JP2008075500A - Crankshaft supporting structure of engine - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a crankshaft supporting structure of an engine in which the total width dimension of particularly the crankcase portion is reduced and the increase of vibration and noise by an unbalance force between crankshafts are prevented by increasing the supporting rigidity of the crankshafts. <P>SOLUTION: One and the other side crankshafts 11, 12 are disposed at the positions apart from the center crankshaft 10 to the anti-cylinder side. A crankshaft supporting member 19 comprises a first supporting member 17 and a second supporting member 18 disposed between the first supporting member 17 and a case side supporting part 2e. The one and the other side crankshafts 11, 12 are supported on a first split surface of the first supporting member 17 and the second supporting member 18. The center crankshaft 10 is supported on the second split surface of the second supporting member 18 and the case side supporting part 2e. The first and second split surfaces are formed to extend parallel to each other. The second supporting member 18 is formed on the center side and one and the other side crankshafts 11, 12 by one common member. <P>COPYRIGHT: (C)2008,JPO&INPIT

Description

  The present invention relates to a crankshaft support structure for an engine having three crankshafts.

As a technique for increasing the engine output, for example, there are two crankshafts connected to each other by gears (see Non-Patent Document 1, for example).
Dictionary of History of Automotive Technology, Asakura Shoten, Kenji Higuchi, September 1996, first edition

  The conventional engine can increase the engine displacement and increase the engine output accordingly. However, the conventional crankshaft support structure supports two crankshafts using independent bearing caps, which increases the number of bolts required and increases the space required for tightening. There is a problem that the compactness of the dimension in the width direction is impaired. Furthermore, since the support rigidity of each crankshaft is low, there is a problem that vibration and noise due to the unbalance force between the crankshafts increase.

  The present invention has been made in view of the above-described conventional problems. In particular, even when the number of crankshafts is three, the overall width of the crankcase portion can be shortened, and the support rigidity of the crankshaft can be increased. An object of the present invention is to provide a crankshaft support structure for an engine that can increase the vibration and noise due to the unbalanced force between the crankshafts.

  The invention of claim 1 includes a center crankshaft, one side and another side crankshaft arranged in parallel to one side and the other side of the center crankshaft, and a crankshaft support member for supporting each crankshaft. In the engine crankshaft support structure provided, the one side crankshaft and the other side crankshaft are disposed at positions away from the central crankshaft on the side opposite to the cylinder, and the crankshaft support member includes: a first support member; A second support member disposed between the first support member and a case-side support portion formed on the crankcase, and the one-side and other-side crankshafts include the first member and the second support shaft. The center crankshaft is supported by one and other bearing portions formed on the first split surface with the support member, and the central crankshaft is formed on the second split surface between the second support member and the case side support portion. The first and second split surfaces are supported by bearings. Is formed so as to extend in parallel with each other, the second support member is characterized in that the central, one side, and a common one member to the other side crankshaft.

  The invention of claim 2 is characterized in that, in claim 1, the second support member is constituted by a plate-like member separate from the crankcase.

  The invention of claim 3 is characterized in that, in claim 1, the second support member is constituted by a low case forming a part of the crankcase.

  According to a fourth aspect of the present invention, in any one of the first to third aspects, the first support member is constituted by a single member common to one side and the other side crankshaft.

  According to a fifth aspect of the present invention, in the fourth aspect, the first and second support members include an outer bolt disposed outside the one side and the other side crankshaft, a central crankshaft and the one side and the other side crankshaft. It is characterized in that it is fastened and fixed to the case side support part by an inner bolt arranged between the two.

  According to the first aspect of the present invention, the one-side and other-side crankshafts are supported by the one-side and other-side bearing portions formed on the first split surfaces of the first support member and the second support member. Since the shaft is supported by the central bearing portion formed on the second split surface of the second support member and the case side support portion, and the first and second split surfaces are formed to extend in parallel with each other, The first and second split surfaces can be easily machined with high machining accuracy, and high arrangement accuracy of each crankshaft can be ensured. Further, since the first and second split surfaces are arranged in parallel, all the fastening bolts can be drilled and assembled from the same direction, and the manufacturing man-hours as a whole can be reduced.

  Further, since the second support member is composed of one member common to the center, one side, and the other side crankshafts, the support rigidity of the three crankshafts can be improved, and irregularities from the respective crankshafts can be obtained. Vibration and noise due to unbalanced force between the crankshafts caused by input can be reduced.

