JP2014206098A - Screw compressor - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a screw compressor needing neither a complex structure nor a control unit for changing the position of a Vi-variable valve for every condition in the control of the Vi-variable mechanism in a Vi-variable screw compressor, thereby to make the screw compressor highly efficient and inexpensive throughout one year by a simple control.SOLUTION: The inside of a cylinder of a Vi-variable mechanism is partitioned into three cylinder chambers, of which at least one cylinder chamber has its internal pressure changed to establish a pressure difference between the cylinder chambers thereby to control the position of the Vi-variable valve on the basis of the Vi values set at three stages.

Description

The present invention relates to a screw compressor used for refrigerant compression of a refrigerator, for example, and more particularly to a screw compressor provided with an internal volume ratio (hereinafter referred to as Vi) variable valve that adjusts the timing of discharge start according to the operating pressure ratio. Is.

Vi in the screw compressor is a ratio of the tooth space space volume at the time of suction and the tooth space space just before the discharge as shown in Patent Document 1, for example, and the volume when the suction is completed. It represents the ratio to the volume when the discharge port opens. And, when the Vi variable valve is a fixed type screw compressor, for example, if a low compression ratio operation is performed with a screw compressor in which Vi is set so that proper compression is performed at a medium compression ratio, the gas is discharged before the discharge port opens. Is over-compressed above the discharge pressure, and extra compression is performed. On the other hand, when the operation is performed at a high compression ratio, the discharge port opens before reaching the discharge pressure, resulting in an under-compressed state in which a backflow of gas occurs. All of these cause power loss and reduce efficiency.

For such a problem, a Vi variable valve, which is a slide valve that adjusts the discharge start timing to vary Vi, is provided, and the opening of the Vi variable valve is driven by the driving force from the driving device in accordance with the operating pressure ratio. Has been proposed (see, for example, Patent Document 1).

Further, in Patent Document 2, as shown in FIGS. 1 and 2, an optimal Vi value is calculated from the discharge pressure HP and the suction pressure LP, the current Vi value is obtained from the position detection means, and the current Vi value and the optimal Vi value are calculated. In order to reduce the difference with the Vi variable valve, it is controlled by the drive unit connected to the Vi variable valve, and in order to approach the optimum Vi value during actual operation, the opening adjustment of the Vi variable valve is adjusted so that the motor drive power is minimized. Is going.

JP-A-62-87687 (2nd page) Japanese Patent No. 4147891 (FIGS. 1 and 2)

In a Vi variable screw compressor, as a control method of the Vi variable mechanism, in addition to the discharge pressure and the suction pressure, the rotation frequency, current, and voltage are detected and control is performed so that the compressor driving power is minimized. There is a problem that a complicated structure and a control unit for changing the position of the Vi variable valve for each condition are required.

The present invention has been made to solve the above-described problems, and an object of the present invention is to provide a highly efficient screw compressor by realizing a Vi variable mechanism with simple control.

A screw compressor according to the present invention includes a casing, a screw rotor that compresses a refrigerant inside the casing, a motor that rotates the screw rotor, and a sliding device that changes the internal volume ratio Vi by sliding on the casing. In a screw compressor provided with a Vi variable mechanism having a Vi variable valve,
The Vi variable mechanism includes a cylinder, a piston partition wall provided in the cylinder and having an opening, a first piston connected to the Vi variable valve via a first rod, and the first And at least two pistons separated from the first piston, which are provided so as to sandwich the piston partition wall with respect to the piston and connected by a second rod penetrating the opening,
Inside the cylinder, at least three cylinder chambers are formed by two pistons connected by the first piston and the second rod,
The position of the Vi variable valve is controlled by moving the first piston by changing the pressure in at least one of the three cylinder chambers.

According to the present invention, since the position control of the Vi variable valve can be realized by switching the pressure in the cylinder of the Vi variable mechanism, an inexpensive high-efficiency screw compressor can be obtained without requiring a complicated control unit. .

It is sectional drawing of the side view which shows schematic structure of the screw compressor which concerns on Embodiment 1 of this invention. It is sectional drawing of the side view of the Vi variable mechanism which concerns on Embodiment 1 of this invention. It is sectional drawing of the side view at the time of Vi value large of the Vi variable mechanism which concerns on Embodiment 1 of this invention. It is sectional drawing of the side view at the time of Vi value of the Vi variable mechanism which concerns on Embodiment 1 of this invention. It is sectional drawing of the side view at the time of Vi value small of the Vi variable mechanism which concerns on Embodiment 1 of this invention. It is sectional drawing of the side view at the time of Vi value large of the Vi variable mechanism which concerns on Embodiment 2 of this invention. It is sectional drawing of the side view at the time of Vi value middle of the Vi variable mechanism which concerns on Embodiment 2 of this invention. It is sectional drawing of the side view at the time of Vi value small of the Vi variable mechanism which concerns on Embodiment 2 of this invention. It is sectional drawing of the side view of the Vi variable mechanism which concerns on Embodiment 3 of this invention. It is sectional drawing of the side view at the time of Vi value 100% load of the Vi variable mechanism which concerns on Embodiment 3 of this invention. It is sectional drawing of the side view at the time of Vi value 75% load of the Vi variable mechanism which concerns on Embodiment 3 of this invention. It is sectional drawing of the side view at the time of Vi value 50% load of the Vi variable mechanism which concerns on Embodiment 3 of this invention. It is sectional drawing of the side view at the time of Vi value 25% load of the Vi variable mechanism which concerns on Embodiment 3 of this invention.

Embodiment 1
1 is a cross-sectional view in side view showing a schematic configuration of a screw compressor according to Embodiment 1 of the present invention. The screw compressor according to the first embodiment is, for example, a single screw compressor, a cylindrical casing body 1, a screw rotor 2 that is accommodated in the casing body 1 and compresses a refrigerant, and the screw rotor 2 is rotated. A driving motor 3 is provided.

