JP2010043544A - Variable compression ratio internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a technology applied to a variable compression ratio internal combustion engine provided with a variable compression ratio mechanism changing the mechanical compression ratio of the internal combustion engine and the variable valve timing mechanism changing the valve timing of the internal combustion engine, and easily and accurately controlling the valve timing especially in the variable compression ratio internal combustion engine of which the valve timing is changed due to an influence of the variable compression ratio mechanism when the mechanical compression ratio is changed. <P>SOLUTION: A reference position of valve timing is learned (S106) at a specific mechanical compression ratio (S103). The acquired learned value is defined as a value which is not changed according to mechanical compression ratio of the internal combustion engine, and the controlled variable of the valve timing is determined based on the learned value and a specified value predetermined as a value of the valve timing according to an operation state (S107). <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention provides a variable compression ratio mechanism that changes the mechanical compression ratio of the internal combustion engine by changing the relative position of the piston at the top dead center of the internal combustion engine to change the volume of the combustion chamber, and the valve timing of the internal combustion engine. The present invention is applied to a variable compression ratio internal combustion engine having a variable valve timing mechanism that changes the mechanism mechanically. Among the variable compression ratio internal combustion engines, in particular, the variable valve timing mechanism and the variable compression ratio mechanism variable are mechanically linked, and set by the valve timing mechanism when the mechanical compression ratio set by the variable compression ratio mechanism changes. The valve timing is also related to changing.

  In recent years, a technique for making the mechanical compression ratio of an internal combustion engine variable has 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 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 relatively moving the internal combustion engine, thereby changing the mechanical 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 for changing the volume of the combustion chamber and the stroke of the piston and thereby changing the mechanical compression ratio of the internal combustion engine has been proposed (see, for example, Patent Document 2).

  In order to change the mechanical compression ratio of the internal combustion engine, when changing the arrangement, size, etc. of some of the mechanical elements of the internal combustion engine, the rotation of the camshaft that drives the intake and exhaust valves of the internal combustion engine and the piston of the combustion cycle The relative relationship with the position may be off. Then, when the intake / exhaust valve is directly driven by the rotation of the camshaft, or when the valve timing that is the opening / closing timing of the intake / exhaust valve is controlled based on the rotation phase of the camshaft, the piston is dead in the compression stroke. There is a possibility that the valve timing of the intake / exhaust valve deviates from the timing that should be originally with respect to the timing at a predetermined position such as a point.

  On the other hand, it has been proposed to perform the following control. In this proposal, the variable valve timing mechanism is adjusted to the most retarded position at the top dead center of the piston at a specific mechanical compression ratio, and the valve timing at that time is used as a reference. Then, the relative operation amount of the valve timing from the reference according to the operating state is stored in the map as a specified value, and the valve timing is operated by the specified value from the reference to control the target value. In addition, learning control is performed on the specified value so that the valve timing can be accurately controlled to the target value. Further, the learning value in the learning control is corrected in consideration of the change in the valve timing due to the change in the mechanical compression ratio, and the valve timing is controlled to the target value based on the corrected learning value and the specified value. (See cited document 3).

That is, in the above-described conventional technology, in the valve timing control of the internal combustion engine, the learning value is corrected according to the value of the mechanical compression ratio of the internal combustion engine, and the valve timing is controlled using the corrected learning value. The influence of the change in the valve timing caused by the change in the ratio was suppressed. However, the above-described conventional technique has a disadvantage in that the control becomes complicated because the learning value needs to be corrected every time the mechanical compression ratio of the internal combustion engine is changed. If the mechanical compression ratio of the internal combustion engine cannot be detected accurately due to a failure of the compression ratio sensor, etc., not only the control accuracy of the compression ratio of the internal combustion engine is lowered, but also the control accuracy of the valve timing is lowered. There was an inconvenience.
JP 2003-206871 A JP 2001-317383 A JP 2006-105095 A JP 2007-332798 A

  The present invention has been made in view of the above situation, and includes a variable compression ratio mechanism that changes the mechanical compression ratio of the internal combustion engine and a variable compression ratio that includes a variable valve timing mechanism that changes the valve timing of the internal combustion engine. Applies to internal combustion engines. The purpose of the variable compression ratio internal combustion engine, in which the valve timing of the variable valve timing mechanism changes due to the operation of the variable compression ratio mechanism, particularly when the mechanical compression ratio is changed, is simpler or more accurate. It is to provide a technique that makes it possible to control the valve timing to a target value.

  In order to achieve the above object, the present invention has the following features regarding the valve timing control of the variable compression ratio internal combustion engine in which the valve timing by the variable valve timing mechanism changes due to the operation of the variable compression ratio mechanism. . That is, the reference valve timing that is a reference for valve timing control is learned as a predetermined value that does not change depending on the mechanical compression ratio of the internal combustion engine. The valve timing is controlled to a target value based on the relative valve timing variation from the reference valve timing.

