JP2019085974A - Air compressor and control method of air compressor - Google Patents

Abstract

To obtain an air compressor with reduced load torque at start-up.SOLUTION: The air compressor is provided that comprises: a compressor body 2; a motor 6 driving the body 2; and a current supply circuit 21 supplying current to the motor 6. The circuit 21 is switchable between a stationary operation mode in which rated voltage of the power supply is applied to the motor and a start mode in which a voltage lower than the rated voltage is applied to the motor. A compressor 1 further comprises; an intake regulation valve 100 that is switchable between the valve opened state and closed state; and a control device 20 controlling the modes of the circuit 21 and opened and closed state of the valve 100. The control device 20 determines whether the motor 6 has reached the rated number of revolutions, and closes valve 100 and puts the circuit 21 into the start mode during the period from start up to the start of steady operation in which it is determined that the number of revolutions of the motor 6 has reached the rated number of revolutions, and the control device 20 switches the circuit 21 to the steady operation mode and opens the valve 100 in synchronization with this switching during the period after the start of steady operation.SELECTED DRAWING: Figure 1

Description

  The present invention relates to an air compressor.

  At the start of the compressor, especially at low temperatures, the torque of the motor can not reach the load torque necessary to start the compressor, the rotation of the motor stalls, and the motor can not be stably started. Problems can arise. Patent Document 1 discloses that in a compressor provided with a star-delta circuit for supplying current to a motor, the star time is derived based on the temperature of oil lubricating the compressor body.

JP, 2015-78607, A

  However, Patent Document 1 does not disclose means for reducing the load torque required to start the compressor.

  An object of the present invention is to reduce load torque required to start a compressor.

  One aspect of the present invention is a compressor body that compresses and discharges air drawn from a suction port, a motor that drives the compressor body, and a current that receives a supply of power from a power supply and supplies a current to the motor A supply circuit, wherein the current supply circuit is switchable between a steady operation mode for applying a rated voltage of the power supply to the motor and a start mode for applying a voltage lower than the rated voltage to the motor; An intake control valve switchable between an open valve state enabling suction of air from the valve and a closed valve state blocking the suction of air from the suction port; a mode of the current supply circuit; and And a controller for controlling the open / close state, wherein the controller judges whether or not the rotational speed of the motor has reached a rated rotational speed, and starting the supply of current to the motor starts. Electric motor During the period until the steady operation start time when it is determined that the rotational speed has reached the rated rotational speed, the intake adjustment valve is closed and the current supply circuit is put into the start mode, and after the steady operation start time A period of time provides the air compressor which switches the current supply circuit to the steady operation mode and opens the intake control valve synchronously with the switching.

  From the start of supply of current to the motor to the period when the voltage applied to the motor is lower than the rated voltage (starting period) before the number of revolutions of the motor reaches the rated number of revolutions, the intake control valve closes. Be done. That is, during the start-up period, the suction of air from the suction port is shut off, and the air is not supplied to the compressor body. Therefore, during the start-up period, the torque required for the compressor body to compress air is unnecessary, and the load torque required for starting the motor can be reduced. Therefore, the rotation of the motor can be prevented from stalling and the motor can be stably started.

  The air compressor may be oil-cooled, and may further include an oil separation and recovery device that separates and recovers lubricating oil from compressed air discharged from the compressor body. In addition, the control device controls at least one of the temperature of the lubricating oil in the oil separation and recovery device and the temperature of the oil in an oil supply line for supplying the oil in the oil separation and recovery device to the compressor body. The start period may be determined based on the determination, and when the start period has elapsed from the start, it may be determined that the rotational speed of the motor has reached the rated rotational speed.

