Patent Grant
7043909
Not applicable.
1. Field of the Invention
This invention relates to Stirling cycle devices, specifically linearly driven single- and multi-cylinder Beta type devices.
2. Description of the Prior Art
Stirling cycle devices are well-known, and are operable as engines or heat pumps. Thermodynamic properties of a working gas contained within the device are exploited by compression, expansion, heating, and cooling, according to the Stirling thermodynamic cycle of the working gas, wherein more energy is obtained from the expansion of a heated quantity of gas than is required to compress the same quantity of gas that is cooled.
When the device is operated as an engine, its basic function is to convert a thermal differential to rotational energy. A thermal differential is externally provided between two physical portions of the device, and the shaft rotates. In this mode, the device is an engine.
When the device is operated as a heat pump, its basic function is to convert rotational energy of a shaft to a thermal differential. The shaft is rotated by external means, and the device produces a thermal differential between two physical portions of itself.
(For simplicity, unless otherwise noted, this narrative assumes that the device under description is being operated as an engine, and it is understood that the device could be operated as a heat pump by reversing operation. Conversely, if heat pump mode is being described, it is understood that the device could be operated as an engine by reversing operation.)
Many techniques have been developed to increase the effectiveness of the Stirling cycle device. Usually these techniques involve excessive mechanical linkages or size, exotic materials, and unusual construction methods. Although effectiveness may be improved, expense and complexity are increased, which reduces the device's viability.
U.S. Pat. No. 5,394,700, “Stirling Engine with Ganged Cylinders and Counter Rotational Operating Capability”, inventor Steele, is hereby incorporated by reference.
Disclosed herein is a new Beta type Stirling engine, where the power piston and the displacer coaxially occupy a common cylinder. The cylinder is sealed to allow a working gas contained within to be contained at a higher pressure than the atmosphere surrounding the cylinder. Inventive linkage is provided so that the engine can be engaged with cam grooves provided in a cam body such as a face cam or a barrel cam. As the cam body turns, the cam grooves operate the linkage so that the strokes of the power piston and displacer are out of phase by a phase angle determined by the positions shapes of the cam grooves, relative to each other. The grooves in the cam body can be shaped to provide any stroke, dwell, and phase angle desired.
The engine otherwise operates like a conventional Stirling engine, where a thermal differential is provided between the displacement chamber and the compression chamber. Typically, heat is applied to the displacer end of the engine, and a cold region is provided around the compression chamber.
The cam body can be within the pressurized assembly, as illustrated, with only the output shaft extending out of the pressurizable housing.
In its simplest implementation, a single cylinder would be used with a face cam. If a barrel cam is used, a plurality of single-cylinder engines can be engaged into a common barrel cam, thus making a composite multi-cylinder barrel-cam or “clustered” engine. Cylinder counts of 1, 2, 3, 4, 5, 6, or even more are achievable.
Previous multi-cylinder Stirling engines have been referred to as “square-four”, “inline”, “V”, “radial”, “horizontal opposed”. The “cluster” configuration specified herein is new and unique to Stirling devices.
Included among the objects and advantages of this invention are:
List of Drawing Figures:
Displacer shaft 302 is connected to displacer 301. Hollow power piston shaft 402 is connected to and penetrates power piston 401. Displacer shaft 302 passes through power piston 401 and hollow power piston shaft 402 as shown. This construction allows independent coaxial action of shafts 302 and 402, which terminate at yokes 304 and 404. Mounted to yoke 304 is cam roller 303. Mounted to yoke 404 is cam roller 403. Yokes 304 and 404 are kept in alignment by guide rods 208 as shown. Cam rollers 303 and 403 engage cam grooves 102 and 103, respectively, in a cam body configured as face cam 101′. As cam 101′ turns, cam grooves 102 and 103 and cam rollers 303 and 403 interact to cause a fixed reciprocating relationship between the motions of power piston 401 and displacer 301. Cam grooves 102 and 103 can be infinitely shaped to cause whatever stroke, dwell, and phase angle is desired for piston 401 and displacer 301. Multiple cycles per cam 101″ revolution can also be provided. In the Figures, a single cycle per cam 101″ revolution is shown.
Guide rods 208 are fixed at one end to engine bulkhead 203, and fixed at the other end with guide rod keeper 212, which also supports face cam 101′ at face cam pivot 213, located at rotational center of face cam 101′.
Device 100 is operated like a conventional Stirling device. The application of thermal differential 104 causes power piston 401 and displacer 301 to reciprocate, thus turning cam 101′. Conversely, turning of cam 101′ will produce thermal differential 104, thus operating as a heat pump.
Since cylinders 201 are oriented in the same direction, their hot and cold regions 209 and 210 coincide, and multi-cylinder engine 100″ is operated like a conventional Stirling device.
These embodiments meet Objects and Advantages listed above, as follows—
The embodiments shown have the minimum possible moving parts for a device of this type. Consequently, it is compact, elegant, highly versatile, and minimal in weight. Reduction of moving parts improves manufacturability and reliability.
It can be seen, that by having a single shaft penetration from the pressurized area to the non-pressurized area, that only one housing seal is needed, and pressurization is improved.
It can also be seen that rotary output of the cam is produced by linear action of the power piston.
It can also be seen that the cam grooves are infinitely configurable, thus providing infinitely settable stroke, dwell, and linear reciprocation cycles per cam revolution.
It can also be seen that the design has a well-supported and strong assembly. The use of guide rods to support and guide the yokes adds superior alignment capabilities to the beta type Stirling design that has not existed in the past and has always been a weakness which has required at times the addition of rollers or guides within the displacer cylinder. This alignment feature constrains the displacer and the power piston to remain centered within the cylinder and to not rub or touch the cylinder wall. In the case of the power piston, only the power piston seal actually touches the cylinder wall thus reducing friction and wear of these vital components, thus improving reliability.
The preferred “clustered” embodiment has the additional advantage that all pistons, displacers, linkages, and the cam, are all contained within a common pressurizable housing. The only moving element that passes through the housing is the single output shaft, thus providing a very pressurizable housing by virtue of a single output shaft seal.
While there is shown and described a preferred embodiment of the invention, it is to be distinctly understood that this invention is not limited thereto but may be variously embodied to practice within the scope of the following claims.
For example, if a perfectly pressurizable engine housing is desired, a magnetic coupling may be used to transfer power through the housing, rather than an output shaft.
Further, electromechanical conversion means can be included within the pressurizable housing, coupled to the output shaft. In this fashion, electromechanical conversion means such as a motor, alternator, or generator, and the Stirling device can be contained within one pressurizable housing, and only motor/generator wires pass through the housing, thus maximizing integrity of the pressurizable housing because no shaft seals are required, and making a hermetically sealed device possible. In this fashion, a hermetically sealed Stirling heat pump or Stirling generator can be provided.
Further, although the inventive device is described as an engine that can convert thermal energy to mechanical kinetic energy, said device is also operable as a heat pump, as is well known in the Stirling art. Consequently, as a heat pump, ‘hot’ region and ‘cold’ region can be transposed, depending on which direction the output shaft is rotated.
This application is entitled to the benefit of Provisional Patent Application Ser. No. 60/448,070, filed 2003 Apr. 18.
| Number | Name | Date | Kind |
|---|---|---|---|
| 5394700 | Steele | Mar 1995 | A |
| 5442913 | Cho et al. | Aug 1995 | A |
| 5533335 | Shin | Jul 1996 | A |
| 20030074897 | Rollston | Apr 2003 | A1 |
| Number | Date | Country | |
|---|---|---|---|
| 60448070 | Apr 2003 | US |
