Patent ID: 12214458

DETAILED DESCRIPTION

When an installer is used while a ring gap of a piston ring protrudes radially outward from the piston ring groove, the ends of the ring at the ring gap protruding from the ring groove are caught between an outer peripheral surface of the piston and an inner peripheral surface of the installer. If an attempt is made to further push the piston into the installer in this state, a problem arises in that the piston and the piston ring become damaged.

In light of the problem described above, it is desirable to provide a piston ring installation jig, and a piston ring installation method using the jig, that can cause a ring gap in a piston ring to be accommodated in a ring groove of a piston when installing the piston ring in the ring groove of the piston.

In the following, some embodiments of the disclosure are described in detail with reference to the accompanying drawings. Note that the following description is directed to illustrative examples of the disclosure and not to be construed as limiting to the disclosure. Factors including, without limitation, numerical values, shapes, materials, components, positions of the components, and how the components are coupled to each other are illustrative only and not to be construed as limiting to the disclosure. Further, elements in the following example embodiments which are not recited in a most-generic independent claim of the disclosure are optional and may be provided on an as-needed basis. The drawings are schematic and are not intended to be drawn to scale. Throughout the present specification and the drawings, elements having substantially the same function and configuration are denoted with the same numerals to avoid any redundant description.

First Embodiment

FIG.1is a plan view schematically illustrating a piston ring installation jig10according to a first embodiment of the disclosure, and a piston50.FIG.2is a plan view illustrating a state in which a top ring60and a second ring70, serving as piston rings, have been installed on the piston50using the piston ring installation jig10.FIG.3is a cross-sectional view of the piston ring installation jig10taken along line A-A inFIG.2. InFIG.3, the piston50, the top ring60, the second ring70, and an oil ring80described later, all of which are accommodated in the piston ring installation jig10, are illustrated in a non-cross-sectional state, and a first protrusion28and a second protrusion38, which will be described later, are not illustrated.

The piston ring installation jig10(hereinafter also simply referred to as the “jig10”) is used to install the piston rings, in particular, the top ring60and the second ring70that are compression rings, into ring grooves53,54formed in an outer peripheral surface of the piston50, respectively. As illustrated inFIGS.1and2, the jig10includes a first main body20and a second main body30, each of which is formed in a semi-cylindrical shape so as to surround the outer peripheral surface of the piston50, and a hinge12that couples the first main body20and the second main body30. Hereinafter, the piston50, the top ring60, the second ring70, and the jig10will be described in detail.

As illustrated inFIG.3, the piston50includes a substantially cylindrical head52forming an upper surface50aand including multiple ring grooves53,54,55formed in an outer peripheral surface of the head52, and a skirt58formed continuously with the head52. In the piston50illustrated inFIG.3, the diameter of the head52is larger than the diameter of the skirt58. The multiple ring grooves53,54,55are formed in the outer peripheral surface of the head52at predetermined intervals in an axial direction. In the following description, for convenience, the ring groove53formed at an upper stage of the head52will be referred to as a first ring groove53, the ring groove54formed at a middle stage of the head52will be referred to as a second ring groove54, and the ring groove55formed at a lower stage of the head52will be referred to as a third ring groove55. In the present embodiment, each of the ring grooves53,54,55is formed to have substantially the same depth.

The top ring60(first piston ring) and the second ring70(second piston ring) are respectively installed in the first ring groove53and the second ring groove54of the piston50. In the following description, the top ring60and the second ring70are also collectively referred to as compression rings60,70. The oil ring80is installed in the third ring groove55of the piston50. Each of the compression rings60,70has a gas sealing function of suppressing the outflow of combustion gas from a combustion chamber side to a crank chamber side by maintaining airtightness between the piston50and a cylinder in an internal combustion engine, and also has an oil sealing function of suppressing oil loss via the piston ring, by scraping off excess oil adhering to an inner wall of the cylinder that has not been completely scraped off by the oil ring80. Each of the rings60,70,80is formed of an elastic material so that the diameter thereof can be expanded or reduced.

