Snap ring fitting device and snap ring mounting method

Abstract

To provide a snap ring fitting device and a snap ring mounting method for preventing a diameter-reduced snap ring from being inclined when fitting the snap ring in a peripheral groove of a piston head.SOLUTION: A snap ring fitting device that fits a snap ring into a circumferential groove provided in an inner circumferential surface of a through-hole provided in a piston head and into which a piston pin is inserted, the snap ring fitting device comprising: a ring gripping mechanism that grips both circumferential ends of the snap ring and reduces a diameter of the snap ring, wherein the ring gripping mechanism includes a posture maintaining portion that maintains a horizontal posture of the snap ring whose diameter is reduced.SELECTED DRAWING: Figure 3

Description

[Technical Field]

[0001] The present invention relates to a snap ring fitting device and a method for installing a snap ring. [Background technology]

[0002] It has long been known that two-wheeled and four-wheeled automobiles are indispensable in various industries, for example, for transporting people and goods. In recent years, electric automobiles using electric motors have been developed, but automobiles equipped with engines using internal combustion engines (hereinafter referred to as engine automobiles) are still being produced.

[0003] In an engine using an internal combustion engine such as the one described above, a piston pin is inserted into a through hole (hereinafter referred to as a piston pin mounting hole) consisting of a through hole in the piston head and a through hole in the connecting rod, and the piston head and the connecting rod are connected via the piston pin. Generally, such a piston head is provided with circumferential grooves corresponding to both ends of the piston pin, and snap rings are fitted into these circumferential grooves using an assembly device such as those described in Patent Documents 1 or 2. This restricts longitudinal movement of the piston pin inserted into the piston pin mounting hole and prevents the piston pin from falling out of the piston pin mounting hole. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2000-317743 [Patent Document 2] Japanese Patent Publication No. 2022-110321 Summary of the Invention [Problem to be solved by the invention]

[0005] To fit a snap ring into the circumferential groove of a piston head, the snap ring must be reduced in diameter and then positioned facing the circumferential groove of the piston head while maintaining a horizontal position of the reduced snap ring. However, with conventional assembly devices, the reduced snap ring may be tilted when fitting the reduced snap ring into the circumferential groove. In this case, the reduced snap ring cannot be fitted properly into the circumferential groove, and the fitting process must be repeated, which may reduce the productivity of engine vehicles.

[0006] The present invention has been made in view of the above circumstances, and an object of the present invention is to provide a snap ring fitting device and a snap ring fitting method that do not tilt the reduced-diameter snap ring when fitting the snap ring into the circumferential groove of a piston head. [Means for solving the problem]

[0007] In order to solve the above-mentioned problems, according to one aspect of the present invention, there is provided a snap ring fitting device that is provided in a piston head and fits a snap ring into a circumferential groove provided on the inner peripheral surface of a through hole into which a piston pin is inserted, the snap ring fitting device comprising: a ring gripping mechanism that grips both circumferential ends of the snap ring and reduces the diameter of the snap ring, the ring gripping mechanism having an attitude maintaining portion that maintains the horizontal attitude of the snap ring as it is reduced in diameter.

[0008] In order to solve the above-mentioned problems, according to another aspect of the present invention, there is provided a method for installing a snap ring, in which a snap ring is fitted into a circumferential groove provided on the inner circumferential surface of a through hole that is provided in a piston head and into which a piston pin is inserted, the method including a diameter reduction step of gripping both circumferential ends of the snap ring via a ring gripping mechanism to reduce the diameter of the snap ring, in which, in the diameter reduction step, a part of the snap ring is positioned on an attitude maintaining portion of the ring gripping mechanism as the diameter is reduced, thereby maintaining a horizontal attitude of the snap ring that has been reduced in diameter. [Effects of the Invention]

[0009] As described above, the snap ring fitting device and snap ring mounting method according to the present invention can prevent the snap ring, which has a reduced diameter, from tilting when fitting the snap ring into the circumferential groove of the piston head. [Brief explanation of the drawings]

[0010] [Figure 1] 3A and 3B are diagrams illustrating an example of a piston head, a connecting rod, a piston pin, and a snap ring. [Figure 2] FIG. 4 is a plan view showing an example of the configuration of a snap ring. [Figure 3] FIG. 2 is a perspective view showing a configuration example of a snap ring fitting device. [Figure 4] 4 is an enlarged view of the snap ring fitting device shown in FIG. 3. [Figure 5] FIG. 2 is a front view showing an example of the configuration of a clamping mechanism. [Figure 6] 10A and 10B are explanatory diagrams for explaining the operation of the clamping mechanism. [Figure 7] 10A and 10B are explanatory diagrams for explaining the operation of the clamping mechanism. [Figure 8] FIG. 5 is an enlarged view showing an area E in FIG. 4. [Figure 9] 4 is a flowchart showing an example of a method for attaching a snap ring. [Figure 10] 10A and 10B are explanatory views for explaining the operation of the snap ring fitting device for fitting a snap ring into a circumferential groove of a piston head. [Figure 11] FIG. 10 is an enlarged view showing a main part of a ring gripping mechanism according to a modified example. [Figure 12] FIG. 10 is an enlarged view of a first attitude maintaining unit according to a modified example. DETAILED DESCRIPTION OF THE INVENTION

[0011] A preferred embodiment of the present invention will be described below with reference to the accompanying drawings. The dimensions and scale of each part in the drawings may differ from those of the actual parts. The drawings may be schematic for ease of understanding. Furthermore, the scope of the present invention is not limited to the following exemplary embodiments unless otherwise specified.

