Turning method and clamp for controlling piston wall thickness difference and piston top thickness

Abstract

The invention discloses a turning method and clamp for controlling the wall thickness difference and the top thickness of a piston. The position precision and the top thickness size precision and consistency of a cast non-machined surface of an inner cavity of the piston and the surface of an outer circle finished product are greatly improved. Waste products caused by deflection and deviation of a high-nickel cast iron ring of the piston due to poor position precision of an inner cavity are avoided, waste products caused by deflection and deviation of an annular inner cooling oil duct in the head due to poor position precision of the inner cavity are avoided, and waste products caused by non-uniform inner side chamfer and outer side chamfer of a piston pin hole due to poor position precision of the inner cavity are avoided; through accurate control over the top thickness size, waste products caused by the fact that the piston top thickness size is out of tolerance and the weight of the piston is out of tolerance are avoided, for the piston with the higher top thickness size precision requirement, the problems of measurement grouping and grouping machining are avoided, and the machining efficiency and the size consistency are improved.

Description

Technical Field

[0001] The invention relates to the field of manufacturing aluminum pistons for internal combustion engines, and in particular to a turning method and a fixture for controlling the difference in piston wall thickness and piston top thickness. Background Art

[0002] There are two main process flows for controlling the difference in piston wall thickness and piston top thickness in the industry:

[0003] 1: Use the top surface of the piston blank to axially locate, clamp the outer circle of the piston blank, and turn the positioning stop;

[0004] 2: Use the four points of the piston blank stop to determine the center of the circle, and then use the cone surface of the piston blank top riser to determine the piston axis, the piston top to determine the axial position, turn the piston outer circle and top surface, and then use the top surface to position and clamp the outer circle to turn the positioning stop in subsequent processes.

[0005] The mold used for casting aluminum pistons includes inner mold, outer mold, mold cover and other parts. A series of parts are combined together to form a mold. After each piston is cast, the inner mold, outer mold, mold cover and other parts need to be automatically separated to take out the piston. During the mold closing process, there is a large position deviation when the inner mold, outer mold and mold cover are automatically combined, resulting in an offset of e1 between the outer circle of the piston blank head and the outer circle of the blank skirt, an offset of e2 between the inner cavity of the piston blank and the outer circle of the blank skirt, and an offset of e1+e2 between the inner cavity of the piston blank and the outer circle of the blank head.

[0006] The first process control method has the following problems:

[0007] As attached Figure 1 As shown in the figure, since there is an offset value of e1+e2 between the inner cavity of the piston blank and the outer circle of the blank head, and the first process flow uses the outer circle of the head and the top surface for positioning, it will inevitably lead to a large wall thickness difference between the non-machined casting surface of the inner cavity of the piston and the positioning stop, and the positioning stop is the reference for all subsequent fine machining, thus resulting in an excessive wall thickness difference in the final product; when fine turning the positioning stop, the axial positioning reference is the top surface of the blank. Due to the large dimensional error from the top surface of the casting blank to the inner top of the piston, the dimensional tolerance of the top thickness of the final product and the weight of the finished piston cannot be guaranteed.

[0008] The second process control method has the following problems:

[0009] As attached Figure 2As shown in the figure, the inner edge of the stop end of the blank is on the surface of the inner cavity, and the positioning point is on its edge; the cone surface of the piston top riser and the outer circle of the head are cast in the same mold cover to ensure the coaxiality of the outer circle of the head and the cone surface of the top riser; there is an e1+e2 offset value between the inner cavity and the outer circle of the head, which causes the inner edge of the stop end of the blank and the cone surface of the top riser to also have an e1+e2 offset value, so that the axis of the piston is deviated after positioning and clamping, resulting in the deviation of the machined outer circle and top surface; in the subsequent sequence, when the positioning stop is machined with this outer circle and top surface, it also causes a large wall thickness difference between the non-machined casting surface of the piston inner cavity and the positioning stop, and the positioning stop is all the subsequent fine machining. The axial positioning rod of the fixture is used to support the inner center of the piston blank, and this point is used as the axial positioning reference to process the top surface; because the piston is made of aluminum silicon alloy and has a relatively soft hardness, after the piston blank is axially clamped, a pit is pressed out on the surface of the axial positioning point, which is also the measurement point of the top thickness, resulting in a large change in the actual thickness of the top thickness, and the top thickness tolerance is not easy to control, which ultimately leads to an over-tolerance in the weight of the finished piston. For pistons with strict requirements on the top thickness tolerance, all pistons must be measured and grouped before they can be processed, which is inefficient. Summary of the invention

[0010] The purpose of the present invention is to provide a turning method and a fixture for controlling the difference in piston wall thickness and piston top thickness in view of the above-mentioned prior art problems.

[0011] A turning method for controlling the difference in piston wall thickness and piston top thickness, comprising the following steps:

[0012] S1: Eight points on the inner surface of the piston blank are used as the axial centerline positioning reference. In the piston rough machining outer circle 2 and rough machining top surface 3 processes, the axial positioning of the piston blank is not strictly controlled, and the focus is on controlling the coaxiality of the rough machining outer circle of the blank and the inner axis of the piston blank;

[0013] S2: Use floating pressure plate 1 to assist in pressing the top surface of the piston, and turn the outer circle and top surface of the piston;

[0014] S3: In the process of piston finishing, a high-precision sensor is used to automatically measure the axial position of the piston inner top online, control the distance from each piston inner top to the stop surface, and automatically adjust the machining program coordinates according to the sensor detection results;

[0015] S4: Accurately control the distance from the piston stop plane to the inner top of the piston, and form the piston top thickness dimension after the top surface finishing process is completed in the subsequent top surface finishing process.

