JP2010248954A - Variable compression ratio device for internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To correct variation in compression ratio of respective cylinders in a variable compression ratio mechanism. <P>SOLUTION: A variable compression ratio device includes the double link type variable compression ratio mechanism, in which a compression ratio is determined by the rotation position of a control shaft 18 equipped with an eccentric shaft. The control shaft 18 comprises separate members of a control shaft body 21 of a linearly-continuing-bar shape and a cylindrical member 22 attached to the control shaft body 21 and forming the eccentric shaft. The cylindrical member 22 includes a first part 22A supporting a control ling 15 and a second part 22B having mounting and adjusting functions with respect to the control shaft body 21, and is fixed to the control shaft body 21 by fastening a movable part 30 cut out by slits 28, 29 with a bolt 31 and a nut 32. The central part of the bolt 31 is exposed inside a mounting hole 27 and is meshed with a female screw 25 of a recessed groove shape on the outer peripheral surface of the control shaft body 21, and therefore the mounting position of the cylindrical member 22 can be adjusted through rotational manipulation of the bolt 31. <P>COPYRIGHT: (C)2011,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 linearly continuous control shaft main body, and a cylindrical member that is inserted through the control shaft main body to form the eccentric shaft. A mounting hole is provided at an eccentric position, and at least a part in the axial direction is cut into a C shape by a slit extending in the axial direction so as to be elastically deformable, and a bolt arranged so as to cross the slit is tightened As a result, it is fixed to the control shaft body.

  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, fine adjustment of the compression ratio can be easily performed.

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. The perspective view which shows a cylindrical member with a control link edge part. The same perspective view seen from the direction different from FIG. Sectional drawing along a volt | bolt. Explanatory drawing of the direction of the load which acts on a control shaft.

    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. In the figure, a part of the length of the control shaft main body 21 is omitted. For example, in the case of the control shaft 18 for an in-line four-cylinder internal combustion engine, the crank bearing bracket 7 and the control bearing bracket 8 are used as described above. Are provided at five locations, and cylindrical members 22 are attached between the journal portions 21, respectively. Here, at positions corresponding to the respective cylindrical members 22 on the outer peripheral surface of the control shaft main body 21, female screw portions 25 for position adjustment described later are formed in a concave groove shape along the circumferential direction.

  The cylindrical member 22 has an outer peripheral surface 22a having a perfect circular cylindrical surface, and the other end of the control link 15 is rotatably fitted as shown in FIGS. A perfect circular mounting hole 27 is formed at a position eccentric to the center of the outer peripheral surface 22a. The diameter of the mounting hole 27 is set so that it can be slidably inserted into the control shaft body 21 and the gap becomes as small as possible. In addition, the axial dimension of the cylindrical member 22 is larger than the axial dimension of the end portion of the control link 15, and when combined with the control link 15, the half of the length of the cylindrical member 22 is the control link 15. Projects from the end face. That is, the cylindrical member 22 can be seen in the axial direction by being divided into two parts, ie, the first portion 22A and the second portion 22B, and the first portion 22A is mainly used as the eccentric shaft 19 as the control link 15. The end portion is supported, and the second portion 22 </ b> B mainly has an attachment / adjustment function for the control shaft main body 21.

  An axial slit 28 extending in the axial direction from the end surface of the cylindrical member 22 is formed along the radial direction of the mounting hole 27 at one end of the cylindrical member 22 serving as the second portion 22B. That is, when the cylindrical member 22 is viewed in the axial direction, the cylindrical member 22 is cut into a substantially C shape by the axial slit 28. The axial slit 28 reaches an intermediate portion in the axial direction of the cylindrical member 22, and a circumferential slit 29 is further continuous at the tip thereof. The circumferential slit 29 extends along the axis orthogonal plane of the mounting hole 27 and extends in the circumferential direction of the cylindrical member 22 over an appropriate angle range (for example, about 90 ° to 180 °). As an example, the circumferential slit 29 extends in an angular range of 180 °, and the axial slit 28 that is the starting point of the circumferential slit 29 is the thickest circumferential position due to the eccentricity of the mounting hole 27 (that is, The position is 180 degrees different from the eccentric direction. Accordingly, the tip 29 a (see FIG. 3) of the circumferential slit 29 reaches the circumferential position where it is the thinnest due to the eccentricity of the mounting hole 27.

  By providing the axial slit 28 and the circumferential slit 29 in this way, a portion of about 180 ° in the second portion 22B is separated from the remaining portion including the first portion 22A as the movable portion 30 and has a diameter. Elastically deformable in the direction. The cylindrical member 22 is manufactured from a suitable steel and subjected to heat treatment necessary for ensuring strength and rigidity, but the tip 29a of the circumferential slit 29 reaches the thinnest part of the cylindrical member 22, Since the movable portion 30 tends to be displaced with this thin portion as a swing fulcrum, the movable portion 30 can be elastically deformed easily. As can be easily understood, the slit width of the circumferential slit 29 may be as small as possible, but the axial slit 28 can only allow the necessary displacement of the movable portion 30. The slit width is required.

