Positioning clamp for piston pin hole machining

Abstract

The invention provides a positioning clamp for piston pin hole machining, and belongs to the technical field of machining. The clamp comprises a base, a positioning disc, a positioning block, a stand column, a cross beam, a pressing mechanism and a sliding supporting assembly. The positioning disc is installed on the base and used for being matched with a bottom spigot of the piston. The positioning block is used for circumferential positioning of the piston. The cross beam is rotatably connected to the stand column through a rotating shaft assembly. The pressing mechanism is arranged on the cross beam and used for pressing the top end face of the piston downwards. The sliding supporting assembly is arranged on the cross beam and used for providing supporting in the rotating process of the cross beam. The principle of lower positioning and upper pressing is adopted, pressing force acts on the top, with the strongest rigidity, of the piston, extrusion deformation of the skirt portion of the thin-wall piston during clamping is effectively avoided, and the machining precision is remarkably improved. Meanwhile, the sliding supporting assembly integrated with the universal wheels enables operation to be convenient and efficient, labor intensity is reduced, and the piston pin hole machining device is suitable for efficient and high-precision machining of piston pin holes.

Description

Technical Field

[0001] This invention belongs to the field of machining technology, specifically relating to a positioning fixture for machining piston pin holes. Background Technology

[0002] The piston is a key component in an internal combustion engine, typically a thin-walled cylindrical part, which is prone to deformation during machining, affecting machining accuracy. The machining of piston pin holes requires extremely high positional accuracy. Currently, common methods for machining piston pin holes include: Figure 5 As shown, the piston skirt is positioned using the top stop and pressed against the bottom end face of the piston skirt with a pressure plate. Then, the pin hole is machined on a horizontal machining center.

[0003] However, the above processing method has obvious drawbacks: due to the thin outer wall thickness and poor rigidity of the piston bottom, when the pressure plate is directly pressed against the bottom end face, it is very easy to cause extrusion deformation of the piston bottom outer circle. This deformation not only affects the stability and repeatability of clamping, but also introduces clamping stress into the processing, resulting in problems such as out-of-tolerance pin hole position accuracy and poor cylindricity in the final processed part, which seriously restricts the processing quality and efficiency.

[0004] Therefore, there is an urgent need for a new type of clamp that can effectively avoid piston deformation during clamping, improve positioning accuracy and clamping efficiency. Summary of the Invention

[0005] The technical problem solved by this invention: In view of the shortcomings of the prior art, the purpose of this invention is to provide a positioning fixture for machining piston pin holes. By changing the positioning and clamping positions, the fixture selects the part of the piston with higher rigidity for clamping, thereby fundamentally avoiding clamping deformation. At the same time, it designs an easy-to-operate sliding support component to achieve efficient, stable and high-precision piston clamping.

[0006] To achieve the above objectives, the present invention adopts the following technical solution: A positioning fixture for machining piston pin holes includes a base, a positioning plate, a positioning block, a column, a crossbeam, a clamping mechanism, and a sliding support assembly. The positioning plate is fixedly installed on the base and is used to cooperate with the bottom stop of the piston for positioning. The positioning block is fixedly installed on the base and is used to limit the piston in the circumferential direction; The column is fixedly mounted on the base; The crossbeam is rotatably connected to the column via a pivot assembly; The clamping mechanism is mounted on the crossbeam and is used to press down on the top end face of the piston; The sliding support assembly is disposed on the crossbeam and is used to provide support during the rotation of the crossbeam.

[0007] Further defining the above scheme, the column includes a first column and a second column set at the same height, and the two ends of the crossbeam are respectively connected to the first column and the second column through the first rotating shaft assembly and the second rotating shaft assembly; The first rotating shaft assembly includes a bolt I and a nut I, and one end of the crossbeam is connected to the first column via the bolt I and the nut I; The second rotating shaft assembly includes a bolt II and a nut II mounted on the second column. When the crossbeam rotates to the working position, the U-shaped groove on the crossbeam engages with the bolt II and is locked by the nut II.

