BS ISO 12251 pdf download

BS ISO 12251 pdf download

BS ISO 12251 pdf download Diesel engines — Clamp mounted CR fuel injectors — Mounting dimensions
1 Scope
This International Standard specifies dimensional requirements for clamp mounted CR fuel injectors and their corresponding cylinder head features in diesel engines.
According to the injector nozzle capnut, the clamp mounted CR fuel injectors can be divided into two types:
a) Type A, where the nozzle capnut is straight (see Figure 4).
b) Type B, where the nozzle capnut is stepped (see Figure 5).
Each clamp mounted CR fuel injector type is subdivided by a series of different sizes.
NOTE This differentiation corresponds to the relationship between the two guide diameters of the clamp mounted CR fuel injectors.
2 Symbols
For the purposes of this document, the following symbols apply:
D 1 = injector shaft diameter
D 2 = injector upper guide diameter
D 3 = capnut diameter
D 4 = injector lower guide diameter
D 5 = injector nozzle shaft diameter
d 6 = bore for upper guide diameter
d 7 = bore for lower guide diameter
d 8 = bore for nozzle shaft
l 1 = overall injector length
l 2 = distance between sealing face and upper guide diameter of injector
l 3 = overlapping (upper guide diameter/cylinder head)
l 4 = injector clamping width
l 5 = clamp width
l 6 = injector clamping height
l 7 = distance between sealing face and datum B on injector
l 8 = distance between sealing face and datum C on injector
NOTE l 7 and l 8 are dependent on the cylinder head design as agreed between injector manufacturer and customer.
3 General requirements
3.1 Clamp mounting arrangement
A typical clamp mounting arrangement is shown in Figure 1 (schematically).
3.2 Injector guiding dimensions
The important injector guiding dimensions are shown in Figure 2 (schematically).
3.3 Concentricity of the nozzle shaft
The determination of the concentricity, ∅c, of the nozzle shaft relative to the axis of the two guide diameters,∅D 2 and ∅D 4 , is shown in Figure 3 (schematically).
The concentricity, ∅c, is the result of the form and position tolerances of the two guide diameters, based on the production conditions, and is specified by the injector manufacturer by simultaneously taking into consideration the compatibility with the dimensional structure of the cylinder head.
The purpose of this concentricity is to determine the position of the nozzle shaft (centre axis of ∅D 5 ) related to the cylinder head bore, ∅d 8 ; this is important in order to ensure that the nozzle shaft does not interfere with the bore in the cylinder head (see Tables 2 and 4, table footnote c, and Figure 3, key item c).

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