Compressor and method for monitoring compressor

Abstract

This compressor is provided with: a compressor body (1) that is housed in a housing (4); an electric motor (2) that drives the compressor body (1); an electromagnetic switch (6) that opens and closes an electric path that supplies current to the electric motor (2); a temperature sensor (9) provided in the housing (4); and a control device (7) that counts the opening / closing of the electromagnetic switch (6), stores the cumulative number of openings / closings, and controls the electromagnetic switch (6). The control device (7) corrects the counted number of openings / closings of the electromagnetic switch (6) according to the temperature detected by the temperature sensor (9), and outputs a signal to the outside when the cumulative number of openings / closings exceeds a threshold value.

Description

Compressor and compressor monitoring method

[0001] The present invention relates to a compressor and a method for monitoring a compressor.

[0002] For example, when the contacts of an electromagnetic switch are cut to turn off an electric motor, the electricity that was flowing until then continues to flow, causing sparks and wearing out the contacts. This phenomenon is more pronounced the larger the current, and shortens the life of the electromagnetic switch.

[0003] To address this phenomenon, Patent Document 1 discloses a load control device that records the number of openings and closings with a correction such that the higher the current (main circuit current) when the contacts of the electromagnetic switch (electromagnetic contactor) are disconnected, the larger the added value of the number of openings and closings, thereby making it possible to accurately grasp the remaining lifespan of the electromagnetic switch.

[0004] Japanese Patent Application Publication No. 6-78438

[0005] However, in the electromagnetic switches of compressors, the current that flows temporarily when the contacts are connected (inrush current) is often larger than the current that flows when the contacts are disconnected (breaking current), and the magnitude of the inrush current has a large impact on the remaining life.

[0006] Furthermore, in Patent Document 1, the electromagnetic switch is normally closed, and the temperature of the contacts rises due to continuous operation. It is believed that the arc discharge that occurs when the switch is interrupted attacks the heated contacts, causing contact wear and shortening the lifespan. However, in a compressor, because of the intermittent operation control that keeps the tank pressure within a specified range, the compressor is frequently turned on and off in a short period of time. Therefore, the temperature of the contacts is unlikely to rise due to the rated current, and the lifespan is unlikely to be shortened due to the interrupting current. This is also believed to be the reason why inrush current has a greater impact on the remaining lifespan of a compressor than the interrupting current.

[0007] That is, in a compressor, the inrush current has a greater effect on the remaining life of the electromagnetic switch than the breaking current, and it is difficult to accurately determine the remaining life using the correction based only on the breaking current as in Patent Document 1.

[0008] An object of the present invention is to provide a compressor that allows the remaining life of an electromagnetic switch of the compressor to be accurately determined.

[0009] In order to achieve the above object, the present invention comprises a compressor main body housed in a housing, an electric motor that drives the compressor main body, an electromagnetic contactor that opens and closes an electric circuit that supplies current to the electric motor, a temperature sensor provided in the housing, and a control device that counts the opening and closing of the electromagnetic contactor, stores the cumulative number of opening and closing times, and controls the electromagnetic contactor, wherein the control device corrects the count number of opening and closing times of the electromagnetic contactor based on the temperature detected by the temperature sensor, and outputs a signal to the outside when the cumulative number of opening and closing times exceeds a threshold value.

[0010] According to the present invention, the remaining life of the electromagnetic switch of the compressor can be accurately determined, and the accuracy of compressor maintenance management can be improved. Problems, configurations, and effects other than those described above will become clear from the description of the following embodiments.

[0011] 1 is a front view of a compressor according to a first embodiment of the present invention, with a portion of the front panel being see-through; FIG. 2 is a partial cross-sectional view of a compressor main body in a loaded state; FIG. 3 is a partial cross-sectional view of a compressor main body in an unloaded state; FIG. 4 is a control circuit diagram of a compressor according to a first embodiment of the present invention; FIG. 5 is a time chart schematically showing the operation of an electric motor and the pressure in a tank when a control device executes intermittent operation control; FIG. 6 is a time chart schematically showing the operation of an electric motor and the pressure in a tank when a control device executes continuous operation control; FIG. 7 is a diagram showing an example of a flowchart of an electromagnetic switch opening / closing process and an electromagnetic switch life determination process executed by a control device of a first embodiment; FIG. 8 is a diagram showing an example of a flowchart of an electromagnetic switch opening / closing process and an electromagnetic switch life determination process executed by a control device of a second embodiment; FIG. 9 is a table showing an example of an inrush current of an electric motor mounted in a compressor; Fig. 10 is a diagram showing an example of a flowchart of an electromagnetic switch opening / closing process and an electromagnetic switch life determination process executed by a control device of a third embodiment. Fig. 11 is a diagram showing an example of a flowchart of an electromagnetic switch opening / closing process and an electromagnetic switch life determination process executed by a control device of a fourth embodiment. Fig. 12 is a diagram showing an example of a flowchart of an electromagnetic switch opening / closing process and an electromagnetic switch life determination process executed by a control device of a fifth embodiment.

[0012] The configurations and operations of compressors according to first to fifth embodiments of the present invention will be described below with reference to the drawings. In each drawing, the same reference numerals denote the same parts.

[0013] 1 is a front view of a compressor 10 according to a first embodiment of the present invention, with a portion of a front panel being see-through. The compressor 10 according to this embodiment is, for example, a reciprocating air compressor that compresses air by reciprocating a piston.

[0014] As shown in FIG. 1, the compressor 10 includes a compressor main body 1 that sucks in and compresses air, an electric motor 2 that drives the compressor main body 1, a tank 3 that stores the air compressed by the compressor main body 1, a housing 4 that securely houses these devices, an unloader device 5 that reduces the startup load of the compressor main body 1, an electromagnetic switch 6 that opens and closes an electrical circuit that supplies current to the electric motor 2, a control device 7 that controls the compressor 10, and a stop valve 8 that opens and closes a pipe that discharges the compressed air stored in the tank 3 out of the compressor 10.

[0015] The compressor body 1 is housed in a housing 4, and by reciprocating a piston, draws air into a cylinder 11, compresses it, and discharges the compressed air into a tank 3. The compressor body 1 is provided with a cylinder 11 and a cylinder head 12 (see FIGS. 2 and 3).

[0016] The electric motor 2 is, for example, an inductance motor, and is connected to a power source via an electromagnetic switch 6. When the electric motor 2 is driven, a pulley fixed to the output shaft of the electric motor 2 rotates a pulley 13 fixed to the crankshaft of the compressor body 1 via, for example, a V-belt 21, causing the piston to reciprocate.

[0017] The tank 3 is a device for storing compressed air, and provides compressed air to the customer's equipment by leveling out the pulsation of the compressed air discharged from the compressor main body 1. The tank 3 is provided with a pressure sensor (described later) that detects the pressure inside the tank 3. In addition, a drain discharge device 32 that discharges liquid accumulated inside the tank 3 to the outside is provided at the bottom of the tank 3. The volume of the tank 3 can be increased by attaching an external tank.

