JP6252063B2 - Piston equipped with a piston ring and method of manufacturing an engine incorporating the piston - Google Patents

Description

  The present invention relates to a piston to which a piston ring is attached and a method for manufacturing an engine incorporating the piston.

In an engine in which the cylinder block and the cylinder head are separate, the piston is inserted into the cylinder of the cylinder block using various conventionally known piston insertion devices before the cylinder head is assembled to the cylinder block.
A piston ring is installed in the ring groove of the piston, and in the piston insertion device, the piston ring is inserted into the cylinder together with the piston in a state where the diameter of the piston ring is reduced. It is in pressure contact with the inner peripheral surface.
The piston is inserted from the flat upper surface side of the cylinder block to which the cylinder head is attached.

The present applicant has studied (developed) a cylinder block in which a cylinder head is integrally provided from the viewpoint of cost reduction and friction reduction. In such a cylinder block, the piston is mounted on the crankcase. It must be inserted into the cylinder from the bottom side of the cylinder block to be worn.
On the other hand, bearing portions including a crank metal that supports the crankshaft are located on both sides of the cylinder block on the lower surface of the cylinder block, and the lower surface of the cylinder block is not flat like the upper surface of the cylinder block.
For this reason, a conventional piston insertion device cannot be used, and there is some contrivance to insert a piston fitted with a piston ring whose diameter is larger than the inner diameter of the cylinder into the cylinder from the lower surface side of the cylinder block. Necessary.

Patent Document 1 proposes a piston in which a piston ring is reduced in diameter to a ring groove by a mechanical configuration.
According to this configuration, it is advantageous to insert the piston with the piston ring into the cylinder from the lower surface side of the cylinder block.

JP 2009-228587 A

However, the above prior art requires the addition of a mechanical configuration such as providing a locked portion at both ends of the piston ring and providing a recess in which the locked portion is locked in the ring groove of the piston. Therefore, design changes are required for both the piston ring and the piston, which is disadvantageous in reducing costs.
The present invention has been devised in view of the above circumstances, and the object of the present invention is to change the design of both the piston ring and the piston without changing the piston ring. It is another object of the present invention to provide a piston that is advantageous for easy and reliable insertion into a cylinder and a method of manufacturing an engine incorporating the piston.

In order to achieve the above-mentioned object, the invention according to claim 1 is a piston having a piston ring mounted in a ring groove, and the piston is made of a hydrocarbon-based oil that is solid at room temperature and at least in the radial direction of the piston ring. It has a piston ring coating layer covering an outer peripheral surface, and the piston ring coating layer holds the piston ring in a state of being reduced in diameter in the ring groove.
The invention according to claim 2 is characterized in that the piston ring covering layer is provided with at least one concave groove extending in a direction intersecting the circumferential direction of the piston ring.
The invention according to claim 3 is characterized in that a chamfer is formed at an end portion of the outer peripheral surface of the piston ring coating layer near the top of the piston.

The invention according to claim 4 is an engine manufacturing method in which a piston having a piston ring mounted in a ring groove is assembled, wherein the piston ring is mounted in the ring groove inside a coating layer forming die. A substantially cylindrical filling chamber capable of accommodating a piston portion is provided, and the piston portion having the piston ring mounted in the ring groove is disposed in the filling chamber, and the molten hydrocarbon-based oil is filled. A covering step of filling and solidifying a chamber and forming the piston ring covering layer on the piston in a state where the diameter of the piston ring is reduced; an engine assembling step of attaching the piston having the piston covering layer to the engine; and the engine The piston covering layer of the piston assembled to the piston is removed and the piston ring is expanded by its elasticity. And having a removal step.
According to a fifth aspect of the present invention, the covering step includes a piston disposing step of disposing a piston on which a piston ring held in a state of being reduced in diameter by the ring groove is disposed in the filling chamber.
The invention described in claim 6 is characterized in that, in the coating step , the piston ring is maintained in a state of being reduced in diameter by a condensing force of the hydrocarbon oil when the hydrocarbon oil is cooled and solidified.
The invention according to claim 7 is characterized in that, in the coating step , pressure is applied to the hydrocarbon oil.
The invention according to claim 8 is characterized in that, in the coating removal step, the piston coating layer is removed by melting the hydrocarbon oil by cranking the engine.
The invention according to claim 9 is characterized in that, in the coating removal step, the piston coating layer is removed by melting the hydrocarbon oil by warming up the engine.

According to the first aspect of the present invention, no design change is required for both the piston ring and the piston, and the piston ring is held in a state of being reduced in diameter in the ring groove by the piston ring coating layer . In addition, the piston ring coating layer made of hydrocarbon oil that is solid at room temperature is softer than metal, and its shape is destroyed by abutting against the inner wall of the cylinder so that it does not become an obstacle when inserted into the cylinder. . Moreover, since the piston ring coating layer is formed of a hydrocarbon-based oil that is solid at room temperature, it functions as a lubricant that smoothly inserts the piston with the piston ring into the cylinder.
Therefore, it is advantageous to smoothly insert the piston with the piston ring into the cylinder from the upper surface side of the flat cylinder block and the lower surface side of the uneven cylinder block.
Therefore, a piston with a piston ring can be incorporated into a cylinder block in which the cylinder head is integrally provided. This eliminates the head tightening bolt, and a cylinder hole due to the axial force of the head tightening bolt during assembly. It is expected to reduce friction by suppressing deformation and moving the piston smoothly up and down.
According to the second aspect of the present invention, when the piston is inserted into the cylinder, the air in the cylinder can be released from the concave groove to the outside of the cylinder, which is advantageous in smoothly inserting the piston into the cylinder. Become.
According to the third aspect of the present invention, it is easy to align the axis of the piston ring coating layer with the axis of the cylinder using chamfering as a guideline, which is advantageous in smoothly inserting the piston into the cylinder.