[0008] Further defining the above solution, the clamping mechanism includes a pressure plate, a connecting block, a top block, a first elastic element, and a sleeve; A sleeve is fixed on the crossbeam, and the top block and the sleeve form the threaded pair. A handle I for driving the top block to rotate is connected to the top block. The lower end of the connecting block is connected to the pressure plate, and the upper end is connected to the top block; the upper end of the connecting block is fitted with the first elastic element, and the top block drives the connecting block and the pressure plate to move in the vertical direction through a threaded pair.

[0009] Further defining the above solution, the sliding support assembly includes a handle II, a slide rod, a second elastic element, and a caster wheel; the slide rod is slidably connected to the crossbeam via bolts III and nuts III; the second elastic element is fitted onto the slide rod to provide a downward elastic force to the slide rod; the caster wheel is installed at the bottom end of the slide rod; and the handle II is connected to the end of the crossbeam.

[0010] As a further limitation of the above solution, the sliding support assembly also includes a handle III, which is threadedly connected to the slide rod and is used to overcome the elastic force of the second elastic element to lift the slide rod and the caster wheel.

[0011] Further specifying the above solution, the first elastic element and the second elastic element are helical springs.

[0012] To further define the above solution, a limiting groove is provided on the base, and when the crossbeam is in a non-working position, the bottom of the caster wheel falls into the limiting groove.

[0013] As a further limitation of the above scheme, the base is provided with lifting lugs.

[0014] Further defining the above scheme, the positioning disk is mounted on the base by screw I; the positioning block is fixed on the base by screw II.

[0015] Advantages of this invention compared to existing technologies: 1. This solution fundamentally eliminates clamping deformation: This invention innovatively changes the traditional positioning and clamping approach, utilizing the piston's bottom stop for primary radial positioning, while applying clamping force to the piston's most rigid top end face. This "lower positioning, upper clamping" method completely avoids clamping force acting on the thin-walled piston skirt, thus eliminating piston deformation caused by clamping at its source, ensuring the stability of the machining datum, and greatly improving the machining accuracy and shape accuracy of the piston pin hole; 2. This solution offers high positioning accuracy and stability: A precision-machined positioning disc mates with the piston's bottom stop, ensuring high positioning accuracy. Circumferential positioning is achieved using a positioning block, guaranteeing that the piston pin hole axis is parallel to the machine tool spindle, resulting in consistent and reliable repeatability. 3. This solution is highly efficient and reduces labor intensity: The designed sliding support assembly, especially the use of casters to support the tilting of the crossbeam, makes the movement of the heavy crossbeam easy and effortless. Clearly defined limit grooves and working position locking structures ensure clear, fast, and accurate operation steps, significantly improving single-piece clamping efficiency and reducing worker labor intensity. 4. This solution has a simple, reliable structure and wide applicability: the entire fixture has a compact structure, and most of the parts are standard parts or simple machined parts, resulting in low manufacturing and maintenance costs. Its design principles can be extended to the machining and clamping of other similar thin-walled, easily deformable rotating parts, demonstrating good versatility and application prospects. Attached Figure Description

[0016] Figure 1 This is a front view of the structure of the present invention; Figure 2 This is a cross-sectional view of the structure of the present invention; Figure 3 This is a three-dimensional structural diagram of the crossbeam in the working state in this invention; Figure 4 This is a three-dimensional structural diagram of the crossbeam in the non-working position in this invention; Figure 5 This is a schematic diagram of piston clamping in the prior art; The labels in the diagram are as follows: 1-base, 2-lifting lug, 3-screw I, 4-first column, 5-crossbeam, 6-nut I, 7-bolt I, 8-pressure plate, 9-first elastic element, 10-connecting block, 11-top block, 12-handle I, 13-sleeve, 14-second column, 15-nut II, 16-bolt II, 17-second elastic element, 18-bolt III, 19-nut III, 20-handle II, 21-handle III, 22-slide bar, 23-caster wheel, 24-screw II, 25-positioning block, 26-positioning plate, 27-piston, 28-limiting groove, A-lower surface of pressure plate, B-top end face of piston, C-a characteristic surface of piston, X-mating surface on crossbeam, Y-mating surface on column II. Detailed Implementation

[0017] The technical solutions of the embodiments of the present invention will be clearly and completely described below with reference to the accompanying drawings. Obviously, the described embodiments are only some embodiments of the present invention, and not all embodiments. Based on the embodiments of the present invention, all other embodiments obtained by those skilled in the art without creative effort are within the scope of protection of the present invention.