More specifically, a variable compression ratio mechanism that changes the volume of the combustion chamber by changing the relative position of the piston at the top dead center of the internal combustion engine to change the mechanical compression ratio of the internal combustion engine;
A variable valve timing mechanism that mechanically changes and sets the valve timing of the intake valve and / or the exhaust valve of the internal combustion engine;
Valve timing learning means for learning and storing a reference valve timing as a reference for operation of the variable valve timing mechanism;
A valve timing control means for controlling the valve timing to a target value by changing the valve timing by the variable valve timing mechanism from the reference valve timing by a specified value according to the operating state;
A variable compression ratio internal combustion engine in which a valve timing set by the valve timing mechanism changes mechanically in conjunction with a mechanical compression ratio set by the variable compression ratio mechanism;
The reference valve timing is an invariable value depending on the mechanical compression ratio of the internal combustion engine.

  Here, in the conventional valve timing control, at the top dead center of the piston, the variable valve timing mechanism is operated to the most retarded position that is the mechanical operation limit, and the valve timing at that time is learned to perform the valve timing control. It was the standard. Therefore, in a variable compression ratio mechanism in which the valve timing set by the valve timing mechanism changes in conjunction with the mechanical compression ratio set by the variable compression ratio mechanism, when the mechanical compression ratio changes, the valve timing control is performed. There was an inconvenience that the standard itself changed.

  As a countermeasure against this inconvenience, the learning value is corrected each time the mechanical compression ratio of the variable compression ratio internal combustion engine is changed based on the relationship between the mechanical compression ratio and the change in valve timing, and the corrected learning value is used. Therefore, a technique for controlling the valve timing has been proposed.

However, in the technique in which the above countermeasure is incorporated, there is an inconvenience that a calculation for correcting the learning value is required every time the mechanical compression ratio is changed, and the control becomes complicated. In addition, when a sensor that detects the mechanical compression ratio of an internal combustion engine fails, it is highly possible that the influence will affect not only the mechanical compression ratio control but also the valve timing control, and the valve timing control should be executed with high accuracy. There were cases where it was difficult.

  On the other hand, in the present invention, a value that does not change depending on the mechanical compression ratio of the internal combustion engine is adopted as the reference of the valve timing control, so that the valve timing control and the mechanical compression ratio control can be separated. As a result, it is not necessary to perform an operation for correcting the learning value every time the mechanical compression ratio is changed, and the control can be simplified. Further, since the possibility that the influence of the sensor detecting the mechanical compression ratio is affected by the valve timing control is reduced, the valve timing control can be executed with high accuracy.

  In the present invention, the valve timing learning means may learn, as a reference valve timing, a valve timing determined based on a mechanical reference of the variable valve timing mechanism at a specific mechanical compression ratio. Good.

  Here, the valve timing determined based on the mechanistic reference of the variable valve timing mechanism is, for example, the most retarded angle position (projection) where the operation of the variable valve timing mechanism is mechanically limited by contact between members. It may be a contact position). Alternatively, it may be a most advanced angle position (abutment position) where the operation of the variable valve timing mechanism is mechanically limited by contact between members.

  When learning and storing the reference valve timing, the valve timing learning means controls the compression ratio of the internal combustion engine to a predetermined mechanical compression ratio and operates the variable valve timing mechanism to the abutting position. By storing the timing, the reference valve timing can be learned and acquired more easily and accurately.

  Further, in the present invention, the valve timing learning means determines a valve timing determined based on a mechanical reference of the variable valve timing mechanism at an arbitrary mechanical compression ratio, as a mechanical compression ratio and a valve timing in the internal combustion engine. May be corrected to a valve timing value at a specific mechanical compression ratio and learned as a reference valve timing.

  In other words, in the present invention, the mechanical compression ratio is not particularly defined when the valve timing learning means learns and stores the reference valve timing, and is performed at an arbitrary mechanical compression ratio. Then, the acquired reference valve timing is corrected to a valve timing value at a specific mechanical compression ratio using the relationship between the mechanical compression ratio of the internal combustion engine and the valve timing, and is learned and stored as a reference valve timing.

  According to this, learning and storage of the reference valve timing can be performed at an arbitrary opportunity, and further, the value of the reference valve timing can be corrected to a value at a specific mechanical compression ratio and stored. According to this, it is possible to increase the degree of freedom with respect to the learning timing of the reference valve timing, and it is possible to more easily acquire the learning value in the mechanical compression ratio that is the basis of the reference valve timing.

  In the present invention, the specific mechanical compression ratio may be a maximum compression ratio that can be set by the variable compression ratio mechanism.

At this maximum compression ratio, the position of the piston at the top dead center is the highest, so that the interference between the piston and the intake valve or the exhaust valve is most likely to occur. If the reference valve timing is determined at this maximum compression ratio, the reference of valve timing control can be directly learned and stored in a situation where the interference between the piston and the intake valve or the exhaust valve is most likely to occur. It becomes possible to determine the relationship of the mechanical compression ratio. As a result, it is possible to more reliably avoid interference between the intake valve or the exhaust valve and the piston.

  In the present invention, the specific mechanical compression ratio may be a minimum compression ratio that can be set by the variable compression ratio mechanism.

  At this minimum compression ratio, the position of the piston at the top dead center is the lowest, so that the interference between the piston and the intake valve or the exhaust valve is least likely to occur. Then, in the state where the interference between the piston and the intake / exhaust valve is least likely to occur, the reference valve timing can be learned and stored more safely, and the internal combustion caused by the interference between the piston and the intake valve or the exhaust valve during the execution of learning. Engine failure can be suppressed.

