JPS6223590A - Reverse thrust preventing apparatus for screw expansion machine - Google Patents

Abstract

PURPOSE:To prevent the breakage of a rotor due to the generation of reverse thrust on starting and on stop by detecting the position in the axial direction of a rotor and controlling the hydraulic pressure supplied in to the chamber on one side of a cylinder for shifting a rotor shaft in the axial direction. CONSTITUTION:When a rotor 1 shifts in the reverse thrust direction, the gap DELTAS between a detection collar 15 installed at the edge part of a rotor shaft 1b and a gap detector 16 varies, and the variation quantity is detected by the gap detector 16. While, at the edge part of the rotor shaft 1a, a cylinder 6 for shifting the rotor 1 in the axial direction is formed, and oil is supplied to one side chamber 8 of the cylinder 6 from an oil tank 11 through a pressure control valve 13 and an oil feeding pump12. Since the gap detector 6 adjusts the opening degree of the pressure control valve 13 according to the dimension of the gap DELTAS, generation of the reverse thrust on the rotor can be automatically prevented.

Description

DETAILED DESCRIPTION OF THE INVENTION [Field of Industrial Application] The present invention relates to a reverse thrust prevention device for a screw expander.

[Prior art]

Conventionally, there has been no known screw expander equipped with a device for preventing reverse thrust that occurs when starting or stopping.

On the other hand, in a screw compressor, as shown in FIG. 2, a large thrust force 24 acts on the rotor 21 from the discharge port 23 side toward the suction port 22 side due to the gas pressure difference.
Excessive thrust force acts on the thrust bearing. Therefore, a cylinder device 27 is provided which has a piston 26 mounted on the rotor shaft 25 as a component, and a pressure fluid source is provided for the suction side chamber 28 of the suction side and discharge side chambers formed on both sides of the piston 26. It is known that the thrust bearing is configured to supply hydraulic pressure or compressed gas from 29, thereby offsetting and reducing the thrust force, thereby improving the life of the thrust bearing.

By the way, in the screw expander, a reverse thrust force is generated due to a thrust reversal phenomenon peculiar to a positive displacement expander when starting and stopping. In other words, due to the drop in inlet gas pressure at startup and stop, the gas expands inside the expander by a predetermined internal expansion ratio according to the finger pressure diagram, and after the pressure drops below the back pressure, the gas expands near the outlet port. Increase the pressure to back pressure. As a result, a reverse thrust force is generated in the opposite direction to the thrust force generated during steady operation.

However, in this way, there is a device to prevent reverse thrust force that occurs only when starting and stopping a screw expander.
It is impossible to apply the thrust force reduction device in the above-mentioned screw compressor as it is.

[Purpose of the invention]

The present invention has been made in order to solve the above-mentioned conventional problems, and prevents the occurrence of reverse thrust when starting and stopping a screw expander, thereby preventing the occurrence of troubles caused by reverse thrust. The purpose is to

[Structure of the invention]

The reverse thrust prevention device for a screw expander of the present invention is provided with a rotor position detection device that detects the axial displacement of the rotor, a cylinder device whose component is a piston attached to the rotor shaft, and a cylinder device with a piston mounted on the rotor shaft. A control valve is provided to control the pressure in at least one of the inlet-side chamber and the outlet-side chamber formed on both sides of the piston by a signal from the rotor position detection device, and reverse thrust occurs when starting or stopping. When the rotor is displaced in the axial direction, this is detected and the control valve is actuated to apply an opposing force to the reverse thrust, thereby preventing trouble from occurring due to rotor displacement. .

〔Example〕

An embodiment of the present invention will be described below with reference to FIG.

An inlet 2 and an outlet 3 are provided at both ends of the rotor 1, and rotor shafts 1a and 1b extending from the rotor 1 on both sides are rotatably supported by a radial bearing and a thrust bearing 4 (not shown). A piston 5 is attached to one end of one rotor shaft 1a, and a cylinder device 6 having this piston 5 as a component is provided. Of the chambers 7 and 8 on the outlet side and inlet side formed on both sides of the piston 5 of this cylinder device 6, the outlet side chamber 7 is connected to a pressure fluid source 9 such as hydraulic pressure or high pressure gas via an on-off control valve 10. It is configured to be able to supply pressure fluid. In addition, oil pressure is supplied to the chamber 8 on the inlet side from an oil tank 11 by an oil supply pump 12, and the oil supply pump 12 is provided with a bypass passage 14 equipped with a pressure control valve 13 so that the supplied oil pressure can be adjusted. has been done.

