JPS59119084A - Capacity controlling apparatus for screw compressor - Google Patents

Abstract

PURPOSE:To enable to move a slide valve from its minimum-load position without fail at the time of starting a compressor, by taking out pressure near the position of a piston when the load becomes minimum. CONSTITUTION:A chamber A in a cylinder 4 is always balanced on the low- pressure side while the pressure in a chamber B is high. When a slide valve 3 is located at its minimum-load position, pressure is taken out from a hole 13 formed in the high-pressure chamber B in the cylinder 4 at a position near a hydraulic piston 5 and the pressure is detected by a pressure switch 11. Here, if the slide valve 3 is not located at its minimum-load position, the hydraulic piston 5 is located on the right side of the hole 13, so that the pressure switch 11 is not operated. This ON-OFF switching of the pressure switch 11 is used for control at the time of starting a driving motor.

Description

[Detailed Description of the Invention] [Field of Application of the Invention] The present invention is a screw compression system that continuously adjusts the capacity by switching the hydraulic pressure and operating a slide valve by opening and closing a number of solenoid valves. This relates to a capacity control device for a machine.

[Prior art]

A conventional capacity control device for a screw compressor that continuously adjusts the capacity will be explained with reference to FIG. 1. In a screw compressor 1, refrigerant gas enters through a suction port 6 and is compressed by a screw rotor 2. and is discharged from the discharge lower. Here, the capacity of the screw compressor 1 can be adjusted by moving the slide valve 3, which forms part of the outer periphery of the screw rotor 2, in the axial direction of the screw rotor 2. This is done by bypassing the air to the suction side through the opening 8 formed between the slide valve 3 and the screw compressor 1. The slide valve 3 operates in conjunction with a hydraulic piston 5 in the cylinder 4 to open and close chambers A and B in the cylinder 4, which are controlled by the hydraulic piston 5, by the opening and closing operations of electromagnetic valves 20, 21, and 22. The slide valve is actuated via the hydraulic piston by supplying and discharging hydraulic pressure. That is,
If the pressure on the A chamber side partitioned by the hydraulic piston 5 in the cylinder 4 is low and the pressure on the B chamber side is high, the hydraulic piston 5
Then, the slide valve 3 moves to the left, the opening 8 becomes larger, and the load increases. This person will explain the operation of the solenoid valves 20, 21 and 22 for controlling the pressure in chamber B. First, when reducing the load, open the solenoid valves 20 and 21.
Close. Through this operation, the pressurized oil supplied through the oil supply pipe 9 passes through the solenoid valve 20 and fills the B chamber, and the A chamber is drained through the solenoid valve 21 to communicate with the low pressure side. , the hydraulic piston 5 is pushed to the left and the load e is reduced. When increasing the load, the solenoid valve 22 is opened and the solenoid valve 2L1.21 is closed. By this operation, the pressure in chamber B becomes low. In addition, although the pressure in the A chamber is maintained at a low pressure state when the load is reduced, the slide valve 3 always has a pressure between the discharge side pressure (approximately 13 kg/cal) and the low pressure side pressure (approximately 1 clause/d). A difference occurs, and a force to compensate for this pressure difference is applied in the direction of increasing the right-hand side load.For this reason, the pressure in the passenger compartment is low, but the slide valve and hydraulic piston 5 are under load. move in the direction of increasing the value, that is, to the right.

In this way, it is possible to adjust the capacity of the system screw compressor by changing the hydraulic circuit.

However, the conventional example of the above structure has the following problems.

Since the screw compressor is normally started under the minimum load condition, oil is supplied to the oil supply pipe 9 using an oil pump (not shown) before starting the screw compressor, and the solenoid valves 20 and 21 are opened to forcibly close the slide valve 3. is moved to the minimum load position, but for some reason the slide valve 3 may not move to the minimum load position and remain in the intermediate position. The load increases, and the overcurrent of the motor may cause the machine to stop or burn out.

The above causes are due to the oil pump's lubricating time being short, the resistance of the oil supply piping being large and the oil not being completely supplied into the Bfi, or the sliding resistance of the slide valve 3 and piston 5 being large and the slide valve 3 and piston 5 may not be able to reach the minimum load side. For this reason, it is necessary to detect that the screw compressor is at its minimum load when starting up.

