JP2010180806A - Variable compression ratio device of internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To easily correct fluctuation of compression ratios of respective cylinders in a variable compression ratio mechanism. <P>SOLUTION: In the variable compression ratio device including the double-link type variable compression ratio mechanism in which a compression ratio is determined by a rotation position of a control shaft 18 having an eccentric shaft 19, the control shaft 18 includes separate members including a linearly continuous rod-like control shaft body 21, a cylinder member 22 attached to the control shaft body 21 and structuring the eccentric shaft 19. The control shaft body 21 includes a serration part 24 between journal parts 21 and a serration parallel with an axis is formed. The cylinder member 22 includes an attach hole 26 at a position eccentric in relation to a cylindrical outer peripheral surface 22a and a corresponding serration is formed on its inner peripheral surface. After temporarily assembling and measuring fluctuation of the compression ratios, the fluctuation of the compression ratios of the respective cylinders are decreased by reassembling the respective cylinder members 22 and changing a phase. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to a variable compression ratio device for an internal combustion engine using a multi-link type piston-crank mechanism, and more particularly to improvement of a control shaft thereof.

  In order to variably control the compression ratio of an internal combustion engine, a multi-link variable compression ratio device using a multi-link piston-crank mechanism is known, as exemplified in Patent Document 1. The piston and crankshaft of the internal combustion engine are connected via a plurality of link members, and are provided with a control link that restricts the degree of freedom of these link members. By changing the dynamic fulcrum position), the piston position is relatively displaced up and down to change the compression ratio. To change the control link swing fulcrum position, a control shaft having an eccentric shaft to which the control link base end is connected is used, and the rotational position of the control shaft is changed by an actuator such as an electric motor or a hydraulic mechanism. It is the composition which makes it.

  Further, Patent Document 2 applies a similar multi-link piston-crank mechanism to a fixed compression ratio engine, divides an auxiliary shaft corresponding to the control shaft for each cylinder, and finely adjusts each support position by a shim. A technique is disclosed in which the variation in the compression ratio of each cylinder is made small as possible.

JP 2002-215902 A JP 2007-231751 A

  In the multi-link variable compression ratio apparatus as described above, the compression ratio varies easily from cylinder to cylinder, and this must be dealt with by recombining the pistons with different heights.

  Further, the technique of Patent Document 2 is premised on a fixed compression ratio engine, and naturally cannot be applied to a variable compression ratio device that variably controls the compression ratio. If this is configured as a variable compression ratio device, an actuator is required for each cylinder.

  The present invention has a control link in which a piston and a crankshaft of an internal combustion engine are connected via a plurality of link members and limits the degree of freedom of these link members, and the base end of the control link is controlled A variable compression ratio device for an internal combustion engine is premised on that it is slidably connected to an eccentric shaft of the shaft and the compression ratio changes depending on the position of the eccentric shaft according to the rotational position of the control shaft by an actuator. The control shaft includes a control shaft main body that is linearly continuous and a cylindrical member that is attached to the control shaft main body and forms the eccentric shaft. A mounting hole is provided at an eccentric position, and the eccentric direction with respect to the control shaft main body can be adjusted.

  That is, the control shaft has a control shaft main body and a cylindrical member that are configured as separate parts, and the cylindrical member is fixed to the control shaft main body after adjusting the eccentric direction thereof. Therefore, the swing support position of the control link can be finely adjusted so as to cancel out an error in the actual compression ratio at a specific control position, for example, the highest compression ratio position or the lowest compression ratio position.

  According to the present invention, in a variable compression ratio device using a multi-link type piston-crank mechanism, the compression ratio can be easily finely adjusted.

