Articulated rod engine
Articulated-rod engines are internal combustion engines with a piston rod articulated by a rocker arm mounted in the engine housing . With a large stroke / bore ratio, this enables shorter piston rods or less piston rod deflection.
The principle of the articulated connecting rod motor could not prevail and never got beyond the prototype stage with a few one-offs.
Lever engine
In 1920, the American inventor Alvah L. Powell (1863-1924) filed a patent under US patent number 1384343, which described the articulated connecting rod itself. Four years later, in 1924, Powell registered a patent for an entire engine with an articulated connecting rod under US Pat. No. 1663261; this engine was installed in four vehicles of the American brand Elcar in 1930 .
In the early 1950s, Lever Motors Corp. from Charleston, USA developed a "direct current flushed two-stroke engine with inlet valves and outlet slots". The core of this development was a modified articulation of the connecting rod on a rocker arm, which was rotatably mounted in the motor housing. The aim of this modified kinematics of the crank drive was to allow the piston to stay longer in the bottom dead center (because of the longer time for the flushing process, which is important in two-stroke engines). In theory, this had some positive effects on engine running and efficiency . The longer dwell time at bottom dead center gave the engine more time to discharge the resulting exhaust gases, which increased heat dissipation and improved the air mixture for the next cycle. Furthermore, the guidance by the rocker arm resulted in a lower inclination of the connecting rod, which should result in smoother running.
Even then, the benefit of this kinematics, which was implemented by using additional moving joints and levers instead of a classic crank drive with connecting rod, was controversial. The trade journal ATZ wrote in 1952: "Whether the connection of a normal connecting rod with two further levers and three further pins outweighs the intended advantages appears at least questionable."
Mederer engine
In the 1970s, about 50 years after the first development of the articulated connecting rod principle, the German inventor Gerhard Mederer proposed a crank drive concept. Mederer wanted to change the passage of the piston at top dead center on the basis of static considerations. Based on the fact that the conventional crank drive barely develops any torque in the area of the highest compression at top dead center, Gerhard Mederer wanted to increase the available torque by increasing the effective lever arm near top dead center with an intermediate lever. One effect was that the piston overcomes top dead center faster than would be the case with a normal connecting rod. This should result in a higher torque. Like the Lever engine, the Mederer design had a connecting rod between the crankshaft and the lever and a second between the lever and the piston.
All Mederer designs achieved a shortened dwell time of the piston in the area of the top dead center due to its built-in lever.
This principle has advantages and disadvantages. Due to the faster moving piston, an enlarged lever arm is now available shortly after top dead center, when the maximum gas pressure is expressed in the combustion chamber, compared to the conventional crank drive . In theory, this enables increased performance, lower gas temperatures and, associated with this, improved exhaust gas behavior in this phase.
Mederer was only able to partially counter a disadvantage of the Mederer crank drive, the higher, additional inertia forces that arise because the crank drive has to accelerate the piston more strongly at top dead center. The higher accelerations that occur before and after reaching top dead center and the associated strong inertia forces on the crank drive were absorbed by Mederer in specially developed crankcases and bearings. The joints of the connecting rods were made particularly durable and therefore heavy. Nevertheless, the highest permissible speed had to be reduced. Therefore, it initially envisaged its first use in the area of slower running engines. If such engines were used in vehicles, the higher torque would have made a gearbox of correspondingly larger dimensions necessary for torque conversion .
