Pressure reduction system, control device, and control method

Abstract

The pressure reducing system (3) is provided with: an electric pump (7) that reduces the pressure of a primary space with respect to a secondary space; and a control device (8) that controls a motor (7M) of the electric pump (7), the control device (8) being provided with: a torque command generation section (111) that generates a torque command in such a manner that the motor (7M) operates in accordance with an operation command; a limiter (116) that limits the torque command to a limit value or less; a power conversion circuit (10) that generates and supplies driving power corresponding to the torque command that has passed through the limiter (116) to the motor (7M); and a limit changing section (117) that temporarily increases the limit value in response to the primary space being reduced in pressure being opened with respect to the secondary space.

Description

Technical Field

[0001] This disclosure relates to a pressure reduction system, a control device, and a control method. Background Technology

[0002] Patent Document 1 discloses a motor control device for a vacuum pump, comprising: a load detection unit that detects the load of the motor based on the pressure inside the vacuum pump, the rotational speed of the rotor, or the axial force of the rotor; and a control unit that controls the voltage applied to the motor during steady-state rotation in response to the detection output of the load detection unit, thereby controlling the motor to minimize the variation in rotor speed relative to load variations.

[0003] Existing technical documents

[0004] Patent documents

[0005] Patent Document 1: Japanese Patent Application Publication No. 3-85393 Summary of the Invention

[0006] The problem that the invention aims to solve

[0007] This disclosure provides a decompression system that helps to improve the efficiency of processes for decompressing the primary side space relative to the secondary side space.

[0008] Solution for solving the problem

[0009] One aspect of the pressure reduction system disclosed herein includes: an electric pump for reducing pressure on the primary side space relative to the secondary side space; and a control device for controlling the motor of the electric pump. The control device includes: a torque command generation unit for generating a torque command in a manner that causes the motor to operate according to an action command; a limiter for limiting the torque command to below a limit value; a power conversion unit for generating drive power corresponding to the torque command passed by the limiter and supplying it to the motor; and a limit changing unit for temporarily increasing the limit value in response to the opening of the pressure-reduced primary side space relative to the secondary side space.

[0010] The control device of another aspect of this disclosure includes: a torque command generation unit that generates a torque command for an electric pump motor that causes the primary side space to depressurize relative to the secondary side space according to an operation command; a limiter that limits the torque command to a limit value below a limit value; a power conversion unit that generates drive power corresponding to the torque command passed by the limiter and supplies it to the motor; and a limit changing unit that temporarily increases the limit value in response to the opening of the depressurized primary side space relative to the secondary side space.

[0011] Another aspect of the control method of this disclosure includes the following steps: generating a torque command by means of an electric pump motor that causes the primary side space to depressurize relative to the secondary side space according to an action command; limiting the torque command to a limit value; generating drive power corresponding to the torque command limited to the limit value and supplying it to the motor; and temporarily increasing the limit value in response to the opening of the depressurized primary side space relative to the secondary side space.

[0012] Invention Effects

[0013] According to this disclosure, a decompression system can be provided that helps to improve the efficiency of the process for decompressing the primary side space relative to the secondary side space. Attached Figure Description

[0014] Figure 1 This is a schematic diagram illustrating the structure of a processing system.

[0015] Figure 2 This is a schematic diagram illustrating the configuration of a control device.

[0016] Figure 3 This is a block diagram illustrating the hardware configuration of a control circuit.

[0017] Figure 4 This is a flowchart illustrating the control process.

[0018] Figure 5 This is a flowchart illustrating the control process. Detailed Implementation

[0019] Hereinafter, the embodiments will be described in detail with reference to the accompanying drawings. In the description, the same reference numerals are used to refer to the same elements or elements having the same function, and repeated descriptions are omitted.

[0020] [Processing System]

[0021] Figure 1 The processing system 1 shown is an apparatus that performs processing in the primary side space while the primary side space is depressurized relative to the secondary side space by a pump. The content of the processing performed in the primary side space is not particularly limited; specific examples include film deposition or etching processes in semiconductor manufacturing.

[0022] like Figure 1 As shown, the processing system 1 includes a vacuum device 2 and a depressurization system 3. The vacuum device 2 includes a chamber 4, an opening / closing member 5, and a valve 6. The chamber 4 contains processing objects such as semiconductor wafers. An opening 4a is formed in the upper part of the chamber 4 for the loading / unloading of processing objects. The opening 4a may also be formed in the side of the chamber 4.

[0023] The opening / closing member 5 isolates the internal space 4b of the chamber 4 from the external space 4c of the chamber 4 by blocking the opening 4a. As an example, the opening / closing member 5 opens and closes the opening 4a in conjunction with the loading / unloading of the object to be processed relative to the chamber 4, keeping the opening 4a closed during processing of the object within the chamber 4. The valve 6 opens and closes a flow path that connects the internal space of the chamber 4 to the external space of the chamber 4.

