Cylinder Liner

Abstract

The present invention relates to a cylinder liner. By suppressing the gap generated in the joint between the outer peripheral surface of the cylinder liner substrate and the cylinder body, the joint strength between the cylinder liner and the cylinder body is improved. The cylinder liner (10) for casting has a substrate (12) and a plurality of protrusions formed on a base surface (12S) as the outer peripheral surface of the substrate (12), and the drag coefficient CD defined by the following mathematical formula (5) is 10 to 35%. In which, S p is the cross-sectional area of ​​the cylindrical protrusion area, S0 is the cross-sectional area of ​​the cylindrical outer area without protrusion, S1 is the hypothetical flow path area, P1 is the dynamic pressure of the molten metal, ρ is the molten metal density, U is the flow velocity of the molten metal in the cylindrical outer area measured by the visualization experiment, PD is the dynamic pressure, SA is the projection area of ​​the protrusion, SB is the obstacle area, and R1 is the resistance. Mathematical formula (1) is S p +S0=S1, mathematical formula (2) is P1=ρU 2 / 2, mathematical formula (3) is PD=P1×S1, mathematical formula (4) is R1=P1×SB, and mathematical formula (5) is CD=R1 / PD.

Description

Technical Field

[0001] The invention relates to a cylinder sleeve. Background Art

[0002] In a cylinder block for an automobile engine, a cylinder liner, which is one of the important functional components constituting the interior of the engine, is disposed on the inner circumference of the cylinder. One method for manufacturing a cylinder block with a cylinder liner is as follows: the cylinder liner is preliminarily disposed in a casting mold for the cylinder block, a casting material is flowed into the casting mold, and the outer circumference of the cylinder liner is cast with the casting material.

[0003] In the manufacture of such a cylinder block, it is known that the outer peripheral surface of the cylinder liner, which is pre-arranged in the casting mold, has a plurality of protrusions in order to improve the bonding strength between the cylinder liner and the cylinder block (for example, see Patent Documents 1 and 2). In addition, by providing protrusions on the outer peripheral surface of the cylinder liner substrate (referring to the cylinder liner main body part of the cylinder liner that is substantially cylindrical except for the protrusions, hereinafter sometimes referred to as "substrate"), and then making the shape of the protrusions narrow in the middle, an attempt is made to improve the bonding strength between the cylinder liner and the cylinder block (for example, see Patent Document 3).

[0004] Prior art literature

[0005] Patent Literature

[0006] Patent Document 1: Japanese Patent Application Publication No. 2005-194983

[0007] Patent Document 2: Japanese Patent Application Publication No. 2009-264347

[0008] Patent Document 3: Japanese Patent No. 6340148

[0009] However, when manufacturing a cylinder block, when the casting material is made to flow into the mold of the cylinder block equipped with the cylinder liner and the outer periphery of the cylinder liner is cast by the casting material, the casting material sometimes cannot fully cover the area between the protrusions on the outer peripheral surface of the cylinder liner base. This phenomenon is particularly likely to occur when using sand gravity casting or low-pressure mold casting. In addition, even when using high-pressure mold casting, this phenomenon is often found in areas where molten metal is difficult to reach, such as between the cylinder liner and the adjacent cylinder liner. If a gap is generated in the joint between the outer peripheral surface of the cylinder liner and the cylinder block, sometimes the joint strength cannot be fully obtained. Summary of the invention

[0010] Therefore, an object of the present invention is to provide a cast-in cylinder liner capable of improving the joint strength between the cylinder liner and the cylinder block by suppressing the occurrence of voids in the joint portion between the outer peripheral surface of the cylinder liner base and the cylinder block.

[0011] In order to solve the above-mentioned problems, the inventors of the present invention have conducted various studies on methods and mathematical formulas for expressing the characteristics of the cylinder liner. As a result, they have found that the cross-sectional area S of the cylindrical protrusion region is p , the cross-sectional area S0 of the cylindrical outer region, the imaginary flow path area S1 which is the sum of these factors, the dynamic pressure P1 of the molten metal, the dynamic pressure PD, the projection area SA of the protrusion, and the obstacle area SB, an insight was obtained that allowed the cylinder liner to be determined to have extremely good characteristics.

