JP2010203345A - Bearing structure for double link type internal combustion engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To avoid an increase of the dimension of a main bearing cap 24, and to fasten the main bearing cap with a bolt at a position near a bearing hole 25 for a crankshaft, in a double link type piston-crank mechanism including a control shaft. <P>SOLUTION: A main bearing cap 24 is fixed to a bulkhead 22 of a cylinder block 21, and a bearing hole 25 for a crankshaft is formed between them. A control shaft bearing cap 26 is fixed to the main bearing cap 24, and a bearing hole 27 for a control shaft is formed between them. Since the center O2 of the control shaft is offset with respect to one side from a position immediately below the center O1 of the crankshaft, an interface 35 between the main bearing cap 23 and the bulkhead 22 is inclined correspondingly. <P>COPYRIGHT: (C)2010,JPO&INPIT

Description

  The present invention relates to an improvement in the bearing structure of a crankshaft and a control shaft in an internal combustion engine using a multi-link type piston-crank mechanism.

  The present applicant has previously proposed various configurations using a multi-link piston-crank mechanism as a piston-crank mechanism of a reciprocating internal combustion engine (for example, Patent Documents 1 and 2). The upper link is connected to the piston via a piston pin, the lower link is connected to the upper link via the upper pin so as to be swingable, and is rotatably attached to the crank pin of the crankshaft. And a control link that is pivotally connected to the lower link via a control pin and has the other end pivotably supported by the internal combustion engine body. There are advantages that the stroke characteristics can be made close to simple vibrations and that the variable compression ratio mechanism can be configured by changing the support position of the control link. 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. 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.

  The control shaft is arranged in parallel with the crankshaft so as to be shared by a plurality of cylinders and is rotatably supported by the engine body. However, Patent Document 1 discloses a main bearing portion on the cylinder block side and the main bearing portion. A configuration is disclosed in which a crankshaft is supported between a main bearing cap to be attached and a control shaft is supported between the main bearing cap and a control shaft bearing cap attached to the main bearing cap.

  Patent Document 2 uses a ladder frame in which a plurality of main bearing caps are connected in the front-rear direction with a side wall forming a part of a crankcase, and a control shaft is provided between the ladder frame and the control shaft bearing cap. Is disclosed.

JP 2002-215902 A JP 2007-162637 A

  In the multi-link type piston-crank mechanism as described above, generally, the control shaft is not positioned directly below the crankshaft (specifically, its main journal portion), but is arranged offset to the left and right. Therefore, in the above conventional configuration, the bearing cap becomes a large-sized one that extends left and right, which contributes to an increase in the weight of the entire engine.

  In addition, since the main bearing cap needs to be fastened to the cylinder block side with a bolt at a position adjacent to the bearing hole, in Patent Documents 1 and 2, a bearing for a crankshaft in which one bolt is offset from each other. It is arranged between the hole and the bearing hole for the control shaft, but in order to insert the bolt through the two bearing holes in this way, the two bearing holes are relatively offset from side to side. It is necessary and the position of the control shaft is restricted. Also, if bolts are arranged on both sides of the two bearing holes without using the bolts passing between the two bearing holes, one bolt is a bearing for the crankshaft due to the offset of the bearing hole for the control shaft. The bearing hole for the crankshaft is greatly deformed when subjected to a combustion load or the like because it is far away from the hole.

  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 restricts the degree of freedom of these link members. It is premised on a multi-link internal combustion engine that is swingably connected to the eccentric shaft of the shaft and whose compression ratio changes according to the rotational position of the control shaft. The crankshaft is supported between a main bearing portion on the cylinder block side and a main bearing cap attached to the main bearing portion, and the control shaft is a control attached to the main bearing cap and the main bearing cap. It is bearing between the shaft bearing cap.

  In the present invention, a plane passing through the center of the crankshaft and perpendicular to the center axis of the cylinder is defined as a first reference plane, and a plane passing through the center of the crankshaft and parallel to the center axis of the cylinder is defined as a second reference plane. Sometimes, the center of the control shaft is offset to the left or right with respect to the second reference surface, and the joining surface of the cylinder block and the main bearing cap extends along the direction of the offset. Inclined with respect to the reference plane.

