03 Axle System LG958L

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LG958L Training Material

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Tuesday, May 19, 2015

Chapter V Drive Axle


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Overview of LG958L Drive Axle

CONTENTS

Structure of LG Drive Axle

Structure and Principle of Main Drive

Structure and Principle of Differential


Half Shaft

Wheel Reducer

Cause Analysis of Common Malfunctions of Drive Axle


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The drive axle of the wheel loader is located at the end of the transmission systemand is the general term for all transmission mechanism between the drive shaft andthe drive wheels. Its mainly functioned to transmit the torque from the drive shaftto the drive wheels to reduce the output speed of the transmission and increase thetorque and realize the differential function between the wheels on two sides. Inaddition, the drive axle housing also plays a role for load carrying and power

transmission.The wheel loader generally adopts drive mode of both front and rear axles, namely4-wheel drive.The LG958L loader adopts A510A drive axles. The front axle is fixed on the frontframe and the rear axle is of swin t e drive axle and is installed on the rear frame

Chapter V Drive Axle


via rear axle bracket. The rear axle is capable of vertical swing of 11 with respect tothe rear frame, with the purpose of guaranteeing the stable ground touch of fourwheels and improving the trafficability of loader while the complete machine istraveling on a rough road.In addition to the different installation modes, another difference between the frontaxle and rear axle is the main drive. For the main drives of the front and rear driveaxles, the spiral direction of the spiral bevel gear pair is different. The main drive ofthe front axle is in left-handed direction and the driven spiral bevel gear is in right-handed direction. The spiral direction of the rear axle is in opposite direction of thefront axle.


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Section I Structure of Drive Axle

The drive axle of the loader ismainly composed of axlehousing, main drive (includingdifferential), half shaft, wheelreducer, tire, and wheel rim

assemblies. Its structure isshown in Figure 5-1.

The drive axle is installed onthe frame to carry the load


and convey to the wheels. Thehousing of the drive axle is themounting carrier for maindrive, half shaft, and wheelreducer.

Figure 5-1 Structure of Drive Axle1 Tire 2 Wheel rim assembly 3 Planetary carrier 4 Inner gear ring 5 Planetary shaft6 Planetary gear 7 Sun gear 8 Wheel rim nut 9 Bearing 10 Bearing 11 Oil seal

12 Axle housing wheel support 13 Half shaft 14 Breather hole 15 Main drive


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Section II Main Drive1. Structure of main drive

The main drive is functioned to further reduce the speed and increase the torquefor the power transmitted from the transmission and alters the rotating axis ofinput shaft by 90 and transmits to the wheel reducer via differential and halfshaft.



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The structure of main drive is shown in Figure 5-2.The main drive is mainly composed of differential and main reducer that iscomposed of one pair of spiral bevel gears.

Figure 5-2 Main Drive


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Cylindricalroller bearing


To ensure sufficient carrying rigidity of the drive spiral bevel gear, the drivespiral bevel gear is integrated with the shaft. Its front support is on twotapered roller bearings that come into close contact by small ends and its rearsupport is on the cylindrical roller bearing to form transversal support.

Tapered rollerbearing


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Differentialright housing

Differentialleft housing


Carrier



The annular driven bevel gear is fixed on the flange on the right housing ofthe differential by bolts. The differential housing is supported by twotapered roller bearings within the seat bores on two ends of the carrier.

Driven bevel

gear

Bolt


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Tapered roller

bearing


While assembling the main reducer, the tapered roller bearings shall have certain

assembly preload, namely the tapered roller bearings shall be applied with certainpreload on the basis of eliminating the bearing gap. To adjust the preload oftapered roller bearings, the adjustment washer is installed on one end of the spacerbushing between the bearing inner races. If too tight, increase the total thickness ofwasher. Otherwise, reduce the total thickness of washer.

Spacerbushing


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Its intended to reduce the axial movement of gear shaft due to theaxial force generated during the transmission of bevel gears, in order topromote the support rigidity of the shaft and guarantee the normal

engagement of bevel gear pair. However, the gear shaft cant be tootight, or it will easily accelerate the wear of tapered roller bearing.The pre-tightened torque of the tapered roller bearing can be obtainedby measuring the rotating torque of the drive bevel gear (as shown inFigure 5-3). Generally, the rotating torque is 1.5~2.6N.m.