  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, even in a variable compression ratio internal combustion engine in which the valve timing changes due to the operation of the variable compression ratio mechanism when the mechanical compression ratio is changed, the valve timing can be controlled more easily or accurately. Can do.

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

  FIG. 1 is a diagram illustrating a schematic configuration of a variable compression ratio internal combustion engine (hereinafter simply referred to as “internal combustion engine”) 1 in which a mechanical compression ratio is variable. In this embodiment, an intake pipe 19 is connected to the combustion chamber in the cylinder 2 via an intake port 18 provided in the cylinder head 10. The intake of the intake air into the cylinder 2 is controlled by the intake valve 5. Opening and closing of the intake valve 5 is controlled by rotational driving of the intake side cam 7. An exhaust pipe 21 is connected via an exhaust port 20 provided in the cylinder head 10. Exhaust discharge to the outside of the cylinder 2 is controlled by an exhaust valve 6. Opening and closing of the exhaust valve 6 is controlled by rotational driving of the exhaust side cam 8. Further, a fuel injection valve 17 is provided at the intake port 18, and a spark plug 16 is provided at the top of the cylinder 2. The piston 15 connected to the crankshaft 13 of the internal combustion engine 1 via the connecting rod 14 reciprocates in the cylinder 2.

  Here, in the internal combustion engine 1, the mechanical compression ratio of the internal combustion engine 1 is changed by moving the cylinder block 3 relative to the crankcase 4 in the axial direction of the cylinder 2 by the variable compression ratio mechanism 9. That is, the variable compression ratio mechanism 9 is constituted by the cylinder block 3, the cylinder head 10 and the piston 15 by moving the cylinder head 10 together with the cylinder block 3 relative to the crankcase 4 in the axial direction of the cylinder 2. The volume of the combustion chamber is changed, and as a result, the mechanical compression ratio of the internal combustion engine 1 is variably controlled. For example, when the cylinder block 3 is relatively moved away from the crankcase 4, the combustion chamber volume increases and the mechanical compression ratio decreases.

The variable compression ratio mechanism 9 includes the shaft portion 9a, a cam portion 9b having a circular cam profile fixed to the shaft portion 9a while being eccentric with respect to the central axis of the shaft portion 9a, and the cam portion 9b. A movable bearing portion 9c having an outer shape and rotatable relative to the shaft portion 9a and attached in an eccentric state like the cam portion 9b, a worm wheel 9d provided concentrically with the shaft portion 9a, and a worm wheel 9d And a motor 9f that rotationally drives the worm 9e. The cam portion 9 b is installed in a storage hole provided in the cylinder block 3, and the movable bearing portion 9 c is installed in a storage hole provided in the crankcase 4. Here, the driving force from the motor 9f is transmitted to the shaft portion 9a via the worm 9e and the worm wheel 9d. Then, the cam block 9 b and the movable bearing portion 9 c in an eccentric state are driven, so that the cylinder block 3 is moved relative to the crankcase 4 in the axial direction of the cylinder 2.

  The internal combustion engine 1 is also provided with an electronic control unit (hereinafter referred to as “ECU”) 90 for controlling the internal combustion engine 1. The ECU 90 includes a CPU, a ROM, a RAM, and the like for storing various programs and maps to be described later, and controls the operating conditions of the internal combustion engine 1 according to the operating conditions of the internal combustion engine 1 and the driver's request. Unit.

  Here, the accelerator opening sensor 92 is electrically connected to the ECU 90, and the ECU 90 receives a signal corresponding to the accelerator opening, and calculates an engine load and the like required for the internal combustion engine 1 according to this signal. A crank position sensor 91 is electrically connected to the ECU 90. The ECU 90 receives a signal corresponding to the rotational angle of the output shaft of the internal combustion engine 1, and the engine rotational speed of the internal combustion engine 1, the engine rotational speed and the gears. The vehicle speed or the like of the vehicle on which the internal combustion engine 1 is mounted is calculated from the ratio or the like.

  Further, a motor 9f that constitutes the variable compression ratio mechanism 9 is electrically connected to the ECU 90. The motor 9f is driven by a command from the ECU 90, and the mechanical compression ratio of the internal combustion engine 1 is changed by the variable compression ratio mechanism 9. The change in the mechanical compression ratio of the internal combustion engine 1 is performed based on the operating state of the internal combustion engine 1. For example, when the operating state of the internal combustion engine 1 is expressed by an engine load and an engine speed, the cylinder block 3 is connected to the crankcase 4 as the engine speed changes from a low engine load to a high engine load or from a low engine speed to a high engine speed. The motor 9f is driven in a direction away from the engine to shift the mechanical compression ratio of the internal combustion engine 1 from a high compression ratio to a low compression ratio.

