Selector lever
A selector lever (or the frequency of use according to [descending, according to DWDS]: gear lever, gear stick, gear knob, gear lever, selector lever, gear selector lever, manual lever, gear selector switch or foot shift lever) in the sense of automotive engineering allows the selection of the gear ratio of the vehicle transmission , possibly the separation of the power flow between the engine and driven wheels (clutch control) and, if the transmission has a reversal of the direction of rotation ( reverse gear , rarely with motorcycles), also the control of the direction of travel.
In specialist circles, this selector lever, to which, for example, the lever and the shift gate (see picture of the Audi R8 gate shift ) belong, is considered to be a shifting system and, together with the connection to the transmission (for example, consists of a linkage, cable), is an “external shifting element” "Or" shift actuation ". In terms of terminology, there are the “inner shifting elements” such as shift sleeves and synchronizer rings . Functionally, the driver controls the transmission via the selector lever.
history
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The first gear selector levers on motor vehicles were simple rods that protruded from the gearbox and thus made it possible to select the gear. The gearbox was close to the driver's seat and could be shifted directly.
A gate shift, in which the gear lever is guided in slideways, was first used in the Packard Model A in 1899 and patented by James Ward Packard , but only later became generally accepted. Most early vehicles had the lever on the outside of the body, where the handbrake lever was located. In the course of vehicle development, various concepts ( front-wheel drive with transverse installation of the transmission, rear engine , transaxle ) led to the transmission being moved away from the driver's seat, which required a spatial separation of the operation from the actual transmission.
Initially, purely mechanical solutions were developed for this. Alternatively, mixed electrical / mechanical and purely electrically connected selector levers (shift-by-wire) were developed.
In commercial vehicles, hydraulic switching is also carried out, with the driver actuating a master cylinder via the selector lever, which then acts on the working cylinder in or on the transmission. Because of the compressed air supply for the brake system, electrical / pneumatic circuits are also available, see Electropneumatic circuit, EPS .
technology
The differentiating feature for gearshift systems in current cars is the type of connection to the transmission:
- Purely mechanical connections
- Electrical connection (shift-by-wire) via a special interface or via the vehicle bus (mostly CAN )
In addition, there are mixed forms in which some functions are carried out via mechanical connecting elements and others via electrical connections. The selection in each individual case depends on the interface that the transmission offers the selector lever.
Various functions are required of the selector lever in automatic transmissions:
- Detection of the gear selected by the driver and transmission to the transmission
- Illumination of the speed step display (partially)
- Highlighting of the selected speed level by the lighting (partially)
- Shifting the selector lever locks (if available, then partially through the transmission)
- Detection of whether the unlock key or P key has been pressed
- Mutual locking of ignition lock and P-position (depending on national regulations)
In the case of manual transmissions in particular , the reversing light is also switched via the selector lever.
Mechanical connection
Since the mechanics were controllable much earlier than the electronics, most vehicles still have a mechanical connection. Shift levers are coupled to the transmission, for example, via a linkage, a multi-joint kinematic chain or via cables.
Even today, the mechanical connection is still common, even if the transmission has an internal electronic control. The reason is usually that with proven and reliable transmissions, changes to a purely electronically controlled transmission with an electronic selector lever are postponed as far as possible for reasons of cost and changes as little as possible across different vehicle platforms and generations.
Advantages :
- Inexpensive, simple and robust construction.
- Mostly easy to repair, beneficial for maintenance in emerging and developing countries.
- Powerless switching is possible, in particular to open the positive connection in the transmission if the vehicle has to be pushed in the event of failure.
- Even in an emergency, individual control with purely mechanical gearboxes (e.g. engine brake with over-revving of the engine in the event of brake failure on a downhill slope), where electronic controls would prevent actuation.
From today's point of view, the mechanical connection between the selector lever and the gearbox has various disadvantages compared to other gearshift systems, because the installation must take into account various points that restrict free positioning in the interior.