[0024] The pressure reducing system 3 reduces pressure on the internal space 4b relative to the external space 4c of the chamber 4 when the valve 6 is in the "closed" state and the opening 4a is blocked by the opening 4a. The pressure reducing system 3 has an electric pump 7 and a control device 8.

[0025] The electric pump 7 has a motor 7M, which uses the power generated by the motor 7M according to the power supply to depressurize the primary side space relative to the secondary side space. For example, the electric pump 7 is a gas delivery type vacuum pump, which depressurizes the primary side space by transferring gas from the primary side space to the secondary side space. The gas delivery method of the electric pump 7 can be either volumetric transfer or momentum transfer.

[0026] The primary side refers to the upstream side in the direction of gas delivery by the electric pump 7, and the secondary side refers to the downstream side in the direction of gas delivery by the electric pump 7. Furthermore, the primary side space refers to the space connected to the primary side of the electric pump 7, and the secondary side space refers to the space connected to the secondary side of the electric pump 7. The primary side of the electric pump 7 is connected to the internal space 4b of the chamber 4, and the secondary side of the electric pump 7 is connected to the external space 4c. Therefore, in the pressure reduction system 3, the internal space 4b of the chamber 4 corresponds to the primary side space, and the external space 4c of the chamber 4 corresponds to the secondary side space.

[0027] When valve 6 is in the "closed" state and opening / closing member 5 blocks opening 4a, the primary space is closed relative to the secondary space. This closure means that no leakage flow path is formed between the secondary and primary spaces that does not pass through electric pump 7. The state of no leakage flow path includes the state where a small leakage flow path with greater resistance than the pressure-reducing flow path passing through electric pump 7 is formed.

[0028] At least when valve 6 is in the "open" state or when the opening / closing member 5 opens opening 4a, the primary space is open relative to the secondary space. Here, "open" means that the aforementioned leakage flow path is formed between the secondary space and the primary space. The external space 4c of chamber 4, which serves as the secondary space, can also be open to the atmosphere. In this case, by at least keeping valve 6 in the "open" state or opening opening 4a of the opening / closing member 5, the primary space is open to the atmosphere.

[0029] Control device 8 controls motor 7M of electric pump 7. For example, Figure 2As shown, the control device 8 includes a power conversion circuit 10 and a control circuit 100. The power conversion circuit 10 (power conversion unit) converts the power supplied from the power source 9 (hereinafter referred to as "power supply power") into drive power and supplies it to the motor 7M. As an example, the power conversion circuit 10 includes a rectifier circuit 11, a smoothing capacitor 12, an inverter circuit 13, and a current sensor 14. The rectifier circuit 11, for example, is a diode bridge circuit that converts the power supply power into DC power. The smoothing capacitor 12 smooths the DC power.

[0030] The inverter circuit 13 performs the power conversion between the aforementioned DC power and the aforementioned drive power. For example, in the power operation state, the inverter circuit 13 converts DC power into drive power and supplies it to the motor 7M, and in the regenerative state, it converts the power generated by the motor 7M into DC power. It should be noted that the power operation state refers to the state in which the motor 7M operates using the drive power supplied from the inverter circuit 13, and the regenerative state refers to the state in which the motor 7M supplies the generated power corresponding to its operation to the inverter circuit 13.

[0031] For example, the inverter circuit 13 has multiple switching elements 15, which performs the aforementioned power conversion by switching the multiple switching elements 15 on / off. The switching elements 15 are, for example, power MOSFETs (Metal Oxide Semiconductor Field Effect Transistors) or IGBTs (Insulated Gate Bipolar Transistors), which are switched on / off according to a gate drive signal.

[0032] The current sensor 14 detects the current flowing between the inverter circuit 13 and the motor 7M (hereinafter referred to as "output current"). For example, the current sensor 14 can be configured to detect the current of all three phases (U phase, V phase, and W phase) of a three-phase AC circuit, or it can be configured to detect the current of any two phases of the three-phase AC circuit. As long as zero-phase current is not generated, the sum of the currents of the U phase, V phase, and W phase is zero. Therefore, even when detecting the current of two phases, information about the current of all three phases can be obtained.

[0033] The configuration of the power conversion circuit 10 shown above is merely an example. The configuration of the power conversion circuit 10 can be arbitrarily changed as long as it can generate drive power for the motor 7M. For example, the rectifier circuit 11 can also be a PWM (Pulse Width Modulation) converter circuit or a matrix converter circuit that converts AC power to DC power. The power conversion circuit 10 can also be a matrix converter circuit that performs bidirectional power conversion between power supply and drive power without undergoing DC conversion. When the power supply is DC power, the power conversion circuit 10 may not have a rectifier circuit 11.