Structure explanatory drawing which shows an example of the whole structure of a multilink type variable compression ratio apparatus. The exploded perspective view of a control axis. It is sectional drawing of the state which assembled | attached the cylindrical member, Comprising: (a) is a figure when assembled | attached in a standard position, (b) is a figure when assembled | attached by shifting 1 pitch. Explanatory drawing of the direction of the load which acts on a control shaft. The perspective view of the control-axis main body of 2nd Example. It is sectional drawing of the state which assembled | attached the cylindrical member in 2nd Example, Comprising: (a) is a figure when assembled | attached in a standard position, (b) is a figure when the phase of a cylindrical member is shifted.

  FIG. 1 shows an example of a basic configuration of a multi-link variable compression ratio device to which the present invention is applied. As shown in the figure, the piston 1 slides in a cylinder 6 formed in a cylinder block 5. The piston 1 is connected to one end of an upper link 11 through a piston pin 2 so as to be swingable. The other end of the upper link 11 is rotatably connected to one end portion of the lower link 13 via a first connecting pin 12. The lower link 13 is swingably attached to the crankpin 4 of the crankshaft 3 at the center thereof. The piston 1 receives combustion pressure from a combustion chamber defined above. The crankshaft 3 is rotatably supported on the cylinder block 5 by a crank bearing bracket 7.

  One end of a control link 15 is rotatably connected to the other end of the lower link 13 via a second connecting pin 14. The other end of the control link 15 is swingably supported by a part of the internal combustion engine body, and the position of the swing fulcrum 16 is displaced with respect to the internal combustion engine body in order to change the compression ratio. It is possible. Specifically, a control shaft 18 extending in parallel with the crankshaft 3 is provided, and the other end of the control link 15 is rotatably fitted to an eccentric shaft 19 provided eccentric to the control shaft 18. The control shaft 18 is rotatably supported between the crank bearing bracket 7 and the control bearing bracket 8.

  Therefore, when the control shaft 18 is rotationally driven by an actuator such as an electric motor (not shown) to change the compression ratio, the center position of the eccentric shaft 19 serving as the swing fulcrum 16 of the control link 15 moves relative to the engine body. . As a result, the motion restraint condition of the lower link 13 by the control link 15 changes, the stroke position of the piston 1 with respect to the crank angle changes, and consequently the engine compression ratio changes.

  The present invention is not limited to the specific type of multi-link variable compression ratio device as shown in the figure, but can be applied to various types of variable compression ratio devices using a multi-link type piston-crank mechanism. It is possible.

  FIG. 2 is an exploded perspective view of the control shaft 18 which is a main part of the present invention. As shown in the figure, the control shaft 18 has a rod-like control shaft main body 21 that is linearly continuous, and a number corresponding to the number of cylinders that are attached to the control shaft main body 21 and constitute the eccentric shaft 19 (1 in the figure). (Only one is shown) and the cylindrical member 22. The figure shows, as an example, a control shaft 18 for an in-line four-cylinder internal combustion engine. As described above, journal portions 23 that are pivotally supported between the crank bearing bracket 7 and the control bearing bracket 8 are provided at five locations. In addition, a serration portion 24 is formed between the journal portions 21. The serration portion 24 has serrations parallel to the central axis of the control shaft 18, and as shown in FIG. 3, a number of triangular cross-section teeth portions 24 a extending in the axial direction and valley portions therebetween. In particular, the teeth 24a and the valleys are formed at a constant pitch and the same cross-sectional shape over the entire circumference. Further, the bottom of the valley portion is substantially equal to the diameter of the journal portion 21, and the tooth portion 24 a protrudes from the outer peripheral surface of the journal portion 21 to the outer peripheral side.

  On the other hand, the cylindrical member 22 has a cylindrical surface with an outer peripheral surface 22a and a mounting hole 26 at a position eccentric to the center of the outer peripheral surface 22a. A serration parallel to the axial direction corresponding to the serration of the serration portion 24 is formed on the inner peripheral surface of the mounting hole 26. That is, as shown in FIG. 3, a large number of triangular tooth portions 27a extending in the axial direction and valley portions therebetween are formed over the entire circumference, and these tooth portions 27a and valley portions are They are formed at the same pitch and the same cross-sectional shape over the entire circumference.

