JP2003129972A - Scroll pump - Google Patents

Abstract

PROBLEM TO BE SOLVED: To eliminate the possibility of stopping the rotation of a pump even in using a gas-liquid mixed solvent such as non-compressible water and liquefied gas, or to prevent the breakage of a scroll pump. SOLUTION: Gaps 6, 7 are formed between a fixed scroll 2 and a turning scroll 3 at the beginning of compression to make liquid in a compression chamber 5 communicate with a discharge port, whereby pressure in the compression chamber is restricted to the predetermined pressure to reduce size of the scroll pump 1 without increasing the mechanical strength of the fixed scroll and the turning scroll and suppress the vibration of the scroll pump during operation.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention is used for a nuclear fusion device, a linear motor car, a superconducting power generator, and a superconducting electricity storage device, which use a superconducting coil cooled by a liquefied gas such as liquid helium or liquid nitrogen. Regarding scroll pump.

Further, it generally relates to the structure of a mechanical pump which requires a constant protrusion pressure and a constant flow rate regardless of the form of the substance to be delivered (liquid or gas, or a mixture thereof).

[0003]

2. Description of the Related Art Centrifugal pumps using high-speed impellers are mainly used for liquid nitrogen, liquid helium and liquid hydrogen in spallation neutron sources and superconducting test equipment.

The centrifugal pump is composed of a housing in which a plurality of blades (impellers) are attached to the tip of a rotary shaft and which surrounds this. A liquid suction port is installed in the central bottom part of the housing, and a liquid projecting port is provided in the peripheral part of the wing (side surface of the housing). When the impeller rotates at a high speed of several thousand rpm, the liquid in the housing is rotated by being pushed by the impeller, and the centrifugal force causes the liquid to be pressed against the peripheral portion of the housing while rotating. When the liquid reaches the liquid outlet in the tangential direction of the outer periphery of the housing, the liquid is delivered from the outlet with a constant pressure.

In order to increase the flow rate and the projecting pressure with a centrifugal pump that is widely used in conventional liquefied gas circulation systems, it is necessary to increase the impeller size or increase the rotation speed. At this time, on the surface opposite to the surface where the impeller pushes the liquid, the surface pressure tends to decrease, and when the liquid reaches the limit of boiling because the rotation speed increases, the liquid vaporizes on the impeller surface and bubbles. Therefore, so-called cavitation in which bubbles are crushed at the next moment is likely to occur. If cavitation occurs, the flow rate becomes unstable and problems such as damage to the impeller surface occur, which is not preferable from the viewpoint of stable operation of the loop.

Further, in the closed loop system in which the liquefied gas is cooled while circulating, it is necessary to circulate the gas in the loop to cool the entire system at first. As the cooling progresses and a part of the liquid is mixed in the gas, if this gas circulates, the liquid may collect at a low position in the loop, and finally the liquid may be blocked in the pipe. At this time, if the inside of the centrifugal pump housing is not sufficiently filled with the liquid (gas-liquid mixed state), the density ratio of the gas and the liquid will drop and the pump protrusion pressure will become extremely small, so the liquid accumulated in the middle of the pipe Since it can't be sent any more, gas circulation stops.

As a countermeasure against this, another pump dedicated to gas is installed at the beginning of the operation of the loop, and at first, the gas in the loop is circulated by the pump so that the gas is sufficiently liquefied and the liquid is supplied into the pump. If this happens, you can consider switching to a liquid pump.

However, with this method, it is difficult to grasp how to precool the liquid pump and the timing of switching from gas to liquid, which is extremely difficult from the viewpoint of controllability. there is a possibility.

Further, the development of a magnetic bearing type centrifugal pump for delivering both gas and liquid with one pump is also underway in the United States. However, since a high speed rotation of several hundred thousand rpm is required for circulating the gas, there is a concern that heat will be generated due to eddy current in the magnetic bearing, heat will enter from the motor, and the like. Further, when the magnetic bearing is put into practical use, the gap between the rotor shaft and the partition wall is small in the magnetic bearing portion, and if small fine powder is mixed in, the magnetic bearing portion may be burned.