[0034] The control circuit 100 controls the power conversion circuit 10 to generate drive power for the motor 7M to operate according to the operation command. For example, the control circuit 100 is configured to perform the following processes: generate a torque command in a manner that causes the electric pump 7 to operate according to the operation command; and control the power conversion circuit 10 to generate drive power corresponding to the torque command and supply it to the electric pump 7.

[0035] When the primary side space is closed relative to the secondary side space, the motor 7M operates according to the operation command, thereby depressurizing the primary side space relative to the secondary side space. To quickly re-depressurize the primary side space relative to the secondary side space after it opens and closes, the control circuit 100 continues to operate the motor 7M even when the primary side space is open relative to the secondary side space. When the primary side space is open relative to the secondary side space, by operating the motor 7M, gas is transported from the primary side space to the secondary side space through the aforementioned depressurization path, and gas returns from the secondary side space to the primary side space through the aforementioned leakage path.

[0036] When the primary side space is depressurized relative to the secondary side space, and then opens relative to the secondary side space, the required torque for the electric pump 7 to continuously perform actions corresponding to the operation command can sometimes become excessive. In response, the control circuit 100 also performs a process to limit the torque command below a limit value. The control power conversion circuit 10 generates drive power corresponding to the torque command limited to the limit value and supplies it to the motor 7M. By limiting the torque command below the limit value, it is possible to prevent the torque command from becoming excessive, but the operation of the electric pump 7 may deviate from the operation command.

[0037] When the opening of the primary side space relative to the secondary side space is released, and the decompression of the primary side space resumes, the required torque command gradually decreases, and the operation of the motor 7M corresponding to the operation command gradually recovers. However, the recovery of the operation of the motor 7M corresponding to the operation command takes time, thus reducing the efficiency of the process for decompressing the primary side space relative to the secondary side space. In contrast, the control circuit 100 also performs a process of temporarily increasing the limit value in response to the opening of the decompressed primary side space relative to the secondary side space. As a result, deviations of the operation of the motor 7M from the operation command are suppressed. Therefore, this contributes to the efficiency of the process for decompressing the primary side space relative to the secondary side space.

[0038] For example, the control circuit 100 has a torque command generation unit 111, a limiter 116, a current information acquisition unit 112, a voltage command generation unit 114, a speed estimation unit 113, a PWM control unit 115, and a limit change unit 117 as functional components. The control circuit 100 repeatedly performs a control cycle implemented by these components at a predetermined control period.

[0039] The torque command generation unit 111 generates torque commands in each control cycle in a manner that causes the motor 7M to operate according to the action command. As an example, the action command includes a target speed, and the torque command generation unit 111 generates the torque command in a manner that causes the speed of the motor 7M to follow the target speed. For example, the torque command generation unit 111 generates the torque command by performing proportional calculations, proportional / integral calculations, or proportional / integral / derivative calculations on the deviation between the target speed and the speed of the motor 7M.

[0040] Limiter 116 restricts the torque command generated by torque command generation unit 111 to below a limit value in each control cycle. For example, if the torque command exceeds the limit value, limiter 116 changes the value of the torque command to the limit value.

[0041] Alternatively, when starting the stopped motor 7M to begin decompression of the primary side space relative to the secondary side space, the torque command generation unit 111 gradually increases the speed of the motor 7M to the target speed with an acceleration that keeps the torque command below the aforementioned limit value. For example, the torque command generation unit 111 calculates the speed command value in the current control cycle based on the speed pattern of gradually increasing to the target speed with the aforementioned acceleration and the number of control cycles executed after the motor 7M is started, and generates a torque command in such a way that the speed of the motor 7M follows the speed command value.

[0042] The current information acquisition unit 112 acquires the detected value of the output current from the current sensor 14 in each control cycle. The voltage command generation unit 114 generates a voltage command in each control cycle to make the motor 7M produce a torque that follows the torque command passed through the limiter 116. For example, the voltage command generation unit 114 calculates a current command corresponding to the torque command and generates a voltage command such that the output current follows the current command.

[0043] The speed estimation unit 113 estimates the speed of the motor 7M based on the voltage command and the output current in each control cycle. Specific examples of methods for estimating the speed of the motor 7M include using an extended induced voltage observer.

[0044] The speed estimation result obtained by the speed estimation unit 113 is used to generate the torque command executed by the torque command generation unit 111. The speed estimation performed by the speed estimation unit 113 and the generation of the torque command using the result can also be performed in the same control cycle. In this case, the speed estimation unit 113 estimates the speed of the motor 7M based on the voltage command and output current generated in the previous control cycle, before the torque command generation unit 111 generates the torque command.

[0045] The generation of torque commands using the speed estimation results obtained by the speed estimation unit 113 can also be performed in the next control cycle after the control cycle in which the speed estimation is performed by the speed estimation unit 113. In this case, after the speed estimation unit 113 generates a voltage command by the voltage command generation unit 114, it uses the generation result to estimate the speed of the motor 7M.

