The single-turn spring linear compressor is a schematic diagram of the principle of a linear compressor with a single-sided spring. When the compressor is at rest, by placing the initial position of the piston at the top dead center position, the spring connected to the piston is in a free length state. During operation, the piston is displaced from the initial position (top dead center) by the gas load. After the sports center, it runs back and forth between the top dead center and the bottom dead center.
For a single-sided spring linear compressor, when the design stroke amplitude of the linear compressor is determined to be X, the distance between the initial position of the piston and the center of motion is 4X equal to the design stroke amplitude of the piston, ie 4X=X, the offset The amount is produced by the action of the gas force load.
2.2 Design and development of the prototype According to the design of the linear compressor, the exhaust volume and the design conditions, the piston stroke and diameter are optimized, the design stroke is determined, and the resonant spring is determined according to the gas force linearization result under the design conditions. The stiffness and the quality of the moving parts are then structurally designed for the linear compressor.
Schematic diagram of the prototype of the one-sided spring linear compressor developed for the design. The compressor prototype mainly includes: a linear motor composed of an inner stator, an outer stator, a permanent magnet mover and an excitation coil, a cylinder, a piston, a resonance spring, an intake valve and an exhaust valve. The resonant spring is arranged between the motor mover and the compressor body by a cylindrical spiral compression spring.
For the design and development of the dynamic magnetic single-sided spring linear compressor prototype, the main parameters are as shown in Table 1. One-side spring linear compressor prototype 3 prototype feasibility verification, in the case of constant frequency fixed exhaust pressure, within a certain voltage range, The distance from the center of motion of the single-side spring linear compressor to the top dead center remains constant as the voltage rises. This is the distance from the center of motion of the single-sided spring linear compressor to the top dead center (4X) from the previous structural analysis. The effect of the load is generated, that is, the exhaust pressure is constant, and the distance from the center of motion to the top dead center (4X) is also unchanged. When the voltage continues to increase, the distance from the center of motion of the compressor to the top dead center (4X) will increase sharply. This is because the serious collision of the cylinder causes the compressor stroke to be asymmetrical and the motion center to the top dead center distance (4X) appears larger. Increase.
The fixed exhaust pressure air compression test found that when the exhaust pressure is lower than the designed exhaust pressure, the cylinder stroke occurs when the compressor stroke does not reach the design stroke. As shown in (b), before the severe cylinder crash phenomenon, the compressor stroke linearly increases with the increase of voltage under the same exhaust pressure. There is a slight collision in this linear zone, but because we use a venting structure similar to a mushroom valve, even if there is a slight impact cylinder, the operating parameters of the compressor will not be disordered; Under gas pressure, the higher the exhaust pressure value, the greater the voltage required to reach the top dead center position.
Therefore, the single-side spring linear compressor control can adjust the voltage value to make the piston reach the top dead center position during the movement, and ensure that the compressor does not hit the cylinder.
Medium (b) and (c) respectively show that in a certain frequency range, the compressor stroke and power increase linearly with the increase of voltage in a certain voltage range. When the voltage exceeds this area, the piston stroke and power There has been a surge of phenomena. In this case, we believe that there is a serious crash in the compressor, which leads to instability of various parameters of the compressor operation.
3.3 Air compression of different resonant spring stiffness, under the same exhaust pressure, the linear compressor stroke using 4 sets of springs as the resonant spring group is smaller than the compressor using 2 sets of springs, that is, the stiffness of the metal resonant spring of the single-side spring linear compressor is larger. The smaller the stroke is; when the compressor reaches the same stroke, the compressor with a high stiffness of the metal resonant spring will have a higher exhaust pressure. The offset (motion center to top dead center distance) of the one-sided spring linear compressor analyzed with the prototype structure is consistent with the action of the gas force load.
As shown in (b), the exhaust pressure of the one-sided spring linear compressor increases with increasing voltage with a certain valve opening.
