Inverter device

Abstract

To improve reliability of an inverter device.SOLUTION: A controller 50 lowers a threshold value of predetermined correlation temperature in accordance with lowering of ambient temperature in a housing 21 so that temperature of a switching element 40 does not reach heat resistance temperature of the switching element 40. Therefore, even if the correlated temperature detected by a correlated temperature sensor 52 changes in accordance with the ambient temperature in the housing 21, it is possible to avoid a situation in which the correlated temperature becomes difficult to reach a predetermined threshold value. As a result, it is possible to avoid a problem of the temperature of the switching element 40 reaching heat resistance temperature of the switching element 40 before the correlation temperature reaches the threshold value.SELECTED DRAWING: Figure 2

Description

[Technical Field]

[0001] The present invention relates to an inverter device. [Background technology]

[0002] The inverter device includes a housing, a circuit board, switching elements, and a control unit. The circuit board is accommodated in the housing. The switching elements are mounted on the circuit board. The control unit controls the switching operation of the switching elements. The inverter device may also include a temperature sensor. The temperature sensor is mounted on the circuit board. The inverter device may also include a refrigerant flow path. The refrigerant flow path is provided in the housing. A refrigerant flows through the refrigerant flow path to cool the switching elements. The temperature sensor detects the temperature of the switching elements, as in Patent Document 1, for example. When the temperature of the switching elements rises and the temperature of the switching elements detected by the temperature sensor reaches a predetermined threshold, the control unit stops the switching operation of the switching elements. In this way, overheating of the switching elements is suppressed by preventing the temperature of the switching elements from reaching their heat resistance temperature. [Prior art documents] [Patent documents]

[0003] [Patent Document 1] Japanese Patent Application Laid-Open No. 2014-166021 Summary of the Invention [Problem to be solved by the invention]

[0004] In such inverter devices, it may be difficult to directly detect the temperature of the switching element. In such cases, a temperature sensor detects a correlation temperature that correlates with the temperature of the switching element. Then, when the correlation temperature reaches a predetermined threshold, a control unit stops the switching operation of the switching element. In this way, the temperature of the switching element is prevented from reaching its heat resistance temperature.

[0005] Here, for example, if the flow of refrigerant through the refrigerant flow path is stopped, or the flow rate of the refrigerant through the refrigerant flow path is reduced, it may become difficult for the refrigerant to cool the switching elements. As a result, the temperature of the switching elements increases, and the correlation temperature correlated with the temperature of the switching elements also increases. At this time, if the ambient temperature inside the housing decreases, the correlation temperature correlated with the temperature of the switching elements may also decrease in accordance with the decrease in ambient temperature. If the flow of refrigerant through the refrigerant flow path is stopped, or the like, and the correlation temperature increases, it becomes difficult for the correlation temperature to reach a predetermined threshold. As a result, the temperature of the switching elements may reach their heat resistance temperature before the correlation temperature reaches the threshold, thereby reducing the reliability of the inverter device. [Means for solving the problem]

[0006] An inverter device that solves the above problem is an inverter device comprising: a housing, a circuit board accommodated in the housing, switching elements mounted on the circuit board, a control unit that controls the switching operation of the switching elements, a temperature sensor mounted on the circuit board and detecting temperature, and a refrigerant flow path provided in the housing and through which a refrigerant flows to cool the switching elements, wherein the switching elements do not have a function of detecting temperature, and the temperature sensor comprises: a correlated temperature sensor that detects a correlated temperature that is correlated with the temperature of the switching elements and that rises as the flow rate of the refrigerant decreases and falls as the flow of the refrigerant increases, and an ambient temperature sensor that detects the ambient temperature within the housing, and the control unit lowers a predetermined threshold value of the correlated temperature in accordance with a decrease in the ambient temperature so that the temperature of the switching elements does not reach the heat resistance temperature of the switching elements.