[0046] It should be noted that the electric pump 7 may also have a speed sensor that detects the speed of the motor 7M. In this case, the torque command generation unit 111 may also use the detection value obtained from the speed sensor to generate a torque command, and the control circuit 100 may not have a speed estimation unit 113.

[0047] In each control cycle, the PWM control unit 115 controls the power conversion circuit 10 to generate drive power corresponding to the torque command passed by the limiter 116 and supplies it to the motor 7M. For example, in each control cycle, the PWM control unit 115 switches the on / off state of multiple switching elements 15 of the inverter circuit 13 by applying a voltage to the motor 7M corresponding to the voltage command generated by the voltage command generation unit 114.

[0048] The limit change unit 117 temporarily increases the limit value in response to the opening of the depressurized primary side space relative to the secondary side space. For example, the limit change unit 117 temporarily changes the limit value from the normal limit value to an increased limit value that is larger than the normal limit value in response to the opening of the depressurized primary side space relative to the secondary side space.

[0049] The limit change unit 117 can also change the limit value from a normal limit value to an increased limit value after the primary side space is opened relative to the secondary side space and the speed of the motor 7M decreases to meet the prescribed speed reduction condition. As a specific example of the speed reduction condition, the speed of the motor 7M can be reduced to a prescribed reduction determination speed.

[0050] The limit change unit 117 can also sense the opening of the primary side space relative to the secondary side space based on the torque command. Alternatively, the limit change unit 117 can sense the opening of the primary side space relative to the secondary side space based on a comparison between the torque command generated by the torque command generation unit 111 and the limit value before the increase (normal limit value). For example, the limit change unit 117 may sense the opening of the primary side space relative to the secondary side space in response to the torque command generated by the torque command generation unit 111 exceeding the normal limit value.

[0051] In the electric pump 7, as the pressure difference between the secondary and primary sides increases, the torque required to make the motor 7M operate at the target speed decreases. Therefore, when the motor 7M operates according to the operation command under a first level of pressure difference between the secondary and primary sides, a first torque is required. When the motor 7M operates according to the operation command under a second level of pressure difference between the secondary and primary sides, which is smaller than the first level, a second torque larger than the first torque is required. The limit changing unit 117 can also change the limit value within the range of the first torque to the second torque. For example, the above-mentioned ordinary limit value can also exceed the first torque and be less than the second torque. The increased limit value can also exceed the ordinary limit value and be less than the second torque.

[0052] The pressure difference between the secondary and primary spaces reaches its maximum when the primary space is depressurized to approximately a vacuum. Furthermore, the pressure difference between the secondary and primary spaces reaches its minimum (zero) when the primary space is open relative to the secondary space. The first level can be the maximum, and the second level can be the minimum, but there are no particular restrictions on the first and second levels except that the second level is smaller than the first level.

[0053] The limit change unit 117 can also, after increasing the limit value, release the state of increasing the limit value when the torque command is reduced to meet the specified torque reduction condition. For example, the limit change unit 117 can also, after changing the limit value from a normal limit value to an increased limit value, change the limit value from an increased limit value back to a normal limit value when the torque command is reduced to meet the aforementioned torque reduction condition.

[0054] The torque reduction condition may also include the case where the torque command is reduced to less than the increased limit value (increased limit value). For example, the limit change unit 117 may change the limit value from the increased limit value back to the normal limit value after changing the limit value from the normal limit value to the increased limit value, when the torque command is reduced to less than the increased limit value.

[0055] The limit change unit 117 can also deactivate the state of increasing the limit value if the torque command has not decreased to the point where the torque reduction condition is met, and the state of increasing the limit value continues until the specified continuity condition is met. For example, the limit change unit 117 can also change the limit value from the increased limit value back to the normal limit value after changing the limit value from the normal limit value, if the torque command has not decreased to the point where the torque reduction condition is met, and the state of increasing the limit value continues until the specified continuity condition is met.

[0056] The continuing condition may also include the case where the torque command accumulates to a predetermined accumulation level. For example, the limit change unit 117 may change the limit value from an increasing limit value to a normal limit value if the torque command has not decreased to the level required to satisfy the torque reduction condition but has accumulated to the aforementioned accumulation level.

[0057] The continuing condition may also include a situation where the state of increasing the limit value continues throughout the entire specified period. For example, the limit change unit 117 may change the limit value from an increased limit value to a normal limit value if the state of increasing the limit value continues throughout the entire specified period without reducing the torque command to meet the torque reduction condition.

[0058] As an example, the limit change unit 117 checks whether the torque command exceeds the normal limit value in each control cycle. If the torque command exceeds the normal limit value in a consecutive predetermined number of control cycles, the limit change unit 117 senses that the primary side space is open relative to the secondary side space.

