Fig. 2.4. A cranked shaft: 1 – a gear wreath of the gauge of position of a cranked shaft; 2 – a bolt of fastening of a gear wreath of the gauge of position of a cranked shaft; 3 – a cranked shaft; 4 – the bottom loose leaf of a cranked shaft with a persistent fillet of the radical bearing; 5 – a cover of the radical bearing; 6 – a bolt of fastening of a cover of the radical bearing; 7 – the bottom loose leaf of the radical bearing; 8 – the top loose leaf of the radical bearing; 9 – the top loose leaf of a cranked shaft with a persistent fillet of the radical bearing
The cranked shaft of the engine is shown on fig. 2.4.
Remove pistons and rods.
Remove the holder of a back epiploon and a back epiploon of a cranked shaft.
Covers of radical bearings should be numbered.
Turn away cover bolts, remove covers together with loose leaves of bearings.
Take out a cranked shaft from support.
Remove from a cranked shaft a gear wreath of the gauge of position of a cranked shaft.
Take out loose leaves from the block of cylinders and remove persistent half rings of the central bearing.
At dismantling put on covers of radical bearings of a cranked shaft of a label that at the subsequent assemblage to establish them on former places.
Check of a technical condition
Clear a cranked shaft solvent and dry its compressed air.
Examine radical and шатунные shaft necks on presence of damages, non-uniform deterioration and cracks.
Spend a copper coin on the bearing. If the bearing erases copper, means, its surface is too rough also it it is necessary to process.
Be convinced of cleanliness of oil channels. Eliminate the found out defects or replace defective details.
Check up конусность and ovality of necks of a shaft.
Nominal diameter of necks of a shaft, mm:
The radical..... 50
Ovality both конусность radical and шатунных necks of a shaft no more than 0,005.
Check up necks of epiploons of a cranked shaft on presence of wear tracks or damages. If epiploons have wiped flutes on necks new epiploons will pass oil.
Loose leaves radical and шатунных bearings check external survey on presence отслаивания, fusion traces, прихвата. Defective loose leaves replace.
On loose leaves it is impossible to spend any подгоночные operations. At teases, risks or отслоениях replace loose leaves new.
Check of backlashes between loose leaves and necks of a cranked shaft
For backlash check between loose leaves and necks of a cranked shaft measure diameter radical and шатунных necks, and also internal diameter of loose leaves. The backlash is defined as a difference between diameter of a neck and internal diameter of the loose leaf.
Nominal backlashes (engines 1,3), mm:
Between loose leaves and radical necks of a cranked shaft №1, 2, 4, 5..... 0,028–0,046
Between loose leaves and a radical neck №3 (the central neck)..... 0,034–0,52
Between loose leaves and шатунными necks..... 0,024–0,042
Nominal backlashes (engines 1,1), mm:
Between loose leaves and radical necks of a cranked shaft №1, 2, 3, 4, 5...... 0,020–0,038
Between loose leaves and шатунными necks..... 0,012–0,041
Check of backlashes by means of the calibrated plastic wire
Backlash check between loose leaves and shaft necks can be spent by means of the calibrated plastic wire.
Before check wipe necks of a shaft and loose leaves for removal of oil, greasing and other pollution.
Put on a working surface of a neck a piece of the calibrated plastic wire. The length of a piece of a wire should be equal to width of the corresponding loose leaf. Besides, the wire should not block lubricant apertures.
Establish a cranked shaft, loose leaves and covers of bearings.
Tighten bolts of fastening of covers the demanded moment, thus it is necessary to watch, that the shaft did not turn.
Remove covers of bearings. Define backlashes between loose leaves of the bearing and shaft necks on width of the most flattened site of a wire by means of a scale put on packing of a wire.
If backlashes exceed maximum permissible, replace loose leaves of bearings. If replacement of loose leaves does not possible to receive normal backlashes, прошлифуйте necks of a cranked shaft till next repair size and establish loose leaves of the corresponding repair size.
Check up forward and back epiploons of a cranked shaft on presence of damages and deterioration of condensing edges. Replace defective epiploons.
Installation of a cranked shaft
Establish the top loose leaves of radical bearings of a cranked shaft in support in the block of cylinders.
At a reuse of loose leaves of radical bearings of a cranked shaft establish them on former places according to the labels put at dismantling.
Establish persistent half rings.
Lay a cranked shaft in support, preliminary having greased necks with engine oil.
Establish covers of radical bearings with the bottom loose leaves and tighten bolts of fastening of covers the demanded moment in a following order:
– A cover of the average bearing;
– A cover of 2nd bearing;
– A cover of 4th bearing;
– A cover of the forward bearing;
– A cover of the back bearing.
