Piston engine

The invention relates to a piston engine as stated in the introductory part of claim 1 , including a piston engine for converting thermal energy to kinetic energy. Examples are steam engines powered by steam from a boiler and combustion engines (otto or diesel engines) supplied with liquid or gaseous fuel to a piston chamber.

Background

A need exists for simplified piston engines, e.g. for various combustion engines to be fuelled by liquid or gaseous fuel, and which may be manufactured with less complicated equipment than current combustion engines, particularly combustion engines with crank shafts.

Parallel thereto, an increased need for the use of various bio fuels to power engines has evolved. Prior art steam engine technology has not been suitable for current needs in regard of efficiency and compact design. Prior art steam engines have a complicated design, low thermal efficiency, high weight and are clumsy.

Various prior art crank systems can transform a linear piston movement into a rotational movement, which can then be used to power an electric generator or another energy converter, such as pumps. From EP patent application 0 471 451 (Jaguar Cars 1991) a rocker dish mechanism is used in a motor, wherein two or more piston rods are linked to a rotatating dish connected to a crank arm. Thus the piston movement is converted into a rotational movement or vice versa. When used in a combustion engine, this mechanism will suffer from a harmful impact load of the crank shaft. To avoid rotational movement of the rocker mechanism, a double cardan joint is needed.

From Proc. Institute Mech. Eng. VoI 208 (1994) page 361 , a rotational converter for a Stirling motor is known, in which two rigid piston rods are linked at the ends of a rocker yoke which is pivotably linked to a crank arm connected to a central shaft, parallel to the piston rods. This shaft is integrated with an electric generator to carry the rotor thereof. This rotational mechanism is not suited for rotational converters needing valve control or a combustion engine with inlet and outlet as a minimum.

From GB patent specification 225433 (Nagelman 1924), a piston engine as defined in the introductory part of claim 1 is known. The rigid connection at the prior art rocker member is unsuitable for such engines.

Object

The main object of the invention is to provide an improved piston engine, including a piston motor suitable for converting thermal energy into kinetic energy with a rotating shaft outlet which can be manufactured and maintained more easily than corresponding prior art piston engines.

A particular object is to provide a piston engine with particular simplicity, which can be manufactured with simple equipment and without demanding skill. Thus it is an object to provide a piston engine, for purposes where low cost is an important requirement, e.g. in areas with transport problems for the supply of "imported" fuels, or for economic reasons, e.g. to power electric generators infrequently used, e.g. at holiday cottages, or where the costs should be kept at a low level, e.g. in poor areas.

This piston engine should function for different thermal processes involving oscillating pistons with piston rods. Further objects will appear from the following description of examples.

The Invention

The invention is stated in claim 1. Further features of the invention are stated in claims 2 to 8.

This piston engine may be used for various conversions of various thermal energies into kinetic rotational energy. Two particularly interesting areas of use, as stated in the dependent claims, are as a steam engine and as a two or four stroke combustion engine, both with two or four cylinders. In both cases, a direct drive valve system with favourable operational properties can be provided. The invention allows large conduits and short opening intervals. This will enable rapid and efficient filling, both with steam and gas for combustion. The piston engine according to the invention may also have fuel injection.

vlultiple units of the piston engine according to the invention may be arrayed to a larger slant.

A particular favourable use of the piston engine according to the invention is for powering an electric generator, using the dissipated thermal energy for heating water. This will provide a heat and power plant. Such heat and power plants may be built in various sizes using modular units. Using steam, bio fuel can be used, which is available also in rural areas with limited energy supply, in particular electricity supply, and with dependence on fossil fuels growing expensive and scarce. This will allow provision of electric power to areas now lacking power supply.

Used as a steam engine, it will be possible to utilize the energy completely from the one cylinder, to avoid the need for a high pressure piston and a low pressure piston.

A further advantage of the invention is the option to change the control, e.g. to adapt to various steam pressures, by changing between slide valve bodies with different characteristics. Thus a heat power plant according to the invention may be adapted for different kinds of fuel creating different steam pressures.

Example

The invention will now be described with reference to the drawings, wherein

Figure 1 shows an axially sectioned side view of an embodiment of the invention, used for a steam engine which may power a pump or an electric generator,

Figure 2 shows a corresponding view of the steam engine of Figure 1 , offset 90°, Figure 3 shows a cross section of the steam engine of Figures 1 and 2, along the line A-A,

Figure 4 shows a corresponding cross section as Figure 3, along the line B-B, while Figure 5 shows an end view of the crank-rocker mechanism of the example.

In Figures 1 and 2 a cylinder block 11 is shown, with two cylinders 12, 13 being arranged on opposite sides of a power shaft 14. To accommodate a valve body 15 axially, being connected to the power shaft and driven thereby, the cylinder block 11 is enlarged with a collar 16 at the outlet side of the power shaft.

