JP4976239B2 - Compressor protection method for cooling device - Google Patents

Description

  The present invention relates to a compressor protection method for a cooling device for controlling a compressor in a cooling device using a refrigeration cycle for circulating a refrigerant.

  In general, in a laser processing machine, the load on the laser side varies greatly depending on the material of the workpiece, the plate thickness, the processing speed, the surface roughness, and the like. Therefore, the cooling device that supplies (circulates) the coolant to the laser processing machine is required to have a cooling performance that can sufficiently follow such load fluctuations, and in particular, such as a mirror that greatly affects the processing accuracy. In order to ensure the thermal stability of the optical parts and avoid the deterioration of the processing quality, a high degree of precision cooling accuracy with little temperature fluctuation is required.

Conventionally, a cooling device disclosed in Patent Document 1 is known as a cooling device used for such applications. The cooling device includes a cooling liquid tank that stores a cooling liquid returned from an object to be cooled such as a laser processing machine, a liquid feeding pump that sends out a cooling liquid flowing out from a supply port of the cooling liquid tank, and a liquid feeding pump. It is equipped with a cooler (heat exchanger) that cools the coolant discharged from the pump by heat exchange and supplies it to the object to be cooled, and detects the temperature of the coolant that has flowed out of the cooler with a temperature sensor. Based on the control system for controlling the cooling temperature of the cooler based on the temperature, more specifically, based on the temperature detected by the temperature sensor, the rotation frequency (rotation speed) of the compressor in the refrigeration cycle for circulating the refrigerant to the cooler is an inverter. A control system having a control function to control is provided.
JP 2003-329355 A

  By the way, in the conventional cooling apparatus mentioned above, especially the compressor protection method, there existed the following problems to be solved.

  First, if the heat dissipation efficiency of the condenser is reduced during operation of the cooling system due to the ambient temperature becoming higher than the set ambient temperature condition, the compressor's maximum operable speed is usually limited. Even so, the operation of the compressor is stopped to protect it (safety). In this case, the operation of the compressor is stopped by providing a high-pressure switch that detects the upper limit of the refrigerant pressure. However, an expensive high-pressure switch is required, which increases the cost associated with this and further increases the installation. Ensuring manufacturing man-hours and installation space is compelling.

  Secondly, the high pressure switch is a protection means that is finally used from the viewpoint of protecting the compressor. Usually, control for preventing the compressor from being overloaded until the high pressure switch is turned on. Done. However, there is a possibility that the operation of the compressor will not stop even though the compressor is overloaded due to failure of the high pressure switch or processing system, response delay, etc., which is not always sufficient from the viewpoint of protecting the compressor. It cannot be said that it is in a protected environment.

  An object of the present invention is to provide a compressor protection method for a cooling device that solves the problems existing in the background art.

  The compressor protection method for a cooling device according to the present invention circulates a refrigerant by connecting at least an inverter-controlled compressor 2, a condenser 3, an expansion valve 4 and a heat exchanger 5 in order to solve the above-described problems. When protecting the compressor 2 in the cooling device 1 using the refrigeration cycle Cc to be made, one or more different from the temperature of the refrigerant discharged from the condenser 3 during operation of the compressor 2 (condensed refrigerant temperature Tc) in advance. The rate determination values D1, D2a, D2b with respect to the rate of increase ΔTc of the condensed refrigerant temperature Tc corresponding to the temperature determination values Tj1, Tj2 and the respective temperature determination values Tj1,... Are set differently for each temperature determination value Tj1,. Time determination ranges Z1, Z2, and Z3 with respect to the operation time t at the time of determination are set corresponding to each temperature determination value Tj1..., And the condensed refrigerant temperature Tc is detected during operation of the compressor 2. When the condensed refrigerant temperature Tc reaches each temperature determination value Tj1..., The current detection value (Tc) at the condensed refrigerant temperature Tc sequentially detected at a predetermined sampling interval Δtx and immediately before the detection value (Tc). The increase rate ΔTc of the condensed refrigerant temperature Tc is obtained using the average value Tca of the plurality of detection values (Tc...) At the above, and the increase rate ΔTc is equal to or higher than the increase rate determination values D1, D2a. It is characterized in that the operation of the compressor 2 is stopped on the condition that the operation time t at this time satisfies the time determination range Z1... Corresponding to the temperature determination value Tj1.

