Lubricating oil passage structure for a cylinder block

A lubricating oil passage structure for a cylinder block having a plurality of cylinders separated from each other by journal walls and arranged in a row, bearing bores formed in the journal walls for rotatably supporting a pair of rotary shafts in parallel with the crankshaft of the engine on either side of the cylinder row, comprising: a hollow gallery member internally defining three galleries extending in parallel with the crankshaft in the hollow gallery member, and mechanically connecting the bearing caps with each other. Lubricating oil passages extend from these oil galleries to the bearings for the crankshaft and the rotary shaft linearly and in parallel with the bolts for securing bearing caps for the crankshaft bearings to the journal walls. Thus, the lubricating oil passages can be formed in a single manner, and the lengths of the passages are minimized. Furthermore, the gallery member can effectively reinforce the journal walls.

TECHNICAL FIELD 
The present invention relates to a lubricating oil passage structure for a 
cylinder block for an internal combustion engine having a rotary shaft in 
the cylinder block in addition to a crankshaft, and in particular to such 
a lubricating oil passage structure for a cylinder block for an in-line, 
multi-cylinder internal combustion engine having a pair of rotary shafts 
such as counter balancer shafts rotating in synchronism with a crankshaft 
and arranged in the cylinder block on either side of a cylinder row. 
BACKGROUND OF THE INVENTION 
It is known to support a pair of balancer shafts with bearing bores 
provided in parts of journal walls located on either side of the cylinders 
and to rotate them in synchronism with the crankshaft for the purpose of 
cancelling the secondary unbalanced inertia force which is produced in 
most commonly used reciprocating piston engines for vehicles or 
four-stroke, in-line, four-cylinder engines. Supply of lubricating oil to 
the bearings of balancer shafts and a crankshaft is generally carried out 
by using lubricating oil passages branching out from a main gallery 
extending in a cylinder block side wall in parallel with the cylinder row 
and into different journal walls as disclosed in Japanese utility model 
laid open publication No. 62-156622 and Japanese utility model laid open 
publication No. 63-4318. 
Since lubricating oil supply passages in journal walls are typically formed 
either by machine drilling or by combination of casting and machine 
drilling, the manufacturing process becomes increasingly complex, and the 
journal walls tend to have a reduced rigidity as the number of the parts 
to be lubricated in each journal wall increases, and the lubricating oil 
supply passages crisscrosses the interior of each journal wall. Further, 
unevenness of the distribution of lubricating oil to different bearings 
could become a problem. 
BRIEF SUMMARY OF THE INVENTION 
In view of such problems of the prior art, a primary object of the present 
invention is to provide an improved lubricating oil passage structure for 
a cylinder block for an internal combustion engine having a rotary shaft 
in addition to a crankshaft. 
A second object of the present invention is to provide a lubricating oil 
passage structure of the above-mentioned kind which is easy to form in an 
automated manufacturing process. 
A third object of the present invention is to provide a lubricating oil 
passage structure of the above-mentioned kind which can effectively 
reinforce the rigidity and mechanical strength of the journal walls. 
A fourth object of the present invention is to provide a lubricating oil 
passage structure of the above-mentioned kind which permits compact design 
of the engine. 
These and other objects of the present invention can be accomplished by 
providing a lubricating oil passage structure for a cylinder block having 
a plurality of cylinders separated from each other by journal walls and 
arranged in a row, first bearing bores formed in the journal walls in 
cooperation with bearing caps attached to associated end portions of the 
journal walls by threaded bolts for rotatably supporting a crankshaft in 
parallel with the cylinder row along longitudinal ends of the cylinders, 
and second bearing bores formed in the journal walls for rotatably 
supporting a rotary shaft in parallel with the crankshaft on one side of 
the cylinder row, comprising: a hollow gallery member internally defining 
an oil gallery extending in parallel with the crankshaft in the hollow 
gallery member, and mechanically connecting the bearing caps with each 
other; and lubricating oil passages each branching out from the oil 
gallery defined in the hollow gallery member into an associated one of the 
second bearing bores and extending in parallel with holes for receiving 
the threaded bolts for attaching the bearing caps to the journal walls. 