Cons :
- Transmission of structure-borne noise into the interior, for which, for example, vibration absorbers are used.
- Necessity of decoupling the movement of the transmission in its storage, for example during load changes , so that no reaction can be seen on the selector lever
- Friction of the mechanics (shift comfort)
- Heat radiation in the vicinity of the exhaust system
- Sealing and noise problems ( NVH ) with the required passage openings to the interior
- Crash behavior of the entire external circuit
- Danger to other vehicle components due to misuse and incorrect operation, for example over-revving the engine when switching or damage to the synchronizer rings due to incompletely separated clutch ("Greetings from the transmission")
- Restricted laying, e.g. B. by minimal bending radii of the cables or straight sections in the rod guide.
In addition, wear and tear in the transmission can increase in some vehicles if, for example, the driver lets his hand rest on the gear knob for a long time.
Even if the demand for robust and inexpensive manual transmissions will increase due to the entry of the emerging countries into individual transport, mechanical gearshifts are likely to be used less and less for new developments in the higher vehicle segments, so that electronic gearshift systems will become more widespread.
Shift-by-wire
Shift-by-wire systems (as part of drive-by-wire ) only have one electrical connection to the transmission. This requires actuators in the transmission that convert electrical signals into gear or drive step changes. The selector lever is connected via electronic interfaces, which can control the gear selection as well as the lighting in the selector lever. For interior design and vehicle production, the vehicle bus (mostly CAN ) is a simple and flexible way of connecting the selector lever to the transmission. Another option is communication via pulse width modulation with defined duty cycles. If the transmission control unit takes over the corresponding tasks, shift-by-wire systems can manage without a microcontroller with software on the selector lever. In shift-by-wire systems, the selector lever often has its own control unit. This takes care of the detection of the selector lever position, the mechanical blocking of impermissible positions, (if provided) the lighting of the selected gear and communication on the vehicle bus via the selector lever position. The decision as to whether and at what speed a certain gear may be shifted (e.g. reverse gear at high speed) is usually made by the transmission control unit.
Advantages and disadvantages
Advantages of shift-by-wire:
- When connected via the CAN bus, two lines for the bus plus power supply (especially ignition plus , permanent plus and ground ) are sufficient to exchange all information with the transmission and other control units (e.g. instrument cluster ).
- The selector lever can be placed anywhere in the driver's work area, and it is connected via freely relocatable electrical connections.
- With a suitable design, the selector lever can simply be adopted unchanged for installation in several platforms and series or adapted by configuring the software.
- Fast assembly in vehicle production, while mechanical connections may require additional installation and adjustment work during installation.
- Free choice of the type of actuation, actuation forces and travel, actuation locks
- Additional functions such as force feedback , automatic retraction and extension of the selector lever
- Due to the lack of a mechanical connection, less interfering noises get from the transmission into the passenger compartment
Disadvantages of shift-by-wire:
- In contrast to mechanical connections, currentless switching is not possible.
- There is no forced connection between gear and selector lever position, so that the transmission has a time lag compared to the selector lever position.
- If the tasks are no longer taken over by the control unit of the transmission, the selector lever requires its own control unit ( embedded system ) with its own software and a microcontroller .
- Due to the decoupling of the gear position and the selector lever position, shift-by-wire shifts often only offer tip shifts. The selector lever position does not allow any conclusions to be drawn about the selected gear. Depending on the system, the gear selected in the gearbox is signaled to the driver by displays in the instrument cluster or on the selector lever itself; these displays are synchronized with the gearbox and not with the selector lever position.
service
The type of operation depends on the gearbox. Manual transmissions are usually designed as an H shift (4-speed) or corresponding extensions.