  Furthermore, since the one side and the other side crankshafts are arranged on one side, the other side and the lower side of the central crankshaft, the crankshafts are arranged in the engine width direction while avoiding interference between each crankshaft and the large end of the connecting rod. The crankcase portion of the engine can be made compact in width.

  According to the invention of claim 2, since the second support member is composed of a plate-like member that is separate from the crankcase, the shape and structure of the second support member are simple, and work and assembly work Is easy.

  According to the invention of claim 3, since the second support member is constituted by a lower case that forms a part of the crankcase, the wall portion that forms a part of the crankcase functions as a portion that functions as the second support member. As a result, the rigidity of the second support member itself is increased, and as a result, the support rigidity of the crankshaft can be further improved.

  According to the invention of claim 4, since the second support member common to the three crankshafts is fixed to the case side support portion by one first support member common to the one side and the other crankshaft, Since the rigidity of the first and second support members themselves is high, the support rigidity of each crankshaft can be further improved.

  According to the invention of claim 5, the first and second support members are arranged between the outer bolts arranged on the outer side of the one side and the other side crankshaft, and the center crankshaft and the one side and the other side crankshaft. Because it is fixed to the case side support part by fastening with the inner bolt arranged in the center bolt, the bolt for fixing the center crankshaft and the bolt for fixing the inner crankshaft on the one side and the other side are shared as the inner bolt. Accordingly, the number of bolts to be tightened can be reduced, and the number of bolt hole machining operations and assembly operations can be reduced accordingly.

Hereinafter, embodiments of the present invention will be described with reference to the accompanying drawings.
FIGS. 1-5 is a figure for demonstrating the multiple crankshaft engine which concerns on 1st Embodiment of this invention.

In the figure, 1 is a water-cooled 4-cycle 12-cylinder engine having a 3-year crankshaft. The engine 1 includes left and right cylinder portions 2a and 2b formed so as to form a symmetrical V bank, a cylinder block 2 having a crankcase portion 2c common to both cylinder portions, and the crankcase portion 2c. An oil pan 3 coupled to the lower mating surface 2d, left and right cylinder heads 4 and 5 coupled to the upper mating surfaces 2h and 2h of the left and right cylinder portions 2a and 2b, and the left and right cylinder heads. 4 and 5 and left and right head covers 6 and 7 mounted on the upper mating surfaces.

  Here, since the left and right cylinder portions 2a and 2b are symmetrical and have basically the same structure, the left cylinder portion 2a will be mainly described below, and the right cylinder portion 2b will be described as necessary.

  Inner and outer cylinder bores 8 and 9 are formed in the left cylinder portion 2a so as to be positioned on the inner and outer sides of the V bank. As shown in FIG. 1, the inner and outer cylinder bores 8 and 9 are formed such that their cylinder bore axes 8a and 9a are parallel to each other. As a result, the inner and outer cylinder bores 8 and 9 of the left cylinder portion 2a and the inner and outer cylinder bores 8 and 9 of the right cylinder portion 2b form a predetermined bank angle (for example, 60 °).

  As shown in FIGS. 1 and 4, the inner cylinder bore 8 and the outer cylinder bore 9 are positioned on the left crankshaft (counter crankshaft) 11 side, which will be described later, on the side wall of the inner cylinder bore 8 when viewed in the crankshaft direction. The portion j2 that is located on the side of the center crankshaft (mating crankshaft) 10 (to be described later) on the side wall of the outer cylinder bore 9 is adjacently disposed in the direction perpendicular to the crankshaft so as to overlap in the crankshaft direction.

  Further, the inner cylinder bore 8 and the outer cylinder bore 9 have the crankshaft end portion k2 of the inner cylinder bore 8 and the crankshaft end portion k1 of the outer cylinder bore 9 over each other when viewed in a direction perpendicular to the crankshaft and the cylinder bore axis. It is arranged close to the crankshaft so as to wrap.

  Furthermore, the cylinder head side mating surface 2h of the inner cylinder bore 8 and the outer cylinder bore 9 is orthogonal to the axes 8a and 9a of the cylinder bores 8 and 9, and forms the same plane across the cylinder bores.

