JP2019039367A - Internal combustion engine - Google Patents

Abstract

To reduce sliding resistance of a piston, and to reduce the risk of generating preignition.SOLUTION: A through hole HL1 penetrating in a vertical direction is formed in a cylinder block 16. A cylinder liner 18 in a cylindrical shape is attached to the through hole HL1 in such a manner of extending in the vertical direction. A piston 12 is accommodated in the cylinder 18 movably in the vertical direction. Cross-hatching processing is applied to an area above a reference position PR1 (a position of a piston ring 141 at the point of time when the piston 12 reaches a top dead center) of an inner peripheral surface of the cylinder liner 18. Dimple processing is applied to an area below the reference position of the inner peripheral surface of the cylinder liner 18.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an internal combustion engine, and in particular, a cylinder block in which a through-hole penetrating in the vertical direction is formed, a cylindrical cylinder liner mounted in the through-hole so as to extend in the vertical direction, and a sliding in the vertical direction. The present invention relates to an internal combustion engine including a piston movably accommodated in a cylinder liner.

  An example of this type of internal combustion engine is disclosed in Patent Document 1. According to this document, a cylinder bore that slidably accommodates a piston of an engine is defined in the cylinder liner, and a surface treatment for preventing seizure with the piston is applied to the inner peripheral surface of the cylinder bore. Here, the surface treatment is to perform dimple processing on the inner peripheral surface of the cylinder bore using a fine particle shot material made of molybdenum disulfide.

  This can reduce the sliding resistance with the piston while preventing scuffing. In particular, the sliding resistance can be reduced by improving the retention of the lubricating oil, reducing the processing burr, reducing the contact area with the piston, and the like.

JP 2011-38494 A

  However, in the technique of Patent Document 1, deposits are easily generated in the dimples by mixing the lubricating oil and the combustion component. The generated deposit is scraped into the combustion chamber and grows and can become an ignition source that causes pre-ignition.

  Therefore, a main object of the present invention is to provide an internal combustion engine that can reduce the sliding resistance of the piston and reduce the risk of occurrence of pre-ignition.

  An internal combustion engine according to the present invention includes a cylinder block having a through-hole penetrating in the vertical direction, a cylindrical cylinder liner mounted in the through-hole so as to extend in the vertical direction, and a cylinder movably in the vertical direction An internal combustion engine having a piston accommodated in a liner, wherein cross-hatching is performed above the reference position on the inner peripheral surface of the cylinder liner, and dimple processing is performed below the reference position on the inner peripheral surface of the cylinder liner This is an internal combustion engine.

  By performing dimple processing on the inner peripheral surface below the reference position, the sliding resistance of the biston is reduced. Moreover, the risk of pre-ignition is reduced by applying cross-hatch processing to the inner peripheral surface above the reference position.

  The above object, other objects, features and advantages of the present invention will become more apparent from the following detailed description of embodiments with reference to the drawings.

It is an illustration figure which shows an example of the structure of an internal combustion engine. It is an illustration figure which shows an example of the cylinder liner which comprises the internal combustion engine shown in FIG. It is an illustration figure which shows another example of the structure of an internal combustion engine. It is an illustration figure which shows an example of the cylinder liner which comprises the internal combustion engine shown in FIG.

  Referring to FIGS. 1 and 2, an engine (internal combustion engine) 10 of this embodiment is an engine that employs a port injection method, and includes a cylinder block 16 in which a through hole HL1 is formed. The through hole HL1 has a uniform inner diameter dimension and extends in the vertical direction. The cylinder liner 18 has an outer diameter that matches the inner diameter of the through hole HL1, is formed in a cylindrical shape, and is attached to the through hole HL1 in a posture extending in the vertical direction. As a result, the central axis of the cylinder liner 18 overlaps the central axis of the through hole HL1.

  The inner diameter dimension of the cylinder liner 18 is smaller than the outer diameter dimension of the cylinder liner 18 by the thickness of the cylinder liner 18 in the radial direction. The inner diameter of the cylinder liner 18 is also uniform in the length direction (vertical direction).

  The piston 12 has an outer diameter that is slightly smaller than the inner diameter of the cylinder liner 18, and is accommodated in the cylinder liner 18 so as to be movable in the vertical direction. Piston rings 141 to 143 are attached to the outer peripheral surface of the piston 12. Among these, the piston ring 141 corresponds to a top ring, the piston ring 142 corresponds to a second ring, and the piston ring 143 corresponds to an oil ring.

