JP2010265885A - Compression ratio switching determination device for variable compression ratio internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To determine completion of switching of a compression ratio of an internal combustion engine with a simple structure.
In a variable compression ratio internal combustion engine equipped with a variable compression ratio device capable of discretely switching a compression ratio, vibrations / sounds accompanying the switching of the compression ratio are detected by vibration / sound detection means 71a, 71c to compress the compression ratio. Since the ratio switching completion determination circuit 73 determines the compression ratio switching completion based on the vibration or the sound, the piston position detecting means and the in-cylinder pressure detecting means which have been conventionally required become unnecessary, and the mounting position to the internal combustion engine is eliminated. The completion of switching of the compression ratio can be determined using the vibration / sound detection means 71a and 71c having a high degree of freedom in the mounting method. If an existing knock sensor is used as the vibration / sound detection means, it is not necessary to provide special vibration / sound detection means 71a, 71c, and the cost can be reduced.
[Selection] FIG.

Description

  The present invention relates to a variable compression ratio internal combustion engine having a compression ratio variable device capable of discretely switching a compression ratio, and more particularly to a compression ratio switching determination device that determines completion of switching of the compression ratio.

  In a double piston type variable compression ratio internal combustion engine in which an outer piston is provided so as to be movable up and down with respect to an inner piston coupled to the upper end of the connecting rod, compression is performed by detecting the relative position of the outer piston with respect to the inner piston by a distance sensor. A method for determining completion of ratio switching is known from Japanese Patent Application Laid-Open Publication No. 2004-228707.

  Further, in a variable compression ratio internal combustion engine that changes the compression ratio by moving the position of the main bearing that supports the crankshaft up and down, the one that determines completion of switching of the compression ratio based on the pressure detected by the combustion chamber pressure sensor is as follows. This is known from US Pat.

Japanese Utility Model Publication No. 63-164535 JP 2004-332723 A

  By the way, what was described in the said patent documents 1 and 2 is not only low in the attachment position and the attachment method at the time of attaching a distance sensor and a combustion chamber pressure sensor to an internal combustion engine, but in order to attach the sensor. There is a problem that it is necessary to perform a large additional work on the engine, which causes an increase in cost.

  The present invention has been made in view of the above-described circumstances, and an object thereof is to make it possible to determine the completion of switching of the compression ratio of an internal combustion engine with a simple structure.

  In order to achieve the above object, according to the first aspect of the present invention, in a variable compression ratio internal combustion engine equipped with a variable compression ratio device capable of discretely switching the compression ratio, the vibration accompanying the switching of the compression ratio. Alternatively, a compression ratio in a variable compression ratio internal combustion engine comprising: vibration / sound detection means for detecting sound; and determination means for determining completion of switching of the compression ratio based on the output of the vibration / sound detection means. A switching determination device is proposed.

  According to a second aspect of the present invention, in addition to the configuration of the first aspect, the determination unit determines whether or not the compression ratio has been switched when the frequency of the vibration or the sound is in a specific frequency band. A compression ratio switching determination apparatus for a variable compression ratio internal combustion engine is proposed.

  According to the invention described in claim 3, in addition to the configuration of claim 1 or claim 2, crank angle detection means for detecting the crank angle of the internal combustion engine is provided, and the determination means includes the vibration or the A compression ratio switching determination apparatus for a variable compression ratio internal combustion engine is proposed, which determines completion of switching of a compression ratio based on the crank angle when sound is detected.

  According to the invention described in claim 4, in addition to the configuration of any one of claims 1 to 3, a variable compression ratio, wherein a hidden Markov model is applied to the determination means. A compression ratio switching determination device for an internal combustion engine.

  The compression ratio switching completion determination circuit 73 of the embodiment corresponds to the determination unit of the present invention.

  According to the configuration of the first aspect, in the variable compression ratio internal combustion engine having the compression ratio variable device capable of discretely switching the compression ratio, the vibration / sound accompanying the switching of the compression ratio is detected by the vibration / sound detection means. Since the determination means determines the completion of switching of the compression ratio based on the vibration or the sound, the piston position detecting means and the in-cylinder pressure detecting means, which are conventionally required, become unnecessary, and the mounting position and the mounting method to the internal combustion engine are eliminated. The completion of switching of the compression ratio can be determined using vibration / sound detection means having a high degree of freedom. If an existing knock sensor is used as the vibration / sound detection means, it is not necessary to provide a special vibration / sound detection means, and the cost can be reduced.

  According to the second aspect of the present invention, the compression ratio switching completion is determined when the vibration or sound frequency is in the specific frequency band. Therefore, the compression ratio switching vibration or switching sound is distinguished from the knocking vibration or sound. Therefore, it is possible to accurately determine the completion of the compression ratio switching.

  According to the third aspect of the present invention, since the crank angle of the internal combustion engine is detected by the crank angle detection means and the switching of the compression ratio is determined based on the crank angle when vibration or sound is detected, the compression ratio The switching vibration or switching sound can be distinguished from the knocking vibration or sound, and the completion of switching of the compression ratio can be accurately determined.