  In order to tighten the movable part 30 in the radial direction, a bolt 31 and a nut 32 that are orthogonal to the axial slit 28 are provided on the thick part side of the cylindrical member 22. The bolt 31 is inserted into a bolt through hole 34 (see FIG. 5) formed along the tangential direction of the mounting hole 27 so as to cross the axial slit 28, and a head 35 having a hexagonal hole 35a is formed. The nut 32 abuts against the seating surface 39 at the other end of the mounting hole 27 via the washer 36 and the nut 32 abuts against the seating surface 39 at the other end of the mounting hole 27. Further, the bolt 31 has a first screw portion 31A having a small diameter at a tip portion and a second screw portion 31B having a large diameter at an intermediate portion. The nut 32 is screwed into the first screw portion 31A on the distal end side. A deformed portion 38 for rotating the bolt 31 is provided at the tip of the bolt 31 protruding from the nut 32. As the deformed portion 38, for example, a prismatic protrusion or a rectangular recess having an appropriate shape can be used. However, in the illustrated example, a flat prismatic protrusion that can be picked with an appropriate tool is used. ing.

  By tightening the movable portion 30 in the inner diameter direction with the bolt 31 and the nut 32, the inner peripheral surface of the mounting hole 27 in the second portion 22B comes into pressure contact with the outer peripheral surface of the control shaft main body 21, and the cylindrical member 22 is caused by the frictional force thereof. Can be fixed in a desired posture. An appropriate frictional force enhancer (for example, a medium strength anaerobic screw locking agent is preferable) is applied between the inner peripheral surface of the mounting hole 27 and the outer peripheral surface of the control shaft main body 21. You may make it do.

  By the way, in this embodiment, the bolt through hole 34 of the bolt 31 is provided at a position slightly interfering with the diameter of the mounting hole 27. Therefore, as shown in FIGS. An elongated opening 41 is formed between the side surface 34 and the mounting hole 27, and the second threaded portion 31 </ b> B of the bolt 31 projects into the mounting hole 27 through the opening 41. . The female screw portion 25 on the outer peripheral surface of the control shaft main body 21 described above is formed corresponding to the bolt 31 exposed from the opening 41, and has a concave groove shape along the circumferential direction. A thread corresponding to the second screw portion 31B is engraved. As shown in FIG. 5, the female screw portion 25 extends in an arc shape in the cross section of the control shaft main body 21, and the second screw portion 31 </ b> B of the bolt 31 is engaged with the screw thread on the inner surface thereof. . Therefore, when the bolt 31 is rotated, the bolt 31 along the tangential direction of the control shaft main body 21 tries to move linearly with respect to the female screw portion 25, so that the cylindrical member 22 moves in the circumferential direction with respect to the control shaft main body 21. . Thereby, it is possible to adjust the circumferential mounting position of the cylindrical member 22.

  That is, for example, in the case of an in-line four-cylinder internal combustion engine, four cylindrical members 22 are provided, but when assembling with respect to the control shaft main body 21, the individual phases can be assembled while being finely adjusted from the reference 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 reference 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.

  Here, the bolt 31 is arranged generally along the vertical direction of the internal combustion engine, like the control link 15. In particular, the head 35 of the bolt 31 faces the upper side of the engine and includes a nut 32. Is arranged so as to face down the engine.

  The assembly of the piston 1 of the internal combustion engine and the cylinder block 5 of the above-described variable compression ratio device is performed from the crankcase side, for example, with the engine (cylinder block 5) in an inverted position. The control shaft 18 is incorporated in the cylinder block 5 in a state in which each cylindrical member 22 is inserted into the control shaft main body 21 and the control link 15 is assembled. Then, in order to finely adjust the compression ratio of each cylinder, the bolt 31 is rotated using the deformed portion 38 at the tip, and the mounting position of the cylindrical member 22 of each cylinder with respect to the control shaft main body 21 is adjusted. When the position of each cylindrical member 22 is determined, the cylindrical member 22 is firmly fixed to the control shaft main body 21 by rotating and tightening the nut 32. Since the nut 32 and the deformed portion 38 are located toward the lower surface side of the cylinder block 5, the work can be easily performed from the crankcase side. It is also possible to adjust the compression ratio using the bolt 31 described above, and in this case, the compression ratio can be adjusted without removing the control link 15.

