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Accuracy depiction of spur gear transmission
Source: China Bearing Network Time: 2014-04-03
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The demand of modern industry for gear transmission; summarized in the following four items:
1. The change of the transmission ratio within the scale of demand is as high as possible. The member V is a master. (Accurate motion)
2, the demand for instantaneous transmission ratio changes as much as possible. Staff V 㔠龋 龋 龋 穸 穸 肷 ( ( ( ( ( ( ( ( ( (
3. The demand can be excellently touched under the load of the working tooth surface; to ensure the satisfactory bearing capacity and service life. (Touch accuracy)
4. The required gear pair has proper flank clearance (interval between the non-working surfaces of the meshing teeth; to compensate for thermal deformation and storage of lubricating oil.)
Gears and gears with different uses and different operating conditions pay different attention to the above four requirements. For example, the emphasis of the steering system of the control system or the follow-up system is the motion accuracy; to ensure the master and slave. The movement of the moving gear is harmonious. The focus of the gear shifting of the car and the tractor is the smoothness of the work; to reduce the noise. The focus of the low-speed heavy-duty gear transmission (such as the gear transmission of the rolling mill) is the tooth surface touch accuracy; to ensure the tooth surface The touch is outstanding. The high-speed heavy-duty gear transmission in the turbine has a high demand for three-point accuracy; and it requires a large flank clearance; to ensure a large flow of lubricating oil passes.
Second, the identification target of the gear error is to check the gear; the following identification targets are established for the spur gear:
1. Identification target of motion accuracy (1) Tangential induction error ΔFi
It is said that the measured gear and the ambition accurate measurement of the single-plane meshing transformation are related to the rotation angle of the measuring gear; the maximum difference between the measured gear and the theoretical rotation angle of the measured gear in one revolution of the measured gear. It is an inductive target. .
(2) cumulative error ΔFp of the week; K cumulative error ΔFpk.
The boundary said: on the indexing circle of the measured gear; the maximum difference between the practice arc length and the nominal arc length between the two ipsilateral tooth faces is an inductive target.
(3) Ring gear radial runout ΔFr and common normal length change ΔFw
A, ring gear radial runout ΔFr
The definition: in the gear one-turn scale; the probe is in the tooth groove or on the gear teeth; double-sided touch in the middle of the tooth height; the maximum change of the probe related to the gear axis. It is a unidirectional target. (radial direction)
B, the length of the common normal line changes ΔFw
The definition: in the one-week scale of the gear; the difference between the maximum and minimum values ​​of the common normal line length is a tangential target of tangential nature.
(4) Radial induction error ΔFi′′
Radial induction error ΔFi′′: when the measured gear and the ambition accurate measuring gear double-sided meshing transformation; within the one rotation of the measured gear; the maximum variation of the distance between the double teeth. It is a radial single target.
To sum up: about gears; errors affecting the accuracy of transmission motion can be identified by an inductive target or two single-objective targets. Radial properties; tangential properties each take a single talent to reflect the various processing elements to the movement Accuracy impact.
2, the identification of the accuracy of the operation (1) tangential one tooth induction error Δfi@
The definition: on the tangential induction error record curve; the maximum fluctuation of the small ripple. It is an inductive target.
(2) Radial one-tooth induction error Δfi′′
It is said that the radial inductive error records the maximum fluctuation of small ripples on the curve.
In mass production; Δfi′′ is the surrogate target of Δfi@ (also an inductive target).
(3) Tooth shape error Δff and base section error Δfpb
A. Tooth shape error Δff: on the tooth end face; the tooth-shaped working part is divided; the crest chamfer contains some normal spacing between the two tooth shapes that accommodate the actual tooth shape. It is a unidirectionality. The goal.
B. Base section error Δfpb: the difference between the practice base section of the measured gear and the nominal base section. It is a one-way target.
(4) Tooth shape error Δff and circumferential section error Δfpt
Weekly error Δfpt: on the index circle; the difference between the practice week and the nominal week. It is a one-way goal.
(5) Weekly error Δfpt and base section error Δfpb
In summary: Δfi@ is the inductive goal for identifying the smoothness of gear operations. The spur gear Δfi@ is caused by the base section error and the tooth profile error. When using the single target to identify the accuracy of the spur gear; Incision method; in principle, the targets of Δff and Δfpb can be selected. The prototyping method or the fan-forming method is related to the single-tooth indexing grinding gear Δff and Δfpt. In this case, the target can be selected as to whether the diameter is larger or lower. 7-level precision gear; due to the limited measurement of the involute viewer; the price is more expensive; therefore, the target of Δfpt and Δfpb should be selected.
