Compressor and method for controlling a compressor

Abstract

To prevent the freezing of condensate in the compressor at low temperatures. [Solution] The compressor comprises an electric motor, a compressor body having a compressor mechanism driven by the electric motor that discharges compressed air, and a control board that controls the operation of the electric motor. The control board stops the operation of the electric motor when the discharge pressure of the compressor body reaches a predetermined stop pressure, starts the electric motor when the discharge pressure reaches a predetermined return pressure that is lower than the stop pressure, and increases the return pressure when the ambient temperature of the compressor body falls below a predetermined temperature threshold.

Description

Technical Field

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

Background Art

[0002] As conventional compressors, gas compressors that generate compressed air used as a power source in production lines, or as an air source for machine tools, presses, air blowers and the like are well known. There are also package-type gas compressors that achieve space saving by integrating a compressor main body and a motor for driving the same, with a control circuit, an operation panel and the like housed together in a package. Further, some compressors are provided with a temperature detection device that detects the discharge temperature of the compressor main body. In such a conventional compressor, forced warm-up operation is performed to prevent freezing of compressor cooling water when the discharge temperature drops to, for example, 5°C or lower, and control for stopping this forced warm-up operation when the discharge temperature rises to, for example, 7 to 8°C or higher is installed in some cases.

[0003] For example, Patent Document 1 discloses a configuration in which a controller is connected to a motor that drives a compressor main body, the controller is configured to receive a signal from a cold region specification setting switch on an operation panel, and a sensor that detects the discharge temperature of compressed air is connected to the controller. Further, Patent Document 1 discloses a configuration in which when the cold region specification setting switch is ON, the discharge temperature detected by the sensor is input to the controller, and when the discharge temperature is 5°C or lower, the controller operates the motor to perform forced warm-up operation of the compressor main body, and when the discharge temperature reaches 5°C or higher, the controller stops the motor to stop the forced warm-up operation of the compressor main body.

Prior Art Documents

Patent Documents

[0004]

Patent Document 1

Summary of the Invention

Problem to be Solved by the Invention

[0005] However, forcing the system to operate solely for warm-up presents challenges in terms of power consumption. Furthermore, because the system detects the discharge temperature to determine whether to warm up, it can only perform warm-up when the temperature drops below 5°C, and the warm-up may be delayed in response to the temperature drop, potentially causing the coolant to freeze.

[0006] If the ambient temperature around the compressor is low, there is a risk of drain freezing. If the drain freezes, it can cause damage to the tank and dryer where the drain is mainly generated. Even in such cases, it is necessary to protect the compressor and surrounding equipment.

[0007] The present invention aims to provide a compressor and a method for controlling the compressor that suppress the freezing of drain water at low temperatures. [Means for solving the problem]

[0008] A compressor according to one aspect of the present invention comprises an electric motor, a compressor body having a compressor mechanism driven by the electric motor for discharging compressed air, and a control unit for controlling the operation of the electric motor. The control unit stops the operation of the electric motor when the discharge pressure of the compressor body reaches a predetermined stop pressure, starts the electric motor when the discharge pressure reaches a predetermined return pressure that is less than the stop pressure, and increases the return pressure when the ambient temperature of the compressor body falls below a predetermined temperature threshold. A compressor control method according to one aspect of the present invention is a compressor control method comprising a compressor body having an electric motor and a compressor mechanism driven by the electric motor that discharges compressed air, wherein the operation of the electric motor is stopped when the discharge pressure of the compressor body reaches a predetermined stop pressure, the electric motor is started when the discharge pressure reaches a predetermined return pressure that is less than the stop pressure, and the return pressure is increased when the ambient temperature of the compressor body falls below a predetermined temperature threshold. [Effects of the Invention]

[0009] According to the present invention, when the ambient temperature is below a temperature threshold, the recovery pressure is increased, which speeds up the restart of the compressor, and the heat generated by the compressor operation can suppress drain freezing. [Brief explanation of the drawing]

[0010] [Figure 1] This is a perspective view showing the external appearance of a compressor according to Embodiment 1, which is an example of applying the present invention. [Figure 2] This is a perspective view showing the internal configuration of a compressor according to Embodiment 1, which is an example of applying the present invention. [Figure 3] This figure shows the conceptual configuration of a compressor according to Embodiment 1, which is an example of applying the present invention. [Figure 4] This figure shows the functional block of the control board in a compressor according to Embodiment 1, which is an example of applying the present invention. [Figure 5] This flowchart shows the control by the control board in a compressor of Embodiment 1, which is an example of applying the present invention. [Figure 6] This flowchart shows the control by the control board in a compressor of Embodiment 2, which is an example of applying the present invention. [Figure 7] This is a flowchart illustrating the control by the control board in a compressor of Embodiment 3, which is an example of applying the present invention. [Figure 8] This is a flowchart illustrating the control by the control board in a compressor of Embodiment 3, which is an example of applying the present invention. [Modes for carrying out the invention]

[0011] Embodiments of the compressor and compressor control method of the present invention will be described below with reference to the drawings. In the drawings used herein, the same or corresponding components are denoted by the same or similar reference numerals, and repeated descriptions of these components may be omitted.

[0012] In the following Embodiments 1 to 3, a packaged scroll compressor that forms a compression chamber between a fixed scroll and an orbiting scroll and compresses air by orbiting motion is described as an example of the compression system of the compressor main body, but the compressor of the present invention is not limited to the packaged type. Similarly, the compressor is not limited to a scroll compressor, and is applicable to other compressors such as reciprocating compressors, screw compressors, and turbo compressors. The working fluid is also not limited to air, and the present invention is applicable to compressors using other gases such as nitrogen as the working fluid.