Try the Mederer engine
A few years after Mederer's designs became known, J. Blumberg and J. Gerster examined one of his first realized crank drives by examining a single-cylinder diesel engine first in series with a conventional connecting rod and then after conversion with an articulated connecting rod. In the 49th edition of MTZ from 1988, they reported: “Measured against the hopes of the inventor, the results of the test runs fell far short of the original expectations. Both in full-load operation and in part-load operation, higher specific consumption levels were measured than with the base engine. The expected high torque of the articulated connecting rod engine in the middle speed range did not materialize. "
Controversy and media coverage
Mederer always remained convinced of the effectiveness of the articulated connecting rod principle. He often doubted the results of investigations on Mederer engines because he was not involved in the investigations. Among other things, he questioned the informative value of the values of the test benches used. As a counterexample, he used the car he was using, a Mercedes W123 converted with an articulated connecting rod . According to Mederer, TÜV Munich certified this vehicle with significantly reduced fuel consumption and pollutant emissions. For this he received a gold medal at the 1991 inventors' fair in Nuremberg and a state prize at the international craft fair in Munich. Nevertheless, the idea of the articulated connecting rod was not pursued by any engine or automobile manufacturer ; In tests by various manufacturers, the engine was judged to have increased nitrogen oxide emissions, excessive vibrations and inertia forces that were difficult to control. Mederer, who described his engine as "the beginning of a new age of engines", also received support from German daily newspapers and magazines in his plan to make the crank drive he had developed better known. In its January 1995 issue, Focus wrote : "The invention of a Franconian garage tinkerer doesn't seem to fit the German automotive industry". Reports are also circulating on the Internet that portray the Mederer engine as a promising, innovative invention. Some of these are insufficiently verifiable or simply wrong. They therefore have no scientific relevance .
Foreign manufacturers have never adopted the articulated connecting rod principle either. The weekly newspaper Die Zeit on August 11, 1995 reported a statement made by the Japanese vehicle manufacturer Isuzu, according to Mederer : "If your engine is only half as good as the TÜV report promises, we want it." To this day, Isuzu does not sell any corresponding motors. Further serious developments in the articulated connecting rod technology were not possible for Mederer until his death.
Current development
The idea of the articulated-rod engine did not go beyond the testing stage in either the Mederer engine or that of Powell and is of no relevance in engine construction today.
At the moment work is being done on gasoline engines with variable crankshaft drives , which allow the compression ratio to be adjusted . The mechanisms for controlling the piston stroke differ fundamentally from the articulated connecting rod technology.
literature
- Stefan Zima: Unusual engines . Book publisher vogel, Würzburg 2005, ISBN 3-8023-1995-8 .
- Patent DE10003467 : articulated connecting rod kinematics. Registered on January 24, 2000 , published October 31, 2001 , inventor: Gerhard Mederer.
- Patent EP0314773 : engine or work machine , in particular internal combustion engine. Registered on May 3, 1988 , published October 28, 1991 , inventor: Gerhard Mederer (Driving or working engine, in particular an internal combustion engine).
Web links
Individual evidence
- ↑ Patent US1384343 : Transmission for engines. Filed on Dec. 8, 1920 , published on July 12, 1921 , Applicant: AL Powell Power Co, inventor Powell Alvah L ..
- ↑ a b Patent US1663261 : Engine. Registered on March 19, 1924 , published March 20, 1928 , inventor: Leigh Powell Alvah.
- ↑ http://www.lincoln-highway-museum.org/Powell/Mags/AA-07-1966-150.pdf
- ^ The Powell Lever Motor. Retrieved April 6, 2013 .
- ↑ ATZ: two-stroke engine from the Levi Motors Group. In: ATZ . April 1952, p. 93 .
- ↑ Blumenberg, J. and Gerster, J .: Trials with a series model after conversion to an articulated connecting rod . In: MTZ . March 1988.
- ↑ a b Lewe, T .: A man is fighting for the kink in the connecting rod . In: Frankfurter Allgemeine Zeitung . November 22, 1994.
- ↑ a b Wolfgang Blum: The trick with the kink . In: The time . August 11, 1995.
- ^ Certificate from the inventors' fair in Nuremberg. (JPG) (No longer available online.) Mederer, archived from the original on April 2, 2015 ; accessed on March 21, 2015 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ^ Certificate from the craft fair in Munich. (JPG) (No longer available online.) Mederer, archived from the original on April 2, 2015 ; accessed on March 21, 2015 . Info: The archive link was inserted automatically and has not yet been checked. Please check the original and archive link according to the instructions and then remove this notice.
- ↑ a b Heiner Sieger: The trick with the connecting rod kink . In: Focus . January 1995.
- ↑ With variable compression, car engines run economically clean. Retrieved April 6, 2013 .