The outer diameters of the compression rings60,70are formed to be larger than the outer diameter of the head52of the piston50and the outer diameter of the oil ring80. The outer diameter of the oil ring80is formed to be slightly larger than the outer diameter of the head52of the piston50. As illustrated inFIG.3, in a state in which the oil ring80is installed on the piston50, the entire periphery of the oil ring80is almost completely accommodated in the third ring groove55.

As illustrated inFIG.4, when the compression rings60,70are assembled to the piston50, portions of the compression rings60,70in the circumferential direction protrude radially outward from the ring grooves53,54, respectively. InFIG.4, portions of the top ring60and the second ring70, which are accommodated in the ring grooves53,54of the piston50, respectively, are indicated by broken lines. As illustrated inFIG.2, the top ring60and the second ring70are each formed in an annular shape, and include ring gaps62,72, respectively, that are formed by portions of the top ring60and the second ring70being cut out, so that the top ring60and the second ring70can be expanded or contracted. In the present embodiment, the top ring60and the second ring70have substantially the same outer diameter, inner diameter, and thickness.

As described above, the jig10includes the first main body20, the second main body30, and the hinge12that couples the first main body20and the second main body30.

As illustrated inFIGS.2and3, the first and second main bodies20,30are each formed in a semi-cylindrical shape, and are disposed opposing each other so as to form a cylindrical shape surrounding the outer peripheral surface of the piston50in a set state. In the present embodiment, as illustrated inFIG.1, first end portions21a,31a, which are one end portions, in the circumferential direction, of the main bodies20,30are coupled to each other via the hinge12, and second end portions21b,31b, which are the other end portions thereof, are configured to open and close. In the present embodiment, the height (length in the axial direction) of each of the main bodies20,30is set to be slightly higher than the height of the piston50.

FIG.5is a cross-sectional view of the piston ring installation jig10taken along line B-B inFIG.3, andFIG.6is a cross-sectional view of the piston ring installation jig10taken along line C-C inFIG.3. InFIGS.5and6, the outer circumference of the head52of the piston50is indicated by a thick broken line, the top ring60is indicated by an imaginary line inFIG.5, and the second ring70is indicated by an imaginary line inFIG.6.

The first and second main bodies20,30include substantially semicircular arc-shaped grooves24,36formed in inner peripheral surfaces22a,32athereof, respectively. Portions of the top ring60and the second ring70in the circumferential direction are fitted into the grooves24,36, respectively. Outer peripheral surfaces22b,32bof the main bodies20,30are each formed in a curved surface shape having no unevenness. As illustrated inFIGS.3and5, the first main body20includes the first groove24in a region corresponding to the first ring groove53of the piston50. Further, as illustrated inFIGS.3and6, the second main body30includes the second groove36in a region corresponding to the second ring groove54of the piston50. Here, the region corresponding to the first ring groove53and the region corresponding to the second ring groove54refer to regions in which the inner peripheral surfaces22a,32aof the main bodies20,30oppose the first ring groove53and the second ring groove54of the piston50, respectively, in the set state in which the piston50is accommodated in the jig10.

In the present embodiment, as illustrated inFIG.2, in a state in which a bottom surface of the jig10and a bottom surface of the piston50coincide in the axial direction, the first groove24and the second groove36are formed in the inner peripheral surfaces22aand32aof the main bodies20,30, opposing the first ring groove53and the second ring groove54of the piston50, respectively. The first groove24has a circular arc shape whose circle center is biased more to the outer peripheral side of the first main body20than the circle center of the inner peripheral surface22aof the first main body20. The second groove36has a circular arc shape whose circle center is biased more to the outer peripheral side of the second main body30than the circle center of the inner peripheral surface32aof the second main body30.

As illustrated inFIGS.3and6, the first main body20includes a first non-groove-formed portion27that is flush with the inner peripheral surface22aof the first main body20, in the region corresponding to the second ring groove54of the piston50. As illustrated inFIG.6, the first protrusion28protruding radially inward is formed at the first non-groove-formed portion27. Further, as illustrated inFIGS.3and5, the second main body30includes a second non-groove-formed portion35that is flush with the inner peripheral surface32aof the second main body30, in the region corresponding to the first ring groove53of the piston50. As illustrated inFIG.5, the second protrusion38protruding radially inward is formed at the second non-groove-formed portion35.