[0016] Furthermore, a turning method for controlling the piston wall thickness difference and the piston top thickness, the step S1 comprises the following sub-steps:

[0017] Points N1-0, N1-1, N2-0, and N2-1 control two degrees of freedom in the long axis direction of the piston cavity;

[0018] Points N3-0, N3-1, N4-0, and N4-1 control the three degrees of freedom in the short axis direction of the piston cavity.

[0019] Furthermore, a turning method for controlling the difference in piston wall thickness and piston top thickness is provided, wherein the piston top surface is pressed by a floating pressure plate, and the floating pressure plate only provides a clamping force and does not limit the freedom of the piston blank.

[0020] Furthermore, a turning method for controlling the difference in piston wall thickness and piston top thickness, the step S3 comprises the following sub-steps:

[0021] S31: The high-precision sensor is installed on the machine tool turret. After the probe coordinates are calibrated, a special control program is compiled to compare the Z-axis coordinate data of the center of the piston inner top measured by the probe with the original coordinate system each time, and calculate the compensation amount;

[0022] S32: According to the compensation result, the control program automatically adjusts the origin of the original coordinate system, and automatically calls the processing program to complete the piston positioning stop processing;

[0023] S33: The sensor measurement accuracy is ≤0.002. The actual processing size accuracy of the piston top thickness is only related to the movement accuracy of the machine tool itself. The clamping positioning error in the piston axis direction will not affect the actual processing size accuracy of the piston top thickness. The previous process of the fine turning stop process does not need to strictly control the consistency of the top thickness size, but only needs to ensure that the top surface has a fine processing allowance.

[0024] Further, a turning method for controlling the difference in piston wall thickness and piston top thickness also includes a piston fixture control method with a draft angle on the inner cavity side wall and a piston fixture control method with no draft angle on the inner cavity side wall;

[0025] The control method of the piston fixture with a draft angle on the inner cavity side wall is divided into the following steps: before piston processing, during piston processing, and after piston processing;

[0026] The control method of the piston clamp with no draft angle on the inner cavity side wall is divided into the clamp position and the release position state before processing and the piston inner cavity is inserted into the clamp state.

[0027] Furthermore, a turning method for controlling the difference in piston wall thickness and piston top thickness, the control method for the piston fixture having a draft angle on the inner cavity side wall comprises the following steps:

[0028] a1: Before piston processing:

[0029] a11: The spindle cylinder pull rod retracts, driving the positioning shaft push rod to move backward;

[0030] a12: Under the action of the spring force, the front push rod is pushed forward, pushing the short-axle front positioning block forward until the short-axle front positioning block is blocked by the positioning body and cannot move;

[0031] At the same time, the rear push rod is pushed forward under the action of the spring force, pushing the short-axle rear positioning block to move forward until the short-axle rear positioning block is blocked by the short-axle front positioning block and cannot move;

[0032] a13: Under the action of the long-axis floating spring, the long-axis floating push rod is pushed forward, pushing the long-axis floating block forward until the long-axis floating block is blocked by the limit pin installed on the positioning body and cannot move;

[0033] At the same time, under the action of the limit pin, the long-axis floating block is reset to the designed position in the circumferential direction;

[0034] a14: There is a height difference between the positioning inclined surfaces of the short-axis front positioning block and the short-axis rear positioning block, and the positioning inclined surface of the short-axis rear positioning block is higher than the positioning inclined surface of the short-axis front positioning block; there is also a height difference between the positioning inclined surface of the long-axis floating block and the positioning body inclined surface, and the positioning inclined surface of the long-axis floating block is higher than the positioning body inclined surface;

[0035] a2: Piston processing:

[0036] a21: The inner cavity of the piston is inserted into the fixture, the inclined surface of the piston stop end in the long axis direction fits with the positioning conical surface of the long axis floating block, and the inclined surface of the piston stop end in the short axis direction fits with the inclined surface on the short axis rear positioning block;

[0037] a22: The tailstock pressure plate presses the top surface. During the pressing process, the pressure plate pushes the piston to move toward the spindle end. The piston pushes the long-axis floating block and the short-axis rear positioning block backward in the opposite direction and compresses the corresponding spring at the same time until the height difference between the positioning inclined surfaces of the short-axis front positioning block and the short-axis rear positioning block is eliminated;

[0038] a23: The tailstock pressure plate continues to move toward the spindle end to press the top surface of the piston. The piston pushes the long-axis floating block, the short-axis front positioning block, and the short-axis rear positioning block to move backward in the opposite direction and compresses the corresponding springs at the same time until the inclined surface of the positioning point at the front end of the positioning body contacts the inclined surface of the positioning point on the side of the piston inner cavity. At this time, the piston is in the final clamping state, and the outer circle and top surface of the piston can be rough-machined;

[0039] a3: After the piston is processed:

[0040] a31: The tailstock pressure plate moves backward to release the piston. Because the inner cavity of the piston is tightly fitted with the long-axis floating block, the short-axis front positioning block, and the short-axis rear positioning block and cannot be separated, it moves away from the spindle under the action of the spring thrust until the short-axis front positioning block reaches the travel limit position;

[0041] a32: The spindle cylinder pushes the positioning shaft push rod to move toward the tailstock to disengage the piston from the long shaft floating block, the short shaft front positioning block, and the short shaft rear positioning block. Remove the piston after processing and prepare for the next processing.

