JPH02221733A - Balancer shaft driver for internal combustion engine - Google Patents

Abstract

PURPOSE:To lower a central position of an engine body by setting up a driving gear being driven by a crankshaft via an endless transmission belt and a reverse driving pulley in the lower part of a driven gear as one body with a balancer shaft in mesh. CONSTITUTION:A second wrapping transmission system T2 is rolled on a second driving pulley 29 of a crankshaft 9, and it rotates and drives a first balancer shaft 21 by a timing belt 39 given tension by a tenstioner 47 via a reverse driving pulley 37, a driving gear 40 and a driven gear 41 and a second balancer shaft 22 via a forward driving pulley 38, respectively. In this case, the driving gear 40 is set up to be engaged with a lower part of the driven gear 41, and the center of gravity of a cylinder block 1 is lowered. In addition, the reverse driving pulley 37 is approximated to the side of the driving pulley 29 to the utmost, and such a possibility that a wrapping angle of the belt 39 onto the pulley 37 might be lessened is avoided. Thus, stability of a vehicle is well promoted and, what is more, transmission efficiency can be improved in a compact structure.

Description

Detailed Description of the Invention A3 Object of the Invention (1) Industrial Application Field The present invention provides eccentric weight portions each located above a crankshaft and symmetrically with respect to a vertical line that includes the axis of the crankshaft. The first and second balancer shafts are rotatably supported on the engine body in parallel with the crankshaft, a driven gear is fixed to the first balancer shaft, and a rotating shaft has a drive gear at one end that meshes with the driven gear. An endless power transmission band is provided between a driven wheel for reverse rotation fixed to the other end of the shaft, a driven wheel for forward rotation fixed to the second balancer shaft, and a driven wheel fixed to the crankshaft. The present invention relates to a parallel shaft drive device for a suspended internal combustion engine.

(2) Prior Art Conventionally, such a device has been used, for example, in Japanese Unexamined Patent Publication No. 62-25141.
It is publicly known from Publication No. 4 and the like.

(3) Problems to be Solved by the Invention By the way, the weight of a rotating shaft having a driving gear and a driven wheel for reverse drive at both ends, and a member rotatably supporting the rotating shaft is relatively large, and By installing it in the engine body, it is necessary to avoid the center of gravity of the engine body being in an upward position, but with the above conventional one,
The drive gear meshes with the upper part of the driven gear fixed to the balancer shaft, and the reverse drive driven wheel is placed above the balancer shaft, which is disadvantageous from the perspective of improving the stability of the engine body. It is.

The present invention has been made in view of the above circumstances, and it is an object of the present invention to provide a balancer shaft drive device for an internal combustion engine that can lower the center of gravity of the engine body and improve stability.

B8 Structure of the Invention (1) Means for Solving the Problems According to the first feature of the invention, the driving gear is disposed to mesh with the lower part of the driven gear.

According to a second feature of the invention, the axis of the drive gear is
Disposed on the crankshaft side of a straight line that is almost orthogonal to the straight line connecting the center of the drive wheel and the center of the driven gear and passing through the center of the driven gear, as well as a straight line that connects the centers of the driven gear and the driven wheel for normal rotation drive. Ru.

Furthermore, according to the third feature of the present invention, the chord length between the driving wheel and the driven wheel for reverse rotation drive, and the chord length between the driven wheel for reverse rotation drive and the driven wheel for forward rotation drive, whichever is greater. A tensioner is pressed against the transmission band.

(2) Effect According to the configuration of the first feature above, it is possible to lower the center of gravity of the engine body by arranging the driven wheel for reverse drive, the drive gear, the rotating shaft, etc. at a position lower than the first balancer shaft. be.

Further, according to the configuration of the second feature, the reverse drive driven wheel can be brought as close as possible to the driving wheel side.

Furthermore, according to the configuration of the third feature, it is possible to avoid a reduction in the angle of the transmission band around the reverse drive driven wheel.