[0007] This prevents the correlation temperature from becoming difficult to reach the predetermined threshold even if the correlation temperature detected by the correlation temperature sensor changes in accordance with the ambient temperature inside the housing. As a result, it is possible to avoid a problem in which the temperature of the switching element reaches the heat resistance temperature of the switching element before the correlation temperature reaches the threshold. Furthermore, for example, if the ambient temperature inside the housing drops and the correlation temperature detected by the correlation temperature sensor also drops in accordance with the drop in ambient temperature, the control unit lowers the correlation temperature threshold in accordance with the drop in ambient temperature. Suppose the flow of refrigerant through the refrigerant flow path stops, for example, and the flow rate of refrigerant through the refrigerant flow path decreases, causing the correlation temperature to rise. Even in such a case, it is possible to prevent the correlation temperature detected by the correlation temperature sensor from becoming difficult to reach the predetermined threshold. As a result, it is possible to avoid a problem in which the temperature of the switching element reaches the heat resistance temperature of the switching element before the correlation temperature reaches the threshold. This improves the reliability of the inverter device.

[0008] In the inverter device, the circuit board may have a current-carrying pattern to which the switching elements are electrically connected, and the correlation temperature sensor may detect the temperature of the current-carrying pattern.

[0009] According to this, since the temperature of the current pattern to which the switching element is electrically connected is highly correlated with the temperature of the switching element, the correlated temperature sensor can accurately detect the correlated temperature that is correlated with the temperature of the switching element.

[0010] In the above inverter device, the housing has a boss to which the circuit board is fastened with bolts, and a heat sink that is provided between the switching element and the refrigerant flow path and that transfers heat from the switching element to the boss, and the circuit board has a heat transfer pattern that is provided between the boss and the correlated temperature sensor, and the correlated temperature sensor detects the temperature of the heat sink via the boss and the heat transfer pattern.

[0011] According to this, the temperature of the heat sink via the heat transfer pattern provided between the boss and the correlation temperature sensor is highly correlated with the temperature of the switching element, and therefore the correlation temperature sensor can accurately detect the correlation temperature that is correlated with the temperature of the switching element.

[0012] In the inverter device, the control unit may control the threshold value so that, when the flow rate of the refrigerant is reduced multiple times, the peak value of the correlation temperature is further away from the heat resistance temperature than the previous peak value of the correlation temperature.

[0013] According to this, even if the refrigerant flow rate is reduced multiple times, the control unit controls the threshold value so that the peak value of the correlation temperature is farther from the heat resistance temperature than the previous peak value of the correlation temperature. This makes it easier to avoid the problem of the temperature of the switching element reaching the heat resistance temperature of the switching element before the correlation temperature reaches the threshold value. Therefore, the reliability of the inverter device can be improved. [Effects of the Invention]

[0014] According to the present invention, the reliability of the inverter device can be improved. [Brief explanation of the drawings]

[0015] [Figure 1] FIG. 1 is a cross-sectional view of an electric compressor according to an embodiment. [Figure 2] FIG. 2 is a cross-sectional view for explaining the inverter device. [Figure 3] FIG. 3 is a graph for explaining the operation of the embodiment. DETAILED DESCRIPTION OF THE INVENTION

[0016] An embodiment of an inverter device will be described below with reference to Figures 1 to 3. The inverter device of this embodiment is mounted on an electric compressor. <Outline of electric compressor> As shown in FIG. 1 , the electric compressor 10 includes a compressor housing 11. The compressor housing 11 is cylindrical. The compressor housing 11 is made of a metal material. The compressor housing 11 is made of aluminum, for example. The electric compressor 10 includes a rotating shaft 12. The rotating shaft 12 is accommodated in the compressor housing 11. The rotating shaft 12 is rotatably supported by the compressor housing 11. The electric compressor 10 includes a compression unit 13 and a motor 14. The compression unit 13 and the motor 14 are accommodated in the compressor housing 11. The compression unit 13 is driven by the rotation of the rotating shaft 12. The compression unit 13 compresses a fluid. The compression unit 13 is an impeller connected to a first end of the rotating shaft 12. Therefore, the electric compressor 10 of this embodiment is a centrifugal type.