[0013] <Embodiment 1> A compressor 100 and a method for controlling the compressor according to Embodiment 1 will be described with reference to Figures 1 to 5.

[0014] First, the overall configuration of the compressor 100 will be described with reference to Figures 1 to 3. Figure 1 is a perspective view showing the external appearance of the compressor 100 in Embodiment 1, Figure 2 is a perspective view showing the internal configuration of the compressor 100 in Embodiment 1, and Figure 3 is a diagram showing the schematic configuration of the entire compressor related to Embodiment 1.

[0015] The compressor 100 shown in Figure 1 and Figure 2 is a single-stage compressor having one compressor main body 103 and one electric motor 104, and the front panel constituting a part of its housing 120 is detachably attached to the housing 120 other than the front panel by a holding mechanism such as screws. Further, an operation unit 117 for a user to operate the compressor 100 is provided on the front side.

[0016] As shown in Figure 3, the compressor 100 includes a housing 120, a filter 102, a compressor main body 103, an electric motor 104, a check valve 105, an aftercooler 106, a tank 107, a dryer 108, a switch 110, a control board 111 (control unit) that controls the operation of the electric motor 104, a pressure sensor 112, a magnet switch 113, a main body temperature sensor 114, an ambient temperature sensor 115, a fan 116, and the like.

[0017] The casing 120 is a case that accommodates each component of the compressor 100. As shown in Figure 2, inside the casing 120, a machine room 121 that accommodates the electric motor 104 and the compressor main body 103, and a control room 122 that accommodates the control board 111, are each partitioned by a panel.

[0018] In the compressor 100, as shown in Figure 3, air 101 supplied from the outside to the inside of the compressor 100 passes through the filter 102 and is supplied to the compressor main body 103.

[0019] The compressor main body 103 includes a compressor mechanism (not shown) that compresses supplied air and discharges the compressed air.

[0020] The electric motor 104 and the compressor main body 103 are connected by a belt, whereby the power of the electric motor 104 is transmitted to the compressor main body 103 to drive the compressor main body 103. The air compressed in the compressor main body 103 passes through the check valve 105 and the aftercooler 106 to be temporarily stored in the tank 107, then passes through the dryer 108 and is supplied to the outside as compressed air 109.

[0021] In the compressor 100, the switch 110 of the operation unit 117 is used to perform an operation of starting and stopping the entire compressor, and the operation of each component of the compressor 100 is controlled by the control board 111.

[0022] Further, the control board 111 issues a command to the magnet switch 113 in accordance with the pressure in the tank 107 detected by the pressure sensor 112, thereby performing intermittent operation control of the compressor main body 103.

[0023] Furthermore, in the compressor 100 of the present embodiment, a main body temperature sensor 114 that measures the side surface temperature of the compressor main body 103 as the temperature of the discharge portion region that discharges compressed air, and an ambient temperature sensor 115 that measures the temperature of air near the intake port 118 as the ambient temperature AT of the compressor 100 are provided.

[0024] Furthermore, the system controls the system to issue an alarm or malfunction alert if the ambient temperature AT of the compressor 100, as measured by the ambient temperature sensor 115, is outside the specified range of the compressor 100. In addition, if the temperature difference between the ambient temperature AT and the temperature of the compressor body 103, as measured by the main unit temperature sensor 114, exceeds a predetermined threshold, the system controls the system to issue an alarm or malfunction alert to prevent failure of the compressor body 103.

[0025] The temperature measured by the main unit temperature sensor 114 is approximately 100°C while the compressor 100 is in operation, as the temperature of the air discharged from the compressor body 103 is approximately 200°C. On the other hand, the temperature measured by the ambient temperature sensor 115 is located near the air intake port 118 of the housing 120, and is therefore the temperature at the location where the compressor 100 operates, for example, around room temperature (for example, within the range of 0°C to 40°C).

[0026] Furthermore, the discharge temperature measured by the main unit temperature sensor 114 is not limited to the side temperature of the compressor body 103, but can also be configured to measure the temperature of the components between the compressor body 103 and immediately before the aftercooler 106, or the temperature of the compressed air itself in that section.

[0027] Similarly, the ambient temperature AT measured by the ambient temperature sensor 115 is not limited to the temperature of the air near the intake port 118. It is also possible to directly measure the temperature outside the housing 120 near the intake port 118, or to measure the ambient temperature inside the housing 120 other than the intake port 118. For example, the ambient temperature inside the housing 120 can be the temperature of the space inside the housing 120 excluding the machine room 121, which is partitioned within the housing 120 and houses the electric motor 104 and the compressor body 103 (for example, the control room 122). In other words, ambient temperature AT includes both the temperature of the space where the compressor 100 is located (in other words, the ambient temperature outside the housing 120) and the ambient temperature inside the housing 120 excluding the machine room 121.

[0028] Furthermore, the ambient temperature AT is not limited to being measured by an ambient temperature sensor 115 provided by the compressor 100. For example, the temperature of the environment (space) in which the compressor 100 is installed may be measured by a temperature sensor outside the compressor 100, and the control board 111 of the compressor 100 may acquire the ambient temperature AT measured from that temperature sensor.

[0029] The fan 116 cools the compressor body 103, dryer 108, etc. by blowing cooling air. The fan 116 is a cooling unit that cools the components of the compressor 100.