In the case of automated and automatic transmissions, four designations have become internationally accepted based on legal requirements, from which there are seldom deviations:
- P : "park" (park position with mechanical locking of the gear against rolling away)
- R : "reverse" (reverse gear)
- N : "neutral" (idle)
- D : "drive"; "Continuous operation" (forward travel with automatic gear selection)
In addition, there are legal requirements that a higher braking effect must be available below 40 km / h. As a result, the engine braking effect can be better used on downhill stretches and the risk of the brakes overheating is lower.
This function is implemented by the transmission by locking the higher gears and offering them in various ways on the selector lever:
- Newer transmissions have a manual tip gate (see also Tiptronic ) which, for example, with “ M ” as a stable middle position between “ + ” (upshift) and “ - ” (downshift).
- Older transmissions (e.g. Mercedes) have the levels " S " and " L " (highest engine braking torque), or " 3 ", " 2 " and " 1 " if there is no tip lane.
These speed steps are usually lined up after D, known schemes are PRNDSL or PRND-3-2-1.
Other designations that are regularly found on the selector lever are:
- “ S ” (Sport) for a sport mode that shifts automatically like D, but follows a “sportier” shift strategy. Since such transmissions also have a tip lane with which the engine braking effect can be controlled on downhill slopes, confusion with “S” as a low gear ratio for driving downhill is impossible.
- " E " (Economy) for particularly economical shift strategies
- " B " for hybrid vehicles to increase the braking effect through recuperation with the engine brake and downshifting, for example because the braking effect through recuperation is not sufficient when driving downhill
Occasionally, such options are implemented using additional switches for the drive program on the selector lever. In all-wheel drive vehicles, control elements of the all -wheel drive are also placed near the gear selector lever, provided that differential locks can be engaged.
Parking position
Position P must provide additional protection for the vehicle against rolling away; this function is often implemented by a mechanical lock in the transmission.
After numerous accidents with “self-propelled vehicles”, it has become common for the driver to only be able to leave position P if the driver applies the service brake. In the case of the self-propelled vehicles, the drivers stated that their vehicle accelerated even though they had stepped on the brakes. Many of these accidents were attributed to mixing up the brake and accelerator pedals, but due to the public attention, the affected vehicle manufacturers still suffered a decline in sales. The principle that the engine management system ignores the accelerator pedal when the brake is applied has meanwhile become widespread and is increasingly being used in manual transmissions after reports in 2009 about alleged self-sustaining Toyota.
In some countries, the ignition lock must also be locked (parking lock, keylock, interlock) so that the ignition key can only be removed when the gear selector lever and gearbox are in P. Conversely, it must not be possible to move the selector lever out of P if the ignition has not been switched on with the ignition key. This regulation results in somewhat different operating concepts with regard to the locks in the selector lever:
- If the ignition key can be removed regardless of the selector lever position (mainly in Europe), there are usually locks that prevent a change from D to N or from R to N or P until the driver also depresses the brake pedal.
- In countries in which the ignition key can only be switched off and removed in the P position (USA, Canada), such locks are usually missing.
The respective concepts ensure that the driver can always interrupt the power transmission in the drive train even in the event of a technical problem, either by switching off the ignition (concept 1) or by switching to N (concept 2).
Some operating concepts have an Auto-P function in conjunction with shift-by-wire. The transmission automatically engages P if a combination of the following circumstances occurs (depending on the manufacturer, this is considered differently): the vehicle is stationary, the driver's seat is not (no longer) occupied, the ignition key is removed or the door is opened.
In contrast to some national laws, there is an engine run-on circuit for certain near-series special vehicles , in which the engine can continue to run in P even though the ignition key has been removed.
Monostable and multistable selector lever
The first selection levers for automatic transmissions were multi-stable, i.e. H. the selector lever assigned a stable position of the selector lever to every possible position. This property resulted from the purely mechanical connection between the selector lever and the transmission.
Since the first manual shift gates ( Tiptronic gate), not every position has been stable. If the selector lever is in the manual gate (M), + and - can only be switched by tapping. After the driver lets go, the selector lever returns to the M position.