According to the invention of claim 4, the piston ring coating layer for holding the piston ring in a reduced diameter in the ring groove by using the mold can be easily and reliably manufactured, and the piston ring coating layer is provided. This is advantageous for reducing the cost of the piston.
According to the fifth aspect of the present invention, the reduced diameter state of the piston ring is formed on the mold side, which is advantageous in forming the piston ring coating layer in which the piston ring has a desired reduced diameter state.
According to the invention described in claim 6, since the condensing force of the hydrocarbon oil is used, it is advantageous for easily and surely manufacturing the piston ring coating layer that maintains the reduced diameter in the ring groove. It becomes.
According to the seventh aspect of the present invention, it is advantageous in reducing the diameter of the piston ring by the condensing force of the hydrocarbon oil, and the holding force for holding the piston ring in a reduced diameter state in the ring groove is larger. This is advantageous in forming the piston ring coating layer .
According to the invention of claim 8 or claim 9, the piston ring coating layer is formed of a hydrocarbon-based oil, and the hydrocarbon-based oil is quickly melted by the heat of the combustion chamber, vaporized, and burned with the fuel. Or, it mixes with engine oil and functions as engine oil. Therefore, it is not necessary to provide any process for removing the piston ring coating layer, and there is no problem of increasing the cost of the engine using the piston having the piston ring coating layer .

(A) is a top view of the piston in which the piston ring coating layer of 1st Embodiment was formed, (B) is the same front view. (A) is a top view of the piston in which the piston ring coating layer of the modification of 1st Embodiment was formed, (B) is the same front view. (A) is a top view of the piston in which the piston ring coating layer of 2nd Embodiment was formed, (B) is the same front view. (A) is a top view of the piston in which the piston ring coating layer of 3rd Embodiment was formed, (B) is the same front view. (A) is a top view of the piston in which the piston ring coating layer of 4th Embodiment was formed, (B) is the same front view. (A), (B) is a front view of the piston in which the piston ring coating layer of 5th Embodiment was formed. It is explanatory drawing which manufactures the piston in which the piston ring coating layer of 1st Embodiment was formed, (A) is a cross-sectional front view which shows the relationship between a metal mold | die and a piston, (B) is a molten state in a metal mold | die. It is a cross-sectional front view of the state filled with the hydrocarbon-based oil component. It is explanatory drawing which manufactures the piston in which the piston ring coating layer of 2nd Embodiment was formed, (A) is a cross-sectional top view of the state with which the hydrocarbon-type oil component of the molten state was filled in the metal mold | die, (B) FIG. It is explanatory drawing which manufactures the piston in which the piston ring coating layer of 3rd Embodiment was formed, (A) is a cross-sectional top view of the state with which the hydrocarbon-type oil component of the molten state was filled in the metal mold | die, (B) FIG. It is explanatory drawing which manufactures the piston in which the piston ring coating layer of 4th Embodiment was formed, (A) is a cross-sectional top view of the state which filled the molten hydrocarbon-type oil component in the metal mold | die, (B) FIG. (A), (B) is explanatory drawing which manufactures the piston in which the piston ring coating layer of 5th Embodiment was formed, and sectional front view of the state which filled the molten hydrocarbon-type oil component in the metal mold | die It is. It is explanatory drawing which inserts into a cylinder the piston with which the piston ring was mounted | worn from the lower surface of the cylinder block integrated with a cylinder head.

Next, an embodiment of the present invention will be described.
First, from the first embodiment, as shown in FIG. 1, the piston 10 has a head portion 10A constituting the bottom surface of the combustion chamber and a skirt portion 10B following the head portion 10A.
The outer peripheral surfaces of the head portion 10A and the skirt portion 10B are formed as cylindrical surfaces, and three ring grooves 12 are formed on the outer peripheral surface 1002 of the head portion 10A at intervals in the axial direction of the piston 10. Are respectively equipped with piston rings 14. The piston rings 14 are a compression ring, a top ring 14A, a second ring 14B, and an oil ring 14C.
In FIG. 1A, reference numeral 1410 indicates a cut of the piston ring 14, and this cut 1410 is omitted in the front view of FIG. 1B and the front view of the following embodiments for the sake of clarity. ing.
A pin boss portion 16 is provided in the skirt portion 10 </ b> B, and a piston pin insertion hole 18 for connecting the piston 10 and the connecting rod 17 is formed in the pin boss portion 16.

The three piston rings 14 are covered with a piston ring covering layer 20.
The piston ring coating layer 20 is configured as a single body having a single outer peripheral surface 2002 that covers the three piston rings 14.
The outer peripheral surface 2002 is coaxial with the outer peripheral surface of the piston 10, and the outer peripheral surface 2002 covers the outer peripheral surface 1002 of the head portion 10 </ b> A from the top of the piston 10 to the lower end of the head portion 10 </ b> A together with the three piston rings 14.
The outer circumferential surface 2002 of the piston ring coating layer 20 does not need to be coaxial with the outer circumferential surface 1002 of the head portion 10A. However, as will be described later, the outer circumferential surface 2002 of the piston ring coating layer 20 is the outer circumferential surface of the head portion 10A. When positioned on the same axis as 1002, the outer peripheral surface 2002 of the piston ring coating layer 20 is aligned when the axis of the piston 10 is aligned with the axis of the cylinder 50 when the piston 10 is inserted into the cylinder 50 (see FIG. 12). It is advantageous in using as a guide.
Further, the outer peripheral surface 2002 of the piston ring coating layer 20 is not limited to a cylindrical surface, and may be formed by a plurality of flat side surfaces constituting a polygonal column. In short, the outer peripheral surface 2002 looks like the piston ring coating layer 20 at first glance. A shape that allows the center axis to be understood is preferable for the above-mentioned standard.
Further, as shown in FIG. 2, three piston rings 14 may be individually covered and three piston ring covering layers 20 separated in the axial direction of the piston 10 may be provided. Providing a single piston ring coating layer 20 that covers all of the two piston rings 14 is advantageous in simplifying the structure of the mold for forming the piston ring coating layer 20 and reducing costs, as will be described later.

