JP4490942B2 - Engine for four-wheel drive vehicle - Google Patents

Description

  According to the present invention, four front and rear wheel drive shafts extending in the front-rear direction of a vehicle so as to transmit power to front wheels and rear wheels and a crank shaft extending in the vehicle width direction are rotatably supported by a crankcase of an engine body. The present invention relates to an engine for a wheel drive vehicle.

A crankshaft is rotatably supported by a crankcase formed by combining a pair of case halves that can be divided into left and right, and the power from the crankshaft is transmitted to the front and rear wheels. The front and rear wheel drive shafts extending in the longitudinal direction of the vehicle are rotatably supported, and the front and rear wheel drive shafts are disposed below a plurality of bearing portions provided in the crankcase to rotatably support the crankshaft. An engine for a four-wheel drive vehicle is known from Patent Document 1.
JP 2001-347843 A

  By the way, the crankshaft may be rotatably supported by the split surface of the crankcase in which the upper and lower case halves that can be divided vertically by the split surface are coupled to each other. In that case, the bearings provided in the lower case half to support the lower half of the crankcase are fastened to the upper case half with fastening bolts arranged on both sides of the crankshaft, and are driven by front and rear wheels. The shaft has to be arranged below the crankshaft between the two bearing portions adjacent to each other in the direction along the axis of the crankshaft, or below the bearing portion. In order to make it low, it is desirable to make the front and rear wheel drive shafts as close as possible to the crankshaft.

  The present invention has been made in view of such circumstances, and the center of gravity of the engine body can be set low by bringing the front and rear wheel drive shafts close to the crankshaft supported by the split surface of the crankcase that can be divided vertically. An object of the present invention is to provide a four-wheel drive vehicle engine.

  In order to achieve the above object, the invention according to claim 1 is characterized in that the front and rear wheel drive shafts extending in the front and rear direction of the vehicle so as to transmit power to the front wheels and the rear wheels and the crank shaft extending in the vehicle width direction In an engine for a four-wheel drive vehicle that is rotatably supported by a crankcase of a main body, the crankcase can be divided vertically by a split surface, and upper and lower case halves are coupled to each other, A plurality of bearings in the lower case half are spaced apart in a direction along the axis of the crankshaft so as to rotatably support the crankshaft having an axis arranged on a split surface in cooperation with the upper case half. A plurality of crank webs provided on the crankshaft, and a pair of the crank webs between the pair of bearing portions adjacent to each other in the axial direction of the crankshaft. A connecting rod connected to the crankshaft via a crankpin is disposed between the webs, and is viewed from a direction along the axis of the crankshaft below the crank web adjacent to one of the pair of bearing portions. The front and rear wheel drive shafts are arranged so that at least a part thereof overlaps with the rotation trajectory of the connecting rod.

  According to a second aspect of the present invention, in addition to the configuration of the first aspect of the invention, the plurality of bearing portions are arranged on both sides of the crankshaft and are screwed into the upper case half. A pair of boss portions through which the fastening bolts are respectively inserted are integrally provided so as to extend downward, and at least one lower portion of the boss portions is the front and rear wheels as viewed from the direction along the axis of the crankshaft. It is arranged at a position overlapping with the drive shaft.

  According to a third aspect of the present invention, in addition to the configuration of the second aspect of the invention, adjacent to the bearing portion closest to the axially central portion of the crankshaft among the plurality of bearing portions arranged in the axial direction of the crankshaft. The front and rear wheel drive shafts (12) are arranged below the crank web.

  Furthermore, the invention according to claim 4 is arranged in front of the crankshaft, in addition to the configuration of the invention according to claim 1, on the split surface that is inclined to be rearwardly raised in a state where the engine body is mounted on the vehicle. The balancer shaft to be rotated is supported rotatably.

  According to the first aspect of the present invention, it is possible to avoid the interference with the connecting rod and the bearing portion, and to bring the front and rear wheel drive shafts close to the crankshaft, thereby reducing the center of gravity of the engine body.

  According to the second aspect of the present invention, the pair of bosses provided on the bearing portion of the lower case half are relatively long, so that the crankshaft supported by the split surface of the crankcase that can be divided vertically can be used. The support rigidity can be increased and the front and rear wheel drive shafts are cranked so that the lower part of at least one of the bosses is arranged at a position overlapping the front and rear wheel drive shafts when viewed from the direction along the axis of the crankshaft. By making it close to the shaft, the center of gravity of the engine body can be set lower.