  In this case, according to a preferred aspect of the invention, a maximum temperature determination value Tju larger than each temperature determination value Tj1... Is set, and the operation of the compressor 2 is stopped when the condensed refrigerant temperature Tc reaches the maximum temperature determination value Tju. be able to. On the other hand, the current determination value Iis for the inverter input current Ii flowing into the inverter circuit 8i from the power supply circuit 8s of the inverter unit 8 that drives and controls the electric motor 7 provided in the compressor 2 is set in advance. If the inverter input current Ii is detected and the inverter input current Ii becomes equal to or greater than the current determination value Iis, the operation of the compressor 2 can be stopped. The current determination value Iis can be obtained from the power supply frequency fp and the rotational speed R of the compressor 2.

  According to the compressor protecting method of the cooling device 1 according to the present invention by such a method, the following remarkable effects are obtained.

  (1) An expensive high pressure switch that detects the upper limit of the refrigerant pressure and protects the compressor 2 becomes unnecessary. As a result, the cost can be reduced, and further, the number of manufacturing steps and installation space associated with the mounting can be reduced.

  (2) Since the increase rate determination values D1, D2a are different for each temperature determination value Tj1,..., The temperature determination values Tj1... And the increase rate determination values D1, D2a. Judgment can be made.

  (3) If the condensing refrigerant temperature Tc reaches each temperature determination value Tj1..., The compressor 2 is operated on condition that the operation time t at this time satisfies the time determination range Z1. Since the operation is stopped, it is possible to perform a more precise and accurate determination by combining the temperature determination values Tj1... And the time determination ranges Z1.

  (4) According to a preferred embodiment, if the operation of the compressor 2 is stopped when the inverter input current Ii flowing into the inverter circuit 8i becomes equal to or greater than the current determination value Iis, for example, due to a failure of a condenser fan or the like Even if the refrigerant pressure suddenly rises (abnormally rises), the condensed refrigerant temperature Tc and the rate of increase ΔTc are delayed, and even if the refrigerant pressure becomes higher than the original refrigerant pressure at which the operation is stopped, the inverter input accompanying the abnormal rise in the refrigerant pressure The increase in the current Ii can be detected and the operation can be stopped quickly, and a sufficient protection environment for the compressor 2 can be established.

  (5) If the current determination value Iis is obtained from the power supply frequency fp and the rotation speed R of the compressor 2 according to a preferred embodiment, a more precise combination of the power supply frequency fp and the rotation speed R of the compressor 2 is achieved. And an accurate current judgment value Iis can be set.

  Next, the best embodiment according to the present invention will be given and described in detail with reference to the drawings.

  First, the structure of the cooling device 1 which can implement the compressor protection method according to the present embodiment will be described with reference to FIGS. 3 and 4.

  FIG. 3 shows the overall configuration of the cooling device 1. The cooling device 1 includes a heat exchanger (cooler) 5, and a refrigeration cycle Cc is connected to the primary side 5 f of the heat exchanger 5, and a coolant circuit Cm is connected to the secondary side 5 s of the heat exchanger 5. To do.

  FIG. 4 shows a specific example of the coolant circuit Cm. The coolant circuit Cm includes a coolant tank 11 that stores coolant (cooling water, coolant, etc.) W. The coolant tank 11 is laser processed via a coolant supply line 12s and a coolant return line 12r. Connected to a cooled object H such as a machine (FIG. 3). In the middle of the coolant supply line 12s, a liquid feed pump 13 for supplying the coolant W stored in the coolant tank 11 to the object to be cooled H is connected, and heat is supplied to the liquid feed pump 13. The secondary side 5s of the exchanger 5 is connected in series. The coolant tank 11 includes a tank cover 11c that covers the upper end opening. The coolant supply line 12s is provided with a fluid pressure gauge 15 that detects the pressure of the coolant W and a liquid temperature sensor 16 that detects the temperature (liquid temperature) Tw of the coolant W, and the coolant tank 11 includes A liquid supply port 17, a drain line 18, a float switch 19, a liquid level gauge 20, a strainer 21 and the like are provided.