Tighten bolts of fastening of covers in regular intervals in two-three receptions before reception of the demanded moment of an inhaling.
Covers of bearings establish an arrow towards a pulley of a cranked shaft, considering numbers of covers.
The moments of an inhaling of bolts of fastening of covers of radical bearings of engines, Н·м:
1,1 l...... 50–55
1,3; 1,5; 1,6 l..... 55–60
The moments of an inhaling of bolts of fastening of covers of rods of engines, Н·м:
1,1 l...... 20–23
1,3; 1,5; 1,6 l...... 32–35
Be convinced of ease of rotation of a cranked shaft and conformity with norm of an axial backlash of a shaft (a backlash between a persistent fillet of loose leaves of the average radical bearing and cheeks of a cranked shaft).
Rating value of an axial backlash of a cranked shaft of engines, mm:
1,1 l...... 0,05–0,25
1,3; 1,5; 1,6 l..... 0,005–0,175
Establish an epiploon in an aperture in the holder of a back epiploon of a cranked shaft and запрессуйте it оправкой against the stop, trying not to admit a warp.
Establish the holder of a back epiploon and a sealing lining and tighten five bolts of its fastening.
Before installation put engine oil on a working edge of an epiploon and an interfaced surface of a cranked shaft.
Establish a back cover of the block of cylinders and tighten bolts of fastening of a cover.
Establish covers of rods.
Tighten bolts of fastening of covers.
Fig. 2.5. A flywheel of the engine of cars with a mechanical transmission: 1 – a gear wreath of a flywheel; 2 – a flywheel; 3 – a bolt of fastening of a flywheel to a flange of a cranked shaft
The flywheel of the engine of cars with a mechanical transmission is shown on fig. 2.5.
Fig. 2.6. A flywheel of the engine of cars with an automatic transmission: 1, 3 – connecting flanges of a flywheel; 2 – a leading flange of a flywheel; 4 – a bolt of fastening of a flywheel to a flange of a cranked shaft
The flywheel of the engine of cars with an automatic transmission is shown on fig. 2.6.
Check up a condition of a gear rim of a flywheel and in case of damage of teeths replace a flywheel. If on a flywheel of from outside conducted disk of coupling cracks owing to an overheat are found out, it is necessary to replace a flywheel. The gear wreath of a flywheel should not be turned at a twisting moment 590 Н·м (60 кгс·м) or to move in an axial direction at effort 3,9 кН (400 кгс).
Before removal of a flywheel from a cranked shaft put the labels defining their mutual position in the collected condition. At engine assemblage industrially the flywheel is balanced in gathering with cranked shaft. Thus, their mutual position at engine repair should not be broken.
On the surface of a flywheel adjoining to a flange of a cranked shaft, and a basic surface of a conducted disk of coupling scratches and teases are not supposed. The admission неплоскостности a basic surface of a conducted disk of coupling makes 0,06 mm.
Scratches and teases on a basic surface of a conducted disk of coupling remove проточкой, removing a layer of metal in the thickness no more than 1 mm. Pierce as well a surface adjoining to a flange of a cranked shaft. At проточке it is necessary to provide parallelism of these surfaces. Admissible непараллельность makes 0, 1 mm.
The moment of an inhaling of bolts of fastening of a flywheel of engines, Н·м:
1,1 l..... 70–80
1,3 l..... 130–140
1,5; 1,6 l...... 120–130
Useful data and councils
Bearings of engines
What bearings are established in your engine? Not all motorists can answer such question intelligibly.
Nevertheless bearings there are. And not any, but quite defined. They are durable, but are not eternal, and when fail, without understanding of an essence of the matter not to manage. Well and for professionals-repairmen it is the most usual matter.
As the bearing works
Sliding bearings serve in modern automobile engines as support for cranked and camshafts practically in all cases. Bearings качения (ball, roller, needle) apply to the similar purposes only in small motorcycle motors.
Necessary working capacity of bearings of sliding is reached by use of effect of a so-called oil wedge. At rotation of a smooth shaft in a backlash between shaft and an aperture oil moves. As the loading operating on a shaft, causes its excentric displacement, oil is as though tightened in a narrowed part of a backlash and forms the oil wedge interfering contact of a shaft with walls of an aperture. The more pressure and viscosity of oil in a backlash, the the big loading (before contact of surfaces) maintains the sliding bearing.
Actual pressure of oil in a wedge zone reaches 50–80 МПа (500–800 kg/sm 2), and in some designs and it is more. It in hundreds times above, than in submitting system (system of greasing of the engine). However it is not necessary to think that pressure of giving influences bearing work a little. The it above, the goes oil prorolling through the bearing more intensively and is better it is cooled by that.