[0018] The housing 4 is made up of multiple, generally plate-shaped members that cover the compressor 10 from six sides, and has a base 41 , a front panel 42 , a left side panel 43 , a right side panel 44 , a rear panel 45 , and a top panel 46 .

[0019] A mount 47 is fixed to the top of the base 41 via vibration-isolating rubber. The electric motor 2 is fixed to the mount 47 with bolts, and a mounting base 48 is welded to the mount 47. The compressor body 1 is fixed to the top of the mounting base 48 with bolts, and the tank 3 is fixed to the left of the mounting base 48 with bolts.

[0020] In addition, an operation / stop switch 72 and a display 73 of the control device 7, which will be described later, are attached to the front panel 42, a stop valve 8 is attached to the left side panel 43, and a temperature sensor 9 is attached near the air intake 12a (see Figures 2 and 3) on the inside surface of the rear panel 45.

[0021] The unloader device 5 is a device for forcibly opening the suction valve 12c (see FIGS. 2 and 3) to place the compressor body 1 in an unloaded state. The unloader device 5 of this embodiment includes a three-way solenoid valve 51, unloader piping 52, and an unloader piston 53 (see FIGS. 2 and 3). Note that the configuration of the unloader device 5 is not limited to the example shown here, as long as it can open and close the suction valve 12c in response to commands from the control device 7.

[0022] The three-way solenoid valve 51 is a solenoid valve that switches the communication destination of the unloader pipe 52 between the tank 3 and the outside air in response to a command (control signal) output from the control device 7. The unloader pipe 52 is a pipe that connects the three-way solenoid valve 51 and an unloader piston 53. The unloader piston 53 will be described later.

[0023] FIG. 2 is a partial cross-sectional view of the compressor body 1 in a loaded state, and FIG. 3 is a partial cross-sectional view of the compressor body 1 in an unloaded state.

[0024] The compressor body 1 includes a cylindrical cylinder 11 in which a piston reciprocates, and a cylinder head 12 attached to the tip of the cylinder 11 for sucking in air and discharging compressed air.

[0025] The cylinder head 12 is provided with an air intake port 12a for taking in air through a filter and an air discharge port 12b for discharging compressed air, and is equipped with a suction valve 12c, a discharge valve 12d, and an unloader piston 53.

[0026] The intake valve 12c is a valve located between the air intake 12a and the opening of the cylinder 11. When the pressure in the compression chamber 11a drops below the air pressure at the air intake 12a while the piston is descending, the pressure difference causes the valve to open, drawing air into the cylinder 11.

[0027] The discharge valve 12d is a valve provided between the air discharge port 12b and the opening of the cylinder 11. When the pressure in the compression chamber 11a rises above the air pressure at the air discharge port 12b while the piston is rising, the valve opens due to the pressure difference, and the compressed air in the cylinder 11 is discharged from the air discharge port 12b.

[0028] The unloader piston 53 is one of the components constituting the unloader device 5 and forcibly opens the closed suction valve 12c shown in Figure 2 as shown in Figure 3, thereby opening the compression chamber 11a of the compressor body 1 and maintaining an unloaded state. The unloader piston 53 is provided with a pipe connection port to which the unloader pipe 52 is connected and a protrusion 53a that protrudes due to compressed air flowing in from the pipe connection port, thereby opening the suction valve 12c. The unloader piston 53 configured in this manner is fixed to the cylinder head 12 so that the tip of the protrusion 53a contacts the suction valve 12c.

[0029] 4 is a control circuit diagram of the compressor 10 according to this embodiment. As shown in Fig. 4, the control circuit of the compressor 10 includes a pressure sensor 31 that measures the pressure in the tank 3, a three-way electromagnetic valve 51 that switches the communication destination of the unloader pipe 52, an electromagnetic switch 6 that opens and closes an electrical circuit AC1 that supplies current from a power source AC to the motor 2, a temperature sensor 9 that detects an abnormality in the compressor 10, and a control device 7 that controls the three-way electromagnetic valve 51, the electromagnetic switch 6, and the like.

[0030] The pressure sensor 31 is a sensor that detects the pressure inside the tank 3 as described above, and is electrically connected to the control device 7 , and the pressure value inside the tank 3 detected by the pressure sensor 31 is transmitted to the control device 7 .

[0031] As described above, the three-way solenoid valve 51 is a solenoid valve that switches the connection of the unloader pipe 52 (see Figure 1) between the tank 3 and the atmosphere, and operates in response to commands from the control device 7 to which it is electrically connected.

[0032] The electromagnetic switch 6 is a device that opens and closes a circuit by the action of an electromagnet and also breaks the circuit when an overload occurs. It has a contact 61 and a thermal relay 62 and is electrically connected to the electric motor 2 and the control device 7.

[0033] The contact 61 is the part that opens and closes the circuit, and in this embodiment, an A contact (a contact that is open (OFF state) when no current flows through the coil (normally), and closes (ON state) when current flows through the coil) is used, and the circuit is closed and current is supplied to the electric motor 2 by command from the control device 7.

[0034] The thermal relay 62 is a relay that opens and closes contacts using heat generated by current to protect the electric motor 2 from overload. When an excessive current flows through the electric motor 2, the contacts 61 are opened and the circuit is cut off to prevent burning or other damage.

[0035] The temperature sensor 9 is, for example, a sensor attached to the inner surface of the rear panel 45 near the air intake 12a (see FIGS. 2 and 3) inside the housing 4. In this embodiment, the value detected by the temperature sensor 9 is not only used to detect abnormalities in the compressor 10, but also used as a correction means for improving the accuracy of the count of opening and closing of the electromagnetic switch 6, which is counted to determine the remaining life of the electromagnetic switch 6. Note that in this embodiment, the temperature detected by the temperature sensor 9, which is attached to the inner surface of the rear panel 4 near the air intake 12a (see FIGS. 2 and 3) and detects failures in the compressor 10, is used to correct the life of the electromagnetic switch 6. However, a temperature sensor separate from the temperature sensor 9 may be attached to the electromagnetic switch 6 to detect the temperature of the electromagnetic switch 6.

[0036] As described above, the control device 7 is a device that controls the three-way solenoid valve 51, the electromagnetic switch 6, etc. based on the detected values ​​of the pressure sensor 31 and the temperature sensor 9. The control device 7 is provided with a control board 71, an operation / stop switch 72, a display 73, and an electronic circuit 74.

[0037] The control board 71 is a printed circuit board on which an operation / stop switch 72, a display 73, and an electronic circuit 74 are mounted.

[0038] The operation / stop switch 72 is a switch for starting the operation of the compressor 10 when it is stopped, or for stopping the operation of the compressor 10 when it is running.