  In this embodiment, the end portion of the control link 15 is directly fitted to the outer peripheral surface 22a of the cylindrical member 22 serving as the eccentric shaft 19, but if necessary, the cylindrical member 22 and the control link 15 An appropriate bearing member may be interposed between the two.

  The cylindrical member 22 provided with serrations as described above is inserted into the control shaft main body 21 along the axial direction and assembled. In the variable compression ratio mechanism, in a multi-cylinder internal combustion engine, basically, the cylinder members 22 of all the cylinders are assembled so as to have the same eccentric direction. FIG. 3A shows a state assembled at such a standard position. In the drawing, in order to represent the respective rotational positions of the control shaft main body 21 and the cylindrical member 22, for convenience, one tooth portion 24a on the control shaft main body 21 side is provided with an index M1 and one tooth on the cylindrical member 22 side is illustrated. An index M2 is attached to the portion 27a. In consideration of workability in the assembly process, it is desirable to actually provide the control shaft main body 21 and the cylindrical member 22 with indexes similar to these indexes M1 and M2.

  In the standard position of FIG. 3A, the two indexes M1 and M2 are adjacent to each other. On the other hand, FIG. 3B shows a state in which the phase of the cylindrical member 22 is shifted in the arrow direction and assembled by one pitch of serration compared to the standard position. When assembled with the phase changed in this way, in the variable compression ratio mechanism as shown in FIG. 1, the position of the swing fulcrum 16 of the control link 15 when the control shaft 18 is at a certain rotational angle position, that is, the center of the control shaft 18 The amount of eccentricity differs from the standard position, and as a result, the compression ratio slightly changes. Therefore, by using this, the compression ratio can be finely adjusted so that the variation in the compression ratio of each cylinder becomes small.

  As a specific work procedure, the control shaft 18 in which each cylindrical member 22 is assembled at the standard position as described above is once assembled to the above-described variable compression ratio device and temporarily assembled together with the cylinder head and the cylinder block. . Then, the compression ratio is inspected for each cylinder, the variation is measured, and the control shaft 18 becomes a standard compression ratio, for example, the highest compression ratio, the lowest compression ratio, or the most frequently used common compression ratio. At this position, the necessary phase difference (that is, the number of pitches to be shifted) of the cylindrical member 22 is calculated so that the compression ratios of the respective cylinders have substantially the same compression ratio. Based on this, after taking out the control shaft 18 from the variable compression ratio device, the cylindrical member 22 of each cylinder is re-assembled into the control shaft main body 21 with the phase shifted by the required number of pitches. Then, after the final assembly, the variation in the compression ratio of each cylinder is inspected again.

  Note that the cylindrical member 22 can be moved in the axial direction when it is simply inserted into the control shaft main body 21, but if necessary, the cylindrical member after final adjustment using a fixing member such as a knock pin or a snap ring. You may fix so that 22 may not move to an axial direction. Alternatively, a thrust bearing that regulates the axial position of the cylindrical member 22 may be provided on the bearing mechanism side with respect to the journal portion 21, and the control shaft main body 21 and the cylindrical member 22 may be used without being particularly fixed.

  FIG. 4 shows the multi-link type piston-crank mechanism of FIG. 1 as a so-called skeleton diagram. As can be easily understood from this figure, the combustion load acting on the piston 1 of the engine is controlled by the control link 15. As shown by the arrow F in FIG. Here, the solid line in the skeleton diagram corresponds to the highest compression ratio position, and the broken line in the skeleton diagram corresponds to the lowest compression ratio position, as shown, between the highest compression ratio position and the lowest compression ratio position. Since the control shaft 18 rotates only about 90 ° or more, even if the number of pitches of the cylindrical member 22 is slightly changed, there is no change in the tendency of the eccentricity to increase monotonously. If the phase of the cylindrical member 22 is adjusted so that the actual compression ratio becomes uniform, the variation in the compression ratio is reduced over the entire range from the highest compression ratio to the lowest compression ratio.