[0012] One embodiment of the present invention based on the above findings is a cylinder liner for insert casting, comprising a base body and a plurality of protrusions formed on a base surface as an outer peripheral surface of the base body, wherein a drag coefficient CD defined by the following mathematical formula (5) is 10 to 35%.

[0013] In the cross section of the cylinder liner cut into a disc, the cross-sectional area S of the cylindrical protrusion region as the region where the protrusion is formed is p The sum of the cross-sectional area S0 of the cylindrical outer region existing outside the cylindrical protrusion region is defined as the virtual flow path area S1.

[0014] S p +S0=S1…(1)

[0015] The dynamic pressure P1 of the molten metal as the fluid during casting is ρU 2 / 2 (where ρ is the density of the molten metal and U is the flow velocity of the molten metal in the cylindrical outer region measured by a visualization experiment).

[0016] P1=ρU 2 / 2…(2)

[0017] The product of the dynamic pressure P1 and the virtual flow path area S1 is defined as the dynamic pressure PD.

[0018] PD=P1×S1…(3)

[0019] The projection area SA of the protrusion is converted to obtain the obstacle area SB, and the product of the dynamic pressure P1 and the obstacle area SB is defined as the resistance R1.

[0020] R1=P1×SB…(4)

[0021] The resistance force R1 is divided by the dynamic pressure PD to obtain the resistance coefficient CD.

[0022] CD=R1 / PD…(5)

[0023] The above-mentioned method focuses on the fact that the protrusions become a resistance to the flow of molten metal, and is derived from the point of view that the preferred protrusion distribution is defined by the "drag coefficient". By estimating the "drag coefficient" (or "drag index") when the molten metal flows (molten metal fluidity) during pouring according to the protrusion density, its preferred range is found. In addition, by calculating the loss coefficient based on the shrinkage resistance caused by the reduction of the flow path area when the molten metal flows from the area without protrusions to the area with protrusions, its preferred range is found. In addition, by calculating the dynamic pressure based on the dynamic pressure when the molten metal flows, the ratio of the resistance (dynamic pressure × obstacle projection area) relative to this can be specified. As a result of various visualization experiments based on these situations, the following insights are obtained: if the drag coefficient is large, the flow of molten metal is hindered, and if it is small, the temperature of the molten metal drops quickly and hinders the flow of molten metal. According to these results, it is preferred that when the drag coefficient CD is 10 to 35%, the improvement of the molten metal fluidity during sand mold gravity casting or low-pressure casting becomes more significant, the gap at the interface between the cylinder liner and the cylinder body is reduced, and the bonding strength is improved. Of course, the same effect is also obtained in high-pressure die casting.

[0024] In the cylinder liner of the above-described embodiment, the projection area SA of the protrusion may be an axial projection area of ​​the protrusion assumed to be cylindrical and parallel to the central axis of the cylinder liner, or may be a circumferential projection area viewed from a tangential direction of the circumference.

[0025] In the cylinder liner of the above-described embodiment, the loss coefficient calculated from the contraction resistance of the fluid derived as the flow path area decreases from the virtual flow path area S1 to the actual flow path area S2 is preferably 0.03 to 0.14.

[0026] In the cylinder liner of the above-described embodiment, the obstacle area SB can be defined as follows.

[0027] The number of protrusions per unit area is N A .

[0028] It is assumed that the arrangement of the protrusions is the same, the center-to-center distance p between the protrusions is the same pitch, and the protrusions protrude in the radial direction of the base.

[0029] It is assumed that the protrusions are arranged on the same circumference of the base surface at a pitch that is the same as the distance p between the centers of the protrusions.

[0030] According to the diameter D of the base surface b The distance p between the centers of the protrusions is used to calculate the number of protrusions N arranged on the base surface along the circumferential direction. B .

[0031] N B =πD b / p…(6)

[0032] · The average height of the protrusions h av , average diameter d av and the number of protrusions N B The product of is set as the obstacle area SB.

[0033] SB=h av ×d av ×N B …(7)

[0034] According to the present invention, it is possible to provide a cast-in cylinder liner capable of improving the joining strength between the cylinder liner and the cylinder block by suppressing the occurrence of voids in the joining portion between the outer peripheral surface of the cylinder liner base and the cylinder block. BRIEF DESCRIPTION OF THE DRAWINGS

[0035] Figure 1 It is a cross-sectional view perpendicular to the axial direction schematically showing a joint between a cylinder liner and a cylinder block.

