Inspection and data processing of the hottest cams

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Camshaft detection and data processing

1 overview

camshaft is the core component of motorcycle, automobile, aircraft and other engines. Its function is to ensure the correct valve timing of the engine and control the timing opening and closing of the valve group according to a certain motion law

the position and shape of each cam on the camshaft are the main factors that affect the valve opening and closing clearance and valve distribution efficiency. At present, under the condition that automatic production line has been widely used in camshaft processing, the traditional detection methods and detection data need to be manually processed, with a large amount of information and low efficiency. The quality information can not be fed back in time, which is far from meeting the requirements of high-efficiency and high-precision production. However, it is not mature to require expensive automatic cam detection devices, computer data processing systems, display and printing equipment. Another method must be adopted to make the cam detection meet the needs of production

for this reason, this paper uses the method of manual detection of domestic digital display cam detector combined with self-made computer data processing program to detect the cam. It does not need expensive automatic cam detection device, but also can display and print the detection results through self-made program

2 camshaft inspection contents

engine camshaft inspection contents generally include:

· correct selection of inspection benchmark

· accurately determine the detection position

· solve (calculate) the starting angle of detection

· correctly select the starting position of lift (Reference), i.e. "zero lift"

· detect the cam lift and the circular jump of the base circle

· process the cam lift detection data to calculate the lift error meeting the requirements of "minimum condition"

· give the actual base circle radius of each cam

· determine the eligibility of cam lift according to relevant professional standards and lift tolerance requirements

· others, such as the diameter of the reference journal, the surface roughness of the cam profile, etc

· make a practical conclusion on the inspected camshaft

3 selection of inspection standard

generally, the engine cam is not marked with inspection standard. For the cam without reference, the position of its actual contour relative to the ideal contour, that is, the detection position of the cam shall be determined according to the requirements of "minimum condition". Therefore, the benchmark for realizing the ideal detection position of the cam cannot be arbitrarily specified. It should also be selected according to the actual conditions of the cam and the requirements of "minimum conditions"

suppose that m and N are two points on the left and right contour of the cam. When the cam has a position error Da, the lift error of M and N can be calculated from the cam detection equation h=h (a, R, R0, RC) and subtracted from equation (1) to obtain

△ α= (△ hm- △ HN)/(hm'-hn') (2)

according to equation (2), only when m and N are the "sensitive points" with the largest absolute value of the left and right lift change rates of the cam, and the lift errors of the left and right "sensitive points" are equal △ α Minimum value for. "Sensitive point" is the "best" datum of cam

4 solution of detection starting angle and lift detection skills

Figure 1 automatic cam detection device

the detection of cam lift can be automatically measured by the automatic cam detection device shown in Figure 1 according to the program, and the detection results can be displayed or printed through computer processing. It can also be tested manually on the cam tester. In manual inspection, the key is to solve the starting angle of lift inspection according to the requirements of "minimum condition". How to establish (solve) the formula for starting angle of cam detection,

0=[h'm (M- α m)-h'n( n- α n) ]/(h'm-h'n) (3)

the author has made a detailed introduction in the "method for solving the starting angle of cam detection" in the first issue of Metrology Technology in 1994 and the "method for solving the accurate value of the" minimum condition "lift error of cam" in the second issue of Metrology technology in 1999. There is no need to repeat it here

5 processing of lift detection data

take the detection data based on "sensitive points" as iterative data, find out the maximum and minimum points of lift error on the left and right sides of the cam, determine the equidistant points (the maximum or minimum equidistant error points, if they meet the "criteria", this paper takes the maximum and maximum points as examples), and obtain the equidistant equation, that is,

esm- (△ ha+h'a · △) α)= esn-(△hb+hb'·△ α)

solve the above equations to obtain △ α= [(ESM ESN) - (△ ha- △ HB)]/(h'a-hb') (4)

where ESM and ESN - deviation of left and right lift of cam

△ ha, △ HB - lift error at the maximum point of the left and right errors of the cam

ha, Hb -- lift change rate at the maximum point of the left and right errors of the cam

△ α—— Reference conversion amount

lift error complying with the requirements of "minimum condition", calculate

△ H (I) = △ hi+hi'·△ α (5)

where △ Hi, △ H (I) - lift error of measured points before and after datum conversion

hi'-- lift change rate of the measured point

the cam reference conversion (lift data processing) process is shown in Figure 2

(a) detection of lift error curve (lift unqualified)

(b) compliance with "minimum condition" lift error curve (lift unqualified)

(c) compliance with "minimum condition" lift error curve

Figure 2 evaluation of cam lift error curve compliance with "minimum condition" and determination of lift eligibility

there are many cams on one camshaft of the engine. For example, there are more than 180 measuring points for each cam at an interval of 1 °, There are more than 500 data for a single cylinder shaft, and more data for multi cylinder engines. Therefore, the processing workload of detection data is quite large, and manual calculation is time-consuming, laborious and prone to errors. For this reason, the following computer processing program is given: 1 engine cam lift error conversion program

5 defdbla-h

10 input "input the number of points and left points measured in the latest issue of the journal utilization of materials and interfaces:", I, m

15 input "input the upper and lower deviation of left and right side lift:", Es1, ei1, ES2, ei2

