JPH02217646A - Balancer shaft driving device of internal combustion engine - Google Patents

Abstract

PURPOSE:To improve the locational accuracy and enhance the mounting rigidity by locating No.1, No.2 vase members of a balancer shaft driver device with respect to the engine body using a common knock member, and by fastening with a common bolt. CONSTITUTION:With rotation of a crank shaft, No.1 balancer shaft 21 is rotated through a timing belt 39, reverse rotation driving pulley 37, driving gear 40 on a rotary shaft 44 pivoted on a gear case (No.2 case member) 42, and follower gear 41 pivoted on a pump case (No.1 case member) 13. These members 13, 42 are located with respect to a cylinder block 1 by a common knock member 95 and fastened by a bolt 43. Therein the amount of thermal expansion of the gear case 42 bearing the rotary shaft 44 shall be smaller than the amount of thermal expansion of the pump case 13 bearing the balance shaft 21 so as to suppress change in the backlash between the two gears 40, 41 due to rise of the temp. Thus the locational accuracy and mounting rigidity are enhanced, and increase in gearing sound can be prevented.

Description

Detailed Description of the Invention A1 Object of the Invention (1) Industrial Application Field The present invention relates to a first case member, in which a balancer shaft having an eccentric weight portion is rotatably supported by the engine body, and which is attached to the engine body. and a second case member attached to the first case member, a driven gear is fixed to one end of the balancer shaft, and a driven gear is rotatably supported by the second case member parallel to the balancer shaft. A driving gear provided at the inner end of the rotating shaft and meshing with the driven gear is housed in the gear chamber, and a driven wheel for reverse driving is fixed to the outer end of the rotating shaft protruding from the second case member. The present invention relates to a balancer shaft drive device for an internal combustion engine in which a rotating shaft is interlocked and connected to a crankshaft via a wrapped transmission system.

(2) Prior Art Conventionally, a device in which driving force from a crankshaft is transmitted to a balancer shaft via a pair of gears is known, for example, from Japanese Utility Model Application Publication No. 56-608/11.

(3) Problems to be solved by the invention By the way, in such a device, the first
A pair of gears are disposed between the case member and a second case member attached to the first case member,
In order to improve the relative positional accuracy of the reverse drive driven wheel with respect to the crankshaft, it is necessary to improve the positional accuracy of the second case member with respect to the engine body. In order to improve such positional accuracy, it is necessary to position the first case member with respect to the engine body using a plurality of knock members, and to position the second case member with respect to the first case member using a plurality of knock members. is possible.

However, when positioning is performed between the engine body and the first case member and between the first case member and the second case member, the positioning error of the second case member with respect to the engine body is
The positioning error of the case member and the positioning error of the second case member relative to the first case member overlap,
Although many knocking members are used, it is difficult to say that the positioning accuracy is excellent.

The present invention has been made in view of the above circumstances, and it is possible to easily improve the positioning accuracy of the second case member with respect to the engine body, and to improve the rigidity of the attachment of the first and second case members to the engine body. An object of the present invention is to provide a balancer shaft drive device for an internal combustion engine.

B5 Structure of the Invention (1) Means for Solving the Problems According to the first feature of the present invention, both ends of a plurality of cylindrical knock members having axes parallel to the balancer axis and passing through the first case member. The bolts are fitted into the second case member and the engine body, respectively, and a bolt that engages with the second case member and passes through the knock member is screwed into the engine body.

According to the second feature of the present invention, the first case member is provided with a bearing hole for rotatably supporting the balancer shaft, and the second case member has a coefficient of thermal expansion smaller than that of the first case member. Formed by material.

(2) Effect According to the structure of the first feature, the first and second case members are positioned relative to the engine body by a common knock member, and are attached to the engine body by a common bolt.

Further, according to the configuration of the second feature, the amount of thermal expansion of the second case member supporting the rotating shaft on which the drive gear is provided is smaller than the amount of thermal expansion of the first case member supporting the balancer shaft; Therefore, it is possible to suppress backlash changes in the driving gear and the driven gear due to temperature rise.

