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The basic performance is common to all models, such as the full-time 4WD with the Torsen LSD center differential transfer.
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Differential(Sado Sochi) is a kind of mechanical mechanism that detects the difference in movement between two parts, orpowerA device that makes a difference and sorts.gearDifferential gears usingscrewThere are things that use.
Differential gear[Note 1]Or abbreviatedDifferential gear,DifferentialAlso called.Will be described laterLimited slip differential When comparing with (LSD)Open differentialAlso called.AutomobileSuch asWheelIt is a power transmission device used for vehicles with a mark, and is the most familiar one among differential devices.
When a car turns a curve, there is a speed difference (difference in rotation speed) between the inner and outer wheels, but it is the same from the power source while absorbing ittorqueCan be sorted and communicated..In other words, one engine output can be distributed and transmitted to two different rotation speeds...Differential gears are commonly used in automobiles with three or more wheels and are installed near the center of the shafts of the left and right wheels to drive.Not required for non-powered wheels or two-wheeled vehicles that do not have a pair of drive wheels.
Equipment of differential gear
Drive wheels (ie, drive wheels) in a typical carFront-wheel drive vehicleIn the case of front wheels,Rear wheel drive vehicleIn the case of the rear wheel,Four-wheel drive vehicleIn the case of, it has one set of differential gears (both front and rear), but in the case of a four-wheel drive vehicle, it has another differential gear (center differential) to absorb the difference in rotation between the front wheels and the rear wheels. There is.this isFull-time XNUMXWDThe engine output is first transmitted to the center differential, and then distributed to the front and rear differentials.
Part-time XNUMXWDSuch asTwo wheelsIn some car models that can switch between four-wheel drive and four-wheel drive, the driving force can be taken out.transferSome are only equipped and do not have a center differential...This is because on unpaved roads, the tires and the road surfaceFrictionBecause the tires are small, even if there is a difference in rotation between the front wheels and the rear wheels, the tires will forcibly slip with the road surface, so a differential is not required.However, in a situation such as a paved road where slipping is unlikely to occur, the torque (circulation torque) generated by the wheels that cannot slip causes an input in the opposite direction to the drive mechanism, which causes a heavy burden and damages the mechanism (torque circulation phenomenon).This also applies when the center differential of the full-time XNUMXWD is directly connected.Also, if you turn the steering wheel a lot in a parking lot or the like and make a small turn, the reverse input torque will cause the brake to be applied to either tire, making the entire vehicle body uncomfortable.vibrationMay cause a tight corner braking phenomenon.
In the differential gear, power is first transmitted to the outer ring gear...The ring gear is directly connected to the side gears that connect to the left and right axles and the frame that houses the pinion gears (small gears) that connect them, and each rotates...If one of the side gears is rotated with the ring gear fixed, the other will rotate in the opposite direction via the pinion gear.
On the other hand, if one side of the wheel is fixed and the ring gear is turned, the other wheel will rotate at twice the speed.The actual wheel rotation fluctuates steplessly even in the middle, and the average value of the rotation speeds of both wheels becomes equal to the rotation speed of the ring gear.As a result, the vehicle can run smoothly, whether straight or curved, without the wheels slipping.The speed obtained from the rotation of the ring gear at that time is the value of the left and right center lines of the vehicle.
On the other hand, there are also problems.If one of the wheels falls into a groove or rides on ice, and is in a no-load state or near no-load state, the binding force (torque) on that wheel becomes extremely small and it spins idle. It becomes impossible to rotate the wheel that is in contact with one of the grounds...For this reason, it is difficult to escape in actual driving..
In order to solve the "defect of idling the wheel side in the no-load state" that the open differential has, the fixing / opening of the differential device is controlled in some way.Diff lock(DL : Differential Lock, Differential fixing device) was devised.As the name implies, it forcibly fixes the differential, and works to transmit the driving force to the ground wheel by suppressing the rotation of the side gears and preventing the wheels from slipping in the no-load state.As a result, it is extremely close to the road surface such as mud roads and freezing roads.Coefficient of frictionWhen driving on low rough roads,stackState orDerailingIt is possible to improve the running performance when escaping from time.Also,Drag racingThe diff lock mechanism prevents the loss of driving force due to the slip of one wheel and improves the starting acceleration ability in the situation where the traction to the drive shaft becomes extremely large and slip occurs, such as at the start of. In 4WD, not only the axle but also the center differential can be fixed to further improve the escape performance from the stack.Center diff lockSuch mechanisms have also been put into practical use.
