JP6526523B2 - Cylinder block - Google Patents

Description

  The present invention relates to a cylinder block.

  Conventionally, for example, a cylinder block described in Patent Document 1 is known. In the cylinder block described in Patent Document 1, a heat insulating coating layer is provided between the inner peripheral surface of the cylinder formed in the cylinder block and the outer peripheral surface of the cylinder liner. The material of the thermal barrier coating layer has a thermal conductivity lower than the thermal conductivity of the material of the cylinder liner, and the thermal insulation of the combustion chamber is achieved.

Unexamined-Japanese-Patent No. 2014-231791

  In the above prior art, as described above, the material of the thermal barrier coating layer has a thermal conductivity lower than the thermal conductivity of the material of the cylinder liner. Therefore, the combustion chamber may be thermally insulated even after warm-up of the internal combustion engine, and in this case, the oil film in the cylinder liner may become thin and the lubricating performance may be reduced.

  The present invention has been made in view of the above-mentioned circumstances, and an object of the present invention is to provide a cylinder block which can achieve both heat insulation of a combustion chamber in cold condition and reduction in lubrication performance after warm-up.

  The cylinder block according to the present invention is a cylinder block used in an internal combustion engine, and includes a cylinder block body in which a cylinder bore is formed, a cylinder liner disposed inside the cylinder bore and guiding a piston, and an inner circumferential surface of the cylinder bore. The thermal conductivity of the material of the coating portion is lower than the thermal conductivity of the material of the cylinder liner when the internal combustion engine is cold. After warm-up, the thermal conductivity of the material of the cylinder liner is higher.

  In the cylinder block, the transfer of heat (combustion heat) generated by the combustion to the cylinder block is suppressed by the coating portion when cold. Therefore, the heat shield of the combustion chamber at the cold time is realized. On the other hand, after warm-up, the coating does not significantly shield the combustion chamber from heat, and the transfer of the combustion heat to the cylinder block is less likely to be impeded in the coating. Therefore, it is suppressed that the temperature of a cylinder liner becomes high too much and the oil film in a cylinder liner becomes thin, and suppression of the fall of the lubricating performance after warm-up is realized. Therefore, it is possible to achieve both the heat insulation of the combustion chamber in the cold state and the suppression of the decrease in the lubricating performance after the warm-up.

  In the cylinder block according to the present invention, at least a part of the coating portion may be disposed between the upper end of the cylinder liner and a position below the upper end in the axial direction of the cylinder liner by a predetermined distance. The temperature of the cylinder liner is particularly likely to rise between the upper end of the cylinder liner and a position lower than the upper end in the axial direction of the cylinder liner by a predetermined distance until the fuel is ignited and burned to a certain extent. Therefore, by providing at least a part of the coating portion in the range, it is possible to effectively shield the combustion chamber from heat.

  In the cylinder block according to the present invention, the material of the cylinder liner may be cast iron, and the material of the coating portion may be platinum rhodium. According to this configuration, the above-described effects are suitably exhibited.

  In the cylinder block according to the present invention, the material of the cylinder liner may be an aluminum alloy, and the material of the coating portion may be brass. According to this configuration, the above-described effects are suitably exhibited.

  According to the present invention, it is possible to provide a cylinder block capable of achieving both heat insulation of the combustion chamber in the cold state and suppression of deterioration of the lubricating performance after the warm-up.

It is a sectional view showing a cylinder block concerning an embodiment. It is a fragmentary sectional view which shows the cylinder liner of FIG. It is a graph which shows the temperature characteristic of thermal conductivity.

  Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the drawings. In the following description, the same or corresponding elements are denoted by the same reference numerals and redundant description will be omitted. The directions of "upper" and "lower" correspond to the reciprocating direction of the piston in the internal combustion engine. Also, the term "upper" corresponds to the top dead center side of the piston, and the term "lower" corresponds to the bottom dead center side of the piston.

  As shown in FIG. 1, a cylinder block 1 according to the present embodiment is used, for example, in an internal combustion engine such as a diesel engine mounted on a vehicle. As shown in FIG. 1, the cylinder block 1 includes a cylinder block body 1 a and a cylinder liner 2. The cylinder liner may be configured as a part of the cylinder block, but in the present embodiment, a case where it is configured as a separate body will be described as an example.