The three piston rings 14 are held in a state of being reduced in diameter in the ring groove 12 by the piston ring coating layer 20. Specifically, the piston ring 14 is held in a state where the diameter is reduced to a size smaller than the inner diameter of the cylinder 50 so that the piston 10 can be easily inserted into the cylinder 50. Alternatively, the piston ring 14 is held in a state in which the outer peripheral surface 1402 is reduced in diameter to be equal to or smaller than the diameter of the outer peripheral surface 1002 of the head portion 10A. Alternatively, the piston ring 14 has an outer peripheral surface 1402 positioned on the same surface as the outer peripheral surface 1002 of the head portion 10A, or an inner peripheral surface 1404 in contact with the bottom surface 1202 of the ring groove 12. Is retained.
In the present embodiment, the piston ring coating layer 20 holds the piston ring 14 in a state of being reduced in diameter so that the outer peripheral surface 1402 is positioned on the same surface as the outer peripheral surface 1002 of the head portion 10A of the piston 10. Yes.
The diameter-reduced state of the piston ring 14 is mainly formed by the piston ring coating layer 20 portion located radially outward of the outer peripheral surface 1402 of the piston ring 14.
The piston ring coating layer 20 is formed of a hydrocarbon-based oil that is solid at room temperature.
The hydrocarbon oil component that is solid at normal temperature preferably has a melting point of 90 ° C. or higher, and is quickly melted and vaporized by the heat of the combustion chamber during cranking or smoothing operation during the manufacturing process or during warm-up operation. It burns with or mixes with engine oil and functions as engine oil.
Various conventionally known materials such as paraffin can be used as such a hydrocarbon oil component that is solid at normal temperature, and paraffin is used in the present embodiment.

According to the piston 10 to which the piston ring 14 of the present embodiment is attached, the piston ring 14 is held in a state of being reduced in diameter in the ring groove 12 by the piston ring coating layer 20.
Also, the piston ring coating layer 20 made of a hydrocarbon-based oil that is solid at room temperature is softer than metal and is deformed by contacting the inner wall of the cylinder 50 (or the inner wall of the cylinder liner). There is no obstacle during insertion into the cylinder 50.
Further, although the shape of the piston ring coating layer 20 is broken by contacting the inner wall of the cylinder 50, it is formed of a hydrocarbon-based oil that is solid at room temperature, so that it is used as a lubricant (wax) when the piston 10 is inserted. This is advantageous for smoothly inserting the piston 10 with the piston ring 14 into the cylinder 50.
Therefore, as shown in FIG. 12, the axis of the piston 10, that is, the axis of the piston ring coating layer 20 may be aligned with the axis of the cylinder 50, and the piston 10 may be inserted into the cylinder 50. The piston 10 is inserted smoothly because the piston ring 14 is held in the ring groove 12 by the piston ring coating layer 20 in a reduced diameter state.

Accordingly, in the cylinder block 52 integrated with the cylinder head, the piston 5 is mounted with the piston ring 14 from the lower surface 52A side of the cylinder block 52 where the bearing portions 5204 including the crank metal 5202 are located on both sides of the cylinder 50 and are not flat end surfaces. This is advantageous in smoothly inserting 10 into the cylinder 50.
Such insertion of the piston 10 into the cylinder 50 may be performed manually, or mechanically automatically using a jig that supports the piston 10 coaxially with the cylinder 50 and moves the piston 10 linearly. This is optional.
When the piston 10 is inserted manually, the axis of the piston ring coating layer 20 is relative to the axial center of the cylinder 50 with the outer peripheral surface 2002 of the piston ring coating layer 20 having a size larger than the outer diameter of the piston 10 as a guide. Since the centers can be aligned, it is advantageous in smoothly inserting the piston 10 into the cylinder 50.

When the piston 10 is inserted into the cylinder 50, the piston ring coating layer 20 portion located radially outward from the outer peripheral surface 1402 of the piston ring 14 abuts against the inner wall of the cylinder 50 (or the inner wall of the cylinder liner). The shape is broken, and the piston ring 14 is inserted into the cylinder 50 together with the piston 10.
When the piston 10 is inserted into the cylinder 50, when the shape of the piston ring coating layer 20 portion located radially outward from the outer peripheral surface 1402 of the piston ring 14 is broken by the inner wall of the cylinder 50, the piston ring coating layer 20. The reduced diameter state of the piston ring 14 is released. The diameter of the piston ring 14 is expanded by its elasticity, and the outer peripheral surface 1402 of the piston ring 14 directly contacts the inner wall of the cylinder 50, or elastically contacts the inner wall of the cylinder 50 via the remaining piston ring coating layer 20 portion. .
On the other hand, adhering remaining and piston ring coating layer 20 moiety on the outer circumferential surface 1002 of the head portion 10A, piston ring coating layer 20 portion that remains radially outwardly from the outer circumferential surface 1402 of the piston ring 14, the inner wall of the cylinder 50 The piston ring coating layer 20 is rapidly melted by the heat of the combustion chamber at the time of cranking at the time of manufacture, at the time of warming-up operation, and vaporized and burned with fuel, or mixed into the engine oil. Functions as engine oil.
The piston ring 14 functions as a compression ring and an oil ring by the piston ring 14 being elastic on the inner wall of the cylinder 50.