  Generally, the viscosity of the lubricating oil increases as the temperature of the lubricating oil decreases. Therefore, when the temperature is low, the load torque required to start the motor is large, and the time required for the motor to reach the rated speed is lengthened. When the starter, which is a current supply circuit, is switched to the steady operation mode of applying the rated voltage of the power supply to the motor (for example, contact of a star delta starter) even though the number of revolutions of the motor has not reached the rated speed. When the starter is switched from the star connection to the delta connection, a large current flows in the starter and the motor. As a result, starter failure (e.g., contactor welding) and over-current breakers can cause the supply of current to the motor to cease. By determining the appropriate length of the start-up period based on the temperature of the lubricating oil, it is possible to more reliably switch the current supply circuit to the steady-state operating mode after the rotational speed of the motor reaches the rated rotational speed. Therefore, the rotation of the motor can be prevented from stalling and the motor can be stably started.

  The air compressor further includes a current measuring unit that measures the magnitude of the current supplied to the motor, and the control device measures the current by the current measuring unit after the supply of the current to the motor is started. It may be determined that the number of revolutions of the motor has reached the rated number of revolutions when the magnitude of the determined current falls below a predetermined threshold.

  In starting a motor, generally, immediately after power supply to the motor is started, the largest current flows in the motor. When the acceleration of the motor is completed and the rotational speed of the motor reaches the rated rotational speed, the current flowing through the motor decreases and converges to a substantially constant value. This convergence value can be predicted from the specifications of the motor. Therefore, when the value of the current flowing through the motor falls below the expected convergence value, it can be determined that the rotational speed of the motor has reached the rated rotational speed. By switching the current supply circuit to the steady operation mode when the value of the current flowing through the motor falls below the expected convergence value, the current supply circuit can be operated more reliably after the rotational speed of the motor reaches the rated speed. It is possible to switch to the steady operation mode. Therefore, the stall of the rotation of the motor due to the insufficient acceleration can be prevented, and the motor can be stably started.

  Further, according to another aspect of the present invention, there is provided a compressor body which compresses and discharges air drawn from a suction port, a motor for driving the compressor body, and power supplied from a power supply to supply current to the motor A current supply circuit for supplying a current supply circuit capable of switching between a steady operation mode for applying a rated voltage of the power supply to the motor and a start mode for applying a voltage lower than the rated voltage of the power supply to the motor; An intake control valve switchable between an open valve state enabling suction of air from the suction port and a closed valve state blocking suction of air from the suction port; a mode of the current supply circuit; There is provided a control method of an air compressor including: This method closes the intake adjustment valve, sets the current supply circuit in the start mode, and determines that the current supply circuit operates in the steady state when it is determined that the rotational speed of the motor has reached a rated rotational speed. The mode is switched to the mode, and the intake control valve is opened in synchronization with the switching.

  According to the present invention, it is possible to reduce the load torque required to start the compressor.

BRIEF DESCRIPTION OF THE DRAWINGS The schematic diagram which shows the air compressor concerning 1st Embodiment of this invention. The flowchart which shows the step of starting the electric motor of 1st Embodiment. The schematic diagram which shows the specific example of a current supply circuit. The schematic diagram which shows the other specific example of a current supply circuit. The schematic diagram which shows the air compressor concerning 2nd Embodiment of this invention. The flowchart which shows the step of starting the electric motor of 2nd Embodiment. The flowchart which shows the step of starting the electric motor of the modification of 2nd Embodiment. The schematic diagram which shows the air compressor concerning 3rd Embodiment of this invention. The flowchart which shows the step of starting the electric motor of 3rd Embodiment. The flowchart which shows the step of starting the electric motor of the modification of 3rd Embodiment.

First Embodiment
FIG. 1 shows an oil-cooled air compressor 1 according to a first embodiment of the present invention. The air compressor 1 includes an intake control valve 100, a compressor body 2 which is a screw compressor, an electric motor 6, an oil separation and recovery device 8, a current supply circuit 21, an oil temperature sensor 19, and a control device 20. Equipped with

  The compressor body 2 includes a pair of male and female rotors (screw rotors) 3. The rotor 3 is rotationally driven by the motor 6. The compressor body 2 is provided with a suction port 4 for sucking the air in the upstream.