[0030] Figure 4 is a functional block diagram of the control board 111 in Embodiment 1.

[0031] As shown in Figure 4, the control board 111 includes, as its functional configuration, a pressure control unit 201, an ambient temperature determination unit 202, a pressure setting determination unit 203, a pressure setting change unit 204, a fan operation determination unit 205, and a storage unit 206.

[0032] The pressure control unit 201 processes the sensor inputs from the pressure sensor 112, the compressor body temperature sensor 114, and the ambient temperature sensor 115, and issues commands to open and close the magnetic switch 113 and to operate the fan 116.

[0033] The pressure control unit 201 executes the operating state flow of the compressor 100 shown in Figure 5, based on the ambient temperature AT and pressure setting determined by the ambient temperature determination unit 202 and the pressure setting determination unit 203, the pressure setting changed by the pressure setting change unit 204 if necessary, and the fan operation determination result of the fan operation determination unit 205.

[0034] Specifically, the pressure control unit 201 of the control board 111 controls the operation of the electric motor 104 based on either the normal operation mode (first operation mode) or the low-pressure shift mode (second operation mode).

[0035] The normal operation mode is a mode in which the compressor 100 is operated until the pressure of the compressed air to be discharged (discharge pressure P) reaches a preset stop pressure (hereinafter, the stop pressure in the normal operation mode will be referred to as "Pmax"). When the discharge pressure P becomes equal to the stop pressure Pmax (P=Pmax), the operation is stopped, and then the operation is resumed when the discharge pressure P becomes equal to the recovery pressure (hereinafter, the recovery pressure in the normal operation mode will be referred to as "Pu") (P=Pu).

[0036] On the other hand, the low-pressure shift mode is similar to the normal operating mode in that it stops operation when the discharge pressure P becomes equal to the stop pressure (hereinafter, the stop pressure in the low-pressure shift mode will be referred to as "P'max") (P=P'max), and resumes operation when the discharge pressure P becomes equal to the return pressure (hereinafter, the return pressure in the low-pressure shift mode will be referred to as "P'u") (Pu=P'u). The difference from the normal operating mode is that when the low-pressure shift mode is selected, the stop pressure P'max and the return pressure P'u are reduced from the normal operating mode by the shift pressure Ps (for example, 0.1 MPa), and each set pressure is reduced (P'max=Pmax-Ps, P'u=Pu-Ps). This makes it possible to save energy without any effort for users who are using the compressor 100 at a higher pressure than necessary.

[0037] The user can freely select between the normal operating mode and the low-voltage shift mode using the operation unit 117, and the result of the user's selection is stored in the memory unit 206 of the control board 111.

[0038] The memory unit 206 stores in advance the values ​​of the stop pressure Pmax (hereinafter also referred to as "normal stop pressure Pmax") and the return pressure Pu (hereinafter also referred to as "normal return pressure Pu") set in the normal operation mode, as well as the value of the shift pressure Ps in the low-pressure shift mode. The memory unit 206 also stores in advance the value of the temperature threshold T, which will be described later. The values ​​of the normal stop pressure Pmax, normal return pressure Pu, shift pressure Ps, and temperature threshold T can be arbitrarily set by the user. Furthermore, as will be described later, the shift pressure Ps is the same for the shift pressure relative to the stop pressure and the shift pressure relative to the return pressure (the shift pressure is common to both the stop pressure and the return pressure), but different values ​​may be set for each.

[0039] Next, the control flow of the compressor 100 in this embodiment will be explained using Figure 5. Figure 5 is a conceptual diagram showing the operation flow of the compressor 100 in Embodiment 1. In Figure 5, the main operating components of each step are the various parts within the control board 111, but hereafter, it will be described as the control board 111. Also, hereafter, the stop pressure P'max and the return pressure P'u in low-pressure shift mode will be referred to as "low-pressure stop pressure P'max" and "low-pressure return pressure P'u," respectively.

[0040] As shown in Figure 5, first, the control board 111 starts the flow (step S301) and starts the operation of the compressor 100 (step S302), and then determines whether the low-pressure shift mode is enabled or not (step S303). If it is determined to be enabled, the process proceeds to step S305. On the other hand, if it is determined to be disabled, the process proceeds to step S304 and the process ends.

[0041] If the low-voltage shift mode is determined to be valid in step S303, the control board 111 transitions to low-voltage shift mode control.

[0042] In low-pressure shift mode control, first, the control board 111 sets the low-pressure stop pressure P'max to a value that is lowered by the shift pressure Ps from the normal stop pressure Pmax (step S305), and sets the low-pressure return pressure P'u to a value that is lowered by the shift pressure Ps from the normal return pressure PuP'u (step S306).

[0043] Next, the control board 111 performs a loop process (step S307) for drain freeze prevention control using the low-pressure stop pressure P'max set in step S305 and the low-pressure return pressure P'u set in step S306. In this specification, "prevention" of drain freeze does not mean completely preventing the occurrence of drain freeze, but also includes suppressing drain freeze (making it less likely to occur or reducing its degree).

[0044] In drain freeze prevention control, the control board 111 first compares the ambient temperature (hereinafter referred to as "ambient temperature AT") with a temperature threshold T (5°C as an example). If the ambient temperature AT is less than or equal to the temperature threshold T, the process proceeds to step S309; ​​otherwise, the process proceeds to step S312.