According to the present embodiment, no design change is required for both the piston ring 14 and the piston 10, and the piston ring 14 is held in a reduced diameter state by the piston ring coating layer 20. Therefore, it goes without saying that the piston 10 to which the piston ring 14 is mounted is advantageous from the upper surface side of the flat cylinder block and that it can be easily and reliably inserted into the cylinder 50 even from the lower surface 52A side of the uneven cylinder block 52. It becomes.
Therefore, in particular, the engine E in which the cylinder head and the cylinder block 52 are integrated and the piston 10 to which the piston ring 14 is attached must be inserted into the cylinder 50 from the lower surface 52A side of the cylinder block 52 is easily manufactured. This is advantageous for reducing the cost of the engine E having the cylinder block 52 integrated with the cylinder head.
Further, the engine E (see FIG. 9) in which the piston 10 having the piston ring covering layer 20 is incorporated is connected to the cylinder 50 from the upper surface side of the cylinder block or from the lower surface 52A side of the cylinder block 52. Since it is easily and reliably inserted, it is advantageous in reducing the cost of the engine E.
Further, the cylinder head cylinder block integrated structure makes it possible to omit the head tightening bolt. As a result, the cylindrical hole (cylinder) deformation due to the axial force of the bolts during assembly is suppressed, and the piston 10 is smoothly moved up and down, and a reduction in friction is expected.
The piston ring coating layer 20 is formed of a hydrocarbon-based oil, and the hydrocarbon-based oil is rapidly melted by the heat of the combustion chamber and vaporized and burned with the fuel, or mixed with the engine oil and engine oil. Function as. Therefore, it is not necessary to provide any process for removing the piston ring coating layer 20, and there is no problem of increasing the cost of the engine E using the piston 10 having the piston ring coating layer 20.

Next, a second embodiment will be described with reference to FIG.
In the following embodiments, the same parts and members as those in the first embodiment are denoted by the same reference numerals, and the description thereof is omitted.
In the second embodiment, the outer circumferential surface 2002 of the piston ring covering layer 20 is provided with a plurality of concave grooves 22 extending in a direction intersecting with the circumferential direction of the outer circumferential surface 2002 at intervals in the circumferential direction.
The piston ring coating layer 20 holds the piston ring 14 in such a state that its outer peripheral surface 1402 is reduced in diameter so as to be positioned on the same surface as the outer peripheral surface 1002 of the head portion 10A of the piston 10.
In the embodiment shown in FIG. 2, the concave groove 22 extends linearly in a direction orthogonal to the circumferential direction of the outer peripheral surface 2002, that is, in a direction parallel to the axial direction of the piston 10.
The outer peripheral surface 1002 portion of the head portion 10A and the outer peripheral surface 1402 portion of the piston ring 14 are alternately exposed on the bottom surface 2202 of the concave groove 22, and the outer peripheral surface 1002 portion of the head portion 10A and the outer peripheral surface of the piston ring 14 are exposed. A portion 1402 constitutes a bottom surface 2202 of the groove 22.

According to the second embodiment, the same effect as that of the first embodiment can be obtained, and when the piston 10 is inserted into the cylinder 50 from the lower surface 52A side of the cylinder block 52 as shown in FIG. This is a case where a spark plug mounting hole (not shown) is closed, an intake port 5208 is closed by an intake valve 5206, an exhaust port is closed by an unshown exhaust valve, and the cylinder head side of the cylinder 50 is closed. However, since the air in the cylinder 50 can escape from the concave groove 22 to the outside of the cylinder 50, it is advantageous in smoothly inserting the piston 10 into the cylinder 50.
In addition, since the outer peripheral surface 1402 of the piston ring 14 is exposed on the bottom surface 2202 of the concave groove 22, the piston ring 14 can be held in a reduced diameter from the mold side when the piston ring coating layer 20 is formed. Therefore, the piston ring 14 is not limited to a reduced diameter state in which the outer peripheral surface 1402 of the piston ring 14 is positioned on the same surface as the outer peripheral surface 1002 of the head portion 10A, and the piston ring 14 has a desired reduced diameter state smaller than the inner diameter of the cylinder 50. This is advantageous in forming the piston ring coating layer 20.

Next, a third embodiment will be described with reference to FIG.
In the third embodiment, concave portions that are recessed inward in the radial direction from the outer peripheral surface 1002 of the head portion 10A at a plurality of locations spaced in the circumferential direction of each piston ring 14 on the outer peripheral surface 2002 of the piston ring covering layer 20. 24 is provided.
The height of the recess 24 is smaller than the width of the ring groove 12, and the outer peripheral surface 1402 portion of the piston ring 14 is exposed on the bottom surface of the recess 24.
In the third embodiment, the piston ring covering layer 20 holds the inner peripheral surface 1404 of the piston ring 14 in a state where the piston ring covering layer 20 is in contact with the bottom surface 1202 of the ring groove 12.

Also according to the third embodiment, since the outer peripheral surface 1402 portion of the piston ring 14 is exposed on the bottom surface of the recess 24, the piston ring 14 is reduced in diameter from the mold side when the piston ring coating layer 20 is formed. Can be retained. Therefore, the piston ring coating layer 20 is not limited to the state in which the inner peripheral surface 1404 of the piston ring 14 is in contact with the bottom surface 1202 of the ring groove 12, and the piston ring 14 is in a desired reduced diameter state smaller than the inner diameter of the cylinder 50. It is advantageous in forming.
From the viewpoint of smoothly inserting the piston 10 into the cylinder 50, the piston ring coating layer 20 may be used to hold the piston ring 14 in a state in which the diameter of the piston ring 14 is smaller than the inner diameter of the cylinder 50. It is not necessary to keep the inner peripheral surface 1404 in contact with the bottom surface 1202 of the ring groove 12. However, when the inner peripheral surface 1404 of the piston ring 14 is held in contact with the bottom surface 1202 of the ring groove 12 as in this embodiment, the piston ring 14 is in the most contracted state, and the cylinder of the piston 10 This is advantageous for smooth insertion into 50.

Next, a fourth embodiment will be described with reference to FIG.
In the embodiment shown in FIG. 5, the concave groove 22 extends spirally on the outer peripheral surface 2002 of the piston ring coating layer 20.
Further, the outer peripheral surface 1402 of the piston ring 14 is not exposed to the bottom surface 2202 of the concave groove 22, and is located on the radially inner side with respect to the bottom surface 2202 of the concave groove 22.
Even in the fourth embodiment, as in the second embodiment, the same effects as in the first embodiment can be obtained, and even when the cylinder head side of the cylinder 50 is closed. Since the air in the cylinder 50 can escape from the concave groove 22 to the outside of the cylinder 50, it is advantageous in smoothly inserting the piston 10 into the cylinder 50. From the viewpoint of releasing the air in the cylinder 50 to the outside of the cylinder 50, at least one concave groove 22 is sufficient.

