Title of Invention

PISTON INSERTING JIG AND PISTON INSERTING METHOD

Abstract

To insert a piston P of a small piston assembly Q into a cylinder sleeve S, a piston-inserting jig is provided. The piston-inserting jig comprises a guide cylinder 3 for guiding the piston P to an entrance of the cylinder sleeve S, and a set plate 2 which is integrally formed with the guide cylinder 3. The set plate 2 is provided with a set opening 2h for allowing the axis of the piston P to coincide with the axis of the cylinder sleeve S. The set opening 2h engages a knock-pin n of a cylinder block B. Provided on an inner surface of the guide cylinder 3 is a tapered surface 3t for reducing the diameter of a piston ring Pr. The set plate 2 and the guide cylinder 3 are respectively provided at each side thereof with cutouts 2k and 3k which are wider than the connecting rod. The jig 1 can be pulled out after installation. As a result, when the piston of the small piston assembly is inserted into the cylinder sleeve, it is possible to prevent the piston ring from being caught or damaged by the cylinder sleeve and to improve workability. ABSTRACT PISTON INSERTING PISTON INSERTING KETHOD To insert a piston P of a small piston assembly into a cylinder sleeve S, a piston-inserting jig is provided. The piston-inserting jig comprises a guide cylinder 3 for guiding the piston P to an entrance of the cylinder sleeve S, and a set plate 2 which is integrally formed with the guide cylinder 3. The set plate 2 is provided with a set opening 2h for allowing the axis of the piston P to coincide with the axis of the cylinder sleeve S. The set opening 2h engages a knock-pin n of a cylinder block B. Provided on an inner surface of the guide cylinder 3 is a tapered surface 3t for reducing the diameter of a piston ring Pr. The set plate 2 and the guide cylinder 3 are respectively provided at each side thereof with cutouts 2k and 3k which are wider than the connecting rod. The jig 1 can be pulled out after installation. As a result, when the piston of the small piston assembly is inserted into the cylinder sleeve, it is possible to prevent the piston ring from being caught or damaged by the cylinder sleeve and to improve workability.

