JPS6142116B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a suction piping system for a multi-type compressor unit.

As shown in Fig. 1, the multi-type compressor unit is equipped with a plurality of compressors 1, 2, and 3 mounted on, for example, a liquid receiver 4, and the discharge and suction sides are connected in parallel. It is well known that the compressor is configured to perform capacity control by combining the operation and stop of each compressor. In the figure, 5 is a discharge pipe, 6 is a suction pipe, 7 is a suction header, 8 is a suction accumulator, and 9 is a pressure equalizing oil pipe that communicates between the crank cases of the compressors 1 to 3. In such a multi-type compressor unit, the suction pipes 6 of each compressor are individually branched out from the suction header 7 and connected to each other, so that the refrigerant gas returned from the evaporator is sucked into each compressor. Here, the refrigerant contains refrigerant machine oil that has circulated through the refrigerant circuit, and this oil also needs to be sucked into the compressor and recovered at the same time. When suctioning and recovering such return oil, it is important to ensure that the refrigerant gas and oil are collected evenly and not unevenly in some of the compressors that are in operation, and that if some of the compressors are stopped due to unloading, It is desirable to prevent excess oil from being collected and stored in the compressor while it is stopped, and to return the oil to the compressor little by little so that a large amount of oil does not return all at once. It can be done. In other words, if the amount of oil returned to each compressor is not collected equally, it will not be possible to maintain equal pressure and oil in the crankcase of each compressor using the normal pressure equalization oil pipe system, which may cause oil-out operation in some cases. There is.
In addition, if oil containing a large amount of refrigerant stays in the compressor when it is stopped, the oil may accumulate in the cylinder head and form an oil trap, or the oil in the crankcase may cause oil forming when the compressor is restarted. This will cause oil to run out. Furthermore, if a large amount of oil is intensively sucked into the compressor at once, there is a risk that oil hammer may occur and damage the compressor.

By the way, the conventional general connection structure between the suction header and each suction pipe is shown in Figures 2 and 3.
As shown in the figure. That is, each suction pipe 6 has its suction end 61 cut at an angle of approximately 45 degrees, passes through the upper wall of the suction header 7, and draws the suction pipe 6 into the suction header 7 with its suction end 61 directed toward the upstream side of the refrigerant flow. It has an opening near the bottom. As a result, the oil flows into the suction header 7 together with the refrigerant gas, and the oil accumulated at the bottom of the suction header is sucked little by little together with the refrigerant gas into the suction pipe 6 of the compressor in operation. However, in a structure in which a suction pipe 6 with a pipe diameter not much different from the pipe diameter of the suction header 7 is drawn into the suction header 7 so as to cross this cross section as shown in the figure, the suction pipe 6 is connected to the suction pipe 6. The cross-sectional area of the refrigerant gas remaining except for 6 is significantly narrowed. For this reason, a large pressure loss occurs in the suction header as the refrigerant gas passes through it, and in particular, a large pressure drop occurs before and after each suction pipe, which is connected to the downstream side of the suction header with respect to the flow of refrigerant. The pressure drop tends to be large in the compressor connected to the suction pipe. As a result,
As shown in Figure 1, simply connecting the crankcases of compressors 1 to 3 with normal pressure equalizing oil pipes 9 will not maintain equal pressure and oil, and the compressor connected to the upstream side of the suction header will be connected to the downstream side. Oil leaks toward the crankcase of the compressor, causing the upstream compressor to run out of oil, and conversely, an excessive amount of oil enters the downstream compressor, causing problems such as oil hammer. . For this reason, if the suction pipe 6 is not deeply inserted into the suction header 7 as shown in Fig. 4, but the suction end 61 is opened on the upper surface of the suction header, a sufficient cross-sectional area for refrigerant gas can be secured. The suction pipe 6 is unable to smoothly suck in small amounts of oil accumulated at the bottom of the suction header 7, and when the oil accumulates to a certain limit level, a large amount of oil is sucked into the suction pipe 6 at once. There is a great risk of oil hammer. Furthermore, in order to avoid the occurrence of the above-mentioned troublesome phenomenon, it may be possible to select the pipe diameter of the suction header 7 to be sufficiently larger than the pipe diameter of the suction pipe 6 to ensure the necessary passage cross-sectional area for the refrigerant gas. In such a structure, in the case of three compressors, the suction header pipe 7
The pipe diameter of the suction pipe 6 must be approximately five times or more larger than that of the suction pipe 6, resulting in a larger structure and significantly higher manufacturing cost.

The present invention has been made with the above points in mind, and its purpose is to eliminate the above-mentioned drawbacks of the conventional art, and to smoothly collect and collect the oil flowing into the suction header evenly and in small quantities into each compressor in operation. In addition to maintaining equal pressure and oil in the crankcase of each compressor, this multi-type compressor has a simple structure and can be implemented at low cost without returning excess oil to the compressor when it is stopped. An object of the present invention is to provide a suction piping device for a suction unit.

According to the present invention, the suction end of the refrigerant gas suction pipe of each compressor is opened on the upper surface of the suction header, and the suction end of the oil return capillary tube is connected to each suction pipe separately from the suction pipe. This is achieved by opening the end of the capillary tube toward the upstream side of the flow of refrigerant at the bottom of the suction header, and connecting the other end of the capillary tube, which is raised upward from the bottom of the suction header, to the middle of the suction pipe.

Next, the present invention will be explained in detail based on illustrated embodiments.

