C and the shaft portion 9a is rotated in the direction opposite to the arrow direction, the state shown in FIG. 3B or FIG. The cylinder block 3 can be slid relative to the crankcase 4 downward or at the bottom dead center and moved in the proximity direction.

  As described above, the compression ratio can be changed by driving the motor 12 by the ECU 100 to rotate the cam shaft 9 or the shaft portion 9 a and moving the cylinder block 3 relative to the crankcase 4. FIG. 3A shows a state of the highest compression ratio εH in which the cylinder block 3 is closest to the crankcase 4, and the angular position (second angle) θH of the shaft portion 9a at this time is 180 °. On the other hand, FIG. 3C shows a state of the lowest compression ratio εL where the cylinder block 3 is farthest from the crankcase 4, and the angular position (first angle) θL of the shaft portion 9a at this time is 0 °. is there. That is, the cam shaft 9 rotates 180 ° from an angle θL (= 0 °) corresponding to the lowest compression ratio εL to an angle θH (= 180 °) corresponding to the highest compression ratio εH.

  In normal basic control except during cam shaft 9 rotation control, which will be described later, the ECU 100 follows a predetermined map as shown in FIG. 4, for example, an internal combustion engine load (engine load) detected by the accelerator position sensor 52. ) Based on KL, the rotation angle θ of the motor 12 and thus the cam shaft 9 is controlled to control the compression ratio ε.

  At this time, as shown in the figure, the ECU 100 controls the camshaft 9 so that the compression ratio ε decreases as the engine load KL increases. More specifically, the ECU 100 maintains the compression ratio ε at the maximum compression ratio εH when the engine load KL is between the minimum load KLmin and a predetermined intermediate load KL1, and the engine load KL is from the intermediate load KL1 to the maximum load KLmax. When the engine load KL increases, the camshaft 9 is controlled so that the compression ratio ε gradually decreases to the minimum compression ratio εL as the engine load KL increases.

  Such basic control can achieve both improvement in combustion efficiency in the low load region and knocking suppression in the high load region.

  By the way, lubricating oil is supplied between the cam shaft 9 and the bearing (that is, between the fixed cam 9c and the bearing hole 5 and between the movable cam 9b and the cam storage hole 8), and an oil film is formed. 9 smooth rotation operations are ensured.

  However, a load due to the weight of the cylinder block 3 or the combustion pressure generated in the cylinder 2 is always applied to the gap between the camshaft 9 and the bearing. The camshaft 9 does not always rotate at a high speed like the crankshaft 20 or the valve drive camshafts Ci and Ce, but repeats a stopped state and a rotation at a low speed. For this reason, it is difficult for the lubricating oil supplied to the gap between the camshaft 9 and the bearing to be evenly supplied to the entire gap, and it is easy to prolong the period during which the load concentrates in a part of the gap. When a sufficient amount of lubricating oil is not supplied to a part of the gap where the load is concentrated, the oil film thickness of the part becomes thin, and in some cases, the oil film is cut. If the oil film thickness in the gap between the camshaft 9 and the bearing becomes thin or the oil film breaks, it causes fretting wear, and the rotation resistance of the camshaft 9 increases and rotation failure occurs. To do. When the rotation failure of the cam shaft 9 occurs, the power consumption of the motor 12 increases excessively. Furthermore, if the state of running out of the oil film continues, a so-called locking phenomenon that causes the cam shaft 9 to become unrotatable may occur, and the compression ratio may not be changed.

  Therefore, in the present embodiment, the camshaft 9 (specifically, the shaft portion 9a) is periodically fixed while the camshaft 9 is stopped during basic control in order to maintain or restore the oil film between the camshaft 9 and the bearing. Rotation control is performed to rotate automatically and forcibly. By this rotation control, the oil film thickness between the cam shaft 9 and the bearing can be equalized, and the above problem can be solved while preventing the oil film from being cut.

  In the rotation control, the ECU 100 reciprocates or swings the cam shaft 9 a plurality of times within a predetermined angle range. Note that the number of reciprocating rotations may be one, but a plurality of times is preferable because it is advantageous for oil film retention and oil film thickness equalization. Alternatively, the rotation may be one-way instead of reciprocating.

  By the way, when the reciprocating rotation of the cam shaft 9 is performed, the compression ratio also changes at the same time, which may cause deterioration in fuel consumption and drivability. Therefore, when the reciprocating rotation of the camshaft 9 is performed, it is necessary to consider so as not to deteriorate fuel consumption and drivability.

