1. Overview
limited slip differential, the English called LimitedSlipDifferential, referred to as LSD. Limited slip differential, by definition is modified to limit a differential wheel slip, it means both the drive wheel rotational speed difference is allowed within a certain range in order to ensure the normal type differential curve traveling performance and the like. In fact LSD according to different configurations it can be divided into several types, and each also has its own special LSD.
2, functions and principles
Before talking about the mechanical LSD, the reader be sure to know the function and operation principle of differential. The operating principle of the differential itself, also belong to professional-grade construction, simple to use words to describe, most readers may be difficult to understand, so I first with a daily phenomenon and most easily accessible situation to explain the original design features and necessity of differential.
existing vehicle steering wheel design is based on the Ackerman principle fifth set, which is within the curve of the steering wheel angle is greater than the outer wheel. Then the trigonometric function calculated by the rotation of the inner wheel will be shorter than the distance from the outside of the wheel, as soon as there are differences from the equal inner and outer wheel (left and right wheel) rotational speed is inconsistent, if the transmission output from the propeller shaft by no difference speed detector to separate the left and right outputs, then the vehicle can not adjust the left and right wheel speed when cornering. When the slow and not by excess friction when to take over, the curve will be cornering at high speed due to the extra wheel rotation and friction, causing the tire to jump off the ground using the joint axle and the vehicle body hanger up occurs when the inner body plus the centrifugal force driven up, it is natural turning direction toward the other side capsized.
so that the vehicle left and right wheels is definitely not a coaxial type, especially in the design of modern front-wheel drive car again the majority, there is no differential structure, the driver can not control the steering wheel, as long as the driver turns the steering wheel, tire borrow force feedback generated by the ground, strong push back the steering wheel center origin, result manipulation can not exist, so the differential is placed in the center of the drive wheel drivetrain essential elements.
Since the differential is aWith angle gear and basin-type gear drive, internal gear, and a differential side comprising the pinion. When the vehicle is straight, there is no differential action, the differential side gears and pinion gear as a whole will not revolving basin gear differential action, as soon as the vehicle turns, the resistance is not the same outer wheel, the differential gear sets by the action of drag force Further rotation of the adjustment function generating left and right wheel speed. Since the left and right wheel speed of change and adjustment by the tire and the ground impedance to generate free, so subsequent usage will not cause a vehicle traveling state. Instance when the vehicle fell into a pothole, the wheel would have no any friction at all, the ground wheels relative there is a huge resistance, this time the role of differential will make all the power back to the low friction wheel. Will fall into the pit wheel kept turning, and landing gear but no action completely, so the wheels can not travel.
There is also a phenomenon belonging to the tracking condition, the output performance of the so-called phenomenon that when cornering the wheels Bigfoot throttle, particularly evident in the power output, the output torque plus a centrifugal force forcing the vehicle wheel lifted off the ground or generate slippage, if there is an idle, it has the power to idle pulley transmission (because of less resistance), the vehicle still can not accelerate progress.
Another driving mode belonging to intense exercise slipping generated, this phenomenon is neither turning the vehicle, nor left and right wheels disposed in different conditions of the road surface friction coefficient, that is, at 8.04 during acceleration giant power output, with the difference in right and left drive shaft length and tire a little inconsistent, resulting in instantaneous power exports to the friction of a weak, non-stop round began to idle, unable to play another round, of course, not vehicles move forward. In order to address these phenomena, so that more of the average power delivered to the left and two on the right wheel, limiting the differential left and right sliding rate proportional to accomplish this goal, the limited-slip differential is the solution to the problem standard parts.
Differential good solution when the car left and right rough road driving and steering wheel rotation speed different requirements; however, the attendant is present such that the differential automotive power not effective when the side wheel slip transmission, i.e. the slipping wheel can not generate a driving force without slipping wheel and no sufficient torque. Our car designers have been working hard, so differential lock appeared. Differential lock a good solution to the problem of automotive power transmission occurs when one side of the wheel slip, that is, locking rear differential, so that the differential no longer work, the right and left drive wheels of all availableTo the same torque. But the problem of human nature always give a never-ending process. Meanwhile differential lock and then solve the original problem has brought new problems.
This differential lock is only intended for use off-road vehicles, on the field non-paved road, road adhesion is not, even though a number of wheel slip when the differential locking does not matter, at least no security problem. But when about friction imbalances appear on a paved good road, due to the friction of the tire and the dry ground is quite large, high-speed turns when the differential lock is very dangerous, because the extra round in the corners of the rotation and friction , causing the tire to jump off the ground using the joint axle and the vehicle body hanger up, when the inside of the vehicle body together with the centrifugal force driving upward, toward the other side it is natural rollover turning direction.
