Compressor

Abstract

To realize suitable operation according to on a load level of an inverter in a compressor.SOLUTION: A compressor 1 comprises a motor 30, an inverter 40 that controls the motor 30, a compressor body 20 that is driven by the motor 30 and compresses fluid, a load level determination unit 51 that determines a load level of the inverter 40, and a rotation speed adjustment unit 52 that adjusts an acceleration or deceleration of the motor 30 based on the load level determined by the load level determination unit 51.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a compressor. [Background technology]

[0002] Compressors equipped with a motor controlled by an inverter are known. For example, Patent Document 1 discloses an electric compressor equipped with an AC motor that drives a scroll compressor and an inverter device that controls the AC motor.

[0003] In the electric compressor, the inverter device includes a switching circuit that supplies current to the AC motor and a motor control unit that controls the switching circuit. The motor control unit measures the elapsed time from when the AC motor stops to when it starts in order to control the switching circuit in accordance with the load of the scroll compressor, calculates a target acceleration of the rotor when the AC motor is started based on the measured elapsed time, and controls the switching circuit so that the rotor starts at the target acceleration. [Prior art documents] [Patent documents]

[0004] [Patent Document 1] Japanese Patent Application Laid-Open No. 2015-142389 Summary of the Invention [Problem to be solved by the invention]

[0005] In the electric compressor of Patent Document 1, the target acceleration is calculated from the elapsed time from when the motor stops until it starts, so the calculated acceleration cannot be changed during startup (acceleration), and feedback control according to the load on the inverter cannot be performed.Furthermore, no consideration is given to changing the acceleration or deceleration during load operation after startup.

[0006] An object of the present invention is to realize a compressor that operates in a suitable manner according to the load level of an inverter. [Means for solving the problem]

[0007] The present invention provides a compressor comprising: a motor; an inverter that controls the motor; a compressor body that is driven by the motor and compresses a fluid; a load level determination unit that determines the load level of the inverter; and a rotation speed adjustment unit that adjusts the acceleration or deceleration of the motor based on the load level determined by the load level determination unit.

[0008] With this configuration, the load level determination unit can determine the load level of the inverter, and the rotation speed adjustment unit can appropriately adjust the acceleration or deceleration of the motor according to the load level. That is, feedback control can be performed according to the load level of the inverter, and the acceleration or deceleration can be appropriately changed not only during startup operation but also during load operation. In this way, the compressor can be operated appropriately according to the load level of the inverter. Here, the load level of the inverter indicates the tolerance for the specifications of the motor or inverter.

[0009] The load degree determining unit may determine the load degree based on a state value of the inverter, and the state value may include at least one of an output current, a control axis deviation, and a torque.

[0010] With this configuration, the output current, the control axis deviation, and the torque are all suitable as state values ​​because they can be easily obtained as values ​​indicating the load on the inverter. Furthermore, since these state values ​​all have a large effect on the compressor, it is useful to be able to adjust the acceleration or deceleration of the motor based on these state values.

[0011] The state value may be any one of an output current, a control axis deviation, or a torque, and the load level determination unit may determine that the load level is medium when the state value is greater than a predetermined lower threshold and equal to or less than a predetermined upper threshold, may determine that the load level is high when the state value is greater than the upper threshold, and may determine that the load level is low when the state value is equal to or less than the lower threshold.

[0012] This configuration allows the load level to be easily determined based on any one of the output current, the control axis deviation, and the torque. Furthermore, the load level can be evaluated in three stages, simplifying control. Here, the upper and lower thresholds can be suitably set based on the specifications of the motor or inverter.

[0013] The state values ​​may include at least two of output current, control axis deviation, and torque, and the load level determination unit may determine that the load level is high when at least one of the state values ​​is greater than a predetermined upper threshold, may determine that the load level is low when all of the state values ​​are equal to or less than a predetermined lower threshold, or may determine that the load level is medium when at least one of the state values ​​is greater than the lower threshold and all of the state values ​​are equal to or less than an upper threshold.

[0014] This configuration allows the load level to be determined in a composite manner based on at least two of the output current, the control axis deviation, and the torque. Furthermore, the load level can be evaluated in three stages, simplifying control. Here, the upper and lower thresholds can be suitably set based on the specifications of the motor or inverter.

[0015] The rotation speed adjustment unit may set the acceleration or deceleration of the motor high when the load level determination unit determines that the load level is low, may set the acceleration or deceleration of the motor low when the load level determination unit determines that the load level is high, or may set the acceleration or deceleration of the motor to a medium level when the load level determination unit determines that the load level is medium.