The motor 3 includes a stator 3a inscribed and fixed to the casing body 1 and a motor rotor 3b disposed inside the stator 3a, and the rotational speed is controlled by an inverter system. The screw rotor 2 and the motor rotor 3 b are arranged on the same axis line, and both are fixed on the screw shaft 4.

A plurality of spiral grooves (screw grooves) are formed in the screw rotor 2, and the screw grooves are rotationally driven in conjunction with the motor rotor 3 b fixed on the screw shaft 4. In a groove space formed adjacent to the cylindrical surface of the screw rotor 2, a compression chamber 5 is surrounded by an inner cylindrical surface of the casing body 1 and a pair of gate rotors (not shown) engaged with and engaged with the groove. It is formed.

The casing body 1 is separated by a partition wall (not shown) into a discharge pressure side and a suction pressure side. A discharge chamber 6 and a discharge port 7 that opens to the discharge chamber 6 are formed on the discharge pressure side of the casing body 1, and a suction chamber 8 is formed on the suction pressure side.
Note that the relationship between the discharge pressure and the suction pressure is discharge pressure> suction pressure, and the discharge pressure is high.

The casing body 1 is provided with a drive device 10 that forms part of the Vi variable mechanism, and a pair of Vi variable valves 11 that are connected to the first rod 9 and are movable in the axial direction. A part of the discharge port 7 is formed in the.

The surface of the Vi variable valve 11 in the direction of the driving device 10 including the discharge port 7 is in contact with the discharge chamber 6, and the surrounding pressure is a high discharge pressure. On the other hand, the surface of the Vi variable valve 11 in the direction of the motor 3 is in contact with the suction chamber 8 separated from the discharge chamber 6 by the partition wall, and the ambient pressure is a low suction pressure.

Therefore, a differential pressure due to the discharge pressure and the suction pressure (discharge pressure−suction pressure> 0) is generated at both ends of the Vi variable valve 11, and the direction of the motor 3 (the black arrow in FIG. The force to move in the direction is always generated. Note that the driving device 10 connected to the other Vi variable valve 11 is not shown.

FIG. 2 is a side sectional view of the Vi variable mechanism including the driving device 10 according to the first embodiment. The drive device 10 includes a cylinder 12 for moving the position of the Vi variable valve 11 therein. Inside the cylinder 12, a first piston 13, a second piston 14, and a third piston 15 are provided in order from the side closer to the Vi variable valve 11.

The first piston 13 is connected by the Vi variable valve 11 and the first rod 9, and the second piston 14 and the third piston 15 are connected by the second rod 16 independently of the first piston 13.

A first piston partition wall 17 that is partially opened is provided inside the cylinder 12. The 2nd piston 14 and the 3rd piston 15 are installed in the composition which sandwiches the 1st piston partition wall 17.

The diameters of the first piston 13 and the third piston 15 are the same as the diameter of the cylinder 12, and a seal member 18 is attached to a portion where the first piston 13 or the third piston 15 contacts the inner peripheral surface of the cylinder 12. . The space in contact with the left and right of the first piston 13 and the space in contact with the left and right of the third piston 15 are separated by a seal member 18.

The diameter of the second piston 14 is larger than the diameter of the opening of the first piston partition wall 17 and smaller than the diameters of the cylinder 12, the first piston 13 and the third piston 15. As a result, the space sandwiched between the first piston 13 and the third piston 15 is not separated by the second piston 14.

The area where the first piston 13 receives pressure from the left and right spaces is larger than the area where the Vi variable valve 11 receives the discharge pressure from the discharge chamber 6 and the area where the suction pressure is received from the suction chamber 8. As a result, the force that the Vi variable valve 11 tries to move in the direction of the motor 3 can be made smaller than the force that the first piston 13 receives from the left and right spaces.

Three cylinder chambers are formed in the cylinder 12 as the first piston 13 and the third piston 15 are installed. The three cylinder chambers are the first cylinder chamber 19 a sandwiched between the first piston 13 and the wall of the cylinder 12 on the Vi variable valve 11 side, and the second cylinder chamber 19 b sandwiched between the first piston 13 and the third piston 15. The third piston 15 and the Vi variable valve 11 are a third cylinder chamber 19c sandwiched between opposite walls.

At this time, the 2nd piston 14 connected with the 3rd piston 15 and the 2nd rod 16 is installed in the 2nd cylinder room 19b.
The length of the second rod 16 is shorter than the distance between the wall on the Vi variable valve 11 side of the cylinder 12 and the first piston partition wall 17. For this reason, the second piston 14 does not contact the wall on the Vi variable valve 11 side.

Each of the three cylinder chambers is provided with a pressure introduction hole for introducing the pressure in the compressor. The pressure introduction hole 119a provided in the first cylinder chamber 19a communicates with the discharge chamber 6, and the discharge pressure is constantly introduced into the first cylinder chamber 19a.

A pressure introducing hole 119b provided in the cylinder chamber 19b communicates with the suction chamber 8 through the electromagnetic valve 20a and also communicates with the discharge chamber 6 through the electromagnetic valve 20b. A pressure introducing hole 119c provided in the cylinder chamber 19c communicates with the suction chamber 8 through the electromagnetic valve 21a and also communicates with the discharge chamber 6 through the electromagnetic valve 21b.

The solenoid valves 20a, 20b, 21a, and 21b are controlled to be opened and closed by a control device (not shown).

Next, the operation will be described. In the Vi variable mechanism according to the first embodiment of the present invention, control according to three large, medium, and small Vi values is possible.

(Operation when Vi value is large)
FIG. 3 is a side sectional view of the Vi variable mechanism according to Embodiment 1 when the Vi value is large. By positioning the Vi variable valve 11 at a position closest to the direction of the cylinder 12, the timing at which the discharge port 7 opens can be delayed. In addition, the same code | symbol is attached | subjected to the same structure as the structure shown in FIG. 2, and description is abbreviate | omitted.