A detection collar 15 for detecting movement of the rotor 1 is attached to the other rotor shaft 1b, and a constant gap ΔS is provided between the detection collar 15 and the gap detector 1 on the expander casing.
6 are arranged. These detection collars 15 and gap detector I6 constitute a rotor position detection device. The gap detector 16 is configured to output a signal to a regulator 17 when the detected gap exceeds a predetermined value, and further outputs a control signal from the regulator 17 to the opening/closing control valve 1o and the pressure control valve 13. is configured to output.

In the above configuration, during normal operation of the screw expander, the pressure on the inlet 2 side is high and the pressure on the outlet 3 side is low, so the rotor 1 has a thrust force of 18 from the inlet side to the outlet side.
acts, and the thrust force is supported by the thrust bearing 4. In addition, in order to reduce this thrust force 18, regulated hydraulic pressure is supplied from a pressure fluid source 9 to the chamber 7 on the outlet side of the cylinder device 6 via an on-off control valve 10 to counteract the thrust force 18. The force that offsets this is the rotor 1
It is acting on

On the other hand, when starting or stopping the screw expander, the rotor 1
A thrust force 19 in the opposite direction acts on.

Therefore, when the rotor 1 moves in the reverse thrust direction, the gap ΔS between the detection collar 15 and the gap detector 16 changes, and the amount of change is detected by the gap detector 16. Before the amount of change in the gap ΔS reaches a limit value that causes contact between the end faces of the rotor 1 or between the rotors 1, the gap detector 16
A signal is output from the regulator 17 to the regulator 17, a control signal is output from the regulator 17 to the on-off control valve 10 and the pressure control valve 13, the on-off control valve 10 or the pressure control valve 13 is controlled, and the outlet side of the cylinder device 6 is controlled. The pressure of the pressurized fluid supplied to the chamber 7 is lowered, or the pressure of the oil supplied to the chamber 8 on the inlet side is increased. As a result, the rotor 1 is pressed in a direction opposite to the reverse thrust direction, preventing reverse thrust force from acting on the rotor 1, and restricting the movement of the rotor 1, thereby preventing troubles caused by contact of the rotor 1, etc. be done.

In the above embodiment, the oil supply pump 12 was used, but gas pressure may also be used. In addition, although pressure fluid is supplied to the chamber 7 on the outlet side of the chambers on both sides of the cylinder device 6 and the pressure in the chamber 8 on the inlet side is increased, the pressure fluid is simply supplied to the chamber 7 on the outlet side. It is also possible to simply supply the pressure fluid and reduce the pressure of the pressure fluid.

〔Effect of the invention〕

According to the reverse thrust prevention device for a screw expander of the present invention, the rotor position detection device that detects the axial displacement of the rotor and the cylinder device that presses the rotor shaft in the axial direction are provided as described above, and the piston of the cylinder device is provided. Since the pressure in one of the two chambers is controlled by a control valve that is activated by a signal from the rotor position detection device, reverse thrust occurs when starting or stopping, and the rotor is When the rotor is displaced in the axial direction, the control valve is actuated and a force opposing the reverse thrust is applied, so that troubles caused by displacement of the rotor can be reliably prevented.

[Brief explanation of drawings]

FIG. 1 is a block diagram of an embodiment of the present invention, and FIG. 2 is a schematic block diagram of a conventional example. 1 is a rotor, 5 is a piston, 6 is a cylinder device, 7 and 8
1 is a chamber, 9 is a pressure fluid source, 10 is an opening/closing control valve, 12 is an oil supply pump, 13 is a pressure control valve, 15 is a detection collar, 16 is a gap detector, 17 is a regulator, and 19 is a reverse thrust force.

Claims (1)

[Claims] 1. A rotor position detection device for detecting the axial position of the rotor is provided, and a cylinder device whose component is a piston attached to the rotor shaft is provided, and an inlet side chamber formed on both sides of the piston of this cylinder device. A reverse thrust prevention device for a screw expander, comprising a control valve that controls the pressure of at least one of the chambers on the outlet side based on a signal from the rotor position detection device.