  According to the fourth aspect of the present invention, since the hidden Markov model is applied to the judging means, it becomes possible to distinguish between the switching vibration and the background vibration, and the compression ratio of each cylinder is analyzed by analyzing the crank angle. The completion of switching can be determined. Further, by utilizing the fact that the switching timing is limited, it is possible to ensure high determination accuracy regardless of the S / N ratio.

1 is a longitudinal sectional front view of a main part of an internal combustion engine provided with a variable compression ratio device (first embodiment). The exploded perspective view from the upper part of the above-mentioned compression ratio variable device (the 1st embodiment). The disassembled perspective view from the downward direction of the compression ratio variable apparatus (1st Embodiment). The principal part enlarged view of FIG. 1 (low compression ratio state) (1st Embodiment). FIG. 5 is a sectional view taken along line 5-5 in FIG. 4 (first embodiment). FIG. 6 is a sectional view taken along line 6-6 in FIG. 5 (first embodiment). FIG. 7 is a sectional view taken along line 7-7 in FIG. 5 (first embodiment). FIG. 8 is a sectional view taken along line 8-8 in FIG. 5 (first embodiment). FIG. 5 is a view corresponding to FIG. 4 showing a high compression ratio state (first embodiment). FIG. 10 is a sectional view taken along line 10-10 in FIG. 9 (first embodiment). FIG. 11 is a cross-sectional view taken along line 11-11 in FIG. 10 (first embodiment). FIG. 12 is a sectional view taken along line 12-12 of FIG. 10 (first embodiment). FIG. 13 is a sectional view taken along line 13-13 in FIG. 5 (low compression ratio state) (first embodiment). FIG. 14 is a diagram corresponding to FIG. 13 showing a high compression ratio state (first embodiment). 1 is a block diagram of a compression ratio switching completion change determination device (first embodiment). FIG. The figure which shows the change of the load which acts on a piston (1st Embodiment). The flowchart of fuel injection amount control and ignition timing control. A map for retrieving a target compression ratio (first embodiment). Explanatory drawing of the generation | occurrence | production time of the switching vibration of a low compression ratio-> high compression ratio (1st Embodiment). Explanatory drawing of the generation | occurrence | production time of the switching vibration of a high compression ratio-> low compression ratio (1st Embodiment). The flowchart of a compression ratio switching completion determination (1st Embodiment). Explanatory drawing of the crank angle which a compression ratio switching vibration generate | occur | produces (1st Embodiment). Explanatory drawing of the frequency band of the natural frequency of compression ratio switching vibration (1st Embodiment). The map which searches the threshold value of the vibration amplitude for compression ratio switching completion determination (1st Embodiment). Explanatory drawing of a hidden Markov model (2nd Embodiment). Explanatory drawing of the method of compression ratio switching determination (2nd Embodiment). The flowchart of compression ratio switching completion determination (2nd Embodiment).

  Hereinafter, a first embodiment of the present invention will be described with reference to FIGS.

  1 and 5, an engine body 1 of an internal combustion engine E includes a cylinder block 2 having a cylinder bore 2a, a crankcase 3 coupled to the lower end of the cylinder block 2, and a pent roof type connected to the upper end of the cylinder bore 2a. The cylinder head 4 has a combustion chamber 4a and is coupled to the upper end of the cylinder block 2. The cylinder head 4 is provided with an intake port 30i and an exhaust port 30e that open to the ceiling surface of the combustion chamber 4a. An intake valve 31i and an exhaust valve 31e that are opened and closed, and a spark plug 32 that faces an electrode at the center of the combustion chamber 4a are provided.

  A small end 7a of a connecting rod 7 is connected via a piston pin 6 to a piston 5 slidably fitted in the cylinder bore 2a, and a large end 7b of the connecting rod 7 is connected via a pair of left and right bearings 8 and 8. And connected to a crank pin 9a of a crank shaft 9 rotatably supported by the crank case 3.

  As shown in FIGS. 2 to 5, the piston 5 is slidably fitted to a piston inner 5 a connected to the small end portion 7 a of the connecting rod 7 through a piston pin 6 and an outer peripheral surface of the piston inner 5 a. The piston outer 5b has a top surface facing the combustion chamber 4a, and a plurality of piston rings 10a to 10c that are slidably in close contact with the inner peripheral surface of the cylinder bore 2a are mounted on the outer periphery of the piston outer 5b. Is done.

  The piston inner 5a slides on the inner peripheral surface of the cylinder bore 2a except for a pair of pin boss portions 11, 11 supporting both ends of the piston pin 6 and a portion corresponding to the outer ends of the pin boss portions 11, 11. A pair of arc-shaped skirt portions 12 and 12 that are freely fitted are integrally formed. The piston pin 6 is hollow.