  According to the third aspect of the present invention, the front and rear wheel drive shafts are disposed close to the center of the engine body in the direction along the axis of the crankshaft, and the four-wheel drive vehicle can be easily made into a four-wheel independent suspension. Become.

  According to the fourth aspect of the present invention, the balancer shaft can be easily assembled to the crankcase, and the balancer shaft is disposed below the crankshaft to further lower the center of gravity of the engine body. Can do.

  DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiments of the present invention will be described below based on one embodiment of the present invention shown in the accompanying drawings.

  1 to 9 show an embodiment of the present invention. FIG. 1 is a side view of a four-wheel drive vehicle, FIG. 2 is a side view of an engine body, and FIG. 3 is a sectional view taken along line 3-3 of FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. 2, FIG. 5 is an enlarged view of the main part of FIG. 3, FIG. 6 is a cross-sectional view taken along line 6-6 of FIG. 8 is a sectional view taken along line 8-8 in FIG. 7, and FIG. 9 is a sectional view taken along line 9-9 in FIG.

  In FIG. 1, a pair of left and right front wheels WF are suspended on the front part of a body frame F provided in the four-wheel drive vehicle, and a pair of left and right rear wheels WR are suspended on the rear part of the body frame F. Between the front wheels WF... And the rear wheels WR..., An engine body 11 of, for example, a two-cylinder engine E is mounted on the body frame F, and the power from the engine E is used as the front wheels WF. The front and rear wheel drive shafts 12 for transmission to WR... Have an axis extending along the front and rear direction of the body frame F and pass through the lower part of the engine body 11. The power output from the front ends of the front and rear wheel drive shafts 12 The power transmitted to the front wheels WF through the front drive shaft 13, the universal joint 14 and the front differential 15 and output from the rear end of the front and rear wheel drive shaft 12 is universal joint 16, the rear drive shaft 17 and It is transmitted to both rear wheels WR through the front differential 18.

  A vehicle body cover 19 that covers most of the vehicle body frame F and the engine E is attached to the vehicle body frame F, and a riding seat 20 is provided on the vehicle body cover 19. Further, a throttle body 21 for each cylinder is connected to the rear side wall of the cylinder head 31 in the engine body 11, and the upstream ends of both the throttle bodies 21 are disposed above the engine body 11 and in front of the riding seat 20. It is commonly connected to an air cleaner 22 covered with the vehicle body cover 19. Moreover, fuel injection valves 23 are attached to the throttle bodies 21. On the other hand, upstream ends of exhaust pipes 24 and 25 for each cylinder are connected to the front side wall of the cylinder head, and these exhaust pipes 24 and 25 face forward in the traveling direction of the four-wheel drive vehicle. The exhaust body 24 is curved so as to pass to the right side of the engine body 11, and the downstream ends of both exhaust pipes 24, 25 are connected to an exhaust muffler via a common exhaust pipe 26 common to the exhaust pipes 24, 25. 27, the exhaust muffler 27 is disposed behind the engine body 11.

  2 and 3, the engine body 11 includes a crankcase 29 that rotatably supports a crankshaft 28 whose axis is along the vehicle width direction (a direction perpendicular to the paper surface of FIG. 2), and the crankcase 29. A cylinder block 30 coupled to the upper part, a cylinder head 31 coupled to the upper part of the cylinder block 30, and a head cover 32 coupled to the upper part of the cylinder head 31 are provided.

  When the engine body 11 is mounted on the vehicle, the cylinder block 30 is provided with a pair of cylinder bores 33, 33 arranged side by side with an inclined axis so as to rise forward, and the cylinder bores 33. Pistons 34, which are slidably fitted are connected to the crankshaft 28 via connecting rods 42, 42 and crank pins 28a, 28a.

