WO2020178895A1

WO2020178895A1 - Screw compressor

Info

Publication number: WO2020178895A1
Application number: PCT/JP2019/008079
Authority: WO
Inventors: 駿岡田; 雅章上川; 雅浩神田
Original assignee: 三菱電機株式会社
Priority date: 2019-03-01
Filing date: 2019-03-01
Publication date: 2020-09-10
Also published as: JP7112031B2; US20220082099A1; EP3933204A4; JPWO2020178895A1; EP3933204A1

Abstract

This screw compressor comprises an internal volume ratio variable mechanism including a variable Vi valve that enables a Vi value, which is an internal volume ratio, to be varied. In the screw compressor, the position of the variable Vi valve is controlled in two stages, and the position of the variable Vi valve when the Vi value is large is set so that compressor efficiency during operation at a predetermined high-load condition or high-compression-ratio condition reaches a Vi value equal to or greater than a set efficiency that has been set in advance.

Description

Screw compressor

The present invention relates to a screw compressor used for refrigerant compression such as a refrigerator or an air conditioner.

The screw compressor is equipped with a variable internal volume ratio valve (hereinafter referred to as a variable Vi valve), which is a slide valve that adjusts the discharge start timing to make the internal volume ratio Vi variable, and is provided from the drive device according to the operating compression ratio. There is one that adjusts the opening degree of the variable Vi valve by the driving force of (see, for example, Patent Document 1). The internal volume ratio in the screw compressor is the ratio of the tooth groove space volume at the time of suction to the tooth groove space volume just before discharge, and represents the ratio between the volume when suction is completed and the volume when the discharge port is opened. ing.

As shown in FIGS. 1 and 2 of Patent Document 1, the variable Vi valve of Patent Document 1 has an optimum Vi value calculated from a discharge pressure HP and a suction pressure LP, and a current Vi value obtained from a position detecting means. Is controlled so that the difference between Further, in order to approach the optimum Vi value during actual operation, the opening degree of the variable Vi valve is adjusted so that the motor drive power becomes the minimum.

The screw compressor has an appropriate compression ratio commensurate with the internal volume ratio, and under operating conditions in which the compression ratio during actual operation is the appropriate compression ratio, inadequate compression loss does not occur. However, when the operation is performed at a low compression ratio lower than the proper compression ratio, the gas is over-compressed to the pressure equal to or higher than the discharge pressure before the discharge port is opened, and extra compression work is performed. On the contrary, when the operation is performed at a compression ratio higher than the proper compression ratio, the discharge port opens before the discharge pressure is reached, resulting in an insufficient compression state in which a reverse gas flow occurs. All of these cause a loss of power and reduce efficiency.

Therefore, as in Patent Document 1, the position of the variable Vi valve is steplessly set so as to have an internal volume ratio that can obtain high compressor efficiency with respect to the compression ratio (discharge pressure / suction pressure) according to the operating load. A technique has been proposed in which the internal volume ratio is made variable by adjusting to.

Japanese Patent No. 4147891

In Patent Document 1, the position control of the variable Vi valve is performed steplessly, and the control amount of the variable Vi valve is calculated from the detection results of the discharge pressure, the suction pressure, and the rotation frequency. In other words, in Patent Document 1, the position control of the variable Vi valve is stepless control, which complicates the configuration and control.

The present invention has been made to solve the above problems, and an object thereof is to obtain a screw compressor capable of simplifying the configuration and control while varying the internal volume ratio. ..

The screw compressor according to the present invention is a screw compressor provided with an internal volume ratio variable mechanism including a variable Vi valve that changes the Vi value, which is the internal volume ratio, and controls the position of the variable Vi valve in two stages. The position of the variable Vi valve when the Vi value is large is such that the compressor efficiency during operation under a predetermined high load condition or high compression ratio condition is equal to or higher than the preset set efficiency. It is set to be a Vi value.

According to the present invention, since the position control of the variable Vi valve is set to two stages, the configuration and control can be simplified while the internal volume ratio is variable.

