JP6739646B2 - Screw compressor - Google Patents

Description

The present invention relates to a screw compressor having a variable mechanism that changes an internal volume ratio.

Conventionally, a screw compressor is provided with a variable internal volume ratio valve (hereinafter referred to as a variable Vi valve) that is a slide valve that adjusts the timing of discharge start to make the internal volume ratio variable, There is one in which the position of the variable Vi valve is adjusted by the driving force from the driving device. Here, the internal volume ratio is the ratio of the volume of the compression chamber when the suction is completed and the volume of the compression chamber when the discharge is completed.

Generally, a screw compressor does not cause an inappropriate compression loss if the compression ratio, which is the discharge pressure/suction pressure during operation, is operated at an appropriate compression ratio that matches the internal volume ratio. However, when the operation is performed at a low compression ratio lower than the proper compression ratio, the gas compressed until the discharge port is opened is over-compressed above the discharge pressure, and extra compression work is performed. On the other hand, when the operation is performed at a higher compression ratio than the proper compression ratio, the discharge port opens before reaching the discharge pressure, resulting in a state of insufficient compression that causes a reverse flow of gas. All of these cause power loss and lower efficiency. In order to suppress the efficiency decrease due to such power loss, it is necessary to operate at an optimum internal volume ratio.

Therefore, conventionally, a screw compressor has been proposed in which the position of the variable Vi valve is adjusted to make the internal volume ratio variable (for example, refer to Patent Document 1). In Patent Document 1, the position of the variable Vi valve is adjusted in two stages by switching each of the two solenoid valves to open or close without using complicated control for adjusting the position of the variable Vi valve. Specifically, in Patent Document 1, a piston is connected to a variable Vi valve via a lot, and suction pressure or discharge pressure is appropriately switched and supplied via two electromagnetic valves before and after in the moving direction of the piston. It is configured. The position of the variable Vi valve can be adjusted in two stages by creating a pressure difference before and after the piston so that the piston can be moved to two different positions.

Japanese Patent No. 5881403

In Patent Document 1 described above, two solenoid valves are required to adjust the position of the variable Vi valve in two stages. Further, in order to increase the number of stages, a plurality of solenoid valves are needed.

The present invention has been made to solve the above problems, and an object thereof is to obtain a screw compressor capable of adjusting the internal volume ratio in multiple stages with a simple configuration by reducing the number of solenoid valves used. And

The screw compressor according to the present invention, a casing having a discharge chamber and a suction chamber inside, a plurality of grooves forming the compression chamber is formed on the outer peripheral surface, a screw rotor arranged to rotate in the casing, , A variable Vi valve that moves in the axial direction of the screw rotor and switches the stop position to change the internal volume ratio, which is the ratio of the volume of the compression chamber at the completion of suction to the volume of the compression chamber at the completion of discharge, A drive device including a Vi piston connected to the Vi valve and a drive cylinder that movably accommodates the Vi piston therein, and a pressure switching mechanism that switches a pressure introduced into the drive device are provided. , The Vi piston is divided into two cylinder chambers, and the drive unit moves the Vi piston by controlling the pressure in one of the two cylinder chambers to control the position of the variable Vi valve. The pressure switching mechanism is a solenoid valve that opens and closes a first flow path that connects the discharge chamber and one cylinder chamber, and switches the discharge pressure from the discharge chamber to one cylinder chamber. A switching cylinder that communicates with the first flow path between the solenoid valve and one cylinder chamber, a switching piston that is movably accommodated inside the switching cylinder, and a spring that is compressed by the movement of the switching piston. The switching cylinder is provided with a first switching cylinder chamber in which a suction pressure is always introduced and a spring is arranged, and a second switching cylinder chamber communicating with the first flow path by a switching piston. The second flow path that is partitioned and connects the first switching cylinder chamber and one cylinder chamber is opened/closed according to the position of the switching piston that receives the spring force of the spring, and the first valve is opened/closed by opening/closing the solenoid valve. The flow passage is opened and closed, and the second flow passage is opened and closed by the movement of the switching piston, so that the pressure in one cylinder chamber changes.

According to the present invention, the pressure supplied to the Vi piston connected to the variable Vi valve via the lot can be changed by one solenoid valve, and the internal volume ratio can be set in a plurality of stages with a simple configuration. An adjustable screw compressor can be obtained.

It is a schematic block diagram of the screw compressor which concerns on Embodiment 1 of this invention. FIG. 3 is a schematic diagram illustrating a drive device and a pressure switching mechanism in the screw compressor according to Embodiment 1 of the present invention. FIG. 3 is an operation schematic diagram of a drive device and a pressure switching mechanism when the internal volume ratio is large in the screw compressor according to Embodiment 1 of the present invention. FIG. 3 is an operation schematic diagram of a drive device and a pressure switching mechanism when the internal volume ratio is small in the screw compressor according to Embodiment 1 of the present invention. FIG. 7 is an operation schematic diagram of a drive device and a pressure switching mechanism when the internal volume ratio is large in the screw compressor according to Embodiment 2 of the present invention. FIG. 6 is an operation schematic diagram of a drive device and a pressure switching mechanism when the internal volume ratio is small in the screw compressor according to Embodiment 2 of the present invention. It is a schematic diagram explaining the drive device and pressure switching mechanism in the screw compressor which concerns on Embodiment 3 of this invention. FIG. 11 is an operation schematic diagram of a drive device and a pressure switching mechanism when the internal volume ratio is large in the screw compressor according to the third embodiment of the present invention. FIG. 11 is an operation schematic diagram of a drive device and a pressure switching mechanism when the internal volume ratio is medium in the screw compressor according to the third embodiment of the present invention. FIG. 11 is an operation outline diagram of a drive device and a pressure switching mechanism when the internal volume ratio is small in the screw compressor according to the third embodiment of the present invention. FIG. 13 is an operation schematic diagram of a drive device and a pressure switching mechanism when the internal volume ratio is large in the screw compressor according to Embodiment 4 of the present invention. FIG. 13 is an operation schematic diagram of a drive device and a pressure switching mechanism when the internal volume ratio is medium in the screw compressor according to the fourth embodiment of the present invention. FIG. 14 is an operation outline diagram of a drive device and a pressure switching mechanism when the internal volume ratio is small in the screw compressor according to the fourth embodiment of the present invention. It is a schematic block diagram of the screw compressor which concerns on Embodiment 5 of this invention. It is a schematic block diagram of the screw compressor which concerns on Embodiment 6 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 1 according to the first embodiment is a single screw compressor, and has a cylindrical casing 2, a cylindrical screw rotor 5 housed in the casing 2, and a rotational drive of the screw rotor 5. And a motor 3. The motor 3 is composed of a stator 3a which is inscribed in the casing 2 and is fixed thereto, and a motor rotor 3b which is arranged inside the stator 3a. The motor 3 may be an inverter type whose rotation speed is controlled by an inverter or a constant speed type which operates at a constant rotation speed.

The screw rotor 5 and the motor rotor 3b 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 5, a plurality of spiral screw grooves 5a are formed. The screw rotor 5 is connected to a motor rotor 3b fixed to the screw shaft 4 and is rotationally driven. In addition, the space inside the screw groove 5a formed in the screw rotor 5 is surrounded by the inner peripheral surface of the casing 2 and a pair of gate rotors (not shown) that engage and engage with the screw groove 5a. The chamber 6 is formed.

