Cylinder liner

A cylinder liner having an outer circumferential surface having a plurality of groups of annular grooves, wherein each of the groups of annular grooves has two longitudinal grooves communicating the individual annular grooves with each other, forming an outlet and an inlet for the cooling oil and disposed at locations spaced apart by 180.degree. in a circumferential direction, and the outlet communicates with the inlet in series in the adjoining groups of annular grooves. The outer circumferential surface has further a longitudinal groove connected to the lower end of the longitudinal groove forming the outlet of the lowermost group of annular grooves, a circumferential groove connected to the lower end of the longitudinal groove, and a longitudinal groove having the upper end connected to the circumferential groove and the lower end released, and the lowermost longitudinal groove is disposed at a circumferential position differing from the longitudinal grooves in the groups of annular grooves.

BACKGROUND OF THE INVENTION 
1. Field of the Invention 
This invention relates to a cylinder liner provided with cooling oil 
grooves at its outer circumferential surface. 
2. Description of the Related Art 
In prior art cooling systems for engines, cooling water is normally used 
for cooling operation. A cylinder block is typically provided with cooling 
water passages in case of a dry cylinder liner and, in case of a wet 
cylinder liner, a concave portion formed at an inner circumferential 
surface of a bore part of the cylinder block and an outer circumferential 
surface of a cylinder liner define the cooling water passage. The cooling 
water flows from a lower part of the cylinder liner to an upper part 
thereof and further flows to the cylinder head to cool the 
However, because improvement of engine performance in recent years has 
become an essential requirement, heat generated in a combustion chamber is 
also increased and a temperature at an upper part of the cylinder liner 
near the combustion chamber becomes excessively high. Accordingly, in view 
of designing engines having a compact size as well as a high speed and a 
high load capacity, the prior art cooling structure for the cylinder has a 
problem that the upper part of the cylinder liner near the combustion 
chamber cannot be sufficiently cooled. 
In order to accommodate the foregoing, it has been proposed to provide a 
cylinder liner in which an outer circumferential surface of the cylinder 
liner is formed with a plurality of annular grooves, in which the 
plurality of annular grooves described above are divided into a plurality 
of groups of annular grooves, where each of the groups of annular grooves 
has two longitudinal grooves communicating the annular grooves with each 
other. The two longitudinal grooves forming an outlet and an inlet, 
respectively, for the cooling oil are disposed at locations spaced apart 
by 180.degree. in a circumferential direction. The outlet communicates 
with the inlet in series with the adjoining groups of annular grooves. A 
total sectional area of the annular grooves in each of the groups of 
annular grooves is decreased from a lower part toward an upper part in an 
axial direction of the cylinder liner (referenced in Japanese Utility 
Model Application No. 62-60967). 
With the foregoing, a flow of cooling oil directed from the upper part of 
the cylinder liner to the lower part thereof will be described, wherein 
the cooling oil flows around the outer circumference of the cylinder liner 
through groups of the annular grooves, and thereafter moves from the 
longitudinal groove forming the outlet of the group of annular grooves 
toward the longitudinal groove forming the inlet of the adjoining next 
stage group of annular grooves. The cooling oil then flows from the 
longitudinal groove into the annular grooves of the group of annular 
grooves, flows around the outer circumference of the cylinder liner, and 
then the cooling oil is moved to the lower adjoining group of annular 
grooves in the same manner. 
The cooling oil is then discharged into the oil pan from a discharging 
longitudinal groove disposed on the extension line of the longitudinal 
groove forming the outlet of the lowermost group of annular grooves. 
In this case, if the cooling oil drops onto the arm part of the crankshaft, 
the balance weight or the bearing of the connecting rod connected to the 
pin or the like when the cooling oil is discharged into the oil pan, a 
substantial flow rate of the cooling oil is flowed down, causing a load to 
be applied to the rotation of the crankshaft. 
In addition, when the cooling oil strikes against the arm part of the 
rotating crankshaft, the cooling oil is dispersed to mix air during its 
dispersion and the cooling oil having air mixed therein is dropped into 
the oil pan. When air is mixed in the lubricant oil stored in the oil pan, 
the air flows into tee lubricant oil passages or the cooling oil passages 
together with the lubricant oil, so that the lubricating performance or 
the cooling performance is reduced. 
Accordingly, the cooling oil to be discharged into the oil pan is 
preferably dropped onto the main shaft of the crankshaft. 
However, if the circumferential positions of the longitudinal groove 
forming the outlet of the lowermost group of annular grooves are disposed 
above the main axis of the crankshaft, the longitudinal groove forming the 
inlet for the cooling oil in the group of annular grooves is disposed 
above the main axis of the crankshaft. 