  For example, when the center of the control shaft is on the right side of the second reference plane, that is, when offset from the position just below the center of the crankshaft along the second reference plane in the counterclockwise direction, the joint surface is The first reference plane is inclined at an appropriate angle in the same counterclockwise direction. Due to this inclination, as the distance measured along the joint surface, the distance between the center of the crankshaft and the center of the control shaft is reduced, and the size of the main bearing cap necessary for including both is reduced. And when a bolt is arranged through the outside of the two bearing holes for bearing these two shafts, the span between the bolts can be made relatively short.

  According to the present invention, the main bearing cap can be reduced in size, the bolt can be disposed close to the bearing hole for the crankshaft, and deformation of the bearing hole due to combustion load or the like can be suppressed.

1 is a front view of an essential part of an internal combustion engine showing a first embodiment of a bearing structure according to the present invention. The front view of the principal part of the internal combustion engine which similarly shows 2nd Example. The front view of the principal part of the internal combustion engine which similarly shows 3rd Example. The front view of the principal part of the internal combustion engine which similarly shows 4th Example. The skeleton figure of a multiple link type piston-crank mechanism.

  Hereinafter, an embodiment of the present invention will be described in detail with reference to the drawings. In the following description, “up / down” basically refers to the vertical direction of the cylinder, and “left / right” means the left / right direction when the central axis of the cylinder is regarded as vertical. To do. Of course, the present invention is not necessarily limited to the configuration in which the cylinders are arranged vertically.

  First, the structure of a multi-link piston-crank mechanism in a multi-link internal combustion engine to which the bearing structure of the present invention is applied will be described with reference to the skeleton diagram of FIG. This is basically the same as that of Patent Documents 1 and 2 described above, and one end of the upper link 3 swings via a piston pin 2 to a piston 1 that slides up and down in a cylinder (not shown). Connected as possible. The other end of the upper link 3 is rotatably connected to one end of the lower link 5 via an upper pin 4. The lower link 5 is swingably attached to the crankpin 7 of the crankshaft 6 at the center thereof. Note that the lower link 5 is actually divided into two parts in the vertical and horizontal directions, and is integrated by a bolt (not shown). Further, the crankshaft 6 is rotatably supported by the cylinder block as will be described later, and in the illustrated example, the crankshaft 6 rotates around the point O1 in the arrow ω direction (that is, in the clockwise direction).

  One end of a control link 8 is rotatably connected to the other end of the lower link 5 via a control pin 9. The other end of the control link 8 is swingably supported by a part of the internal combustion engine body, and the position of the swing fulcrum can be displaced with respect to the internal combustion engine body in order to change the compression ratio. It has become. Specifically, a control shaft 10 extending in parallel with the crankshaft 6 is provided, and the other end of the control link 8 is rotatably fitted to an eccentric shaft 11 provided eccentric to the control shaft 10. The control shaft 10 is positioned below the crankshaft 6 and is rotatably supported so as to reciprocate at a predetermined angle as indicated by an arrow θ around a point O2 with a bearing structure described later. It is linked to an appropriate actuator mechanism (not shown).

  Therefore, when the control shaft 10 is rotationally driven by the actuator mechanism in order to change the compression ratio, the center position of the eccentric shaft 11 serving as the swing fulcrum of the control link 8 moves relative to the engine body. As a result, the motion constraint condition of the lower link 5 by the control link 8 changes, the stroke position of the piston 1 with respect to the crank angle changes, and the engine compression ratio is changed accordingly.

  In this embodiment, unlike the above-described Patent Documents 1 and 2, etc., the three points of the center of the upper pin 4, the center of the crank pin 7 and the center of the control pin 9 in the lower link 5 are aligned. Yes.