[0036] Figure 2 It is a cross-sectional view schematically illustrating a main body portion, a protruding region, a cylindrical outer region, etc. of a cylinder liner in one embodiment of the present invention.

[0037] Figure 3 This is a diagram schematically showing a change in the flow path area when the molten metal flows from the virtual flow path area S1 to the actual flow path area S2 obtained by subtracting the obstacle (area SB).

[0038] Figure 4 This is a diagram for explaining the method of considering the number of protrusions per unit area, the configuration of the protrusions, the arrangement of the protrusions, etc. when calculating the obstacle area SB.

[0039] Figure 5 This is a table showing various numerical values ​​related to cylinder liners of Examples 1 to 6 of the present invention and Comparative Examples 1 and 2 and results of joint strength evaluation.

[0040] Description of reference numerals:

[0041] 10…cylinder liner; 12…cylinder liner substrate (the substrate or main body of the cylinder liner); 12S…base surface (the outer peripheral surface of the cylinder liner substrate); 14…protrusion; 20…cylinder body; A1…cylindrical protrusion area; A2…cylindrical outer area; CD…drag coefficient; D0…outer diameter or outer diameter of the cylindrical outer area; D b ...diameter of the base surface; D p ... the outer diameter of the cylindrical protrusion area; h ... the height of the protrusion; h av ...average height of protrusions; d ...diameter of protrusions; d av ...average diameter of protrusions; N A ...Number of protrusions per unit area; N B...number of protrusions arranged on the base surface along the circumferential direction; P1...dynamic pressure of molten metal; PD...dynamic pressure; p...center distance between protrusions; R1...resistance; S1...imaginary flow path area; S2...actual flow path area; SA...projection area of ​​protrusions; SB...obstruction area; S0...cross-sectional area of ​​cylindrical outer area; S p ... the cross-sectional area of ​​the cylindrical protrusion; S t …area ratio of the cross section of the protrusion perpendicular to the height direction (projection area ratio at the radial position of 0.3 mm); U…flow velocity of the molten metal in the cylindrical outer area measured by a visualization experiment; W…circumferential direction of the cylinder liner; X…center axis; ρ…molten metal density. DETAILED DESCRIPTION

[0042] Next, the configuration of the present invention will be described in detail based on an example of the embodiment shown in the accompanying drawings (refer to Figure 1 to Figure 4 ).

[0043] Figure 1 1 is a cross-sectional view schematically showing the joint between the cylinder liner and the cylinder body. The lower part of the figure is the cylinder liner 10, and the upper part is the cylinder body 20. The cylinder liner 10 includes a cylinder liner base 12 and a plurality of protrusions 14 (see Figure 1 ).also, Figure 2 A cross-sectional view of the cylinder liner and cylinder body (after being cut into a circular slice) is shown.

[0044] The cylinder liner base 12 is a portion of the cylinder liner 10 that constitutes a substantially cylindrical cylinder liner body except for the protrusions 14. In the present embodiment, the outer peripheral surface of the cylinder liner base 12 is referred to as a base surface 12S, and its diameter is D b The following description is given (refer to Figure 2 ).

[0045] A plurality of protrusions 14 are formed on the base surface 12S. Most of the protrusions 14 are tapered, and the casting material constituting the cylinder body 20 enters (is poured into) between these plurality of tapered protrusions 14, thereby achieving a strong connection between the top of the tapered protrusion 14 (the portion from the tapered portion to the front end) existing on the base surface 12S of the cylinder liner 10 and the cylinder body 20 through the anchoring effect. Figure 2 In the figure, the height of the protrusion 14 is denoted as h, and the cylindrical region where the plurality of protrusions 14 exist is denoted as a "cylindrical protrusion region" and is indicated by the symbol A1. The outer diameter D of the cylindrical protrusion region A1 is p is the diameter D of the base surface 12S b The size after adding twice the value of the protrusion height h (D p =D b +2h). In addition, the average height h of the protrusions 14 (the average height h of the protrusions) av, mm) is not particularly limited, but is usually 0.3 or more, and may be 0.4 or more, and is usually 0.9 or less, and may be 0.7 or less. The area ratio S of the cross section perpendicular to the height direction of the protrusion is t , the average diameter of the protrusions d av and the average height of the protrusions h av The outer diameter D of the cylindrical protrusion area A1 can be measured by a three-dimensional measuring machine or the like. p For example, it can be measured using a vernier caliper, etc. In this case, the measurement is performed at the tip of the protrusion.