Figure 5-3 Measurement of bearing rotating torque


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Thrust bolt


To guarantee the sufficient support rigidity of the drive bevel gear, the thrust bolt isinstalled on the back of the driven spiral bevel gear to restrain the deformation ofthe driven spiral bevel gear, in order to prevent the excessive deformation of drivenspiral bevel gear from impairing the normal working. During the assembly anddebugging, pay attention to generally adjust the gap between the back of thedriven spiral bevel gear and the end of thrust bolt to 0.2~0.4mm.

Adjustment method: Screw in the thrust bolt, till it comes into contact with thelarge spiral back. Then, screw out by 1/4 turn and lock the thrust bolt.


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Tapered roller

bearing


The preload for the tapered roller bearings supporting the differential housing is adjustedby rotating the adjustment nuts on two ends. At the time of adjustment, rotate the drivebevel gear with hand to position the bearing rollers to correct places.After the proper adjustment, the differential subassembly shall be capable of being rotatedby a torque of 2.9~3.9N.m.It must be pointed out that the adjustment of preload for tapered roller bearing shall beconducted before the engagement of the gears.

Adjustmentnut


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2. Adjustment of engagement status for spiral bevel gearsThe adjustment of engagement status for spiral bevel gear refers to the adjustmentof backlash and engagement contact area.While adjusting the backlash of spiral bevel gear pair, press the probe of dial gaugeagainst the tooth face at large end edge of driven spiral bevel gear and then rotatethe driven spiral bevel gear to directly measure the backlash, as shown in Figure 5-4.


Specific measurement method of backlash:Fix the stand of dial gauge on the bracket, place the probe of dial gaugeperpendicular to the tooth face of driven spiral bevel gear, rotate the driven spiralbevel gear back and forth with hand, and observe the variation amplitude of thedial gauge, which is the measured backlash. Generally, its required to measure at3~4 different places along the circumference. The backlash shall be 0.20~0.35mm.

Figure 5-4 Measurement of Backlash


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Measurement method of engagement contact area:While measuring the engagement contact area of bevel gear pair, firstly

apply red paint (such as red lead) to the teeth (generally three teeth) of thedriven spiral bevel gear, rotate the driven spiral bevel gear repeatedly withhand, and check the contact trace. The correct engagement status is asbelow: The contact area shall be no less than 60% in both tooth length andtooth height directions and the engagement trace shall be in the middlewith slight offset towards small end in tooth height direction and shallslightly close to the small end in tooth length direction, as shown in Figure5-5. Large endForward carrying face


Figure 5-5 Correct engagement trace

Reverse carrying face

Contact area closes to large end and tooth topContact area closes to center


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Adjustment of backlash:

The backlash is adjusted by rotating the adjustment nut to change the position of driven

spiral bevel gear (when necessary, adjust by moving the drive spiral bevel gear assembly).If the gap is above the specified value, close the driven spiral bevel gear towards the drivespiral bevel gear. Otherwise, move it away from the drive spiral bevel gear. To maintain theproperly adjusted preload for the differential tapered roller bearings, the number of turnsthe adjustment nut on one end is screwed in shall be equal to the number of the turns theadjustment nut on the other end is screwed out.

Adjustment method for engagement contact area:

a. When the engagement trace closes to the large end or small end of the gear, firstlymove the axial position of driven spiral bevel gear. If there is no change of backlash,ad ust the axial mountin osition of the drive s iral bevel ear.


b. When the engagement trace closes to the tooth top or tooth root of the gear, firstlymove the axial position of drive spiral bevel gear. If there is no change of backlash,adjust the axial mounting position of the driven spiral bevel gear.

The position of drive spiral bevel gear is changed by adjusting the thickness ofadjustment washer.

The position of driven spiral bevel gear is changed by moving the adjustment nut. Toprevent impairing the tension of the tapered roller bearings on two ends ofdifferential, the number of turns the adjustment nut on one end is screwed out shallbe equal to the number of the turns the adjustment nut on the other end is screwedin.