[0039] The display 73 is a device that displays characters and images based on the electric signal sent from the electronic circuit 74. The display 73 of this embodiment may also display the life of the electromagnetic switch 6.

[0040] The electronic circuit 74 is a component that controls the electrically connected devices, and includes a processing device 75, a memory device 76, electrical components such as resistors, capacitors, and oscillator circuits, and power elements such as transistors and relays. The pressure sensor 31, the three-way solenoid valve 51, the electromagnetic switch 6, and the temperature sensor 9 are electrically connected to the electronic circuit 74.

[0041] The processing device 75 is a processor such as a CPU (Central Processing Unit) mounted on a microcomputer, an FPGA (Field Programmable Gate Array), etc. The processing device 75 processes the detection value sent from the pressure sensor 31 into a command for the electromagnetic switch 6 or the three-way solenoid valve 51. The processing device 75 also counts the opening and closing of the electromagnetic switch 6, corrects the count number of opening and closing of the electromagnetic switch 6 based on the detection value sent from the temperature sensor 9, and sends the corrected count to the storage device 76. When the cumulative number of opening and closing of the electromagnetic switch 6 stored in the storage device 76 exceeds a threshold, the processing device 75 outputs a signal to the outside.

[0042] The storage device 76 stores the control application program for the processing device 75, the number of switching operations related to the life of the electromagnetic switch 6 calculated taking into account inrush current, the cumulative number of switching operations of the electromagnetic switch 6 counted by the processing device 75, and the like. The storage device 76 includes a random access memory (RAM) for processing and storing data, and a read-only memory (ROM) for storing the control application program in advance. The storage device 76 must update and store the cumulative number of switching operations of the electromagnetic switch 6 each time, and must be rewritable and must not lose the cumulative number of switching operations of the electromagnetic switch 6 even if the AC power source is cut off. Therefore, the storage device 76 is preferably a rewritable nonvolatile memory, such as a hard disk drive (HDD) or a solid state drive (SSD).

[0043] Fig. 5 is a time chart that schematically shows the operation of the motor 2 and the pressure in the tank 3 when the control device 7 executes intermittent operation control. Fig. 6 is a time chart that schematically shows the operation of the motor 2 and the pressure in the tank 3 when the control device 7 executes continuous operation control.

[0044] When the control device 7 detects that the pressure value in the tank 3 detected by the pressure sensor 31 during operation of the compressor 10 has reached a predetermined stop pressure Poff, it controls either the electromagnetic switch 6 or the three-way solenoid valve 51. When the control device 7 controls the electromagnetic switch 6, an intermittent operation control method is used, and when the control device 7 controls the three-way solenoid valve 51, a continuous operation control method is used. The intermittent operation control method and the continuous operation control method are described below.

[0045] (Intermittent operation control method) When the control device 7 detects that the pressure value in the tank 3 detected by the pressure sensor 31 during operation of the compressor 10 has reached a predetermined stop pressure Poff, the control device 7 performs an opening control to the electromagnetic switch 6 to separate the contacts 61. This stops the power supply to the motor 2, and as shown in Figure 5, the motor 2 stops, power to the compressor main body 1 is lost, and the operation of compressing air in the compressor main body 1 stops.

[0046] After the compressor main body 1 stops, the compressed air in the tank 3 is consumed by the operation of the customer's equipment connected to the stop valve 8, and eventually the return pressure Pon is reached.

[0047] When the control device 7 detects that the pressure value in the tank 3 detected by the pressure sensor 31 after the motor 2 has stopped has reached the return pressure Pon, it performs a closing control to bring the electromagnetic switch 6 into contact with the contact 61. This resumes the supply of power to the motor 2, and as shown in Figure 5, the motor 2 starts up, power is restored to the compressor main body 1, and the compressor main body 1 resumes compressing the air.

[0048] This method can reduce power consumption by stopping the motor when the pressure inside the tank 3 reaches the stop pressure Poff. However, since the motor 2 is restarted at the return pressure Pon, the electromagnetic switch 6 is frequently opened and closed, which may shorten the life of the electromagnetic switch 6.

[0049] (Continuous operation control method) When the control device 7 detects that the pressure value in the tank 3 detected by the pressure sensor 31 during operation of the compressor 10 has reached a preset stop pressure Poff, it controls the three-way solenoid valve 51 to connect the unloader pipe 52 to the tank 3. As a result, the compressed air in the tank 3 flows into the unloader pipe 52, and the compressed air that has flowed into the unloader pipe 52 causes the protruding portion 53a of the unloader piston 53 to protrude, and the protruding portion 53a presses against the suction valve 12c to forcibly open it (see FIG. 3).

[0050] By opening the suction valve 12c, the compressed air in the compression chamber 11a is released to the outside air through the suction valve 12c and is no longer discharged from the air discharge port 12b to the tank 3, thereby stopping the supply of compressed air from the compressor body 1 to the tank 3. Therefore, as shown in Figure 6, the electric motor 2 continues to operate while remaining ON, and the power of the electric motor 2 does not become zero even though it drops due to unloaded operation.

[0051] In other words, in the continuous operation control method, the control device 7 operates the unloader device 5 to forcibly open the suction valve 12c, stops the supply of compressed air from the compressor main body 1 to the tank 3, operates the compressor in an unloaded state, and operates the electric motor 2 continuously.

[0052] After the supply of compressed air from the compressor main body 1 to the tank 3 is stopped, the air is consumed by the operation of the customer's equipment connected to the stop valve 8, and the return pressure Pon is eventually reached.

[0053] When the control device 7 detects that the pressure value of the tank 3 detected by the pressure sensor 31 after the electric motor 2 has stopped has reached the return pressure Pon, it controls the unloader device 5 to stop forcibly continuing to open the suction valve 12c.

[0054] Specifically, the control device 7 controls the three-way solenoid valve 51 to connect the unloader pipe 52 to the atmosphere. As a result, the compressed air in the unloader pipe 52 is released to the atmosphere, the protruding portion 53a of the unloader piston 53 is retracted, and the suction valve 12c is no longer forcibly opened. As a result, the compressed air in the compression chamber 11a is not released to the outside air through the suction valve 12c, but is discharged from the air discharge port 12b to the tank 3, and the supply of compressed air from the compressor main body 1 to the tank 3 is resumed.

[0055] This continuous operation control method is used to suppress the load on the electromagnetic contactor 6, etc., when the motor 2 is repeatedly stopped and started in a short period of time (for example, when the amount of air discharged from the compressor body 1 is small compared to the amount of air consumed by the customer's equipment, or when the capacity of the tank 3 is small).

[0056] In other words, the continuous operation control method is a method in which no-load operation is performed when the pressure in the tank 3 reaches the stop pressure Poff, and when the pressure reaches the return pressure Pon, operation returns to normal load operation, eliminating the opening and closing control of the electromagnetic switch 6.

