JPH041487A - Screw compressor - Google Patents

Abstract

PURPOSE:To make automatic control over the regulation of an internal volumetric ratio Vi performable in a simple structure by installing a lifting internal volumetric ratio Vi regula tor valve and a control valve formed for making a passage selectable, respectively, and making them so as to produce a state of the internal volumetric ratio Vi suited to discharge pressure during operation of a compressor and pressure just before discharge without any operation from the outside. CONSTITUTION:Gas of suction pressure Ps is sucked from an inlet port 1 and compressed by a screw rotor 4 in rotation, and then is discharged to a discharge passage 13 of discharge pressure Pd from a discharge port 3 by way of a discharge port 2. In addition, a first chamber 23 of a control valve 21 to be connected to a discharge adjacent space comes to discharge adjacent pressure Po and a second chamber 24 to be interconnected to the discharge passage 13 to the discharge pressure Pd, respectively. When it is set by Po>Pd, a valve stem 28 is moved to the side of a passage 16 together with a diaphragm 22, and a valve element 27 opens this passage 16. On the other hand, since pressure almost equal to the discharge pressure Pd acts on one end 12 of an internal volumetric ratio Vi regulator valve 7 when it is in a moving limit at the rotor side, this Vi regulator valve 7 is shifted to the counter- rotor side. In consequence, the suction side of the discharge port 2 comes to a B position, thus the internal volumetic ratio Vi is minimized.

Description

DETAILED DESCRIPTION OF THE INVENTION (Field of Industrial Application) The present invention relates to a screw compressor with variable internal volume ratio (hereinafter referred to as Vi).

(Prior Art) Conventionally, a screw compressor equipped with an l/vi control valve 61 as shown in FIG. 12 is known.

This screw compressor is formed by rotatably housing a pair of male and female screw rotors 65 that engage with each other in a casing 64 that has a suction port 62 on one side and a discharge port 63 on the other side. The casing 64 also has a partition wall 6 inside.
6, the first chamber 67 on the rotor side and the second chamber 6 on the anti-rotor side
The first chamber 67 and the second chamber 68 are provided with inlets 69X, 69Y, and 70X, 70Y for pressurized oil.A cylinder 71 is fixed thereto, and the partition wall 66 is connected to C-shaped retaining rings on both sides. It is fixed by 72.

A first piston 7 is slidably disposed in the first chamber 67 on the rotor side.
3, a second piston 74 is slidably provided in the second chamber 68 on the side opposite to the rotor, and the first piston 73 connects the VirA control valve 61 to the rotor 65 and the casing 64 via the first piston rod 75. The second piston 74 moves the slide valve 77 between the rotor 65 and the casing 64 via the second piston rod 76.
It is formed so that it can move forward and backward between it and the inner wall. Also,
Vi! The retreat position of the II mode valve 61 is restricted by a stopper 78 that is a part of the casing 64.

Further, the second piston rod 76 passes through the first piston rod door 5 so as to be relatively movable, and the slide valve 77
operates in the operating space of the Vi control valve 61 or its extension space, and controls the retreating position of the slide valve 77 via the Vi control valve 61.
This is how it is formed.

By the way, in a screw compressor, Vi=v 1/
v o (v l: theoretical maximum gL after confinement Vo: theoretical minimum volume just before discharge), and the specific heat ratio is .

When the external compression ratio is expressed as Pd/Ps (Pd: discharge pressure, Ps: suction pressure), the adiabatic efficiency is maximized when ViK=Pd/Ps.

Therefore, in order to achieve this maximum efficiency, the compressor's V
To increase i, move the Vi control valve 61 to the right in FIG.
■1 control is performed by using the PII control valve 61 as the seat valve 61.

Separately, when operating at full load, the slide valve 77 is brought into contact with the 1 control valve 61 as shown in FIG. While the sucked gas is fully compressed and discharged to the discharge port 63, in the case of partial load or no-load operation, only the slide valve 77 is moved to the right in FIG.
1, so that the gas sucked in through the suction port 62 can escape to the suction port 62 through the gap without being compressed in part or in its entirety.

(Problems to be Solved by the Invention) Vi! of the above conventional device! The Im control valve is of a slide valve type and has the advantage that Vi can be adjusted steplessly within a certain range.