  Furthermore, the compressor body 2 includes the discharge port 5 on the downstream side. The discharge port 5 is connected to the oil separation and recovery device 8 via the discharge flow path 7. The rotor 3 of the compressor body 2 rotationally driven by the motor 6 compresses the air supplied from the suction port 4 and discharges the compressed air to the discharge port 5.

  The compressed air discharged from the discharge port 5 contains a large amount of oil. The compressed air flows into the oil separation and recovery unit 8 through the discharge flow path 7. The oil separation and recovery device 8 includes an oil separation element 9 disposed at the top and an oil tank 10 disposed at the bottom. The oil separation element 9 separates the compressed air containing the oil flowing into the oil separation and recovery unit 8 into a gas and a liquid (compressed air and oil). The oil separated by the oil separation element 9 is temporarily stored in the oil tank 10 disposed below by gravity.

  The compressed air separated from the oil by the oil separation element 9 flows from the outlet of the oil separation and recovery unit 8 to the air flow path 12. Most of the compressed air supplied to the air flow path 12 is supplied to the air flow path 13. A portion of the compressed air supplied to the air flow path 12 is also supplied to the air flow path 14. The air flow path 13 is fluidly connected downstream (not shown), and compressed air is provided downstream to a supply destination (not shown). The air flow path 13 is provided with a pressure holding valve 11 that holds the pressure of the compressed air at a predetermined pressure or higher on the primary side.

  The oil tank 10 at the lower part of the oil separation and recovery unit 8 is connected to the compressor body 2 via the oil supply line 17. The lubricating oil stored in the oil tank 10 of the oil separation and recovery device 8 flows to the compressor body 2 through the oil supply line 17 due to the pressure difference between the inside of the oil separation and recovery device 8 and the inside of the compressor body 2.

  In order to prevent the high temperature lubricating oil from flowing to the compressor body 2, the lubricating oil stored in the oil tank 10 of the oil separation and recovery unit 8 is cooled after passing through an oil cooler (not shown). It may flow to the compressor body 2.

  The intake control valve 100 is disposed on the upstream side of the compressor body 2 and is connected to the suction port 4 of the compressor body 2 through an intake flow passage 18. The intake control valve 100 includes a suction portion 101 and a cylinder portion 102 formed above the suction portion 101.

  In the illustrated example, the suction portion 101 has an L-shaped suction casing 103. The suction casing 103 is provided at one end with an air filter (not shown) in contact with the atmosphere, and has an inlet 106 capable of introducing air into the suction space portion 105 in the suction casing 103, and the other end (lower end in FIG. 1) ), The outlet 107 is provided. An intake flow passage 18 connected to the suction port 4 of the compressor body 2 is fluidly connected to the outlet 107.

  The cylinder portion 102 has a cylinder casing 104 formed above the suction casing 103. The cylinder casing 104 may be integrally formed with the suction casing 103.

  A valve seat 109 sealable by a valve body 108 is formed around the outlet 107. The valve body 108 has a plate-like shape extending in a direction perpendicular to the vertical direction. A vertically extending guide rod 110 is provided at the center of the valve body 108. The guide rod 110 extends through the upper end wall of the suction casing 103 into the cylinder casing 104. A piston member 111 is fixed to the upper end of the guide rod 110 in the cylinder casing 104, for example, by screwing.

  The piston member 111 is attached so as to be able to slide the side wall in the cylinder casing 104 up and down. The piston member 111 divides the space in the cylinder casing 104 into a lower space portion 112 below the piston member 111 and an upper space portion 113 above the piston member 111. The lower space 112 and the upper space 113 are not in fluid communication. The lower space portion 112 is connected to the air flow path 15, and the upper space portion 113 is connected to the air flow path 16.

  Under the piston member 111 in the cylinder casing 104, that is, in the lower space portion 112, a coiled spring 114 for winding the guide rod 110 is attached. The coil spring 114 biases the piston member 111 upward.