[0016] According to this configuration, when the load on the inverter is high (i.e., when the tolerance is small), setting the motor acceleration or deceleration low prevents the compressor from operating beyond the tolerance and avoids breakdown. Also, when the load on the inverter is low (i.e., when the tolerance is large), setting the motor acceleration or deceleration high shortens the startup operation time (the time from the start of startup to load operation) and improves the ability to follow the target pressure during load operation. Also, when the load on the inverter is medium (i.e., when the tolerance is medium), setting the motor acceleration or deceleration to a medium level allows stable operation to continue. Here, high, low, and medium acceleration or deceleration indicate relative relationships and do not indicate absolute specific values.

[0017] The rotation speed adjustment unit may set the acceleration of the motor to an initial value during startup operation of the compressor main body and then begin adjusting the acceleration of the motor, and the initial value may be the acceleration that was set at the end of the previous startup operation.

[0018] According to this configuration, by using the previously set value as the initial value of the acceleration of the motor at the time of startup operation, a reliable value can be adopted as the acceleration of the motor.

[0019] When the compressor switches to load operation, the rotation speed adjustment unit may set the acceleration or deceleration of the motor to an initial value and then start adjusting the acceleration or deceleration of the motor, and the initial value may be the acceleration or deceleration that was set at the end of the previous load operation.

[0020] According to this configuration, by using the previously set value as the initial value of the acceleration or deceleration of the motor during load operation, a reliable value can be adopted as the acceleration or deceleration of the motor. [Effects of the Invention]

[0021] According to the present invention, it is possible to realize a compressor that operates in a suitable manner according to the load level of the inverter. [Brief explanation of the drawings]

[0022] [Figure 1] 1 is a schematic configuration diagram of a compressor according to a first embodiment. [Figure 2] 4 is a flowchart showing a control method during startup operation in the first embodiment. [Figure 3] 4 is a flowchart showing a control method during load operation in the first embodiment. [Figure 4] 6 is a graph showing time-series data of discharge pressure, motor rotation speed, and operating state. [Figure 5] 10 is a flowchart showing a control method during startup operation in the second embodiment. [Figure 6] 10 is a flowchart showing a control method during load operation in the second embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0023] Hereinafter, an embodiment of the present invention will be described with reference to the accompanying drawings.

[0024] (First embodiment) Referring to FIG. 1, a compressor 1 of the first embodiment includes an intake regulating valve 10, a compressor body 20, a motor 30, an inverter 40, and a control device 50.

[0025] The intake regulating valve 10 is disposed upstream of the compressor main body 20 and is fluidly connected to the compressor main body 20 via piping 21. The intake regulating valve 10 regulates the amount of air drawn into the compressor main body 20. When the intake regulating valve 10 is closed, the compressor main body 20 performs no-load operation without drawing in any air. When the intake regulating valve 10 is opened, the compressor main body 20 draws in air and performs loaded operation. Note that, although air is used as an example of the fluid to be compressed here, fluids other than air may also be compressed.

[0026] Compressor body 20 has an inlet port 22 and a discharge port 23. A motor 30 is mechanically connected to compressor body 20, and compressor body 20 is driven by motor 30. When compressor body 20 is driven by motor 30, it draws in air through intake control valve 10, piping 21, and inlet port 22. The drawn-in air is compressed inside compressor body 20 and discharged from discharge port 23. Pipe 24 is fluidly connected to discharge port 23, and this pipe 24 extends to any supply destination.

[0027] In this embodiment, the compressor body 20 is of a screw type. That is, the compressor body 20 has a pair of male and female screw rotors inside. The screw rotors are driven to rotate by a motor 30, thereby compressing the air. However, the type of the compressor body 20 is not particularly limited and can be any type.

[0028] An inverter 40 is electrically connected to the motor 30. The inverter 40 controls the rotation speed of the motor 30.

[0029] The control device 50 performs arithmetic processing and overall control of the compressor 1. The control device 50 includes, for example, a central processing unit (CPU) or a microprocessing unit (MPU) that implements predetermined functions in cooperation with software. The control device 50 may be configured with hardware circuits, such as dedicated electronic circuits or reconfigurable electronic circuits, designed to implement predetermined functions, or may be configured with various semiconductor integrated circuits. Examples of various semiconductor integrated circuits include CPUs, MPUs, microcomputers, digital signal processors (DSPs), field programmable gate arrays (FPGAs), and application-specific integrated circuits (ASICs). The control device 50 may also include storage devices such as random access memory (RAM) and read-only memory (ROM). Specifically, the control device 50 may be configured with an information processing device such as a desktop computer, laptop computer, workstation, or tablet terminal, or a printed circuit board with equivalent functions.

[0030] The control device 50 realizes predetermined functions by reading out stored data and programs and performing various arithmetic processing. The programs executed by the control device 50 may be provided from an external device using a communication unit or the like that communicates in accordance with a predetermined communication standard, or may be stored on a portable recording medium.

