JPH0458092A - Capacity control device for screw compressor - Google Patents

Abstract

PURPOSE:To quickly increase the output of a compressor with a slide valve operated even when the difference in pressure is low where the difference in pressure can hardly be distinguished by providing a pressure difference detector detecting the difference in pressure between the suction side and the discharge side of the compressor, and thereby interposing a closing valve for an auxiliary pressurizing passage, which is opened when the difference in pressure is low at the time of capacity control to a load-up side. CONSTITUTION:When capacity control to load-up side is performed, if the difference in pressure between high pressure at the discharge side and low pressure at the suction side in a compressor 1 is lower than a definite one, the difference in pressure is detected by a pressure difference detector 13, a closing valve 14 provided for an auxiliary pressurizing passage 12 is opened, gas under intermediate pressure in the halfway of the compression stroke of the compressor 1 which is higher in pressure than the suction side, is introduced into either of a rod side chamber 10 which performs load-up control, and a head side chamber 9. This thereby allows a piston 5 to be moved by means of the difference in pressure between pressure acting on the rod side chamber 10 and pressure acting on the head side chamber 9, that is, the difference in pressure between pressure at a high pressure side to which intermediate pressure is added and pressure at the suction side (low pressure side), thereby making it possible to increase the output of the compressor with the slide valve 4 operated.

Description

Detailed Description of the Invention (Industrial Field of Application) The present invention relates to a capacity control device for a screw compressor mainly used in a refrigeration system, and more specifically, to a capacity control device for a screw compressor used mainly in a refrigeration system. The present invention relates to a capacity control device for a screw compressor, which controls the capacity of a compressor by selectively communicating with the piston and operating a slide valve to the load-up side by moving a piston using a pressure difference between high and low levels.

(Prior art) Conventionally, hydraulic pressure was used to selectively communicate the rod side chamber and head side chamber of the piston with the high pressure side oil area and the low pressure side area, and the slide valve was moved by the pressure difference between the high and low pressures, and the screw For example, the one that controls the capacity of the compressor is disclosed in Japanese Patent Application Laid-Open No. 1986-
This is already known as disclosed in Japanese Patent No. 49391.

As shown in FIG. 2, this prior art has a slide valve (
C) and the piston (D) are connected via the rod (E), while the head side chamber (F) is always communicated with the suction side via the piping (G), and the piston (D) is interposed in the piping (G). The rod side chamber (M) is connected to the suction side and the pressure oil source (J) through a solenoid valve (L) installed in a solenoid valve (H) and an oil supply pipe (K) connected to the pressure oil source (J). Pressure oil is introduced from the pressure oil source (J) into the rod side chamber (M) so that the pressure oil can selectively communicate with the piston (D).
) to load down the rod side chamber (M), and discharge pressure oil from the rod side chamber (M) to remove the slide valve CC').
The capacity of the screw compressor is controlled by moving the piston (D) by the differential pressure acting before and after the piston (D), and by moving the slide valve (C) that is linked to the piston (D) to perform load-up. That's what I do.

(Problems to be Solved by the Invention) By the way, the pressure in the high-pressure side oil region is used as the pressure oil source (J), and the piston (D) is moved by the pressure difference between the high and low pressures, and the slide valve (C) For those that perform capacity control, when it is difficult to create a pressure difference between the high-pressure side oil area and the suction side, such as during startup, in a large refrigeration system where it is difficult to create a pressure difference, or during cooling operation in winter, the piston (D)
This causes the problem that capacity control cannot be performed properly and load-up cannot be performed quickly. In addition, in order to avoid such problems, it is possible to use a separately provided oil pump as the pressure oil source (J), but the problem is that the structure of the entire compressor becomes complicated due to the separately provided oil pump. occurs.

The present invention is intended to solve the above problems, and its purpose is to perform load-up control using the pressure in the high-pressure side oil region without installing a separate oil pump, while also controlling the high pressure on the discharge side and the low pressure on the suction side. The object of the present invention is to provide a capacity control device for a screw compressor that can quickly load up by moving a slide valve even when the pressure difference between the high and low pressures is low.