[0059] Subsequently, the limit change unit 117 checks in each control cycle whether the speed of the motor 7M meets the aforementioned speed reduction condition. If the speed of the motor 7M meets the speed reduction condition, the limit change unit 117 changes the limit value from the normal limit value to the increased limit value. When the limit value is changed from the normal limit value to the increased limit value, the limiter 116 limits the torque command value below the increased limit value.

[0060] After changing the limit value from a normal limit value to an increased limit value, the limit change unit 117 checks in each control cycle whether the torque command has decreased to meet the torque reduction condition and whether the state of increasing the limit value continues to meet the continuous condition. If the torque command meets the torque reduction condition or the state of increasing the limit value continues to meet the continuous condition, the limit change unit 117 changes the limit value from the increased limit value to a normal limit value. When the limit value is changed from the increased limit value to a normal limit value, the limiter 116 limits the torque command value below the normal limit value.

[0061] Figure 3 This is a block diagram illustrating the hardware configuration of the control circuit 100. For example... Figure 3 As shown, the control circuit 100 includes one or more processors 191, memory 192, storage 193, input / output ports 194, and switch control circuitry 195. The memory 193 may be a computer-readable storage medium, such as non-volatile semiconductor memory. The memory 193 stores a program that causes the control circuit 100 to perform the following processes: generating a torque command for the motor 7M of the electric pump 7, which depressurizes the primary side space relative to the secondary side space, according to an operation command; limiting the torque command below a limit value; generating drive power corresponding to the torque command limited below the limit value and supplying it to the motor 7M; and temporarily increasing the limit value in response to the opening of the depressurized primary side space relative to the secondary side space.

[0062] Memory 192 temporarily stores the program loaded from the storage medium of memory 193 and the calculation results obtained by processor 191. Processor 191 and memory 192 cooperate to execute the above program, thereby forming the functional blocks of control circuit 100. Input / output port 194 performs electrical signal input / output between itself and current sensor 14 according to instructions from processor 191. Switch control circuit 195 outputs drive signals to inverter circuit 13 for switching the switching element 15 on / off according to instructions from processor 191.

[0063] It should be noted that the control circuit 100 is not necessarily limited to having each function constituted by a program. For example, the control circuit 100 may also have at least some functions constituted by a dedicated logic circuit or an ASIC (Application Specific Integrated Circuit) that integrates the dedicated logic circuit.

[0064] [Control Process]

[0065] Next, as an example of a control method, a control process executed by the control circuit 100 is illustrated. This control process includes the following steps: generating a torque command by operating the motor 7M of the electric pump 7, which depressurizes the primary space relative to the secondary space, according to an action command; limiting the torque command below a limit value; controlling the power conversion circuit 10 to generate drive power corresponding to the torque command limited below the limit value and supplying it to the motor 7M; and temporarily increasing the limit value in response to the opening of the depressurized primary space relative to the secondary space.

[0066] For example, Figure 4 As shown, the control circuit 100 first executes steps S01 and S02. In step S01, the torque command generation unit 111 generates a torque command in a manner that causes the motor 7M to operate according to the action command. For example, the torque command generation unit 111 generates a torque command in a manner that causes the speed of the motor 7M to follow the target speed. In step S02, the limiter 116 checks whether the torque command exceeds the normal limit value.

[0067] If it is determined in step S02 that the torque command exceeds the normal limit value, the control circuit 100 executes step S03. In step S03, the limiter 116 changes the torque command to the normal limit value.

[0068] Next, the control circuit 100 executes step S04. If it is determined in step S02 that the torque command does not exceed the normal limit value, the control circuit 100 executes step S04 instead of step S03. In step S04, the current information acquisition unit 112 acquires the detected value of the output current from the current sensor 14.

[0069] Next, the control circuit 100 executes steps S05, S06, S07, and S08. In step S05, the voltage command generation unit 114 generates a voltage command to cause the motor 7M to produce a torque that follows the torque command passed through the limiter 116. For example, the voltage command generation unit 114 calculates a current command corresponding to the torque command and generates the voltage command such that the output current follows the current command. In step S06, the PWM control unit 115 starts turning on / off multiple switching elements 15 based on the voltage command generated in step S05.

[0070] In step S07, the speed estimation unit 113 estimates the speed of the motor 7M based on the voltage command and the output current. The estimation result in step S07 is used in the next control cycle to generate the torque command executed by the torque command generation unit 111. In step S08, the limit change unit 117 checks whether the primary side space is open relative to the secondary side space. For example, the limit change unit 117 checks whether the chamber state indicating whether the primary side space is open relative to the secondary side space is "open".

[0071] If it is determined in step S08 that no opening of the primary side space relative to the secondary side space is detected, the control circuit 100 executes step S11. In step S11, the limit change unit 117 confirms whether the number of consecutive control cycles in which the torque command exceeds the normal limit value is above a predetermined sensing threshold.

