Fixture for piston without pattern draft on inner cavity side wall and implementation method

Abstract

According to the characteristic that the side wall of the inner cavity of the piston is free of the draft angle, the circular arc in the circumferential direction of the positioning face of the clamp is the same as the corresponding position of the piston, and the inner side wall of the piston 20 is tensioned through radial expansion and contraction of an expansion claw of the clamp; the circumferential shape and size of the clamp positioning point are the same as those of the side wall of the piston inner cavity, so that the positioning precision of the piston inner cavity is high; the expansion claws are high in expansion and contraction motion precision and are in symmetrical motion, under the condition that the actual size change of the side wall of the inner cavity of the piston blank is large, the positioning precision of the clamp is guaranteed, and the wall thickness difference of the inner cavity of the piston is accurately controlled; the clamp is provided with three pairs of expansion claws, expansion of the first pair of expansion claws at the front end of the clamp is driven by a machine tool spindle oil cylinder, the other two pairs of expansion claws are driven by springs in the clamp to generate expansion actions, and retraction actions are driven by the oil cylinder. The three pairs of tensioning claws synchronously act to tension the inner side wall of the piston 20, and the stroke of the tensioning claws is adjustable.

Description

Technical Field

[0001] The invention relates to the field of manufacturing aluminum pistons for internal combustion engines, and in particular to a clamp for a piston with no draft angle on the inner cavity side wall and a realization method thereof. Background Art

[0002] The aluminum piston of an internal combustion engine is generally inlaid with a high-nickel cast iron ring on the outer circle of the head. The cast iron ring is cast together with the aluminum body of the piston during the piston casting; an annular internal cooling oil channel is cast inside the head, as shown in the attached Figure 1 As shown in the figure, the inner edge of the piston pin hole is generally designed with machined chamfers, and the outer edge of the piston pin hole is designed with chamfers. When the piston wall thickness difference is large, it will cause the following problems: Figure 2 As shown in the figure, the inclination and position of the high nickel cast iron ring are difficult to meet the design requirements, causing the problem of uneven thickness of the cast iron material on the upper and lower sides of the cast iron ring groove. In severe cases, there will be no cast iron material to be processed on the lower side of the iron ring groove; it will also cause the annular internal cooling oil channel in the head to deviate beyond the tolerance, causing poor cooling of the piston head and causing perforation during engine operation; as shown in the attached figure Figure 3 As shown, it will also cause the inner and outer casting surfaces of the piston to deviate, leading to poor symmetry of the machined chamfers of the inner edge of the piston pin hole and the outer chamfers of the piston pin hole. The rest of the machined surfaces of the piston where they meet the casting surfaces will be deviated. The thickness of the inner top of the internal combustion engine piston has a direct impact on the weight of the finished piston, and should be strictly controlled during the machining process, otherwise the piston weight will be unqualified.

[0003] However, in actual production, the inner top surface of the piston is a non-machined casting surface, and the top surface of the piston is a machined surface. The piston top thickness is the distance from the inner top center casting surface to the machined top surface of the piston. Generally, the tolerance requirement is high. Due to the large casting tolerance, it is difficult to control the final top thickness tolerance, which ultimately affects the product weight. Summary of the invention

[0004] The purpose of the present invention is to provide a clamp and implementation method for a piston with no draft angle on the inner cavity side wall in view of the above-mentioned prior art problems.

[0005] A clamp for a piston with no draft angle on the inner cavity side wall, comprising a clamp body, a short-axis front cone top rod, a short-axis front expansion claw, a short-axis rear cone top rod, a short-axis rear expansion claw, a long-axis rear cone top rod, a long-axis rear expansion claw, a long-axis spring, a short-axis rear end spring, a pull ring, a pull plate, a sleeve, a retaining ring, a pull rod, a front end cover plate, an internally threaded cylindrical pin, a hexagonal flange nut, a hexagonal thin nut, and a screw;

[0006] The clamp body comprises a conical surface, a short axis front cone guide hole, a short axis rear cone guide hole, a long axis rear cone guide hole, a front expansion claw guide square hole, a rear expansion claw guide square hole, a rear expansion claw guide stepped square hole, a pull plate guide hole, a retaining ring mounting hole, a connection assembly stopper, and a positioning pin hole;

[0007] The clamp body is connected via the short-axis front cone guide hole and the short-axis front cone ejector rod;

[0008] The clamping body is connected via a short-axis front cone guide hole and a short-axis rear cone top rod;

[0009] The clamp body is connected via a long-axis rear cone guide hole and a long-axis rear cone top rod;

[0010] The clamp body is connected with the short-shaft front expansion claw through the front expansion claw guide square hole;

[0011] The clamp body is connected with the short-shaft rear expansion claw through the rear expansion claw guide square hole;

[0012] The clamp body is connected with the long-axis rear expansion claw through the rear expansion claw guide stepped square hole;

[0013] The clamp body fixes the retaining ring through the retaining ring mounting hole;

[0014] The long-axis rear cone top rod is connected to the short-axis rear end spring, the sleeve and the long-axis spring are assembled in the long-axis rear cone top rod, the pull ring and the pull plate are fixed, the internal threaded cylindrical pin is connected to the clamp and the pull ring respectively, the pull rod is installed on the pull plate, the front end cover plate is arranged in front of the clamp, and the hexagonal flange nut and the hexagonal thin nut lock the short-axis front cone top rod.

[0015] Further, a fixture for a piston with no draft angle on the inner cavity side wall, the short-axis front cone ejector rod comprises a short-sleeved front cone outer circle, a short-sleeved rear sliding cylinder, a short front rod dovetail groove, a positioning cylinder, and a locking thread;

[0016] The short-axis rear cone ejector rod comprises a short-sleeved rear cone outer circle, an ejector rod guide hole, a short rear rod dovetail groove, and a short-sleeved rear cylindrical surface;

[0017] The long-axis rear cone top rod comprises a long-axis rear cone outer circle, a long rear rod dovetail groove, a long-axis rear hole, and a long sleeve spring hole;

[0018] The short-axis front expansion claw comprises a short front expansion claw square surface and a short front claw dovetail groove;

[0019] The short-axis rear expansion claw comprises a short rear expansion claw square surface and a short rear claw dovetail groove;

[0020] The long-axis rear expansion claw comprises a long rear expansion claw stepped square surface and a long rear claw dovetail groove;

[0021] The pull plate comprises a pull plate outer circle, a pull plate upper hole, a spring mounting annular countersunk hole, and a pull plate countersunk hole;

[0022] The guide hole of the short-axis front cone and the outer circle clearance of the short-sleeved front cone are matched, so that the short-axis front cone ejector rod can slide freely axially on the clamp body;

[0023] The short-shaft rear cone guide hole and the short-sleeve rear cone outer circle clearance match each other, so that the short-shaft rear cone top rod can slide freely axially on the clamp body;

[0024] The long-axis rear cone guide hole and the long-axis rear cone outer circle clearance match each other, so that the long-axis rear cone top rod can slide freely axially on the clamp body;

[0025] The square hole of the front expansion claw guide and the square surface of the short front expansion claw are clearance-matched, so that the short-axis front expansion claw can slide freely axially on the clamp body;

[0026] The square hole of the rear expansion claw guide and the square surface of the short rear expansion claw are clearance-matched, so that the short-axis rear expansion claw can slide freely axially on the clamp body;

[0027] The rear expansion claw guide stepped square hole and the long rear expansion claw stepped square surface are clearance-matched, so that the long-axis rear expansion claw can slide freely axially on the clamp body;

[0028] The pull plate guide hole and the outer circle of the pull plate are clearance-matched, so that the pull plate can slide freely axially on the clamp body.