[0057] This method consumes a lot of power because the motor 2 is not stopped even when the pressure inside the tank 3 reaches the stop pressure Poff. However, since the electromagnetic switch 6 does not repeatedly open and close, the load on the electromagnetic switch 6 is reduced. Also, since the compressor body 1 is cooled by a pulley fan directly connected to the crankshaft, this method has the advantage of being able to continuously cool the compressor body 1.

[0058] FIG. 7 is a diagram showing an example of a flowchart of the opening and closing process of the electromagnetic switch 6 and the process of determining the life of the electromagnetic switch 6, which are executed by the control device 7 of this embodiment.

[0059] The control device 7 counts the opening and closing of the electromagnetic switch 6, stores the cumulative number of opening and closing times, and controls the electromagnetic switch 6. The control device 7 also corrects the count number of opening and closing times of the electromagnetic switch 6 based on the temperature detected by the temperature sensor 9, and outputs a signal to the outside when the cumulative number of opening and closing times becomes equal to or exceeds the opening and closing number threshold value.

[0060] Specifically, the processing device 75 of the control device 7 executes the processing shown in FIG. 7 based on the program stored in the memory device 76, the ambient temperature Ta of the electromagnetic switch 6 in the housing 4 detected by the temperature sensor 9, and the pressure Pt in the tank 3 detected by the pressure sensor 31.

[0061] First, the flow of FIG. 7 is started by operating the operation button of the operation / stop switch 72 to start operation of the compressor 10, and in step 1, the processing device 75 brings the contacts 61 into contact with each other to close the electromagnetic contactor 6 and start the electric motor 2.

[0062] Next, in step 2, the processing device 75 determines whether the ambient temperature Ta of the electromagnetic switch 6 detected by the temperature sensor 9 exceeds a predetermined temperature (hereinafter referred to as the temperature threshold T1). The temperature threshold T1 is the upper limit of the temperatures detected by the temperature sensor 9 that do not affect the life of the electromagnetic switch 6.

[0063] If the ambient temperature Ta does not exceed the temperature threshold value T1 (NO), in step 3, the processing device 75 counts the detected number of opening and closing of the electromagnetic switch 6 as one, and adds one to the cumulative number of opening and closing times stored in the memory device 76.

[0064] If the ambient temperature Ta exceeds the temperature threshold T1 (YES), in step 4, the processing device 75 adds a value corrected by the difference between the detected temperature (ambient temperature Ta) and the temperature threshold T1 to the number of times the electromagnetic switch 6 is opened and closed, in order to take into account the effect of the ambient temperature Ta on the lifespan of the electromagnetic switch 6. Specifically, for example, (Ta - T1) x 0.05 times is added to the detected number of times the electromagnetic switch 6 is opened and closed, and this is added to the cumulative number of times the electromagnetic switch 6 is opened and closed. Therefore, if the ambient temperature Ta exceeds the temperature threshold T1 (YES), the processing device 75 corrects the number of times the electromagnetic switch 6 is counted to a larger value as the temperature detected by the temperature sensor 9 increases.

[0065] Next, the processing device 75 determines whether the cumulative number of switching operations is equal to or greater than the threshold number of switching operations in step 5. The threshold number of switching operations in this embodiment is the electrical switching endurance number of times at which the electromagnetic switch 6 reaches its electrical lifespan, specifically, the rated electrical switching endurance number of times at which the electromagnetic switch 6 is estimated to reach the end of its electrical lifespan when a rated load is connected to the electromagnetic switch 6.

[0066] If the cumulative number of opening and closing times is equal to or greater than the electrical opening and closing durability number of the electromagnetic switch 6 (YES), the processing device 75 proceeds to step 6, and if the cumulative number of opening and closing times does not exceed the electrical opening and closing durability number of the electromagnetic switch 6 (NO), the processing device 75 skips steps 6 and 7 and proceeds to step 8.

[0067] In step 6, the processing device 75 outputs a signal to the outside to notify the user of the end of the life of the electromagnetic switch 6. The signal to be output to the outside is, for example, a display of the end of the life of the electromagnetic switch 6 on the display 73 provided in the housing 4, or a notification to a remote device via wireless communication. That is, in step 6, the processing device 75 performs at least one of, for example, displaying on the display 73 that the electromagnetic switch 6 has reached the end of its life, and notifying a remote device via wireless communication that the electromagnetic switch 6 has reached the end of its life. Then, after executing step 6, the processing device 75 proceeds to step 7.

[0068] Step 7 is a step for determining whether or not the user has responded to the notification of the end of life of the electromagnetic switch 6 in step 6. If the user has responded and operated the stop button of the operation / stop switch 72 in step 7 (YES), the compressor 10 stops operating and the flow ends. If the user has not responded to the notification of the end of life of the electromagnetic switch 6 (NO), the flow proceeds to step 8.

[0069] If it is determined in step 5 that the cumulative number of opening and closing operations does not exceed the electrical opening and closing durability number of the electromagnetic contactor 6 (NO), or if the user does not respond to the notification of the end of the life of the electromagnetic contactor 6 (NO) in step 7, the processing device 75 controls the intermittent operation of the compressor 10 in steps 8 to 1.

[0070] Specifically, in step 8, the processing device 75 operates the electric motor 2 until the pressure Pt in the tank 3 detected by the pressure sensor 31 reaches the stop pressure Poff. When the pressure Pt reaches or exceeds the stop pressure Poff, the processing device 75 separates the contacts 61 to open the electromagnetic switch 6 and stop the electric motor 2 in step 9, and continues to stop the electric motor 2 in step 10 until the pressure Pt in the tank 3 detected by the pressure sensor 31 reaches the return pressure Pon. When the pressure Pt reaches the return pressure Pon, the processing device 75 returns to step 1, closes the contacts 61 to close the electromagnetic switch 6 and start the electric motor 2.

[0071] The processor 75 then executes steps 1-10 until the user responds in step 7.

[0072] (Effect) In the compressor 10, the electromagnetic contactor 6 generates heat due to the current that flows when the electromagnetic contactor 6 is opened and closed. However, the inrush current that occurs when the electromagnetic contactor 6 is closed (when the motor 2 is turned from OFF to ON) is greater than the interrupting current that occurs when the electromagnetic contactor 6 is opened (when the motor 2 is turned from ON to OFF), and the magnitude of the inrush current is the dominant factor in the heat generation of the electromagnetic contactor 6.

[0073] Furthermore, in the compressor 10, the electric motor 2 is frequently turned on and off, so that the heat generated by the electromagnetic switch 6 due to the inrush current becomes even more pronounced, and the temperature inside the housing is likely to rise.