  The crankcase 29 can be divided up and down by a split surface 50 that is inclined so as to rise rearward when the engine body 11 is mounted on the vehicle, and upper and lower case halves 29a and 29b are coupled to each other. The cylinder block 30 and the upper case 29a are integrally formed. Further, as shown in FIG. 2, the first crankcase cover 35 is fastened with a plurality of bolts 38... 130 on the left side of the crankcase 29 with the four-wheel drive vehicle facing forward in the traveling direction. The second crankcase cover 36 is fastened by a plurality of bolts 39 (see FIG. 2), and the third crankcase cover is located on the right side of the crankcase 29 in a state of facing forward in the traveling direction of the four-wheel drive vehicle. 37 is fastened by a plurality of bolts 40 (see FIG. 3). An oil pan 41 is fastened to the lower part of the crankcase 29.

  A generator 44 covered with a first crankcase cover 35 is connected to one end of the crankshaft 28 that rotatably passes through the left side wall of the crankcase 29, and the generator 44 is connected to the crankshaft 28. An outer rotor 45 fixed to one end and an inner stator 46 fixed to the first crankcase cover 35 so as to be surrounded by the outer rotor 45 are provided.

  A starter motor 47 is attached to the upper portion of the crankcase 29 as shown in FIG. 2, and a gear 48 to which power is transmitted from the starter motor 47 is connected to the outer rotor 45 via a one-way clutch 49. Connected to

  The other end of the crankshaft 28 that rotatably passes through the right side wall of the crankcase 29 is rotatably supported by a third crankcase cover 37, and a torque converter 51 is attached to the other end of the crankshaft 28. The

  A first main shaft 52 having an axis parallel to the crankshaft 28 is rotatably supported on the crankcase 29 behind the crankshaft 28 and penetrates the first main shaft 52 coaxially so as to be relatively rotatable. Both ends of the second main shaft 53 are rotatably supported by the crankcase 29 and the third crankcase cover 37. In addition, the axes of the first and second main shafts 53 and 54 are arranged on the split surface 50 in the crankcase 29, that is, on the coupling surfaces of the upper and lower case halves 29a and 29b. Further, a counter shaft 54 having an axis parallel to the first and second main shafts 52 and 53 is disposed obliquely below the first and second main shafts 52 and 53. Two crankcase covers 36 and a crankcase 29 are rotatably supported.

  Between the crankcase 29 and the third crankcase cover 37, a transmission cylinder shaft 55 is mounted on the first main shaft 52 so as to be relatively rotatable. The transmission cylinder shaft 55 receives rotational power from the crankshaft 28. Power is transmitted through the torque converter 51, the drive gear 56 connected to the crankshaft 28 via the torque converter 51, the driven gear 57 and the damper spring 58 that mesh with the drive gear 56. A first hydraulic clutch 59 is provided between the transmission cylinder shaft 55 and the first main shaft 52, and is connected to the driven cylinder shaft 55 and the second main shaft 53 between the transmission cylinder shaft 55 and the second main shaft 53. A second hydraulic clutch 60 disposed at a position sandwiching 57 between the first hydraulic clutch 59 and the first hydraulic clutch 59 is provided so as to be connected according to the action of hydraulic pressure.

  A gear transmission mechanism 64 that constitutes the hydraulic automatic transmission 63 together with the first and second hydraulic clutches 59 and 60 is an alternative between the first and second main shafts 52 and 53 and the counter shaft 54. A gear train having a plurality of shift stages that can be established is provided. In this embodiment, a first gear train G1 and a third gear gear are provided between the first main shaft 52 and the counter shaft 54. A train G3 and a reverse gear train GR are provided, and a second gear train G2 and a fourth gear train G4 are provided between the second main shaft 53 and the counter shaft 54.

  Referring also to FIG. 4, the first-speed gear train G1 meshes with the first-speed drive gear 65 and the first-speed drive gear 65 provided integrally with the first main shaft 52 and is axially moved. The third-speed gear train G3 is composed of a first-speed driven gear 66 that is supported at a fixed position so as to be relatively rotatable with respect to the counter shaft 54. The third-speed gear train G3 is integrally provided with the first main shaft 52. It comprises a gear 67 and a third-speed driven gear 68 that meshes with the third-speed drive gear 67 and is supported on the counter shaft 54 so as to be relatively rotatable with a constant axial position. The reverse gear train GR includes a first reverse drive gear 65, a first reverse idle gear 69 that meshes with the first speed drive gear 65, and a second reverse idle gear that is formed integrally with the first reverse idle gear 69. The first and second reverse idle gears are composed of a gear 70 and a reverse driven gear 71 that meshes with the second reverse idle gear 70 and is supported by the counter shaft 54 so as to be relatively rotatable with a constant axial position. 69 and 70 are rotatably supported by a reverse idle shaft 72 having an axis parallel to the first main shaft 52, the second main shaft 53, and the counter shaft 54 and having both ends supported by the crankcase 29. . Moreover, the axis of the first and second reverse idle gears 69 and 70, that is, the axis of the reverse idle shaft 72, is disposed in front of the counter shaft 54 as shown in FIG.