In each cylinder 12, 13 a piston 17, 18 is arranged with a piston rod 19, 20 which is linked to a gudgeon pin 21 , 22. The piston rods 19, 20 are linked to a rocker frame element, in the following called "rocker frame" 23 with a pin bolt 24, 25.

The piston rods 19, 20 and the rocker frame 23 are connected with a crank system 26 carried by the outlet shaft 14 which is driven thereby. The driven end of the outlet shaft 14 has a crank arm 27 extending from the axis and being balanced by a counterweight 28 on the opposite side. The crank arm 27 carries a crank pin 29 extending from the crank arm and making an angle of about 17,5° to the axis 30 of the outlet shaft 14. Rigid connection of the crank pin 29 will require zero tolerance in the arrangement of links and shafts. To meet this requirement, the crank pin 29 is linked to the crank arm 27 with a crossing pin 29A.

The rocker frame 23 is clamped between the crank system 26 and the cylinder block 11 as described in the following. The rocker frame 23 has internally a connecting element 31 carried pivotably by the crank pin 29. The connecting element 31 has an inner bore 32 with a bearing for axially movable engagement with the crank pin 29 and two juxtaposed pivoting pins 33, 34 with an axis 35 crossing the axis 30 of the power shaft. The pivoting pins 33-34 are engaging the rocker frame 23.

To hold the rocker frame 23, a pair of arms 36, 37 extend forklike from the cylinder block 11 , parallel to the power shaft 14. The free end of each arm 36, 37 provides a bearing for a pin 38, 39 extending from the rocker frame 23, centrally to this. The axis 40 for the pins 38, 39 and the axis 35 has a common section to the axis 30 of the power shaft 14.

This propulsion structure can be utilized for a steam engine and for a combustion engine. Said engines require adaptation of the valve arrangements, the supply system and the lubrication system, based on prior art. In the following, an example of a valve arrangement for a steam engine will be described.

In Figures 3 and 4 details of a valve body 15 being a sleeve in the cylinder block 11 are shown. The valve body 15 is connected to the power shaft 14 and controls the connection between a steam inlet opening 41 at the collar 16, the opening 42, 43 to and from each , cylinder 12, 13 and the outlet conduit 46 from the motor.

The valve body 15 has conduits connecting the different openings 41 - 46 internally in a sequence which provide inlet of steam under pressure and outlet of residual steam.

Figure 5 shows the two arms 36, 37 providing a fork which is holding the rocker frame 23 pivotably on the pins 38, 39. The rocker frame 23 at each end has a fork 47, 48, each

being linked to a piston rod 19, 20. In the opening of the annular rocker frame 23, the connecting element 31 is linked.

The valve body 15 (Figures 1- 4) is provided with conduits for controlling the steam flow, Said conduits comprise an annular conduit 51 at the mouth of the inlet conduit 41. Further they comprise an annular conduit 52 at the mouth of the outlet conduit 46. The annular conduits 51 , 52 each has an axial conduit 53, 54 to the conduits connected to the chamber 55, 56 of the respective cylinders 12 and 13. The conduits 53 of the valve body are designed to feed the steam engine adequately at different steam pressures. Thus it is possible to adapt a given engine to different modes of use by exchanging valve bodies.

The engine shaft 14 is connected to the tubular valve body 15 over a flywheel 59 with a locking pin 60. The engine shaft 14 can also be connected to a generator, a pump or other equipment to be powered, with a prior art connection. If the invention is to be utilized for a combustion engine, supply of a lubricant is needed. A combustion engine will also need cooling. This may be done with air blown past cooling ribs or with liquid cooling.

The invention can be used for both two and four stroke combustion engines. To provide a four stroke combustion engine, the power shaft can have cam dishes for controlling valves. Such mechanisms may be based on known technology. The invention can also be used as a converter for the kinetic energy from a Stirling motor.

The engine may also be adapted for four cylinders, particularly for a four stroke combustion engine, pairs of cylinders being connected.

The invention may be manufactured of easily available metals, with comparatively simple machining and reasonable low tolerances. This makes the novel engine available for manufacturing in areas without advanced tools.

The piston engine according to the invention may be designed for modular manufacturing, operating with a common shaft, making one engine size available for manufacturing engine assemblies for different sizes of generators. Such modular design may also be used for engines powering vehicles. This will make the manufacturing simpler and the provision of spare parts more convenient.

The embodiments shown may also be modified by arranging the valve housing and the valve body eccentric to the drive shaft, either directly in the cylinder block or as supplemental chain driven elements.

The rocker frame 23 may be journalled by a holder different from a fork, e.g. between two elements extending U-shaped from an engine base. The term "cylinder housing" for the parts containing the pistons, is intended to include structures with single cylinders combined to an integrated structure.

The invention can also be used for pumps and compressors with pistons.