[0031] The control device 50 has, as its functional components, a load level determination unit 51 and a rotation speed adjustment unit 52. These are realized by the cooperation of the above-mentioned hardware and software. These may also be interpreted as corresponding circuits.

[0032] Load degree determination unit 51 determines the load degree of inverter 40 based on the state value of inverter 40. The state value may include at least one of output current, control axis deviation, and torque. The output current, control axis deviation, and torque may be detected by any sensor configured integrally with inverter 40. However, the sensor may also be an external sensor separate from inverter 40. Since the output current, control axis deviation, and torque can all be easily obtained as values ​​indicating the load degree of inverter 40, they are suitable as state values ​​of inverter 40.

[0033] In this embodiment, the load degree of the inverter 40 is determined based on the above state values ​​by the load degree determination unit 51. Here, the load degree of the inverter 40 is also referred to as the tolerance for the specifications of the motor 30 or the inverter 40.

[0034] The output current refers to the current that the inverter 40 supplies to the motor 30. The larger the output current, the lower the tolerance for the specifications of the motor 30 or the inverter 40. Therefore, it can be determined that the larger the output current, the higher the load on the inverter 40.

[0035] The control axis deviation refers to the deviation of the rotating shaft of motor 30 from its normal state. More specifically, inverter 40 estimates the position of the rotating shaft of motor 30 from the current and magnetic flux, and controls motor 30 based on the estimated position of the rotating shaft of motor 30. The deviation between the rotating shaft estimated by inverter 40 and the actual rotating shaft of motor 30 is called the control axis deviation. The larger the control axis deviation, the lower the accuracy with which inverter 40 controls motor 30, and when the control axis deviation exceeds a certain value, inverter 40 will no longer be able to control motor 30. Therefore, it can be determined that the larger the control axis deviation, the higher the load on inverter 40.

[0036] Torque refers to the torque that inverter 40 applies to motor 30. The greater the torque, the lower the tolerance for the specifications of motor 30 or inverter 40. Therefore, it can be determined that the greater the torque, the higher the load on inverter 40.

[0037] Since each of the above state values ​​has a large effect on the compressor, it is useful to be able to adjust the acceleration or deceleration of the motor based on the state value. In this embodiment, the state value of the inverter 40 is one of the output current, the control axis deviation, or the torque. The following description will be given taking the case where the output current is used as the state value of the inverter 40 as an example.

[0038] Specifically, the load level determination unit 51 determines that the load level is medium when the output current is greater than a predetermined lower threshold and equal to or less than a predetermined upper threshold, determines that the load level is high when the output current is greater than the upper threshold, and determines that the load level is low when the output current is equal to or less than the lower threshold. Here, the upper threshold and the lower threshold can be suitably set based on the specifications of the motor 30 or the inverter 40.

[0039] The rotation speed adjustment unit 52 adjusts the acceleration or deceleration of the motor 30 based on the load level determined by the load level determination unit 51. In this embodiment, the rotation speed adjustment unit 52 sets the acceleration or deceleration of the motor 30 high when the load level determination unit 51 determines that the load level is low, sets the acceleration or deceleration of the motor 30 low when the load level determination unit 51 determines that the load level is high, and sets the acceleration or deceleration of the motor 30 to a medium level when the load level determination unit 51 determines that the load level is medium.

[0040] The compressor 1 of this embodiment is controlled differently depending on whether it is in a stopped state, a startup operation, or a load operation state.

[0041] In the stopped state, the rotation speed of the motor 30 is zero, and the intake control valve 10 is also closed.

[0042] In the startup operation, the compressor 1 is started from a stopped state, and the rotation speed of the motor 30 increases from zero to the rated rotation speed (maximum rotation speed in the specifications). In the startup operation, the intake control valve 10 is closed, and no-load operation is performed. The control of the startup operation will be described later.

[0043] During load operation, the intake control valve 10 is opened and load operation is performed. During load operation, the rotation speed of the motor 30 is adjusted according to the set discharge pressure, and the compressor 1 discharges air at the set discharge pressure. Control of load operation will be described later.

[0044] Hereinafter, the control during startup operation will be described with reference to FIG. 2, and the control during load operation will be described with reference to FIG.

[0045] 2, when the startup operation is started (step S2-1), the rotation speed adjustment unit 52 sets the acceleration of the motor 30 of the compressor main body 20 to an initial value (step S2-2), and then starts adjusting the acceleration of the motor 30 (step S2-3 and subsequent steps). This initial value is the acceleration that was set at the end of the previous startup operation. The initial value may be set to a standard acceleration in the specifications of the motor 30.