On the other hand, in this device, the capacity adjustment slide valve 77 and the Vi control valve 61 are arranged in the same sliding space, and when adjusting the capacity, it is only necessary to move the slide valve 77, but when you want to change Vi, , slide valve 77 and Vi! II section valve 6
1 needs to be linked. That is, in this case, the first
Piston 73. It is necessary to open and close hydraulic passages to the spaces on both sides of the second piston 74 to operate each valve.

In this way, the slide valve type Vi control valve 61 is often provided together with the slide valve 77, resulting in an extremely complicated structure and unstable operation.

Moreover, equipment failures are likely to occur, such as contact or sticking between the screw rotor 65 and the valve, trouble with piston sliding parts, and casing destruction due to liquid compression caused by oil sealed in the cylinder.

Furthermore, it is difficult to control the vi regulating valve 61, and at present, Vi is adjusted each time by manual operation to approximately match the pressure ratio of the operating conditions.

Furthermore, in this device, when vi is increased, the Vi control valve 61 moves to the discharge side, so even during no-load operation, it is not possible to completely eliminate the compression of the gas sucked in by the screw rotor. There are various problems such as loss.

The present invention has been made to address the above-mentioned conventional problems, and aims to provide a screw compressor equipped with a control valve that has a simple structure, minimizes the causes of failure, and is easy to handle. It is something.

(Means for Solving the Problems) In order to solve the above problems, a first invention provides a rotor that rotatably accommodates a pair of male and female screw rotors, one of which opens at the suction port and the other opens at the discharge port, and mesh with each other. On the discharge side of a casing having a chamber, there is an internal volume ratio of an elevating type, which becomes part of the wall surface of the rotor chamber when the end is at the rotor side movement limit, and becomes a part of the discharge port wall surface when it is at the anti-rotor side movement limit. The pressure in the pressure chamber on the anti-rotor side of the control valve and this internal volume ratio control valve is approximately the suction pressure when the pressure immediately before discharge is higher than the discharge pressure, and approximately the discharge pressure when the discharge pressure is higher than the pressure immediately before discharge. A control valve is provided so that the flow path can be switched to adjust the pressure.

Further, in a second aspect of the invention, the valve portion of the internal volume ratio adjustment valve is V-shaped in cross section, and each side of the 7-shape is formed along the tooth tip line of the rotor, and the internal volume ratio adjustment valve is V-shaped in cross section. The piston portion of the valve has an arcuate cross-sectional profile on the anti-discharge side that extends outward from the valve portion.

(Function) By configuring as in the first invention, Vi! Ii
The control valve controls the discharge pressure while the device is operating without any external operation.
It operates automatically to create a VR condition that matches the pressure immediately before discharge, and because it uses an elevating type Vi control valve, the limit of the valve's movement toward the rotor side can be determined reliably and easily using the valve seat. This eliminates problems such as contact between the valve and rotor and wear.

Furthermore, if the rotor tooth space pressure becomes abnormally high, VitA
Since the moderation valve is fully opened automatically and quickly, it is possible to avoid damage to the equipment due to abnormal pressure, for example when liquid (e.g. refrigerant liquid, oil, etc.) enters the rotor chamber and liquid compression occurs. It becomes like this.

Moreover, by configuring as in the second invention, it becomes easy to secure the required valve seat area, and it becomes easy to process the vi control valve and its sliding space with high precision.

(Example) Next, one embodiment of the present invention will be described with reference to the drawings.

FIG. 1 shows a screw compressor according to a first embodiment of the first invention, in which a pair of male and female screw rotors 4 are meshed with each other, one opening into a suction port 1 and the other opening into a discharge port 3 via a discharge boat 2. An elevating type Vitl1 control valve 7 is provided on the discharge side of a casing 6 having a rotor chamber 5 which rotatably accommodates the rotor chamber 5. This Vi8 valve 7 consists of a valve part 8 and a piston part 9, and is always urged toward the rotor by a spring 10, so that the piston part 9 comes into contact with the valve seat 11 on the caning side when moving toward the rotor. It has become. One end 12 of the Vi control valve 7 becomes a part of the wall surface of the rotor chamber 5 when it is at the rotor side movement limit, and becomes a part of the wall surface of the discharge port 3 when it is at the anti-rotor side movement limit. The discharge passage 13 following the discharge port 3 is provided with, for example, an oil separation and recovery device (not shown), in which oil is removed from the discharged gas before being sent out, and the removed oil is stored in an oil sump at the bottom of the oil separation and recovery lid. It is designed to be temporarily stored in the section. Furthermore, an oil flow path is connected to the oil reservoir section 20 through an oil cooler, an oil filter, etc. (not shown), and to a lubrication point such as the rotor chamber 5 DEG bearing shaft sealing section.