  Next, the opening / closing operation of the intake valve 5 and the exhaust valve 6 in the internal combustion engine 1 and the opening / closing mechanism for performing the opening / closing operation will be described with reference to FIGS. 2 and 3 are diagrams mainly showing the mechanism of the valve timing control system of the internal combustion engine 1. FIG. 2 (a) shows that the cylinder block 3 approaches the crankcase 4 and the mechanical compression ratio of the internal combustion engine 1 is relatively high. FIG. 2B shows a state where the mechanical compression ratio is high (hereinafter simply referred to as “high compression ratio”). FIG. 2B shows that the cylinder block 3 is moved away from the crankcase 4 and the mechanical compression ratio of the internal combustion engine 1 is relatively low. This shows a state where the mechanical compression ratio (hereinafter simply referred to as “low compression ratio”) is achieved. As shown in FIG. 2, the mechanical compression ratio of the internal combustion engine 1 is changed by the relative movement of the cylinder block 3 in the axial direction of the cylinder 2 by Δh. FIG. 3 is a diagram schematically showing the vicinity of the top of the cylinder head 10 with the intake valve 5 and the exhaust valve 6 as the center.

  In the internal combustion engine 1, the intake valve 5 is opened and closed by the intake side cam 7. The intake side cam 7 is attached to the intake side camshaft 22, and an intake side pulley 24 is provided at the end of the intake side camshaft 22. Further, a variable rotation phase mechanism (hereinafter referred to as “intake side VVT”) 23 that can change the relative rotation phase between the intake side camshaft 22 and the intake side pulley 24 is provided. The intake side VVT 23 controls the relative rotation phase between the intake side camshaft 22 and the intake side pulley 24 in accordance with a command from the ECU 90. Further, an intake side cam angle sensor 93 that detects the rotation angle of the intake side camshaft 22 is provided, and the intake side cam angle sensor 93 and the ECU 90 are electrically connected.

  The opening / closing operation of the exhaust valve 6 is performed by the exhaust side cam 8. The exhaust side cam 8 is attached to the exhaust side cam shaft 25, and an exhaust side pulley 27 is provided at the end of the exhaust side cam shaft 25. Further, a variable rotation phase mechanism (hereinafter referred to as “exhaust side VVT”) 26 that can change the relative rotation phase between the exhaust side camshaft 25 and the exhaust side pulley 27 is provided. The exhaust side VVT 26 controls the relative rotation phase between the exhaust side camshaft 25 and the exhaust side pulley 27 in accordance with a command from the ECU 90. Further, an exhaust side cam angle sensor 94 that detects the rotation angle of the exhaust side camshaft 25 is provided, and the exhaust side cam angle sensor 94 and the ECU 90 are electrically connected. Note that the intake side VVT 23 and the exhaust side VVT 26 correspond to a variable valve timing mechanism in this embodiment.

  The rotation of the intake camshaft 22 and the exhaust camshaft 25 is driven by the driving force of the crankshaft 13. Specifically, a timing belt 33 is hung on a crank pulley 32, an intake pulley 24, and an exhaust pulley 27 provided on the crankshaft 13, and the timing belt 33 is further provided on the crankcase 4 side. The first crankcase pulley 30, the second crankcase pulley 31 and the first cylinder block pulley 28 and the second cylinder block pulley 29 provided on the cylinder block 3 side are also engaged.

  The timing belt 33 is applied to the crank side pulley 32, the first crankcase side pulley 30, the first cylinder block side pulley 28, the intake side pulley 24, the exhaust side pulley 27, and the second cylinder block side pulley. 29, in order of the second crankcase pulley 31.

  The first crankcase side pulley 30 and the second crankcase side pulley 31 are in contact with the outer peripheral surface of the timing belt 33, and the other crank side pulley 32, first cylinder block side pulley 28, and intake side pulley 24. The exhaust side pulley 27 and the second cylinder block side pulley 29 are in contact with the inner peripheral surface of the timing belt 33.

  In this manner, the intake side camshaft 22 and the exhaust side camshaft 25 are driven to rotate by the driving force of the crankshaft 13, so that the intake side cam 7 and the exhaust side cam 8 cause the intake valve 5 and the exhaust valve 6 to move. Opening and closing operations are performed.

  Here, when the mechanical compression ratio of the internal combustion engine 1 is changed by the variable compression ratio mechanism 9, for example, from the high compression ratio state shown in FIG. 2 (a) to the low compression ratio state shown in FIG. 2 (b). When the change is made, the cylinder block 3 relatively moves in the direction away from the crankcase 4 as described above. Accordingly, the first cylinder block side pulley 28 and the second cylinder block side pulley 29 provided in the cylinder block 3 also move in accordance with the change in the mechanical compression ratio. As a result, the length L1 of the timing belt 33 between the first crankcase side pulley 30 and the first cylinder block side pulley 28 and the second crankcase side pulley 31 and the second cylinder block side pulley 29 are between. The length L2 of the timing belt 33 applied to is changed with the change of the mechanical compression ratio. With such a configuration, even if the cylinder block 3 moves, the total length of the timing belt 33 does not change.

  In the internal combustion engine 1, the relationship between the crank angle and the cam angles of the intake and exhaust valves 5 and 6 is based on signals from the crank position sensor 91, the intake side cam angle sensor 93, and the exhaust side cam angle sensor 94. The intake phase VVT 23 and the exhaust side VVT 26 feedback control the rotational phases of the intake side camshaft 22 and the exhaust side camshaft 25 so as to achieve an appropriate relationship.