  When the rotation direction ω of the crankshaft 6 is viewed in the clockwise direction, the center O2 of the control shaft 10 is to the right of the center O1 of the crankshaft 6 (more specifically, to the right of the second reference plane described later). Further, the center of the eccentric shaft 11 in the control shaft 10 is arranged on the right side of the control shaft 10. That is, in the above-described multi-link type piston-crank mechanism, the combustion load acting on the piston 1 acts on the control link 8 as a tensile force upward in the figure, but the tensile force due to this combustion load acts against the control shaft 10. An eccentric shaft 11 is arranged so as to act as a clockwise torque.

  FIG. 1 shows a first embodiment of the bearing structure of the crankshaft 6 and the control shaft 10 described above. As shown in the figure, a main bearing portion 23 is provided at the center of the lower edge of the bulkhead 22 between the cylinders of the cylinder block 21, and a main bearing cap 24 having a rectangular shape is opposed to the main bearing portion 23. It is attached. The main bearing portion 23 and the main bearing cap 24 each have a semicircular recess, and a combination of both forms a true circular crankshaft bearing hole 25. The main journal portion of the crankshaft 6 is fitted into the bearing hole 25 via a bearing metal (not shown) and is thereby rotatably supported.

  The bottom surface 24a of the main bearing cap 24 is formed in a plane parallel to the top surface 24b of the main bearing cap 24, that is, the joint surface with the cylinder block 21, and a relatively small control shaft bearing cap 26 is attached thereto. ing. The bottom surface 24a of the main bearing cap 24 and the control shaft bearing cap 26 each have a semicircular recess, and a combination of both forms a true circular control shaft bearing hole 27. The journal portion of the control shaft 10 is fitted into the bearing hole 27 via a bearing metal (not shown) or directly, and is thereby rotatably supported. The control shaft bearing hole 27 has a smaller diameter than the crankshaft bearing hole 25, and accordingly, the dimension of the control shaft bearing cap 26 in the width direction is smaller than the dimension of the main bearing cap 24 in the width direction.

  Here, a plane that passes through the center O1 of the crankshaft 6 and is orthogonal to the center axis L1 of the cylinder (not shown) is defined as a first reference plane P1, and passes through the center O1 of the crankshaft 6 and is parallel to the center axis L1 of the cylinder. When the flat surface is the second reference plane P2, the center O2 of the control shaft bearing hole 27 is offset to the right of the second reference plane P2, as described above.

  Further, the crankshaft bearing hole 25 and the control shaft bearing hole 27 partially overlap each other on the projection projected along the center axis L1 of the cylinder. That is, the control shaft bearing hole 27 is offset from right below the crankshaft bearing hole 25 to the right side, but the offset is relatively small.

  The main bearing cap 24 and the control shaft bearing cap 26 are attached using three bolts 31, 32, 33 as a whole in the illustrated example, but the bolt 31 on the left side of the figure is the main bearing cap 24. The tip is threadably engaged with the bulkhead 22 of the cylinder block 21. That is, only the main bearing cap 24 is fastened to the cylinder block 21 side. The central bolt 32 passes through the control shaft bearing cap 26, and the tip portion is screwed into the main bearing cap 24. That is, the control shaft bearing cap 26 is fastened to the main bearing cap 24. The bolt 33 on the right side of the figure passes through both the control shaft bearing cap 26 and the main bearing cap 24, and the tip portion is screwed into the bulkhead 22 of the cylinder block 21. That is, the control shaft bearing cap 26 and the main bearing cap 24 are both fastened to the cylinder block 21 together.

  Here, the joint surface 35 between the upper surface 24b of the main bearing cap 24 and the bulkhead 22 of the cylinder block 21 is slightly inclined in the counterclockwise direction with respect to the first reference surface P1. The direction of this inclination corresponds to the direction of offset of the control shaft 10 with respect to the second reference plane P2. That is, in the illustrated example, the center O2 of the control shaft 10 is offset to the right side, that is, counterclockwise from the position immediately below the crankshaft 6 along the second reference plane P2. 35 is inclined counterclockwise from the first reference plane P1. This inclination direction is opposite to the rotation direction ω of the crankshaft 6. The inclination angle is determined when a plane that is orthogonal to the straight line L2 connecting the center O1 of the crankshaft 6 and the center O2 of the control shaft 10 and passes through the center O1 of the crankshaft 6 is defined as the third reference plane P3. In addition, the joint surface 35 is set so as to be positioned between the first reference surface P1 and the third reference surface P3. In other words, the bonding surface 35 is inclined with respect to the first reference plane P1 at an inclination angle equal to or less than the angle α from the second reference plane P2 to the straight line L2. In addition, such an inclination may form the whole lower surface of a half skirt type | mold cylinder block as an inclined surface, and it is good also considering only a part of bulk head 22 lower edge to which the main bearing cap 24 is attached as an inclined surface.

