JPS63143396A - Capacity control device of screw compressor - Google Patents

Abstract

PURPOSE:To freely change the starting time of delivery by the screw compressor in the caption by installing control valves which can be moved along rotor-axes in grooves provided on both sides of the groove in which a central control valve is fitted movably along a rotor-axes in a rotor-casing. CONSTITUTION:A central control valve 10 is installed so that it can be moved along the rotor-axes in a groove 9 formed in a rotor-casing 4. Control valves 12 are installed so that they can be moved along the rotor-axes in the grooves 11 provided on both sides of the groove 9 in the rotor-casing 4. By moving the central control valve 10 and the control valves 12 simultaneously or nonsimultaneously and controlling the by-pass timing, the starting time of delivery can be freely changed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a capacity control device for a screw compressor that can freely change the discharge start timing depending on the degree of capacity control of the compressor.

Generally, in a screw compressor, as shown in Fig. 1, a male rotor 1 and a female rotor 2 mesh synchronously in contact or in a non-contact state (in the latter case, a synchronous gear is required), and a working chamber 3
(Male rotor 1, female rotor 2, rotor casing 4
(refers to the groove-shaped space formed by the side casing 5 or 6), the fluid is compressed by hermetically reducing the volume of the working chamber 3, and then discharged. To control the capacity of the rotor, a slide valve 8 is used which moves in the groove 7 in the axial direction of the rotor.

That is, the working chamber 3 when the capacity of the compressor is not controlled.
The PV diagram (pressure-volume diagram) of is shown by a solid line in Fig. 2, and during volume control, the slide valve 8 is moved to the position shown in the figure, and suction is fully drawn into the working chamber 3. The fluid is returned to the suction side as it is without being compressed by an amount corresponding to S, and then compression is started by hermetic reduction of the volume of the working chamber 3, and when the pressure becomes almost equal to the pressure on the discharge side, the fluid is discharged. It looks like it will be done.

At this time, the PV diagram during capacity control of the compressor is shown by a chain double-dashed line in FIG.

Now, in the conventional capacity control device for a screw compressor as described above, once the degree of capacity control of the compressor is determined, the timing to start discharging the fluid in the working chamber 3 is uniquely determined according to this degree, and the discharge side If the pressure in the working chamber 3 fluctuates and becomes higher or lower than the standard value, as is clear from Figure 3, which shows the PV diagram of the working chamber 3, there will be excess or insufficient compression in the working chamber 3. There is a problem in which a work loss, that is, a power loss, occurs corresponding to the shaded area.

Furthermore, there is also the drawback that noise is generated at this time.

This is due to the fact that the discharge start timing cannot be freely changed according to the degree of capacity control of the compressor. Ideally, the discharge start timing can also be freely changed according to the rotation speed of the compressor. It is desirable to have a structure that allows for

Further, the above-mentioned drawbacks also appear when this screw compressor is used as a supercharger for an internal combustion engine.

In other words, when a screw compressor is used as a supercharger as shown in Fig. 4, generally the supply air in the working chamber 3 is returned to the suction side for a certain period of time (normally, this period is Since the working chamber 3 is configured to communicate with the discharge side after the compression process (optimized at the engine capacity), the slide valve 8 can be moved in the partial load range of the engine to prevent overload. When the capacity of the feeder is controlled, as described in FIG. 3, losses occur due to overcompression within the working chamber 3, and noise is also generated.

This is a phenomenon that occurs because the discharge start timing of the intake air in the working chamber 3 is too late, and can be solved if the discharge start timing can be changed.

Furthermore, the slide valve 8 is moved fully to control (reduce) the capacity of the supercharger until the discharge side becomes negative pressure, and the working chamber 3
If the communication between the working chamber 3 and the discharge side is started just before (near) the intake air in the chamber finishes returning to the suction side, the working chamber 3
As is clear from Figure 5, which shows the P-V diagram of
It should be possible to improve the engine's fuel efficiency (even in diesel engines, by reducing the idle noise of the engine, etc.)
(The intake air may be throttled to create negative pressure in the intake passage.)

Conventionally, after the intake air in the working chamber 3 has been returned to the intake side,
Since it is connected to the discharge side after a certain period of compression process, it is completely impossible for power to be generated.

This is because the discharge start timing of the intake air in the working chamber 3 cannot be freely changed depending on the degree of capacity control of the supercharger.