  On the other hand, the piston outer 5b ends the peripheral wall on which the piston rings 10a to 10c are mounted at a position facing the upper end surface 12a of the skirt portions 12 and 12. The piston outer 5b is integrally formed with a pair of ear portions 13, 13 that are opposed to the outer ends of the pin boss portions 11, 11. These are provided with long holes 14 and 14 having a long diameter in the axial direction of the piston 5, and the long holes 14 and 14 have both end portions of the extension shaft 15 penetrating the hollow portion of the piston pin 6. The extension shaft 15 is slidably fitted along the axial direction of the piston 5 and is fixed to the piston pin 6 by press fitting or the like. Thus, by fitting the elongated holes 14 and 14 and the extension shaft 15, the piston inner 5 a and the piston outer 5 b are allowed to slide in the axial direction while being prevented from rotating relative to each other. , 14, the lower sliding limit of the piston inner 5 a with respect to the piston outer 5 b is regulated.

  A pair of inner sliding flat surfaces 23, 23 extending in the axial direction of the piston pin 5 are formed on both sides of the outer peripheral surface of the piston inner 5 a facing both end surfaces of the piston pin 6. , 23 are formed on the inner side surfaces of the ear portions 13, 13 of the piston outer 5b. The sliding flat surfaces 23, 24 are also formed on the piston inner 5a and the piston outer 5b. Relative sliding in the axial direction is allowed while preventing relative rotation. Therefore, the relative rotation of the piston inner 5a and the piston outer 5b is made strong by the fitting between the long holes 14, 14 and the extension shaft 15 and the contact between the inner and outer sliding flat surfaces 23, 24. Can be blocked.

  2, 3 and 5, the piston inner 5 a and the piston outer 5 b are formed by slidably fitting the extension shaft 15 and the long holes 14, 14 and a pair of arcuate surfaces 33 on the outer periphery of the piston inner 5 a. 33 and a slidable fitting of the inner peripheral surface 42a of the female spline 42 of the piston outer 5b, a sufficient axial relative sliding support length can be obtained, and stable axial relative sliding can be ensured. . The circular arc surfaces 33 and 33 are vertically formed so as to connect the upper end surfaces 12 a of the pair of skirt portions 12 and 12 and the first support surface 17.

  As clearly shown in FIG. 3 to FIG. 5, the upper part of the piston inner 5 a has an upward first annular support surface 17 in order from the outer peripheral side, and a first pivot that stands from the inner peripheral edge of the first support surface 17. 18, an annular second support surface 19 formed at the upper end of the first pivot 18, a second pivot 20 rising from the inner peripheral edge of the second support surface 19, and an upper end surface of the second pivot 20. An annular third support surface 21 is formed coaxially with the piston inner 5a. The second pivot 20 is divided into a plurality of blocks along the circumferential direction in order to reduce the weight, and an opening 22 is provided at the center of the second pivot 20 so that the small end 7a of the connecting rod 7 faces. The scattered lubricating oil generated in the crankcase 3, that is, in the crank chamber 3 a passes through the opening 22.

  An annular lock plate 25 mounted on the first support surface 17 is rotatably fitted to the first pivot 18 and is fitted to the second pivot 20 so as to face the upper surface of the lock plate 25. The annular first pressing plate 26 to be joined is fixed to the second support surface 19 by a plurality of screws 27, 27. Further, an annular lift member 28 placed on the first presser plate 26 is rotatably fitted to the second pivot 20, and a second presser plate 29 facing the upper surface of the inner peripheral edge of the lift member 28. Are fixed to the third support surface 21 by a plurality of screws 34, 34.

  The lift member 28 can reciprocate between a lift position B and a lift release position A set around the second pivot 20, and the piston outer 5 b is moved toward the piston inner 5 a with the reciprocal rotation. It constitutes a main part of a cam mechanism 37 that holds alternately at a position L (see FIGS. 4 and 5) and a high compression ratio position H (see FIGS. 9 and 10) near the combustion chamber 4a.

  That is, as shown in FIGS. 4, 5, and 8, the cam mechanism 37 includes the lift member 28 and a plurality of first cam peaks 38 in an annular arrangement that protrude integrally with the upper surface of the lift member 28. 38 ... and second cam peaks 39, 39 ... arranged in an annular arrangement projecting from the lower surface of the head portion of the piston outer 5b. Each of the cam peaks 38, 39 has a flat top surface. At the same time, both side surfaces aligned in the arrangement direction of the cam peaks 38 and 39 are formed in a rectangular cross-sectional shape that is a vertical surface with respect to the top surface.

  Thus, when the lift member 28 is in the lift release position A, the upper second cam peaks 39, 39... Can enter and leave the valley between the first cam peaks 38, 38. 13), the transition of the piston outer 5b to the low compression ratio position L or the high compression ratio position H is permitted. When the first and second cam peaks 38 and 39 mesh with each other and the top surface of at least one cam peak comes into contact with the valley bottom between the other cam peaks, the cam mechanism 37 is in an axially contracted state, and the piston outer 5b is lowered. A compression ratio position L is given.

  When the lift member 28 is at the lift position B, the first and second cam peaks 38 and 39 abut each other on a flat top surface (see FIG. 14), so that the cam mechanism 37 is in the axially expanded state. Thus, the high compression ratio position H is given to the piston outer 5b. At this time, the extension shaft 15 fixed to the piston pin 6 as described above comes into contact with the lower side surfaces of the long holes 14 and 14 of the ear portions 13 and 13 in the piston outer 5b, whereby the piston outer 5b is compressed at a predetermined high compression. Moving beyond the specific position H to the combustion chamber 4a side is prevented.