[0072] If, in step S11, the number of consecutive control cycles in which the torque command exceeds the normal limit value is determined is not greater than the sensing threshold, the control circuit 100 returns the processing to step S01. Then, until the number of consecutive control cycles in which the torque command exceeds the normal limit value becomes greater than the sensing threshold, the primary side space is considered closed relative to the secondary side space, and control cycles with the limit value set to the normal limit value are repeatedly performed.

[0073] If, in step S11, it is determined that the number of consecutive control cycles in which the torque command exceeds the normal limit value exceeds a sensing threshold, the control circuit 100 executes step S12. In step S12, the limit change unit 117 senses that the primary side space is open relative to the secondary side space and changes the chamber state from "closed" to "open". Afterward, the control circuit 100 returns the process to step S01.

[0074] If it is determined in step S08 that the primary side space is open relative to the secondary side space, the control circuit 100 executes step S13. In step S13, the limit change unit 117 checks whether the speed of the motor 7M meets the aforementioned speed reduction condition.

[0075] If, in step S13, it is determined that the speed of motor 7M does not meet the speed reduction condition, the control circuit 100 returns the processing to step S01. Then, until the speed of motor 7M meets the speed reduction condition, the limit value is maintained at the normal limit value, and the control loop is repeated.

[0076] If, in step S13, it is determined that the speed of motor 7M meets the speed reduction condition, the control circuit 100 executes step S14. In step S14, the limit changing unit 117 changes the limit value from a normal limit value to an increased limit value.

[0077] Next, as Figure 5 As shown, the control circuit 100 executes steps S21 and S22. In step S21, the torque command generation unit 111 generates a torque command in a manner that causes the motor 7M to operate according to the action command. For example, the torque command generation unit 111 generates a torque command in a manner that causes the speed of the motor 7M to follow the target speed. In step S22, the limiter 116 checks whether the torque command exceeds the increase limit value.

[0078] If it is determined in step S22 that the torque command exceeds the increase limit value, the control circuit 100 executes step S23. In step S23, the limiter 116 changes the torque command to the increase limit value.

[0079] Next, the control circuit 100 executes step S24. If it is determined in step S22 that the torque command has not exceeded the increase limit value, the control circuit 100 executes step S24 instead of step S23. In step S24, the current information acquisition unit 112 acquires the detection value of the output current from the current sensor 14.

[0080] Next, the control circuit 100 executes steps S25, S26, S27, and S28. In step S25, the voltage command generation unit 114 generates a voltage command to cause the motor 7M to produce a torque that follows the torque command passed through the limiter 116. For example, the voltage command generation unit 114 calculates a current command corresponding to the torque command and generates the voltage command such that the output current follows the current command. In step S26, the PWM control unit 115 starts turning on / off multiple switching elements 15 based on the voltage command generated in step S25.

[0081] In step S27, the speed estimation unit 113 estimates the speed of the motor 7M based on the voltage command and the output current. The estimation result in step S27 is used in the next control cycle to generate the torque command executed by the torque command generation unit 111. In step S28, the limit change unit 117 confirms whether the torque command has been reduced to meet the above-mentioned torque reduction condition.

[0082] If, in step S28, it is determined that the torque command has not been reduced to meet the torque reduction condition, the control circuit 100 executes step S31. In step S31, the limit change unit 117 confirms whether the state of increasing the limit value continues until the above-mentioned continuity condition is met.

[0083] If, in step S31, it is determined that the state of increasing the limit value has not continued until the continuity condition is met, the control circuit 100 returns the processing to step S21. Thereafter, until the torque command decreases to the point where the torque reduction condition is met, or the state of increasing the limit value continues until the aforementioned continuity condition is met, the control loop of setting the limit value to the increasing limit value is repeatedly performed.

[0084] If, in step S31, it is determined that the state of increasing the limit value will continue until the continuity condition is met, the control circuit 100 executes step S32. In step S32, the limit changing unit 117 changes the limit value from an increased limit value to a normal limit value. Afterward, the control circuit 100 returns the process to step S21. Thereafter, it is assumed that the primary side space is still open relative to the secondary side space, and the control loop of setting the limit value to a normal limit value is repeatedly performed.

[0085] If, in step S28, it is determined that the torque command has been reduced to meet the torque reduction condition, the control circuit 100 executes step S33. In step S33, the limit change unit 117 confirms whether the limit value is an increase limit value.

[0086] If the limit value is determined to be an increasing limit value in step S33, the control circuit 100 executes step S34. In step S34, the limit changing unit 117 changes the limit value from an increasing limit value to a normal limit value.

[0087] Next, the control circuit 100 executes step S35. If it is determined in step S33 that the limit value is not an increasing limit value, the control circuit 100 executes step S35 instead of step S34. In step S35, the limit changing unit 117 senses that the primary side space is closed relative to the secondary side space and changes the chamber state from "open" to "closed". Afterwards, the control circuit 100 returns the process to step S01. Then, assuming that the primary side space is closed relative to the secondary side space, the control loop restarts with the limit value set to the normal limit value.