Under certain conditions the operating mode with the minimum friction (it also name liquid) can be broken. It happens at fall of viscosity of oil, for example because of its overheat owing to insufficient giving, and decrease in frequency of rotation of a cranked shaft at loading increase.
Quite often, especially after engine repair, not optimum geometry of knot affects also. At an insignificant deviation of the form of surfaces from cylindrical, at a warp of axes and other defects of details probably local increase of specific loading (i.e. the loading carried to the area of a surface) above an admissible limit. Then the oil film in these parts becomes thin, and shaft and bearing surfaces start to adjoin on microroughnesses. There is the mode of semiliquid greasing characterised by increase of a friction and a gradual warming up of the bearing. Further it can lead to a so-called boundary friction with full contact of the rubbing surfaces the overheat, схватывание (teases), jamming, fusion and bearing destruction will be which consequence.
It is clear that in operation the mode of a boundary friction is unacceptable. Nevertheless it takes place at infringement of giving of oil, and it occurs because of its shortage in картере more often: or owing to oversight of the driver, or at pallet damage картера as a result of arrival on an obstacle.
The mode of semiliquid greasing is admissible only for short time when he has not time to affect deterioration of the bearing. An example – start-up of the cold engine. However, here there is other danger: at very low temperature oil can become too viscous and its normal giving is restored too long (20–30 with and more). In this case and semiliquid greasing is capable to affect deterioration of details considerably.
Perfection of a design of automobile engines is connected with constant increase of frequency of rotation of a cranked shaft and increase in capacity of the engine. The tendency to increase in compactness of designs, including reduction of width and diameter of bearings is simultaneously observed. It means that specific pressure grow in friction knot. And as loading on the bearing at engine work cyclically changes on size and a direction the probability of so-called fatigue failure of details increases. To provide working capacity of bearings in such conditions, special designs, materials and technologies are required.
As the sliding bearing is arranged
Usually bearings of cranked shaft in modern engines are carried out in the form of thin-walled loose leaves or plugs in the thickness from 1,0 to 2,5 mm (it is rare more). Loose leaves of radical bearings of a cranked shaft do more thickly because of necessity to place in them a circular flute for oil giving to шатунным to bearings. The general tendency – reduction of a thickness of loose leaves which now averages 1,8–2,0 mm at radical and 1,4–1,5 mm at шатунных bearings. The loose leaves are more thin, the is better they adjoin to a surface of the case of the bearing (bed), by that is better taken away warmly from the bearing, the geometry, a less admissible backlash and noise at work is more exact, it is more knot resource.
That at installation in bed the loose leaf has precisely accepted its form, in a free condition it should have a tightness on diameter of bed (so-called straightening) and not cylindrical form of variable radius. Besides, for good прилегания to a surface and keeping from проворачивания the tightness is necessary and on length of the loose leaf – it name выступанием. All these parametres depend on a thickness, width and diameter of loose leaves, straightening averages 0,5–1,0 mm, and выступание – 0,04–0,08 mm. However still it is not enough for reliable work of the bearing of it. About a line of a socket a thickness of loose leaves reduce by 0,010–0,015 mm to avoid задиров in these parts. Teases can appear owing to aperture deformation in the bearing case in the block of cylinders under the influence of working loading when the working backlash in the bearing is small.
Materials for loose leaves can be different. Their choice depends on a choice of a material of a cranked shaft and its heat treatment, degree of speeding up of the engine and the set resource. To a certain extent affect here and traditions of automobile firm.
Loose leaves always become the multilayered. A loose leaf basis – a steel tape which provides durability and reliability of landing in the bearing case. On a basis in the various ways put a layer (or some layers) the special antifrictional material which thickness makes 0,3–0,5 mm. The basic requirements to an antifrictional material are a low friction on a shaft, high durability and heat conductivity (i.e. heat from a shaft surface to the bearing case is good to take away ability). The first requirement is better provide soft metals, for example alloys with the big maintenance of tin and lead (in particular, widely known баббиты).
In the past баббиты were widely applied on малофорсированных низкооборотных engines. With growth of loadings durability of such loose leaves with a thick layer баббита has appeared insufficient. The problem has been solved by replacement of all this layer by original "sandwich" – the lead-tin bronze covered thin (0,03–0,05 mm) a layer of the same баббита. The loose leaf became multilayered.