The cylinder chamber 19 a located closest to the Vi variable valve 11 communicates with the discharge chamber 6, and discharge pressure is constantly introduced from the discharge chamber 6. The cylinder chamber 19b is opened with the solenoid valve 20a, the solenoid valve 20b is closed and the suction pressure is introduced from the suction chamber 8. The cylinder chamber 19c is opened with the solenoid valve 21a, and the solenoid valve 21b is closed and the suction chamber 8 is closed. Suction pressure is introduced.

As a result, the cylinder chamber 19b and the cylinder chamber 19c have the same pressure, and the pressure in the cylinder chamber 19a is higher than the pressure in the cylinder chamber 19b and the cylinder chamber 19c.

The area of the pressure received by the first piston 13 from the left and right cylinder chambers is larger than the area of the discharge pressure received by the Vi variable valve 11 from the discharge chamber 6 and the suction pressure received from the suction chamber 8. For this reason, the first piston 13 moves in the direction of the cylinder chamber 19b (the reverse direction with respect to the Vi variable valve 11) by the differential pressure between the cylinder chamber 19a and the cylinder chamber 19b.

The second piston 14 is pushed by the first piston 13 and moves in the direction of the cylinder chamber 19c. The third piston 15 connected by the second piston 14 and the second rod 16 also moves in the direction of the wall opposite to the Vi variable valve 11 in conjunction with the second piston 14. When the second piston 14 stops at a point where it comes into contact with the first piston partition wall 17, the third piston 15 and the first piston 13 also stop similarly.

Since the Vi variable valve 11 is connected to the first piston 13 and the first rod 9, the Vi variable valve 11 moves in the direction of the cylinder 12 in conjunction with the first piston 13 and stops at the position where the timing of opening the discharge port 7 is the latest. To do.

(Operation when the Vi value is medium)
FIG. 4 is a side sectional view of the Vi variable mechanism according to Embodiment 1 when the Vi value is medium. By positioning the Vi variable valve 11 at a position closer to the direction of the motor 3 than the position when the Vi value is large, the timing of opening the discharge port 7 can be made earlier than when the Vi value is large. In addition, the same code | symbol is attached | subjected to the same structure as the structure shown in FIG. 2, and description is abbreviate | omitted.

The cylinder chamber 19 a communicates with the discharge chamber 6, and discharge pressure is constantly introduced from the discharge chamber 6. The solenoid valve 20a is opened in the cylinder chamber 19b, the suction pressure is introduced from the suction chamber 8 with the solenoid valve 20b closed, and the solenoid valve 21a is closed and the solenoid valve 21b is opened in the cylinder chamber 19c from the discharge chamber 6. Discharge pressure is introduced.

As a result, the cylinder chamber 19a and the cylinder chamber 19c are equal in pressure, and the pressure in the cylinder chamber 19b is lower than the pressure in the cylinder chamber 19a and the cylinder chamber 19c.

Since the pressure in the cylinder chamber 19b is lower than the pressure in the cylinder chamber 19c, the third piston 15 moves in the direction of the Vi variable valve 11 (the direction of the black arrow in FIG. 4) due to the differential pressure. The first piston 13 is pushed by the second piston 14 connected by the third piston 15 and the second rod 16 and moves in the direction of the Vi variable valve 11.

When the third piston 15 stops at a point where it comes into contact with the first piston partition wall 17, the second piston 14 also stops in conjunction with it, and the first piston 13 stops similarly.
Since the Vi variable valve 11 is connected to the first piston 13 by the first rod 9, the position of the Vi variable valve 11 moves in conjunction with the first piston 13. As the first piston 13 stops, the Vi variable valve 11 stops at a position where the opening timing of the discharge port 7 is earlier than when the Vi value is large.

(Operation when Vi value is small)
FIG. 5 is a side sectional view of the Vi variable mechanism according to Embodiment 1 when the Vi value is small. By positioning the Vi variable valve 11 at a position closer to the direction of the motor 3 than the position at the middle of the Vi value, the timing of opening the discharge port 7 can be made earlier than at the middle of the Vi value. In addition, the same code | symbol is attached | subjected to the same structure as the structure shown in FIG. 2, and description is abbreviate | omitted.

The cylinder chamber 19 a communicates with the discharge chamber 6, and discharge pressure is constantly introduced from the discharge chamber 6. The cylinder chamber 19b is closed with the solenoid valve 20a, the solenoid valve 20b is opened, and the discharge pressure is introduced from the discharge chamber 6. The cylinder chamber 19c is opened with the solenoid valve 21a, and the solenoid valve 21b is closed and the suction chamber 8 is closed. Suction pressure is introduced.

As a result, the cylinder chamber 19a and the cylinder chamber 19b have the same pressure, and the pressure in the pressure cylinder chamber 19c is lower than that in the cylinder chamber 19a and the cylinder chamber 19b.
There is no differential pressure between the cylinder chamber 19a and the cylinder chamber 19b, and the first piston 13 does not receive a differential pressure from the left and right cylinder chambers. For this reason, the first piston 13 is affected by the differential pressure received by the Vi variable valve 11 from the discharge chamber 6 and the suction chamber 8.

Since the Vi variable valve 11 always has a force to move in the direction of the motor 3, the Vi variable valve 11 moves in the direction of the motor 3. The first piston 13 moves until it stops in contact with the wall on the Vi variable valve 11 side, and the Vi variable valve 11 stops at a position where the timing of opening the discharge port 7 is earlier than when the Vi value is in the middle.

Further, since the pressure in the cylinder chamber 19c is lower than the pressure in the cylinder chamber 19b, the third piston 15 is in the direction opposite to the direction of the Vi variable valve 11 due to the differential pressure (the direction of the black arrow on the left side in FIG. 5). Move to. When the second piston 14 stops at a point where it contacts the first piston partition wall 17, the third piston 15 connected by the second rod 16 also stops in conjunction.