Further, the inside of the casing 2 is divided into a discharge pressure side and a suction pressure side by a partition wall (not shown), and a discharge chamber 7 and a discharge port 8 opening to the discharge chamber 7 are formed on the discharge pressure side. A suction chamber 16 is formed on the suction pressure side. The discharge pressure is the pressure of the refrigerant discharged from the compression chamber 6 by compressing the refrigerant in the compression chamber 6. The suction pressure is the pressure of the refrigerant sucked into the compression chamber 6. The relationship between the discharge pressure and the suction pressure is discharge pressure>suction pressure.

Further, between the inner peripheral surface of the casing 2 and the outer peripheral surface of the screw rotor 5, a pair of variable Vi valves 9 that are movable in the axial direction of the screw shaft 4 are arranged. The variable Vi valve 9 forms a part of the discharge port 8 and is connected to the drive device 11 via the lot 10. In FIG. 1, only the drive device 11 connected to one variable Vi valve 9 is shown, and the drive device 11 connected to the other variable Vi valve 9 is omitted.

The drive device 11 is driven by gas pressure, and includes a cylinder 12 and a Vi piston 13 housed in the cylinder 12 and movable in the cylinder 12 in the axial direction. The Vi piston 13 is connected to the variable Vi valve 9 via the lot 10 and is configured to be movable in the cylinder 12 in the axial direction. The Vi piston 13 corresponds to the Vi piston or the first Vi piston of the present invention.

As a characteristic configuration of the first embodiment, a pressure switching mechanism 21 shown in FIG. 2 described later that switches the pressure to be introduced into the drive device 11 is provided, and the pressure switching mechanism 21 has a component configuration of two solenoid valves. It has a simpler structure than the one provided.

The screw compressor 1 further includes a control device 50 (see FIG. 1) that opens and closes a solenoid valve 27 of the pressure switching mechanism 21, which will be described later. The control device 50 can be configured by hardware such as a circuit device that realizes the function, or can be configured by an arithmetic device such as a CPU and software executed on the arithmetic device.

The configurations of the drive device 11 and the pressure switching mechanism 21 will be described below with reference to FIG. In addition, in the following, the "flow path" may be formed by providing a hole inside the wall of the casing 2 or the cylinder 12, or may be formed by using a pipe.

FIG. 2 is a schematic diagram illustrating a drive device and a pressure switching mechanism in the screw compressor according to the first embodiment of the present invention. In FIG. 2, the suction pressure is on the right side of the variable Vi valve 9, and the discharge pressure is on the left side of the variable Vi valve 9.
First, the variable Vi valve 9 will be described. The variable Vi valve 9 includes a valve body 9a, a guide portion 9b, and a connecting portion 9c, and the valve body 9a and the guide portion 9b are connected by the connecting portion 9c. Further, one end of the lot 10 is connected to the drive device side end 9h of the guide portion 9b, and the other end is connected to the end surface of the Vi piston 13 on the variable Vi valve 9 side. The space between the discharge port side end portion 9d of the valve body 9a and the discharge port side end portion 9e of the guide portion 9b forms a discharge gap 9f communicating with the discharge port 8.

In the drive device 11, the space inside the cylinder 12 is partitioned by the Vi piston 13 into a cylinder chamber 14a on the variable Vi valve side (right side in the drawing) and a cylinder chamber 14b on the opposite side (left side in the drawing). The cylinder 12 corresponds to the drive cylinder of the present invention, the cylinder chamber 14a corresponds to the first cylinder chamber of the present invention, and the cylinder chamber 14b corresponds to the second cylinder chamber of the present invention.

The cylinder 12 has a pressure introduction hole 114a formed on the cylinder chamber 14a side, and a pressure introduction hole 114b and a pressure relief hole 114c formed on the cylinder chamber 14b side. The cylinder chamber 14a communicates with the discharge chamber 7 of FIG. 1 through the pressure introducing hole 114a and the flow path 15a, and the discharge pressure is constantly introduced from the discharge chamber 7 into the cylinder chamber 14a.

The cylinder chamber 14b is connected to the pressure switching mechanism 21 via the pressure introduction hole 114b and the flow path 15b, and the pressure switching mechanism 21 switches introduction or interruption of the discharge pressure. The cylinder chamber 14b communicates with the discharge chamber 7 via the pressure switching mechanism 21 and the flow path 30, and the pressure switching mechanism 21 switches the introduction or blocking of the discharge pressure from the discharge chamber 7. The channel 30 is a channel including the channel 15b, the channel 28c, and the channel 28d, and corresponds to the first channel of the present invention.

Further, the cylinder chamber 14b communicates with the suction chamber 16 via the pressure relief hole 114c and the flow passage 15c, and a throttle mechanism 15ca is provided in the middle of the flow passage 15c. The throttling mechanism 15ca is provided to suppress the pressure in the cylinder chamber 14b from escaping from the pressure relief hole 114c to the suction chamber side, and is specifically configured by, for example, a capillary tube, an orifice, or the like. The diaphragm mechanism 15ca corresponds to the second diaphragm mechanism of the present invention.

The pressure switching mechanism 21 includes an electromagnetic valve 27, a cylinder 22, a switching piston 23, a rod 24 connected to the switching piston 23, and a spring 25 that is compressed by the movement of the switching piston 23. The cylinder 22 accommodates the switching piston 23 inside so as to be movable in the axial direction. The spring 25 is externally inserted into the rod 24 and arranged in a cylinder chamber 26a described later. When the spring 25 has a natural length, the switching piston 23 is located at the position shown in FIG. 3 described later. The switching piston 23 and the rod 24 do not necessarily have to be separate parts, and may be an integrally molded product. The pressure switching mechanism 21 corresponds to the first mechanism of the present invention.

As described above, the pressure switching mechanism 21 has only one electromagnetic valve and has a simpler structure than the structure including two electromagnetic valves. That is, the solenoid valve requires a solenoid portion for converting electrical energy into mechanical motion for opening and closing the solenoid valve by magnetic force in addition to the configuration of a cylinder, a piston, a rod, and a spring. The solenoid portion is composed of a coil, a yoke, a sleeve, a core and a plug nut, the core is composed of a movable iron core or a plunger, and the plug nut is composed of a fixed iron core. Therefore, the configuration including two electromagnetic valves tends to be expensive. However, since the pressure switching mechanism 21 has one solenoid valve and the other components are the cylinder 22, the switching piston 23, the rod 24, and the spring 25, the pressure switching mechanism 21 can be constructed at a lower cost than the configuration using two solenoid valves.

Hereinafter, the pressure switching mechanism 21 will be described in detail.
The solenoid valve 27 opens and closes a flow path 28d that connects the discharge chamber 7 and the cylinder 22 to switch the discharge pressure from the discharge chamber 7 into a cylinder chamber 26b of the cylinder 22 described later, or shuts it off. Since the cylinder chamber 26b communicates with the cylinder chamber 14b of the drive device 11 via the flow path 28c, the solenoid valve 27 switches the introduction or interruption of the discharge pressure from the discharge chamber 7 to the cylinder chamber 14b. Can also be said.