  The valve body 108 disposed at the lower end of the guide rod 110 can move up and down. Therefore, when the downward force applied to the upper surface of the piston member 111 is larger than the upward force applied to the lower surface of the piston member 111, the guide rod 110 and the valve body 108 move downward together with the piston member 111.

  In the illustrated example, the air compressor 1 further includes a three-way solenoid valve 115. An air flow path 14 for flowing compressed air from the oil separation and recovery device 8, an air flow path 15 connected to the lower space 112 of the cylinder casing 104, and an air flow connected to the upper space 113 of the cylinder casing 104 The passage 16 is connected to three ports of the three-way solenoid valve 115 respectively. The three-way solenoid valve 115 is electrically connected to the controller 20. The control device 20 controls the three-way solenoid valve 115 to fluidly connect the air flow path 16 and the air flow path 15 with the first state in which the air flow path 16 and the air flow path 14 are fluidly connected. And the second state can be switched.

  In the illustrated example, the suction space portion 105 in the suction casing 103 and the intake flow passage 18 downstream of the intake adjustment valve 100 are fluidly connected via the air flow passage 116. A check valve 117 is attached to the air flow passage 116.

  The operation of opening the intake control valve 100 will be described. The controller 20 puts the three-way solenoid valve 115 in the first state (ie, fluidly connects the air flow passage 16 and the air flow passage 14). Therefore, the compressed air from the oil separation and recovery unit 8 is supplied to the upper space 113, and the pressure in the upper space 113 is increased. As a result, the downward force applied to the upper surface of the piston member 111 is increased. When the downward force is larger than the upward force applied to the lower surface of the piston member 111 mainly due to the biasing force of the coil spring 114, the guide rod 110 and the valve body 108 move downward together with the piston member 111. Do. Therefore, a gap is generated between the valve body 108 and the valve seat 109, and the outlet 107 of the intake control valve 100 is opened. Therefore, the air taken in from the inlet 106 of the intake control valve 100 is supplied to the suction port 4 of the compressor main body 2 through the outlet 107 of the intake control valve 100 and the intake flow path 18.

  Next, the operation of closing the intake control valve 100 will be described. The controller 20 puts the three-way solenoid valve 115 in the second state (that is, fluidly connects the air flow passage 16 and the air flow passage 15). Therefore, air in the upper space 113, which is a high pressure, flows into the lower space 112, and the pressure in the upper space 113 decreases. This reduces the downward force applied to the upper surface of the piston member 111. When the downward force is smaller than the upward force applied to the lower surface of the piston member 111 mainly due to the biasing force of the coil spring 114, the guide rod 110 and the valve body 108 move upward together with the piston member 111 Do. Therefore, the gap between the valve body 108 and the valve seat 109 is closed, and the outlet 107 of the intake control valve 100 is closed.

  As described above, the intake control valve 100 shuts the valve open state that enables the introduction of air from the outlet 107 to the suction port 4 and the introduction of air from the outlet 107 to the suction port 4 by the control device 20. It can be switched to the closed state.

  Electric power is supplied to the motor 6 from a power supply 22 via a current supply circuit (starter) 21. The current supply circuit 21 is connected to the control device 20. The direct start (full voltage start) method, which is one of the general methods for starting a motor, has a problem that a large current flows when the motor is started. In order to prevent this, a starter which is a current supply circuit 21 is provided, and the current supply circuit 21 applies a voltage lower than the rated voltage of the power supply 22 to the motor 6 by the controller 20; The steady operation mode of applying the rated voltage of 22 to the motor 6 can be switched. Further details of the operation of the motor 6 at startup will be described later.

  An oil temperature sensor 19 for measuring the temperature of the lubricating oil stored in the oil tank 10 is attached to the oil separation and recovery unit 8. Alternatively, the oil temperature sensor 19 may be attached to the oil supply line 17 to measure the temperature of the lubricating oil in the oil supply line 17. Alternatively, the oil temperature sensor 19 may be attached to both the oil separation and recovery unit 8 and the oil supply line 17. The oil temperature sensor 19 is connected to the controller 20 so that the controller 20 can obtain the temperature of the lubricating oil measured by the oil temperature sensor 19.