On the other hand, many scroll compressors are used in home air conditioners as one of the positive displacement compressors. A scroll compressor is a combination of two spiral partition plates, which will be described later in detail, and one orbiting scroll moves circularly to compress the CFCs in the area sandwiched between the two scroll plates. It is a compressor that is sent out while being processed.

The characteristic of this compressor is that it is a low rotation type compressor in which gas (CFC) is continuously sent out while being compressed, and mechanical vibration is small,
It also has the characteristic that the amount of heat generated is small.

[0012]

However, since the volume of the region between the two partition plates decreases with the rotation of the gas scroll plate, incompressible liquids such as water and liquefied gas will cause a problem in pumping. When the scroll pump stops rotating or is operated by applying an excessive driving force, the scroll pump is temporarily braked, which may cause vibration or damage.

An object of the present invention is to provide a scroll pump in which the rotation of the pump is not stopped even when a gas-liquid mixed medium such as incompressible water or liquefied gas is used or the scroll pump is prevented from being damaged. It is in.

[0014]

In order to achieve the above object, the present invention is designed so that, in the initial stage of operation, the liquid in the compression chamber is circulated to the discharge port by the gap formed between the fixed scroll and the orbiting scroll. Therefore, the pressure inside the compression chamber is suppressed to a predetermined pressure, and the scroll pump is downsized and the vibration during operation of the scroll pump is suppressed without increasing the mechanical strength of the fixed scroll and the orbiting scroll.

[0015]

BEST MODE FOR CARRYING OUT THE INVENTION A scroll pump 1 according to an embodiment of the present invention will be described in detail below with reference to FIGS. FIG. 1 is a plan view of the scroll pump 1, and FIG. 2 is a sectional view taken along the line AA of FIG.

The scroll pump 1, which is a positive displacement mechanical pump, has a pair of spiral partition plates (scroll plates) each having a length of 1.5 turns, and the scroll plates are moved to deliver a liquid, a gas, or a mixture thereof. It is a positive-displacement scroll pump that is characterized.

The scroll pump 1 is provided with a fixed scroll 2 and an orbiting scroll 3, and the fixed scroll 2 and the orbiting scrolls 3 are arranged so as to be eccentric by a predetermined distance and mesh with each other with their phases shifted by 180 °. There is.
The side surface of the spiral wrap 2A of the fixed scroll 2 and the side surface of the spiral wrap 3A of the orbiting scroll 3 are in line contact with each other at two locations 4 to form a compression chamber 5. The location 4 on one end side of the compression chamber 5 forms a line contact as described above, and the gaps 6 and 7 are formed on the other end side.

The gaps 6 and 7 communicate between the compression chamber 5 and the central discharge port 8. The sizes of the gaps 6 and 7 are such that the gas-liquid mixed medium 9 such as liquid can be circulated at the initial phase of operation of the scroll pump 1 shown in FIG. Reference numeral 9 is an inlet.

Next, a case where the scroll pump 1 is used in the liquefied gas closed loop system 20 will be described with reference to FIG. In the spallation neutron source, which crushes the target nuclei by the injection of a high-energy proton beam to generate neutrons, and rapidly cools this with liquid hydrogen, the hydrogen gas is circulated in a closed loop while being cooled by a refrigerator, and finally The present invention relates to the structure of a pump that circulates liquid hydrogen in the interior.

That is, the liquefied gas closed loop system 20 has a gas chamber 21 in which a liquefied gas such as liquid helium, liquid nitrogen, liquid hydrogen, etc.
The cooling hydrogen gas is cooled to 200 ° C., and the cooling hydrogen gas is compressed by the compression chamber of the scroll pump 1 to be stored in the storage chamber 2.
3, a heat source 24 indicated by an arrow in the storage chamber 23, such as a neutron, is cooled and a so-called gas-liquid mixed refrigerant 20B containing a liquid is cooled.
Then, the gas-liquid mixed refrigerant 20B is supplied again from the storage chamber 23 to the gas chamber 20 and circulates in the liquefied gas closed loop system 20. During circulation, the scroll pump 1 is operated as in the phase 90 °, the phase 180 °, the phase 180 °, the phase 270 °, and the phase 0 ° as shown in FIG.