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Contact area ofdriven bevel gear tooth

faceAdjustment method

Movement direction ofgear

Move the driven gear towardsdrive gear. If the backlash is toosmall, move outward the drive

gear.

Move the driven gear away fromdrive gear. If the backlash is toolarge, move inward the drive

ear.

Table 5-1 Adjustment of Contact Area and Backlash during Installation of SpiralBevel Gears


The adjustment of contact area is of great influence on the operation performanceand service life and must be conducted carefully.

Move the drive gear towardsdriven gear. If the backlash is toosmall, move outward the drivengear.

Move the drive gear away from

driven gear. If the backlash is toolarge, move inward the drivengear.


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3. Judgment method for rotation direction of spiral bevel gear

The spiral direction of the spiral bevel gear is expressed by the tooth trace direction,for which the judgment method is as below:

Observed towards the tooth face of bevel gear, the spiral bevel gear is left-handed ifthe tooth trace is in counterclockwise direction from small end to large end,otherwise the spiral bevel gear is right-handed.


Right-handed gear Left-handed gear


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Front axle drive spiral bevel gear,left-handed

Front axle driven spiral bevel gear,ri ht-handed

Judgment examples


Rear axle drive spiral bevel gear,right-handed

Rear axle driven spiral bevel gear,left-handed


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1. Structure of differential

The drive axle differential of the wheel loader adopts symmetric bevel geardifferential. Its mainly composed of differential left and right housings, crossshaft, four planetary bevel gears, and two half shaft gears (as shown in Figure 5-6).

Section III Structure and Principle of Differential


1 Bearing 2 Left housing 3 Gasket 4 Half shaft gear 5 Washer 6 Planetarygear 7 Driven gear 8 Right housing 9 Cross shaft 10 Bolt

5-6 Breakdown diagram of differential constituent parts


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The differential left and right housings are fitted by bolts. The driven spiral bevel gearof the main drive is fixed on the flange of differential right housing by bolts. The

journal of the cross shaft is embedded in the bore formed by corresponding slots onthe parting surface between left and right housings. Each journal is attached with astraight bevel gear (planetary gear) under floating state, which is engaged with twostraight bevel half shaft gears. The journals of two half shaft gears are supported incorresponding left and right seat bores of the differential housings respectively andare connected with half shaft via inner spline.

The differential is mainly functioned for differential function against the unequal speedbetween left and right wheels, in order to reduce the wear of tires.

While traveling linearly under same road condition, there is no relative movement


speed. The differential starts to act under the following conditions: While traveling on rough road.

While making a turn: The inner and outer wheels on one same axle have differenttraveled distances and speeds and the left and right half shafts rotate underdifferent speeds. In such case, there is a relative rotation between planetary gearand half shaft gear to adapt to two unequal rotation speeds.

While changing the rotation travels of left and right wheels under unequal airpressure between left and right wheels.


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The back of the differential planetary gear and the inner surface ofcorresponding place of differential housing are made spherical surfaces toensure that the planetary gear is centered to help the correct engagementwith two half shaft gears. As the planetary gear and half shaft gear are ofstraight bevel gear, while transmitting the torque, a high axial force isapplied along the axis direction of planetary gear and half shaft gear and

there is relative movement between gear and differential housing. Toreduce the wear between gear and differential housing, the anti-wear plainwasher is installed between the half shaft gear and differential housing andthe anti-wear spherical washer is installed between the planetary gear anddifferential housin . The anti-wear washers are enerall made of steel.


When the washer is worn after certain service time of the loader, replacewith new anti-wear washer to prolong the service life of differential.

The gears in the differential are lubricated by the gear oil within thedifferential housing. The differential housing is machined with port for inletand outlet of lubricating oil. To guarantee good lubrication betweenplanetary gear and cross shaft journal, a plane is milled on the cross shaftjournal and the orifices are drilled between teeth of planetary gear as oilpassages.


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2. Working principle of differential Kinetic characteristic

The symmetric bevel gear differential adopted by the drive axle ofwheel loader is a planetary gear mechanism. The differential housingsand planetary gear shaft (cross shaft) are integrated to form theplanetary carrier. In addition, the differential is functioned as a drivepart as the differential housings are rigidly connected with the driven

spiral bevel gear of the main drive.