[0074] Therefore, in the compressor 10 of this embodiment, the effect on the lifespan of the electromagnetic contactor 6 of the temperature detected by the temperature sensor 9 provided inside the housing 4 is calculated by, for example, (Ta-T1) x 0.05 times, which is added to the count of one opening and closing of the electromagnetic contactor 6 and added to the cumulative number of openings and closings, and when this cumulative number of openings and closings reaches the opening and closing number threshold, it is notified that the electromagnetic contactor 6 has reached the end of its lifespan.

[0075] In this way, by estimating the heat generation amount of the electromagnetic contactor 6 due to the ON / OFF of the electric motor 2 from the temperature detected by the temperature sensor 9, and correcting the count number of opening and closing of the electromagnetic contactor 6 based on the detected temperature to manage the cumulative number of openings and closings, it is possible to take into account the shortened lifespan of the electromagnetic contactor 6 due to the inrush current that frequently occurs due to the intermittent operation of the electric motor 2, and therefore the remaining lifespan of the electromagnetic contactor 6 can be accurately grasped.

[0076] That is, according to this embodiment, the remaining life of the electromagnetic switch 6 of the compressor 10 can be accurately determined, and the accuracy of compressor maintenance management can be improved.

[0077] Furthermore, in the compressor 10 of this embodiment, the "temperature sensor 9 provided inside the housing" can be, for example, a temperature sensor 9 provided at the compressed air intake port of a standard compressor 10, so there is no need to provide a new current sensor to detect inrush current. Therefore, many existing compressor 10 configurations can be used, and cost increases can be suppressed.

[0078] Furthermore, since the lifespan of the electromagnetic switch is notified, for example, by a display, unlike an alert warning that warns of replacement after the end of the electromagnetic switch's lifespan, the replacement time can be predicted, as with the replacement of consumables such as filters and oil, and the replacement of the electromagnetic switch 6 can be carried out in a planned manner. Furthermore, the notification of the lifespan of the electromagnetic switch can be sent to a remote device via wireless communication. For example, by notifying the notification of the lifespan of the electromagnetic switch to a mobile device of a maintenance technician or uploading it to the cloud, the maintenance technician can know the lifespan of the compressor and provide services such as suggesting maintenance to users.

[0079] In the above description, the compressor 10 includes the unloading device 5. However, the opening and closing process of the electromagnetic switch 6 and the process of determining the life of the electromagnetic switch 6 in this embodiment can be performed without including the unloading device 5, and the compressor 10 does not necessarily need to include the unloading device 5.

[0080] 8 is a diagram showing an example of a flowchart of an electromagnetic switch opening / closing process and an electromagnetic switch life determination process executed by a compressor control device according to a second embodiment of the present invention. The compressor according to this embodiment differs from the compressor 10 according to the first embodiment in the following points.

[0081] That is, the compressor 10 according to the first embodiment notifies the end of the life of the electromagnetic contactor 6 when the cumulative number of opening and closing operations of the electromagnetic contactor 6, the count of which is corrected based on the temperature detected by the temperature sensor 9, becomes equal to or exceeds the electrical opening and closing durability number of times.

[0082] On the other hand, the compressor according to this embodiment notifies the end of the life of the electromagnetic contactor 6 when the cumulative number of opening and closing times of the electromagnetic contactor 6 counted without correction becomes equal to or greater than the corrected electrical opening and closing durability number obtained by correcting the rated electrical opening and closing durability number of the electromagnetic contactor 6 in accordance with the inrush current of the electric motor 2 and the rated current of the electromagnetic contactor 6 (YES in step 205).

[0083] Specifically, the processing device 75 of this embodiment closes the electromagnetic contactor 6 in step 1, and then, without performing step 2 of the first embodiment (determining whether the ambient temperature Ta exceeds the temperature threshold value T1), counts the detected number of openings and closings of the electromagnetic contactor 6 as one in step 3, and adds one to the cumulative number of openings and closings stored in the memory device 76.

[0084] Next, in step 205, the processing device 75 determines whether the cumulative number of opening and closing operations is equal to or greater than the corrected electrical opening and closing endurance number obtained by correcting the rated electrical opening and closing endurance number of the electromagnetic contactor 6 according to the inrush current of the electric motor 2 and the rated current of the electromagnetic contactor 6. If the cumulative number of opening and closing operations is equal to or greater than the corrected electrical opening and closing endurance number (YES), the processing device 75 proceeds to step 6; if the cumulative number of opening and closing operations is less than the corrected electrical opening and closing endurance number (NO), the processing device 75 proceeds to step 8.

[0085] Here, the corrected electrical switching durability number obtained by correcting the rated electrical switching durability number of the electromagnetic switch 6 will be described with reference to FIGS.

[0086] Fig. 9 is a table showing an example of an inrush current of the electric motor 2 mounted on a compressor. Fig. 10 is a table showing an example of a combination of the rated current and the rated electrical switching durability number of the electromagnetic switch 6 mounted on a compressor. Fig. 11 is a table showing an example of the types of the electric motor 2 and the electromagnetic switch 6 mounted on a compressor, the correction coefficient for the electrical switching durability number of the electromagnetic switch 6, and the corrected electrical switching durability number (a value obtained by multiplying the rated electrical switching durability number by the correction coefficient).

[0087] As shown in Fig. 9, the inrush current varies depending on the output of the electric motor 2 mounted in the compressor and the compressor system (type of compressor). Also, as shown in Fig. 10, there are electromagnetic switches 6 with different combinations of rated current and rated electrical switching durability count, and the electromagnetic switch model in the figure indicates the identifier of that combination.

[0088] As shown in Fig. 9, the inrush current varies depending on the output of the electric motor 2 mounted on the compressor and the compressor system (type of compressor). Note that the amount of current required varies depending on the number of windings and the number of magnetic poles of the electric motor, so the inrush current does not necessarily increase with increasing output. Therefore, even in this embodiment, the output β of the No. 2 electric motor may be greater than the output γ of the No. 3 electric motor. Furthermore, as shown in Fig. 10, the rated current and rated electrical switching durability of the electromagnetic switch 6 mounted on the compressor vary depending on its model.

[0089] On the other hand, the indicator of electrical durability of the electromagnetic switch 6 is defined as closing a current six times the rated current of the contacts 61 and breaking a current one time the rated current of the contacts 61. Therefore, if the inrush current exceeds six times the rated current, it is considered that the electrical switching durability count of the electromagnetic switch 6 will decrease. Therefore, in this embodiment, when the inrush current of the electric motor 2, which is determined based on the type of compressor 10 and the output of the electric motor 2, exceeds six times the rated current of the installed electromagnetic switch 6, the corrected electrical switching durability count used in step 205 is corrected to a value smaller than the electrical switching durability count (e.g., the rated electrical switching durability count).

[0090] Furthermore, the inventors have considered that the reduced life (number of electrical switching durability cycles) L'c of the electromagnetic switch 6 can be calculated by the following formula.