Vi! A flow path 1 is provided in the pressure chamber 14 on the anti-rotor side of the F1 control valve 7.
5. A flow path 16 is connected to the flow path 15, and the flow path 15 communicates with the oil trap section of the oil separation and recovery device whose inside is approximately equal to the discharge pressure Pd, and the control valve 7 due to rapid oil flow in the intermediate portion. A throttle valve 17 is provided to prevent hunting, and the flow path 16 communicates with the suction port 1 via a control valve 2I.

This control valve 21 includes a first chamber 23 and a second chamber 24 separated by a diaphragm 22, and the first chamber 23 has a flow path 25.
communicates with the space just before discharge in the rotor chamber 5 at point X,
The second chamber 24 communicates with the discharge flow path 13 through a flow path 26 . Further, a valve rod 28 that operates a valve body 27 that opens and closes the flow path 16 is attached to the diaphragm 22 through the partition wall between the second chamber 24 and the flow path 16, and
A spring 29 provided within the diaphragm 22. Valve stem 28
The valve body 27 is always biased toward the side where the flow path 16 is closed.

Next, the operation of the above device will be explained.

Gas at a suction pressure Ps is sucked in from the suction port 1 by the rotating screw rotor 4, is compressed, passes through the discharge port 2, and is discharged from the discharge port 3 into the discharge flow path 13 at the discharge pressure Pd. Further, the first chamber 23 communicating with the space immediately before discharge has a pressure P immediately before discharge. , the second chamber 24 communicating with the discharge flow path 13 has a discharge pressure Pd.

Then, in the case of Po>Pd (strictly speaking, Pa>Pd+α when the pressure by the spring 29 is α), the valve rod 28 is moved to the flow path 16 side together with the diaphragm 22,
Valve body 27 opens flow path 16 . Therefore, the oil guided into the pressure chamber 14 by the flow path 15 and having a pressure approximately equal to the discharge pressure Pd escapes toward the flow path 16 that is approximately equal to the suction pressure Ps, and the pressure inside the pressure chamber 14 becomes equal to the suction pressure Ps. Get closer.

On the other hand, since a pressure approximately equal to the discharge pressure Pd acts on one end 12 of the V+m control valve 7 when it is at the rotor side movement limit, the i control valve 7 is moved toward the side opposite to the rotor. As a result, as shown in FIG. 1, the suction side of the discharge boat 2 is at position A when the Vi control valve 7 is at the rotor side travel limit, but becomes position B, and Vi is at position A. The maximum (hereinafter referred to as vi■aK) was the minimum Vi (
Hereinafter, it will be referred to as Viein).

On the other hand, in cases other than the above, the vi control valve 7 closes the flow path 16, the pressure in the pressure chamber 14 is approximately equal to the discharge pressure Pd, and the vi control valve 7 is maintained at the rotor side movement limit position. Then, as described above, the position on the suction side of the discharge boat 2 becomes A, and the state becomes Vimax (the state shown in FIG. 1).

When the discharge pressure Pd changes in this way, an adjustment of 1 V] is automatically performed in accordance with the discharge pressure Pd so as not to waste power.

Note that when the suction pressure PG is constant, a change in the discharge pressure Pd directly means a change in the external compression ratio. Figure 2 shows the relationship between this external compression ratio and track breaking efficiency, where the solid line curve I is for this device, and the two-dot chain curves ■ and ■
However, in the case of a device where Vi is fixed, V imax and V 1m1n, this device shows that a state of high heat insulation efficiency is maintained.

