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转向系统

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维基百科，自由的百科全书

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Part of car steering mechanism: tie rod, steering arm, king pin axis (using ball joints)
Ackermann steering geometry

转向系统是一个由连杆和许多其他部件组成的系统，使车辆能够按照所需的路线行驶。铁路是一个例外，通过铁路轨道与铁路道岔（在英式英语中也称为“点”）相结合来提供转向功能。转向系统的主要用途是允许驾驶员引导车辆。

简介

最经典的转向装置是使用位于驾驶员前方的手动方向盘，通过转向柱转动前轮，转向柱可能包含万向节（也可能是可折叠转向柱设计的一部分），使其稍微偏离直线。不同类型的车辆有时会有不同的设计；例如，舵柄或后轮转向。推土机和坦克等履带式车辆通常采用差速转向，也就是说，履带通过离合器和制动器以不同的速度甚至相反的方向移动，以实现转向。

地面车辆的转向

基本的几何原理

  • Ackermann steering
    Ackermann steering
  • Bell-crank steering
    Bell-crank steering
  • Rack-and-pinion steering
    Rack-and-pinion steering
  • Short rack-and-pinion steering
    Short rack-and-pinion steering

转向的基本目的是确保车轮指向所需的方向。这通常通过一系列连杆、枢轴和齿轮来实现。其中一个基本概念是主销倾角，每个车轮在车轮前方的枢轴点处转向；这使得转向装置倾向于朝行驶方向自动定心。 连接转向箱和车轮的转向连杆通常符合阿克曼转向几何结构的变化，说明在转弯时，内侧车轮行驶的路径半径小于外侧车轮，因此适合在直线路径上行驶的前束度不适合转弯。车轮与垂直面形成的角度，即外倾角，与轮胎一样，也会影响转向动力学。

Caster angle θ indicates kingpin pivot line and gray area indicates vehicle's tire with the wheel moving from right to left. A positive caster angle aids in directional stability, as the wheel tends to trail, but a large angle makes steering more difficult.
Curves described by the rear wheels of a conventional automobile. While the vehicle moves with a constant speed its inner and outer rear wheels do not.

Rack and pinion, recirculating ball, worm and sector

Rack and pinion steering mechanism: 1 steering wheel; 2 steering column; 3 rack and pinion; 4 tie rod; 5 kingpin
Rack and pinion unit mounted in the cockpit of an Ariel Atom sports car chassis, atypical of contemporary production automobiles
Non-assisted steering box of a motor vehicle

Many modern cars use rack and pinion steering mechanisms, where the steering wheel turns the pinion gear; the pinion moves the rack, which is a linear gear that meshes with the pinion, converting circular motion into linear motion along the transverse axis of the car (side to side motion). This motion applies steering torque to the swivel pin ball joints (that replaced previously used kingpins) of the stub axle of the steered wheels via tie rods and a short lever arm called the steering arm.

The rack and pinion design has the advantages of a large degree of feedback and direct steering "feel". A disadvantage is that it is not adjustable, so that when it does wear and develop lash, the only resolution is replacement.

BMW began to use rack and pinion steering systems in the 1930s, and many other European manufacturers adopted the technology. American automakers adopted rack and pinion steering beginning with the 1974 Ford Pinto.[1]

Older designs use two main principles: the worm and sector design and the screw and nut. Both types were enhanced by reducing the friction; for screw and nut it is the recirculating ball mechanism, which is still found on trucks and utility vehicles. The steering column turns a large screw which meshes with the nut by recirculating balls. The nut moves a sector of a gear, causing it to rotate about its axis as the screw is turned; an arm attached to the axis of the sector moves the Pitman arm, which is connected to the steering linkage and thus steers the wheels. The recirculating ball version of this apparatus reduces the considerable friction by placing large ball bearings between the screw and the nut; at either end of the apparatus the balls exit from between the two pieces into a channel internal to the box which connects them with the other end of the apparatus; thus, they are "recirculated".