There are roughly three types of diff locks. Normally, the diff lock is in the diff lock state, but the diff lock is automatically released when various conditions such as the rotation difference and torque difference between the power source and the left and right wheels are met.Auto diff lock..Normally it functions as an open differential, but a mechanism has been added to force it into a fixed state by operating the driver's switch or lever.Selectable diff lock..The open differential is simply fixed completely by welding or other methods.Spool diffIt is roughly divided into.
However, since the diff lock abandons the differential function, there is a drawback that the turning performance and the like are extremely deteriorated during the differential fixing, the difference in rotation between the left and right wheels cannot be absorbed, and the tire wear becomes severe.Even in the case of an auto diff lock that considers cornering performance relatively, in many cases differential fixing and fixing release controlCentrifugal forceIntermittent withDog clutchIn many cases, the drive feel changed suddenly depending on the driving conditions, and the drivability was not always good.For exampleMuscle carOf the eraAmerican carUsed a lot inDetroit LockerIn the case of a wheel that detects the difference in rotation between the left and right wheels during turning and releases the fixing, the fixing is suddenly released during cornering, so handling is difficult.UndersteerからOversteerThere was a unique operating characteristic that changed at once.To overcome these shortcomings, the limited slip differential (LSD) described below was devised and is now available.Off-roadSpecial emphasis on drivingCross countryOnly type 4WD vehicles and some transport trucks are equipped with selectable diff locks, and almost all general sports vehicles are LSD except for competition vehicles that require extreme straight-line performance such as drag racing. It is migrating.
Limited slip differential
As the name suggests, the differential is limited according to the conditions, and like the diff lock, it prevents the drawback of the diff gear, which prevents the driving force from being transmitted to the road surface when the drive wheels slip.A diff lock that stops the differential of the differential reduces the turning performance, so limit the differential only when necessary.Limited slip differential (LSD, Differential limiting device) was devised.As a result, even if the load on the inner ring is released during cornering and the vehicle slips, the driving force can be reliably transmitted.In addition, even when one wheel slips on rough roads or slippery road conditions, the differential is automatically limited, and the degree is not fixed like a diff lock, so extreme changes in maneuverability are unlikely to occur.
There are various types of LSD depending on the differential limiting method, but they can be broadly divided into "Torque sensitive","Rotation sensitive""Active control typeCan be classified into 3 types.
Torque sensitive type
A method that limits the differential when the reaction force of the input torque exceeds a certain level.
- Mechanical type (multi-plate clutch type)
- Built-in multi-plateclutchuse.While it can exert a large differential limiting force, it requires regular maintenance.Before the following Torsen type, helical type and viscous coupling were put into practical use, they were used as genuine products, but they are a little difficult for amateurs to handle, and they require frequent maintenance and wear out quickly. Due to over-equipment on public roads, it is now rarely adopted with a few exceptions, such as special-purpose cars for competition.By convention, the term "mechanical LSD" refers to this multi-plate clutch LSD...The initial torque can be changed to adjust the differential limiting force and response.
- Planetary gear type
- Combine multiple gears and use the tooth surface resistance of those gears or the frictional force with the differential case.Although it is not as good as the mechanical type, it exerts a strong differential limiting force and maintenance is the same as usual (so-called open differential).
- Quaife LSD
- Helical gearUsedPlanet gearsIt is a mechanism, and is characterized in that the planetary gear is held by inserting the planetary gear into the semi-cylindrical holding portion inside the differential case instead of the shaft.To generate the differential limiting force, the thrust force of the sun gear is used in addition to the resistance force generated when the planetary gear is pressed against the differential case by the meshing reaction force with the sun gear.It differs from the Torsen LSD Type B and Helical LSD, which will be described later, in that the left and right planetary gears mesh with each other at the center of the differential.
- Torsen LSD
- Abbreviation for torque sensitive (= torque sensitive type)JTEKTTrademark name.
