JP3708857B2 - Housing for balance shaft - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a housing that accommodates a balance shaft provided with a counterweight for canceling an excitation force generated by an engine piston.
[0002]
[Prior art]
A balance shaft equipped with a counterweight for canceling the secondary excitation force generated by the piston of the engine is placed under the crankshaft in the oil pan, and the crankshaft shaft is connected via a chain / sprocket mechanism or gear mechanism. A balancing device that transmits rotation to a balance shaft is known, for example, in Japanese Utility Model Publication No. 5-39233.
[0003]
Since the balance shaft of the balancing device is provided below the oil level in the oil pan, the entire balance shaft is covered with a housing in order to prevent the balance shaft from causing inconvenience due to stirring of the lubricating oil. Yes.
[0004]
By the way, in order to promote the downsizing of the engine, it is preferable that the balancing device is disposed as close to the crankshaft as possible.
[0005]
[Problems to be solved by the invention]
However, in order to dispose the balancing device close to the crankshaft, a part of the housing has to be cut out in order to avoid interference with the large end of the connecting rod. Cutting the housing causes a reduction in the rigidity of the housing.
[0006]
The present invention has been devised to solve such problems of the prior art, and its main purpose is to ensure high rigidity while avoiding interference with the connecting rod large end. The object is to provide a balance shaft housing.
[0007]
[Means for Solving the Problems]
In order to achieve such an object, in claim 1 of the present invention, the two balance shafts (13L and 13R) that rotate in reverse to cancel the vibration generated by the piston of the engine are connected to the crankshaft ( 1L). ) in order to support and accommodate at lower and upper housing (14U) and the lower housing (14L) and of the balance shaft housing consisting configured to cover the lower side of the balance shaft that covers the upper side of the balance shaft, said upper housing Is an opening (42F / 42R) in which at least a portion of the two balance shafts covering the upper part of each counterweight (19) is cut so as not to interfere with the locus of the large end portion (41) of the connecting rod, and its outer peripheral portion A fastening portion (fastening boss 40) for the engine main body provided on the side of the two balance shafts (4 ) In comparison with the assumed that lies in the higher have position towards the outside (47) closer to the fastening portion. In this way, the outer portion located in the vicinity of the fastening portion with respect to the engine body having essentially high rigidity compensates for the reduction in the rigidity of the housing due to the provision of the opening in order to avoid interference with the connecting rod .
[0008]
DETAILED DESCRIPTION OF THE INVENTION
Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.
FIG. 1 shows a reciprocating piston engine to which the present invention is applied. The engine E is an in-line four-cylinder engine in which the crankshaft 1 extends in the horizontal direction, and includes a head cover 2, a cylinder head 3, a cylinder block 4, a lower block 5, a balance device 6, and an oil pan 7. .
[0009]
The balancing device 6 is for reducing the secondary vibration of the engine E caused by the reciprocating motion of the piston. The balance device 6 is encased in the oil pan 7 and has a lower surface of the lower block 5 (below the crankshaft 1). ). The balancing device 6 includes a large sprocket 8 fixed to the front end of the crankshaft 1 (hereinafter referred to as the crank pulley or chain case side) and the left side (hereinafter referred to as the left and right direction toward the crank pulley or chain case). The crankshaft 1 via a small sprocket 9 fixed to the front end of a balance shaft (to be described later in detail) and an endless link chain 10 spanned between the large and small sprockets 8 and 9. The rotation of is transmitted.
[0010]
The endless link chain 10 is secured by a chain guide 11 fixed to the left side of the center of the crankshaft on the front surface of the lower block 5 and fixed to the right side of the small sprocket 9 on the front end surface of the balancing device 6. An appropriate tension is always applied by the chain tensioner 12.
[0011]
As shown in FIGS. 2 and 3, the balancing device 6 supports and accommodates a pair of left and right balance shafts 13L and 13R having substantially the same shape, and these two balance shafts 13L and 13R in parallel with each other. Accordingly, an upper housing 14U and a lower housing 14L that are vertically divided into two along a plane passing through the centers of the balance shafts 13L and 13R are provided.