  Next, the operation of the motor 6 will be described with reference to FIG. Since the steady operation of the motor 6 is known, the description thereof is omitted, and the period from the start when supply of current to the motor 6 starts to the start of steady operation when the rotational speed of the motor 6 reaches the rated speed (start period Only the operation (starting operation) of the motor 6 will be described.

  First, at step S101 in FIG. 2, the temperature of the lubricating oil in the oil tank 10 and / or the oil supply line 17 of the oil separation and recovery device 8 is measured by the oil temperature sensor 19.

  In the next step S102, the controller 20 determines the length of the start-up period based on the temperature of the lubricating oil measured in step S101. The length of the start-up period is preset with respect to the temperature of the lubricating oil assumed, and may be selected by the controller 20 corresponding to the temperature of the lubricating oil measured in step S101. Alternatively, the length of the start-up period may be derived by a pre-programmed equation using the temperature of the lubricating oil measured in step S101. Generally, the viscosity of the lubricating oil increases as the temperature of the lubricating oil decreases. Therefore, when the temperature is low, the load torque required to start the motor 6 is large, and the time required for the rotational speed of the motor 6 to reach the rated rotational speed becomes long. When the current supply circuit 21 switches to the steady operation mode in which the rated voltage of the power supply 22 is applied to the motor 6 despite the number of revolutions of the motor 6 not reaching the rated speed, a large current flows in the motor 6 . As a result, a failure of the current supply circuit (starter) 21 and a stop of the current supply to the motor 6 by the overcurrent breaker can occur. Therefore, by determining the appropriate length of the start-up period based on the temperature of the lubricating oil, it is possible to more reliably switch the current supply circuit 21 to the steady operation mode after the rotation speed of the motor 6 reaches the rated rotation speed. it can. Thus, in general, the length of the start-up period is set to increase as the temperature of the lubricating oil decreases.

  In step S103, the control device 20 closes the intake control valve 100 (confirms that the valve is closed). As a result, the torque required for the compressor body 2 to compress air becomes unnecessary, and the load torque required for starting the motor 6 can be reduced. Here, step S103 has been described as being performed after steps S101 and S102, but step S103 may be performed before step S101.

  Next, in step S104, the control device 20 places the current supply circuit 21 in the start mode. Then, current is supplied to the motor 6.

  In step S105, the control device 20 determines whether or not the starting period determined in step S102 has passed after step S104 is completed. If the start-up period has elapsed, the process proceeds to step S106. In addition, when a start-up period passes, it means that it was judged that the rotation speed of the electric motor 6 reached the rated rotation speed.

  In step S106, the control device 20 switches the current supply circuit 21 to the steady operation mode.

  In step S107, the intake air adjustment valve 100 is switched to the open state in synchronization with the switching of the current supply circuit 21 to the steady operation mode in step S6. Here, “synchronization” includes performing switching of the current supply circuit 21 and switching of the intake adjustment valve 100 simultaneously, but the present invention is not limited to this, and both switching operations may be performed slightly before and after. . That is, the switching of the intake control valve 100 to the open state may be performed some time after the switching of the current supply circuit 21 to the steady operation mode, and vice versa. Therefore, step S107 may be performed immediately before step S106.

  Next, specific examples of the current supply circuit 21 are shown in FIG. 3 and FIG. The current supply circuit 21 of FIG. 3 is an example of a star-delta circuit which is a starter. In order to make the connection between the current supply circuit 21 and the motor 6 clearer, FIG. 3 also shows the motor 6. A power supply 22 (see FIG. 1), which is a three-phase AC power supply, is connected upstream of the current supply circuit 21 of FIG. The control device 20 can control the contactors 31, 32 and 33 such as magnetic contactors to switch between star connection and delta connection of the star-delta circuit. The star-connected current supply circuit 21 corresponds to the start mode of the current supply circuit 21 described above, and the delta-connected current supply circuit 21 corresponds to the steady operation mode of the current supply circuit 21 described above. Thus, a known star delta start system can be applied to the motor 6 according to the first embodiment of the present invention.

