The cold extrusion of the involute tooth spline mainly adopts the reduced diameter extrusion square diagram i as shown in Fig. i for the involute toothed spline shaft of a certain type of car transmission, and its tooth shape parameter is the number of teeth! =12, modulus "=1.25, pressure angle a=20., displacement coefficient = 0.60, tip circle diameter = 16.75 mm, root circle diameter = 14.0 mm, involute spline effective length is 44 mm; The opening spline portion is connected with the fork, and functions as a shifting shift. Since the involute tooth spline and the fork only transmit torque, the spline has a low requirement for the motion accuracy of the tooth shape. Involute gear parts with low motion accuracy are suitable for mass production by cold extrusion.
2 Involute tooth spline cold extrusion forming principle method. The reduced diameter extrusion is a positive extrusion method with a small degree of deformation, and the blank section is only slightly reduced, and the reduced diameter pressing force is lower than the yielding force of the rod portion of the extruded material. This method is mainly applied to the forming of toothed parts (gears, splines, etc.).
When the involute spline is cold pressed, the extrusion die is mounted on the work surface of the extrusion apparatus, and the workpiece blank is placed in the upper and lower mold cavities.
When the upper die is moved downward, the workpiece blank is forced into the toothed cavity of the extrusion die. With the continuous downward movement of the extrusion upper die, the toothed cavity of the extrusion die is brought into contact with the workpiece blank, that is, the same tooth profile as the extrusion die is pressed out on the outer surface of the workpiece blank.
3 Cold extrusion process of involute toothed spline shaft 3.1 Development of cold extrusion drawing The toothed part of the spline shaft is cold extrusion processed by reducing the diameter of the extrusion, the outer hexagon and the groove part It is processed by subsequent machining methods. Due to the high requirements of the shaft part and surface quality of the part, the subsequent machining allowance should be left. A cold extrusion drawing of an involute toothed spline.
3.2 Determination of the diameter of the extruded blank of the toothed part In the cold extrusion process, the determination of the diameter of the extruded part of the toothed part is one of the key factors determining the success of the extrusion process.
The correct extruded blank diameter is generally near the indexing circle (or the median diameter of the tooth). The formula is: (or medium diameter shield diameter; Ad is the diameter change is determined by the structure and material properties of the extrusion. .
Bars in their supply state have higher strength and hardness and internal organization is not uniform. Therefore, the material of the extruded blank must be softened and annealed before cold extrusion to improve the cutting performance of the material, improve the plastic deformation performance, and reduce the deformation resistance.
The annealing process is as shown, the hardness after annealing is 140*170HBS. The annealing process of 45 steel 3.3.2 When the extruded blank is processed, the steps are required to have good coaxiality and good surface quality. .
3.3.3 Surface Lubrication of Extruded Blanks During the cold extrusion forming of involute splines, the deformation zone is concentrated near the tooth profile, making the metal flow at that location very severely deformed. To obtain a tooth-shaped extrusion with good surface quality, it is necessary to surface-lubricate the extruded blank after machining. The process uses a phosphating solution containing zinc phosphate as a main raw material to surface-treat the extruded blank, and then uses a molten stearic acid soap as a saponification liquid for surface lubrication treatment.
4 mold structure design 4.1 cold extrusion die structure The cold extrusion die structure as shown in the figure is characterized by the upper and lower molds using the guide sleeve for guiding and guiding precision, the mold structure is simple, and the processing is convenient; the upper die is fastened with a nut Fastening, the lower mold is fastened by the lower molding plate, which is advantageous for the "centering" of the upper and lower molds and the replacement of the mold is faster.
4.2 Involute spline extrusion toothed core design Involute spline extrusion toothed core as shown. The design of the core mainly includes selecting appropriate tooth parameters and tooth diameters, and determining the angle, length and fillet size of the extrusion transition section, the extrusion section and the ejection section.
4.2.1 Tooth shape design of tooth profile core The tooth profile design of the core is required to be able to coldly extrude the workpiece tooth shape according to the specified tooth thickness and tooth height, so the modulus and number of teeth of the core tooth shape should be The workpieces are the same. Considering the problems of thermal expansion and contraction of the extruded workpiece and elastic recovery of the die and the extruded workpiece, the pressure angle and the displacement coefficient of the core tooth shape cannot be the same as the tooth profile pressure angle or the displacement coefficient of the spline shaft.
Normally, the pressure angle is kept constant by correcting the core tooth-shaped displacement coefficient. Its displacement coefficient! Mainly related to the modulus pressure angle a of the gear and the degree of extrusion deformation e, which can be expressed by the following empirical formula: the number is determined by the size of M; the correction coefficient for the pressure angle a is determined by the magnitude of a. % is the correction factor of the degree of deformation, which is determined by the geometry of the gear, the shape and size of the extruded blank, and the properties of the extruded material.
The tooth-shaped deformation coefficient determined by the formula (2) is only a theoretical value, and the final value of the displacement coefficient needs to be determined in the test.
In addition, in order to reduce the cold extrusion forming force and solve the problem that the extrusion tooth shape can be assembled without subsequent processing, the height of the tooth tip of the core is smaller than the root height of the tooth profile of the workpiece, and the root height of the extrusion core is high. The crest is larger than the tooth profile of the workpiece.
According to the above empirical formula, it is determined that the displacement coefficient X=0.44 of the illustrated involute spline gear core is constant.