(3) Example Hereinafter, an example in which the present invention is applied to a DOHC type in-line four-cylinder internal combustion engine will be explained with reference to the drawings. The main body E has a cylinder head 2 on the top of the cylinder block 1.
An oil pan 3 is connected to the lower part of the cylinder block 1, and a head cover 4 is connected to the upper part of the cylinder head 2. Moreover, the engine body E is arranged so that the joining surface of the cylinder block l and the oil pan 3 is aligned with the horizontal line.

The cylinder block I is made of an aluminum alloy and has an upper cylinder barrel portion 1a and a lower crankcase portion 1b. In the cylinder barrel part 1a,
Four cylinder bores 5 are arranged in series, and pistons 6 are slidably fitted into these cylinder bores 5, respectively. Also, crank case part 1
b, a plurality of journal bearings 7 are spaced apart along the arrangement direction of each cylinder bore 5, and bearing caps 8 are respectively fixed to the lower surface of each journal bearing 7. The crankshaft 9 is rotatably supported by the journal bearings 7..., and the crank pins 9a of the crankshaft 9 and the pistons 6...
and are connected via connecting rods 10... Further, each of the bearing caps 8 . . . is integrally coupled by a bridge member 11.

At one end of the crankshaft 9 in the axial direction, an oil pump 12 driven by the crankshaft 9 is disposed on the outer surface IC of the side wall of the cylinder block 1 . This oil pump 12 includes a rotor 14 fixed to a crankshaft 9 within a pump case 13 attached to the side wall outer surface IC of the cylinder block l.
An oil strainer 17 is connected to a suction port 15 provided in the pump case 13 via a suction pipe 16. Further, a discharge port 18 provided in the pump case 13 is connected to a lubricating oil passage 19 bored in the cylinder block 1 parallel to the crankshaft 9 . The other axial end of the crankshaft 9 projects slightly from the other end side wall of the cylinder block 1, and a transmission is connected to the other end of the crankshaft 9 via a clutch (not shown).

5, 6 and 7, above the crankshaft 9 there are first and second balancers parallel to the crankshaft 9 on both sides of the lower part of each cylinder bore 5... A shaft 21.22 is rotatably arranged. These balancer shafts 21 and 22 suppress secondary vibrations of the engine, and are inserted into the cylinder block l with one axial end protruding from the side wall outer surface IC of the cylinder block l.

Both balancer shafts 21 and 22 have eccentric weight portions 21a spaced apart from each other near the other end in the axial direction.

21b; 22a, 22b, and the cylinder block l is provided with a pair of bearing holes 23° and 24 that support a portion of the first balancer shaft 21 near the other end in the axial direction, and A pair of bearing holes 25 and 26 that support a portion of the second balancer shaft 22 that is closer to the other end in the axial direction, and a bearing hole 27 that supports a portion of the second balancer shaft 22 that is closer to the other end in the axial direction are provided.

The first and second balancer shafts 21 and 22 are arranged as close as possible to the rotation locus of the crankshaft 9 (the circle indicated by the chain line in FIG. 4) while avoiding mutual interference. , are disposed so as to have their axes at symmetrical positions with respect to the vertical line L1 including the axis of the crankshaft 9, that is, at positions on the horizontal line L2 perpendicular to the vertical line L1 and at the same distance from the vertical line L1. Moreover, both balancer shafts 21.22
is a water jacket 95 provided in the cylinder block l.
The lower deck part 1d is rotatably supported at a lower position than the lower deck part 1d, and since the lower deck part 1d is constructed with high rigidity, it is possible to stably support both balancer shafts 21 and 22. becomes.

One end of the crankshaft 9 protrudes from the pump case 13 of the oil pump 12, and the first driving pulley 2 of the first winding transmission TI is attached to the protruding end of the crankshaft 9.
8 is fixed, and the second winding transmission device T is located on the side farther from the cylinder block l than the first drive pulley 28.
A second drive boot IJ29 serving as the second drive wheel is fixed.