  The current supply circuit 21 of FIG. 4 corresponds to a known reactor start method. In order to make the connection between the current supply circuit 21 and the motor 6 clearer, FIG. 4 also shows the motor 6. A power supply 22 (see FIG. 1) which is a three-phase alternating current power supply is connected upstream of the current supply circuit 21 of FIG. At the start of the motor 6, the controller 20 closes the contactor 41 and opens the contactor 42 to place the current supply circuit 21 in the start mode. By inserting the reactor between the power supply 22 and the motor 6 in this manner, a voltage drop due to the reactor occurs, and the starting current flowing to the motor 6 can be reduced. In the steady operation mode, the controller 20 closes the contactor 42 and shorts the reactor. Therefore, the rated voltage of the power supply 22 is supplied to the motor 6. Thus, a well-known reactor start system can be applied to the motor 6 of the first embodiment of the present invention.

  Although not shown, the current supply circuit 21 may have a conduffer configuration in which a three-phase autotransformer is inserted between the power supply 22 and the motor 6 when the motor 6 is started. Thus, a known condor starting system can be applied to the motor 6 of the first embodiment of the present invention.

  As described above, in the first embodiment of the present invention, by closing the intake control valve 100 at the start of the motor 6, the torque required for the compressor body 2 to compress air is unnecessary. Become. Therefore, the load torque required to start the motor 6 can be reduced, and the rotational speed of the motor 6 can be more reliably rated at the start time determined using the temperature of the lubricating oil. Therefore, the rotation of the motor 6 can be prevented from stalling after switching to the steady operation mode, and the motor 6 can be stably started.

Second Embodiment
FIG. 5 shows an air compressor 1 according to a second embodiment of the present invention. In FIG. 5, the same reference numerals as in FIG. 1 indicate the same or corresponding portions. Further, in the following description, in principle, parts different from the first embodiment will be described, and description of the other parts will be omitted.

  The wire between the current supply circuit 21 and the motor 6 is connected to a current sensor 23 which is a current measuring unit that measures the value of the current supplied to the motor 6. The current sensor 23 is connected to the controller 20, so that the controller 20 can obtain the current value measured by the current sensor 23. As described above, in the second embodiment of the present invention, the controller 20 obtains the value of the current supplied to the motor 6 instead of the temperature of the lubricating oil of the first embodiment of the present invention.

  Next, the start operation of the motor 6 will be described with reference to FIG. First, in step S201 of FIG. 6, the control device 20 closes the intake control valve 100 (confirms that the valve is closed).

  Next, in step S202, the control device 20 places the current supply circuit 21 in the start mode. Then, current is supplied to the motor 6.

  In step S203, control device 20 determines whether or not the current value measured by current sensor 23 is less than or equal to a predetermined value. In starting of the motor 6, generally, the largest current flows in the motor 6 immediately after power supply to the motor 6 is started. When the acceleration of the motor 6 is completed and the rotational speed of the motor 6 reaches the rated rotational speed, the current flowing through the motor 6 becomes smaller and converges to a substantially constant value. This convergence value can be predicted from the specifications of the motor 6. Therefore, when the value of the current flowing through the motor 6 becomes smaller than the expected convergence value, it can be determined that the rotational speed of the motor 6 has reached the rated rotational speed. If the current value measured by the current sensor 23 is less than or equal to a predetermined value, the process proceeds to step S204.

  In step S204, the control device 20 switches the current supply circuit 21 to the steady operation mode.

  In step S205, the intake air adjustment valve 100 is switched to the open state in synchronization with the switching of the current supply circuit 21 to the steady operation mode in step S204. As in the case of the first embodiment of the present invention, step S205 may be performed immediately before step S204.