It is a schematic block diagram of the screw compressor which concerns on Embodiment 1 of this invention. 1 is a schematic diagram of an internal volume ratio variable mechanism including a drive device for a screw compressor according to Embodiment 1 of the present invention. It is an operation schematic diagram when the Vi value is large in the screw compressor which concerns on Embodiment 1 of this invention. It is an operation schematic diagram when the Vi value is small in the screw compressor which concerns on Embodiment 1 of this invention. It is an operation schematic diagram when the Vi value is large in the screw compressor which concerns on Embodiment 2 of this invention. It is an operation schematic diagram when the Vi value is small in the screw compressor which concerns on Embodiment 2 of this invention. It is a figure which shows the modification of the screw compressor which concerns on Embodiment 1 and Embodiment 2 of this invention.

Embodiment 1.
1 is a schematic configuration diagram of a screw compressor according to Embodiment 1 of the present invention.
The screw compressor according to the first embodiment is a single screw compressor, and has a cylindrical casing body 1 and a screw rotor 3 housed in the casing body 1 as shown in the schematic configuration in FIG. And a motor 2 for driving the screw rotor 3 to rotate. The motor 2 is composed of a stator 2a that is inscribed in the casing body 1 and is fixed thereto, and a motor rotor 2b that is arranged inside the stator 2a, and the number of rotations is controlled by an inverter system. Capacity control for operating the screw compressor at a desired operating compression ratio can be realized by controlling the rotation speed by driving the inverter of the motor 2.

The screw rotor 3 and the motor rotor 2b are arranged on the same axis, and both are fixed to the screw shaft 4. Further, on the outer peripheral surface of the screw rotor 3, a plurality of spiral grooves (hereinafter, referred to as screw grooves) 3a are formed. The screw rotor 3 is connected to a motor rotor 2b fixed to the screw shaft 4 and is rotationally driven. Further, the space in the screw groove 3a formed in the screw rotor 3 is surrounded by the inner cylinder surface of the casing main body 1 and a pair of gate rotors (not shown) that mesh and engage with the groove to form a compression chamber 5. To do.

Inside the casing body 1, the discharge pressure side and the suction pressure side are separated by a partition wall (not shown), and a discharge chamber 6 and a discharge port 7 opening to the discharge chamber 6 are formed on the discharge pressure side. ing. Inside the casing body 1, a suction chamber 16 is formed on the suction pressure side. Further, the casing body 1 is provided with a pair of variable Vi valves 8 which are connected to the pair of rods 9 and the drive device 10 and are movable in the axial direction. The variable Vi valve 8 forms part of the discharge port 7. The drive device 10 connected to the other variable Vi valve 8 is not shown.

FIG. 2 is a schematic diagram of an internal volume ratio variable mechanism including a driving device for a screw compressor according to Embodiment 1 of the present invention.
The drive device 10 constitutes a part of an internal volume ratio variable mechanism (hereinafter referred to as a variable Vi mechanism), and connects a piston 12 provided in a cylinder 11 and a variable Vi valve 8 with a rod 9. It is configured to do.

The variable Vi valve 8 is composed of a valve body 8a, a guide portion 8b, and a connecting portion 8c. A connecting portion 8c is provided at the discharge port side end portion 8e of the guide portion 8b, and the rod 9 is connected to the end surface on the drive device 10 side. Further, the discharge port side end portion 8d of the valve body 8a and the discharge port side end portion 8e of the guide portion 8b are connected by a connecting portion 8c, and a discharge gap 8f communicating with the discharge port 7 is formed. There is.

The inside of the cylinder 11 is divided into two space chambers by the piston 12, and the cylinder chamber 13a and the cylinder chamber 13b are formed on the front side (variable Vi valve direction) and the rear side (anti-variable Vi valve direction) of the piston 12. .. The cylinder 11 is provided with a pressure introduction hole 113a on the cylinder chamber 13a side which is closer to the variable Vi valve 8. Further, the cylinder 11 is provided with a pressure introducing hole 113b on the cylinder chamber 13b side farther from the variable Vi valve 8.