[0018] In the description of this invention, it should be understood that the terms "upper", "lower", "front", "rear", "left", "right", "top", "bottom", "inner", "outer", etc., indicate the orientation or positional relationship based on the orientation or positional relationship shown in the accompanying drawings. They are only for the convenience of describing this invention and simplifying the description, and do not indicate or imply that the device or element referred to must have a specific orientation, or be constructed and operated in a specific orientation. Therefore, they should not be construed as limitations on this invention.

[0019] It should be noted that, in this document, the terms "comprising," "including," or any other variations thereof are intended to cover non-exclusive inclusion, such that a process, method, article, or apparatus that comprises a list of elements includes not only those elements but also other elements not expressly listed, or elements inherent to such a process, method, article, or apparatus. Unless otherwise specified, an element defined by the phrase "comprising one..." does not exclude the presence of other identical elements in the process, method, article, or apparatus that includes said element.

[0020] Please see Figure 1-5 The embodiments of the present invention are described in detail below.

[0021] like Figures 1 to 4 As shown, the positioning fixture for machining piston pin holes provided by the present invention mainly consists of a base 1, a positioning part, a clamping part, and a flipping locking part.

[0022] The base 1 serves as the foundation platform for the entire fixture, and its bottom can be fixed to the machine tool worktable using anchor bolts or T-slot bolts. Lifting lugs 2 are welded to or threaded onto the base 1 to facilitate the overall lifting and transportation of the fixture.

[0023] The positioning section includes a positioning disc 26 and a positioning block 25. The positioning disc 26 is precisely fixed to the central area of ​​the base 1 by screws I3. Its upper part is machined with a precision positioning stop that mates with the bottom stop of the piston 27 to be processed, used to achieve radial positioning (center positioning) of the piston 27. The positioning block 25 is fixed to the base 1 by screws II24 and is located to the side front of the positioning disc 26. The outer circumferential side of the piston 27 usually has a marking line (or process boss) to indicate the direction of the pin hole. During clamping, rotating the piston 27 aligns the marking line with the side of the positioning block 25, thus completing the circumferential positioning of the piston pin hole axis and ensuring that the pin hole axis is parallel to the machine tool spindle.

[0024] The column section includes a first column 4 and a second column 14, both of which are of equal height and vertically welded to the base 1, and are symmetrically distributed on both sides of the positioning plate 26.

[0025] The crossbeam 5 is rotatably mounted between the two columns via a pivot assembly. Specifically, one end of the crossbeam 5 is hinged to the first column 4 via bolt I7 and nut I6, allowing the crossbeam 5 to rotate around the axis of bolt I7. When the crossbeam 5 rotates to the working position, the U-shaped groove on the other end of the crossbeam 5 engages with bolt II16 and is locked to the second column 14 by nut II15.

[0026] The clamping mechanism is mounted on the crossbeam 5. A sleeve 13 is welded onto the crossbeam 5. The top block 11 and the sleeve 13 form a threaded transmission pair. The upper part of the connecting block 10 is connected to the lower end of the top block 11 by threads or other means, and the lower part is connected to the pressure plate 8. A first elastic element 9 is installed between the upper end of the connecting block 10 and the crossbeam 5. When the handle I12 is rotated clockwise, the top block 11 is rotated and screwed downwards, pushing the connecting block 10 and the pressure plate 8 downwards, compressing the first elastic element 9. The lower surface A of the pressure plate 8 presses against the top end face B of the piston 27, achieving reliable clamping. The function of the first elastic element 9 is twofold: first, to provide a certain pre-tightening buffer to prevent overpressure; and second, to assist in lifting the pressure plate 8 when it is released. When the handle I12 is rotated counterclockwise, the top block 11 rises, and under the restoring force of the first elastic element 9, the connecting block 10 and the pressure plate 8 rise accordingly, disengaging from the piston.