  The air compressor 1 according to the second embodiment of the present invention is not limited to the oil-cooled air compressor 1 but also includes an oil-free air compressor 1.

  As described above, in the second embodiment of the present invention, the load adjustment torque required to start the motor 6 can be reduced by closing the intake control valve 100 when the motor 6 is started. Furthermore, in the second embodiment of the present invention, it is determined whether or not the rotational speed of the motor 6 has reached the rated rotational speed by measuring the current flowing through the motor 6, so that the rotation of the motor 6 stalls more reliably. Can be prevented and the motor 6 can be stably started.

  Next, a modification of the second embodiment of the present invention will be described. In the modification of the second embodiment of the present invention, the control device 20 acquires the number of rotations of the motor 6 measured by the number-of-rotations measuring unit (not shown).

  FIG. 7 is a flowchart showing the starting operation of the motor 6 according to a modification of the second embodiment of the present invention. In step S303 of the modification of the second embodiment of the present invention, the control device 20 determines whether the rotational speed of the motor 6 measured by the rotational speed measuring means is a rated rotational speed. Steps S301, S302, S304 and S305 other than step S303 of the modification of the second embodiment of the present invention are the same as the steps of the second embodiment of the present invention.

  As described above, in the modification of the second embodiment of the present invention, it can be determined more reliably whether the rotational speed of the motor 6 has reached the rated rotational speed. Therefore, the rotation of the motor 6 can be more reliably prevented from stalling, and the motor 6 can be stably started.

Third Embodiment
FIG. 8 shows an air compressor 1 according to a third embodiment of the present invention. In FIG. 8, the same reference numerals as in FIGS. 1 and 5 indicate the same or corresponding portions. Further, in the following description, in principle, portions different from the first embodiment and portions different from the second embodiment will be described, and description of the other portions will be omitted.

  In the third embodiment of the present invention, the air compressor 1 includes both the oil temperature sensor 19 and the current sensor 23. The oil temperature sensor 19 and the current sensor 23 are connected to the controller 20, and thus the controller 20 obtains the temperature of the lubricating oil measured by the oil temperature sensor 19 and the current value measured by the current sensor 23 can do.

  Next, the start operation of the motor 6 will be described with reference to FIG. First, at step S401 in FIG. 9, the temperature of the lubricating oil in the oil tank 10 and / or the oil supply line 17 of the oil separation and recovery device 8 is measured by the oil temperature sensor 19.

  In the next step S402, the controller 20 determines the length of the start-up period based on the temperature of the lubricating oil measured in step S401.

  In step S403, the control device 20 closes the intake control valve 100 (confirms that the valve is closed). Step S403 may be performed before step S401.

  Next, in step S404, the control device 20 places the current supply circuit 21 in the start mode. Then, current is supplied to the motor 6.

  In step S405, the control device 20 determines whether or not the starting period determined in step S402 has passed after step S404 is completed. If the start-up period has not elapsed, the process proceeds to step S406. If the start-up period has elapsed, the process proceeds to step S407.

  In step S406, control device 20 determines whether the current value measured by current sensor 23 is less than or equal to a predetermined value. If the current value measured by the current sensor 23 is less than or equal to a predetermined value, the process proceeds to step S407. If the current value is not less than the predetermined value, the process returns to step S405.

  In step S407, the control device 20 switches the current supply circuit 21 to the steady operation mode.

  In step S408, the intake air adjustment valve 100 is switched to the open state in synchronization with the switching of the current supply circuit 21 to the steady operation mode in step S6. As in the case of the first and second embodiments of the present invention, step S408 may be performed immediately before step S407.

  Next, a modification of the third embodiment of the present invention will be described. In the modification of the third embodiment of the present invention, the control device 20 acquires the number of rotations of the motor 6 measured by the number-of-rotations measuring unit (not shown).