Next, a fifth embodiment will be described with reference to FIG.
In the fifth embodiment, a chamfer 2004 is formed at the end of the outer peripheral surface 2002 of the piston ring coating layer 20 of the first embodiment near the top of the piston.
As shown in FIG. 6A, the chamfer 2004 may be a chamfer 2004 in which a cross-sectional shape cut by a plane passing through the axis of the piston ring coating layer 20 is formed by a straight line 2004A, as shown in FIG. 6B. Alternatively, a chamfer 2004 formed by a curve 2004B may be used.
According to the fifth embodiment, in addition to the same effects as the first embodiment can be exhibited, piston ring coating layer 20 to the axis of the cylinder 50 a chamfer 2004 of the piston ring coating layer 20 as a guide , The piston 10 can be inserted into the cylinder 50, which is advantageous in smoothly inserting the piston 10 into the cylinder 50.

Next, a method for manufacturing the piston 10 having the piston ring coating layer 20 will be described.
First, the manufacturing method of the piston 10 to which the piston ring 14 of the first embodiment is mounted will be described.
As shown in FIG. 7A, the coating layer molding die 30 for forming the piston ring coating layer 20 is composed of an upper die 30A and a lower die 30B. The upper mold 30A and the lower mold 30B are formed of a metal material, or are formed of a synthetic resin material having a melting point higher than that of the hydrocarbon oil C.
A cylindrical recess 32 into which the skirt portion 10B of the piston 10 is inserted is formed on the upward mating surface 3002 of the lower mold 30B so as to open upward.
On the downward mating surface 3004 of the upper mold 30A, a cylindrical recess 34 for forming a piston ring coating layer is formed in an open downward shape, and a molten hydrocarbon-based oil C is supplied to the upper portion of the recess 34. The supply path 36 to be opened is opened.
The inner peripheral surface 3402 of the recess 34 is formed with an inner diameter that is larger than the outer diameter of the piston ring 14 that has been expanded by its elasticity.

Therefore, when the skirt portion 10B of the piston 10 to which the piston ring 14 is attached is inserted into the recess 32 of the lower die 30B and the mating surfaces 3002 and 3004 of the lower die 30B and the upper die 30A are aligned, the piston ring 14 is attached. The head portion 10A of the piston 10 is accommodated in the concave portion 34 of the upper mold 30A. In the present embodiment, the concave portion 34 of the upper mold 30A is a filling chamber that accommodates the head portion 10A of the piston 10 to which the piston ring 14 is mounted, and the inner peripheral surface of the concave portion 34 is coaxial with the piston 10. Is provided.
In addition, when the outer peripheral surface 2002 of the piston ring coating layer 20 is formed in a shape other than the cylindrical surface, for example, a plurality of flat side surfaces constituting a polygonal column, the peripheral surface of the recess 34 has a shape corresponding to the side surface. It only has to be formed. Therefore, the concave portion 34 of the upper mold 30A becomes a substantially cylindrical filling chamber that houses the head portion 10A of the piston 10 to which the piston ring 14 is mounted.

As shown in FIG. 7A, if the head portion 10A of the piston 10 to which the piston ring 14 is mounted is accommodated in the recess 34 of the upper mold 30A, the hydrocarbon-based oil C in the molten state is supplied to the supply passage 36. To the recess 34. In the present embodiment, paraffin is used as the hydrocarbon-based oil C, and the melting point of the paraffin is 105 ° C., so the temperature of the paraffin filled in the recess 34 is 105 ° C. or higher.
And if the hydrocarbon oil C is filled in the recessed part 34, the hydrocarbon oil C will be gradually cooled to normal temperature (20 degreeC-25 degreeC).
The hydrocarbon oil C is solidified by this slow cooling, and the piston ring 14 is reduced in diameter by the condensing force of the hydrocarbon oil C at this time.
When the hydrocarbon-based oil C is gradually cooled to room temperature, the hydrocarbon-based oil C is solidified, and the diameter of the piston ring 14 is reduced in the ring groove 12 by the solidified hydrocarbon-based oil as shown in FIG. A piston ring covering layer 20 is formed to hold the state in a closed state.

Note that the diameter reduction of the piston ring 14 due to the condensing force of the hydrocarbon oil C is performed by the condensing force of the hydrocarbon oil C located outside the outer peripheral surface 1402 of the piston ring 14, so that the hydrocarbon oil C When the piston ring 14 is cooled, a uniform condensing force acts in the circumferential direction of the piston ring 14, and the piston ring 14 is reduced in diameter so as to be substantially coaxial with the piston 10.
Further, the diameter reduction of the piston ring 14 is performed by the condensing force of the hydrocarbon oil C located outside the outer peripheral surface 1402 of the piston ring 14, so that the hydrocarbon system positioned outside the outer peripheral surface 1402 of the piston ring 14. If the amount of the oil C is increased, the diameter of the piston ring 14 is further reduced. Therefore, by appropriately determining the outer diameter of the recess 34, the outer peripheral surface 1402 of the piston ring 14 is reduced in diameter to the same diameter as the outer peripheral surface 1002 of the head portion 10A, or the piston ring 14 A state is formed in which the diameter of the piston ring 14 is reduced so that the outer peripheral surface 1402 is smaller than the diameter of the outer peripheral surface 1002 of the head portion 10A.
In the present embodiment, the piston ring coating layer 20 holds the piston ring 14 in a state of being reduced in diameter so that the outer peripheral surface 1402 is positioned on the same surface as the outer peripheral surface 1002 of the head portion 10A of the piston 10. Yes.

Therefore, according to the manufacturing method of the present embodiment, it is possible to easily and reliably manufacture the piston 10 in which the piston ring coating layer 20 that holds the piston ring 14 in the ring groove 12 in a reduced diameter state is formed. This is possible and is advantageous in reducing the cost of the piston 10 having the piston ring coating layer 20.
Moreover, since the reduced diameter state of the piston ring 14 is formed by the condensing force of the hydrocarbon-based oil C during cooling, the structure of the coating layer forming die 30 is simplified, and the cost of the piston 10 having the piston ring coating layer 20 is reduced. This is advantageous in achieving this.