In the control when the Vi value is small, the discharge pressure may be introduced into the cylinder chamber 19c by closing the solenoid valve 21a and opening the solenoid valve 21b. In this case, the cylinder chamber 19a, the cylinder chamber 19b, and the cylinder chamber 19c are all at the same pressure by the discharge pressure, and there is no differential pressure in the three cylinder chambers.

The second piston 14 and the third piston 15 are stopped because the differential pressure force that holds the position does not act on them, and is not affected by the differential pressure between the discharge chamber 6 and the suction chamber 8 that the Vi variable valve 11 receives. The state becomes unstable. However, the first piston 13 is not affected by the state of the second piston 14 and the third piston 15, and the Vi variable valve is affected by the differential pressure between the discharge chamber 6 and the suction chamber 8 received by the Vi variable valve 11. 11 and stops in contact with the wall on the Vi variable valve 11 side.

When the first piston 13 is in contact with the wall on the Vi variable valve 11 side and maintains the stopped state, the Vi variable valve 11 stops at a position where the timing of opening the discharge port 7 is earlier than when the Vi value is in the middle.

Here, the large, medium, and small Vi values in the Vi variable mechanism will be described. Any value can be set as the Vi value. In addition to the coefficient of performance indicating the rated energy consumption efficiency of COP in refrigeration and air-conditioning equipment, there is a coefficient of performance of the refrigerator throughout the period called IPLV (period performance coefficient), and efficient control is possible by setting this value become.

In the American Refrigeration and Air Conditioning Industry Association, 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 of operation efficiency varies depending on the load during operation. In particular, at 75% load and 50% load, they are 0.42 and 0.45, respectively, and the weighting is large.

In the Japan Refrigeration and Air Conditioning Industry Association, the same index is defined as the following formula, and the weighting at 75% load and 50% load is large as in the American Refrigeration and Air Conditioning Industry Association.
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 addition, COP at 100% load is the most important index for evaluating the performance of refrigeration and air conditioning equipment. For this reason, the three levels of Vi values are: an optimal value at 100% load when the Vi value is large, an optimal value at 75% load when the Vi value is medium, and an optimal value at 50% load or 25% load when the Vi value is small. By setting so as to be, efficient control is possible.

Note that the present invention is not limited only to the case classification based on 100% load, 75% load, 50% load, and 25% load, and the Vi value is arbitrarily set according to the size of the load. What is necessary is just to move the Vi variable valve 11 by controlling opening and closing of the electromagnetic valve to a position corresponding to the Vi value. For example, when the 0 to 100% load is divided into three stages (large load> medium load> small load), the Vi value is large when the load is large, the Vi value is medium when the load is medium, and the Vi value is small when the load is small. Set to.

A control device (not shown) determines how much load the screw compressor is driven by the difference between the set temperature and the internal temperature. When controlling the Vi value according to the case classification based on 100% load, 75% load, 50% load, and 25% load, three types are extracted from the following load patterns, and electromagnetic control is performed. Open / close control of the valves 20a, 20b, 21a, 21b is performed.
At 100% load When the load exceeds 75% At 75% load When the load exceeds 50%, or when it is 75% or less At 50% load When the load exceeds 25% or 50% or less When the load is 25% When the load is 25% or less

According to the first embodiment, the simple Vi variable valve 11 based on only the pressure difference between the discharge pressure and the suction pressure of the cylinder chambers 19a, 19b, 19c, which is generated by opening and closing the electromagnetic valves 20a, 20b, 21a, 21b. The movable control makes it possible to obtain a highly efficient and inexpensive screw compressor throughout the year without the need for special equipment.

The shape of the first piston partition wall 17 is not particularly limited. As long as the second piston 14 can be stopped at the position where the first piston partition wall 17 and the second piston 14 are in contact with each other after passing through the second rod 16, the operation is not affected in any shape.

Further, the pressure introduced into the cylinder chambers 19a, 19b, 19c is not limited to the discharge pressure and the suction pressure. For example, an intermediate pressure that is lower than the discharge pressure and higher than the suction pressure may be introduced.

In addition, the valves 20a, 20b, 21a, and 21b for exchanging pressure are not limited to electromagnetic valves, and for example, electric valves may be introduced.

Embodiment 2
As a second embodiment of the present invention, an example in which the pressure in the cylinder chamber 19a is variable and the suction pressure is constantly introduced into the cylinder chamber 19b located in the center will be described. FIG. 6 is a side sectional view of the Vi variable mechanism according to Embodiment 2 when Vi is large. In addition, the same code | symbol is attached | subjected to the same structure as the structure shown in FIG. 2, and description is abbreviate | omitted.

  The cylinder chamber in the cylinder 12 in the second embodiment has the following configuration. A pressure introducing hole 119a provided in the first cylinder chamber 19a communicates with the suction chamber 8 through the electromagnetic valve 20a and also communicates with the discharge chamber 6 through the electromagnetic valve 20b. A pressure introduction hole 119b provided in the cylinder chamber 19b communicates with the suction chamber 8 and constantly introduces a suction pressure into the second cylinder chamber 19b. A pressure introducing hole 119c provided in the cylinder chamber 19c communicates with the suction chamber 8 through the electromagnetic valve 21a and also communicates with the discharge chamber 6 through the electromagnetic valve 21b.

Also in the second embodiment, it is possible to set three large, medium, and small Vi values as the Vi variable mechanism as in the first embodiment. The operation at each setting will be described.

(Operation when Vi value is large)
FIG. 6 is a side sectional view of the Vi variable mechanism according to Embodiment 2 when the Vi value is large. By positioning the Vi variable valve 11 at a position closest to the direction of the cylinder 12, the timing at which the discharge port 7 opens can be delayed. In addition, the same code | symbol is attached | subjected to the same structure as the structure shown in FIG. 2, and description is abbreviate | omitted.