In this embodiment, the intake side camshaft 22 and the exhaust side camshaft 25
The intake side VVT 23 and the exhaust side VVT 26 are controlled by how many times the engine is rotated from the most retarded position. That is, the position at which the intake side camshaft 22 and the exhaust side camshaft 25 are most retarded (hereinafter referred to as the most retarded position) is set as a reference position, and the reference position is used in accordance with the operating state of the internal combustion engine 1. The angles of the intake side camshaft 22 and the exhaust side camshaft 25 are advanced. The advance amount from the reference position is stored in the ECU 90 in advance as a map of the relationship between the operating state of the internal combustion engine 1 (for example, the engine speed and the engine load) and the advance amount. It can be obtained by substituting the operating state of the internal combustion engine 1.

  However, in the internal combustion engine 1, when the high compression ratio state shown in FIG. 2 (a) is changed to the low compression ratio state shown in FIG. 2 (b), the timing belt length L1 becomes short, and the timing belt length. L2 becomes longer. As a result, when the crankshaft 13 is at a specific rotation angle, for example, when the position of the piston 15 is at the top dead center of the compression stroke, the phases of the intake pulley 24 and the exhaust pulley 27 are as shown in FIG. The high compression ratio state shown in FIG. 2 is different from the low compression ratio state shown in FIG. That is, when the high compression ratio state shown in FIG. 2A is used as a reference, in the low compression ratio state shown in FIG. 2B, the rotational phases of the intake side pulley 24 and the exhaust side pulley 27 are shifted by ΔTv.

  When the learning value is acquired in a state where the rotational phase is shifted by ΔTv, the rotational phase is shifted by ΔTv due to the displacement of the most retarded angle positions of the intake side camshaft 22 and the exhaust side camshaft 25. Further, the target values of the intake side VVT 23 and the exhaust side VVT 26, that is, the advance amounts of the intake side camshaft 22 and the exhaust side camshaft 25 are also shifted.

  Therefore, the valve timings of the intake valve 5 and the exhaust valve 6 with respect to the timing when the piston position is at the top dead center of the compression stroke are the high compression ratio state shown in FIG. 2 (a) and the low compression ratio state shown in FIG. 2 (b). However, there is a possibility that the valve timing may deviate from an appropriate timing as the compression ratio is changed. That is, as a result of the change of the compression ratio, there is a possibility that the valve timing suitable for the combustion performed in the cylinder 2 cannot be obtained.

  On the other hand, in the conventional valve timing control, the rotational phase shift of the intake side pulley 24 and the exhaust side pulley 27 when the mechanical compression ratio is changed is obtained in advance in association with the mechanical compression ratio, and the intake side When the VVT 23 and the exhaust side VVT 26 are controlled, the learning value is corrected by a deviation amount obtained in advance.

  That is, the target values of the operation amounts of the intake side VVT 23 and the exhaust side VVT 26 are the most retarded values of the prescribed values determined in relation to the operating state of the internal combustion engine and the phases of the intake side camshaft 22 and the exhaust side camshaft 25. The learned value of the valve timing at this time is determined, and the learned value is corrected by the rotational phase shift of the intake side pulley 24 and the exhaust side pulley 27 due to the change in the mechanical compression ratio of the internal combustion engine 1.

  The specified values in this case are, for example, the intake side camshaft 22 and the exhaust side camshaft from the most retarded position determined from the operating state of the internal combustion engine 1 when the mechanical compression ratio of the internal combustion engine 1 is the maximum compression ratio. The advance amount is 25, and is obtained in advance by experiments and the like from the relationship with the operating state of the internal combustion engine 1 and is mapped and stored in the ECU 90. The learning value is corrected by adding the valve timing deviation amount ΔTv to the reference learning value based on the most retarded position of the valve timing at the maximum compression ratio.

Since the intake side pulley 24 and the exhaust side pulley 27 are interlocked with the crankshaft 13 via the timing belt 33, the rotation phase of the intake side VVT 23 and the exhaust side VVT 26 changes the rotation angle of the crankshaft 13. The relative relationship between the rotation angles of the intake side camshaft 22 and the exhaust side camshaft 25 is changed, and the valve timings of the intake valve 5 and the exhaust valve 6 with respect to the piston position of the piston 15 become appropriate timings.

  FIG. 4 shows the relationship between the specified value in the previous control of the valve timing, the corrected learned value, and the valve timing control amount. Here, the zero point is an absolute reference defined in relation to the angle of the crankshaft. The valve timing control amount means an amount that is actually advanced from the most retarded position in order to set the valve timing to a target valve timing defined by a specified value in each compression ratio. As shown in the figure, the corrected learning value is a learning value obtained by correcting ΔTv, which changes depending on the mechanical compression ratio, in addition to the learning value obtained by learning control at the maximum compression ratio.

  Thus, in the conventional control of the valve timing, for example, the learning value related to the most retarded position of the intake valve 5 and the exhaust valve 6 in the case of the maximum compression ratio is used as the change in the valve timing due to the change in the mechanical compression ratio. Thus, the valve timing control amount that is the amount by which the intake side VVT 23 and the exhaust side VVT 26 are actually advanced is determined. Therefore, each time the mechanical compression ratio in the internal combustion engine 1 is changed, complicated learning and control for deriving the valve timing control amount by correcting the learning value related to the valve timing control of the intake side VVT 23 and the exhaust side VVT 26 by ΔTv. Had gone.