According to a more specific aspect of the present invention, third 
bearing bores are formed in the journal walls for rotatably supporting 
another rotary shaft in parallel with the crankshaft on the opposite side 
of the cylinder row, and third lubricating oil passages are provided in a 
similar manner as the second lubricating oil passages to lubricate the 
third bearing bores. 
Thus, the lubricating oil supply passages leading to the bearing bores for 
supporting a rotary shaft may be simplified as it is formed separately 
from that for the crankshaft and externally of the main body of the 
cylider block. Further, since the gallery member may be provided 
separately from the cylinder block, the rigidity of the journal walls may 
be favorable increased by advantageous arrangement thereof. In particular, 
since the lubricating oil passages may be drilled in the same direction as 
the threaded holes for receiving the threaded botls for mounting bearing 
caps, the manufacturing process is extremely simplified. 
Also, owing to the above mentioned structure, the lubricating oil supply 
passages may be passed in the shortest path without being interfered by 
the bolt holes for mounting the bearing caps, and the increase in the 
dimensions of the bearing caps can be effectively prevented. 
A particulalry favorable result can be achieved when the lubricating oil 
passages extend from the oil gallery to the second bearing bores between 
an adjacent one of the threaded bolts for attaching the bearing caps to 
the journal walls and a plane parallel with the holes for receiving the 
threaded bolts and tangential to an external end of a profile of the 
second bearing bores, more preferably a plane parallel with the holes for 
receiving the threaded bolts and passing through the center of the profile 
of the second bearing bores. According to a preferred embodiment of the 
present invnetion, the lubricating oil passages are each communicated with 
an associated one of the second bearing bores tangentially at an internal 
end of the profile of the second bearing bores. 
Moreover, by arranging a plurality of oil galleries for the crank journals 
and the bearing bores for the rotary shafts in parallel with each other, 
the bearing caps are thereby connected with each other in the manner of a 
ladder, and the rigidity of the journal walls against bending and twisting 
deformations can be increased even further. Preferably, center lines of 
the lubricating oil passages are offset slightly inwards from a center 
line of the oil gallery so as to maximize this effect without increasing 
the dimensions of the gallery member. 
According to a preferred embodiment of the present invention, a 
communicating passage extending perpendicularly to the oil galleries and 
communicating the oil galleries with one another is provided adjacent to 
one of the bearing caps corresponding to one of the journal walls which is 
subjected to a relatively large load, for instance the middle journal wall 
of an in-line four-cylinder engine.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT 
FIG. 1 is a plan view of a cylinder block 1 of an in-line four-cylinder 
engine constructed according to the present invention. This cylinder block 
1, which is made, for instance, by casting aluminum alloy, defines a water 
jacket 4 between a cylinder block outer wall 2 and a cylinder block inner 
wall 3, and cylinder bores 6a through 6d slidably receiving pistons (not 
shown in the drawings) are formed by liners 5 integrally embedded in the 
cylinder block inner wall 5 inside the water jacket 4 during casting 
process. 
The upper surface of the cylinder block 1 is provided with a cylinder head 
mounting surface 7 which is shaped into a precise and smooth plane. In the 
parts of the cylinder head mounting surface 7 surrounding the water jacket 
4 are provided ten threaded bolt holes 8 extending in parallel with the 
axial lines of the cylinders substantially at equal interval, each pair of 
the threaded holes 8 being positioned on either side of a portion 
intermediate between adjacent cylinder bores 6a through 6d, and additional 
pairs being arranged on either side of a portion located at either 
longitudinal end of the cylinder row. These bolt holes 8 are provided with 
internal threads for receiving threaded head bolts for securing a cylinder 
head (not shown in the drawings) on the cylinder head mounting surface 7. 