Discharge pressure is introduced into the cylinder chamber 19a by closing the electromagnetic valve 20a and opening the electromagnetic valve 20b. The cylinder chamber 19b communicates with the suction chamber 8, and suction pressure is constantly introduced. The suction pressure is introduced into the cylinder chamber 19c by opening the solenoid valve 21a and closing the solenoid valve 21b.

As a result, the cylinder chamber 19b and the cylinder chamber 19c have the same pressure, and the pressure in the cylinder chamber 19a is higher than the pressure in the cylinder chamber 19b and the cylinder chamber 19c.

The area of the pressure that the first piston 13 receives from the left and right cylinder chambers is larger than the area of the discharge pressure that the Vi variable valve 11 receives from the discharge chamber 6 and the suction pressure that the suction chamber 8 receives. For this reason, the first piston 13 moves in the direction of the cylinder chamber 19b (the reverse direction with respect to the Vi variable valve 11) by the differential pressure between the cylinder chamber 19a and the cylinder chamber 19b.

The second piston 14 is pushed by the first piston 13 and moves in the direction of the cylinder chamber 19c. The 3rd piston 15 connected with the 2nd piston 14 and the 2nd rod 16 also moves, and moves to the wall direction on the opposite side to Vi variable valve 11. FIG. When the second piston 14 stops at a point where it comes into contact with the first piston partition wall 17, the first piston 13 and the third piston 15 also stop similarly.

Since the Vi variable valve 11 is connected by the first piston 13 and the first rod 9, it moves in conjunction with the first piston 13 and stops at a position where the timing of opening the discharge port 7 is the latest.

(Operation when the Vi value is medium)
FIG. 7 is a side sectional view of the Vi variable mechanism according to the second embodiment when the Vi value is medium. By positioning the Vi variable valve 11 at a position closer to the direction of the motor 3 than the position when the Vi value is large, the timing at which the discharge port 7 opens can be made earlier than when the Vi value is large. In addition, the same code | symbol is attached | subjected to the same structure as the structure shown in FIG. 2, and description is abbreviate | omitted.

Discharge pressure is introduced into the cylinder chamber 19a by closing the electromagnetic valve 20a and opening the electromagnetic valve 20b. The cylinder chamber 19b communicates with the suction chamber 8, and suction pressure is always introduced. The discharge pressure is introduced into the cylinder chamber 19c by closing the solenoid valve 21a and opening the solenoid valve 21b.

As a result, the cylinder chamber 19a and the cylinder chamber 19c are equal in pressure, and the pressure in the cylinder chamber 19b is lower than the pressure in the cylinder chamber 19a and the cylinder chamber 19c.

Since the pressure in the cylinder chamber 19c is higher than the pressure in the cylinder chamber 19b, the third piston 15 moves in the direction of the Vi variable valve 11 (the direction of the black arrow in FIG. 7) due to the differential pressure. The second piston 14 connected by the third piston 15 and the second rod 16 also moves in the direction of the Vi variable valve 11, and the first piston 13 is also pushed by the second piston 14 to move in the direction of the Vi variable valve 11. Move to.

When the third piston 15 stops at a point where it comes into contact with the first piston partition wall 17, the second piston 14 stops in conjunction with it, and the first piston 13 stops in the same manner.

Since the Vi variable valve 11 is connected to the first piston 13 by the first rod 9, the position of the Vi variable valve 11 moves in conjunction with the first piston 13. As the first piston 13 stops, the first piston 13 stops at a position where the opening timing of the discharge port 7 is earlier than when the Vi value is large.

(Operation when Vi value is small)
FIG. 8 is a side sectional view of the Vi variable mechanism according to Embodiment 2 when the Vi value is small. By positioning the Vi variable valve 11 at a position closer to the direction of the motor 3 than the position at the middle of the Vi value, the timing of opening the discharge port 7 can be made earlier than at the middle of the Vi value. In addition, the same code | symbol is attached | subjected to the same structure as the structure shown in FIG. 2, and description is abbreviate | omitted.

The suction pressure is introduced into the cylinder chamber 19a by opening the electromagnetic valve 20a and closing the electromagnetic valve 20b. The cylinder chamber 19b communicates with the suction chamber 8, and the suction pressure is always introduced, and the discharge pressure is introduced into the cylinder chamber 19c by closing the electromagnetic valve 21a and opening the electromagnetic valve 21b.

As a result, the cylinder chamber 19a and the cylinder chamber 19b have the same pressure, and the cylinder chamber 19c is in a state higher than the pressure in the cylinder chamber 19a and the cylinder chamber 19b.

Since there is no differential pressure between the cylinder chamber 19a and the cylinder chamber 19b, the first piston 13 is not affected by the left and right cylinder chambers. For this reason, the first piston 13 is affected by the differential pressure that the Vi variable valve 11 receives from the discharge chamber 6 and the suction chamber 8.

Since the Vi variable valve 11 always has a force to move in the direction of the motor 3, the Vi variable valve 11 moves in the direction of the motor 3. The first piston 13 moves until it stops in contact with the wall on the Vi variable valve 11 side, and the Vi variable valve 11 stops at a position where the timing of opening the discharge port 7 is earlier than when the Vi value is in the middle.

Further, since the pressure in the cylinder chamber 19c is higher than the pressure in the cylinder chamber 19b, the third piston 15 moves in the direction of the Vi variable valve 11 due to the differential pressure. The second piston 14 connected by the third piston 15 and the second rod 16 also moves in conjunction. The third piston 15 stops at a point where it comes into contact with the first piston partition wall 17, and the second piston 14 also stops in conjunction with it.

In the control when the Vi value is small, the solenoid valve 21a is opened and the solenoid valve 21b is closed as in the first embodiment, and the suction pressure is introduced into the cylinder chamber 19c so that the cylinder chamber 19a, the cylinder chamber 19b, and the cylinder chamber 19c Alternatively, the suction pressure may be equal.

According to the second embodiment, even when the pressure in the cylinder chamber 19b located at the center is fixed, the same effect as in the first embodiment can be obtained.