  In the conventional valve timing control described above, if the sensor for controlling the mechanical compression ratio becomes abnormal, not only the mechanical compression ratio but also the valve timing control may become abnormal. It was not desirable from the viewpoint of stability.

  Therefore, in this embodiment, the valve timing control amount is obtained from the learning value (without correction by ΔTv) and the specified value with reference to a specific valve timing that does not change with the mechanical compression ratio. For example, as shown in FIG. 5, the most retarded angle positions of the intake valve 6 and the exhaust valve 6 at the maximum compression ratio may be used as a reference. Then, the valve timing is controlled to the target value by advancing the intake valve 5 and the exhaust valve 6 from the learned value with respect to the reference using the specified value stored in the map according to the operation state as the valve timing control amount. .

  According to this, the learning value for determining the valve timing control amount does not change depending on the mechanical compression ratio as described with reference to FIG. Therefore, it is not necessary to correct the learning value and calculate the valve timing control amount each time the mechanical compression ratio in the internal combustion engine 1 changes, so that the processing can be simplified. In addition, since the learning value and valve timing control amount are not affected by the mechanical compression ratio, even if a sensor abnormality occurs for the compression ratio measurement, the situation where the valve timing is also affected by this is avoided. it can.

  FIG. 6 shows a valve timing learning / control routine in this embodiment. This routine is a program stored in the ROM of the ECU 90, and is a routine executed every predetermined period while the internal combustion engine 1 is operating.

  When this routine is executed, first, in S101, the vehicle speed, the accelerator opening, the shift state, and the state of the internal combustion engine (the rotational speed, the intake amount, the compression ratio, etc.) are detected. When the processing of S101 ends, the process proceeds to S102.

  In S102, it is determined whether or not a valve timing learning condition is satisfied. In this embodiment, the valve timing learning condition is determined by whether or not the internal combustion engine is in an idle state. If a negative determination is made here, the process proceeds to S107. On the other hand, if a positive determination is made, the process proceeds to S103.

  In S 103, the mechanical compression ratio of the internal combustion engine 1 is controlled to the maximum compression ratio that can be changed by the variable compression ratio mechanism 9. When the process of S103 ends, the process proceeds to S104.

  In S104, the intake side VVT 23 and the exhaust side VVT 26 are retarded to the most retarded position which is a mechanical retardable limit, and the valve timing at that time is acquired. The exhaust VVT may be learned on the advance side. When the process of S104 ends, the process proceeds to S105.

  In S105, the mechanical compression ratio of the internal combustion engine 1 at this time is detected. Specifically, it may be detected from the output of an in-cylinder pressure sensor (not shown). Alternatively, the position of the cylinder block 3 relative to the crankcase 4 may be detected by measuring with a sensor (not shown). Here, if the difference between the mechanical compression ratio targeted in S103 and the mechanical compression ratio actually detected in S105 is greater than or equal to an allowable value, it is determined that the variable compression ratio mechanism 9 or the sensor is abnormal. In this case, measures such as notifying the driver and prohibiting the change of the mechanical compression ratio may be executed, but the description is omitted here. When the process of S105 ends, the process proceeds to S106.

  In S106, the learning value (absolute position from the zero point (timing phase difference)) of the most retarded position of the valve timing is updated with the value acquired in S104. The updated learning value is stored in a memory in the ECU 90. When the process of S106 ends, the process proceeds to S107.

  In S107, the valve timing control amount is calculated from the learned value of the most retarded position of the valve timing of the intake side VVT 23 and the exhaust side VVT 26 and the specified value read from the specified value map. Specifically, if there is a difference between the latest learned value and the most retarded angle position that is the reference for the specified value, the advance amount obtained by correcting the specified value by the difference is set as the valve timing control amount. To do. Then, based on the obtained valve timing control amount, the intake side VVT 23 and the exhaust side VVT 25 are operated to control each valve timing to the target valve timing. When the process of S107 ends, this routine is temporarily ended. In the above-described valve timing learning / control routine, the ECU 90 that executes the processing of S107 in particular corresponds to the valve timing control means in this embodiment.

  As described above, in this embodiment, the valve timing control amount is not affected by the change in valve timing caused by the change in the mechanical compression ratio of the internal combustion engine 1. Therefore, a complicated process of correcting the learning value each time the mechanical compression ratio is changed and calculating the valve timing control amount one by one using the corrected learning value and the specified value becomes unnecessary, and the control is simplified. In the control according to the present embodiment, the mechanical compression ratio is controlled to a predetermined compression ratio when the learning value is updated, and the valve timing control amount is calculated with respect to the updated learning value. Therefore, it is possible to reduce the frequency of using the value of the mechanical compression ratio for valve timing control, and reduce the probability that an abnormality related to the compression ratio, such as an abnormality in the detection sensor of the mechanical compression ratio, affects the valve timing control. It becomes possible to do.

  Note that the ECU 90 that executes the processing of S104 and S106 in the valve timing learning / control routine of this embodiment corresponds to valve timing learning means in this embodiment. Further, the learned value of the most retarded position of the valve timing of the intake side VVT 23 and the exhaust side VVT 26 corresponds to the reference valve timing in this embodiment.