[0042] Furthermore, a turning method for controlling the difference in piston wall thickness and piston top thickness, the piston fixture control method for the inner cavity side wall without a draft angle comprises the following steps:

[0043] b1: The state of the fixture and the released position before processing:

[0044] b11: The main shaft cylinder pull rod retracts, driving the front cone push rod of the short shaft to move to the right through the dovetail groove to drive the front expansion claw of the short shaft to retract toward the center;

[0045] b12: The step surface on the short-shaft front cone push rod drives the short-shaft rear cone push rod to move to the right, and drives the short-shaft rear expansion claw to retract toward the center through the dovetail groove;

[0046] b13: 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 upper step surface of the long-axis rear cone top rod;

[0047] b14: ​​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;

[0048] b2: The inner cavity of the piston is inserted into the fixture:

[0049] b21: The positioning point of the piston in the long axis direction fits 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:

[0050] b22: The pull ring moves to the left to release the step surface 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 dovetail groove on the long-axis rear cone top rod pushes the two long-axis rear expansion claws to expand out of the positioning points on the inner wall of the tensioning piston at both sides at the same time.

[0051] b23: The front cone top rod of the stub shaft moves to the left, the upper step surface is released from the rear cone top rod of the stub shaft, and the rear cone top rod of the stub shaft moves to the left under the action of the spring force of the rear end spring of the stub shaft, and the two rear expansion claws of the stub shaft are pushed to expand out of the positioning points on the inner wall of the tensioning piston at both sides through the dovetail groove of the rear cone top rod of the stub shaft;

[0052] S24: The front cone push rod of the short shaft moves to the left, and pushes the two front expansion claws of the short shaft to expand out of the positioning points on the inner wall of the tensioning piston at both sides through the dovetail groove;

[0053] b25: 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.

[0054] A turning fixture for controlling the difference in piston wall thickness and piston top thickness, including a piston fixture with a draft angle on the inner cavity side wall and a piston fixture without a draft angle on the inner cavity side wall;

[0055] The piston fixture with a draft angle on the inner cavity side wall includes a positioning body, a positioning shaft push rod, a short shaft front positioning block, a short shaft rear positioning block, a long shaft floating block, a front push rod and a rear push rod, a positioning body transition plate, a spring mounting body, a long shaft floating spring top cover, a long shaft floating push rod, a long shaft floating spring, a spring top cover, a spring bottom cover, a spring, a long shaft floating block spring cover, a limit pin, a pull rod connecting rod, and a main shaft transition body;

[0056] The positioning shaft push rod, the long shaft floating block, the limit pin, the front push rod and the rear push rod are arranged on the positioning body;

[0057] The short shaft front positioning block and the short shaft rear positioning block are respectively connected and fixed to the positioning shaft top rod, and the positioning body transition plate is connected and fixed to the positioning body;

[0058] The spring mounting body and the positioning body transition plate are connected and fixed, and the long-axis floating push rod is connected to the positioning body transition plate;

[0059] The spring, spring top cover, spring bottom cover, long-axis floating spring top cover, long-axis floating spring, and long-axis floating block spring cover are arranged on the spring mounting body;

[0060] The limit pin is installed on the positioning body and the long axis floating block, the pull rod connecting rod is arranged on the spindle transition body, and the spindle transition body connects the spring installation body and the machine tool spindle;

[0061] The piston fixture with no draft angle on the inner cavity side wall comprises 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;

[0062] The clamping bodies are respectively connected to the short-axis front cone top rod, the short-axis rear cone top rod, the long-axis rear cone top rod, the short-axis front expansion claw, the short-axis rear expansion claw and the long-axis rear expansion claw;

[0063] The clamp body fixes the retaining ring, 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, and the pull ring and the pull plate are fixed;

[0064] The internal thread 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 body, and the hexagonal flange nut and the hexagonal thin nut lock the short shaft front cone top rod.

[0065] The beneficial effects of the present invention are as follows: through a turning method and a fixture for controlling the difference in piston wall thickness and piston top thickness, the position accuracy and top thickness dimensional accuracy and consistency of the piston inner cavity casting non-machined surface and the outer cylindrical finished surface are greatly improved; the deflection and offset of the high-nickel cast iron ring of the piston due to poor inner cavity position accuracy to produce scrap, the deflection and offset of the annular internal cooling oil channel in the head due to poor inner cavity position accuracy to produce scrap, and the uneven inner chamfer and outer chamfer of the piston pin hole due to poor inner cavity position accuracy to produce scrap; through precise control of the top thickness dimension, the piston top thickness dimension out-of-tolerance leading to the piston weight out-of-tolerance to produce scrap is avoided, and for pistons with higher top thickness dimension accuracy requirements, the problems of measurement grouping and group processing are avoided, thereby improving processing efficiency and dimensional consistency. BRIEF DESCRIPTION OF THE DRAWINGS

[0066] Figure 1 This is the flow chart of the first process control method.

[0067] Figure 2 This is the flow chart of the second process control method.

[0068] Figure 3 The invention discloses a flow chart of a turning method for controlling the difference in piston wall thickness and piston top thickness.

[0069] Figure 4 It is a schematic diagram of the axis centerline positioning reference.

[0070] Figure 5 It is a plane diagram of the stop.

[0071] Figure 6 This is a schematic diagram of top surface finishing.

[0072] Figure 7 This is a schematic diagram of the piston before processing.

[0073] Figure 8 This is a schematic diagram of piston processing.

[0074] Fig. 9 This is a schematic diagram of the piston after processing.

[0075] Fig.10 This is a schematic diagram of the clamping position and the released position before processing.

[0076] Fig.11 It is a schematic diagram of the state where the inner cavity of the piston is inserted into the fixture.

[0077] Fig.12 Schematic diagram of a fixture with a piston having a draft angle on the inner cavity side wall.

[0078] Fig.13 This is a schematic diagram of a fixture with a piston having a draft angle on the inner cavity side wall.

[0079] Fig.14 It is a schematic diagram of the fixture for the piston with no draft angle on the inner cavity side wall.

[0080] In the figure, 1-floating pressure plate, 2-rough processed outer circle, 3-rough processed top surface, 4-stop surface.

