JP2002070950A - Balancer device for internal combustion engine - Google Patents

Abstract

PROBLEM TO BE SOLVED: To avoid interference with an oil level simultaneously with generating natural lubrication, by receiving a gear 20 of a balancer shaft 15 into a housing 12 without providing a complicated constitution. SOLUTION: A housing 12, comprising a housing upper/lower 13, 14, is formed with a pair of shaft receiving chambers 21 independent of each other in the inside. A balancer shaft 15 having a weight part 29 of semicircular section is received to the shaft receiving chamber 21. A pair of the balancer shafts 15 are rotated in a reverse direction to each other by a gear 20 meshed with each other. The housing upper/lower 13, 14 are tightened together by a bolt for fixing to a cylinder block side. A small hole 46 is formed through in the upward of a gear receiving part 25, a drip of lubricating oil in a crankcase, collected in a recessed part 45, is supplied to the gear 20 through the small hole 46.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an improvement in a balancer device that is driven in synchronization with a crankshaft so as to suppress rotational vibration of an internal combustion engine.

[0002]

2. Description of the Related Art In order to suppress the rotational vibration of an internal combustion engine,
2. Description of the Related Art There is conventionally known a balancer device in which a pair of balancer shafts having eccentric weights having a semicircular cross section are provided in parallel with a crankshaft, and the balancer shaft is rotated synchronously with the crankshaft.

For example, in US Pat. No. 4,703,724 and Japanese Utility Model Application Laid-Open No. Sho 62-28937, a housing is mounted below a cylinder block in a crankcase of an internal combustion engine, and a pair of balancer shafts are rotatably housed in the housing. 1 shows a balancer device configured to perform the above operation.

In this balancer device, the balancer shaft is driven by a crankshaft via, for example, a chain, a timing belt, or a gear mechanism. In general, as described in the above-mentioned prior art, A gear is provided on each balancer shaft, meshes with each other, and the rotation of the crankshaft is transmitted to one of the balancer shafts via a chain or the like. That is, the rotation of the crankshaft is first transmitted to one balancer shaft, and the other balancer shaft is driven in the opposite direction via a pair of gears that mesh with each other.

[0005]

SUMMARY OF THE INVENTION
In Japanese Patent Application Laid-Open No. 2-28937, a pair of gears meshing with each other are arranged so as to be exposed to the outside of the housing. Therefore, the lubricating oil surface oscillating in the crankcase and the gear rotating at high speed interfere with each other. There is a problem that an increase in loss due to stirring of the lubricating oil and mixing of air into the lubricating oil are caused.

On the other hand, in the device of US Pat. No. 4,703,724, the gear located at the end of the housing is covered by a cover member attached to the housing, so that interference between the lubricating oil surface and the gear is avoided. Have been. However, in this device, the housing is integrally cast over the entire circumference of the balancer shaft so as to form a substantially cylindrical shape with both front and rear ends open. Therefore, when assembling the balancer shaft to the housing, the balancer shaft is inserted into the housing in the axial direction. Therefore, a gear having a diameter larger than that of the balancer shaft needs to be separately provided in advance, and only the balancer shaft is inserted into the housing, and thereafter, the gear is attached to the tip of the shaft portion of the balancer shaft protruding from the end of the housing. As a result, there is a problem that the assembly process is restricted. Further, the outer diameter of the weight portion of the balancer shaft cannot be made larger than the inner diameter of the bearing portion, and it is generally difficult to ensure a sufficiently large eccentric mass.

Further, when the gears meshing with each other are accommodated in the housing as described above, some kind of lubrication mechanism for the gears is required.

[0008]

SUMMARY OF THE INVENTION Accordingly, the present invention has a housing mounted below a cylinder block in a crankcase of an internal combustion engine, an eccentric weight portion, and is rotatably housed in the housing. And a pair of balancer shafts arranged in parallel and side by side with each other, wherein the pair of balancer shafts have gears that mesh with each other, and one of the balancer shafts is driven by the output of the internal combustion engine. Thus, in the balancer device of the internal combustion engine in which both balancer shafts rotate in opposite directions, the housing is vertically divided into a housing upper and a housing lower, and between the housing upper and the housing lower. It is characterized in that the balancer shaft is housed together with the gear. It is set to.

