The single-turn spring linear oil-free silent air compressor is a schematic diagram of the principle of a linear compressor with a single-sided spring. When the oil-free silent air compressor is stationary, the spring connected to the piston is in a free length state by arranging the initial position of the piston at the top dead center position, and the piston is from the initial position (top dead center) under the action of the gas load during operation. After shifting to the center of motion, it reciprocates between top dead center and bottom dead center.
For a one-side spring linear oil-free silent air 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 motion center is 4X equal to the design stroke amplitude of the piston, ie 4X=X The offset is generated by the action of the gas force load.
2.2 Prototype design and development According to the design of the linear oil-free silent air compressor design exhaust volume and design conditions, the piston stroke and diameter are optimized, the design stroke is determined, and the gas force linearization result according to the design conditions The stiffness of the resonant spring and the mass of the moving parts are determined, and then the structural design of the linear compressor is performed.
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 distance from the center of motion to the top dead center (4X) is large. Increase.
The fixed exhaust pressure air compression test found that when the exhaust pressure is lower than the designed exhaust pressure, the cylinder stroke will occur if the compressor stroke does not reach the design stroke. As shown in (b), before the severe cylinder crash, the compressor stroke linearly increases with the increase of voltage at 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 one-side spring linear oil-free silent air 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 the compressor has experienced a serious collision of cylinders, resulting in 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 with 4 sets of springs as the resonant spring group is smaller than the compressor with 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 pressure corresponding to the stiffness of the metal resonant spring will be higher. This offset from the one-sided spring linear compressor of the prototype configuration analysis (moving center to top dead center distance) 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 the valve opening degree, as the voltage increases, the compressor discharge pressure increases, 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 approaches the peak value, so the unit stroke is compressed. The power consumption drops significantly. 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 is reduced due to the increase of the compressed gas volume and the increase of the copper loss. increase.
It can also be seen in (c) that the compressor using two sets of metal springs as the resonant spring group has a higher voltage value required for the resonance point of the compressor using the 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 it resonates.
The change law of compressor discharge pressure, piston stroke, power and unit stroke power consumption with 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 frequency of the power supply increases. This is because the compressor discharge pressure is low, and the ideal matching area of the rotor mass and the resonant spring stiffness is not reached. Therefore, the natural frequency of the compressor 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 with increasing frequency. 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 single-spring linear linear compressor has a small spring stiffness value. In order to obtain a better frequency characteristic of the single-side spring linear compressor, the quality of the moving parts of the compressor is also reduced when the power supply 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.