The widths of the protrusions28,38are set to be smaller than the widths of the ring gaps62,72of the compression rings60,70, respectively. Further, the protruding lengths of the protrusions28,38are set to be equal to or less than the depths of the ring grooves53,54, respectively.

In the present embodiment, as illustrated inFIGS.5and6, the grooves are formed so that the top ring60and the second ring70are accommodated in the grooves formed in the inner peripheral surface of the cylindrical jig10, over a range of a length that is approximately two thirds of the entire circumference of each of the top ring60and the second ring70, in a state in which the second end portions21b,31bof the main bodies20,30are closed.

For example, as illustrated inFIG.5, continuous grooves34a,34bare formed at both end portions of the second main body30in the circumferential direction, continuous with the first groove24of the first main body20. The second non-groove-formed portion35is provided between these continuous grooves34a,34b. Further, as illustrated inFIG.6, continuous grooves26aand26bare formed at either end portion, in the circumferential direction, of the first main body20, continuous with the second groove36of the second main body30. The first non-groove-formed portion27is provided between these continuous grooves26a,26b. The first and second grooves24,36are formed so as to have the largest groove depth at center portions of the main bodies20,30in the circumferential direction, respectively. The groove depths of the first and second grooves24,36gradually decrease from the center portions toward the continuous grooves26a,26b,34a,34b, respectively. Further, in the present embodiment, the first and second protrusions28,38are provided so as to be positioned at the center portions of the first and second main bodies20,30in the circumferential direction, respectively.

Next, a piston ring installation method using the jig10described above will be described. In the installation method using the jig10, the compression rings60,70are assembled to the piston50so that portions of the compression rings60,70excluding the ring gaps62,72are inserted into the grooves24,36of the main bodies20,30, respectively, and the ring gaps62,72are positioned in the ring grooves53,54of the piston50, respectively. Hereinafter, installation steps will be described in detail.

First, the top ring60, the second ring70, and the oil ring80are fitted into the first ring groove53, the second ring groove54, and the third ring groove55of the piston50, respectively (step of fitting piston rings).

Thereafter, the rings60,70are rotated so that the ring gap62of the top ring60is positioned in the first ring groove53, the ring gap72of the second ring70is positioned in the second ring groove54, and the ring gaps62,72are positioned at positions shifted by 180 degrees from each other in the circumferential direction (step of rotating piston rings). In the present embodiment, the ring gaps62,72are positioned at portions of the ring grooves53,54at which the groove depths are the largest.

In this state, as illustrated inFIG.2, the second end portions21b,31b(seeFIG.1) of the first and second main bodies20,30are closed, and the piston50installed with the piston rings is accommodated in the jig10. At this time, as illustrated inFIG.5, the second protrusion38of the second main body30is inserted into the ring gap62of the top ring60(seeFIG.5), and the first protrusion28of the first main body20is inserted into the ring gap72of the second ring70(seeFIG.6). As a result, the ring gaps62,72of the rings60,70are positioned with respect to the ring grooves53,54of the piston50(step of positioning using the jig10). In a case where the protrusions38,28are not appropriately positioned with respect to the ring gaps62,72, the second end portions21b,31bof the first and second main bodies20,30cannot be made to abut against each other and close. In such a case, the top ring60and/or the second ring70are rotated so that the positioning is appropriate.

The rings60,70,80installed on the piston50in this manner are brought into a state in which the ring gap62of the top ring60is accommodated in the first ring groove53of the piston50, and the ring gap72of the second ring70is accommodated in the second ring groove54of the piston50, as illustrated inFIG.4. In this state, the jig10is removed, and the piston50is inserted into the cylinder by using an installer90, as illustrated inFIG.7.

The installer90is formed in a cylindrical shape. An inner peripheral surface92of the installer90is formed in a tapered shape having an inner diameter that becomes smaller toward one end portion. Pushing the piston50downward inFIG.7along the tapered surface causes the diameters of the top ring60and the second ring70, both of which partially protrude from the piston50, to reduce. At this time, since the ring gaps62,72of the rings60,70are accommodated in the ring grooves53,54of the piston50, respectively, both end portions of the rings60,70do not become sandwiched between the outer peripheral surface of the piston50and the inner peripheral surface92of the installer90, and be caused to curl up. Thus, the separation distance of each of the ring gaps62,72of the rings60,70inside the installer90can be appropriately reduced, and thus the piston50and the rings60,70can be prevented or inhibited from being damaged at the time of installation.

