JPH05280467A - Multi-cryopump - Google Patents

Abstract

PURPOSE:To permit the combined control of the cool-down acceleration control and the control for optimizing the valve opening/closing time by reading the completion time point of the acceleration control operation from the electric current wave form supplied to a pump motor, operating a valve timing control means, and supplying the signal into a relay. CONSTITUTION:One motor 24 of three pump motors for cryopumps is connected with a power source through an electric current sensor 14, transformer 2, and an inverter 1, and the rest pump motors 25 and 26 are connected with the electric power source through the opened relays 3 and 4, besides the electric current sensors 15 and 16. The electric current signal 12 supplied from each electric current sensor 14-16 is supplied into an acceleration control means 9, and each pump motor 24-26 is revolved at each high speed by the acceleration control signal 13. After the completion of the high speed revolution control, each electric current signal 12 supplied from the electric current sensor 15-16 is switching- supplied into a valve timing control means 10, and the ON/OFF signal for each relay 3, 4 can be supplied. Accordingly, the dispersion of the refrigeration faculty can be suppressed to the min., and the cool-down time can be shortened drastically.

Description

Detailed Description of the Invention

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a multi-cryo pump for controlling the opening / closing of a valve for intake / exhaust of a working gas by continuing the high-speed rotation control of a pump motor.

As disclosed in Japanese Laid-Open Patent Publication No. 3-15677, a Macchi cryo pump is known. The basic configuration will be described with reference to known examples thereof in FIGS. 7 and 8.

7 and 8 show three cryopumps P.
_{An example in which 1} , P ₂ and P ₃ are operated by one compressor 40 is shown. In FIG. 7, as representatively shown by the cryopump P ₁ , each cryopump includes an expansion cylinder 30 that adiabatically expands the working gas inside to obtain refrigeration, and an expansion piston 31 that reciprocally slides in the expansion cylinder 30. The electric motors 24, 25, 26 for driving the expansion piston 31, the regenerator 32 interposed between the expansion cylinder 30 and the compressor 40 to exchange heat with the working gas, and the reciprocating motion of the expansion piston 31. High pressure valve (valve) 33 that operates in response to the discharge port of the compressor 40 to communicate with the regenerator 32, and low pressure that operates according to the reciprocating motion of the expansion piston 31 to communicate the intake port of the compressor 40 to the regenerator 32. The valve 34 (valve) 34.

The cryopumps P ₁ , P _{2 having} the above structure
At P ₃ , when the electric motors 24, 25, 26 rotate and the expansion piston 31 starts moving from the top dead center to the bottom dead center, the high pressure valve 33 opens and the working gas from the compressor 40 Is heat-exchanged in the regenerator 32, and the cooled working gas is introduced into the expansion cylinder 30. After that, the high pressure valve 33 is closed at a predetermined timing and the low pressure valve 3 is closed.
When 4 is opened, the working gas is sucked into the compressor 40, at which time the volume of the space (expansion space) in the expansion cylinder 30 increases, and the expansion space undergoes adiabatic expansion to generate cryogenic temperature. When the expansion piston 31 descends, the high pressure valve 33 is opened and the low pressure valve 34 is closed at a predetermined timing, so that the working gas is supplied to the expansion space. At this time, the working gas exchanges heat with the cold air stored therein in the regenerator 32 before entering the expansion space.

In FIG. 8, the compressor 40 is connected to the three cryopumps P ₁ , P ₂ and P ₃ via the working gas pipe 41 as described above. The compressor 40 is connected to the electric motors 24, 25, 26 of the cryopumps P ₁ , P ₂ , P ₃ via a power line 42, and the valve timing control means 10 is connected to the power line 42. The current sensors 14 and 1 which are interposed and detect the supply current supplied to the power supply lines to the electric motors 24, 25 and 26.
5 and 16 are interposed. Further, relays 3 and 4 which are power source opening / closing means in the present invention are interposed in power source lines to the electric motors 24 and 25 of the cryopumps P ₁ and P ₂ .

The electric motor for driving the cryopump is designed to rotate at a constant rotation in synchronism with the frequency. However, the load changes during one revolution of each stroke of the cryopump, and the current flowing through the electric motor. Also changes in proportion to it. Therefore, according to the configuration described above, the operating position of each cryopump can be detected by detecting the current supplied to the electric motor that drives each cryopump by each current detection unit, and the maximum supply current can be obtained. At some point it can be detected that the cryopump is in the high pressure gas intake stroke. Then, the valve opening / closing timing control means controls the opening / closing of each power source opening / closing means so that the maximum value of the current supplied to each cryopump is at equal intervals, so that the working gas from the compressor is efficiently and uniformly supplied to each cryopump. Can be supplied to.