[0017] The motor 14 has a cylindrical stator 15 and a cylindrical rotor 16. The rotor 16 is disposed inside the stator 15. The rotor 16 is configured to be rotatable integrally with the rotating shaft 12. The rotor 16 is fixed to the rotating shaft 12. The stator 15 surrounds the rotor 16. The stator 15 has a cylindrical stator core 17 and a motor coil 18. The motor coil 18 is wound around the stator core 17. When power is supplied to the motor coil 18, the rotor 16 rotates and the rotating shaft 12 rotates integrally with the rotor 16. The compression unit 13 is driven in conjunction with the rotation of the rotating shaft 12. In this manner, the motor 14 drives the compression unit 13.

[0018] <Inverter device> As shown in FIGS. 1 and 2, the inverter device 20 includes a housing 21, a circuit board 30, and a switching element 40. The housing 21 is made of a metal material. For example, the housing 21 is made of aluminum. The housing 21 includes a housing main body 22 and a cover member 23. The housing main body 22 is cylindrical. The housing main body 22 is connected to the outer peripheral surface of the compressor housing 11. The cover member 23 is plate-shaped. The cover member 23 is connected to the housing main body 22 in a state where the opening of the housing main body 22 is closed.

[0019] 2, the housing main body 22 has a boss 24. Therefore, the housing 21 has the boss 24. The boss 24 protrudes from an inner surface 22a of the housing main body 22 that faces the cover member 23 toward the cover member 23. A female screw hole 24a is formed in the tip surface of the boss 24.

[0020] The housing 21 has a heat sink 25. The heat sink 25 has a plate-shaped base 26 and a plurality of fins 27. The plurality of fins 27 protrude from a first surface 26a, which is a surface of the base 26 located on one side in the thickness direction of the base 26. The first surface 26a of the base 26 faces an inner surface 22a of the housing main body 22. The plurality of fins 27 protrude from the first surface 26a of the base 26 toward the inner surface 22a of the housing main body 22.

[0021] The space defined by the first surface 26a of the base 26, the plurality of fins 27, and the inner surface 22a of the housing main body 22 serves as a refrigerant flow path 28. Therefore, the refrigerant flow path 28 is provided in the housing 21. A refrigerant flows through the refrigerant flow path 28. The refrigerant is, for example, cooling water.

[0022] The circuit board 30 is accommodated in the housing 21. A through hole 31 is formed in the circuit board 30. The through hole 31 penetrates the circuit board 30 in the thickness direction of the circuit board 30. The circuit board 30 is fixed to the boss 24 by a bolt 32 inserted into the through hole 31 and screwed into the female threaded hole 24a of the boss 24. Therefore, the circuit board 30 is fastened to the boss 24 by the bolt 32. The circuit board 30 is accommodated in the housing 21 with the thickness direction of the circuit board 30 coinciding with the thickness direction of the cover member 23.

[0023] The circuit board 30 has a lead insertion hole 33 formed therein. The lead insertion hole 33 penetrates the circuit board 30 in the thickness direction of the circuit board 30. The circuit board 30 has a current-carrying pattern 34. The current-carrying pattern 34 is continuous with the lead insertion hole 33. The circuit board 30 has a heat transfer pattern 35. The heat transfer pattern 35 is continuous with the through hole 31. The heat transfer pattern 35 is thermally coupled to the boss 24 via a bolt 32.

[0024] The switching element 40 has an element body 41 and leads 42. The switching element 40 is disposed relative to the heat sink 25 with the element body 41 placed on a second surface 26b, which is the other surface of the base 26 of the heat sink 25 in the thickness direction of the base 26. The leads 42 protrude from the element body 41. The tip ends of the leads 42 are inserted into the lead insertion holes 33. The switching element 40 is mounted on the circuit board 30 by soldering the tip ends of the leads 42 to the lead insertion holes 33 of the circuit board 30. The leads 42 and the current-carrying pattern 34 are electrically connected. Therefore, the switching element 40 is electrically connected to the current-carrying pattern 34.