Next, a second embodiment of the present invention will be described. In the first embodiment of the present invention, the example in which the learning value is updated at the maximum compression ratio that can be changed by the variable compression ratio mechanism 9 has been described. On the other hand, in this embodiment, the most retarded positions of the intake side VVT 23 and the exhaust side VVT 26 are acquired at an arbitrary mechanical compression ratio, converted into values at a specific mechanical compression ratio, and the learning value is updated. Will be described.

  FIG. 7 shows a valve timing learning / control routine 2 in this embodiment. The difference between this routine and the valve timing learning / control routine described in the first embodiment is that the process of S103 is deleted, the process of S201 is executed instead of the process of S104, and instead of the process of S106. The process of S202 is executed. Only the differences between this routine and the valve timing learning / control routine will be described below.

  First, in this routine, since the process of S103 is deleted, it is assumed that the machine compression ratio is not changed to a learning value update. That is, valve timing learning is performed at the mechanical compression ratio at the time when this routine is executed.

  That is, in S201, the intake side VVT 23 and the exhaust side VVT 26 are first retarded to the most retarded position, which is a mechanical retardable limit, and the valve timing at that time is acquired. When the process of S201 ends, the process proceeds to S105. In S105, the actual mechanical compression ratio at the time of valve timing learning is detected. Here, if the difference between the mechanical compression ratio (target value determined from the operating state) and the mechanical compression ratio actually detected in S105 is greater than or equal to the allowable value, it is determined that the variable compression ratio mechanism 9 or the sensor is abnormal. This is equivalent to the valve timing learning / control routine. When the process of S105 ends, the process proceeds to S202.

  In S202, the value of the valve timing obtained in S201 is set to a mechanical compression ratio that is a specific mechanical compression ratio, here, as an example, the maximum compression ratio that can be set by the variable compression ratio mechanism 9, as shown in FIG. Convert to valve timing in case. More specifically, the conversion may be performed by multiplying the valve timing obtained in S201 by a correction coefficient created in advance based on a graph of the relationship between the valve timing and the mechanical compression ratio. Thereby, the valve timing when the mechanical compression ratio is the specific compression ratio (the highest compression ratio of the variable compression ratio mechanism 9) is obtained.

  Next, the learning value (zero point) of the most retarded position of the valve timing is obtained by the valve timing value obtained when the mechanical compression ratio is the specific compression ratio (the maximum compression ratio of the variable compression ratio mechanism 9) obtained above. The absolute position (timing phase difference) from is updated. The updated learning value is stored in a memory in the ECU 90. When the process of S202 ends, the process proceeds to S107. The subsequent control is equivalent to the valve timing learning / control routine.

  As described above, in this embodiment, at the time of learning the valve timing, the mechanical compression ratio is not changed to a specific mechanical compression ratio one by one, and the intake side VVT 23 and the exhaust side VVT 26 remain at the current compression ratio. The valve timing at the retarded angle position is acquired, and then the learned value is updated after converting the acquired valve timing value into a value when the mechanical compression ratio becomes a specific mechanical compression ratio. According to this, it is possible to learn the valve timing more easily.

  In the valve timing control according to the present embodiment, the most retarded angle positions of the intake side VVT 23 and the exhaust side VVT 26 when the mechanical compression ratio is the maximum compression ratio that can be changed by the variable compression ratio mechanism 9 are used as reference positions. This reference position is the most retarded position among the positions that can be taken by the intake side VVT 23 and the exhaust side VVT 26 at an arbitrary mechanical compression ratio. Further, the change in the VVT most retarded position due to the change in the mechanical compression ratio is not noticed in the valve timing control. Then, depending on the combination of the target valve timing and the mechanical compression ratio, the intake side VVT 23 or the exhaust side VVT 26 may move further to the retard side than the most retarded position, which is the movement limit determined mechanically. There was a case where a mechanical collision occurred in the VVT 23 or the exhaust side VVT 26.

  Therefore, in the above-described embodiment, the most retarded positions of the intake side VVT 23 and the exhaust side VVT 26 at each mechanical compression ratio are mapped and stored, and the valve timing control at each mechanical compression ratio is performed in the intake side VVT 23 and the exhaust side. When the valve timing of the side VVT 26 is controlled so as not to be retarded from the most retarded position of each VVT, or when it is controlled near the most retarded position of each VVT, the change (movement) speed is slowed down. You may take action such as. The same applies to the case where the reference position is the most advanced position of the intake side VVT 23 and the exhaust side VVT 26. That is, in this case, in the valve timing control at each mechanical compression ratio, control is performed so that the valve timing of the intake side VVT 23 and the exhaust side VVT 26 does not advance from the most advanced angle position of each VVT, When controlling near the most advanced position of the VVT, measures such as slowing down the change (movement) speed may be taken.

  In the valve timing learning / control routine and the valve timing learning / control routine 2 described above, the learning value of the valve timing, which is the reference for the control of the valve timing, is obtained based on the state where the internal combustion engine is the maximum compression ratio. .

  At the highest compression ratio, the position of the piston at the top dead center is the highest, so that the interference between the piston and the intake valve or the exhaust valve is most likely to occur. Therefore, in the above-described embodiment, it is possible to directly learn the reference for controlling the valve timing in a situation where the interference between the piston 15 and the intake valve 5 or the exhaust valve 6 is most likely to occur. The relationship can be determined. As a result, it is possible to avoid interference between the intake valve 5 or the exhaust valve 6 and the piston 15 due to a deviation in valve timing.