[0012] In the following description, for convenience of explanation, mutually orthogonal X-axis, Y-axis, and Z-axis directions are defined, but the present invention is not limited to this definition. The X-axis, Y-axis, and Z-axis directions are three mutually orthogonal axial directions, and are common to all of the drawings described below. As illustrated in FIG. 2 , a direction along the X-axis direction as viewed from an arbitrary point is denoted as the X1 direction, and a direction opposite to the X1 direction is denoted as the X2 direction. The X-axis direction is a direction that includes both the X1 direction and the X2 direction. Similarly, mutually opposite directions along the Y-axis direction from an arbitrary point are denoted as the Y1 direction and the Y2 direction. The Y-axis direction is a direction that includes both the Y1 direction and the Y2 direction. Furthermore, mutually opposite directions along the Z-axis direction from an arbitrary point are denoted as the Z1 direction (vertically downward) and the Z2 direction (vertically upward). The Z-axis direction is a direction that includes both the Z1 direction and the Z2 direction. Furthermore, the XY plane including the X-axis and Y-axis corresponds to a horizontal plane, and the X-axis direction, Y-axis direction, and Z-axis direction correspond to the longitudinal direction of bar B, the lateral direction of bar B, and the vertical direction, respectively, as described below.

[0013] 1. Embodiment FIG. 1 is a diagram showing an example of a piston head 1 to which a snap ring R is attached by a snap ring fitting device 100 (hereinafter simply referred to as "fitting device 100") according to this embodiment, a connecting rod 2 connected to this piston head 1, and a piston pin 3 inserted into a through hole (hereinafter referred to as a piston pin fitting hole) consisting of a through hole H provided in the piston head 1 and a through hole (not shown) in the connecting rod 2 to connect the piston head 1 and the connecting rod 2.

[0014] The fitting device 100 is a device for reducing the diameter of the snap ring R and fitting the snap ring R into a circumferential groove T provided on the inner circumferential surface of the through hole H. The piston head 1, connecting rod 2, and piston pin 3 are components that constitute an engine (e.g., a reciprocating engine) of a vehicle such as a two-wheeled vehicle or a four-wheeled vehicle.

[0015] The piston pin 3 is inserted into the piston pin mounting hole. With the piston pin 3 inserted into the piston pin mounting hole, a snap ring R fits into a circumferential groove T of the piston head 1, restricting longitudinal movement of the piston pin 3. This prevents the piston pin 3 from falling out of the piston pin mounting hole.

[0016] FIG. 2 is a plan view showing an example of the configuration of a snap ring R according to this embodiment. The snap ring R has a C-shaped shape when viewed along the Z-axis direction, and as shown in FIG. 2, is configured to be symmetrical with respect to the central axis X. As shown in the figure, the snap ring R has a C-shaped main body R1 and widened portions R2 and R3 provided on both circumferential ends of the main body R1. A first through-hole h1 is provided in the widened portion R2, and a second through-hole h2 is provided in the widened portion R3. The snap ring R is an integral unit of the main body R1 and the widened portions R2 and R3.

[0017] The radial width of the C-shaped main body R1 gradually decreases from the central axis X toward both circumferential ends E1, E2 of the snap ring R, as shown in Figure 2. The widths of the widened portions R2, R3 are greater than the width of the main body R1, as shown in the figure. The snap ring R is not particularly limited, and may be, for example, a standard product, a commercially available product, or one equivalent to a standard product or a commercially available product.

[0018] [Configuration of snap ring fitting device] Fig. 3 is a perspective view showing a configuration example of the fitting device 100, and Fig. 4 is an enlarged view of the fitting device 100 shown in Fig. 3 as seen in the X1 direction. The fitting device 100 has a ring gripping mechanism 10, a lifting mechanism 20, and a moving mechanism 30.

[0019] <Ring gripping mechanism> The ring gripping mechanism 10 includes a clamping mechanism 11, an elastic member 12, a connecting portion 13, a first position maintaining portion 14, and a second position maintaining portion 15. The first position maintaining portion 14 is an example of the "position maintaining portion" in the claims. The second position maintaining portion 15 is another example of the "position maintaining portion" in the claims.

[0020] (Pinch mechanism) 5 is a front view showing an example of the configuration of the clamping mechanism 11. As shown in FIG. 5, the clamping mechanism 11 has an L-shaped first clamping piece 111, an L-shaped second clamping piece 112, and a rotation shaft 113.

[0021] The first clamping piece 111 has a first gripping portion 1111, a first L-shaped portion 1112, and a first pressed portion 1113. The first L-shaped portion 1112 has a thin portion 1112h1, a thick portion 1112h2, an end portion 1112E1 located on the X2 direction side when the clamping mechanism 11 is viewed in the Y1 direction, an end portion 1112E2 opposite to the end portion 1112E1, and a first bent portion 1112b.