As shown in (c), the power consumption per unit stroke of a single-sided spring linear compressor will increase significantly with the change of voltage, then decrease and then increase. Because of the valve opening, as the voltage increases, the compressor discharge pressure increases, and the corresponding stroke increases, resulting in an increase in the amount of compressed air and an increase in copper loss. These factors increase the power consumption per unit stroke. When the voltage continues to increase, the stiffness of the resonant unit composed of the equivalent stiffness of the compressed gas and the metal spring makes the natural frequency of the compressor close to the power supply frequency, and the compressor approaches the resonance state. At this time, the compressor efficiency is close to the highest value, and thus the unit stroke The pressure consumption of the compressor is significantly reduced. When the voltage continues to increase, the exhaust pressure continues to increase, and the compressor is far away from the resonance zone. The power consumption of the compressor is increased due to the increase of the amount of compressed gas and the increase of copper loss. Increase again.
It can also be seen in (c) that a compressor using two sets of metal springs as a resonant spring group has a higher voltage value required for a resonance point of a compressor using four sets of metal springs. Because the compressor is close to the resonance state, the equivalent spring stiffness of the compressed gas and the resonant unit stiffness of the metal spring are required to make the natural frequency of the compressor close to the power supply frequency, and the corresponding voltage value is also high. Therefore, the one-side spring compressor using two sets of metal springs as the resonance unit has a higher voltage value when resonance occurs.
Compressor exhaust pressure, piston stroke, power and unit stroke power consumption vary with the power frequency.
(d) The variable-frequency performance curve of the single-side spring linear compressor under the fixed valve opening degree.
The conversion performance of the single-side spring linear compressor (c) shows that the power of the compressor decreases with the increase of the power frequency because the exhaust pressure is reduced and the compressor stroke is reduced (a) and (b). The gas pressure and compressor stroke decrease as the power frequency increases. This is because the compressor discharge pressure is low and does not reach the ideal matching area of ​​the rotor mass and the resonant spring stiffness at the design, so the compressor natural frequency is low. As the power supply frequency increases, the compressor moves away from the resonance area, causing the exhaust pressure to decrease and the stroke to decrease. In addition, at the same frequency, the exhaust pressure can be increased by increasing the voltage, and the stroke of the corresponding compressor piston is also increased because of compression. The position of the center of motion of the machine increases as the exhaust pressure increases away from the top dead center position.
The combined action results in a reduction in the consumption of compressed gas.
As shown in (d), the unit power consumption of the compressor increases as the frequency increases. Because the power frequency is close to the natural frequency of the compressor, the compressor efficiency is high. When the power frequency is increased, the compressor is far away from the resonance region, and the efficiency is reduced, resulting in an increase in the unit power consumption of the compressor; in the case of the same frequency, Increasing the voltage causes the exhaust pressure to increase, so that the unit power consumption of the compressor also increases.
Under the fixed valve opening degree, the single-side spring linear compressor frequency conversion performance experiment shows that the compressor works at a high efficiency near its natural frequency, so in the design of the single-side spring linear compressor, a higher frequency is obtained. Characteristic, the design of the compressor's power supply frequency and natural frequency ratio is approximately equal to 1, usually slightly greater than 1. Because the distance between the initial position of the single-side spring linear compressor piston and the motion center is equal to the design stroke amplitude of the piston, ie 4X = X Therefore, the spring stiffness value of the single-side spring linear compressor is small, so that the frequency characteristics of the single-side spring linear compressor are better, and the quality of the moving parts of the compressor is also reduced when the power frequency is constant. From the point of view of product material, the single-side spring linear compressor utilizes compressed gas as a gas spring to reduce the amount of resonant spring, while reducing the mass of the moving parts of the compressor, so that the inertia of the compressor is reduced, and the linear compressor is light. Purpose.
4 Conclusion Through the development of a new type of dynamic magnetic single-side spring linear compressor prototype, and based on this, the prototype air compression experimental study was carried out. The conclusion is as follows: Through the prototype air compression experiment, the feasibility of the single-side spring linear compressor is verified, and it uses compressed gas as the gas spring to reduce the amount of resonant spring and reduce the quality of the moving parts of the compressor. The advantages of linear compressor lightening; prototype experiments show that when the compressor discharge pressure conditions change, the compressor piston can be operated at the top dead center position by adjusting the voltage value.
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