  As shown in FIGS. 4, 5, and 7, the lock plate 25 reciprocates between an unlock position C (see FIG. 12) and a lock position D (see FIG. 7) set around the first pivot 18. The main part of the lock mechanism 40 that holds the axially contracted state of the cam mechanism 37 at the lock position D is formed.

  That is, the lock mechanism 40 is formed on the inner periphery of the piston outer 5b so that the lock plate 25, the male spline 41 formed on the outer periphery of the lock plate 25, and the male spline 41 are slidably fitted. The female spline 42 and an annular lock groove 43 that allows the upper end of the groove portion of the female spline 42 to communicate with each other and allow the teeth of the male spline 41 to rotate and enter, and the piston outer 5b has a low compression. When the position is switched between the specific position L and the high compression ratio position H, the lock plate 25 is set to the unlock position C, the male spline 41 is placed in a sliding relationship with the female spline 42, and the piston outer When 5b comes to the low compression ratio position L, the lock plate 25 is rotated to the lock position D so that the tooth portion of the male spline 41 enters the lock groove 43, and the tooth portion of the male spline 41 and the female spline 41 By abutting the end faces to each other with the teeth portion of the in-42, a low compression ratio position L of the piston outer 5b is locked.

  As shown in FIGS. 2 and 10, in order to strengthen the pressing of the lock plate 25 by the first pressing plate 26, it is arranged in a plurality of grooves of the male spline 41 and supports the lower surface of the outer peripheral portion of the first pressing plate 26. Are formed integrally with the piston inner 5a, and the outer periphery of the first pressing plate 26 is fixed to the bosses 35, 35 with a plurality of screws 27 ', 27'. Of course, the bosses 35, 35... Are formed so as not to prevent the male spline 41 from turning to the unlocked position C and the locked position D.

The piston inner 5a is provided with first and second actuators 45 ₁ and 45 _{2 for} driving the lift member 28 and the lock plate 25, respectively, with reference to FIGS. 5, 6, 13 and 14. explain.

First, a description from the first actuator 45 _1. The piston inner 5 a has a bottomed cylinder hole 46 ₁ extending in parallel to one side of the piston pin 6, and a series of lengths penetrating the upper wall of the intermediate part of the cylinder hole 46 ₁ and the first pressing plate 26. A hole 47 ₁ is provided, and a pressure receiving pin 48 ₁ protruding from the lower surface of the lift member 28 faces the cylinder hole 46 ₁ through the long hole 47 ₁ .

The pressure receiving pin 48 _1, disc-shaped slider 49 ₁ to obtain play in the radial direction in the cylinder bore 46 within ₁ loosely fitted in the cylinder bore 46 ₁ is mounted for relative swinging. An operating plunger 50 ₁ and a bottomed cylindrical return plunger 51 ₁ are slidably fitted into the cylinder hole 46 ₁ with the slider 49 ₁ interposed therebetween. Accordingly, the slider 49 ₁ is interposed between the pressure receiving pin 48 ₁ and the operating plunger 50 ₁ and the return plunger 51 ₁ , but the pressure receiving pin 48 ₁ around the rotation center of the lift member 28. The arc motion is allowed by the slider 49 ₁ moving in the cylinder hole 46 ₁ while sliding between the actuating plunger 50 ₁ and the return plunger 51 ₁ . Moreover, since the contact between the pressure receiving pin 48 ₁ and the operation plunger 50 ₁ and the return plunger 51 ₁ is always surface contact, the wear resistance of the contact portion is ensured.

A hydraulic chamber 52 ₁ facing the inner end of the operating plunger 50 ₁ is defined in the cylinder hole 46 ₁ , and when hydraulic pressure is supplied to the hydraulic chamber 52 ₁ , the operating plunger 50 ₁ receives the hydraulic pressure and the slider 50 ₁ receives the hydraulic pressure. The lift member 28 is rotated to the lift position B via 49 ₁ and the pressure receiving pin 48 ₁ , and the elongated hole 47 ₁ has a size that does not hinder the movement of the pressure receiving pin 48 ₁ at that time. ing.

Also the open end of the cylinder bore 46 _1, the cylindrical spring holding tube 53 ₁ is engaged through the retaining ring 54 _1, between the plunger 51 ₁ returning said this spring holding cylinder 53 _1, its return spring 55 ₁ return for biasing the plunger 51 ₁ on the pressure receiving pin 48 ₁ side is provided in a compressed state.

Thus, the lift release position A of the lift member 28 is defined by the pressure receiving pin 48 ₁ coming into contact with the inner end wall of the elongated hole 47 _{1 on} the side of the actuating plunger 51 ₁ (see FIG. 13). position B is defined by the pressure receiving pin 48 ₁ comes into contact with the spring holding tube 53 ₁ through a slider 49 ₁ and return the plunger 51 ₁ (see FIG. 14).