The cylinder chamber 13a communicates with the discharge chamber 6 of FIG. 1 through the pressure introduction hole 113a and the flow path 15a, and the discharge pressure is constantly introduced. The cylinder chamber 13b communicates with the discharge chamber 6 of FIG. 1 via the pressure introduction hole 113b and the flow path 15b, and enters the suction chamber 16 of FIG. 1 via the flow path 15c branched from the middle of the flow path 15b. It is in communication. The flow path 15b is provided with a solenoid valve 14b that opens and closes the flow path 15b, and the flow path 15c is provided with a solenoid valve 14a that opens and closes the flow path 15c. Discharge pressure or suction pressure is selectively introduced into the cylinder chamber 13b by opening and closing the

solenoid valves

14a and 14b.

The

solenoid valves

14a and 14b described above are merely examples, and may be any valve means capable of opening/closing or switching the flow path, for example, a stop valve or a three-way valve. In the case of a three-way valve capable of switching the flow path, one may be provided at the branch portion of the flow path, and therefore the solenoid valve 14a and the solenoid valve 14b can be omitted. Further, the flow path 15a, the flow path 15b and the flow path 15c may be formed inside the walls of the casing main body 1 and the cylinder 11, or may be connected by using piping.

Next, the operation of the variable Vi valve 8 will be described. According to this variable Vi mechanism, the Vi value can be set in two ways, large and small.

(I) Operation when the Vi value is large FIG. 3 is a schematic view of the operation when the Vi value is large in the screw compressor according to the first embodiment of the present invention.
When the Vi value is large, the drive device 10 positions the variable Vi valve 8 in the left direction indicated by the arrow in the figure, thereby delaying the opening timing of the discharge port 7.

That is, when the Vi value is large, the solenoid valve 14a is opened and the solenoid valve 14b is closed to set the suction pressure in the cylinder chamber 13b. On the other hand, the cylinder chamber 13a is connected to the discharge chamber 6, and a discharge pressure is constantly introduced. Therefore, the piston 12 tends to move to the left in the figure due to the pressure difference in the cylinder 11.

On the other hand, with respect to the variable Vi valve 8 connected to the piston 12, a suction pressure acts on the suction side end 8g of the valve body 8a, and a discharge pressure immediately after discharge acts on the discharge port side end 8d. Further, the same pressure as the pressure acting on the discharge port side end portion 8d acts on the discharge port side end portion 8e of the guide portion 8b in mutually opposite directions. Further, a discharge pressure acts on the drive device side end portion 8h of the guide portion 8b. Therefore, the loads acting on the discharge port side end portion 8d and the discharge port side end portion 8e inside the variable Vi valve 8 are offset. Therefore, the variable Vi valve 8 tends to move to the right in the figure due to the pressure difference acting on the drive device side end portion 8h and the suction side end portion 8g.

Here, the area of both end faces in the moving direction of the piston 12 is set to be larger than the area of the drive device side end portion 8h of the variable Vi valve 8. Therefore, the piston 12 and the variable Vi valve 8 move to the left in the figure due to the pressure difference between the two areas. Then, since the variable Vi valve 8 stops at a position where the piston 12 hits the wall surface of the cylinder chamber 13, the variable Vi valve 8 is accurately positioned at a position having a large Vi value.

(Ii) Operation when the Vi value is small FIG. 4 is a schematic diagram of the operation when the Vi value is small in the screw compressor according to the first embodiment of the present invention.
When the Vi value is small, the drive device 10 positions the variable Vi valve 8 in the right direction indicated by the arrow in the figure, thereby accelerating the opening timing of the discharge port 7.

That is, when the Vi value is small, the solenoid valve 14a is closed and the solenoid valve 14b is opened to set the discharge pressure in the cylinder chamber 13b. On the other hand, since the cylinder chamber 13a is connected to the discharge chamber 6 and the discharge pressure is constantly introduced, there is no pressure difference in the cylinder chamber 13.

On the other hand, with respect to the variable Vi valve 8 connected to the piston 12, a suction pressure acts on the suction side end 8g of the valve body 8a, and a discharge pressure immediately after discharge acts on the discharge port side end 8d. Further, the same pressure as the pressure acting on the discharge port side end portion 8d acts on the discharge port side end portion 8e of the guide portion 8b in mutually opposite directions. Further, a discharge pressure acts on the drive device side end portion 8h of the guide portion 8b.