Openings 10 communicating with the interior of a crank case are formed in 
the cylinder head mounting surface 7 on either side of the first and the 
fourth cylinder bores 6a and 6d which are located on either longitudinal 
end of the cylinder row. These openings 10 are substantially symmetric 
with respect to the associated cylinder bores 6a and 6d, and one of the 
openings 10 for each of the cylinder bores 6a and 6d serves as an oil 
return passage for returning the lubricating oil which has lubricated a 
valve actuating mechanism in the cylinder head back to an oil pan, and the 
other openings 10 serve as crank case ventilating passages for allowing 
flow of blow-by gas between the cylinder head and the crank case. In the 
present embodiment, the engine is mounted on the vehicle in an inclined 
state (refer to FIG. 13) so that the passages located on the right hand 
side of FIG. 1 serve primarily as the oil return passages. 
In a right hand side part of the portion of the cylinder block outer wall 2 
located between the second and third cylinder bores 6b and 6c is provided 
a lubricating oil supply passage 11 in parallel with the threaded bolt 
holes 8 to supply lubricating oil to the valve actuating mechanism (not 
shown in the drawings). 
As shown in FIG. 2, journal walls 13a through 13e defining bearing halves 
12 for rotatably supporting journals of a crankshaft as described 
hereinafter are provided in both ends of the cylinder row and intermediate 
parts between the mutually adjoining cylinder bores 6a through 6d. These 
journal walls 12a through 13e extend in parallel with the axial lines of 
the cylinders, and perpendicular to the plane which is perpendicular to 
the cylinder axial lines, and ten bolt holes 14 are formed in the lower 
surfaces of the journal walls, each pair of the bolt holes being provided 
in each of the journal walls, to attach a bearing cap on the lower surface 
of each of the journal walls. The lower surface of the cylinder block 1 
which is finished into a plane to attach an oil pan thereto is provided 
with an oil pan flange 15 extending laterally outwards, and a plurality of 
bolt holes 16 are provided in the oil pan flange 15. 
As shown in FIG. 3, a pair of balancer shafts 17 extend in parallel with 
the cylinder row on either side of the first through third cylinder bores 
6a through 6c. Each of the balancer shafts 17 consists of a counter weight 
portion 18 having a center of gravity off-set from its axial center, and 
an extension shaft portion 19 extending from one end of the counter weight 
portion 18. A first bearing potion 20a is provided at the free end of the 
extension shaft portion 19, a second bearing portion 20b is provided at 
the other end of the counter weight portion 18, and a third bearing 
portion 20c is provided at an intermediate part of the counter weight 
portion 18. 
Each of the counter weight portions 18 is located on one or the other side 
of the second and third cylinder bores arranged along the cylinder row, 
and the first through third bearing portions 20a through 20c are rotatably 
supported by a first bearing bore 21a provided in the first journal wall 
13a adjacent to the first cylinder bore 6a, a second bearing bore 21b 
provided in the fourth journal wall 13d located between the third and 
fourth cylinder bores 6c and 6d, and a third bearing bore 21c provided in 
the third journal wall 13c located between the second and third cylinder 
bores 6b and 6c, respectively. 
In this way, the balancer shafts 17 are supported by the cylinder block 1 
in a sufficiently rigid manner so as to control any twisting deformation 
of the balancer shafts 17. 
As best shown in FIG. 3, the openings 10 are located in the cylinder block 
so as to avoid the counter weight portions 18 of the balancer shafts 
because the eccentric counter weight portions 18 would create undesirable 
resistance to the flow of blow-by gas through these openings 10. The 
openings 10 adjoining the cylinder bore 6a at one of the longitudinal ends 
of the cylinder row are each located under the associated extension shaft 
portion 19 but the other openings 10 adjoining the cylinder bore 6d at the 
other longitudinal end of the cylinder row are totally unobstructed by the 
balancer shafts 17 so that an unobstructed free flow of blow-by gas may be 
achieved through these openings 10 adjoining the latter cylinder bore 6d. 