That is, when the drive shaft 11 connected to the orbiting scroll 3 is rotated clockwise C from the position of the phase 270 °, the orbiting scroll 3 is moved in the arrow direction X toward the discharge port 8 side which is the center direction of the compression chamber 5. While revolving, the gas-liquid mixed refrigerant 20B in the compression chamber 5 is compressed and discharged to the discharge port 8, and the orbiting scrolls 3 revolve from the position of phase 270 ° to the initial operation position of phase 0 °.

In general, the cooling liquid is incompressible with respect to the compression force in the compression chamber, so it is less likely to be compressed than gas, and the compression force in the compression chamber increases. Conventionally, the compression chamber is not provided with a means for releasing the increasing compression force, so that the mechanical strength of the scroll plate constituting the compression chamber is increased, or a large driving force is applied in order to overcome the compression force at the initial stage of operation, that is, at the initial stage of compression. When applied, the orbiting scrolls revolved and stopped repeatedly, and there was a fear that vibration would not occur.

Therefore, in the present invention, the gas-liquid mixed refrigerant, particularly the cooling liquid, in the compression chamber 5 has gaps 6 and 7 at the initial position of compression.
Since it circulates through the discharge port 8, a predetermined compression force is maintained in the compression chamber, and the mechanical strength of the scroll plate constituting the compression chamber 5 is not increased as in the conventional case. The size can be reduced by the amount provided.

Further, since a large compressive force is not applied at the initial stage of operation, a large driving force is not required for the scroll pump 1 and the vibration of the scroll pump 1 can be prevented. That is, in this embodiment, the orbiting scroll 3 has a phase of 270 °.
The gas-liquid mixed refrigerant 20B is continuously circulated to the discharge port 8 through the gaps 6 and 7 while revolving from the position (1) to the position at the initial phase of compression of 0 °. In other words, since the orbiting scrolls 3 always maintain the gaps 6 and 7 while revolving, the scroll pump 1 can be further downsized by the amount that the scroll pump 1 does not require a large driving force, and the scroll pump 1 can be made smaller. The life of 1 can be extended.

In this embodiment, the size of the gap is 100
Change from μm to 150 μm. The reason for this is that in the initial position of compression, the cooling liquid has gaps 6, 7 when the thickness is 100 μm or less.
There is a risk that the flow resistance during circulation of the fluid will increase, the mechanical strength of the scroll plate will increase, or the scroll pump 1 will vibrate. If it is 150 μm or more, a desired compression force cannot be obtained in the compression chamber. And, the gap of 100 μm to 150 μm is convenient for achieving the above-mentioned effects, especially when the pressure in the compression chamber is 3 atm or more.

Further, each of the end portions of the fixed scroll 2 and the orbiting scroll 3 is formed to have a spherical surface portion 13 having a curved shape. With this configuration, even if the side surface of the spiral wrap 2A of the fixed scroll 2 and the side surface of the spiral wrap 3A of the orbiting scroll 3 slide at the line contact point 4 due to the spherical surface portion 13, the side surfaces of the scroll wrap 3A and the side surface of the orbiting scroll 3 are in contact with each other. Is less likely to be damaged, there is no fear of forming a communication path communicating with the outside at the line contact portion 4, and the compression chamber 5 can hold a desired compression force.

Further, a ceramic material having a high hardness such as TiN or SiC is provided on the surfaces of the fixed scroll 2 and the orbiting scroll 3 to prevent the thinning of the scroll plate, the crankshaft and the bearing due to the friction without using a lubricant. , Can extend the life.

Further, by coating the surface of the fixed scroll 2 and the orbiting scroll 3 with a material having a small friction coefficient such as diamond-like coating and resin coating, it is possible to prevent the fixed scroll and the orbiting scroll from being worn.

Further, by coating the surfaces of the fixed scroll 2 and the orbiting scroll 3 with a material having a small friction coefficient such as diamond-like coating and resin coating, the same effect as described above can be achieved.

[0030]

As described above, according to the present invention, it is possible to reduce the size of the scroll pump and suppress the vibration during the operation of the scroll pump.

