JP2927064B2 - Multi-type cryogenic refrigerator - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-type cryogenic refrigerator, and more particularly, to a plurality of cryogenic expanders via a branch pipe between a high-pressure gas pipe and a low-pressure gas pipe extending from a compressor unit. And a multi-type cryogenic refrigerator comprising a plurality of cryogenic refrigerators connected in parallel.

[0002]

2. Description of the Related Art Conventionally, a multi-type cryogenic refrigerator is disclosed in
No. 3,887,955. This refrigerator includes, as shown in FIG. 11, one compressor unit A having a compressor and two cryogenic expanders B. Each of the expanders B is connected to the compressor unit. A high-pressure gas pipe C and a low-pressure gas pipe D extending from A are connected in parallel via a high-pressure branch pipe E and a low-pressure branch pipe F, respectively, and high-pressure gas is supplied from one compressor unit A to each expander B. In addition to distributing and supplying, the low-pressure gas discharged from each expander B is returned to the compressor unit A and circulated. Each of the expanders B has an injection passage (not shown) for introducing high-pressure gas and discharging low-pressure gas.
A switching valve device (not shown) having a valve body for alternately switching the injection / discharge passage between a high-pressure gas passage and a low-pressure gas passage, and a synchronous motor for driving the valve body; A displacer (not shown) that reciprocates by discharging the low-pressure gas.

[0003] Each of these expanders B is shown in FIG.
(A) As shown in (b), by starting and stopping the motors,
It is operated in a cycle of an injection process for injecting high-pressure gas and a discharge process for discharging expanded low-pressure gas.
When the start / stop timing of each motor is not taken into consideration, the operation in which the injection stroke and the discharge stroke in a plurality of expanders are alternately performed as shown in FIG.
As shown in (1), the injection stroke and the discharge stroke are synchronized or, although not shown, the operation is performed in an intermediate state between FIGS. 10 (a) and (b).

On the other hand, when a plurality of expanders B are operated by using one compressor unit A, in the operation in which injection is simultaneously performed in each of the expanders B, the high pressure discharged from the compressor unit A is high. The gas will be distributed to each of the expanders B, and as a result, the flow rate of the high-pressure gas to each of the expanders B will decrease. Therefore, when the injection stroke in each of the expanders B is shifted, In comparison, the operating differential pressure in the expander B, that is, the height differential pressure, is reduced, and the capacity is reduced accordingly.

That is, as shown in FIG. 10A, when the start / stop timing of each motor is shifted by a half cycle and the high-pressure gas from one compressor unit A is alternately supplied to each expander B, the expansion The operating differential pressure ΔP due to the difference between the high-pressure gas and the low-pressure gas on the machine B side is maximized, and the refrigeration capacity proportional to this operating differential pressure can be maximized. Further, as shown in FIG. When the start / stop timing of the motor is synchronized and the high-pressure gas from one compressor unit A is distributed and supplied to each expander B at the same time, the difference between the high-pressure gas and the low-pressure gas on the expander B side is obtained. , The operating pressure difference ΔP is minimized, and the refrigeration capacity proportional to the operating pressure difference is minimized.

Therefore, conventionally, Japanese Patent Laid-Open Publication No.
As shown in FIG. 5 (described in FIG. 12), a magnetic body H is provided on a displacer G of each of the expanders B, and a cylinder J containing the displacer G is opened and closed by the magnetic body H. A magnetic proximity switch K is provided to detect the operating position of the displacer G by a stroke detector composed of the proximity switch K and the magnetic body H to control the start / stop timing of the valve driving motor. What has been proposed.

[0007]

However, since this conventional multi-type cryogenic refrigerator detects the operating position of the displacer G and controls the start / stop timing of the valve drive motor, the conventional multi-type cryogenic refrigerator has various functions. There is a variation in the start / stop timing of the motor in relation to the refrigeration capacity of the expander, and it is difficult to control this start / stop timing with high accuracy, and there is a problem that the refrigeration capacity of each expander cannot be equalized, Further, when there is a capacity difference between the respective expanders, it is difficult to control the start / stop timing. In addition, since it is necessary to incorporate the sensor into the displacer G and the cylinder J, the incorporation of this sensor is very complicated and the cost is high. Further, since the sensor uses a magnetic material, there is a problem that the start / stop timing of the motor cannot be controlled at a location where a magnetic field exists.