[0046] In addition, a cylindrical outer region A2 is assumed around the cylindrical protrusion region A1, and the diameter of the outer circumference thereof is set to D0 (see Figure 2 The cylindrical outer region A2 is located on the outer (peripheral) side of the cylindrical region where the plurality of protrusions 14 exist. Figure 3 It schematically shows the molten metal in the cylinder 20 flowing from the virtual flow path (area S1 (=S p +S o )) is a diagram showing the actual flow path (area S2) after the obstacle (area SB) is subtracted. The following is a diagram showing the consideration method here. First, when the flow path width (size from the tip of the protrusion 14) of the cylindrical outer area A2 is set to α (as an example, 0.5 mm in this embodiment), the size of the outer diameter D0 of the cylindrical outer area A2 is D0=D p +2α(refer to Figure 2 ). At this time, the imaginary flow path area is the diameter D p The area of ​​the circle - the diameter D b The area of ​​the circle with diameter D0 is the area of ​​the circle with diameter D p On the other hand, the actual flow path area is the area obtained by subtracting the obstacle area SB from the virtual flow path area (in other words, the flow path area is reduced in the part where the protrusion exists). At this time, if the virtual flow path area and the actual flow path area are regarded as "tubes" of the same area, the image is as follows: Figure 3 shown.

[0047] Furthermore, the joining of the cylinder liner 10 and the cylinder body 20 is achieved by allowing the molten metal to flow into the outer peripheral surface of the cylinder liner 10 arranged in the casting mold. At this time, depending on the formation conditions of the multiple intermediate tapered protrusions 14 existing on the base surface 12S of the cylinder liner substrate 12, the molten metal may not be distributed between the protrusions 14. In this regard, the following indicators are introduced in this embodiment, and by making the resistance coefficient CD among them within a specified range, preferably 10 to 35%, a cylinder liner 10 that can improve the fluidity of the molten metal during low-pressure casting and improve the joining strength is achieved. The resistance coefficient CD, etc. are determined as follows.

[0048] First, in the cross section after the cylinder liner 10 is cut into discs (refer to Figure 2 ), the cross-sectional area S of the cylindrical protrusion region A1 as the region where the protrusion 14 is formed p The sum of the cross-sectional area S0 of the cylindrical outer region A2 existing outside the cylindrical protrusion region A1 is defined as the virtual flow path area S1 (Formula (1)).

[0049] S p +S0=S1…(1)

[0050] In addition, the dynamic pressure P1 of the molten metal as the fluid during insert casting is ρU 2 / 2 (where ρ is the density of the molten metal, and U is the flow rate of the molten metal in the cylindrical outer area A2 measured by a visualization experiment) (Mathematical formula (2)). In addition, in this embodiment, the flow rate is set to 1 m / s, but the flow rate itself varies depending on the casting method. For example, in the case of aluminum alloy, the density ρ of the molten metal is about 2500 kg / m 3 .

[0051] P1=ρU 2 / 2…(2)

[0052] The product of the dynamic pressure P1 and the virtual flow path area S1 is defined as the dynamic pressure PD (Formula (3)).

[0053] PD=P1×S1…(3)

[0054] The projection area SA of the protrusion 14 is converted to obtain the obstacle area SB, and the product of the dynamic pressure P1 and the obstacle area SB is defined as the resistance R1 (Formula (4)).

[0055] R1=P1×SB…(4)

[0056] The resistance force R1 is divided by the dynamic pressure PD to obtain the drag coefficient CD (Formula (5)).