  The cylinder block main body 1a is a block body constituting an internal combustion engine main body. As a material of the cylinder block main body 1a, for example, cast iron (gray cast iron, CV cast iron, spheroidal graphite cast iron, etc.), aluminum alloy or the like is used. A plurality of cylinder bores B are formed in the cylinder block body 1a. The cylinder bore B is a through hole extending along the central axis C, and has a circular cross section. The cylinder block body 1a has a cooling water flow path through which cooling water flows around the cylinder bore B (not shown). The cylinder liner 2 is inserted into the cylinder bore B.

  The cylinder liner 2 is a cylindrical component that guides the piston 3 while maintaining airtightness with the piston 3. As a material of the cylinder liner 2, for example, cast iron or an aluminum alloy is adopted (details will be described later). The piston 3 reciprocates inside the cylinder liner 2 in the direction of the arrow A. The piston 3 is connected to a crankshaft (not shown) via a connecting rod 5. A piston ring 3 a is fitted in the piston 3. The piston ring 3 a is in contact with the inner circumferential surface 2 a of the cylinder liner 2. Lubricating oil (for example, engine oil) is supplied to the inner circumferential surface 2 a of the cylinder liner 2 for lubrication when the piston 3 slides.

  The outer peripheral surface 2 b of the cylinder liner 2 faces the inner peripheral surface 1 c of the cylinder bore B, and a part or all of the outer peripheral surface 2 b is in contact with the inner peripheral surface 1 c of the cylinder bore B. On the upper end side of the cylinder liner 2, a flange 2c that protrudes outward in the radial direction is formed. The lower surface of the flange 2c is in contact with the side edge of the cylinder bore B in the upper surface 1b of the cylinder block body 1a.

  A head gasket 4 is disposed on the upper surfaces of the cylinder block body 1a and the cylinder liner 2, and a cylinder head (not shown) is mounted thereon. The head gasket 4 is a component for ensuring air tightness between the cylinder block body 1 a and the cylinder head. The cylinder liner 2, the piston 3 and the cylinder head define a combustion chamber E. In the combustion chamber E, the fuel injected from the injector (not shown) is burned.

Here, as shown in FIG. 2, the cylinder liner 2 is provided with a coating portion M so as to cover the outer peripheral surface 2 b of the cylinder liner 2. The coating portion M has a cylindrical shape coaxial with the cylinder liner 2. The coating portion M is provided between the inner peripheral surface 1 c of the cylinder bore B and the outer peripheral surface 2 b of the cylinder liner 2. The upper end portion Ma of the coating portion M is disposed to be continuous with the lower surface of the flange 2 c of the cylinder liner 2. Lower portion Mb of the coating unit M has reached the lower position beyond the predetermined distance L _A10 from the upper end 2d. The coating portion M is interposed on a heat transfer path from the combustion chamber E to the cooling water flow path of the cylinder block body 1 a via the cylinder liner 2.

The predetermined distance _LA10 is a distance from the upper end 2d of the cylinder liner 2 to the upper end surface 3b of the piston 3 when the rotation angle of the crankshaft is 10 ° after the top dead center. The period from the top dead center to 10 ° after the top dead center corresponds to the period until the fuel injected into the combustion chamber E is ignited and burned to a certain degree. The temperature is likely to rise. Therefore, in order to cover the outer peripheral surface 2b of the cylinder liner 2 constituting the combustion chamber E in this period, a part of the coating portion M is an upper end 2d of the cylinder liner 2 and an axial direction of the cylinder liner 2 from the upper end 2d And a position below the predetermined distance _{LA10 in the} vertical direction). The predetermined distance _LA10 is not limited, and is appropriately set in consideration of the heat shielding effect (insulation) of the combustion chamber E in the cold state in the range of the length Lr or less of the cylinder liner 2 in the vertical direction can do.

  The coating portion M can be formed by, for example, a metal film treatment process such as plating, thermal spraying, and sputtering. The thickness of the coating portion M is, for example, in the range of 0.3 to 1.5 mm, substantially uniform on the upper end portion Ma side of the coating portion M, and gradually reduced on the lower end portion Mb side of the coating portion M There is.

  The coating portion M shields the combustion chamber E from heat. In the cold state, the coating portion M suppresses the transfer of the combustion heat of the fuel injected in the combustion chamber E to the cylinder block body 1a. FIG. 3 is a graph showing temperature characteristics of thermal conductivity. In FIG. 3, the solid line X indicates the temperature characteristic of the thermal conductivity Kc of the material of the cylinder liner 2, and the broken line Y indicates the temperature characteristic of the thermal conductivity Km of the material of the coating portion M.