In this case, the gear is integrated with the balancer shaft in advance, and is arranged between the housing upper and the housing lower which can be divided vertically. In the assembled state, the gear is located in the housing and does not interfere with the lubricating oil level.

The housing upper and the housing lower are integrated with each other by appropriate means such as bolts. Preferably, a plurality of housing upper and housing lower members are provided for fixing the housing to the cylinder block side. At least some of the bolts pass through both the housing upper and the housing lower, and the bolts fasten the housing upper and the housing lower together. In addition to the bolts for co-fastening, a bolt or the like for directly connecting the housing upper and the housing lower may be provided. Further, the housing does not necessarily have to be fixed to the cylinder block itself, and includes a case where the housing is fixed to a member substantially integrated with the cylinder block, for example, a bearing cap or the like.

In the case where the balancer shaft is driven by a crankshaft via a chain, a third aspect is provided.
As described above, one end of one balancer shaft extends from the gear and protrudes through an opening at the end of the housing, and a sprocket for driving a chain can be attached here. .

Preferably, each balancer shaft has at least two weight portions separated in the axial direction, and the shaft portion between the two weight portions is the weight portion. Of the housing upper and the housing lower, and are sandwiched between semi-circular bearing portions of the housing upper and the housing lower, respectively. That is, it is possible to secure a large outer diameter of the weight portion without being limited by the diameter of the bearing portion.

Further, it is preferable that the housing upper is provided with an opening that opens upward at a position above the gear. This opening is open into the crankcase.

According to a more specific embodiment of the present invention, the opening is provided immediately above the gear.

That is, a large amount of lubricating oil droplets are constantly scattered in the crankcase in which the housing is disposed, as the crankshaft rotates. Further, the lubricating oil returning from the cylinder head side or the lubricating oil supplied to the cylinder drops from the upper wall surface of the crankcase. These oil droplets are supplied to gears in the housing through openings formed in the upper surface of the housing.

[0016]

According to the present invention, since the gear is housed in the housing, interference between the gear rotating at a high speed and the lubricating oil surface can be avoided. By dividing the housing into a housing upper and a housing lower, a balancer shaft previously integrated with the gear can be assembled to the housing,
In addition, a separate cover member for covering the gear is not required. In addition, the outer diameter of the weight portion can be set large without being restricted by the diameter of the bearing portion.

Further, according to the second aspect of the present invention, the housing upper and the housing lower are fastened together by using bolts for fixing to the cylinder block side, so that the number of parts and steps are reduced, and the housing is mounted on the housing upper. The disadvantages resulting from the division into the housing lower and the housing lower can be significantly reduced.

Further, according to the fourth and fifth aspects of the present invention, the gears inside the housing can be naturally lubricated without forming a complicated lubricating oil passage. Problems such as an increase in the size of the housing can be avoided.

[0019]

DESCRIPTION OF THE PREFERRED EMBODIMENTS One embodiment of the present invention will be described below in detail with reference to the drawings.

FIG. 2 shows a cross section of a main part of an internal combustion engine provided with a balancer device 1 according to the present invention. A frame-shaped oil pan is formed on a flange 4 at a lower edge of a skirt 3 of a cylinder block 2. An upper 5 is attached, and an oil pan lower 7 is attached to a flange 6 at a lower edge thereof. The cylinder block 2 has a deep skirt shape, and a crankshaft 10 is supported on a bulkhead 8 thereof through a bearing cap 9.

The balancer device 1 is housed in a crankcase 11 constituted by the oil pan upper 5 and the oil pan lower 7 and has a cylinder block 2.
Mounted at the bottom. The housing 12 constituting the balancer device 1 is formed into a housing upper 13 and a housing lower 14 so as to be divided into two parts. The housing 12 accommodates a pair of balancer shafts 15 and is integrally formed by a plurality of bolts 16. Are combined. The housing upper 13 has four legs 17 and bolts 18 penetrating the legs 17 and the housing lower 14.
Thereby, the entire housing 12 is fixed to the bulkhead 8 of the cylinder block 2. That is, the housing upper 13 and the housing lower 14 are fastened together to the cylinder block 2 by the bolts 18. One of the balancer shafts 15 is linked to the crankshaft 10 via a chain 19, and
The pair of balancer shafts 15 are interlocked so as to rotate in opposite directions via a gear 20 (see FIG. 4) inside the housing 12. Specifically, the crankshaft 10 rotates in the direction of the arrow ω, and accordingly, the pair of balancer shafts 15 rotate as shown by the arrows ω ₁ and ω ₂ , respectively. The dashed line W in FIG. 2 indicates the rotation locus of the counterweight.