Second actuator 45 _2, first actuator 45 ₁ and is axially symmetrical or point-symmetrically disposed across the piston pin 6, the pressure receiving pin 48 ₂ is protruded from the lower surface of the lock plate 25. Since the other configuration is the same as that of the first actuator 45 ₁ , in the drawing, the parts corresponding to the first actuator 45 ₁ are denoted by the same reference numerals with only the subscript “ ₂ ”, and the details thereof are described. Description is omitted.

Thus, unlocking position C of the lock plate 25, the pressure receiving pin 48 ₂ elongated hole 47 ₂ is defined by abutting the actuating plunger 50 ₂ side inner end wall, the locking position D of the locking plate 25, the pressure receiving is defined by the pin 48 ₂ is brought into contact with the spring holding cylinder 53 ₂ via the slider 49 ₂ and the return plunger 51 _2.

By the way, if the operation strokes of the pressure receiving pins 48 ₁ and 48 ₂ are defined by the inner end walls of the long holes 47 ₁ and 47 ₂ , the operation strokes of the pressure receiving pins 48 ₁ and 48 ₂ can be defined with high accuracy. If the operation strokes of the pressure receiving pins 48 ₁ and 48 ₂ are restricted by bringing the operation plungers 50 ₁ and 50 ₂ and the return plungers 51 ₁ and 51 ₂ into contact with the inner end walls of the cylinder holes 46 ₁ and 46 ₂ , respectively. The load can be removed from the pressure receiving pins 48 ₁ and 48 _{2 at} the operation limit of the pressure receiving pins 48 ₁ and 48 ₂ .

Thus, the first and second actuators 45 ₁ and 45 ₂ are configured to have substantially the same structure, and below the lift member 28 and the lock plate 25 that are stacked one above the other with the first pressing plate 26 interposed therebetween. It arrange | positions so that the axis line of piston inner 5a may be pinched | interposed. In addition, compatibility is given to parts corresponding to each other of the first and second actuators 45 ₁ and 45 ₂ . As a result, the components of the first and second actuators 45 ₁ and 45 ₂ can be shared, and the cost can be greatly reduced.

As shown in FIGS. 1 and 6, a cylindrical oil chamber 57 is defined between the piston pin 6 and the extension shaft 15 fitted in the hollow portion thereof. First and second distribution oil passages 58 ₁ , 58 ₂ connected to the hydraulic chambers 52 ₁ , 52 ₂ of the second actuators 45 ₁ , 45 ₂ are provided across the piston pin 6 and the piston inner 5a. The oil chamber 57 is connected to an oil passage 59 provided across the piston pin 6, the connecting rod 7 and the crankshaft 9. The oil passage 59 is connected to an oil pump 61 serving as a hydraulic pressure source via an electromagnetic switching valve 60, and The oil sump 62 is switchably connected. The oil sump 62 is an oil pan attached to the bottom of the crankcase 3, and therefore the lubricating oil of the internal combustion engine E is used as the operating oil for the first and second actuators 45 ₁ and 45 ₂ .

  In FIG. 4, the extension shaft 15 has a hollow portion 15b whose open surfaces at both ends are closed by end plates 15a and 15a. The hollow portion 15b is a piston through a through hole 16a in the central portion of the extension shaft 15. The hollow portion 15 b communicates with a cylindrical oil chamber 57 in the pin 6, and the hollow portion 15 b is inserted into the long holes 14, 14 of the ear portions 13, 13 through the injection holes 16 b, 16 b at both ends of the extension shaft 15. Communicated. At that time, it is desirable that the nozzle holes 16b at the respective ends of the extension shaft 15 are arranged so as to open toward the lower end surface of the corresponding long holes 14, and in the illustrated example, the nozzle holes 16b are arranged at the ends of the extension shaft 15. Even if the piston pin 6 rotates, at least one injection hole 16b is directed to the lower end surface of the long hole 14 even if the piston pin 6 rotates.

  As shown in FIG. 15, the internal combustion engine E is provided with vibration detecting means 71a for detecting the vibration and crank angle detecting means 71b for detecting the crank angle. A vibration detection circuit 72 is connected to the vibration detection means 71a, and the vibration detection circuit 72 includes a filter circuit 72a, a rectification detection circuit 72b, and a gain switching circuit 72c. Note that a knock sensor already provided in the internal combustion engine E can also be used as the vibration detecting means 71a, so that the number of parts and the cost can be further reduced.

  The vibration of the internal combustion engine E detected by the vibration detection means 71a is filtered by the filter circuit 72a, shaped by the rectification detection circuit 72b, and after gain adjustment by the gain switching circuit 72c, the crank angle detection means 71b is connected. It is output to the compression ratio switching determination completion circuit 73, where it is determined whether or not the compression ratio switching of the internal combustion engine E has been completed.

  Next, the operation of the embodiment of the present invention having the above configuration will be described.

  First, changes in the load acting on the piston outer 5b will be described with reference to FIG. The load acting on the piston outer 5b includes an in-cylinder pressure load based on the pressure of the combustion chamber 4a and an inertial force load based on the raising and lowering of the piston 5, and the load (hereinafter referred to as the load) acting on the piston outer 5b. , Referred to as piston load).