The first winding transmission T1 connects an intake valve camshaft 30 rotatably supported on the cylinder head 2 in parallel with the crankshaft 9 to drive the intake valve mechanism, and an exhaust valve mechanism. Timing for driving the exhaust side valve operating camshaft 31, which is rotatably supported on the cylinder head 2 in parallel with the crankshaft 9, and the water pump 32, which is attached to the outer surface IC of the side wall of the cylinder block l. The transmission system includes a first drive pulley 28, camshaft drive driven pulleys 33 and 34 fixed to both camshafts 30 and 31, respectively, and a water pump drive driven pulley fixed to the pump shaft 32a of the water pump 32. Pulley 35 and each pulley 2B, 33, 3
4.35, and a first timing belt 36 as an endless first transmission band.

The second winding transmission device T2 includes first and second balancer shafts 2
1 and 22, and includes a second drive pulley 29, a reverse drive driven boot IJ37 as a reverse drive driven wheel connected to the first balancer shaft 21, and a transmission system fixed to the second balancer shaft 22. A driven pulley 38 for normal rotation drive as a driven wheel for normal rotation drive, and a second timing belt 3 as an endless transmission band suspended around each pulley 29, 37, 38.
It consists of 9. Moreover, the second timing belt 39
runs in the running direction shown by arrow D2, and the second timing belt 39 runs along the running direction along the second drive pulley 2.
9 to the driven pulley 37 for reverse rotation drive and the driven pulley 38 for forward rotation drive, and each pulley 2
The outer diameters of 9, 37, and 38 are set such that the outer diameter of the second drive boob IJ29>the outer diameter of the driven boob IJ37 for reverse rotation drive>the outer diameter of the driven pulley 38 for normal rotation drive.

Referring to FIGS. 8 and 9 together, a gear case 42 that covers a portion of the pump case 13 is attached to the pump case 13 at a portion corresponding to the first balancer shaft 21. That is, the gear case 42 is attached to the cylinder block 1 together with the pump case 13 by bolts 43. The reverse rotation driven driven boob IJ37 is fixed to an end of a rotating shaft 44 that projects from the gear case 42 and is rotatably supported by the gear case 42 in parallel with the first balancer shaft 21. In addition, one end of the first balancer shaft 21 is rotatably supported by the pump case 13 and is connected to the gear case 4.
2, a driven gear 41 is fixed to the end of the first balancer shaft 21 between the pump case 13 and the gear case 42, and a drive gear 40 is integrally provided at the inner end of the rotating shaft 44. are interlocked with each other. Therefore, the first
Power from the reverse drive driven pulley 37 is transmitted to the balancer shaft 21 via gears 40 and 41 that mesh with each other. i.e. the first and second balancer shafts 21.2
2 are rotated in opposite directions.

The drive gear 40 is meshed with the lower part of the driven gear 41. Moreover, the axis of the rotating shaft 44, which is provided with the reverse drive driven pulley 37 and the drive gear 40 at both ends, is set at an angle β of approximately 90 degrees with the straight line L3 connecting the center of the second drive boob IJ29 and the center of the driven gear 41. It is disposed on the crankshaft 9 side (the area shown by diagonal lines in FIG. 7) with respect to the straight line L4 passing through the center of the gear 41 and the straight line L2 connecting the centers of the driven gear 41 and the driven pulley 38 for normal rotation driving.

Referring to FIG. 10, above the crankshaft 9, the cylinder block 1 has a support shaft 45 parallel to the crankshaft 9.
will be planted. The support shaft 45 has a large diameter threaded portion 45 on the base end side.
a and a shaft portion 45b having a male thread 45C with a smaller diameter than the large diameter threaded portion 45a on the tip side are coaxially connected via a flange portion 45d, and the flange portion 45d is placed in contact with the side wall outer surface IC. It is implanted in the cylinder block 1 by screwing together the large-diameter threaded portion 45a so that they are in contact with each other.

This support shaft 45 has a first
A first tensioner 46 for adjusting the tension of the timing belt 36 is supported, and the first tensioner 46
On the axially outer side than
Tensioner 47 is supported.