  On the other hand, the refrigeration cycle Cc includes a compressor 2, a condenser 3, and an expansion valve (electronic expansion valve) 4 as main functional units, and the refrigerant outflow side of the electronic expansion valve 4 is the primary side of the heat exchanger 5. The other end port (refrigerant outlet port) of the primary side 5 f of the heat exchanger 5 is connected to the refrigerant inflow side of the compressor 2 via the refrigerant strainer 31. Thereby, a refrigeration cycle Cc (refrigerant circuit) in which the refrigerant circulates in the direction of arrow Fc is configured. The basic function of such a refrigeration cycle Cc is the same as a known refrigeration cycle. In the refrigeration cycle Cc, the temperature of the refrigerant discharged from the compressor 2, that is, the discharge refrigerant temperature sensor 33 that detects the discharged refrigerant temperature To, and the temperature of the refrigerant discharged from the condenser 3, that is, the condensed refrigerant temperature Tc are set. Various sensors such as a condensing refrigerant temperature sensor 34 to be detected and a cooler inlet temperature sensor 35 to detect the refrigerant temperature on the inlet side of the cooler 5 are attached, and the condenser 3 is air-cooled. A fan 36 is attached. An arrow Ff indicates the direction of air blown by the condenser fan 36. Further, an electric motor 7 is used to drive the compressor 2, and the electric motor 7 is connected to the inverter unit 7. The illustrated electric motor 7 is a sensorless brushless DC motor that operates by a 120 ° energization method, and includes three star-connected windings (field coils). The inverter unit 8 includes an inverter circuit 8i and a DC power supply circuit 8s. The output unit of the inverter circuit 8i is connected to the electric motor 7, and the AC input unit of the DC power supply circuit 8s is connected to a three-phase AC power supply.

  The sensors 33, 34, 35, the condenser fan 36, the inverter circuit 8 i, and the electronic expansion valve 4 and the liquid temperature sensor 16 are connected to a control unit (controller) 51. The control part 51 comprises the principal part of a control system, and has a function which manages control of the whole cooling device 1 containing the refrigerating cycle Cc. The inverter circuit 8i is provided with a radiator temperature sensor 43 for detecting the temperature of the radiator included in the inverter circuit 8i, that is, the inverter radiator temperature Ti, and between the inverter circuit 8i and the DC power supply circuit 8s. A current detector 44 for detecting the magnitude of the inverter input current Ii flowing from the DC power supply circuit 8 s into the inverter circuit 8 i is provided, and the radiator temperature sensor 43 and the current detector 44 are also connected to the control unit 51. The control unit 51 includes an operation unit using an operation panel and a display unit using a liquid crystal display panel, and has a computer function with a built-in CPU and memory, and performs various processes and controls according to a previously stored control program. (Sequence control) is executed.

  Next, the compressor protection method according to this embodiment including the operation of the cooling device 1 will be described with reference to the drawings.

  First, the basic operation of the cooling device 1 will be described. Now, it is assumed that the cooling device 1 is normally operated by normal operation. In this case, in the coolant circuit Cm, the coolant W stored in the coolant tank 11 is supplied to the object to be cooled H via the coolant supply line 12s by the operation of the liquid feed pump 13, and the object to be cooled is also supplied. The coolant W that has cooled H by heat exchange is returned to the coolant tank 11 via the coolant return line 12r. At this time, the coolant W flowing through the coolant supply line 12 s is cooled by the cooler (heat exchanger) 5. That is, the coolant W flowing into the cooler 5 is cooled by heat exchange with the cooled refrigerant in the refrigeration cycle Cc. In the refrigeration cycle Cc, the refrigerant circulates in the direction of the arrow Fc by the operation of the compressor 2, and the refrigerant is cooled by the refrigeration cycle Cc. In FIG. 4, arrows Fw... Indicate the direction in which the coolant W flows.

  Then, the liquid temperature Tw of the coolant W supplied to the object to be cooled H is detected by the liquid temperature sensor 16 and given to the control unit 51. Thus, the control unit 51 gives a control command to the inverter circuit 8i and varies the number of rotations (rotational speed) of the electric motor 7, thereby performing the foot-back control so that the liquid temperature Tw becomes the set target temperature. At this time, a DC voltage is applied to the input part of the inverter circuit 8i from the DC power supply circuit 8s, and the inverter circuit 8i performs known inverter control for switching the DC voltage by an internal switching element.

  Next, the compressor protection method of the cooling device according to the present embodiment will be described with reference to FIGS.

  First, a control method for setting the controllable protection speed of the compressor 2, that is, the maximum operable speed Rmax for limiting the speed of the compressor 2, will be described with reference to FIG.

