Compression principle The compression principle of a scroll compressor is as shown. A spirally-shaped stationary scroll disk and an orbiting scroll created by an involute curve or the like are engaged with each other to form a plurality of compression chambers. If the orbiting scroll is rotated, the volume of the compression chamber is reduced toward the center, and the volume is reduced, and the compressed refrigerant is sucked by this action. Since there are several sets of compression chambers at this time, this stroke is continuously repeated in order.
In the home appliance technology, a fine-hole type throttling device was used for the oil supply in the compression chamber, but we know that this device has a structural limitation on reducing the oil flow, so the intermittent oil supply device using the rotary motion has been redeveloped. , achieved 2wt% dimensionless oil flow. Such a device is provided as an oil supply means from the high pressure portion to the intermediate pressure portion, and is provided on the movable scroll for the inner side (high pressure portion) and the outer side (intermediate pressure portion) of the annular seal located on the back surface of the movable scroll. Oil hole. The ratio of the intermediate pressure portion to the oil supply hole is set to a predetermined value, and the oil supply amount can be adjusted to an arbitrary value. By optimizing the oil supply to this compression chamber, the efficiency (ηcomp) is improved under all conditions A to D.
The three efficiencies of the motor efficiency (ηmo) can be expressed by equation (1). Ηcomp = ηcηmcηmo (1) Therefore, whether or not these efficiencies can be improved becomes the key to the overall efficiency of the compressor. The performance evaluation and high efficiency of the compressor were carried out in the case of 2.8 kW air conditioner using the four typical performance evaluation conditions (hereinafter referred to as conditions) shown in Table 1. These performance evaluation conditions are determined by the operating conditions of the room air conditioner.
When the material of the parts is different, the end seal is not used, and the method of improving the compression efficiency is found by controlling the vortex tip clearance at the time of assembly. The results of studying the relationship between the vortex tip clearance and the performance using an orbiting scroll without an end seal are shown. In the figure, the horizontal axis δ* represents the dimensionless gap of the vortex tip clearance δ0 divided by the vortex height, and the vertical axis represents the efficiency (ηcomp) ratio of the endless sealed product and the end sealed product.
If δ* is too large, the leakage of refrigerant from the top of the vortex increases, especially in the condition D where the capacity is small. on the other hand. If δ* is too small, since the vortex tip of the orbiting scroll is in contact with the fixed scroll, the input is increased, and the efficiency is lowered under the entire condition. According to these studies, the efficiency (ηcomp) was improved under all conditions by setting the end seal and the dimensionless gap δ* to an appropriate range (δ*=25 to 40).
Technology for improving compression efficiency Optimizing the oil supply amount of the compression chamber In the present scroll compressor, the compression chamber is sealed by injecting high-pressure oil into a predetermined amount of compression chamber. In general, if the amount of oil supplied to the compression chamber is increased, the sealing of the compression chamber can be improved, and the leakage loss of the refrigerant can be reduced. On the other hand, if the amount of oil supplied is too large, the amount of heat that the oil brings into the compression chamber is increased, and since the suction refrigerant is heated and then expanded, the volumetric efficiency is lowered. From this, it can be known that there is an optimum value for the amount of oil supplied to the compression chamber. Under Condition A, the results of the relationship between the oil supply amount and the performance of the compression chamber were investigated as shown. In the figure, the dimensionless oil flow rate on the horizontal axis is the value of the oil supply amount to the compression chamber divided by the refrigerant circulation amount. Since the R410A scroll compressor has a very small gap in the compression chamber, it is clear that if the amount of oil supplied to the compression chamber is reduced, the efficiency is improved under the entire conditions. However, in order to lubricate the thrust bearing portion described later, it is necessary to consider a certain amount of oil, and the dimensionless oil flow rate under the condition A is changed from 8 wt% to 2 wt%, thereby improving the efficiency.
Relationship between oil supply and performance of the compressor 3.2.2 Endless sealing The scroll compressor uses aluminum alloy for the material of the movable scroll and cast iron for the material of the fixed scroll. During operation, the temperature of the compression device portion rises. However, since the thermal expansion coefficient of the aluminum alloy is larger than that of the cast iron, the vortex of the orbiting scroll extends approximately 10 μm in the axial direction from the stationary scroll. At this time, in order to make the movable scroll The vortex tip does not contact the vortex bottom of the fixed scroll, and the vortex height of the orbiting scroll is set lower than that of the fixed scroll, and the end seal is provided by the vortex tip of the movable scroll, thereby reducing the The refrigerant at the tip clearance leaks.
However, under the condition D where the compressor rotation speed is low and the differential pressure between the exhaust pressure and the suction pressure is small, it is clear that a part of the end seal faces away from the sealing surface and sometimes does not function effectively. Therefore, the results of detailed study of refrigerant leakage have been carried out, and it has been found that even if the relationship between the vortex tip clearance and the performance of the two scrolls is intermittent, the optimization of the exhaust bypass device of the intermittent oil supply device is inherent to the scroll compressor. The volume ratio (intake completion volume/compression termination volume), however, in general, this volume is consistent with a condition in which the pressure ratio is large (for example, Condition A).
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