  The second speed gear train G2 is capable of axially sliding operation within a limited range with a second speed drive gear 73 supported relative to the second main shaft 53 so that the axial position is constant. And a second speed driven gear 74 that is supported on the counter shaft 54 and is engaged with the second speed drive gear 73 so as not to rotate relative to the countershaft 54. The fourth speed gear train G4 has a constant axial position. The fourth-speed drive gear 75 is rotatably supported on the second main shaft 53, and the fourth-speed drive gear 75 is meshed with the fourth-speed drive gear 75. And a fourth speed driven gear 76.

  A first shifter 77 is splined to the counter shaft 54 between the first and third speed driven gears 66 and 68, and the first shifter 77 is engaged with the first speed driven gear 66. A position for establishing the first speed gear train G1, a position for engaging the third speed driven gear 68 to establish the third speed gear train G3, and the first and third speed driven gears 66, 68. It is possible to move in the axial direction of the counter shaft 54 by switching between intermediate positions that do not engage any of them. A second shifter 78 is splined to the second main shaft 53 between the second-speed drive gear 73 and the fourth-speed drive gear 75, and the second shifter 78 is connected to the second-speed drive gear 75. 73 is engaged with the second speed gear train G2 to establish the second speed gear train G2, is engaged with the fourth speed drive gear 75 is established with the fourth speed gear train G4, and the second and fourth speeds. It is possible to move in the axial direction of the second main shaft 53 by switching between an intermediate position that is not engaged with any of the drive gears 73 and 75. Further, the second speed driven gear 74 of the second speed gear train G2 maintains the meshed state with the second speed drive gear 73, and engages with the reverse driven gear 71 and the reverse driven gear 97. The second shifter 78 can move in the axial direction between the positions where the engagement with the second shifter 78 is released, and the second shifter 78 is in the intermediate position where it does not engage with any of the second and fourth speed drive gears 73 and 75. The reverse gear train GR is established by moving the speed driven gear 74 to a position where it is engaged with the reverse driven gear 71.

  Thus, when the first hydraulic clutch 89 is in the power transmission state and power is transmitted from the crankshaft 28 to the first main shaft 52, the first speed gear train G1, the third speed gear train G3, and Power is transmitted from the first main shaft 52 to the counter shaft 54 via a gear train that is alternatively established in the reverse gear train GR, and the second hydraulic clutch 60 is in a power transmission state and the second main shaft. 53, when power is transmitted from the crankshaft 28 to the counter shaft from the second main shaft 53 via a gear train alternatively established from the second gear train G2 and the fourth gear train G4. Power is transmitted to 54.

  Incidentally, power for driving the first shifter 77, the second shifter 78, and the second speed driven gear 74 in the axial direction is obtained by a shift motor 80 (see FIG. 2) attached to the upper part of the crankcase 29.

  As clearly shown in FIG. 2, a transmission shaft 81 having an axis parallel to the counter shaft 54 is disposed below and behind the counter shaft 54. The transmission shaft 81 includes the second crankcase cover 36, the crankshaft A support cylinder 82 attached to the case 29 is rotatably supported. In addition, the drive gear 83 fixed to the counter shaft 54 is engaged with the driven gear 84 fixed to the transmission shaft 81 between the crankcase 29 and the second crankcase cover 36, and the transmission shaft 81 is interlocked with the counter shaft 54. Connected.

  A drive bevel gear 85 is integrally provided on the transmission shaft 81, and a driven bevel gear 86 fixed to the front and rear wheel drive shaft 12 passing through the lower part of the crankcase 29 in the front-rear direction is located behind the axis of the transmission shaft 81. Meshes with the drive bevel gear 85.