(3) Embodiment An embodiment in which the present invention is applied to a balancer shaft drive device for a DOHC type in-line four-cylinder internal combustion engine will be explained below with reference to the drawings. 4, the engine body E is constructed by connecting the throat 2 to the cylinder at the top of the cylinder block 1, the oil pan 3 at the bottom of the cylinder block 1, and the head cover 4 at the top of the cylinder head 2. be combined.

The cylinder block 1 includes an upper cylinder barrel portion 1a and a lower crankcase portion 1b, and is made of an aluminum alloy. In the cylinder barrel part 1a,
Four cylinder bores arranged in series are provided, and pistons 6 are slidably fitted into these cylinder bores 5, respectively. Also, the crank case part 1b
, 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, . . .
crank bin 9a... and each of 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 l. This oil pump 12 has a first oil pump attached to the side wall outer surface IC of the cylinder block 1.
Aluminum alloy pump case 1 as a case member
A rotor 14 fixed to the crankshaft 9 is housed in the pump case 13, and 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 l parallel to the crankshaft 9. The other end of the crankshaft 9 in the axial direction projects slightly from the side wall of the other end of the cylinder block l, and a transmission is connected to the other end of the crankshaft 9 via a clutch (not shown).

5 and 6, a first balancer shaft 21 and a second balancer shaft 22 are located above the crankshaft 9 at substantially symmetrical positions with respect to a vertical plane passing through the axis of the crankshaft 9. It is arranged parallel to the crankshaft 9 and rotatable. These balancer shafts 21 and 22 suppress secondary vibrations of the engine, and are inserted into the cylinder block 1 with one axial end protruding from the side wall outer surface IC of the cylinder block 1. Both balancer shafts 21 and 22 have eccentric weight portions 21a, 21bH22a and 22b spaced apart from each other near the other end in the axial direction, and the cylinder block l has a first balancer A pair of bearing holes 23, 2 that support a portion of the shaft 21 near the other end in the axial direction
4 is provided, and a pair of bearing holes 25 and 26 for supporting a portion of the second balancer shaft 22 near the other end in the axial direction and a pair of bearing holes 27 for supporting a portion of the second balancer shaft 22 near the one end in the axial direction are provided. It will be done.

One end of the crankshaft 9 protrudes from the pump case 13 of the oil pump 12, and the first driving boo IJ2 of the first winding transmission system TI is attached to the protruding end of the crankshaft 9.
8 is fixed, and a second winding transmission system T2 is mounted on the side farther from the cylinder block 1 than the first drive pulley 28.
The second drive pulley 1J29 is fixed, and both drive pulleys IJ2
B, 29 is rotationally driven in the direction shown by the arrow in FIG.

The first winding transmission system T1 connects an intake side valve camshaft 30 rotatably supported on the cylinder head 2 parallel to the crankshaft 9 to drive the intake side valve mechanism, and an exhaust side valve mechanism. Rad 2 to the cylinder parallel to the crankshaft 9 to drive
This is a timing transmission system for driving an exhaust side valve drive camshaft 31 which is rotatably supported by
The drive pulley 28, the camshaft drive driven pulleys 33 and 34 fixed to both camshafts 30 and 31, respectively, the water pump drive driven pulley 35 fixed to the pump shaft 32a of the water pump 32, and each pulley 2B. , 33.34
．． 35 and a first timing belt 36 which is wound around the timing belt 35.

The second winding transmission system T2 includes first and second balancer shafts 21
, 22, the second drive pulley 29, the reverse drive driven pulley 37 as a reverse drive driven wheel interlocked and connected to the first balancer shaft 21,
A driven pulley 38 for forward rotation drive provided on the balancer shaft 22
and an endless second wheel suspended from each pulley 29.37.38.
It is composed of a timing belt 39.