[0025] Heat generated from the switching elements 40 is dissipated via the heat sink 25 to the refrigerant flowing through the refrigerant flow path 28. Therefore, the refrigerant flowing through the refrigerant flow path 28 cools the switching elements 40. In this way, the inverter device 20 is provided in the housing 21, and includes the refrigerant flow path 28 through which the refrigerant that cools the switching elements 40 flows. The heat sink 25 is provided between the switching elements 40 and the refrigerant flow path 28, and transfers the heat of the switching elements 40 to the boss 24.

[0026] <Control unit> The inverter device 20 includes a control unit 50. The control unit 50 controls the switching operation of the switching elements 40. The control unit 50 is a microcomputer mounted on the circuit board 30. The control unit 50 can be realized, for example, by one or more dedicated hardware circuits and / or one or more processors (control circuits) that operate according to a computer program (software). The processor includes a CPU and memory such as RAM and ROM, and the memory stores, for example, program code or instructions configured to cause the processor to execute various processes. The memory, i.e., computer-readable medium, includes any available medium that can be accessed by a general-purpose or dedicated computer.

[0027] The control unit 50 periodically turns the switching element 40 ON / OFF based on an external command. Specifically, the control unit 50 performs pulse width modulation control (PWM control) on the switching element 40 based on the external command. More specifically, the control unit 50 generates a control signal using a carrier signal (carrier wave signal) and a command voltage value signal (comparison signal). The control unit 50 then converts DC power into AC power by controlling the ON / OFF of the switching element 40 using the generated control signal. The converted AC power is supplied to the motor coil 18 as drive power. This causes the rotor 16 to rotate, and the rotating shaft 12 to rotate integrally with the rotor 16. Therefore, the motor 14 rotates the rotating shaft 12.

[0028] <Temperature sensor> The inverter device 20 includes a temperature sensor 51. The temperature sensor 51 detects temperature. The temperature sensor 51 is mounted on the circuit board 30. The temperature sensor 51 includes a correlation temperature sensor 52 and an ambient temperature sensor 53. The correlation temperature sensor 52 includes a current-carrying pattern temperature sensor 54 and a heat-transfer pattern temperature sensor 55. Therefore, the inverter device 20 includes the current-carrying pattern temperature sensor 54 and the heat-transfer pattern temperature sensor 55.

[0029] The current conduction pattern temperature sensor 54 is mounted on the circuit board 30 at a location that overlaps with the current conduction pattern 34 in the thickness direction of the circuit board 30. The current conduction pattern temperature sensor 54 is configured to be able to detect the temperature THp of the current conduction pattern 34. Therefore, the correlation temperature sensor 52 detects the temperature THp of the current conduction pattern 34. The temperature THp of the current conduction pattern 34 correlates with the temperature Tj of the switching element 40. Therefore, the current conduction pattern temperature sensor 54 detects a correlated temperature that correlates with the temperature Tj of the switching element 40. The current conduction pattern temperature sensor 54 is electrically connected to the control unit 50. Information regarding the temperature THp of the current conduction pattern 34 detected by the current conduction pattern temperature sensor 54 is transmitted to the control unit 50.

[0030] The heat transfer pattern temperature sensor 55 is mounted on the circuit board 30 at a location overlapping the heat transfer pattern 35 in the thickness direction of the circuit board 30. The heat transfer pattern temperature sensor 55 is configured to detect the temperature of the heat transfer pattern 35. Heat from the heat sink 25 is transferred to the heat transfer pattern 35 via the boss 24 and the bolt 32. Therefore, the heat transfer pattern 35 is provided between the heat sink 25 and the heat transfer pattern temperature sensor 55. Therefore, the heat transfer pattern 35 is provided between the boss 24 and the correlation temperature sensor 52. The heat transfer pattern temperature sensor 55 is configured to detect the temperature THc of the heat sink 25 via the heat transfer pattern 35. Therefore, the heat transfer pattern temperature sensor 55 detects the temperature THc of the heat sink 25 by detecting the temperature of the heat transfer pattern 35. In this way, the correlation temperature sensor 52 detects the temperature THc of the heat sink 25 via the boss 24 and the heat transfer pattern 35. The temperature THc of the heat sink 25 correlates with the temperature Tj of the switching element 40. Therefore, the heat transfer pattern temperature sensor 55 detects a correlation temperature that correlates with the temperature Tj of the switching element 40. The heat transfer pattern temperature sensor 55 is electrically connected to the control unit 50. Information regarding the temperature THc of the heat sink 25 detected by the heat transfer pattern temperature sensor 55 is transmitted to the control unit 50.

