1、Cylindrical Coil Compression Springs Made from Round Rods Quality Requirements for Mass Production 1 Purpose Vehicle suspension springs are generally produced, in largeicale manufacture, on largely automatic production lines. The production tolerances obtained thereby are generally closer than in DI
2、N 2096 1). They are subject to statistical relationships which, according to lengthy examination, allow prior calculations to be made. This Standard is intended to enable the permissible deviations to be established, of functionally important charac- teristics in the design of vehicle suspension spr
3、ings. DIN 2096 Part 2 2 Scope The permissible deviations quoted are valid for cylindrical coil compression springs which satisfy the following conditions: - Largescale production, minimum lot size 5000 pieces - Rod length 1 up to 4300 mm - Rod diameter d from 9 to 18 mm - Length of unloaded spring (
4、free length) LO up to 600 mm - External coil diameter De up to 180mm - Number of active coils n from 5 to 12 - Spring index w from 6 to 12 - Total spring deflection s, 180 mm and more 1) DIN 2096, January 1974 edition is to be given the number DIN 2096 Part 1, at the next revision. Continued on page
5、s 2 to 7 Sole sale rights of German Standards (DIN-Normen) are with Beuth Verlag GmbH. Berlin 30 04.81 DIN 2096 Teil 2 engl. Preisgr. 6 Vertr.-Nr. 0106 Page 2 3 Symbols, designations, units DIN 2096 Part 2 Designation Unit Symbol Permissible deviation of the coil diameter Permissible deviation of th
6、e spring force F at specified spring length L mm N AD AF Permissible deviation of the spring rate R Permissible deviation of the total number nt of coils N/mm - AR Ant _ External coil diameter Internal coil diameter Spring force mm mm N Spring force at test length L,* Spring forces at spring lengths
7、 LI, L2 N N Length of the unloaded spring (free length) Lengths of spring under forces FI, F2 Quality grade coefficient Spring rate Deviation of spring form from the cylindrical form Diameter of rod mm mm - N/mm mm rnm Diameter of rod at ends of spring Factor used in determination of the permissible
8、 deviation of the spring rate R mm - Spring deflection Total spring deflection, to solid length Lc mm mm I mm Mean coil diameter Di F Fc the0 Theoretical spring force associated with solid length L, IN Spring length Solid length, shortest possible spring length (all coils in contact) L Test length I
9、 mm LO LltL2 Q R b d 1 Length of rod I mm - Number of active coils Total number of coils - n nt S SC D d w=- Spring index I- DIN 2096 Part 2 Page 3 a De-2 4 Testing and permissible deviation of spring force and spring rate 4.1 Test arrangement For test purposes, the springs are held in seating fixtu
10、res. In the case of springs having ends closed and formed flat, plane- parallel seating fixtures are used, having a centralizing feature for the internal diameter of the end coils. Springs whose end coils terminate with the full thickness of the wire are held in seatings with helical abutment surfac
11、es, which centralize the end coils on the internal diameter and support them over an angle of 270O. The pitch m of the seating fixture should correspond to the diameter of the rod from which the end coils are wound. For angle 270O: m = 0.75 .do. Before the spring force and spring rate are checked, t
12、he springs are to be compressed to solid length L, at least once. b C gm m P De-2do-3 oftang 2*d, do 0,75*do 0,5*do Length r rb7 Il cl-i I I t r.y U Figure 1. Seating fixture for coil compression springs having ends without tangs 2) I 1 A I 4.2 Spring force The spring force must be checked in the ra
13、nge of the spring deflection of 0,3 * s, to 0.7 s, Permissible deviation of the spring force: AF pa = f (0,Ol F, + Q FPa) For coefficient Q: Quality grade A: Q = 0.01 Quality grade B: Q = 0.02 Detail x The quality grade A requires greater effort in order to keep within the narrower tolerances. The t
14、olerance zone of a quality grade can further be sub-divided intotest groups. The quantitative distribution of springs among these test groups is obtained from the statistical distribution together with the standard deviation belonging to the particular production lot. 2) Tangs is the term applied to
15、 the straight run-out ends of the rod. Page 4 DIN 2096 Part 2 The tolerance zone of each test group (group width) should be20.02 . Fpruf, and should be at least 60 N. In consideration of deviations which are possible in the cross-checking of spring forces, the limits of tolerance may be exceeded by