[0029] Further, a fixture for a piston with no draft angle on the inner cavity side wall, the retaining ring comprises a retaining ring outer circle and a stroke adjustment threaded hole;

[0030] The conical surface of the clamping body is in contact with the long axis positioning points N2-0 and N2-1 of the piston inner cavity for positioning;

[0031] The connection assembly stop of the clamp body is connected and fixed to the machine tool spindle by screws;

[0032] The retaining ring mounting hole and the retaining ring outer circle are assembled and fixed to limit the axial sliding limit travel position of the pulling plate.

[0033] Furthermore, a fixture for a piston with no draft angle on the inner cavity side wall, wherein the short-axis front cone guide hole and the short-sleeve front cone outer circle clearance cooperate to ensure the movement accuracy of the short-axis front cone ejector rod in the short-axis front cone guide hole;

[0034] The ejector rod guide hole and the short-sleeved rear sliding cylindrical surface are clearance-matched to ensure the movement accuracy of the short-axis rear cone ejector rod in the ejector rod guide hole.

[0035] Further, a fixture for a piston with a side wall of an inner cavity having no draft angle, the sleeve comprises an outer cylindrical surface of the sleeve;

[0036] The pull ring comprises a pull ring cylindrical surface and an anti-rotation positioning pin hole;

[0037] The outer cylindrical surface of the sleeve is sleeved in the rear hole of the long axis, the rear hole of the long axis is sleeved on the rear cylindrical surface of the short sleeve, the long axis spring is installed in the spring hole of the long sleeve, and the long axis spring is sleeved on the outer cylindrical surface of the sleeve;

[0038] The positioning cylinder surface and the upper hole of the pull plate are assembled and connected, and the short shaft front cone ejector rod and the pull plate are fastened by locking threads and locking nuts;

[0039] The cylindrical surface of the pull ring is assembled in the countersunk hole of the pull disc, and the pull ring and the pull disc are fixed by screws;

[0040] One end of the internal threaded cylindrical pin is installed in the positioning pin hole of the clamp body with an interference fit, and the other end of the internal threaded cylindrical pin is installed in the anti-rotation positioning pin hole on the pull ring with a clearance fit, so that the pull ring can slide freely along the axial direction of the internal threaded cylindrical pin.

[0041] Furthermore, a clamp for a piston with no draft angle on the inner cavity side wall, the end surface K7 of the short shaft rear cone top rod is connected to the short shaft rear end spring, and the short shaft rear expansion claw is pushed to move radially outward to tighten the positioning point of the inner cavity side wall of the piston under the action of the spring force;

[0042] The long axis spring pushes the long axis rear cone top rod to move axially forward, and the long axis rear rod dovetail groove of the long axis rear cone top rod drives the long axis rear expansion claw to slide radially outward to tighten the positioning point of the piston inner cavity side wall;

[0043] One end of the long axis spring is in contact with the end surface K8 of the long sleeve spring hole, and the other end of the long axis spring is in contact with the bottom surface K9 of the spring mounting annular countersunk hole. Under the elastic force of the long axis spring, the long axis rear cone top rod pushes the long axis rear expansion claw to move radially outward to the positioning point on the inner cavity side wall of the tensioning piston through the long rear rod dovetail groove;

[0044] The spring at the rear end of the short shaft pushes the short shaft rear cone top rod to move axially forward, and the short shaft rear expansion claw is driven by the short rear rod dovetail groove of the short shaft rear cone top rod to slide radially outward to tighten the positioning point of the piston inner cavity side wall.

[0045] Furthermore, a clamp for a piston with no draft angle on the inner cavity side wall, wherein two short front rod dovetail grooves are arranged on the short shaft front cone ejector rod, the two short front rod dovetail grooves and the short front claw dovetail groove have a sliding clearance fit, and the conical surface K1 on the short shaft front cone ejector rod and the inclined surface K4 on the short shaft front expansion claw contact each other, which are relative sliding surfaces and are force-bearing surfaces during operation;

[0046] When the short-shaft front cone push rod moves axially forward and backward, the short-shaft front expansion claw is driven to perform radial expansion and contraction movement in the front expansion claw guide square hole of the clamp body through the short front rod dovetail groove, thereby tightening or loosening the positioning points N4-0 and N4-1 on the side wall of the piston inner cavity;

[0047] The short-axis rear cone top rod is provided with two short-axis rear rod dovetail grooves, and the two short-axis rear rod dovetail grooves are matched with the short-axis rear claw dovetail groove sliding clearance, and the conical surface K2 on the short-axis rear cone top rod and the inclined surface K5 on the short-axis rear expansion claw contact each other, which are relative sliding surfaces and are force-bearing surfaces during operation;

[0048] When the short-axis rear cone top rod moves axially forward and backward, the short-axis rear expansion claw is driven to perform radial expansion and contraction movement in the rear expansion claw guide square hole of the clamp body through the short rear rod dovetail groove, thereby tightening or loosening the positioning points N3-0 and N3-1 on the side wall of the piston inner cavity;

[0049] The long-axis rear cone top rod is provided with two long rear rod dovetail grooves, and the two long rear rod dovetail grooves are matched with the long front claw dovetail grooves in sliding clearance, and the conical surface K3 on the long-axis rear cone top rod and the inclined surface K6 on the long-axis rear expansion claw are in contact with each other, which are relative sliding surfaces and are force-bearing surfaces during operation;

[0050] When the long-axis rear cone top rod moves axially forward and backward, the long-axis rear expansion claw is driven to perform radial expansion and contraction movement in the rear expansion claw guide stepped square hole of the clamp body through the long rear rod dovetail groove, thereby tightening or loosening the piston inner cavity side wall positioning points N1-0 and N1-1.

[0051] Further, a clamp for a piston with no draft angle on the inner cavity side wall, the tie rod comprises a tie rod assembly stop and a tie rod thread;

[0052] The pull plate and the pull ring are assembled to form a movement space for the long-axis rear cone top rod, which is used to limit the axial movement stroke of the long-axis rear cone top rod;

[0053] During the loosening process, the pull ring is used to pull the long-axis rear cone top rod to move backward, driving the long-axis rear expansion claw to retract and loosen the piston;

[0054] During the clamping process, the pull plate moves forward under the push of the pull rod, and the axial travel restriction of the pull ring on the long-axis rear cone top rod is automatically cancelled. The pull plate compresses the long-axis spring. Under the action of the spring force, the long-axis rear cone top rod pushes the long-axis rear expansion claw to slide outward through the inclined surface of the long-axis rear rod dovetail groove, tightening the side wall of the inner cavity of the piston;

[0055] The sleeve isolates the long-axis spring and the short-axis rear end spring to prevent mutual interference during movement.

[0056] Further, a clamp for a piston with no draft angle on the inner cavity side wall, the retaining ring limits the movement stroke of the pull plate, and the stroke position of the pull plate is adjusted by adjusting the position of the threaded hole by adjusting the stroke;

[0057] The rear end of the pull rod is connected to the main shaft cylinder pull rod through the pull rod thread, transmitting the thrust or pulling force of the main shaft cylinder to provide movement for the clamp;

[0058] The front end cover plate prevents chips from entering the interior of the clamp body;

[0059] The internally threaded cylindrical pin limits the pull ring from rotating during movement.