  The in-cylinder pressure suddenly increases during the compression stroke, reaches a peak value at the compression top dead center, then decreases rapidly during the expansion stroke, and reaches a bottom value of approximately atmospheric pressure at the bottom expansion dead point. It is maintained at a value near the bottom value in the intake stroke. Therefore, when the upward piston load is positive and the downward piston load is negative, the in-cylinder pressure load decreases rapidly from a substantially zero value in the compression stroke and reaches the bottom value at the compression top dead center. It rapidly increases in the expansion stroke, returns to a substantially zero value at the expansion bottom dead center, and is maintained at a substantially zero value in the subsequent exhaust stroke and intake stroke. On the other hand, the inertial load changes to a sine curve, increases from a negative value to a positive value in the compression stroke, decreases from a positive value to a negative value in the expansion stroke, increases from a negative value to a positive value in the exhaust stroke, and is inhaled. Decrease from positive value to negative value in the process.

  As a result, the piston load acting on the piston outer 5b becomes a positive value (upward) in the period from the second half of the exhaust stroke to the first half of the intake stroke through the exhaust top dead center, and becomes negative (downward) in the period before and after that. Become.

  As shown in FIGS. 3 to 8 and 13, the lift member 28 of the cam mechanism 37 is in the lift release position A, and the lock plate 25 is engaged with the lock groove 43. Is assumed to be held at the low compression ratio position L on the piston inner 5a side. Therefore, the compression ratio of the internal combustion engine E operated in this state is controlled to be relatively low.

In order to obtain a high compression ratio state in order to improve the output, for example, at high speed operation of the internal combustion engine E from such a state, the switching valve 60 is energized, that is, the on state, and the oil passage 59 is connected to the oil pump 61. Connecting. In this way, the hydraulic oil discharged from the oil pump 61 passes through the upstream oil passage 59a of the crankshaft 9, the downstream oil passage 59b of the connecting rod 7, the first and second distribution oil passages 58 ₁ and 58 ₂ , and the first and second distribution oil passages 58 ₁ and 58 _2. It is supplied to the hydraulic chambers 52 ₁ , 52 ₂ of the second actuators 45 ₁ , 45 ₂ .

Then, first, the pressure receiving pin 48 ₂ receive in conjunction with slider 49 ₂ hydraulic plunger 50 of the _second actuator 45 ₂ hydraulic chamber 52 ₂ of the hydraulic, so to press against the biasing force of the return spring 55 _2, receiving pin 48 ₂ rotates the lock plate 25 from the locking position D (see FIG. 7) to the unlocked position C (see FIG. 9), the female spline 42 of the male spline 41 and the piston outer 5b of the lock plate 25 The sliding fitting is possible.

  Therefore, the piston outer 5b moves to the high compression ratio position H by the action of the following piston load. That is, as explained with reference to FIG. 16, when the piston load that has been acting downward until then changes near the exhaust top dead center, the piston outer 5b moves away from the piston inner 5a toward the combustion chamber 4a. Accordingly, the extension shaft 15 that is displaced and supported by the piston inner 5a relatively descends the long holes 14 and 14 of the ear portions 13 and 13 of the piston outer 5b, and the lower end walls of the long holes 14 and 14 are moved downward. The piston outer 5b is prevented from being displaced at a predetermined high compression ratio position H.

Therefore, the movement limit of the piston outer 5b toward the high compression ratio position can be restricted without using a special stopper member, which can contribute to simplification of the structure of the device. Moreover, the impact at the time of restricting the movement limit of the piston outer 5b to the high compression ratio position side is directly transmitted from the piston outer 5b to the piston pin 6 via the long holes 14 and 14 and the extension shaft 15 that are in contact with each other. Since it is not transmitted to the piston inner 5a, it is possible to prevent the influence of the impact on the cam mechanism 37, the lock mechanism 40, the first and second actuators 45 ₁ , 45 _{2 and the} like provided in the piston inner 5a. Durability and operational stability can be ensured.

When the piston outer 5b comes to the high compression ratio position H, the first cam peaks 38, 38... Of the lift member 28 disengage from the valleys between the second cam peaks 39, 39. in 45 _1, already pushed against the urging force of the hydraulic chamber 52 actuating plunger 50 ₁ had received the oil pressure of ₁ returns the pressure receiving pin 48 ₁ with the slider 49 _first spring 55 _1, the lift member 28 It rotates from the lift release position A to the lift position B. Therefore, as shown in FIG. 14, the first cam peaks 38, 38... And the second cam peaks 39, 39. That is, the cam mechanism 37 is in the axially expanded state.

  In this way, the piston outer 5b is held at the high compression ratio position H by the axially expanded state of the cam mechanism 37 and the contact between the extension shaft 15 and the lower end walls of the elongated holes 14 and 14. Therefore, the piston inner and the outer 5a, 5b can move up and down in the cylinder bore 2a integrally while increasing the compression ratio, and can contribute to the improvement of the output performance of the internal combustion engine E. Moreover, in the cam mechanism 37, the contact surfaces of the top surfaces of the first and second cam peaks 38 and 39 in the annular arrangement that contact each other are evenly distributed over the entire circumference of the piston 5, and the total area thereof is wide. The cam mechanism 37 can sufficiently withstand a large in-cylinder pressure in the expansion stroke and compression stroke of the internal combustion engine E.