[0012]
The balance shafts 13L and 13R are interlocked and connected to each other by helical gears 15L and 15R integrally coupled to the balance shafts 13L and 13R. Here, as described above, the driving force of the crankshaft 1 is transmitted to the left balance shaft 13L via the large sprocket 8, the endless link chain 10, and the small sprocket 9. As a result, the left balance shaft 13L is rotationally driven in the same direction as the crankshaft 1 at twice the rotational speed of the crankshaft 1, and the right balance shaft 13R rotates in the opposite direction by the meshing of the helical gears 15L and 15R. Driven.
[0013]
Thrust receiving surfaces 16 are formed in portions of the upper housing 14U corresponding to the helical gears 15L and 15R. Further, this portion is open upward, and part of the tooth surfaces of the helical gears 15L and 15R are exposed in the oil pan, and the lubricating oil that drops from above or scatters in the oil pan 7 is provided. The helical gears 15L and 15R enter the meshing portions and the thrust receiving surface 16, and the portions are sufficiently lubricated.
[0014]
The balance shafts 13L and 13R are integrally formed with a first journal portion 17 having a relatively small diameter on the front end side and a second journal portion 18 having a relatively large diameter on the rear end side. A counterweight 19 that is divided into two parts before and after the second journal portion 18 is integrally formed on the rear end side of each balance shaft 13L and 13R. The counterweight 19 has a center of gravity biased radially outward from the center of rotation.
[0015]
On the other hand, the first journal portion 17 of each of the balance shafts 13L and 13R is supported by a first bearing hole 25 provided in the first bearing wall 25a that is integral with the front end portion of the lower housing 14L. The second journal portion 18 of each balance shaft is supported by a second bearing hole 26 having a two-part metal bearing formed by joining the upper and lower housings 14U and 14L to each other.
[0016]
When the balance shafts 13L and 13R are accommodated in the housings 14U and 14L, the front ends of the balance shafts 13L and 13R are inserted into the first bearing holes 25, and the first journal portions 17 are inserted into the first bearings. The second journal portions 18 of the balance shafts 13L and 13R are placed on the halved portions of the second bearing holes 26 on the lower housing 14L side, and further supported in this state on the upper housing 14U side. 2 If the upper and lower housings 14U and 14L are joined to each other after the halved portions of the bearing holes 26 are aligned with the second journal portions 18 of the balance shafts 13L and 13R, the balance shafts 13L and 13R are It will be rotatably accommodated in the housings 14U and 14L.
[0017]
As shown in FIG. 3, a trochoid type lubricating oil pump 27 is provided on the front end surfaces of the upper and lower housings 14U and 14L to pump the lubricating oil to various parts of the engine. The lubricating oil pump 27 includes an outer rotor 29 received in a pump housing 28 bolted to the front end surfaces of both housings 14U and 14L, and an inner rotor 30 connected to the front end of the right balance shaft 13R. The inner rotor 30 that rotates integrally with the right balance shaft 13R cooperates with the outer rotor 29, and is sucked from the oil strainer 31 attached to the bottom wall of the lower housing 14L through the suction pipe 32 that is integrally formed on the bottom wall of the lower housing 14L. The lubricating oil in the oil pan 7 is pumped to various parts of the engine through oil passages (not shown) provided in the lower block 5 and the cylinder block 4 and the like.
[0018]
The upper and lower housings 14U and 14L are located at the positions of the left and right sides of the portion between the helical gears 15L and 15R and the front counterweight 19 and the second bearing wall 26a that supports the second journal portion 18. A total of five bolts B1 and B2 are fastened to each other, and in particular, it is considered that the portion of the second bearing wall 26a where the radial acceleration due to the rotation of the counterweight 19 acts is less likely to be loosened.
[0019]
The balancing device 6 configured as described above is formed by a through bolt B3 inserted from below into a bolt hole H provided in a boss portion 40 integrally formed on the left and right sides of the second bearing wall 26a and on both sides of the pump housing 28. Fastened to the lower surface of the lower block 5.