[0046] In this embodiment, three values ​​a1, a2, and a3 can be set as the acceleration of the motor 30. The accelerations a1, a2, and a3 have increasing values ​​in this order (a1>a2>a3), and the values ​​a1, a2, and a3 are suitably set according to the type of the motor 30 and the inverter 40.

[0047] After the acceleration of the motor 30 is set to the initial value (for example, a2) (step S2-2), it is then determined whether the output current is equal to or less than the lower limit threshold (step S2-3). That is, it is determined whether the load level is low.

[0048] If the output current is equal to or less than the lower threshold (Y: step S2-3), the load level is determined to be low, and a determination is made as to whether a predetermined waiting time Tx or more has elapsed since the last acceleration change (step S2-4). If the predetermined waiting time Tx or more has not elapsed (N: step S2-4), the process returns to determining the output current (step S2-3). If the predetermined waiting time Tx or more has elapsed (Y: step S2-4), the acceleration is set to a1, which is a value greater than a2 (step S2-5). Setting the predetermined waiting time Tx in this manner prevents the acceleration from being changed unnecessarily frequently. The same applies to the predetermined waiting times Ty and Tz, which will be described later.

[0049] If the output current is not equal to or less than the lower threshold (N: step S2-3), it is determined whether the output current is equal to or less than the upper threshold (step S2-6). That is, it is determined whether the load level is medium or high. If the output current is equal to or less than the upper threshold (Y: step S2-6), it is determined that the load level is medium, and it is determined whether a predetermined waiting time Ty or more has elapsed since the previous acceleration change (step S2-7). If the predetermined waiting time Ty or more has not elapsed (N: step S2-7), the process returns to determining the output current (step S2-3). If the predetermined waiting time Ty or more has elapsed (Y: step S2-7), the acceleration is set to a2 (step S2-8).

[0050] If the output current is not equal to or less than the upper threshold (N: step S2-6), the load is determined to be high, and a determination is made as to whether a predetermined waiting time Tz or more has elapsed since the previous acceleration change (step S2-9). If the predetermined waiting time Tz or more has not elapsed (N: step S2-9), the process returns to determining the output current (step S2-3). If the predetermined waiting time Tz or more has elapsed (Y: step S2-9), the acceleration is set to a3, which is a value smaller than a2 (step S2-10).

[0051] When the acceleration of the motor 30 is set to a1, a2, or a3 (steps S2-5, S2-8, S2-10), it is determined whether the rotation speed of the motor 30 has reached the rated rotation speed (step S2-11). If the rotation speed of the motor 30 has not reached the rated rotation speed (N: step S2-11), the process returns to determining the output current (step S2-3). If the rotation speed of the motor 30 has reached the rated rotation speed (Y: step S2-11), the startup operation is terminated (step S2-12). After the startup operation is completed, the process transitions to load operation.

[0052] Referring to FIG. 3, when load operation is started (step S3-1), the rotation speed adjustment unit 52 sets the acceleration or deceleration of the motor 30 to an initial value during load operation of the compressor main body 20 (step S3-2), and then starts adjusting the acceleration or deceleration of the motor 30 (steps S3-3 and onward). This initial value is the acceleration or deceleration that was set at the end of the previous load operation. Note that, unlike startup operation, load operation not only involves increasing the rotation speed of the motor 30 but also decreasing it. When the rotation speed of the motor 30 is increased, the acceleration is adjusted, and when the rotation speed of the motor 30 is decreased, the deceleration is adjusted. Therefore, the control of load operation shown in FIG. 3 differs from the control of startup operation shown in FIG. 2 in that it is a flowchart that includes acceleration and deceleration.

[0053] During load operation, in addition to the accelerations a1, a2, and a3 of the motor 30 described above, three values ​​b1, b2, and b3 can be set as the deceleration of the motor 30. The decelerations b1, b2, and b3 have increasing values ​​in this order (b1>b2>b3), and the values ​​of b1, b2, and b3 are set appropriately depending on the type of motor 30 and inverter 40.

[0054] Once the acceleration or deceleration of the motor 30 is set to the initial value (e.g., a2 or b2) (step S3-2), it is then determined whether the output current is equal to or less than the lower limit threshold (step S3-3). That is, it is determined whether the load is low.

[0055] If the output current is equal to or less than the lower threshold (Y: step S3-3), the load level is determined to be low, and a determination is made as to whether a predetermined waiting time Tx or more has elapsed since the last acceleration change (step S3-4). If the predetermined waiting time Tx or more has not elapsed (N: step S3-4), the process returns to determining the output current (step S3-3). If the predetermined waiting time Tx or more has elapsed (Y: step S3-4), the acceleration is set to a1, which is a value greater than a2, or the deceleration is set to b1, which is a value greater than b2 (step S3-5).