In addition, by using the elevating type i control valve 7 and reliably setting the limit of movement toward the rotor side with the valve seat II, problems such as contact between the vi control valve 7 and the screw rotor 4, and wear can be avoided. It is also designed not to occur.

Furthermore, in the unlikely event that liquid (e.g. refrigerant liquid) is present in the rotor chamber 5.

Even if fluid (oil, etc.) enters the tooth space and the pressure in the tooth space becomes abnormally high due to liquid compression, the control valve 21 will automatically operate to expand the discharge boat 2 to point B and clear the tooth space. It is designed to quickly open to the discharge port 3 side to prevent damage to the screw rotor due to liquid compression.

Here, the size of the Vi control valve 7 is V jmar, V
It is determined by the value of 1ain. Further, the position X of the rotor example of the flow path 25 is the tooth tip gA on the most discharge side as shown in FIG.
(In this specification, it means a spiral line along the top of the teeth of the screw rotor) reaches point B, and if L is the axial distance of one tooth at the tip of the screw rotor 4, , a position on the suction side from point B by a distance (L-β) (the meaning of β will be described later) is desirable. Under ideal conditions in which a phenomenon occurs in which the space just before the discharge opens to the discharge boat 2, the pressure tends to become equal to the discharge pressure Pd.

However, in reality, there is flow resistance, and the above phenomenon begins to appear when the space just before the discharge opens into the discharge boat 2 and then advances a little further toward the discharge side.

The above β means this slightly advanced distance.

Furthermore, the spring 10 is actually provided in Vimax.
In this state, the pressure P0 immediately before discharge is slightly higher than the discharge pressure Pd, so this is to cancel out this increased pressure.

3 to 5 show a screw compressor according to a second embodiment of the first invention, which differs from the device shown in FIG. 1 in that a control valve 21g is provided in place of the control valve 21, and a Except for the flow path configuration, is the rest substantial? The two parts are the same, and corresponding parts are given the same numbers and their explanation will be omitted.

The control valve 21a in this embodiment has two opposing faces a and b.
, a C boat, and a spool 32 slidably inserted into a casing 31 having a first driving fluid inlet y and a second driving fluid inlet 2 on two faces perpendicular to these two faces. This spool 32 is formed with a long groove 33 that communicates with the C boat 1 at all times, and a through hole 34 that communicates the a port or the b boat with the C boat via the long groove 33. The suction port 1 is connected to the oil separation and recovery device by the B boat through a flow path 36, the C boat is connected to the pressure chamber 14 through a flow path 37, and the first driving fluid inlet/outlet y is connected to the discharge flow path 13 through a flow path 38. To, the second
The driving fluid inlet/outlet Z communicates with the space just before discharge through a flow path 39 .

Then, P, > Pd (strictly speaking, P o > P d+
In the case α), as shown in FIG. 4, the spool 32 is moved to the left side in the figure, and the 8 boats and the C port are brought into communication, and the pressure in the pressure chamber 14 is approximately the suction pressure Ps.
is approximately equal to . Therefore, as in the case of the first embodiment, ■i control valve 7 moves to the side opposite to the rotor, and the device has a voltage of V 1m.
The state becomes 1n.

On the other hand, if p, < Pd, as shown in FIG. 5, the spool 32 is moved to the right in the figure, and the b port and C boat are brought into communication, and the pressure inside the pressure chamber 14 is The pressure becomes approximately equal to the discharge pressure Pd.

Therefore, as in the case of the first embodiment, the Vj control valve 7 moves to the rotor side, and the device is in the state of Vimax! ! (the state shown in FIG. 3).

Note that in this example, P. If =Pd, the spool 32 does not move, so the device maintains its previous state.

6 and 7 show a screw compressor according to a third embodiment of the first invention, which differs from the device shown in FIG. 1 in that it has a first capacity control valve 41. Except for the provision of the second capacity control valve 42 and the flow path configuration connected thereto, the others are substantially the same.
The same numbers are given to mutually corresponding parts, and the explanation is omitted.

As shown in FIG. 6, the vi control valves 7. First capacity control valve 41.
Since the second capacity control valves 42 are provided at appropriate positions, the rotor side surfaces of each valve appear at different heights in the cross section taken along the line ■-■ in FIG. , since the drawing would be complicated, in FIG. 7, the heights of the above-mentioned surfaces are made the same for convenience, and the representation is simplified.

