CPC2 type forklift transmission, 10% of the 名媛直播 have abnormal noise during the factory test and cannot pass through smoothly. Upon inspection, it is found that the abnormal noise is emitted from the input shaft assembly (see Figure 1), accompanied by the relative axial direction of the gear and the bearing sleeve. Displacement and rotation displacement phenomena. The analysis shows that the large diameter of the spline in the shaft sleeve is out of tolerance with respect to the radial direction of the outer circle of the shaft sleeve, which causes the bearing and the front and rear gears to be squeezed.
1 Cause analysis
After analysis, the causes of the large deviation of the spline in the shaft sleeve (hereinafter referred to as the sleeve) relative to the radial runout of the sleeve are mainly due to the following aspects.
1.1 Positioning error when machining sleeve
(1) When finely grinding the outer circle of each section of the sleeve A, B, C and D (see Figure 2), the large diameter of the splined inner hole of the sleeve and the large diameter of the spline taper mandrel are used for positioning, outside the grinding For circles C and D, since the outermost wall thickness of the sleeve is only 4.5mm and is in a suspended state, when the radial grinding force is large, elastic deformation will occur, resulting in the radial runout of the sleeve outer circle. .
(2) Analyze from the extreme phenomenon, if the large diameter of the spline in the bushing is in contact with the large diameter of the spline taper mandrel on the G surface, the length from the contact position to the outermost edge P of the workpiece outer circle is 146mm. The maximum diameter taper of the spline taper mandrel used for positioning is 1:3000, and the actual taper length is 200mm, so the diameter difference x of the large end and the small end is 1:3000=x:200, x=200/3000=0.067 mm, its maximum inclination y is: 0.067:200=y:146, y=146×0.067/200=0.0489≈0.05mm, when the outer circles of A, B and C have been ground out in sections, grinding the outer circles D to P At the point, especially when the grinding wheel is blunt, and the dressing is not timely, the radial cutting force will increase. When the tension of the sleeve pressed into the spline taper mandrel is exceeded, the positioning reliability changes, resulting in irregular tilt , Seesaw phenomenon, leading to radial run-out tolerance of the outer circle of the sleeve.
(3) There are debris on the mating surface or center hole of the spline taper mandrel.
(4) There are debris or burrs in the inner hole of the spline of the sleeve.
The combined effect of the above four conditions leads to a phenomenon: the shaft sleeve after grinding the outer circle of each section of A, B, C, D is checked without removing the spline taper core shaft. The outer circle of each section is relative to the inner spline of the sleeve The radial runout of the outer diameter of the large diameter is not necessarily out of tolerance, but if the sleeve and spline taper mandrel are removed and reinstalled and then inspected, it may be out of tolerance.
1.2 The measurement method is unreasonable
Because the measurement method of the radial runout of the outer sleeves of the sleeves A, B, C, and D in the process is not clearly specified, the measurement method of the flat plate and the V-block with a dial indicator is often used in the actual measurement. The C and D planes are used as a reference to measure the radial runout of the outer circles of the A and B planes, which cannot truly reflect the radial runout of the outer circle of the bushing, which can easily lead to misjudgment.
2 Improvement measures and effects
After discovering the above problems, the following measures were taken:
(1) Change the large diameter taper of spline taper mandrel from 1:3000 to 1:5000 to improve the reliability of positioning.
(2) The clamping direction is specified. The large diameter of the large end of the spline taper mandrel and the large diameter of the spline in the sleeve must be in contact at the F end, and the axial distance from the positioning surface to the processing position should be as short as possible.
(3) Specify the number of times to dress the grinding wheel. When grinding 10 pieces of the outer circle of the bushing, dress the grinding wheel once.
(4) Based on the large diameter of the spline in the sleeve, use the large diameter positioning of the spline taper core shaft to measure the radial runout of the outer circle of each segment of A, B, C, and D, and use the measurement results of clamping twice to determine the shaft Whether the radial runout of each section of the sleeve is qualified, it is stipulated that the measurement results of the first clamping and the second clamping are not allowed to exceed the tolerance.
(5) Add a deburring and cleaning process before the heat treatment of the sleeve, and add a cleaning process after the heat treatment of the sleeve.
(6) Set the process of grinding the outer circle as a key process to improve the quality of the process and remind the operator to keep the mating surface of the spline taper mandrel and the center hole clean.
Through the above measures, the pass rate of the outer circle radial runout of each section of the shaft sleeve is improved, and the abnormal noise problem that occurs in the factory test of the transmission is better controlled. The gear and the bearing sleeve are not squeezed by external force, and the relative axial displacement and rotation occur The phenomenon of displacement is reduced accordingly.