The inside of the cylinder 22 is partitioned into a cylinder chamber 26a and a cylinder chamber 26b by a switching piston 23. The cylinder 22 has a pressure introduction hole 214a formed on the cylinder chamber 26a side, and a pressure introduction hole 214d and a pressure relief hole 214c formed on the cylinder chamber 26b side. Further, the cylinder 22 is formed with a pressure relief hole 214b which is opened and closed depending on the position of the switching piston 23. The cylinder 22 corresponds to the switching cylinder of the present invention, the cylinder chamber 26a corresponds to the first switching cylinder chamber of the present invention, and the cylinder chamber 26b corresponds to the second switching cylinder chamber of the present invention.

The cylinder chamber 26a communicates with the suction chamber 16 of FIG. 1 through the pressure introduction hole 214a and the flow path 28a, and the suction pressure is constantly introduced from the suction chamber 16 into the cylinder chamber 26a. Further, the cylinder chamber 26b communicates with the discharge chamber 7 of FIG. 1 through the pressure introducing hole 214d, the flow path 28d and the electromagnetic valve 27. When the electromagnetic valve 27 is opened, the cylinder chamber 26b is discharged. Pressure is introduced.

The pressure relief hole 214b communicates with the flow path 28c through the flow path 28b, and the flow path 28b is provided with a throttling mechanism 28ba. The throttle mechanism 28ba is provided to suppress the discharge pressure in the cylinder chamber 14b from being introduced into the cylinder chamber 26a when the electromagnetic valve 27 is switched from open to closed. The throttle mechanism 28ba is composed of an orifice, a capillary tube, or the like. The flow channel 28b corresponds to the second flow channel of the present invention, and the throttle mechanism 28ba corresponds to the first throttle mechanism of the present invention.

Next, the operation of the variable Vi valve 9 will be described together with the operation of the pistons of the drive device 11 and the pressure switching mechanism 21. In the first embodiment, the value of the internal volume ratio (hereinafter referred to as the Vi value) can be set in two steps, large and small. The internal volume ratio is the ratio of the volume of the compression chamber when the suction is completed and the volume of the compression chamber when the discharge is completed.

(1) Operation when Vi value is large FIG. 3 is an operation outline diagram of the drive device and the pressure switching mechanism when the internal volume ratio is large in the screw compressor according to Embodiment 1 of the present invention. In FIG. 3 and each of the figures described later, the black-painted display of the solenoid valve indicates that the solenoid valve is in the “closed” state, and the white-out display indicates that the solenoid valve is in the “open” state. Further, in FIG. 3 and each of the drawings described later, the arrow in the drawing indicates the moving direction of the Vi piston.

When the Vi value is large, by closing the electromagnetic valve 27, the drive device 11 positions the variable Vi valve 9 in the leftward direction shown by the arrow in the figure, thereby delaying the timing of opening the discharge port 8. ..

First, the operation of the pressure switching mechanism 21 will be described. When the Vi value is large, the solenoid valve 27 is closed to equalize the pressure of the cylinder chamber 26b with the cylinder chamber 14b of the drive device 11 that is in communication with the drive device 11 via the flow path 28c. Specifically, the pressures of the cylinder chamber 26b and the cylinder chamber 14b are the discharge pressure immediately after the solenoid valve 27 is switched from open to closed. However, since the cylinder chamber 14b communicates with the suction chamber 16 via the throttle mechanism 15ca, the pressures of the cylinder chamber 26b and the cylinder chamber 14b approach the suction pressure over time. Further, since the suction pressure is constantly introduced into the cylinder chamber 26a, the switching piston 23 moves to the cylinder chamber 26b side by the action of the spring 25 when the pressure in the cylinder chamber 26b approaches the suction pressure side. , The pressure relief hole 214b is opened.

By opening the pressure relief hole 214b, the cylinder chamber 26a and the cylinder chamber 14b communicate with each other through the flow passage 28b and the flow passage 15b, and the pressure of the cylinder chamber 14b of the drive device 11 is the same as the cylinder chamber 26a. Becomes That is, the pressure switching mechanism 21 introduces the suction pressure into the cylinder chamber 14b when the electromagnetic valve 27 is closed.

Next, operations of the drive device 11 and the variable Vi valve 9 will be described. The cylinder chamber 14a is connected to the discharge chamber 7, and the discharge pressure is constantly introduced. Therefore, due to the pressure difference in the cylinder 14, the Vi piston 13 tries to move to the left in the drawing.

On the other hand, with respect to the variable Vi valve 9 connected to the Vi piston 13, suction pressure acts on both ends in the moving direction, that is, the suction side end 9g of the valve body 9a, and the guide unit 9b on the drive unit side. The discharge pressure acts on the end portion 9h. Further, the discharge pressure immediately after discharge acts on the discharge port side end portion 9d of the valve body 9a, and the discharge pressure on the discharge port side end portion 9d of the guide portion 9b is the same as the discharge pressure acting on the discharge port side end portion 9d. However, they act in the opposite directions to the discharge port side end portion 9d. Therefore, the loads acting on the discharge port side end portion 9d and the discharge port side end portion 9e are canceled out, and the variable Vi valve 9 has the pressure of the pressure acting on the drive device side end portion 9h and the suction side end portion 9g. It tries to move to the right in the figure due to the difference.

Here, the area of the front and rear surfaces of the Vi piston 13 in the moving direction is larger than the area of the drive device side end portion 9h that receives the discharge pressure in the variable Vi valve 9. Therefore, the Vi piston 13 and the variable Vi valve 9 move leftward in the drawing due to the pressure difference between the front and rear surfaces of the Vi piston 13 in the moving direction. Then, the variable Vi valve 9 is stopped at a position where the Vi piston 13 comes into contact with the wall surface of the cylinder chamber 14b, and is accurately positioned at a position having a large Vi value.

(2) Operation when Vi value is small FIG. 4 is an operation outline diagram of the drive device and the pressure switching mechanism when the internal volume ratio is small in the screw compressor according to Embodiment 1 of the present invention.
When the Vi value is small, the solenoid valve 27 is opened, and the drive device 11 positions the variable Vi valve 9 in the right direction shown by the arrow in the figure, thereby advancing the timing at which the discharge port 8 is opened.

First, the operation of the pressure switching mechanism 21 will be described. When the Vi value is small, the solenoid valve 27 is opened so that the pressure in the cylinder chamber 26b becomes the discharge pressure. Further, the suction pressure is constantly introduced into the cylinder chamber 26a to be the suction pressure, and the suction pressure and the spring force act on the switching piston 23 in the direction opposite to the acting force from the cylinder chamber 26b. To do. Due to the relationship of these acting forces on the switching piston 23, the switching piston 23 moves to the cylinder chamber 26a side and closes the pressure relief hole 214b.

By closing the pressure relief hole 214b, the cylinder chamber 14b of the drive device 11 does not communicate with the cylinder chamber 26a of the pressure switching mechanism 21 but communicates with the cylinder chamber 26b, and the same discharge pressure as that of the cylinder chamber 26b is obtained. Become. The cylinder chamber 14b communicates with the suction chamber 16 via the pressure relief hole 114c and the flow passage 15c, but since the flow passage 15c is provided with the throttling mechanism 15ca, the pressure in the cylinder chamber 14b is The discharge pressure is maintained while the solenoid valve 27 is open.