[0081] A1-positioning body, A2-positioning shaft push rod, A3-short shaft front positioning block, A4-short shaft rear positioning block, A5-long shaft floating block, A6-front push rod, A7-rear push rod, A8-positioning body transition plate, A9-spring mounting body, A10-long shaft floating spring top cover, A11-long shaft floating push rod, A12-long shaft floating spring, A13-spring top cover, A14-spring bottom cover, A15-spring, A16-long shaft floating block spring cover, A17-limit pin, A18-pull rod connecting rod, A19-spindle transition body.

[0082] In the figure, B1-clamp body, B2-short shaft front cone push rod, B3-short shaft front expansion claw, B4-short shaft rear cone push rod, B5-short shaft rear expansion claw, B6-long shaft rear cone push rod, B7-long shaft rear expansion claw, B8-long shaft spring, B9-short shaft rear end spring, B10-pull ring, B11-pull plate, B12-sleeve, B13-blocking ring, B14-pull rod, B15-front end cover plate, B16-inner thread cylindrical pin, B17-hexagonal flange nut, B18-hexagonal thin nut, B19-screw, 20-piston. DETAILED DESCRIPTION

[0083] 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.

[0084] As attached Figures 3 to 6 As shown, a turning method for controlling the difference in piston wall thickness and piston top thickness comprises the following steps:

[0085] S1: Eight points on the inner surface of the piston blank are used as the axial centerline positioning reference. In the piston rough machining outer circle 2 and rough machining top surface 3 processes, the axial positioning of the piston blank is not strictly controlled, and the focus is on controlling the coaxiality of the rough machining outer circle of the blank and the inner axis of the piston blank;

[0086] S2: Use floating pressure plate 1 to assist in pressing the top surface of the piston, and turn the outer circle and top surface of the piston;

[0087] S3: In the process of piston finishing turning, the axial position of the piston inner top is automatically measured online by a high-precision sensor, the distance from the inner top of each piston to the stop surface 4 is controlled, and the machining program coordinates are automatically adjusted according to the sensor detection results;

[0088] S4: Accurately control the distance from the piston stop plane 4 to the inner top of the piston, and form the piston top thickness dimension after the top surface finishing process is completed in the subsequent top surface finishing process.

[0089] Among them, the distance from the stop plane 4 to the inner top of the piston is L4, the top surface finishing distance is L5, and the piston top thickness is L1.

[0090] Furthermore, a turning method for controlling the piston wall thickness difference and the piston top thickness, the step S1 comprises the following sub-steps:

[0091] Points N1-0, N1-1, N2-0, and N2-1 control two degrees of freedom in the long axis direction of the piston cavity;

[0092] Points N3-0, N3-1, N4-0, and N4-1 control the three degrees of freedom in the short axis direction of the piston cavity.

[0093] Furthermore, a turning method for controlling the difference in piston wall thickness and piston top thickness is provided, wherein the piston top surface is pressed by a floating pressure plate 1, and the floating pressure plate 1 only provides a clamping force and does not limit the freedom of the piston blank.

[0094] Furthermore, a turning method for controlling the difference in piston wall thickness and piston top thickness, the step S3 comprises the following sub-steps:

[0095] S31: The high-precision sensor is installed on the machine tool turret. After the probe coordinates are calibrated, a special control program is compiled to compare the Z-axis coordinate data of the center of the piston inner top measured by the probe with the original coordinate system each time, and calculate the compensation amount;

[0096] S32: According to the compensation result, the control program automatically adjusts the origin of the original coordinate system, and automatically calls the processing program to complete the piston positioning stop processing;

[0097] S33: The sensor measurement accuracy is ≤0.002. The actual processing size accuracy of the piston top thickness is only related to the movement accuracy of the machine tool itself. The clamping positioning error in the piston axis direction will not affect the actual processing size accuracy of the piston top thickness. The previous process of the fine turning stop process does not need to strictly control the consistency of the top thickness size, but only needs to ensure that the top surface has a fine processing allowance.

[0098] Further, a turning method for controlling the difference in piston wall thickness and piston top thickness also includes a piston fixture control method with a draft angle on the inner cavity side wall and a piston fixture control method with no draft angle on the inner cavity side wall;

[0099] The control method of the piston fixture with a draft angle on the inner cavity side wall is divided into the following steps: before piston processing, during piston processing, and after piston processing;

[0100] The control method of the piston clamp with no draft angle on the inner cavity side wall is divided into the clamp position and the loosened position state before processing, and the inner cavity of the piston B20 is inserted into the clamp state.

[0101] As attached Figures 7 to 9 As shown, a turning method for controlling the difference in piston wall thickness and piston top thickness, the control method for the piston fixture with a draft angle on the inner cavity side wall comprises the following steps:

[0102] a1: Before piston processing:

[0103] a11: The spindle cylinder pull rod retracts, driving the positioning shaft push rod A2 to move backward;

[0104] a12: Under the action of the spring force, the front push rod A6 is pushed forward, pushing the short-axle front positioning block A3 to move forward until the short-axle front positioning block A3 is blocked by the positioning body A1 and cannot move;

[0105] At the same time, the rear push rod A7 is pushed forward under the action of the spring force, pushing the short-axle rear positioning block A4 to move forward until the short-axle rear positioning block A4 is blocked by the short-axle front positioning block A3 and cannot move;

[0106] a13: Under the action of the long-axis floating spring A12, the long-axis floating push rod A11 is pushed forward, pushing the long-axis floating block A5 forward until the long-axis floating block A5 is blocked by the limit pin A17 installed on the positioning body A1 and cannot move;

[0107] At the same time, under the action of the limit pin A17, the long-axis floating block A5 is angularly reset to the designed position in the circumferential direction;

[0108] a14: There is a height difference between the positioning inclined surfaces of the short-axis front positioning block A3 and the short-axis rear positioning block A4, and the positioning inclined surface of the short-axis rear positioning block A4 is higher than the positioning inclined surface of the short-axis front positioning block A3; there is also a height difference between the positioning inclined surface of the long-axis floating block A5 and the positioning body A1, and the positioning inclined surface of the long-axis floating block A5 is higher than the positioning body A1;