11 and 12, the first tensioner 46
, a plurality of balls 50 are interposed between an inner ring 48 supported by a shaft portion 45b of a support shaft 45 and an outer ring 49 in sliding contact with the outer surface of the first timing belt 36. A ring-shaped support member 51 press-fitted onto the outer surface of the base end is provided with a pair of protrusions 51a and 51b protruding outward along a diameter line. One protrusion 51a has a support hole 5.
2 is bored, and a shaft 53 that passes through the support hole 52 and is fixed to the cylinder block l allows the first tensioner 4
6 is swingably supported. The inner ring 48 has an arc-shaped elongated hole 54 centered on the shaft 53, and the shaft portion 45b of the support shaft 45 is inserted into the elongated hole 54. The other end of the first tension spring 55, whose one end is engaged with the cylinder block l, is engaged with the other protrusion 51b, and the spring force of the first tension spring 55 causes the outer ring 49 of the first tensioner 46 to It is pressed against the first timing belt 36 from the outside, thereby applying a certain tension to the first timing belt 36.

The second tensioner 47 includes a plurality of balls 57 interposed between an inner ring 56 and an outer ring 58 that slides on the outer periphery of the second timing belt 39 . Further, one end of a tension arm 59 is fixed to the inner ring 56, which is rotatably supported by a shaft 60 parallel to the crankshaft 9 and fixed to the cylinder block l. Furthermore, an arc-shaped elongated hole 61 centered on the shaft 60 is bored in the center of the inner ring 56, and the shaft portion 45b of the support shaft 45 is inserted into the elongated hole 61.

Further, a second tension spring 62 is stretched between the other end of the tension arm 59 and the cylinder block 1, and the spring force of the second tension spring 62 causes the outer ring 58 to
is pressed against the second timing belt 39 from the outside,
Thereby, a constant tension is applied to the second timing belt 39.

The width of the outer ring 58 in the second tensioner 47 is set smaller than the width of the outer ring 49 in the first tensioner 46.

Thus, the first timing belt 36 in the first winding transmission T1 connects the slack side between the first driving pulley 28 and the water pump driving driven pulley 35 to the first tensioner 4.
By being pressed from the outside toward the inside at 6, the gear case 42 is curved deeply inward, and the gear case 42 is disposed in the empty space created by the curve. Moreover, the first
The angle α formed by the direction in which the first timing belt 36 is pressed by the tensioner 46 and the direction in which the second timing belt 39 is pressed by the second tensioner 47 is set to 90 degrees or more, preferably 120 degrees or more, for example 130 degrees.

Referring again to FIG. 7, the second tensioner 47 has a chord length 11 of the second timing belt 39 between the reverse drive driven pulley 37 and the second drive pulley 29 when the second tensioner 47 is not in pressure contact with the second tensioner 47; The chord length 12 of the second timing belt 39 between the driven pulley 37 for reverse rotation drive and the driven pulley 38 for forward rotation drive, whichever is larger, is pressed against the second timing belt 39, and in this embodiment, Since A2>ff1l, the second tensioner 47 is pressed against the outer periphery of the second timing belt 39 between the reverse drive driven pulley 37 and the forward drive driven pulley 38. Moreover, the position where the second tensile liner 47 is pressed against the second timing belt 39 is set to a position where either of the driven pulleys 37 for reverse rotation drive and the driven pulley 38 for forward rotation drive is offset to one side from the center of the chord length between them. .

By the way, in the second winding transmission T2, the second timing belt 39 is moved along the running direction D2 to the second driving pulley 2.
9 to the reverse rotation drive driven pulley 37 and the forward rotation drive driven pulley 38, so during normal operation of the engine, the forward rotation drive driven pulley 38 and the second drive pulley 2 are wound.
9, the second timing belt 39 is in a tensioned state.

Therefore, during the normal operation, the driven pulley 3 for driving forward rotation
It is wasteful to press the second tensioner 47 against the second timing belt 39 between the reverse drive pulley 37 and the second drive pulley 29. It is only necessary to consider the space between the reverse drive driven pulley 37 and the forward rotation drive driven boo 1138.