[0045] If the ambient temperature AT is 5°C or less below the temperature threshold T, the control board 111 sets the ambient temperature drop flag F (step S309). Then, the control board 111 sets the low-pressure stop pressure P'max to return it from the modified value (which is reduced by the shift pressure Ps) back to the normal stop pressure Pmax (step S310), and sets the low-pressure recovery pressure P'u to return it from the modified value back to the normal recovery pressure Pu (step S311). Then, the process proceeds to step S312.

[0046] In step S312, the control board 111 checks for the presence or absence of the ambient temperature drop flag F (step S312). If the ambient temperature drop flag F is set, it performs an ambient temperature check (step S313). If the ambient temperature drop flag F is not present, it proceeds to step S317 and does not perform the ambient temperature check (step S313).

[0047] In ambient temperature determination (step S313), the control board 111 compares the ambient temperature AT with a pre-set deletion threshold Td (10°C as an example) to determine the deletion of the ambient temperature drop flag F. The value of 10°C for the deletion threshold Td is used as an example to prevent chattering caused by changing the settings of the low-pressure stop pressure P'max and low-pressure return pressure P'u based on the comparison of the ambient temperature and the temperature threshold T. Any other value that can effectively prevent chattering may be used.

[0048] If the ambient temperature AT is greater than or equal to the deletion threshold Td, the ambient temperature decrease flag F is deleted (step S314), the low-pressure stop pressure P'max is set to a value that is lower than the normal stop pressure Pmax by the shift pressure Ps (step S315), and the low-pressure return pressure P'u is set to a value that is lower than the normal return pressure Pu by the shift pressure Ps (step S316). Then, the process proceeds to step S317.

[0049] If the ambient temperature AT is less than the deletion threshold Td, steps S314 through S316 are not performed, and the process proceeds to step S317.

[0050] During the processing of the drain freeze prevention control loop (S307), the user may terminate the low-pressure shift mode. In step S317, it is confirmed whether or not the termination of the low-pressure shift mode by the user was accepted during the drain freeze stop control loop processing by checking whether the low-pressure shift mode is invalid.

[0051] If the control board 111 determines in step S317 that the low-pressure shift mode is invalid, it exits the drain freeze prevention control loop processing in S317 and proceeds to step S319. In step S319, the control board 111 sets the low-pressure stop pressure P'max to be returned to the original normal stop pressure Pmax from the modified value (decreased by the shift pressure), and in step S320, it sets the low-pressure return pressure P'u to be returned to the original normal return pressure Pu from the modified value. Then, with the end of the low-pressure shift mode, it proceeds to step S304 and terminates the process.

[0052] If the control board 111 determines in step S317 that the low-pressure shift mode is effective, it proceeds to step S318 to loop the drain freeze prevention control and repeats the process from S307.

[0053] As described above, the control board 111 controls the operation of the electric motor 104.

[0054] In this embodiment, if the ambient temperature AT decreases (when the ambient temperature decrease flag F is generated), the low-pressure recovery pressure P'u is set to return from being reduced by the shift pressure to the normal recovery pressure Pu. Similarly, the stop pressure is set to return from being reduced by the shift pressure to the normal stop pressure Pmax.

[0055] In contrast, when the ambient temperature AT decreases, the control board 111 only needs to increase the low-pressure recovery pressure P'u and the low-pressure stop pressure P'max to at least that level, and it is not essential that they be returned to the normal recovery pressure Pu and normal stop pressure Pmax values, respectively. In other words, when the ambient temperature AT decreases in low-pressure shift mode control, it is desirable to return the low-pressure recovery pressure P'u and the low-pressure stop pressure P'max to the normal recovery pressure Pu and normal stop pressure Pmax, respectively, but it is also acceptable to increase them to approach the normal recovery pressure Pu and normal stop pressure Pmax, respectively. Furthermore, when the ambient temperature AT decreases, it is desirable that the low-pressure recovery pressure P'u and the low-pressure stop pressure P'max do not increase beyond the normal recovery pressure Pu and normal stop pressure Pmax.

[0056] According to the above embodiments, the following effects and advantages are achieved.

[0057] In this embodiment, when the ambient temperature AT is low, the control by the low-pressure shift mode, which is performed for energy saving, is canceled, and the low-pressure stop pressure P'max and the low-pressure return pressure P'u are set to values ​​that have risen to the normal stop pressure Pmax and the normal return pressure Pu, respectively. This delays the timing of stopping the compressor 100 and speeds up the timing of restarting the compressor 100, and prevents drain freezing due to the heat generated by the operation of the compressor 100. Thus, according to this embodiment, the effects of energy saving and drain freezing prevention can be appropriately demonstrated depending on the situation.

[0058] Furthermore, the control in this embodiment delays the timing of stopping the compressor 100 or advances the timing of restarting operation by changing the low-pressure stop pressure P'max and the low-pressure return pressure P'u, and does not forcibly warm up the compressor separately from normal operation. Therefore, power consumption can be suppressed while warming up (preventing drain freezing). Also, drain freezes when the ambient temperature AT decreases, but in low-temperature environments, the discharge temperature of the compressor 100 is usually higher than the ambient temperature AT. Since the control in this embodiment is executed based on the ambient temperature AT, it can warm up earlier than if it were controlled based on the discharge temperature, and the freezing of drain can be prevented even more effectively.

[0059] <Embodiment 2> A compressor 100 and a control method for the compressor 100 according to Embodiment 2 of the present invention will be described.

[0060] This embodiment differs from Embodiment 1 described above in its method for setting the low-pressure stop pressure P'max and the low-pressure return pressure P'u in the drain freeze prevention control.

