JP2002325488A - Method and apparatus for forcedly vibrating fluid in tube - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a low-cost driving method which drives a pulse tube refrigerator with a stabilized optimum frequency. SOLUTION: By detecting the pressure inside a tube with a pressure sensor 40, and carrying out its positive feedback to the drive signal of an actuator 22, an oscillation circuit of an electromechanical system is formed, and an operating gas is subjected to vibration by the oscillation circuit.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method and an apparatus for forcibly vibrating a fluid in a pipe, and more particularly to a method for installing a pipe at a pipe end suitable for use in a pulse tube refrigerator, a Stirling refrigerator, an oscillating flow type heat pipe and the like. The present invention relates to a method and an apparatus for forcibly vibrating a fluid in a pipe for driving a given actuator to forcibly vibrate the fluid in the pipe.

[0002]

2. Description of the Related Art A pulse tube refrigerator (PTR) is known which generates a cold by a thermoacoustic effect by applying a periodically fluctuating pressure to a working gas (usually helium or the like) sealed in a tube. FIG. 1 shows a so-called basic pulse tube refrigerator (B-PT) in which a pulse tube 12 and a regenerator 14 are arranged in series.
R) The schematic configuration of 10 is shown. In the figure, 10A is a low temperature heat exchange section, 10B and 10C are room temperature heat exchange sections, and 20 is a compressor reciprocated by, for example, a linear motor.

The B-PTR is expected to have a long life, high reliability, and low cost due to a simple structure because it does not have a sliding part such as a piston. Further, it is necessary to use an ozone depleting gas such as Freon. There is no expectation of the advantage of low environmental impact.

[0004] In order to generate cold in such a B-PTR, it is necessary to excite a pneumatic vibration mode having an endothermic effect in the low-temperature heat exchange section 10A in the center of the PTR 10 shown in FIG. This is achieved by adding pressure fluctuations from the compressor 20 at the natural period of the corresponding air column. However, the response of the air column is maximum in the natural period, and as the drive period moves away from the natural period,
Decrease sharply. Therefore, in order to drive the PTR efficiently, it is necessary to have an accurate and stable driving frequency.

As shown in FIG. 2, when the PTR 10 is electrically driven by a vibration type actuator 22 such as a linear motor, an AC power source having an appropriate frequency is required as a driving power source. When the actuator 24 is used, the actuator 22 is converted into an AC power supply having an appropriate frequency via the inverter 26 to drive the actuator 22.
When a commercial AC power supply 28 is used, as shown by a broken line in FIG. 2, a converter 30 is further provided to convert the DC power, and then the AC power is again converted by the inverter 26.

[0006]

However, since the inverter 26 is expensive compared to the cost of the PTR main body, it becomes an obstacle to reducing the cost of the entire system. Further, in order to obtain an effective output, the frequency must be strictly adjusted to an optimum frequency (resonance frequency of the PTR column). Further, in order to stably maintain the optimum frequency, a high-performance inverter is required, which has a problem that the cost is further increased.

The present invention has been made to solve the above-mentioned conventional problems, and does not require the use of an expensive inverter, does not require adjustment of a driving frequency, and has a stable optimum frequency. The task is to always obtain the best performance.

[0008]

SUMMARY OF THE INVENTION According to the present invention, there is provided a method for forcibly vibrating a fluid in a pipe for driving an actuator provided at the pipe end to forcibly vibrate the fluid in the pipe. Thus, the above problem is solved by forming an oscillation circuit composed of an electro-mechanical system by positively feeding back the drive signal of the actuator and causing the fluid to vibrate by the oscillation circuit.

Further, in a forced fluid vibration device for a fluid in a pipe for driving an actuator provided at a pipe end to forcibly vibrate the fluid in the pipe, a pressure sensor for detecting a pressure in the pipe, and a pressure sensor for the pressure sensor. A positive feedback circuit for providing positive feedback of an output signal to a drive signal of an actuator, and an oscillation circuit including an electro-mechanical system formed by these components to vibrate the fluid to solve the above-described problem. It is.

Further, an electrodynamic voice coil of the same type is used as the actuator and the pressure sensor.

In a system composed of a speaker and a microphone, a howling phenomenon often occurs. Similarly, the response of the air column of the PTR is positively fed back to the amplifier for driving the actuator, so that the
A mechanical composite oscillation circuit is formed.

In an electric system, there is always some noise. The response of the PTR to these noises is P
The natural period component of TR is dominant. When the natural vibration response of the PTR is applied as a positive feedback control signal to the drive amplifier, the natural period component of the driving force increases. By repeating this loop, when the loop gain is larger than 1, the amplitude of the driving force gradually increases as shown in FIG.
It reaches the maximum value determined by the power supply and the performance of the drive amplifier. The driving frequency at this time is the optimum frequency PTR
And is stable irrespective of environmental temperature, load conditions, fluctuations in the power supply, and the like. The present invention is an application of this principle.

[0013]

Embodiments of the present invention will be described below in detail with reference to the drawings.

In this embodiment, as shown in FIG. 4, a pressure sensor 40 for detecting the pressure in the pulse tube 12 and an output signal of the pressure sensor 40 are converted into a drive signal of the vibration type actuator 22 via a drive amplifier 42. A positive feedback circuit for positive feedback is provided, and a working fluid (for example, helium) in the pulse tube 12 is forcibly vibrated by an oscillation circuit formed of the electro-mechanical system. .