It is to be noted that when filling the hydrocarbon-based oil component C in the molten state into the recess 34 from the supply path 36, the hydrocarbon-based oil component C is pressurized, and the hydrocarbon-based oil component C is pressurized in the recess 34. When the oil C is gradually cooled to room temperature, it is advantageous in reducing the diameter of the piston ring 14 due to the condensing force of the hydrocarbon oil C, and the piston ring 14 is held in a reduced diameter in the ring groove 12. This is advantageous in forming the piston ring coating layer 20 having a larger holding force.

Next, a method for manufacturing the piston 10 to which the piston ring 14 according to the second embodiment is mounted will be described. In the following description of the manufacturing method, the same reference numerals are given to the same members and locations as those used in the above manufacturing method, and the description thereof is omitted.
As shown in FIGS. 8A and 8B, the upper mold 30A is formed of two movable parts 30C and 30C that are movable toward and away from each other, and these divided parts 30C and 30C form a piston ring coating layer. And a mating surface 3006 passing through the center of the cylindrical recess 34 for use. And the recessed part 34 is formed when the mating surface 3006 of two division bodies 30C and 30C joins.
The skirt portion 10B of the piston 10 to which the piston ring 14 is attached is inserted into the recess 32 of the lower mold 30B, the mating surfaces 3002 and 3004 of the lower mold 30B and the upper mold 30A are aligned, and the mating surfaces 3006 of the divided bodies 30C and 30C are aligned. When combined, the head portion 10A of the piston 10 to which the piston ring 14 is attached is accommodated in the recess 34 of the upper mold 30A. The concave portion 34 of the upper mold 30A is a filling chamber that accommodates the head portion 10A of the piston 10 to which the piston ring 14 is mounted, and the inner peripheral surface of the concave portion 34 is provided coaxially with the piston 10.
A plurality of protrusions 38 are formed on the inner peripheral surface 3402 of the recess 34 at intervals in the circumferential direction of the inner peripheral surface 3402.
When the recesses 34 are formed, the tips 38 of the protrusions abut against the outer peripheral surface 1002 of the head portion 10A, and the outer peripheral surface 1402 of the piston ring 14 is positioned on the same plane as the outer peripheral surface 1002 of the head portion 10A. It is formed with the dimensions to be made.
In the present embodiment, the plurality of protrusions 38 constitute a diameter reducing means for reducing the diameter of the piston ring 14 by contacting a plurality of locations spaced in the circumferential direction of the outer peripheral surface 1402 of the piston ring 14.

In the present embodiment, the two divided bodies 30C and 30C are separated from each other on the mating surface 3002 of the lower mold 30B, the skirt portion 10B is inserted into the recess 34 of the lower mold 30B, and the two divided bodies 30C and 30C are When the mating surfaces 3006 are brought close to each other, the head portion 10A of the piston 10 to which the piston ring 14 is attached is accommodated in the concave portion 34 of the upper mold 30A, and at the same time, the protrusions 38 abut against the outer peripheral surface 1402 of the piston ring 14. The piston ring 14 is held in a reduced diameter state in which the outer peripheral surface 1402 of the piston ring 14 is positioned on the same surface as the outer peripheral surface 1002 of the head portion 10A.
Next, a state in which the piston ring 14 is reduced in diameter in the ring groove 12 by filling the hydrocarbon oil C in a molten state into the recess 34 from the supply path 36 and gradually cooling the hydrocarbon oil C to room temperature. A piston ring covering layer 20 is formed to be held on the surface.
Then, as shown in FIG. 3 (B), the concave groove 22 extending linearly in the direction parallel to the axial direction of the piston 10 on the outer peripheral surface 2002 of the piston ring covering layer 20 by the protrusions 38. Is formed.

In the present embodiment, unlike the above-described embodiment, the piston ring 14 is not shrunk by the condensing force of the hydrocarbon-based oil C during solidification, but the piston ring 14 is connected to the ring groove 12 by the protrusion 38. A reduced diameter state that is displaced radially inward is forcibly created.
Therefore, according to the manufacturing method of this embodiment, the piston ring 14 it is possible to easily and reliably produce the piston 10 to the piston ring coating layer 20 is formed to hold the state of being reduced in diameter, piston rings This is advantageous in reducing the cost of the piston 10 having the coating layer 20.
Also in this embodiment, when filling the hydrocarbon-based oil C in the molten state into the recess 34 from the supply path 36, a pressure is applied to the hydrocarbon-based oil C, and the pressure is applied to the hydrocarbon-based oil C in the recess 34. When the hydrocarbon-based oil C is gradually cooled to room temperature while being applied, it is advantageous in forming the piston ring coating layer 20 having a larger holding force for maintaining the reduced diameter state of the piston ring 14.

Next, a manufacturing method of the piston 10 to which the piston ring 14 of the third embodiment is attached will be described.
As shown in FIGS. 9A and 9B, the upper mold 30A is formed by three movable parts 30D, 30D, and 30D that are movable toward and away from each other, and these divided parts 30D, 30D, and 30D are pistons. It has a mating surface 3006 that passes through the center of the cylindrical recess 34 for forming the ring coating layer . And the recessed part 34 is formed when the mating surface 3006 of three division body 30D, 30D, 30D joins.
The skirt portion 10B of the piston 10 to which the piston ring 14 is attached is inserted into the recess 32 of the lower mold 30B, the mating surfaces 3002 and 3004 of the lower mold 30B and the upper mold 30A are aligned, and the mating surfaces 3006 of the divided bodies 30C and 30C are aligned. When combined, the head portion 10A of the piston 10 to which the piston ring 14 is attached is accommodated in the recess 34 of the upper mold 30A. The concave portion 34 of the upper mold 30A is a filling chamber that accommodates the head portion 10A of the piston 10 to which the piston ring 14 is mounted, and the inner peripheral surface of the concave portion 34 is provided coaxially with the piston 10.
A plurality of rod-like protrusions 39 are formed on the inner peripheral surface 3402 of the recess 34 at intervals in the circumferential direction of the inner peripheral surface 3402 and at intervals in the axial direction of the inner peripheral surface 3402.
The protrusions 39 have such dimensions that when the recesses 34 are formed, their tips contact the outer peripheral surface 1402 of the piston ring 14 so that the inner peripheral surface 1404 of the piston ring 14 contacts the bottom surface 1202 of the ring groove 12. Is formed.
In the present embodiment, the plurality of protrusions 39 constitute a diameter reducing means for reducing the diameter of the piston ring 14 by contacting a plurality of locations spaced in the circumferential direction of the outer peripheral surface 1402 of the piston ring 14.