[0091]

[0092] In the above formula 1, Is is the inrush current (A) of the electric motor 2, Ie is the rated current (A) of the electromagnetic switch 6, Lc is the rated electrical switching durability number (times) of the electromagnetic switch 6, and f ＯＮ－ＯＦＦ is the switching frequency of the electromagnetic switch 6 (times / h).

[0093] The lifespan L'c of the electromagnetic switch 6 calculated by the above formula varies depending on the inrush current and rated current, and the inrush current differs depending on the output of the electric motor 2. Furthermore, because the electric motor 2 and the electromagnetic switch 6 installed in a compressor differ depending on the model of the compressor, the lifespan L'c of the electromagnetic switch 6 also differs depending on the model of the compressor. For example, the lifespan L'c of the electromagnetic switch 6 in a small air compressor is 50 to 100% of the rated electrical switching durability number of the electromagnetic switch 6, and in some cases the lifespan may reach half of the rated electrical switching durability number.

[0094] The electrical switching durability of the electromagnetic switch 6 varies depending on conditions such as the load capacity (contact voltage and contact current), type, switching frequency, and ambient temperature. Also, when the contacts are switched, an inrush current several times to several tens of times the steady-state current can occur depending on the type of load. Therefore, the lifespan of the electromagnetic switch 6 varies greatly depending on the inrush current conditions.

[0095] Specifically, in this embodiment, a correction coefficient is calculated from the model and usage of the compressor, and a corrected electrical switching durability count is calculated in advance by multiplying the correction coefficient by the rated electrical switching durability count of the electromagnetic switch, and this corrected electrical switching durability count is stored in the memory device 76 of the control device 7.

[0096] For example, in a compressor (No. 2 in FIG. 11) of compressor type A equipped with an electric motor 2 (No. 2 in FIG. 9) with an output β and an electromagnetic switch 6 (No. 1 in FIG. 10, electromagnetic switch type a) with a rated current of 5 amperes, the inrush current of the electric motor 2 is 45 amperes as shown in FIG. 9, which is 9 times, more than 6 times, the rated current of the electromagnetic switch 6. Therefore, it is thought that the life of the electromagnetic switch of this compressor will be reduced from the rated electrical switching durability of 200,000 times of the electromagnetic switch shown in No. 1 in FIG. 10.

[0097] In this case, the corrected electrical switching durability number is calculated in advance as 140,000 times by multiplying a correction coefficient of 0.7 calculated from the compressor model and usage method by the rated electrical switching durability number of 200,000 times of the electromagnetic switch shown in No. 1 in Fig. 10, and this is stored in the storage device 76 of the control device 7.

[0098] On the other hand, in a compressor of compressor type A equipped with an electric motor 2 (No. 2 in FIG. 9) with an output of β kW and an electromagnetic switch 6 (No. 2 electromagnetic switch type b in FIG. 10) with a rated current of 10 amperes, the inrush current of the electric motor (45 amperes) is 4.5 times, but less than 6 times, the rated current of the electromagnetic switch (10 amperes). Therefore, it is considered that the life of the electromagnetic switch 6 equipped in this compressor will not decrease from the rated electrical switching durability count of 200,000 times of the electromagnetic switch shown in No. 2 in FIG. 10. In this case, the rated electrical switching durability count of the electromagnetic switch (200,000 times) is stored in the storage device 76 as a corrected electrical switching durability count.

[0099] [Effect] The compressor of this embodiment notifies the life of the electromagnetic switch 6 when the cumulative number of switching operations becomes equal to or greater than the corrected electrical switching durability number calculated using the inrush current of the motor, the rated current of the electromagnetic switch, and the rated electrical switching durability number. Therefore, the life of the electromagnetic switch can be accurately known using the inrush current of the motor, the rated current of the electromagnetic switch, and the rated electrical switching durability number, and the accuracy of compressor maintenance management can be improved.

[0100] Furthermore, since the influence of the inrush current on the lifespan of the electromagnetic switch can be reflected without using a high-performance electrical sensor that can detect the value of the inrush current, the remaining lifespan of the electromagnetic switch 6 can be accurately grasped without incurring any cost.

[0101] 12 is a diagram showing an example of a flowchart of an electromagnetic switch opening / closing process and an electromagnetic switch life determination process executed by a compressor control device according to a third embodiment of the present invention. The compressor according to this embodiment differs from the compressor 10 according to the first embodiment in the following points.

[0102] That is, in the compressor 10 according to the first embodiment, the opening and closing count threshold is the rated electrical opening and closing durability count of the magnetic switch 6, and it is determined in step 5 whether the cumulative opening and closing count of the electromagnetic switch 6 is equal to or greater than the rated electrical opening and closing durability count. On the other hand, in the compressor according to the present embodiment, the opening and closing count threshold is a corrected electrical opening and closing durability count obtained by correcting the rated electrical opening and closing durability count of the electromagnetic switch 6 in accordance with the inrush current of the motor 2 and the rated current of the electromagnetic switch 6, and it is determined in step 205 whether the cumulative opening and closing count of the electromagnetic switch 6 is equal to or greater than the corrected electrical opening and closing durability count, as in the second embodiment.

[0103] In addition, in this embodiment, the opening and closing count threshold value is the corrected electrical opening and closing endurance count, and as shown in the second embodiment, the corrected electrical opening and closing endurance count is corrected to a value smaller than the rated electrical opening and closing endurance count (for example, by multiplying the rated electrical opening and closing endurance count by a correction coefficient of 0.7) when the inrush current of the electric motor 2 exceeds six times the rated current of the electromagnetic contactor 6.

[0104] [Effect] In the compressor according to this embodiment, in step 4, as in the first embodiment, the count number of opening and closing of the electromagnetic switch 6 is corrected based on the temperature detected by the temperature sensor 9, and further, in step 205, as in the second embodiment, the accumulated number of opening and closing of the electromagnetic switch 6 is compared with a corrected electrical opening and closing durability number obtained by correcting the electrical opening and closing durability number of the electromagnetic switch 6 based on the inrush current of the electric motor 2 and the rated current of the electromagnetic switch 6.

[0105] Therefore, as in the first embodiment, it is possible to take into consideration the shortening of the life of the electromagnetic switch 6 due to inrush currents that frequently occur with intermittent operation of the electric motor 2. Furthermore, as in the second embodiment, it is possible to accurately determine the life of the electromagnetic switch using the inrush current of the electric motor, the rated current of the electromagnetic switch, and the rated electrical switching durability count, thereby improving the accuracy of compressor maintenance management. Furthermore, since the effect of inrush current can be reflected in the life of the electromagnetic switch without using a high-performance electrical sensor that can detect the value of inrush current, it is possible to more accurately determine the remaining life of the electromagnetic switch 6 without incurring additional costs.

