Gear transmission noise has always been a problem for people. After repeated tests, analysis and improvement tests, it is concluded that all aspects of production must be comprehensively controlled to effectively reduce the noise of gear transmission.
Note 1: Control the accuracy of the gear
The basic requirements of gear precision: verified by practice, the gear precision must be controlled in GB10995-887~8, the line speed is higher than 20m/s gear, the pitch limit deviation, the ring gear radial runout tolerance, the tooth direction tolerance must be stable 7 levels of precision. In the case of a 7-stage precision gear, the tooth portion is chamfered, and the root boss is strictly prevented.
Note 2: Control the quality of raw materials
High-quality raw materials are a prerequisite for the production of high-quality products. The company uses the largest materials, 40Cr and 45 steel, to make gears. No matter the route, the raw materials must pass the strict chemical composition test, grain size measurement and purity evaluation after arriving at the factory. Its purpose is to adjust the heat treatment deformation in time to improve the quality of the tooth profile processing.
Note 3: Prevent heat treatment deformation
After rough machining, the tooth blank is refined into forgings for normalizing or quenching and tempering to: 1. soften the steel for cutting; 2. eliminate residual stress; gear transmission; 3. refine the grain and improve the structure. Improve the mechanical properties of steel; 4, in order to finally be able to handle the preparation of the organization.
It should be noted that in the normalizing or quenching and tempering treatment, it is necessary to keep the temperature of the furnace evenly, and to use the station tool to uniformly heat and cool the workpiece, and it is strictly prohibited to stack them together. For gears that need to be drilled to reduce weight, the drilling sequence should be arranged after heat treatment. To reduce distortion. Tooth surface induction hardening should use a lower quenching temperature and shorter heating time, uniform heating, slow cooling.
Note 4: Guarantee the accuracy of the blank
The accuracy of the size of the gear hole is required to be distributed around the middle of the deviation of the hole, and is set at ±0.003~±0.005mm. If it is out of tolerance and within the design requirements of the hole, it must be classified and transferred to the cutting process. The end face bounce and radial runout of the tooth blank are 6 levels, which are set in the range of 0.01~0.02mm.
Note 5: Cutting teeth processing measures
Outsourced gear cutters must be inspected and must meet AA requirements. After the gear cutter is sharpened, the radiality of the front edge of the tool, the adjacent circumferential pitch of the chip pocket, the maximum cumulative error of the chip pocket circumference, and the parallelism between the front of the cutter and the axis of the bore must be checked. Under the premise of not affecting the strength of the gear, increase the height coefficient of the crown, increase 0.05~0.1m, improve the tooth height coefficient of the cutter, and avoid the tooth root interference of the gear. The gear of M=1~2 adopts the tooth top rounding hob, and the rounding amount is R=0.1~0.15m. Eliminate the burr of the tooth tip and improve the tooth tip interference during gear transmission.
The gear cutting equipment should be inspected once a year for accuracy. If it is not required, it must be repaired. The operator should also perform self-tests frequently, especially when the radial clearance of the machine tool spindle is controlled below 0.01 mm, the cutter shaft diameter is less than 0.005 mm, and the cutter shaft is moved below 0.008 mm. The installation accuracy of the tool: the tool radial runout is controlled below 0.003mm, and the end face is beaten below 0.004mm.
The precision of the cutting tool, the gap between the outer diameter of the mandrel and the hole of the workpiece is guaranteed to be within 0.001~0.004mm. The thread on the mandrel must be ground by a threaded bed under the C-top positioning: verticality ≦0.003mm, diameter jump ≦0.005mm. The nut must ensure that the internal thread is clamped to the reference surface at one time. The parallelism of the washer is ≦0.003mm.
Note 6: Take other materials and heat treatment, surface treatment
1. Powder metallurgy forming technology can be utilized, and the teeth are high-frequency quenched after gear forming. 2, using cast iron, gear cutting process, and then soft nitriding treatment. 3, using 40Cr material, gear cutting work, using soft nitriding treatment or tooth copper plating.
The above is the precautions for the production of gears. To correct the gear transmission noise, gear materials and heat treatment are essential. The accuracy of the blank is guaranteed, and the accuracy of the gear is the key.