[0060] A method for realizing a fixture for a piston without a draft angle on the inner cavity side wall, comprising the following steps:

[0061] S1: The clamping position and release position before processing:

[0062] S11: The main shaft cylinder pull rod retracts, driving the short shaft front cone push rod to move to the right and drive the short shaft front expansion claw to retract toward the center through the short front rod dovetail groove;

[0063] S12: The step surface K10 on the short-shaft front cone push rod drives the short-shaft rear cone push rod (4) to move rightward, and drives the short-shaft rear expansion claw to retract toward the center through the dovetail groove of the short rear rod;

[0064] S13: At the same time, the short-axis front cone top rod, the pull plate, the pull ring, and the pull rod are connected and fixed as a whole by screws and nuts. When the short-axis front cone top rod moves to the right, the pull ring also moves to the right and drives the long-axis rear cone top rod to move to the right through the step surface K11 on the long-axis rear cone top rod;

[0065] S14: The dovetail groove of the long-axis rear cone top rod drives the long-axis rear expansion claw to retract the pull rod toward the center, and the limit position of the rightward movement is controlled by the limit screw on the retaining ring;

[0066] S2: The inner cavity of the piston is inserted into the fixture:

[0067] S21: The positioning points N2-0 and N2-1 in the long axis direction of the piston are aligned with the conical surface of the clamping body, and the main shaft cylinder moves to the left, driving the pull rod, pull plate, pull ring, and short shaft front cone ejector rod to move to the left as a whole:

[0068] S22: The pull ring moves to the left to release the step surface K11 of the long-axis rear cone top rod. The long-axis spring pushes the long-axis rear cone top rod to the left under the action of the spring force. The long-axis rear rod dovetail groove on the long-axis rear cone top rod pushes the two long-axis rear expansion claws to expand to both sides and tighten the positioning points N1-0 and N1-1 on the inner cavity side wall of the tensioning piston at the same time.

[0069] S23: The short-shaft front cone push rod moves to the left, and the upper step surface K10 is released from the short-shaft rear cone push rod. The short-shaft rear cone push rod moves to the left under the action of the spring force of the short-shaft rear end spring, and pushes the two short-shaft rear expansion claws to expand out of the tension piston inner cavity side wall positioning points N3-0 and N3-1 to both sides through the short rear rod dovetail groove of the short-shaft rear cone push rod; S24: The short-shaft front cone push rod moves to the left, and pushes the two short-shaft front expansion claws to expand out of the tension piston inner cavity side wall positioning points N4-0 and N4-1 to both sides through the short rear rod dovetail groove;

[0070] S25: The tailstock pressure plate presses the top surface, the piston is in an accurately positioned and reliably clamped state, and the outer circle and top surface of the piston can be rough-machined.

[0071] The beneficial effects of the present invention are as follows: through a clamp and an implementation method for a piston with no draft angle on the inner cavity side wall, according to the characteristic that the inner cavity side wall of the piston has no draft angle, the arc of the clamp positioning surface in the circumferential direction is the same as the corresponding position of the piston, and the radial expansion and contraction of the clamp's own claws are used to clamp the inner wall of the piston; the circumferential shape and size of the clamp positioning point are the same as the corresponding position of the inner cavity side wall of the piston, so that the positioning accuracy of the piston inner cavity is relatively high; in the case that the actual size of the inner cavity side wall of the piston blank changes greatly, because the expansion and contraction movement of the clamp claws is high in accuracy and is symmetrical, the positioning accuracy of the clamp is guaranteed and the wall thickness difference of the inner cavity of the piston is accurately controlled; the clamp has three pairs of claws, the expansion and contraction of the first pair of claws at the front end of the clamp is driven by the machine tool spindle cylinder, and the other two pairs of claws are driven by springs in the clamp to produce an expansion action, while the retraction action is driven by the cylinder. BRIEF DESCRIPTION OF THE DRAWINGS

[0072] Figure 1 It is a schematic diagram of the structure of an aluminum piston in an internal combustion engine.

[0073] Figure 2 It is a schematic diagram of the deflection of the high nickel cast iron ring and the annular inner coolant oil channel.

[0074] Figure 3 This is a schematic diagram showing that the chamfered corners on the inner side of the pin hole and the chamfered corners on the outer side of the piston pin hole are of different sizes.

[0075] Figure 4 Schematic diagram of the piston inner cavity side wall without draft angle.

[0076] Figure 5 The present invention is a schematic diagram of a fixture structure for a piston with no draft angle on the inner cavity side wall.

[0077] Figure 6 It is a schematic diagram of the specific structure of the clamp.

[0078] Figure 7 It is a schematic diagram of the short-axis front cone push rod structure.

[0079] Figure 8 It is a schematic diagram of the short-axis rear cone push rod structure.

[0080] Fig. 9 It is a schematic diagram of the long-axis rear cone top rod structure.

[0081] Fig.10 It is a schematic diagram of the short-axle front expansion claw structure.

[0082] Fig.11 It is a schematic diagram of the short-axle rear expansion claw structure.

[0083] Fig.12 It is a schematic diagram of the long-axis rear expansion claw structure.

[0084] Fig.13 It is a schematic diagram of the pull plate structure.

[0085] Fig.14 It is a schematic diagram of the retaining ring structure.

[0086] Fig.15 It is a schematic diagram of the structure.

[0087] Fig.16 It is a schematic diagram of the pull ring structure.

[0088] Fig.17 It is a schematic diagram of the pull rod structure.

[0089] Fig.18 This is a schematic diagram of the clamping position and the released position before processing.

[0090] Fig.19 It is a schematic diagram of the state where the inner cavity of the piston is inserted into the fixture.

[0091] In the figure, I1-piston head, I2-piston pin hole, I3-high nickel cast iron ring, I4-annular internal cooling oil channel, I5-outer chamfer of piston pin hole, I6-inner chamfer of pin hole, I7-high nickel cast iron ring is skewed, I8-annular internal cooling oil channel is skewed, I9-inner chamfer of pin hole is of different sizes, I10-outer chamfer of piston pin hole is of different sizes.

[0092] In the figure, 1-clamp body, 2-short shaft front cone top rod, 3-short shaft front expansion claw, 4-short shaft rear cone top rod, 5-short shaft rear expansion claw, 6-long shaft rear cone top rod, 7-long shaft rear expansion claw, 8-long shaft spring, 9-short shaft rear end spring, 10-pull ring, 11-pull plate, 12-sleeve, 13-blocking ring, 14-pull rod, 15-front end cover plate, 16-inner threaded cylindrical pin, 17-hexagonal flange nut, 18-hexagonal thin nut, 19-screw, 20-piston.

[0093] In the figure, BA1-conical surface, BA3-short front rod dovetail groove, BA5-short rear rod dovetail groove, BA7-long rear rod dovetail groove, BA9-short front claw dovetail groove, BA11-short rear claw dovetail groove, BA13-long rear claw dovetail groove.