[0061] Figure 6 is a flowchart showing the control flow of the compressor in Embodiment 2.

[0062] In this embodiment, as shown in Figure 6, the processing after assigning the ambient temperature drop flag F (S309) differs from that of Embodiment 1. The processing of steps S301 to S309 and steps S312 to S320 of the control flow in this embodiment is the same as in Embodiment 1, so a description is omitted.

[0063] If the ambient temperature drop flag F is set in step S309, the control board 111 determines whether the difference between the low-pressure stop pressure P'max and the normal return pressure Pu is below a predetermined difference threshold (for example, 0.1 MPa) (step S401). If the difference is 0.1 MPa or more, the control board 111 sets the low-pressure return pressure P'u to be reduced by the shift pressure Ps and then returned to the original normal return pressure Pu (step S402). If the difference is less than 0.1 MPa, the control board 111 sets the low-pressure return pressure P'u to the value obtained by subtracting 0.1 MPa from the low-pressure stop pressure P'max (step S403).

[0064] When step S402 or step S403 is executed, the process proceeds to step S312. The subsequent processing is the same as in Embodiment 1.

[0065] Thus, in this embodiment, when the ambient temperature AT decreases, only the low-pressure recovery pressure P'u is changed, and the low-pressure stop pressure P'max is not changed. This allows for measures to prevent drain freezing while stabilizing the pressure supplied to the user's equipment. In other words, by changing (setting) the low-pressure recovery pressure P'u to be at least larger than the current set value when the ambient temperature AT decreases, drain freezing can be prevented.

[0066] Furthermore, in this embodiment, the differential threshold can be set considering the components that make up the compressor 100 and other equipment that affects the compressor 100 (for example, equipment that receives compressed air from the compressor). For example, the differential threshold can be set to a value (for example, 0.1 MPa) such that the magnetic switch 113 that switches the operation of the compressor 100 ON and OFF does not switch frequently and the load does not become large.

[0067] This embodiment 2 provides the same effects and advantages as embodiment 1.

[0068] <Embodiment 3> A compressor 100 and a control method for the compressor according to Embodiment 3 of the present invention will be described.

[0069] Figures 7 and 8 are flowcharts showing the control flow of the compressor 100 in Embodiment 2.

[0070] In this embodiment, as shown in Figures 7 and 8, the content of the drain freeze prevention control loop processing differs from that of Embodiment 1. The processing of steps S301 to S304 and steps S317 to S320 of the control flow in this embodiment is the same as in Embodiment 1, so a description is omitted.

[0071] In this embodiment, a first temperature threshold T1, a second temperature threshold T2, and a third temperature threshold T3 are set as temperature thresholds. The set temperatures are set in the order of first temperature threshold T1, second temperature threshold T2, and third temperature threshold T3 (T1>T2>T3). Furthermore, the second temperature threshold T2 corresponds to the "first determination threshold" in the claims, and the third temperature threshold T3 corresponds to the "second determination threshold" in the claims.

[0072] As shown in Figure 7, when the drain freeze prevention control loop processing is executed in step S317, the control board 111 compares the ambient temperature AT with the first temperature threshold T1 (10°C as an example) to determine the ambient temperature. If the ambient temperature AT is greater than the first temperature threshold T1, the process proceeds to step S512. The processing from step S512 onward will be described later.

[0073] If the ambient temperature AT is below the first temperature threshold T1, the control board 111 sets the first ambient temperature drop flag F1 (step S502) and proceeds to step S503.

[0074] In step S503, the ambient temperature AT is compared with a second temperature threshold T2 (for example, 7°C) to determine the ambient temperature. If the ambient temperature AT is greater than the second temperature threshold T2, the control board 111 stops the operation of the fan 116 (step S504) and proceeds to step S512.

[0075] If the ambient temperature AT is less than the second temperature threshold T2, the control board 111 sets the second ambient temperature drop flag F2 (step S505) and proceeds to step S506.

[0076] In step S506, the ambient temperature AT is compared with the third temperature threshold T3 (5°C as an example) to determine the ambient temperature. If the ambient temperature AT is greater than the third temperature threshold T3, the control board 111 sets the low-pressure stop pressure P'max to a value obtained by lowering the normal stop pressure Pmax by half the shift pressure Ps (P'max = Pmax - (Ps / 2)) (step S507), and sets the low-pressure return pressure P'u to a value obtained by lowering the normal return pressure Pu by half the shift pressure Ps (P'u = Pu - (Ps / 2)) (step S508). Once step S508 is completed, the process proceeds to step S512.

[0077] If the ambient temperature AT is below the third temperature threshold T, the control board 111 sets the third ambient temperature drop flag F3 (step S509), sets the low-pressure stop pressure P'max to the normal stop pressure Pmax (step S510), and sets the low-pressure return pressure P'u to the normal return pressure Pu (step S511). Once step S511 is completed, the process proceeds to step S512.

[0078] In step S512, the control board 111 determines whether or not the first ambient temperature drop flag F1 exists. If the first ambient temperature drop flag F1 exists, the control board 111 determines whether or not the second ambient temperature drop flag F2 exists (step S513) (see Figure 8). If the first ambient temperature drop flag F1 does not exist, the process proceeds to step S317, where the control board 111 determines whether or not the low-voltage shift mode is invalid.