[0056] If the output current is not equal to or less than the lower threshold (N: step S3-3), it is determined whether the output current is equal to or less than the upper threshold (step S3-6). That is, it is determined whether the load level is medium or high. If the output current is equal to or less than the upper threshold (Y: step S3-6), it is determined that the load level is medium, and it is determined whether a predetermined waiting time Ty or more has elapsed since the last change in acceleration or deceleration (step S3-7). If the predetermined waiting time Ty or more has not elapsed (N: step S3-7), the process returns to determining the output current (step S3-3). If the predetermined waiting time Ty or more has elapsed (Y: step S3-7), the acceleration is set to a2 or the deceleration is set to b2 (step S3-8).

[0057] If the output current is not equal to or less than the upper threshold (N: step S3-6), the load is determined to be high, and a determination is made as to whether a predetermined waiting time Tz or more has elapsed since the last change in acceleration or deceleration (step S3-9). If the predetermined waiting time Tz or more has not elapsed (N: step S3-9), the process returns to determining the output current (step S3-3). If the predetermined waiting time Tz or more has elapsed (Y: step S3-9), the acceleration is set to a3, which is a value smaller than a2, or the deceleration is set to b3, which is a value smaller than b2 (step S3-10).

[0058] When the acceleration of the motor 30 is set to a1, a2, or a3, or the deceleration is set to b1, b2, or b3 (steps S3-5, S3-8, and S3-10), the presence or absence of a stop command to stop operation of the compressor 1 is determined (step S3-11). If there is no stop command (N: step S3-11), the process returns to determining the output current (step S3-3). If there is a stop command (Y: step S3-11), the loaded operation is terminated (step S3-12). At this time, the compressor 1 enters a stopped state via no-load operation. The stop command may be issued by user input, or may be issued automatically for safety reasons when the discharge pressure exceeds a predetermined threshold, as will be described later as an automatic stop pressure.

[0059] An example of the discharge pressure of the compressor 1, the rotation speed of the motor 30, and the operating state (load, no load, stopped) will be described with reference to Fig. 4. In the upper, middle, and lower graphs, the horizontal axis is aligned to the same time.

[0060] The upper graph shows the discharge pressure of compressor 1. Pressure P1 indicates the automatic stop pressure, pressure P2 indicates the set target pressure, and pressure P3 indicates the automatic return pressure. Automatic stop pressure P1 is the pressure at which, if the discharge pressure rises any higher, the system switches to no-load operation or a stopped state for safety reasons. Target pressure P2 is the pressure of air supplied to any supply destination set by the user. Automatic return pressure P3 is the pressure at which, if the discharge pressure drops any lower, the system switches from no-load operation or a stopped state to a loaded operation. In this way, the operation in which the discharge pressure drops below automatic return pressure P3 and the system switches from no-load operation or a stopped state to a loaded operation is called automatic return operation. Here, automatic return operation is considered to be included in startup operation.

[0061] The graph in the middle shows the rotation speed of the motor 30. The rotation speed r1 indicates the maximum rotation speed according to the specifications, and the rotation speed r2 indicates the minimum rotation speed according to the specifications. The maximum rotation speed r1 is also called the rated rotation speed.

[0062] The graph at the bottom shows the operating state of the compressor 1. That is, it shows whether the compressor 1 is in a loaded operation, a no-load operation, or a stopped state.

[0063] When startup operation begins at time t0, the rotation speed of the motor 30 is increased at an initial value at an acceleration a2 (the slope of the motor rotation speed graph) until time t1. At this time, the discharge pressure is zero, and no-load operation is being performed. Next, from time t1, the rotation speed of the motor 30 is increased at an acceleration a1. This is because the acceleration is changed based on the load level of the inverter 40, as described above. This change can be confirmed by the change in the slope of the motor rotation speed graph at time t1. At time t2, the rotation speed of the motor 30 reaches the rated rotation speed r1, load operation begins, and the discharge pressure begins to increase. In this manner, startup operation is performed from time t0 to time t2. In this example, when the rotation speed of the motor 30 reaches the rated rotation speed r1 at time t2, the operation is switched from no-load operation to load operation. Regardless of the rotation speed of the motor 30, the operation may be switched from no-load operation to load operation after a certain time has elapsed since the startup operation began, or after a certain time has elapsed since the rotation speed of the motor 30 reached the rated rotation speed r1. It is preferable to switch from no-load operation to loaded operation when the rotation speed of the motor 30 reaches the rated rotation speed r1, as this improves the ability to follow the target pressure.