According to the present invention, when a plurality of expanders are operated, the load torque of the motor for driving the valve body increases due to an increase in the operating differential pressure in each expander, and conversely, the terminal voltage of the motor decreases. In other words, focusing on the fact that the operating differential pressure can be detected by detecting the terminal voltage, the terminal voltage is minimized, and the operating differential pressure, that is, the ability proportional to the operating differential pressure is maximized. The purpose is to detect the voltage of each expander when the motor is driven, and control the start / stop timing of the motor based on the detected value,
The point is that the refrigerating capacity of each expander can be improved by controlling the voltage of each motor to be a minimum.

[0009]

In order to achieve the above object, according to the present invention, a plurality of branch pipes 2a, 3a are provided between a high pressure gas pipe 2 and a low pressure gas pipe 3 extending from a compressor unit 1. Are connected in parallel, and each of the expanders 4 is connected to a cylinder 5 having a heat stage 51.
And a motor housing 7.
An injection / discharge passage 81 having a high pressure side pressure receiving surface 21a and a low pressure side pressure receiving surface 21b for introducing a high pressure gas and discharging a low pressure gas to the cylinder 5 includes a high pressure gas passage 9 and a low pressure gas passage 10. And the valve element 2 that alternately switches between
Switching valve device 2 comprising a synchronous motor 22 for driving the motor 1
In a multi-type cryogenic refrigerator having a built-in zero, a voltage detector 14 for detecting a voltage when the motor 22 is driven is provided.
And a motor drive control device 15 for controlling the start / stop timing of each motor 22 in each expander 4 so that the voltage of each motor 22 becomes a minimum value.

[0010]

The high pressure gas pressure in the high pressure gas passage 9 acts on the high pressure side pressure receiving surface 21a of the valve element 21 in each of the expanders 4, and the low pressure gas in the cylinder 5 is applied to the low pressure side pressure receiving surface 21b. Since the low-pressure gas pressure at the time of discharging to 10 acts, the valve element 21 is pressed against the injection / discharge passage 81 by an operation differential pressure due to the difference between the high pressure and the low pressure.
As shown in FIG. 6, the load torque of each of the motors 22 for driving the valve element 21 increases in proportion to the increase in the operating differential pressure, that is, the height differential pressure. 4, the voltage between the terminals of each of the motors 22 is
As shown in FIG. 7, the voltage decreases in inverse proportion to the increase in the load torque of the motor, and the inter-terminal voltage decreases in inverse proportion to the increase in the operating differential pressure as shown in FIG.
Therefore, the operation differential pressure, that is, the capacity can be detected by detecting the terminal voltage.

When operating a plurality of expanders, the voltage of the motor 22 in each expander is detected by the voltage detector 14, and based on the detected value, the motor drive controller 15 The start / stop timing of each motor 22 can be controlled so that the voltage of each motor 22 becomes the minimum value, so that each expander can be operated at the maximum operating differential pressure. Can be improved, the performance of each expander can be equalized, and the pressure pulsation can be reduced. Further, even when expanders having different capacities are used, the gas distribution can be optimized, and the voltage of the motor is detected to control the start / stop timing of the motor. Therefore, the start / stop timing of the motor can be controlled without any problem even in a location where there is a magnetic field.

[0012]

DESCRIPTION OF THE PREFERRED EMBODIMENTS In the embodiment shown in FIG.
One high-pressure gas pipe 2 and one low-pressure gas pipe 3 extending from one compressor unit 1 are connected to three high-pressure side branch pipes 2 a and 3.
Three cryogenic expanders 4 used as a cryopump head are connected in parallel via the three low-pressure side branch pipes 3a,
The high-pressure gas is distributed and supplied from the compressor unit 1 to each expander 4, and the low-pressure gas discharged from each expander 4 is returned to the compressor unit 1 and circulated.

Each of the expanders 4 has a heat stage 51 at an end and an intermediate portion as shown in FIGS.
A cylinder 5 containing a displacer 6 reciprocating between the introduction of high-pressure gas and the discharge of low-pressure gas;
a, 3a having connection ports 71, 72,
And a motor housing 7 connected to the cylinder 5. An injection / discharge passage 81 for introducing high-pressure gas and discharging low-pressure gas to the cylinder 5 in communication with the connection ports 71 and 72 is provided in the motor housing 7. A high-pressure gas passage 9 having a high-pressure side pressure receiving surface 21a and a low-pressure side pressure receiving surface 21b, and a high-pressure gas passage 9 communicating the injection / discharge passage 81 with the connection port 71 and a low-pressure gas passage communicating with the connection port 72. 10 and a switching valve device 20 comprising a synchronous motor 22 for driving the valve element 21 for alternately switching the valve element 21, and controlling the opening and closing of each valve element 21 by controlling the start and stop of each motor 22. By connecting the injection passage 81 to the high-pressure gas passage 9, high-pressure gas is introduced into each cylinder 5 from the high-pressure gas pipe 2, and the displacer 6 is moved back, and Passage 8 Is communicated with the low-pressure gas passage 10 to move the displacer 6 forward and expand the gas in each of the cylinders 5. The expanded low-pressure gas is discharged into the low-pressure gas passage 10, and the high-pressure gas By repeating introduction and discharge, the heat stage 51
Try to get a very low temperature.