[0027] The sliding support assembly includes a slide rod 22, a second elastic element 17, a handle II 20, a handle III 21, and a caster wheel 23. The slide rod 22 is connected to the crossbeam 5 via bolts III 18 and nuts III 19, allowing the slide rod 22 to slide up and down within a certain range. The second elastic element 17 is fitted onto the slide rod 22, with its upper end abutting against the crossbeam 5 and its lower end abutting against a shoulder on the slide rod. The handle II 20 is threaded onto the crossbeam 5. The handle III 21 is connected to the slide rod 22, and the caster wheel 23 is threaded onto the bottom end of the slide rod 22.

[0028] Preferably, the first elastic element 9 and the second elastic element 17 are helical springs.

[0029] A limiting groove 28 is provided on the positioning plate 26. When the crossbeam 5 is in a non-working position, the bottom of its omnidirectional wheel 23 falls into the limiting groove 28.

[0030] Working principle and clamping process: Initial state (e.g.) Figure 4 When the crossbeam 5 is in the non-working position (raised state), nuts I6 and II15 are in a loose state. The first elastic element 9 and the second elastic element 17 are in a natural or slightly compressed state. At this time, under the action of the second elastic element 17, the bottom of the universal wheel 23 of the sliding support assembly falls into the limiting groove 28 on the base 1. This design provides the crossbeam 5 with a stable parking position when not in use, preventing it from swinging randomly.

[0031] Step 1: Place the piston. Hoist the piston 27 onto the positioning plate 26, ensuring its bottom stop aligns with the positioning stop of the positioning plate 26. Then rotate the piston 27 until the marking line on its side aligns with the positioning block 25, completing the piston's positioning.

[0032] Step 2: Rotate the crossbeam. The operator holds handle II20 with one hand and lifts handle III21 upwards with the other. Lifting handle III21 compresses the second elastic element 17, causing the slide bar 22 and caster wheel 23 to move upwards as a whole until the bottom of caster wheel 23 is completely disengaged from the limiting groove 28. At this point, while keeping handle III21 in the lifted state, pushing handle II20 will easily rotate the crossbeam 5 counterclockwise around the axis of bolt I7. Because caster wheel 23 has contacted the upper surface of base 1, the sliding friction has changed to rolling friction, greatly reducing the resistance.

[0033] Step 3: Lock the crossbeam. Continue to rotate the crossbeam 5. When a U-shaped groove on the crossbeam 5 passes over bolt II 16, and the X-side of the crossbeam 5 is in contact with the Y-side of the second column 14 (as shown in Figure 3), it indicates that the crossbeam 5 has reached the precise working position. At this time, the center of the pressure plate 8 coincides with the center of the piston 27. First, tighten nut II 15 so that the U-shaped groove of the crossbeam 5 locks bolt II 16 and is in contact with the Y-side, achieving lateral locking. Then tighten nut I 6 to further enhance the rigidity of the hinge point. After locking, handle III 21 can be released. The caster wheel 23 touches the ground slightly under the action of the second elastic element 17, but the main support and locking are now provided by bolt II 16 and nuts I 6 / II 15.

[0034] Step 4: Press the piston. Rotate handle I12 clockwise to activate the pressing mechanism, causing the pressure plate 8 to press down and finally firmly press against the top end face B of the piston 27, as shown. Figure 2 As shown. The clamping is now complete, and machining can begin.

[0035] The disassembly process is the reverse of the above process: first, rotate handle I12 in the opposite direction to release the piston; then, loosen nuts I6 and II15; rotate the crossbeam 5 clockwise to return it to its initial position, and the caster wheel 23 automatically falls into the limiting groove 28 under the action of the second elastic element 17; finally, lift away the processed piston and proceed to the next cycle.

[0036] This invention, through its ingenious structural design, achieves "lower positioning and upper clamping" of the piston, perfectly solving the problem of clamping deformation in the processing of thin-walled pistons, while greatly improving the efficiency and convenience of clamping operations.

[0037] It will be apparent to those skilled in the art that the present invention is not limited to the details of the exemplary embodiments described above, and that the invention can be implemented in other specific forms without departing from its spirit or essential characteristics. Therefore, the embodiments should be considered in all respects as exemplary and non-limiting, and the scope of the invention is defined by the appended claims rather than the foregoing description. Thus, all variations falling within the meaning and scope of equivalents of the claims are intended to be included within the present invention. No reference numerals in the claims should be construed as limiting the scope of the claims.