4.2.2 Squeezing transition section of toothed core The key to designing the transition section of toothed core extrusion is to select the appropriate slope. When the slope is too large, although the metal flow is short and the friction is low, the radial pressure component during the extrusion process is large, so that the axial pressure component required for extrusion is reduced, which increases The extrusion force makes the axial flow of the metal more difficult and causes the upsetting of the extruded blank "to make the extrusion difficult to continue. When the inclination is too small, the metal has a long flow path and a large friction force, which also causes the extrusion. It is difficult to flow metal during the pressing process. In this process, the slope of the extrusion section of the core is 52.5.~30. It is suitable.
4.2.3 Length of the extrusion section of the toothed core The length of the extrusion section of the toothed core has a certain influence on the quality of the toothed part after extrusion. The length of the toothed core extrusion section is 4.0, 7.0 mm is most suitable. If the length of the extrusion section is C>7.0mm, the frictional force of the shell IJ metal will greatly increase the flow difficulty, and the rod portion of the extrusion member is easily bent and unstable, which affects the normal production of the extrusion; when the extrusion force is small, However, the extruded toothed portion is easily distorted.
4.2.4 Ejection return section of the toothed core design The design method of the ejecting return section of the toothed core is similar to the extrusion transition section mainly by selecting the appropriate slope. When the inclination is too large, although the flow of the metal is short, the friction is low, and the extrusion is easy to form. However, in the process of the ejection and returning, the extrusion section is short, which tends to cause the extrusion to be thick, which makes the extrusion difficult. Ejection; when the inclination is too small, the ejecting guide section is long, and the extrusion member is easy to eject, but the extrusion process is difficult to perform normally due to the long flow path of the metal during the extrusion process and the large friction force. In the process, the gradient of the ejection core of the film core is 45.~60. It is suitable.
4.3 Processing of toothed cores chrome steel 12MV. The material must be fully forged to make the metal matrix dense, improve the carbide non-uniformity and improve its processability and performance to extend the service life of the toothed core. The hardness of the core after heat treatment is 60~62HRC. Usually the toothed core is a non-standard special internal toothed part, so the machining of the internal tooth shape must be made on a special wire cutting machine. Its processing route is: cutting! Cross change forging! Spheroidizing annealing! Rough machining! Quenching and tempering! Finished car processing! Wire cutting internal tooth shape! Polished internal tooth shape! Stress relief annealing! test.
5 Cold extrusion molding process test 5.1 Positioning of cold extrusion blanks To achieve a stable and smooth extrusion process, reliable blanks are very important. When the spline is squeezed, in addition to ensuring the coaxiality requirements of the upper and lower molds, the root diameter of the toothed core and the cold extruded blank (the gap of the liver portion of 13.9 mm less can not be greater than 0.20 mm to ensure the blank The part is well positioned in the toothed core. At the same time, the cold extruded blank should be positioned within the upper mold to a length of 50, 55 mm to avoid distortion of the blank when subjected to the pressing force.
5.2 Test equipment selection and test adjustment For the long-axis spline shaft shown, a hydraulic machine with a lower forming speed should be selected. The process uses a YX32-100 four-column hydraulic press for extrusion processing.
A series of adjustments must be carried out before extrusion, including the adjustment of the hydraulic machine, the installation and adjustment of the mold base and the mold, and the adjustment of the ejection stroke. The correct installation or adjustment of the mold will determine whether the cold extrusion can proceed smoothly and the degree of distortion of the cold extrusion. The mold must be adjusted to ensure that the upper and lower molds have a high degree of concentricity.
5.3 Process parameters Selecting the extrusion process parameters, including the forming speed, extrusion time, and pressing force, the pressure of the second stage is easy, the forming and extrusion strokes are the same as the flower 1 - use maintenance - engine power Control system line breakage and poor contact failure analysis Ge Xiulong (Jiaxing Vocational and Technical College) is prone to line breakage, poor contact failure and fault code display. Combined with the failure example analysis, the detection method and maintenance method are proposed for the line breakage and poor contact failure of the faultless code display.
Key words Engine electronic control system open contact failure Most electronic control system faults can directly use the engine diagnostic instrument to read the fault code and solve it according to the fault handling process. However, line faults (such as open circuit, poor line contact, etc.) are generally difficult to make accurate judgments. This article takes the 2003 Accord (2.4L) vehicle engine electronic control system as an example to solve the line fault (such as The ship's cause, manifestation, range of influence and detection method were analyzed in detail.
The forming speed is 8~10mm/s, the pressing time is about 10s, and the pressing pressure is 490/588kW. The extrusion stroke is based on the length of the spline segment required by the part and the limit is adopted by the rigid stopper.
6 Conclusion Through mass production practice, it is shown that the use of cold extrusion molding process to produce splined shafts with involute profiles has the following advantages: the degree of deformation during spline extrusion is small, and the life of cold extrusion die is greatly increased. It is improved, and the manufacturing cost of the toothed core is very low, and the completion process is simple.
Cold-pressed involute toothed spline is full, clear outline, 2 line break and poor contact causes and manifestations 2.1 Line thermal oxidation due to long-term high temperature conditions on the engine (such as throttle position sensor, advance The gas branch pipe pressure sensor, engine coolant temperature sensor, crank position sensor, camshaft position sensor, intake air temperature sensor, air-fuel ratio sensor, sub-heating oxygen sensor, etc.) are easily oxidized to generate oxides such as CUO and Fe23. The contact resistance is formed; at the same time, the wire harness insulation layer is also easy to age and can meet the design requirements of the product.
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