[0057] CD=R1 / PD…(5)

[0058] Here, as described below, an example of a method for calculating (consideration method) the projection area SA of the protrusion 14 is given. That is, assuming that the protrusion 14 is cylindrical, the projection area SA of the protrusion 14 along the central axis X (refer to Figure 2 ) parallel to the axial or circumferential direction (in Figure 2 and Figure 4The projection area SA of the protrusion 14 is the area when projected in the tangent direction of the protrusion 14 (indicated by the symbol W in the figure). For example, it can be measured using a microscope. At this time, the width of the protrusion 14 is the size of the widest part near the top in the protrusion 14 that tapers in the middle, and is the size near the center of the protrusion height in the protrusion 14 that does not taper in the middle. Alternatively, the projection area SA of the protrusion 14 can be obtained based on "the area ratio S of the cross section perpendicular to the height direction of the protrusion 14 measured by a three-dimensional measuring machine." t The value calculated is the calculated diameter d" of the protrusion 14 × the calculated height h of the protrusion 14 measured by the three-dimensional measuring machine. In addition, the cross-sectional area and diameter of the protrusion 14 measured by the three-dimensional measuring machine can be measured at any position. For example, when measuring the "0.3mm position", it is sufficient to adjust the "threshold value" to "display range center + threshold value = 0.3mm". The area ratio S of the cross section of the protrusion 14 perpendicular to the height direction is t (%) corresponds to the projected area ratio of the protrusion 14 observed from the outer peripheral side of the cylinder liner 10 in the height direction of the protrusion 14. In the protrusion 14 having a tapered shape, it can be the area ratio of the portion corresponding to the maximum diameter portion near the protrusion tip. As a three-dimensional measuring machine, VR-3000 manufactured by Keyence can be used.

[0059] The specific example of the method of obtaining the obstacle area SB is as follows. First, the number of protrusions 14 per unit area (10 mm×10 mm as an example) is N. A Here, the arrangement of the protrusions 14 is uniform as in hexagonal coordination, the center-to-center distance p between the protrusions 14 is the same pitch, and each protrusion 14 is assumed to protrude in the radial direction of the cylinder liner base 12 (refer to Figure 4 ). In addition, it is assumed that the protrusions 14 are arranged in the circumferential direction W of the base surface 12S at the same pitch as the center-to-center distance p of the protrusions 14 (see Figure 4 In the example shown in the figure, only one row of protrusions 14 arranged in parallel is considered. In addition, the center-to-center distance p can be obtained by, for example Therefore, according to the diameter D of the base surface 12S, b The number of protrusions 14 arranged on the base surface 12S along the circumferential direction W (protrusion count) N is calculated. B (Equation (6)) Calculate the average height h of the protrusions av , average diameter d av and the number of protrusions N B The product of is taken as the obstacle area SB (Formula (7)). In addition, since the number of protrusions N is obtained by calculation A and the number of protrusions N B , so it may not be an integer.

[0060] N B =πDb / p…(6)

[0061] SB=h av ×d av ×N B …(7)

[0062] The number of protrusions per unit area N can be calculated by dividing the number of protrusions obtained as the number of protrusions existing in the field of view (including protrusions on the boundary portion) minus the number of protrusions on the boundary portion of the field of view × 1 / 2 by the field of view area. A .

[0063] Furthermore, when introducing the above-described method of obtaining, the following may be considered.

[0064] ·The imaginary flow path and the actual flow path are replaced with tubes, and their diameters (D1 and D2) are estimated.

[0065] Contraction coefficient Cc = 0.582 + 0.0418 / (1.1 - D2 / D1)

[0066] Loss coefficient ζ = (1 / Cc-1) 2

[0067] (The preferred range of the loss coefficient ζ is 0.03 to 0.14, and more preferably 0.05 to 0.13)

[0068] An example of a method for manufacturing the above-mentioned cylinder liner 10 will be described below.

[0069] The composition of the cast iron as the material of the cylinder liner 10 is not particularly limited, but is typically a composition of flake graphite cast iron corresponding to JIS FC250 in consideration of wear resistance, sintering resistance, and workability, and the following compositions can be exemplified.

[0070] C: 3.0-3.7% by mass

[0071] Si: 2.0-2.8 mass%

[0072] Mn: 0.5-1.0 mass%

[0073] P: 0.25 mass% or less

[0074] S: 0.15 mass % or less

[0075] Cr: 0.5 mass% or less

[0076] Remainder: Fe and inevitable impurities

[0077] The method for manufacturing the cylinder liner 10 is not particularly limited, and may be gravity casting or centrifugal casting. However, the centrifugal casting method is preferably used, and typically includes the following steps A to E.