Next, in order to switch the internal combustion engine E from the high compression ratio state to the low compression ratio state again, the switching valve 60 is turned off, that is, a non-energized state, and the oil passage 59 is opened to the oil sump 62. Then, the hydraulic chambers 52 ₁ and 52 ₂ of the first and second actuators 45 ₁ and 45 ₂ connected to the downstream oil passage 59b are depressurized, and the pressure receiving pins 48 ₁ and 48 of the first and second actuators 45 ₁ and 45 ₂ are reduced. ₂ is placed under the control of return plungers 51 ₁ and 51 ₂ that receive the urging forces of the return springs 55 ₁ and 55 ₂ , respectively.

Thus, when the hydraulic pressure chamber 52 _1, 52 ₂ is depressurized, first, the first actuator 45 _1, returns the plunger 51 ₁ and pushed into the hydraulic chamber 52 ₁ side pressure receiving pin 48 ₁ with slider 49 _1, lift The member 28 is rotated to the lift release position A, and the first cam peaks 38, 38... And the second cam peaks 39, 39. When the piston load that has been acting upward until then changes in the vicinity of the suction bottom dead center, as shown in FIG. 13, the piston outer 5b has first cam peaks 38, 38... And second cam peaks 39. , 39..., 39 are meshed with each other and displaced so as to be close to the piston inner 5 a, and the top of one cam crest 39 hits the bottom of the valley between the other cam crests 38. Position L is determined

When the piston outer 5b reaches the low compression ratio position L, the male splines 41 of the lock plate 25, since it is possible enter the locking groove 43 of the piston outer 5b, the spring plunger 51 ₂ return of the second actuator 45 ₂ returns 55 the pressure receiving pin 48 ₂ with slider 49 _{2 2} with a force and pushes the hydraulic chamber 52 ₂ side, rotates the lock plate 25 to the locking position D, and the locking mechanism 40 in a locked state. That is, the male spline 41 of the lock plate 25 is opposed to the upper end surface of the female spline 42 of the piston outer 5b, thereby preventing the two splines 41 and 42 from sliding relative to each other.

  Next, control of the fuel injection amount and ignition timing of the internal combustion engine E will be described based on the flowchart of FIG.

  First, in step X1, the rotational speed and load of the internal combustion engine E, which are control parameters, are applied to the map of FIG. 18, and the target compression ratio (high compression ratio or low compression ratio) is retrieved. If the compression ratio is switched at the subsequent step X2, a compression ratio switching command is output at step X3, and it is determined at the subsequent step X4 that the switching of the compression ratio has been completed. At the subsequent step X5, the fuel injection amount and the ignition timing are determined. Is changed to a value corresponding to the compression ratio after switching.

  Next, determination of the completion of switching of the compression ratio of the internal combustion engine E in step X4 will be described.

  As described above, switching from the low compression ratio state to the high compression ratio state is completed near the exhaust top dead center after the switching command is output, and switching vibration is generated at that time (see FIG. 19). . Further, switching from the high compression ratio state to the low compression ratio state is completed in the vicinity of the intake bottom dead center after the switching command is output, and switching vibration occurs at that time (see FIG. 20). On the other hand, vibration due to knocking occurs in the latter half of the expansion stroke, and the generation timing is different from switching vibration. The frequency of the switching vibration is in a predetermined frequency band specific to each internal combustion engine E, and is different from the frequency band of knocking vibration. Therefore, it is possible to determine the completion of compression ratio switching based on the above two characteristics.

  When a compression ratio switching command is output in step Y1 of the flowchart of FIG. 21, vibration data in the region of the crank angles A1deg to A2deg detected by the crank angle detection means 71b in step Y2 is fetched from the vibration detection circuit 72. As shown in FIG. 22, the range of crank angles A1 deg to A2 deg is a region near the exhaust top dead center when the low compression ratio is switched to the high compression ratio, and the intake bottom dead center is switched when the high compression ratio is switched to the low compression ratio. This is the area near the point.

  In the next step Y3, the frequency analysis of the vibration waveform is performed by the compression ratio switching completion determination circuit 73, and in step Y4, the maximum value of the amplitude in the frequency band from B1 kHz to B2 kHz including the natural frequency of the switching vibration is calculated (see FIG. 23). ).

  If the maximum value of the amplitude exceeds the threshold value (see FIG. 24) set in accordance with the rotational speed of the internal combustion engine E in subsequent step Y5, it is determined in step Y6 that the compression ratio switching has been completed, and the threshold value If it does not exceed, it is determined in step Y7 that the switching of the compression ratio has not been completed.

  As described above, according to the present embodiment, there is no need to detect the piston position by the distance detection means or the in-cylinder pressure detection by the in-cylinder pressure detection means, and the degree of freedom of the attachment position and the attachment method is high. Completion of switching of the compression ratio can be determined using the vibration detecting means 71a that requires less modification to the internal combustion engine E. Further, if an existing knock sensor is used as the vibration detecting means 71a, it is not necessary to provide the special vibration detecting means 71a, and the cost can be reduced.