[0079] As shown in Figure 8, if the second ambient temperature drop flag F2 is present, the control board 111 determines whether or not the ambient temperature drop flag F3 is present (S517). If the third ambient temperature drop flag F3 is not present, the ambient temperature AT is compared with the first flag deletion threshold Td1 (13°C as an example) to determine the ambient temperature (step S514). The first flag deletion threshold Td1 is the threshold for deleting the first ambient temperature drop flag F1, and is set to a value greater than the first temperature threshold T1 (Td1 > T1).

[0080] If the ambient temperature AT is greater than or equal to the first flag deletion threshold Td1, the control board 111 deletes the first ambient temperature drop flag F1 (step S515) and operates the fan 116 (step S516). If the ambient temperature AT is less than the first flag deletion threshold Td1, steps S515 and S516 are not performed, and the process proceeds to step S317 (see Figure 7).

[0081] If it is determined in step S517 that the third ambient temperature decrease flag F3 exists, the process proceeds to step S522; otherwise, the process proceeds to step S518.

[0082] In step S518, the control board 111 compares the ambient temperature AT with the second flag deletion threshold Td2 (10°C as an example) to determine the ambient temperature. The second flag deletion threshold Td2 is the threshold for deleting the second ambient temperature drop flag F2, and is set to a value greater than the second temperature threshold T2 (Td2 > T2).

[0083] If the ambient temperature AT is greater than or equal to the second flag deletion threshold Td2, the control board 111 deletes the second ambient temperature drop flag F2 (step S519), sets the low-pressure stop pressure P'max to a value lowered by the shift pressure Ps from the normal stop pressure Pmax, and sets the low-pressure return pressure P'u to a value lowered by the shift pressure Ps from the normal return pressure Pu. If the ambient temperature AT is less than the second flag deletion threshold Td2, the process from step S519 to step S521 is skipped, and the process proceeds to step S317 (see Figure 7).

[0084] In step S522, the control board 111 compares the ambient temperature AT with the third flag deletion threshold Td3 (8°C as an example) to determine the ambient temperature. The third flag deletion threshold Td3 is the threshold for deleting the third ambient temperature drop flag F3, and is set to a value greater than the third temperature threshold T3 (Td3 > T3).

[0085] If the ambient temperature AT is greater than or equal to the third flag deletion threshold Td3, the control board 111 deletes the third ambient temperature drop flag F3 (step S523), sets the low-pressure stop pressure P'max to a value obtained by lowering the normal stop pressure Pmax by half the shift pressure Ps (P'max = Pmax - (Ps / 2)) (step S524), and sets the low-pressure return pressure P'u to a value obtained by lowering the normal return pressure Pu by half the shift pressure Ps (P'u = Pu - (Ps / 2)) (step S525). If the ambient temperature AT is not less than the third flag deletion threshold Td3, the process from steps S523 to S525 is skipped, and the process proceeds to step S317 (see Figure 7).

[0086] The process from step S317 onwards, as shown in Figure 7, is the same as in Embodiment 1.

[0087] In this embodiment, the decrease in ambient temperature AT is determined in stages by three temperature thresholds T1, T2, and T3, and the fan 116 is stopped or the settings for the stop pressure and return pressure are changed by a shift amount corresponding to each stage. By stopping the fan 116, the temperature drop inside the compressor body 103 and, consequently, the housing 120 is suppressed, thus providing an effect of preventing drain freezing.

[0088] More specifically, when the ambient temperature AT is less than or equal to the second temperature threshold T2 and greater than the third temperature threshold T3, the low-pressure stop pressure and low-pressure return pressure are set from a value reduced by the shift pressure Ps to a value reduced by half the shift pressure Ps from the normal stop pressure and normal return pressure (shift amount is Ps / 2). When the ambient temperature AT is less than or equal to the third temperature threshold T3, the low-pressure stop pressure and low-pressure return pressure are set to return to the normal stop pressure and normal return pressure from a value reduced by the shift pressure Ps (shift amount is Ps). Here, half the value of the shift pressure Ps corresponds to the "first shift amount" in the claims, and the value of the shift pressure Ps corresponds to the "second shift amount" in the claims.

[0089] In other words, in this embodiment, the freezing of the drain is prevented by performing a process that gradually limits the flow rate based on the ambient temperature AT. According to this embodiment, the energy-saving effect of the low-pressure shift mode can be further enhanced while preventing the freezing of the drain.

[0090] Furthermore, this embodiment provides the same effects and advantages as Embodiment 1.

[0091] The following modifications are also within the scope of the present invention, and it is possible to combine the configurations shown in the modifications with the configurations described in the embodiments described above, or to combine the configurations described in the different embodiments described above, or to combine the configurations described in the following different modifications. Furthermore, it is possible to add, delete, or replace some of the configurations in each embodiment with other configurations.

[0092] <Example 1> If the compressor 100 is equipped with multiple compressor units 103, when the ambient temperature AT decreases, it can be controlled to set the stop pressure and recovery pressure for each unit individually. This allows for energy saving effects in low-pressure shift mode while suppressing the freezing of drain.

[0093] <Modification 2> In each of the above embodiments, drain freeze prevention control is performed during the execution of the low-pressure shift mode, but is not limited thereto. In other words, drain freeze prevention control is not limited to compressors 100 in which the control board 111 is configured to execute the low-pressure shift mode.

[0094] For example, drain freeze prevention control may be performed during normal operation. In this case, when the ambient temperature AT exceeds a predetermined temperature threshold, the effect of preventing drain freeze can be obtained by setting the recovery pressure to a higher pressure (increasing the recovery pressure). In this case, as in the embodiments described above, in addition to increasing the recovery pressure, the freezing of the drain can be further suppressed by setting the stop pressure to a higher pressure (increasing the stop pressure).