[0078] <Step A: Suspension Preparation Step>

[0079] Step A is a step of preparing a suspension by combining a refractory base material, a binder and water in a prescribed ratio. Diatomaceous earth is typically used as a refractory base material, but is not limited to this. The content of diatomaceous earth in the suspension is usually more than 15% by mass and less than 35% by mass, and the average particle size of diatomaceous earth is usually more than 0.015mm and less than 0.035mm. As a binder, bentonite is typically used, but is not limited to this. The content of bentonite in the suspension is usually more than 3% by mass and less than 9% by mass. The content of water in the suspension is usually more than 62% by mass and less than 80% by mass.

[0080] <Step B: Coating agent preparation step>

[0081] Step B is a step of preparing a coating agent by adding a predetermined amount of a surfactant to the suspension prepared in step A. The type of surfactant is not particularly limited, and one of known surfactants such as a cationic surfactant, an anionic surfactant, a nonionic surfactant, and an amphoteric surfactant is used, or a combination of two or more surfactants is used. The amount of the surfactant is usually 0.003% by mass or more and 0.04% by mass or less.

[0082] <Step C: Coating Agent Application Step>

[0083] Step C is a step of applying a coating agent to the inner circumferential surface of a cylindrical mold that becomes a casting. The coating method is not particularly limited, but spray coating is typically used. When applying the coating agent, it is preferred to apply the coating agent in a manner that a layer of the coating agent forms a substantially uniform thickness throughout the entire circumference of the inner circumferential surface of the mold. In addition, when the coating agent is applied to form a coating agent layer, it is preferred to impart a moderate centrifugal force by rotating the cylindrical mold. At this time, a surfactant acts to form a concave hole in the coating agent layer for forming a projection that tapers in the middle.

[0084] The thickness of the mold coating layer is preferably selected within the range of 1.3 to 1.8 times the height of the protrusion 14, but is not limited thereto. When the mold coating layer is set to this thickness, the temperature of the mold is preferably set to 300°C or less.

[0085] <Process D: Cast iron pouring process>

[0086] Step D is a step of pouring cast iron into a rotating mold having a dried coating layer. At this time, the molten metal fills the concave holes of the coating layer having a tapered shape described in the previous step, thereby forming a tapered protrusion 14 on the surface of the cylinder liner 10. In addition, it is preferable to apply a moderate centrifugal force at this time.

[0087] <Process E: Removal and finishing process>

[0088] Step E is a step of taking the manufactured cylinder liner 10 out of the casting mold and removing the mold coating layer on the surface of the cylinder liner 10 by, for example, shot peening.

[0089] After the above steps, the manufacturing of the cylinder liner 10 is completed.

[0090] In the cylinder liner 10 of the present embodiment, the center-to-center distance and the protrusion area ratio of the plurality of protrusions formed on the base surface 12S of the cylinder liner substrate 12 are within an appropriate range, so by using the cylinder liner 10 and manufacturing a composite body with the cylinder block 20 by sand mold gravity casting or low-pressure mold casting, the molten metal of the cylinder block 20 is spread between the protrusions 14 of the cylinder liner 10. Therefore, the gap at the interface between the cylinder liner 10 and the cylinder block 20 is reduced, and the bonding force between the cylinder liner 10 and the cylinder block 20 is improved.

[0091] The above-described embodiment is an example of a preferred implementation of the present invention, but the present invention is not limited thereto and can be implemented in various modified forms without departing from the spirit of the present invention.

[0092] [Example]

[0093] The present invention is described in more detail below by way of examples, but the scope of the present invention is not limited to the following examples. For example, in this embodiment, the protrusion 14 is described as being tapered in the middle, but this is only a preferred example. In fact, some or all of the plurality of protrusions 14 may not be tapered in the middle, but this does not hinder the application of the present invention.

[0094] The methods for measuring various physical properties of the cylinder liner 10 used in this embodiment are as follows.

[0095] <Area ratio S of the cross section of the protrusion perpendicular to the height direction t , the average diameter of the protrusions d av >

[0096] 1) The protrusions 14 in the measurement field (12 mm×9 mm) were measured at a magnification of 25 times using a three-dimensional measuring machine VR-3000 manufactured by KEYENCE.

[0097] 2) The measured data was opened with the attached analysis software and the curvature correction was performed. The correction condition was quadratic surface correction.

[0098] 3) The reference plane is set. The reference plane is automatically set on the device side by specifying the area. When the reference plane is set, the center of the display range is determined. The center of the display range is a value automatically determined based on the measured properties of the cylinder liner 10.