In FIG. 5, first, the suction pipe 6 for sucking refrigerant gas is connected to the suction end 61 of the suction pipe 6 opened to the upper surface of the suction header 7 disposed laterally, as in FIG. 4. On the other hand, an oil return capillary tube 10 is provided for each suction pipe separately from the suction pipe 6.
is piped. The capillary tube 10 has its suction end opened near the bottom of the suction header 2, rises upward from there, and connects the other end to the middle of the suction pipe 6. Further, in order to open the suction end of the capillary tube 10 toward the upstream side of the flow of refrigerant, the suction tube is cut obliquely toward the upstream side at an angle of θ=40° to 60° as shown in the figure. There is. Moreover, what is important here is that the rising height h of the capillary tube 10 is set lower than the pressure head corresponding to the dynamic pressure acting on the suction end of the capillary tube 10. Note that the suction header 7, suction pipe 6, and capillary tube 10
The state of mutual welding is clearly shown in the plan view of FIG.

Next, the operation of the suction piping device having the above configuration will be explained. Assuming that all the compressors 1 to 3 are in operation in FIG. 6, the refrigerant gas returning to the suction header 7 is sucked into each suction header 1 to 3 through each suction pipe 6. In this case, the suction end 61 of the suction pipe 6 does not go deep into the suction header 7 as shown in FIG. 2, and there is a thin oil return capillary tube 10 inside the suction header that hardly poses an obstacle to the gas flow. It crosses only slightly, and a sufficient gas passage cross-sectional area is ensured over the entire region from the upstream end to the downstream end. Therefore, no large pressure loss occurs within the suction header, and each compressor can suck in refrigerant gas under the same conditions, and equal pressure and oil can be maintained between the crankcases.
In addition, in this state, point P and point Q shown in FIG.
In other words, of both openings of the capillary tube 10, the total pressure, which is the sum of static pressure and dynamic pressure, acts on the suction end at point P, whereas at point Q, which is the connection point with the suction pipe 6, there is a static pressure. Since only pressure acts, point P and Q
A pressure difference corresponding to the dynamic pressure applied to the suction end of the capillary tube 10 is generated between the two points. Therefore, due to this pressure difference, the water head of the rising height h of the capillary tube 10 is overcome and the suction header 7
The oil collected at the bottom of the tank is fed into the suction pipe 6 little by little through the capillary tube 10. By appropriately selecting the diameter of the capillary tube 10, this amount of oil can be equally sucked into and recovered by each compressor without leaving any oil in the suction header. In addition, if unloading causes one-lung operation with some compressors stopped, refrigerant gas and oil will be sucked into the operating compressor in the same manner as above, but the suction pipe of the stopped compressor will be injected with gas. Since no longer flows, the total pressure acts on point Q, and the pressure at point P and point Q becomes the same. Moreover, between point P and point Q, there is a rising height h of the capillary tube 10.
is present, so oil will not flow into the stopped compressor through the capillary tube 10.

In the illustrated example, the compressor is disposed below the suction header, but the compressor may be disposed above the suction header in the same manner. In this case, the oil return capillary tube 10 is connected to the middle of the rising portion of the suction pipe 6, as shown in FIG. Also the 7th
As shown in the figure, the suction end of the capillary tube 10 may penetrate through the lower surface of the suction header 7 from below and open at the bottom. In this case, once the capillary tube 10 is pulled out downward, it makes a U-turn and rises upward, and the other end is connected to the suction pipe 6 at a predetermined rising height h.
In this configuration, as compared to FIG. 5, the capillary tube 10 does not cross the inside of the suction header 7, so the fluid resistance is reduced accordingly, and the pressure loss inside the suction header can be reduced.

As described above, according to the present invention, in a multi-type compressor unit composed of a plurality of compressors, a simple oil return capillary tube is added between the suction header and each suction pipe for each compressor. This structure eliminates all the various drawbacks of conventional compressors, such as oil shortage due to pressure balance between compressors, and oil hammer caused by sucking a large amount of oil at once, and improves reliability. A high-performance multi-type compressor unit can be obtained.

[Brief explanation of the drawing]

Fig. 1 is a front view showing the schematic configuration of a multi-type compressor unit, Fig. 2 is a sectional view of a conventional suction piping device, Fig. 3 is an enlarged sectional view taken along the arrow in Fig. 2, and Fig. 4 is a cross-sectional view of a conventional suction piping device. FIG. 5 is a partial structural diagram of a conventional example, FIG. 5 is a cross-sectional view of the configuration of an embodiment of the present invention, FIG. 6 is a plan view showing the suction piping of the compressor unit based on the embodiment of FIG. 5, and FIG. FIG. 7 is a sectional view of a main part of another embodiment. 1, 2, 3: Compressor, 6: Suction pipe, 7:
Suction header, 10: Capillary tube for oil return.

Claims (1)

[Claims] 1. In a multi-type compressor unit equipped with a plurality of compressors and in which the refrigerant gas suction pipes of each compressor are individually branched from a suction header arranged laterally, the suction end of each suction pipe is connected to the suction header. The suction end of the oil return capillary tube, which is opened on the upper surface and is piped separately for each suction pipe, is opened toward the upstream side of the flow of refrigerant at the bottom of the suction header; A suction piping device for a multi-type compressor, characterized in that the other end of the capillary tube raised upward is connected to the middle of the suction pipe. 2. In the suction piping device according to claim 1, the rising height of the oil return capillary tube is smaller than the pressure head corresponding to the dynamic pressure acting on the opening end of the capillary tube on the suction header side. Specified multi-type compressor suction piping system.