JP2007309123A - Variable compression ratio internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology for restraining generation of noise caused by deposition of carbon to a top surface of a piston, in a variable compression ratio internal combustion engine. <P>SOLUTION: When generating a carbon stamp where the carbon deposited on the top surface of the piston collides with a combustion chamber ceiling surface (S102), the compression ratio is reduced (S103). Afterwards, control for removing the carbon deposited on the top surface of the piston is performed (S104). When knocking is caused (S105), the knocking is reduced by ignition timing delay processing (S106). <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a variable compression ratio internal combustion engine having a function of changing the compression ratio of an internal combustion engine.

  In recent years, a technique for changing the compression ratio of an internal combustion engine for the purpose of improving the fuel consumption performance and output performance of the internal combustion engine has been proposed. As this type of technology, the cylinder block and the crankcase are connected so as to be relatively movable, and a camshaft is provided at the connecting portion, and the camshaft is rotated to connect the cylinder block and the crankcase in the axial direction of the cylinder. A technique has been proposed in which the volume of the combustion chamber is changed by relative movement to the internal combustion engine, thereby changing the compression ratio of the internal combustion engine (see, for example, Patent Document 1).

  Further, the connecting rod is divided into two, a connecting member connected to the crankshaft is connected to a swinging member capable of swinging around a predetermined swinging center, and the swinging center is moved by rotating the camshaft. Thus, a technique has also been proposed in which the volume of the combustion chamber and the stroke of the piston are changed, thereby changing the compression ratio of the internal combustion engine (see, for example, Patent Document 2).

In the above technique, the compression ratio changes as the volume of the combustion chamber changes in the cylinder axis direction. Therefore, when the compression ratio of the internal combustion engine is set high, the height of the combustion chamber decreases and the compression is reduced. The distance between the top surface of the piston at the top dead center and the ceiling surface of the combustion chamber is shortened. When carbon is accumulated on the top surface of the piston, the carbon accumulated on the top surface of the piston collides with the ceiling surface of the combustion chamber or a member disposed on the ceiling surface of the combustion chamber near the compression top dead center. (This is called "carbon stamp"). This sometimes causes noise in the internal combustion engine.
JP 2003-206871 A JP 2001-317383 A JP 2005-180303 A Japanese Utility Model Publication No. 3-95025 Japanese Patent Laid-Open No. 11-50857

  The present invention has been made in view of the above-described prior art, and an object of the present invention is to suppress the generation of noise caused by the accumulation of carbon on the top surface of a piston in a variable compression ratio internal combustion engine. Is to provide.

  The present invention for achieving the above object, when carbon deposited on the top surface of the piston collides with the top surface of the combustion chamber or a member disposed on the ceiling surface of the combustion chamber at the compression top dead center, The greatest feature is to reduce the compression ratio.

More specifically, a variable compression ratio mechanism that changes the compression ratio of the internal combustion engine by changing the volume of the combustion chamber of the internal combustion engine and / or the stroke of the piston;
Carbon that detects that carbon deposited on the top surface of the piston collides with a ceiling surface of the combustion chamber or a member disposed on the ceiling surface of the combustion chamber near the compression top dead center of the internal combustion engine Stamp detection means;
With
The carbon stamp detection means causes carbon deposited on the top surface of the piston to collide with a ceiling surface of the combustion chamber or a member disposed on the ceiling surface of the combustion chamber near the compression top dead center of the internal combustion engine. If it is detected, the compression ratio of the internal combustion engine is lowered by the variable compression ratio mechanism.

  Then, when the carbon deposited on the top surface of the piston collides with the ceiling surface of the combustion chamber or a member disposed on the ceiling surface, the top surface of the piston at the compression top dead center and the ceiling of the combustion chamber. The distance to the surface can be increased, and collision between the carbon and the ceiling surface or a member disposed on the ceiling surface can be suppressed.

  Here, the carbon stamp detecting means detects vibration or impact generated in the combustion chamber at the compression top dead center, and the carbon and the member provided on the ceiling surface or the ceiling surface from the frequency and generation timing thereof It is good also as a means to detect a collision with. Here, examples of the members disposed on the ceiling surface of the combustion chamber include ignition plugs, in-cylinder fuel injection valves, various sensors, and the like.