[0094] In the figure, BD1-short shaft front cone guide hole, BD2-short shaft rear cone guide hole, BD3-long shaft rear cone guide hole, BD4-pull plate guide hole, BD5-blocking ring mounting hole, BD6-connecting assembly stop, BD9-locating pin hole, BD11-short sleeve front cone outer circle, BD12-short sleeve rear sliding cylinder, BD13-locating cylinder, BD14-locking thread, BD15-short sleeve rear cone outer circle, BD16-top rod guide hole, BD17-short sleeve rear cylindrical surface, BD18-long shaft rear cone outer circle, BD19-long shaft rear hole, BD20-long sleeve spring hole, BD22-pull plate outer circle, BD23-pull plate countersunk hole, BD25-pull plate upper hole, BD26-pull rod assembly stop, BD30-blocking ring outer circle, BD33-sleeve outer cylindrical surface, BD37-pull ring cylindrical surface, BD38-anti-rotation locating pin hole, BD41-pull rod thread.

[0095] In the figure, BL1-front expansion claw guide square hole, BL3-rear expansion claw guide square hole, BL5-rear expansion claw guide stepped square hole, BL7-spring mounting annular countersunk hole, BL9-short front expansion claw square surface, BL11-short rear expansion claw square surface, BL13-long rear expansion claw stepped square surface. DETAILED DESCRIPTION

[0096] In order to have a clearer understanding of the technical features, purposes and effects of the present invention, specific embodiments of the present invention are now described with reference to the accompanying drawings.

[0097] As attached Figure 4 As shown, by combing through the structural characteristics of existing aluminum pistons, for a piston with no draft angle on the inner cavity side wall, it is necessary to use the inner cavity side wall of the piston 20 blank as a positioning reference in the rough turning process of the outer circle and the top surface of the blank, so as to better control the axial centerline position accuracy of the inner cavity surface of the piston 20 and ultimately ensure the piston wall thickness difference.

[0098] As attached Figures 5-6 As shown, it is specifically a clamp for a piston with no draft angle on the inner cavity side wall, including a clamp body 1, a short shaft front cone top rod 2, a short shaft front expansion claw 3, a short shaft rear cone top rod 4, a short shaft rear expansion claw 5, a long shaft rear cone top rod 6, a long shaft rear expansion claw 7, a long shaft spring 8, a short shaft rear end spring 9, a pull ring 10, a pull plate 11, a sleeve 12, a retaining ring 13, a pull rod 14, a front end cover plate 15, an internal thread cylindrical pin 16, a hexagonal flange nut 17, a hexagonal thin nut 18, and a screw 19;

[0099] The clamp body 1 includes a conical surface BA1, a short axis front cone guide hole BD1, a short axis rear cone guide hole BD2, a long axis rear cone guide hole BD3, a front expansion claw guide square hole BL1, a rear expansion claw guide square hole BL3, a rear expansion claw guide stepped square hole BL5, a pull plate guide hole BD4, a retaining ring mounting hole BD5, a connection assembly stop BD6, and a positioning pin hole BD9;

[0100] The clamp body 1 is connected with the short-axis front cone guide hole BD1 and the short-axis front cone top rod 2;

[0101] The clamp body 1 is connected via the short-axis front cone guide hole BD1 and the short-axis rear cone top rod 4;

[0102] The clamp body 1 is connected via the long-axis rear cone guide hole BD3 and the long-axis rear cone top rod 6;

[0103] The clamp body 1 is connected to the short-axis front expansion claw 3 through the front expansion claw guide square hole BL1;

[0104] The clamp body 1 is connected to the short-axis rear expansion claw 5 through the rear expansion claw guide square hole BL3;

[0105] The clamp body 1 is connected to the long-axis rear expansion claw 7 through the rear expansion claw guide stepped square hole BL5;

[0106] The clamp body 1 fixes the retaining ring 13 through the retaining ring mounting hole BD5;

[0107] The long-axis rear cone top rod 6 is connected to the short-axis rear end spring 9, the sleeve 12 and the long-axis spring 8 are assembled in the long-axis rear cone top rod 6, the pull ring 10 and the pull plate 11 are fixed, the internal threaded cylindrical pin 16 is respectively connected to the clamp 1 and the pull ring 10, the pull rod 14 is installed on the pull plate 11, the front end cover plate 15 is arranged in front of the clamp body 1, and the hexagonal flange nut 17 and the hexagonal thin nut 18 lock the short-axis front cone top rod 2.

[0108] As attached Figures 7 to 13 As shown, a clamp for a piston with no draft angle on the inner cavity side wall, the short-axis front cone ejector rod 2 includes a short-sleeved front cone outer circle BD11, a short-sleeved rear sliding cylinder BD12, a short front rod dovetail groove BA3, a positioning cylinder BD13, and a locking thread BD14;

[0109] The short-axis rear cone push rod 4 includes a short-sleeved rear cone outer circle BD15, a push rod guide hole BD16, a short rear rod dovetail groove BA5, and a short-sleeved rear cylindrical surface BD17;

[0110] The long-axis rear cone top rod 6 includes a long-axis rear cone outer circle BD18, a long rear rod dovetail groove BA7, a long-axis rear hole BD19, and a long sleeve spring hole BD20;

[0111] The short-axis front expansion claw 3 includes a short front expansion claw square surface BL9 and a short front claw dovetail groove BA9;

[0112] The short-axis rear expansion claw 5 includes a short rear expansion claw square surface BL11 and a short rear claw dovetail groove BA11;

[0113] The long-axis rear expansion claw 7 includes a long rear expansion claw stepped square surface BL13 and a long rear claw dovetail groove BA13;

[0114] The pull plate 11 includes a pull plate outer circle BD22, a pull plate upper hole BD25, a spring mounting annular countersunk hole BL7, and a pull plate countersunk hole BD23;

[0115] The short-axis front cone guide hole BD1 and the short-sleeve front cone outer circle BD11 are clearance-matched, so that the short-axis front cone top rod 2 can slide freely axially on the clamp body 1;

[0116] The short-axis rear cone guide hole BD2 and the short-axis rear cone outer circle BD15 are clearance-matched, so that the short-axis rear cone top rod 4 can slide freely axially on the clamp body 1;

[0117] The long-axis rear cone guide hole BD3 and the long-axis rear cone outer circle BD18 are clearance-matched, so that the long-axis rear cone top rod 6 can slide freely axially on the clamp body 1;

[0118] The front expansion claw guide square hole BL1 and the short front expansion claw square surface BL9 are clearance-matched, so that the short-axis front expansion claw 3 can slide freely axially on the clamp body 1;

[0119] The rear expansion claw guide square hole BL3 and the short rear expansion claw square surface BL11 are clearance-matched, so that the short-axis rear expansion claw 5 can slide freely axially on the clamp body 1;

[0120] The rear expansion claw guide stepped square hole BL5 and the long rear expansion claw stepped square surface BL13 are clearance-matched, so that the long-axis rear expansion claw 7 can slide freely axially on the clamp body 1;

[0121] The pull plate guide hole BD4 and the pull plate outer circle BD22 are clearance-matched, so that the pull plate 11 can slide freely axially on the clamp body 1.

[0122] As attached Fig.14 As shown, a clamp for a piston with no draft angle on the inner cavity side wall, the retaining ring 13 includes a retaining ring outer circle BD30 and a stroke adjustment threaded hole;

[0123] The conical surface BA1 of the clamp body 1 is in contact with the long axis positioning points N2-0 and N2-1 of the inner cavity of the piston 20 for positioning;

[0124] The connection assembly stop BD6 of the clamp body 1 is connected and fixed to the machine tool spindle by screws 19;

[0125] The retaining ring mounting hole BD5 and the retaining ring outer circle BD30 are assembled and fixed to limit the axial sliding limit stroke position of the pulling plate 11.