[0022] The thin portion 1112h1 is a portion of the first L-shaped portion 1112 that protrudes in the Y2 direction in stages from the end portion 1112E1 toward the thick portion 1112h2, and its thickness increases in stages. The thick portion 1112h2 is thicker than the thin portion 1112h1, and is a portion of the first L-shaped portion 1112 that has a constant thickness from the thin portion 1112h1 to the end portion 1112E2.

[0023] As an example, the first gripping portion 1111 is provided on a surface facing the Y2 direction of the thick portion 1112h2 of the first L-shaped portion 1112. As shown in Fig. 5, the first gripping portion 1111 is composed of a flat portion 1111a that is trapezoidal when viewed in the Y1 direction, and a gripping pin 1111b that protrudes from the flat portion 1111a in the Z1 direction.

[0024] The first pressed portion 1113 is a cylindrical body having an annular shape when viewed in the Y1 direction, and is provided, for example, on the surface of the end portion 1112E1 facing the Y2 direction. As shown in Fig. 4, the first pressed portion 1113 is attached to the end portion 1112E1 by threading a nut n onto a portion of a screw P that passes through a through hole of the first pressed portion 1113 and the end portion 1112E1 of the first L-shaped portion 1112 and protrudes from the end portion 1112E1 in the Y1 direction.

[0025] The second clamping piece 112 has a second gripping portion 1121, a second L-shaped portion 1122, and a second pressed portion 1123. The second L-shaped portion 1122 has the same configuration as the first L-shaped portion 1112, and since the second L-shaped portion 1122 is obtained by inverting the first L-shaped portion 1112 shown in Fig. 5 by 180° around the Z axis, a detailed description thereof will be omitted.

[0026] As an example, the second gripping portion 1121 is provided on a surface facing the Y2 direction of the thick portion 1122h2 of the second L-shaped portion 1122. The second gripping portion 1121 has the same configuration as the first gripping portion 1111, and since the second gripping portion 1121 is obtained by inverting the first gripping portion 1111 shown in Fig. 5 by 180° around the Z axis, a detailed description thereof will be omitted.

[0027] The second pressed portion 1123 is a cylindrical body having an annular shape when viewed in the Y1 direction, and is attached to the surface of the end portion 1122E1 of the second L-shaped portion 1122 facing the Y2 direction in the same manner as the first pressed portion 1113.

[0028] As shown in Figure 5, the clamping mechanism 11 of this embodiment is configured so that a first clamping piece 111 faces a second clamping piece 112, which corresponds to the first clamping piece 111 shown in the same figure, flipped 180 degrees around the Z axis, and so that a first bent portion 1112b of the first clamping piece 111 and a second bent portion 1122b of the second clamping piece 112 overlap in the Y-axis direction.

[0029] The material constituting the first and second gripping portions 1111, 1121 is not particularly limited, but is preferably a material having a higher hardness than the material constituting the snap ring R. Specifically, the material constituting the first and second gripping portions 1111, 1121 is preferably SKD11, SCM435 (chrome molybdenum steel), gauge steel (for example, SK5 or SKS3), SKH material, or the like.

[0030] The rotation shaft 113 passes through the first and second bent portions 1112b, 1122b in the Y1 direction. The rotation shaft 113 pivotally supports (supports via a shaft) the first and second bent portions 1112b, 1122b of the first and second clamping pieces 111, 112, which overlap in the Y-axis direction, along the Y-axis direction. The first clamping piece 111 and the second clamping piece 112 are connected via the rotation shaft 113, and are configured to be rotatable around the Y-axis with the rotation shaft 113 as the center so that the first and second gripping portions 1111, 1121 move toward or away from each other (see FIGS. 6 and 7).

[0031] 6 and 7 are explanatory diagrams for explaining the operation of the clamping mechanism 11, with FIG. 6 showing the clamping mechanism 11 in an open state and FIG. 7 showing the clamping mechanism 11 in a closed state.

[0032] The lifting mechanism 20, which will be described later, presses the first and second pressed portions 1113 and 1123 in the Z1 direction via the bar B as it moves the bar B in the Z1 direction. This causes the first and second clamping pieces 111 and 112 of the clamping mechanism 11, which is in the open state, to rotate around the pivot shaft 113 in the direction of the solid arrow (see FIG. 6 ), transitioning the clamping mechanism 11 from the open state to the closed state. The "open state" described above refers to a state in which the first clamping piece 111 and the second clamping piece 112 are fully open, and this also applies to the following description. The bar B is an example of a "pressing member" in the claims. The bar B may have various shapes, not limited to the rod shape shown in the figure, as long as it can press the first pressed portion 1113 and the second pressed portion 1123, respectively.

[0033] On the other hand, when the lifting mechanism 20 moves the bar B that presses the first and second pressed portions 1113, 1123 in the Z2 direction, the elastic member 12 described later pulls the first clamping piece 111 (first L-shaped portion 1112) in the X1 direction with the pivot shaft 113 as a fulcrum, and simultaneously pulls the second clamping piece 112 (second L-shaped portion 1122) in the X2 direction with the pivot shaft 113 as a fulcrum, causing the first and second clamping pieces 111, 112 to abut against the bar B and rotate around the pivot shaft 113 in the direction of the dotted arrow (see Figure 7). Furthermore, when the lifting mechanism 20 further moves the bar B, which is in contact with the first and second pressed portions 1113, 1123, in the Z2 direction, and moves the bar B away from the first and second pressed portions 1113, 1123, the first and second clamping pieces 111, 112 further rotate in the direction of the dotted arrow around the pivot axis 113 due to the action of the elastic member 12 similar to that described above, and the clamping mechanism 11 transitions to the open state shown in Figure 6.