  The cylinder bores 8 and 9 are staggered so as to be alternately positioned in the crankshaft direction as shown in FIG. 4 when viewed in the direction of the cylinder bore axes 8a and 9a. Specifically, in the left cylinder portion 2a, from the rear side of the engine, the outer cylinder bore 9, the inner cylinder bore 8, the outer cylinder bore 9,... And the crankshaft interval t1, t2,. Arranged at intervals in the direction perpendicular to the axis. On the other hand, in the right cylinder portion 2b, from the rear side of the engine, the outer cylinder bore 9 ′, the inner cylinder bore 8 ′,... They are arranged at intervals. Further, the cylinder bores 8 and 9 of the left cylinder part 2a are displaced by t3 as a whole from the right cylinder part 2b to the engine front side.

  As described above, the outer cylinder bores 9 and 9 'of the left and right cylinder portions 2a and 2b are disposed at the rear end of the cylinder block 2 of the engine 1 of the present embodiment 1 so as to be located outside the V bank. The inner cylinder bores 8 and 8 'are disposed so as to be deviated forward from the rear end portion in the longitudinal direction of the engine and located inside the V bank. Therefore, a relatively wide space A is formed at the rear end portion of the cylinder block 2 as indicated by hatching in FIG. In the present embodiment, a driving force transmission mechanism that transmits the driving force to the camshaft using the space A is disposed.

  The engine 1 according to this embodiment is a three-crankshaft engine having a plurality of crankshafts, specifically, a center crankshaft 10 and left and right crankshafts 11 and 12. The center crankshaft 10 is disposed in the center of the crankcase 2c of the cylinder block 2 in the engine width direction and perpendicular to the V bank bisector L. The left crankshaft 11 is disposed on the left side (one side) and below the central crankshaft 10, and the right crankshaft 12 is disposed on the right side (other side) and below the central crankshaft 10. The three crankshafts 10 to 12 are arranged so as to be parallel to each other and symmetrical. Accordingly, the central crankshaft 10 is located on the upper side, the left and right crankshafts 11 and 12 are located on the lower side, and a straight line connecting the axes of the crankshafts and the axis lines of the outer cylinder bores 9 and 9 '. 9a and 9a ′ form a W-shape, and the center crankshaft 10 and the axis lines 8a and 8a ′ of the inner cylinder bores 8 and 8 ′ form a V-shape.

  The outer cylinder bore 9 is offset by t5 from the plane B including the axis of the left crankshaft 11 or the right crankshaft 12 and parallel to the cylinder bore axis 9a to the inside of the V bank. The inner cylinder bore 8 is offset from the plane B ′ including the center of the central crankshaft 10 and parallel to the cylinder bore axis 8a by t6 to the outside of the V bank. Therefore, the interval t7 between the cylinder bores 8 and 9 is narrower by (t5 + t6) than the interval between the left and right crankshafts 11 and 12 and the central crankshaft 10.

  A left outer piston 13 disposed in the outer cylinder bore 9 of the left cylinder portion 2a is connected to the left crankshaft 11 by a left outer connecting rod 14. The left inner piston 15 disposed in the inner cylinder bore 8 of the left cylinder portion 2a is connected to the central crankshaft 10 by a left inner connecting rod 16. Similarly, the outer side of the right cylinder portion 2b, the right outer side and the inner pistons 13 'and 15' disposed in the inner cylinder bores 9 'and 8' are connected to the right crankshaft 12 by the outer and inner connecting rods 14 'and 16'. , Connected to the central crankshaft 10.

  Each of the crankshafts 10 to 12 includes a bearing wall portion (crankcase side support portion) 2e formed so as to form a vertical wall in the crankcase portion 2c of the cylinder block 2, and a tightening bolt on the bearing wall portion 2e. The bearing block 19 is supported by a bearing block 19 that is detachably tightened and fixed by 20a and 20b. Therefore, the bearing wall portion 2e and the bearing block 19 are divided into two vertically. As shown in FIG. 5, the bearing wall 2e of the cylinder block 2 defines the crankcase 2c in three crank chambers C1, C2, C3 having substantially the same size in the crankshaft direction. Are arranged as follows. The lower end surface of each bearing wall 2e is flush with the lower mating surface 2d, and a concave portion having a boundary wall 2f extending in the vertical direction and a split surface 2g extending in the horizontal direction is formed in the middle thereof. Has been.