On the other hand, the step-out phenomenon that occurs when the number of rotations of the electric motor increases can be detected by the current detecting means of the current flowing through the electric motor, and the acceleration control means can detect the abnormal fluctuation of the current. This step-out phenomenon can be performed by the rotation speed correction means by outputting to the inverter a correction signal for decreasing the rotation speed of the electric motor by a predetermined amount from the rotation speed of the electric motor at the time of detecting an abnormal change, thereby enabling the electric motor. It is possible to stabilize the driving of the electric motor and to shorten the start-up time (cooling descent time) while keeping the rotation speed as high as possible.

An example of the so-called cool-down accelerating means described above, in place of the valve timing control means 10, sends the currents detected by the current sensors 14, 15, 16 to a step-out detection circuit (not shown) to obtain a measured current value. On the basis of this, an abnormal change in the current is detected to determine whether step out has occurred, and the determination result (rotational speed drop signal) is output to an inverter (not shown).

Next, the cause of step-out will be briefly described.
During normal operation, the electric motor is used at a frequency of 50 Hz to 60 Hz and is rotated at a rotation speed synchronized with that frequency. However, if the frequency is increased to rotate at a higher rotation speed, the cooling time will be shortened. It has been known. On the other hand, if the number of rotations of the electric motors 24, 25, 26 is increased, the electric motor 2
The drive current is reduced due to the influence of the coils of 4, 25, and 26, and the drive torque is reduced. When the expansion space reaches an extremely low temperature near the reached temperature, the mass flow rate of the working gas increases, the load on the current motors 24, 25, 26 increases, and rotation failure (step-out phenomenon) occurs, and the cold head becomes the reference. Ultimate temperature (very low temperature)
Does not reach Therefore, if the rotation of the electric motor is stably maintained at the highest possible frequency that does not cause the step-out phenomenon, the reference temperature can be reached while shortening the cooling time of the cryogenic refrigerator. It will be possible. Therefore, it has been proposed to install the step-out detection circuit and the inverter as described above.

[0010]

SUMMARY OF THE INVENTION As described above, the present invention provides a means for controlling the opening / closing timing of a valve for intake / exhaust of a working gas, and a high rotation speed while preventing a rotation failure of an electric motor. Although the means for driving the electric motor have been developed respectively, there is no cryopump that uses them in combination. Therefore, it is an object of the present invention to solve the above-mentioned problems of the conventional technology.

[0011]

In order to solve the above-mentioned problems, the present invention basically employs means for controlling the valve opening / closing timing in response to an acceleration control end signal. Specifically, the present invention adiabatically expands working gas from a compressor, which is sucked and discharged according to the movement of a piston reciprocated by an electric pump motor, in a chamber defined by the piston. In a multi-clar ion pump that produces extremely low temperatures, at least one of the pump motors for the cryopumps is connected to the power supply via the current sensor, transformer and inverter, and the remaining pump motors are powered by the current sensor and activated. The gas intake / exhaust valve opening / closing relay, the transformer and the inverter are connected to each other, and the current signal from each current sensor is supplied to the acceleration control means via the waveform reading means, and the acceleration control signal from the acceleration control means is supplied. Send to the inverter to rotate each pump motor at high speed, and after finishing the high speed rotation control of the pump motor, send the current signal from the current sensor. And switching the supply to the valve timing control means via the form reading means, to provide a multi cryopump, characterized in that to allow supply on-off signal to each relay.

[0012]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 shows a multi-cryo pump P ₁ , P ₂ , P ₃ in which _one compressor unit 40 drives three pump units 24, 25, 26 in order to reduce the cool-down time. Acceleration control means for rotating the motors 24, 25, 26 as fast as possible and valve timing control for controlling opening / closing of valves in the pump units so that helium gas can be appropriately supplied to the three pump units after the cooldown is reached. FIG. 3 is a block diagram of a cool-down acceleration method for a multi-cryopump including means (10). In the figure, the hatched arrow indicates the pump motor power supply. The commercial power source passes through the inverter (1), and the frequency-converted three-phase power source is converted by the Scott connection transformer (2) into a two-phase power source capable of driving a synchronous motor. The motor (6, 7) is directly supplied to one pump motor 0 (5) via the relay 1 (3) and the relay 2 (4). FIG. 2 shows a basic operation flowchart of the block diagram of FIG. When the power is turned on, the acceleration control means starts its operation, and after the lapse of a specified time, the acceleration control is stopped and the valve timing control is started. The time to execute the acceleration control is adjusted to the time when the pump unit finishes the cool down.After the cool down, the valve timing control is performed to ensure the consistency of the performance between the pump units, and after the specified time by the timer circuit, Control ends.