[Purpose of the invention]

The present invention was invented in view of the above, and an object of the present invention is to easily detect the minimum load position of the slide valve and to ensure that the slide valve starts at the minimum load position at the time of activation.

[Summary of the invention]

The A chamber side in the hydraulic cylinder is always balanced with the low pressure side by opening and closing the solenoid valve 23, and the B chamber side is always on the high pressure side when the load is less than 100%.

In order to achieve the above object, the present invention extracts the pressure on the B chamber side near the piston when the minimum load is reached.

This position produces high pressure at minimum load. The present invention is characterized in that by detecting this high pressure, the pressure switch is operated to detect the load position.

[Embodiments of the invention]

An example of the present invention will be explained below with reference to FIG.

The difference between this example and the conventional example shown in FIG. 1 is that when the slide valve 3 is at the minimum load position, the cylinder wall near the hydraulic piston 15 in the B chamber is located on the still pressure side of the cylinder chamber 4. The structure is such that the pressure is taken out through the hole 13 and connected to the pressure switch 11 (69).The other parts are the same as those of the conventional example shown in FIG.

The A chamber side in the cylinder 4 is always balanced on the low pressure side, and the B chamber side is on the contrary high pressure sb. At this time, when the slide valve 3 is at the minimum load, B is the high pressure side near the hydraulic piston 5.
The pressure is taken out through the hole 13 of the cylinder 4 on the chamber side and detected by the pressure switch 11.

According to the above structure! >, pressure switch 11 due to the pressure of Bg
works. Here, the low pressure side pressure is usually about IK9/cxi
z The pressure on the high pressure side is about 13 Kg/d, which is hD, and there is a sufficient pressure difference, and the set value may be set to about I Q Kg /cal. Here, if the slide valve 3 is not in the minimum load position, the hydraulic piston 5 is on the right side of the hole 13,
Therefore, the hole 13 indicates the pressure on the A chamber side, which is the low pressure side, and therefore the pressure switch 11 does not operate. This ON-OF'F' operation of the pressure switch can be electrically detected to detect that the slide valve 3 of the screw compressor 1 is at the minimum load position, and this can be used to control the start-up of the drive motor. That is, the electric motor may be driven when the pressure gauge inch is operating, and an alarm signal may be issued when it is not operating.

FIG. 3 shows another embodiment, and this embodiment is different from the embodiment shown in FIG. 12 and the hole 13 near the hydraulic piston 5 on the side of chamber B, which is at high pressure, are detected, and both pressures are connected to the differential pressure switch 11', and the pressure difference between the two pressures is detected by the differential pressure switch 11' It can detect and identify the operation. If the slide valve 3 is not in the minimum load position, the hydraulic piston 5 is located on the right side of the hole 13, so the holes 12 and 13 indicate the pressure on the A chamber side that can be used with low pressure, and therefore the differential pressure switch 11 'doesn't work. This ON-OFF operation of the differential pressure switch may be electrically detected to detect that the slide valve 3 is at the minimum load position, and this may be used to control the start-up of the drive motor 1 of the screw compressor 1. That is, when the differential pressure switch is operating, the electric @iso is driven, and when it is not operating, it is sufficient to issue an alarm signal.

〔Effect of the invention〕

As explained above, according to the present invention, it is possible to easily detect that the screw compressor is at the minimum load, and it is possible to easily detect that the screw compressor is at the minimum load. It is possible to prevent the increase in load, stoppage or burnout of the motor due to overcurrent of the motor.

[Brief explanation of drawings]

Fig. 1 is a system diagram showing a conventional capacity control device for a screw compressor, Fig. 2 is a system diagram of a capacity control device showing one embodiment of the present invention, and Fig. 3 is a system diagram showing a capacity control device showing another embodiment. This is a diagram of the system.

Claims (1)

[Claims] A slide valve that forms part of the casing that houses the screw rotor, and a piston connected to this slide valve are housed in a cylinder chamber, and high pressure oil is supplied and discharged to the left and right chambers of the piston to move the slide valve and control the capacity. The slide valve is at the minimum load position in the equipment used! At some point, the pressure in the high pressure chamber near the piston that acts on the piston is taken out and engaged with the pressure switch, or alternatively, the differential pressure switch is engaged, and the pressure switch or the differential pressure is activated at the detected pressure. A capacity control device for a screw compressor, characterized by operating a switch and detecting the minimum load position of a slide valve.