[0064] From time t2 to t3, the rotation speed of the motor 30 is maintained at the rated rotation speed r1, but the discharge pressure gradually increases and reaches the set discharge pressure P2 at time t3. From time t3 to time t4, the rotation speed is controlled to maintain the discharge pressure at P2. The acceleration or deceleration rate related to the increase or decrease in the rotation speed at this time is updated as appropriate according to the flowchart shown in Figure 3. In this way, load operation is performed from time t2 to t4.

[0065] At time t4, the discharge pressure reaches the automatic stop pressure P1, and the system switches to no-load operation. At this time, the rotation speed of the motor 30 has dropped to the minimum rotation speed r2. After no-load operation continues for a certain period of time, the system switches from no-load operation to a stopped state at time t5. The rotation speed of the motor 30 drops from the minimum rotation speed r2 toward zero. As a result, the discharge pressure gradually drops.

[0066] When the discharge pressure drops to the automatic return pressure P3, the operation is switched from the stopped state to no-load operation at time t6. This causes the rotation speed of the motor 30 to increase. Next, at time t7, the rotation speed of the motor 30 reaches the rated rotation speed r1, the operation is switched to loaded operation, and the discharge pressure gradually increases. The acceleration that determines the rate of increase in the rotation speed at this time is updated as appropriate according to the flowchart shown in Figure 2. In the illustrated example, the acceleration at the end of the previous startup operation (i.e., the acceleration a1 at time t2) is set as the initial value, and this acceleration is maintained without change from time t6 to t7. In this way, the startup operation is performed from time t6 to t7.

[0067] At time t8, the discharge pressure reaches the target pressure P2, and from time t8 onwards, load operation is carried out, with the rotation speed being controlled so as to maintain the discharge pressure at P2. The acceleration or deceleration rate relating to the increase or decrease in the rotation speed at this time is updated as appropriate in accordance with the flowchart shown in Figure 3. In this way, load operation is carried out from time t8 onwards.

[0068] The compressor 1 of this embodiment provides the following advantages.

[0069] The load level of the inverter 40 can be determined by the load level determination unit 51, and the acceleration or deceleration of the motor 30 can be suitably adjusted by the rotation speed adjustment unit 52 in accordance with the load level. That is, feedback control can be performed in accordance with the load level of the inverter 40, and the acceleration or deceleration can be suitably changed not only during startup operation but also during load operation. In this way, the compressor can be operated in a manner suitable for the load level of the inverter 40.

[0070] In addition, the load level can be easily determined based on either the output current, the control axis deviation, or the torque. Furthermore, the load level can be evaluated in three stages for one state value, simplifying control.

[0071] Furthermore, when the load on the inverter 40 is high (i.e., when the tolerance is small), setting the acceleration or deceleration of the motor 30 low prevents the compressor from operating beyond the tolerance and avoids breakdown. When the load on the inverter 40 is low (i.e., when the tolerance is large), setting the acceleration or deceleration of the motor 30 high shortens the startup operation time (the time from startup to load operation) and improves the ability to follow the target pressure during load operation. When the load on the inverter 40 is medium (i.e., when the tolerance is medium), setting the acceleration or deceleration of the motor 30 to a medium level allows stable operation to continue. Here, high, low, and medium acceleration or deceleration indicate relative relationships and do not indicate absolute specific values.

[0072] Furthermore, by using the previously set value as the initial value of the acceleration of the motor 30 during startup operation, a reliable value can be used as the acceleration of the motor 30.

[0073] Furthermore, by using the previously set value as the initial value of the acceleration or deceleration of the motor 30 during load operation, a reliable value can be used as the acceleration or deceleration of the motor.

[0074] (Second embodiment) 5 and 6, the flowchart showing the control method for the compressor 1 of the second embodiment differs from the first embodiment in that multiple state values ​​of the inverter 40 are taken into consideration. Other than this, the second embodiment is substantially the same as the first embodiment. Therefore, the description of the parts shown in the first embodiment may be omitted.

[0075] In this embodiment, the state values ​​of the inverter 40 include at least two of the output current, the control axis deviation, and the torque. In the following, as an example, the state values ​​of the inverter 40 will be described as including all of the output current, the control axis deviation, and the torque.

[0076] The load level determination unit 51 determines that the load level is high when at least one of the state values ​​is greater than a predetermined upper threshold, determines that the load level is low when all of the state values ​​are equal to or less than a predetermined lower threshold, and determines that the load level is medium when at least one of the state values ​​is greater than the lower threshold and all of the state values ​​are equal to or less than the upper threshold. Here, the upper threshold and the lower threshold can be suitably set based on the specifications of the motor 30 or the inverter 40.

[0077] Hereinafter, the control during startup operation will be described with reference to FIG. 5, and the control during load operation will be described with reference to FIG.