[Brief description of drawings]

FIG. 1 is a plan view of a scroll pump shown as an embodiment of the present invention.

FIG. 2 is a sectional view taken along line AA of FIG.

FIG. 3 is a system diagram in which the scroll pump of the present invention of FIGS. 1 and 2 is used in a liquefied gas closed loop system.

FIG. 4 is a plan view showing the revolution position of the scroll pump of the present invention used in FIGS. 1 to 3.

[Explanation of symbols]

1 ... Scroll pump, 2 ... Orbiting scroll, 3 ... Fixed scroll, 4 ... Line contact point, 5 ... Compression chamber, 6, 7 ... Gap, 8 ... Discharge port.

   ─────────────────────────────────────────────────── ─── Continued front page    (72) Inventor Yukio Ogawa             3-1-1 Sachimachi, Hitachi City, Ibaraki Prefecture Stock Association             Hitachi, Ltd. Nuclear Business Division (72) Inventor Hidenori Michishita             3-1-1 Sachimachi, Hitachi City, Ibaraki Prefecture Stock Association             Hitachi, Ltd. Nuclear Business Division (72) Inventor Tomokazu Aso             4 of 2 Shirane Shirane, Tokai Village, Naka-gun, Ibaraki Prefecture             Japan Atomic Energy Research Institute Tokai Research Center (72) Inventor Masaki Kaminaga             4 of 2 Shirane Shirane, Tokai Village, Naka-gun, Ibaraki Prefecture             Japan Atomic Energy Research Institute Tokai Research Center (72) Inventor Ryutaro Hino             4 of 2 Shirane Shirane, Tokai Village, Naka-gun, Ibaraki Prefecture             Japan Atomic Energy Research Institute Tokai Research Center (72) Inventor Pichai Clit Mitley             4 of 2 Shirane Shirane, Tokai Village, Naka-gun, Ibaraki Prefecture             Japan Atomic Energy Research Institute Tokai Research Center F-term (reference) 3H029 AA02 AB03 AB04 BB21 BB31                       BB44 CC03 CC05 CC38 CC40                 3H039 AA03 AA08 AA12 BB02 BB04                       BB07 CC02 CC03 CC05 CC36

Claims (6)

[Claims] 1. An orbiting scroll that is revolvably accommodated so as to face the fixed scroll so as to form a compression chamber between the orbiting scroll and the fixed scroll, and the orbiting scroll is revolved to orbit the center of the compression chamber. The gas-liquid mixed medium in the compression chamber is compressed while being moved to a discharge port, and a gap is provided at the discharge port so that the compression chamber and the discharge port communicate with each other at the initial stage of compression. And a scroll pump. 2. An orbiting scroll that is revolvably accommodated so as to face the fixed scroll so as to form a compression chamber between the orbiting scroll and the fixed scroll. A gap for compressing the gas-liquid mixed medium in the compression chamber and discharging it to the discharge port is provided by moving the compression chamber to the discharge port, and the gap allows communication between the compression chamber and the discharge port at the initial stage of compression, and the size of the gap. The scroll pump is characterized in that the thickness is in the range of 100 μm to 150 μm. 3. The scroll pump according to claim 1, wherein each of the end portions of the fixed scroll and the orbiting scroll has a spherical surface portion having a curved shape. 4. The scroll pump according to claim 1, wherein a ceramic material having high hardness such as TiN or SiC is provided on the surfaces of the fixed scroll and the orbiting scroll. 5. The scroll pump according to claim 1, wherein surfaces of the fixed scroll and the orbiting scroll are coated with a material having a small coefficient of friction such as diamond-like coating and resin coating. 6. The gas from the gas chamber is supplied to a refrigerator, the cooling gas cooled by the refrigerator is sent to the scroll pump, and the cooling gas compressed by the compression chamber of the scroll pump is supplied to the storage chamber. The scroll pump according to claim 1 or 2, wherein the scroll pump is used in a liquefied gas closed loop system that cools a heat source of the storage chamber and circulates a cooling medium again to the gas chamber, the refrigerator, and the like. pump.