JPH0578679B2 - - Google Patents

Description

[Detailed description of the invention]

INDUSTRIAL APPLICATION FIELD This invention relates to a fluid drive device for conveying fluid such as gas or liquid. Prior Art In order to obtain an inexpensive fluid drive device, it is desirable to use reciprocating motion as the drive source. The device shown in FIG. 2 which uses reciprocating motion as a driving source has a space 11 with a volume of V.
The drive tube 12 with a cross-sectional area of A and a length of L satisfies the Helmholtz resonance condition, and the diaphragm 13 attached to the housing 10 containing the space 11 is driven at a frequency of ₀ determined by equation (1). Then, the columnar fluid 19 inside the drive tube 12 vibrates with a double amplitude ab in the horizontal direction in the figure as if it were a single body. The resonance frequency ₀ of the resonator composed of the space 11 and the drive tube 12 is

[C] Calculated using equation (1). Here, C is the sound velocity of the fluid, π is pi, and α is the correction coefficient. The vibration motion of this columnar fluid 19 constitutes a second driving source. In an example of a drive tube with a diameter of 18 mm and a length of 160 mm and a resonance frequency of 135 Hz, ab was approximately 10 mm. When the columnar fluid 19 moves to the right in the figure, from a to b, the fluid in the ab portion of the drive tube 12 is driven to the right. When the columnar fluid 19 reaches the position of the maximum amplitude b on the right side, the movement changes from b to a to the left. As the columnar fluid 19 moves to the left, negative pressure is generated at the inlet of the drive tube 12, but the fluid driven rightward continues to flow rightward along the axis of the drive tube 12 due to inertial force. . As a result, the negative pressure generated at the end of the drive tube 12 has the following effects:
Fluid from the surrounding area flows in. As the columnar fluid 19 moves to the left, the surrounding fluid also continues to flow in. When the columnar fluid 19 reaches the position a of maximum amplitude on the left side, it changes its direction of motion to the right again. At this time, the fluid flowing in from the surroundings is driven to the right without flowing into the columnar fluid 19 portion, and flows as shown by curve A in the figure, and then becomes a flow B.
This situation can be observed using a stroboscope and smoke. In the process in which the fluid that has flowed into the drive tube AB section is driven to the right and becomes the flow B, it is assumed that part of the fluid near the drive tube 12 flows to the right due to the viscous force of the flow B. It will be done. The state of the flow of this wake and the state of the flow in the immediate vicinity of the exit of the drive pipe 12 are difficult to observe and have not been fully elucidated. Thereafter, by repeating the same process, a continuous flow is formed in the right direction around the axis of the drive tube 12. When the flow velocity was measured at a position 5 cm downstream (to the right) of outlet b on the axis of the drive pipe 12, the flow velocity fluctuation was +0.8 m/sec with respect to the average flow velocity of 3.4 m/sec.
It was confirmed that a rightward flow with a constant velocity and little pulsation was formed. This fluid drive device can form a flow within a few cycles after starting operation, and can obtain a highly responsive flow. In addition, while the reciprocating diaphragm 13 is used as the first drive source and the second drive source formed as the reciprocating movement of the columnar fluid 19 inside the drive tube 12 is used as the direct drive source, a smoothing device is not required. A smooth flow can be obtained, and since it does not have large rotational inertia unlike a rotary drive source such as an electric motor, it is possible to perform flow control with good responsiveness. Problems to be Solved by the Invention However, although the principle of driving the fluid in this device is based on the Helmholtz resonance phenomenon, the resonant frequency of the Helmholtz resonance phenomenon tends to change due to changes in the temperature of the fluid, so it is difficult to drive the diaphragm. If the frequency of the power source 17 remains constant, it will deviate from the resonance phenomenon and the fluid driving efficiency will decrease. Further, reciprocating drive sources generally have lower work efficiency than rotary drive sources. Therefore, this conventional fluid drive device has the disadvantage that the work efficiency decreases due to temperature changes of the fluid, etc., and the work efficiency is kept to the maximum by always matching the driving frequency of the diaphragm to the resonance frequency. It is necessary. Means for Solving the Problems In order to solve the above-mentioned problems, the present invention detects the vibration state of the fluid by installing a pressure sensor in the casing or the drive pipe that forms the space, and uses the signal to detect the vibration state of the diaphragm. The drive power source is equipped with a control device that controls the drive frequency. Effect: By using this technical means, the frequency of the drive power source is controlled by the signal from the pressure sensor attached to the housing or the drive tube so that the vibration state inside the space formed by the housing or the drive tube is maximized. If controlled by a device, the Helmholtz resonance phenomenon will be maintained at maximum conditions, and work efficiency will also be maintained at its maximum. Embodiment FIG. 1 is a cross-sectional view showing an embodiment of the present invention.
A pressure sensor 21 is mounted inside the housing 10. A pressure signal detected by the pressure sensor 21 is transmitted to the control device 22 via the connection cable 23.
The control device 22 is electrically connected to the power supply device 20. Other configurations and operations are the same as the conventional example shown in FIG. Next, this device will be explained. When this device is started, the columnar fluid 19 within the drive tube 12 undergoes a violent oscillating motion as described in the conventional example. This means that intense pressure oscillations are occurring within the space 11 as well. The pressure sensor 21 detects this pressure vibration. Now, if the Helmholtz resonance frequency of this device changes due to a change in the temperature of the fluid, etc., the power supply device 2
If the zero frequency, that is, the vibration frequency of the diaphragm 13 remains constant, the resonance condition collapses and the pressure in the space 11 decreases. Therefore, since the output signal of the pressure sensor 21 decreases, the frequency of the power supply device 20 is controlled by the control device 22 using the decrease in the signal so that the decrease in the signal becomes zero.
Alternatively, if the level of the output signal of the pressure sensor 21 is controlled to be maximum, the diaphragm 12 will always vibrate in accordance with the Helmholtz resonance frequency, and the fluid drive efficiency will also be maintained at its maximum. It turns out. Effects of the Invention The present invention provides a fluid drive that uses a reciprocating drive source, maintains a stable flow rate with little pulsation component, maintains flow characteristics with good controllability, and can always be used at maximum work efficiency. The device can be provided at low cost.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing a fluid drive device according to an embodiment of the present invention, and FIG. 2 is a cross-sectional view showing a conventional example. DESCRIPTION OF SYMBOLS 10... Housing, 11... Space, 12... Drive tube, 13... Vibration plate, 20... Power supply device, 21...
...Pressure sensor, 22...Control device, 23...Connection cable.

Claims (1)

[Claims] 1. A diaphragm is airtightly provided inside a hollow container to form a space with a volume V, and a drive pipe having a cross-sectional area A and a length L is connected to the space facing the volume V and communicating with the outside, and A resonance system including a frequency variable power supply device for driving the diaphragm is configured, a pressure sensor is provided facing the space of the volume V or the inside of the drive tube, and the output of the pressure sensor is maximized. A fluid drive device comprising: a control device for controlling the frequency of the frequency variable power supply device.