One end of each of the balancer shafts 17 projecting out of the first 
journal wall 13a carries a timing pulley 22 securely attached thereto 
(refer to FIG. 13). Each of the balancer shafts 17 rotates at twice the 
speed of the crankshaft 33 and in opposite direction with respect to the 
other timing pulley 22 by passing a timing belt 26 around the timing 
pulleys 22 and another timing pulley 25 securely attached to the 
crankshaft 33. In the present embodiment, the timing belt 26 is passed 
around the timing pulleys and controlled by a tension pulley 27 mounted on 
the corresponding end surface of the cylinder block in such a manner that 
the timing pulley 22 on the left hand side turns in clockwise direction 
while the timing pulley 22 on the right hand side turns in counter 
clockwise direction as seen in FIGS. 1 and 3. 
A large diameter bore 23 is provided in the second journal wall 13b located 
between the first and second cylinder bores 6a and 6b to pass the second 
and third bearing portions 20b and 20c therethrough, and the fifth journal 
wall 13e adjacent to the fourth cylinder bore 6d is provided with a tool 
access opening 24 for the convenience of machining the second bearing bore 
21b. This tool access opening 24 is closed by mounting a transmission case 
(not shown in the drawings) thereon. 
As shown in FIGS. 4 through 8, the lower surfaces of the journal walls 13a 
through 13e which are finished into smooth planes are each centrally 
provided with one of the aforementioned bearing halves 12, and bearing 
caps 30a through 30e are securely mounted on these lower surfaces. 
Each of the bearing caps 30a through 30e is provided with a smooth and 
planar upper surface which abuts the lower surface of the associated 
journal wall 13a through 13e, and the upper surface of each of the bearing 
caps 30a through 30e is centrally provided with a bearing half 31 
corresponding to one of the bearing halves 12. These bearing halve 12 and 
31 define substantially circular bearing profiles into each of which is 
fitted a bearing metal 32 for rotatably supporting the crankshaft 33. The 
lower surface of each of the bearing caps 30a through 30e is also finished 
flat so that they may be joined together by attaching a gallery member 34 
thereto. 
The gallery member 34 which is made by integral casting comprises a 
plurality of legs 35a through 35e which are attached to the lower surfaces 
of the bearing caps 30a through 30e, and three hollow portions 36a through 
36c which connect the legs 35a through 35e with one another along the 
direction of the cylinder row. The first hollow portion 36a or the central 
one of the hollow portions 36a through 36c connects the lower ends of all 
the leg portions 35a through 35e with each other, and the second and third 
hollow portions 36b and 36c extending along either side of the first 
hollow portion 36a connect the outer and lower ends of the first through 
fourth leg portions 35a through 35d substantially immediately below the 
associated balancer shafts 17. By thus extending the hollow portions 36b 
and 36c located on either side along the outer and lower ends of the leg 
portions 35a through 35 d, the rigidity of the gallery member 34 can be 
ensured in a simple and efficient manner. Further, a connecting member 37 
extends across the fourth leg portion 35d and the fifth leg portion 35e on 
each side of the first hollow member 36a. The hollow portions 36a through 
36c are connected to each other by a connecting tube 38 extending 
perpendicularly to the hollow portions 36a through 36c to communicate the 
interiors of the hollow members 36a through 36c with each other. Axial 
ends of the hollow portions 36a through 36c, and the connecting tube 38 
are closed by plugs 39. 
The bearing caps 30a through 30e and the leg portions 35a through 35e of 
the gallery member 34 are provided with bolt holes 40 and 41 at those 
parts corresponding to the bolt holes 14 of the journal walls 13a through 
13e in a coaxial manner. By passing a pair of bolts 42, for each of the 
journal walls 13a through 13e, through the associated bolt holes 14 via 
the bolt holes 40 and 41, the bearing caps 30a through 30e and the leg 
portions 35a through 35e are integrally attached to the associated journal 
walls 13a through 13e. 