(Means for Solving the Problem) In order to achieve the above object, the present invention provides a slide valve (
4) and a piston (5) for adjusting the position of the slide valve (4), the rod side chamber (10) of the piston (5).
) and the head side chamber (9) are selectively communicated with the high pressure side oil region via the switching means (7), and the slide valve (
In the capacity control device for a screw compressor, the screw compressor (4) is operated to the load-up side to perform capacity control, and the compressor (1) is connected to a high pressure pipe (15) communicating with the high pressure side oil area.
) is provided with an auxiliary pressurizing passage (12) that communicates during the compression process, and a differential pressure detector (13) is provided to detect the differential pressure between the suction side pressure and the discharge side pressure of the compressor (1). , the auxiliary pressurizing passage (12) is equipped with an on-off valve (14) that opens when controlling the capacity to the load-up side and when the pressure difference is low.

(Function) When performing capacity control on the load-up side, the compressor (
1) When the differential pressure between the discharge side high pressure and the suction side low pressure is below a certain level, the differential pressure detector (13) detects this differential pressure, and the auxiliary pressure passage (12) detects the differential pressure. ) is opened, and the intermediate pressure gas during the compression process of the compressor (1), which is higher than the suction side pressure, is transferred to the rod side chamber (10) and the head side chamber (10) for load-up control.
9), the height differential pressure is low (both the piston (5) and the rod side chamber (10)
The slide valve (4) can be moved by the differential pressure acting on the head side chamber (9), that is, the differential pressure between the high pressure side pressure to which the intermediate pressure is added and the suction side (low pressure side) pressure.
) can be quickly moved to the load-up side.

Therefore, the slide valve (4) can be moved using the differential pressure between the high-pressure oil area and the low-pressure side without installing a separate oil pump. By operating the slide valve (4), the compressor (
1) can be loaded quickly.

(Example) Figure 1 schematically shows an example of a refrigeration system using the screw compressor capacity control device of the present invention. The refrigerant pipe (3) connected to the side and the suction side is equipped with an oil separator (31), a condenser (32), a liquid receiver (
33), an expansion valve (34), and an evaporator (35) are interposed, and the refrigerant is circulated by the operation of the compressor (1) to form a refrigeration cycle.

Further, the compressor (1) is movably arranged with two slide valves (4) (4) for controlling the capacity of the compressor (1), and a piston (5) is movably arranged. An internal cylinder (51) is provided, and the piston (5) and the slide valves (4) (4) are interlocked via a rod (52).

On the other hand, an oil tank (61), an oil filter (62) and an oil cooler ( 63) are connected in order, and oil can be supplied to each part of the compressor (1) that requires lubrication through the oil supply pipe (6).

Further, the oil supply pipe (6) is a high pressure side oil area,
A high pressure pipe (15) is connected to this oil supply pipe (6), and
A low pressure pipe (8) communicating with the suction side of the compressor (1) is provided, and these high pressure pipes (15) and low pressure pipes (8) are connected to two primary boats (P) and two secondary boats (T). Next side switching bow)
(A) and (B), through a switching means (hereinafter referred to as a switching valve) (7) consisting of an electromagnetically operated switching valve,
It communicates with the cylinder (51).

That is, the high pressure pipe (15) is connected to the primary side boat (P) of the switching valve (7), and the other primary side boat (P) is connected to the high pressure pipe (15).
(T) is defined by a low pressure pipe (8) communicating with the suction side of the compressor (1), and one of the secondary side switching boats (A) and (B) is defined by the piston (5), respectively. A head side pipe (91) that communicates with the head side chamber (9) that is connected to the head side chamber (9) and a rod side pipe (11) that communicates with the rod side chamber (10) are connected to the other side, and the switching valve (7) is electromagnetically connected to the head side pipe (91) that communicates with the head side chamber (9). A high pressure pipe (15) which communicates the rod side chamber (10) and the head side chamber (9) with the oil supply pipe (6) which is a high pressure side oil region via the switching valve (7) by controlling switching. and low pressure pipe (8
), and the high pressure pipe (15
) to the rod side chamber (10) and the low pressure pipe (8) to the head side chamber (9), thereby moving the slide valve (4) in the direction of the arrow through movement of the piston (5). and load up the high pressure pipe (1).
5) to the head side chamber (9) and the low pressure pipe (8) to the rod side chamber (10), the slide valve (4) is moved in the opposite direction of the arrow through the movement of the piston (5). By moving the slide valve (4) as described above, the screw compressor (
1) Capacity control is performed.