In FIG. 1, the acceleration control is performed by current sensors CT ₀ (14), CT ₁ (15), which are installed in power supply lines connected to the pump motors 24, 25 and 26, respectively.
A current signal obtained from CT ₂ (16) is passed through a waveform reading means (8) and an acceleration control means (9) to output a control signal (13) to an inverter (1). The waveform reading means 0 (8-0) is a current sensor CT ₀ (14) installed in the power supply line connected to the pump motor 0 (5).
The signal obtained from the drive pulse (1) is passed through an amplifier circuit (8-0-1) and one is passed through a waveform shaping circuit (8-0-2).
7), the other is passed through the full-wave rectifier circuit (8-0-3) through the integrator circuit (8-0-4), the part beyond this is further divided into two systems of signals, and one is shaped into the waveform shaping circuit (8 -0-6) is used as the valve timing control signal 0 (19), and the other is applied to the amplifier circuit (8-0-5) and the step-out signal 0 (1)
8). A step-out signal and a valve timing signal configured by the same circuit are arranged for the pump 1 (25) and the pump 2 (26) respectively, and the waveform reading means 1 is provided.
(8-1) and waveform reading means 2 (8-2). The acceleration control means (9) outputs a step-out signal 0-2 (18, 20, 2).
2) is divided into two systems, and one system is impedance-converted (18-1, 20-1, 22-1) and offset (18-2, 20-2, 22-2) (first system), The other system is integrated (18-3, 20-3, 22-3) and converted into impedance (18-4, 20-4, 22-4) (second system), and both are compared (18-5, 18-5). 20-
5, 22-5).

The waveform in the first system is a sinusoidal waveform synchronized with the rotation of the pump motor (5, 6, 7), and the offset circuit (18-2, 20-2, 22-2).
The waveform level is lowered at. The waveform in the second system is obtained by uniformly averaging sinusoidal waveforms. Therefore, when the pump motor is operating normally without step-out, a sine wave-shaped first system wave exists below the second system waveform. At this point, step-out occurs and the pump motor (5,
When the waveform of the current flowing in (6, 7) changes suddenly, the wave of the first system changes rapidly, but the waveform of the second system changes in the integrating circuit (18-3, 20-3, 22-3). Because it goes through, the response is delayed. Therefore, the comparison circuits (18-5, 2
The levels of the two inputs (0-5, 22-5) are reversed. This state is judged to be out of step. The step-out signal thus obtained is logically summed (9-1) in three systems and applied to the sampling circuit (9-2). The sampling circuit (9-2) uses the drive pulse (1) obtained from the waveform reading means 0 (8-0).
7) is frequency-divided into a clock, which is used as a frequency output signal (13-1) and a reference frequency output signal (13-2) for the inverter (1). Sampling (9-
2) With respect to the output, the counter circuit (9-3) counts the number of out-of-steps, and the D / A circuit (9-4) converts it into a frequency output signal. Furthermore, the sampling output (9-2) is subjected to signal level conversion (9-5), and the reference frequency output (13-2) signal is supplied to the inverter (1) while step out occurs.

FIG. 3 shows an acceleration control flowchart. When the acceleration control is started, it operates at the reference frequency for about 30 seconds. During this period, the comparison circuits (18-5, 20-5, 22-
In 5), since the second system starts up slowly, it is determined that the virtual system is out of step until it catches up with the first system. Comparison circuit 3
When the system is all out of the virtual step-out state, the inverter outputs the maximum rotation frequency. If step-out occurs here, the frequency is lowered to the reference frequency and the output frequency is lowered by a certain amount Δf. This operation is repeated every time step out occurs. And
When a predetermined time has passed, the frequency f is lowered to the reference frequency, and the acceleration control ends.