In order to solve the above-mentioned drawbacks, the present invention attempts to provide a capacity control device that can freely change the discharge start timing depending on the degree of capacity control of the compressor, and will be described below with reference to the drawings.

FIG. 6 shows an embodiment of the capacity control device for a screw compressor according to the present invention, in which a groove 9 formed in the rotor casing 4 is shown.
A central control valve 10 is provided which is movable in the rotor axial direction, and the central control valve 10 is movable in the rotor axial direction through grooves 11 formed on both sides of the groove 9 in which the central control valve 10 is fitted and which is formed in the rotor casing 4. The central control valve 10 and the control valve 12 are supported by linear ball bearings, etc., as shown in the cross-sectional view on the right, so that they can move smoothly (7th As shown in the figure, shafts 17 and 18 each having a circular cross section may be integrally formed and supported by bearings).

The inner wall surfaces of each of the central control valve 10 and the control valve 12 form part of the inner peripheral surface of the rotor casing 4,
They are adapted to be moved by levers 15 and 16, respectively.

The levers 15 and 16 may each be driven by a dedicated drive device, or only the lever 16 may be driven by the drive device, and the lever 15 may be interlocked with the lever 16 via a cam, and the profile of this cam may be adjusted as appropriate. By determining the control position of the lever 15, the control position of the lever 15 may be freely determined corresponding to that of the lever 16. The control position is as shown in Fig. 8).

When controlling the capacity of the compressor, the levers 15 and 16 move the central control valve 10 and the control valve 12 to the positions shown in the figure (Fig. 6), and the fluid fully sucked into the working chamber 3 flows through the groove 9. , 11 through a portion communicating with the suction side of the passage 13.
The fluid remaining in the working chamber 3 is then hermetically compressed by reducing the volume of the working chamber 3, until the pressure becomes almost equal to the pressure on the discharge side. The liquid is discharged from the passage 14 to the discharge side via the portion of the groove 9 that communicates with the discharge side.

In such a case, when pressure fluctuation occurs on the discharge side and becomes higher or lower than the standard value, the central control valve 10 is moved by the lever 15 and the working chamber 3
Control is performed so that the discharge is started when the pressure inside becomes almost equal to the pressure on the discharge side.

Therefore, the excess or deficiency of compression within the working chamber 3 disappears, and there is no work loss, ie, power loss, corresponding to the shaded area in FIG. 3, and no noise is generated.

In this way, the timing of starting discharge of the fluid in the working chamber 3 can be freely changed according to the situation with respect to the degree of capacity control of the compressor, thereby achieving the object of the present invention.

When controlling the capacity of the compressor, the control valve 12 may be moved and the central control valve 10 may also be moved at the same time, or depending on the situation, the control valve 12 may be moved but the central control valve 10 may be moved. There may be cases where it is not allowed.

That is, in the present invention, the central control valve 10 and the control valve 12
By moving the fluid in the working chamber 3 simultaneously or asynchronously, the timing of the return end when the fluid in the working chamber 3 is returned to the suction side through the portions communicating with the suction side of the grooves 9 and 11 and the inside of the working chamber 3 can be determined. When the remaining fluid is discharged to the discharge side through the portion of the groove 9 that communicates with the discharge side, the discharge start timing is changed simultaneously or asynchronously.

Next, considering the case where such a screw compressor is used as a supercharger for an internal combustion engine, when controlling the supercharger to maximize its capacity and fully supercharging, the central control valve 10,
The control valve 12 is in the position shown in Fig. 8, but in the partial load range of the engine, the control valve 12 is moved appropriately as shown in Fig. 6 to reduce wasteful charge air compression work loss of the supercharger and The central control valve 10 is appropriately moved to control the discharge start timing of the intake air in the working chamber 3, thereby preventing over- or under-compression within the working mass 3.

In this way, the timing of the discharge start of the intake air in the working chamber 3 can be freely changed according to the degree of capacity control of the supercharger, thereby achieving the object of the present invention.

Therefore, the central control valve 10 and the control valve 12 are moved fully to control (reduce) the capacity of the supercharger until the pressure on the discharge side becomes negative pressure. (In the engine, the engine is kept in a low load range including the idling state), and communication between the working chamber 3 and the discharge side is started near (usually just before) the time when the intake air in the working chamber 3 finishes returning to the suction side. Therefore, the work corresponding to the shaded area in Figure 5, that is, the power, is generated in the supercharger,
It will be easily understood that the fuel efficiency of the engine can be improved (at this time, the intake air in the working chamber 3 may also be discharged through a small discharge port formed in the side casing 6).
.