Therefore, the variable Vi valve 8 moves to the right in the figure due to the differential pressure between the discharge pressure acting on the drive device side end 8h and the suction pressure acting on the suction side end 8g. Then, since the variable Vi valve 8 stops at a position where the piston 12 hits the wall surface of the cylinder chamber 13, the variable Vi valve 8 is accurately positioned at a position where the Vi value is small. The variable Vi valve 8 may be positioned at a position where the suction side end portion 8g of the variable Vi valve 8 contacts the wall surface of the casing body 1 as shown in FIG.

Here, the setting of the Vi value will be described. There are two policies for setting the Vi value: one is to secure a wide operating range as an issue, and the other is to set the improvement of "rated performance" or "period coefficient of performance", which is one of the indicators of energy saving, as an issue. The setting method according to each policy will be described below.

(Securing a wide operating range)
To secure a wide operating range, the Vi value on the large side may be set as follows. The operating range is set by setting an upper limit temperature for, for example, the temperature of the discharged refrigerant gas or the temperature of the winding of the motor stator in order to protect the compressor. When the evaporation temperature is constant, it is possible to secure a wide operating range by being able to raise the condensation temperature as high as possible within the range below the upper limit temperature. On the other hand, when the condensation temperature is constant, the evaporation temperature can be made as low or as high as possible, which will ensure a wide operating range.

The temperature of the discharged refrigerant gas tends to rise during operation under high compression ratio conditions, and the winding temperature tends to rise under high load conditions or high compression ratio conditions. Here, the high compression ratio condition is a high condensation temperature and low evaporation temperature condition, and the high load condition is a high condensation temperature and high evaporation temperature condition. Therefore, when the temperature of the discharged refrigerant gas and the winding temperature are about to reach the upper limit temperature during operation under a high load condition or a high compression ratio condition, the temperature of the discharged refrigerant gas and the winding temperature do not reach the upper limit temperature. It becomes necessary to change the operation. It is necessary to take measures such as reducing the rotation speed of the compressor to lower the condensation temperature and keep the operating temperature condition within the operating range. In other words, if you want to continue the operation while keeping the condensation temperature high, the temperature of the discharged refrigerant gas and the winding temperature will rise during operation under high load conditions or high compression ratio conditions, so it is necessary to take measures such as lowering the condensation temperature. The operating range is narrowed.

The temperature of the discharged refrigerant gas and the winding temperature under a certain operating condition tend to decrease as the compressor efficiency under the operating condition increases. Therefore, by increasing the compressor efficiency during operation under high load conditions or high compression ratio conditions, it is possible to suppress the rise in the discharged refrigerant gas temperature and winding temperature without taking measures such as lowering the condensation temperature. As a result, a wide operating range can be secured. The compressor efficiency is determined by the internal structure of the compressor and structural elements such as the number of windings of the motor.

Therefore, the Vi value on the large side is set so that the compressor efficiency becomes equal to or higher than the preset set efficiency during operation under a predetermined high load condition or high compression ratio condition. The compressor efficiency is a value that changes according to the Vi value, and is represented by a graph that is convex when the horizontal axis represents Vi and the vertical axis represents the compressor efficiency. That is, there is a Vi value that maximizes the compressor efficiency. Based on this, the Vi value on the large side may be the Vi value when the compressor efficiency is maximum, or may be set to a value equal to or higher than the set efficiency in short. The setting efficiency may be appropriately set according to the performance required for the screw compressor and the like. For example, when the maximum efficiency is set to 100%, the set efficiency may be set to 95% or more.

When configuring a screw compressor that secures a wide operating range, the Vi value is set as described above. Therefore, the position when the variable Vi valve 8 moves to the high Vi value side is set to be the set Vi value.