Full Text

PISTON INSERTING JIG AND PISTON INSERTING METHOD BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a for inserting a piston integrally assembled with a crankshaft and a connecting rod into a cylinder sleeve. 2. Description of the Prior Art In a conventional engine assembling process for a motorcycle a small piston assembly in which a crankshaft, a connecting rod and a piston are integrally assembled is installed in a cylinder block. As shown in Fig. 8, the cylinder block B is usually mounted on a workbench so that the axial direction of a cylinder sleeve S can be vertical. An operator holds a crankshaft C and inserts the piston P into the cylinder sleeve S by allowing the axis of the piston P to be vertical. Once the piston P is inserted into the cylinder sleeve S, the operator vertically moves the crankshaft C several times so that a piston ring Pr is adapted to the cylinder sleeve S. However, in such a method, it is difficult to insert the piston P into the cylinder sleeve S putting the piston P in the vertical position. The diameter of the piston ring Pr is also formed larger than that of the cylinder sleeve S. Accordingly, the piston ring Pr is caught or damaged by the cylinder sleeve S. Under these circumstances, an applicant of the present invention has proposed a device which can automate such an piston inserting operation in Japanese Patent Application No. Heir 11-29321 (29321/1999). According to this device, a cylinder block is arranged to pass through a workbench on which the cylinder block is mounted to allow a piston receiving member which is inserted into a cylinder sleeve to move vertically. When a piston is depressed in a condition such that a top portion of the piston is mounted on the piston-receiving member and, at the same time, the piston receiving member is moved down, the piston can be inserted into the cylinder sleeve holding the piston's position. However, although said technique has the effect of preventing the piston ring from being caught or damaged by the cylinder sleeve to a certain extent, there is a disadvantage that it takes a large number of man-hours to perform a piston ring installation and the like. SUMMARY OF THE INVENTION It is therefore an object of the present invention to prevent a piston ring from being caught or damaged by a cylinder sleeve and to provide an improved piston inserting jig for better workability. To attain the above-mentioned object according to the present invention, a piston inserting jig is provided for inserting a piston of a small piston assembly in which a crank-shaft, a connecting rod and the piston are integrally assembled into a cylinder sleeve, which comprises a guide cylinder for guiding the piston to an entrance of the cylinder sleeve and a set plate for positioning the guide cylinder in a predetermined position of a cylinder block, characterized in that the guide cylinder is provided with a piston ring diameter reducing means for reducing the diameter of a piston ring when the piston is inserted into the cylinder sleeve and the set plate is provided with a positioning means for allowing the axis of the cylinder sleeve to coincide with that of the guide cylinder, wherein each side of the guide cylinder and the set plate is provided with a cutout which is wider than the connecting rod. If the set plate is positioned in a predetermined position on the cylinder block to allow the axis of the cylinder sleeve to coincide with that of the guide cylinder and the piston is depressed along the guide cylinder, the piston can be inserted into the cylinder sleeve as is. In this case, the piston is depressed, reducing the diameter of the piston ring, by the piston ring diameter reducing means of the guide cylinder and the piston during depression is maintained in position by the guide cylinder. Accordingly, the piston can be inserted smoothly. The diameter reducing means of the guide cylinder is, for example, a tapered surface which can be formed by tapering an inner surface of the guide cylinder. The diameter of an entrance side is slightly larger than that of the piston ring, while the diameter of an exit side is substantially the same as that of the cylinder sleeve. The positioning means of the set plate can be formed, for example, by using a knock-pin and the like of the cylinder block, wherein the knock-pin engages an engaging opening provided on the set plate. A cutout, which is wider than the connecting rod, is formed on each side of the guide cylinder and the set plate. Accordingly, an inserting jig can be removed by allowing the cutout to pass the axis of the connecting rod after the piston has been inserted into the cylinder sleeve. On the contrary, if the cutout is not provided, the inserting jig can not be removed because the inserting jig interferes with the crankshaft and the like. The above and other objects, features and advantages of the present invention will become more apparent from the following description when taken in conjunction with the accompanying drawings. BRIEF DESCRIPTION OF THE DRAWINGS Fig. 1 is a longitudinal sectional view of a piston-inserting jig according to the present invention; Fig. 2 is a plan view of the piston-inserting jig according to the present invention; Fig. 3 is a side view as seen from the arrow direction A of Fig. 2; Fig. 4 is a plan view of a cylinder block; Fig. 5 is a view explaining a piston inserting condition; Fig. 6 is a plan view showing a condition in which the jig is removed after a piston has been inserted; Fig. 7 is a perspective view of a small piston assembly; and Fig. 8 is an explanatory view of a conventional piston inserting operation. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Preferred embodiments of the present invention will now be described with reference to the accompanying drawings. A piston-inserting jig according to the present invention was developed as an auxiliary jig, as shown in Fig. 7, for inserting a piston P of a small piston assembly Q, in which a crank-shaft C, a connecting rod R, and the piston P are connected to one another, into a cylinder sleeve S of a cylinder block B in which a half body of a crank case and a cylinder are integrally assembled. Thus, it is possible to make workability easy and to prevent a piston ring Pr from being caught or damaged by a cylinder sleeve S. Namely, the present piston-inserting jig 1 is, as shown in Figs. 1 through 3, provided with a set plate 2 for positioning the jig 1 in a predetermined position of the crank case, and a guide cylinder 3 for guiding the insertion of the piston P. Once the set plate 2 is positioned in the predetermined position, an axis of the guide cylinder 3 is caused to coincide with that of the cylinder sleeve S. The set plate 2 is integrally formed with the guide cylinder 3 by allowing one end portion of the guide cylinder 3 to pass through the set plate 2 at the intermediary portion thereof. The set plate 2 is provided, at two places in a diagonal direction, with set openings 2h as a positioning means. The set openings 2h are formed to coincide with the positions of knock-pins provided in two places on a split surface of a crankcase of the cylinder block B shown in Fig. 4. When the set plate 2 is mounted on the split surface, the knock pins n can be inserted into