  Meanwhile, as shown in FIG. 2, the front portion of the precursor wheel drive shaft 12 is supported by the crankcase 29 via a ball bearing 89, and the front and rear wheel drive shaft 12 and the crankcase 29 are outside the ball bearing 89. An annular seal member 90 is interposed therebetween.

  On the other hand, an opening 91 having a larger diameter than the driven bevel gear 86 is provided at the rear end of the crankcase 29 so that the front and rear wheel drive shafts 12 can be inserted. On the other hand, a bearing holding member 93 having a cylindrical portion 93 a that penetrates the rear portion of the front and rear wheel drive shaft 12 is fastened to the crankcase 29 by a plurality of bolts 95.

  Moreover, the driven bevel gear 86 is fitted to the front and rear wheel drive shaft 12 so as not to be relatively rotatable from the rear end of the front and rear wheel drive shaft 12, and the inner ring 92a of the ball bearing 92 held by the holding member 93; A driven bevel gear 86 is sandwiched between an annular receiving step portion 12a provided on the outer periphery of the front and rear wheel drive shaft 12 and facing rearward. Further, an annular seal member 94 is interposed between the cylindrical portion 93 a of the bearing holding member 93 and the front and rear wheel drive shafts 12 outside the ball bearing 92.

  The hydraulic pressures of the first and second hydraulic clutches 59 and 60 in the hydraulic automatic transmission 63 are controlled by a hydraulic control unit 98 including a plurality of control valves including a control valve that is electrically controlled. The hydraulic control unit 98 is attached to the upper part of the crankcase 29, that is, the upper part of the upper case half 29.

  5 and 6, the crankshaft 28 having an axis line disposed on the split surface 50 of the crankcase 29 has three journal portions 28b, 28b, 28b disposed on both sides of the pair of cylinder bores 33, 33. The three bearing portions 99, 100, 101 arranged in order from the left side in the state of facing forward in the traveling direction of the vehicle should support the journal portion 28b in a freely rotatable manner in cooperation with the upper case half body 29a. The lower case half body 29b is provided at intervals along the axis of the crankshaft 28.

  A pair of boss portions 104, 105 through which a pair of fastening bolts 102, 103,... That are arranged on both sides of the crankshaft 28 and screwed into the upper case half 29a are respectively inserted into the bearing portions 99-101. Are integrally provided so as to extend downward.

  The front and rear wheel drive shaft 12 is disposed below the crankshaft 28 at a position corresponding to a pair of bearing portions 99 and 100 adjacent to each other in the axial direction of the crankshaft 28 among the bearing portions 99 to 101. The lower part of at least one of the boss parts 104, 105, in this embodiment, the lower part of the boss part 104 located on the front side in the state of being mounted on the vehicle, is viewed from the direction along the axis of the crankshaft 28. It is arranged at a position overlapping the wheel drive shaft 12.

  Meanwhile, a pair of bearing portions 99, 100; 100, 101 adjacent to each other in the axial direction of the crankshaft 28 are provided with a pair of crank webs 28c, 28c provided on the crankshaft 28 and the crank webs 28c. , 28c, connecting rods 42, which are connected to the crankshaft 28 via crankpins 28a, are respectively arranged, and the crankshaft among the plurality of bearing portions 99 to 101 arranged in the axial direction of the crankshaft 28 is disposed. The front and rear wheel drive shafts 12 are disposed below the crank web 28c adjacent to the bearing portion 100 closest to the axial center portion of the 28.

  Moreover, the connecting rod 42 draws a rotation trajectory T indicated by a chain line in FIG. 6 on the projection onto the plane orthogonal to the axis of the crankshaft 28, but the front and rear wheel drive shaft 12 follows the axis of the crankshaft 28. As viewed from the direction, the connecting rod 42 is disposed so as to at least partially overlap the rotation locus T.

  The split surface 50 of the crankcase 29 is disposed so as to be inclined rearward when the engine body 11 is mounted on the vehicle. The split surface 50 has an axis parallel to the crankshaft 28 and the crankshaft 28. The balancer shaft 106 driven by the transmission power from the shaft is rotatably supported, and the balancer shaft 106 is disposed in front of the crankshaft 28.