Further, as in the first embodiment, the pressure introduced into the cylinder chambers 19a, 19b, 19c is not limited to the discharge pressure and the suction pressure, and for example, an intermediate pressure may be introduced.

In addition, the valves 20a, 20b, 21a, and 21b for exchanging pressure are not limited to electromagnetic valves, and for example, electric valves may be introduced.

Embodiment 3
As a third embodiment of the present invention, an example in which four cylinder chambers are provided inside the cylinder 12 will be described. FIG. 9 is a cross-sectional view of the Vi variable mechanism according to the fourth embodiment in a side view. In addition, the same code | symbol is attached | subjected to the same structure as the structure shown in FIG. 2, and description is abbreviate | omitted.

Inside the cylinder 12, a first piston 13, a second piston 14, a third piston 15, a fourth piston 22 and a fifth piston 23 are provided in order from the side closer to the Vi variable valve 11. The fourth piston 22 and the fifth piston 23 are connected by a third rod 24 and are configured independently of the first piston 13, the second piston 14, and the third piston 15.

Inside the cylinder 12, a first piston partition wall 17 and a second piston partition wall 25, which are partially opened, are provided. The fourth piston 22 and the fifth piston 23 are installed so as to sandwich the second piston partition wall 25.

The diameter of the fifth piston 23 is the same as the diameter of the cylinder 11, and a seal member 18 is attached to the cylinder contact portion in contact with the inner peripheral surface of the cylinder 12 to separate the spaces in contact with the left and right of the fifth piston 23.

The diameter of the fourth piston 22 is larger than the diameter of the opening of the second piston partition wall 25 and smaller than the diameters of the cylinder 12, the third piston 15 and the fifth piston 23. As a result, the fourth piston 22 does not separate the space sandwiched between the third piston 15 and the fifth piston 23.

Four cylinder chambers are formed inside the cylinder 12 as the fifth piston 23 is installed. The four cylinder chambers are a first cylinder chamber 19a sandwiched between the wall of the cylinder 12 on the side of the Vi variable valve 11 and the first piston 13, a second cylinder chamber 19b sandwiched between the first piston 13 and the third piston 15, and a second cylinder chamber 19b. A third cylinder chamber 19d sandwiched between the third piston 15 and the fifth piston 23, and a fourth cylinder chamber 19e sandwiched between walls opposite to the fifth piston 23 and the Vi variable valve 11. At this time, the fourth piston 22 connected by the fifth piston 23 and the third rod 24 is installed in the third cylinder chamber 19d.

The length of the second rod 16 is shorter than the distance between the wall of the cylinder 12 on the Vi variable valve 11 side and the first piston partition wall 17. For this reason, the second piston 14 does not contact the wall on the Vi variable valve 11 side. The length of the third rod 24 is shorter than the distance between the first piston partition wall 17 and the second piston partition wall 25. For this reason, the fourth piston 22 does not contact the first piston partition wall 17.

Each of the four cylinder chambers is provided with a pressure introduction hole for introducing the pressure in the compressor. The pressure introduction hole 119a provided in the first cylinder chamber 19a communicates with the discharge chamber 6, and the discharge pressure is always introduced into the first cylinder chamber 19a.

A pressure introducing hole 119b provided in the cylinder chamber 19b communicates with the suction chamber 8 through the electromagnetic valve 20a and also communicates with the discharge chamber 6 through the electromagnetic valve 20b. A pressure introducing hole 119d provided in the cylinder chamber 19d communicates with the suction chamber 8 through the electromagnetic valve 26a and also communicates with the discharge chamber 6 through the electromagnetic valve 26b. The pressure introducing hole 119e provided in the cylinder chamber 19e communicates with the suction chamber 8 through the electromagnetic valve 27a and communicates with the discharge chamber 6 through the electromagnetic valve 27b.

The solenoid valves 20a, 20b, 26a, 26b, 27a, and 27b are controlled to be opened and closed by a control device (not shown).

Next, the operation will be described. In the third embodiment, four Vi values can be set as the Vi variable mechanism. For example, it is efficient by setting the Vi value in four stages to an optimum value at 100% load, an optimum value at 75% load, an optimum value at 50% load, and an optimum value at 25% load. Control is possible.

(Operation when Vi value is 100% load)
FIG. 10 is a side sectional view of the Vi variable mechanism according to Embodiment 3 when the Vi value is 100% loaded. By positioning the Vi variable valve 11 at a position closest to the direction of the cylinder 12, the timing at which the discharge port 7 opens can be delayed. In addition, the same code | symbol is attached | subjected to the same structure as the structure shown in FIG. 9, and description is abbreviate | omitted.

A discharge pressure is constantly introduced into the cylinder chamber 19a in connection with the discharge chamber 6. The cylinder chamber 19b is opened with the solenoid valve 20a and the solenoid valve 20b is closed to introduce the suction pressure. The cylinder chamber 19d is opened with the solenoid valve 26a and the solenoid valve 26b is closed to introduce the suction pressure.

By opening the solenoid valve 27a and closing the solenoid valve 27b in the cylinder chamber 19e and introducing the suction pressure, the cylinder chamber 19b, the cylinder chamber 19d, and the cylinder chamber 19e become equal pressure, and the pressure in the cylinder chamber 19a is the cylinder chamber. It becomes a state higher than the pressure of 19b, cylinder chamber 19d, and cylinder chamber 19e.

Since the area of the pressure received by the first piston 13 is larger than the area of the discharge pressure received by the Vi variable valve 11 from the discharge chamber 6 and the suction pressure received from the suction chamber 8, the first piston 13 has a cylinder chamber 19a and a cylinder chamber 19b. Is moved in the direction of the cylinder chamber 19b (the reverse direction with respect to the Vi variable valve 11).

