JPS5877144A - Stirling-cycle machine - Google Patents

Abstract

(57) [Summary] This bulletin contains application data before electronic filing, so abstract data is not recorded.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention is based on Stirling
Concerning machines using thermodynamic cycles. Such machines, as is known, include at least one of each of two essential moving parts, the motions of which are similar to each other but out of phase within certain limits.

One of these parts is usually configured as a displacement device, often comprising a plunger movable with a gap inside the cylinder, thereby displacing a quantity of gas in alternating directions between the two ends of the cylinder. It is a feature of this cycle that one end of the displacement device is kept cold compared to the other end, so a Stirling machine (acting as a heat pump) is used in the refrigerator. The relatively hot end of the displacement device is connected via a heat exchanger to another essential moving part of the machine called a compressor, typically comprising a piston movable within a cylinder.

This moving part constitutes the interface between the machine and the machine work, and when the machine acts as a heat pump, this part is driven externally. However, when the machine operates in reverse, or as an engine, external power is used to maintain a suitable temperature differential across the displacement device. The resulting pressure pulsations inside the machine drive the compressor pistons to perform external mechanical work.

It is known that compressors/expanders are connected to electromagnetic devices, for example of the "coil and magnet" type, which generate electrical energy when the machine works as an engine, and when the machine works as a heat pump. When it receives such energy, it acts as an external compressor drive device. Several types of Stirling heat pumps are known in which the displacement device acts as a "free piston" and is decoupled from the motion of the compressor itself by being designed to obtain oscillations of appropriate natural frequencies. The displacement device responds to the compressor output with a motion that exhibits the appropriate phase difference between the two. However, often both the displacement device and the compressor are driven, and the drive device is connected by a mechanical device, so that the phase difference can be controlled. These mechanical devices can be complex. Controlling the amplitude of movement of the displacement device and compressor is also difficult.

By connecting an electromagnetic motion control device to the displacement device and jointly controlling both this device and the electromagnetic device already coupled to the compressor, adjust and control the phase difference and amplitude of these two moving parts of the machine The invention results from the realization that the problem is greatly simplified.

The present invention includes a Star 1 non-cycle machine with a displacement device and a compressor, with the compressor connected to an electromagnetic device that serves as a power source for the compressor in one mode of operation of the machine and as a source of driven electrical energy in the other mode of operation. The second electromagnetic device is connected and the relationship between the movement of the displacement device and the compressor is controlled by the second electromagnetic device.

The second electromagnetic device serves to control the stroke of the displacement device. The device also includes a coil carried by the plunger of the displacement device and movable within the magnetic field of the stationary magnet. The coil is connected in series with a variable resistance, thereby varying its influence on the movement of the displacement device plunger.

In the case described above, the second electromagnetic device thus provides a variable damping of the movement that the displacement device plunger is caused to perform in free response to another power source, for example to a driven compressor. Alternatively, the second electromagnetic device can also positively drive the displacement device, and the coil is connected to a power supply. This is preferably the same power supply that drives or is driven by the compressor, and a suitable phase shifting device is provided between the power supply and one of the electromagnetic devices, carried out by the displacement device and the compressor/expander. This ensures that the motions performed are of equal frequency, but out of phase to the extent necessary for the Stirling cycle on which the machine is operating.

Further, the electromagnetic device may include a transducer that senses position, velocity, or acceleration and is associated with moving parts of either the displacement device or the compressor, or both, the output of which transducer detects the motion and relative Used to improve motor control.

For example, when the machine is operating as a heat pump, the output of the transducer associated with the compressor may be used to control the drive so that the compressor piston does not strike the end of its cylinder. Always exercise with maximum amplitude strokes while avoiding. Such improved control can reduce ambient temperature and/or l! l
! It has particular benefits when the thermal load on the machine is changing, or when the machine is entirely mobile and undergoing acceleration or changes in conditions. Similarly, the transducer associated with the displacement device is used to control the amplitude of movement of the displacement device plunger and further to control its phase in conjunction with the phase of the compressor/expander as a means of controlling the output of the machine. It will be done. Although it is relatively easy to obtain accurate phase differences between the displacement device and the compressor without continuous monitoring of pushinger position when the motion of these sections is sinusoidal, it is difficult to use such monitoring. This makes it even more possible to achieve complex non-sinusoidal movements. For example, if a compressor piston performs a sinusoidal motion, then for optimal Stirling cycle operation, the displacement device plunger motion must be sometimes at the same frequency and out of phase, but not completely sinusoidal. It must be in

The invention is particularly adapted to a Stirling cycle machine serving as a refrigerator and also includes a method of operating a Stirling cycle machine comprising a displacement device member and a compressor member, one of which is connected to a first electromagnetic one driven by a second electromagnetic device, the other controlled by at least a second electromagnetic device, both electromagnetic devices being interrelated by a device having the capability of external variations, whereby the relative phases of the movements of the displacement device and the compressor and ('or) amplitude may be varied to meet variations in operating conditions.