FIGS. 3 and 4 show details of the balancer device 1, in which the balancer shaft 15 is shown by imaginary lines. Each of the housing upper 13 and the housing lower 14 is cast from an aluminum alloy, and has a substantially symmetrical shape with respect to the dividing surface as shown in FIG. Are formed in parallel. Each shaft accommodating chamber 21 is partitioned back and forth by a substantially central first bearing portion 22. That is, it is partitioned into the first weight accommodation section 23 at the front and the second weight accommodation section 24 at the rear. Further, between the gear housing 25 located at the front end of the housing 12 and the first weight housing 23, the second
A bearing 26 is provided. The first and second bearing portions 2
Lubricating oil is supplied to the cylinder blocks 2 and 26 from the cylinder block 2 side via an oil hole 27 and an oil groove 28.

The balancer shaft 15 has a shaft portion rotatably supported by the first and second bearing portions 22 and 26 and a portion corresponding to the first and second weight accommodating portions 23 and 24. Weight portion 2 having a semicircular cross section (see FIG. 1)
9 are formed. A gear 20 meshing with each other is attached to the front end, and this gear 20 is housed in a gear housing 25. Weight part 2
The outer diameter of 9 is larger than the diameter of the shaft portion supported by the first and second bearing portions 22 and 26. The front end of one balancer shaft 15 protrudes through an opening at the end of the housing 12, and a sprocket 31 that meshes with the above-described chain 19 is attached thereto.

As shown in FIG. 3, a plurality of ribs 41 to 44 are provided on the upper surface of the housing upper 13 along a direction perpendicular to the axis of the balancer shaft 15. These ribs 41 to 44 allow the housing 12
Rigidity is improved. A concave portion 45 opened upward between the rib 42 located above the gear housing portion 25 and the rib 41 located at the forefront end of the housing 12.
Is formed in a portion corresponding to the bottom wall of the concave portion 45, that is, an opening or small hole 46 that opens upward.
Are formed through. The small hole 46 opens at a position above the gear 20, particularly at a position directly above the gear 20. The small hole 46 opens the upper part of the gear housing 25 to the bottom of the recess 45.

The left and right shaft storage chambers 21 are formed independently as shown in FIG. The first and second weight accommodating portions 22 and 23, which are main parts of each shaft accommodating chamber 21, are formed in a substantially cylindrical shape as shown in FIG. Is
It is not a perfect circle but a shape that approximates an involute curve. Specifically, a gap 32 generated between the outer peripheral surface of the weight portion 29 and the lower portion 32a of the housing 12 is the narrowest, and the balancer shaft 1
5 so that the inner peripheral surface 23 gradually increases along the rotation direction
a and 24a are formed. In the lower part of the housing 12 where the gap 32 is largest, an oil discharge port 33 is formed so as to open in a tangential direction. That is, with the oil discharge port 33 interposed,
The portion 32a having the smallest gap 32 and the portion 32 having the largest gap
b are adjacent to each other, and an oil discharge port 33 is opened at a portion serving as a step.

3 and 4, when viewed in the axial direction of the balancer shaft 15, the oil outlet 33 is provided only at the front and rear ends of the first and second weight accommodating portions 23 and 24. Is provided. That is, the first and second
An oil discharge port 3 is provided in a portion adjacent to the bearing portions 22 and 26.
3 is open. And each weight accommodation part 23,2
The inner peripheral surfaces 23a and 24a of 4 are not completely cylindrical surfaces in the axial direction, but have a shape that is slightly thinner at the center and larger in diameter at both ends. In other words, the oil outlet 33 has a gentle tapered surface from the central portion in the axial direction. Accordingly, a step 34 in the rotational direction is formed at the center of each of the weight storage sections 23 and 24 having no oil discharge port 33 in a shape bent in a mountain shape as shown in FIG. An opening for machining is provided on the rear end surface of the housing 12, but is finally closed by a plug 35 made of synthetic resin or the like.