The second piston 14 is pushed by the first piston 13 and moves in the direction of the cylinder chamber 19d, and the third piston 15 connected by the second piston 14 and the second rod 16 also moves in the direction of the cylinder chamber 19d. To do. When the second piston 14 stops at a point where it comes into contact with the first piston partition wall 17, the third piston 15 and the first piston 13 also stop similarly.

Since the Vi variable valve 11 is connected by the first piston 13 and the first rod 9, the position is moved in the direction of the motor 3 in conjunction with the first piston 13, and the timing for opening the discharge port 7 is the latest. Stop at

Further, since there is no differential pressure between the cylinder chamber 19d and the cylinder chamber 19e, the differential pressure force for maintaining the position does not act on the fourth piston 22 and the fifth piston 23, and the Vi variable valve 11 receives. It is not affected by the differential pressure between the discharge chamber 6 and the suction chamber 8.

When the fourth piston 22 is in a position in contact with the third piston 15, the fourth piston 22 is pushed by the third piston 15 and moves in the direction of the cylinder chamber 19 e and is connected by the third rod 24. Although it moves in conjunction with the 5 piston 23, the third piston 15 stops and the fourth piston 22 and the fifth piston 23 also stop.

(Operation when Vi value is 75% load)
FIG. 11 is a side sectional view of the Vi variable mechanism according to the third embodiment when the Vi value is 75% loaded, and the Vi variable valve 11 is closer to the direction of the motor 3 than when the Vi value is 100% loaded. By being positioned, it becomes possible to make the opening timing of the discharge port 7 earlier than when the Vi value is 100% loaded. In addition, the same code | symbol is attached | subjected to the same structure as the structure shown in FIG. 9, and description is abbreviate | omitted.

A discharge pressure is constantly introduced into the cylinder chamber 19a in connection with the discharge chamber 6. The cylinder chamber 19b is opened with the solenoid valve 20a and the solenoid valve 20b is closed to introduce the suction pressure. The cylinder chamber 19d is opened with the solenoid valve 26a and the solenoid valve 26b is closed to introduce the suction pressure.

By closing the solenoid valve 27a and opening the solenoid valve 27b in the cylinder chamber 19e and introducing the discharge pressure, there is no differential pressure between the cylinder chamber 19b and the cylinder chamber 19d. The pressure in the chamber 19e is higher than the pressure in the cylinder chamber 19b and the cylinder chamber 19d.

Since the pressure in the cylinder chamber 19e is higher than the pressure in the cylinder chamber 19d, the fifth piston 23 moves in the direction of the Vi variable valve 11 due to the differential pressure. The fourth piston 22 connected by the fifth piston 23 and the third rod 24 also moves in the direction of the Vi variable valve 11 and then stops at the point where the fifth piston 23 contacts the second piston partition wall 25.

The third piston 15 is pushed by the fourth piston 22 and moves in the direction of the Vi variable valve 11. The second piston 14 connected by the third piston 15 and the second rod 16 also moves together, and is pushed by the second piston 14 so that the first piston 13 also moves in the direction of the Vi variable valve 11. In conjunction with the stop of the fifth piston 23, the fourth piston 22, the third piston 15, the second piston 14, and the first piston 13 also stop.

Since the Vi variable valve 11 is connected to the first piston 13 by the first rod 9, the position of the Vi variable valve 11 moves in the direction of the motor 3 in conjunction with the first piston 13. As the first piston 13 stops, the Vi variable valve 11 stops at a position where the opening timing of the discharge port 7 is earlier than when the Vi value is 100%.

(Operation when Vi value is 50% load)
FIG. 12 is a cross-sectional side view of the Vi variable mechanism according to the third embodiment when the Vi value is 50% loaded, and the Vi variable valve 11 is closer to the direction of the motor 3 than when the Vi value is 75% loaded. By being positioned, it becomes possible to make the opening timing of the discharge port 7 earlier than when the Vi value is 75% loaded. In addition, the same code | symbol is attached | subjected to the same structure as the structure shown in FIG. 9, and description is abbreviate | omitted.

A discharge pressure is constantly introduced into the cylinder chamber 19a in connection with the discharge chamber 6. The cylinder chamber 19b is opened with the solenoid valve 20a and the solenoid valve 20b is closed to introduce the suction pressure. The cylinder chamber 19d is closed with the solenoid valve 26a and the solenoid valve 26b is opened to introduce the discharge pressure.

By opening the electromagnetic valve 27a and closing the electromagnetic valve 27b in the cylinder chamber 19e and introducing the suction pressure, the pressure in the cylinder chamber 19a and the cylinder chamber 19d is higher than the pressure in the cylinder chamber 19b and the cylinder chamber 19e. Become.

Since the pressure in the cylinder chamber 19d becomes higher than the pressure in the cylinder chamber 19b, the third piston 15 moves in the direction of the Vi variable valve 11 due to the differential pressure. After the second piston 14 connected by the third piston 15 and the second rod 16 also moves in the direction of the Vi variable valve 11, the third piston 15 stops at a point where it contacts the first piston partition wall 17. The first piston 13 is pushed by the second piston 14 and moves in the direction of the Vi variable valve 11. When the third piston 15 stops, the second piston 14 and the first piston 13 also stop.

Since the Vi variable valve 11 is connected to the first piston 13 by the first rod 9, the position of the Vi variable valve 11 moves in the direction of the motor 3 in conjunction with the first piston 13. As the first piston 13 stops, it stops at a position where the opening timing of the discharge port 7 is earlier than when the Vi value is 75%.

Further, since the pressure in the cylinder chamber 19d becomes higher than the pressure in the cylinder chamber 19e, the fifth piston 23 moves in the direction of the cylinder chamber 19e (the reverse direction with respect to the Vi variable valve 11) due to the differential pressure. The fourth piston 22 connected by the fifth piston 23 and the third rod 24 also moves together and moves in the direction of the wall opposite to the Vi variable valve 11. When the fourth piston 22 stops at a point where it comes into contact with the second piston partition wall 25, the fifth piston 23 also stops in the same manner.