The recirculating ball mechanism has the advantage of a much greater mechanical advantage, so that it was found on larger, heavier vehicles while the rack and pinion was originally limited to smaller and lighter ones; due to the almost universal adoption of power steering, however, this is no longer an important advantage, leading to the increasing use of rack and pinion on newer cars. The recirculating ball design also has a perceptible lash, or "dead spot" on center, where a minute turn of the steering wheel in either direction does not move the steering apparatus; this is easily adjustable via a screw on the end of the steering box to account for wear, but it cannot be eliminated because it will produce excessive internal forces at other positions and the mechanism will wear very rapidly. This design is still in use in trucks and other large vehicles, where rapidity of steering and direct feel are less important than robustness, maintainability, and mechanical advantage.

The worm and sector was an older design, used for example in Willys and Chrysler vehicles, and the Ford Falcon (1960s). To reduce friction the sector is replaced by a roller or rotating pins on the rocker shaft arm.

Generally, older vehicles use the recirculating ball mechanism, and only newer vehicles use rack-and-pinion steering. This division is not very strict, however, and rack-and-pinion steering systems can be found on British sports cars of the mid-1950s, and some German carmakers did not give up recirculating ball technology until the early 1990s.

Other systems for steering exist, but are uncommon on road vehicles. Children's toys and go-karts often use a very direct linkage in the form of a bellcrank (also commonly known as a Pitman arm) attached directly between the steering column and the steering arms, and the use of cable-operated steering linkages (e.g. the capstan and bowstring mechanism) is also found on some home-built vehicles such as soapbox cars and recumbent tricycles.

Power steering

主条目：Power steering

Power steering helps the driver of a vehicle to steer by directing some of its engine power to assist in swiveling the steered road wheels about their steering axes. As vehicles have become heavier and switched to front-wheel drive, particularly using negative offset geometry, along with increases in tire width and diameter, the effort needed to turn the wheels about their steering axis has increased, often to the point where major physical exertion would be needed were it not for power assistance. To alleviate this, auto makers have developed power steering systems, or more correctly power-assisted steering, since on road-going vehicles there has to be a mechanical linkage as a fail-safe. There are two types of power steering systems: hydraulic and electric/electronic. A hydraulic-electric hybrid system is also possible.

A hydraulic power steering (HPS) uses hydraulic pressure supplied by an engine-driven pump to assist the motion of turning the steering wheel. Electric power steering (EPS) is more efficient than hydraulic power-steering, since the electric power-steering motor only needs to provide assistance when the steering wheel is turned, whereas the hydraulic pump must run constantly. In EPS, the amount of assistance is easily tunable to the vehicle type, road speed, and driver preference. An added benefit is the elimination of the environmental hazard posed by leakage and disposal of hydraulic power-steering fluid. In addition, electrical assistance is not lost when the engine fails or stalls, whereas hydraulic assistance stops working if the engine stops, making the steering doubly heavy as the driver must now turn not only the very heavy steering—without any help—but also the power-assistance system itself.

Speed-sensitive steering

A development of power steering is speed-sensitive steering, where the steering is heavily assisted at low speed and lightly assisted at high speed. Auto makers perceive that motorists might need to make large steering inputs while manoeuvering for parking, but not while traveling at high speed. The first vehicle with this feature was the Citroën SM with its Diravi layout,[2] although rather than altering the amount of assistance as in modern power steering systems, it altered the pressure on a centering cam which made the steering wheel try to "spring" back to the straight-ahead position. Modern speed-sensitive power steering systems reduce the mechanical or electrical assistance as the vehicle speed increases, giving a more direct feel. This feature is gradually becoming more common.Template:Clarify timeframe

Four-wheel steering

Honda Prelude Mk III rear steering box
Speed-dependent four-wheel steering.
Early example of four-wheel steering. 1910 photograph of 80 hp Caldwell Vale tractor in action.
1937 Mercedes-Benz Type G 5 with four-wheel steering.
Sierra Denali with Quadrasteer, rear steering angle.
Articulated Arnhem trolleybus demonstrating its four-wheel steering on front and rear axles (2006).
Heavy transport trailer with all-wheel steering remote controlled by a steersman walking at the rear of the trailer (2008).
2007 Liebherr-Bauma telescopic handler using crab steering.
Hamm DV70 tandem roller using crab steering to cover maximum road surface (2010).
Agricultural slurry applicator using crab steering to minimise soil compaction (2009).

Four-wheel steering is a system employed by some vehicles to improve steering response, increase vehicle stability while maneuvering at high speed, or to decrease turning radius at low speed.