  As a result of the inclination of the joint surface 35 as described above, the minimum width direction dimension (along the joint surface 35) of the main bearing cap 24 that needs to include the crankshaft bearing hole 25 and the control shaft bearing hole 27 is required. The dimension in the width direction is relatively small. Since each bolt 31, 32, 33 is arranged perpendicular to the joint surface 35, the bolt 31 arranged adjacent to the left end of the crankshaft bearing hole 25 and the control shaft bearing hole 27 are arranged. The distance (the distance in the direction along the joint surface 35) between the bolt 33 arranged adjacent to the right end in the figure is shortened, and deformation of the crankshaft bearing hole 25 due to combustion load or the like is suppressed. The bolt 33 on the right side of the figure is farther from the center O1 of the crankshaft 6 than the bolt 31 on the left side of the figure. However, since the combustion load acts on the control shaft 10 in the tension direction (upward in the figure), there is no so-called opening. . On the other hand, the bolt 31 on the left side of the figure passes through only the main bearing cap 24 and is shorter in length than the bolt 33 on the right side. Can be maintained.

  Two bearing holes 25 and 27 are included between the central axes L3 and L4 of the bolts 31 and 33 located on the left and right of the crankshaft bearing hole 25 (including extensions thereof).

  Next, FIG. 2 shows a second embodiment of the bearing structure according to the present invention. In the second embodiment, the inclination of the joint surface 35 is larger than that in the first embodiment described above. In order to facilitate the comparison of each embodiment, the absolute positions of the crankshaft 6 and the control shaft 10 in the space are all drawn in the same manner in the first to fourth embodiments.

  In this embodiment, two planes that are orthogonal to two straight lines L5 and L6 that are in contact with both the crankshaft bearing hole 25 and the control shaft bearing hole 27 and that pass through the center O1 of the crankshaft 6 are the fourth. When the reference surface P4 and the fifth reference surface P5 are used, the joint surface 35 is located between the fourth reference surface P4 and the fifth reference surface P5. In particular, the joint surface 35 is located at the center of the two reference surfaces P4 and P5. In other words, the straight line L2 connecting the center O1 of the crankshaft 6 and the center O2 of the control shaft 10 and the joint surface 35 are orthogonal to each other, and the main bearing cap 24 and the control shaft bearing cap 26 basically have the above-described configuration. The shape is symmetrical with respect to the straight line L2.

  In the second embodiment, the main bearing cap 24 and the control shaft bearing cap 26 are attached using four bolts 31, 32, 33, and 34 as a whole, and a pair of bolts at the left end and the right end in the figure. 31 and 34 pass through only the main bearing cap 24, and the tip ends are screwed into the bulkhead 22 of the cylinder block 21. That is, only the main bearing cap 24 is fastened to the cylinder block 21 side. The pair of bolts 32, 33 in the center penetrate the control shaft bearing cap 26, and the front end portions are screwed into the main bearing cap 24. That is, the control shaft bearing cap 26 is fastened to the main bearing cap 24.

  In such a configuration, the main bearing cap 24 can be evenly fastened on both sides of the crankshaft bearing hole 25.

  FIG. 3 shows a third embodiment of the bearing structure according to the present invention. In the third embodiment, the inclination of the joint surface 35 is larger than that of the second embodiment described above. In this embodiment, two planes that are orthogonal to two straight lines L5 and L6 that are in contact with both the crankshaft bearing hole 25 and the control shaft bearing hole 27 and that pass through the center O1 of the crankshaft 6 are the fourth. When the reference surface P4 and the fifth reference surface P5 are used, the bonding surface 35 is located between the fourth reference surface P4 and the fifth reference surface P5. In particular, the bonding surface 35 is It coincides with the fourth reference plane P4. In other words, the joint surface 35 is orthogonal to the straight line L5 that contacts the left end of the crankshaft bearing hole 25 and the left end of the control shaft bearing hole 27.