Further, in the present invention, further comprising a carbon removing means for removing carbon deposited on the top surface of the piston,
By the carbon stamp detection means, carbon deposited on the top surface of the piston collides with a member disposed on the ceiling surface of the combustion chamber or the ceiling surface of the combustion chamber near the compression top dead center of the internal combustion engine. When it is detected, the compression ratio of the internal combustion engine is lowered by the variable compression ratio mechanism, and the carbon accumulated on the top surface of the piston may be removed by the carbon removing means. .

  As described above, if it is detected that the carbon deposited on the top surface of the piston collides with the ceiling surface of the combustion chamber or a member disposed on the ceiling surface of the combustion chamber, the compression ratio is lowered. By doing so, the occurrence of noise for the time being can be avoided. In the present invention, in addition to this, control is performed to remove carbon deposited on the top surface of the piston.

  By doing so, carbon deposited on the top surface of the piston can be removed, so that it is possible to more reliably suppress the carbon from colliding with the ceiling surface of the combustion chamber or the member disposed on the ceiling surface of the combustion chamber. As a result, noise caused by carbon deposited on the top surface of the piston can be more reliably suppressed. Further, since the carbon deposited on the top surface of the piston can be removed, the restriction of the compression ratio can be released after the removal, and the original high compression ratio can be restored.

  Here, the carbon removing means, for example, caused slight knocking by performing control to advance the ignition timing in the internal combustion engine or control to make the air-fuel ratio of the air-fuel mixture lean, and accumulated on the top surface of the piston. Carbon may be removed. Further, the carbon accumulated on the top surface of the piston may be removed by performing both the control for advancing the ignition timing in the internal combustion engine and the control for making the air-fuel ratio of the air-fuel mixture lean. When control for advancing the ignition timing in the internal combustion engine is performed, combustion can be caused in a state where the in-cylinder pressure in the combustion chamber is increased, and slight knocking can be generated. On the other hand, if the air-fuel ratio of the air-fuel mixture of the internal combustion engine is made lean, the cooling effect due to the heat of vaporization of the fuel is suppressed, so the temperature in the cylinder rises. Thereby, slight knocking can be generated. Alternatively, when the intake air amount with respect to the same fuel injection amount is increased to make the air-fuel ratio lean, the in-cylinder pressure can be increased and mild knocking can be generated.

  The means for solving the above-described problems of the present invention can be used in combination as much as possible.

  According to the present invention, in the variable compression ratio internal combustion engine, it is possible to suppress the generation of noise due to the accumulation of carbon on the top surface of the piston.

  The best mode for carrying out the present invention will be exemplarily described in detail below with reference to the drawings.

  The internal combustion engine 1 described below is a variable compression ratio internal combustion engine, and a compression ratio is obtained by moving a cylinder block 3 having a cylinder 2 in the direction of the central axis of the cylinder 2 with respect to a crankcase 4 to which a piston is connected. Is to change.

First, the configuration of the variable compression ratio mechanism according to the present embodiment will be described with reference to FIG. As shown in FIG. 1, a plurality of raised portions are formed at lower portions on both sides of the cylinder block 3, and a cam storage hole 5 is formed in each raised portion. The cam storage hole 5 has a circular shape and is formed so as to be perpendicular to the axial direction of the cylinder 2 and parallel to the arrangement direction of the plurality of cylinders 2. All the cam storage holes 5 are located on the same axis. The pair of axes of the cam storage holes 5 on both sides of the cylinder block 3 are parallel.

  The crankcase 4 is formed with a standing wall portion so as to be positioned between the plurality of raised portions in which the above-described cam housing holes 5 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. Moreover, when the cap 7 is attached to each standing wall portion, a circular bearing housing hole 8 is formed. The shape of the bearing storage hole 8 is the same as that of the cam storage hole 5 described above.

  Similar to the cam housing hole 5, the plurality of bearing housing holes 8 are perpendicular to the axial direction of the cylinder 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 bearing housing holes 8 are also formed on both sides of the cylinder block 3, and the plurality of bearing housing holes 8 on one side are all located on the same axis. The pair of axes of the bearing housing holes 8 on both sides of the cylinder block 3 are parallel. Further, the distance between the cam housing holes 5 on both sides and the distance between the bearing housing holes 8 on both sides are the same.