[0126] Furthermore, a fixture for a piston with no draft angle on the inner cavity side wall, wherein the short-axis front cone guide hole BD1 and the short-sleeved front cone outer circle BD11 are clearance-matched to ensure the movement accuracy of the short-axis front cone ejector rod 2 in the short-axis front cone guide hole BD1;

[0127] The push rod guide hole BD16 and the short-sleeved rear sliding cylinder BD12 are clearance-matched to ensure the movement accuracy of the short-axis rear cone push rod 4 in the push rod guide hole BD16.

[0128] As attached Figures 14 to 16 As shown, a clamp for a piston with no draft angle on the inner cavity side wall, the sleeve 12 includes a sleeve outer cylindrical surface BD33;

[0129] The pull ring includes a pull ring cylindrical surface BD37 and an anti-rotation positioning pin hole BD38;

[0130] The outer cylindrical surface BD33 of the sleeve is sleeved in the long-axis rear hole BD19, the long-axis rear hole BD19 is sleeved on the short-sleeve rear cylindrical surface BD17, the long-axis spring 8 is installed in the long-sleeve spring hole BD20, and the long-axis spring 8 is sleeved on the outer cylindrical surface BD33 of the sleeve;

[0131] The positioning cylinder BD13 and the upper hole BD25 of the pull plate are assembled and connected, and the short shaft front cone ejector rod 2 and the pull plate 11 are fastened by the locking thread BD14 and the locking nut;

[0132] The pull ring cylindrical surface BD37 is assembled in the pull plate counterbore BD23, and the pull ring 10 and the pull plate 11 are fixed by screws 19;

[0133] One end of the internal threaded cylindrical pin 16 is installed in the positioning pin hole BD9 of the clamp body 1 with an interference fit, and the other end of the internal threaded cylindrical pin 16 is installed in the anti-rotation positioning pin hole BD38 on the pull ring 10 with a clearance fit, so that the pull ring 10 can slide freely along the axial direction of the internal threaded cylindrical pin 16.

[0134] Furthermore, a clamp for a piston with no draft angle on the inner cavity side wall, the end surface K7 of the short-shaft rear cone top rod 4 is connected to the short-shaft rear end spring 9, and the short-shaft rear expansion claw 5 is pushed radially outward to move the positioning point of the inner cavity side wall of the tensioning piston 20 under the action of the spring force;

[0135] The long axis spring 8 pushes the long axis rear cone top rod 6 to move axially forward, and the long rear rod dovetail groove BA7 of the long axis rear cone top rod 6 drives the long axis rear expansion claw 7 to slide radially outward to tighten the positioning point of the inner cavity side wall of the piston 20;

[0136] One end of the long axis spring 8 is in contact with the end surface K8 of the long sleeve spring hole BD20, and the other end of the long axis spring 8 is in contact with the bottom surface K9 of the spring mounting annular countersunk hole BL7. Under the elastic force of the long axis spring 8, the long axis rear cone top rod 6 pushes the long axis rear expansion claw 7 to move radially outward to the positioning point on the inner cavity side wall of the tensioning piston 20 through the long rear rod dovetail groove BA7;

[0137] The short shaft rear end spring 9 pushes the short shaft rear cone top rod 4 to move axially forward, and the short shaft rear dovetail groove BA5 of the short shaft rear cone top rod 4 drives the short shaft rear expansion claw 5 to slide radially outward to tighten the positioning point of the inner cavity side wall of the piston 20.

[0138] Furthermore, a clamp for a piston with no draft angle on the inner cavity side wall, wherein two short front rod dovetail grooves BA3 are arranged on the short shaft front cone push rod 2, and the two short front rod dovetail grooves BA3 and the short front claw dovetail groove BA9 are matched with sliding clearances, and the conical surface K1 on the short shaft front cone push rod 2 and the inclined surface K4 on the short shaft front expansion claw 3 are in contact with each other, which are relative sliding surfaces and are force-bearing surfaces during operation;

[0139] When the short-axis front cone push rod 2 moves axially forward and backward, the short-axis front expansion claw 3 is driven to perform radial expansion and contraction movement in the front expansion claw guide square hole BL1 of the clamp body 1 through the short front rod dovetail groove BA3, thereby tightening or loosening the positioning points N4-0 and N4-1 on the inner cavity side wall of the piston 20;

[0140] The short-axis rear cone top rod 4 is provided with two short-axis rear rod dovetail grooves BA5, and the two short-axis rear rod dovetail grooves BA5 are matched with the short-axis rear claw dovetail groove BA11 in a sliding clearance. The conical surface K2 on the short-axis rear cone top rod 4 and the inclined surface K5 on the short-axis rear expansion claw 5 are in contact with each other, which are relative sliding surfaces and are force-bearing surfaces during operation.

[0141] When the short-axis rear cone top rod 4 moves axially forward and backward, the short-axis rear expansion claw 5 is driven to perform radial expansion and contraction movement in the rear expansion claw guide square hole BL3 of the clamp body 1 through the short rear rod dovetail groove BA5, thereby tightening or loosening the positioning points N3-0 and N3-1 on the inner cavity side wall of the piston 20;

[0142] The long-axis rear cone top rod 6 is provided with two long rear rod dovetail grooves BA7, and the two long rear rod dovetail grooves BA7 are matched with the long front claw dovetail groove BA13 in sliding clearance, and the conical surface K3 on the long-axis rear cone top rod 6 and the inclined surface K6 on the long-axis rear expansion claw 7 are in contact with each other, which are relative sliding surfaces and are force-bearing surfaces during operation;

[0143] When the long-axis rear cone top rod 6 moves axially forward and backward, it drives the long-axis rear expansion claw 7 to perform radial expansion and contraction movement in the rear expansion claw guide stepped square hole BL5 of the clamp body through the long rear rod dovetail groove BA7, thereby tightening or loosening the positioning points N1-0 and N1-1 on the inner cavity side wall of the piston 20.

[0144] As attached Fig.17 As shown, a clamp for a piston with no draft angle on the inner cavity side wall, the pull rod includes a pull rod assembly stop BD26 and a pull rod thread BD41;

[0145] The pull plate 11 and the pull ring 10 are assembled to form a movement space for the long-axis rear cone top rod 6, which is used to limit the axial movement stroke of the long-axis rear cone top rod 6;

[0146] During the release process, the pull ring 10 pulls the long-axis rear cone top rod 6 to move backward, driving the long-axis rear expansion claw 7 to retract and release the piston 20;

[0147] During the clamping process, the pull plate 11 moves forward under the push of the pull rod 14, and the axial travel restriction of the pull ring 10 on the long-axis rear cone top rod 6 is automatically cancelled. The pull plate 11 compresses the long-axis spring 8. Under the action of the spring force, the long-axis rear cone top rod 6 pushes the long-axis rear expansion claw 7 to slide outward through the inclined surface of the long-axis rear rod dovetail groove BA7, tightening the inner cavity side wall of the piston 20;

[0148] The sleeve 12 isolates the long-axis spring 8 and the short-axis rear end spring 9 to prevent mutual interference during movement.