In modern engines сталебронзобаббитовые loose leaves usually carry out четыреххслойными (under баббитом there is still very thin layer of nickel) or even five-layer when for improvement extra earnings from above the most thin layer of tin is put on a working surface. So bearings on many foreign engines look.
Along with it the wide circulation was received also by steel-aluminium loose leaves. As an antifrictional material alloys of aluminium with tin, lead, silicon, zinc or cadmium both with coverings, and without them here serve. Most often in world practice the alloy of aluminium from 20 % of tin without a covering is used. It well resists to high loadings and speeds of rotation of modern engines, including
Diesel engines, and simultaneously possesses satisfactory "softness". Nevertheless steel-aluminium loose leaves are more rigid, than баббитовые (or with баббитовым a covering), therefore are more inclined to teases in the conditions of insufficient greasing.
Auxiliary and camshafts of engines rotate, as a rule, with smaller frequency, than cranked, and test much smaller loadings, therefore it is easier than a condition of their work. Loose leaves and plugs of these shaft usually do of the materials similar described. Besides, here sometimes apply баббит or bronze without a covering. Frequently these bearings at all have no plugs or loose leaves and are formed directly растачиванием apertures in a head of the block of cylinders. In such designs the head is executed from an alloy of aluminium with silicon which possesses quite good antifrictional properties.
The general for bearings of modern engines, especially if it is a question of support of cranked shaft, conformity of a material and a design of loose leaves to a material and shaft working conditions (frequency of rotation, loading, a greasing condition etc.) is. Therefore any replacement of details when, for example, at repair put loose leaves from other engine, cannot be recommended. Otherwise the durability of the repaired unit can appear very small. To dare at such step, it is necessary to have the corresponding information.
Loose leaves of bearings of sliding represent very exact (precision) details. To guarantee small, but quite defined (on the average 0,03–0,06 mm) working backlashes in bearings, at manufacturing maintain a thickness of the loose leaf with accuracy about 5–8 microns, and length – 10–20 microns. Infringement of these requirements can lead to change of a working backlash in the bearing or density of landing of the loose leaf in the case that is inadmissible as can lead to decrease in reliability and a resource of all engine as a whole.
Who makes sliding bearings
Complexity of all circle of the problems connected with creation of high-quality automobile bearings of sliding, has led to that their manufacture has gradually passed to specialised firms. Abroad many of such firms simultaneously let out also other details for engines, and deliveries go both on conveyors of automobile factories, and to sale – in the form of spare parts. Some firms such are a part of known transnational industrial and commercial and industrial corporations. From world manufacturers of bearings of sliding for engines it is necessary to note first of all firms Kolbenschmidt (KS), Glyco, TRW, Sealed Power, Glacier, Clevite, Bimet. Last years bearings have started to do and such firms "coryphaeuses", as Mahle and Goetze. Among "young" it is necessary to mention the specialised firm King (Israel) which has begun release of bearings in the early eighties of the last century. The majority of the listed manufacturers lets out the huge nomenclature of bearings and delivers the production in spare parts everywhere, including on our market (through dealers or the wholesale trading companies). Basically, of course, it is bearings for engines of foreign cars – European, Japanese and American.
It is possible to find loose leaves in sale both standard, and the various repair sizes (different from standard, as a rule, no more than on 0,75 mm) for the majority of widespread models. On less widespread models, and also in need of purchase of loose leaves большего the repair size usually it is necessary to make out the order and to wait on the average for 5-10 days (at different trading firms these terms are various).
Quality of such production usually does not cause doubts neither on geometry, nor on materials. Though, if there is a choice and doubts in to what firm-manufacturer to prefer, it is necessary to mean the following. Such firms as Kolbenschmidt, Glyco, Glacier are one of the basic suppliers for mass production. At purchase of their products it is possible even to receive the same loose leaves that put on engines «at a birth». The difference consists only in absence on new details of an emblem of firm – the manufacturer of the car. By the way, search "native" (or so-called original) loose leaves of the repair sizes can appear problematic. Not all automobile firms deliver repair loose leaves in spare parts, and the price of loose leaves in "original" packing, as a rule, considerably above, than directly from their manufacturer.
Loose leaves of manufacture of other, less eminent firms are usually cheaper, though will find out differences as manufacturing difficultly. Moreover, if there is a choice here it is possible to try to consider and car service conditions. So, rather cheap loose leaves, strangely enough, resist to bad quality oils and маслофильтрам, "walking" on our shops and the markets, than more expensive сталебронзобаббитовые is slightly better. It use practice under repair steel-aluminium loose leaves of firm King instead of regular бронзобаббитовых, in particular, has shown: such replacement does not put a damage of reliability of engines, but allows to save considerably.