Abstract: A piston for an internal combustion engine has a plurality of recesses formed in a skirt including an upper, a lower, and a central portion. The recesses in the upper portion close to an upper boundary of the central portion have lower ends located upwardly at a given distance away from the upper boundary. The recesses in the central portion close to the upper boundary have upper ends located downwardly at the given distance away from the upper boundary. The recesses in the lower portion close to the lower boundary have upper ends located downwardly at the given distance away from the lower boundary. The recesses in the central portion closer to the lower boundary have lower ends located upwardly at the given distance away from the lower boundary. This enhances lubrication between the piston and an inner wall of a cylinder bore and reduces a friction loss of the piston.

Abstract: [Problem to be Solved] A space from a skirt to a side wall is uniformly deformed in a wide range without a bias. [Solution] A piston 1 has two pin bosses 3 disposed so as to face each other at an interval, a side wall 4 disposed on both sides of the pin boss 3, and a skirt 5 provided continuously to the side wall 4, and a pin hole 3a into which a piston pin 1a can be inserted is formed in the pin boss 3. Inner walls 10 of the side wall 4 and the skirt 5 are continuous with each other and disposed by facing on both sides of a pin boss axis C1 with the pin boss axis C1 between them. A horizontal section of the inner wall 10 is formed along a specific oval shape E.

Abstract: [Problem to be Solved] A space from a skirt to a side wall is uniformly deformed in a wide range without a bias. [Solution] A piston 1 has two pin bosses 3 disposed so as to face each other at an interval, a side wall 4 disposed on both sides of the pin boss 3, and a skirt 5 provided continuously to the side wall 4, and a pin hole 3a into which a piston pin 1a can be inserted is formed in the pin boss 3. Inner walls 10 of the side wall 4 and the skirt 5 are continuous with each other and disposed by facing on both sides of a pin boss axis C1 with the pin boss axis C1 between them. A horizontal section of the inner wall 10 is formed along a specific oval shape E.

Abstract: A piston for an internal combustion engine has a plurality of recesses formed in a skirt including an upper, a lower, and a central portion. The recesses in the upper portion close to an upper boundary of the central portion have lower ends located upwardly at a given distance away from the upper boundary. The recesses in the central portion close to the upper boundary have upper ends located downwardly at the given distance away from the upper boundary. The recesses in the lower portion close to the lower boundary have upper ends located downwardly at the given distance away from the lower boundary. The recesses in the central portion closer to the lower boundary have lower ends located upwardly at the given distance away from the lower boundary. This enhances lubrication between the piston and an inner wall of a cylinder bore and reduces a friction loss of the piston.

Abstract: A resin coat film 39 formed on a skirt portion 10 of a piston 7 has a four-sided outer peripheral region knurled at upper and lower regions thereof corresponding in a rear view of the piston 7 to an upper skirt part 36 and a lower skirt part 38 of the skirt portion 10 extending in parallel with an axial direction of left and right piston pin boss portions 15 and 14, with a combination of short vertical grooves 43A and 43B and medium-length vertical grooves 42A and 42B extending in parallel with a central axis C of a piston crow portion 9, and at left and right edge regions thereof, with long vertical grooves 41.

Abstract: A resin coat film 39 formed on a skirt portion 10 of a piston 7 has a four-sided outer peripheral region knurled at upper and lower regions thereof corresponding in a rear view of the piston 7 to an upper skirt part 36 and a lower skirt part 38 of the skirt portion 10 extending in parallel with an axial direction of left and right piston pin boss portions 15 and 14, with a combination of short vertical grooves 43A and 43B and medium-length vertical grooves 42A and 42B extending in parallel with a central axis C of a piston crow portion 9, and at left and right edge regions thereof, with long vertical grooves 41.