Referring to FIGS. 8 and 9 together, a gear case 42 as a second case member that covers a part of the pump case 13 is attached to the pump case 13 at a portion corresponding to the first balancer shaft 21. It will be done.

The gear case 42 is made of a material having a smaller coefficient of thermal expansion than the pump case 13, such as cast iron, and is attached to the cylinder block 1 together with the pump case 13 by bolts 43.

Moreover, in order to determine the positions of the pump case 13 and the gear case 42 with respect to the cylinder block 1, a plurality of cylindrical knock members 95 having an axis parallel to the balancer shaft 21 are provided.
are arranged to penetrate through the pump case 13, and both ends of the knock members 95 are fitted into the cylinder block 1 and the gear case 42, respectively. Therefore, the bolt 43
is screwed into the cylinder block 1 by passing through each knock member 95 while engaging the gear case 42 with its head.

A gear chamber 9 is provided between the pump case 13 and the gear case 42.
4 is formed. The reverse rotation drive driven pulley 37 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 . Moreover, one end of the first balancer shaft 21 is thrust into the gear chamber 94 while being rotatably supported by the pump case 13 . That is, the pump case 13 attached to the side wall outer surface 1c of the cylinder block 1 has a first
A bearing hole 13a for rotatably supporting one end of the balancer shaft 21 is bored, and one end of the first balancer shaft 21 is inserted into the gear chamber 94 between the pump case 13 and the gear case 42 through the bearing hole 13a. Being rushed into. In the gear chamber 94, the driven gear 41 fixed to the end of the first balancer shaft 21 and the drive gear 40 integrally provided at the inner end of the rotating shaft 44 are meshed with each other. Therefore, the power from the reverse drive driven pulley 37 is transmitted to the first balancer shaft 21 via the gears 40 and 41 that mesh with each other. That is, both balancer shafts 21 and 22 are driven to rotate in opposite directions.

Further, the tooth width DI along the axial direction of the driving gear 40 is
The tooth width D2 along the axial direction of the driven gear 41 is set larger than the tooth width D1. Moreover, the tooth width D2 has margins D2a and D2 on both sides of the tooth width corresponding to @radius D1.
b.

Referring also to FIG. 9, above the crankshaft 9, a support shaft 45 parallel to the crankshaft 9 is implanted in the cylinder block 1. The support shaft 45 has a large diameter threaded portion 45a on the base end side and a male threaded thread 45c having a smaller diameter than the large diameter threaded portion 45a.
A shaft portion 45b having a distal end thereof is coaxially connected via a flange portion 45d, and the flange portion 45
d in contact with the side wall outer surface 1c, and the large diameter threaded portion 45
It is installed in the cylinder block 1 by screwing the parts a.

A first tensioner 46 for adjusting the tension of the first timing belt 36 in the first winding transmission system T1 is supported on this support shaft 45, and on the axially outer side of the first tensioner 46, The second in the second winding transmission system T2
A second tensioner 47 for adjusting the tension of the timing belt 39 is supported.

In FIGS. 1O and 11, the first tensioner 46
, a plurality of poles 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 51. A support hole 52 is bored in a, and the first tensioner 46 is swingably supported by a shaft 53 that passes through the support hole 52 and is fixed to the cylinder block 1. Therefore, in the inner circle 48,
An arc-shaped elongated hole 54 centered on the shaft 53 is bored, and the shaft portion 45b of the support shaft 45 is inserted into the elongated hole 54. Further, the other end of a first tension spring 55 whose one end is secured to the cylinder block 1 is engaged with the other protrusion 51b, and the spring force of the first tension spring 55 causes the first
The outer ring 49 of the tensioner 46 is connected to the first timing belt 3
6 from the outside, thereby applying a constant tension to the first timing belt 36.

The second tensioner 47 has a plurality of balls 5 between an inner ring 56 and an outer ring 58 that is in sliding contact with the second timing belt 39.
7 is interposed. Further, one end of a tension arm 59 which is rotatably supported by a shaft 60 fixed to the cylinder block 1 parallel to the crankshaft 9 is connected to the inner ring 56.
is fixed to.