[0034] (elastic member) As shown in Figure 5, as an example, the elastic member 12 is connected to the first clamping piece 111 (first L-shaped portion 1112) via a ring-shaped connecting portion C1 and connected to the second clamping piece 112 (second L-shaped portion 1122) via a ring-shaped connecting portion C2.

[0035] The elastic member 12 always pulls the first clamping piece 111 toward the second clamping piece 112, and pulls the second clamping piece 112 toward the first clamping piece 111. As a result, the elastic member 12 maintains the open state of the clamping mechanism 11 except when the first and second pressed portions 1113, 1123 are pressed by the bar B. Note that the elastic member 12 according to this embodiment is typically a spring, but is not limited to this and may be a known elastic member other than a spring, such as rubber.

[0036] (Connection part) As shown in FIG. 4, the connecting portion 13 has a first portion 131 and a second portion 132, and is connected to the clamping mechanism 11 and a frame 30F of the moving mechanism 30, which will be described later. The first portion 131 is connected to the frame 30F via a handle HL and rotatably supports the first and second clamping pieces 111, 112 via a rotation shaft 113. The first portion 131 is an L-shaped structure when viewed in the X-axis direction and has a predetermined width in the X-axis direction. The second portion 132 is a semi-cylindrical structure that extends from the first portion 131 in the Z1 direction. The second portion 132 has a lower end surface 132S (see FIG. 8) arranged on the Z1 direction side.

[0037] In this embodiment, the operator of the fitting device 100 can remove the ring gripping mechanism 10 from the frame 30F by operating the handle HL. The operator can then remove the ring gripping mechanism 10 from the frame 30F by operating the handle HL, and replace the current ring gripping mechanism 10 with a new ring gripping mechanism that matches the shape of the new snap ring. This makes it possible to reduce the diameter of not only snap rings of a specific shape, but also snap rings of various shapes, and fit them into the circumferential groove T of the piston head 1.

[0038] (1st posture maintenance part) 8 is an enlarged view of region E in FIG. 4. As shown in FIG. 8, the first position maintaining unit 14 has a portion 141 and a plate 142. The first position maintaining unit 14 may be an integral unit of the portion 141 and the plate 142, or the portion 141 and the plate 142 may be separate bodies. The portion 141 is provided on the lower end surface 132S of the second portion 132, and is a structure that protrudes from the lower end surface 132S in the Z1 direction. The portion 141 may be an integral unit of the lower end surface 132S, or may be a separate member from the lower end surface 132S.

[0039] Plate 142 is a plate-like structure provided on the bottom side of portion 141, and as shown in Fig. 8, protrudes in the Y1 direction beyond the end face of portion 141 facing the Y1 direction. The width of plate 142 in the X-axis direction is greater than the width of portion 141 in the X-axis direction. Similarly, the width of plate 142 in the Y-axis direction is greater than the width of portion 141 in the Y-axis direction. As will be described later, a portion of a reduced-diameter snap ring R is positioned on the upper surface side of plate 142 protruding in the Y1 direction (see Fig. 10c).

[0040] (Second posture maintenance part) 8, the second attitude maintaining unit 15 has a portion 151, an L-shaped portion 152, and a protrusion 153. The second attitude maintaining unit 15 may be an integrated unit of the portion 151, the L-shaped portion 152, and the protrusion 153, or may be configured such that these are separate bodies.

[0041] The portion 151 is provided on the lower end surface 132S of the second portion 132 and is a structure having a predetermined width in the X-axis direction. The portion 151 is an integral part of the portions 151a to 151c. The portion 151a is a portion of the portion 151 that protrudes in the Z1 direction from the lower end surface 132S. The portion 151b is a portion of the portion 151 that protrudes in the Y2 direction from the outer circumferential surface at the end of the second portion 132 on the Z1 direction side. The portion 151c is a portion of the portion 151 that is connected to the portions 151a and 151b. Note that the portions 151a to 151c shown in FIG. 8 are separated for the sake of convenience of explanation, but in reality, these are an integral part and not separate.

[0042] The L-shaped portion 152 is a portion of the second posture maintaining portion 15 that has an L-shape when viewed in the X1 direction. The width of the L-shaped portion 152 in the X-axis direction is approximately the same as the width of the portion 151 in the X-axis direction. As shown in FIG. 8, the protrusion 153 is a portion of the second posture maintaining portion 15 that protrudes in the Y2 direction from the portion 151. The width of the protrusion 153 in the X-axis direction is approximately the same as the width of the portion 151 in the X-axis direction. A dimension D1 between the end face of the protrusion 153 facing the Y2 direction and the end face of the plate 142 facing the Y1 direction is smaller than the inner diameter r of the snap ring R before it is reduced in diameter (see FIG. 2).

