Principle, structural characteristics, types and application of vortex vacuum pump

1. Working principle of vortex vacuum pump

The working chamber of the vortex vacuum pump is composed of a pair of vortex disk pairs with conjugate profile. A scroll is a scroll like structure with one or several involute spiral grooves on its surface. A static scroll plate and a dynamic scroll plate are interleaved and assembled together. The anti rotation mechanism ensures 180 ° phase difference between the dynamic and static scroll plates. Thus, a pair of scroll plate pairs constitute the pumping mechanism of oil-free scroll vacuum pump. A couple of crescent shaped closed cavities are formed by the contact between the static scroll and the dynamic scroll on several straight lines (several points on the cross section), and the driving of the dynamic scroll on the crankshaft

Moving around the center of the vortex body, the contact point moves along the vortex surface to achieve suction, compression and exhaust. Driven by the electric motor, every revolution of the crankshaft, a new set of crescent cavity is formed, which can realize the suction, compression and exhaust circulation of the vortex vacuum pump, and form the containment and forced transmission of the extracted gas.

2. Structure type of vortex vacuum pump

2.2.1 public transfer

The revolution type is a fixed vortex (known as a static vortex), and the other is rotating around it (known as a moving vortex disk). The rotating vortex disk is driven by the crank shaft, and the position of the sealing point rotates synchronously with the main shaft. It has the advantages of simple structure, few parts, small whirling speed and less mechanical wear, but it needs balance design. The vortex vacuum pump uses the outermost vortex ring to contain gas to form a closed suction cavity. In order to reduce the flow guide between the end of the vortex disk and the air inlet, the air inlet is often located near the end of the outer circle of the vortex disk. At the same time, in order to ensure that the gas in the central compression chamber is discharged as much as possible during the exhaust process, the exhaust hole is generally set near the center of the static vortex disk. Because the internal compression ratio of the vortex pump is not very large, the exhaust valve is often set to eliminate the insufficient compression, but the volume between the exhaust valve and the top of the vortex ring should be as small as possible. In order to improve the pumping speed or reduce the size of the vortex disk, two-sided vortex is often designed.

2.2.2 rotary type

The rotary type is composed of two scroll spindles installed on the bearings on both sides, one of which is directly driven by the motor, the other is driven by the cross slip ring mechanism and rotates at the same angle. The sealing position of the pump forms a line, the direction is always the same, and the pump adopts the vertical structure. The drive motor is in the upper part of the casing and the vortex disk is in the lower part. Because of its constant sealing direction, the rotary radial seal is not only convenient for human control, but also can avoid the unloading operation required by the side contact of the vortex ring. However, its overall structure is complex, there are many parts and high mechanical wear.

2.2.3 difference between transformation and rotation

(1) The form of rotation is different. The revolution type is that one vortex is stationary and the other is dynamic. The dynamic vortex moves around the static vortex for revolution and translation. However, the two self transforming vortices rotate synchronously and in the same direction around their own axis.

(2) Sealing position and direction are different. The radial sealing position of the two scroll teeth of the rotary type forms a line, and the direction of the sealing line is always fixed. However, the position and direction of the radial seal of revolution type scroll machinery rotate synchronously with the main shaft. That is to say, the direction of the radial sealing line changes 360 ° when the main shaft rotates for one circle.

(3) The direction of the radial force and the tangential force is different. The revolution type vortex machine makes eccentric revolution with the crankshaft by the dynamic vortex, so the dynamic vortex rotates around the crankshaft synchronously in the direction of the gas radial force and the tangential force. However, the position and direction of the gas radial force and tangential force on the two whirlpools are always the same. The radial force is in the direction of the seal line, and the tangential force is perpendicular to the direction of the seal line. Therefore, it is not possible to use the eccentric sleeve or the sliding shaft sleeve radial random mechanism to automatically adjust the side clearance of the scroll teeth, so as to achieve the radial sealing. The revolution type scroll crankshaft bears uniform load, while the transformation scroll crankshaft bears local load, which should be paid special attention in design.

(4) The balance is different. In the rotating vortex, since the eccentric axis is not used, the two vortices rotate around their own axis respectively. Without considering the eccentric mass of the vortices, the existence of centrifugal force can be ignored, and the balance block does not need to be set. In order to make the machine work smoothly, the eccentric mass of the moving vortex must be considered and the balance weight should be set to balance the centrifugal inertia force and moment of the East vortex.

(5) Overturning moment and axial force are different. Because both of the two rotating scroll plates bear the same overturning moment and gas axial force, the axial force thrust and bearing load should be considered in the design. However, there is only one rotating disk in the common transformation, so only the overturning moment and axial force of the rotating disk need to be considered.

3. Structure characteristics of vortex vacuum pump

The vortex vacuum pump is mainly composed of 5 parts:

① Dynamic and static vortex disk pair and base: a vortex disk structure formed by one or several involute helices. A pair of auxiliary mechanisms of a static vortex disk and a dynamic vortex disk are staggered, and the 180 ° phase difference between them is ensured.

② Crankshaft: an eccentric mechanism to ensure the rotating of the rotating turbine disk around the static turbine disk.

③ Seal: a sealing device to ensure the end face and tooth top seal of the dynamic and static discs.

④ Anti rotation mechanism: a mechanism to ensure 180 ° phase difference between the dynamic and static disks.

⑤ Motor: power mechanism with output of about 1500 R / min.

Its main moving parts only have one dynamic scroll, so the power transmission is simple. Under the same size, the moving radius is small, the parts are few, the structure is simple and compact, the size of the whole machine is small, the gap between the dynamic and static scroll, between the moving disk and the pump cavity is small, and there is no friction between the moving parts and the pump cavity in the pump.