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. Furthermore, 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 be attached to the second timing belt 39 from the outside. The second timing belt 39 is pressed against the second timing belt 39, thereby applying a certain tension to the second timing belt 39. In this second tensioner 47, the width of the outer ring 58 is the same as that of the first tensioner 4.
The width is set smaller than the width of the outer ring 49 in No. 6.

Thus, the first timing belt 36 in the first winding transmission system T1 connects the slack side between the first drive pulley 28 and the water pump driving driven boob 1135 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 between 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.

The first winding transmission system T1 and the second winding transmission system T2 are covered by a side cover 65, and the support shaft 45
The distal end thereof passes through the side cover 65 and projects outward. Moreover, the nut 6 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 tensioner 47.
6 is rotatably engaged with the side cover 65, and the nut 66 can be rotated from outside the side cover 65. By tightening the nut 66, the inner rings 4856 of the first and second tensioners 46, 47 are attached to the support shaft 4.
5 and are allowed to move relative to each other in a plane perpendicular to the axis of the parts 5 and 5 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 system T3 is attached to the axially inner side of the rotating ring 67. and the fourth winding transmission system T4
A fourth drive pulley 69 is integrally provided on the axially outer side.

The third winding transmission system T3 is a transmission system for driving the AC generator 70 and air conditioner compressor 71 attached to the cylinder block 1, and is fixed to the third drive pulley 68 and the human power 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 each pulley 68, 72.7.
3 and an endless belt 74 suspended around the belt 3. The fourth transmission system T4 is a transmission system for driving the power steering hydraulic pump 75 attached to the cylinder head 2, and is fixed to the fourth drive boo IJ69 and the input shaft of the hydraulic pump 75. It is composed of a driven pulley 76 for driving a hydraulic pump, and an endless belt 77 suspended around both pulleys 69 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 1.
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 l 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 holes 23 and 2 of the balancer shaft 21
4, the bridge member 11, the bearing cap 8, and the cylinder block 1 have a lower end connected to a side oil passage 84.
Oil supply passages 88 and 88 are drilled to communicate with the bearing holes 23 and 24 at their upper ends, respectively, and the bridge member 111 is connected to the bearing cap 8 and the cylinder block 1 at one axial end of the crankshaft 9. An oil supply passage 89 communicating with the side oil passage 84 extends vertically and is bored;
The oil supply passage 89 communicates with an oil supply passage 90 bored in the bomb case 13.

This oil supply path 90 is connected to the balancer shaft 2 in the pump case 13.
1 bearing part, and also communicates with the rotary shaft 44 bearing part in the gear case 42. Bearing hole 2 of balancer shaft 22
5, 26, and 27, the bridge member 11,
The bearing cap 8 and the cylinder block 1 have a lower end communicating with the side oil passage 85 and an upper end communicating with the bearing hole 25,
26 and 27, respectively, are drilled therein.

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

Referring again to FIGS. 7 and 8, the second winding transmission system T
A rotating shaft 44 to which the second reverse drive driven pulley 37 is fixed.
is rotatably supported by the gear case 42 via a cylindrical bearing metal 96. Lubricating oil is supplied between the bearing metal 96 and the rotating shaft 44 from an oil supply path 90, and in order to prevent the lubricating oil that has flowed out from the rotating shaft 44 and the bearing metal 96 from leaking from the axially outer end of the gear case 42. An oil seal 97 is interposed between the gear case 42 and the rotating shaft 44 at a position axially outward from the bearing metal 96.