[0106] 13 is a diagram showing an example of a flowchart of the opening and closing process of the electromagnetic switch 6 and the process of determining the number of electrical opening and closing durability of the electromagnetic switch 6, which are executed by the control device 7 of the compressor according to a fourth embodiment of the present invention. The compressor according to this embodiment differs from the compressor 10 according to the first embodiment in the following points.

[0107] That is, in the first embodiment, if in step 5 the cumulative number of opening and closing operations stored in the memory device 76 exceeds the electrical opening and closing durability number of the electromagnetic contactor 6 (YES), in step 6 the processing device 75 notifies the user that the electromagnetic contactor 6 has reached the end of its life by displaying an indication on the display 73, etc., and proceeds to step 7.

[0108] In contrast, in this embodiment, if in step 5 the cumulative number of opening and closing times stored in the memory device 76 exceeds the electrical opening and closing durability number of the electromagnetic contactor 6 (YES), in step 406 the processing device 75 notifies the user that the electromagnetic contactor 6 has reached the end of its life by displaying an indication on the display 73, etc., and performs at least one of control to increase the stop pressure Poff and control to decrease the return pressure Pon, thereby expanding the difference (pressure range) between the stop pressure Poff and the return pressure Pon, and proceeds to step 7.

[0109] The control of the fourth embodiment can be applied to the second embodiment. In this case, step 6, which is executed when it is determined in step 205 of the second embodiment shown in Fig. 8 that the cumulative number of switching operations is equal to or greater than the corrected electrical switching durability number of times (YES), is replaced with step 406.

[0110] (Effect) In this embodiment, if the cumulative number of opening and closing operations stored in the memory device 76 exceeds the electrical opening and closing durability number of the electromagnetic contactor 6 in step 5 (YES), the processing device 75 notifies the user in step 406 by displaying on the display 73 or the like that the electromagnetic contactor 6 has reached the electrical opening and closing durability number of times, and increases the difference between the stop pressure Poff and the return pressure Pon.

[0111] This allows the number of times the electromagnetic contactor 6 is opened and closed to be reduced after the cumulative number of times it is opened and closed stored in the memory device 76 exceeds the number of times it can electrically open and close the electromagnetic contactor 6 until the user responds to the notification and stops operating the compressor.

[0112] For example, in the compressor according to this embodiment, before the number of electrical opening and closing cycles of the electromagnetic switch 6 exceeds the durability number, if the difference between the stop pressure Poff and the return pressure Pon is 0.05 MPa and Tcyc (see FIG. 5) is 1 minute, the number of opening and closing cycles of the electromagnetic switch 6 will be 60 times / h.

[0113] On the other hand, when the cumulative number of switching operations stored in the storage device 76 exceeds the electrical switching durability number of the electromagnetic switch 6, the processing device 75 increases the difference between the stop pressure Poff and the return pressure Pon to, for example, three times, 0.15 MPa, in step 406. In this case, Tcyc becomes 3 minutes and the number of switching operations of the electromagnetic switch 6 becomes 20 times / h, so the number of switching operations of the electromagnetic switch 6 decreases.

[0114] Therefore, in the compressor according to this embodiment, when the cumulative number of opening and closing times of the electromagnetic contactor 6 exceeds the electrical opening and closing durability number, the number of opening and closing times of the electromagnetic contactor 6 is reduced, thereby extending the period from when a notification is received that the electromagnetic contactor 6 has reached the electrical opening and closing durability number until the electromagnetic contactor 6 no longer operates due to its lifespan, and thereby extending the period during which the user can respond to the notification.

[0115] Fifth Embodiment FIG. 14 is a diagram showing an example of a flowchart of the opening and closing process of the electromagnetic switch 6 and the process of determining the life of the electromagnetic switch 6, which are executed by a compressor control device according to a fifth embodiment of the present invention.

[0116] The compressor according to this embodiment differs from the compressor 10 according to the first embodiment in the following points.

[0117] That is, in the first embodiment, if the user does not respond to the notification of the end of life of the electromagnetic switch 6 by the processing device 75 in step 7, the processing device 75 controls the compressor 10 to operate intermittently (steps 8 to 1).

[0118] In contrast, in this embodiment, if the user does not respond to the notification of the end of life of the electromagnetic switch 6 by the processing device 75 in step 7, the processing device 75 controls the compressor 10 to operate continuously (steps 508 to 501).

[0119] Specifically, in step 7, if the user does not respond to the notification of the end of life of the electromagnetic switch 6 by the processing device 75 (NO), the processing device 75 proceeds to step 508.

[0120] Next, in step 508, the processing device 75 operates the electric motor 2 until the pressure Pt in the tank 3 detected by the pressure sensor 31 reaches the stop pressure Poff.

[0121] When the pressure Pt reaches or exceeds the stop pressure Poff, the processing device 75 controls the three-way solenoid valve 51 to connect the unloader pipe 52 to the tank 3 (unload control) in step 509. As a result, compressed air in the tank 3 flows into the unloader pipe 52, and the protruding portion 53a of the unloader piston 53 connected to the unloader pipe 52 protrudes and presses the suction valve 12c, forcing the suction valve 12c to remain open (see FIG. 3). Then, the compressed air in the compression chamber 11a is not discharged from the air discharge port 12b to the tank 3 but is released into the outside air from the air intake port 12a, so that the supply of compressed air to the tank 3 is stopped while the electric motor 2 continues to operate.

[0122] Next, in step 510, the processing device 75 performs unloading control on the three-way solenoid valve 51 until the pressure Pt in the tank 3 detected by the pressure sensor 31 reaches the return pressure Pon. Then, when the pressure Pt reaches the return pressure Pon, the processing device 75 releases the unloading control on the three-way solenoid valve 51 in step 501. Specifically, the processing device 75 controls the three-way solenoid valve 51 to release the communication between the unloader pipe 52 and the tank 3 and to connect the unloader pipe 52 to the atmosphere. As a result, the compressed air in the unloader pipe 52 is released to the atmosphere, the protruding portion 53a of the unloader piston 53 is retracted, the forced opening of the suction valve 12c is released, and the supply of compressed air from the compressor main body 1 to the tank 3 is resumed.

[0123] Then, in step 7, the processing device 75 executes the continuous operation control (steps 508 to 501) until the user responds to the notification by the processing device 75 that the electromagnetic switch 6 has reached the end of its life.

[0124] The control of the fifth embodiment can also be applied to the second embodiment. In this case, if the user does not respond to the notification of the end of life of the electromagnetic switch 6 by the processing device 75 in step 7 of the second embodiment shown in Fig. 8, the compressor is controlled to operate continuously (steps 508 to 501).

[0125] (Effect) In this embodiment, if the user does not respond to the notification of the end of life of the electromagnetic contactor 6 by the processing device 75 and does not terminate the operation of the compressor 10 in step 7 (NO), the processing device 75 controls the electric motor 2 to operate continuously (steps 508 to 501).