  The outer peripheral surfaces of the piston rings 141 to 143 are continuously in contact with the inner peripheral surface of the cylinder liner 18. As a result, the piston 12 slides up and down in the cylinder liner 18 while maintaining the same posture.

  On the cylinder block 16, a cylinder head 20 in which an intake pipe 22, an exhaust pipe 24 and a combustion chamber 30 are formed is disposed. An intake valve 26 is provided at the joint between the intake pipe 22 and the fuel chamber 30, and an exhaust valve 28 is provided between the exhaust pipe 28 and the combustion chamber 30. Further, a fuel injection device 32 is provided at a position upstream of the intake valve 26 of the intake pipe 22, and an ignition plug 34 is provided at the upper portion of the combustion chamber 30.

  The engine 10 having such a structure is a four-cycle type and repeats the steps in the order of an intake process → compression process → combustion / expansion process → exhaust process → intake process →

  In the intake process, the intake valve 26 is opened and the piston 12 is lowered. Thus, an air-fuel mixture obtained by mixing the fuel injected from the fuel injection device 32 and the intake air is supplied to the combustion chamber 30. In the compression process, the intake valve 26 is closed and the piston 12 is raised. The air-fuel mixture supplied to the combustion chamber 30 is compressed by the piston 12.

  In the combustion / expansion process, the ignition plug 34 is ignited at a timing immediately before the piston 12 reaches top dead center. As a result, the air-fuel mixture is combusted and expanded, and the piston 12 descends. In the exhaust process, the exhaust valve 28 is opened and the piston 12 is raised. The combustion gas remaining in the combustion chamber 30 is discharged to the exhaust pipe 24 as the biston 12 rises. The exhaust valve 28 is closed immediately before the next intake process starts.

  When the position of the piston ring 141 when the piston 12 reaches the top dead center is set as the reference position PR1, the range 18a above the reference position PR1 on the inner peripheral surface of the cylinder liner 18 is subjected to cross hatching, Of the inner peripheral surface of the cylinder liner 18, a range 18b below the reference position PR1 is subjected to dimple processing (see FIG. 2).

  The sliding resistance between the piston 12 and the cylinder liner 18 is reduced by applying dimple processing to the range 18b. Reduction of sliding resistance contributes to improvement of fuel consumption. In addition, the concern that the deposit generated in the dimples is scraped into the combustion chamber 30 and accumulates and grows can be reduced by performing cross hatching in the range 18a. Where deposits grown and deposited can be an ignition source causing pre-ignition, reducing the concern that deposits will grow and deposit means reducing the risk of pre-ignition.

  Referring to FIGS. 3 and 4, an engine 10 ′ of another embodiment is an engine that employs a direct injection method, and its structure is substantially the same as engine 10 shown in FIG. 1. Therefore, the duplicate description regarding the same structure is omitted.

  The fuel injection device 32 is disposed not at a position upstream of the intake valve 26 of the intake pipe 22 but at a position slightly above the fuel chamber 30 and on the intake valve 26 side. The fuel injection direction is obliquely downward. The ignition plug 34 provided in the engine 10 shown in FIG. 1 is not shown in FIG. Further, the boundary (= reference position PR1) between the range 18a where the cross hatching is performed and the range 18b where the dimple processing is performed is matched with the intersection of the straight line extending in the fuel injection direction and the inner peripheral surface of the cylinder liner 18.

  The intersection of the straight line extending in the fuel injection direction and the inner peripheral surface of the cylinder liner 18 is set as a reference position PR1, and cross hatching is performed above the reference position PR1, so that fuel droplets are mixed with oil in the dimples and deposits are generated. The generated concern can be reduced, and the risk of occurrence of pre-ignition can be reduced. Note that the dimple process reduces the sliding resistance and improves the fuel efficiency, as in the embodiment shown in FIG.

10, 10 '... engine 12 ... piston 16 ... cylinder block 18 ... cylinder liner 30 ... combustion chamber 32 ... fuel injection device

Claims (1)

A cylinder block in which a through-hole penetrating in the vertical direction is formed;
An internal combustion engine comprising: a cylindrical cylinder liner mounted in the through hole so as to extend in the vertical direction; and a piston accommodated in the cylinder liner so as to be movable in the vertical direction,
Cross hatching is performed above the reference position on the inner peripheral surface of the cylinder liner,
An internal combustion engine in which dimple processing is performed below the reference position on the inner peripheral surface of the cylinder liner.

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