  Moreover, focusing on the fact that the compression ratio switching vibration frequency band is different from the knock vibration frequency band, and the compression ratio switching vibration generation timing is also different from the knock vibration generation timing, the compression ratio switching vibration is identified from the knock vibration. Therefore, it is possible to accurately determine the completion of the compression ratio switching.

  Next, a second embodiment of the present invention will be described with reference to FIGS.

  The second embodiment is another plan of step X4 (compression ratio switching completion determination) in FIG.

  In the present embodiment, the hidden Markov model used in the field of speech recognition is applied, and the switching completion of the compression ratio is determined by estimating the vibration at the time of switching.

  The hidden Markov model is a further expansion of the degree of freedom of a stochastic model that follows a Markov process. When the state transitions stochastically and cannot be observed directly from the outside, but only the output symbol is observable, by designing the model appropriately, the versatility by learning is high and the adjustment by the designer is possible. It is unnecessary and can exhibit high robustness even in an environment where the S / N ratio is poor.

For hidden Markov models,
Akio Ando, “Real-Time Speech Recognition”, The Institute of Electronics, Information and Communication Engineers, published on September 1, 2003, Shunichi Amari and three other authors, “Statistics of Pattern Recognition and Learning”, Iwanami Shoten Co., Ltd., April 2003 Issued on November 11 Kiyohiro Shikano and other four authors, “Speech Recognition System”, Ohm Co., Ltd., published May 15, 2001.

  As shown in FIGS. 25 and 26, in applying the hidden Markov model to the determination of the completion of the switching of the compression ratio, first, the vibration waveform at the time of switching and the background vibration waveform such as knocking and valve seating when there is no switching, A hidden Markov model database is constructed by measuring fundamental frequency and spectrum analysis in time series and learning its characteristics. Next, an algorithm for estimating whether or not it is a switching vibration is assembled by calculating the likelihood (probability) between the hidden Markov model generated from the input signal and the database model.

  That is, the vibration waveform is measured at step Z1 in the flowchart of FIG. 27, the feature quantity of each phase is calculated at step Z2, a hidden Markov model is generated at step Z3, the model generated at step Z4 and the model of the database The likelihood of is calculated. In the following step Z5, the likelihood Pb of the switching vibration is compared with the likelihood Pa of the background vibration, which is a threshold value. If (the likelihood Pb of the switching vibration) ≦ (the likelihood Pa of the background vibration), the step Z6 Thus, it is determined that the compression ratio is not switched, and if (switching vibration likelihood Pb)> (background vibration likelihood Pa), it is determined in step Z7 that the compression ratio is switched.

  When the compression ratio switching is determined from the likelihood Pb of the switching vibration in the step Z7, the hidden Markov model is re-learned and updated using the determined vibration data. As a result, the Hidden Markov Model is always kept in an optimal state, and can cope with individual variability and annual changes.

  As described above, according to the present embodiment, it is possible to distinguish between the compression ratio switching vibration and the background vibration using the hidden Markov model, and by analyzing by crank angle, the compression ratio of each cylinder is analyzed. The completion of switching can be determined. Furthermore, it is possible to ensure high determination accuracy regardless of the S / N ratio by utilizing the fact that the switching timing is limited.

  The embodiments of the present invention have been described above, but various design changes can be made without departing from the scope of the present invention.

  For example, in the embodiment, the vibration detection means 71a detects the vibration of the internal combustion engine E and performs the compression ratio switching completion determination. However, as shown in FIG. 15, the internal combustion engine E is generated instead of the vibration detection means 71a. A sound detection means 71c such as a microphone that detects sound waves to be detected is provided, and compression ratio switching completion determination can be made in the same manner as in the embodiment based on the frequency, generation time, and amplitude of the sound waves. When the sound detection means 71c is adopted, it can be provided away from the internal combustion engine E, so that the degree of freedom of the mounting position is further increased.

71a Vibration detection means 71b Crank angle detection means 71c Sound detection means 73 Compression ratio switching completion determination circuit (determination means)

Claims (4)

In a variable compression ratio internal combustion engine equipped with a variable compression ratio device capable of discretely switching the compression ratio,
Vibration / sound detection means (71a, 71c) for detecting vibration or sound accompanying the switching of the compression ratio, and determination means for determining completion of switching of the compression ratio based on the output of the vibration / sound detection means (71a, 71c) (73). A compression ratio switching determination device for a variable compression ratio internal combustion engine.   The compression in the variable compression ratio internal combustion engine according to claim 1, wherein the determination means (73) determines completion of switching of the compression ratio when the frequency of the vibration or the sound is in a specific frequency band. Ratio switching determination device.   Crank angle detection means (71b) for detecting the crank angle of the internal combustion engine is provided, and the determination means (73) determines completion of switching of the compression ratio based on the crank angle when the vibration or the sound is detected. The compression ratio switching determination device for a variable compression ratio internal combustion engine according to claim 1 or 2, characterized in that:   The compression ratio switching determination apparatus for a variable compression ratio internal combustion engine according to any one of claims 1 to 3, wherein a hidden Markov model is applied to the determination means (73).

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