  7 to 9, the balancer shaft 106 has balancer weights 107 and 107 at positions corresponding to the cylinder bores 33 of the cylinder block 30 and is rotatably supported by the split surface 50. Thus, a driven gear 109 that meshes with a drive gear 108 provided on the crankshaft 28 is fixed to the balancer shaft 106, and the rotational power of the crankshaft 28 is applied to the balancer shaft 106 via the drive gear 108 and the driven gear 109. Communicated.

  A water pump 110 is disposed on the outer side of the balancer shaft 106 in the axial direction. The water pump 110 is disposed on the left outer side of the balancer shaft 106 when the engine body 11 is mounted on a vehicle. The pump housing 112 of the water pump 110 covers the generator 44 and cranks it. The first crankcase cover 35 attached to the case 29 is supported by a pump support portion 111 provided integrally with the first crankcase cover 35.

  The pump housing 112 includes a housing main body 113 supported by the pump support portion 111 and a cover member 114 fastened to the housing main body 113, and a fitting cylinder portion 113a provided in the housing main body 113 includes the pump support. It is liquid-tightly fitted to the support cylinder part 111a provided in the center part of the part 111.

  A pump chamber 115 is formed in the pump housing 112, and a pump shaft 117 whose one end is connected to the impeller 116 housed in the pump chamber 115 so as not to be relatively rotatable is a fitting cylinder portion of the housing main body 113. 113 a is penetrated coaxially with the balancer shaft 106. A connecting shaft portion 106 a that is coaxially provided at one end of the balancer shaft 106 is fitted to the other end of the pump shaft 117 coaxially and in a relatively non-rotatable manner, and the pump shaft 117 rotates together with the balancer shaft 106. Further, a ball bearing 118, an annular seal member 119, and a mechanical seal 120 are interposed between the pump shaft 117 and the fitting cylinder portion 113a.

  Thus, at least a part of the pump housing 112 including the housing main body 113 and the cover member 114 is fastened together with the first crankcase cover 35 to the crankcase 29. In this embodiment, the housing main body 113 and The outer peripheral portion of the cover member 114 is fastened to the outer periphery of the cover member 114, two of which are fastened together with the first crankcase cover 35 together with the first crankcase cover 35 by bolts 130 and 130, and the remaining one is the bolt 131. Thus, the housing main body 113 and the cover member 114 are fastened to each other.

  By the way, the cylinder block 30 and the cylinder head 31 in the engine body 11 are provided with a water jacket 121, and the water jacket 121 is supplied with cooling water from the water pump 110.

  The housing main body 113 and the cover member 114 constituting the pump housing 112 are integrally provided with water passage forming portions 113b and 114a that cooperatively form a water passage 122 communicating with the pump chamber 115, and these water passage forming portions 113b. 114a are fastened to each other by a bolt 132 and are fastened to the cylinder block 30 by a bolt 133. Moreover, the water channel forming portions 113b and 114a are connected to the water jacket 121 in the cylinder block 30 so as to connect the water channel 122 to the cylinder block 30 side beyond the coupling surface to the crank case 29 of the first crank case cover 35. It is extended.

  On the other hand, the cooling water led out from the water jacket 121 in the cylinder head 31 is introduced into a thermostat 123 disposed at the rear part of the cylinder head 31. The thermostat 123 is connected to a first return pipe 124 provided on the cover member 114 of the pump housing 112 so as to communicate with the pump chamber 115 of the water pump 110 via a hose 125 and is connected to the front of the engine E. The radiator 126 (see FIG. 1) supported by the vehicle body frame F is connected via a hose 127. Further, a second return pipe 128 provided on the cover member 114 in the pump housing 112 so as to communicate with the pump chamber 115 is connected to the radiator 126 via a hose 129.

  Thus, when the temperature of the introduced cooling water is low, the thermostat 123 cools the amount of cooling water circulating in the radiator 126 so as to bypass the radiator 126 and increase the amount of cooling water flowing to the hose 125 side. Change according to water temperature.