  In the third embodiment, the main bearing cap 24 and the control shaft bearing cap 26 are attached using three bolts 32, 33 and 34 as a whole, and the bolt 32 on the left side of the figure is attached to the control shaft. Both the bearing cap 26 and the main bearing cap 24 are penetrated, and the tip portion is screwed into the bulkhead 22 of the cylinder block 21. That is, the control shaft bearing cap 26 and the main bearing cap 24 are both fastened to the cylinder block 21 together. The central bolt 33 passes through the control shaft bearing cap 26, and the tip portion is screwed into the main bearing cap 24. That is, the control shaft bearing cap 26 is fastened to the main bearing cap 24. The bolt 34 on the right side of the figure penetrates only the main bearing cap 24, and the tip end is screwed into the bulkhead 22 of the cylinder block 21. That is, only the main bearing cap 24 is fastened to the cylinder block 21 side.

  In such a configuration, the width-direction dimension required for the main bearing cap 24 (width-direction dimension along the joint surface 35) is further reduced, and the left and right bolts 32, 34 that fasten the main bearing cap 24 are cranked. The shaft bearing hole 25 can be disposed closer to the shaft bearing hole 25.

  Next, FIG. 4 shows a fourth embodiment of the bearing structure according to the present invention. In this embodiment, two planes that are orthogonal to two straight lines L5 and L6 that are in contact with both the crankshaft bearing hole 25 and the control shaft bearing hole 27 and that pass through the center O1 of the crankshaft 6 are the fourth. When the reference surface P4 and the fifth reference surface P5 are used, the bonding surface 35 is located between the fourth reference surface P4 and the fifth reference surface P5. In particular, the bonding surface 35 is It coincides with the fifth reference plane P5. In other words, the joint surface 35 is orthogonal to the straight line L6 that contacts the right end of the crankshaft bearing hole 25 and the right end of the control shaft bearing hole 27. Therefore, in this embodiment, the inclination of the joint surface 35 is larger than that of the first embodiment, but smaller than that of the second and third embodiments.

  In the fourth embodiment, the main bearing cap 24 and the control shaft bearing cap 26 are attached by using three bolts 31, 32, 33 as a whole, and the bolt 31 on the left side of the figure is the main bearing cap. Only the cap 24 is penetrated, and the tip portion is screwed into the bulkhead 22 of the cylinder block 21. That is, only the main bearing cap 24 is fastened to the cylinder block 21 side. The central bolt 32 passes through the control shaft bearing cap 26, and the tip portion is screwed into the main bearing cap 24. That is, the control shaft bearing cap 26 is fastened to the main bearing cap 24. The bolt 33 on the right side of the figure passes through both the control shaft bearing cap 26 and the main bearing cap 24, and the tip portion is screwed into the bulkhead 22 of the cylinder block 21. That is, the control shaft bearing cap 26 and the main bearing cap 24 are both fastened to the cylinder block 21 together.

  Also in this embodiment, as in the third embodiment, the width-direction dimension required for the main bearing cap 24 (the dimension in the width direction along the joint surface 35) is reduced, and the left and right bolts that fasten the main bearing cap 24 are reduced. 31 and 33 can be disposed close to the crankshaft bearing hole 25.

  In each of the above embodiments, the main bearing cap 24 is illustrated as an independent type. However, as disclosed in Patent Document 2 and the like, the present invention has a plurality of main bearing caps. The same applies to the case of using a ladder frame that is connected back and forth by side walls that form part of the case. In each of the above embodiments, the main bearing cap is fastened to the cylinder block side by a pair of left and right bolts, but may be fixed to the cylinder block by a larger number of bolts.