[0043] In this embodiment, when the clamping mechanism 11 reduces the diameter of the snap ring R, both circumferential ends E1 and E2 of the snap ring R enter between the L-shaped portion 152 and the protrusion 153, and these ends E1 and E2 are sandwiched between the L-shaped portion 152 and the protrusion 153 (see FIG. 10c). This prevents the snap ring R from tilting about the Y axis as it reduces in diameter. That is, the second attitude maintaining unit 15 according to this embodiment prevents the snap ring R from tilting about the Y axis as it reduces in diameter, and together with the first attitude maintaining unit 14, can maintain the horizontal attitude of the snap ring R. Note that the "horizontal attitude" mentioned above means an attitude in which the thickness direction of the snap ring R is aligned with the Z axis direction, and this also applies in the following explanation.

[0044] As described above, it is desirable that the ring gripping mechanism 10 of this embodiment be equipped with both the first posture maintaining unit 14 and the second posture maintaining unit 15 as the "posture maintaining unit," but it may also be in a form in which either the first posture maintaining unit 14 or the second posture maintaining unit 15 (for example, the second posture maintaining unit 15) is omitted, such as by providing only the first posture maintaining unit 14 as long as the horizontal posture described above can be maintained.

[0045] <Lifting mechanism> The lifting mechanism 20 includes a drive source (not shown) such as a servo motor, and an optional slide mechanism (not shown) driven by the drive source, and is configured to be movable in the Z-axis direction by this slide mechanism. As shown in Fig. 3, the lifting mechanism 20 supports the bar B extending in the X-axis direction, and raises and lowers the bar B in the Z1 or Z2 direction so as to be able to press the first pressed portion 1113 and the second pressed portion 1123 in parallel. The lifting mechanism 20 can adjust the degree of opening of the clamping mechanism 11 that abuts against the bar B by adjusting the amount of movement of the bar B in the Z-axis direction.

[0046] <Movement mechanism> The movement mechanism 30 includes a frame 30F extending in the Z-axis direction and any slide mechanism (not shown), such as a ball screw mechanism or a cylinder mechanism, connected to the frame 30F. The slide mechanism is connected to the ring gripping mechanism 10 via the frame 30F and is also connected to the slide mechanism of the lifting mechanism 20. This allows the movement mechanism 30 to move the ring gripping mechanism 10 and the lifting mechanism 20. Specifically, the movement mechanism 30 can move the ring gripping mechanism 10 in the X-axis direction, Y-axis direction, or Z-axis direction via the frame 30F, and can move the slide mechanism of the lifting mechanism 20 in the X-axis direction or Y-axis direction.

[0047] <How to install the snap ring> Fig. 9 is a flowchart showing an example of a method for attaching the snap ring R, and Fig. 10 is an explanatory diagram for explaining the operation of the fitting device 100 for fitting the snap ring R into the circumferential groove T of the piston head 1. The method for attaching the snap ring R performed by the fitting device 100 will be described below with reference to Figs. 9 and 10 as appropriate.

[0048] The method for attaching the snap ring R according to this embodiment includes an insertion step (step St1), a diameter reduction step (step St2), and an attachment step (step St3), as shown in Figure 9. These steps will be described below.

[0049] [Step St1: Insertion process] The movement mechanism 30 moves the ring gripping mechanism 10 to a position where the first and second orientation maintaining units 14, 15 can pass through the snap ring R in the Z1 direction. Next, the movement mechanism 30 moves the ring gripping mechanism 10 in the Z1 direction, as shown in FIG. 10a. At this time, because the dimension D1 is smaller than the inner diameter r of the snap ring R as described above, the first and second orientation maintaining units 14, 15 pass through the snap ring R in the Z1 direction, as shown in FIG. 10b. Here, in step St1, as the first and second orientation maintaining units 14, 15 pass through the snap ring R, the gripping pin 1111b passes through a first through hole h1 provided at one circumferential end E1 of the snap ring R, and the gripping pin 1121b passes through a second through hole h2 provided at the other circumferential end E2 of the snap ring R.

[0050] [Step St2: Diameter reduction process] Next, a diameter reduction step is performed in which both circumferential ends E1, E2 of the snap ring R are gripped by the ring gripping mechanism 10, and the diameter of the snap ring R is reduced. Specifically, the lifting mechanism 20 presses the first and second pressed portions 1113, 1123 in the Z1 direction via the bar B as the bar B moves in the Z1 direction. As a result, the first clamping piece 111 passing through the first through-hole h1 and the second clamping piece 112 passing through the second through-hole h2 rotate in the direction of the solid arrow around the rotation axis 113 (see FIG. 6), and the first and second clamping pieces 111, 112 reduce the diameter of the snap ring R. Here, as shown in FIG. 10c, the inner diameter r1 of the snap ring R after the diameter reduction becomes smaller than the dimension D1, and the snap ring R inevitably enters between the lower end surface 132S and the plate 142. As a result, as the diameter of the snap ring R is reduced, a portion of the snap ring R is positioned above the portion of the plate 142 of the first attitude maintaining unit 14 that protrudes in the Y1 direction. Therefore, when fitting the snap ring R into the through hole H into which the piston pin 3 is inserted, the snap ring R can be inserted into the through hole H while the bottom side of the snap ring R is supported by the plate 142, and even if the snap ring R whose diameter is reduced begins to tilt around the X axis, it is ultimately supported by the plate 142, preventing the snap ring R from tilting around the X axis. The first attitude maintaining unit 14 according to this embodiment prevents the snap ring R whose diameter is reduced from tilting around the X axis and, together with the second attitude maintaining unit 15, can maintain the horizontal attitude of the snap ring R.