[0149] Further, a clamp for a piston with no draft angle on the inner cavity side wall, the retaining ring 13 limits the movement stroke of the pull plate 11, and the stroke position of the pull plate 11 is adjusted by adjusting the stroke adjustment threaded hole position;

[0150] The rear end of the pull rod 14 is connected to the main shaft cylinder pull rod through the pull rod thread BD41, transmitting the thrust or pulling force of the main shaft cylinder to provide movement for the clamp;

[0151] The front end cover plate 15 prevents chips from entering the interior of the clamp body 1;

[0152] The internally threaded cylindrical pin 16 limits the pull ring 10 from rotating during the movement.

[0153] A method for realizing a fixture for a piston without a draft angle on the inner cavity side wall, comprising the following steps:

[0154] As attached Fig.18 As shown, S1: the clamping position and the release position before processing:

[0155] S11: The main shaft cylinder pull rod retracts, driving the short shaft front cone push rod 2 to move to the right through the short front rod dovetail groove BA3 to drive the short shaft front expansion claw 3 to retract toward the center;

[0156] S12: The step surface K10 on the short-shaft front cone push rod 2 drives the short-shaft rear cone push rod (4) to move rightward, and drives the short-shaft rear expansion claw 5 to retract toward the center through the short rear rod dovetail groove BA5;

[0157] S13: At the same time, the short-axis front cone top rod 2, the pull plate 11, the pull ring 10, and the pull rod 14 are connected and fixed as a whole by screws and nuts. When the short-axis front cone top rod 2 moves to the right, the pull ring 10 also moves to the right and drives the long-axis rear cone top rod 6 to move to the right through the step surface K11 on the long-axis rear cone top rod 6;

[0158] S14: The long rear rod dovetail groove BA7 of the long-axis rear cone top rod 6 drives the long-axis rear expansion claw 7 to retract the pull rod 14 toward the center, and the limit position of the rightward movement is controlled by the limit screw on the retaining ring 13;

[0159] As attached Fig.19 As shown, S2: the inner cavity of the piston 20 is inserted into the fixture:

[0160] S21: The long axis direction positioning points N2-0 and N2-1 of the piston 20 are fitted and positioned with the conical surface BA1 of the clamp body 1. At this time, the gaps between the inner wall of the piston and the clamp body 1, the long axis rear expansion claw 7, the short axis front expansion claw 3, and the short axis rear expansion claw 5 are Wa, Wb, and Wc. The main shaft cylinder moves to the left, driving the pull rod 14, the pull plate 11, the pull ring 10, and the short axis front cone push rod 2 to move to the left as a whole:

[0161] S22: The pull ring 10 moves to the left to release the step surface K11 of the long-axis rear cone top rod 6. The long-axis spring 8 pushes the long-axis rear cone top rod 6 to move to the left under the action of the spring force. The long rear rod dovetail groove BA7 on the long-axis rear cone top rod 6 pushes the two long-axis rear expansion claws 7 to expand out of the inner cavity side wall positioning points N1-0 and N1-1 of the tensioning piston 20 to both sides at the same time.

[0162] S23: The short-shaft front cone push rod 2 moves to the left, and the upper step surface K10 is released from the short-shaft rear cone push rod 4. The short-shaft rear cone push rod 4 moves to the left under the spring force of the short-shaft rear end spring 9, and pushes the two short-shaft rear expansion claws 5 to expand out of the inner cavity side wall positioning points N3-0 and N3-1 of the tensioning piston 20 to both sides through the short rear rod dovetail groove BA5 of the short-shaft rear cone push rod 4; S24: The short-shaft front cone push rod 2 moves to the left, and pushes the two short-shaft front expansion claws 3 to expand out of the inner cavity side wall positioning points N4-0 and N4-1 of the tensioning piston 20 to both sides through the short rear rod dovetail groove BA5;

[0163] S25: The tailstock pressure plate presses the top surface, and the piston 20 is in an accurately positioned and reliably clamped state, and the outer circle and top surface of the piston 20 can be rough-machined.

[0164] The present invention provides a clamp and an implementation method for a piston with no draft angle on the inner cavity side wall. According to the characteristic of no draft angle on the inner cavity side wall of the piston, the arc of the clamp positioning surface in the circumferential direction is the same as the corresponding position of the piston, and the radial expansion and contraction of the clamp's own claws are used to tighten the inner wall of the piston 20; the shape and size of the clamp positioning point in the circumferential direction are the same as the corresponding position of the inner cavity side wall of the piston, so that the positioning accuracy of the piston inner cavity is relatively high; the expansion and contraction movement of the claws is high in accuracy and is symmetrical, and when the actual size of the inner cavity side wall of the piston blank changes greatly, the positioning accuracy of the clamp is guaranteed and the wall thickness difference of the inner cavity of the piston is accurately controlled; the clamp has three pairs of claws, and the expansion and contraction of the first pair of claws at the front end of the clamp is driven by the machine tool spindle cylinder, and the other two pairs of claws are driven by springs in the clamp to produce an expansion action, while the retraction action is driven by the cylinder; the three pairs of claws act synchronously to tighten the inner wall of the piston 20, and the claw stroke is adjustable.

[0165] The above shows and describes the basic principles and main features of the present invention and the advantages of the present invention. It should be understood by those skilled in the art that the present invention is not limited to the above embodiments. The above embodiments and descriptions are only for explaining the principles of the present invention. Without departing from the spirit and scope of the present invention, the present invention may have various changes and improvements, which fall within the scope of the present invention to be protected. The scope of protection of the present invention is defined by the attached claims and their equivalents.

Claims

1. A clamp for a piston with no draft angle on the inner cavity side wall, characterized in that: It comprises a clamp body (1), a short-axis front cone top rod (2), a short-axis front expansion claw (3), a short-axis rear cone top rod (4), a short-axis rear expansion claw (5), a long-axis rear cone top rod (6), a long-axis rear expansion claw (7), a long-axis spring (8), a short-axis rear end spring (9), a pull ring (10), a pull plate (11), a sleeve (12), a retaining ring (13), a pull rod (14), a front end cover plate (15), an internally threaded cylindrical pin (16), a hexagonal flange nut (17), a hexagonal thin nut (18), and a screw (19); The clamp body (1) comprises a conical surface (BA1), a short axis front cone guide hole (BD1), a short axis rear cone guide hole (BD2), a long axis rear cone guide hole (BD3), a front expansion claw guide square hole (BL1), a rear expansion claw guide square hole (BL3), a rear expansion claw guide stepped square hole (BL5), a pull plate guide hole (BD4), a retaining ring mounting hole (BD5), a connection assembly stop (BD6), and a positioning pin hole (BD9); The clamp body (1) is connected via a short-axis front cone guide hole (BD1) and a short-axis front cone top rod (2); The clamp body (1) is connected via a short-axis front cone guide hole (BD1) and a short-axis rear cone top rod (4); The clamp body (1) is connected via a long-axis rear cone guide hole (BD3) and a long-axis rear cone top rod (6); The clamp body (1) is connected to the short-shaft front expansion claw (3) via the front expansion claw guide square hole (BL1); The clamp body (1) is connected to the short-shaft rear expansion claw (5) via the rear expansion claw guide square hole (BL3); The clamp body (1) is connected to the long-axis rear expansion claw (7) via the rear expansion claw guide stepped square hole (BL5); The clamp body (1) fixes the retaining ring (13) through the retaining ring mounting hole (BD5); The long-axis rear cone top rod (6) is connected to the short-axis rear end spring (9), the sleeve (12) and the long-axis spring (8) are assembled in the long-axis rear cone top rod (6), the pull ring (10) and the pull plate (11) are fixed, the internal thread cylindrical pin (16) is respectively connected to the clamp (1) and the pull ring (10), the pull rod (14) is installed on the pull plate (11), the front end cover plate (15) is arranged in front of the clamp body (1), and the hexagonal flange nut (17) and the hexagonal thin nut (18) lock the short-axis front cone top rod (2).