The invention is also defined by the claims, the contents of which are to be considered as forming part of this disclosure. The invention will now be described in detail, by way of example only, with reference to the accompanying drawings.

FIG. 1 shows a Stirling machine comprising a displacement device 1 and a compressor 2, communicated by a heat exchanger 3 and containing a gaseous working medium such as helium. Is the machine described as if the machine operated as a whole as a heat pump? is positively driven, but it should be understood that the machine can be operated in the opposite direction and act as a motor, in which case power is drawn from the device 2.

As is customary in some Stirling cycle machines, the displacement device 1 comprises a piston 4 movable within a cylinder 5 and separated from it by a small annular gap. The walls of the gap act as a regenerative heat exchanger, and the back and forth movement of the piston within the cylinder displaces the gas through the gap 6 in alternating directions between the blind or end 8 and opposite end 9 of the cylinder, and this cycle The operation of causes end 8 to be relatively cool and end 9 to be relatively warm. End 9 is heat exchanger 3
adjacent to. The compressor 2 comprises a cylinder 10 containing a piston 11 driven through a rod 12 by a first electromagnetic device 13, which acts as a motor in this mode of operation of the machine and of course as a generator in the opposite mode. .

The piston 4 is connected to one end of the rod 14, and the piston 4 is connected to one end of the rod 14.
The axial movement is directed by two flat helical springs 15 connecting the housing 16 to a fixed structure. Housing 16 also encloses a second electromagnetic device that includes fixed and movable parts. The fixed part has a permanent magnet 17 and a core 18.

The movable part is the rim 2 of the platform 21 carried by the rod 14.
A cylindrical coil 19 is carried on the cylindrical coil 19. A gas-tight seal 14α isolates the displacement device drive mechanism from parts of the machine containing the gaseous working medium.

For efficient operation of the Stirling cycle, the piston of the displacement device and the compressor must be moved with appropriate amplitude and the same frequency, but at least out of phase and with different movement patterns as much as possible. is necessary. FIG. 1 shows one method according to the invention, according to which the motions of pistons 4 and 11 are maintained in a similar pattern (e.g., generally sinusoidal), but different phase capture motion with equal frequency. obtain. In FIG. 1, the second electromagnetic device acts as an electromagnetic motor and positively drives the piston 4, and the alternating EMF source 26 is connected to the coil 19 via a phase angle changing device 28 and a power amplifier 29. Next, the first electromagnetic device 13 is connected to the piston 11 of the compressor 2.
comprises a coil 30 supported on a platform 31 carried by a rod 12 and movable within the magnetic field of a fixed magnet 32 and a core 38. coil 30
are connected to the same alternating EMF generator 26 via a power amplifier 27. In response to the output of the generator 26, the pistons 4 and 11 reciprocate sinusoidally at the same frequency, causing the device 2
By adjusting 8, the relative phase of the two pistons can be changed.

Electronic phase shifting devices suitable for use as device 28 are now readily available and relatively low cost, and many of the prior art devices in which a single power source was connected to the two pistons by a mechanical coupling are now readily available and relatively inexpensive. The device described above with respect to FIG. 1 makes it possible to obtain the necessary amplitude and phase relationship between the displacement device and the piston movement of the compressor more simply and compactly than in a machine. However, the present invention ensures that only the compressor piston is driven and the free response of the displacement device to the compressor output is such that the displacement device captures at the same frequency but with an appropriate phase shift and amplitude. The advantages of other known types of Stirling cycle machines in which the displacement device is designed can also be applied. The "Beat" type machine is one well-known Stirling engine that works in this way. It will be readily appreciated that accurately achieving and sustaining such free response requires, first, accurate design and manufacturing, and then careful maintenance. The present invention achieves at least the correct amplitude without the need for such precise initial manufacturing, and offers the possibility of recovering any fluctuations during use with simple adjustments. In a machine according to this aspect of the invention, as shown in FIG. However, the coil 19 of the second electromagnetic device is no longer connected to the generator 26. Instead, the coil is simply a variable resistor 8, as shown in FIG.
5 in series. The series combination of coil and resistor then acts as a variable damper, whereby the movement, in particular the amplitude of the response, of the displacement device piston 4 to the pulsating power received from the compressor 2 via the heat exchanger 8 can be varied. Since the efficiency of machine i depends precisely on optimizing the stroke amplitude of the compressor and the displacement device, especially the latter, it is necessary to change the stroke amplitude of the displacement device piston (also of the compressor piston) during operation of the machine. The ability to do so is valuable. Generally, but not always, an optimum amplitude is what is of the utmost importance, and that is possible without running the risk of the piston hitting the end wall of its cylinder. Once the machine is adjusted to obtain these amplitudes at machine start-up, changes in the temperature of the displacement device or compressor brought about either by machine operation or by variations in ambient conditions will cause its amplitude to be corrected during use. This will deleteriously change the piston stroke unless it is done.

