VR engine

from Wikipedia, the free encyclopedia
Schematic top view of in-line engine (left), V-engine (center) and VR-engine (right)

A VR motor is a reciprocating engine with features of a V-type engine and an in-line engine , namely per connecting rod a separate crank pin and a separate right-angle bend of the crank shaft , but by about 15  degrees crossed cylinders , under a common cylinder head .

history

Lancia

The V-engine with a narrow cylinder angle was developed by the Italian company Lancia & C., which is why the design was called the "Lancia principle". The basis for this was a patent from Lancia & C. dated July 1, 1915: By moving the crank pins of opposing connecting rods in the V-engine, the uniform ignition interval of the respective V-engine (V12: 60 degrees, V8: 90 degrees) could be achieved despite a lower actual Cylinder bank angle are maintained.

This was implemented for the first time in two Lancia V12 aircraft engines with a cylinder angle of 50 degrees and 350 hp (257 kW) and 600 hp (441 kW). This was followed by two engines for automobiles: a V8 with 45 degrees and a V12 with 30 degrees, which Vincenzo Lancia applied for a patent in September 1918.

In 1919 Lancia presented a chassis without a body with a V12 engine and a 13 ° 6 'cylinder angle at the exhibitions in Paris and London. The bore was 80 millimeters and the stroke 130 millimeters. The engine developed 150 hp (110 kW) from 7837 cm³ at 2200 rpm. However, the vehicle did not go into series production.

The first production vehicles with VR engines came out in 1922: the Lancia Lambda with V4 engine and the Lancia Trikappa with V8 engine. The cylinder angle of both V-engines was 14 degrees.

In 1930, the Matchless Silver Hawk production motorcycle with a VR4 engine was presented to the public. In the same year, Röhr Auto AG began building VR engines with eight cylinders, 2.5 l displacement and 10 ° cylinder angles for the Röhr 8 . Over the decades, Lancia produced other compact VR engines for longitudinal installation (e.g. 1937 Lancia Aprilia and 1963 Lancia Fulvia ) and used such engines until 1976.

Volkswagen

VR6 engine in the Corrado (1991–1995)
VR6 engine of the Touareg, cut open (2005-2010)

Volkswagen has been building six-cylinder engines based on the VR concept since 1991. These Volkswagen VR engines were originally designed for vehicles with transversely installed engines and are therefore long-stroke in order to save additional installation width. In the VW development, in contrast to the Lancia development, the cylinder axes do not intersect in the middle of the crankshaft, but below ("set crank drive"). On March 7, 1991, Volkswagen presented its VR6 engine to the general public for the first time at the Geneva Motor Show .

The first vehicle with this six-cylinder engine was the Passat B3 . VR6 engines were later also used in the Atlas , Bora , CC , Corrado , Eos , Golf III , Golf IV , Golf V , New Beetle RSi , Passat B4 , Passat B6 , Passat B7 , Passat (NMS) , Phaeton , Sharan I. , Touareg I , Touareg II and Vento . Also with the group subsidiaries Audi in the A3 8P , Q7 4L , TT 8J and TT 8N , with Porsche in the Cayenne (type 9PA) and Cayenne (type 92A) , with Seat in the Leon I and Alhambra I , with Škoda in the Superb II and with Volkswagen Commercial vehicles in the T4 and T5 . As well as in the Artega GT , Ford Galaxy , Mercedes-Benz V 280 , Dehler Optima, Itasca Sunstar and the Winnebago motorhomes Rialta and Vista. VR6 gas engines from Volkswagen are used in forklifts from Jungheinrich , Linde and Still . The AMAG Group offered to 2002 in Switzerland the Seat Leon Cupra with a by a compressor supercharged VR6 engine in a small series of approximately 75 pieces.

From 1997 to 2005 Volkswagen also produced VR5 engines that were used in the Golf IV , Bora , New Beetle and Passat B5 vehicles as well as in the Seat Toledo II .

The Bugatti Veyron 16.4 introduced in 2005 and its successor, the Chiron , built in 2016, have an eight-liter double-V engine with two VR8 cylinder banks (15 degrees cylinder angle and 90 degrees bank angle) as the drive.

Horex

A motorcycle with a particularly compact VR 6-cylinder engine has been marketed under the type designation Horex VR6 since the end of 2012 / beginning of 2013. Volkswagen was involved in the development of the engine as part of a consulting contract.

Reasons for developing the VR concept

The VR concept makes it possible to combine the shortness of the V-engine with the narrow width of the in-line engine. The first VR aircraft engine from Lancia could be made ten centimeters narrower by reducing the cylinder angle by 10 degrees. Only in this way was it able to meet the structural requirements that were based on the aerodynamics of Caproni 's aircraft .