In the above configuration, the first and second oil holes 27
The lubricating oil supplied to the second bearing portions 22 and 26 flows out to the first and second weight accommodating portions 23 and 24 after lubrication, and is discharged to the outside of the housing 12 through the oil discharge port 33. Here, the weight portion 29 rotates at a high speed in each of the weight accommodating portions 23 and 24, but the inner peripheral surfaces 23a and 2
The lubricating oil flows smoothly in the rotational direction and is efficiently discharged from the oil discharge port 33 because the 4a is gradually positioned to the outer peripheral side in the rotational direction. In particular, since the oil discharge port 33 is adjacent to the bearing portions 22 and 26, the lubricating oil flowing out of the bearing portions 22 and 26 is immediately discharged. In addition, the lubricating oil that has received the centrifugal force is directed toward the front and rear ends where the weights of the weight accommodating portions 23 and 24 are relatively large, and is reliably guided to the oil outlet 33.

The oil level in the crankcase 11 is lower than the housing 12 when the engine is operating, and the oil discharge port 33 is kept open.

Further, the oil discharge port 33 is caused by the swing of the oil level or the like.
In the above configuration, the lubricating oil tends to enter, but in the above configuration, the gap 32a on the side serving as the lubricating oil inlet becomes very small along with the rotation of the weight portion 29, so that the intrusion of the lubricating oil is suppressed. Is done.

On the other hand, in the concave portion 45 on the upper surface of the housing 12, oil droplets scattered in the crankcase 11 and oil droplets dropped from the upper wall surface of the crankcase 11 collect. The lubricating oil in the recess 45 passes through the small hole 46 and
5 and supplied to the gear 20. As a result, the gear 20 is properly lubricated.

[Brief description of the drawings]

FIG. 1 is a sectional view taken along the line AA of FIG. 3 showing one embodiment of a balancer device according to the present invention.

FIG. 2 is a sectional view of a main part of an internal combustion engine provided with the balancer device.

FIG. 3 is a sectional view taken along line BB of FIG. 2;

FIG. 4 is a plan view of the lower housing along the line CC in FIG. 3;

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 ... Balancer device 12 ... Housing 13 ... Housing upper 14 ... Housing lower 15 ... Balancer shaft 18 ... Bolt 20 ... Gear 25 ... Gear accommodating part 41, 42 ... Rib 45 ... Recess 46 ... Small hole

Claims (6)

[Claims] 1. A housing mounted below a cylinder block in a crankcase of an internal combustion engine, having an eccentric weight portion, rotatably housed in the housing, and arranged in parallel with each other and side by side. And a pair of balancer shafts arranged in the above. The pair of balancer shafts have gears that mesh with each other, and one of the balancer shafts is driven by the output of the internal combustion engine so that both balancer shafts are in opposite directions. In the balancer device for an internal combustion engine that rotates, the housing is vertically divided into a housing upper and a housing lower, and the balancer shaft is housed together with the gear between the housing upper and the housing lower. A balancer device for an internal combustion engine. 2. At least some of a plurality of bolts for fixing the housing to the cylinder block side pass through both the housing upper and the housing lower, and the bolts are used to fix the housing upper and the housing lower. The balancer device for an internal combustion engine according to claim 1, wherein are tightened together. 3. An end of one balancer shaft extends from the gear and protrudes through an opening in an end of the housing, and a sprocket for driving a chain is mounted on the one end. The balancer device for an internal combustion engine according to claim 1 or 2, wherein: 4. The internal combustion engine according to claim 1, wherein the housing upper is provided with an opening that opens upward at a position above the gear. Balancer device. 5. The balancer device for an internal combustion engine according to claim 4, wherein the opening is provided immediately above the gear. 6. Each balancer shaft has at least two weight portions separated in the axial direction, and a shaft portion between the two weight portions is formed to have a smaller diameter than an outer diameter of the weight portions. The balancer device for an internal combustion engine according to any one of claims 1 to 5, wherein the balancer device is held between semi-circular bearing portions of the housing upper and the housing lower.