[0038] Furthermore, it should be understood that although this specification describes embodiments, not every embodiment contains only one independent technical solution. This narrative style is merely for clarity. Those skilled in the art should consider the specification as a whole, and the technical solutions in each embodiment can also be appropriately combined to form other embodiments that can be understood by those skilled in the art.

Claims

1. A positioning fixture for machining a piston pin bore, characterized by: It comprises a base (1), a positioning disc (26), a positioning block (25), a column, a crossbeam (5), a pressing mechanism and a sliding support assembly; The positioning disc (26) is fixedly installed on the base (1) and used for cooperating with the bottom stop of the piston (27) to position; The positioning block (25) is fixedly installed on the base (1) and used for circumferentially limiting the piston (27); The column is fixedly arranged on the base (1); The crossbeam (5) is rotatably connected to the column through a rotating shaft assembly; The pressing mechanism is arranged on the crossbeam (5) and used for pressing the top end surface of the piston (27) downward; The sliding support assembly is arranged on the crossbeam (5) and used for providing support during the rotation of the crossbeam (5); The base (1) is provided with an eye (2).

2. The positioning fixture for machining a piston pin bore according to claim 1, characterized in that: The column comprises a first column (4) and a second column (14) arranged at the same height, and the two ends of the crossbeam (5) are connected to the first column (4) and the second column (14) through the first rotating shaft assembly and the second rotating shaft assembly respectively; The first rotating shaft assembly comprises a bolt I (7) and a nut I (6), and one end of the crossbeam (5) is connected to the first column (4) through the bolt I (7) and the nut I (6); The second rotating shaft assembly comprises a bolt II (16) and a nut II (15) arranged on the second column (14), and when the crossbeam (5) is rotated to the working position, the U-shaped groove on the crossbeam (5) cooperates with the bolt II (16) and is locked by the nut II (15).

3. The positioning fixture for machining a piston pin bore according to claim 1, characterized in that: The pressing mechanism comprises a pressing disc (8), a connecting block (10), a top block (11), a first elastic member (9) and a sleeve (13); The crossbeam (5) is fixedly provided with the sleeve (13), the top block (11) and the sleeve (13) constitute a threaded pair, and the top block (11) is connected with a handle I (12) for driving the rotation of the top block (11); The lower end of the connecting block (10) is connected with the pressing disc (8), and the upper end of the connecting block (10) is connected with the top block (11); the upper end of the connecting block (10) is sleeved with the first elastic member (9), and the top block (11) drives the connecting block (10) and the pressing disc (8) to move along the vertical direction through the threaded pair.

4. The positioning fixture for machining a piston pin bore according to claim 3, characterized in that: The sliding support assembly comprises a handle II (20), a sliding rod (22), a second elastic member (17) and a universal wheel (23); the sliding rod (22) is connected to the crossbeam (5) in a slidable manner through a bolt III (18) and a nut III (19); the second elastic member (17) is sleeved on the sliding rod (22) to provide the sliding rod (22) with downward elastic force; the universal wheel (23) is installed at the bottom end of the sliding rod (22); and the handle II (20) is connected with the end of the crossbeam (5).

5. The positioning fixture for machining of a piston pin bore according to claim 4, characterized in that: The sliding support assembly further comprises a handle III (21), the handle III (21) is threadedly connected with the sliding rod (22), and is used for overcoming the elastic force of the second elastic member (17) to lift the sliding rod (22) and the universal wheel (23).

6. The positioning fixture for machining a piston pin bore according to claim 4, characterized in that: The first elastic member (9) and the second elastic member (17) are helical springs.

7. The positioning fixture for machining a piston pin bore according to claim 4, characterized in that: The base (1) is provided with a limiting groove (28), and the bottom of the universal wheel (23) falls into the limiting groove (28) when the cross beam (5) is in a non-working position.

8. The positioning fixture for machining of a piston pin bore according to claim 1, characterized in that: The positioning disc (26) is installed on the base (1) through a screw I (3), and the positioning block (25) is fixed on the base (1) through a screw II (24).

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