JPS603356Y2 - screw compressor - Google Patents

Description

[Detailed description of the invention] In a screw compressor, as shown in FIGS. 1 and 2, a male rotor 1 having a helical protuberance 1a and a female rotor 2 having a helical groove 2a that engages with the helical protuberance 1a are attached at both ends. When rotates in the direction of the arrow in the working chamber 6 consisting of two parallel and mutually overlapping cylindrical cavities formed in the case 5 closed by the front case 3 and the rear case 4, the helical ridge 1a engages. The sealed working space 7 defined by the spiral groove 2a and the inner surface of the working chamber 6 changes its volume, and during this time gas is sucked into the sealed working space 7 from the suction passage 8 communicating with a suction port (not shown), and is compressed and discharged. It is discharged from the outlet 9 through the discharge passage 13.

Furthermore, the discharged gas passes through an oil separator element 10 for separating oil contained therein, is discharged into the housing 12, and is then sent to the outside via a discharge pipe 11.

14 is oil, and 15 is an oil return hole.

Figure 3 shows the volume change in one sealed working space corresponding to the rotation angle of the rotor in this type of screw compressor, and Figures 4 and 5 show the pressure change in the sealed working space at this time. Shown below.

Therefore, in FIG. 3, any one sealed action space 7
The volume at the completion of gas suction in a is V.

As the rotor rotates, its volume gradually decreases, and when it reaches the volume V1, this sealing space 7a opens to the discharge port 9, and thereafter the gas in this space 7a is transferred to the discharge passage 1.
Exhale after step 3.

The change in volume of the sealing space 7b, which opens to the discharge port 9 subsequent to the sealing space 7a, is shown by dotted lines.

Design volume ratio V.

/V□ and the design pressure ratio π determined by the physical properties of the compressed gas.

It is desirable to operate the screw compressor directly at (πo = (,?)K, where K is a polytropic index), but since the pressure inside the discharge pipe 11 fluctuates depending on the load, it is not possible to operate the compressor at other pressure ratios. There are many cases where it is forced.

What is the pressure ratio when the screw compressor is actually operated, that is, the operating pressure ratio? r (?r=PD/P, where PD is the pressure inside the discharge pipe and Ps is the suction pressure), the situation of pressure change in the sealed action space 7a when π is larger than WQ is the fourth
As shown by the solid line in the figure, π is π.

The situation of pressure change in the sealed working space 7a when the pressure is smaller is as shown by the solid line in FIG.

That is, in either case, large pressure fluctuations are observed after the sealed action space 7a opens to the discharge port 9.

In addition, in FIGS. 4 and 5, P indicates the pressure in the sealed action space 7a at the time of starting discharge.

And π is π.

When the pressure is larger, the pressure inside the discharge passage 13, which is approximately equal to the pressure inside the discharge pipe PD, is higher than the pressure inside the space 7a P0 at the time when the sealing action space 7a opens to the discharge port 9. Gas temporarily flows back into the space 7a, and an extra amount of work is required for the gas that flows back.

On the other hand, π is π. When it is smaller, the pressure inside the space 7a is P1 at the time when the sealing action space 7a opens to the discharge port 9.
Since the internal pressure PD of the discharge passage is smaller, gas is temporarily and suddenly discharged from the space 7a into the discharge passage 13 via the discharge port 9, and the amount of work is reduced by the amount of gas that is temporarily and rapidly discharged. It will be wasted.

The present invention was proposed in order to solve the problems of the above-mentioned conventional devices, and the present invention will be specifically explained below with reference to the drawings.

FIG. 6 is a partial vertical sectional view showing one embodiment of a screw compressor to which the present invention is applied.

In the figure, a pressure adjustment hole 16 drilled in the carrier case 4 is used to control the airtight working space 7 from when it is in the compression process just before entering the discharge stroke to when the gas is discharged from the discharge port 9. The discharge cavity 17 is connected to a discharge cavity 17 having a space for receiving the pressure and relaxing the pressure fluctuation.

In this embodiment, one end of the pressure adjustment hole 16 is opened at the lower part of a discharge cavity 17 formed in the carrier case 4.

Further, 18 is a lid for covering the discharge cavity 17;
Reference numeral 9 denotes a tail pipe inserted into the discharge cavity 17 for guiding the gas received in the discharge cavity 17 into the oil separator element 10.

20 indicates a filter. There is no other difference from the conventional one,
Components that are the same as those in FIG. 1 are given the same reference numerals.

By the way, during the period from when the sealing space 7a enters the discharge stroke until it opens to the discharge port 9 (or the rotation angle of the rotor), the sealing space 7a is communicated with the inner space of the discharge cavity 17 through the pressure adjustment hole 16. and discharge cavity 1
7 and the pressure in the discharge passage 13 are the pressure in the discharge pipe 11.
As long as there is a difference between the pressure inside the sealed action space 7a and the pressure inside the discharge cavity 17, gas flows through the pressure adjustment hole 16 in a direction that reduces this pressure difference. .