[0109] a2: Piston processing:

[0110] a21: The inner cavity of the piston is inserted into the fixture, the inclined surface of the piston stop end in the long axis direction fits with the positioning conical surface of the long axis floating block A5, and the inclined surface of the piston stop end in the short axis direction fits with the inclined surface on the short axis rear positioning block A4;

[0111] a22: The tailstock pressure plate presses the top surface. During the pressing process, the pressure plate pushes the piston to move toward the spindle end. The piston pushes the long-axis floating block A5 and the short-axis rear positioning block A4 backward in the opposite direction and compresses the corresponding spring at the same time until the height difference between the positioning inclined surfaces of the short-axis front positioning block A3 and the short-axis rear positioning block A4 is eliminated;

[0112] a23: The tailstock pressure plate continues to move toward the spindle end to press the top surface of the piston. The piston pushes the long-axis floating block A5, the short-axis front positioning block A3, and the short-axis rear positioning block A4 backward and compresses the corresponding springs at the same time until the inclined surface of the positioning point at the front end of the positioning body A1 contacts the inclined surface of the positioning point on the side of the piston inner cavity. At this time, the piston is in the final clamping state, and the outer circle and top surface of the piston can be rough-machined;

[0113] a3: After the piston is processed:

[0114] a31: The tailstock pressure plate moves backward to release the piston. Because the inner cavity of the piston is tightly fitted with the long-axis floating block A5, the short-axis front positioning block A3, and the short-axis rear positioning block A4 and cannot be separated, it moves away from the spindle under the action of the spring thrust until the short-axis front positioning block A3 reaches the travel limit position.

[0115] a32: The spindle cylinder pushes the positioning shaft push rod A2 to move the piston toward the tailstock and disengage the piston from the long shaft floating block A5, the short shaft front positioning block A3, and the short shaft rear positioning block A4. Remove the piston after processing and prepare for the next processing.

[0116] As attached Figures 10-11 As shown, a turning method for controlling the difference in piston wall thickness and piston top thickness, the control method for the piston fixture without a draft angle on the inner cavity side wall comprises the following steps:

[0117] b1: The state of the fixture and the released position before processing:

[0118] b11: The main shaft cylinder pull rod retracts, driving the short shaft front cone push rod B2 to move to the right through the dovetail groove to drive the short shaft front expansion claw B3 to retract toward the center;

[0119] b12: The step surface on the short-shaft front cone push rod B2 drives the short-shaft rear cone push rod B4 to move to the right, and drives the short-shaft rear expansion claw to retract toward the center through the dovetail groove;

[0120] b13: At the same time, the short-axis front cone top rod B2, the pull plate B11, the pull ring B10, and the pull rod B14 are connected and fixed as a whole by screws and nuts. When the short-axis front cone top rod B2 moves to the right, the pull ring B10 also moves to the right and drives the long-axis rear cone top rod B6 to move to the right through the upper step surface of the long-axis rear cone top rod B6;

[0121] b14: ​​The dovetail groove of the long-axis rear cone top rod B6 drives the long-axis rear expansion claw B7 to retract the pull rod B14 toward the center, and the limit position of the rightward movement is controlled by the limit screw on the retaining ring B13;

[0122] b2: The inner cavity of piston B20 is inserted into the fixture:

[0123] b21: The long axis direction positioning point of piston B20 fits the conical surface of clamp body B1, and the main shaft cylinder moves to the left, driving the pull rod B14, pull plate B11, pull ring B10, and short axis front cone push rod B2 to move to the left as a whole:

[0124] b22: The pull ring B10 moves to the left to release the step surface of the long-axis rear cone top rod B6. The long-axis spring B8 pushes the long-axis rear cone top rod B6 to the left under the action of the spring force. The dovetail groove on the long-axis rear cone top rod B6 pushes the two long-axis rear expansion claws B7 to expand out of the inner cavity side wall positioning points of the tensioning piston B20 at both sides at the same time.

[0125] b23: The short-shaft front cone top rod B2 moves to the left, and the upper step surface is released from the short-shaft rear cone top rod B4. The short-shaft rear cone top rod B4 moves to the left under the action of the spring force of the short-shaft rear spring B9, and pushes the two short-shaft rear expansion claws B5 to expand out of the inner cavity side wall positioning points of the tensioning piston B20 to both sides through the dovetail groove of the short-shaft rear cone top rod B4.

[0126] S24: The short-shaft front cone push rod B2 moves to the left, and pushes the two short-shaft front expansion claws B3 to both sides to expand out of the inner cavity side wall positioning points of the tensioning piston B20 through the dovetail groove;

[0127] b25: The tailstock pressure plate presses the top surface, and the piston B20 is in an accurately positioned and reliably clamped state, and the outer circle and top surface of the piston B20 can be rough-machined.