  However, the reference mechanical compression ratio is not necessarily the highest compression ratio, and may be another specific mechanical compression ratio. Of course, the minimum compression ratio may be used. At the lowest compression ratio, the position of the piston at the top dead center is the lowest, so that the interference between the piston 15 and the intake valve 5 or the exhaust valve 6 hardly occurs. Then, the reference valve timing can be learned more safely in the state where the interference between the piston 15 and the intake valve 5 or the exhaust valve 6 hardly occurs, and the piston 15 and the intake valve 5 or the exhaust valve during the learning are executed. 6 can be prevented from malfunctioning due to interference with the engine 6.

  In addition, the present invention is applied in the above-described embodiment because the cylinder block 3 and the crankcase 4 are connected so as to be relatively movable, a cam shaft is provided at the connecting portion, and the cam shaft is rotated to turn the cylinder block. 3 is a variable compression ratio internal combustion engine in which the crankcase 4 and the crankcase 4 are relatively moved in the axial direction of the cylinder 2. However, it will be appreciated that the present invention may be applied to other types of variable compression ratio internal combustion engines.

  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 variable compression ratio internal combustion engine of a type that changes the volume of the combustion chamber and the stroke of the piston, thereby changing the mechanical compression ratio of the internal combustion engine.

It is sectional drawing which shows schematic structure of the internal combustion engine which concerns on the Example of this invention. It is a figure for demonstrating the change of the valve timing which arises when changing the variable compression ratio mechanism which concerns on the Example of this invention, and a mechanical compression ratio. It is the schematic which shows the valve timing control mechanism of the variable compression ratio internal combustion engine which concerns on the Example of this invention. It is a graph which shows the relationship between the mechanical compression ratio in a prior art, a correction | amendment learning value, valve timing control amount, and a defined value. It is a graph which shows the relationship between the mechanical compression ratio in Example 1 of this invention, a learning value, valve timing control amount, and a regulation value. It is a flowchart which shows the valve timing learning and control routine in Example 1 of this invention. It is a flowchart which shows the valve timing learning and control routine 2 in Example 2 of this invention. It is a figure for demonstrating conversion of the learning value of the valve timing learning and control routine 2 in Example 2 of this invention.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Internal combustion engine 2 ... Cylinder 3 ... Cylinder block 4 ... Crankcase 5 ... Intake valve 6 ... Exhaust valve 7 ... Intake side cam 8 ... Exhaust side cam 9 Variable compression ratio mechanism 9a Shaft 9b Cam 9c Movable bearing 9d Worm wheel 9e Worm 9f Motor 10 Cylinder head 13 .. Crankshaft 14 ... Connecting rod 15 ... Piston 16 ... Spark plug 17 ... Fuel injection valve 18 ... Intake port 19 ... Intake pipe 20 ... Exhaust port 21 ... Exhaust Pipe 22 ... intake side camshaft 24 ... intake side pulley 25 ... exhaust side camshaft 27 ... exhaust side pulley 28 ... first cylinder block side pulley 29 ... second cylinder block side The -30 ... First crankcase side pulley 31 ... Second crankcase side pulley 32 ... Crank side pulley 33 ... Timing belt 90 ... ECU
91 ... Crank position sensor 92 ... Accelerator opening sensor 93 ... Intake side cam angle sensor 94 ... Exhaust side cam angle sensor

Claims (5)

A variable compression ratio mechanism for changing the volume of the combustion chamber by changing the relative position of the piston at the top dead center of the internal combustion engine to change the mechanical compression ratio of the internal combustion engine;
A variable valve timing mechanism that mechanically changes and sets the valve timing of the intake valve and / or the exhaust valve of the internal combustion engine;
Valve timing learning means for learning and storing a reference valve timing as a reference for operation of the variable valve timing mechanism;
A valve timing control means for controlling the valve timing to a target value by changing the valve timing by the variable valve timing mechanism from the reference valve timing by a specified value according to the operating state;
A variable compression ratio internal combustion engine in which a valve timing set by the valve timing mechanism changes mechanically in conjunction with a mechanical compression ratio set by the variable compression ratio mechanism;
The variable compression ratio internal combustion engine, wherein the reference valve timing is a value that does not change depending on a mechanical compression ratio of the internal combustion engine.   The valve timing learning unit learns, as a reference valve timing, a valve timing determined based on a mechanical reference of the variable valve timing mechanism at a specific mechanical compression ratio. Variable compression ratio internal combustion engine.   The valve timing learning means determines a valve timing determined based on a mechanical reference of the variable valve timing mechanism at an arbitrary mechanical compression ratio based on a known relationship between the mechanical compression ratio and the valve timing in the internal combustion engine. The variable compression ratio internal combustion engine according to claim 1, wherein the value is corrected to a valve timing value at a specific mechanical compression ratio and learned as a reference valve timing.   The variable compression ratio internal combustion engine according to claim 2, wherein the specific mechanical compression ratio is a maximum compression ratio that can be set by the variable compression ratio mechanism.   4. The variable compression ratio internal combustion engine according to claim 2, wherein the specific mechanical compression ratio is a minimum compression ratio that can be set by the variable compression ratio mechanism.

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