[0078] 5, when the startup operation is started (step S5-1), the rotation speed adjustment unit 52 sets the acceleration of the motor 30 to an initial value during the startup operation of the compressor main body 20 (step S5-2), and then starts adjusting the acceleration of the motor 30 (step S5-3 and subsequent steps). This initial value is the acceleration that was set at the end of the previous load operation.

[0079] In this embodiment, similarly to the first embodiment, three types of values ​​a1, a2, and a3 can be set as the acceleration of the motor 30. The accelerations a1, a2, and a3 have increasing values ​​in this order (a1>a2>a3), and the values ​​of a1, a2, and a3 are suitably set according to the types of the motor 30 and the inverter 40.

[0080] Once the acceleration of the motor 30 is set to the initial value (e.g., a2) (step S5-2), it is then determined whether all state values ​​are equal to or less than the lower limit threshold (step S5-3). That is, it is determined whether the load level is low.

[0081] If all state values ​​are below the lower threshold (Y: step S5-3), the load level is determined to be low, and a determination is made as to whether a predetermined waiting time Tx or more has elapsed since the last acceleration change (step S5-4). If the predetermined waiting time Tx or more has not elapsed (N: step S5-4), the process returns to determining all state values ​​(step S5-3). If the predetermined waiting time Tx or more has elapsed (Y: step S5-4), the acceleration is set to a1, which is a value greater than a2 (step S5-5).

[0082] If all the state values ​​are not equal to or less than the lower threshold (N: step S5-3), it is determined whether all the state values ​​are equal to or less than the upper threshold (step S5-6). That is, it is determined whether the load level is medium or high. If all the state values ​​are equal to or less than the upper threshold (Y: step S5-6), it is determined that the load level is medium, and it is determined whether a predetermined waiting time Ty or more has elapsed since the last acceleration change (step S5-7). If the predetermined waiting time Ty or more has not elapsed (N: step S5-7), the process returns to determining all the state values ​​(step S5-3). If the predetermined waiting time Ty or more has elapsed (Y: step S5-7), the acceleration is set to a2 (step S5-8).

[0083] If all state values ​​are not equal to or less than the upper threshold (N: step S5-6), the load is determined to be high, and a determination is made as to whether a predetermined waiting time Tz or more has elapsed since the last acceleration change (step S5-9). If the predetermined waiting time Tz or more has not elapsed (N: step S5-9), the process returns to determining all state values ​​(step S5-3). If the predetermined waiting time Tz or more has elapsed (Y: step S5-9), the acceleration is set to a3, which is a value smaller than a2 (step S5-10).

[0084] When the acceleration is set to one of a1, a2, and a3 (steps S5-5, S5-8, and S5-10), it is determined whether the rotation speed of the motor 30 has reached the rated rotation speed (step S5-11). If the rotation speed of the motor 30 has not reached the rated rotation speed (N: step S5-11), the process returns to determining all state values ​​(step S5-3). If the rotation speed of the motor 30 has reached the rated rotation speed (Y: step S5-11), the startup operation is terminated (step S5-12). After the startup operation is terminated, the process transitions to load operation.

[0085] 6, when load operation is started (step S6-1), the rotation speed adjustment unit 52 sets the acceleration or deceleration of the motor 30 to an initial value during load operation of the compressor body 20 (step S6-2), and then starts adjusting the acceleration or deceleration of the motor 30 (step S6-3 and subsequent steps). This initial value is the acceleration or deceleration that was set at the end of the previous load operation.

[0086] In load operation, as in the first embodiment, in addition to the accelerations a1, a2, and a3 of the motor 30, three values ​​b1, b2, and b3 can be set as the deceleration of the motor 30. The decelerations b1, b2, and b3 have increasing values ​​in this order (b1>b2>b3), and the values ​​of b1, b2, and b3 are suitably set depending on the type of motor 30 and inverter 40.

[0087] Once the acceleration or deceleration of the motor 30 is set to the initial value (e.g., a2 or b2) (step S6-2), it is then determined whether all state values ​​are equal to or less than the lower threshold (step S6-3). That is, it is determined whether the load level is low.

[0088] If all state values ​​are below the lower threshold (Y: step S6-3), the load level is determined to be low, and a determination is made as to whether a predetermined waiting time Tx or more has elapsed since the last acceleration change (step S6-4). If the predetermined waiting time Tx or more has not elapsed (N: step S6-4), the process returns to determining all state values ​​(step S6-3). If the predetermined waiting time Tx or more has elapsed (Y: step S6-4), the acceleration is set to a1, which is a value greater than a2, or the deceleration is set to b1, which is a value greater than b2 (step S6-5).