The power is transmitted from the drive spiral bevel gear of mainreducer to the driven spiral bevel gear and is transmitted to the drivewheels in turn throu h differential housin s cross shaft lanetar ear


half shaft gear, and half shaft.When the wheels on two sides are rotating at same speed, theplanetary gears rotate around the axis of half shaft the revolution. Ifthe resistance is different between wheels on two sides, the planetarygear rotates around its axis the autogiration, while performing theabove-mentioned revolution. Therefore, two half shaft gears drive thewheels on two sides for rotation at different speeds.


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5-7 Schematic diagram for common bevel gear differential

Assuming that the rotating angular speed is (n0

in revolution per minute) and theangular speeds of half shaft gears are

l

and 2

respectively (n1

and n2

in revolutionper minute respectively), then the following equation is established:

2l

2

2n0

n1

n2


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The above equation is the kinetic characteristic equation for symmetrictype bevel gear differential with equal diameters of two half shaft gears.It indicates that the sum from the speeds of left and right half shaft gearsis equal to two times of the speed of the differential housing and isrelevant to the speed of planetary gear. Therefore, while the loader is

making a turn or is running under other working condition, by means ofthe autogirations of planetary gears at corresponding speeds, the drivewheels on two sides can roll, instead of slide, at different speeds on theground. This equation also indicates:


en e spee o a s a gear on one s e s zero, e spee o

the half shaft gear on the other side is two times of the differentialhousing speed.

When the speed of differential housing is zero, if the half shaft gearon one side is rotating under the application of other external

torque, the half shaft gear on the other side will rotate at samespeed in opposite direction.


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It can be learnt from the above equation:

1. When the resistance torque is unequal between the left and right half

shafts, its difference enables the torque applied on the planetary gear to

overcome the friction resistance torque Mr within the differential so that the

planetary gears rotate for differential function.

2. When there is a speed difference between left and right wheels, the torque

will be non-uniformly distributed onto the left and right half shafts so that ahigher torque is distributed onto the half shaft with lower speed and a lower

torque is distributed onto the half shaft with faster speed.


.

applied onto the differential.As the symmetric type bevel gear differential that is extensively applied at

present features really low friction torque, it can be considered that the torque

is always uniformly distributed, no matter whether the left and right drive

wheels are under same speed or not, which is the transmission characteristic

of different speeds without different torques for common differentials. This

characteristic can meet the traveling and operating needs of loader on

common roads. However, when the loader is operating under extremely poor

ground, it will seriously impair the trafficability of the loader.


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3. Working principle of differential Distribution of torqueFor symmetric type bevel gear differential, assuming that the torquefrom the main reducer is Mo, the torques distributed to the inner andouter half shafts by the differential are M2 and M1 respectively, and thefriction resistance torque within differential is Mr, then:

M2M1Mo M2M1Mr


5-8 Diagram for torque distribution of differential

1 Half shaft gear 2 Half shaft gear 3 Planetary gear shaft 4 Planetary gear


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Section IV Half Shaft


The half shaft is the solid shaft for transmission of power between differential andwheel reducer. Its inner end is connected with the half shaft gear of differential viaspline and its outer end is connected with the sun gear of wheel reducer via splineand retainer. The left and right half shafts of the loader drive axle adopt full floatingstructure. This structure enables two ends of half shaft to carry only the torque,

without any counterforce or bending torque. To prevent the axial play of half shaftunder the application of the lateral force, the engagement end with the sun gear ofwheel reducer is limited by pillar (or steel ball). The torque and movement from themain drive is transmitted to the half shaft via differential and then is transmitted tothe wheel reducer via half shaft.


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Section V Wheel ReducerThe wheel reducer is the final torque enhancement and speed reduction mechanism in

the transmission system. It can increase the reduction ratio of transmission to meet thetraveling and working requirements of the complete machine. In addition, as it canaccordingly reduce the speed ratios of main drive and transmission, it reduces thetransmitted torques of these parts and reduces their structural sizes.The wheel reducer adopts planetary transmission mechanism. The entire mechanism iscomposed of drive sun gear, fixed gear ring, driven planetary carrier, and planetary gear,

of which the working principle is shown in the figure.