In the present embodiment, the three divided bodies 30D, 30D, and 30D are separated from each other on the mating surface 3002 of the lower mold 30B, and the skirt portion 10B is inserted into the recess 34 of the lower mold 30B. When the mating surfaces 3006 are aligned by bringing 30D and 30D close to each other, the head portion 10A of the piston 10 to which the piston ring 14 is attached is accommodated in the concave portion 34 of the upper mold 30A, and at the same time, the protrusion 39 is the outer peripheral surface 1402 of the piston ring 14. The state in which the inner peripheral surface 1404 of the piston ring 14 is in contact with the bottom surface 1202 of the ring groove 12 is maintained.
Next, a state in which the piston ring 14 is reduced in diameter in the ring groove 12 by filling the hydrocarbon oil C in a molten state into the recess 34 from the supply path 36 and gradually cooling the hydrocarbon oil C to room temperature. A piston ring covering layer 20 is formed to be held on the surface.
Then, due to the plurality of protrusions 39, the outer circumferential surface 2002 of the piston ring coating layer 20 is spaced apart in the circumferential direction as shown in FIG. Is formed.

In the present embodiment, as in the above-described embodiment, the piston ring 14 is reduced in diameter by the protrusion 39 instead of reducing the diameter of the piston ring 14 by the condensing force of the hydrocarbon-based oil C during solidification. Force a reduced diameter state.
In the present embodiment, the inner peripheral surface 1404 of the piston ring 14 is brought into contact with the bottom surface 1202 of the ring groove 12 by the protrusion 39, so that the piston ring coating layer 20 in a state where the diameter of the piston ring 14 is most reduced is formed. The
Therefore, according to the manufacturing method of the present embodiment, it is possible to easily and reliably manufacture the piston 10 in which the piston ring coating layer 20 that holds the piston ring 14 in the most contracted state in the ring groove 12 is formed. This is advantageous in reducing the cost of the piston 10 having the piston ring coating layer 20.
In the present embodiment, the protrusion 39 on the coating layer forming die 30 side is brought into contact with the outer peripheral surface 1402 of the piston ring 14 to forcibly create a reduced diameter state of the piston ring 14. The surface 1404 is not limited to the reduced diameter state in contact with the bottom surface 1202 of the ring groove 12, but the piston ring 14 is set to a desired reduced diameter state smaller than the inner diameter of the cylinder 50, or the piston ring 14 is set to the outer periphery of the head portion 10A. It is also possible to form the piston ring coating layer 20 having a desired diameter reduction state smaller than the surface 1002.

Also in this embodiment, when filling the hydrocarbon-based oil C in the molten state into the recess 34 from the supply path 36, a pressure is applied to the hydrocarbon-based oil C, and the pressure is applied to the hydrocarbon-based oil C in the recess 34. When the hydrocarbon-based oil C is gradually cooled to room temperature while being applied, the piston ring coating layer 20 has a higher holding force for holding the inner peripheral surface 1404 of the piston ring 14 in contact with the bottom surface 1202 of the ring groove 12. It is advantageous in forming.
In the embodiment shown in FIGS. 8 and 9, the case where the diameter reducing means is configured on the coating layer forming die 30 side such as the protrusions 38 and the protrusions 39 provided on the inner peripheral surface of the recess 34 has been described. However, as the diameter reducing means, for example, a pin is reciprocated by an actuator from a plurality of locations spaced in the circumferential direction of the inner peripheral surface of the concave portion 34, and the outer peripheral surface 1402 of the piston ring 14 is displaced by these pins. Various conventionally known structures can be adopted as the diameter reducing means, such as forming a reduced diameter state of the ring.

Next, a method for manufacturing the piston 10 to which the piston ring 14 according to the fourth embodiment is mounted will be described.
As shown in FIG. 10, the upper mold 30A is not composed of a plurality of divided bodies 30C like the covering layer forming mold 30 shown in FIGS. 8 and 9, but the single die like the covering layer forming mold 30 shown in FIG. On the inner peripheral surface 3402 of the recess 34 of the upper mold 30A, the spirally extending protrusions 40 are formed at intervals in the circumferential direction.
The tip of the protrusion 40 is formed so as to be positioned on a single virtual cylindrical surface having a dimension larger than the outer diameter of the piston ring 14 coaxially with the piston 10 and expanded by its elasticity.
In this embodiment, when the skirt portion 10B is inserted into the recess 32 of the lower die 30B and the mating surfaces 3002 and 3004 of the lower die 30B and the upper die 30A are aligned, the head portion 10A of the piston 10 to which the piston ring 14 is attached. Is accommodated in the recess 34 of the upper mold 30 </ b> A coaxial with the piston 10.
Then, the hydrocarbon oil C in a molten state is filled into the recess 34 from the supply path 36, and the hydrocarbon oil C is gradually cooled to room temperature (20 ° C. to 25 ° C.).
By this slow cooling, the hydrocarbon oil C is solidified, and the piston ring 14 is reduced in diameter by the condensing force of the hydrocarbon oil C at this time, and the piston ring 14 is moved into the ring groove 12 by the solidified hydrocarbon oil C. A piston ring covering layer 20 is formed which is held in a reduced diameter state.
And the groove | channel 22 which extends on the outer peripheral surface 2002 of the piston ring coating layer 20 spirally by the protrusion 40 is formed.