[0031] The temperature Tj of the switching element 40 increases as the flow rate of the coolant flowing through the coolant flow path 28 decreases, and decreases as the flow rate of the coolant increases. Therefore, the temperature THp of the current conduction pattern 34, which is a correlation temperature correlated with the temperature Tj of the switching element 40, also increases as the flow rate of the coolant decreases, and decreases as the flow rate of the coolant increases. Similarly, the temperature THc of the heat sink 25, which is a correlation temperature correlated with the temperature Tj of the switching element 40, also increases as the flow rate of the coolant decreases, and decreases as the flow rate of the coolant increases. In this way, the correlation temperature sensor 52 detects a correlation temperature that correlates with the temperature Tj of the switching element 40 and increases as the flow rate of the coolant flowing through the coolant flow path 28 decreases, and decreases as the flow rate of the coolant increases. Note that the switching element 40 does not have the function of detecting the temperature Tj.

[0032] The ambient temperature sensor 53 is mounted on the circuit board 30 at a location away from the current-carrying pattern 34 and the heat-transfer pattern 35. The ambient temperature sensor 53 is mounted on the circuit board 30 at a location that is not affected by the heat of the current-carrying pattern 34 and the heat-transfer pattern 35. The ambient temperature sensor 53 detects the ambient temperature THa inside the housing 21. Therefore, the ambient temperature sensor 53 detects a temperature different from the temperature Tj of the switching element 40 and a correlated temperature correlated with the temperature Tj of the switching element 40. The ambient temperature sensor 53 is electrically connected to the control unit 50. Information related to the ambient temperature THa inside the housing 21 detected by the ambient temperature sensor 53 is transmitted to the control unit 50.

[0033] <Control of control unit> The control unit 50 pre-stores a threshold value OT(THp) of the temperature THp of the current conduction pattern 34. The control unit 50 pre-stores a program for stopping the switching operation of the switching element 40 when the temperature THp of the current conduction pattern 34 detected by the current conduction pattern temperature sensor 54 increases and reaches the threshold value OT(THp). In this way, the control unit 50 stops the switching operation of the switching element 40 when the correlation temperature detected by the correlation temperature sensor 52 increases and reaches the predetermined threshold value OT(THp). The threshold value OT(THp) is set to a temperature at which the temperature Tj of the switching element 40 does not reach the heat resistance temperature TjLim of the switching element 40 when the temperature THp of the current conduction pattern 34 increases and reaches the threshold value OT(THp). The threshold value OT(THp) is determined in advance by experiment or the like.

[0034] The control unit 50 pre-stores a threshold value OT(THc) for the temperature THc of the heat sink 25. The control unit 50 pre-stores a program for stopping the switching operation of the switching element 40 when the temperature THc of the heat sink 25 detected by the heat transfer pattern temperature sensor 55 increases and reaches the threshold value OT(THc). In this way, the control unit 50 stops the switching operation of the switching element 40 when the correlation temperature detected by the correlation temperature sensor 52 increases and reaches the predetermined threshold value OT(THc). The threshold value OT(THc) is set to a temperature at which the temperature Tj of the switching element 40 does not reach the heat resistance temperature TjLim of the switching element 40 when the temperature THc of the heat sink 25 increases and reaches the threshold value OT(THc). The threshold value OT(THc) is determined in advance by experiment or the like.