A high-pressure gas pressure in the high-pressure gas passage 9 acts on the high-pressure side pressure receiving surface 21a of the valve body 21 in each of the expanders 4, and a low-pressure gas in the cylinder 5 is applied to the low-pressure side pressure receiving surface 21b. The valve element 21 is pressed against the passage block 8 by a low operating pressure caused by the difference between the high pressure and the low pressure when the low pressure gas pressure is discharged to the gas passage 10, so that the valve element 21 is driven. The load torque of each motor 22 increases in proportion to the increase in the operating differential pressure as shown in FIG. 6, and the voltage between the terminals of each motor 22 in each expander 4 is as shown in FIG. As shown in (2), it decreases in inverse proportion to the increase in the load torque of the motor. Therefore, according to FIGS. 6 and 7, the operating differential pressure and the inter-terminal voltage have a relationship in which the inter-terminal voltage is inversely proportional to the increase in the operating differential pressure as shown in FIG.

That is, the synchronous motor 22 in each of the expanders 4 uses a three-phase synchronous motor such as a synchronous motor, and has a first terminal a as an R-phase power supply and a second terminal b as an S-phase power supply. The first terminal a circuit is connected to an RC circuit having a resistor and a capacitor, and the RC circuit is connected to a third terminal c. The terminal voltage V ₁ between the second terminal b and the third terminal c and the terminal voltage V ₂ between the second terminal b and the third terminal c are inversely proportional to the increase in the operating pressure difference as shown in FIG.

In FIG. 1, reference numeral 11 denotes each cylinder 5
A heat panel attached to the end side heat stage 51 of
Reference numeral 12 denotes an intermediate-stage heat stage 51 of each of the cylinders 5.
Reference numeral 13 denotes a baffle attached to each heat shield 12.

According to the present invention, in the multi-type cryogenic refrigerator configured as described above, the voltage detector 14 for detecting _{one of} the terminal voltages V ₁ and V ₂ in each of the motors 22 is provided. together, said start-stop timing of each of the motors 22 in each expander 4, wherein it is the terminal voltage V ₁ of the respective motor 22 is provided with a motor drive control device 15 for controlling so that the minimum value.

The motor drive control device 15 in the embodiment shown in FIGS. 1 and 3 performs the operation of the target minimum value V _{1 at} which the terminal voltage V ₁ of the motor becomes minimum when all the expanders 4 are operated. A calculation unit for calculating and setting (i);
A storage unit for storing the target minimum value V (i) is provided, and the start / stop timing of each motor 22 is controlled so that the motor terminal voltage V ₁ in each expander 4 becomes the target minimum value V (i). That's what we do. That is, when three expanders 4 are connected as shown in FIG. 1, a target minimum value V (i) that minimizes the voltage between terminals of each motor when all the expanders 4 are operated is set in advance, When the second expander 4 is operated while the specific expander 4 is operating, the motor in the expander 4 is controlled based on the constraint of the target minimum value V (i). When the third expander 4 is further operated, the expander 4 is operated under the constraint of the target minimum value V (i) based on the second expander 4 that is operated immediately before. Is to control the motor in.

Next, the operation of the refrigerator having three cryogenic expanders 4 will be described with reference to the flowchart shown in FIG.

First, according to the number N of expansion machines 4 connected before the start, a target minimum value V (i) at which the terminal voltage V ₁ of the motor 22 becomes minimum when all the expansion machines 4 are operated. Is initialized.

In step S1, the N0.1 motor 22 of the first expander (N0.1) serving as a reference is started, and the number of machines i when the motor 22 is started is set to one.

In step S2, it is determined whether the number i of operating motors is equal to or greater than the number of connected motors. If NO, that is, if the number i of operating motors is one, step S3
Before operating the motor of the second expander 4, the operating number i is set to be 2 and then, in step S 4, the motor 22 in the second expander 4 is operated.
(N0.2) is started.