Cam shafts 9 are respectively inserted into the two rows of cam storage holes 5 and bearing storage holes 8 arranged alternately. As shown in FIG. 1, the cam shaft 9 includes a shaft portion 9a and a cam portion 9b having a right circular cam profile fixed to the shaft portion 9a in a state of being eccentric with respect to the central axis of the shaft portion 9a. The movable portion 9c has the same outer shape as the cam portion 9b and is rotatably attached to the shaft portion 9a. The cam shaft 9b and the movable bearing portion 9c are alternately arranged. The pair of cam shafts 9 have a mirror image relationship. Further, a mounting portion 9d of a gear 10 described later is formed at the end portion of the cam shaft 9. The center axis 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.

  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. Since the outer shape of the movable bearing portion 9c is a perfect circle having the same diameter as the cam portion 9b, the outer surface of the plurality of cam portions 9b and the outer surfaces of the plurality of movable bearing portions 9c are rotated by rotating the movable bearing portion 9c. Can be matched with the side.

A gear 10 is attached to one end of each camshaft 9. Worm gears 11a and 11b are engaged 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, the pair of cam shafts 9 rotate in opposite directions via the gear 10. The motor 12 is fixed to the cylinder block 3 and moves integrally with the cylinder block 3.

  Next, a method for controlling the compression ratio in the internal combustion engine 1 having the above-described configuration will be described in detail. 2 (a) to 2 (c) are cross-sectional views showing the relationship between the cylinder block 3, the crankcase 4, and the cam shaft 9 constructed between them. 2A to 2C, the central 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 peripheries 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 cam housing hole 5 and the bearing housing hole 8 here.

  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. 2B is obtained. 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 can be slid to the top dead center side with respect to the crankcase 4. 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 bearing housing hole 8 and the cam housing hole 5, respectively, and allow the position of the shaft portion 9a to move inside the bearing housing hole 8 and the cam housing hole 5, respectively. is doing.

  By using the mechanism as described above, the cylinder block 3 can be moved relative to the crankcase 4 in the axial direction of the cylinder 2, and the compression ratio can be variably controlled. The configuration described above corresponds to the variable compression ratio mechanism in the present embodiment.

  Next, a state in which the compression ratio in the internal combustion engine 1 is set near the maximum compression ratio in the variable range will be considered with reference to FIG. FIG. 3 shows details of the vicinity of the combustion chamber of the internal combustion engine 1 in this state. Here, the state where the compression ratio is in the vicinity of the maximum compression ratio in the variable range is a state where the cylinder block 3 is close to the crankcase 4 and thus the height of the combustion chamber is close to the minimum. On the other hand, in the piston 15 of the internal combustion engine 1, carbon generated by combustion may adhere to the top surface and accumulate. Then, when the compression ratio is set high, the carbon deposited on the piston 15 may collide with the ceiling surface 20a of the combustion chamber 20. As a result, noise caused by this may occur in the internal combustion engine 1.

  Therefore, in this embodiment, the cylinder block 3 is provided with the acceleration sensor 25, and by detecting vibration or impact, it is determined whether or not the carbon deposited on the piston 15 collides with the ceiling surface 20a of the combustion chamber 20. I decided to judge. When it is determined that the carbon deposited on the piston 15 collides with the ceiling surface 20a of the combustion chamber 20, the compression ratio is reduced. In this embodiment, the output signal of the acceleration sensor 25 is input to the ECU 30, and the motor 12 is operated by the signal from the ECU 30 to change the compression ratio.

  FIG. 4 shows a carbon stamp prevention routine in this embodiment. This routine is a program stored in the ROM of the ECU 30 and is executed by the ECU 30 at predetermined intervals while the internal combustion engine 1 is in operation.

  When this routine is executed, first, vibration or impact is acquired by the acceleration sensor 25 in S101. Specifically, the output signal of the acceleration sensor 25 is input to the ECU 30. When the processing of S101 ends, the process proceeds to S102.