[0035] The control unit 50 pre-stores a program for lowering the threshold values ​​OT(THp) and OT(THc) in response to a decrease in the ambient temperature THa detected by the ambient temperature sensor 53. Therefore, the control unit 50 lowers the threshold values ​​OT(THp) and OT(THc) in response to a decrease in the ambient temperature THa. The control unit 50 also pre-stores a program for raising the threshold values ​​OT(THp) and OT(THc) in response to an increase in the ambient temperature THa detected by the ambient temperature sensor 53. Suppose the ambient temperature THa detected by the ambient temperature sensor 53 increases and reaches a predetermined temperature. Then, even if the ambient temperature THa detected by the ambient temperature sensor 53 increases above the predetermined temperature, the threshold values ​​OT(THp) and OT(THc) are set not to increase in response to the increase in the ambient temperature THa. In this way, the control unit 50 controls the predetermined correlation temperature thresholds OT(THp), OT(THc) based on the ambient temperature THa inside the housing 21 so that the temperature Tj of the switching element 40 does not reach the heat resistance temperature TjLim of the switching element 40.

[0036] The control unit 50 pre-stores a program for controlling the threshold value OT(THp) so that, when the refrigerant flow rate is reduced multiple times, the peak value of the temperature THp of the current conduction pattern 34 is farther from the heat resistance temperature TjLim than the peak value of the temperature THp of the previous current conduction pattern 34. The control unit 50 pre-stores a program for controlling the threshold value OT(THc) so that, when the refrigerant flow rate is reduced multiple times, the peak value of the temperature THc of the heat sink 25 is farther from the heat resistance temperature TjLim than the previous peak value of the temperature THc of the heat sink 25. In this way, the control unit 50 pre-stores a program for controlling the threshold values ​​OT(THp) and OT(THc) so that, when the refrigerant flow rate is reduced multiple times, the peak value of the correlation temperature is farther from the heat resistance temperature TjLim than the previous peak value of the correlation temperature. Therefore, when the refrigerant flow rate is reduced multiple times, the control unit 50 controls the threshold values ​​OT(THp) and OT(THc) so that the peak value of the correlation temperature is farther from the heat resistance temperature TjLim than the previous peak value of the correlation temperature.

[0037] [Operation of the embodiment] Next, the operation of this embodiment will be described. 3, for example, if the flow of the refrigerant in the refrigerant flow path 28 is stopped and the flow rate of the refrigerant flowing through the refrigerant flow path 28 decreases, it may become difficult for the refrigerant to cool the switching element 40. As a result, the temperature Tj of the switching element 40 rises, and the temperature THp of the current-carrying pattern 34 and the temperature THc of the heat sink 25, which are correlated temperatures correlated with the temperature Tj of the switching element 40, also rise. Note that, as shown in FIG. 3, the temperature Tw of the refrigerant is constant.

[0038] Consider, for example, a case where the ambient temperature THa in the housing 21 drops. In this case, the temperature THp of the current conduction pattern 34 detected by the current conduction pattern temperature sensor 54 and the temperature THc of the heat sink 25 detected by the heat transfer pattern temperature sensor 55 also drop in response to the drop in ambient temperature THa. At this time, the control unit 50 lowers the threshold values ​​OT(THp) and OT(THc) in response to the drop in ambient temperature THa. Now, suppose that the flow of refrigerant through the refrigerant flow path 28 is stopped, for example, and the flow rate of refrigerant flowing through the refrigerant flow path 28 decreases, causing the temperature THp of the current conduction pattern 34 and the temperature THc of the heat sink 25 to rise. Even in such a case, it is possible to prevent the temperature THp of the current conduction pattern 34 detected by the current conduction pattern temperature sensor 54 from reaching the threshold value OT(THp). As a result, a problem is avoided in which the temperature Tj of the switching element 40 reaches the heat resistance temperature TjLim of the switching element 40 before the temperature THp of the current conduction pattern 34 detected by the current conduction pattern temperature sensor 54 reaches the threshold value OT(THp). Also, a problem is avoided in which the temperature THc of the heat sink 25 detected by the heat transfer pattern temperature sensor 55 is unlikely to reach the threshold value OT(THc). As a result, a problem is avoided in which the temperature Tj of the switching element 40 reaches the heat resistance temperature TjLim of the switching element 40 before the temperature THc of the heat sink 25 detected by the heat transfer pattern temperature sensor 55 reaches the threshold value OT(THc).