Therefore, in the refrigeration system configured as described above, the screw compressor capacity control device shown in FIG.
An auxiliary pressure passage (12) communicating with the compressor (1) during the compression process is provided, and a differential pressure detector ( 13
) is provided in the auxiliary pressurizing passage (12), and an on-off valve (1
4) is installed, and when the differential pressure is low, an intermediate pressure during the compression process, that is, an intermediate pressure lower than the pressure immediately before discharge but higher than the suction pressure, is applied to the high pressure pipe (15), The pressure inside the high-pressure pipe (15) is increased so that load-up control can be performed appropriately even when the differential pressure is low.

That is, the condensation pressure of the condenser (32) and the evaporator (35)
When loading up when the differential pressure between the high pressure and the low pressure determined by the evaporation pressure of is low, the rod side chamber (1
Even if high pressure, that is, oil in the high pressure side oil region is introduced into the compressor (1), the piston (5) does not operate quickly and the desired capacity control cannot be performed appropriately. By applying intermediate pressure during the compression process to the rod side chamber (10), a pressure difference of more than a predetermined value is generated between the rod side chamber (10) and the head side chamber (9), and this pressure difference causes the piston (5 ) can be operated quickly to appropriately control the desired capacity.

Next, the operation of the capacity control device for the screw compressor (1) configured as described above will be explained.

The high-pressure refrigerant gas discharged from the compressor (1) separates oil in the oil separator (31), enters the condenser (32), and becomes liquid refrigerant. This liquid refrigerant passes through the expansion valve (34), removes heat from the evaporator (35), and vaporizes, and the low-pressure gas refrigerant is sucked into the compressor (1).

On the other hand, the oil separated from the gas refrigerant by the oil separator (31) is cooled by the oil cooler (63) and then sent to each part of the compressor (1) via the oil supply pipe (6).

When the compressor (1) is to be loaded up when a sufficient differential pressure between the high pressure side oil area and the suction side is obtained, the switching valve (7) is switched and the -next side boat is loaded. (P) and the secondary side switching boat (B), and the - next side boat (T) and the secondary side switching boat (A) are communicated, and by this switching, the rod side chamber ( 10
) is subjected to high pressure from the high-pressure side oil area and becomes high pressure, while the head side chamber (9) communicates with the suction side via the low-pressure pipe (8) and becomes low pressure, so both chambers ( 9) (10
) causes the piston (5) to move into the head side chamber (9).
direction, and in conjunction with this movement, the slide valve (4
) moves in the direction of the arrow to load up.

On the other hand, when attempting to load down the compressor (1), switch the switching valve (7),
-Next side port) (P) and secondary side switching boat (A),
In addition, the negative side boat (T) and the secondary side switching port) (B)
The head side chamber (9) is connected to the high pressure pipe (
High-pressure oil pressure is applied from the piston (15) to create a high pressure, while the rod side chamber (10) communicates with the suction side via the low-pressure pipe (8) to create a low pressure, and the differential pressure causes the piston (
5) moves toward the rod side chamber (10), and in conjunction with this movement, the slide valve (4) moves in the opposite direction to the arrow to perform load down.

Further, when the slide valve (4) is moved in a desired direction and then stopped at a desired position as described above, the switching valve (7) is set to the neutral position. Then, the negative side bow of the switching valve (7) (P) (
The communication between the high pressure pipe (15) and the low pressure pipe ( 8), the piston (5) is stationary and the slide valve (4) is held at a desired position.

Next, a case will be described in which load-up is performed when the differential pressure between the high pressure on the discharge side and the low pressure on the suction side is low.

In this case, the switching valve (7) is switched to the load-up side, and the differential pressure detector (13) detects that the differential pressure between the high pressure on the discharge side and the low pressure on the suction side is below a certain level. It is detected that the on-off valve (14) is
14) since it outputs a signal to open the auxiliary pressure passage (
12) is opened, and the boats (P) (B) of the switching valve (7) are opened in the rod side chamber (10).
) During the compression process of the compressor (1), a gas refrigerant having an intermediate pressure higher than the low pressure on the suction side is introduced. Therefore, the boat (A) of the switching valve (7)
A pressure difference is created between the head side chamber (9), which communicates with the low pressure pipe (8) through the pipe (T) and has a low pressure, and due to this pressure difference, the piston (5) moves quickly to The slide valve (4) can be moved in the direction of the arrow, and load-up can be performed quickly.