  Next, the operation of this embodiment will be described. The crankcase 29 can be divided into upper and lower split surfaces 50, and upper and lower case halves 29a and 29b are connected to each other. The plurality of bearings 99, 100 are provided on the lower case half 29b with a space in the direction along the axis of the crankshaft 28 so that the crankshaft 28 with the shaft is rotatably supported in cooperation with the upper case half 29a. 101 between the pair of bearing portions 99, 100 adjacent to each other in the axial direction of the crankshaft 28 among the bearing portions 99-101, and a pair of crank webs 28c provided on the crankshaft 28. A connecting rod 42 connected to the crankshaft 28 via a crankpin 28a is disposed between the crank webs 28c. Under the crank web 28c adjacent to one of the bearing portions 99, 100, the front and rear wheel drive shafts 12 are arranged so as to at least partially overlap the rotation trajectory T of the connecting rod 42 when viewed from the direction along the axis of the crankshaft 28. Is arranged. For this reason, interference with the connecting rod 42 and the bearing portion 100 can be avoided, the front and rear wheel drive shafts 12 can be brought close to the crankshaft 28, and the center of gravity of the engine body 11 can be lowered.

  In addition, a pair of bosses 104 and 105, which are respectively inserted through the pair of fastening bolts 102 and 103 that are arranged on both sides of the crankshaft 28 and screwed into the upper case half body 29a, are respectively provided on the bearings 99 to 101. Positions that are integrally provided so as to extend, and a lower portion of the boss 104 that is at least one of the bosses 104 and 105 overlaps with the front and rear wheel drive shaft 12 when viewed from the direction along the axis of the crankshaft 28. Is arranged.

  Therefore, the crankshaft 28 supported by the split surface 50 of the crankcase 29 can be divided vertically by making the pair of boss portions 104, 105... Provided in the bearing portions 99 to 101 of the lower case half body 29b relatively long. The support rigidity can be increased, and the lower part of at least one of the bosses 104, 105... Is arranged at a position overlapping the front and rear wheel drive shaft 12 when viewed from the direction along the axis of the crankshaft 28. Thus, by bringing the front and rear wheel drive shafts 12 close to the crankshaft 28, the center of gravity of the engine body 11 can be set low.

  The front and rear wheel drive shafts 12 are disposed below the crank web 28c adjacent to the bearing portion 100 closest to the axial central portion of the crankshaft 28 among the plurality of bearing portions 99 to 101 arranged in the axial direction of the crankshaft 28. Therefore, the front and rear wheel drive shafts 12 are arranged close to the center of the engine body 11 in the direction along the axis of the crankshaft 28, so that the four-wheel drive vehicle can be easily set as a four-wheel independent suspension.

  Further, since the balancer shaft 106 disposed in front of the crankshaft 28 is rotatably supported on the split surface 50 that is disposed to be inclined rearward when the engine body 11 is mounted on the vehicle, the crankcase of the balancer shaft 106 is supported. 29 can be easily assembled, and the balancer shaft 106 can be disposed below the crankshaft 28 to further reduce the center of gravity of the engine body 11.

  Further, the pump housing 112 of the water pump 110 is supported by a pump support portion 111 provided integrally with a first crankcase cover 35 that covers the generator 44 connected to one end of the crankshaft 28 and is attached to the crankcase 29. Therefore, when the water pump 110 is disposed, a cover dedicated to the water pump 110 is not necessary, and the number of parts can be reduced. Moreover, the water pump 110 has an axis parallel to the crankshaft 28, is rotatably supported by the crankcase 29, and is disposed on the axially outer side of the balancer shaft 106 driven by the transmission power from the crankshaft 28. Therefore, it is not necessary to secure a dedicated space in the crankcase 29 for arranging the water pump 110, and the crankcase 29 can be made compact.

  Further, since the pump housing 112 includes a housing main body 113 supported by the pump support portion 111 and a cover member 114 fastened to the housing main body 113, the housing main body 113 is used as a pump for the first crankcase cover 35. Since the pump housing 112 can be configured by fastening the cover member 114 to the housing main body 113 while being supported by the support portion 111, the assembling property of the water pump 110 can be improved.