- Type A with strong differential limiting force, type B with wide settable differential limiting force using helical gear, type C with unequal torque distribution for center differential, and type C inside open differential There is a built-in twin differential (which has the functions of a front differential and a center differential).Generally, type A is called Torsen type and type B is called helical type.
- Helical LSD
- Originally a type of Torsen type, it is customarily treated as a different type, partly because the automobile manufacturers that adopt it have advertised it individually.It is characterized by using helical gears as planetary gears and engaging the planetary gears at both ends of the differential.
- Ball Tech LSD
- The effect is obtained by moving the drum by flowing the ball over the drum with a zigzag groove.In principle, it is close to a planetary gear type.
- Sure Track LSD
- camTo utilize the frictional force.Like the Torsen LSD, it is not as good as the mechanical type, but it has a strong differential limiting force and is not as severe as the mechanical type.
- Super LSD
- The bottom of the side gear of the open differential has a cone clutch shape, and the thrust force due to the meshing of the bevel gear is used to generate the differential limiting force.Although the differential limiting force cannot be set high due to its structure, it is characterized by being able to be produced at a low cost of open differential + α..
Rotation sensitive type
A method that limits the differential when the difference in rotation between the left and right wheels (or the front and rear axles in the case of a center differential) exceeds a certain level.
- Viscous LSD
- Viscous couplingTo utilize the shear resistance of the enclosed silicone oil.It is relatively slow to respond and has a weak limiting effect, but it is easy to handle, so it is often prepared as a genuine automobile manufacturer along with the helical type.
- Orifice LSD
- A cam-driven oil pump is built into the differential to take advantage of the resistance of the enclosed silicone oil flow through the orifice.Although the differential limiting force is high and the setting range is wide, its adoption is limited to competition applications because it is very expensive.
Active control type
An electronically controlled differential device in which a computer dynamically controls the differential limiting effect based on information from various sensors.Often used in racing cars such as rallies,World Rally ChampionshipUse in[Note 2].
There are two types of physical mechanisms: a hydraulic type that adjusts the effect by adjusting the pressure of the friction plate with hydraulic pressure, and a method that uses an electromagnetic clutch..
Unlike traditional LSD, instead of using a device in the differential case for differential limiting,brakeIs characterized by usingTraction control technologyIt is a derivative system of.When the system detects wheel slippage, it brakes only the slippery wheels to simulate the same effect as the differential limiting device.
Even before such a device appeared, it was an open differential with a drive shaft.Parking brakeOnly in vehicles with the same braking wheels, one wheel slipsstackWhen you doStart on a slopeBy applying the brake to the drive shaft including the idling wheels by intermittently pulling the parking brake in the same way as above, the idling wheels are forcibly stopped, and as a result, the same as the differential limiting device. Driving technology that simulates the effect ofUnpaved roadWas used when driving on snowy roads.
Yaw control differential
By incorporating a transmission in the differential, creating speedup or deceleration by the transmission, and transmitting it to the left and right output shafts with an electronically controlled clutch,ActiveDue to the torque change of the left and right wheelsI do. AlsoSH-AWDHas a speed-up function with a transmission on the input side of the rear wheel differential, and has three sets of transmissions for the left and right wheels (AYC,ATTSIs 2 sets).
One way wheel
It's not a differential gear, but it's aimed at the same effectFour wheel drive miniThere is an upgraded part "One-way wheel" (structure similar to a freehub of a four-wheel drive vehicle).As a mechanismBicycleIt is exactly the same as the one used for, which eliminates cornering resistance by putting a pinion gear inside the wheel and letting the outer tire spin when cornering.Furthermore, one-way wheels are used when it is necessary to absorb not only the left-right differential but also the front-rear differential.In principle, Mini XNUMXWD has front wheels and rear wheels that are linked at exactly the same number of revolutions, so in principle when mixing large and small diameter wheels[Note 3]One-way wheels are to be used at least on the small diameter side.