[0023] Then, in step S5, the terminal voltage V ₁ of the N0.2 motor 22 in the second unit expander is detected, the voltage V ₁ is at step S6, the pre-set target minimum value V (i) Be compared.

In this comparison, when the voltage V ₁ is equal to or less than the target minimum value V (i), the start / stop timing of the N0.1 motor 22 of the first expander 4 and the N / N of the second expander 4
Since the start / stop timing of the 0.2 motor 22 is performed with an appropriate deviation, the operation of the N0.2 motor of the second expander is continued, the process returns to step S2, and the process returns to step S3 via step S2. Move on, this step S3
Before operating the N0.3 motor of the third expander 4 in step S4, the operating number i is set to 3 and step S4.
Then, the N0.3 motor 22 in the third expander is started. In this case the same, is detected terminal voltage V ₁ of the N0.3 motor in step S5, are compared targeted minimum value V (i) set in advance in step S6.

[0025] Then, the case voltage V ₁ is below the target minimum value V (i) In this comparison, the operation of N0.3 motor is continued, the flow returns to step S2.

In this case, the number i of operation becomes 3 and becomes equal to the number N of connection. Therefore, the process returns in step S2, and the operation of each motor is continued.

On the other hand, if the detected value of the inter-terminal voltage V ₁ in the N0.2 motor 22 exceeds the target minimum value V (i) in the comparison in step S6,
In step S7, N
0.2 Stop the motor 22 once. Then, step S8
In step S9, the timer is set for T seconds to start timing. In step S9, it is determined whether the timer has expired. If the timer has not expired, the timer is continued.
Furthermore, the process returns to step S5 if time is up, the detection value of the terminal voltage V ₁ of the N0.2 motor in step S6 is again compared with the target minimum value V (i), below the target minimum value V (i) Then, the process returns to step S2, the N0.2 motor is restarted in step S4, and the determination in step S6 is repeated.

In the step S6, the N
For N0.2 motor even when the detected value of the inter-terminal voltages V ₁ exceeds the target minimum value V (i) in 0.3 motor 22 similar to step S7~ step S9 and step S5, the control of the step S6 Is performed, and the detection value of the terminal voltage V ₁ of the N0.3 motor 22 is changed to the target minimum value V
(I) After the following, the process returns to step S2, the N0.3 motor 22 is restarted in step S4, and the determination in step S6 is repeated. Therefore, by the above control, the N0.2 and N0.3 motors 22 are controlled to the minimum inter-terminal voltage when three motors are connected, and each expander 4 is operated at the maximum operating differential pressure.

When the time is measured by the timer in step S9, the rated frequency of each motor 22 is 50 Hz.
The optimum time corresponding to 60 Hz is set in advance.

As described above, the start / stop timing of the motor 22 in the three expanders 4 is shifted by 1/3 cycle to 3
By inter-terminal voltage V ₁ is controlled to be minimized in the base during operation, since the operation differential pressure of each expander can be maximized, with equally the refrigerating capacity of each expander 4, each refrigeration capacity In addition, by shifting the injection / ejection cycle by 1/3 cycle, the variation of the pressure pulsation in each expander 4 can be reduced. In the embodiment described above, as a method of controlling the operation of the plurality of expanders, a target minimum value V (i) is set, and N0.2 and N are set based on the target minimum value V (i).
0.3 Although the control is performed so as to shift the operation timing of the motor 22, the control may be performed as shown in the flowchart of FIG. In step S10, the flow chart shown in FIG.
0.1 Start the motor 22, and in step S11
The N0.2 and N0.3 motors 22 of the third and third expanders 4 are synchronized so that their start and stop timings are synchronized, in other words, the terminal voltage V ₁ of the N0.2 and N0.3 motors 22. It is activated so that is maximized.

Then, in step S12, N0.
After stopping the motor 2 and the N0.3 motor 22, step S1
3, the time T ₁ for restarting the N0.2 motor 22;
For example, 140 seconds and a time T ₂ for restarting the N0.3 motor 22 are set, for example, 280 seconds.

Thereafter, in step S14, the time T ₁
There is judged whether elapsed, in the case of yes is than restarting the N0.2 motor 22 at step S15, and whether the elapsed time T ₂ in step S16 it is determined, in the case of yes Is Step S17
Then, the N0.3 motor 22 is restarted.