[0099] 4) Set the threshold. The threshold is set to about 1 / 2 to 1 / 4 of the protrusion height, for example, 0.1 mm to 0.3 mm. This time, the threshold is set to the center of the display range + the threshold value of 0.3.

[0100] 5) The measurement results are reviewed. The area exceeding the height of the display range center + threshold, that is, the area exceeding 0.3 mm from the substrate surface is considered as protrusions 14, and the number of protrusions can be measured based on the number of protrusions. At this time, the number of protrusions is the number of protrusions existing in the field of view (including protrusions on the boundary) - the number of protrusions on the boundary of the field of view × 1 / 2.

[0101] 6) Based on the measured three-dimensional data, the cross-sectional area of ​​each protrusion 14 in the display range center + threshold is calculated (the "cross-sectional area" referred to in this example is equivalent to the cross-sectional area at the above-mentioned 0.3 mm position in this example). In addition, the axial projection area of ​​the protrusion 14 is assumed to be a rectangle, and the projection area equivalent to the radial projection area (roughly circular) is derived here, and the area ratio S of the cross section perpendicular to the height direction of the protrusion is calculated by dividing the total of the cross-sectional areas of the protrusions by the measured area. t The average diameter d of the protrusions was obtained by dividing the total cross-sectional area of ​​the protrusions by the number of protrusions and calculating the average area of ​​each protrusion. av .

[0102] <The average height of the protrusions h av >

[0103] 1) The height h of each protrusion is the sum of the display range center + threshold + maximum height after measurement. The average value of the height h of each protrusion in the field of view is set as the average height h of the protrusion. av In addition, the center of the display range is a value automatically determined based on the measured properties of the cylinder liner 10, indicating the height of the protrusion 14 from the base surface of the cylinder liner substrate 12 to the reference plane, with the base surface being regarded as the base surface 12S. The threshold value indicates the height from the reference plane, and the maximum height indicates the height from the center of the display range + the threshold value to the front end of the protrusion 14.

[0104] In addition, the area ratio S of the cross section of the protrusion 14 perpendicular to the height direction is t , average diameter d av , average height h avIt is an average value of four locations (four fields of view) measured on one cylinder liner 10. The four locations are preferably two locations at opposing positions about 20 mm from both ends of the cylinder liner 10 and locations offset by about 90° from both ends, but are not limited thereto.

[0105] experiment:

[0106] Preparation of coating agent

[0107] Using the following raw materials, a coating agent was prepared.

[0108] Refractory material: diatomaceous earth 17-25 mass%

[0109] Diatomaceous earth average particle size: 0.018~0.034mm

[0110] Binder: bentonite 4-7% by mass

[0111] Surfactant: 0.003-0.02% by mass

[0112] Water: 68-79% by mass

[0113] ·Production of cylinder liner

[0114] The cylinder liners of the embodiments and comparative examples were produced by centrifugal casting using the molten metal of the following composition. The composition of the cast cylinder liners is:

[0115] C: 3.4 mass %,

[0116] Si: 2.4 mass%,

[0117] Mn: 0.7 mass %,

[0118] P: 0.12 mass %,

[0119] S: 0.035 mass %,

[0120] Cr: 0.25 mass%,

[0121] The remainder is Fe and inevitable impurities (equivalent to JIS FC250).

[0122] Made Figure 5The cylinder liners of Examples 1 to 6 and Comparative Examples 1 to 2 shown in the table. In any of the embodiments, the temperature of the cylindrical mold in step C is appropriately changed within the range of 220 to 280°C, and the Gno (lining) is set to 40 to 70G to form a coating layer. Among them, the height of the protrusion is appropriately changed by appropriately changing the thickness of the coating layer within the range of 0.6 to 1.0 mm. In addition, after step D, cast iron is poured by setting Gno (pouring) to 100 to 130G and the mold temperature to 200 to 260°C. Thereafter, the obtained cast iron cylindrical part is cut, the inner circumference is cut, and the wall thickness is adjusted.

[0123] The dimensions of the cast iron cylindrical component thus obtained are the outer diameter D p The outer diameter (including the height of the protrusion) is 85mm, the inner diameter is 77mm, and the total length is 130mm.