[0128] As attached Figures 12-14 As shown, a turning fixture for controlling the difference in piston wall thickness and piston top thickness includes a piston fixture with a draft angle on the inner cavity side wall and a piston fixture without a draft angle on the inner cavity side wall;

[0129] The piston fixture with a draft angle on the inner cavity side wall includes a positioning body A1, a positioning shaft push rod A2, a short shaft front positioning block A3, a short shaft rear positioning block A4, a long shaft floating block A5, a front push rod A6, a rear push rod A7, a positioning body transition plate A8, a spring mounting body A9, a long shaft floating spring top cover A10, a long shaft floating push rod A11, a long shaft floating spring A12, a spring top cover A13, a spring bottom cover A14, a spring A15, a long shaft floating block spring cover A16, a limit pin A17, a pull rod connecting rod A18, and a main shaft transition body A19;

[0130] The positioning shaft push rod A2, the long axis floating block A5, the limit pin A17, the front push rod A6, and the rear push rod A7 are arranged on the positioning body A1;

[0131] The short shaft front positioning block A3 and the short shaft rear positioning block A4 are respectively connected and fixed to the positioning shaft top rod A2, and the positioning body transition plate A8 is connected and fixed to the positioning body A1;

[0132] The spring mounting body A9 is connected and fixed to the positioning body transition plate A8, and the long axis floating push rod A11 is connected to the positioning body transition plate A8;

[0133] The spring A15, spring top cover A13, spring bottom cover A14, long axis floating spring top cover A10, long axis floating spring A12, and long axis floating block spring cover A16 are arranged on the spring mounting body A9;

[0134] The limit pin A17 is installed on the positioning body A1 and the long axis floating block A5, the pull rod connecting rod A18 is arranged on the spindle transition body A19, and the spindle transition body A19 connects the spring installation body A9 and the machine tool spindle;

[0135] The piston clamp with no draft angle on the inner cavity side wall comprises a clamp body B1, a short-axis front cone top rod B2, a short-axis front expansion claw B3, a short-axis rear cone top rod B4, a short-axis rear expansion claw B5, a long-axis rear cone top rod B6, a long-axis rear expansion claw B7, a long-axis spring B8, a short-axis rear end spring B9, a pull ring B10, a pull plate B11, a sleeve B12, a retaining ring B13, a pull rod B14, a front end cover plate B15, an internal thread cylindrical pin B16, a hexagonal flange nut B17, a hexagonal thin nut B18, and a screw B19;

[0136] The clamp body B1 is respectively connected to the short-axis front cone top rod B2, the short-axis rear cone top rod B4, the long-axis rear cone top rod B6, the short-axis front expansion claw B3, the short-axis rear expansion claw B5 and the long-axis rear expansion claw B7;

[0137] The clamp body B1 fixes the retaining ring B13, the long-axis rear cone top rod B6 is connected to the short-axis rear end spring B9, the sleeve B12 and the long-axis spring B8 are assembled in the long-axis rear cone top rod B6, and the pull ring B10 and the pull plate B11 are fixed;

[0138] The internal thread cylindrical pin B16 is connected to the clamp B1 and the pull ring B10 respectively, the pull rod B14 is installed on the pull plate B11, the front end cover plate B15 is arranged in front of the clamp body B1, and the hexagonal flange nut B17 and the hexagonal thin nut B18 lock the short shaft front cone push rod B2.

[0139] This solution uses a turning method and fixture to control the difference in piston wall thickness and piston top thickness, and has the following advantages:

[0140] 1. The wall thickness difference between the inner cavity of the piston and the outer circle is smaller, with better consistency and stability, and the wall thickness difference of the piston is controlled within ≤0.15;

[0141] 2. The piston top thickness dimension accuracy is higher, the top thickness dimension consistency and stability are better, and the piston top thickness dimension deviation is avoided, which leads to the piston weight deviation and produces scrap;

[0142] 3. Use a high-precision sensor to directly measure the coordinates of the center point of the inner top of the piston, and automatically compensate for the difference between the workpiece Z coordinate and the machining program coordinate, which is equivalent to using the center point of the inner top of the piston as the axial rough reference, realizing the unification of the machining reference and the measurement reference, and the machining error of the piston top thickness is small, and the consistency and stability are better;

[0143] 4. It avoids the need to measure and group the top thickness dimensions to ensure the piston top thickness tolerance, thus greatly improving production efficiency.

[0144] 5. There is no damage to the non-machined casting surface at the inner top of the piston. The positioning clamping points are more dispersed and the indentation at the contact points is not obvious, which will not cause the appearance of the non-machined casting surface of the inner cavity of the piston to be damaged and produce waste;

[0145] 6. The fixture positioning accuracy is higher, the operation efficiency is higher, and the product processing efficiency is higher;

[0146] 7. It has strong adaptability to the changes in the inner size of the piston blank caused by casting, and there will be no situation where it cannot be clamped. When the size of the blank changes greatly, the fixture will still automatically adapt to such changes and still ensure the accuracy, consistency and stability of the wall thickness difference between the inner cavity of the piston and the outer circle.

[0147] 8. The control requirements for the piston top thickness are removed in the rough machining of the outer circle and the rough machining of the top surface of the blank, which reduces the control items, simplifies the fixture structure design, and saves the fixture cost.

[0148] 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 turning method for controlling the difference in piston wall thickness and piston top thickness, characterized in that: The steps are: S1: Eight points on the inner surface of the piston blank are used as the axial centerline positioning reference. In the piston rough machining outer circle (2) and rough machining top surface (3) processes, the axial positioning of the piston blank is not strictly controlled, and the focus is on controlling the coaxiality between the rough machining outer circle of the blank and the inner axis of the piston blank; S2: Using the floating pressure plate (1) to assist in pressing the piston top surface, and turning the piston outer circle and top surface; S3: In the piston finishing process, the axial position of the piston inner top is automatically measured online by a high-precision sensor, the distance from the inner top of each piston to the stop surface (4) is controlled, and the machining program coordinates are automatically adjusted according to the sensor detection results; S4: The distance from the piston stop surface (4) to the inner top of the piston is precisely controlled to form the piston top thickness dimension after the top surface finishing process is completed.

2. A turning method for controlling piston wall thickness difference and piston top thickness as claimed in claim 1, characterized in that: The step S1 comprises the following sub-steps: Points N1-0, N1-1, N2-0, and N2-1 control two degrees of freedom in the long axis direction of the piston cavity; Points N3-0, N3-1, N4-0, and N4-1 control the three degrees of freedom in the short axis direction of the piston cavity.