  As an example of a specific work procedure for adjusting the compression ratio, the control shaft 18 in which each cylindrical member 22 is once assembled at the reference position is temporarily assembled together with the cylinder head and the cylinder block as the above-described variable compression ratio device. 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 of the cylindrical member 22 is calculated so that the compression ratio of each cylinder becomes substantially the same compression ratio. Based on this, the mounting position of the cylindrical member 22 of each cylinder is corrected by the rotation operation of the bolt 31, and after the final assembly, the variation in the compression ratio of each cylinder is inspected again.

  In addition, after the final compression ratio adjustment is completed, since the frequency of needing readjustment of the bolt 31 is low, there is no problem even if the frictional force enhancer is applied as described above.

  FIG. 6 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 circumferential position of the cylindrical member 22 is slightly changed, there is no change in the tendency of the amount of eccentricity to increase monotonously. If the phase of the cylindrical member 22 is adjusted so that the actual compression ratio of the cylinder is uniform, the variation in the compression ratio is reduced over the entire range from the highest compression ratio to the lowest compression ratio.

  The combustion load F acts on the eccentric shaft 19, that is, the cylindrical member 22 in the rotational direction. In the above configuration, the inner peripheral surface of the cylindrical member 22 and the outer peripheral surface of the control shaft main body 21 that are tightened in the radial direction by the bolts 31. The torque due to the combustion load F is supported by the frictional force between them. That is, the engagement between the bolt 31 and the female screw portion 25 is used for adjusting the position of the cylindrical member 22, and there is no problem such as rattling of the cylindrical member 22 due to the backlash.

  Note that, in the configuration in which the control shaft main body 21 and the cylindrical member 22 are separate members as described above, the control shaft main body 21 has a simple rod shape, so that compared to the conventional configuration in which the eccentric shaft 19 is integrally provided, For example, there is an advantage that deformation (bending) does not occur when the quenching process is performed, and the correction process is unnecessary.

  As mentioned above, although one Example of this invention was described, this invention is not limited to the said Example, A various change is possible. For example, in the said Example, although the 1st thread part 31A and the 2nd thread part 31B of the volt | bolt 31 are the screws from which a diameter differs, both are comprised as the substantially continuous same screw. Is also possible. Further, the circumferential slit 29 may be omitted or shorter. The cylindrical member 22 has a first portion 22A that supports the end portion of the control link 15 as the eccentric shaft 19 and a second function of attaching and adjusting the control shaft main body 21 in order to facilitate processing. The portion 22B includes the same outer peripheral surface and inner peripheral surface (mounting hole 27). However, the present invention is not limited to this, and both may have different shapes. In the second portion 22B, The outer peripheral surface may be concentric with the inner peripheral surface (mounting hole 27).

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 25 ... Female thread part 27 ... Mounting hole 28 ... Axial slit 29 ... Slit in the circumferential direction 31 ... Bolt 32 ... Nut

Claims (7)

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 that is inserted through the control shaft main body and constitutes the eccentric shaft,
The cylindrical member has a mounting hole at a position eccentric with respect to the outer peripheral edge, and at least a part in the axial direction is cut into a C shape by a slit extending in the axial direction and can be elastically deformed. A variable compression ratio device for an internal combustion engine, wherein the variable compression ratio device is fixed to the control shaft body by tightening bolts arranged to cross.   The axial slit is provided with a slit extending in the axial direction from one end of the cylindrical member to an intermediate portion in the axial direction of the cylindrical member, and continuously extending in the circumferential direction. The variable compression ratio device for an internal combustion engine according to claim 1.   The variable compression ratio device for an internal combustion engine according to claim 1 or 2, wherein a friction force enhancing agent is applied between an inner peripheral surface of the mounting hole and an outer peripheral surface of the control shaft main body. The bolt includes a first threaded portion on the distal end side and a second threaded portion on the proximal end side than the first threaded portion, and is inserted into a bolt through hole along a tangential direction of the mounting hole. The cylindrical member is fastened and fixed by a nut that is screwed into the threaded portion of 1.
Further, the second threaded portion projects from the opening on the side surface of the bolt through hole into the mounting hole, and the second threaded portion is formed on the female threaded portion formed in the circumferential groove shape on the control shaft body. The variable compression ratio device for an internal combustion engine according to any one of claims 1 to 3, wherein the portions are engaged with each other.   5. The mounting position of the cylindrical member in the control shaft main body is adjusted in the circumferential direction by the second screw portion and the female screw portion by rotating the bolt with respect to the cylindrical member. A variable compression ratio device for an internal combustion engine as described.   The front end of the bolt to which the nut is screwed is provided with a deformed portion for rotating the bolt, and the front end of the bolt is directed downward of the internal combustion engine when the internal combustion engine is assembled. Item 6. The variable compression ratio device for an internal combustion engine according to Item 4 or 5.   The axial slit is disposed at a circumferential position that is relatively thick due to the eccentricity of the mounting hole with respect to the outer peripheral edge of the cylindrical member. A variable compression ratio device for an internal combustion engine as described.

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