  As shown in FIG. 3, the solid line X and the broken line Y intersect at the temperature T0. The thermal conductivity Km of the material of the coating portion M is lower than the thermal conductivity Kc of the material of the cylinder liner 2 at a temperature lower than the temperature T0, and the thermal conductivity of the material of the cylinder liner 2 at a temperature higher than the temperature T0 Higher than the rate Kc. The temperature T0 is higher than the liner temperature in the cold state of the internal combustion engine and lower than the liner temperature after the warm-up, when compared with the temperature of the inner circumferential surface 2a of the cylinder liner 2 (hereinafter simply referred to as liner temperature). That is, the thermal conductivity Km of the material of the coating portion M is lower than the thermal conductivity Kc of the material of the cylinder liner 2 when cold, and after the warm-up is higher than the thermal conductivity Kc of the material of cylinder liner 2 high. As a material of coating part M which has such a characteristic, platinum rhodium can be adopted when the material of cylinder liner 2 is cast iron, and when the material of cylinder liner 2 is aluminum alloy, it is brass. It can be adopted.

  After warm-up is a state where warm-up of the internal combustion engine is completed. After the warm-up, for example, the liner temperature is high enough to prevent the fuel injected into the combustion chamber E from evaporating and adhering to the surface of the inner peripheral surface 2 a of the cylinder liner 2 as droplets. After the warm-up, for example, a state in which the temperature T of the cooling water in the cylinder block main body 1a is Tw or more may be mentioned. As Tw, 70 ° C can be illustrated. Generally, after warm-up, if the liner temperature becomes too high, the viscosity of the lubricating oil on the inner peripheral surface 2a of the cylinder liner 2 decreases, the oil film on the inner peripheral surface 2a becomes thinner, and the lubricating performance decreases. There are times when

  The cold state is a state in which the internal combustion engine has not been completely warmed up. At cold time, the liner temperature is lower than after warm-up. The cold state includes, for example, a state where the temperature of the cooling water in the cylinder block main body 1a is less than Tw, a case where the number of combustions after the start of the internal combustion engine is less than a predetermined number, and the like. Generally, in the cold state, the fuel injected into the combustion chamber E is less likely to evaporate compared with after warm-up, and may adhere to the inner circumferential surface 2 a of the cylinder liner 2 as droplets. As a result, the possibility of white smoke emissions and misfires increases.

  When cold, the thermal conductivity Km of the material of the coating portion M is lower than the thermal conductivity Kc of the material of the cylinder liner 2. Therefore, at the portion where the coating portion M is provided between the inner peripheral surface 1c of the cylinder bore B and the outer peripheral surface 2b of the cylinder liner 2, the combustion heat is transmitted through the cylinder liner 2 and the cylinder block main body 1a to the cylinder block body 1a. Transmission to the cooling water of the cooling water flow path of is suppressed. Therefore, the liner temperature is higher than when the coating portion M is not provided. That is, the heat shielding of the combustion chamber E is realized by the coating portion M. As a result, compared to the case where the coating portion M is not provided, the fuel injected into the combustion chamber E is more easily evaporated, and the adhesion of the fuel as droplets to the inner peripheral surface 2 a of the cylinder liner 2 is reduced. And the potential for white smoke emissions and misfires is reduced.

  After the warm-up, the thermal conductivity Km of the material of the coating portion M is higher than the thermal conductivity Kc of the material of the cylinder liner 2. Therefore, compared with the case where the coating part M is not provided, the transmission of the combustion heat to the cylinder block main body 1a is less likely to be hindered in the coating part M. In other words, the heat shielding effect of the combustion chamber E is strongly influenced by the thermal conductivity Kc of the material of the cylinder liner 2 (liner base material), and the degree of the thermal conductivity Km of the material of the coating portion M is small. Therefore, the liner temperature is substantially equal to that in the case where the coating portion M is not provided. As a result, the increase in temperature of the cylinder liner 2 is suppressed, and the decrease in viscosity of the lubricating oil on the inner peripheral surface 2 a of the cylinder liner 2 due to the increase in the liner temperature is suppressed. That is, reduction in the lubricating performance after warm-up is realized.