2. A clamp for a piston without a draft angle on the inner cavity side wall as claimed in claim 1, characterized in that: The short-axis front cone push rod (2) comprises a short-sleeved front cone outer circle (BD11), a short-sleeved rear sliding cylinder (BD12), a short front rod dovetail groove (BA3), a positioning cylinder (BD13), and a locking thread (BD14); The short-axis rear cone ejector rod (4) comprises a short-sleeved rear cone outer circle (BD15), an ejector rod guide hole (BD16), a short rear rod dovetail groove (BA5), and a short-sleeved rear cylindrical surface (BD17); The long-axis rear cone top rod (6) comprises a long-axis rear cone outer circle (BD18), a long rear rod dovetail groove (BA7), a long-axis rear hole (BD19), and a long sleeve spring hole (BD20); The short-axis front expansion claw (3) comprises a short front expansion claw square surface (BL9) and a short front claw dovetail groove (BA9); The short-axis rear expansion claw (5) comprises a short rear expansion claw square surface (BL11) and a short rear claw dovetail groove (BA11); The long-axis rear expansion claw (7) comprises a long rear expansion claw stepped square surface (BL13) and a long rear claw dovetail groove (BA13); The pull plate (11) comprises a pull plate outer circle (BD22), a pull plate upper hole (BD25), a spring mounting annular countersunk hole (BL7), and a pull plate countersunk hole (BD23); The short-axis front cone guide hole (BD1) and the short-sleeve front cone outer circle (BD11) are clearance-matched, so that the short-axis front cone top rod (2) can slide freely axially on the clamp body (1); The short shaft rear cone guide hole (BD2) and the short sleeve rear cone outer circle (BD15) are clearance-matched, so that the short shaft rear cone top rod (4) can slide freely axially on the clamp body (1); The long-axis rear cone guide hole (BD3) and the long-axis rear cone outer circle (BD18) are clearance-matched, so that the long-axis rear cone top rod (6) can slide freely axially on the clamp body (1); The front expansion claw guide square hole (BL1) and the short front expansion claw square surface (BL9) are clearance-matched, so that the short-axis front expansion claw (3) can slide freely axially on the clamp body (1); The rear expansion claw guide square hole (BL3) and the short rear expansion claw square surface (BL11) are clearance-matched, so that the short-axis rear expansion claw (5) can slide freely axially on the clamp body (1); The rear expansion claw guide stepped square hole (BL5) and the long rear expansion claw stepped square surface (BL13) are clearance-matched, so that the long-axis rear expansion claw (7) can slide freely axially on the clamp body (1); The pull plate guide hole (BD4) and the pull plate outer circle (BD22) are clearance-matched, so that the pull plate (11) can slide freely axially on the clamp body (1).

3. A clamp for a piston without a draft angle on the inner cavity side wall according to claim 1, characterized in that: The retaining ring (13) comprises a retaining ring outer circle (BD30) and a stroke adjustment threaded hole; The conical surface (BA1) of the clamp body (1) is in contact with the long axis positioning points N2-0 and N2-1 of the inner cavity of the piston (20) for positioning; The connection assembly stop (BD6) of the clamp body (1) is connected and fixed to the machine tool spindle via screws (19); The retaining ring mounting hole (BD5) and the retaining ring outer circle (BD30) are assembled and fixed to limit the axial sliding limit travel position of the pull plate (11).

4. A clamp for a piston without a draft angle on the inner cavity side wall according to claim 2, characterized in that: The short-axis front cone guide hole (BD1) and the short-axis front cone outer circle (BD11) are clearance-matched to ensure the movement accuracy of the short-axis front cone ejector rod (2) in the short-axis front cone guide hole (BD1); The push rod guide hole (BD16) and the short-sleeved rear sliding cylinder (BD12) are clearance-matched to ensure the movement accuracy of the short-axis rear cone push rod (4) in the push rod guide hole (BD16).

5. A clamp for a piston without a draft angle on the inner cavity side wall according to claim 2, characterized in that: The sleeve (12) comprises a sleeve outer cylindrical surface (BD33); The pull ring comprises a pull ring cylindrical surface (BD37) and an anti-rotation positioning pin hole (BD38); The outer cylindrical surface (BD33) of the sleeve is sleeved in the long-axis rear hole (BD19), the long-axis rear hole (BD19) is sleeved on the short-sleeve rear cylindrical surface (BD17), the long-axis spring (8) is installed in the long-sleeve spring hole (BD20), and the long-axis spring (8) is sleeved on the outer cylindrical surface (BD33) of the sleeve; The positioning cylinder (BD13) and the upper hole (BD25) of the pull plate are assembled and connected, and the short shaft front cone ejector rod (2) and the pull plate (11) are fastened by means of a locking thread (BD14) and a locking nut; The pull ring cylindrical surface (BD37) is assembled in the pull plate countersunk hole (BD23), and the pull ring (10) and the pull plate (11) are fixed by screws (19); One end of the internally threaded cylindrical pin (16) is installed in the positioning pin hole (BD9) of the clamp body (1) with an interference fit, and the other end of the internally threaded cylindrical pin (16) is installed in the anti-rotation positioning pin hole (BD38) on the pull ring (10) with a clearance fit, so that the pull ring (10) can slide freely along the axial direction of the internally threaded cylindrical pin (16).

6. A clamp for a piston with no draft angle on the inner cavity side wall according to claim 2, characterized in that: The end surface K7 of the short-shaft rear cone top rod (4) is connected to the short-shaft rear end spring (9), and under the action of the spring force, the short-shaft rear expansion claw (5) is pushed to move radially outward to the positioning point on the inner cavity side wall of the tensioning piston (20); The long-axis spring (8) pushes the long-axis rear cone top rod (6) to move axially forward, and the long-axis rear rod dovetail groove (BA7) of the long-axis rear cone top rod (6) drives the long-axis rear expansion claw (7) to slide radially outward to tighten the positioning point on the inner cavity side wall of the piston (20); One end of the long axis spring (8) is in surface contact with the end surface K8 of the long sleeve spring hole (BD20), and the other end of the long axis spring (8) is in surface contact with the bottom surface K9 of the spring mounting annular countersunk hole (BL7). Under the elastic force of the long axis spring (8), the long axis rear cone top rod (6) pushes the long axis rear expansion claw (7) to move radially outward to the positioning point on the inner cavity side wall of the tensioning piston (20) through the long rear rod dovetail groove (BA7); The short shaft rear end spring (9) pushes the short shaft rear cone top rod (4) to move axially forward, and the short shaft rear rod dovetail groove (BA5) of the short shaft rear cone top rod (4) drives the short shaft rear expansion claw (5) to slide radially outward to tighten the positioning point on the inner cavity side wall of the piston (20).