In this embodiment, as an example, the capacity can be controlled in three stages, and the first capacity control valve 41. Each of the second capacity control valves 42 is slidably provided in a through hole whose one end opens into the rotor chamber 5, and the pressure chambers 43, 44 on the anti-rotor side are connected to the first three-way through passages 45, 46. The C boat of the switching valve 47 communicates with the H boat of the second three-way switching valve 48 . In addition, the d port of the first three-way switching valve 47 and the g port of the second three-way switching valve 48 communicate with the oil reservoir section of the oil recovery and separation, which is approximately equal to the discharge pressure Pd, via the flow path 49, and the first three-way switching valve The f-port of the valve 47 and the i-boat of the second three-way switching valve 48 communicate with the suction port 1 via the flow path 50 .

Further, a bypass flow path 51 opened at the lower side of each of the through holes is provided to communicate with each other, and a second
The through hole of the capacity control valve 42 is communicated with the suction port l.

For example, a detector such as a pressure switch or a temperature switch is provided in the discharge flow path 13, and the first three-way switching valve 47. The second three-way switching valve 48 is controlled.

More specifically, full load state 1! A case will be explained in which the load is 65% or 30% of (100%), for example.

During full load operation, d and C of the first three-way switching valve 47
The boat, the g and h boats of the second three-way switching valve 48 communicate with each other, and the pressure in the pressure chambers 43 and 44 is approximately equal to the discharge pressure Pd and higher than the pressure in the tooth space in the corresponding rotor chamber.
Capacity control valve 41. The second capacity control valve 42 is pushed to the rotor side moving end, and the rotor chamber 5 and the bypass passage 51 are cut off.

Therefore, the gas sucked in from the suction port 1 by the screw rotor 4 is compressed in its entirety without being bypassed.

Therefore, in this embodiment, in this case, the dimensions of the screw rotor 4 are determined so that the pressure in the tooth space at point X is slightly higher than the discharge pressure Pd, and the ViEQ1 control valve 7 is moved to the side opposite to the rotor. It is formed so that V1m1n is reached. FIG. 8 is an acupressure diagram in this full-load operating state, showing that almost no overcompression is performed.

Then, in the operating state of 65% load, the d and C boats of the first three-way switching valve 47 and the glue and i boats of the second three-way switching valve 48 communicate with each other, and the pressure in the pressure chamber 43 reaches the discharge pressure Pd. substantially equal, the first capacity control valve 41 has moved toward the rotor side, the pressure within the pressure chamber 44 is approximately equal to the suction pressure Ps, and is lower than the pressure within the corresponding tooth space within the rotor chamber, and has moved toward the anti-rotor side. becomes. As a result, the suction gas is returned to the suction port l from the bypass flow path 51 at the position of the second capacity control valve 42, and a 65% partial load operation is performed.

In addition, in this case, the pressure in the tooth space at point X is lower than the discharge pressure Pd, and the control valve 7 moves toward the rotor and
In the imax state, the suction gas is compressed to a pressure that slightly exceeds the discharge pressure Pd and is discharged.

FIG. 9 is an acupressure diagram in this 65% load operating state, showing that almost no overcompression occurs.

Furthermore, when the load is 35%, the first three-way switching valve 4
7 eJ boat, second three-way switching valve 48 glue.

The i-boat communicates, the pressure in the pressure chambers 43 and 44 becomes approximately equal to the suction pressure Ps, and both the first capacity control valve 41 and the second capacity control valve 42 move toward the side opposite to the rotor, and from their respective positions. The suction gas is returned to the suction port 1 via the bypass flow path 5I, and operation at 35% load is performed.

In addition, in this case, the ViU @ control valve 7 moves to the rotor side and is in the state of Vimax, and the suction gas is at the discharge pressure Pd.
After being compressed to near , it is discharged.

Figure 10 is a finger pressure diagram in this 35% load operating state, and compared to the case where the compressed gas is discharged at a pressure lower than the discharge pressure Pd, which is shown by the broken line, this device is better only in the hatched area. This indicates that the power will be reduced.

