Analysis of invalidation of assembly of gimbal cross axle and design are improved
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The be no longer in force of 3 packets of go back that office of 3 packets of services of company of Cong Mou of inclined embossing author provides in observe, case of inclined embossing of cross axle journal is more severe, bearing ferrule wall also produces corresponding embossing, but deepness should compare cross axle light. Classics analysis, install the bearing on gimbal assembly, when bearing when circumferential total gap is bigger, needle roller easy generation is askew, it is certain to cause generation of cross axle journal and axes to tilt the embossing of angle, expand when embossing deepness deeper when, needle roller cannot rotation, because this makes attrition obstruction increases, of aggravate impress outspread. Its suitable circumferential total space should be controlled in 0.
1 ～ 0.
Inside 4mm limits, in JB/T3232 given circumferential total space is do not exceed 0.
5mm. 2.
Exhaustion flakes the use condition with minor role is placed in transmission shaft, the needle bearing internal diameter on gimbal assembly and cross axle journal swing repeatedly inside lesser angle limits, when cross axle and bearing radial windage as when wear away and expanding, can bring about product load concentration, the place with great load produces fatigue impress can prematurely, develop the exhaustion that becomes large area to flake thereby. Be in office of head of cross axle axis especially, because stress focuses an effect, its suffer those who hold position to pour horn to be gnawed entirely almost, serious when occurrence agglomeration phenomenon can play in high temperature condition. 3.
Because the ablation that be short of oil does not add the bearing that pour lubricating oil or goes up as a result of gimbal on schedule in the user in use process sealed and bad, bring about bearing inchoate break oil and dustproof cover material to not be able to bear or endure microtherm, mouth of oil seal lip issues generation ageing crackle in winter chill climate, make grease inchoate prediction of a person's luck in a given year. Additional, gimbal assembly produces high temperature because of be short of oil in move, make bearing and axial diameter are bitten dead, cause needle roller to break off and sealed damage with dustproof outer garment, ferrule surface has ablation mark, form of this kind of invalidation all is belonged to be not normal invalidation form. 4.
Author of needle roller invalidation observes discovery from inside sample of gimbal assembly invalidation, surface of most needle roller is put in hole of hemp dot, hemp and large area exhaustion to flake, head of a few needle roller is broken off, a few needle roller is in from needle roller head 1.
Place of 5mm left and right sides is put in hempener hole to mix the phenomenon that gnaw an injury, needle roller ruptures also is for the most part rupture from here, the happening of this kind of circumstance basically reachs design of circumferential total space to concern with parameter of bearing structure dimension. 5.
Spacer invalidation spacer is gimbal assembly in above all the component of invalidation, spacer invalidation form ruptures for nylon spacer and wear away. Sample of spacer of author anatomize invalidation discovers, the periphery of spacer has apparent flaw, spacer periphery has crackle and fragment. Apparent, spacer periphery is spacer suffers go up the place that force causes stress to center, once spacer periphery is destroyed, its axial force will be total by the rest of spacer bears, force will add the susceptive on spacer unit area, whole spacer will be destroyed. Because this need designs reasonable spacer appearance and bearing structure. In the meantime, as a result of spacer every time invalidation is destroyed accompanying grind loss effect, so spacer material must choose the stuff with intensity and more expensive wearability. 6.
Cross axle ruptures of cross axle rupturing is commonly in the user serious overweighted premise falls or happen below unusual element condition, the gimbal in because gimbal is when the design,abiding by ministerial standard JB/T8925-2008 completely is static twist intensity safety factor 2.
The regulation of 5 times, but the 5 ％ of 2 ％ ～ that in leader plant the breakdown proportion that produces inside 3 bag period still takes total trouble, although this kind of circumstance is paroxysmal, but inevitable also, because of this pair of gimbal static twist intensity to match, must of the paroxysmal breakdown that in engine the ability of 3 times above of torque of the biggest output prevents special overload to cause appear. 7.