  First, the operation of the compressor 2 is started by turning on an operation switch (not shown), and the condensed refrigerant temperature Tc detected from the condensed refrigerant temperature sensor 34 is taken into the control unit 51. At this time, as shown in FIG. 5, the data related to the condensed refrigerant temperature Tc is taken in at a predetermined sampling period Δtx [s] (illustrated is 1 [s]), and the process (from the start of operation to the initial start mode) ( Control). In the initial start mode, the starting temperature monitoring value Tcc with respect to the condensed refrigerant temperature Tc, two different monitoring times Δta and Δtb, and the rotational speeds Rs, Ra, and Rb that increase the maximum operating speed Rmax stepwise are set in advance. Set. In the illustrated example, the temperature monitoring value Tcc at start-up is 52 [° C.], the monitoring time Δta is 120 [s], the monitoring time Δtb is 270 [s], the rotational speed (initial rotational speed) Rs is 1800 [rpm], and the rotational speed (First rotation speed) Ra is 2700 [rpm], and rotation speed (maximum rotation speed) Rb is 3000 [rpm].

  In the initial start mode, when the operation is started, the control unit 51 sets the maximum operable rotational speed Rmax for the compressor 2 to the initial rotational speed Rs. In FIG. 6, the operation start time is indicated by ts. Further, the control unit 51 measures the monitoring time Δta from the start of operation, and if the monitoring time Δta has elapsed, whether or not the condensed refrigerant temperature Tc is equal to or lower than the starting temperature monitoring value Tcc, that is, satisfies the condition of Tc ≦ Tcc. Determine whether or not. And if the conditions of Tc <= Tcc are satisfy | filled, control which increases the driving | operation maximum rotation speed Rmax from the initial rotation speed Rs to 1st rotation speed Ra will be performed. However, even if the monitoring time Δta elapses, if the condition of Tc ≦ Tcc is not satisfied, the operable maximum rotational speed Rmax is maintained at the initial rotational speed Rs. Whether or not the condition of Tc ≦ Tcc is satisfied is subsequently determined, and a process of increasing to the first rotational speed Ra is performed when the condition of Tc ≦ Tcc is satisfied. Control based on this monitoring time Δta is the first step.

  Further, when the control unit 51 continues to count the time and the monitoring time Δtb has elapsed from the operation start time ts, it is determined whether or not the first rotation number Ra is set. At this time, if the first rotation speed Ra is set, control is performed to further increase the operable maximum rotation speed Rmax from the first rotation speed Ra to the maximum rotation speed Rb. However, if the initial rotational speed Rs remains even when the monitoring time Δtb has elapsed, the operable maximum rotational speed Rmax is maintained as the initial rotational speed Rs. Control based on the monitoring time Δtb after the elapse of the monitoring time Δta is the second step. In FIG. 6, change data Qp related to the maximum operable speed Rmax indicated by a solid line indicates a case where the condensed refrigerant temperature Tc is equal to or less than the starting temperature monitoring value Tcc, and also relates to the maximum operable speed Rmax indicated by a virtual line. The change data Qo indicates the case where the condensed refrigerant temperature Tc exceeds the starting temperature monitoring value Tcc. In FIG. 6, the elapsed time of the monitoring time Δta is indicated by tc1, and the elapsed time of the monitoring time Δtb is indicated by tc2.

  By the way, the reason for performing the control in the initial start mode is as follows. That is, normally, when starting the compressor 2, in order to ensure the supply of lubricating oil to the compressor 2 at the time of starting and prevent the lubricating oil from being mixed into the refrigerant, the maximum operable speed Rmax is initially set. The actual number of rotations is limited by increasing the number of rotations Rs step by step. However, in the compressor protection method according to the present embodiment, the maximum operable rotation speed Rmax is basically set based on the condensing refrigerant temperature Tc. Therefore, when the ambient temperature is high and the condensing refrigerant temperature Tc rises rapidly, There arises a problem that the maximum possible rotational speed Rmax is excessively lowered. Therefore, a decrease in the cooling capacity is prevented by performing the control in the initial start mode. Note that the initial start mode ends through the first step and the second step. Therefore, by performing such control in the initial start mode, it is possible to ensure supply of the lubricating oil to the compressor 2 at the start and prevent the lubricating oil from being mixed into the refrigerant, and in an environment where the ambient temperature is high. Even so, it is possible to avoid the problem that the condensing refrigerant temperature Tc rises rapidly and the cooling capacity is lowered by excessively reducing the maximum operable speed Rmax.