3 solution
a. ABS is solved by an electronic device like a drive wheel slip occurs at one side, both sides of the electronic sensors to collect a limited slip differential of the wheel speed difference, when computer found the speed difference exceeds a set value, ABS brakes work drive pulley fight, fight pulley forced to reduce speed, but this way of working is to ensure the safety of the primary purposes, at the expense of speed at the expense of the frequent job status under prone to failure, reliability is not high. As more and more emphasis on vehicle performance today, this system is a high-performance car is never be tolerated, so there will be the latter.
II. Limited slip differential (LSD) limited-slip differential, by definition is an improved differential limiting wheel slip, it means both the drive wheel rotational speed difference is allowed within a certain range to ensure class differentials normal cornering and other driving performance. In fact LSD according to different configurations it can be divided into several types, and each also has its own special LSD.
4, classified according to the different needs of
cornering performance of the play, straight sprint pleasure, Hill offensive and defensive skills, everyone needs to rely on LSD’s blessing, many of the original performance version of the vehicle is also equipped with LSD equipment, and the type LSDFormula structure and mechanical properties by different, can be subdivided into torque induction type, sticky coupling type, a helical gear, and other standard mechanical LSD. So many versions, with the ultimate aim is the same, but the process of change is different, in response to the driver’s needs and driving characteristics, can there be so many styles to produce.
LSD torque induction spiral gear is set, using the same left and right two-group is defined friction slip effect, since the helical gears taken transversely and longitudinally staggered base gear, the clutch plate lossless , the use of flooding after the vehicle, its low failure rate, repair and maintenance have become more simple, though not a strong performance in terms of power output, but the practical principles of its biggest advantages.
It is a common differential gear change from the worm gear, and the mounting position and the same form, by means of self-locking worm drive feature (torque can be transmitted to the worm wheel of the worm, the worm wheel and the worm shaft when subjected to a torque greater than the friction force between the transmitted torque, and can not rotate) to achieve anti-slip function. The famous Audi quattro is using this structure, there are many high-performance vehicles are based on the original of this type, like the original RX-7FD3S LSD is quite famous. LSD torque characteristic of the induction type, although it uses less used in the movement, but with the mechanical friction portion better comparison, and the maintenance is very simple, which is its biggest advantage.
LSD helical gear is still using its internal structure is a helical gear, unlike inductive LSD torque gears is helical gears configured LSD this all “horizontal”, and the output shaft is running in the same direction, size reduction planetary gear ratio reaches a rate limiting function, in that its biggest weakness defining a minor proportion of the locking torque slip, but also because servicing and maintenance without the use of special attention, but does not require the use of special oil LSD, so the original the plant Honda1.8 liter type-R, SilviaS15 … etc. to drive the front wheels newer, almost all of this type of LSD, LSD there is such a phenomenon that the higher the vehicle roof, the rotational drive of the left and right round, and we will not move forward or backward together, so in the year TIS1: 9 Touring car specification vehicle inspection process, it can be mixed cross the border secretly alter hiding weapons!
LSD inside the helical gear configuration with torque induction LSD somewhat similar, the sameThe ordinary differential spur gear change from the helical teeth, but instead of using two different friction, but to change the mounting position of the gear and form, through the mounting position of the form and only the helical gear can be achieved, using a gear the deceleration limit rotational speed difference than the left and right wheels. This LSD maximum attainable difference in rotational speed is relatively small. Further, torque induction type gear arranged longitudinally, and such lateral helical gear device, compared with LSD. And a mechanical LSD compared to its biggest weakness is less restrictive locking torque range, but nothing special trouble is not on the maintenance and use.
LSD locking balls special features of this design, when the small ball is moved in a curved groove, the cut groove of the drum is actuated to start to play a limited-slip effect, particularly its actuation principle and general product is very different, currently not considered mainstream products. In terms of ball locking feature of LSD because its structure is quite special, so you can play a very sleek effect, in turn, said that this LSD is not suitable for people in the street like a hurricane, and the last differential may deadlock and play maximum torque, it is worth the sum of the note, the most suitable for the race against the clock occasions.
first viscous coupling type LSD is disposed in VAG (Audi / VW) cars, during a multi-plate clutch pack, together with a combination of silicone oil, which is heated by friction after the silicone oil expands, forcing the to engage the clutch plate locking wheel difference, the structure can be said to be the most simple and small size, low cost, is suitable for a mass LSD type. About a decade ago when selected with LSD or belongs, is the most popular of such viscous coupling type style, as you can see, this is a combination of a plurality of LSD clutch plates together through the silicone oil is sprayed into difference in rotation between the left and right tires produced, the viscosity of silicone oil, and then do lock. At this point we should not be difficult to imagine the effect of such a structure is not very good, because the viscosity of the silicone oil will produce differences in performance depending on the temperature, and therefore reactive regarded as the worst, the bright side, this is just a LSD suitable types of general public use only.