In electric radio-controlled cars and the like, a front differential that has a one-way effect may be used, and by further reducing the diameter of the front wheels, the front wheels may be set to drive only when the rear wheels slip.However, in the case of this mechanism, since the drive of the outer ring is canceled (sliding) in the acceleration direction with respect to the drive on the inner ring side, a load due to centrifugal force is applied to the outer ring during cornering due to the structure of the vehicle called an automobile, and the outer ring. It is virtually impossible to slide the drive of the outer ring to the acceleration side under the normal situation where the driving force of the vehicle is strongly required.For this reason, installation examples in actual vehicles are limited to very low-speed vehicles.
Some differentials use screws.By rotating two screws with slightly different pitches at the same time, it is possible to move by the difference.An example of using thisMicrometerIt is a highly accurate measurement of dimensions from very small movements.In the case of the figure, if A has a pitch of 0.8 mm and B has a pitch of 1 mm, the difference is 0.2 mm in one rotation.
There are various theories about the invention of differential gears, but here are some known examples from ancient times to the present day.
- BC2634 Chinese legendYellow EmperorBySouth-pointing chariotWas used.
- 1th century BCAround GreeceFound on the seabed off the coast of AntikytheraAntikythera mechanismIncluded a planar differential mechanism.
- 1810 By Rudolph Ackermann of GermanyCarriageA four-wheel steering system was invented, which was mistakenly referred to as a differential by later writers.
- 1827 French mechanical engineer and watchmakerOnesiphore Peckle Steam carAt that time, he developed a differential gear and obtained a patent for it.This is the technology used in modern automobiles.
- 1832 By Richard Roberts of Englandsteam locomotivePatent registered as a load compensation gear for.
- 1876 BritishJames starleyIt is,BicycleFor (3, 4 wheels)Chain driveInvented the differential device.Later, it will be used in cars by Karl Benz.Starley is in the UKRoverA person who is connected to a car.
- 1897 The differential was used by David Sealer in Austria's first steam car.
Four-wheeled vehicle without a differential
Go-kartPower is directly transmitted to the left and right wheels, which is omitted even in simple automobiles such as.There is no particular problem if such a car runs straight, but depending on the skill of the driver, one of the wheels may slip when trying to turn, making it difficult to control and damaging the tires and road surface.Go-kart,Racing cartIn the case of, the differential device is not required because the technique of adjusting the rigidity of the vehicle body frame and running so that one of the drive wheels rises from the ground when cornering is used.This is to make a light car body without a heavy differential device.
- ^ British: differential gear
- ^ The World Rally Championship has been banned since 2006 except for the center differential. Totally banned from 2011 to 2016. From 2017, the ban will be lifted only for the center differential.
- ^ There is also a way to remove the propeller shaft or remove the gear on one side of the dual-axis motor to make it two-wheel drive, but in that case it is a miniXNUMXWDDoes not hold as.
- ^ a b c MFi 2008, p. 52.
- ^ a b MFi 2008, pp. 53-54.
- ^ MFi 2008, p. 53.
- ^ MFi 2008, p. 50.
- ^ a b MFi 2008, p. 54.
- ^ Shusuke Inagaki 2005, p. 111.
- ^ a b MFi 2008, p. 57.
- ^ Shusuke Inagaki 2005, p. 114.
- ^ "Driving on snowy roads For a comfortable snow drive”. As of May 2016, 10オ リ ジ ナ ル[Broken link]More archives.2015/2/2Browse.
- Shusuke Inagaki"Rally car engineering by Mitsubishi technology in the fastest category on public roads"Sankaido, 2005.ISBN 4-381-08849-2.
- "Complete understanding of drive system Chapter 3: Convert drive" "Motor Fan illustrated] Volume 24,Sanei Shobo, 2008.
- - Radio controlled carDifferential
- (Limited slip differential / LSD)
- Diff lock(Differential fixing device)
- en: Whippletree (mechanism) -Linkage parts used when pulling things with multiple horses and cows.
- Spur gear --For front-wheel drive vehicles, etc.Engine drive shaft and axle are parallel Integrated differential carrier and transmissionTransaxleOften incorporated intogear.
- Hypoid --Rear-wheel drive vehicles, 4WD vehicles, etc.Engine drive shaft and axle are vertical Often incorporated into an independent differential carrierBevel gearA kind of
- Gear oil --The oil grade used changes depending on the type of differential and the direction of intersection between the engine drive shaft and the axle (with or without hypoid gear).