[0039] Furthermore, even if the flow rate of the refrigerant is reduced multiple times, the control unit 50 controls the thresholds OT(THp) and OT(THc) so that the peak value of the correlation temperature is further away from the heat-resistant temperature TjLim than the previous peak value of the correlation temperature. This makes it easier to avoid a problem in which the temperature Tj of the switching element 40 reaches the heat-resistant temperature TjLim of the switching element 40 before the correlation temperature reaches the thresholds OT(THp) and OT(THc).

[0040] [Effects of the embodiment] The above embodiment can provide the following effects. (1) The control unit 50 decreases the predetermined correlation temperature thresholds OT(THp) and OT(THc) in accordance with a decrease in the ambient temperature THa in the housing 21 so that the temperature Tj of the switching element 40 does not reach the heat-resistant temperature TjLim of the switching element 40. Therefore, even if the correlation temperature detected by the correlation temperature sensor 52 changes in accordance with the ambient temperature THa in the housing 21, it is possible to prevent the correlation temperature from becoming less likely to reach the predetermined thresholds OT(THp) and OT(THc). As a result, it is possible to avoid a problem in which the temperature Tj of the switching element 40 reaches the heat-resistant temperature TjLim of the switching element 40 before the correlation temperature reaches the thresholds OT(THp) and OT(THc). Therefore, it is possible to improve the reliability of the inverter device 20.

[0041] Consider a case where the ambient temperature THa in the housing 21 decreases, and the correlated temperature detected by the correlated temperature sensor 52 also decreases accordingly. In this case, the control unit 50 decreases the correlated temperature thresholds OT(THp) and OT(THc) accordingly. Here, suppose that the flow of refrigerant through the refrigerant flow path 28 is stopped, for example, and the flow rate of the refrigerant through the refrigerant flow path 28 decreases, causing the correlated temperature to rise. Even in such a case, it is possible to prevent the correlated temperature detected by the correlated temperature sensor 52 from reaching the predetermined thresholds OT(THp) and OT(THc). As a result, it is possible to prevent the temperature Tj of the switching element 40 from reaching the heat resistance temperature TjLim of the switching element 40 before the correlated temperature reaches the thresholds OT(THp) and OT(THc). This can improve the reliability of the inverter device 20.

[0042] (2) The temperature THp of the current-carrying pattern 34 to which the switching element 40 is electrically connected is highly correlated with the temperature Tj of the switching element 40. Therefore, the correlated temperature sensor 52 can accurately detect the correlated temperature that is correlated with the temperature Tj of the switching element 40.

[0043] (3) The temperature THc of the heat sink 25 via the heat transfer pattern 35 is highly correlated with the temperature Tj of the switching element 40. Therefore, the correlated temperature sensor 52 can accurately detect the correlated temperature correlated with the temperature Tj of the switching element 40.

[0044] (4) Even if the refrigerant flow rate is reduced multiple times, the control unit 50 controls the thresholds OT(THp) and OT(THc) so that the peak value of the correlation temperature is farther from the heat-resistant temperature TjLim than the previous peak value of the correlation temperature. This makes it easier to avoid a problem in which the temperature Tj of the switching element 40 reaches the heat-resistant temperature TjLim of the switching element 40 before the correlation temperature reaches the thresholds OT(THp) and OT(THc). This improves the reliability of the inverter device 20.

[0045] (5) The switching element 40 does not have a function to detect the temperature Tj. In this way, even if a switching element 40 that does not have a function to detect the temperature Tj is employed, it is possible to avoid the problem that the temperature Tj of the switching element 40 reaches the heat resistance temperature TjLim of the switching element 40. Therefore, an inexpensive switching element 40 can be employed, thereby reducing the cost of the inverter device 20.

[0046] [Example of change] The above embodiment can be modified as follows: The above embodiment and the following modifications can be combined with each other within the scope of technical compatibility.

[0047] In the above-described embodiment, the inverter device 20 may not include the current pattern temperature sensor 54 . In the above embodiment, the inverter device 20 may not include the heat transfer pattern temperature sensor 55.

[0048] In the above-described embodiment, the coolant flowing through the coolant passage 28 is not limited to cooling water, and may be, for example, air. In the above-described embodiment, the compression unit 13 is not limited to a centrifugal type, and may be, for example, a scroll type, a piston type, a vane type, or a rotary type.