In the case of a multi-cylinder type engine, there is a problem that an 
arrangement of the inlets for the cooling oil above the main axis of the 
crankshaft causes the supplying passages formed in the cylinder block for 
supplying the cooling oil to the inlets for the cooling oil to be bypassed 
around bolt holes, and a formation of the supplying passages for the 
cooling oil extending from the side surface of the cylinder block to the 
inlets for the cooling oil in the cylinder liners is not facilitated due 
to the fact that the bolt holes used for fastening the cylinder liners to 
the cylinder block are disposed at the lateral positions between the bores 
of the cylinder block. 
SUMMARY OF THE INVENTION 
It is an object of the present invention to provide a cylinder liner in 
which a cooling oil supplying passage communicating with an inlet for the 
cooling oil in the cylinder liner may be easily formed in a cylinder 
block. 
The cylinder liner of the present invention contains an outer 
circumferential surface having a plurality of groups of annular grooves, 
wherein each of the groups of annular grooves has two longitudinal grooves 
allowing communication between the annular grooves. The two longitudinal 
grooves forming an outlet and an inlet, respectively, for the cooling oil 
are disposed at locations spaced apart by 180.degree. in a circumferential 
direction. The outlet communicates with the inlet in series with the 
adjoining groups of annular grooves. A total sectional area of the annular 
grooves in each of the groups of annular grooves is decreased from a lower 
part toward an upper part thereof. The outer circumferential surface has 
further a longitudinal groove connected to the lower end of the 
longitudinal groove forming the outlet of the lowermost group of annular 
grooves, and a circumferential groove connected to the lower end of the 
longitudinal groove and a longitudinal groove having an upper end 
connected to the circumferential groove and a lower end released, wherein 
the longitudinal groove having the upper end connected to the 
circumferential groove and the lower end released is disposed at a 
different circumferential position than the longitudinal grooves in the 
groups of annular grooves. 
An outer circumferential surface at a higher position than the uppermost 
group of annular grooves may be provided with one annular groove 
communicating with the longitudinal groove forming the inlet of the 
uppermost group of annular grooves. 
According to the cylinder liner of the present invention, in the case where 
the cylinder liner is installed in the cylinder block in such a way so 
that the position of the cooling oil discharging groove in the cylinder 
liner is disposed above the main axis of the crankshaft, the cooling oil 
inlet of the cylinder liner is disposed at the circumferential position 
apart from above the main axis of the crankshaft, so that the cooling oil 
supplying passage extended from the side surface of the cylinder block to 
the cooling oil inlet in the cylinder liner can be arranged at a position 
far apart from the bolt holes used in fastening the cylinder liner, 
wherein the bolt holes are disposed at the lateral positions between the 
bores of the cylinder block. The cooling oil supplying passage can then be 
easily formed.

DESCRIPTION OF THE PREFERRED EMBODIMENT 
Cooling oil grooves are formed at an outer circumferential surface of a 
cylinder liner of a 96 HP in-line four cylinder diesel engine, with, for 
example, an inner diameter of 84 mm, and a stroke of 89 mm. 
That is, as shown in FIGS. 1 and 2, the cylinder liner 1 has a flange 2 at 
its upper end, and an outer circumferential surface 3 of the cylinder 
liner below the flange 2 is formed with eighteen annular grooves 4 in an 
axially spaced-part relationship. These annular grooves 4 are divided into 
three groups of annular grooves. 
The three groups of annular grooves are the first group 4A of annular 
grooves ranging from the first annular groove 4 at the upper end of the 
cylinder liner to the fourth annular groove 4, the second group 4B of 
annular grooves ranging from the fifth annular groove 4 to the tenth 
annular groove 4 and the third group 4C of annular grooves ranging from 
the eleventh annular groove 4 to the last eighteenth annular groove 4. 
In the first group 4A of annular grooves, two longitudinal grooves 5 and 6 
communicating the annular grooves 4 with each other are provided at two 
positions spaced apart by 180.degree. in a circumferential direction of 
the cylinder liner 1, in which one longitudinal groove 5 forms a cooling 
oil inlet and the other longitudinal groove 6 forms a cooling oil outlet. 