In this case, the central control valve 10 (lever 15) is linked to the control valve 12 (lever 16) via a cam with a suitable profile, so that the accelerator pedal drives the control valve 12 (lever 16). do.

Furthermore, by using a three-dimensional cam as the cam and moving the three-dimensional cam in its axial direction, it is also possible to move the central control valve 10 to the optimal control position for various conditions.

If more intake air is required to be supplied to the engine, the control valve 12 and central control valve 10 are moved to supply more intake air to the engine via the supercharger.

Instead of driving the control valve 12 (lever 16) with an accelerator pedal, in a diesel engine with a pneumatic governor, negative pressure introduced into the governor can be used.

That is, as shown in FIG. 9, the control valve 12 (lever 16 ).

Reference numeral 20 is a throttle valve that is linked to the accelerator pedal, and since the negative pressure generated by the small ventilator 21 is introduced into the pneumatic governor, the drive device 22 moves the control valve 12 to a control position according to the fuel injection amount. It will be forced.

As a method for moving the control valve 12, there is another method using a computer.

In other words, when information such as the degree of opening of the accelerator pedal and the rotational speed of the engine are input into the computer as electrical signals, the computer outputs calculation results corresponding to these input values, and the output signal from this computer operates the stepping motor. The control valve 12 is moved.

The objective of the invention is thus fully achieved.

In FIG. 6, the central control valve 10 plays the role of changing the return end timing when returning the fluid in the working chamber 3 to the suction side,
FIG. 10 shows an embodiment in which the control valve 12 plays the role of changing the discharge start timing when discharging the fluid remaining in the working chamber 3 to the discharge side (the central control valve 10, the control valve (The lever for moving 12 is omitted.)

That is, in FIG. 10, the central control valve 10 and the control valve 1
2 simultaneously or asynchronously to return the fluid in the working chamber 3 to the suction side through the part of the groove 9 that communicates with the suction side, and when the fluid remains in the working chamber 3. The discharge start timing when the fluid is discharged to the discharge side through the part of the groove 11 (which may include the groove 9) that communicates with the discharge side is changed simultaneously or asynchronously. be.

In this way, the timing of starting discharge of the fluid in the working chamber 3 can be freely changed according to the situation with respect to the degree of capacity control of the compressor, thereby achieving the object of the present invention.

As a means for moving the central control valve 10 and the control valve 12, in addition to using a lever, there is also a method using a rack and pinion.

Since the present invention is configured as described above, the timing at which fluid in the working chamber starts to be discharged can be freely changed depending on the degree of capacity control of the compressor.

[Brief explanation of the drawing]

Figure 1 is a diagram of the capacity control device of a conventional screw compressor.
Figures 2, 3, and 5 are PV diagrams, Figure 4 is a diagram of an internal combustion engine with a supercharger, Figures 6, 7, 8, and 10 are diagrams of a capacity control device for a screw compressor according to the present invention, FIG. 9 is a diagram of the drive device. 1 is a male rotor, 2 is a female rotor, 3 is a working chamber, 4 is a rotor casing, 5 and 6 are side casings, 7 and 9
・11 is a groove, 8 is a slide valve, 10 is a central control valve, 12
is a control valve, 13 and 14 are passages, 15 and 16 are levers, 1
7 and 18 are shafts, 19 is an intake passage, 20 is a throttle valve, 21 is a small vent cherry, and 22 is a drive device.

Claims (1)

[Claims] (1) A screw compressor having a male rotor and a female rotor is provided with a central control valve movable in the axial direction of the rotor in a groove formed in a rotor casing, and both sides of the groove into which the central control valve is fitted. a control valve that is movable in the rotor axial direction in a groove formed in the rotor casing, and the inner wall surface of each of the central control valve and the control valve is in contact with the inner circumferential surface of the rotor casing. forming a part and communicating the fluid in the working chamber of the screw compressor to the suction side of the groove by moving the central control valve and the control valve simultaneously or asynchronously. Simultaneously or non-simultaneously changing the return end timing when returning to the suction side and the discharge start timing when discharging the fluid remaining in the working chamber to the discharge side via a portion communicating with the discharge side of the groove. A capacity control device for a screw compressor.