  On the other hand, when the first step in the initial start mode is completed, the compressor 2 is controlled based on the condensed refrigerant temperature Tc in the normal operation mode in parallel with the initial start mode. In the normal operation mode, two different upper limit temperature monitoring values Tu1, Tu2, one lower limit temperature monitoring value Td1, a temperature setting value Tos for the discharged refrigerant temperature To, a temperature setting value Tis for the inverter radiator temperature Ti, compression A unit rotational speed Ruc for decreasing the maximum operable speed Rmax for the machine 2 in steps and a unit rotational speed Rdc for increasing the maximum operable speed Rmax in steps are set. In the example, the upper temperature monitoring value Tu1 is 52 [° C.], the upper temperature monitoring value Tu2 is 53 [° C.], the lower temperature monitoring value Td1 is 50 [° C.], and the temperature setting value Tos is 95 [° C.] The temperature set value Tis is 80 [° C.], the unit rotational speed Ruc is 240 [rpm], and the unit rotational speed Rdc is 90 [rpm].

  In the normal operation mode, the control unit 51 variably sets the maximum operable rotation speed Rmax for the compressor 2 in a stepwise manner based on the condensed refrigerant temperature Tc. At this time, the control for decreasing or increasing the maximum operable speed Rmax is that a predetermined interval time Δti (for example, 60 [s]) has elapsed from the previously performed control (processing) for decreasing or increasing. To condition. As a result, the next control for reducing the maximum operable speed Rmax can be stably performed.

  First, it is assumed that the condensed refrigerant temperature Tc is lowered to the lower limit temperature monitoring value Td1 or lower, that is, the condition of Tc ≦ Td1 is satisfied. In this case, in addition to this condition, the controller 51 determines that the discharged refrigerant temperature To obtained from the discharged refrigerant temperature sensor 33 is equal to or lower than the temperature set value Tos (To ≦ Tos), and the inverter radiator temperature obtained from the radiator temperature sensor 43. The current maximum operation speed is satisfied on condition that Ti is equal to or less than the temperature set value Tis (Ti ≦ Tis) and that the number of circuits of the compressor 2 is the maximum operation speed Rmax. Control (processing) for increasing the number Rmax by the unit rotational speed Rdc is performed. In FIG. 6, tc4 indicates a point in time when the condition of Tc ≦ Td1 is satisfied. As described above, at least the lower limit side temperature monitoring value Td1 is reached, the discharge refrigerant temperature To is equal to or lower than the temperature setting value Tos, and the inverter radiator temperature Ti is the temperature as control for increasing the maximum operable speed Rmax. If the control performed under the condition that it is equal to or less than the set value Tis is included, more reliable and reliable control can be performed as compared with the case where the determination is made only by the lower limit side temperature monitoring value Td1.

  On the other hand, it is assumed that the condensed refrigerant temperature Tc is equal to or higher than the upper limit temperature monitoring value Tu1, that is, the condition that Tc ≧ Tu1 is satisfied. In this case, in addition to this condition, the control unit 51 satisfies the condition that the increase rate ΔTc of the condensed refrigerant temperature Tc is equal to or higher than the increase rate monitoring value Du (ΔTc ≧ Du). Control is performed to reduce the rotational speed Rmax by the unit rotational speed Ruc. As shown in FIG. 5, the rate of increase ΔTc is the average of the condensed refrigerant temperatures Tc at the last five sampling times t2 to t6 when the current condensed refrigerant temperature Tc is, for example, the condensed refrigerant temperature Tc at the sampling time t7. The deviation from the value Tca is used. The upper limit temperature monitoring value Tu1 is set to a temperature lower than the normal upper limit temperature monitoring value Tu2, but if the rate of increase ΔTc is large, it can be determined that there is a high possibility of reaching the normal upper limit temperature monitoring value Tu2. Then, the control using the upper limit temperature monitoring value Tu1 and the increase rate monitoring value Du is performed. By such control, the unit rotational speed Ruc can be decreased even before the normal upper limit temperature monitoring value Tu2 is reached, so that more reliable and reliable control can be performed.