Similarly, in the second group 4B of annular grooves, two longitudinal 
grooves 7 and 8 communicating the annular grooves 4 with each other are 
provided at the same two positions in the circumferential direction as the 
longitudinal grooves 5 and 6 of the first group 4A of annular grooves, in 
which the longitudinal groove 7 located at the cooling oil outlet side of 
the first group 4A of annular grooves forms a cooling oil inlet and the 
other longitudinal groove 8 forms a cooling oil outlet. Also in the third 
group 4C of annular grooves, two longitudinal grooves 9 and 10 
communicating the annular grooves 4 with each other are provided at the 
same two positions in the circumferential direction as the longitudinal 
grooves 7 and 8 of the second group 4B of annular grooves in their 
circumferential directions, in which the longitudinal groove 9 located at 
the cooling oil outlet side of the second group 4B of annular grooves 
forms a cooling oil inlet and the other longitudinal groove 10 forms a 
cooling oil outlet. 
The longitudinal groove 6 forming the cooling oil outlet of the first group 
4A of annular grooves and the longitudinal groove 7 forming the cooling 
oil inlet of the second group 4B of annular grooves are communicated in 
series by a longitudinal groove 1 which is located at the same 
circumferential location as those of said longitudinal grooves 6 and 7 and 
is formed at the outer circumferential surface of the cylinder liner 
between the fourth annular groove 4 and the fifth annular groove 4. In 
addition, similarly, the longitudinal groove 8 forming the cooling oil 
outlet of the second group 4B of annular grooves and the longitudinal 
groove 9 forming the cooling oil inlet of the third group 4C of annular 
grooves are communicated in series by a longitudinal groove 12 which is 
located at the same circumferential location as those of said longitudinal 
grooves 8 and 9 and is formed at the outer circumferential surface of the 
cylinder liner 1 between the tenth annular groove 4 and the eleventh 
annular groove 4. 
The annular grooves 4 are formed in a plane perpendicular to an axis of the 
cylinder liner 1 and have rectangular sectional shapes. Their widths and 
depths are all the same. Longitudinal grooves 5, 6, 7, 8, 9, 10, and 12 
have also rectangular sectional shapes, are disposed in parallel with an 
axis of the cylinder liner 1 and their widths and depths are all the same. 
A lower part of the outer circumferential surface 3 of the cylinder liner 
is formed with discharging grooves. That is, the discharging grooves are 
comprised of a longitudinal groove 13 connected to the lower end of the 
longitudinal groove 10 forming an outlet of the third group 4C of annular 
grooves and disposed on an extension line of the longitudinal groove 10; 
an annular groove 14 connected to the lower end of the longitudinal groove 
13 and formed in a plane perpendicular to an axis of the cylinder liner 1; 
and two longitudinal grooves 15 having their upper ends connected to the 
annular groove 14, extended down to the lower end of the cylinder liner 1 
and disposed in parallel with an axis of the cylinder liner The 
longitudinal grooves 15 are disposed at locations spaced apart by 
180.degree. in their circumferential direction. Their circumferential 
positions are disposed at locations apart by about 60.degree. in the same 
direction from the longitudinal grooves 5, 7 and 9 forming inlets, and the 
longitudinal grooves 6, 8 and 10 forming outlets which are made at each of 
the groups of annular grooves 4A, 4B and 4C. When the cylinder liner is to 
be installed in a cylinder block 16 to be described later, the discharging 
longitudinal grooves 15 are placed above the main axis of the crankshaft. 
Although the aforementioned discharging annular groove 14 is formed around 
an entire circumference in the outer circumferential surface 3 of the 
cylinder liner, it may not be formed around the entire circumference, but 
may be formed at a part of the entire circumference. Although the 
longitudinal grooves 15 below the groove 14 preferably extend down to the 
lower end of the cylinder liner, it is sufficient that in case the 
cylinder liner has the lower end smaller in diameter than the upper part 
thereof, the grooves extend down to the upper end position of the small 
diameter part thereof. 
The discharging longitudinal grooves 13 and 15 have rectangular cross 
sections, their widths and depths are the same as those of the 
longitudinal grooves 5, 6, 7, 8, 9 and 10 of the groups of annular 
grooves. The discharging annular groove 14 has a rectangular cross section 
and its depth is the same as that of the annular groove 4 in the groups of 
annular grooves. However, it is preferable that the width of the 
discharging annular groove 14 is relatively large. In the preferred 
embodiment of the present invention, the groove width of the discharging 
annular groove 14 is three to five times of that of the annular groove 4 
in the groups of annular grooves. 
The cylinder liners 1 are respectively fitted into the bore parts of the 
cylinder block 16 (as shown in FIG. 2), and a spacing defined by the inner 
circumferential surface 17 of the bore part and the grooves 4 to 15 of the 
cylinder liner 1 forms the cooling oil passage 18. In this case, the 
cylinder liner 1 is installed in such a way that the discharging 
longitudinal grooves 15 extending down to the lower end of the cylinder 
liner are disposed above the main axis line X of the crankshaft (as shown 
in FIG. 3). Accordingly, the longitudinal groove 5 forming the inlet for 
the cooling oil in the cylinder liner 1 is disposed at a circumferential 
position apart by about 60.degree. from above the main axis line X of the 
crankshaft. Cooling oil supplying passages 19 (refer to FIG. 3) connected 
to the longitudinal grooves 5 are extended linearly in a lateral direction 
from the side surface of the cylinder block 16 to the longitudinal grooves 
5. In this way, the cooling oil supplying passages 19 can be disposed 
linearly at the positions avoiding the bolt holes 20 for use in fastening 
the cylinder liner (as shown in FIG. 3) arranged at lateral positions 
between the bores of the cylinder block 16, so that the cooling oil 
supplying passages 19 to be disposed in the cylinder block 16 may be 
easily formed. 
Accordingly, as shown in FIG. 1, the cooling oil passing through the 
cooling oil supplying passage 19 in the cylinder block 16 and flowing into 
the longitudinal groove 5 forming the inlet of the first group 4A of 
annular grooves in the cylinder liner flows in the annular grooves 4 in 
the first group 4A of annular grooves toward an opposite side of 
180.degree. and flows from the longitudinal groove 6 forming the outlet of 
the first group 4A of the annular grooves into the longitudinal groove 7 
forming the inlet of the second group 4B of annular grooves. 
The cooling oil flows in the annular grooves 4 in the second group 4B of 
annular grooves toward the opposite side of 180.degree., and flows from 
the longitudinal groove 8 forming the outlet of the second group 4B of 
annular grooves into the longitudinal groove 9 forming the inlet of the 
third group 4C of annular grooves. 
The cooling oil flows in the annular grooves 4 in the third group 4C of 
annular grooves toward the opposite side of 180.degree., then flows from 
the longitudinal groove 10 forming the outlet of the third group 4C of 
annular grooves into the longitudinal groove 13 containing to the 
longitudinal groove 10, then flows into the annular groove 14, flows 
around the annular groove 14, drops from the two longitudinal grooves 15 
at the lowest end onto the main axis of the crankshaft (not shown), and 
thereafter flows down into the oil pan (not shown). 
In this case, the total sectional areas of the annular grooves for the 
cooling oil in the three groups 4A, 4B, and 4C of annular grooves have a 
ratio of 2:3:4. A flow speed of the cooling oil flowing in each of the 
groups 4A, 4B and 4C of annular grooves is as follows. A flow speed of the 
cooling oil in the second group 4B of annular grooves is faster than that 
of the cooling oil in the third group 4C of the annular grooves, and a 
flow speed of the cooling oil in the first group 4A of annular grooves is 
faster than that of the cooling oil in the second group 4B of annular 
grooves. 
Accordingly, the coefficient of heat-transfer of the cooling oil is 
increased as it goes up to the upper part of the cylinder liner 1, and as 
a result the cooling capability is increased from a lower part toward an 
upper part and an appropriate cooling corresponding to the temperature 
gradient in an axial direction of the cylinder liner is carried out. 
Although in the aforementioned preferred embodiment, the sectional shape of 
the annular groove is a rectangular one, this is not limited to a 
rectangular one but it may be a V-shape, a semi-circular one and there is 
no specific limitation. However, in order to increase a thermal transfer 
area, a rectangular shape as in the present preferred embodiment, or a 
square shape is preferable. 
In the aforementioned preferred embodiment, a plurality of annular grooves 
spaced-apart in an axial direction of the cylinder liner are divided into 
the three groups of annular grooves, and a total sectional area of the 
annular grooves for the cooling oil in each of the groups of annular 
grooves is decreased from a lower part toward an upper part. However, it 
is also preferable that the annular grooves may be divided into two groups 
of annular grooves or more than three groups of annular grooves and then a 
total sectional area of the annular grooves for the cooling oil in each of 
the groups of annular grooves may be decreased from a lower part toward 
and upper part. 
In the cylinder liner of the present invention, an outer circumferential 
surface at an upper position than the uppermost group of annular grooves 
may be provided with one annular groove communicating with the 
longitudinal groove forming the inlet of the uppermost group of annular 
grooves. 
The aforementioned cooling structure may be used in both gasoline and 
diesel engines. In addition, in the aforementioned cooling structure, a 
cylinder block consisting of an aluminum die casting or a sectional 
cylinder block may be used. 
Although the present invention has been described with reference to the 
preferred embodiment, it is apparent that the invention is not limited to 
the aforementioned preferred embodiment, but various modifications can be 
attained without departing from its scope.