[0088] [Effects of this implementation method]

[0089] As described above, the pressure reduction system 3 includes: an electric pump 7 that reduces pressure on the primary side space relative to the secondary side space; and a control device 8 that controls the motor 7M of the electric pump 7. The control device 8 includes: a torque command generation unit 111 that generates a torque command so that the motor 7M operates according to an action command; a limiter 116 that limits the torque command to a limit value below a certain limit; a power conversion circuit 10 that generates drive power corresponding to the torque command passed through the limiter 116 and supplies it to the motor 7M; and a limit change unit 117 that temporarily increases the limit value in response to the opening of the pressure-reduced primary side space relative to the secondary side space.

[0090] When the primary side space is open to the secondary side space, the torque command required to keep the motor continuously operating in accordance with the action command may sometimes exceed the limit value. In this case, since the torque command is limited to the limit value, the operation of motor 7M will deviate from the action command. When the opening of the primary side space relative to the secondary side space is closed and the decompression of the primary side space begins again, the required torque command will gradually decrease, and the operation of motor 7M will gradually correspond to the action command.

[0091] However, when the primary space is open relative to the secondary space, if the movement of motor 7M deviates too much from the action command, time is required until the movement of motor 7M corresponds to the action command. Therefore, the efficiency of the process for depressurizing the primary space decreases. In contrast, according to the depressurization system 3, in response to the opening of the primary space relative to the secondary space, the limit change unit 117 temporarily increases the limit value, thereby suppressing the deviation of the movement of motor 7M from the action command. Therefore, this contributes to improving the efficiency of the process for depressurizing the primary space relative to the secondary space.

[0092] Alternatively, the motion command may include a target speed, and the torque command generation unit 111 generates the torque command in such a way that the speed of the motor 7M follows the target speed. In this case, by temporarily increasing the limit value by the limit change unit 117, the deviation of the motor 7M's motion from the motion command is more reliably suppressed.

[0093] Alternatively, after the primary side space is opened relative to the secondary side space, the limit change unit 117 increases the limit value after the speed of the motor 7M decreases to meet the prescribed speed reduction condition. When the limit value is increased after the torque command value is limited to the limit value, the torque command will increase sharply. If the torque command increases sharply while the speed of the motor 7M is high, the drive power may become excessive for the capacity of the power conversion circuit 10. By waiting until the speed of the motor 7M meets the prescribed speed reduction condition before increasing the limit value, the excessive drive power can be suppressed.

[0094] Alternatively, the limit change unit 117 can sense the openness of the primary side space relative to the secondary side space based on torque commands. In this case, the device configuration can be simplified.

[0095] Alternatively, the limit change unit 117 can sense the opening of the primary side space relative to the secondary side space based on a comparison between the torque command generated by the torque command generation unit 111 and the limit value before the increase. In this case, the opening of the primary side space relative to the secondary side space can be sensed with high sensitivity.

[0096] Alternatively, when starting the motor 7M to begin decompression of the primary side space, the torque command generation unit 111 gradually increases the speed of the motor 7M to the target speed with an acceleration that keeps the torque command below the limit value. In this case, it is possible to suppress the false sensing of the opening of the primary side space relative to the secondary side space during the startup of the motor 7M.

[0097] Alternatively, when the pressure difference between the secondary and primary spaces is at a first level, the motor 7M operates at a target speed, requiring a first torque. When the pressure difference between the secondary and primary spaces is at a second level smaller than the first level, a second torque larger than the first torque is required. The limit changing unit 117 changes the limit value within the range of the first torque to the second torque. In this case, it is possible to suppress overload of the power conversion circuit 10 caused by excessive drive power relative to its capacity.

[0098] Alternatively, after amplifying the limit value, the limit change unit 117 may release the state of increasing the limit value once the torque command is reduced to meet the specified torque reduction condition. In this case, by maintaining the state of increasing the limit value before the torque command is reduced from the start of decompression in the primary space relative to the secondary space, deviations of the motor 7M's operation from the operation command can be suppressed more reliably.

[0099] Alternatively, the torque reduction condition may include a situation where the torque command decreases to a value less than the increased limit value. After increasing the limit value, the limit change unit 117 releases the state of increasing the limit value when the torque command decreases to a value less than the increased limit value (increased limit value). In this case, deviations of the motor 7M's operation from the operation command can be suppressed more reliably.

[0100] Alternatively, the limit change unit 117 may continue increasing the limit value until a specified duration condition is met, provided that the torque command has not been reduced to the level required to satisfy the torque reduction condition. In this case, a balance between high efficiency and overload suppression can be achieved.