  In the above embodiment, the engagement of the control shaft main body 21 and the cylindrical member 22 is serration, but it can be replaced with a spline.

  Next, FIG. 5 and FIG. 6 show a second embodiment of the present invention. In this embodiment, the serration in the serration portion 24 of the control shaft main body 21 is spiral, corresponding to this. The serration in the mounting hole 26 of the cylindrical member 22 is also spiral. Therefore, the eccentric direction of the cylindrical member 22 can be continuously changed by moving the cylindrical member 22 along the spiral with respect to the control shaft main body 21. FIG. 6 shows that the cylindrical member 22 is rotated in the arrow direction (clockwise direction) from the standard position shown in FIG. 6A, as is clear from the position of the index M2 attached to the cylindrical member 22 for reference (b). The example adjusted to the position shown in FIG. In this embodiment, the amount of eccentricity, that is, the compression ratio can be continuously finely adjusted, and in particular, an amount smaller than one serration pitch can be adjusted. When the necessary adjustment amount is large, the cylindrical member 22 can be extracted once and reassembled at a position shifted by one pitch, as in the above-described embodiment. Accordingly, it is sufficient that the amount of displacement in the rotational direction by the spiral is one pitch of serration, and the helix angle of the spiral can be set relatively small. Therefore, the axial component force with respect to the combustion load from the control link 15 is relatively small.

  In this embodiment, it is desirable to fix the finally adjusted cylindrical member 22 to the control shaft main body 21 with a knock pin or the like.

  In the above embodiment, the meshing between the control shaft main body 21 and the cylindrical member 22 is a helical serration. However, instead of this, a helical spline may be used.

DESCRIPTION OF SYMBOLS 1 ... Piston 3 ... Crankshaft 11 ... Upper link 13 ... Lower link 15 ... Control shaft 18 ... Control shaft 19 ... Eccentric shaft 21 ... Control shaft main body 22 ... Cylindrical member 24 ... Serration part 26 ... Mounting hole

Claims (6)

A piston and a crankshaft of an internal combustion engine are connected via a plurality of link members, and have a control link that limits the degree of freedom of these link members, and the base end of the control link is an eccentric shaft of the control shaft A variable compression ratio device for an internal combustion engine, wherein the compression ratio changes depending on the position of the eccentric shaft according to the rotational position of the control shaft by an actuator.
The control shaft is composed of a linearly continuous control shaft main body and a cylindrical member which is attached to the control shaft main body and constitutes the eccentric shaft, and the cylindrical member is eccentric with respect to the outer peripheral edge. A variable compression ratio device for an internal combustion engine, characterized by having an attachment hole at a position and adjusting an eccentric direction with respect to a control shaft main body.   2. The variable compression ratio device for an internal combustion engine according to claim 1, wherein an outer peripheral edge of the cylindrical member forms a cylindrical surface, and a base end of the control link is slidably fitted therein.   2. A linear serration or spline that can be engaged with each other at an arbitrary relative angular relationship is provided on the inner peripheral surface of the mounting hole and the outer peripheral surface of the control shaft corresponding thereto. 3. A variable compression ratio device for an internal combustion engine according to 2.   2. A spiral serration or spline is provided on the inner peripheral surface of the mounting hole and the outer peripheral surface of the control shaft corresponding to the mounting hole, and the eccentric direction can be adjusted along the spiral serration or spline. Or a variable compression ratio device for an internal combustion engine according to 2;   The variable compression ratio device for an internal combustion engine according to any one of claims 1 to 4, wherein the control shaft main body is provided with a plurality of cylindrical members corresponding to the number of cylinders. .   6. The variable compression ratio device for an internal combustion engine according to claim 5, wherein an eccentric direction of each cylindrical member with respect to the control shaft main body is adjusted so as to cancel a variation in compression ratio of each cylinder.

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