Active four-wheel steering

In an active four-wheel steering system, all four wheels turn at the same time when the driver steers. In most active four-wheel steering systems, the rear wheels are steered by a computer and actuators.[3] The rear wheels generally cannot turn as far as the front wheels. There can be controls to switch off the rear steering and options to steer only the rear wheels independently of the front wheels. At low speed (e.g. parking) the rear wheels turn opposite to the front wheels, reducing the turning radius, sometimes critical for large trucks, tractors, vehicles with trailers and passenger cars with a large wheelbase, while at higher speeds both front and rear wheels turn alike (electronically controlled), so that the vehicle may change position with less yaw and improved build-up of the lateral acceleration, enhancing straight-line stability.[3][4] The "snaking effect" experienced during motorway drives while towing a travel trailer is thus largely nullified.[可疑]

Four-wheel steering found its most widespread use in monster trucks, where maneuverability in small arenas is critical, and it is also popular in large farm vehicles and trucks. Some of the modern European Intercity buses also utilize four-wheel steering to assist maneuverability in bus terminals, and also to improve road stability. Mazda were pioneers in applying four-wheel steering to automobiles, showing it on their 1984 Mazda MX-02 concept car, where the rear wheels counter-steered at low speeds.[5] Mazda proceeded to offer a version of this electronic four-wheel steering system on the Mazda 626 and MX6 in 1988. The first rally vehicle to use the technology was the Peugeot 405 Turbo 16, which debuted at the 1988 Pikes Peak International Hill Climb.[6]

Previously, Honda had four-wheel steering as an option in their 1987–2001 Prelude and Honda Ascot Innova models (1992–1996). General Motors offered Delphi's Quadrasteer in their Silverado/Sierra and Suburban/Yukon. Due to low demand, GM discontinued the technology at the end of the 2005 model year.[7] Nissan/Infiniti offer several versions of their HICAS system as standard or as an option in much of their line-up.

In the early 2000s, a new generation of four-wheel steering systems was introduced into the market. In 2001 BMW equipped the E65 7 series with an all-wheel steering system (optional, called 'Integral Active Steering'), which is available on the current 5, 6, and 7 series,[8][9][4] as an option. Renault introduced an optional all-wheel steering called '4control'[10][11][12] in 2009, at first on the Laguna GT, which is currently available on the Talisman,[11] Mégane[10] and Espace[12] vehicle lines. In 2013, Porsche introduced a system on the 911 Turbo as standard equipment.[13] Since 2016, the Panamera has been offered with optional all-wheel steering.[14] The 2014 Audi Q7 was launched with an optional system.[15] Also the Japanese OEMs offer luxury segment vehicles equipped with all-wheel steering, such as Infiniti on its QX70 model ('Rear Active Steering')[16] and Lexus on the GS.[17] Italian manufacturers have launched the technology in the model years 2016–17 with the Ferrari F12tdf,[18] the Ferrari GTC4Lusso[19] as well as the Lamborghini Aventador S Coupé.[20]

Crab steering

Crab steering is a special type of active four-wheel steering. It operates by steering all wheels in the same direction and at the same angle. Crab steering is used when the vehicle needs to proceed in a straight line but at an angle: when changing lanes on a highway at speed, when moving loads with a reach truck, or during filming with a camera dolly.

Rear wheel steering can also be used when the rear wheels may not follow the path taken by the front wheel tracks (e.g. to reduce soil compaction when using rolling farm equipment).

Passive rear-wheel steering

Many modernTemplate:Clarify timeframe vehicles have passive rear-wheel steering. On many vehicles, when cornering, the rear wheels tend to steer slightly to the outside of a turn, which can reduce stability. The passive steering system uses the lateral forces generated in a turn (through suspension geometry) and the bushings to correct this tendency and steer the wheels slightly to the inside of the corner. This improves the stability of the car through the turn. This effect is called compliance understeer; it, or its opposite, is present on all suspensions. Typical methods of achieving compliance understeer are to use a Watt's link on a live rear axle, or the use of toe control bushings on a twist beam suspension. On an independent rear suspension it is normally achieved by changing the rates of the rubber bushings in the suspension. Some suspensions typically have compliance oversteer due to geometry, such as Hotchkiss live axles, semi-trailing arm IRS, and rear twist beams, but may be mitigated by revisions to the pivot points of the leaf spring or trailing arm, or additional suspension links, or complex internal geometry of the bushings.