Note that, in the embodiment described above, descriptions of “first”, “second”, and “third” are merely used for convenience to distinguish the multiple main bodies, multiple ring grooves, and multiple piston rings.

Second Embodiment

Next, a second embodiment of the piston ring installation jig10will be described with reference toFIGS.8to11.FIG.8is a side view illustrating a state in which the piston rings are installed on the piston50using the piston ring installation jig10according to the second embodiment of the disclosure.FIG.9is a cross-sectional view of the piston ring installation jig10taken along line D-D inFIG.8. InFIG.9, the outer shape of the piston50is indicated by a thick solid line. Note that, inFIG.9, the piston50, the top ring60, the second ring70, and the oil ring80described later, all of which are accommodated in the piston ring installation jig10, are illustrated in a non-cross-sectional state, and a protrusion48described later is not illustrated. Since the configurations of the piston50, the top ring60, the second ring70, and the oil ring80are the same as those in the first embodiment, description thereof will be omitted.

The jig10according to the present embodiment includes a main body40and a pedestal49. The main body40includes a groove42, and the protrusion48.

As illustrated inFIGS.8and9, the main body40is formed in a semi-cylindrical shape so as to surround the outer peripheral surface of the piston50in the set state in which the piston50is set. The pedestal49on which the main body40is placed is attached to an outer peripheral surface42bof the main body40. The protrusion48for positioning the piston50with respect to the main body40protrudes from the inner peripheral surface42aof the main body40. In the present embodiment, the surface of the protrusion48is formed in a surface shape conforming to the outer peripheral shape of the skirt58of the piston50. By placing the piston50at the protrusion48, the piston50is stably held in the main body40.

FIG.10is a cross-sectional view of the piston ring installation jig10taken along line E-E inFIG.9.FIG.11is a cross-sectional view of the piston ring installation jig10taken along line F-F inFIG.9. InFIGS.10and11, the outer periphery of the head52of the piston50is indicated by a thick broken line, the top ring60is indicated by an imaginary line inFIG.10, and the second ring70is indicated by an imaginary line inFIG.11.

As illustrated inFIGS.9and10, the main body40includes a groove44at the inner peripheral surface42ain a region corresponding to the first ring groove53of the piston50. The groove44extends in a substantially semicircular arc shape along the circumferential direction of the main body40. The groove44has a circular arc shape whose circle center is biased more to the outer peripheral side of the main body40than the circle center of the inner peripheral surface42aof the main body40. As illustrated inFIG.10, the groove44is formed so as to have the largest groove depth at a center portion of the main body40in the circumferential direction.

As illustrated inFIG.11, the main body40includes a non-groove-formed portion47that is flush with the inner peripheral surface42aof the main body40, in the region corresponding to the second ring groove54of the piston50. The protrusion48protruding radially inward is formed at the non-groove-formed portion47. The width of the protrusion48is set to be smaller than the width of the ring gap72of the second ring70, and the protruding length of the protrusion48is set to be equal to or less than the depth of the second ring groove54.

In the jig10according to the present embodiment, in a state in which the piston50installed with the piston rings is set in the jig10, as illustrated inFIGS.8to11, the ring gap62of the top ring60is accommodated in the first ring groove53, and the protrusion48of the jig10is inserted into the ring gap62. Further, the ring gap72of the second ring70is accommodated in the second ring groove54. In this way, in the jig10according to the present embodiment, the ring gaps62,72of the rings60,70can be appropriately accommodated in the ring grooves53,54of the piston50, respectively.

Note that the disclosure is not limited to the embodiments described above, and various modifications can be made without departing from the spirit of the disclosure.

For example, the number of the compression rings60,70for which the positioning of the ring gaps62,72is performed by the jig10is not limited to two, and it is sufficient that there be at least one.

With the piston ring installation jig according to the disclosure, when installing a piston ring in a ring groove of a piston, the ring gap of the piston ring can be accommodated in the ring groove.