5-9 Working principle of wheel reducer1 Gear ring 2 Planetary carrier 3 Half shaft 4 Planetary gear 5 Wheel hub 6 Sun gear


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The sun gear and half shaft are connected together by spline. The gear ringis fixed on the wheel support on two ends of the drive axle housing viaspline and its stationary. The planetary gear that engages with the sungear and gear ring is installed on the planetary carrier via roller bearing andplanetary gear shaft. The planetary carrier and wheel rim are fixed together

by wheel rim bolts and therefore the wheel rim rotates along with theplanetary carrier.

The power from the main drive is transmitted to planetary gear via halfshaft and sun gear so that the planetary gear rolls along the stationary


.

To improve the engagement conditions of sun gear and planetary gear andensure uniform distribution of engagement load, the half shaft is underfloating state, instead of being under stationary support.

The lubrication system of the wheel reducer is an independent system and

the oil level access hole and screw plug are fitted on the end cap of theplanetary carrier. The filler port and screw plug are fitted on the end face ofthe planetary carrier.


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Section VI Tire-Wheel Rim Assembly

The tire-wheel rim assemblies of the loader are the main traveling parts and

are functioned to carry the weight of complete machine, relieve the impactforce from the ground, and generate drive force and braking force by means ofthe adhesion between tires and road.

1. Wheel rim

The wheel rim is composed of wheel rim body, retainer, and lock ring. Afterbeing installed onto the wheel rim, the tire is restrained by the wheel rim bodyand retainer and is locked by lock ring.

The wheel rim is fixed onto the planetary carrier of drive axle wheel reducer


and the power is transmitted to the wheel rim and tire via the planetary carrier.

2. Tire

The wheel loader generally adopts low pressure wide tires, featuring largesectional size, good elasticity, and low ground pressure. While traveling oroperating on soft foundation, the tire features low sink, high adhesion, and

good traction and trafficability. While traveling or operating on rough road, thetire can ensure the good damping and shock absorption performance of theloader.


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1. Normally, the front axle is subject to higher force and the rearaxle is subject to lower force. Why is the rear axle main drivemalfunctioned earlier?

This is mainly caused by the improper operations of the operator.

When the insertion angle of the bucket is too large, the frontwheels of the loader will be off the ground and all insertion forcewill be carried by the rear axle so that the rear axle will be damageddue to overload.

Section VII Analysis of Common Malfunctions of Drive Axle


2. What is the cause for full permeation of gear oil in the driveaxle brake disc? How to solve this problem?

The oil permeation of the brake disc is generally caused by thedamaged dual-lip framework oil seal at the final drive, which causes

external leakage of gear oil and oil contamination on brake discand impairs the braking effects. This is really dangerous. Timelydisassemble the tire, planetary carrier, and wheel hub for repair andreplacement.


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3. What is the cause for abnormal sound within the axle casing?

(1) Incorrect operations. If the insertion angle of the bucket is too highduring the working, the front wheels will be off the ground and therear axle main drive will be easily damaged. If the bucket load is toohigh, the rear wheels will be off the ground and the front axle maindrive will be easily damaged. Once the gears are damaged, it will

generate abnormal sound.

(2) Noise due to improper backlash between drive and driven gears. Theexcessive backlash will lead to impact between teeth of gears. The

-


,

accelerate the wear, and cause heating of drive axle.(3) Improper adjustment of assembly gap, leading to over-size or

under-size bearing gap and causing noise.

(4) The stagnation of differential planetary gear and cross shaft and the

wear of adjustment washer will lead to excessive backlash of bevelgears and cause noise.


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4. How to solve the leakage of main drive oil seal? What arethe precautions for installation of new oil seal?

Troubleshooting:

Disassemble the drive shaft, disassemble the lock nut with specialsocket, take out the flange, disassemble the oil seal seat and oil

seal, and replace with new oil seal.Caution:

Check the oil seal for presence of aging, cracking, and damage. Do


not expand the oil seal too forcible, in order to prevent plasticdeformation. Immerse the oil seal into the fluid at the temperatureclosing to the working temperature as close as possible and theninstall the oil seal. Use special tool.


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THE ENDTHE ENDTHE ENDTHE END


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03 Axle System LG958L