[0089] If all the state values ​​are not equal to or less than the lower threshold (N: step S6-3), it is determined whether all the state values ​​are equal to or less than the upper threshold (step S6-6). That is, it is determined whether the load level is medium or high. If all the state values ​​are equal to or less than the upper threshold (Y: step S6-6), it is determined that the load level is medium, and it is determined whether a predetermined waiting time Ty or more has elapsed since the last change in acceleration or deceleration (step S6-7). If the predetermined waiting time Ty or more has not elapsed (N: step S6-7), the process returns to determining all the state values ​​(step S6-3). If the predetermined waiting time Ty or more has elapsed (Y: step S6-7), the acceleration is set to a2 or the deceleration is set to b2 (step S6-8).

[0090] If all state values ​​are not equal to or less than the upper threshold (N: step S6-6), the load is determined to be high, and a determination is made as to whether a predetermined waiting time Tz or more has elapsed since the last change in acceleration or deceleration (step S6-9). If the predetermined waiting time Tz or more has not elapsed (N: step S6-9), the process returns to the determination of all state values ​​(step S6-3). If the predetermined waiting time Tz or more has elapsed (Y: step S6-9), the acceleration is set to a3, which is a value smaller than a2, or the deceleration is set to b3, which is a value smaller than b2 (step S6-10).

[0091] When the acceleration of the motor 30 is set to a1, a2, or a3, or the deceleration is set to b1, b2, or b3 (steps S6-5, S6-8, and S6-10), it is determined whether or not a stop command to stop operation of the compressor 1 has been issued (step S6-11). If there is no stop command (N: step S6-11), the process returns to determining all state values ​​(step S6-3). If there is a stop command (Y: step S6-11), the load operation is terminated (step S6-12). At this time, the compressor 1 goes through no-load operation and then enters a stopped state.

[0092] According to the compressor 1 of this embodiment, the load level can be determined in a composite manner based on all of the output current, the control axis deviation, and the torque. Furthermore, the load level can be evaluated in three stages for each state value, thereby simplifying control. Here, the upper and lower thresholds can be suitably set based on the specifications of the motor or inverter. Alternatively, the load level may be determined in a composite manner based on only two of the output current, the control axis deviation, and the torque.

[0093] Although specific embodiments of the present invention and their modifications have been described above, the present invention is not limited to the above-described embodiments and can be implemented with various modifications within the scope of the present invention. [Explanation of symbols]

[0094] 1 Compressor 10. Intake adjustment valve 20 Compressor body 21 Piping 22 Intake port 23 Discharge port 24 Piping 30 motor 40 inverter 50 Control device 51 Load level judgment section 52 Rotation speed adjustment unit

Claims

1. A motor; an inverter for controlling the motor; a compressor body driven by the motor and compressing a fluid; a load degree determination unit that determines a load degree of the inverter; a rotation speed adjusting unit that adjusts the acceleration or deceleration of the motor based on the load level determined by the load level determining unit; A compressor comprising:

2. the load degree determination unit determines the load degree based on a state value of the inverter; The compressor according to claim 1 , wherein the state value includes at least one of an output current, a control shaft deviation, and a torque.

3. the state value is one of an output current, a control axis deviation, or a torque; 3. The compressor according to claim 2, wherein the load degree determination unit determines that the load degree is medium when the state value is greater than a predetermined lower threshold and equal to or less than a predetermined upper threshold, determines that the load degree is high when the state value is greater than the upper threshold, and determines that the load degree is low when the state value is equal to or less than the lower threshold.

4. the state values ​​include at least two of an output current, a control axis deviation, and a torque; 3. The compressor according to claim 2, wherein the load degree determination unit determines that the load degree is high when at least one of the state values ​​is greater than a predetermined upper threshold, determines that the load degree is low when all of the state values ​​are equal to or less than a predetermined lower threshold, and determines that the load degree is medium when at least one of the state values ​​is greater than the lower threshold and all of the state values ​​are equal to or less than an upper threshold.

5. 2. The compressor according to claim 1, wherein the rotation speed adjustment unit sets the acceleration or deceleration of the motor to a high value when the load level determination unit determines that the load level is low, sets the acceleration or deceleration of the motor to a low value when the load level determination unit determines that the load level is high, and sets the acceleration or deceleration of the motor to a medium value when the load level determination unit determines that the load level is medium.

6. the rotation speed adjustment unit sets the acceleration of the motor to an initial value at the start-up operation of the compressor body, and then starts adjusting the acceleration of the motor; The compressor according to claim 5 , wherein the initial value is the acceleration that was set at the end of a previous startup operation.

7. the rotation speed adjustment unit sets the acceleration or deceleration of the motor to an initial value when the compressor switches to a load operation, and then starts adjusting the acceleration or deceleration of the motor; The compressor according to claim 5, wherein the initial value is the acceleration or deceleration that was set at the end of the previous load operation.

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