20 input "input the starting angle of detection:", ao

25 dim a (I), B (I), C (I), H (I)

30 for s=1 to i

35 input "input the measured point angle value in sequence:", a (s)

40 input "input the measured point lift error value in sequence:", B (s)

45 input "input the measured point lift change rate value in sequence:", C (s)

50 next so China has been importing foreign garbage to make up the gap s

55 d=b (1): e=b (1): f=b (1): g=b (1)

60 for j=1 to m

65 if d>b (J) then goto 75

70 d=b (J): n=j

75 if E80 e=b (J): 0=j

90 next j

100 for k=m+1 to i

110 if f>b (k) then goto 130

120 f=b (k): p=k

130 if g140 g=b (k): q=k

150 next k

160 print "maximum point on the left side:", a (n), B (n), C (n)

165 print "minimum point on the left side:", a (o), B (o), C (o)

170 print "maximum point on the right side:", a (P), B (P), C (P)

175 print "minimum point on the right side:" a (q), B (q), C (q)

180 if ABS (C (n))>abs (C (o)) and ABS (C (P))>abs (C (o) then: goto 210

190 if ABS (C (n))>abs (C (q)) and ABS (C (P))>abs (C (Q) then: goto 210

200 print "the two minimum points shall be equidistant: l=0:if B (n)>b (P) then print" the maximum point is ", B (n) else print" the maximum point is ", B (P): goto to 220

210 print" the two maximum points shall be equidistant ": l=1:if B (o)>b (q) then print" the minimum point is ", B (q) else print "minimum point: B (o)"

230 dd=3#/180

240 a1=a1*dd:a2+a2*dd:a3=a3*dd:a4=a4*dd

250 if l=0 goto 270

260 a11= ((es1-es2) - (b (n) -b (P))/(C (n) -c (P))

265 a10=ao+a11:goto 280

270 a11+ ((ei1-ei2) -b (o) -b (q))/(C (o) -c (q))

275 a10=ao+a11

280 print "detect the initial rotation angle, conversion amount and optimal solution value of initial rotation angle:", Ao, a11, A10

290 for t=1 to i:h (T) =b (T) +c (T) *a11

300 "lift error value before and after conversion:", a (T), H (T): next t

310 d=h (1): e=h (1)

320 for t=1 to i

330 if d>h (T) then goto 350

340 d=h"t

380 h10=d-e

390 print" the minimum width of the containment area is: ", H10

400 print "maximum error point rotation angle and error value:", a (m), H (m)

410 print "minimum error point rotation angle and error value:", a (n), H (n)

420 end

6 lift eligibility determination

after converting the detected lift error curve into the form of lift error curve meeting the requirements of "minimum conditions", the shape of the minimum containment area is consistent with the shape of the lift tolerance zone, However, the lift out of tolerance as shown in Figure 2 (b) may still occur

when the lift error curve is out of tolerance, never arbitrarily determine that the cam is unqualified

through analysis, if the evaluation starting position (rotation angle) of the cam is changed, that is, the over handicap can be moved into the tolerance zone through the change of the evaluation benchmark without causing other qualified points to move out of the tolerance zone, then the unqualified lift becomes qualified. Although the width of the minimum containment area is increased (not meeting the "minimum condition") the lift of the cam is acceptable

as shown in Figure 2 (c), change the cam evaluation starting angle ((0)) to △ α 1, the over tolerance C moves into the tolerance zone. At this time, the change direction of the different boundary point a on the same side is consistent with C, and the change direction of the same boundary point D on the different side is opposite to C. if both a and C do not move out of the tolerance Zone, the cam lift is qualified. Thus,

eim- (△ hc+hc'· △ α 1) =0 (point C falls on the tolerance zone line) (6)

│ esm- (△ ha+ha'· △ α 1)│≥0 (7)

│ein=(△hd+hd'·△ α) │≥ 0 (8)

the △ α 1= (eim- △ HC)/hc'(data center display 9)

substitute equation (9) into equation (7) and equation (8) to get

│ (esm- △ HA)/ha' │ ≥│ (eim- △ HC)/hc'│ (esn- △ HD)/hd ≥│ (ein- △ HC)/hc' (10)

make K1 = hc/ha, K2 = hc/hd, and get

.K1 (esm- △ HD) │ ≥│ eim- △ HC │ ≤ │ K2 (ein- △ HD) │ (11)

where △ HC - lift error of super handicap C

△ ha -- lift error of point a on the same side as C

△ HD -- lift error at the same boundary point D on the opposite side of C

esm, EIM -- up and down deviation of left lift of cam

ein -- lower deviation of the lift on the right side of the cam

h'a, h'c, hd'-- lift change rate of error limit points a, C, D

equation (11) is the qualified judgment equation of cam lift. It should be noted here that when the super handicap is not C but a, C is the same boundary point on the same side, and B is the same boundary point on the different side; When B is the super handicap, D is the ipsilateral outlier. A is the same boundary point on the opposite side; When D is the super handicap, B is the same boundary point on the same side, and C is the same boundary point on the different side. When using the judgment formula of equation (11), K1, K2 and the subscript in the selection formula shall be correctly determined according to the difference of the super handicap. (end)

Copyright © 2011 JIN SHI