  In S102, it is determined from the vibration or impact data acquired in S101 whether a carbon stamp has occurred. Here, the determination method as to whether or not the carbon stamp is generated is determined based on whether or not the amplitude or frequency of the vibration or impact acquired in S101 is unique when the carbon stamp is generated. Details of this method will be described later. If it is determined in S102 that a carbon stamp has been generated, the process proceeds to S103. On the other hand, if it is determined that no carbon stamp has occurred, the process proceeds to S105.

  In S103, the map storing the relationship between the operating state of the internal combustion engine 1 and the compression ratio used for the compression ratio change control is changed from the normal time map to the carbon stamp time map with the upper limit compression ratio limited. The If it does so, since the maximum value of the compression ratio which can be taken in the same driving | running state becomes low, a compression ratio falls as a result. When the process of S103 ends, the process proceeds to S104.

  In S104, a process of removing carbon deposited on the top surface of the piston 15 is executed. Specifically, the ignition timing in the combustion chamber 20 is advanced. As a result, the ignition timing of the air-fuel mixture coincides with the timing when the piston 15 rises, and the pressure rise of the air-fuel mixture before combustion in the combustion chamber can be made steep. As a result, slight knocking can be generated. The carbon deposited on the top surface of the piston 15 is removed by this slight knocking. When the process of S104 is completed, this routine is temporarily ended.

  In S104, the control may be performed so that the air-fuel ratio of the air-fuel mixture in the combustion chamber 20 is lean, so that slight knocking may be generated to remove carbon deposited on the top surface of the piston 15. If the air-fuel ratio of the air-fuel mixture of the internal combustion engine 1 is made lean, the cooling effect due to the heat of vaporization of the fuel is suppressed, so the temperature in the cylinder rises. Further, when the intake air amount for the same fuel injection amount is increased to make the air-fuel ratio lean, the in-cylinder pressure increases. Due to these effects, mild knocking can be generated. Furthermore, both the control for advancing the ignition timing in the internal combustion engine 1 and the control for making the air-fuel ratio of the air-fuel mixture lean may be performed. By doing so, it is possible to more reliably cause slight knocking and remove carbon deposited on the top surface of the piston 15.

  On the other hand, in S105, it is determined whether knocking has occurred. Specifically, vibration or shock data is further acquired by the acceleration sensor 25, and the determination is made based on whether the acquired vibration or shock timing and frequency are unique to knocking. Since the determination of the occurrence of knocking is a known technique, a detailed description thereof will be omitted. If it is determined that knocking has not occurred, this routine is immediately terminated. If it is determined that knocking has occurred, the process proceeds to S106.

  In S106, a process for retarding the ignition timing in the combustion chamber 20 is executed. Then, knocking is suppressed by the reverse effect of the process in S104. When the process of S106 ends, this routine is temporarily ended.

Next, a method for determining whether or not a carbon stamp is generated in S102 will be described with reference to FIGS. FIG. 5 shows a change in the combustion pressure in the combustion chamber 20 and a time window for vibration or impact data sampling. Since the combustion in the combustion chamber ends at a timing after TDC, the combustion pressure reaches a maximum value after TDC. The sampling of vibration or shock data is performed in synchronization with TDC.

  Here, vibration or impact due to the carbon stamp always occurs in the vicinity of TDC. On the other hand, vibration or impact due to knocking often occurs near the maximum of the combustion pressure. Furthermore, vibrations or shocks due to abnormal combustion such as plague often occur at a timing before TDC. That is, by sampling the vibration or impact data in synchronization with the TDC, it becomes possible to separate the vibration or impact of knocking or plague from the vibration or impact caused by the carbon stamp.

  The time window for sampling the vibration data may be a rectangular window indicated by A in the figure, a trigonometric function, or a Hanning window indicated by B in the figure.

  FIG. 6 shows a process for determining whether or not a carbon stamp is generated from the acquired vibration or impact data. As shown at the left end of the figure, the signal obtained by the acceleration sensor 25 first passes through the frequency filter 50, so that only the vibration of a specific frequency is extracted. Here, the frequency of the vibration or impact usually generated by knocking is 7 KHz to 10 KHz, and the vibration or impact generated by the carbon stamp is a lower frequency. Therefore, by appropriately setting the frequency window of the frequency filter 50 here, it is possible to more reliably distinguish the vibration or impact caused by knocking from the vibration or impact caused by the carbon stamp.