  Further, it is assumed that the condensing refrigerant temperature Tc is equal to or higher than the upper limit temperature monitoring value Tu2, that is, the condition that Tu2 <Tc is satisfied. In this case as well, control (processing) is performed to decrease the current operable maximum rotational speed Rmax by the unit rotational speed Ruc. The upper limit temperature monitoring value Tu2 is a so-called regular upper limit temperature monitoring value that is determined only by the condensed refrigerant temperature Tc. In FIG. 6, tc3 indicates a time point when the condition of Tc ≧ Tu1 and the condition of ΔTc ≧ Du, or the condition of Tu2 <Tc is satisfied. Therefore, by performing such a normal operation mode, it is possible to set an accurate (optimum) operable maximum rotational speed Rmax that can avoid overloading of the compressor 2, thereby improving the operation efficiency of the compressor 2 and Contributes to improved durability. Moreover, since the restriction (control) on the refrigerant pressure can be accurately performed even in an environment with a high ambient temperature, it is possible to avoid the ON of the high pressure switch due to the upper limit high pressure as much as possible. As a result, high control accuracy with respect to the cooling temperature can be maintained, and stable operation in an environment with a high ambient temperature can be ensured.

  On the other hand, even if such a limitation on the rotational speed of the compressor 2 is performed, it is not possible to cope with a larger overload, so the compressor 2 (electric motor 7) is protected by the compressor protection method according to the present embodiment. Control to stop.

  Next, the processing procedure of the compressor protection method for stopping the compressor 2 will be described with reference to the flowchart shown in FIG. 1 and FIG.

  First, various determination values, which are stop conditions, are set in advance. That is, two different temperature determination values Tj1 and Tj2 with respect to the condensed refrigerant temperature Tc during operation of the compressor 2, a maximum temperature determination value Tju larger than the two temperature determination values Tj1 and Tj2, and each temperature determination value Tj1 and Tj2 Time determination ranges Z1, Z2, and Z3 for the operation time t at the time of determination are set corresponding to the increase rate determination values D1, D2a, D2b, the temperature determination values Tj1,... With respect to the corresponding increase rate ΔTc of the condensed refrigerant temperature Tc. . In the case of illustration, the temperature judgment value Tj1 is 40 [° C.], the temperature judgment value Tj2 is 50 [° C.], the maximum temperature judgment value Tju is 58 [° C.], the increase rate judgment value D1 is 2.0 [° C./Δtx], The increase rate determination value D2a is 1.5 [° C / Δtx], the increase rate determination value D2b is 1.0 [° C / Δtx], the time determination range Z1 is 10 [s] or more, and the time determination range Z2 is 10 [s]. The time determination range Z3 is 60 [s] or more.

  In FIG. 7, a hatched range Ak is a range corresponding to the stop condition. Now, assume that during operation, the condensed refrigerant temperature Tc is equal to or higher than the maximum temperature determination value Tju, that is, Tc> Tju is satisfied (steps S1 and S3). In this case, the control unit 51 performs control to immediately stop the operation of the compressor 2 on condition that the operation time t satisfies the time determination range Z1 (step S2) (step S4). On the other hand, it is assumed that the condensed refrigerant temperature Tc is equal to or higher than Tj1, that is, Tc> Tj1 (step S5). In this case, the controller 51 satisfies that the operation time t satisfies the time determination range Z1 (step S2), and the increase rate ΔTc of the condensed refrigerant temperature Tc is equal to or higher than the increase rate determination value D1 (ΔTc ≧ D1) (step S6). As a condition, the control immediately stops the operation of the compressor 2 (step S4).

  When the operation time t satisfies the time determination range Z2 (step S7) and the condensed refrigerant temperature Tc is equal to or higher than Tj2, that is, Tc> Tj2 (step S8), the control unit 51 performs the condensed refrigerant. Control that immediately stops the operation of the compressor 2 is performed (step S4) on condition that the increase rate ΔTc of the temperature Tc is equal to or higher than the increase rate determination value D2a (ΔTc ≧ D2a) (step S9). Furthermore, when the operation time t satisfies the time determination range Z3 (step S7) and the condensed refrigerant temperature Tc is equal to or higher than Tj2, that is, Tc> Tj2 (step S10), the control unit 51 performs the condensed refrigerant. Control that immediately stops the operation of the compressor 2 is performed on the condition that the rate of increase ΔTc of the temperature Tc is equal to or greater than the rate of increase determination value D2b (ΔTc ≧ D2b) (step S11) (step S4).