The first winding transmission device Tl and the second winding transmission device T2 are
It is covered by a side cover 65, and the tip of the support shaft 45 passes through the side cover 65 and projects outward. In addition, a nut 66 that is screwed onto the male thread 45c at the tip of the support shaft 45 and comes into contact with the inner ring end surface of the second tension goner 47 is rotatably engaged with the side cover 65. Can be rotated. By tightening the napht 66, the inner rings 48.56 of the first and second tensioners 46.47 are allowed to move relative to each other in a plane perpendicular to the axis of the support shaft 45 and are brought into contact with each other.

A rotating ring 67 that protrudes outward from the side cover 65 is fixed to the crankshaft 9, and a third drive pulley 68 of the third winding transmission T3 is attached to the axially inner side of the rotating ring 67. and the fourth drive boob IJ69 of the first winding transmission Tl is integrally provided on the outer side in the axial direction.

The third winding transmission T3 is a transmission system for driving the AC generator 70 and air conditioner compressor 71 attached to the cylinder block l, and is fixed to the third drive pulley 68 and the input shaft of the AC generator 70. A driven pulley 72 for driving an AC generator, a driven pulley 73 for driving a compressor fixed to the input shaft of a compressor 71 for an air conditioner, and an endless belt 74 suspended around each pulley 68, 72° 73. configured.

The fourth S transmission device T4 is a transmission system for driving the power steering hydraulic pump 75 attached to the cylinder head 2, and is connected to the fourth drive pulley 69 and the hydraulic pressure fixed to the input shaft of the hydraulic pump 75. It is composed of a driven pulley 76 for driving the pump, and an endless belt 77 that is suspended around both boos IJ69 and 76.

Next, to explain the configuration of the lubrication oil supply system, an oil pump 12 is connected to the lubrication oil passage 19 provided in the cylinder block l.
The lubricating oil supplied from the oil filter 80 is guided to an oil filter 80 attached to the side surface of the cylinder block 1 at a portion corresponding to the journal bearing 7 located between the two inner cylinder bores 5, 5 along the arrangement direction. Furthermore, the cylinder block 1 includes an oil passage 81 that guides the lubricating oil from the oil filter 80 upward toward the valve mechanism side, and an oil passage 82 that guides the lubricating oil downward.
and are drilled.

On the other hand, the bridge member 11 that interconnects the bearing caps 8... has a central oil passage 83 corresponding to the crankshaft 9.
and each balancer shaft 21, 22 on both sides of the central oil passage 83.
Side oil passages 84 and 85 respectively corresponding to the lateral oil passages 84 and 85 are bored parallel to the crankshaft 9.

The bridge member 11 also includes the oil passages 83, 84.8.
A communication oil passage 86 that connects the oil passages 83 to 5 communicates with each other.
The oil passages 83 to 85 are perforated at a longitudinally intermediate portion thereof to be orthogonal to each of the oil passages 83 to 85.

The bridge member 11 and each bearing cap 8...
In order to supply lubricating oil to the supporting portion of the crankshaft 9, oil supply passages 87 are formed, each extending upward and communicating with the central oil passage 83 at its lower end. In addition, the bearing hole 23 of the first balancer shaft 21
, 24, the bridge member 11, the bearing cap 8, and the cylinder block 1 have oil supply passages 88, 88 whose lower ends communicate with the side oil passage 84 and whose upper ends communicate with the bearing holes 23, 24, respectively. Further, an oil supply passage 89 extending vertically is formed in the bridge member 11, the bearing cap 8, and the cylinder block 1 on one axial end side of the crankshaft 9, the lower end of which communicates with the side oil passage 84. The oil supply passage 89 communicates with an oil supply passage 90 bored in the pump case 13 .

This oil supply path 90 communicates with the first balancer shaft 21 support in the pump case 13 and also communicates with the rotary shaft 44 support in the gear case 42 . At the portion corresponding to the bearing holes 25, 26, 27 of the second balancer shaft 22, the bearing cap 8 and cylinder block 1 of the bridge member 1L include:
Oil supply passages 91 are bored, each having a lower end communicating with the side oil passage 85 and an upper end communicating with the bearing holes 25, 26, and 27, respectively.