3, touch accuracy identification target gear operation; two tooth surface touch is outstanding; ability to ensure uniform load on the tooth surface. In the direction of the tooth height; tooth shape error will affect the touch of the two tooth surface, in the tooth width direction; The error will affect the touch of the two tooth faces.
The tooth misalignment is formed when the gear is machined; the tool feed direction is not parallel with the direction of the gear reference axis. For example, the tool guide rail is slanted in the radial direction and the tangential direction of the tooth blank, and the positioning end of the tooth blank faces the reference axis. The adjustment error of the machine tool drive chain is also the primary cause of the tooth misalignment.
The identification goals of the tooth surface touch accuracy are:
1 tooth orientation error (△Fβ)
On the indexing cylindrical surface; the tooth width is useful in some scales (the end chamfer is somewhat outside); the end face spacing between the two depicting tooth lines that accommodate the practice tooth line and the smallest interval is the tooth misalignment.
The tooth line is the intersection of the tooth surface and the indexing cylinder surface. Usually the tooth line of the spur gear is a straight line; the tooth line of the helical gear is a spiral line. The tooth line can be corrected; for example, the high speed heavy duty gear To compensate for the amount of deformation of the teeth under the load; improve the bearing capacity of the gear teeth; often change to drum-shaped teeth or trim the two ends of the teeth.
The tooth orientation error is measured in the middle of the tooth height; it is usually measured with a special tooth orientation viewer.
2 Touch line error (â–³Fb)
When a pair of helical gears are engaged; they should be touched along a straight line in the meshing plane; this is the touch line. The touch line error is also seen in the tangent plane of the base cylinder; the two parallel to the nominal touch line and the practical touch line The normal spacing between straight lines. It affects the size of the tooth surface touch mottle. The touch line errors all reflect the tooth shape error and the tooth direction error; it is a primary target for identifying the uniformity of the helical gear load distribution.
3 Axial pitch error (â–³FPX)
For a wide helical gear; on a straight line parallel to the reference axis of the gear and passing through the middle of the tooth height; the difference between the practical spacing and the nominal spacing between the two identical side tooth faces is called the axial pitch error ΔFPX. It is measured along the normal direction of the tooth surface; it directly affects the size of the wide bevel gear touch mottle.
4. The identification of the backlash is to make the gears have a certain backlash when meshing; the spacing in the box should be increased or the gear teeth should be thinned. Considering the characteristics of the box processing and gear processing; the thinning tooth thickness should be selected. The method obtains the flank clearance (that is, the pitch in the base). The thickness reduction of the tooth is obtained by adjusting the radial orientation of the cutter and the blank; the error will affect the size of the backlash. In addition, a few pains and movements The pain can also lead to uneven tooth thickness; the backlash during gear operation is not uniform.
To control the amount of tooth thickness reduction; to obtain the necessary backlash; the following identification targets can be selected:
1 tooth thickness error (â–³ES)
The tooth thickness error refers to the difference between the practical value of the tooth thickness and the nominal value on the cylindrical surface of the gear indexing. About the helical gear; refers to the normal tooth thickness.
In order to ensure a certain flank clearance; the upper error of the tooth thickness (ESS); the lower error (ESi) is usually negative.
The tooth thickness error can be measured by the gear vernier caliper in the middle of the tooth height; the tooth top circle is used as the measurement reference; the tooth top is the chord height; the chord tooth thickness on the measuring circle is measured.
2 common normal line uniform length error (â–³EWm)
The common normal line length error â–³EW refers to the difference between the uniform value of the common normal length and the nominal value within one week of the gear. That is, â–³EWm =(W1+W2+...+W3)/z W is the uniformity of the z-number of the gear teeth in the nominal formula. The length is because the tangential weight of the motion error makes the length of the common normal line in the gear change in one week; in order to eliminate the influence of the motion error; so the uniform value is taken. The gear is thinned due to the thinning of the tooth thickness, and the length of the common normal line is also reduced.å’‚ å’‚ ã– é’é‘ é’é‘ é’é‘ é’é‘ é’é‘ é’é‘ é’é‘ é’é‘ é’é‘ é’é‘ . . . . . . . . . . . . . . . . . . . . . ..
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