[0126] As a result, after the cumulative number of opening and closing times exceeds the electrical opening and closing durability number of the electromagnetic switch 6, opening and closing of the electromagnetic switch 6 can be suppressed until the user responds to the alert. For example, if a compressor that starts and stops once per minute is operated for eight hours, the number of opening and closing times of the electromagnetic switch 6 will be 480. On the other hand, in the compressor of this embodiment, after the cumulative number of opening and closing times of the electromagnetic switch 6 exceeds the electrical opening and closing durability number, the compressor continues to operate until the user responds to the alert, so the number of opening and closing times of the electromagnetic switch 6 will be one when the compressor is stopped.

[0127] Therefore, in the compressor according to this embodiment, once the cumulative number of opening and closing times of the electromagnetic switch 6 reaches or exceeds the electrical opening and closing durability number, continuous operation control is performed to suppress the opening and closing of the electromagnetic switch 6. Therefore, even after the electromagnetic switch 6 reaches the electrical opening and closing durability number, the compressor can be operated without being shut down for a long period of time, and therefore, maintenance of the compressor to replace the electromagnetic switch 6 can be performed at leisure without rushing.

[0128] The present invention is not limited to the above-described embodiments and includes various modifications. For example, the above-described embodiments have been described in detail to clearly explain the present invention, and are not necessarily limited to those including all of the described configurations. Furthermore, it is possible to replace part of the configuration of one embodiment with the configuration of another embodiment, or to add the configuration of another embodiment to the configuration of one embodiment. Furthermore, it is possible to add, delete, or replace part of the configuration of each embodiment with other configurations.

[0129] Furthermore, the above-described configurations, functions, etc. may be partially or entirely implemented in hardware, for example, by designing them as integrated circuits. Furthermore, the above-described configurations, functions, etc. may be implemented in software, with a processing device (microcomputer) interpreting and executing a program that implements each function. Information such as the program, table, and file that implements each function can be stored in a memory, a recording device such as a hard disk or SSD (Solid State Drive), or a recording medium such as an IC card, SD card, or DVD.

[0130] The embodiments of the present invention may be modified as follows. For example, in the above embodiment, the compressor is a reciprocating type. However, this is not limited to this, and for example, the compressor may be a screw type or a scroll type, or may be a booster compressor that receives a primary pressure from an external source and recompresses the air. Furthermore, in the above embodiment, the compressor is an air compressor. However, this is not limited to this, and a compressor for another gas, for example, nitrogen, may be used.

[0131] 1...Compressor body, 11...Cylinder, 12c...Suction valve, 2...Motor, 3...Tank, 31...Pressure sensor, 4...Housing, 45...Rear panel, 5...Unloader device, 51...Three-way electromagnetic valve, 52...Unloader piping, 53...Unloader piston, 6...Electromagnetic switch, 61...Contact point, 7...Control device, 72...On / off switch, 73...Display, 75...Processing device, 76...Storage device, 9...Temperature sensor, 10...Compressor

Claims

1. A compressor comprising: a compressor body housed in a housing; an electric motor for driving the compressor body; an electromagnetic contactor for opening and closing an electric circuit which supplies current to the electric motor; a temperature sensor provided within the housing; and a control device which counts the opening and closing of the electromagnetic contactor, stores a cumulative number of opening and closing times, and controls the electromagnetic contactor, wherein the control device corrects the count number of opening and closing times of the electromagnetic contactor based on the temperature detected by the temperature sensor, and outputs a signal to the outside when the cumulative number of opening and closing times becomes equal to or exceeds an opening and closing number threshold value.

2. A compressor according to claim 1, characterized in that the opening and closing frequency threshold is a frequency indicating the electrical opening and closing durability frequency of the electromagnetic switch.

3. A compressor as claimed in claim 1, characterized in that the opening and closing count threshold is a corrected electrical opening and closing count obtained by correcting the electrical opening and closing count of the electromagnetic contactor in accordance with the inrush current of the motor and the rated current of the electromagnetic contactor.

4. A compressor as claimed in claim 1, characterized in that the opening and closing frequency threshold is corrected to a smaller value when the inrush current of the motor, which is determined based on the type of the compressor and the output of the motor, exceeds six times the rated current of the electromagnetic contactor.

5. A compressor according to claim 1, characterized in that the control device corrects the number of counts of opening and closing of the electromagnetic switch to a larger value as the temperature detected by the temperature sensor increases.

6. A compressor as claimed in claim 1, characterized in that, when the cumulative number of opening and closing cycles becomes equal to or greater than the threshold number of opening and closing cycles, the control device increases the difference between the return pressure and the stop pressure of the compressor.

7. A compressor as claimed in claim 1, characterized in that, when the cumulative number of opening and closing cycles becomes equal to or greater than the threshold number of opening and closing cycles, the control device controls the compressor to operate continuously.

8. A compressor as claimed in claim 1, characterized in that the control device determines whether the temperature detected by the temperature sensor exceeds a temperature threshold, and if the detected temperature exceeds the temperature threshold, corrects the opening and closing count number of the electromagnetic contactor by adding a value corrected based on the difference between the detected temperature and the temperature threshold to the opening and closing count number of the electromagnetic contactor.

9. A compressor according to claim 1, characterized in that the temperature sensor is provided at the intake port of the compressor body and detects the temperature of the gas sucked into the compressor body.

10. A compressor as claimed in claim 1, characterized in that the signal output to the outside is a display of the life of the electromagnetic contactor on a display provided on the housing, or a notification via wireless communication to a remote device that the electromagnetic contactor has reached the end of its life.

11. A method for monitoring a compressor as claimed in claim 1, comprising monitoring whether the cumulative number of switching operations is equal to or greater than a rated electrical switching durability number of operations or a corrected electrical switching durability number of operations.

12. A method for monitoring a compressor according to claim 11, characterized in that the count number added to the cumulative number of opening and closing operations is corrected based on the temperature detected by the temperature sensor.

13. A method for monitoring a compressor as set forth in claim 11, characterized in that the rated electrical switching durability count is corrected in accordance with the inrush current of the motor and the rated current of the electromagnetic switch.

14. A compressor comprising: a compressor body housed in a housing; an electric motor for driving the compressor body; an electromagnetic contactor for opening and closing an electric circuit supplying current to the electric motor; and a control device for counting the opening and closing of the electromagnetic contactor, storing a cumulative number of opening and closing times, and controlling the electromagnetic contactor, wherein the control device outputs a signal to the outside when the cumulative number of opening and closing times reaches or exceeds a corrected electrical opening and closing durability number obtained by correcting the electrical opening and closing durability number of the electromagnetic contactor in accordance with an inrush current of the electric motor and a rated current of the electromagnetic contactor.

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