Therefore, according to the manufacturing method of the present embodiment, it is possible to easily and reliably manufacture the piston 10 in which the piston ring coating layer 20 that holds the piston ring 14 in the ring groove 12 in a reduced diameter state is formed. This is possible and is advantageous in reducing the cost of the piston 10 having the piston ring coating layer 20.
Also in this embodiment, when filling the hydrocarbon-based oil C in the molten state into the recess 34 from the supply path 36, a pressure is applied to the hydrocarbon-based oil C, and the pressure is applied to the hydrocarbon-based oil C in the recess 34. When the hydrocarbon oil C is gradually cooled to room temperature in the hung state, it is advantageous for reducing the diameter of the piston ring 14 due to the condensing force of the hydrocarbon oil C, and the piston ring 14 is contracted in the ring groove 12. This is advantageous in forming the piston ring coating layer 20 having a larger holding force for maintaining the diameter.

Next, a method for manufacturing the piston 10 to which the piston ring 14 according to the fifth embodiment is mounted will be described.
As shown in FIG. 11A, an inclined surface 42A having a straight cross-sectional shape cut by a plane passing through the axis of the recess 34 is formed on the outer periphery of the upper end of the recess 34 of the upper mold 30A. Alternatively, as shown in FIG. 11 (B), an inclined surface 42B having a curved cross-sectional shape cut along a plane passing through the axis of the recess 34 is formed on the outer periphery of the upper end of the recess 34 of the upper mold 30A.
Accordingly, the matching surfaces 3002 and 3004 of the lower mold 30B and the upper mold 30A are aligned, the head portion 10A of the piston 10 on which the piston ring 14 is mounted is accommodated in the concave portion 34 of the upper mold 30A, and the hydrocarbon oil C in a molten state is stored. A chamfer 2004 is formed by the inclined surfaces 42 </ b> A and 42 </ b> B by filling the recess 34 from the supply path 36 and gradually cooling to the normal temperature.
That is, the piston ring coating layer 20 having the outer peripheral surface 2002 in which the chamfer 2004 is formed at the end near the top of the piston is obtained.

In the embodiment, the description has been given of the case where the piston 10 held in the state in which the piston ring 14 is reduced in diameter by the piston ring coating layer 20 is inserted into the cylinder 50 of the cylinder block 52 integrated with the cylinder head. The piston 10 in which the piston ring 14 is held in a state where the diameter of the piston ring 14 is reduced by the piston ring coating layer 20 of the present invention can be applied to a case where the cylinder head and the cylinder block 52 are separated from each other. Of course, the present invention can be applied to the case where the piston 10 is inserted into the cylinder 50 from the upper surface side.

DESCRIPTION OF SYMBOLS 10 ... Piston 1002 ... Outer peripheral surface of head part 12 ... Ring groove 1202 ... Bottom surface of ring groove 14 ... Piston ring 1402 ... Outer peripheral surface of piston ring 1404 ... Inner peripheral surface of piston ring 20 ... Piston Ring coating layer 2002 ... outer peripheral surface of piston ring coating layer 2004 ... chamfering 22 ... concave groove 2202 ... bottom surface of concave groove 24 ... concave part 30 ... mold 30A ... upper mold 30B ... lower mold 30C, 30D: Split body 32, 34: Recess 36: Supply path 38, 40 ... Projection 39 ... Projection 42A, 42B ... Inclined surface 50 ... Cylinder 52 ... Bearing part 54 ... Cylinder block C ... ... Hydrocarbon oil

Claims (9)

A piston with a piston ring mounted in the ring groove,
The piston is composed of a hydrocarbon-based oil that is solid at room temperature, and has a piston ring covering layer that covers at least a radially outer peripheral surface of the piston ring,
The piston ring covering layer holds the piston ring in a reduced diameter in the ring groove;
Piston equipped with a piston ring characterized by that. The piston ring covering layer is provided with at least one concave groove extending in a direction intersecting with the circumferential direction of the piston ring.
A piston equipped with the piston ring according to claim 1. A chamfer is formed at the end near the top of the piston on the outer peripheral surface of the piston ring coating layer,
A piston equipped with the piston ring according to claim 1 or 2. An engine manufacturing method in which a piston with a piston ring mounted in a ring groove is assembled,
A substantially cylindrical filling chamber capable of accommodating a portion of the piston in which the piston ring is mounted in the ring groove is provided inside the coating layer molding die,
In the filling chamber, a portion of the piston in which the piston ring is mounted in the ring groove is disposed,
A coating step of filling the solidified hydrocarbon-based oil in a molten state to form a piston ring coating layer on the piston in a state where the piston ring has a reduced diameter;
An engine assembly step of assembling the piston having the piston ring coating layer to the engine;
A coating removing step of removing the piston ring coating layer of the piston assembled in the engine and expanding the piston ring by its elasticity;
The manufacturing method of the engine characterized by having. The covering step includes a piston disposing step of disposing the piston on which the piston ring held in the state where the diameter is reduced in the ring groove is mounted in the filling chamber.
The method of manufacturing an engine according to claim 4. In the covering step , the piston ring is maintained in a state of being reduced in diameter by the condensation force of the hydrocarbon oil when the hydrocarbon oil is cooled and solidified.
The method for manufacturing an engine according to claim 4 or 5, wherein In the coating step , pressure is applied to the hydrocarbon oil.
The method for manufacturing an engine according to any one of claims 4 to 6, wherein: In the coating removal step, the piston ring coating layer is removed by melting the hydrocarbon oil by cranking the engine.
The method for manufacturing an engine according to any one of claims 4 to 7, wherein: In the coating removal step, the piston ring coating layer is removed by melting the hydrocarbon-based oil by warming up the engine.
The method for manufacturing an engine according to any one of claims 4 to 8, wherein:

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