Therefore, as explained above, the differential pressure detector (13) detects the differential pressure between the low pressure on the suction side and the high pressure on the discharge side of the compressor (1), and The auxiliary pressurizing passage (12) is provided to connect the intermediate part of the process with the downstream side boat (P) of the switching valve (7), and the passage (12) is provided with the following steps: In addition, with a simple configuration that only requires an on-off valve (Step 4) that opens when the differential pressure is low, the slide valve can be operated by utilizing the differential pressure between the high-pressure side oil area and the low-pressure side without installing a separate oil pump. (4), the slide valve (4) can be operated reliably to control the volume even in the case of a low pressure difference between the high pressure side oil area and the low pressure on the suction side. This allows the compressor (1) to be quickly loaded.

In the above embodiment, the switching means was constructed using the switching valve (7), but the switching means may be constructed by combining a plurality of electromagnetic valves in addition to the switching valve (7). Further, although the piston (5) is of a double-acting type, it can also be applied to other types of vehicle-acting type.

Further, the high pressure pipe (15) is connected to the oil cooler (6).
3) was connected to the oil supply pipe (6) on the outlet side,
It may also be connected to the oil separator (31) area.

Further, although the rod side chamber (10) is set to high pressure to perform load-up, the head side chamber (9) may be configured to be set to high pressure to perform load-up.

(Effects of the Invention) As explained above, in the capacity control device for a screw compressor according to the present invention, one of the rod side chamber (10) and the head side chamber (9) is selectively communicated with the high pressure side oil region. ,
The compressor (1) is connected to a high pressure pipe (15) communicating with the high pressure side oil area that operates the slide valve (4) to the load-up side.
An auxiliary pressure passage (12) communicating with the compressor during the compression process is provided, and a differential pressure detector (13) is provided to detect the differential pressure between the suction side pressure and the discharge side pressure of the compressor (1), Since the auxiliary pressurizing passage (12) is provided with an on-off valve (14) that opens when the capacity is controlled to the load-up side and when the differential pressure is low, the compressor ( 1)
Even if the differential pressure between the high pressure on the discharge side and the low pressure on the suction side is below a certain level, the differential pressure detector (13) detects this differential pressure and the auxiliary pressure passage (12) is The interposed on-off valve (14) opens, and the intermediate pressure gas during the compression process in the compressor (1), which is higher than the low pressure on the suction side, flows into the rod side chamber (10) and head side chamber (9) where the load-up is performed. ) and the rod side chamber (
10) and the head side chamber (9) to a predetermined pressure difference or more, the piston (5) can be moved, and the slide valve (4) can be quickly moved to the load-up side. Therefore, without installing a separate oil pump, by using the differential pressure between the high pressure side oil area and the low pressure side pressure,
While being able to operate the slide valve (4),
Even when the pressure difference between high and low pressures is low, the slide valve (4
), the compressor (1) can be loaded up quickly and appropriately.

[Brief explanation of drawings]

FIG. 1 is a schematic layout diagram of a refrigeration system to which the capacity control device for a screw compressor of the present invention is applied, and FIG. 2 is an explanatory diagram showing a conventional example. (1)...Screw compressor (4)...
......Slide valve (6)...Piston (7)...Switching valve (switching means) (9)
・・・・・・・・・ (10) ・・・・・・・ (12) ・・・・・・・ (13) ・・・・・・・ (14) ・・・・・・・・・ ( 15) ・・・・・・ Head side chamber Rod side chamber auxiliary pressure passage Differential pressure detector on/off valve High pressure pipe Diagram

Claims (1)

[Claims] 1) Comprising a slide valve (4) and a piston (5) for adjusting the position of the slide valve (4), and switching between the rod side chamber (10) and the head side chamber (9) of the piston (5). In a capacity control device for a screw compressor, the capacity control device for a screw compressor is configured to selectively communicate with a high-pressure side oil region via a means (7) and operate the slide valve (4) to the load-up side to perform capacity control. A high pressure pipe (15) communicating with the side oil area,
An auxiliary pressure passage (12) communicating with the compressor (1) during the compression process is provided, and a differential pressure detector ( 13
) is provided in the auxiliary pressurizing passage (12), and an on-off valve (1
4) A capacity control device for a screw compressor, characterized in that it is equipped with the following.