The time T ₁ , T ₂ is a time difference at which the inter-terminal voltage V ₁ is minimum, that is, when the injection / ejection cycle is, for example, T seconds, it is delayed by ３ cycle with respect to the N0.1 motor 22. and with a time difference to become T ₁ seconds N0.2 motor after restart, there than to restart the N0.3 motor 22 to T ₂ seconds after to N0.1 motor 22 is the time difference delayed 2/3 cycles by this activation regulation is of the inter-terminal voltages V ₁ of N0.2 and N0.3 motor 22 can be a minimum.

In this operation method, the motor start / stop timing of the three expanders 4 can be shifted by ３ cycle to minimize the terminal voltage V ₁ during operation of the three expanders 4. As shown in FIG. 5, the injection / discharge cycle of each motor 22 in each of the three expanders 4 can be shifted by ３ cycle, so that the operating differential pressure of each expander 4 can be maximized.

[0035] In the embodiment described above has been to detect the terminal voltage V ₁ of the said first terminal a and a third terminal c at the time of driving of the motors 22 by the voltage detector 14, In addition, the terminal voltage V ₂ between the second terminal b and the third terminal c when each of the motors 22 is driven may be detected. However, Figure 7, since the direction of variation of the inter-terminal voltages V ₁ than the terminal voltage V ₂ as shown in FIG. 8 large, that detects the inter-terminal voltages V ₁ preferred.

[0036]

As described above, according to the present invention, the voltage detector 14 for detecting the voltage when the synchronous motor 22 for driving the valve element 21 is driven is provided, and the voltage of each motor 22 is detected. , The start / stop timing of each motor 22 is controlled so that the voltage of each motor 22 becomes the minimum value, and the operating differential pressure that increases in inverse proportion to the decrease in the terminal voltage can be maximized. Therefore, the refrigerating capacity of each expander can be improved, the capacity of each expander can be equalized, and the pressure pulsation can be reduced. Further, even when expanders having different capacities are used, the gas distribution can be optimized, and the voltage of the motor is detected to control the start / stop timing of the motor. Therefore, the start / stop timing of the motor can be controlled without any problem even in a location where there is a magnetic field.

[Brief description of the drawings]

FIG. 1 is a circuit diagram of a refrigerator according to the present invention.

FIG. 2 is a partial sectional view in which a part of a cryogenic expander is omitted.

FIG. 3 is an electric circuit diagram of a motor of the cryogenic expander.

FIG. 4 is a flowchart.

FIG. 5 is an explanatory diagram showing a gas injection / discharge cycle when three cryogenic expanders are operated and their operation differential pressures are maximized.

FIG. 6 is a graph showing a relationship between an operating differential pressure and a load torque.

FIG. 7 is a graph showing a relationship between a load torque and a terminal voltage.

FIG. 8 is a graph showing a relationship between an operation differential pressure and a terminal voltage.

FIG. 9 is another flowchart.

FIG. 10 is an explanatory diagram showing a gas injection / discharge cycle when two cryogenic expanders are operated and their operation differential pressures are maximized and minimized.

FIG. 11 is a circuit diagram of a conventional refrigerator.

FIG. 12 is a partial cross-sectional view of the conventional refrigerator in which a part of a cryogenic expander is omitted.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Compressor unit 2 High pressure gas pipe 3 Low pressure gas pipe 4 Cryogenic expander 5 Cylinder 7 Motor housing 9 High pressure gas passage 10 Low pressure gas passage 14 Voltage detector 15 Motor drive control device 20 Switching valve device 21 Valve body 21a High pressure side pressure receiving Surface 21b Low pressure side pressure receiving surface 22 Motor 81 Injection / ejection passage

Continuation of the front page (58) Field surveyed (Int.Cl. ⁶ , DB name) F25B 9/14 540 F25B 9/14 530

Claims (1)

(57) [Claims] A high-pressure gas pipe extending from a compressor unit.
A plurality of cryogenic expanders 4 are connected in parallel between the cryogenic expander 4 and the low-pressure gas pipe 3 via branch pipes 2a, 3a. The motor housing 7 has a high pressure side pressure receiving surface 21a and a low pressure side pressure receiving surface 21b, and an injection / discharge passage 81 for introducing high pressure gas to the cylinder 5 and discharging low pressure gas. In a multi-type cryogenic refrigerator equipped with a switching valve device 20 including a valve body 21 that alternately switches between a passage 9 and a low-pressure gas passage 10 and a synchronous motor 22 that drives the valve body 21, A voltage detector 14 for detecting a voltage at the time of driving is provided, and the start / stop timing of each motor 22 in each expander 4 is controlled so that the voltage of each motor 22 becomes a minimum value. Multi-type cryogenic refrigerator, characterized in that provided over motor drive control device 15.