  The bearing block 19 has a rectangular thick plate shape, and is divided into upper and lower blocks (first and second support members) 18 and 17 so that the bearing portion of the present embodiment as a whole. As seen, the bearing wall portion 2e is divided into an upper and lower block. Further, the end surface 19a of the upper block 17 in the direction perpendicular to the crankshaft (engine width direction) is positioned in the direction perpendicular to the crankshaft by a positioning portion 2f 'formed at the upper part of the boundary wall 2f.

  The central crankshaft 10 includes one relatively short front end journal portion 10a ′ corresponding to the thickness of the bearing wall 2e, three relatively long main journal portions 10a, and the front end side of each main journal portion 10. The three crank arm portions 10b are integrally formed with each other, and the crank pin portion 10c is integrally formed so as to connect the radially outer ends of the respective crank arm portions 10b. A counterweight portion 10b 'is formed on the opposite side of each crank arm portion 10b across the crank axis. Similarly, the left and right crankshafts 11 and 12 include one rear end journal portion 11a 'and 12a', three main journal portions 11a and 12a, crank arm portions 11b and 12b, and crank pin portions 11c and 12c. Counterweight portions 11b 'and 12b'.

  The front end journal portion 10a 'and the main journal portion 10a of the central crankshaft 10 are divided into two parts by a bearing hole g formed in the upper split surface 17b of the upper block 17 and the split surface 2g of the bearing wall 2e. It is pivotally supported via a plain bearing g ′. Further, the rear end journal portions 11a ', 12a' and the main journal portions 11a, 12a of the left and right crankshafts 11, 12 are provided with bearing holes h, formed in the split surfaces 17a, 18a of the upper and lower blocks 17, 18, respectively. It is pivotally supported by i through plain bearings h 'and i'.

  The front and rear journal portions 10a ', 11a', 12a 'of the crankshafts 10, 11, 12 and the bearing holes g, h, i that support the main journal portions 10a, 11a, 12a are viewed from above. Are supported by bearings g ′, h ′, i ′ arranged in a straight line in the direction perpendicular to the crankshaft.

  Here, the upper block (second support member) 17 is common to the central crankshaft 10 and the left and right crankshafts 11 and 12, and the lower half of the bearing hole g and the bearing holes h and i are provided. The upper half is formed on the split surfaces 17b and 17a of one common thick plate member. The lower block (first support member) 18 is common to the left and right crankshafts 11 and 12, and the lower half of the bearing holes h and i is a split surface of one common thick plate member. 18a.

  The bolts for tightening the bearing block 19 are outer bolts 20a, 20a arranged on the outer side in the engine width direction of the left and right crankshafts 11, 12, and between the left, right 11, 12 and the central crankshaft 10. It is comprised by the inner side volt | bolts 20b and 20b arrange | positioned.

  The crank arm portion 10b of the central crankshaft 10 is formed so as to be close to the front bearing wall portion 2e of the crank chambers C1, C2, C3. Large end portions 16a and 16a 'of the inner connecting rods 16 and 16' are arranged in parallel and connected to the crank pin portion 10c between the crank arm portions 10b and 10b so as to be adjacent to each other.

  Further, the crank arm portions 11a, 11a of the left crankshaft 11 are disposed adjacent to the rear side in the crankshaft direction of the crank arm portion 10b of the central crankshaft 10, and a crank pin between the crank arm portions 11a, 11a. The large end portion 14a of the outer connecting rod 14 is connected to the portion 11c. Similarly, the crank arm portions 12b, 12b of the right crankshaft 12 are disposed adjacent to the rear bearing wall portion 2e of the crank chambers C1, C2, C3, and the crank arm portions 12b, 12b are connected to each other. The large end portion 14a 'of the outer connecting rod 14' is connected to the pin portion 12c.

  The crankshaft direction interval between the outer connecting rod 14 connected to the left crankshaft 11 and the inner connecting rod 16 connected to the central crankshaft 10 is the same as the interval between the cylinder bores 9 and 8, t1, t2,. . Similarly, the crankshaft direction interval between the outer connecting rod 14 'connected to the right crankshaft 12 and the inner connecting rod 16' connected to the central crankshaft 10 is t1, which is the same as the interval between the cylinder bores 9 'and 8'. t2. The crankshaft direction interval between the large end portion 14a on the left crankshaft 11 side and the large end portion 14a 'on the right crankshaft 12 side is the same as the crankshaft direction interval between the large end portions 16a and 16a' on the central crankshaft 10 side. t3.