[0051] [Step St3: Installation process] Next, the movement mechanism 30 moves the ring gripping mechanism 10 to a position where the first and second attitude maintaining parts 14, 15 can enter the through-hole H of the piston head 1. Next, the movement mechanism 30 moves the ring gripping mechanism 10 in the Z1 direction, so that the circumferential groove T of the piston head 1 faces the outer peripheral surface of the reduced diameter snap ring R, as shown in FIG. 10d.

[0052] Subsequently, the ring gripping mechanism 10 attaches the snap ring R to the circumferential groove T of the piston head 1. Specifically, when the lifting mechanism 20 moves the bar B that presses the first and second pressed portions 1113 and 1123 in the Z2 direction, as described above, the elastic member 12 pulls the first clamping piece 111 in the X1 direction and the second clamping piece 112 in the X2 direction, so that the first clamping piece 111 passing through the first through-hole h1 and the second clamping piece 112 passing through the second through-hole h2 rotate in the direction of the dotted arrow around the rotation shaft 113 (see FIG. 7). As a result, the snap ring R with a reduced diameter expands, and as shown in FIG. 10e, the inner diameter of the snap ring R becomes an inner diameter r2 (r1 < r2 < r) larger than the dimension D1, and the snap ring R fits into the circumferential groove T. Next, as shown in FIG. 10f, the moving mechanism 30 moves the ring gripping mechanism 10 in the Z2 direction, pulls out the gripping pin 1111b from the first through-hole h1 of the snap ring R, and pulls out the gripping pin 1121b from the second through-hole h2.

[0053] 2. Modified Example As described above, a preferred embodiment of the present invention has been described, but the present invention is not limited to the above-described embodiment and various modifications can be made. Specific modified aspects that can be changed from the aspects of the above-described embodiment are exemplified below.

[0054] FIG. 11 is an enlarged view showing an essential part of the ring gripping mechanism 10 according to the modified example, FIG. 12 is an enlarged view of the first posture maintaining portion 14 according to the modified example, and is an explanatory view for explaining the movement of the snap ring R during the process of reducing the diameter.

[0055] 11, the first attitude maintaining unit 14 according to the modified example may further include a tapered surface 143 in addition to the portion 141 and the plate 142. As shown in FIGS. 11 and 12, the tapered surface 143 is an inclined surface that gradually reduces the distance between the plate 142 and the lower end surface 132S toward the clamping mechanism 11. This allows the snap ring R to be smoothly guided to the upper surface side of the plate 142 via the tapered surface 143 when the snap ring R is reduced in diameter by the ring gripping mechanism 10, without hitting the end surface of the plate 142 and interrupting the reduction in diameter.

[0056] 3. Summary As can be understood from the above explanation, fitting device 100 according to one aspect (Aspect 1) of the snap ring fitting device of the present invention is provided in piston head 1, and fits snap ring R into circumferential groove T provided on the inner circumferential surface of through hole H into which piston pin 3 is inserted. Fitting device 100 is equipped with ring gripping mechanism 10 that grips both circumferential ends E1, E2 of snap ring R and reduces the diameter of snap ring R. Ring gripping mechanism 10 has at least first position maintaining part 14 that maintains a horizontal position of snap ring R whose diameter is reduced.

[0057] According to the above-described first aspect, the horizontal position of the reduced-diameter snap ring R is maintained by the first position maintaining portion 14 and the like. Therefore, when fitting the snap ring R into the circumferential groove T of the piston head 1, the reduced-diameter snap ring R can be maintained in a state in which the snap ring R faces the circumferential groove T without tilting the snap ring R (see FIG. 10d). This allows the snap ring R to be securely fitted into the circumferential groove T. Therefore, according to the fitting device 100 of this embodiment, the snap ring R can be securely fitted into the circumferential groove T, eliminating the need to redo the process of fitting the snap ring R to the piston head 1. As a result, it is possible to prevent a decrease in productivity of engine vehicles.

[0058] Furthermore, according to the fitting device 100 according to the specific example (aspect 2) of aspect 1, The apparatus further includes a lifting mechanism 20 that supports a bar B as a pressing member and lifts and lowers the bar B in the Z-axis direction, The ring gripping mechanism 10 is a first gripping portion 1111 passing through a first through-hole h1 provided at one circumferential end E1 of the snap ring R, a first pressed portion 1113 pressed by the bar B, and an L-shaped first clamping piece 111 having a first bent portion 1112b; a second gripping portion 1121 passing through a second through-hole h2 provided at the other circumferential end E2 of the snap ring R, a second pressed portion 1123 pressed by the bar B, and an L-shaped second clamping piece 112 having a second bent portion 1122b; and A rotation axis 113 passes through the first and second bent portions 1112b and 1122b in the short-side direction (Y-axis direction) of the bar B. a clamping mechanism 11 including: an elastic member 12 connected to the first and second clamping pieces 111, 112, which maintains the open state of the clamping mechanism 11 by pulling the first clamping piece 111 toward the second clamping piece 112 and the second clamping piece 112 toward the first clamping piece 111, with the rotation shaft 113 as a fulcrum; The first clamping piece 111 and the second clamping piece 112 are connected via a rotation shaft 113, and are configured to be rotatable around the rotation shaft 113 so that the first gripping portion 1111 and the second gripping portion 1121 move toward or away from each other; The lifting mechanism 20 presses the first and second pressed portions 1113, 1123 in the Z1 direction via the bar B, thereby rotating the first and second clamping pieces 111, 112 around the pivot axis 113, thereby transitioning the clamping mechanism 11 from the open state to the closed state.