That is, since this type of device is generally formed based on the operating state of 100% load, the Vi control valve 7
In a device not equipped with the first capacity control valve 41., referring to FIG. In a 100% load operating state in which the second capacity control valve 42 has moved to the rotor side, the discharge boat 2
The pressure Po immediately before discharge at a position slightly closer to the suction side than point B at the suction side end of the pump is adjusted so that the pressure Po immediately before discharge is approximately equal to the discharge pressure Pd. For example, the 18th quantity control valve 41. In an operating state of 65% load in which the second capacity control valve 42 is moved to the side opposite to the rotor, the suction gas is hardly compressed, as shown by the broken line in FIG. 10, and the pressure P immediately before discharge is maintained. is discharged at a considerably low level, increasing power consumption.

In contrast, in this embodiment, the first capacity control valve 4I, the second
Since the VI8 node valve 7 is used in conjunction with the capacity control valve 42, the state is V imax during partial load operation, and the suction gas is compressed to a pressure approximately equal to the discharge pressure Pd before being discharged. Highly efficient operation is possible.

In addition, if the first capacity control valve 41 does not have the Vi control valve 7, the pressure in the tooth space at the position corresponding to the first capacity control valve 41 may exceed the discharge pressure Pd depending on the operating pressure conditions, and the first capacity control valve 41 may Although there is a possibility that a hunting phenomenon of the valve 41 may occur, in the case of this embodiment, since the viH valve valve 7 is used, such a phenomenon is prevented from occurring.

On the other hand, if a device without the Vi control valve 7 is configured based on the state during partial load operation, unlike the above case, overcompression will occur during full load operation, resulting in unnecessary power consumption. become.

Note that in the above embodiment, the control valve 21 is used to control the Vi regulating valve 7, but instead of this, the control valve 21a may be used in the flow path configuration shown in FIG. .

Further, in each of the above embodiments, the flow path for operating the valve that is approximately equal to the discharge pressure Pd may be communicated with the discharge port 3 or the discharge flow path 13 instead of the oil separation and recovery device, and the flow path for operating the valve that is approximately equal to the suction pressure Ps Instead of the suction port 1, the operating flow path may be communicated with the tooth groove immediately after the gas is trapped, that is, immediately after the compression is started.

Further, in each of the above embodiments, the case of an oil-filled screw compressor has been described, but the present invention is not limited thereto and can also be applied to an oil-free type screw compressor.

However, in this case, the flow path for valve operation, which is approximately equal to the discharge pressure Pd, will be communicated with the discharge port 3 or the discharge flow path 13.

Next, the second invention will be explained.

The above description of the first invention also applies to the second invention. Therefore, FIGS. 1 to 10 will also be used to show the second invention.

Furthermore, as shown in FIG. 11, in the screw compressor according to the second invention, the valve part 8 of the vi control valve 7 has a V-shaped cross section, and each side 52g, 52b of this V-shape is connected to the tooth tip line of the screw rotor 4. The piston portion 9 has a cross-sectional contour portion 53 on the suction side that extends outward from the valve portion 8 and is formed in an arc shape.

Here, since the piston portion 9 is a pressure receiving portion on which pressure from pressure oil or compressed gas acts, high dimensional accuracy is required. Therefore, a cylindrical piston can be considered, but it cannot be said to be a preferable shape in terms of structure, space, and function. In contrast, in the present invention, since the piston part 9 has an arcuate outline, high-precision machining is possible, and when the Vi control valve 7 is lowered, the discharge boat 2 at V 1m1n is completely blocked. In addition, a sufficient area of the valve seat 11 can be secured so that the piston function can be performed without any problem.

In this embodiment, the above β is set to (1/2) M when the thickness of the i control valve 7 in the rotor axial direction on the boundary line is M (see Fig. 1L).