  Here, the central crankshaft 10 and the left and right crankshafts 11 and 12 are arranged as close to each other as possible in the direction perpendicular to the axis. That is, as shown in FIG. 1, a part of the rotation locus a passing through the outermost ends of the large ends 16a and 16a 'of the inner connecting rods 16 and 16' connected to the central crankshaft 10 is the left and right crankshafts. 11 and 12 and a part of the journal portions 11a and 12a, and the outermost ends of the large end portions 14a and 14a 'of the outer connecting rods 14 and 14' connected to the left and right crankshafts 11 and 12, respectively. The crankshafts 10 to 12 are arranged closer to each other so that a part of the passing rotation trajectories b and b overlaps a part of the journal portion 10 a of the central crankshaft 10.

  Each of the crankshafts 10 to 12 is provided with a relief portion for avoiding interference due to the overlap. Specifically, as shown in FIGS. 1 and 5, in the crank chamber C1 on the rear end side, the outer connecting rod connected to the left and right crankshafts 11 and 12 of the main journal portion 10a of the central crankshaft 10. A central relief portion 10d is formed at a portion of the 14, 14 'facing the large end portions 14a, 14a'. A left relief portion 11d is formed in a portion of the main journal portion 11a of the left crankshaft 11 that faces the large end portions 16a and 16a 'of the inner connecting rods 16 and 16' connected to the central crankshaft 10. ing. Similarly, a right relief portion 12d is formed in a portion of the main journal portion 12a of the right crankshaft 12 facing the large end portions 16a and 16a 'of the inner connecting rods 16 and 16' connected to the central crankshaft 12. Is formed. The central relief portion 10d and the left and right relief portions 11d and 12d are set to have substantially the same axial length. A similar relief portion is also formed in the crank chambers C2 and C3.

  Here, each of the relief portions 10d, 11d, and 12d points to a portion left by removing a part of each main journal portion, and has a substantially fan shape when viewed in the crankshaft direction ( (See FIG. 1). Further, when the cut-out removed portion is viewed in the direction perpendicular to the crankshaft, the outer portion is substantially in line with the shapes of the large end portions 16a, 16a ', 14a, 14a' and the crank arm portions 10b to 12b that support the large end portions 16a, 16a ' It has a trapezoidal shape (see FIG. 5).

  These relief portions 10d to 12d are arranged so that the notch removal portion constituting the relief portion is located on the large end side when the large end portion of each connecting rod comes to an angular position closest to the counterpart crankshaft. In addition, the angular position is set. In other words, as the crankshafts 10 to 12 rotate, a part of the rotation trajectories a and a of the large ends 16a and 16a ′ of the inner connecting rods 16 and 16 ′ connected to the central crankshaft 10, The left and right relief shafts 11d and 12d of the left and right crankshafts 11 and 12 overlap with the left and right crankshafts 11 and 12 and overlap with the left and right crankshafts 11 and 12, respectively. The rotational phases of the crankshafts 10 to 12 are set so that a part of the rotation trajectories b and b of the end portions 14a and 14a 'and the central relief portion 10d of the central crankshaft 10 overlap in the crankshaft direction. Has been.

  The central crankshaft 10, the left crankshaft 11, and the right crankshaft 12 project rearward from the bearing wall 2e at the rear end of the crank chamber C1, and the bearing wall 2e is formed on each projecting portion. A central transmission gear 21, a left transmission gear 22, and a right transmission gear 23 are mounted so as to contact the rear side surface. These transmission gears 21 to 23 are meshed with each other, and the power generated in the outer cylinder bores 9 and 9 is generated in the inner cylinder bores 8 and 8 from the left and right transmission gears 22 and 23 through the central transmission gear 21. The resultant power is output from the central crankshaft 10 to the rear of the engine in a combined state with the motive power. In the engine 1 of this embodiment, the central crankshaft 10 rotates clockwise as viewed from the rear of the engine, and the left and right crankshafts 11 and 12 rotate counterclockwise.

  Combustion recesses 4b and 5b are formed in portions facing the cylinder bores 8 and 9 of the cylinder bore side mating surfaces 4a and 5a of the left and right cylinder heads 4 and 5, respectively. The left combustion recess 4b The intake and exhaust valve holes of the intake port 4c and the exhaust port 4d are opened. Similarly, intake and exhaust valve holes of the intake port 5c and the exhaust port 5d are opened in the right combustion recess 5b. A branch pipe 24a of the intake manifold 24 is connected to the external connection openings of the intake ports 4c and 5c. The main pipe 24b of the intake manifold 24 extends in the crankshaft direction on the upper surfaces of the head covers 6 and 7. ing. Furthermore, an exhaust manifold 25 is connected to the external connection openings of the exhaust ports 4d and 5d.