  Further, the present invention is not limited to the specific type of multi-link piston-crank mechanism as shown in FIG. 5, but is widely applied to internal combustion engines using various types of multi-link piston-crank mechanisms. It is possible to apply.

DESCRIPTION OF SYMBOLS 1 ... Piston 3 ... Upper link 5 ... Lower link 6 ... Crankshaft 8 ... Control link 10 ... Control shaft 21 ... Cylinder block 23 ... Main bearing part 24 ... Main bearing cap 25 ... Bearing hole for crankshaft 26 ... Control shaft bearing cap 27 ... Bearing hole for control shaft 31-34 ... Bolt 35 ... Joining surface

Claims (10)

A piston of an internal combustion engine and a crankshaft 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. In a multi-link internal combustion engine that is connected so as to be able to swing and whose compression ratio changes according to the rotational position of the control shaft,
The crankshaft is supported between a main bearing portion on the cylinder block side and a main bearing cap attached to the main bearing portion, and the control shaft is attached to the main bearing cap and the main bearing cap. Bearing between control shaft bearing cap,
When a plane passing through the center of the crankshaft and perpendicular to the center axis of the cylinder is a first reference plane, and a plane passing through the center of the crankshaft and parallel to the center axis of the cylinder is a second reference plane,
The center of the control shaft is offset to one of the left and right sides with respect to the second reference plane, and the joining surface of the cylinder block and the main bearing cap is aligned with the first reference plane along the offset direction. A bearing structure for a multi-link internal combustion engine, wherein the bearing structure is inclined with respect to the bearing.   A crankshaft bearing hole formed between the main bearing portion and the main bearing cap; and a control shaft bearing hole formed between the main bearing cap and the control shaft bearing cap. The bearing structure for a multi-link internal combustion engine according to claim 1, wherein the bearing structure partially overlaps when projected along the central axis of the cylinder.   The main bearing cap is fastened to the cylinder block by at least two bolts including a pair of bolts arranged on both sides of the bearing hole for the crankshaft, and passes through the center of the pair of bolts closest to the bearing hole. The bearing structure for a multi-link internal combustion engine according to claim 1 or 2, wherein a bearing hole for the control shaft is located between the two straight lines.   The compound bolt according to any one of claims 1 to 3, wherein at least some bolts of the plurality of bolts for fixing the control shaft bearing cap fasten the main bearing cap to the cylinder block together. Bearing structure of a link type internal combustion engine. When a plane perpendicular to the straight line connecting the center of the crankshaft and the center of the control shaft and passing through the center of the crankshaft is the third reference plane,
The bearing structure for a multi-link internal combustion engine according to any one of claims 1 to 4, wherein the joining surface is located between the first reference surface and the third reference surface. When two planes orthogonal to two straight lines contacting both the bearing hole for the crankshaft and the bearing hole for the control shaft and passing through the center of the crankshaft are the fourth and fifth reference planes,
The bearing structure for a multi-link internal combustion engine according to any one of claims 1 to 4, wherein the joining surface is located between the fourth reference surface and the fifth reference surface.   The bearing structure for a multi-link internal combustion engine according to any one of claims 1 to 6, wherein the joint surface is inclined with respect to the first reference surface in a direction opposite to a rotation direction of a crankshaft. .   The multi-link internal combustion engine according to any one of claims 1 to 7, wherein a plurality of main bearing caps are connected back and forth by side walls constituting a part of the crankcase, and are configured as a ladder frame. Engine bearing structure.   When the rotation direction of the crankshaft is viewed in the clockwise direction, the center of the control shaft is offset to the right of the second reference plane, and the center of the eccentric shaft of the control shaft is the center of the control shaft. The bearing structure for a multi-link internal combustion engine according to any one of claims 1 to 8, wherein the bearing structure is disposed on the right side. As the link member,
An upper link connected to the piston via a piston pin;
A lower link that is swingably connected to the upper link via an upper pin and is rotatably attached to the crankpin of the crankshaft, and the tip of the control link is swingably connected via a control pin. When,
10. The bearing structure for a multi-link internal combustion engine according to claim 1, wherein the centers of the upper pin, the crank pin, and the control pin are aligned in a straight line.

Images