When the cool-down is completed and the control shifts from the acceleration control to the valve timing control, it is necessary to stop the function of the acceleration control means (9). Therefore, the drive pulse is applied to the frequency dividing circuit (17-1), and further applied to another frequency dividing circuit (9-6) to be used as the clock of the delay circuit (9-7). If the data input pin of this delay circuit is adjusted to the active level of the basic frequency output signal, the inverter will be operated at the reference frequency after the elapse of a predetermined time (number of pulses). On the contrary, since the valve timing control needs to be stopped when the acceleration control is executed, the reference frequency output signal (13
-2) is taken into the valve timing control (10).

In FIG. 6, the valve timing control prevents the valve timing control from operating during acceleration control (13-
2) level conversion (10-1) and reset (10-
5) is applied. When the reference frequency output (13-2) signal becomes active and the IC reset (10-5) in the valve timing control means (10) is released, the waveform reading means 0 (8-0), 1 (8- From 1), 2 (8-2), the valve timing control signals 0, 1, 2 and the drive pulse signal begin to be processed. Valve timing control signal 0 (1
9) is the reference pump among the three pumps. Here, the reference pump does not perform relay opening / closing (3, 4) when valve timing control is performed by relay opening / closing (3, 4) of two pump units (25, 26) among three pump units. It is defined as a reference pump. As described above, in order to open and close a predetermined valve based on the reference pump, the valve timing control signal 0 (19) is passed through the read prohibition circuit (10-2) for a certain period of time, and the wavelength shaping circuit (10
-6) The reading prohibition circuit (10-2) for a certain period of time may cause two peaks during one rotation of the pump motor due to the wave generated in the valve timing control signal (19, 21, 23), which prevents malfunctions. It is a circuit for doing.

Next, in order to set the valve opening / closing timing of the pump units 1 (25), 2 (26) connected to the relays 1 (3), 2 (4) to a predetermined timing, the wavelength shaping circuit (10-6). ) Output waves (10-7, 10-8)
Shift. For example, when the pump unit 1 (25) is delayed by 120 ° and the pump unit 2 (26) is delayed by 240 ° with respect to the pump unit 0 (24), the pump unit 1 (25) is driven by a motor having 50 pulses per rotation. 16 shifts in pulses, 32 in pump unit 2
Becomes The shifted wave is the valve timing control signal 1
(21) and 2 (23), respectively. If they do not match, the power cutoff circuit (10-10, 10-1
1) operates and excites the relays (3, 4). In addition, after a lapse of a certain period of time, a drive pulse (17) is applied to a timer (10-13) to stop the valve timing control, and after a lapse of a certain period of time, a power cutoff circuit (10-11, 10-1)
2) is reset and the valve timing control is ended.

[0019]

When three multi-units are used, the amount of helium gas supplied to each cryopump is reduced, which affects the refrigerating capacity and the cooling down time. According to the invention,
Minimizes the fluctuation of the refrigerating capacity and greatly reduces the cooldown time.

[Brief description of drawings]

FIG. 1 is an explanatory diagram of a control system of a multi-cryo pump.

FIG. 2 is a flowchart of a cooldown acceleration method.

FIG. 3 is a flowchart of acceleration control.

FIG. 4 is a diagram showing a reading unit of a pump motor current waveform.

FIG. 5 is a diagram showing an acceleration control means.

FIG. 6 is a diagram showing valve timing control means.

FIG. 7 is a diagram showing a layout of a conventional pump.

FIG. 8 is a diagram showing a conventional control system.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Inverter 2 Transformer 3, 4 Relay 8 Waveform reading means 9 Acceleration control means 10 Valve timing control means 24, 25, 26 Electric motor 40 Compressor P ₁ , P ₂ , P ₃ Cryo pump

Claims (1)

[Claims] 1. A cryogenic temperature is generated by adiabatic expansion of a working gas from a compressor, which is sucked and discharged in response to the movement of a piston reciprocated by an electric pump motor, in a chamber defined by the piston in a cylinder. In the multi-clar ion pump, at least one of the pump motors for the cryopump is connected to the power source through the current sensor, transformer and inverter, and the remaining pump motor is powered by the current sensor and working gas intake / exhaust. Connected via a valve opening / closing relay, a transformer and an inverter, supplies current signals from the respective current sensors to the acceleration control means via the waveform reading means, and sends acceleration control signals from the acceleration control means to the inverter. Rotate the pump motor at high speed, and after the high speed rotation control of the pump motor is completed, read the current signal from the current sensor by the waveform reader. A multi-cryo pump characterized in that it is switched and supplied to a valve timing control means through a stage so that an ON / OFF signal can be supplied to each relay.