In each of the embodiments of the invention shown in FIGS. 1 and 2, such modifications are readily accomplished by the operation of a control system that is external to the structure of the machine and does not involve physical movement of components of that structure. However, in typical known devices, modifications are not possible or can only be achieved by adjusting the gas circuit inside the sealed part of the machine. To enable such adjustment, something like a needle valve must be introduced into the design of the circuit, allowing such a valve and its performance to be easily varied in response to changing operating conditions. is often difficult to set.

In the embodiment of the invention shown in FIGS. 1 and 2, the extent to which the relative phases and especially the relative patterns of the movements of the pistons 11 and 4 are changed is controlled based on continuous monitoring of the instantaneous movements of these two pistons. limited by the lack of. Such control is provided in the embodiment shown in FIG. Here the piston rod 14 carries a movable member 40 of a device 41 which monitors the position of the piston 4, but can selectively monitor its velocity or acceleration. The device 41 also comprises a fixed coil 42, and the rod 12 of the piston 11 carries a movable member 43 of a similar monitoring device 44, which is also provided with a fixed coil 45. Two electronic position control devices 46, 47 with function generation capability are provided, the output of device 44 being applied to these two and the output of device 41 being applied only to device 47. Power amplifier 27 receives input from both device 46 and power supply 26;
The output of amplifier 27 drives compressor motor 13 as before. The output of device 47, like that of device 28 in FIG. 1, is fed as before to the coil 19 of the displacement device motor via an amplifier 29. With such control, by appropriate settings of the two devices 46 and 47, a very good control between the movements of the two pistons can be achieved. Such control flexibility is of great value when the machine is affected as a whole by changing external forces caused, for example, by temperature changes or acceleration when the machine is moving. It will be clear that in the latter case monitoring of acceleration is particularly appropriate. In particular, such control facilitates driving the displacement device in a non-sinusoidal manner, and, as already shown, a true Stirling cycle results in the displacement device being driven out of phase in response to truly sinusoidal oscillations of the compressor. This is valuable because it requires motion close to, but not completely sinusoidal.

The control circuit shown in FIG. 3 provides very accurate feedback control of the temperature of the cold end 8 of the displacement device 1 when the machine is used as a heat pump.

Such control can be achieved using a temperature sensor 48, the output of which is fed as an additional input to device 47 and serves to vary the amplitude of the displacement device piston, the amplitude already limited to some extent by device 41 and device 48. further limit.

FIG. 1 shows a displacement device piston 4 of the type known as a gap regenerator, which exchanges heat during the passage of the gaseous working medium of the machine through a gap 6. FIG. Alternatively, as shown in FIG. 4, the piston 4 can be hollow and filled with regenerative material, such as wire mesh 50, forming gas boats 51, 52 in its end walls.

Since heat exchange takes place as the gas passes back and forth inside the piston, an effective gas seal must be provided between the piston 4 and the cylinder 5 to prevent gas shorting.

According to my experience 1. Rod 14 by helical spring 15
The precise alignment provided by the gap 60 makes the gap 60 dimension so small that an effective gap seal can be provided without the need for frictional contact.

Another advantage of the present invention as a whole over mechanical couplings used in the past to synchronize displacement devices and compressors is that the electromagnetic control eliminates the need for moving parts to pass through the walls of the machine. A completely enclosed system is therefore possible, and the expensive working gas can be sealed inside the machine.

[Brief explanation of drawings]

FIG. 1 is a diagrammatic representation of a Stirling cycle machine, partly in section and partly diagrammatically; FIG. 2 is a diagrammatic cross-sectional view of a modified machine; FIG. A partial schematic diagram, FIG. 4, shows a partial alternative to the machine shown in FIG. l: Displacement device 2: Compressor 3: Heat exchanger
4.11: Piston 5 Niji cylinder 10 Niji cylinder 12.14: Rod 30: Coil Patent applicant National Research Development Corporation (2 others)

Claims (1)

[Claims] Stirling with a displacement device (1) and a compressor (2), a first electromagnetic device connected to said compressor and serving as a source of compressor power in one mode of operation of the machine and as a source of driven electrical energy in another mode of operation of the machine. Stirling cycle machine, characterized in that a second electromagnetic device (17, 18, 19) is provided, which is connected to the displacement device and acts as an externally variable control device of the movement of this displacement device.・Cycle machines.