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我厂生产的 NJD131型载货汽车装用的 D433A 型柴油机,是新研制、开发的。在试制过程中,参考了同类先进机型。但在选定气缸盖进、排气门座孔与座圈的尺寸公差及装配工艺时,遇到了标准很难确定的问题。在试制图纸上,要求的技术条件是进、排气门座圈镶入座孔前,要将气门座圈冷冻到-60℃。图纸上气缸盖的进、排气门座孔的尺寸分别为φ47H_7~(+0.025)和φ39H_7~(0.025);进、排气门座圈的外圆尺寸分别为φ47Z8(_(0.136)~(0.175))和φ39Z_aB(_(+0.148)~(0.187));过盈量分别为0.111～0.175mm 和0.123～0.187mm。根据冷缩计算
The D433A diesel engine used in the NJD131 truck loaded by our factory is newly developed and developed. In the trial process, reference to similar advanced models. However, in the selected cylinder head into the exhaust valve seat hole and the seat of the dimensional tolerances and assembly process encountered a standard difficult to determine the problem. In the trial drawings, the technical requirements are into, exhaust valve seat set in front of the seat hole, the valve seat to be frozen to -60 ℃. The dimensions of the intake and exhaust valve seat holes on the cylinder head of the drawing are φ47H_7 ~ (+0.025) and φ39H_7 ~ (0.025) respectively. The outer diameters of the intake and exhaust valve rams are φ47Z8 (_ (0.136) 0.175) and φ39Z_aB (_ (+ 0.148) ~ (0.187)) respectively. The interferences were 0.111 ~ 0.175mm and 0.123 ~ 0.187mm, respectively. According to the shrinkage calculation