Oil seal 9 from between bearing metal 96 and rotating shaft 44
The lubricating oil that has flowed out to the 7 side is returned into the gear chamber 94 via an oil passage 98 provided in the gear case 42. Also, some lubricating oil flows directly into the gear chamber 94 from between the bearing metal 96 and the rotating shaft 44, and lubricating oil also flows into the gear chamber 94 from the part where the first balancer shaft 21 is supported by the pump case 13. do. In order to discharge the lubricating oil that has flowed into the gear chamber 94 in this way, a lubricating oil discharge hole 99 that communicates with the lower part of the gear chamber 94 is bored in the pump case 13, and the lubricating oil discharge hole 99 is also provided in the cylinder flock 1. A lubricating oil discharge hole 101 is bored through which the hole 99 communicates with the inside of the cylinder block 1 .

Further, in the pump case 13, air is introduced into the gear chamber 94 above the lubricating oil discharge hole 99 and near the meshing portion of both gears 40.41, for example, at a portion corresponding to the meshing start position of both gears 40.41. A hole 100 is bored, and the air introduction hole 100 communicates with the inside of the cylinder block l. In other words, the cylinder block 1 to which the pump case 13 is attached
An insertion hole 102 is formed coaxially with the bearing hole 23, 24 in the side wall of the balancer shaft 21 to allow the first balancer shaft 21 to pass therethrough, and the air introduction hole 100 is communicated with the insertion hole 102.

Next, the operation of this embodiment will be described. The rotation of the crankshaft 9 drives both the first to fourth winding transmission systems T1 to T4. As a result, in the first winding transmission system T1, the valve drive camshafts 30 and 31 are driven with a reduction ratio of 1/2 with respect to the crankshaft 9, and the water pump 32 is also driven. In addition, in the second winding transmission system T2, both balancer shafts 2
1.22 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 system T1;
Second timing belt 39 in second winding transmission system T2
Since the second tensioner 47 for adjusting the tension is supported by the common support shaft 45, the tensioner arrangement can be made compact. Moreover, the first winding transmission system T1
In order to drive the valve train camshaft 30.31 and the water pump 32, which require a large drive torque, a larger drive load acts on the second winding transmission system T2, but the first tensioner 46 is operated more than the second tensioner 47. Since it is supported by the support shaft 45 on the inner side in the axial direction, the load applied to the distal end side of the support shaft 45 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, the load on the second winding transmission system T2 is increased by the first winding transmission system T1.
Since the load is smaller than the load of It is possible to reduce the amount of protrusion and contribute to making the entire engine more compact.

Moreover, the pump case 13 and the gear case 42 are positioned with respect to the cylinder block 1 by a plurality of knock members 95, and the position of the gear case 42 with respect to the cylinder block l, that is, the crankshaft 9, is provided with a relatively small number of parts. The positional accuracy of the reverse drive driven pulley 37 with respect to the second drive pulley 29 can be improved. Also, the pump case 13 and gear case 42
is attached to the cylinder block 1 by bolts 43 passing through each knock member 95, so that the fastening rigidity to the cylinder block 1 can be improved, and the rotating shaft 44
It is also possible to prevent the sealing surface between the pump case 13 and the gear case 42 from opening, etc., even in response to the load applied from the second timing belt 39.

Furthermore, in order to reduce weight, the gear case 42 is made of cast iron, whereas the cylinder block 1 and pump case 13 are made of aluminum alloy. It is possible to suppress the change to a small value, and it is possible to minimize the change in backlash of the driving gear 40 and the driven gear 41, thereby avoiding an increase in gear noise.

Further, the tooth width D2 of the driven gear 41 is given margin widths D2a and D2b that allow the tooth width D1 of the driving gear 40 to be accommodated within the tooth width D2, so that the driving gear 40 and the driven gear 41 can be moved somewhat relative to each other in the axial direction. Even in this case, the effective contact width of both gears 40 and 41 can be ensured. Furthermore, since the tooth width D1 of the driving gear 40 is set smaller than the tooth width D2 of the driven gear 41 in order to ensure the above-mentioned effective contact width, the supporting portion of the rotating shaft 44 by the gear case 42 is made relatively long to ensure stable support. It becomes possible to obtain.