[0059] Conventional snap ring assembly devices reduce the diameter of the snap ring using relatively large components that complicate the device configuration, such as the guide means described in Japanese Patent Application Laid-Open No. 2003-317743 or the ring holder portion described in Japanese Patent Application Laid-Open No. 2022-110321. On the other hand, fitting device 100 according to aspect 2 has clamping mechanism 11, which makes the device configuration less complicated than conventional snap ring assembly devices, and can therefore reduce the diameter of snap ring R easily and quickly, and reliably fit snap ring R into circumferential groove T of piston head 1.

[0060] Furthermore, according to the fitting device 100 according to a specific example of aspect 2 (aspect 3), The moving mechanism 30 has a frame 30F extending in the Z-axis direction and is connected to the ring gripping mechanism 10 and the lifting mechanism 20, and is configured to move the ring gripping mechanism 10 in the longitudinal direction (X-axis direction), the lateral direction (Y-axis direction) or the Z-axis direction of the bar B, and to move the lifting mechanism 20 in the longitudinal direction (X-axis direction) or the lateral direction (Y-axis direction), The ring gripping mechanism 10 further includes a connecting portion 13 that is connected to the frame 30F and has a first portion 131 that rotatably supports the first and second clamping pieces 111 and 112 via a rotation shaft 113, and a second portion 132 that extends from the first portion 131 in the Z1 direction; The second portion 132 has a lower end surface 132S disposed on the Z1 direction side, The first attitude maintaining unit 14 is a portion 141 provided on the lower end surface 132S and projecting in the Z1 direction from the lower end surface 132S; and a plate 142 that is provided on the portion 141 and supports a snap ring R having a reduced diameter.

[0061] According to the above-mentioned aspect 3, when the clamping mechanism 11 reduces the diameter of the snap ring R, the snap ring R enters between the lower end surface 132S and the plate 142, and the reduced-diameter snap ring R is supported by the plate 142. Therefore, when attaching the snap ring R to the piston head 1, the snap ring R and the circumferential groove T can be maintained in a state where they face each other without tilting the reduced-diameter snap ring R about the X-axis (see FIG. 10d). This allows the snap ring R to be reliably fitted into the circumferential groove T while being maintained in a horizontal position.

[0062] In addition, according to the fitting device 100 relating to a specific example (aspect 4) of aspect 3, the first posture maintaining unit 14 may further include a tapered surface 143 that gradually reduces the distance between the plate 142 and the lower end surface 132S toward the clamping mechanism 11, as shown in Figures 11 and 12.

[0063] According to the above-mentioned aspect 4, even if the snap ring R is tilted when the clamping mechanism 11 grips both circumferential ends E1, E2 of the snap ring R, as shown in Fig. 12, the snap ring R slides on the tapered surface 143 in the Y2 direction during the process of reducing its diameter, thereby ensuring that the snap ring R assumes a horizontal position after its diameter is reduced. In other words, even if the snap ring R is tilted when the clamping mechanism 11 grips it, the tapered surface 143 can reliably move the snap ring R from the tilted position to the horizontal position.

[0064] Furthermore, according to fitting device 100 according to a specific example (Aspect 5) of any one of Aspects 2 to 4, first and second gripping portions 1111, 1121 are made of a material that is harder than the material that constitutes snap ring R. This prevents gripping pins 1111b, 1121b from bending or breaking when first and second gripping portions 1111, 1121 reduce the diameter of snap ring R, making it easier to reduce the diameter of snap ring R.

[0065] An attachment method according to one aspect (Aspect 6) of the snap ring attachment method of the present invention is a method for fitting a snap ring R into a circumferential groove T provided in the inner circumferential surface of a through hole H that is provided in a piston head 1 and into which a piston pin 3 is inserted, and includes a diameter reduction step (Step St2) in which both circumferential ends E1, E2 of the snap ring R are gripped via a ring gripping mechanism 10 to reduce the diameter of the snap ring R. In the diameter reduction step (Step St2), as the diameter is reduced, a portion of the snap ring R is positioned on a first position maintaining portion 14 of the ring gripping mechanism 10, thereby maintaining the horizontal position of the snap ring R whose diameter has been reduced.