In the present embodiment, the vibration type actuator 22 is supplied with a DC power supply 24 via an amplifier 42. Further, the signal of the air column response is positively fed back as an input signal (control signal) to the amplifier 42 by the pressure sensor 40 installed in the PTR 10. At this time, if necessary, a phase adjuster 44 can be provided as shown by a broken line in order to make the feedback a positive feedback. Further, as shown by the dashed line, the vibration can be started smoothly by additionally providing the vibration trigger device 46.

More specifically, as shown in FIG. 5, electrodynamic voice coils 50a and 50s of the same type are used as the actuator 22 and the pressure sensor 40, and these are connected to the tube 1
2 at both ends (referred to as a drive end and a sensor end).
When the DC power supply 24 is turned on with the output of the pressure sensor 40 (voice coil 50s) as the input of the drive amplifier 42, an electromechanical oscillation circuit is formed, and howling easily occurs. When the tube 12 and the voice coils 50a and 50b are appropriately set, the vibration mode at this time can be the primary natural vibration of the air column of the tube having both ends closed as shown in FIG.
The pressure distribution and the velocity distribution in FIG. 6 show the distribution at a certain moment, and the phase differs between the velocity and the pressure by 90 degrees. Is the largest.

The positive feedback mechanism of howling in the first-order eigenmode can be qualitatively interpreted as follows. That is, when the voice coil 50a on the left side of the figure is regarded as the actuator 22 that performs electric-force conversion, when a drive current is applied, pressure is generated at the drive end on the left side of the figure, and the drive current and Generates a counter electromotive force in the opposite direction. For simplicity, this back electromotive force is proportional to the generated pressure.

On the other hand, the pressure at the sensor end on the right side in the drawing is opposite to the pressure at the drive end in the primary natural vibration mode. Therefore, the electromotive force generated in the voice coil 50s acting as the pressure sensor 40 has the same direction as the drive current applied to the voice coil 50a acting as the actuator 22. That is, positive feedback is realized by directly feeding back the sensor current. When the position of the sensor needs to be a position having the same sign as the pressure of the driving end (for example, a position indicated by an arrow A in FIG. 6) due to some necessity, FIG. Is provided to adjust the phase of the feedback current,
Invert its sign. When a sensor that provides an output proportional to the speed is used as the pressure sensor 40, it is necessary to provide a phase adjuster 44 to shift the phase by 90 degrees. By the way, direct speed feedback is
Since it has a damping effect on vibration, it is widely used in vibration control for suppressing vibration.

The phase adjuster 4 for providing positive feedback
4 can be omitted when a positive feedback signal is obtained by selecting a sensor position with respect to the PTR 10.

When a smoother and more reliable start is required irrespective of electric noise, the trigger device 46 shown in FIG.
Can be installed.

Since the driving method of the present invention can be driven by a DC power supply in essence, it can be used even in a place where there is no commercial power supply. Features can be maximized. The concept of driving the system by forming an oscillating circuit by an electro-mechanical system is not limited to the PTR, and the displacer performs a reciprocating motion out of phase with a change in the gas pressure using gas pulsation. A Stirling refrigerator that cools an object by executing a Stirling cycle and adiabatic expansion, an oscillating flow heat pipe that forcibly excites an oscillating flow in a heat pipe that has a temperature gradient in the axial direction to promote heat diffusion, etc. , And PTRs. Further, the working fluid is not limited to gas, and the actuator and the pressure sensor are not limited to the electrodynamic voice coil.

[0022]

According to the present invention, it is not necessary to use an expensive inverter, only a simple amplifier and a sensor are used, and the cost is low. Further, since the adjustment of the driving frequency is unnecessary and the operation is stabilized at the optimum frequency, the highest performance is always obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a configuration of a basic pulse tube refrigerator that is an example of an object to which the present invention is applied.

FIG. 2 is a block diagram showing a configuration example of a conventional drive power supply of the pulse tube refrigerator.

FIG. 3 is a diagram showing a change state of an actuator output according to the present invention.

FIG. 4 is a block diagram showing a configuration of an embodiment of the present invention.

FIG. 5 is a sectional view of a tube for explaining the principle of the present invention.

FIG. 6 is a diagram showing a velocity distribution and a pressure distribution of a primary natural vibration of an air column having both ends closed.

[Description of Signs] 10 ... Pulse tube refrigerator (PTR) 12 ... Pulse tube 14 ... Cooler 20 ... Compressor 22 ... Actuator 24 ... DC power supply 40 ... Pressure sensor 42 ... Drive amplifier 44 ... Phase adjuster 46 ... Trigger device 50a , 50b ... voice coil type actuator and sensor

Claims (3)

[Claims] In a method for forcibly vibrating a fluid in a pipe by driving an actuator provided at a pipe end to forcibly vibrate the fluid in the pipe, a pressure in the pipe is detected, and a driving signal of the actuator is corrected. A method for forcibly vibrating a fluid in a pipe, comprising forming an oscillation circuit composed of an electro-mechanical system by feedback, and causing the oscillation circuit to vibrate the fluid. 2. A forced fluid vibration device for a fluid in a pipe for driving an actuator provided at a pipe end to forcibly vibrate the fluid in the pipe, comprising: a pressure sensor for detecting a pressure in the pipe; A positive feedback circuit for positively feedbacking an output signal to a drive signal of an actuator; and a vibrating device for a fluid in a pipe, characterized in that the fluid is vibrated by an oscillating circuit comprising an electro-mechanical system formed by them. . 3. The apparatus according to claim 2, wherein the same type of electrodynamic voice coil is used as the actuator and the pressure sensor.