Passive rear-wheel steering is not a new concept, as it has been in use for many years,Template:Clarify timeframe although not always recognised as such.

Articulated steering

Front loader with articulated steering (2007).

Articulated steering is a system by which a vehicle is split into front and rear halves which are connected by a vertical hinge. The front and rear halves are connected with one or more hydraulic cylinders that change the angle between the halves, including the front and rear axles and wheels, thus steering the vehicle. This system does not use steering arms, king pins, tie rods, etc. as does four-wheel steering. If the vertical hinge is placed equidistant between the two axles, it also eliminates the need for a central differential in four-wheel drive vehicles, as both front and rear axles will follow the same path, and thus rotate at the same speed. Articulated haulers have very good off-road performance.

Vehicle-trailer-combinations such as semi-trailers, road trains, articulated buses, and internal transport trolley trains can be regarded as passively-articulated vehicles.

Rear-wheel steering

A few types of vehicle use only rear-wheel steering, notably fork lift trucks, camera dollies, early pay loaders, Buckminster Fuller's Dymaxion car, and the ThrustSSC.[21]

In cars, rear-wheel steering tends to be unstable because, in turns, the steering geometry changes, hence decreasing the turn radius (oversteer), rather than increasing it (understeer). Rear-wheel steering is meant for slower vehicles that need high-maneuverability in tight spaces, e.g. fork lifts.

For heavy haulage or for increased manoeuvrability, some semi-trailers are fitted with rear-wheel steering, controlled electro-hydraulically. The wheels on all or some of the rear axles may be turned through different angles to enable tighter cornering, or through the same angle (crab steering) to move the rear of the trailer laterally.

Steer-by-wire

1971 Lunar Roving Vehicle (LRV) with joystick steering controls.
2012 Honda EV-STER "Twin Lever Steering" concept.

The aim of steer-by-wire technology is to completely remove as many mechanical components (steering shaft, column, gear reduction mechanism, etc.) as possible. Completely replacing conventional steering system with steer-by-wire has several advantages, such as:

  • The absence of steering column simplifies the car interior design.
  • The absence of steering shaft, column and gear reduction mechanism allows much better space utilization in the engine compartment.
  • The steering mechanism can be designed and installed as a modular unit.
  • Without mechanical connection between the steering wheel and the road wheel, it is less likely that the impact of a frontal crash will cause the steering wheel to impact the driver.
  • Steering system characteristics can easily be adjusted to change the steering response and feel.

As of 2020 there are no production cars available that rely solely on steer-by-wire technology due to safety, reliability and economic concerns, but this technology has been demonstrated in numerous concept cars and the similar fly-by-wire technology is in use in both military and civilian aviation applications.

Safety

主条目：Automotive safety

For safety reasons all modern cars feature a collapsible steering column (energy absorbing steering column) which will collapse in the event of a heavy frontal impact to avoid excessive injuries to the driver. Airbags are also generally fitted as standard. Non-collapsible steering columns fitted to older vehicles very often impaled drivers in frontal crashes, particularly when the steering box or rack was mounted in front of the front axle line, at the front of the crumple zone. This was particularly a problem on vehicles that had a rigid separate chassis frame with no crumple zone. Many modern vehicle steering boxes or racks are mounted behind the front axle on the front bulkhead, at the rear of the front crumple zone.

Collapsible steering columns were invented by Béla Barényi and were introduced in the 1959 Mercedes-Benz W111 Fintail, along with crumple zones. This safety feature first appeared[何时？] on cars built by General Motors after an extensive and very public lobbying campaign enacted by Ralph Nader. Ford started to install collapsible steering columns in 1968.[22]

Audi used a retractable steering wheel and seat belt tensioning system called procon-ten, but it has since been discontinued in favor of airbags and pyrotechnic seat belt pre-tensioners.

Cycles

主条目：Countersteering和Bicycle and motorcycle dynamics

Differential steering

主条目：Differential steering

Differential steering is the primary means of steering tracked vehicles, such as tanks and bulldozers; it is also used in certain wheeled vehicles commonly known as skid-steers, and implemented in some automobiles, where it is called torque vectoring, to augment steering by changing wheel direction relative to the vehicle.

Regulations

In the European Union, Russia and Japan, UNECE regulation 79 is related to steering.