  The intake and exhaust valve holes are opened and closed by an intake valve 26 and an exhaust valve 27, respectively. The intake valve 26 and the exhaust valve 27 are driven to open and close by an intake cam shaft 28 and an exhaust cam shaft 29. Here, the intake camshaft 28 is shared by the intake valves 26 and 26 arranged in parallel to each other for the outer and inner cylinder bores 9 and 8, and similarly, the exhaust camshaft 29 is used for the outer and inner cylinder bores 9 and 8. The exhaust valves 27 and 27 are arranged in parallel with each other. The intake camshaft 28 and the exhaust camshaft 29 are rotationally driven by the central crankshaft 10.

  In the engine 1 of the present embodiment, the left and right crankshafts 11 and 12 are arranged on the left side, the right side and the lower side of the central crankshaft 10, so that, for example, compared to a case where three crankshafts are arranged on the same split surface Can be placed close to the engine width direction while avoiding interference between the crankshafts 10 to 12 and the large end of the connecting rod connected to each crankshaft, increasing the engine displacement and increasing the engine output However, the width dimension of the crankcase portion 2c can be made compact.

  Further, in the engine 1 of the present embodiment, the left and right escape portions 11d that avoid interference between the main journal portions 11a and 12a of the left and right crankshafts 11 and 12 and the large end portions 16a and 16a 'of the inner connecting rods 16 and 16'. 12d, and a central relief portion 10d that avoids interference with the large end portions 14a, 14a 'of the outer connecting rods 14, 14' is formed in the main journal portion 10a of the central crankshaft 10 in the same manner. The shaft 10 and the left and right crankshafts 11 and 12 can be arranged as close as possible, and the engine width can be further reduced.

  Furthermore, in the present embodiment, in addition to the proximity arrangement of the crankshaft described above, the outer cylinder bore 9 is connected to the V from the plane B including the axis of the left crankshaft 11 or the right crankshaft 12 and parallel to the cylinder bore axis 9a. Since the inner side of the bank is displaced by t5, the outer width dimensions of the left and right cylinder portions 2a and 2b of the cylinder block 2 can be made more compact.

  Further, since the inner cylinder bore 8 is displaced from the plane B ′ including the center of the central crankshaft 10 and parallel to the cylinder bore axis 8a by t6 to the outside of the V bank, the inner dimension of the V bank can be increased. The V bank space can be used as an arrangement space for auxiliary equipment.

  Further, the left and right crankshafts 11 and 12 are supported by left and right bearing holes h and i formed in the first split surfaces 18a and 17a of the lower block 18 and the upper block 17, and the central crankshaft 10 is supported. The upper block 17 and the bearing portion 2e on the case side are supported by central bearing holes g formed in the second split surfaces 17b and 2g, and the first split surfaces 18a and 17a and the second split surfaces 17b and 2g are supported. Since they are formed so as to extend in parallel to each other, these split surfaces can be easily machined with high machining accuracy, and high arrangement accuracy of the crankshafts 10 to 12 can be secured. Further, since the first split surfaces 18a, 17a and the second split surfaces 17b, 2g are arranged in parallel, the hole machining and assembly of all the tightening bolts 20a, 20b can be performed from the same direction. Manufacturing man-hours can be reduced.

  Further, since the upper block 17 is constituted by one member common to the center, one side, and the other side crankshafts 10 to 12, for example, three crankshafts 10 are provided in comparison with the case where three bearing caps are provided. The support rigidity of ˜12 can be improved, and vibration and noise due to the unbalance force between the crankshafts can be reduced.

  Further, since the upper block 17 is composed of one rectangular thick plate, the shape is simple, there is no difficulty in processing, and processing and assembly operations are easy.

  Further, since the lower block 18 is constituted by one thick plate member common to the left and right crankshafts 11 and 12, the upper block 17 common to the three crankshafts is connected to the bearing portion 2e on the crankcase side. As a result, the support rigidity of the crankshafts 10 to 12 can be further improved.