As described above, the pressure switching mechanism 21 introduces the discharge pressure into the cylinder chamber 14b when the solenoid valve 27 is open.

Next, operations of the drive device 11 and the variable Vi valve 9 will be described. Since the cylinder chamber 14a is connected to the discharge chamber 7 and the discharge pressure is constantly introduced, there is no pressure difference in the cylinder 14.

On the other hand, in the variable Vi valve 9 connected to the Vi piston 13, suction pressure acts on the suction side end portion 9g of the valve body 9a, and discharge pressure acts on the drive device side end portion 9h of the guide portion 9b. It is working. Further, the discharge pressure immediately after discharge acts on the discharge port side end portion 9d of the valve body 9a, and the discharge pressure on the discharge port side end portion 9d of the guide portion 9b is the same as the discharge pressure acting on the discharge port side end portion 9d. However, they act in the opposite directions to the discharge port side end portion 9d. Therefore, the loads acting on the discharge port side end portion 9d and the discharge port side end portion 9e are offset.

Since there is no pressure difference in the cylinder 14, the variable Vi valve 9 is controlled by the differential pressure between the discharge pressure acting on the drive-side end 9h and the suction pressure acting on the suction-side end 9g. Move to the right in the figure. Then, the suction side end portion 9g of the variable Vi valve 9 is stopped at a position where it comes into contact with the wall surface of the casing 2, and the variable Vi valve 9 is accurately positioned at a position with a small Vi value.

As described above, according to the first embodiment, the pressure of one of the cylinder chambers 14a and 14b, here, the cylinder chamber 14b, is changed by opening and closing one solenoid valve 27. , The position of the variable Vi valve 9 is controlled. Here, the pressure of the cylinder chamber 14b is changed by opening and closing the electromagnetic valve 27 to open and close the flow path from the discharge chamber 7 to the cylinder chamber 14b, and the switching piston 23 resists the spring force of the spring 25. It is realized by moving and opening/closing the flow path 28b having the suction pressure. In other words, the pressure in the cylinder chamber 14b is changed by the simple movable control of the switching piston 23 using the pressure difference between the discharge pressure and the suction pressure acting on the switching piston 23 and the spring force of the spring 25. it can. Therefore, the pressure in the cylinder chamber 14b can be changed without using two solenoid valves, and a screw compressor having an inexpensive and simple structure can be obtained.

Further, the number of solenoid valves to be controlled is reduced from two to one as compared with the configuration of Patent Document 1 in which the internal volume ratio can be adjusted in two stages, so control of the solenoid valves can also be simplified.

Embodiment 2.
The second embodiment of the present invention is an embodiment in which the connection destination of the pressure switching mechanism 21 of the first embodiment is changed from the cylinder chamber 14b to the cylinder chamber 14a. More specifically, the pressure switching mechanism 21 is connected to the pressure introducing hole 114a, and the pressure introducing hole 114b communicates with the suction chamber 16.

Next, the operation of the variable Vi valve 9 according to the second embodiment will be described. As in the first embodiment, the Vi value can be set in two steps, large and small.
(1) Operation when Vi value is large FIG. 5 is an operation outline diagram of the drive device and the pressure switching mechanism when the internal volume ratio is large in the screw compressor according to Embodiment 2 of the present invention.
When the Vi value is large, the drive device 11 positions the variable Vi valve 9 in the leftward direction indicated by the arrow in the figure, thereby delaying the timing at which the discharge port 8 opens.

That is, when the Vi value is high, the solenoid valve 27 is opened to set the discharge pressure in the cylinder chamber 14a. On the other hand, since the cylinder chamber 14b is connected to the suction chamber 16 and the suction pressure is constantly introduced, the pressure difference in the cylinder 12 causes the Vi piston 13 to move leftward in the drawing.

On the other hand, in the variable Vi valve 9 connected to the Vi piston 13, suction pressure acts on the suction side end portion 9g of the valve body 9a, and discharge pressure acts on the drive device side end portion 9h of the guide portion 9b. It is working. Further, the discharge pressure immediately after discharge acts on the discharge port side end portion 9d of the valve body 9a, and the discharge pressure on the discharge port side end portion 9d of the guide portion 9b is the same as the discharge pressure acting on the discharge port side end portion 9d. However, they act in the opposite directions to the discharge port side end portion 9d. Therefore, the loads acting on the discharge port side end portion 9d and the discharge port side end portion 9e are canceled out, and the variable Vi valve 9 has the pressure of the pressure acting on the drive device side end portion 9h and the suction side end portion 9g. It tries to move to the right in the figure due to the difference. However, as described above, since the area of the Vi piston 13 is set to be larger than the area of the drive-side end 9h of the variable Vi valve 9, the Vi piston 13 and the variable piston 13 and the variable Vi valve 13 are variable due to the pressure difference between the two surfaces. The Vi valve 9 moves leftward in the figure. Then, the variable Vi valve 9 is stopped at a position where the Vi piston 13 comes into contact with the wall surface of the cylinder chamber 14b, and is accurately positioned at a position having a large Vi value.

(2) Operation when Vi value is small FIG. 6 is an operation schematic diagram of the drive device and the pressure switching mechanism when the internal volume ratio is small in the screw compressor according to the second embodiment of the present invention.
When the Vi value is small, the drive device 11 positions the variable Vi valve 9 in the right direction indicated by the arrow in the drawing, thereby accelerating the timing of opening the discharge port 8.

That is, by closing the solenoid valve 27, the inside of the cylinder chamber 14a is set to the suction pressure. On the other hand, since the cylinder chamber 14b is connected to the suction chamber 16 and the suction pressure is constantly introduced, there is no pressure difference in the cylinder 12.

On the other hand, in the variable Vi valve 9 connected to the Vi piston 13, suction pressure acts on the suction side end portion 9g of the valve body 9a, and discharge pressure acts on the drive device side end portion 9h of the guide portion 9b. It is working. Further, the discharge pressure immediately after discharge acts on the discharge port side end portion 9d of the valve body 9a, and the discharge pressure on the discharge port side end portion 9d of the guide portion 9b is the same as the discharge pressure acting on the discharge port side end portion 9d. However, they act in the opposite directions to the discharge port side end portion 9d. Therefore, the loads acting on the discharge port side end portion 9d and the discharge port side end portion 9e are offset.

Since there is no pressure difference in the cylinder 14, the variable Vi valve 9 is controlled by the differential pressure between the discharge pressure acting on the drive-side end 9h and the suction pressure acting on the suction-side end 9g. Move to the right in the figure. Then, the suction side end portion 9g of the variable Vi valve 9 is stopped at a position where it comes into contact with the wall surface of the casing 2, and the variable Vi valve 9 is accurately positioned at a position with a small Vi value.

The second embodiment is a mode in which the connection destination of the pressure switching mechanism 21 of the first embodiment is changed from the cylinder chamber 14b to the cylinder chamber 14a, and the same effect as that of the first embodiment can be obtained.

Embodiment 3.
In the above-described first and second embodiments, the Vi value is variable in two stages, large and small, but in the third embodiment, the Vi value is divided into three stages, large, medium, and small. A variable structure will be described.

FIG. 7 is a schematic diagram illustrating a drive device and a pressure switching mechanism in a screw compressor according to Embodiment 3 of the present invention. The same components as those shown in FIG. 2 will be assigned the same reference numerals and explanations thereof will be omitted.