Metallographic examines analyse pair of invalidation undertake managing changing an analysis, mix in cross axle, ferrule respectively the position of feature of typical place choice of needle roller, cut issues test specimen, and even if the edge is sectional make take metallographic sample, its metallographic organizes level qualification. To decide the core hardness of cross axle, ferrule and needle roller, with microscopical sclerometer undertook to each spare parts gradient of diamond pyramid hardness distributings respectively determine, its hardness accords with hardness profile rule basically also. The cross axle that takes gimbal, outer lane each one test specimen and test specimen of several needle roller, heat in aqueous solution of 50% hydrochloric acid to 70 ～ 80 ℃ , heat make an appointment with 1h, make hot pickling inspection, burn phenomenon exists in discovering each spare parts is using a process as a result. Because sealed function difference breaks gimbal,judgement of phenomenon of this kind of burn is oil and oil property are bad, burn of each spare parts is premature after bringing about gimbal bearing to give out heat invalidation. Design of Nextpage gimbal assembly is improved 1.
The intensity design of cross axle is improved through be opposite this product undertakes finite yuan of analysis, discover R of ministry of root of journal stage shoulder is small, and it is car treatment is formed, surface roughness is poor, stress concentration, the decision increases round role of ministry of stage shoulder root to cross axle, use grinding of numerical control figuration, the cross axle reoccupy after improving a design is finite yuan of analysis, result stress value is reduced from the 234MPa before improving to the 176MPa after improving (see a picture 2) , stress value fell 24 ％ . The course is static to improving around product to undertake twist pressure test, static twist intensity to raise above of 35 000N M from 28 000N M, raise extent to amount to 25 ％ , after improving static twist intensity safety factor from 2.
5 times raise 3 times above, accordingly, can prevent the cross axle that the client causes below overweighted use condition effectively to rupture. Graph 2 improve around stress to distributing 2.
Form of invalidation of spacer design spacer is broken and wear away, can make change of cross axle axial is moved, accelerate gimbal wear away, because this answers to enhance the intensity of spacer and wearability above all, improve spacer to get force case, prevent stress concentration. Improve around, spacer structure and ferrule and needle roller cooperate a circumstance to if the graph is shown 2 times,contrast. From the graph 3(a) can see, when the axial force of cross axle pounds spacer, as a result of spacer all round by the chamfer retreating a knife of bearing impending, become all round spacer get power the weak point that outspread enlarge goes up. In the meantime, because the end outside spacer and dot of contact of the chamfer that retreat a knife are not planar contact, also can form stress to center a phenomenon. Such, stress of the generation below the pounds load action that relapses in cross axle centers a phenomenon, because this makes be destroyed all round spacer, because the pressure on area of the unit on spacer increases, make whole spacer broken thereby. The spacer structure after improving is like graph 3(b) be shown, it avoided afore-mentioned phenomena completely to happen, in the meantime, still eliminated raceway to retreat the contact of knife chamfer and needle roller, make needle roller gets power even, do not produce stress concentration, avoided needle roller to produce indentation in end panel, gnaw injury and the possibility that break off, make the lengthen of effective contact length of needle roller, make gimbal life is lengthened thereby. Graph 3 improve around structure to pursue 3.
Protruding of needle roller logarithm spends a design to improve in roller bearing, because pressure is contacted between roller of straight element line and raceway,show bizarre distributing, and bring about bearing to produce inchoate and fatigue invalidation. Accordingly, needle roller takes protruding to spend is to remove one of concentration of needle roller stress, main measure that improve needle bearing service life. Considering gimbal work is swing repeatedly below old point of view, suffer hand in change stress action, needle roller happens likely in rotational process askew, make needle roller and journal contact length shorten, and considering treatment craft, finished cost is affected (use line of element of circular arc complete protruding to shape structural design, the production of this kind of needle roller can use scroll type change to bump into means figuration, manufacturing efficiency tall, cost is low) , improve this chose line of element of circular arc complete protruding needle roller to replace needle roller of line of original structure straight element, avoid to use the possibility that ruptures in the process. 4.