From a first oil gallery 43a defined in the center of the first hollow 
member 36a branched out into branched oil passages 44a each of which 
communicates with the interior of an associated one of bearing metals 32 
by passing through the associated one of the leg portions 35a through 35e, 
the associated one of the bearing caps 30a through 30e, and the associated 
one of the journal walls 13a through 13e. From second and third oil 
galleries 43b and 43c defined in the second and third hollow members 36b 
and 36c located on either side of the first hollow member 36a branch out 
into branched oil passages 44b and 44c, respectively, which communicate 
with the interiors of the associated bearing bores 21a through 21c 
supporting the balancer shafts 17 by passing through the first, third and 
fourth leg portions 35a, 35c and 35d, the associated bearing caps 30a, 30b 
and 30c and the journal walls 13a, 13c and 13d, respectively. These 
branched oil passages 44a, 44b and 44c extend in parallel with the bolt 
holes 14, 40 and 41, and the parts of the side branched passages 44b and 
44c located in the journal walls 13a, 13c and 13d are formed during the 
casting process so that the volume of the excess parts may be reduced, and 
a favorable casting result may be obtained. 
The side branched oil passages 44b and 44c are located centrally between 
the axial lines of the adjacent bolt holes 14, 40 and 41 and the axial 
centers of the balancer shafts 17, and are connected to the second and 
third oil galleries 43b and 43c at parts which are located more outwards 
than the axial centers of the second and third oil galleries 43b and 43c. 
A favorable result can be achieved when the lubricating oil passages 44b 
and 44c extend from the oil galleries 43b and 43c to the bearing bores 21a 
between an adjacent one of the threaded bolts 42 and a plane parallel with 
the holes 14, 40 and 41 for receiving the threaded bolts 42 and tangential 
to an external end of a profile of the 21a bearing bores. Thereby, the 
dimensions of the bearing caps may be controlled, and the influences of 
the bolt holes 40 and 41 thereon may be avoided. And, as mentioned 
earlier, since the second and third hollow members 36b and 36 c are 
located substantially exactly under the balancer shafts 17, the side 
branched oil passages 44b and 44c may have minimum lengths. 
At each of the junctions of the bolt holes 40 and 41 and the branched oil 
passages 44a, 44b and 44c at the interfaces between the journal walls, the 
bearing caps and the leg portions, a hollow locating pin 45 is placed 
across the adjoining two parts. 
The lubricating oil supply passage 11 for supplying lubricating oil to the 
valve actuating mechanism extends from the cylinder head mounting surface 
7 to a part slightly above the third bearing bore 21c between the center 
of the adjacent bolt hole 8 for securing the cylinder head and the center 
of the third bearing bore 21c as shown in FIG. 6. On a side surface of the 
cylinder block wall 2 corresponding to the third journal wall 13c through 
which the lubricating oil supply passage 11 is formed is provided an 
island portion 46 for mounting an oil filter F thereon. Inside the third 
journal wall 13c and the island portion 46 are provided an upper 
horizontal passage 47 extending between an end surface of the island 
portion 46 and the lubricating oil passage 11 above the third bearing bore 
21 along a direction perpendicular to the cylinder axial line, and a lower 
horizontal passage 48 communicating a side surface of the cylinder block 
wall 2 with an end of the branched oil passage 44b below the third bearing 
bore 21c along a direction perpendicular to the cylinder axial line. The 
upper horizontal passage 47 is provided with an inner threaded portion at 
its open end for threading the oil filter F therein, and is cast into a 
tapered shape at its inner end to avoid interference with the third 
bearing bore 21c. The open end of the lower horizontal passage 48 is 
closed by a plug 49. A vertical passage 50 extends downwards from the 
upper surface of the island portion 46 in parallel with the cylinder axial 
line at a position externally of the third bearing bore 21c to communicate 
the two passages 48 and 48 with each other. The open end of this vertical 
passage 50 is also closed by a plug 51. 