  Next, only the vibration or shock data within the time window of the data sampling shown in FIG. As a result, only a signal having a specific frequency in the TDC is extracted.

  Next, the stamp determination circuit 52 determines whether the amplitude of the vibration or shock data signal within the above-described time window is greater than a predetermined threshold. Here, when the amplitude of the vibration or impact data signal is larger than the threshold value, it is determined that the carbon stamp is generated, and the carbon stamp flag is turned ON. If the amplitude of the vibration or impact data signal is equal to or less than the threshold value, it is determined that no carbon stamp has occurred, and the carbon stamp flag is turned off. The amplitude threshold value may be experimentally obtained in advance.

  As described above, in this embodiment, it is determined whether or not a carbon stamp is generated from the output of the acceleration sensor 25 provided in the cylinder block 3, and it is determined that a carbon stamp is generated. In order to reduce the compression ratio. Thereby, the carbon stamp can be immediately suppressed. Further, in this embodiment, after that, the ignition timing in the internal combustion engine 1 is advanced to cause a slight knocking to temporarily remove carbon deposited on the top surface of the piston 15. Thereby, the cause of the carbon stamp can be removed.

  Furthermore, in determining whether or not a carbon stamp has occurred, vibration or impact data is sampled from the vicinity of the TDC, and only the signal in the frequency band specific to the carbon stamp is taken out and determined by its amplitude. It is possible to accurately determine the occurrence of the carbon stamp.

  Note that the ECU 30 and the acceleration sensor 25 that execute the processes of S101 and S102 in the above-described carbon stamp prevention routine constitute a carbon stamp detection means in the present embodiment. Moreover, ECU30 which performs the process of S104 is corresponded to the carbon removal means in a present Example.

  In the process of S103 of the carbon stamp prevention routine, a map storing the relationship between the operating state of the internal combustion engine 1 and the compression ratio, which is used for the compression ratio change control, is obtained from the normal time map and the upper limit compression ratio is By changing to a limited carbon stamp hour map, the compression ratio was consequently reduced. However, the method for reducing the compression ratio when it is determined that the carbon stamp is generated is not limited to this.

  For example, the cylinder block 3 and the crankcase 4 may be uniformly separated by a certain distance from the state at that time so as to be uniformly reduced so as to have a predetermined compression ratio. The movement distance when the cylinder block 3 and the crankcase 4 are uniformly separated by a certain distance may be about 1.5 mm. This is because it is generally said that the maximum amount of carbon deposited on the top surface of the piston 15 is about 1.2 mm.

  In the carbon stamp prevention routine, the process of removing carbon deposited on the top surface of the piston 15 is performed in the process of S104. However, this process may be performed at a different timing in another routine. For example, it may be performed when the internal combustion engine 1 is started or when the engine speed decreases. If it does so, it can suppress that the driving | running performance of the internal combustion engine 1 should be influenced by the occurrence of slight knocking.

  Furthermore, it is not always necessary to execute the above-described process for removing carbon. This is because when a predetermined amount or more of carbon is deposited on the piston 15, it often peels off automatically. Therefore, when it is determined that the carbon stamp is generated, the control for reducing the compression ratio alone can sufficiently suppress the noise.

  In the above, a plurality of acceleration sensors 25 may be provided for each cylinder, and the carbon stamp prevention routine may be executed independently for each cylinder.

  Next, a second embodiment of the present invention will be described. In this embodiment, carbon stamps are not generated in addition to the case where carbon stamps are generated, but the volume of the combustion chamber 20 is relatively reduced because carbon is deposited on the top surface of the piston 15. Then, a state where knocking is likely to occur is determined, and control for removing carbon deposited on the top surface of the piston 15 in such a case will be described.

  FIG. 7 shows a flowchart of the carbon stamp prevention routine 2 in the present embodiment. The difference between this routine and the carbon stamp prevention routine described in the first embodiment is that the process of S201 is added after the process of S105. Here, only the difference between this routine and the carbon stamp prevention routine described in the first embodiment will be described.