(Improvement of rated performance or period coefficient of performance)
[Improvement of rated performance: Vi side is large]
The Vi value on the large side is set so that the rated performance is high. The rated performance is the performance under the conditions defined by the industrial standard and represents the performance of the compressor. The rated performance is a value that changes according to the Vi value, and is represented by a graph that is convex upward when the horizontal axis is Vi and the vertical axis is the rated performance. That is, there is a Vi value that maximizes the rated performance. Based on this, the Vi value on the large side may be the Vi value when the rated performance is maximum, or in short, may be set to the Vi value that is equal to or higher than the preset set performance. The set performance may be appropriately set according to the performance required of the screw compressor. For example, it is conceivable to set the set performance to 95% or more when the maximum performance is set to 100%.

When configuring a screw compressor to improve the rated performance, the Vi value is set as described above. Therefore, the position when the variable Vi valve 8 moves to the high Vi value side is set to be the set Vi value.

[Improvement of period coefficient of performance: Vi value small side]
The Vi value on the small side is set as follows. In refrigerating and air-conditioning equipment, in addition to the coefficient of performance indicating energy consumption efficiency of COP, there is a coefficient of performance of refrigerators throughout the period called IPLV or ESSER.

At the American Refrigeration and Air Conditioning Industry Association, the period performance coefficient IPLV is calculated by the following formula.
IPLV=0.01×A+0.42×B+0.45×C+0.12×D
A=COP at 100% load, B=COP at 75% load,
C=COP at 50% load, D=COP at 25% load
According to this calculation formula, the weight to be multiplied differs depending on the load during operation. Of the annual operating time of refrigeration and air conditioning equipment, operation with a 75% load accounts for 42%, and operation with a 50% load accounts for 45%. Therefore, in the calculation formula of IPLV, the weight in these two conditions is large.

Similar indexes are also set by the Japan Refrigeration and Air Conditioning Industry Association and the European Refrigeration and Air Conditioning Industry Association.
In the case of Japan Refrigeration and Air Conditioning Industry Association, it is defined as the following formula.
IPLV=0.01×A+0.47×B+0.37×C+0.15×D
A=COP at 100% load, B=COP at 75% load,
C=COP at 50% load, D=COP at 25% load

In the case of the European Refrigeration and Air Conditioning Industry Association, ESEER is set as the European seasonal energy efficiency ratio. Like IPLV, ESSER is a value obtained by multiplying the energy efficiency ratio of the four operating load conditions by a weighting coefficient, and is calculated by the following formula. Note that EES, which is a value indicating energy consumption efficiency, is used to calculate ESEER, as in COP.
ESEER=0.03×A+0.33×B+0.41×C+0.23×D
A=100% load EER, B=75% load EER,
C=50% load EER, D=25% load EER
As described above, the weights at 75% load and 50% load are large in various indexes representing the coefficient of performance of the refrigerating and air-conditioning equipment over the period.

Here, if an example of the calculation formula of the Japan Refrigeration and Air Conditioning Industry Association is explained, "0.01 x A" is the coefficient of performance by 100% load operation, and "0.47 x B + 0.37 x C + 0.15 x D" is a part. It can be said that it is a coefficient of performance due to load driving.

The Vi value on the small side is set for the purpose of performing efficient operation in partial load operation, and the value of "0.47 x B + 0.37 x C + 0.15 x D" is equal to or higher than the preset set value. Is set to the Vi value. In other words, the Vi value on the small side is set on the basis of the top three driving loads having a large weight in the period performance coefficient.

The value of "0.47 x B + 0.37 x C + 0.15 x D" is a value that changes according to the Vi value, and the horizontal axis is Vi and the vertical axis is "0.47 x B + 0.37 x C + 0.15 x". It is represented by a graph that becomes convex upward when "D" is taken. That is, there is a Vi value that maximizes “0.47×B+0.37×C+0.15×D”. Based on this, the Vi value on the small side may be the Vi value when "0.47 x B + 0.37 x C + 0.15 x D" is the maximum, or in short, it may be a value that is equal to or greater than the set value. .. The set value may be appropriately set according to the performance required for the screw compressor and the like. For example, when the maximum set value is set to 100%, the set value may be set to 95% or more.

When configuring a screw compressor that operates efficiently with partial load operation, the Vi value is set as described above. Therefore, the position when the variable Vi valve 8 moves to the Vi value lower side is set to be the set Vi value.