Newer concepts are completely monostable; H. all positions can be switched by tapping. With this concept, similar to the sequential shifting of a motorcycle, the gear can no longer be recognized by the selector lever position, but the driver needs an additional gear indicator.
Keys
Depending on the version, selector levers can have mechanical or electrical buttons for the following functions:
- P button : In the case of monostable selector levers, gear position P is usually not included in the shift pattern. P can be exited by moving the selector lever, but it is not possible to return to P by moving the selector lever. In these cases, the P speed step is engaged using a dedicated button.
- Unlock button : This is available on many selector levers and must be pressed to move the selector lever from one gear to the next. This avoids accidental activation of the selector lever. As an alternative to the unlock button, some automatic selector levers have a worm or labyrinth alley.
- M button : If there is no tip lane on the selector lever and instead paddles are provided on the steering wheel for manual gear selection, the M button can be used to select the manual gear (M) and control the paddles.
Shift lock
Most transmissions have a reverse gear lock. While manual transmissions usually require multi-axis movement (pushing / pulling in one direction and sliding the selector lever across it), automatic transmissions often have additional locks that only allow the selector lever to move freely under certain conditions. This mostly affects R and D, which can only be activated after the brake has been applied and possibly other conditions (e.g. only when the engine is running). Electrically controlled magnets or pawls are used to provide these functions.
More functions
Occasionally a "rocking function" is provided for low speeds, with which a quick change (within 1 to 2 seconds) between R - N - D and back is possible without using the brake, as this method of "rocking free" is possible with stuck vehicles “Has proven itself. As a rule, this is not a function of the selector lever, but of the transmission control unit, since this usually monitors the actuation of the brake pedal.
activity
While most of the controls are a further development of the mechanical selector lever, shift-by-wire circuits allow completely different operating concepts, for example the outsourcing of functions from the selector lever to steering wheel switches.
Key circuit
In principle, the switching function in automatic transmissions can be implemented not only with levers, but also with switches.
An example of a push button switch can be found at Chrysler in connection with the TorqueFlite automatic transmission, which was advertised as "Push-Button Drive" from around 1956.
The N position simultaneously actuated the starter when the ignition was switched on . Initially, the P position with the gear lock was missing, which was only installed in later models. From a legal point of view, this was not a problem at the time, because the first US laws (FMVSS), which placed certain requirements on the selector lever, were not passed until the end of the 1960s.
The most famous vehicle with the "Push-Button Drive" is probably the Plymouth Fury , which was used as the main actor in the horror film Christine , but it is incorrectly described in the novel.
In Ford- Edsel models, the button switches were built into the middle of the steering wheel and called Teletouch . The Touch Button Ultramatic transmissions from Packard were also operated by a key circuit.
While the Chrysler Push-Button Drive was mechanically connected to the gearbox, the gearbox at Packard and Edsel was electrically controlled, which in both cases was initially less reliable than at Chrysler.
Button circuits can also be found in current commercial vehicles. For current vehicles with a purely electric selector lever, suitable keyboards are occasionally manufactured by third-party suppliers.
Rotary switch
Rotary switches have long been known as a further alternative for automatic transmissions. However, they can only be found in a few vehicles:
- Range Rover Evoque
- On the Jaguar XF , the rotary switch only extends when the start button is pressed
- Chrysler 200
Since rotary switches for manual gearshift (M) of the gearbox do not correspond to the usual operating habits, manual gearshifting is provided by steering wheel buttons or rockers.
Installation position
With some gear selector levers, the structure, direction of actuation and the sequence of the automatic positions depend on whether the vehicle was built as a right-hand drive or a left-hand drive.
Middle and cockpit circuit
The switchgear is usually found in the middle of a car, a little in front of the front seats (center switch or center console switch). A worm or labyrinth alley is sometimes used in automatic transmissions. This reduces the risk of accidental actuation because the selector lever has to be moved in two directions one after the other in order to engage a different gear.