Oil passage 82 that guides lubricating oil from oil filter 80 downward
are communicated with the intermediate portion of the oil supply passage 88 at a portion corresponding to the bearing hole 24, and therefore the lubricating oil from the oil filter 80 is transmitted to each oil passage 83, 84, 85 of the bridge member 11 via the oil supply passage 88. will be supplied to

Next, the operation of this embodiment will be explained. The rotation of the crankshaft 9 drives both the first to fourth winding transmission devices T1 to T4. As a result, in the first winding transmission T1, the valve drive camshaft 30, 31 is driven with a reduction ratio of 1/2 with respect to the crankshaft 9, and the water pump 32
is driven.

In addition, in the second winding transmission T2, both balancer shafts 21°22
are driven in mutually opposite directions with a speed increasing ratio of 2/1 relative to the crankshaft 9.

A first tensioner 46 for adjusting the tension of the first timing belt 36 in the first winding transmission T1, and a first tensioner 46 for adjusting the tension of the second timing belt 39 in the second winding transmission T2. Since the two tensioners 47 are supported by the common support shaft 45, the tensioner arrangement can be made compact. Moreover, in the first winding transmission T1, the valve train camshaft 303 requires a large drive torque.
1 and the water pump 32, a larger drive load acts on the second winding transmission T2.
Since the tensioner 46 is supported by the support shaft 45 with the tensioner 46 axially inward than the second tensioner 47, the support shaft 45
The load applied to the tip side can be minimized.

Furthermore, by setting the angle α between the pressing directions of the first and second tensioners 46 and 47 to 90 degrees or more, preferably 120 degrees or more, the direction of the load applied to the support shaft 45 can be shifted and the overall load can be kept small. , together with the arrangement of the first and second tensioners 46 and 47 described above, the support shaft 4
5 can be further suppressed.

Furthermore, since the load on the second winding transmission T2 is smaller than the load on the first winding transmission Tl, the width of the outer ring 58 of the second tensioner 47 is made smaller than the width of the outer ring 49 of the first winding transmission Tl. As a result, the amount of protrusion of the support shaft 45 from the cylinder block 1 can be reduced, contributing to making the entire engine more compact.

In addition, in the second winding transmission T2, the reverse drive driven pulley 37. which is relatively heavy. Since the drive gear 40 and the rotating shaft 44 are arranged below the first balancer shaft 21, the center of gravity of the engine body E can be lowered, which improves the stability of the engine body E, especially when mounted on a vehicle. can be improved.

Furthermore, since the axis of the rotating shaft 44 is arranged in the shaded area in FIG. The transmission T2 can be constructed compactly.

By the way, by arranging the second winding transmission device T2 as described above, there is a possibility that the winding angle of the second timing belt 39 around the reverse drive driven pulley 37 becomes small. However, the outer diameter of the reverse drive driven pulley 37 is set to be smaller than the outer diameter of the second drive boob IJ29 but larger than the outer diameter of the forward drive driven pulley 38, and furthermore, the outer diameter of the reverse drive driven pulley 37 and The larger section of the chord length 11 of the second timing belt 39 between the second drive pulley 29 and the chord length 12 of the second timing belt 39 between the reverse drive driven pulley 37 and the forward drive driven pulley 38 The second tensioner 47 is set to be in pressure contact with the second timing belt 39 midway. Therefore, the second timing belt 39 to the reverse drive driven pulley 37
The winding can prevent the angle from becoming small and contribute to improving transmission efficiency. Moreover, the second winding transmission device T2
The minimum chord length l of the second timing belt 39 on either side of the second tensioner 47 in . .

7 can be set as large as possible, thereby contributing to reducing the operating noise of the second timing belt 39.

Moreover, the second timing belt 39 of the second tensioner 47
Since the pressure contact position is set to one side from the center of the chord length 12 between the reverse drive driven pulley 37 and the forward drive driven pulley 38, the pressure on both sides of the second tensioner 47 is Since the chord lengths of the second timing belt 39 are not equal, it is possible to prevent an increase in noise due to the overlap of the same frequency components that occurs due to the vibration of the second timing belt 39.