The screw compressor according to the third embodiment further includes a pressure switching mechanism 31 in addition to the first embodiment. Further, in the cylinder chamber 14b of the drive device 11, in addition to the first embodiment, a Vi piston 39, an interlocking piston 40, a connecting portion 41, and a positioning wall 42 are further arranged. The cylinder chamber 14b is divided into two cylinder chambers by the Vi piston 39. That is, the cylinder chamber 14b is partitioned into a cylinder chamber 14c between the Vi piston 39 and the Vi piston 13 and a cylinder chamber 14d on the opposite side. The Vi piston 39 corresponds to the second Vi piston of the present invention.

Further, although the pressure switching mechanism 21 switches the pressure introduced into the cylinder chamber 14b in the first embodiment, the pressure switching mechanism 21 switches the pressure introduced into the cylinder chamber 14c of the cylinder chambers 14b in the third embodiment. I do. The cylinder chamber 14a corresponds to the first cylinder chamber of the present invention, the cylinder chamber 14c corresponds to the second cylinder chamber of the present invention, and the cylinder chamber 14d corresponds to the third cylinder chamber of the present invention.

The Vi piston 39 is connected to the interlocking piston 40 at the connecting portion 41. A positioning wall 42 that extends in a direction orthogonal to the moving direction of the Vi piston 39 is provided between the Vi piston 39 and the interlocking piston 40. A hole 42a is formed in the positioning wall 42, the connecting portion 41 is movably passed through the hole 42a, and the Vi piston 39 is movable in the cylinder chamber 14b together with the interlocking piston 40.

The Vi piston 39 has a position where the Vi piston 39 contacts the positioning wall 42 and stops, and the Vi piston 39 moves away from the positioning wall 42 and the interlocking piston 40 contacts the positioning wall 42 and stops. Positioned at. In the cylinder 12, the Vi piston 13 and the Vi piston 39 can operate independently.

Further, the cylinder 12 has a pressure introduction hole 114e and a pressure relief hole 114f formed on the cylinder chamber 14d side. The cylinder chamber 14d is connected to the pressure switching mechanism 31 via the pressure introducing hole 114e and the flow path 15d, and the pressure switching mechanism 21 switches introduction or interruption of the discharge pressure. Further, the cylinder chamber 14d communicates with the suction chamber 16 via the pressure relief hole 114f, the flow passage 15f, the throttle mechanism 15fa and the flow passage 15c. Further, the cylinder chamber 14c communicates with the suction chamber 16 via the pressure relief hole 114c, the flow passage 15e, the throttle mechanism 15ea and the flow passage 15c.

The pressure switching mechanism 31 has the same configuration as that of the pressure switching mechanism 21, and if the leading “2” of the reference numeral of the constituent portion of the pressure switching mechanism 21 is changed to “3”, the pressure switching mechanism 31 becomes Become. The pressure switching mechanism 31 switches the introduction or interruption of the discharge pressure to the cylinder chamber 14d.

Table 1 below is a table summarizing the open/closed states of the solenoid valve 27 and the solenoid valve 37 when the Vi value is made large, medium, and small in the third embodiment. For the table, refer to the operation description below as appropriate.

(1) Operation when Vi value is large FIG. 8 is an operation outline diagram of the drive device and the pressure switching mechanism when the internal volume ratio is large in the screw compressor according to the third embodiment of the present invention.
When the Vi value is large, the solenoid valve 27 is closed and the solenoid valve 37 is closed as shown in Table 1. By closing the solenoid valve 27, suction pressure is introduced from the pressure switching mechanism 21 into the cylinder chamber 14c. Further, the suction pressure is introduced into the cylinder chamber 14d by closing the solenoid valve 37. Therefore, both the cylinder chamber 14c and the cylinder chamber 14d have the suction pressure, and the cylinder chamber 14b has the suction pressure. The discharge pressure is constantly introduced into the cylinder chamber 14a.

In this way, the discharge pressure is introduced into the cylinder chamber 14a and the suction pressure is introduced into the cylinder chamber 14b with the Vi piston 13 as a boundary. As a result, the same operation as when the Vi value is large in the first embodiment is performed, and the variable Vi valve 9 moves to the left as shown by the arrow in the figure. That is, the driving device 11 delays the timing at which the discharge port 8 opens by locating the variable Vi valve 9 in the leftward direction shown by the arrow in the figure.

(2) Operation during Vi value FIG. 9 is an operation schematic diagram of the drive device and the pressure switching mechanism when the internal volume ratio is medium in the screw compressor according to the third embodiment of the present invention.
During the Vi value, the solenoid valve 27 is closed and the solenoid valve 37 is opened. By closing the solenoid valve 27, suction pressure is introduced into the cylinder chamber 14d. Further, by opening the solenoid valve 37, the discharge pressure is introduced into the cylinder chamber 14d. Further, the discharge pressure is constantly introduced into the cylinder chamber 14a. As a result, the cylinder chamber 14a and the cylinder chamber 14d have the same discharge pressure, and the cylinder chamber 14c has the suction pressure.

Here, the cylinder chamber 14d becomes the suction pressure both when the above Vi value is large and when the below Vi value is small. For this reason, when switching from a state with a large Vi value or a small Vi value to a state with a Vi value, the solenoid valve 37 is closed to open, so that the pressure in the cylinder chamber 14d changes from the suction pressure to the discharge pressure.

More specifically, in the case of switching from the large Vi value to the medium Vi value, the pressure in the cylinder chamber 14d increases from the suction pressure to the discharge pressure when the Vi piston 39 is stopped at the position shown in FIG. Then, the Vi piston 39 moves rightward together with the interlocking piston 40. As the Vi piston 39 moves to the right, the variable Vi valve 9 is pressed by the interlocking piston 40 and moves to the right. Then, when the Vi piston 39 comes into contact with the positioning wall 42 and stops, the Vi piston 13 and the variable Vi valve 9 also stop together, and the positioning state shown in FIG. 9 is obtained.

Further, in the case of switching from the small Vi value to the medium Vi value, the pressure in the cylinder chamber 14d rises from the suction pressure to the discharge pressure from the state where the Vi piston 39 is stopped at the position shown in FIG. On the other hand, the cylinder chamber 14c has a suction pressure because the electromagnetic valve 27 is closed. Therefore, the piston 39 for Vi moves to the right due to the pressure difference between the cylinder chamber 14d and the cylinder chamber 14c, contacts the positioning wall 42, and stops.

Further, when the Vi value described later is small, the cylinder chamber 14a and the cylinder chamber 14c have the discharge pressure, but the solenoid valve 27 is closed by switching to the Vi value, so that the pressure in the cylinder chamber 14c becomes the discharge pressure. Changes to suction pressure. Therefore, the Vi piston 13 moves leftward from the position in FIG. 10 due to the pressure difference between the cylinder chamber 14a and the cylinder chamber 14c, and stops when it comes into contact with the interlocking piston 40, and the positioning state shown in FIG. Become.

As described above, in the case of the Vi value, the Vi piston 13 stops at the position where it contacts the interlocking piston 40 when the Vi piston 39 contacts the positioning wall 42. In this state, the variable Vi valve 9 is located on the right side of the case where the Vi value is large as shown in FIG. 8, and as a result, the timing at which the discharge port 8 opens is earlier than when the Vi value is large.