When the small Vi value side is set as described above and the large Vi value side is set to a Vi value at which the compressor efficiency exceeds the set efficiency during operation under high load conditions or high compression ratio conditions, a wide operating range is provided. It is possible to secure and improve IPLV.

When the small Vi value side is set as described above and the large Vi value side is set to a Vi value at which the rated performance exceeds the set performance when operating under the rated conditions, both the rated performance and the IPLV can be improved.

Note that here, the Vi value on the small side is set based on the top three driving loads that have a large weight in the period performance coefficient. However, as described above, the operation at 75% load and the operation at 50% load account for the majority of the annual operation time. Therefore, the Vi value on the small side may be set on the basis of the top one or the top two driving loads having a large weight in the period performance coefficient.

As described above, in the first embodiment, the variable Vi valve has a simple two-step control based on only the discharge pressure and the suction pressure. This makes it possible to simplify the configuration and control while changing the internal volume ratio without requiring a special device.

Further, the position of the variable Vi valve when the Vi value is set to be large is set so that the compressor efficiency becomes a Vi value equal to or higher than the set efficiency during operation under a high load condition or a high compression ratio condition. As a result, a wide operating range can be secured.

Also, the position of the variable Vi valve when the Vi value is large is set so that the rated performance is the Vi value at which the rated performance is equal to or higher than the set performance. Thereby, the rated performance can be improved.

Further, the position of the variable Vi valve when the Vi value is small is such that a value obtained by multiplying each of the coefficient of performance in the top one to three driving loads by the weight corresponding to the driving load is equal to or more than the set value. It is set to be a value. As a result, the partial load performance can be improved and the compressor efficiency can be improved.

Embodiment 2.
In the first embodiment, the pressure introducing hole 113a of the cylinder chamber 13a is connected to the discharge chamber 6. The pressure introducing hole 113b of the cylinder chamber 13b is connected to the discharge chamber 6 and the suction chamber 16 in the casing body 1 via the solenoid valve 14a and the solenoid valve 14b, respectively, by the flow passage 15b and the flow passage 15c. It was In the second embodiment, the pressure introducing hole 113a is connected to the discharge chamber 6 and the suction chamber 16 in the casing body 1 via the solenoid valve 14a and the solenoid valve 14b, respectively, by the flow passage 15b and the flow passage 15c. .. The pressure introducing hole 113b is connected to the suction chamber 16 in the casing body 1.

Next, the operation of the variable Vi valve 8 in the second embodiment will be described. As in the first embodiment, the Vi value can be set in two ways, large and small.

(I) Operation when the Vi value is large FIG. 5 is a schematic diagram of the operation when the Vi value is large in the screw compressor according to the second embodiment of the present invention.
When the Vi value is large, the drive device 10 positions the variable Vi valve 8 in the left direction indicated by the arrow in the figure, thereby delaying the opening timing of the discharge port 7.

That is, when the Vi value is large, the solenoid valve 14a is closed and the solenoid valve 14b is opened to set the discharge pressure in the cylinder chamber 13a. On the other hand, the cylinder chamber 13b is connected to the suction chamber 16, and a suction pressure is constantly introduced. Therefore, the piston 12 tends to move to the left in the figure due to the pressure difference in the cylinder chamber 13.

Therefore, the loads acting on the discharge port

side end portions

8d and 8e inside the variable Vi valve 8 are offset. Therefore, the variable Vi valve 8 tries to move to the right in the figure due to the pressure difference between the pressure acting on the drive device side end 8h and the pressure acting on the suction side end 8g. However, since the area of both end faces of the piston 12 in the moving direction is set to be larger than the area of the drive device side end portion 8h of the variable Vi valve 8, the piston 12 and the variable Vi valve 8 are affected by the pressure difference between the two areas. Move to the left in the figure. Then, since the variable Vi valve 8 stops at a position where the piston 12 hits the wall surface of the cylinder chamber 13, the variable Vi valve 8 is accurately positioned at a position having a large Vi value.

(Ii) Operation when the Vi value is small FIG. 6 is a schematic diagram of the operation when the Vi value is small in the screw compressor according to the second embodiment of the present invention.
When the Vi value is small, the drive device 10 positions the variable Vi valve 8 in the right direction indicated by the arrow in the figure, thereby accelerating the opening timing of the discharge port 7.