16、0.01 . Fp, including those of the individual test groups. As an alternative to the sorting of springs into test groups, they may be grouped in pairs. The maximum force difference between the springs of a pair is then 5 0.5 -AF. 4.3 Spring rate 4.3.1 Spring rate with linear characteristics The spring
17、 rate must be tested in the range of spring deflection from 0,3 sc bis 0,7 * s, The spring rate R is defined as the differential quotient AF As R=- The difference in spring deflections As used in testing should be 50 mm. Permissible deviation of the spring rate: A,=tkR -R (3) The factor kR is essent
18、ially a function of the number of effective turns and may be taken from the accompanying graph, or calculated from the expression n 700 kR 0,04714- - (4) O.OL0 t I 2 0,032 m LL 0.030 0.028 L 5 6 7 8 9 1011 12 Number of effective turns f - Figure 3. Factor kR as a function of the number of effective
19、turns DIN 2096 Part 2 Page 5 4.3.2 Spring rate with progressive characteristics In the case of coil compression springs with progressive characteristics, testing and determination of the permissible deviations are not possible in the same way as for springs with linear characteristics, since the det
20、ermination of only one differential quotient +f does not describe the form of the rate characteristic. Testing is therefore generally carried out in accordance with the following scheme (Fig. 4): f Li Lptf L2 I LC 0.3 i 10,7xsC Spring deflection s - - Spring length L Where: (1 1 Compress spring to s
21、olid length L, and unload (2) Compress spring to length L1 and read off associated spring force FI (3) Compress spring to length Lpaf and read off associated spring force FpluI (4) Compress spring to length L2 and read off associated spring force F2 (5) Unload spring Figure 4. Diagram of procedure f
22、or inspection testing of compression springs with progressive rate characteristics Page 6 DIN 2096 Part 2 The spring lengths must lie in the range of spring deflection 0,3 - s, to 0,7 * sc The permissible deviation AF Section 4.2. Permissible deviations of the spring forces F1 and F2: of the spring
23、force FPm is calculated from equation (1) with coefficients Q from 5 Rod diameter For vehicle suspension springs,only rodswith the machine-finished surface are employed. Because of the stringent require- ment for accuracy of the spring rate, the rod diameter is not toleranced. The spring manufacture
24、r is thereby afforded the opportunity to make a manufacturing adjustment. 6 Testing and permissible deviation of the end-turn diameter According to the method of assembly adopted in a particular application (spring ends centralized from the internal or external diameter), either the internal coil di
25、ameter Di or the external coil diameter De is toleranced. The permissible deviations of the end coil diameter are: ADe = Di is then given by the equation Di=De- 2do (7) Figure 5. Example of measurement of the external diameter of the end turn 7 Permissible deviation of the total number of turns The
26、permissible deviation of the total number of turns is Ant = k 0,012 * nt The corresponding permissible deviation in mm is: AnteD.n The corresponding permissible deviation in degree is: Ant * 360 In special cases, for example with springs whose end turns terminate with the rod at its full thickness,
27、and which are not held in rotatable spring seating fixtures, a special quality with reduced tolerance can be agreed: Ant = f 0,005 nt (9) DIN 2096 Part 2 Page 7 8 Deviations of form Unlike the practice in DIN 20961), tolerancing of thequantitiesel and e2 isdispensed with, for vehicle suspension spri
28、ngs. Instead of this, a check can be agreed on the deviation b from cylindrical form on the unloaded spring. This deviation of form is tested as shown in Fig. 6, by insertion of the spring into a checking sleeve. The permissible deviation of the cylindrical form is b=+0,015*Lo 1 (IO) Figure 6. Check
29、ing of the form deviation The deviation from the cylindrical form varies in amount and position with loading of the spring. This depends not only on the geometrical properties of the spring (slenderness ratio, spring index, number of turns, pitch of turns) but also on the conditions of production, a
30、nd is not susceptible to accurate determination in advance. Whenever any detriment to the functioning of the spring is to be expected from this cause, agreement should be reached between the spring manu- facturer and user, concerning the critical envelope surface range and loading range. Further Standards DIN 2096 Helical springs made of round bar steel; quality specifications for compression springs quenched and tempered after coiling 1) See page 1