[0020]
As shown in FIGS. 4 and 5, the large end portion 41 of the connecting rod is provided at a portion corresponding to each of the four counterweights 19 provided on the two balance shafts 13L and 13R on the upper wall of the upper housing 14U. Openings 42F and 42R are formed to avoid interference with the rotation trajectory. Since the rigidity of the upper housing 14U is reduced by providing these four openings 42F and 42R, the following reinforcement measures are taken.
[0021]
Upward projecting portions 43 and 44 are formed along the front and outer edges of the two openings 42F located on the front side of the second bearing wall 26a. An upward projecting portion 45 is formed along the rear edge of the two openings 42R on the rear side of the second bearing wall 26a. By providing these protrusions 43, 44, and 45, the rigidity around the openings 42F and 42R is increased.
[0022]
The outer portion 47 is made higher than the central portion 46 between the openings 42F and 42R arranged side by side, that is, the portion between the two balance shafts. Thus, the rigidity around the openings 42F and 42R is enhanced by making the outer portion 47 positioned around the fastening portion with respect to the engine body having essentially high rigidity higher than the central portion 46.
[0023]
It extends along the axis of the balance shafts 13L and 13R between the protrusion 43 provided at the front edge of the two front openings 42F and the rear edge of the opening 48 exposing the tooth surfaces of the helical gears 15L and 15R. It connects with the rib 49 to do. This suppresses a decrease in rigidity of the upper housing 14U due to the provision of the openings 42F and 42R.
[0024]
On both the front and rear surfaces of the second bearing wall 26a, hook-shaped extending walls 50F and 50R having an arcuate contour projecting upward are provided so as to cover a part of each counterweight 19. The free end edge of the extension wall 50F on the front side of the second bearing wall 26a forms the rear edge of the front opening 42F, and the free end edge of the extension wall 50R on the rear side of the second bearing wall 26a becomes the rear end of the rear wall 42F. It forms the front edge of the opening 42R. By extending the flange-like extending walls 50F and 50R from both the front and rear surfaces of the second bearing wall 26a in this way, the rigidity of the second bearing wall 26a is enhanced, and the openings 42F and 42R are provided thereby. The lowering of rigidity of the upper housing 14U is compensated.
[0025]
Extending walls 51 in the direction orthogonal to the axis of the balance shafts 13L and 13R are formed on both the front and rear sides of the upper end surface of the second bearing wall 26a so as to avoid the fastening bolt B2. By providing the extending wall 51 along the second bearing wall 26a in this way, the rigidity of the second bearing wall 26a can be increased, so that the fastening rigidity of the upper and lower housings 14U and 14L can be significantly increased. Moreover, since the extending wall 51 and the extending walls 50F and 50R are connected to each other, the rigidity around the openings 42F and 42R can be greatly improved.
[0026]
【The invention's effect】
As described above in detail, according to the present invention, a great effect can be obtained in enhancing the rigidity of the balance shaft housing provided with the opening for avoiding interference with the connecting rod large end.
[Brief description of the drawings]
FIG. 1 is a front view showing only an essential part of an engine to which the present invention is applied. FIG. 2 is a partial longitudinal cross-sectional view of an oil pan cut along the axis of a left balance shaft. FIG. 3 is a longitudinal sectional view cut along the right balance axis of the balance device. FIG. 4 is a top view of the balance device. FIG. 5 is a perspective view of the upper housing.
1 Crankshafts 13L and 13R Balance shafts 14U and 14L Housing 26a Bearing wall 40 Fastening boss 41 Large end part 42F and 42R of connecting rod Opening 43 and 44 Projection part 46 Central side part 47 Outer part 48 Opening 49 Rib 50F and 50R Extension wall 51 Extension wall

Claims (1)

An upper housing that covers the upper part of the balance shaft and supports the balance shaft so as to support and accommodate two balance shafts that rotate in reverse to cancel the vibration generated by the piston of the engine. A balance shaft housing comprising a lower housing covering a lower portion ;
The upper housing has an opening formed by cutting a portion of the two balance shafts covering at least the upper part of each counterweight so as not to interfere with the locus of the large end of the connecting rod, and fastening to the engine body provided on the outer periphery thereof. And
The balance shaft housing is characterized in that the side edge of the opening is located at a higher position on the outer side closer to the fastening portion than the side between the two balance shafts.

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