7. A clamp for a piston without a draft angle on the inner cavity side wall according to claim 6, characterized in that: The short-axis front cone push rod (2) is provided with two short-axis dovetail grooves (BA3), the two short-axis dovetail grooves (BA3) and the short-axis front claw dovetail groove (BA9) are matched with each other in sliding clearance, and the upper conical surface K1 of the short-axis front cone push rod (2) and the upper inclined surface K4 of the short-axis front expansion claw (3) are in contact with each other, forming relative sliding surfaces and being force-bearing surfaces during operation; When the short-shaft front cone push rod (2) moves axially forward and backward, the short-shaft front expansion claw (3) is driven to perform radial expansion and contraction movement in the front expansion claw guide square hole (BL1) of the clamp body (1) through the short-shaft front rod dovetail groove (BA3), thereby achieving the action of tightening or loosening the positioning points N4-0 and N4-1 on the inner cavity side wall of the piston (20); The short-axis rear cone top rod (4) is provided with two short-axis rear rod dovetail grooves (BA5), the two short-axis rear rod dovetail grooves (BA5) are matched with the short-axis rear claw dovetail groove (BA11) in a sliding clearance, the upper conical surface K2 of the short-axis rear cone top rod (4) and the upper inclined surface K5 of the short-axis rear expansion claw (5) are in contact with each other, and are relative sliding surfaces, and are force-bearing surfaces during operation; When the short-axis rear cone top rod (4) moves axially forward and backward, the short-axis rear expansion claw (5) is driven to perform radial expansion and contraction movement in the rear expansion claw guide square hole (BL3) of the clamp body (1) through the short-axis rear rod dovetail groove (BA5), thereby achieving the action of tightening or loosening the positioning points N3-0 and N3-1 on the inner cavity side wall of the piston (20); The long-axis rear cone top rod (6) is provided with two long rear rod dovetail grooves (BA7), the two long rear rod dovetail grooves (BA7) are matched with the long front claw dovetail groove (BA13) in a sliding clearance, the upper conical surface K3 of the long-axis rear cone top rod (6) and the upper inclined surface K6 of the long-axis rear expansion claw (7) are in contact with each other, and are relative sliding surfaces, and are force-bearing surfaces during operation; When the long-axis rear cone top rod (6) moves axially forward and backward, the long-axis rear expansion claw (7) is driven to perform radial expansion and contraction movement in the rear expansion claw guide stepped square hole (BL5) of the clamp body through the long-axis rear rod dovetail groove (BA7), thereby achieving the action of tightening or loosening the positioning points N1-0 and N1-1 on the inner cavity side wall of the piston (20).

8. A clamp for a piston without a draft angle on the inner cavity side wall according to claim 7, characterized in that: The pull rod comprises a pull rod assembly stop (BD26) and a pull rod thread (BD41); The pull plate (11) and the pull ring (10) are assembled to form a movement space for the long-axis rear cone top rod (6), which is used to limit the axial movement stroke of the long-axis rear cone top rod (6); During the loosening process, the pull ring (10) pulls the long-axis rear cone top rod (6) to move backward, driving the long-axis rear expansion claw (7) to retract and loosen the piston (20); During the clamping process, the pull plate (11) moves forward under the push of the pull rod (14), and the axial travel restriction of the pull ring (10) on the long-axis rear cone top rod (6) is automatically cancelled. The pull plate (11) compresses the long-axis spring (8), and under the action of the spring force, the long-axis rear cone top rod (6) pushes the long-axis rear expansion claw (7) to slide outward through the inclined surface of the long-axis rear dovetail groove (BA7), thereby tightening the inner cavity side wall of the piston (20); The sleeve (12) isolates the long-axis spring (8) and the short-axis rear end spring (9) to prevent mutual interference during movement.

9. A clamp for a piston without a draft angle on the inner cavity side wall according to claim 1, characterized in that: The retaining ring (13) limits the movement stroke of the pull plate (11), and the stroke position of the pull plate (11) is adjusted by adjusting the position of the stroke adjustment threaded hole; The rear end of the pull rod (14) is connected to the main shaft cylinder pull rod through a pull rod thread (BD41), transmitting the thrust or pulling force of the main shaft cylinder to provide movement for the clamp; The front end cover plate (15) prevents chips from entering the interior of the clamp body (1); The internally threaded cylindrical pin (16) limits the pull ring (10) from rotating during movement.

10. A method for implementing a clamp for a piston with no draft angle on the inner cavity side wall, based on the clamp for a piston with no draft angle on the inner cavity side wall as claimed in any one of claims 1 to 9, characterized in that: The steps are: S1: The clamping position and release position before processing: S11: The main shaft cylinder pull rod retracts, driving the short shaft front cone push rod (2) to move to the right through the short front rod dovetail groove (BA3) to drive the short shaft front expansion claw (3) to retract toward the center; S12: The step surface K10 on the short-shaft front cone push rod (2) drives the short-shaft rear cone push rod (4) to move rightward, and drives the short-shaft rear expansion claw (5) to retract toward the center through the short rear rod dovetail groove (BA5); S13: At the same time, the short-axis front cone top rod (2), the pull plate (11), the pull ring (10), and the pull rod (14) are connected and fixed as a whole by screws and nuts. When the short-axis front cone top rod (2) moves to the right, the pull ring (10) also moves to the right and drives the long-axis rear cone top rod (6) to move to the right through the upper step surface K11 of the long-axis rear cone top rod (6); S14: The long rear rod dovetail groove (BA7) of the long shaft rear cone top rod (6) drives the long shaft rear expansion claw (7) to retract the pull rod (14) toward the center, and the limit position of the rightward movement is controlled by the limit screw on the retaining ring (13); S2: The inner cavity of the piston (20) is inserted into the fixture: S21: The long axis positioning points N2-0 and N2-1 of the piston (20) are aligned with the conical surface (BA1) of the clamp body (1) and the main shaft cylinder moves to the left, driving the pull rod (14), the pull plate (11), the pull ring (10), and the short shaft front cone push rod (2) to move to the left as a whole: S22: The pull ring (10) moves to the left to release the step surface K11 of the long-axis rear cone top rod (6), and the long-axis spring (8) pushes the long-axis rear cone top rod (6) to move to the left under the action of the spring force, and the long-axis rear rod dovetail groove (BA7) on the long-axis rear cone top rod (6) pushes the two long-axis rear expansion claws (7) to expand to both sides simultaneously to the positioning points N1-0 and N1-1 on the inner cavity side wall of the tensioning piston (20); S23: the short shaft front cone push rod (2) moves to the left, the upper step surface K10 is released from the short shaft rear cone push rod (4), and the short shaft rear cone push rod (4) moves to the left under the action of the spring force of the short shaft rear end spring (9), and pushes the two short shaft rear expansion claws (5) to expand out of the inner cavity side wall positioning points N3-0 and N3-1 of the tensioning piston (20) to both sides through the short rear rod dovetail groove (BA5); S24: the short shaft front cone push rod (2) moves to the left, and pushes the two short shaft front expansion claws (3) to expand out of the inner cavity side wall positioning points N4-0 and N4-1 of the tensioning piston (20) to both sides through the short rear rod dovetail groove (BA5); S25: The tailstock pressure plate presses the top surface, and the piston (20) is in an accurately positioned and reliably clamped state, and rough machining of the outer circle and the top surface of the piston (20) can be performed.

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