  For this reason, in this embodiment, the cam shaft 9 is reciprocally rotated using only an angle range in which the compression ratio does not change as much as possible when the cam shaft 9 reciprocates. This will be described below.

  FIG. 5 shows the relationship between the rotation angle θ of the camshaft 9 and the compression ratio ε of the internal combustion engine 1. FIG. 6 shows only the rotation angle θ of the cam shaft 9. As shown in the figure and as described above, when the compression ratio ε is the minimum compression ratio εL, the rotation angle θ of the cam shaft 9 is θL = 0 °, and when the compression ratio ε is the maximum compression ratio εH, The rotation angle θ of 9 is θH = 180 °.

  As shown in FIG. 5, as the rotation angle θ increases from θL to θH, the compression ratio ε increases from the lowest compression ratio εL to the highest compression ratio εH. In particular, as the rotation angle θ increases, the compression ratio ε increases like a sine curve. The rotation angle θL at the minimum compression ratio εL corresponds to the angle at the minimum peak of the sine curve, and the rotation angle θH at the maximum compression ratio εH corresponds to the angle at the maximum peak of the sine curve. The rate of change or sensitivity (Δε / Δθ, slope of the diagram in FIG. 5) of the compression ratio ε with respect to the change in the rotation angle θ is highest at both ends of the sine curve, that is, near the minimum compression ratio εL and the maximum compression ratio εH. In particular, it is smaller than the vicinity of the intermediate portion (for example, θ = 90 °).

  Therefore, paying attention to this characteristic, in the present embodiment, in the rotation control, the camshaft 9 is reciprocally rotated within a predetermined angle range near the minimum compression ratio εL, and a predetermined angle near the maximum compression ratio εH. At least one of rotating the camshaft 9 within the range is performed.

  5 and 6 show a first example of such an angle range. In this first example, the angle range near the minimum compression ratio εL is ΔθL1, which is an angle range from the angle θL corresponding to the minimum compression ratio εL to the angle θL1 on the high compression ratio side by the angle range ΔθL1. It is.

  On the other hand, the angle range in the vicinity of the maximum compression ratio εH is ΔθH1, which is an angle range from the angle θH corresponding to the maximum compression ratio εH to the angle θH1 on the low compression ratio side by the angle range ΔθH1.

  For example, ΔθL1 = ΔθH1 = 10 °, θL1 = 10 °, and θH1 = 170 ° can be set.

  Since the camshaft 9 is reciprocally rotated only within the angle ranges ΔθL1 and ΔθH1, changes in the compression ratio due to reciprocal rotation can be suppressed to a minimum. And the rotation range of the cam shaft 9 can be optimized, and deterioration of fuel consumption and drivability can be significantly suppressed.

  7 and 8 show a more preferred second example of such an angle range. In this second example, the angle range near the minimum compression ratio εL is ΔθL2, which is from the angle θL2 located on the anti-high compression ratio side (− side) with respect to the angle θL corresponding to the minimum compression ratio εL. The angle range up to the angle θL2 + located on the high compression ratio side (+ side) with respect to the angle θL.

  On the other hand, the angle range in the vicinity of the maximum compression ratio εH is ΔθH2, which corresponds to the angle θH from the angle θH2 + located on the anti-low compression ratio side (+ side) with respect to the angle θH corresponding to the maximum compression ratio εH. And an angle range up to an angle θH2− located on the low compression ratio side (− side).

  For example, ΔθL2 = ΔθH2 = 10 °, θL2-= − 5 °, θL2 + = 5 °, θH2- = 175 °, and θH2 + = 185 °.

  As described above, in the second example, a part of the angle ranges ΔθL2 and ΔθH2 for performing the reciprocating rotation is set beyond (or protrudes) the angle range (θL to θH) used during normal control. Yes. In this way, an angle range having the same size as that of the first example can be realized in an angle range where the compression ratio change rate is smaller than that of the first example, and the same oil film retention performance can be achieved with a smaller change in compression ratio. Thereby, it is possible to further suppress deterioration of fuel consumption and drivability.

  In this example, θL2− and θL2 + are set symmetrically with respect to θL for the angle range ΔθL2, but they may be set asymmetrically. That is, here, the angle range ΔθL2 is set around θL, but it is not necessary to center around θL. However, it is preferable to set the angle range ΔθL2 so as to include θL.

