Rotary engine

Details Rotary engine Rotary engine

2003-09-09

2004-08-17

Denion, Thomas (Department: 3748)

Internal-combustion engines

Rotary

With compression, combustion, and expansion in a single...

C123S0430AA, C091S491000

Reexamination Certificate

active

06776135

ABSTRACT:

FIELD OF THE INVENTION
The present invention generally relates to a rotary engine and, more particularly, to a rotary engine that improves output efficiency, reduces friction wear, and decreases fuel consumption, and at the same time is easy to manufacture and has the flexibility to increase the number of cylinders to improve the performance of the rotary engine.
DESCRIPTION OF RELATED ART
FIG. 23
shows a conventional reciprocating engine
100
that uses a confined space for sequentially performing the four cycles of intake, compression, combustion, and exhaust, where the crank
110
inside the engine
100
generates the rotational output. The theory behind the traditional engine
100
has been widely applied in our daily lives for all kinds of land, sea, and air transportation, as well as power generating apparatus for agricultural, manufacturing, and military use. Even though the reciprocating engine is broadly accepted and used, it does not mean that the performance has reached perfection. In fact, there are the following bottlenecks in the reciprocating engine
100
regardless whether it is of 2-stroke or 4-stroke design:
(1) Output power cannot be easily increased: reciprocating engine
100
relies on a crank
110
to convert the reciprocating motion of the piston
120
into a rotational motion which is then coupled to an external driving system. The conversion from the reciprocating motion into the rotational motion causes a loss in the output efficiency, which is unavoidable due to structural limitations.
(2) Structure and manufacturing are complex: the output efficiency of the reciprocating engine
100
is highly related to the precision in the manufacture of the crank
110
, wherein the precision of the crankshaft
112
and the crank pin
115
needs to be extremely high. If there is any error in the level of precision, the conversion from reciprocating output to rotational output will be greatly decreased. Moreover, in a four-cylinder reciprocating engine, the internal parts add up to forty linked parts for operation which results in a high manufacturing cost.
(3) Torque-increase causes fuel consumption to increase: a reciprocating engine
100
can increase the stroke, that is to increase the distance between the connecting rod
117
and the crank
110
, to rise torque. If the stroke is increased, the bore of the cylinder
125
also needs to be increased; therefore, fuel consumption is greatly increased, so an increase in torque and a decrease in fuel consumption cannot be achieved simultaneously.
(4) Increase of the number of cylinders is limited: if the number of cylinders is increased to raise the horsepower of the reciprocating engine
100
, the engine overall size is unavoidably increased. Regardless of the configuration of the cylinders, such as straight, boxer, and slant or the type of configuration V, W, and H, the engine size always increases significantly when cylinders are added.
(5) high-rpm causes wear: when the reciprocating engine
100
revolves over 2000 rpm, such high-rpm reciprocating action will cause the piston
120
to experience an extremely high amount of wear, which, at the same time generates a lot of heat, increasing damage to parts and decreasing the lifespan of the engine. As a result, fuel consumption of the engine increases over time.
In order to solve problem (1) of reciprocating engine
100
regarding power output, a German engineer Felix Wankel invented the Wankel rotary engine
150
, which is illustrated in FIG.
24
. An arciform triangular rotor
160
is held within a rotor holding bore
165
, which replaces the cylinder
125
and the piston
120
of the reciprocating engine
100
. The conformance to a peri-trochoidal profile is driven by the requirement that all three bearing points of the Wankel rotor remain in constant contact with the inner surface of the engine. The rotor rotates in a planetary motion through the engaging of a rotor gear on the rotor with a gear on an output shaft. The interplay of the arciform triangular rotor within the rotor holding bore creates three chambers therein. Under planetary motion of the rotor, the chambers outside of the rotor vary their capacities to perform the four cycles of intake (suction), compression, combustion (expansion), and exhaust. The output of the Wankel engine
150
is directly connected to the arciform triangular rotor
160
without the need of motion type conversion. The output of the Wankel engine
150
is twice that of the reciprocating engine
100
, and the overall number of components of the Wankel engine
150
is greatly reduced; therefore, from the market launch in 1958, it caused a great shock in the industry. In the era of the 60s, when power was most sought after, the high output rotary engine was put on sports cars, breaking speed records for sports cars, and the rotary engine seemed poised to take over the traditional reciprocating engine
100
.
Although the Wankel engine
150
improved problem (1) of the reciprocating engine
100
, it failed to successfully solve problems (2), (3), and (4). Furthermore, the path of the arciform triangular rotor
160
is not smooth, so at high-rpm, wear at the tips of the rotor
160
causes the exhaust cavity immediately following the ignition point to rapidly enlarge. This causes a significant portion of the gas pressure to be lost to expansion within the enlarging cavity, instead of being converted into useable torque. The problem of power decreasing and fuel consumption increasing becomes more significant as the engine runs more, and, for about every 30,000 miles, the engine needs rebuilding or replacement. This disadvantage proved fatal for the the Wankel engine
150
, resulting in the higher carbon monoxide exhaust levels and fuel consumption. The architecture of the Wankel engine, i.e., a peri-trochoidal section, makes it difficult to improve the combustibility of the combustion phase to decrease the exhaust quantity of unburned gases. Although the number of parts of the Wankel engine
150
is much less than a conventional engine, the precision of the inner gear
180
and the outer gear
185
of the arciform triangular rotor
160
has to be extremely high, offsetting the cost-savings generally associated with having fewer parts. Furthermore, the arciform triangular rotor
160
is the part that undergoes the most wear in the engine, and, if there is a problem on a Wankel engine
150
, the whole unit is usually replaced, which reduces practicality. The Wankel engine
150
overcomes some of the limitations of the reciprocating engine
100
, but possesses other disadvantages not found in generic reciprocating engines; therefore, market acceptance has not been as rapid as expected.
Beginning with the energy shortage of 1973, vehicle engine research has shifted focus from increasing power to the twin goals of decreasing exhaust emissions and fuel consumption. The shortcomings of the Wankel engine rapidly became apparent and most of the car manufacturers cancelled development of the Wankel engine and returned to designs employing the reciprocating engines. Among all the car manufacturers, only Mazda continued the use of Wankel engine and kept making performance modifications. Mazda launched the RX7 model in 1999 with the use of modern lubricants and ceramic material for the triangular tips to lower the wearing problem of the Wankel engine. However, the use of this material greatly increases the manufacturing cost.
Any novel industrial product must possess advantages and performance that are not found in prior art. Moreover, the setup of the production equipment and production line cannot be too expensive compared to prior art, otherwise existing manufacturers will not the existing product line and business prospects. Possession solely of technical performance is generally not enough for a new design to change the percentage of market share away from conventional technology. Performance has to be combined with ease of manufacturing and low cost to attract manufacturers to invest in or replace production lines.
On inspection of the hist

Affiliated with

Also associated with

Rating

Rotary engine does not yet have a rating. At this time, there are no reviews or comments for this patent.

If you have personal experience with Rotary engine, we encourage you to share that experience with our LandOfFree.com community. Your opinion is very important and Rotary engine will most certainly appreciate the feedback.

Rate now

Comments { 0 }

Profile ID: LFUS-PAI-O-3277920