  Thus, according to the compressor protection method according to the present embodiment, when the condensed refrigerant temperature Tc is detected during the operation of the compressor 2, and the condensed refrigerant temperature Tc reaches the respective temperature determination values Tj1,. An increase rate ΔTc of the condensed refrigerant temperature Tc is obtained, and the operation of the compressor 2 is stopped on condition that the increase rate ΔTc is equal to or higher than the increase rate determination values D1, D2a... Corresponding to the temperature determination values Tj1. Therefore, an expensive high-pressure switch that protects the compressor 2 by detecting the upper limit of the refrigerant pressure becomes unnecessary. As a result, the cost can be reduced, and further, the number of manufacturing steps and installation space associated with the mounting can be reduced. In addition, since the increase rate determination values D1, D2a, and D2b are made different for each temperature determination value Tj1, Tj2, the temperature determination values Tj1,... And the increase rate determination values D1, D2a,. If the condensing refrigerant temperature Tc reaches the respective temperature determination values Tj1,..., The operating time t at this time satisfies the time determination range Z1 corresponding to the temperature determination values Tj1. In addition, since the operation of the compressor 2 is stopped, it is possible to perform a more precise and accurate determination by combining the temperature determination values Tj1... And the time determination ranges Z1.

  By the way, even when the control for stopping the compressor 2 by detecting the condensed refrigerant temperature Tc is performed, if the refrigerant pressure suddenly rises (abnormally rises) due to a failure of the condenser fan or the like, the condensed refrigerant temperature Tc or Since the increase rate ΔTc is delayed, it may be higher than the original refrigerant pressure at which the operation is stopped. Therefore, in the present embodiment, control for stopping the compressor 2 is performed by detecting an increase in the inverter input current Ii accompanying the abnormal increase in the refrigerant pressure.

  Next, the processing procedure of the compressor protection method for stopping the compressor 2 using the inverter input current Ii will be described with reference to the flowchart shown in FIG. 2 and FIG.

  The current determination value Iis for the inverter input current Ii flowing into the inverter circuit 8i from the power supply circuit 8s of the inverter unit 8 that drives and controls the electric motor 7 provided in the compressor 2 is set in advance. The current determination value Iis is obtained from the power supply frequency fp of the three-phase AC power supply input to the AC input unit of the DC power supply circuit 8s and the rotational speed R of the compressor 2. As an example, the current judgment value Iisa when the power supply frequency fp is 50 [Hz] is calculated by the following equation: Iisa = 0.12 · R / 100 + 2.4, and the current judgment value Iisb when the power supply frequency fp is 60 [Hz] is , Iisb = 0.15 · R / 100 + 2.7, respectively. FIG. 8 shows data related to the current determination value Iisa and the current determination value Iisb.

  On the other hand, during the operation of the compressor 2, the control unit 51 performs the following processing (control) on condition that the operation time t satisfies the time determination range Z1 (steps S21 and S22). First, the control part 51 calculates | requires the corresponding electric current determination value Iis from the rotation speed R of the compressor 2 in driving | operation (step S23). In this case, the current determination value Iis may be calculated by the above-described calculation formula each time, or a current determination value Iis corresponding to the rotational speed R may be read by setting a database (data table) obtained in advance. Good. Further, the inverter input current Ii (detected value) flowing into the inverter circuit 8i detected from the current detector 44 is taken in, and the fetched inverter input current Ii is compared with the current judgment value Iis (steps S24 and S25). At this time, when the inverter input current Ii is equal to or greater than the current determination value Iis, that is, when the condition of Ii ≧ Iis is satisfied, the control unit 51 performs control to immediately stop the operation of the compressor 2 (steps S26 and S27). ).

  Therefore, if the operation of the compressor 2 is stopped when the inverter input current Ii flowing into the inverter circuit 8i becomes equal to or greater than the current determination value Iis, for example, the refrigerant pressure due to the failure of the condenser fan or the like. Even if the condensing refrigerant temperature Tc and its rate of increase ΔTc are delayed due to a sudden rise (abnormal rise) of the engine and become higher than the original refrigerant pressure at which the operation is stopped, the inverter input current Ii due to the abnormal rise in the refrigerant pressure Therefore, the operation can be stopped immediately, and a sufficient protection environment for the compressor 2 can be established. Further, if the current determination value Iis is obtained from the power supply frequency fp and the rotation speed R of the compressor 2, a more precise and accurate current determination value combining the power supply frequency fp and the rotation speed R of the compressor 2 is obtained. Iis can be set.

  In addition, when it stops by these stop conditions, driving | operation is restarted by canceling | releasing generation | occurrence | production of a stop condition. When restarting, the compressor 2 is started, and processing in the interrupted start mode is performed. This interrupted start mode is the same as the initial start mode described above, but some set values are made different as necessary. Therefore, the initial start mode can be applied as it is to the interrupt start mode.