  Similarly, for the angle range ΔθH2, θH2− and θH2 + are set symmetrically with respect to θH, but they may be set asymmetrically. That is, here, the angle range ΔθH2 is set with θH as the center, but it is not necessary to have θH as the center. However, it is preferable to set the angle range ΔθH2 so as to include θH.

  The above-described reciprocating angular ranges ΔθL1, ΔθH1, ΔθL2, and ΔθH2 are, for example, 10 ° and are significantly smaller than the angular range described in Patent Document 1 (for example, 180 °). Therefore, in this respect as well, it is possible to minimize the change in the compression ratio and prevent deterioration in fuel consumption and drivability. Further, Patent Document 1 does not disclose or suggest a technical idea that the camshaft 9 is rotated only within a small angle range near the minimum compression ratio εL and / or near the maximum compression ratio εH. Therefore, this embodiment can be distinguished significantly from the technique described in Patent Document 1.

  The reciprocating rotation of the cam shaft 9 can be performed only in one of the angle range near the minimum compression ratio εL and the angle range near the maximum compression ratio εH. This is surely prevented. Hereinafter, a suitable example of the rotation control of the cam shaft 9 will be described.

  FIG. 9 shows a flowchart of the rotation control of the camshaft 9 that is executed by the ECU 100. Here, as the rotation range of the camshaft 9, the angle ranges ΔθL2 and ΔθH2 described in the second example are used.

  In step S101, it is determined whether the camshaft 9 is stopped according to the basic control. If it is stopped, the process proceeds to step S102. If it is not stopped (is operating), the routine is terminated.

In step S102, it is determined whether or not the rotation angle θ of the cam shaft 9 being stopped is smaller than θL2 +.
In the case of yes, it is determined in step S103 whether or not the elapsed time T from the stop start time of the camshaft 9 is longer than the predetermined stop time T1. The elapsed time T is measured by a timer provided in the ECU 100, and the stop time T1 is stored in the ECU 100 in advance. If no, the routine is terminated.

  In the case of yes, it progresses to step S104 and the reciprocating rotation of the cam shaft 9 within the angle range ΔθL2 is executed. That is, according to this rotation control, when the camshaft 9 is stopped for a longer time than the stop time T1 within the range of θL to θL2 + by the basic control, the camshaft 9 is forcibly set between θL2 and θL2 +. By reciprocating a plurality of times, the oil film of the bearing portion is returned to an appropriate state. After the reciprocating rotation, the camshaft 9 is returned to the angular position corresponding to the engine load according to the basic control.

  On the other hand, if step S102 is NO, it is determined in step S105 whether or not the rotation angle θ of the cam shaft 9 being stopped is larger than θH2−. If no, the routine is terminated.

  In the case of yes, it is determined in step S106 whether or not the elapsed time T from the stop start time of the camshaft 9 is longer than the predetermined stop time T2. The stop time T2 is also stored in the ECU 100 in advance. If no, the routine is terminated.

  In the case of yes, it progresses to step S107 and the reciprocating rotation of the cam shaft 9 within the angle range ΔθH2 is executed. That is, according to this rotation control, when the camshaft 9 has been stopped for a longer time than the stop time T2 within the range of θH2- to θH by the basic control, the camshaft 9 is forcibly between θH2- and θH2 +. Is reciprocated a plurality of times, and the oil film of the bearing portion is returned to an appropriate state. After the reciprocating rotation, the camshaft 9 is returned to the angular position corresponding to the engine load according to the basic control.

  When the cam shaft 9 is stopped within the range of θL2 + to θH2- by the basic control, the reciprocating rotation of the cam shaft 9 is not executed. This is because when the reciprocating rotation is performed with respect to the cam shaft 9 within this range, the compression ratio changes relatively greatly, and the fuel consumption and drivability may be deteriorated.

  As is apparent from FIG. 4, when the camshaft 9 is in the range of θH2 to θH by basic control, the engine load is lower than the intermediate load KL1, particularly near the minimum load KLmin. That is, the compression ratio ε is the maximum compression ratio εH. In this case, the engine load is in the normal range and the frequency of use is high, but the combustion pressure is low, and the load on the bearing portion, that is, the surface pressure applied to the camshaft 9 and the bearing is low. Therefore, from the viewpoint of retaining the oil film, the interval for performing the reciprocating rotation of the camshaft 9 can be lengthened.

