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Multi force source fine blanking for core parts of at gearbox

    At gearbox is composed of hydraulic torque converter, clutch, planetary gear mechanism, hydraulic control system, etc. it is assembled on most automatic transmission vehicles. The number of transmission gears is one of the standards to measure its technical content. Most household cars have five or six gears, while luxury cars prefer more automatic transmissions. For example, Benz C cars and BMW series are equipped with 8 / 9 speed automatic transmission.
    As an important part of at transmission, the clutch piston balance system has the following functions: counteracting the centrifugal force acted on the piston by the clutch; realizing faster clutch control and shortening the shift time; assisting the clutch return spring to release the clutch faster; increasing the oil pressure buffer (pressure accumulation function) in the shift process. The core component of the clutch piston balance system is the balance plate (Fig. 1). This paper introduces the die structure design and process formulation of the balance plate in detail.
    Figure 1 balance plate
    Balance plate structure
    The structure and size of the balance plate are shown in Fig. 2.
    Figure 2 structure and size of balance plate
    (1) the material is hc280la cold rolled sheet with a thickness of 4.5mm.
    (2) the balance plate is composed of toothed central hole, 3 stepped surfaces, 6 small holes and 6 toothed half punched holes on the reverse side.
    (3) the position between the center hole and small hole of the belt tooth and the boss tooth should be within 0.08mm, and the step height tolerance should be 0-0.05mm. In order to ensure the positional degree from the center hole and small hole to the boss tooth, one forming is needed to ensure the product accuracy, and the dimensional requirements of three structures should be ensured at one working position.
    Analysis of semi punching process
    (1) process principle.
    Principle of semi punching technology: under the action of three forces, the metal moves to the other direction without damage to the shear zone. It is a fine blanking process for directly processing parts with boss. As shown in Fig. 3, due to dislocation and slip of metal, cold work hardening occurs in the shear zone, and the tensile strength is improved, and the material structure changes.
    (2) process requirements.
    1) The bottom hole is equal to or less than the boss diameter, and there is no crack in the shear zone.
    2) The volume V1 (hole layer extrusion part) is about 1.2 times V2 (material extrusion part), as shown in Fig. 4.
    3) For the boss on the burr side, the compound fine blanking die is required.
    Fig. 3 half punching
    Figure 4 Schematic diagram of boss forming
    4) For the boss on the corner collapse side, the compound fine blanking die with return punch or continuous compound fine blanking die is required.
    5) When grinding with abrasive belt, the parts are free from jamming.
    6) Reverse R or C angle at the root of counterbore to increase the strength of boss.
    Process development
    Process analysis
    Fig. 5 Schematic diagram of machining process
    The processing procedure is shown in Fig. 5. The fine blanking compound forming process is adopted and the continuous compound die is used for processing. The strip is fed from left to right to realize continuous production. The process sequence is as follows.
    The first process: punch positioning hole and half punch convex step 2.
    The second process: punch the center hole, small hole and six boss of belt tooth.
    The third process: punching the profile and the steps with a diameter of 149.3 mm, and at the same time, pay attention to prevent the deformation of the steps and the center hole.