(Operation with a Vi value of 25% load)
FIG. 13 is a cross-sectional side view of the Vi variable mechanism according to the third embodiment when the Vi value is 25% loaded, and the discharge port is formed by positioning the Vi variable valve 11 at the position closest to the direction of the motor 3. 7 can be opened earlier than when the Vi value is 50% loaded. In addition, the same code | symbol is attached | subjected to the same structure as the structure shown in FIG. 9, and description is abbreviate | omitted.

A discharge pressure is constantly introduced into the cylinder chamber 19a in connection with the discharge chamber 6. Discharge pressure is introduced into the cylinder chamber 19b by closing the solenoid valve 20a and opening the solenoid valve 20b, and suction pressure is introduced into the cylinder chamber 19d by opening the solenoid valve 26a and closing the solenoid valve 26b.

By closing the solenoid valve 27a and opening the solenoid valve 27b in the cylinder chamber 19e and introducing the discharge pressure, the pressure in the cylinder chamber 19a, the cylinder chamber 19b, and the cylinder chamber 19e becomes equal to the pressure in the cylinder chamber 19d. Will also be high.

Since there is no differential pressure between the cylinder chamber 19a and the cylinder chamber 19b and the first piston 13 does not receive the differential pressure from the left and right cylinder chambers, the Vi variable valve 11 receives from the discharge chamber 6 and the suction chamber 8. Influenced by differential pressure.

Since the Vi variable valve 11 always has a force to move in the direction of the motor 3, the Vi variable valve 11 moves in the direction of the motor 3. The first piston 13 moves until it stops in contact with the wall on the Vi variable valve 11 side, and the Vi variable valve 11 stops at a position where the timing of opening the discharge port 7 is earlier than when 50% load is applied.

Further, since the pressure in the cylinder chamber 19b is higher than the pressure in the cylinder chamber 19d, the third piston 15 moves in the direction of the cylinder chamber 19d (the direction opposite to the Vi variable valve 11) due to the differential pressure.

Since the pressure in the cylinder chamber 19e is also higher than the pressure in the cylinder chamber 19d, the fifth piston 23 moves in the direction of the cylinder chamber 19d (the direction of the Vi variable valve 11) due to the differential pressure.
The fourth piston 22 connected by the fifth piston 23 and the third rod 24 also moves in conjunction with each other and stops at the place where the third piston 15 comes into contact.

The third piston 15 and the fourth piston 22 maintain a stopped state due to the differential pressure generated when the pressure in the cylinder chamber 19b and the cylinder chamber 19e is higher than the pressure in the cylinder chamber 19d. .

According to the third embodiment, it is possible to control with four levels of Vi values by simple control based only on the discharge pressure and the suction pressure, and it is possible to obtain a more efficient and inexpensive screw compressor. It is.

Although the pressure in the cylinder chamber 19a is fixed in the third embodiment, other cylinder chambers may be fixed. Further, the pressure introduced into the cylinder chambers 19a, 19b, 19d, and 19e is not limited to the discharge pressure and the suction pressure. In addition, the valves 26a, 26b, 26a, 26b for exchanging pressure are not limited to electromagnetic valves.

Similarly to the first piston partition wall 17, the shape of the second piston partition wall 25 is not particularly limited, and the second piston partition wall 25 and the fourth piston 22 are in contact with each other after passing through the third rod 24. If the fourth piston 22 can be stopped, the operation is not affected in any shape.

1 casing body, 2 screw rotor, 3 motor, 3a stator, 3b motor rotor, 4 screw shaft, 5 compression chamber, 6 discharge chamber, 7 discharge port, 8 suction chamber, 9 first rod, 10 drive device, 11 Vi variable Valve, 12 cylinder, 13 1st piston, 14 2nd piston, 15 3rd piston, 16 2nd rod, 17 1st piston partition, 18 Seal member, 19a, 19b, 19c, 19d, 19e Cylinder chamber, 20a, 20b , 21a, 21b, 26a, 26b, 27a, 27b Solenoid valve, 119a, 119b, 119c, 119d, 119e Pressure introduction hole, 22 4th piston, 23 5th piston, 24 3rd rod, 25 2nd piston partition

Claims (6)

A casing,
A screw rotor that compresses the refrigerant inside the casing;
A motor for rotating the screw rotor;
An internal volume ratio variable mechanism having a Vi variable valve for sliding on the casing to change the internal volume ratio Vi;
In a screw compressor with
The internal volume ratio variable mechanism is:
A cylinder,
A piston partition wall provided in the cylinder and having an opening;
A first piston connected to the Vi variable valve via a first rod;
At least two pistons separated from the first piston, which are provided so as to sandwich the piston partition wall with respect to the first piston and are connected by a second rod penetrating the opening. ,
Inside the cylinder, at least three cylinder chambers are formed by two pistons connected by the first piston and the second rod,
A screw compressor, wherein the position of the Vi variable valve is controlled by moving the first piston by changing the pressure in at least one of the three cylinder chambers.   2. The screw compressor according to claim 1, wherein the three cylinder chambers introduce pressure in the compressor through valve means through a pressure introduction hole provided in the cylinder.   The screw compressor according to claim 1 or 2, wherein a discharge pressure or a suction pressure is introduced into the three cylinder chambers.   The three cylinder chambers are characterized in that the discharge pressure in the compressor is introduced into the cylinder chamber closest to the Vi variable valve, and the discharge pressure and the suction pressure introduced into the other two cylinder chambers are switched. The screw compressor as described in any one of Claims 1-3.   The three cylinder chambers introduce a suction pressure in the compressor into a cylinder chamber located in the center, and exchange a discharge pressure and a suction pressure introduced into the other two cylinder chambers. The screw compressor as described in any one of these.   The screw compressor according to any one of claims 1 to 5, wherein the position of the Vi variable valve is controlled based on a Vi value set in at least three stages.

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