  Conversely, when the camshaft 9 is in the range of θL to θL2 + by basic control, the engine load is higher than the intermediate load KL1, particularly near the maximum load KLmax, and the compression ratio ε is the lowest compression ratio. This is a case where it is in the vicinity of εL. In this case, although the frequency of use is low, the combustion pressure is high, and the load on the bearing portion, that is, the surface pressure applied to the camshaft 9 and the bearing is high. Therefore, from the viewpoint of holding the oil film, it is necessary to shorten the interval for performing the reciprocating rotation of the cam shaft 9.

  In view of such circumstances, in the present embodiment, the stop time T2 that defines the former interval is set longer than the stop time T1 that defines the latter interval. As a result, when the camshaft 9 is stopped on the low load side or in the normal range, the interval for performing reciprocal rotation is lengthened, and unnecessary reciprocal rotation is prevented, and fuel consumption and drivability are further deteriorated. Can be suppressed. On the other hand, when the camshaft 9 is stopped on the high load side or near the maximum load, the interval for performing the reciprocating rotation can be shortened to reliably prevent the oil film from running out.

  In the rotation control, the angle ranges ΔθL1 and ΔθH1 described in the first example can be used. In this case, in step S102, it is determined whether or not the rotation angle θ of the cam shaft 9 being stopped is smaller than θL1. In step S104, the reciprocating rotation of the cam shaft 9 is executed within the angle range ΔθL1. On the other hand, in step S105, it is determined whether or not the rotation angle θ of the cam shaft 9 being stopped is larger than θH1. In step S107, the reciprocating rotation of the cam shaft 9 is executed within the angle range ΔθH1.

  The preferred embodiment of the present invention has been described in detail above, but various other embodiments of the present invention are conceivable. For example, the above numerical values are examples and can be changed.

  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 Variable compression ratio internal combustion engine 2 Cylinder 3 Cylinder block 4 Crankcase 9 Cam shaft 20 Crankshaft 21 Compression ratio variable mechanism 100 Electronic control unit (ECU)

Claims (6)

A cylinder block and a crankcase are connected so as to be relatively movable, and a camshaft is rotatably provided at the connecting portion. By rotating the camshaft, the cylinder block and the crankcase are moved relative to each other to increase a compression ratio. A variable compression ratio internal combustion engine to be changed,
In order to maintain an oil film between the cam shaft and a bearing that supports the cam shaft, a rotation unit that periodically and forcibly rotates the cam shaft while the cam shaft is stopped is provided.
The rotating means rotates the cam shaft within a predetermined first angle range near the lowest compression ratio, and rotates the cam shaft within a second angle range near the highest compression ratio. A variable compression ratio internal combustion engine characterized by performing at least one of the above. The first angle range is from a third angle located on the anti-high compression ratio side with respect to the first angle corresponding to the lowest compression ratio to a fourth angle located on the high compression ratio side with respect to the first angle. Angular range,
The second angle range is from a fifth angle located on the anti-low compression ratio side relative to the second angle corresponding to the highest compression ratio to a sixth angle located on the low compression ratio side relative to the second angle. The variable compression ratio internal combustion engine according to claim 1, which is in an angular range. The first angle range is an angle range from a first angle corresponding to the lowest compression ratio to a seventh angle located on the high compression ratio side with respect to the first angle,
The said 2nd angle range is an angle range from the 2nd angle corresponding to the highest compression ratio to the 8th angle located in the low compression ratio side with respect to a 2nd angle. Variable compression ratio internal combustion engine. The rotating means rotates the cam shaft within the first angle range when the cam shaft is stopped for a predetermined first time within the first angle range; and the cam When the shaft is stopped within the second angle range for a predetermined second time, the camshaft is both rotated within the second angle range, and the second time is The variable compression ratio internal combustion engine according to any one of claims 1 to 3, wherein the internal combustion engine is longer than a first time. 5. The camshaft rotates 180 ° between a first angle corresponding to the lowest compression ratio and a second angle corresponding to the highest compression ratio. 6. Variable compression ratio internal combustion engine. In basic control excluding the cam shaft rotation control by the rotating means, the cam shaft is controlled so that the compression ratio is lowered as the load of the internal combustion engine is higher. The variable compression ratio internal combustion engine according to any one of claims 1 to 5.

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