LSD in mechanical modification of vehicles most conventional and most common, and therefore regarded as the highest visibility of LSD, since the left and right set of two clutch plates and the pressure plate, hence referred to as multi-plate multi-disc clutch LSD, this may be the type of LSD by the clutch plate and pressure platePermutations and combinations to achieve the function of a limited slip percentage, the percentage from 25 to 90 percent capacity to complete can be. But the only drawback is difficult to take care of, it is important to use LSD special oil to regular maintenance, long driving or vigorous exercise may need to be replaced repair kit. While poorly or clutch plate assembly Runin placed incorrectly, it can easily lead to damage to the phenomenon of abnormal sound or turns the clutch plate. Mechanical LSD fast response, high sensitivity, a limited slip ratio can be realized according to different combinations of pressure plate and clutch plate, a wide tuning range, but the high cost, good durability, when the clutch plate wear, often a “Ga! Ga! “the noise, it is necessary to do regular maintenance, which is also one of its drawbacks.
The active LSD LSD is a combination of a general cam gear together, and with a mechanical structure using a spherical groove, to accept passively actuated, the differential means in the new high-tech vehicles, since equipped with a hydraulic and electronic control system, it is possible to make the active LSD actuation. Now many manufacturers are studying it, and some also introduced about tire torque control LSD (such as Honda’s SH-AWD system and Mitsubishi’s S-AWC).
5, classified by type actuator
by actuating the LSD different type can be divided 1Way, 1.5Way, 2Way three.
1Way throttle means is turned on and the left and right wheel slip is generated, only the role of one-way type.
2Way whether the throttle is opened or closed, as long as the slip will occur bidirectional actuated. In addition 1.5Way is the only play in the form of small limited-slip effect when oil revenues.
Preferably 2Way is preferred for drift, which is due to slip when the vehicle body, in a continuous operation sometimes be retractable to control the throttle, if used 1Way or 1.5Way LSD, while a tire when the oil revenues lock the great risk of disappearing out of control. Also when some of the earlier practice but will not install LSD differential welded, although the effect can be obtained skid, but will continue pushing head during normal driving, in fact, more difficult to control.
Single / Dual actuator fuel skimmer limited slip direction
in accordance with its mechanical LSDDifferent direction of action of force, and can be divided into OneWay and TwoWay, i.e. so-called one-way OneWay limited slip operation, and also means capable of producing a limited slip operation when refueling. TwoWay is double-acting, i.e. a fuel oil or collapse, can be applied to the drive wheel limited slip function. Configuration can occur if there is half action role in refueling skimmer is called 1.5WayLSD.
Since the area is divided into OneWay, TwoWay, 1.5Way, whether it be because of its features, and in response to different usage conditions, general OneWay type more suitable for front-drive and four-wheel drive types, the former front-wheel drive because in addition to responsible power output, but also responsible for the heavy responsibility of steering, and steering feedback is applied directly on the driver, the driver is exempt from the difficulties of control, and because the curve of oil revenues, the release limit FORCES, can make those who have better control feel, not because of the role of the steering wheel LSD heavy hand is not easy to control.
TwoWay and is widely used in the tail-flick after the drive pattern, and as fuel oil yield Jieneng limited slip, can effectively control the tracking direction, and the locking function when constantly instant throttle opening, also make clear to drive the reaction and effective presentation, provide excellent driving force. And TwoWayLSD if the device in 4WD car, it still can significantly increase the flexibility of four-wheel drive.
between 1.5WayLSD is to want to achieve superior driving performance, but worried about the premise of hard-driving operation evolved between OneWay and TwoWay, which is characterized by TwoWay not have a situation understeer when oil revenues occur, and more OneWay easily identify and control than on the braking point, so the end to see their driving ability and performance tracking size, to identify and select the appropriate LSD in order to effectively use its utility.
The invention of the vehicle from the outset, coaxial carriage drive, will lead to a rollover crisis developed differential, to make a smooth ride, tire damage Mao balance to intense manipulation, slip phenomenon and the need to rely on LSD blessing, All in all sorts of, everyone follows the phenomenon of truth between heaven and earth, and the use on all parts of the operation referred to as physical, if the violation is a violation of the physical principle from big law, which ultimately can not be competent in basic requirements of the vehicle.
like the printing of some people to be able to reach the rear axle limited slip function and a differential gear welded shut, although reach non-slip phenomenon, but in the absence of machineUnder the concept of mechanical principles, its never know as long as the vehicle is traveling, no matter how flat ground, left and right wheels slip always have a presence. This can not be released or supplied by the slip ratio, the vehicle is absolutely difficult to have good tracking resistance, even LSD also belong limited percentage of the slip, so that not only should Hyperactivity, a front wheel drive vehicle but using , will result in instant feedback steering wheel with both hands blow off the tragedy.
Finally, keep in mind when choosing LSD should be noted that practicality requires professional installation of the stores neatly measuring installation, and then use the manual step by step according to the Runin, in order to ensure that the LSD operation up to standard, but not because the new LSD a load causing serious damage.
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Hunan Wantong auto repair schools, differential