  In S201, when it is determined in S105 that knocking has occurred, it is determined whether this knocking has occurred in a normal compression ratio range. That is, in general, it can be said that knocking is more likely to occur as the operating state is higher and the compression ratio is higher. Can be identified. In S201, it is determined whether or not the knocking determined to have occurred in S105 has occurred in a compression ratio range in which knocking is likely to occur.

Here, if it is determined that the knocking that has occurred in S105 has occurred in a compression ratio range in which knocking is likely to occur, it is considered that the knocking is a general knocking, and thus the process directly proceeds to S106. On the other hand, if it is determined that the knocking that has occurred in S105 has occurred at a compression ratio other than the compression ratio range in which knocking is likely to occur, no carbon stamp has been generated, but the top of the piston 15 has not been generated. Since it is determined that carbon accumulates on the surface and the volume of the combustion chamber 20 is relatively small, the process proceeds to S104, and a process for removing carbon is executed.

  As described above, in this embodiment, even when the carbon stamp itself is not generated, the carbon is deposited on the top surface of the piston 15 so that knocking occurs at a compression ratio that does not normally cause knocking. If it is determined that the carbon is removed, the carbon removal treatment is performed.

  If it does so, since carbon can be removed when the sign of carbon stamp generation appears, generation of carbon stamp can be suppressed more reliably.

  In the above embodiment, the configuration in which the cylinder block is moved relative to the crankcase by rotating the camshaft has been described as an example. However, the configuration to which the present invention is applied is not limited to the above. For example, the connecting rod is divided into two parts, a swing member that can swing around a predetermined swing center is connected to the connecting rod that is connected to the crankshaft, and the swing center moves by rotating the camshaft. Thus, the present invention may be applied to a configuration in which the volume of the combustion chamber and the stroke of the piston are changed.

1 is an exploded perspective view showing a schematic configuration of an internal combustion engine according to an embodiment of the present invention. It is sectional drawing which shows progress which the cylinder block in the internal combustion engine which concerns on the Example of this invention moves relatively with respect to a crankcase. It is a figure which shows the detail of the combustion chamber vicinity of the internal combustion engine which concerns on the Example of this invention. It is a flowchart which shows the carbon stamp prevention routine which concerns on Example 1 of this invention. It is a figure explaining the acquisition method of the vibration or impact signal for judging generation | occurrence | production of the carbon stamp based on the Example of this invention. It is a figure for demonstrating the process of the vibration or impact signal which concerns on the Example of this invention. It is a figure which shows the flowchart of the carbon stamp prevention routine 2 which concerns on Example 2 of this invention.

Explanation of symbols

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 15 ... Piston 20 ... combustion chamber 20a ... combustion chamber ceiling 25 ... acceleration sensor 30 ... ECU
50 ... Frequency filter 51 ... Time window circuit 52 ... Stamp determination circuit

Claims (3)

A variable compression ratio mechanism for changing the compression ratio of the internal combustion engine by changing the volume of the combustion chamber of the internal combustion engine and / or the stroke of the piston;
Carbon that detects that carbon deposited on the top surface of the piston collides with a ceiling surface of the combustion chamber or a member disposed on the ceiling surface of the combustion chamber near the compression top dead center of the internal combustion engine Stamp detection means;
With
By the carbon stamp detection means, carbon deposited on the top surface of the piston collides with a member disposed on the ceiling surface of the combustion chamber or the ceiling surface of the combustion chamber near the compression top dead center of the internal combustion engine. If it is detected, the variable compression ratio internal combustion engine reduces the compression ratio of the internal combustion engine by the variable compression ratio mechanism. A carbon removing means for removing carbon deposited on the top surface of the piston;
By the carbon stamp detection means, carbon deposited on the top surface of the piston collides with a member disposed on the ceiling surface of the combustion chamber or the ceiling surface of the combustion chamber near the compression top dead center of the internal combustion engine. When it is detected, the variable compression ratio mechanism lowers the compression ratio of the internal combustion engine, and the carbon removing means removes carbon deposited on the top surface of the piston. The variable compression ratio internal combustion engine according to claim 1. The carbon removing means removes carbon deposited on the top surface of the piston by controlling to advance the ignition timing in the internal combustion engine and / or to make the air-fuel ratio of the air-fuel mixture in the internal combustion engine lean. The variable compression ratio internal combustion engine according to claim 2, wherein:

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