[0124] In addition, the "Joint strength judgment" in the table is judged based on whether there is peeling at the interface between the cylinder liner and the cylinder block when test pieces of approximately 10×10 mm are cut from approximately eight equal parts along the circumference of the cylinder from the interface near the top dead center of the cylinder liner and the cylinder block. In the case where there are many gaps at the interface between the cylinder liner and the cylinder block, the bonding strength is insufficient and peeling occurs. Here, judgment A: the number of test pieces indicating peeling is less than 2, judgment B: the number of test pieces indicating peeling is 3 to 6, and judgment C: the number of test pieces indicating peeling is 7 or more.

[0125] The above-mentioned embodiments and their results focus on the fact that the protrusions become resistance to the flow of molten metal, and are derived from the point of view that the preferred protrusion distribution is defined by the "drag coefficient". By estimating the "drag coefficient" when the molten metal flows (molten metal fluidity) during pouring according to the protrusion density, its preferred range is found. In addition, by calculating the loss coefficient based on the shrinkage resistance caused by the reduction of the flow path area when the molten metal flows from the area without protrusions to the area with protrusions, its preferred range is found. In addition, by calculating the dynamic pressure based on the dynamic pressure when the molten metal flows, the ratio of the resistance (dynamic pressure × obstacle projection area) relative to this can be specified. Based on the results of various visualization experiments in these cases, the following insights are obtained: if the drag coefficient is large, the flow of molten metal is hindered, and if it is small, the temperature of the molten metal drops quickly and hinders the flow of molten metal. According to these results, it can be seen that when the drag coefficient CD is 10 to 35%, preferably 14 to 31%, the improvement of molten metal fluidity during low-pressure casting such as gravity casting becomes more significant, the gap at the interface between the cylinder liner and the cylinder body is reduced, and the bonding strength is improved.

[0126] Industrial Applicability

[0127] The present invention is applicable to cylinder liners.

Claims

1. A cylinder liner, characterized in that: The invention relates to a cylinder liner for insert casting, comprising a base body and a plurality of protrusions formed on a base surface which is an outer peripheral surface of the base body, so as to suppress the generation of gaps at a joint portion between the outer peripheral surface of the base body and the cylinder body of the cylinder liner, and a drag coefficient CD defined by the following mathematical formula (5) is 10 to 35%. In the cross section of the cylinder sleeve cut into a disc, the cross-sectional area S of the cylindrical protrusion region, which is the region where the protrusion is formed, is p The sum of the cross-sectional area S0 of the cylindrical outer region existing outside the cylindrical protrusion region is set as the virtual flow path area S1. S p +S0=S1···(1) The dynamic pressure P1 of the molten metal as the fluid during insert casting is ρU 2 / 2, where ρ is the density of the molten metal, U is the flow rate of the molten metal in the cylindrical outer area measured by a visualization experiment, P1=ρU 2 / 2···(2) The product of the dynamic pressure P1 and the virtual flow path area S1 is defined as the dynamic pressure PD. PD=P1×S1···(3) Obstacle area SB is calculated, and the product of dynamic pressure P1 and obstacle area SB is defined as resistance R1. R1=P1×SB···(4) The resistance R1 divided by the dynamic pressure PD is set as the resistance coefficient CD. CD=R1 / PD···(5), Furthermore, the obstacle area SB is defined in the following manner: The number of protrusions per unit area is N. A , Assuming that the configuration of the protrusions is the same and the center-to-center distance p between the protrusions is the same pitch, according to the number N of the protrusions per unit area A Find the center-to-center distance p between the protrusions, each protruding radially toward the substrate, Assuming that the protrusions are arranged on the same circumference of the base surface with a pitch equal to the distance p between the centers of the protrusions, According to the diameter D of the base surface b and the distance p between the centers of the protrusions, and calculate the number N of protrusions arranged circumferentially on the base surface. B , N B =πD b / p···(6) The average height of the protrusions h av , average diameter d av and the number of protrusions N B The product of is set as the obstacle area SB, SB=h av ×d av ×N B ...(7).

2. The cylinder liner according to claim 1, wherein: The loss coefficient calculated from the contraction resistance of the fluid derived as the flow path area decreases from the virtual flow path area S1 to the actual flow path area S2 obtained by subtracting the obstacle area SB is 0.03 to 0.14.

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