3. A turning method for controlling piston wall thickness difference and piston top thickness according to claim 1, characterized in that: The top surface of the piston is pressed by a floating pressure plate (1), and the floating pressure plate (1) only provides a clamping force and does not restrict the degree of freedom of the piston blank.

4. A turning method for controlling piston wall thickness difference and piston top thickness according to claim 1, characterized in that: The step S3 comprises the following sub-steps: S31: The high-precision sensor is installed on the machine tool turret. After the probe coordinates are calibrated, a special control program is compiled to compare the Z-axis coordinate data of the center of the piston inner top measured by the probe with the original coordinate system each time, and calculate the compensation amount; S32: According to the compensation result, the control program automatically adjusts the origin of the original coordinate system, and automatically calls the processing program to complete the piston positioning stop processing; S33: The sensor measurement accuracy is ≤0.

002. The actual processing size accuracy of the piston top thickness is only related to the movement accuracy of the machine tool itself. The clamping positioning error in the piston axis direction will not affect the actual processing size accuracy of the piston top thickness. The previous process of the fine turning stop process does not need to strictly control the consistency of the top thickness size, but only needs to ensure that the top surface has a fine processing allowance.

5. A turning method for controlling piston wall thickness difference and piston top thickness according to claim 1, characterized in that: It also includes a piston fixture control method with a draft angle on the inner cavity side wall and a piston fixture control method without a draft angle on the inner cavity side wall; The control method of the piston fixture with a draft angle on the inner cavity side wall is divided into the following steps: before piston processing, during piston processing, and after piston processing; The control method of the piston clamp with no draft angle on the inner cavity side wall is divided into the clamp position and the release position state before processing, and the state where the inner cavity of the piston (B20) is inserted into the clamp.

6. A turning method for controlling piston wall thickness difference and piston top thickness according to claim 5, characterized in that: The control method of the piston fixture with a draft angle on the inner cavity side wall is as follows: a1: Before piston processing: a11: The spindle cylinder pull rod retracts, driving the positioning shaft push rod (A2) to move backward; a12: Under the action of the spring force, the front push rod (A6) is pushed forward, pushing the short shaft front positioning block (A3) forward until the short shaft front positioning block (A3) is blocked by the positioning body (A1) and cannot move; At the same time, the rear push rod (A7) is pushed forward under the action of the spring force, pushing the short-axle rear positioning block (A4) to move forward until the short-axle rear positioning block (A4) is blocked by the short-axle front positioning block (A3) and cannot move; a13: Under the action of the long-axis floating spring (A12), the long-axis floating push rod (A11) is pushed forward, pushing the long-axis floating block (A5) forward until the long-axis floating block (A5) is blocked by the limit pin (A17) installed on the positioning body (A1) and cannot move; At the same time, under the action of the limit pin (A17), the long-axis floating block (A5) is angularly reset to the designed position in the circumferential direction; a14: There is a height difference between the positioning inclined surfaces of the short-axis front positioning block (A3) and the short-axis rear positioning block (A4), and the positioning inclined surface of the short-axis rear positioning block (A4) is higher than the positioning inclined surface of the short-axis front positioning block (A3); there is also a height difference between the positioning inclined surface of the long-axis floating block (A5) and the inclined surface of the positioning body (A1), and the positioning inclined surface of the long-axis floating block (A5) is higher than the inclined surface of the positioning body (A1); a2: Piston processing: a21: The inner cavity of the piston is inserted into the fixture, the inclined surface of the piston stop end in the long axis direction fits with the positioning conical surface of the long axis floating block (A5) for positioning, and the inclined surface of the piston stop end in the short axis direction fits with the inclined surface on the short axis rear positioning block (A4) for positioning; a22: The tailstock pressure plate presses the top surface. During the pressing process, the pressure plate pushes the piston to move toward the spindle end. The piston pushes the long-axis floating block (A5) and the short-axis rear positioning block (A4) backward in the opposite direction and compresses the corresponding spring at the same time until the height difference between the positioning inclined surfaces of the short-axis front positioning block (A3) and the short-axis rear positioning block (A4) is eliminated. a23: The tailstock pressure plate continues to move toward the spindle end to press the top surface of the piston. The piston pushes the long-axis floating block (A5), the short-axis front positioning block (A3), and the short-axis rear positioning block (A4) backward and compresses the corresponding springs until the inclined surface of the positioning point at the front end of the positioning body (A1) contacts the inclined surface of the positioning point on the side of the piston inner cavity. At this time, the piston is in the final clamping state, and the outer circle and top surface of the piston can be rough-machined; a3: After the piston is processed: a31: The tailstock pressure plate moves backward to release the piston. Because the inner cavity of the piston is tightly fitted with the long-axis floating block (A5), the short-axis front positioning block (A3), and the short-axis rear positioning block (A4) and cannot be separated, it moves away from the spindle under the action of the spring thrust until it reaches the travel limit of the short-axis front positioning block (A3); a32: The spindle cylinder pushes the positioning shaft push rod (A2) toward the tailstock to move the piston and disengage the piston from the long shaft floating block (A5), the short shaft front positioning block (A3), and the short shaft rear positioning block (A4). Remove the piston after processing and prepare for the next processing.