  FIG. 10 is a flowchart showing the starting operation of the motor 6 according to the modification of the third embodiment of the present invention. In step S506 of the modification of the third embodiment of the present invention, the control device 20 determines whether the rotational speed of the motor 6 measured by the rotational speed measuring means is a rated rotational speed. Steps S501 to S505, S507 and S508 other than step S506 in the modification of the third embodiment of the present invention are the same as the steps of the third embodiment of the present invention.

Reference Signs List 1 air compressor 2 compressor body 3 rotor 4 suction port 5 discharge port 6 motor 7 discharge flow path 8 oil separation and recovery unit 9 oil separation element 10 oil tank 11 pressure storage valve 12 to 16 air flow path 17 oil supply line 18 intake air flow path 19 oil temperature sensor 20 control device 21 current supply circuit 22 power supply 23 current sensor (current measurement unit)
31 to 33 contactors 41 and 42 contactors 100 intake control valve 101 suction portion 102 cylinder portion 103 suction casing 104 cylinder casing 105 suction space portion 106 inlet 107 outlet 108 valve body 109 valve seat 110 guide rod 111 piston member 112 lower space Part 113 Upper space part 114 Coil spring 115 Three-way solenoid valve 116 Air flow path 117 Check valve

Claims (4)

A compressor body that compresses and discharges the air drawn from the suction port;
An electric motor for driving the compressor body;
A current supply circuit that receives power from a power supply and supplies current to the motor, and applies a steady operation mode for applying a rated voltage of the power supply to the motor and a voltage lower than the rated voltage to the motor The current supply circuit switchable to a start mode;
An intake control valve switchable between an open valve state enabling suction of air from the suction port and a closed valve state blocking injection of air from the suction port;
A control device that controls the mode of the current supply circuit and the open / close state of the intake adjustment valve;
The controller is
It is determined whether or not the number of revolutions of the motor has reached the rated number of revolutions,
During a period from start of supply of current to the motor to start of steady-state operation where it is determined that the rotational speed of the motor has reached the rated rotational speed, the intake control valve is closed, Placing the current supply circuit in the start mode;
An air compressor, wherein the current supply circuit is switched to the steady operation mode during a period after the start of the steady operation, and the intake control valve is opened in synchronization with the switching. The air compressor is an oil-cooled air compressor, and further includes an oil separation and recovery device that separates and recovers lubricating oil from the compressed air discharged from the compressor body,
The control device is based on at least one of a temperature of lubricating oil in the oil separation and recovery device, and a temperature of oil in an oil supply line for supplying the oil in the oil separation and recovery device to the compressor body. The air compressor according to claim 1, wherein a start-up period is determined, and it is determined that the rotational speed of the motor has reached the rated rotational speed when the start-up period has elapsed from the start-up time. The air compressor further includes a current measurement unit that measures the magnitude of the current supplied to the motor,
The control device is configured such that, after the supply of current to the motor is started, when the magnitude of the current measured by the current measuring unit becomes equal to or less than a predetermined threshold, the number of revolutions of the motor is the The air compressor according to claim 1, wherein it is determined that the rated rotational speed has been reached. A compressor body that compresses and discharges the air drawn from the suction port;
An electric motor for driving the compressor body;
A current supply circuit for receiving current from the power supply to supply current to the motor, the steady operation mode for applying a rated voltage of the power supply to the motor, and a voltage lower than the rated voltage of the power supply for the motor A current supply circuit switchable to a start mode to apply;
An intake control valve switchable between an open valve state enabling suction of air from the suction port and a closed valve state blocking injection of air from the suction port;
A control method of an air compressor, comprising: a control device for controlling the mode of the current supply circuit and the open / close state of the intake control valve.
Closing the intake control valve to put the current supply circuit in the start mode;
When it is determined that the rotational speed of the motor has reached a rated rotational speed, the current supply circuit is switched to the steady operation mode, and the intake air adjustment valve is opened in synchronization with the switching.

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