JPS62174589A - Device for controlling volume of screw type compressor - Google Patents

Abstract

PURPOSE:To miniaturize a variable volume screw type compressor by forming a cut-off port toward a suction side on the end face of a discharge side casing, and setting the installing direction of a control valve for opening and closing said cut-off port, in such a way that its valve shaft is perpendicular to a rotor shaft. CONSTITUTION:Flow-in passages 33a, 33b for allowing a gas in a operating chamber formed in a rotary casing 20 to escape to a suction side are formed in a bearing head casing 23 positioned on the discharge side of a screw type compressor. And, a control valve mechanism 32b for opening and closing said flow-in passages 33a, 33b is provided in the bearing head casing 23, and is set in such a way that its valve shaft is directed perpendicularly to the shaft of a rotor 22. The control valve mechanism 32b merely has to open and close the flow-in valves 33a, 33b and can be formed in a small shape, enabling the whole variable volume screw type compressor to be miniaturized.

Description

DETAILED DESCRIPTION OF THE INVENTION [Object of the Invention] (Field of Industrial Application) The present invention relates to a capacity control device for a large screw type compression unit.

(Prior Art) A displacement control device for a positive displacement twin-screw compressor conventionally used in a compressor will be explained with reference to FIGS. 6 and 7. In the drawings, 1 is a rotor casing, 2 is a suction casing, 3 is a bearing head casing, and 4 is a rotor casing.
is a compression chamber, 5 is a suction chamber, 6 is a discharge chamber, 7 is a slide valve,
8 is a bushing rod, 9 is a piston, 10 is a cylinder, 11 is a cover, 12 is a frontage, 13 is a bypass chamber communicating with the suction side, 14 is a chamber surrounded by the piston 9, cylinder 10 and suction casing 2, 15 is a cover 11
, a chamber surrounded by a piston 9 and a cylinder 10.

FIG. 6 shows a state in which the frontage 12 is opened and closed by the slide valve 7, and the capacity is 100%. When controlling the container from this state, pressure fluid is introduced into the chamber 15 through the connection hole 16, and at the same time, the pressure in the chamber 14 is released through the connection hole 17. As a result, the piston 9 moves to the left (in the drawing) due to the pressure difference between its front and rear surfaces, and the slide valve 7 moves to the left via the bushing rod 8, resulting in the state shown in FIG. Therefore, the compression chamber 4 communicates with the suction side via the opening 12 and the bypass chamber 13, and a portion of the fluid in the compression chamber 4 is returned to the suction side through the opening 12, reducing the volume of the discharged fluid. The returned fluid is sucked into the compression chamber 4 from the suction port 5 together with the fluid newly flowing into the compressor.

The rate of volume control is achieved by controlling the withdrawal of fluid back to the suction side. When other conditions are fixed, half of the fluid that is returned is determined by the projected area of the opening 12 in the flow direction, and this area is determined by the length of the slide valve 7 in the opening 12 in the moving direction, That is, it is proportional to the stroke length. Therefore, capacity control can be performed by controlling the stroke length of the slide valve 7.

For example, when increasing the capacity from the state shown in FIG. 7, pressurized fluid is applied to the chamber 14, the pressure in the chamber 15 is released, and the slide valve 7 is moved to the right. Conversely, when reducing the capacity, pressure fluid is applied to the chamber 15 to release the pressure in the chamber 14. In this way, by steplessly increasing or decreasing the area of the opening 12, the capacity can be controlled steplessly.

However, the prior art has the following problems.

(D) When the slide valve 7 moves forward, that is, in the direction of volume reduction, a space larger than the stroke length is required on the discharge side, and the size of the discharge chamber 6 and the bearing head casing in which it is formed are required. 3 must be increased in size to ensure the above space.

0 The driving devices such as the piston 9 and the bushing rod 8 that operate the slide valve 7 must have dimensions corresponding to the stroke quality, and the arrangement of the devices requires some ingenuity.

Q9: Parts related to capacity control are large qll.

) Due to the reasons mentioned above (→, 0 and Q), capacity control 1/
An increase in the external dimensions of 3M is unavoidable.

(G) From the standpoint of efficiency during capacity control, the slide valve 7 should not be placed at the intersection of the two rotors, but in this position there are various problems in machining the slide valve 7 and the rotor casing 1. Some ingenuity is required.

(Problems to be Solved by the Invention) As mentioned above, in the capacity control mechanism according to the conventional technology, it is inevitable that the mechanism becomes large and difficult to process. On the other hand, increasing the size of the mechanism is a major hindrance to progressing with the miniaturization of devices. An object of the present invention is to provide a device that is easy to process and can be formed in a small size by significantly differentiating the configuration of the capacity control mechanism from that of the prior art.

[Structure of the invention]

(Means for Solving the Problems) The capacity control device N for a screw compressor of the present invention has a device installed at the end of the casing on the discharge side at the back of the casing constituting the compression chamber for capacity control. A relief hole for releasing fluid from the compression chamber to the suction side, and a control means for opening and closing this relief hole are provided at the end of the casing on the discharge side in a direction perpendicular to the rotor axis. It consists of:

(Function) By opening the control valve located in the middle of the fluid passage that communicates with the relief hole and returns fluid to the suction side, part of the fluid sucked into the compression chamber will flow to the suction side, reducing the suction capacity. . A relief hole is formed at the end of the casing on the discharge side, and a control means for opening and closing this relief hole is formed at an M angle with respect to the rotor axis at the end of the casing on the discharge side. This makes it possible to reduce the size of the device, allow partial assembly of the device, and facilitate processing.

(Example) Hereinafter, the present invention will be described in detail based on the example shown in the drawings.