C0 Effects of the Invention As described above, according to the first feature of the present invention, the driving gear is arranged to mesh with the lower part of the driven gear, so that the driven wheel for reverse drive, the driving gear, the rotating shaft, etc. It is possible to lower the center of gravity of the engine body by placing it below the first balancer axis.

According to a second feature of the invention, the axis of the drive gear is
Disposed on the crankshaft side of a straight line that is almost orthogonal to the straight line connecting the center of the drive wheel and the center of the driven gear and passing through the center of the driven gear, as well as a straight line that connects the centers of the driven gear and the driven wheel for normal rotation drive. Therefore, it is possible to make the reverse drive driven wheel as close as possible to the drive wheel side while avoiding interference with the drive wheel, resulting in a compact configuration.

Furthermore, according to the third feature of the present invention, the chord length between the driving wheel and the driven wheel for reverse rotation drive, and the chord length between the driven wheel for reverse rotation drive and the driven wheel for forward rotation drive, whichever is greater. Since the tensioner is pressed into contact with the transmission band, the arrangement according to the second feature allows the winding of the transmission band around the driven wheel for reverse drive to avoid the angle from becoming small, contributing to improvement in transmission efficiency. .

[Brief explanation of the drawing]

The drawings show one embodiment of the present invention, and FIG. 1 is a longitudinal sectional side view, FIG. 2 is a view taken along the line ■-■ in FIG. 1, and FIG.
Figure 4 is a cross-sectional view taken along the line III-III in the figure, Figure 4 is a cross-sectional view taken along the IV-IV line in Figures 1 and 5, Figure 5 is a cross-sectional view taken along the ■-V line in Figure 3, and Figure 6 is the figure 3. Figure 7 is a schematic layout of the second winding transmission, and Figure 8 is a cross-sectional view along the line ■-■ of Figure 3.
9 is a cross-sectional view taken along line IX-IX in FIG.
0 is a sectional view taken along the line X-X in FIG. 2, FIG. 11 is a plan view of the first tensioner, and FIG. 12 is a sectional view taken along the line xn-xn in FIG. 11. 9... Crankshaft, 21... First balancer shaft, 21
a, 21b, 22a, 22b--Eccentric weight part, 22-
...Second balancer shaft, 29...Second drive pulley as a drive wheel, 37...Reverse drive driven pulley as a reverse drive driven wheel, 38...Normal rotation as a forward drive driven wheel Driving driven pulley, 39... Timing belt as a transmission band, 40... Drive gear, 41... Driven gear, 47... Tensioner, E... Engine body

Claims (3)

[Claims] (1) The first and second balancer shafts, each having an eccentric weight section above the crankshaft and symmetrical with respect to a vertical line that includes the axis of the crankshaft, are parallel to the crankshaft and can be freely rotated in the engine body. a driven gear is fixed to the first balancer shaft, a driven wheel for reverse drive is fixed to the other end of the rotating shaft having a drive gear meshing with the driven gear at one end, and a second balancer shaft. In a balancer shaft drive device for an internal combustion engine, an endless transmission band is suspended between a driven wheel for normal rotation drive fixed to the crankshaft and a drive wheel fixed to the crankshaft.
A balancer shaft drive device for an internal combustion engine, wherein the drive gear is disposed to mesh with a lower part of the driven gear. (2) The axis of the drive gear is a straight line that is almost orthogonal to the straight line connecting the center of the drive wheel and the center of the driven gear and passes through the center of the driven gear, and a straight line that connects the center of the driven gear and the driven wheel for normal rotation drive. The balancer shaft drive device for an internal combustion engine according to item (1), characterized in that it is disposed closer to the crankshaft than the balancer shaft drive device. (3) The tensioner is pressed against the transmission band at the greater of the chord length between the driving wheel and the driven wheel for reverse rotation drive, or the chord length between the driven wheel for reverse rotation drive and the driven wheel for forward rotation drive. The balancer shaft drive device for an internal combustion engine according to item (2), characterized in that: