Cylinder liner

Abstract: A cylinder liner (1) comprises an outer circumferential surface (3) provided with a plurality of groups (4A,4B,4C) of annular grooves (4), a longitudinal groove (6,8,10) communicating the annular grooves with each other and forming an outlet for a cooling liquid in each of the groups of annular grooves, and a longitudinal groove (5,7,9) communicating the annular grooves with each other and forming an inlet for the cooling liquid in each of the groups of annular grooves. The outlet (6,8,10) communicates in series with the inlet (5,7,9) in the adjoining groups (4A,4B,4C) of annular grooves. Sectional areas of the annular grooves in the same group of annular grooves are decreased from an upstream side toward a downstream side.

Description: This invention relates to a cylinder liner for an internal combustion engine having cooling liquid grooves at its outer circumferential surface. In recent years, it has been known to provide a cooling structure for a cylinder liner flowing cooling liquid in grooves arranged at either one or both an outer circumferential surface of the cylinder liner and an inner circumferential surface of cylinder bore in a cylinder block. This is due to the fact that a cooling control can easily be carried out according to positions in the cylinder liner as compared with the cooling structure of jacket type being applied from the past. In order to realize an appropriate cooling corresponding to each of the axial positions of the cylinder liner, for example, the cylinder liner described in Jap. U.M. Publication No. 3-29560 (Jap. U.M. Appln. No. 62-60967) has a plurality of groups of annular grooves at its outer circumferential surface and has longitudinal grooves communicating the annular grooves and forming an outlet and an inlet for a cooling liquid at the surface, wherein the outlet communicates in series with the inlet in adjoining groups of annular grooves and total sectional areas of the annular grooves in the groups of annular grooves are decreased from a lower part toward an upper part. With the foregoing, a flow of cooling liquid directed from the upper part of the cylinder liner to the lower part thereof will be described, wherein the cooling liquid flows around the outer circumference of the cylinder liner through the annular grooves in a group of annular grooves, 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, flows from the longitudinal groove into the annular grooves of the group of annular grooves, flows around the outer circumference of the cylinder liner, then the cooling liquid is moved to the lower adjoining group of annular grooves in the same manner. In this case, since the total sectional areas of the annular grooves in the groups of annular grooves are decreased from the lower part toward the upper part in the cylinder liner, a flow speed at the group of annular grooves at the upper part of the cylinder liner is increased, a coefficient of heat-transfer of the cooling liquid at the upper part of the cylinder liner is increased, and a cooling capability at the upper part of the cylinder liner is increased, which performs an appropriate cooling corresponding to a temperature gradient in the axial direction of the cylinder liner (high at the upper part and low at the lower part). Grooved cylinder liner having the aforesaid structure which has Inner diameter: 84 mm Outer diameter: 93 mm First group of annular grooves Number of annular grooves 3 Width 1 mm Depth 1 mm Second group of annular grooves Number of annular grooves 6 Width 2 mm Depth 1 mm Third group of annular grooves Number of annular grooves 9 Width 3 mm Depth 1 mm was inserted into a transparent plastic cylinder and assembled to get a cooling liquid circulation circuit shown in Fig.7. In this figure, a cooling oil in an oil tank 21 is fed to the groups of annular grooves of the grooved cylinder liner 1A in the cylinder 23 by an oil pump 20 with a flow rate adjusted by a flow rate adjusting valve 22 (25 denotes a cylinder for measuring a flow rate, 26 and 27 denote stop valves), the cooling oil is circulated and an air feeding valve 24 is opened to disperse the air bubbles into the cooling oil and a flow of the cooling oil is observed from outside, resulting in that the following states are obtained. a) The cooling oil flows in general in a laminar flow within a range of flow rate of 7 liters/min per 1 cylinder or less: b) In the flow of the cooling oil in the same group of the annular grooves, a flow speed of the cooling oil flowing in the upstream side annular grooves is slower than that flowing in the downstream side annular grooves. In this case, the fact that the flow speed in the same group of annular grooves is faster at the downstream side means that the cooling capability at the donwstream side is high and the cooling capability at the upstream side is low, so that this state is inconvenient for the cooling of the cylinder liner. Although Jap. Pat. Laid-Open No. 3-78518 (Jap. Pat. Appln. No. 1-212625) or Jap. U.M. Appln. No. 3-22554 (Jap. U.M. laid open No. 4-111 542, not prepublished) provides a description concerning an arrangement in which the sectional areas of the longitudinal grooves communicating the annular grooves with each other in the group of annular grooves are axially varied to make a uniform flow speed in the group of annular grooves, they have some problems that varying depths of the longitudinal grooves of the cylinder liner as means for varying sectional areas of the longitudinal grooves is not preferable due to a variation of the wall thickness and varying widths in a circumferential direction requires a troublesome machining operation. The cylinder liner of the present invention comprises an outer circumferential surface provided with a plurality of groups of annular grooves, a longitudinal groove communicating the annular grooves with each other and forming an outlet for a cooling liquid in each of the groups of annular grooves, a longitudinal groove communicating the annular grooves with each other and forming an inlet for a cooling liquid in each of the groups of annular grooves, the outlet communicates in series with the inlet in the adjoining groups of annular grooves, sectional areas of the annular grooves within at least one said group of annular grooves are decreased from an upstream side toward a downstream side. An outer circumferential surface at a position above 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. With the foregoing, a flow of cooling liquid will be described, wherein the cooling liquid flows around the outer circumference of the cylinder liner through the annular grooves in a group of annular grooves, 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, flows from the longitudinal groove into the annular grooves of the group of annular grooves, flows around the outer circumference of the cylinder liner, then the cooling liquid is moved to the adjoining group of annular grooves in the same manner. Preferably in this case, when the cooling liquid moves from the longitudinal groove forming the outlet of the group of annular grooves to the longitudinal groove forming the inlet of the adjoining next stage group of annular grooves and flows from the longitudinal groove into a plurality of annular grooves of the group of annular grooves, the sectional areas of the annular grooves in at least one said group are decreased from the upstream side toward the downstream side, resulting in that a pressure loss in the downstream side annular grooves is increased and so a cooling liquid is flowed more in the upstream side annular grooves as compared with that of equal sectional areas, a flow speed of the cooling liquid flowing in the annular grooves in the same group of annular grooves can be made uniform and a cooling capability in the group of annular grooves can be made uniform. Then, since it is not hard to vary the sectional areas of the annular grooves, at least preferred embodiments can be more easily manufactured. Embodiments of the invention will now be described, by way of example only, with reference to the accompanying drawings, wherein:- Fig.1 is a development showing a part of the outer circumferential surface of the cylinder liner of one embodiment of the present invention. Fig.2 is a longitudinal sectional view taken at the longitudinal grooves of the cylinder liner to show a bore part of a cylinder block into which the cylinder liner of the first embodiment is fitted. Fig.3 is an enlarged longitudinal section showing the first group of annular grooves in the cylinder liner of the first embodiment fitted in the cylinder block. Fig.4 is an enlarged longitudinal section showing the second group of annular grooves in the cylinder liner of the first embodiment fitted in the cylinder block. Fig.5 is an enlarged longitudinal section showing the third group of annular grooves in the cylinder liner of the first embodiment fitted in the cylinder block. Fig.6 is a development showing a part of an outer circumferential surface of another cylinder liner according to a second embodiment of the present invention. Fig.7 is a configuration view showing a device for observing a flow of the cooling liquid in the grooves of the cylinder liner. Cooling liquid grooves are formed at an outer circumferential surface of a cylinder liner with an inner diameter of 84 mm and an outer diameter of 93 mm in an in line four-cylinder diesel engine. 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 axially spaced-apart relation. 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 third annular groove 4, the second group 4B of annular grooves ranging from the fourth annular groove 4 to the ninth annular groove 4 and the third group 4C of annular grooves ranging from the tenth 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° in a circumferential direction of the cylinder liner 1, in which one longitudinal groove 5 forms a cooling liquid inlet and the other longitudinal groove 6 forms a cooling liquid 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 liquid outlet side of the first group 4A of annular grooves forms a cooling liquid inlet and the other longitudinal groove 8 forms a cooling liquid 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 liquid outlet side of the second group 4B of annular grooves forms a cooling liquid inlet and the other longitudinal groove 10 forms a cooling liquid outlet. The longitudinal groove 6 forming the cooling liquid outlet of the first group 4A of annular grooves and the longitudinal groove 7 forming the cooling liquid inlet of the second group 4B of annular grooves are communicated in series by a longitudinal groove 11 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 1 between the third annular groove 4 and the fourth annular groove 4. In addition, similarly, the longitudinal groove 8 forming the cooling liquid outlet of the second group 4B of annular grooves and the longitudinal groove 9 forming the cooling liquid 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 ninth annular groove 4 and the tenth annular groove 4. As shown in the enlarged view of each of the groups 4A, 4B and 4C of annular grooves in Figs.3 to 5, the annular grooves 4 are made such that the sectional areas of the annular grooves in each of the groups 4A, 4B and 4C of annular grooves are not the same to each other in an axial direction and are decreased from the upper side toward the lower side. As one example, a practical numerical value of the first group 4A of annular grooves is as follows, i.e. a groove width of the first annular groove 4 is 1.5 mm, a groove depth is 1 mm, a groove width of the second annular groove 4 is 1.2 mm, a groove depth is 1 mm, a groove width of the third annular groove 4 is 1.0 mm and a groove depth is 1 mm. That is, a sectional area of the first annular groove 4 is 1.5 mm², a sectional area of the second annular groove 4 is 1.2 mm² and a sectional area of the third annular groove 4 is 1.0 mm² and so they are gradually decreased from the upper part toward the lower part. The cylinder liner is inserted into the aforesaid transparent plastic cylinder, air bubbles are fed while flowing the cooling oil at 2 liters/min and this state is observed from outside, resulting in that it is confirmed that a flow speed of the cooling oil flowing in each of the annular grooves 4 in the first group 4A of annular grooves is substantially constant. In this way, it is easily possible to calculate a size of each of the annular grooves 4 as to the second group 4B of annular grooves and the third group 4C of annular grooves. 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 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. The longitudinal grooves 15 are disposed at locations spaced apart by 180° in their circumferential direction. These discharging grooves 13, 14 and 15 are formed to use a cooling oil as a cooling liquid and to discharge it into an oil pan. For example, when a cooling water is used as a cooling liquid, the cooling water is flowed out to the discharging passage formed in the cylinder block. It is apparent that in the case of the cooling oil, the oil may be flowed out to the discharging passage in the cylinder block. The cylinder liner 1 is fitted into the bore part of a cylinder block 16 (refer to Fig.2), and a spacing defined by an inner circumferential surface 17 of the bore part and the grooves 4 to 15 of the cylinder liner 1 forms a cooling liquid passage 18. A cooling liquid supplying passage 19 connected to the longitudinal groove 5 forming the inlet for the cooling liquid in the first group 4A of annular grooves is disposed in a lateral direction from a side surface of the cylinder block 16 and extended linearly to the longitudinal groove 5. In Fig.1, F denotes a forward position, R denotes a rearward position, T denotes a major thrust direction position and AT denotes a minor thrust direction position. Accordingly, as shown in Fig. 1, the cooling oil passed through the cooling liquid supplying passage 19 in the cylinder block 16 and flowed 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° and flows from the longitudinal groove 6 forming the outlet of the first group 4A of 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° 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 18O°, flows from the longitudinal groove 10 forming the outlet of the third group 4C of annular grooves into the longitudinal groove 13 which continues from the longitudinal groove 10, flows into the annular groove 14, flows around the annular groove 14, and drops from the two longitudinal grooves 15 at the lowest end into the oil pan not shown. With the foregoing arrangement, the total sectional areas of the flow passages for the cooling liquid in the three groups 4A, 4B and 4C of annular grooves are decreased going upwardly, i.e., a total sectional area of the annular grooves 4 in the first group 4A of annular grooves is less than that in the second group 4B of annular grooves and a total sectional area of the annular grooves 4 in the second group 4B of annular grooves is less than that in the third group 4C of annular grooves. Accordingly, a flow speed of the cooling oil flowing in each of the groups 4A, 4B and 4C of annular grooves is set such that a flow speed in the central second group 4B of annular grooves is faster than that in the lower third groups 4C of annular grooves and a flow speed of the upper first group 4A of annular grooves is faster than that in the central second group 4B of annular grooves. Accordingly, the coefficient of heat-transfer of the cooling liquid 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. In addition, since the sectional areas of the annular grooves 4 in each of the groups 4A, 4B and 4C of annular grooves are decreased from the upper part toward the lower part, when the cooling oil flows from each of the longitudinal grooves 5, 7 and 9 into a plurality of annular grooves 4 of each of the groups 4A, 4B and 4C of annular grooves, the cooling oil flows smoothly to the upper annular grooves 4 of each of the groups 4A, 4B and 4C of annular grooves. Accordingly, the flow speed of the cooling oil in the group of annular grooves in each of the groups 4A, 4B and 4C of annular grooves can be made uniform and the cooling capability can be made uniform. Although in the aforesaid 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 or a square shape is preferable. In the aforesaid 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 total sectional areas of the annular grooves for the cooling liquid in the groups of annular grooves are 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 total sectional areas of the annular grooves for the cooling liquid in the groups of annular grooves may be decreased from a lower part toward an upper part. In the aforesaid preferred embodiments, the sectional areas of the annular grooves in each of the groups of annular grooves are decreased from the upstream side toward the downstream side. However, the sectional areas of the annular grooves for all the groups of annular grooves may not be varied. For example, it may also be applicable that the sectional areas of the annular grooves are varied only for the upper and intermediate groups of annular grooves of the cylinder liner. Although it is possible to vary the sectional areas of the annular grooves by varying the depth of the groove, it is preferable that the groove width is varied as indicated in the aforesaid preferred embodiment due to the fact that the wall thickness of the cylinder liner is not varied. In addition, preferred embodiments may also be constructed such that in addition to a plurality of groups of annular grooves, an outer circumferential surface at a position above 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. One such example is indicated in Fig.6. The outer circumferential surface 3 of the cylinder liner 1 is formed with grooves having the same structure as that described in the aforesaid preferred embodiments (provided that the number of annular grooves in the first group 4A of annular grooves is two, the number of annular grooves in the second group of annular grooves is six, and the number of annular grooves in the third group of annular grooves is nine) and further the outer circumferential surface 3 at the position above the uppermost group of annular grooves i.e., the first group 4A of annular grooves is formed with one annular groove 20 communicating with the longitudinal groove 5 forming the inlet of the first group 4A of annular grooves. The aforesaid cooling structure can be applied for a Diesel engine and a gasoline engine. In addition, in the cooling structure, a cylinder block made by aluminum die casting or a sectional cylinder block may be used. Thus, in at least preferred embodiments there is provided a cylinder liner in which a flow speed of a cooling liquid flowing in the annular grooves of a group of annular grooves can be made uniform and a high productivity can be attained.

Claims: A cylinder liner (1) comprising an outer circumferential surface (3) provided with a plurality of groups (4A,4B,4C) of annular grooves (4), a longitudinal groove (6,8,10) communicating the annular grooves with each other and forming an outlet for a cooling liquid in each of said groups of annular grooves, and a longitudinal groove (5,7,9) communicating the annular grooves with each other and forming an inlet for the cooling liquid in each of said groups of annular grooves, wherein the outlet (6,8,10) communicates in series with the inlet (5,7,9) in said adjoining groups (4A,4B,4C) of annular grooves (4), characterized in that: sectional areas of the annular grooves (4) within at least one said group (4A,4B,4C) of annular grooves are decreased from an upstream side toward a downstream side. A cylinder liner (1) according to claim 1 in which total sectional areas of the annular grooves (4) in said groups (4A,4B,4C) of annular grooves are decreased from a lower part toward an upper part in an axial direction of the cylinder liner. A cylinder liner (1) according to claim 1 or 2 in which an outer circumferential surface (3) at a position above said uppermost group of annular grooves (4) is provided with one annular groove (20) communicating with the longitudinal groove (5) forming the inlet of said uppermost group of annular grooves. A cylinder liner (1) according to claim 1, 2 or 3 in which the annular grooves (4) in the or each same group (4A,4B,4C) of annular grooves having sectional areas formed to be decreased from an upstream side toward a downstream side have the same groove depths and varying groove widths. A cylinder liner (1) according to any preceding claim in which the sectional areas of the annular grooves (4) in the same group (4A,4B,4C) of annular grooves for all the groups of annular grooves are decreased from an upstream side toward a downstream side. A cylinder liner (1) according to claim 1, 2, 3 or 4 in which the sectional areas of the annular grooves (4) in the same group (4A,4B,4C) of annular grooves are decreased from an upstream side toward a downstream side in some but not all said groups of annular grooves. A cylinder liner (1) according to any preceding claim in which the number of said groups of annular grooves is two or more.

Inventors: HAMA FUJIO, HARASHINA KENICHI, HAMA, FUJIO, HARASHINA, KENICHI
Applicants: TEIKOKU PISTON RING CO LTD, TEIKOKU PISTON RING CO. LTD.
Application year: 1992
Main classification: F02F1
IPC codes: F02F1, F02B1, F01P3