[0049] In the above embodiment, the inverter device 20 is mounted on the electric compressor 10. However, the present invention is not limited to this. In other words, the inverter device 20 may be mounted on any device. [Note] The technical ideas that can be understood from the above-described embodiment and modifications will be described below.

[0050] <Appendix 1> Housing and a circuit board accommodated within the housing; a switching element mounted on the circuit board; a control unit that controls a switching operation of the switching element; a temperature sensor mounted on the circuit board for detecting a temperature; a refrigerant flow path provided in the housing and through which a refrigerant for cooling the switching elements flows, The switching element does not have a function of detecting temperature, The temperature sensor a correlated temperature sensor for detecting a correlated temperature that correlates with the temperature of the switching element, and that increases as the flow rate of the coolant decreases and decreases as the flow rate of the coolant increases; an ambient temperature sensor for detecting an ambient temperature inside the housing, The control unit lowers the predetermined threshold value of the correlation temperature in accordance with a decrease in the ambient temperature so that the temperature of the switching element does not reach the heat resistance temperature of the switching element.

[0051] <Appendix 2> the circuit board has a current-carrying pattern to which the switching element is electrically connected, The inverter device according to <Supplementary Note 1>, wherein the correlation temperature sensor detects the temperature of the current conduction pattern.

[0052] <Appendix 3> the housing includes a boss to which the circuit board is fastened with a bolt, and a heat sink provided between the switching element and the coolant flow path and configured to transfer heat from the switching element to the boss, the circuit board has a heat transfer pattern provided between the boss and the correlation temperature sensor; The inverter device according to <Supplementary Note 1> or <Supplementary Note 2>, wherein the correlation temperature sensor detects the temperature of the heat sink via the boss and the heat transfer pattern.

[0053] <Appendix 4> The inverter device described in any one of <Appendix 1> to <Appendix 3>, characterized in that when the flow rate of the refrigerant is reduced multiple times, the control unit controls the threshold value so that the peak value of the correlation temperature is further away from the heat resistance temperature than the previous peak value of the correlation temperature. [Explanation of symbols]

[0054] 20... inverter device, 21... housing, 24... boss, 25... heat sink, 28... refrigerant flow path, 30... circuit board, 32... voltage, 34... current conduction pattern, 35... heat transfer pattern, 40... switching element, 50... control unit, 51... temperature sensor, 52... correlation temperature sensor, 53... ambient temperature sensor.

Claims

1. Housing and a circuit board accommodated within the housing; a switching element mounted on the circuit board; a control unit that controls a switching operation of the switching element; a temperature sensor mounted on the circuit board for detecting a temperature; a refrigerant flow path provided in the housing and through which a refrigerant for cooling the switching elements flows, The switching element does not have a function of detecting temperature, The temperature sensor a correlated temperature sensor for detecting a correlated temperature that correlates with the temperature of the switching element, and that increases as the flow rate of the coolant decreases and decreases as the flow rate of the coolant increases; an ambient temperature sensor for detecting an ambient temperature inside the housing, The control unit lowers the predetermined threshold value of the correlation temperature in accordance with a decrease in the ambient temperature so that the temperature of the switching element does not reach the heat resistance temperature of the switching element.

2. the circuit board has a current-carrying pattern to which the switching element is electrically connected, 2. The inverter device according to claim 1, wherein the correlation temperature sensor detects the temperature of the current conduction pattern.

3. the housing includes a boss to which the circuit board is fastened with a bolt, and a heat sink provided between the switching element and the coolant flow path and configured to transfer heat from the switching element to the boss, the circuit board has a heat transfer pattern provided between the boss and the correlation temperature sensor; 3. The inverter device according to claim 1, wherein the correlation temperature sensor detects the temperature of the heat sink via the boss and the heat transfer pattern.

4. 3. The inverter device according to claim 1, wherein the control unit controls the threshold value so that, when the flow rate of the refrigerant is reduced multiple times, the peak value of the correlation temperature is further away from the heat resistance temperature than the previous peak value of the correlation temperature.

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