  Furthermore, the upper block 17 and the lower block 18 are disposed between the outer bolts 20a and 20a disposed outside the left and right crankshafts 11 and 12, and the central crankshaft 10 and the left and right crankshafts 11 and 12, respectively. Since the crankcase side bearing portion 2e is fastened and fixed by the inner bolts 20b and 20b, the central crankshaft fixing bolt and the left and right crankshaft inner fixing bolts are shared. For example, three bearing caps The number of tightening bolts required can be reduced as compared with the case where it is provided, and accordingly, the number of bolt hole machining operations and assembly operations can be reduced.

  In the above embodiment, the case where the upper and lower blocks 17 and 18 of the bearing block 19 supporting the crankshaft are made of thick plates has been described, but the crankshaft support member of the present invention is not limited to this.

  For example, as shown in FIG. 6, the second support member (upper block) may be integrally formed with a lower case 2 c ′ that forms a part of the crankcase portion of the cylinder block 2 as shown in the second embodiment. In FIG. 6, the same reference numerals as those in FIG. 2 denote the same or corresponding parts.

  In the second embodiment, the lower part of the crankcase portion 2c of the cylinder block 2 is divided into a lower case 2c ′. The lower case 2c ′ includes a peripheral wall portion 2p that constitutes a peripheral wall of the crankcase. The left and right side portions of the peripheral wall portion 2p are integrally connected by an upper block 17 'disposed so as to correspond to the above-described crank chambers C1, C2, and C3.

  In the second embodiment, the upper block 17 'is integrally formed with the peripheral wall 2p so as to connect the side walls of the peripheral wall 2p of the lower case 2c', so that the rigidity of the upper block 17 'is increased. As a result, the crankshaft support rigidity can be greatly improved, and as a result, vibration and noise due to unbalanced force due to irregular input from each crankshaft can be more reliably reduced.

1 is a cross-sectional rear view of a three crankshaft engine according to a first embodiment of the present invention. It is a cross-sectional rear view which shows the crankshaft support structure of the said engine. It is a cross-sectional side view (II-II line cross-sectional view of FIG. 2) showing the crankshaft support structure. It is the top view seen in the cylinder bore axial direction of the cylinder block of the engine of the above-mentioned embodiment. It is a top view which shows the arrangement | positioning state of the crankshaft of the said embodiment engine. It is a cross-sectional back view which shows the crankshaft support structure concerning 2nd Embodiment of this invention.

Explanation of symbols

1 Three-crankshaft engine 2 Cylinder block 2c 'Lower case 2e Bearing wall (case side support)
2g, 17b Second split surface 10 Center crankshaft 11, 12 left, right crankshaft (one side, other side crankshaft)
17 Upper block (second support member)
17a, 18a First split surface 18 Lower block (first support member)
19 Bearing block (crankshaft support member)
20a outer bolt 20b inner bolt g 'central bearing (central bearing)
h ', i' Left, right bearing (one side, other side bearing)

Claims (5)

Crankshaft support for an engine comprising a center crankshaft, one side and another side crankshaft arranged in parallel to one side and the other side of the center crankshaft, and a crankshaft support member for supporting each crankshaft In structure
The one-side and other-side crankshafts are arranged at positions away from the central crankshaft on the side opposite to the cylinder,
The crankshaft support member includes a first support member, and a second support member disposed between the first support member and a case-side support portion formed on the crankcase,
The one-side and other-side crankshafts are supported by one-side and other-side bearing portions formed on the first split surfaces of the first member and the second support member, and the central crankshaft is supported by the second support It is supported by a central bearing portion formed on the second split surface of the member and the case side support portion,
The first and second split surfaces are formed to extend parallel to each other,
The crankshaft support structure for an engine, wherein the second support member is composed of one member common to the center, one side, and the other side crankshafts.   2. The crankshaft support structure for an engine according to claim 1, wherein the second support member is constituted by a plate-like member separate from the crankcase.   2. The crankshaft support structure for an engine according to claim 1, wherein the second support member includes a lower case that forms a part of the crankcase.   4. The crankshaft support structure for an engine according to any one of claims 1 to 3, wherein the first support member is composed of one member common to the one side crankshaft and the other side crankshaft.   5. The first and second support members according to claim 4, wherein the first and second support members are disposed between an outer bolt disposed outside one side and the other side crankshaft, and a central crankshaft and the one side and the other side crankshaft. A crankshaft support structure for an engine, which is fastened together with a case-side support portion by an inner bolt.

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