[0101] Alternatively, if the continuous condition includes the accumulation of torque command to a predetermined accumulation level, the limit change unit 117 may release the state of increasing the limit value if the torque command has accumulated to the accumulation level without decreasing to the point where the torque reduction condition is met. In this case, it is possible to suppress the deviation of the motor 7M's operation from the operation command, and at the same time, suppress the drive power from becoming too large for the power conversion circuit 10.

[0102] Alternatively, the continuous condition may include a situation where the state of increasing the limit value continues for a specified period. If the limit change unit 117 releases the state of increasing the limit value for a specified period without reducing the torque command to meet the torque reduction condition, then the state of increasing the limit value is released. In this case, it is possible to suppress the deviation of the motor 7M's operation from the operation command, and at the same time, suppress the drive power from becoming too large for the power conversion circuit 10.

[0103] The implementation methods have been described above, but this disclosure is not necessarily limited to the above-described implementation methods, and various changes can be made without departing from its spirit.

[0104] Explanation of reference numerals in the attached figures

[0105] 3: Pressure reduction system;

[0106] 7: Electric pump;

[0107] 7M: Motor;

[0108] 8: Control device;

[0109] 10: Power conversion circuit (power conversion unit);

[0110] 111: Torque command generation unit;

[0111] 116: Limiter;

[0112] 117: Limit Change Department.

Claims

1. A pressure reduction system, comprising: An electric pump depressurizes the primary side space relative to the secondary side space; and The control device controls the motor of the electric pump. The control device includes: A torque command generation unit generates a torque command so that the motor operates according to an action command. A limiter restricts the torque command below a limit value; The power conversion unit generates drive power corresponding to the torque command passed through the limiter and supplies it to the motor; and The limit change unit temporarily increases the limit value in response to the opening of the depressurized primary side space relative to the secondary side space.

2. The pressure reduction system according to claim 1, wherein, The action command includes the target speed. The torque command generation unit generates the torque command in such a way that the speed of the motor follows the target speed.

3. The pressure reduction system according to claim 2, wherein, After the primary side space is opened relative to the secondary side space, the limit change unit increases the limit value after the motor speed decreases to meet the specified speed reduction condition.

4. The pressure reduction system according to claim 1, wherein, The limit change unit senses the opening of the primary side space relative to the secondary side space based on the torque command.

5. The pressure reduction system according to claim 4, wherein, The limit change unit senses the opening of the primary side space relative to the secondary side space based on a comparison between the torque command generated by the torque command generation unit and the limit value before the increase.

6. The pressure reduction system according to claim 4, wherein, When the motor is started to begin decompression of the primary side space, the torque command generation unit gradually increases the speed of the motor with an acceleration that keeps the torque command below the limit value.

7. The pressure reduction system according to any one of claims 1 to 6, wherein, When the motor operates at a target speed under a pressure difference of a first level between the secondary and primary space, a first torque is required. When the pressure difference between the secondary and primary space is a second level smaller than the first level, a second torque larger than the first torque is required. The limit change unit changes the limit value within the range from the first torque to the second torque.

8. The pressure reduction system according to claim 1, wherein, After amplifying the limit value, the limit change unit releases the state of increasing the limit value when the torque command is reduced to meet the specified torque reduction condition.

9. The pressure reduction system according to claim 8, wherein, The torque reduction condition includes the case where the torque command is reduced to less than the increased limit value. After increasing the limit value, the limit change unit releases the state of increasing the limit value when the torque command is reduced to less than the increased limit value.

10. The pressure reduction system according to claim 8, wherein, If the limit change unit continues the state of increasing the limit value until the specified duration condition is met, the state of increasing the limit value is released.

11. The pressure reduction system according to claim 10, wherein, The sustained conditions include the case where the torque command accumulates to a predetermined accumulation level. The limit change unit deactivates the state of increasing the limit value if the torque command has not decreased to meet the torque reduction condition but has accumulated to the accumulated level.

12. The pressure reduction system according to claim 10 or 11, wherein, The sustained condition includes situations where the state of increasing the limit value continues throughout the specified period. If the limit change unit continues to increase the limit value during the specified period if the torque command is not reduced to meet the torque reduction condition, the limit change unit will deactivate the state of increasing the limit value.

13. A control device comprising: The torque command generation unit generates a torque command according to the operation command of the motor of the electric pump that causes the primary side space to depressurize relative to the secondary side space. A limiter restricts the torque command below a limit value; The power conversion unit generates drive power corresponding to the torque command passed through the limiter and supplies it to the motor; and The limit change unit temporarily increases the limit value in response to the opening of the depressurized primary side space relative to the secondary side space.

14. A control method comprising the following steps: The motor of the electric pump that reduces the pressure of the primary side space relative to the secondary side space generates a torque command according to the operation command. Limit the torque command below the limit value; Generate drive power corresponding to the torque command limited below the stated limit value and supply it to the motor; and The limit value is temporarily increased in response to the opening of the primary side space relative to the secondary side space due to the decompression.

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