Thus, the sealed action space 7a at the time when the discharge port 9 is opened
It is possible to reduce the difference between the internal pressure and the internal pressure of the discharge passage 13, thereby reducing the amplitude of pressure pulsations caused by the opening of the discharge port 9, as shown by the dashed line in FIGS. 4 and 5. It is possible to reduce the noise and vibration of the compressor by increasing the pressure and stabilizing the compressor more quickly.

The pressure equalization effect of the pressure adjustment hole 16 is affected by the cross-sectional area of the pressure adjustment hole 16 and the opening time of the pressure adjustment hole 16, so the operating pressure ratio conditions of the compressor, the rotational speed of the rotor, and the design pressure ratio of the compressor It is necessary to take this into consideration when selecting the number, position, and cross-sectional area of the pressure adjustment holes.

Experimental data are shown in FIG. 7, where the solid line shows the relationship between the compressor operating pressure ratio and the pressure pulsation amplitude for the compressor without pressure adjustment holes, and the dotted line for the compressor with pressure adjustment holes.

As is clear from FIG. 7, the operating pressure ratio region B where the pressure pulsation amplitude is below the allowable value in the case with pressure adjustment holes is significantly expanded compared to that in the region A in the case without pressure adjustment holes. I understand.

FIG. 8 is a diagram showing the relationship between efficiency, operating pressure, and compressor rotation speed, where the solid line shows the efficiency curve for a compressor without pressure adjustment holes, and the dotted line shows an efficiency curve for one with pressure adjustment holes.

As is clear from FIG. 8, the efficiency curve of the case with the pressure adjustment hole is flatter compared to that of the case without the pressure adjustment hole.

Note that the discharge cavity 17 is provided to alleviate pressure fluctuations in the gas discharged from the discharge passage 13, but since this gas contains a large amount of lubricating oil, this oil is separated within the discharge cavity 17. If it accumulates in this lower part, the effective volume of the discharge cavity 17 will be reduced, and as a result, the function of the discharge cavity 17 to alleviate pressure fluctuations will be impaired.

However, in this embodiment, one end of the pressure adjustment hole 16 is opened at the lower part of the discharge cavity 17, so that π>
? When ro, the lubricating oil accumulated in the lower part of the discharge cavity 17 is returned to the sealed action space 7 through the pressure adjustment hole 16, and π<? In the case of RO, the lubricating oil accumulated in the lower part of the discharge cavity 17 is blown up by the gas ejected from the sealed working space 7 through the pressure adjustment hole 16, and is sent from the tail pipe 19 into the oil separator element 10. However, lubricating oil does not accumulate at the bottom of the discharge cavity 17,
Therefore, it is possible to prevent the pressure fluctuation mitigation function of the discharge cavity 17 from deteriorating.

As explained below in detail with respect to the embodiments, the present invention includes a sealed action space in the compression stroke just before entering the discharge stroke, and a space that receives the gas discharged from the discharge port and alleviates the pressure fluctuation. Since the pressure adjustment hole communicates with the lower part of the discharge cavity which leads the gas to the oil separator element, the pressure inside the sealed action space at the time when the sealed action space opens to the discharge port 9 is controlled by the pressure adjustment hole. The difference between the pressure inside the discharge passage and the pressure inside the discharge passage becomes smaller, and even when fluctuations in the pressure inside the discharge passage are unavoidable, the vibration and noise of the screw compressor can be significantly reduced, or the screw compressor can be operated efficiently. In addition, the range of operating pressure ratios that can be operated with low noise can be expanded.

[Brief explanation of drawings]

Fig. 1 is a partial vertical sectional view of a conventional screw compressor, Fig. 2 is a partial sectional view taken along the line ■-■ in Fig. 1, and Fig. 3 shows the internal volume of the sealed action space and the rotor. Figures 4 and 5 are diagrams showing the relationship between the pressure in the sealed working space and the rotor rotation angle. FIG. 5 shows cases where the operating pressure ratio is smaller than the design pressure ratio. FIG. 6 is a partial vertical sectional view showing one embodiment of the present invention;
The figure is a diagram showing the relationship between operating pressure ratio and pressure pulsation amplitude, and FIG. 8 is a diagram showing the relationship between operating pressure ratio and efficiency. Spiral protrusion 1a, male rotor 1, spiral groove 2a, female rotor 2,
Working chamber 6, sealed working space 7, discharge port 9, pressure adjustment hole 16
, discharge cavity 17°

Claims (1)

[Scope of utility model registration request] When a male rotor having a helical ridge and a female rotor having a helical groove that engages with the helical ridge rotate in an operating chamber consisting of two parallel and mutually overlapping cylindrical cavities, the male rotor engages with the helical ridge and the helical groove. In a screw compressor, gas is sucked into the sealed working space from the suction port, compressed, and discharged from the discharge port by changing the volume of the sealed working space, which is limited by the inner surface of the chamber. The lower part of the discharge cavity has a sealed action space in the compression stroke before entering the oil, and a space that receives the gas discharged from the discharge port and alleviates the pressure fluctuation, and the lower part of the discharge cavity is designed to guide the gas to the oil separator element. A screw compressor characterized by communication through adjustment holes.