7. A turning method for controlling piston wall thickness difference and piston top thickness according to claim 5, characterized in that: The control method of the piston fixture without a draft angle on the inner cavity side wall comprises the following steps: b1: The state of the fixture and the released position before processing: b11: The main shaft cylinder pull rod retracts, driving the short shaft front cone push rod (B2) to move to the right through the dovetail groove and driving the short shaft front expansion claw (B3) to retract toward the center; b12: The step surface on the short-shaft front cone push rod (B2) drives the short-shaft rear cone push rod (B4) to move to the right, and drives the short-shaft rear expansion claw to retract toward the center through the dovetail groove; b13: At the same time, the short-shaft front cone top rod (B2), the pull plate (B11), the pull ring (B10), and the pull rod (B14) are connected and fixed as a whole by screws and nuts. When the short-shaft front cone top rod (B2) moves to the right, the pull ring (B10) also moves to the right and drives the long-shaft rear cone top rod (B6) to move to the right through the upper step surface of the long-shaft rear cone top rod (B6); b14: ​​The dovetail groove of the long-axis rear cone top rod (B6) drives the long-axis rear expansion claw (B7) to retract the pull rod (B14) toward the center, and the limit position of the rightward movement is controlled by the limit screw on the retaining ring (B13); b2: The inner cavity of the piston (B20) is inserted into the fixture: b21: The long axis positioning point of the piston (B20) fits the conical surface of the clamp body (B1) and the main shaft cylinder moves to the left, driving the pull rod (B14), pull plate (B11), pull ring (B10), and short shaft front cone ejector rod (B2) to move to the left as a whole: b22: The pull ring (B10) moves to the left to release the step surface of the long-axis rear cone top rod (B6). The long-axis spring (B8) pushes the long-axis rear cone top rod (B6) to the left under the action of the spring force. The dovetail groove on the long-axis rear cone top rod (B6) pushes the two long-axis rear expansion claws (B7) to expand out of the inner cavity side wall positioning points of the tensioning piston (B20) to both sides at the same time; b23: The short shaft front cone push rod (B2) moves to the left, the upper step surface is released from the short shaft rear cone push rod (B4), and the short shaft rear cone push rod (B4) moves to the left under the action of the spring force of the short shaft rear end spring (B9), and pushes the two short shaft rear expansion claws (B5) to expand the positioning points of the inner cavity side wall of the tensioning piston (B20) to both sides through the dovetail groove of the short shaft rear cone push rod (B4); S24: The short-shaft front cone push rod (B2) moves to the left, and pushes the two short-shaft front expansion claws (B3) to expand out of the inner cavity side wall positioning points of the tensioning piston (B20) to both sides through the dovetail groove; b25: The tailstock pressure plate presses the top surface, and the piston (B20) is in an accurately positioned and reliably clamped state, and the outer circle and top surface of the piston (B20) can be rough-machined.

8. A turning fixture for controlling piston wall thickness difference and piston top thickness, based on a turning method for controlling piston wall thickness difference and piston top thickness as claimed in any one of claims 1 to 7, characterized in that: It includes a piston fixture with a draft angle on the inner cavity side wall and a piston fixture with no draft angle on the inner cavity side wall; The piston fixture with a draft angle on the inner cavity side wall comprises a positioning body (A1), a positioning shaft push rod (A2), a short shaft front positioning block (A3), a short shaft rear positioning block (A4), a long shaft floating block (A5), a front push rod (A6), a rear push rod (A7), a positioning body transition plate (A8), a spring mounting body (A9), a long shaft floating spring top cover (A10), a long shaft floating push rod (A11), a long shaft floating spring (A12), a spring top cover (A13), a spring bottom cover (A14), a spring (A15), a long shaft floating block spring cover (A16), a limit pin (A17), a pull rod connecting rod (A18), and a main shaft transition body (A19); The positioning shaft push rod (A2), the long shaft floating block (A5), the limit pin (A17), the front push rod (A6), and the rear push rod (A7) are arranged on the positioning body (A1); The short shaft front positioning block (A3) and the short shaft rear positioning block (A4) are respectively connected and fixed to the positioning shaft top rod (A2), and the positioning body transition plate (A8) and the positioning body (A1) are connected and fixed; The spring mounting body (A9) and the positioning body transition plate (A8) are connected and fixed, and the long-axis floating push rod (A11) is connected to the positioning body transition plate (A8); The spring (A15), spring top cover (A13), spring bottom cover (A14), long-axis floating spring top cover (A10), long-axis floating spring (A12), and long-axis floating block spring cover (A16) are arranged on the spring mounting body (A9); The limit pin (A17) is installed on the positioning body (A1) and the long axis floating block (A5), the pull rod connecting rod (A18) is arranged on the spindle transition body (A19), and the spindle transition body (A19) connects the spring mounting body (A9) and the machine tool spindle; The piston clamp with no draft angle on the inner cavity side wall comprises a clamp body (B1), a short-axis front cone top rod (B2), a short-axis front expansion claw (B3), a short-axis rear cone top rod (B4), a short-axis rear expansion claw (B5), a long-axis rear cone top rod (B6), a long-axis rear expansion claw (B7), a long-axis spring (B8), a short-axis rear end spring (B9), a pull ring (B10), a pull plate (B11), a sleeve (B12), a retaining ring (B13), a pull rod (B14), a front end cover plate (B15), an internally threaded cylindrical pin (B16), a hexagonal flange nut (B17), a hexagonal thin nut (B18), and a screw (B19); The clamp body (B1) is respectively connected to the short-axis front cone top rod (B2), the short-axis rear cone top rod (B4), the long-axis rear cone top rod (B6), the short-axis front expansion claw (B3), the short-axis rear expansion claw (B5) and the long-axis rear expansion claw (B7); The clamp body (B1) fixes the retaining ring (B13), the long-axis rear cone top rod (B6) is connected to the short-axis rear end spring (B9), the sleeve (B12) and the long-axis spring (B8) are assembled in the long-axis rear cone top rod (B6), and the pull ring (B10) and the pull plate (B11) are fixed; The internal thread cylindrical pin (B16) is connected to the clamp (B1) and the pull ring (B10) respectively, the pull rod (B14) is installed on the pull plate (B11), the front end cover plate (B15) is arranged in front of the clamp body (B1), and the hexagonal flange nut (B17) and the hexagonal thin nut (B18) lock the short shaft front cone top rod (B2).

Images