(3) Operation when Vi value is small FIG. 10 is an operation outline diagram of the drive device and the pressure switching mechanism when the internal volume ratio is small in the screw compressor according to the third embodiment of the present invention.
When the Vi value is small, the electromagnetic valve 27 is opened to introduce the discharge pressure from the pressure switching mechanism 21 into the cylinder chamber 14c. Further, the suction pressure is introduced into the cylinder chamber 14d by closing the solenoid valve 37. Further, the discharge pressure is constantly introduced into the cylinder chamber 14a. As a result, the cylinder chamber 14a and the cylinder chamber 14c have a discharge pressure, and the cylinder chamber 14d has a suction pressure. Therefore, in the cylinder 12, there is no pressure difference between the front and rear surfaces of the Vi piston 13 in the moving direction.

Here, as for the variable Vi valve 9 connected to the Vi piston 13, suction pressure acts on both ends in the moving direction, that is, the suction side end 9g of the valve body 9a, as in the first embodiment. The discharge pressure acts on the drive device side end 9h of the guide portion 9b. Further, the discharge pressure immediately after discharge acts on the discharge port side end portion 9d of the valve body 9a, and the discharge pressure on the discharge port side end portion 9d of the guide portion 9b is the same as the discharge pressure acting on the discharge port side end portion 9d. However, they act in the opposite directions to the discharge port side end portion 9d. Therefore, the loads acting on the discharge port side end portion 9d and the discharge port side end portion 9e are canceled out, and the variable Vi valve 9 has the pressure of the pressure acting on the drive device side end portion 9h and the suction side end portion 9g. It moves to the right in the figure due to the difference. Then, the suction side end portion 9g of the variable Vi valve 9 is stopped at a position where it comes into contact with the wall surface of the casing 2, and the variable Vi valve 9 is accurately positioned at a position with a small Vi value. As a result, the timing at which the ejection port 8 opens is earlier than during the Vi value.

According to the third embodiment, by using two pressure switching mechanisms each having one solenoid valve, it becomes possible to control the Vi value in three stages, and an inexpensive and simple screw compressor can be obtained. ..

Fourth Embodiment
The fourth embodiment of the present invention is an embodiment in which the connection destination of the pressure switching mechanism 21 of the third embodiment is changed from the cylinder chamber 14c to the cylinder chamber 14a. More specifically, the pressure switching mechanism 21 is connected to the pressure introducing hole 114a, and the pressure introducing hole 114b communicates with the suction chamber 16.

Next, the operation of the variable Vi valve 9 according to the fourth embodiment will be described. As in the third embodiment, the Vi value can be set in three stages of large, medium and small.

Table 2 below is a table summarizing the open/closed states of the solenoid valve 27 and the solenoid valve 37 when the Vi value is made large, medium, and small in the fourth embodiment. For the table, refer to the operation description below as appropriate.

(1) Operation when Vi value is large FIG. 11 is an operation schematic diagram of the drive device and the pressure switching mechanism when the internal volume ratio is large in the screw compressor according to Embodiment 4 of the present invention.
When the Vi value is large, the solenoid valve 27 is opened and the solenoid valve 37 is closed. By opening the solenoid valve 27, the discharge pressure is introduced from the pressure switching mechanism 21 into the cylinder chamber 14a. Further, the suction pressure is introduced into the cylinder chamber 14d by closing the solenoid valve 37. Pressure is constantly introduced into the cylinder chamber 14c.

In this way, the discharge pressure is introduced into the cylinder chamber 14a and the suction pressure is introduced into the cylinder chamber 14b with the Vi piston 13 as a boundary. As a result, the same operation as when the Vi value is large in the first embodiment is performed, and the variable Vi valve 9 moves to the left as shown by the arrow in the figure. That is, the driving device 11 delays the timing at which the discharge port 8 opens by locating the variable Vi valve 9 in the leftward direction shown by the arrow in the figure.

(2) Operation at Vi Value FIG. 12 is an operation outline diagram of the drive device and the pressure switching mechanism when the internal volume ratio is medium in the screw compressor according to Embodiment 4 of the present invention.
During the Vi value, the solenoid valve 27 is opened and the solenoid valve 37 is opened. The discharge pressure is introduced into the cylinder chamber 14a by opening the solenoid valve 27. Further, by opening the solenoid valve 37, the discharge pressure is introduced into the cylinder chamber 14d. Further, the suction pressure is constantly introduced into the cylinder chamber 14b. As a result, the cylinder chamber 14a and the cylinder chamber 14d have the same discharge pressure, and the cylinder chamber 14c has the suction pressure.

Here, in the case of switching from a large Vi value to a medium Vi value, the pressure in the cylinder chamber 14d rises from the suction pressure to the discharge pressure when the Vi piston 39 is stopped at the position shown in FIG. , Vi piston 39 moves rightward together with interlocking piston 40. As the Vi piston 39 moves to the right, the variable Vi valve 9 is pressed by the interlocking piston 40 and moves to the right. When the Vi piston 39 comes into contact with the positioning wall 42 and stops, the Vi piston 13 and the variable Vi valve 9 also stop in an interlocking manner, and the positioning state shown in FIG. 12 is obtained.

Further, in the case of switching from the small Vi value to the medium Vi value, the pressure in the cylinder chamber 14d increases from the suction pressure to the discharge pressure while the Vi piston 39 is stopped at the position shown in FIG. 13 described later. The cylinder chamber 14c is always at the suction pressure. Therefore, the piston 39 for Vi moves to the right due to the pressure difference between the cylinder chamber 14d and the cylinder chamber 14c, contacts the positioning wall 42, and stops. Further, when the Vi value to be described later is small, the cylinder chamber 14a and the cylinder chamber 14c have suction pressure, but the solenoid valve 27 is closed by switching to the Vi value, so that the pressure in the cylinder chamber 14a becomes the suction pressure. Changes to discharge pressure. Therefore, the Vi piston 13 moves to the left from the position of FIG. 13 due to the pressure difference between the cylinder chamber 14a and the cylinder chamber 14c, and stops when it comes into contact with the interlocking piston 40, and the positioning state shown in FIG. Become.

As described above, in the case of the Vi value, the Vi piston 13 comes into contact with the interlocking piston 40 when the Vi piston 39 comes into contact with the positioning wall 42 and stops. In this state, the variable Vi valve 9 is located on the right side of the case where the Vi value is large as shown in FIG. 11, and as a result, the timing at which the discharge port 8 opens is earlier than when the Vi value is large.

(3) Operation when Vi value is small FIG. 13 is an operation schematic diagram of the drive device and the pressure switching mechanism when the internal volume ratio is small in the screw compressor according to the fourth embodiment of the present invention.
When the Vi value is small, the electromagnetic valve 27 is closed to introduce the suction pressure from the pressure switching mechanism 21 into the cylinder chamber 14a. Also, by closing the solenoid valve 37, the discharge pressure is introduced into the cylinder chamber 14d. Further, the suction pressure is constantly introduced into the cylinder chamber 14c. As a result, the cylinder chamber 14a, the cylinder chamber 14c, and the cylinder chamber 14d become the suction pressure. Therefore, in the cylinder 12, there is no pressure difference between the front and rear surfaces of the Vi piston 13 in the moving direction.