In FIGS. 1 and 2, 20 is a rotor casing;
21.22+, Q77 A pair of rotors that mesh once, 23
24 is the bearing head casing, 24 is the end of the casing on the discharge side, 25.26 is the "J-Ta I sleeve part, 2
7, 28 are bearings, 29 is suction? j, 30 are discharge holes for the fluid that is not returned to the suction side, 32a and 32b are control valve mechanisms, respectively, 33a and 33b are inflow passages for the fluid that is returned to the suction side, and 37 and 38 are the bearing head casing 23; Passages 36a and 36b are provided in the rotor casing 20 and are opposed to each other on the end face of the casing, respectively, and are control valve mechanisms 32a and 32.
An outflow passage 39 communicates with the passages 37 and 38 from b, and a communication passage. The control valve mechanisms 32a and 32b depicted in FIGS. 1 and 2 are similar to those depicted in FIGS. 3 and 4.
The reputation is shown in the figure. In the figure, 42 is a cylinder holder, 43 is a cylinder, 44 is a compression spring,
Reference numeral 45 designates screws 1 to 1, 35a designates an inflow boat, 34a designates an outflow boat, and 4G designates a connection hole for pressure horn control.

Lifting control is performed as follows. FIG. 1 shows a state in which lifting control is being performed.
is in the state shown in FIG. 4, and the three-way switching valve is in the state shown in FIG. 5. In this state, the connection hole 46 is communicated with the suction chamber 29 and released from the pressure, so the piston 45 is moved to the right by the restoring force of the compression spring 44, opening the inflow passage 33a, and some of the fluid in the compression chamber is It passes through the inflow passage 33a, the inflow boat 35a, and the outflow boat 34a, flows from the outflow passage 36a to the passages 37 and 38, and then flows through the communication passage 39 and returns to the suction chamber 29. Then, it mixes with the fluid newly flowing into the suction chamber 29 and is sucked into the compression chamber again.

In this embodiment, two sets of control valve mechanisms are provided, but in the control valve mechanism 32b, as well, a part of the fluid in the compression chamber is transferred from the inflow passage 33b → inflow port → outflow port → outflow passage, just as described above. 36b → passage 37, 38 → communication passage 39 → suction chamber 29.

When the control valve mechanism 32a is a lever, pressure fluid such as discharge gas or appropriate pressure oil is applied to the connection hole 46 from the pressure gi 48, and the piston 45 is moved to the left to be in the state shown in FIG. As a result, the inflow boat 35a is closed and the inflow passage 3
The inflow of fluid from 3a is interrupted. Therefore, the second half of the fluid sucked into the compression chamber from the suction chamber 29 is discharged from the discharge hole 30.
tit is not performed.

To control the rate of capacity control, the inflow passage 33a,
It is necessary to appropriately select the position and size of 33b. In other words, it must be installed at a position that is less than or equal to the compressor's design volume ratio (maximum suction volume/discharge volume) and greater than or equal to 1, but this position is represented by the rotation angle of the rotor, so If the angle is specified, the positions of the two rotors having the same volume ratio on the discharge side end face can be found in a negative direction.

Further, the size of the passage installed in the discharge end face must be determined within a range that does not exceed the width of one tooth with respect to the shape of the end face inside the rotor.

If the width exceeds the width of the tooth, fluid will flow in or out from the adjacent tooth groove when the tooth passes through that passage, and the effect you have decided will be reduced! This is because you will not be able to do it. In this way, by appropriately selecting and covering the position and size of the passage installed on the discharge end face, it becomes possible to precisely control the rate of volume control.

In addition, in this embodiment, two sets of control valve structures are provided, so by changing the opening/closing combination of the 11II sub-valve connected to each of these passages, fine-grained control can be achieved.
Control becomes possible. In other words, if these two sets are expressed as balls 1-A1 and port B, then the total load (both boat A and port B closed) is 100%, and the load 1 (closed to the boat, port 1) is 100%.
8) 75%, load (between ports A, port B closed) 45
Capacity can be controlled in 4 stages: %, load ■ (port (both ports A and B open) 5%).

〔Effect of the invention〕

As described above, according to the configuration of the present invention, parts related to capacity control can be made smaller by employing the relief hole in the end face of the casing and the means installed perpendicular to the rotor shaft for controlling the opening and closing of the relief hole. The external dimensions of the compressor have become smaller, and some parts of the assembly can be partially assembled due to the capacity.
Since it can be attached to the casing after partial assembly, assembly becomes easy. Further, the component parts are easy to process and do not require any special efforts.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional plan view of the device of the present invention, FIG. 2 is an end view of the end face of the bearing head casing located on the discharge side of the neck device of the present invention, viewed from the suction side, and FIGS. The figures are cross-sectional views showing two operating states of the control valve mechanism according to the present invention;
FIG. 5 is an explanatory view showing two positions of the three-way switching valve used in the device of the present invention, and FIGS. 6 and 7 are longitudinal sectional views showing different operating states of the prior art capacity control device. 20...Rotor casing, 22...Rotor, 23...
Bearing head casing, 24... end face, 32a
, 32b...control valve mechanism as control means, 33a
, 33b...Inflow passage as a relief hole. 7 slag fertilizer

Claims (2)

[Claims] (1) Among the casings constituting the compression chamber, the end face of the casing on the discharge side has a relief hole to the suction side for capacity control, and the control means for opening and closing this relief hole is provided at the end of the casing on the discharge side. A capacity control device for a screw compressor, characterized in that the capacity control device is provided in a direction perpendicular to a rotor axis at a portion thereof. (2) The screw according to claim 1, wherein the bearing head casing is provided with a control means in a direction perpendicular to the rotor axis, and the rotor casing is provided with a communication passage that communicates with the relief hole and returns the fluid to the suction side. Capacity control device for type compressor.