the set openings 2h. When the set plate 2 is positioned on the split surface of the crankcase, a lower end portion of the guide cylinder 3 is, as shown in Fig. 5, connected to an upper end portion of the cylinder sleeve S. Accordingly, the lower end portion of the guide cylinder 3 is formed to have a connecting shape designed to coincide with the upper end shape of the cylinder sleeve S. Further, as shown in Fig. 1, an inner surface of the guide cylinder 3 near the upper end portion is formed as a tapered surface 3t serving as a piston ring diameter reducing means. The tapered surface 3t has a larger diameter at its upper opening side and a smaller diameter at its lower side. The diameter of the larger diameter portion of the upper opening side is slightly larger than that of the piston ring Pr and the diameter of the lower, smaller diameter side is slightly smaller than that of the piston ring Pr. Sides of the set plate 2 and the guide cylinder 3 are penetratingly formed with cutouts 2k and 3k, respectively in the vertical direction. Widths of the cutouts 2k and 3k are larger than that of the connecting rod R. These cutouts 2k and 3k are provided to prevent the jig 1 firom interfering with the small piston assembly Q when the jig 1 is pulled out for removal in a manner described below after the piston P has been inserted into the cylinder sleeve S. In this connection, the upper end surface of the guide cylinder 3 is, as shown in Fig. 3, provided with an inclined plane v, formed as if it were obliquely cut away by putting the position of the cutout 3k in the center. The inclined plane serves to prevent the jig 1 from interfering with the connecting rod R when the jig 1 is removed in the manner described below. An operation of the piston-inserting jig 1 will now be described. First, the cylinder block B, of which the cylinder sleeve S is vertically situated and the split surface of the crankcase is directed upwards, is set. As shown by the alternate long and short dash line in Fig. 4, the set openings 2h of the set plate 2 engage the knock-pins n to allow the set plate 2 to be mounted on the split surface. At this time, the lower end portion of the guide cylinder 3 is, as shown in Fig. 5, connected to the upper end portion of the cylinder sleeve S to allow the two axes to coincide. Next, an operator holds the crankshaft C and the like of the small piston assembly Q to let the piston P hang down, and inserts the piston P through the upper opening portion of the guide cylinder 3. As shown in Fig. 5, if the small piston assembly Q is pressed downwards, the diameter of the piston ring Pr is reduced by the tapered potion 3t and the piston P is smoothly inserted into the lower cylinder sleeve S as is. When insertion of the piston P into the cylinder sleeve S is completed, the axis of the crankshaft C of the small piston assembly Q is, as shown in Fig. 6, moved laterally from the axis of the piston P. The connecting rod R is then moved above the cutouts 2k and 3K. If the inserting jig 1 is pulled out directly upward in this condition, the cutouts 2k and 3k pass a portion of the connecting rod. In this manner, the inserting jig 1 can be pulled out without interference. According to the method described above, the piston ring Pr is in a condition in which the diameter thereof is continuously reduced while inserted into the cylinder sleeve S. Further, the vertical position of the piston P can be perfectly maintained while inserted. Accordingly, the inserting operation becomes easy and it is also possible to secure a guarantee of quality in the installation of the piston ring Pr. It is however to be noted that the present invention is not limited to the embodiments described above. If other embodiments have substantially the same construction and the same action and effect as the matters described in claims of the present invention, they belong to the technical scope of the present invention. For example, the set opening 2h as a positioning means of the set plate 2 is one example. As mentioned above, the piston-inserting jig according to the present invention is provided with the guide cylinder which has the piston ring diameter reducing means and the set plate which has the positioning means as a jig for inserting the piston of the small piston assembly into the cylinder sleeve. In each side of the guide cylinder and the set plate, there is also formed a cutout which is wider than the connecting rod. Accordingly, it is possible to insert the piston into the cylinder sleeve while reducing the diameter of the piston ring in such a condition as to maintain the position of the piston. It is also possible to make the installation operation easier and to secure a guarantee of quality after installation. WE CLAIM : 1. A piston-inserting jig for inserting a piston of a small piston assembly in which a crankshaft, a connecting rod and the piston are assembled into a cylinder sleeve comprising: a guide cylinder for guiding the piston to an entrance of the cylinder sleeve a set plate for positioning the guide cylinder in a predetermined position of a cylinder block; characterized in that the guide cylinder is provided with a piston ring diameter reducing means for reducing the diameter of a piston ring when the piston is inserted into the cylinder sleeve and the set plate is provided with a positioning means for allowing the axis of the cylinder sleeve to coincide with an axis of the guide cylinder; wherein each side of the guide cylinder and the set plate is formed with a cutout which is wider than the connecting rod. 2. The piston-inserting jig as claimed in claim 1, wherein a portion of an upper end surface of the guide cylinder is an inclined plane which is formed by putting the cutout in the center. 3. The piston-inserting jig as claimed in claim 1, wherein the piston ring diameter reducing means is provided in which the lower end inner diameter of the guide cylinder is smaller than the inner diameter of the cylinder sleeve. 4. The piston-inserting jig as claimed in claim 1, wherein the set plate is formed with a set opening which engages a knock-pin which is provided on a cylinder block. 5. A piston-inserting method using the piston-inserting jig as claimed in any one of claims 1 through 4 comprising the steps of: mounting the set plate on the cylinder block; inserting the piston into the cyUnder sleeve through an upper end opening portion of the guide cylinder reducing the diameter of the piston ring; moving the crankshaft of the small piston assembly out of the axis of the piston after the insertion is completed; allowing the cormecting rod to coincide with the cutout formed on each side of the guide cylinder and the set plate; and pulling the inserting jig out directly upward in such a condition.

Documents:

0609-mas-2001 others.pdf

0609-mas-2001 petition.pdf

0609-mas-2001 abstract.jpg

0609-mas-2001 abstract.pdf

0609-mas-2001 claims duplicate.pdf

0609-mas-2001 claims.pdf

0609-mas-2001 correspondence others.pdf

0609-mas-2001 correspondence po.pdf

0609-mas-2001 description (complete) duplicate.pdf

0609-mas-2001 description (complete).pdf

0609-mas-2001 drawings.pdf

0609-mas-2001 form-1.pdf

0609-mas-2001 form-18.pdf

0609-mas-2001 form-26.pdf

0609-mas-2001 form-3.pdf

0609-mas-2001 form-5.pdf