Here, as for the variable Vi valve 9 connected to the Vi piston 13, suction pressure acts on both ends in the moving direction, that is, the suction side end 9g of the valve body 9a, as in the first embodiment. The discharge pressure acts on the drive device side end 9h of the guide portion 9b. Further, the discharge pressure immediately after discharge acts on the discharge port side end portion 9d of the valve body 9a, and the discharge pressure on the discharge port side end portion 9d of the guide portion 9b is the same as the discharge pressure acting on the discharge port side end portion 9d. However, they act in the opposite directions to the discharge port side end portion 9d. Therefore, the loads acting on the discharge port side end portion 9d and the discharge port side end portion 9e are canceled out, and the variable Vi valve 9 has the pressure of the pressure acting on the drive device side end portion 9h and the suction side end portion 9g. It moves to the right in the figure due to the difference. Then, the suction side end portion 9g of the variable Vi valve 9 is stopped at a position where it comes into contact with the wall surface of the casing 2, and the variable Vi valve 9 is accurately positioned at a position with a small Vi value. As a result, the timing at which the ejection port 8 opens is earlier than during the Vi value.

The fourth embodiment is a form in which the connection destination of the pressure switching mechanism 21 of the third embodiment is changed from the cylinder chamber 14c to the cylinder chamber 14a, and the same effect as that of the third embodiment can be obtained.

Embodiment 5.
Embodiment 5 of the present invention is an embodiment in which the pressure switching mechanism is simplified.

FIG. 14 is a schematic configuration diagram of a screw compressor according to Embodiment 5 of the present invention.
The screw compressor 1 of the fifth embodiment includes a pressure switching mechanism 21A instead of the pressure switching mechanism 21 of the first embodiment. The pressure switching mechanism 21A is configured to include an electromagnetic valve 27 that opens and closes the flow path 30 that connects the discharge chamber 7 and the cylinder chamber 14b to switch the discharge pressure from the discharge chamber 7 to the cylinder chamber 14b. It is a thing. In other words, this is a configuration in which the switching piston 23, the rod 24, and the spring 25 are removed from the pressure switching mechanism 21 of the first embodiment. The pressure switching mechanism 21A corresponds to the second mechanism of the present invention.

When the Vi value is large, the solenoid valve 27 is closed. As a result, the discharge pressure is not introduced into the cylinder chamber 14b, and the pressure in the cylinder chamber 14b is escaped from the pressure relief hole 114c and finally reaches the suction pressure. As a result, the same pressure state as that described with reference to FIG. 3 is obtained in the cylinder 12, and the same operation is performed.

When the Vi value is small, the solenoid valve 27 is opened and the discharge pressure is introduced into the cylinder chamber 14b. As a result, the same pressure state as that described with reference to FIG. 4 is obtained, and the same operation is performed.

With such a configuration, the fifth embodiment has a configuration in which the switching piston 23, the rod 24, and the spring 25 are removed, as compared with the first embodiment, and further simplification can be performed, and the cost is simple and inexpensive. A screw compressor having a configuration can be obtained.

Sixth Embodiment
The sixth embodiment of the present invention is an embodiment in which the configuration of the second embodiment is simplified, that is, a combination of the second embodiment and the fifth embodiment.

FIG. 15 is a schematic configuration diagram of a screw compressor according to Embodiment 6 of the present invention.
In the sixth embodiment, the pressure switching mechanism 21 of the second embodiment shown in FIG. 7 is applied to the pressure switching mechanism 21A of the fifth embodiment shown in FIG.

With this configuration, the screw compressor can be further simplified as compared with the second embodiment, and the screw compressor having an inexpensive and simple configuration can be obtained.
The opening and closing of the solenoid valves 27 and 37 are the same as those in the second embodiment.

Here, the configuration in which the pressure switching mechanism 21 side is simplified is shown, but the configuration in which the pressure switching mechanism 31 side is simplified may be used, or both the pressure switching mechanism 21 and the pressure switching mechanism 31 may be simplified. Good.

In each of the above-described embodiments, the number of variable Vi valves 9 is one for each drive device 11, but it may be two, and the number is not limited. Further, the pressure introduced into the cylinder chambers 14a, 14b, 26a, 26b is not limited to the discharge pressure and the suction pressure, and for example, an intermediate pressure may be introduced. The intermediate pressure is a pressure lower than the discharge pressure and higher than the suction pressure.

Further, the refrigerant applied to the screw compressor 1 is not limited to a specific refrigerant, but, for example, one having a low global warming potential GWP is selected in consideration of the influence on the environment and the like. It is good. The refrigerant having a low GWP is, for example, R32, HFO-1123, HFO-1234yf, or a mixed refrigerant containing at least one of these. The refrigerant applied to the screw compressor 1 may also be a natural refrigerant such as carbon dioxide.

1 screw compressor, 2 casing, 3 motor, 3a stator, 3b motor rotor, 4 screw shaft, 5 screw rotor, 5a screw groove, 6 compression chamber, 7 discharge chamber, 8 discharge port, 9 variable Vi valve, 9a valve body , 9b guide part, 9c connecting part, 9d discharge port side end part, 9e discharge port side end part, 9f discharge gap, 9g suction side end part, 9h drive device side end part, 10 lot, 11 drive device, 12 cylinder, Piston for 13 Vi, 14 cylinder, 14a cylinder chamber, 14b cylinder chamber, 14c cylinder chamber, 14d cylinder chamber, 15a channel, 15b channel, 15c channel, 15ca throttle mechanism, 15d channel, 15f channel, 15fa throttle Mechanism, 15e flow path, 15ea throttle mechanism, 16 suction chamber, 21 pressure switching mechanism, 21A pressure switching mechanism, 22 cylinder, 23 switching piston, 24 rod, 25 spring, 26a cylinder chamber, 26b cylinder chamber, 27 solenoid valve, 28 flow passage, 28a flow passage, 28b flow passage, 28ba throttle mechanism, 28c flow passage, 28d flow passage, 30 flow passage, 31 pressure switching mechanism, 37 solenoid valve, 39 Vi piston, 40 interlocking piston, 41 connecting portion, 42 positioning wall, 42a hole, 50 control device, 114a pressure introduction hole, 114b pressure introduction hole, 114c pressure relief hole, 114e pressure introduction hole, 114f pressure relief hole, 214a pressure introduction hole, 214b pressure relief hole, 214c pressure relief hole , 214d Pressure introducing hole.