[0066] According to the sixth aspect, the horizontal position of the reduced-diameter snap ring R is maintained. Therefore, when attaching the snap ring R to the piston head 1, the reduced-diameter snap ring R does not need to be tilted, and the snap ring R and the circumferential groove T can be maintained in a state where they face each other (see FIG. 10d). This allows the snap ring R to be securely fitted into the circumferential groove T. Therefore, according to the method for attaching the snap ring R according to this embodiment, the snap ring R can be securely fitted into the circumferential groove T, eliminating the need to redo the process of attaching the snap ring R to the piston head 1. As a result, it is possible to suppress a decrease in productivity of engine vehicles.

[0067] 4. Supplementary Information Although the preferred embodiments of the present invention have been described in detail above with reference to the accompanying drawings, the present invention is not limited to these examples. It is clear that a person skilled in the art to which the present invention pertains can conceive of various modifications and alterations within the scope of the technical ideas set forth in the claims, and it is understood that these also naturally fall within the technical scope of the present invention.

[0068] Furthermore, the effects described in this specification are not limiting. In other words, the present invention may exhibit other effects that will be apparent to those skilled in the art from the description of this specification, in addition to or in place of the above-described effects. [Explanation of symbols]

[0069] 1...Piston head 3...Piston pin 10...Ring gripping mechanism 11...Pinching mechanism 12...Elastic member 13...Connection part 14...First posture maintenance part 15...Second posture maintenance section 20...Lifting mechanism 30...Movement mechanism 30F…Frame 100...Snap ring fitting device 111...First clamping piece 112...Second clamping piece 113...Pivot shaft 131...First part of the connecting part 132...Second part of the connecting part 132S…Lower end surface 141...Part of the first posture maintenance unit 142...Plate 143...Tapered surface 1111...First gripping part 1112b...first bending part 1113...First pressed portion 1121...Second gripping part 1122b…Second bending part 1123...Second pressed portion B...Bar (pressing member) E1...One circumferential end of the snap ring E2: The other end of the snap ring h1…1st through hole h2…Second through hole H: Piston head through hole R...Snap ring T…peripheral groove

Claims

1. A snap ring fitting device is provided in a piston head, and fits a snap ring into a circumferential groove provided on an inner circumferential surface of a through hole into which a piston pin is inserted, a ring gripping mechanism that grips both circumferential ends of the snap ring and reduces the diameter of the snap ring, The ring gripping mechanism has a position maintaining portion that maintains the horizontal position of the snap ring as it contracts.

2. a lifting mechanism that supports the pressing member and raises and lowers the pressing member in the vertical direction, The ring gripping mechanism includes: a first clamping piece having an L-shaped configuration, the first clamping piece including a first gripping portion passing through a first through hole provided at one circumferential end of the snap ring, a first pressed portion pressed by the pressing member, and a first bent portion; a second gripping portion that passes through a second through hole provided at the other circumferential end of the snap ring, a second pressed portion that is pressed by the pressing member, and an L-shaped second clamping piece that has a second bent portion; a rotation axis passing through the first bent portion and the second bent portion in the short-side direction of the pressing member; a clamping mechanism comprising: an elastic member connected to the first and second clamping pieces, the elastic member pulling the first clamping piece toward the second clamping piece and the second clamping piece toward the first clamping piece, with the rotation shaft as a fulcrum, thereby maintaining the clamping mechanism in an open state; the first clamping piece and the second clamping piece are connected via the rotation shaft and are configured to be rotatable about the rotation shaft so that the first gripping portion and the second gripping portion move toward or away from each other; The lifting mechanism presses the first pressed portion and the second pressed portion vertically downward via the pressing member, thereby rotating the first clamping piece and the second clamping piece about the rotation axis, thereby transitioning the clamping mechanism from the open state to the closed state.

2. The snap ring fitting device according to claim 1.

3. a moving mechanism having a frame extending in a vertical direction and connected to the ring gripping mechanism and the lifting mechanism, the moving mechanism being configured to move the ring gripping mechanism in the longitudinal direction, the lateral direction, or the vertical direction of the pressing member, and to move the lifting mechanism in the longitudinal direction or the lateral direction; the ring gripping mechanism further includes a connecting portion having a first portion connected to the frame and rotatably supporting the first clamping piece and the second clamping piece via the rotation shaft, and a second portion extending vertically downward from the first portion, The second portion has a lower end surface disposed vertically downward, The posture maintaining unit is a portion provided on the lower end surface and extending vertically downward from the lower end surface; a plate provided in the portion and supporting the snap ring whose diameter is reduced; The snap ring installation device of claim 2 , comprising:

4. 4. The snap ring fitting device according to claim 3, wherein the position maintaining portion further comprises a tapered surface that gradually reduces the distance between the plate and the lower end surface toward the clamping mechanism.

5. 5. The snap ring fitting device according to claim 2, wherein the first gripping portion and the second gripping portion are made of a material harder than a material constituting the snap ring.

6. A method for attaching a snap ring, comprising fitting the snap ring into a circumferential groove provided on an inner circumferential surface of a through hole provided in a piston head and into which a piston pin is inserted, a diameter reducing step of gripping both circumferential ends of the snap ring via a ring gripping mechanism to reduce the diameter of the snap ring, In the diameter reduction step, a portion of the snap ring is positioned on a position maintaining portion of the ring gripping mechanism as the snap ring is reduced in diameter, thereby maintaining a horizontal position of the snap ring as it is reduced in diameter. How to install a snap ring.

Images