That is, when the Vi value is small, the solenoid valve 14a is opened and the solenoid valve 14b is closed to set the suction pressure in the cylinder chamber 13a. On the other hand, since the cylinder chamber 13b is connected to the suction chamber 16 and the suction pressure is constantly introduced, there is no pressure difference in the cylinder chamber 13.

According to the second embodiment, the same effect as that of the first embodiment can be obtained.

The screw compressor of the present invention is not limited to the structure shown in FIGS. 1 to 6, and may be modified as follows, for example, without departing from the scope of the present invention. is there.

FIG. 7: is a figure which shows the modification of the screw compressor which concerns on Embodiment 1 and Embodiment 2 of this invention.
In this modification, the piston 12 shown in FIG. 1 is deleted and a piston rod 17 is provided. In FIG. 1, there was one piston for each variable Vi valve. On the other hand, in this modification, the piston rod 17 is connected to the rods 9 of the two variable Vi valves 8 via the common mounting plate 18, and one piston rod 17 is provided for every two variable Vi valves. ing. In this way, the number of pistons 12 for the variable Vi valve 8 is not limited.

1 casing body, 2 motor, 2a stator, 2b motor rotor, 3 screw rotor, 3a screw groove, 4 screw shaft, 5 compression chamber, 6 discharge chamber, 7 discharge port, 8 variable Vi valve, 8a valve body, 8b guide part , 8c connecting portion, 8d discharge port side end, 8e discharge port side end, 8f discharge gap, 8g suction side end, 8h drive device side end, 9 rod, 10 drive device, 11 cylinder, 12 piston, 13 Cylinder chamber, 13a cylinder chamber, 13b cylinder chamber, 14a solenoid valve, 14b solenoid valve, 15a flow passage, 15b flow passage, 15c flow passage, 16 suction chamber, 17 piston rod, 18 mounting plate, 113a pressure introduction hole, 113b pressure Introduction hole.

Claims

A screw compressor having an internal volume ratio variable mechanism including a variable Vi valve for varying a Vi value, which is an internal volume ratio, comprising:
Controlling the position of the variable Vi valve in two steps,
The position of the variable Vi valve when the Vi value is large is
A screw compressor in which the compressor efficiency during operation under a predetermined high load condition or high compression ratio condition is set to a Vi value that exceeds a preset set efficiency.
A screw compressor having an internal volume ratio variable mechanism including a variable Vi valve for varying a Vi value, which is an internal volume ratio, comprising:
Controlling the position of the variable Vi valve in two steps,
The position of the variable Vi valve when the Vi value is large is
A screw compressor that is set to have a Vi value that has a rated performance that is equal to or higher than a preset performance.
The position of the variable Vi valve when the Vi value is small is
In the period performance coefficient calculated by weighting each of the four driving loads, a value obtained by multiplying each of the performance coefficients in the top one to three driving loads having a large weight by the weight corresponding to the driving load is obtained. The screw compressor according to claim 1 or 2, which is set to have a Vi value that is equal to or larger than a preset set value.
The internal volume ratio variable mechanism,
A piston connected to the variable Vi valve,
A cylinder accommodating the piston,
The inside of the cylinder is divided into two space chambers by the piston,
The two space chambers are arranged as a cylinder chamber for constantly introducing a discharge pressure and a cylinder chamber for introducing a suction pressure or a discharge pressure via a valve means in the order of being closer to the variable Vi valve. Item 4. The screw compressor according to any one of Item 3.
The internal volume ratio variable mechanism,
A piston connected to the variable Vi valve,
A cylinder accommodating the piston,
The inside of the cylinder is divided into two space chambers by the piston,
The two space chambers are arranged as a cylinder chamber for introducing a suction pressure or a discharge pressure via a valve means and a cylinder chamber for constantly introducing a suction pressure in the order of being closer to the variable Vi valve. Item 4. The screw compressor according to any one of items 3.
The screw compressor according to any one of claims 1 to 5, wherein capacity control is performed by inverter speed control.