[0095] <Variation 3> Furthermore, in the above embodiment 2, when the ambient temperature AT decreases, only the recovery pressure is changed, and the stop pressure is not changed. Alternatively, when the ambient temperature AT decreases, the system may be configured to change only the stop pressure, and not the recovery pressure. By increasing at least one of the recovery pressure and the stop pressure when the ambient temperature AT decreases, the effect of preventing drain freezing can be achieved.

[0096] <Modification 4> In the above embodiment 3, when the first ambient temperature drop flag F1 is set and the second ambient temperature drop flag F2 is not set, the operation of the fan 116 is stopped. In contrast, if the compressor 100 is equipped with a cooling unit other than the fan 116, the operation of the cooling unit may be stopped instead of or in addition to the operation of the fan 116. A cooling unit is a unit that has the function of cooling each component (or the inside of the housing 120) that constitutes the compressor 100, including the housing. For example, if the compressor is equipped with a cooler that has a cooling jacket or Peltier element to cool the compressor body as a cooling unit, the operation of these cooling units may be stopped.

[0097] <Other variations> The embodiments described above are merely illustrative examples to aid in understanding the concept of the present invention and are not intended to limit the scope of the invention. The embodiments may include additions, deletions, or substitutions of various components without departing from the spirit of the invention.

[0098] The various functional units described in each of the above embodiments may be implemented using circuits. The circuits may be dedicated circuits for implementing specific functions, or they may be general-purpose circuits such as processors.

[0099] At least a portion of the processing in each of the above embodiments can also be implemented using a general-purpose computer as the basic hardware. The program that implements the above processing may be provided stored on a computer-readable recording medium. The program is stored on the recording medium as an installable file or an executable file. The recording medium may be a magnetic disk, an optical disk (CD-ROM, CD-R, DVD, etc.), a magneto-optical disk (MO, etc.), or a semiconductor memory. Any recording medium that can store a program and is readable by a computer may be used. Alternatively, the program that implements the above processing may be stored on a computer (server) connected to a network such as the Internet, and downloaded to a computer (client) via the network.

[0100] The configuration, operation, and effects of the embodiment of the present invention configured as described above will be summarized below.

[0101] (1) The compressor 100 comprises an electric motor 104, a compressor body 103 having a compressor mechanism that is driven by the electric motor 104 and discharges compressed air, and a control board 111 that controls the operation of the electric motor 104. The control board 111 stops the operation of the electric motor 104 when the discharge pressure P of the compressor body 103 reaches a predetermined stop pressure, operates the electric motor 104 when the discharge pressure P reaches a predetermined return pressure that is less than the stop pressure, and increases the return pressure when the ambient temperature AT of the compressor body 103 falls below a predetermined temperature threshold.

[0102] Furthermore, in the compressor 100, the control board 111 increases the recovery pressure while not changing the stop pressure when the ambient temperature AT is below the temperature threshold.

[0103] The control method for the compressor 100 involves stopping the operation of the electric motor 104 when the discharge pressure P of the compressor body 103 reaches a predetermined stop pressure, restarting the electric motor 104 when the discharge pressure P reaches a predetermined return pressure that is less than the stop pressure, and increasing the return pressure when the ambient temperature AT of the compressor body 103 falls below a predetermined temperature threshold.

[0104] Furthermore, the compressor control method involves increasing the recovery pressure while maintaining the stop pressure when the ambient temperature is below the temperature threshold.

[0105] With this configuration, when the ambient temperature AT decreases, the timing of restarting the compressor 100 can be accelerated by increasing the recovery pressure. This allows the compressor 100 to warm up and prevents the drain from freezing.

[0106] Furthermore, since it does not involve forced warm-up operation separate from normal operation, it is possible to prevent drain freezing through warm-up while suppressing power consumption. In addition, since the compressor 100 is controlled based on the ambient temperature AT, it can warm up earlier than if it were controlled based on the discharge temperature, further preventing drain freezing.

[0107] (2) In addition, the compressor 100 is configured to execute a low-pressure shift mode that shifts the stop pressure and recovery pressure to a predetermined pressure lower. When the ambient temperature AT of the compressor body 103 falls below a predetermined temperature threshold, the stop pressure and recovery pressure are increased. When the electric motor 104 is being controlled in low-pressure shift mode, if the ambient temperature falls below the temperature threshold, the stop pressure and recovery pressure are increased back to their pre-shift values.

[0108] Furthermore, the compressor control method executes a low-pressure shift mode that shifts the stop pressure and recovery pressure to a predetermined pressure lower. When the ambient temperature AT of the compressor body 103 falls below a predetermined temperature threshold, the stop pressure and recovery pressure are increased. When the electric motor 104 is being controlled in low-pressure shift mode, if the ambient temperature falls below the temperature threshold, the stop pressure and recovery pressure are increased back to their pre-shift values.

[0109] With this configuration, when the ambient temperature AT is low, the low-pressure shift mode control, which is performed for energy saving, is deactivated, and the low-pressure stop pressure P'max and low-pressure return pressure P'u are set to values ​​that have risen to the normal stop pressure Pmax and normal return pressure Pu, respectively. This allows for appropriate energy saving and drain freeze prevention effects depending on the situation.