(Effects of the Invention) As is clear from the above description, according to the first invention, a rotor chamber rotatably accommodates a pair of male and female screw rotors, one of which opens at the suction port and the other opens at the discharge port, and mesh with each other. On the discharge side of the casing, one end becomes part of the wall of the rotor chamber when it is at the limit of movement on the rotor side, and becomes part of the wall of the discharge port when it is at the limit of movement on the anti-rotor side. The pressure in the pressure chamber on the anti-rotor side of the valve and this internal volume ratio adjustment valve is approximately the suction pressure when the pressure immediately before discharge is higher than the discharge pressure, and approximately the discharge pressure when the discharge pressure is higher than the pressure immediately before discharge. It is formed by providing a control valve which is formed to be able to switch the flow path so that the flow path can be changed.

Therefore, the vi control valve can now create a Vi condition that matches the discharge pressure during operation of the device and the pressure immediately before discharge without any external operation, and it has become possible to automatically control vi adjustment with a simple configuration. Since an elevating type Vi control valve is used, the limit of movement of the valve toward the rotor side can be determined reliably and easily using the valve seat, and problems such as contact between the valve and rotor and wear can be eliminated.

Furthermore, if the tooth space pressure of the rotor becomes abnormally high, the control valve will automatically and quickly fully open, so there is no risk of damage to equipment due to abnormal pressure, for example if liquid oil enters the rotor chamber and fluid compression occurs. It can be eliminated.

Note that 80 to 90% of damage to current compressors is caused by liquid compression.

According to the second aspect of the invention, the valve portion of the internal volume ratio regulating valve has a V-shaped cross section, and each side of the 7-shape is formed along the tooth tip line of the rotor, so that the internal volume The piston portion of the ratio control valve has a cross-sectional contour portion on the anti-discharge side that extends outward from the valve portion and is formed into an arc shape.

Therefore, it is easy to secure the required valve seat area, and it is also possible to improve the machining accuracy of the control valve and its sliding space, resulting in improvements in the performance of the device.

[Brief explanation of the drawing]

FIG. 1 is a sectional view of a screw compressor according to a first embodiment of the first invention and a second invention, FIG. 2 is a diagram showing the relationship between external compression ratio and adiabatic efficiency, and FIG. 3 is a diagram showing the relationship between external compression ratio and adiabatic efficiency. 2nd embodiment, a cross-sectional view of a screw compressor according to the second invention, FIGS. 4 and 5 are cross-sectional views of the control valve of the device shown in FIG. 3, and FIG. 6 is a third embodiment of the first invention. . A sectional view of the screw compressor according to the second invention, FIG.
8 to 10 are acupressure diagrams showing the relationship between the gas suction state and pressure of the tooth groove in the device shown in FIGS. 6 and 7, and FIG. 11 is a sectional view taken along the line ■-■ A sectional view of the apparatus according to the second invention, and FIG. 12 is a sectional view of a conventional screw compressor. 1...Suction port, 3...Discharge port, 4...Screw rotor, 5...Rotor chamber, 6...Casing, 7...V
itl1 valve, 8... valve part, 9... piston part, 21
．． 21a... Control valve. Patent applicant: Agent of Kobe Steel, Ltd.
Patent attorney Maeda Ao and 1 other personFigure 1Figure 2Figure 6Figure 7Figure 3Figure 4Figure 5Figure 8Figure 9Figure 10

Claims (2)

[Claims] (1) On the discharge side of a casing, which has a rotor chamber that rotatably accommodates a pair of male and female screw rotors that are open to the suction port and the other to the discharge port and that engage with each other, when one end is at the rotor side movement limit, the rotor An elevating internal volume ratio control valve that becomes part of the wall of the chamber and becomes part of the wall of the discharge port when at the limit of movement on the anti-rotor side, and the pressure inside the pressure chamber on the anti-rotor side of this internal volume ratio control valve. and a control valve configured to be able to switch the flow path so that when the pressure immediately before discharge is higher than the discharge pressure, the pressure is set to approximately suction pressure, and when the pressure immediately before discharge is higher than the pressure immediately before discharge, it is set to approximately discharge pressure. A screw compressor featuring: (2) the valve portion of the internal volume ratio control valve has a V-shaped cross section;
Each side of this V-shape is formed along the tip line of the rotor, and the piston part of the internal volume ratio adjusting valve has an arc-shaped cross-sectional contour on the anti-discharge side that protrudes outward from the valve part. The screw compressor according to claim 1, characterized in that the screw compressor is formed as follows.