The structure of the cockpit circuit (also dashboard circuit, dashboard circuit), in which the switching device is located on the dashboard, is not very different. This location is chosen, for example, to enable free passage between the driver and front passenger seats.
A gear stick, rarely a rotary switch, is used as a control element at this position.
Steering wheel shift
The steering wheel circuit was from the 1940s to the late 1970s, a common type of transmission operation in which the shift lever is mounted on the steering column, in each case on the inside, d. H. right, and for cars with right- hand drive, left on the steering wheel column.
The colloquial term “steering wheel shift” had prevailed, although the shift lever is not mounted on the steering wheel, but on the steering column . The technically more precise term "steering column switch" or "steering column switch" is occasionally used.
In earlier times, larger cars often had a continuous front bench seat and no center console, so that two passengers could sit next to the driver, which was impossible with a center shift. With manual transmissions on the steering column, it was sometimes more difficult to find the right gear or neutral than with an H scheme on the center console. In Europe, manual gearshifts on the center console became the norm, and the relatively rare automatic transmissions used the same position for the selector lever gate.
In the USA, automatic transmissions became the rule and the automatic selector lever mostly stayed on the steering column, opposite the turn signal selector lever. Since there is seldom a choice between forward, reverse or parking, the steering wheel switch is the more compact design, and the center console can be freely used for other purposes. In specially designed electric cars, such as the Tesla Model S or the BMW i3 , the selector lever is usually on the steering wheel, while the electric versions of piston engine cars use the conventional position on the "transmission tunnel".
In the 2010s, the gearshift lever on the steering column experienced a renaissance, first in luxury vehicles. Both Mercedes-Benz and BMW are rearranging the selector levers of their automatic transmissions on the steering column. The shift-by-wire design is advantageous here , as it hardly requires any restrictions with regard to adjustability and crash behavior of the steering column.
A steering column lever or rocker switches are usually used as the control element in this position. On the Ford Edsel, the key switch was located here.
Vehicles with steering wheel gearshift
In the 1960s and 1970s, most mid-range cars were delivered with either a center or steering wheel gearshift. The center shift was considered the sporty, the steering wheel shift as the elegant variant. Some models were only available with a steering wheel gearshift, for example from DKW , Saab and the Renault 16 .
Others
- The Tatra 603 was produced with a rear engine but with a steering wheel gearshift. In other words, the shift linkage had to be routed from the steering column to the rear gearbox in a cumbersome way.
- In the DKW models of the 1950s, which were equipped with a four-speed gearbox, the gears were the opposite of the usual shift pattern: first and third gear were down, second and fourth gear were up.
- The Opel Rekord C had a button at the end of the gear lever that had to be pressed so that reverse gear could be engaged.
- The Trabant built the gear lever together with the steering column, but not the mechanics common for steering wheel shifts, in which the gear lever is moved against the steering column, but the mechanics and shifting pattern of a stick shift.
- While the usual reverse gear position in the H shift is at the rear, in most Volkswagen cars it is at the front.
In right-hand drive vehicles , the arrangement of the gears when shifting the steering wheel is a mirror image.
Revolver and crutch switch
The turret switching or crutch switching is another variant of the mechanical switching. It got its name from the kinked shift rod protruding from the dashboard , the shape of which is reminiscent of a handgun ( revolver ). When the engine is installed lengthways, the shift gates are lengthways, and when the engine is installed transversely, they are across.
The gears are shifted by pulling out, pushing in and turning the shift rod. Well-known cars with this gearshift are Citroën 2CV and Renault 4 , in which the shift rod is angled upwards. On the Lloyd Alexander and the Trabant , the end of the gearshift rod points to the side like a steering wheel shift, and on the Adler Trumpf Junior , the three-wheel delivery van from Tempo and the DKW vehicles with transverse engines, pointing downwards.