Claims (10)

A casing having a discharge chamber and a suction chamber inside,
A plurality of grooves forming the compression chamber are formed on the outer peripheral surface, and a screw rotor arranged to rotate in the casing,
A variable Vi valve that moves in the axial direction of the screw rotor and switches the stop position to change the internal volume ratio that is the ratio of the volume of the compression chamber at the completion of suction to the volume of the compression chamber at the completion of discharge; ,
A drive device including a Vi piston connected to the variable Vi valve and a drive cylinder movably accommodating the Vi piston therein;
A pressure switching mechanism for switching the pressure introduced into the drive device,
The inside of the driving cylinder is divided into two cylinder chambers by the Vi piston.
The drive device controls the position of the variable Vi valve by moving the piston for Vi by changing the pressure in one of the two cylinder chambers,
The pressure switching mechanism opens and closes a first flow path that communicates the discharge chamber and the one cylinder chamber, and switches a discharge valve from the discharge chamber to the one cylinder chamber to switch on or off the discharge pressure, and A switching cylinder communicating with the first flow path between the solenoid valve and the one cylinder chamber, a switching piston movably accommodated inside the switching cylinder, and movement of the switching piston. With a spring that compresses by
In the switching cylinder, the switching piston is provided in a first switching cylinder chamber in which a suction pressure is always introduced and the spring is arranged, and a second switching cylinder chamber communicating with the first flow path. Are separated by
A second flow path that connects the first switching cylinder chamber and the one cylinder chamber is opened and closed according to the position of the switching piston that receives the spring force of the spring;
A screw compressor in which the first flow path is opened and closed by opening and closing the solenoid valve, and the second flow path is opened and closed by movement of the switching piston, so that the pressure in the one cylinder chamber changes. The screw compressor according to claim 1, wherein the second flow path includes a first throttle mechanism. The two cylinder chambers are a first cylinder chamber and a second cylinder chamber in order from the variable Vi valve,
Discharge pressure is always introduced into the first cylinder chamber,
The second cylinder chamber, wherein one corresponds to the cylinder chamber communicates with the suction chamber via the second throttle mechanism, according to claim 1 or claim switch to discharge pressure or suction pressure by opening and closing of the solenoid valve Item 2. The screw compressor according to Item 2 . The two cylinder chambers are a first cylinder chamber and a second cylinder chamber in order from the variable Vi valve,
The first cylinder chamber corresponds to the one cylinder chamber, communicates with the suction chamber via a second throttle mechanism, and switches to discharge pressure or suction pressure by opening and closing the solenoid valve,
The screw compressor according to claim 1 or 2, wherein a suction pressure is always introduced into the second cylinder chamber. A casing having a discharge chamber and a suction chamber inside,
A plurality of grooves forming the compression chamber are formed on the outer peripheral surface, and a screw rotor arranged to rotate in the casing,
A variable Vi valve that moves in the axial direction of the screw rotor and switches the stop position to change the internal volume ratio that is the ratio of the volume of the compression chamber at the completion of suction to the volume of the compression chamber at the completion of discharge; ,
A drive device including a Vi piston connected to the variable Vi valve, and a drive cylinder that movably accommodates the Vi piston therein and is divided into two cylinder chambers by the Vi piston. When,
A pressure switching mechanism for switching the pressure introduced to the drive device ,
A throttle mechanism provided in a flow path communicating with the suction chamber from a pressure relief hole provided in one of the two cylinder chambers ,
The drive device controls the position of the variable Vi valve by moving the Vi piston by changing the pressure of the one cylinder chamber,
The pressure switching mechanism opens and closes a first flow path that connects the discharge chamber and a pressure introduction hole provided in the one cylinder chamber, and introduces or blocks the discharge pressure from the discharge chamber to the one cylinder chamber. A screw compressor having a solenoid valve for switching between the two cylinders, the pressure of the one cylinder chamber changing by opening and closing the solenoid valve. The two cylinder chambers are a first cylinder chamber and a second cylinder chamber in order from the variable Vi valve,
Discharge pressure is always introduced into the first cylinder chamber,
The screw according to claim 5, wherein the second cylinder chamber corresponds to the one cylinder chamber, communicates with the suction chamber through the throttle mechanism, and is switched to a discharge pressure or a suction pressure by opening and closing the solenoid valve. Compressor. The two cylinder chambers are a first cylinder chamber and a second cylinder chamber in order from the variable Vi valve,
The first cylinder chamber corresponds to the one cylinder chamber, communicates with the suction chamber via the throttle mechanism, and switches to discharge pressure or suction pressure by opening and closing the solenoid valve,
The screw compressor according to claim 5 , wherein a suction pressure is constantly introduced into the second cylinder chamber. A casing having a discharge chamber and a suction chamber inside,
A plurality of grooves forming the compression chamber are formed on the outer peripheral surface, and a screw rotor arranged to rotate in the casing,
A variable Vi valve that moves in the axial direction of the screw rotor and switches the stop position to change the internal volume ratio that is the ratio of the volume of the compression chamber at the completion of suction to the volume of the compression chamber at the completion of discharge. ,
A drive device including a first Vi piston connected to the variable Vi valve, and a drive cylinder movably accommodating the first Vi piston therein.
Two pressure switching mechanisms for switching the pressure introduced into the drive device,
The drive device is
A second Vi piston that operates independently of the first Vi piston;
An interlocking piston arranged between the first Vi piston and the second Vi piston and connected to the second Vi piston by a connecting portion;
A positioning wall that is disposed between the second Vi piston and the interlocking piston and that has a hole through which the connecting portion is movably formed;
The inside of the drive cylinder is divided into three cylinder chambers by the first Vi piston and the second Vi piston.
The drive device is
By changing the pressure of at least one of the three cylinder chambers, the second Vi piston is moved to a position in contact with the positioning wall and a position not in contact with the positioning wall, and the second Vi piston In order to control the position of the variable Vi valve by performing the operation of moving the first Vi piston and the operation of moving the first Vi piston independently of the second Vi piston in conjunction with. Yes,
The two pressure switching mechanisms are provided corresponding to two of the three cylinder chambers,
Wherein both the two pressure switching mechanism is composed of a first mechanism,
Before Symbol first mechanism,
An electromagnetic valve that opens and closes a first flow path that connects the discharge chamber and the one cylinder chamber to switch introduction or interruption of the discharge pressure from the discharge chamber to the one cylinder chamber; A switching cylinder communicating with the first flow path between the two cylinder chambers, a switching piston movably accommodated in the switching cylinder, and a spring compressed by the movement of the switching piston. Prepare,
In the switching cylinder, the switching piston is provided in a first switching cylinder chamber in which suction pressure is always introduced and the spring is arranged, and a second switching cylinder chamber communicating with the first flow path. Are separated by
A second flow path that connects the first switching cylinder chamber and the one cylinder chamber is opened and closed according to the position of the switching piston that receives the spring force of the spring;
A screw compressor in which the first flow path is opened/closed by opening/closing the solenoid valve, and the second flow path is opened/closed by movement of the switching piston to change the pressure in the one cylinder chamber. .. The three cylinder chambers are a first cylinder chamber, a second cylinder chamber, and a third cylinder chamber in order of proximity to the variable Vi valve,
Discharge pressure is always introduced into the first cylinder chamber,
The second cylinder chamber and the third cylinder chamber correspond to the two cylinder chambers, communicate with the suction chamber via a throttle mechanism, and are switched to discharge pressure or suction pressure by opening and closing the solenoid valve. Item 8. The screw compressor according to Item 8 . The three cylinder chambers are a first cylinder chamber, a second cylinder chamber, and a third cylinder chamber in order of proximity to the variable Vi valve,
The first cylinder chamber and the third cylinder chamber correspond to the two cylinder chambers, communicate with the suction chamber via a throttle mechanism, and switch to discharge pressure or suction pressure by opening and closing the solenoid valve,
The screw compressor according to claim 8 , wherein a suction pressure is constantly introduced into the second cylinder chamber.

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