Abstract: A plating pretreatment apparatus for a multi-cylinder block includes a plurality of cylinders that performs a plating pretreatment of a cylinder inner wall surface of each of the cylinders using an electrode disposed so as to oppose to the cylinder inner wall surface by sealing one end of the cylinder inner wall surface and introducing a treatment liquid to the cylinder inner wall surface. In such plating pretreatment apparatus, at least one of a power supply device that supplies electricity to the cylinder block and the electrode and a liquid feed pump that feeds the treatment liquid into a gap between the cylinder inner wall surface and the electrode is provided for each of the cylinders.

Abstract: A cylinder block plate processing apparatus in which one end side of an inner peripheral surface of a cylinder of a cylinder block is sealed to circulate a process liquid to perform pre-plating or plating processing of the cylinder inner peripheral surface. The apparatus includes: an apparatus body having a workpiece mount table on which the cylinder block is placed; a workpiece holding tool that is provided on the workpiece mount table so as to be vertically movable; an electrode support member including an electrode cylinder mounted to the apparatus body; a processing solution supply member that supplies a processing solution to the electrode support member; an electrode operated by the electrode cylinder; a sealing jig provided to one end of the electrode; a driving mechanism that drives the sealing jig; and a control circuit that controls operations of the processing solution supply member and the driving mechanism.

Abstract: The present invention provides an apparatus for plating pretreatment of a cylinder block that includes an electrode performing a plating pretreatment of the cylinder inner wall surface. A gap flow channel communicates with an in-electrode flow channel at a position closest to a seal jig, the gap flow channel being adapted to introduce a treatment liquid to the cylinder inner wall surface, the in-electrode flow channel being adapted to receive the treatment liquid having passed through a communicating hole. The present invention is provided a method for pretreating before plating a cylinder block including disposing an electrode to face the cylinder inner wall surface so as to form a gap flow channel, and introducing a treatment liquid to the gap flow channel thereby flowing through the treatment liquid toward a seal jig and then into an in-electrode flow channel through a communicating hole.

Abstract: A cylinder block plate processing apparatus in which one end side of an inner peripheral surface of a cylinder of a cylinder block is sealed to circulate a process liquid to perform pre-plating or plating processing of the cylinder inner peripheral surface. The apparatus includes: an apparatus body having a workpiece mount table on which the cylinder block is placed; a workpiece holding tool that is provided on the workpiece mount table so as to be vertically movable; an electrode support member including an electrode cylinder mounted to the apparatus body; a processing solution supply member that supplies a processing solution to the electrode support member; an electrode operated by the electrode cylinder; a sealing jig provided to one end of the electrode; a driving mechanism that drives the sealing jig; and a control circuit that controls operations of the processing solution supply member and the driving mechanism.

Abstract: A plating pretreatment apparatus for a multi-cylinder block includes a plurality of cylinders that performs a plating pretreatment of a cylinder inner wall surface of each of the cylinders using an electrode disposed so as to oppose to the cylinder inner wall surface by sealing one end of the cylinder inner wall surface and introducing a treatment liquid to the cylinder inner wall surface. In such plating pretreatment apparatus, at least one of a power supply device that supplies electricity to the cylinder block and the electrode and a liquid feed pump that feeds the treatment liquid into a gap between the cylinder inner wall surface and the electrode is provided for each of the cylinders.

Abstract: The present invention provides an apparatus for plating pretreatment of a cylinder block that includes an electrode performing a plating pretreatment of the cylinder inner wall surface. A gap flow channel communicates with an in-electrode flow channel at a position closest to a seal jig, the gap flow channel being adapted to introduce a treatment liquid to the cylinder inner wall surface, the in-electrode flow channel being adapted to receive the treatment liquid having passed through a communicating hole. The present invention is provided a method for pretreating before plating a cylinder block including disposing an electrode to face the cylinder inner wall surface so as to form a gap flow channel, and introducing a treatment liquid to the gap flow channel thereby flowing through the treatment liquid toward a seal jig and then into an in-electrode flow channel through a communicating hole.