Furthermore, since air is introduced into the gear chamber 94 through the air introduction hole 100, the lubricating oil in the gear chamber 94 is smoothly discharged from the lower lubricating oil discharge hole 99, and the lubricating oil is removed by both gears 40 and 41. The stirring resistance can be kept extremely small, and the power for driving the first balancer shaft 21 can be kept small.

Incidentally, an empty space is created in the pump case 13 near the meshing portion of the driving gear 40 and the driven gear 41, and the air introduction hole 100 is arranged in this empty space.

Therefore, the air introduction hole 100 can be provided while avoiding an increase in the size of the pump case 13. Moreover, since the air introduction hole 100 is made to communicate with the insertion hole 102 of the cylinder block 1, it is not necessary to provide a special hole in the cylinder block 1.

C0 Effects of the Invention As described above, according to the first feature of the present invention, both ends of the plurality of cylindrical knock members having axes parallel to the balancer axis and penetrating the first case member are connected to the second case member. A bolt that is fitted into the member and the engine body, and which engages the second case member and passes through the knock member, is screwed into the engine body, so the second case member can be positioned with respect to the engine body with a relatively small number of parts. Accuracy can be improved, and the rigidity of fastening the first and second case members to the engine body can be improved.

According to the second feature of the present invention, the first case member is provided with a bearing hole for rotatably supporting the balancer shaft, and the second case member has a coefficient of thermal expansion smaller than that of the first case member. Since it is made of material, it is possible to suppress changes in the distance between the balancer shaft and the rotary shaft due to temperature changes, suppress changes in backlash of the driving gear and driven gear, and prevent increase in gear noise.

[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 sectional view taken along the line I[l-111 in the figure, Figure 4 is a sectional view taken along the line IV-IV in Figures 1 and 5, Figure 5 is a sectional view taken along the ■-v line in Figure 3, and Figure 6 is the sectional view taken along the Figure 3 is a cross-sectional view taken along line Vl--Vl, and Figure 7 is an enlarged cross-sectional view taken along line ■-■ in Figure 3. Figure 8 is a cross-sectional view taken along line ■-■ in Figure 3.
■ Line enlarged cross-sectional view Figure 9 is a cross-sectional view taken along line IX-IX in Figure 2, Figure 10 is a plan view of the first tensioner, and Figure 11 is a cross-sectional view of the first tensioner.
FIG. 2 is a sectional view taken along the line XI-XI of FIG. 9... Crankshaft, 13... Pump case as first case member, 13a... Bearing hole, 21... Balancer shaft, 21a, 21b... Eccentric weight portion, 37...
A driven pulley for reverse driving as a driven wheel for reverse driving, 40
... Drive gear, 41 ... Driven gear, 42 ... Second
Gear case as a case member, 43... Bolt, 4
4...Rotating shaft, 94...Gear chamber, 95...Knocking member, E...Engine body, T2...Wrap transmission system Fig. 9

Claims (2)

[Claims] (1) A balancer shaft having an eccentric weight part is rotatably supported by the engine body, and a gear chamber is provided between a first case member attached to the engine body and a second case member attached to the first case member. a driven gear that is formed and fixed to one end of the balancer shaft, and a drive gear that is provided at the inner end of the rotating shaft that is parallel to the balancer shaft and rotatably supported by the second case member and meshes with the driven gear. is housed in the gear chamber, and the rotating shaft is interlocked and connected to the crankshaft via a wrap-around transmission system including a reverse drive driven wheel fixed to the outer end of the rotating shaft protruding from the second case member. In the balancer shaft drive device of an engine, the first shaft has an axis parallel to the balancer shaft.
Both ends of the plurality of cylindrical knock members passing through the case member are fitted into the second case member and the engine body, respectively, and bolts that engage with the second case member and pass through the knock members are screwed into the engine body. A balancer shaft drive device for an internal combustion engine, characterized in that: (2) The first case member is provided with a bearing hole for rotatably supporting the balancer shaft, and the second case member is formed of a material having a smaller coefficient of thermal expansion than the first case member. The balancer shaft drive device for an internal combustion engine according to item (1).