The design that sealed structure improves car transmission shaft more and more miniaturization, the space with gimbal accordingly sealed installation is lesser. Additional, because gimbal accepts the turbid impact in use process continuously, must have used be filled with a contact sealed. With usually sealed and different, this kind is filled with sealed interface too, swing as a result of what make move back and forth motion, the grease on sealing surface is squeezed easily to go out, interface is incidental wear away, so, want to get long-term good sealed performance, should decrease as far as possible sealed reach its interface to wear away bilaterally, the filling oil of sealed interface wants sufficient, sealed contact pressure does not pass big, because this requires a design,tighten the structure of force beforehand into complement. On the other hand, in use process, silt and water are the ministry of able to read aloud fluently from bearing is invaded, because this sealed lip mouth wants a consideration,show up stop the inclined plane that push. Be aimed at these elements, design personnel undertook improvement below to original sealed structure: (1) design is flexible contact is sealed the contact of hard extruding type original sealed structure is sealed, change flexible stop promote inclined surface contact sealed, make the complement of interface lube easier, axial tightens force beforehand small, wear and tear is little, sealed performance change is very little, accordingly, flexible stop push inclined surface contact to contact function than extruding type more advantageous, wear away life is long. (2) design adds dustproof lip to prevent advocate sealed interface suffers turbid concussion or dry dust is entered, be necessary to add dustproof lip, because this chose two advocate sealed lip and a waterproof and dustproof lip regard a contact as the lip. (3) design is appropriate sealed tighten force beforehand advocate sealing surface chooses the columnar side in cross axle or bearing. Because round cylinder on size error can be machined very smally, reduced the interference deviation of sealed lip thereby. And original structure among them advocate sealed choice is in surface contact in diameter of shoulder of cross axle axis, sealed lip and ministry of root of cross axle journal pour horn to be in balance to touch, normally the as suitable as sealed lip surface roughness that coordinates a side asks to be in 3.
2 μ M is the following. If exterior surface roughness is differred on the value, can make sealed lip mouth wears away aggravate, produce leakage oil thereby. This second improving is will advocate the sealed interference of sealed lip mouth and mouth of another waterproof and dustproof lip undertakes adjustment, interference from unilateral 0.
10 ～ 0.
15mm is adjusted for 0.
15 ～ 0.
25mm, improved sealed result greatly thereby. 5.
Dustproof cover design improves dustproof cover to be out of shape in the ageing below microtherm condition serious, pass leader plant understanding, because our country is northeast,area and the winter air temperature that export European area are achieved - 35 ～ - 20 ℃ , and temperature of 66 material cold brittleness is the nylon that we use - 20 ℃ left and right sides, cold-resistant sex is poor, accordingly nylon material produces the change of function easily below microtherm condition, cause dustproof cover sclerosis to be out of shape chap ruptures even. Design personnel improved a design to use the dustproof fish trap of figuration of vulcanization of balata of agglutination of framework of a kind of steeliness, experiment through trial-produce, sealed effect is good, and the sealed function that solved the gimbal below microtherm environment. 6.
It is compound that gimbal grease contrast analyses the grease that improves original structure gimbal to be chosen all the time lithium radical fat, this kind of grease is to be in 2 cars are current a few additive increased to raise gimbal on foundation of lithium radical fat extremely press function and drop drop, its index is more than 250 ℃ for drop drop, use temperature - 120 ℃ of 30 ～ , extremely press function to be as high as 2 800N. Although performance of this kind of grease is more current than 2 cars lithium radical fat is advantageous, but the abominable state according to lorry operating ambient conditions, already cannot satisfy the requirement of 3 packets of course of development that uses actually, through searching the function of all sorts of grease, a kind of when discover some company is produced compound make water base the index of fat is more than 280 ℃ for drop drop, use temperature - 200 ℃ of 30 ～ , extremely press function to be as high as 9 800N, its high temperature resistant function and extremely press function to all compare compound lithium base fat is close friends, through typical product function contrast experiments, use this kind of compound make water base of fat wear away life comparing uses former compound lithium base fat life grows 70 ％ above, for this, we chose this kind of grease to replace former compound lithium in the light of this gimbal base fat, popularize application in gimbal series product. Epilogue carries pair of WX0082 gimbal be no longer in force comprehensive analysis, the gimbal after improving is static twisted intensity to raise 25% above, of the improvement that the logarithm protruding that passes design of sealed to gimbal structure, needle roller at the same time spends spacer of nylon of design, bearing, dustproof cover and lubricant grease improve, raised gimbal greatly wear away life, make the service life of gimbal raises travel 50 000km from 20 000km of 1 year of travel, use the information of feedback 1 many year through the client, fault rate reduced 60 ％ above, gained good economic benefits and social benefit, this experience rises in analysis of other product life on get applied extensively. CNC Milling