  Although the best embodiment has been described in detail above, the present invention is not limited to such an embodiment, and the detailed configuration, method, quantity, numerical value, and the like do not depart from the spirit of the present invention. You can change, add, or delete at will. For example, although the case where two temperature determination values Tj1 and Tj2 are set is shown, one or three or more temperature determination values may be set, or three increase rate determination values D1, D2a, and D2b are set. However, one, two, or four or more increase rate determination values may be set. Moreover, although the case where the three time determination ranges Z1, Z2, and Z3 were set was shown, you may set one, two, or four or more time determination ranges. On the other hand, the electric motor 7 is exemplified by a direct current motor, but may be an alternating current motor. The type of the electric motor 7 is not limited, and the inverter circuit 8i (inverter unit 8) can also be configured by various types having the same function. In addition, although the type shown to FIG. 3 (FIG. 4) was illustrated as the cooling device 1, the compressor protection method which concerns on this invention can be utilized similarly with respect to various types of cooling devices other than illustration.

The flowchart which shows the whole process sequence of the compressor protection method which concerns on the best embodiment of this invention, The flowchart which shows the process sequence which stops a compressor using the inverter input current in the compressor protection method, The whole block diagram of the cooling device which implements the compressor protection method, Configuration diagram of a coolant circuit in the cooling device, A time chart for explaining the intake and rise rate of the condensed refrigerant temperature used in the compressor protection method, A time chart showing change data of the maximum operable speed of the compressor used in the compressor protection method; Explanatory diagram of relationship between operating time, condensed refrigerant temperature and rise rate judgment value used for the compressor protection method, Explanatory diagram of relationship between compressor rotation speed, power supply frequency, current judgment value in the compressor protection method,

Explanation of symbols

  1: cooling device, 2: compressor, 3: condenser, 4: expansion valve, 5: heat exchanger, 7: electric motor, 8: inverter unit, 8s: power supply circuit, 8i inverter circuit, Cc: refrigeration cycle, Tc: Condensed refrigerant temperature, Tj1: Temperature judgment value, Tj2: Temperature judgment value, Tca: Average value, Tju: Maximum temperature judgment value, ΔTc: Condensed refrigerant temperature increase rate, D1: Increase rate determination value, D2a: Increase rate Determination value, D2b: Ascent rate determination value, Δtx: Sampling interval, t: Operating time, Z1: Time determination range, Z2: Time determination range, Z3: Time determination range, Ii: Inverter input current, Iis: Current determination value, fp: power supply frequency, R: compressor rotation speed

Claims (4)

  In a compressor protection method for a cooling device that protects the compressor in a cooling device using a refrigeration cycle that circulates a refrigerant by connecting at least an inverter-controlled compressor, a condenser, an expansion valve, and a heat exchanger, One or two or more different temperature judgment values for the temperature of the refrigerant discharged from the condenser during operation of the compressor (condensed refrigerant temperature) and an increase rate determination for the rate of increase of the condensed refrigerant temperature corresponding to each temperature determination value A value is set differently for each temperature determination value, and a time determination range for an operation time at the time of determination is set corresponding to each temperature determination value, and the condensed refrigerant temperature is set during operation of the compressor. And when the condensed refrigerant temperature reaches the respective temperature determination values, the current value of the condensed refrigerant temperature sequentially detected at a predetermined sampling interval is detected. An increase rate of the condensed refrigerant temperature is obtained using an average value of a plurality of detection values immediately before the detection value and the detection value, and the increase rate is equal to or higher than an increase rate determination value corresponding to the temperature determination value; The compressor protection method for a cooling device, wherein the operation of the compressor is stopped on condition that the operation time at this time satisfies a time determination range corresponding to the temperature determination value.   2. The cooling device according to claim 1, wherein a maximum temperature determination value larger than each of the temperature determination values is set, and the operation of the compressor is stopped when a condensed refrigerant temperature reaches the maximum temperature determination value. Compressor protection method.   A current determination value for an inverter input current flowing into the inverter circuit from a power supply circuit of an inverter unit that drives and controls an electric motor included in the compressor in advance, and detecting the inverter input current during operation of the compressor; 2. The compressor protection method for a cooling apparatus according to claim 1, wherein the operation of the compressor is stopped when the inverter input current becomes equal to or greater than the current determination value.   4. The compressor protection method for a cooling apparatus according to claim 3, wherein the current determination value is obtained from a power supply frequency and a rotation speed of the compressor.

Images