Referring also to FIG. 12, supply of lubricating oil to the oil filter F is 
conducted through a first supply passage 53 internally defined in a ridge 
52 extending along the axial line of the balancer shaft 17 in the side 
surface of the cylinder block wall 2. 
One of the side branched oil passages 44b of the third journal wall 13c is 
not only a lubricating oil supply passage for the third bearing bore 21c 
but also a branched oil passage for conducting the lubricating oil which 
has been routed to the oil filter F to the second oil gallery 43b. 
Now the flow of lubricating oil is described in the following. 
The lubricating oil which is supplied from the oil pump (not shown in the 
drawings) under pressure flows into the oil filter F via the first oil 
supply passage 53. The lubricating oil which has been filtered by the oil 
filter F diverges into the upper horizontal oil passage 47 and the 
vertical oil passage 50, and is then supplied to the cylinder head via the 
lubricating oil supply passage 11 on the one hand and to one of the side 
branched oil passages 44b in the third journal wall 13c via the lower 
horizontal oil passage 48 on the other hand. A part of the lubricating oil 
flows upwards through the side branched oil passage 44b, and flows out 
from the third bearing bore 21c. A part of the lubricating oil which has 
flown downwards through the side branched oil passage 44b flows out from 
the first and second bearing bores 21a and 21b provided in the first and 
fourth journal walls 13a and 13d via the second oil gallery 43b and the 
side branched oil passage 44b branching out therefrom. The lubricating oil 
remaining after being distributed to the first oil gallery 43a and the 
third oil gallery 43c via the communicating oil passage 38a defined in the 
connecting tube 38 is supplied to the crank journal portions via the 
central branched oil passage 44a and the bearing bores 21a through 21c for 
the other balancer shaft 17 via the other side branched oil passage 44c. 
In an engine having a crankshaft and a pair of balancer shafts on either 
side thereof, each journal wall is provided with three bearings. 
Therefore, the passages for supplying lubricating oil to these bearings 
tend to be highly complex. Therefore, according to the present invention, 
oil galleries internally defining three hollow portions are provided so as 
to connect the bearing caps 30a through 30e attached to the lower surfaces 
of the journal walls 13a through 13e, for supporting the crankshaft, with 
each other and so as to correspond to the respective shafts, with oil 
supply passages leading various bearings being branched out from the oil 
galleries. In this way, by using oil galleries which are separate from the 
cylinder block, the manufacturing of the engine is simplified as compared 
with the engine structure using a cylinder block internally provided with 
oil galleries, and factors for reducing mechanical strength can be 
eliminated. Further, since the branched oil passages extending from the 
oil galleries to the bearings are in parallel with the holes for receiving 
threaded bolts, a step of replacing tools can be eliminated during the 
drilling process, and the manufacturing process is simplified. 
Additionally, in order to achieve a smooth operation of an engine, it is 
desirable to increase the rigidity of the structure supporting the 
crankshaft, and this can be accomplished in highly desirable manner by 
connecting the bearing caps 30a through 30e with a plurality of hollow 
members 36a through 36c in the manner of a ladder. In particular, in a 
four cylinder engine in which the third journal wall bears the largest 
inertia force of all the journal walls, this portion can be effectively 
reinforced by providing the connecting tube 38 so as to connect the hollow 
members 36a though 36c in the vicinity of the third journal wall 13c. 
Thus, according to the present invention, since passages for supplying 
lubricating oil to a plurality of bearing portions provided in journal 
walls can be achieved in a highly organized fashion, and a significant 
advantage can be gained in simplifying the manufacturing process. 
Furthermore, since the bearing caps are connected by a plurality of hollow 
portions in the manner of a ladder, the rigidity of the journal walls can 
be improved against both bending and twisting deformations, and a 
significant advantage can be gained in improving the performance of the 
engine.