  In the cylinder block 1 configured as described above, the coating portion M can achieve both the heat shielding of the combustion chamber E in the cold state and the suppression of the decrease in the lubricating performance after the warm-up. Specifically, it is suppressed that the heat of combustion is transmitted to the cylinder block body 1a via the cylinder liner 2 and transmitted to the cooling water in the cold state, as compared with the case where the coating portion M is not provided. , Liner temperature is high. That is, by the coating portion M, heat insulation of the combustion chamber E in a cold state is realized. In addition, the heat loss of the combustion chamber E increases the exhaust loss and the exhaust temperature, and the early activation of the aftertreatment device can be expected. On the other hand, after the warm-up, the coating portion M does not largely thermally shield the combustion chamber E, and the transfer of the combustion heat to the cylinder block main body 1a is less likely to be hindered in the coating portion M. Therefore, the liner temperature is substantially equal to that in the case where the coating portion M is not provided. As a result, it is possible to suppress that the temperature of the cylinder liner 2 becomes too high and the oil film in the cylinder liner 2 becomes thin. That is, reduction in the lubricating performance after warm-up is realized. Therefore, it is possible to achieve both the heat insulation of the combustion chamber E in the cold state and the suppression of the decrease in the lubricating performance after the warm-up.

In the cylinder block 1 according to the present invention, at least a part of the coating portion M is disposed between the upper end 2 d of the cylinder liner 2 and a position below the predetermined distance _{LA 10 in} the axial direction of the cylinder liner 2 from the upper end 2 d. It is done. Until the fuel injected into the combustion chamber E is ignited and combusted to a certain extent, the cylinder in the range between the upper end 2 d and a position below the predetermined distance _{LA 10 in} the axial direction of the cylinder liner 2 from the upper end 2 d The temperature of the liner 2 tends to rise. Therefore, by providing at least a part of the coating portion M in the range, it is possible to effectively shield the combustion chamber E from heat.

  As mentioned above, although the suitable embodiment concerning the present invention was described, the present invention is not restricted to the above-mentioned embodiment, it changes in the range which does not change the gist described in each claim, or it applies to other things You may For example, in the above-mentioned embodiment, although explained using a diesel engine as an example of an internal combustion engine, internal combustion engines, such as a gasoline engine, may be used.

  Although the coating M is provided on the outer circumferential surface of the cylinder liner 2 in the above embodiment, the coating M may be provided on the inner circumferential surface 1 c of the cylinder bore B instead of the outer circumferential surface of the cylinder liner 2. The point is that the coating portion M may be provided between the inner peripheral surface 1 c of the cylinder bore B and the outer peripheral surface of the cylinder liner 2. Also, although the cylinder block body 1a and the cylinder liner 2 are separate bodies, the cylinder block body 1a and the cylinder liner 2 may be integrated, or the inner wall portion including the inner circumferential surface 1c in the cylinder bore B may be a cylinder liner (cylinder You may comprise as a liner part.

  In the above embodiment, the upper end portion Ma of the coating portion M is provided to abut on the lower surface of the flange 2c of the cylinder liner 2, but may be provided along the shape of the flange 2c. For example, when the cooling water flow path exists in the side of the flange 2c in the cylinder block main body 1a, the coating heat M is provided along the lower surface and the side surface of the flange 2c so that the combustion heat flows through the flange 2c. Transmission to the cooling water of the cooling water flow passage of the cylinder block main body can be effectively suppressed. In the said embodiment, although the coating part M was provided continuously as a single area | region, you may divide and provide in several area | regions (intermittently).

  DESCRIPTION OF SYMBOLS 1 ... Cylinder block, 1a ... Cylinder block main body, 1c ... Inner peripheral surface, 2 ... Cylinder liner, 2b ... Outer peripheral surface, 2d ... Upper end, 3 ... Piston, B ... Cylinder bore, E ... Combustion chamber, M ... Coating part, Mb ... lower end.

Claims (4)

A cylinder block used in an internal combustion engine, comprising:
A cylinder block body in which a cylinder bore is formed,
A cylinder liner disposed inside the cylinder bore and guiding a piston;
A coating portion provided between an inner peripheral surface of the cylinder bore and an outer peripheral surface of the cylinder liner,
The thermal conductivity of the material of the coating is
A cylinder block which is lower than the thermal conductivity of the material of the cylinder liner when the internal combustion engine is cold and higher than the thermal conductivity of the material of the cylinder liner after the internal combustion engine is warmed up.   The cylinder block according to claim 1, wherein at least a part of the coating portion is disposed between an upper end of the cylinder liner and a position below the upper end in the axial direction of the cylinder liner by a predetermined distance. The material of the cylinder liner is cast iron,
The cylinder block according to claim 1, wherein a material of the coating portion is platinum rhodium. The material of the cylinder liner is an aluminum alloy,
The cylinder block according to claim 1, wherein a material of the coating portion is brass.

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