In the United States, Federal Motor Vehicle Safety Standards 203 and 204 are related to impact protection for the driver from the steering control system and steering control rearward displacement while 49 Code of Federal Regulations § 393.209 is related to steering wheel systems.

水面舰艇的转向

Ships and boats are usually steered with a rudder. Depending on the size of the vessel, rudders can be manually actuated, or operated using a servomechanism, or a trim tab or servo tab system. Boats using outboard motors steer by rotating the entire drive unit. Boats with inboard motors sometimes steer by rotating the propeller pod only (i.e. Volvo Penta IPS drive). Modern ships with diesel-electric drive use azimuth thrusters. Boats power by oars or paddles are steered by generating a higher propulsion force on the side of the boat opposite of the direction of turn. Jet skis are steered by weight-shift induced roll and water jet thrust vectoring.

The rudder of a vessel can steer the ship only when water is passing over it. Hence, when a ship is not moving relative to the water it is in or cannot move its rudder, it does not respond to the helm and is said to have "lost steerage". The motion of a ship through the water is known as "making way". When a vessel is moving fast enough through the water that it turns in response to the helm, it is said to have "steerage way".[23] That is why boats on rivers must always be under propulsion, even when traveling downstream.

飞行器的转向

参见：飞行控制系统和直升机控制系统

飞机在空中飞行时通常通过副翼、扰流板或两者一起来操纵，以使飞机倾斜转弯；尽管方向舵也可用于转动飞机，但它通常用于将不利偏移降至最低，而不是作为直接转向的手段。在地面上，飞机通常通过转动前轮或后轮（使用舵柄或方向舵踏板）或通过差速制动，以及通过高速方向舵以低速操纵。导弹、飞艇和大型气垫船通常由方向舵、推力矢量或两者共同操纵。小型运动气垫船也有类似的方向舵，但主要是由飞行员将重量从一侧转移到另一侧，并使下方更强大的升力失去平衡来操纵。喷气机组和飞行平台仅由推力矢量控制。直升机通过改变主旋翼推力矢量的循环控制和通常由尾桨提供的反扭矩控制来操纵。

另见

参考资料

  • Encyclopedia of German Tanks of World War Two by Peter Chamberlain and Hilary Doyle, 1978, 1999
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  5. ^ Lindell, Hannu. Nelosten vuosi [Year of the Four]. Tekniikan Maailma. Vol. 41 no. 5/85 (Helsinki: TM-Julkaisu). 1985-03-19: Automaailma 3. ISSN 0355-4287 （芬兰语）. 
  6. ^ 1988 Peugeot 405 T16 GR Pikes Peak. [2015-03-16]. 
  7. ^ Murphy, Tom; Corbett, Brian. Quadrasteer Off Course. Wards Auto World. 2005-03-01 [2010-06-11]. （原始内容存档于2011-03-23）. 
  8. ^ AG, BMW. BMW 7 Series Sedan : M Performance. www.bmw.com. [2017-04-06]. （原始内容存档于2017-04-06）. 
  9. ^ AG, BMW. BMW 6 Series Coupé : Driving dynamics. www.bmw.com. [2017-04-06]. （原始内容存档于2017-04-06）. 
  10. ^ 10.0 10.1 Feature | All-New MEGANE Sport Tourer | Cars | Renault UK. Renault. [2017-04-06]. （原始内容存档于2017-04-06） （英国英语）. 
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  12. ^ 12.0 12.1 Equipements | Espace | Véhicules Particuliers | Véhicules | Renault FR. Renault. [2017-04-06]. （原始内容存档于2017-04-07） （fr-FR）. 
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  15. ^ Audi Q7 > Audi configurator UK. www.uk.audi.com. [2017-04-06]. （原始内容存档于2017-04-06） （加拿大英语）. 
  16. ^ INFINITI QX70 Specs - Performance Features & Engine Options. Infiniti. [2017-04-06]. （原始内容存档于2017-04-06） （英国英语）. 
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  23. ^ Smyth, William Henry; Belcher, Edward. The sailor's word-book: An alphabetical digest of nautical terms, including some more especially military and scientific ... as well as archaisms of early voyagers, etc.. London: Blackie and Son. 1867: 654. 

外部链接

查看维基词典中的词条「转向系统」。
检索自“https://zh.wikipedia.org/zhwiki/w/index.php?title=转向系统&oldid=81706740”