[0110] (3) In addition, the compressor 100 has a temperature threshold that includes a second temperature threshold T2 and a third temperature threshold T3 which is smaller than the second temperature threshold T2. The control board 111 increases the low-pressure return pressure P'u by half the value of the shift pressure Ps as the first shift amount when the ambient temperature AT is less than or equal to the second temperature threshold T2 and higher than the third temperature threshold T3. When the ambient temperature AT is less than or equal to the third temperature threshold T3, the control board 111 increases the low-pressure return pressure P'u by a value of the shift pressure Ps which is larger than the first shift amount as the second shift amount.

[0111] Furthermore, in the compressor control method, the temperature thresholds include a second temperature threshold T2 and a third temperature threshold T3 which is smaller than the second temperature threshold T2. The control method increases the low-pressure return pressure P'u by half the value of the shift pressure Ps as the first shift amount when the ambient temperature AT is less than or equal to the second temperature threshold T2 and higher than the third temperature threshold T3. When the ambient temperature AT is less than or equal to the third temperature threshold T3, the low-pressure return pressure P'u is increased by a value of the shift pressure Ps which is larger than the first shift amount as the second shift amount.

[0112] In this configuration, drain freezing is prevented by applying a gradual limiting process based on the ambient temperature AT. This allows for even greater energy savings in the low-pressure shift mode while preventing drain freezing.

[0113] (4) The compressor 100 is also equipped with a fan 116 for cooling the components of the compressor 100, and the control board 111 stops the operation of the fan 116 when the ambient temperature AT falls below a temperature threshold.

[0114] Furthermore, in the compressor control method, when the ambient temperature AT falls below a temperature threshold, the operation of the fan 116 is stopped.

[0115] With these configurations, the operation of the fan 116 can be stopped when the ambient temperature drops, thereby preventing the drain from freezing.

[0116] Although embodiments of the present invention have been described above, these embodiments only represent a part of the application examples of the present invention, and are not intended to limit the technical scope of the present invention to the specific configurations of the above embodiments. [Explanation of Symbols]

[0117] 100... Compressor 103... Compressor unit 104...Electric motor 111... Control board (control unit) 116... Fan (cooling unit)

Claims

1. Electric motor and, A compressor body having a compressor mechanism that is driven by the aforementioned electric motor and discharges compressed air, The system includes a control unit that controls the operation of the electric motor, The control unit, When the discharge pressure of the compressor body reaches a predetermined stop pressure, the operation of the electric motor is stopped. When the discharge pressure reaches a predetermined return pressure that is less than the stop pressure, the motor is operated. When the ambient temperature of the compressor body falls below a predetermined temperature threshold, the recovery pressure is increased. Compressor.

2. In the compressor according to claim 1, The control unit, The system is configured to perform a low-pressure shift mode that shifts the stop pressure and the return pressure to a lower pressure by a predetermined amount. When the ambient temperature of the compressor body falls below the temperature threshold, the stop pressure and the recovery pressure are increased. When the electric motor is being controlled in the low-pressure shift mode, if the ambient temperature falls below the temperature threshold, the stop pressure and the return pressure are increased to return to their values ​​before the shift. Compressor.

3. In the compressor according to claim 2, The temperature threshold includes a first determination threshold and a second determination threshold that is smaller than the first determination threshold. The control unit, If the ambient temperature is below the first determination threshold and higher than the second determination threshold, the return pressure is increased by the first shift amount. If the ambient temperature is below the second determination threshold, the return pressure is increased by a second shift amount that is greater than the first shift amount. Compressor.

4. In the compressor according to claim 1, The control unit, when the ambient temperature is below the temperature threshold, increases the recovery pressure while not changing the stop pressure. Compressor.

5. In the compressor according to claim 1, The compressor is equipped with a cooling unit for cooling its components, The control unit stops the operation of the cooling unit when the ambient temperature falls below the temperature threshold. Compressor.

6. A control method for a compressor comprising an electric motor and a compressor body having a compressor mechanism driven by the electric motor and discharging compressed air, When the discharge pressure of the compressor body reaches a predetermined stop pressure, the operation of the electric motor is stopped. When the discharge pressure reaches a predetermined return pressure that is less than the stop pressure, the motor is operated. When the ambient temperature of the compressor body falls below a predetermined temperature threshold, the recovery pressure is increased. A method for controlling a compressor.

7. In the compressor control method according to claim 6, A low-pressure shift mode is executed, which shifts the stop pressure and the recovery pressure to a lower pressure by a predetermined amount. When the ambient temperature of the compressor body falls below the temperature threshold, the stop pressure and the recovery pressure are increased. When the electric motor is being controlled in the low-pressure shift mode, if the ambient temperature falls below the temperature threshold, the stop pressure and the return pressure are increased to return to their values ​​before the shift. A method for controlling a compressor.

8. In the compressor control method according to claim 7, The temperature threshold includes a first determination threshold and a second determination threshold that is smaller than the first determination threshold. The control method described above is If the ambient temperature is below the first determination threshold and higher than the second determination threshold, the return pressure is increased by the first shift amount. If the ambient temperature is below the second determination threshold, the return pressure is increased by a second shift amount that is greater than the first shift amount. A method for controlling a compressor.

9. In the compressor control method according to claim 6, If the ambient temperature is below the temperature threshold, the recovery pressure is increased while the stop pressure is not changed. A method for controlling a compressor.

10. In the compressor control method according to claim 6, The compressor is equipped with a cooling unit for cooling its components, The control method involves stopping the operation of the cooling unit when the ambient temperature falls below the temperature threshold. A method for controlling a compressor.

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