  Further, the housing main body 113 and the cover member 114 are integrally provided with water passage forming portions 113b and 114a that cooperate to form a water passage 122 communicating with the pump chamber 115 formed in the pump housing 112, respectively. The portions 113b and 114a extend to the cylinder block 30 side beyond the coupling surface to the crankcase 29 of the first crankcase cover 35 so as to connect the water passage 122 to the water jacket 121 in the cylinder block 30. In addition, it is possible to connect the pump chamber 115 to the water jacket 121 of the cylinder block 30 without using a dedicated member only for forming a water channel, and the seal structure between the first crankcase cover 35 and the crankcase 29 is simplified. Can be

  Further, since at least a part of the pump housing 112 is fastened to the crankcase 29 together with the first crankcase cover 35, the water pump 110 is supported by the crankcase 29 via the first crankcase cover 35. The number of parts required for the maintenance can be reduced and the maintainability is also improved.

  Although the embodiments of the present invention have been described above, the present invention is not limited to the above-described embodiments, and various design changes can be made without departing from the present invention described in the claims. It is.

It is a side view of a four-wheel drive vehicle. It is a side view of an engine body. FIG. 3 is a sectional view taken along line 3-3 in FIG. 2. FIG. 4 is a cross-sectional view taken along line 4-4 of FIG. It is a principal part enlarged view of FIG. FIG. 6 is a sectional view taken along line 6-6 of FIG. It is an enlarged side view near a water pump. FIG. 8 is a cross-sectional view taken along line 8-8 in FIG. 7. FIG. 9 is a cross-sectional view taken along line 9-9 in FIG. 7.

Explanation of symbols

DESCRIPTION OF SYMBOLS 11 ... Engine main body 12 ... Front-and-rear wheel drive shaft 28 ... Crank shaft 28a ... Crank pin 28c ... Crank web 29 ... Crank case 29a ... Upper case half body 29b ... Lower case half 42 ... Connecting rod 50 ... Split surfaces 99, 100, 101 ... Bearing parts 102, 103 ... Fastening bolts 104, 105 ... Boss part 106 ... Balancer shaft E ..Engine T ... Rotation locus WF ... Front wheel WR ... Rear wheel

Claims (4)

  A front and rear wheel drive shaft (12) extending in the front-rear direction of the vehicle so as to transmit power to the front wheels (WF) and rear wheels (WR), and a crankshaft (28) extending in the vehicle width direction are engine bodies (11). In the engine for a four-wheel drive vehicle that is rotatably supported by the crankcase (29), the crankcase (29) can be divided vertically by a split surface (50), and upper and lower case halves ( 29a, 29b) are coupled to each other, and the crankshaft (28) having an axis line disposed on the split surface (50) is to be rotatably supported in cooperation with the upper case half (29a). The lower case half (29b) is provided with a plurality of bearing portions (99, 100, 101) at intervals along the axis of the crankshaft (28), and the bearing portions (99 to 101) Of which Between a pair of bearing portions (99, 100) adjacent to each other in the axial direction of the rank shaft (28), a plurality of crank webs (28c) provided on the crank shaft (28) and the crank webs (28c) ) And a connecting rod (42) connected to the crankshaft (28) via a crank pin (28a), and adjacent to one (100) of the pair of bearing portions (99, 100) Below the crank web (28c), the front and rear wheel drive shafts (at least partially overlap the rotational locus (T) of the connecting rod (42) when viewed from the direction along the axis of the crank shaft (28). 12) The engine for four-wheel drive vehicles characterized by the above-mentioned.   A pair of fastening bolts (102, 103) disposed on both sides of the crankshaft (28) and screwed into the upper case half (29a) are respectively inserted into the plurality of bearing portions (99 to 101). A pair of caulking bosses (104, 105) are integrally provided so as to extend downward, and at least one lower part of the bosses (104, 105) is connected to the axis of the crankshaft (28). The four-wheel drive vehicle engine according to claim 1, wherein the engine is disposed at a position overlapping the front and rear wheel drive shafts (12) when viewed from a direction along the direction.   The crank web (28c) adjacent to the bearing portion (100) closest to the central portion in the axial direction of the crankshaft (28) among the plurality of bearing portions (99 to 101) arranged in the axial direction of the crankshaft (28). The four-wheel drive vehicle engine according to claim 1 or 2, wherein the front and rear wheel drive shafts (12) are arranged below the front wheel drive shaft.   A balancer shaft (106) disposed in front of the crankshaft (28) is rotatably supported on the split surface (50) disposed so as to be inclined rearward when the engine body (11) is mounted on the vehicle. The four-wheel drive vehicle engine according to claim 1, wherein

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