The small dimensions also result in advantages in motor vehicle construction. The V4 of the car model Lancia Lambda had a total length of only 58 centimeters including the flywheel despite a displacement of up to 2.5 liters. This allowed the engine, clutch and gearbox to be housed completely in the engine compartment. There was no need for a transmission tunnel that would have compromised the interior space. In front-wheel drive models with an engine in front of the front axle, such as the Lancia Fulvia, the VR engine enables a more neutral driving behavior. Due to the short design, the center of gravity of the engine is less far from the center of the vehicle.

In front-wheel drive cars , the combustion engine is now usually installed transversely. Since, in addition to the engine, the gearbox also has to find space in the engine compartment and is flange-mounted as an extension of the engine, the width of the engine is limited so that four-cylinder engines dominate the market in this arrangement.

A higher number of cylinders can be achieved if the engine is not built as an inline engine but as a V-engine. However, a conflict of objectives arises here due to several requirements:

  • A minimum distance between the cylinders is required so that there is still space for the water cooling channels and the oil paths.
  • The cylinder walls must have a certain minimum thickness, otherwise the wall between the individual cylinders can overheat.
  • The angle of the V-engine must not be too large, otherwise it worsens the impact behavior. An engine that is too wide bridges the plastic deformation zones and may penetrate the passenger compartment in the event of a frontal collision.
  • For particularly smooth running (compensation of inertia forces and moments of higher order), certain cylinder angles are preferred: After the in-line engine, the V-engine with a 60 degree cylinder angle is particularly favorable for the six-cylinder, and for the eight-cylinder, the design with a 90 degree cylinder angle.
  • The V-engine brings increased construction effort and higher costs, because in addition to the more complex engine block, two cylinder banks with their own heads and valve trains are required.
  • With a large cylinder bank angle , engines can be realized that are hardly longer than in-line engines with half the number of cylinders.

The concept of the VR motor is a compromise between the two designs. The VR design shows an additional geometric problem, because in the V design with a cylinder bank angle of only 15 degrees, the cylinders in the lower area would penetrate each other or would have to move further apart. Lancia solved this conflict with relatively long connecting rods.

With a simple tilting of the cylinder banks, as is usual in the V-arrangement, the cylinder center axes and the crankshaft center axis would intersect - as in an in-line engine. “Crossed” cylinder banks, on the other hand, are offset parallel to the outside, thus avoiding penetration of the cylinders even with short connecting rods and small cylinder bank angles; their cylinder center axes intersect below the crankshaft axis. Thus, low overall heights can be achieved, which also allow use in motorcycles. The disadvantage, however, is the greater inclination of the connecting rod, so that the pistons are pressed against their raceways on one side with higher radial forces. The movement characteristics of the crank drive - the assignment of rotary movement and piston movement - becomes asymmetrical to the top dead center.

With VR engines, a common cylinder head can be used for both cylinder banks with a small cylinder bank angle - as with the in-line engine . Due to the V-arrangement of the cylinders, the parting line between cylinder and head is no longer perpendicular to the cylinder axis. The resulting disadvantage is the unequal length of intake and exhaust paths between the two cylinder banks, since fresh gases for all cylinders usually come from one cylinder head side and all exhaust gases are carried away to the other cylinder head side. In addition, this type of cylinder head is more complex to cast and to machine, especially for four-valve engines.

Another common feature of a six-cylinder VR engine and a six-cylinder in-line engine is, for example, its crankshaft with seven bearings and six cranks .

literature

Web links

Commons : Volkswagen VR6 engine  - collection of images, videos and audio files

Individual evidence

  1. ↑ Hans-Hermann Braess , Ulrich Seiffert (Ed.): Vieweg Handbook Automotive Technology . 6th edition. Vieweg + Teubner , 2011, ISBN 978-3-8348-1011-3 , pp. 162 ( limited preview in Google Book search).
  2. ^ Richard van Basshuysen , Fred Schäfer (ed.): Handbook internal combustion engine . 7th edition. Springer Vieweg , 2015, ISBN 978-3-658-04677-4 , p. 11 ( limited preview in Google Book search).
  3. ^ Wolfsburg News. Edition March 7, 2017.
  4. ↑ jungheinrich.at
  5. ↑ gruma.de
  6. ↑ News | STILL Germany. (No longer available online.) Archived from the original on December 13, 2016 ; accessed on September 25, 2018 .
  7. ↑ Seat Leon Cupra 4 Compressor 2.8 L (1M) on seatcupra.de, accessed on February 8, 2018.
  8. ↑ http://www.tourenbike.at/2010/06/17/interview-mit-horex-chef-clemens-neese/ ( Memento from December 7, 2013 in the Internet Archive )