The advantages of arranging the gearshift lever in the dashboard are the easier passage between the front seats and the possibility of moving the gearbox in front of the engine and still being able to operate it precisely without any joint prone to failure.
A disadvantage of the known constructions is that the switch stick can penetrate into the interior of the car in the event of a traffic accident between the passengers and cause injuries.
literature
- Hubert P. Büchs: The external circuit. Library of Technology Volume 267, Verlag Moderne Industrie, Landsberg / Lech 2004, ISBN 3-937889-04-3 .
- Beverly Rae Kimes (Editor): Packard, A History of the Motor Car and the Company , General Edition (1978), Automobile Quarterly, ISBN 0-915038-11-0 .
- Eckhard Kirchner: Power transmission in vehicle transmissions . Springer, Berlin 2007, ISBN 978-3-540-35288-4 , therein Chap. 5.4 "Components of the shift mechanism".
- Harald Naunheimer, Bernd Bertsche, Gisbert Lechner: Vehicle transmissions - basics, construction, selection. Springer, Berlin 2007, ISBN 978-3-540-30625-2 , therein Chap. 9.1 "Systematic of the switching elements".
Web links
- Selector lever suppliers: ZF Friedrichshafen , Küster , Kostal , Jopp , Eissmann
Individual evidence
- ↑ a b There are numerous slang terms for selector lever. The patent offices classify corresponding inventions in the IPC class B60K 20/02 A01, the two terms "selector lever" and "manual gear lever" used there can be regarded as an official definition.
- ↑ DWDS | Home page. In: www.dwds.de. Retrieved August 14, 2016 .
- ↑ " Vehicle transmission " , Section 9, "Switching devices", see literature
- ↑ a b According to Kirchner: Power transmission in vehicle transmissions , see literature
- ↑ Kimes: Packard (1978), pp. 32-35
- ↑ Hubert P. Büchs: The external circuit. P. 35.
- ↑ Note in the operating instructions for the Golf I Cabriolet, 1987 edition (German 7.87), part no. 881.551.150.00, p. 22: "While driving, your hand should not be on the shift lever, the pressure of the hand is transferred to the shift forks in the gearbox and in the long run can lead to premature wear of the shift forks".
- ↑ Article Why manual transmissions still have a future on Heise-Online from April 25, 2012, about a statement by Getrag
- ↑ Federal Motor Vehicle Safety Standard (FMVSS) No. 102 of the National Highway Traffic Safety Administration (NHTSA).
- ↑ Federal Motor Vehicle Safety Standard (FMVSS) No. 102 of the National Highway Traffic Safety Administration (NHTSA) S3.1.2 “Transmission Braking Effect” at speeds of up to 40 km / h
- ↑ Keyword selector lever in the Wiki of Toyota Prius friends
- ↑ Article Expensive satisfaction: NASA report exonerates Toyota. auf heise auto describes the causes and technical measures
- ↑ Federal Motor Vehicle Safety Standard (FMVSS) No. 102 of the National Highway Traffic Safety Administration (NHTSA) S3.1.3 "Starter Interlock", analogously anchored in Canadian legislation
- ↑ Example Audi A8 (D4), see Audi A8 article in Wikipedia
- ↑ Description of the TorqueFlite transmission in the English Wikipedia
- ^ US advertisement for the Chrysler Dodge brand from 1958 on the Chrysler Imperaial Club website : Lean back and turn the wheel / the button drives the automobile.
- ↑ Shift Selector Operation and Code Manual. (PDF; 2.2 MB) from Allison Transmissions
- ↑ See, for example, the patent specification DE 19706625 “Gear shift device for an automatic transmission” from Volkswagen
- ↑ A not very detailed overview picture of the Evoque interior can be found on the Wikipedia Commons
- ↑ A not very detailed overview of the XF interior can be found on the Wikipedia Commons