Motor driving device estimating temperature of component

Abstract

This motor driving device comprises: a motor driving unit that supplies a current to a motor; a current detection unit that detects the value of the current supplied from the motor driving unit to the motor; an atmospheric pressure information input unit to which the value of atmospheric pressure outside the motor driving unit is input; an air temperature information input unit to which the value of air temperature outside the motor driving unit is input; a setting unit that sets the heat generation coefficient of a component of the motor driving unit and the time constant of the transfer function of a primary delay system in accordance with the value of atmospheric pressure; and a temperature estimation unit that calculates a temperature estimation value of the component on the basis of the value of the air temperature and a value obtained by multiplying the heat generation coefficient set by the setting unit, the value of the current detected by the current detection unit, and a transfer function having the time constant set by the setting unit.

Description

Motor drive device that estimates component temperatures

[0001] The present disclosure relates to a motor drive device that estimates the temperature of a component.

[0002] When a motor drive device is in operation, its internal components generate heat. Excessive temperature rises in the components can cause various malfunctions, so several technologies for monitoring the component temperatures have been proposed.

[0003] Japanese Patent Laid-Open No. 05-278935 Japanese Patent Laid-Open No. 2019-062596 Japanese Patent Laid-Open No. 2011-098625 Japanese Patent Laid-Open No. 03-261388 Japanese Patent Laid-Open No. 2007-037292 Japanese Patent Laid-Open No. 2013-219846

[0004] Depending on the installation environment of the motor drive device, the deviation between the actual temperature of the internal components and the estimated temperature may become large. Therefore, it is desirable to accurately estimate the temperatures of the components in the motor drive device.

[0005] According to one aspect of the present disclosure, a motor drive device includes a motor drive unit that supplies a current to the motor to drive the motor, a current detection unit that detects the value of the current supplied from the motor drive unit to the motor, an atmospheric pressure information input unit to which a value of the atmospheric pressure outside the motor drive unit is input, an air temperature information input unit to which a value of the air temperature outside the motor drive unit is input, a setting unit that sets a heat generation coefficient of a component of the motor drive unit and a time constant of a transfer function of a first-order lag system according to the value of the atmospheric pressure, and a temperature estimation unit that calculates an estimated temperature value of the component based on the value obtained by multiplying the heat generation coefficient set by the setting unit, the value of the current detected by the current detection unit, and the transfer function having the time constant set by the setting unit, and the value of the air temperature.

[0006] FIG. 1 is a block diagram showing a motor drive device according to a first embodiment of the present disclosure; FIG. 2 is a flowchart showing an operation flow of the motor drive device according to the first embodiment of the present disclosure; FIG. 3 is a flowchart showing an operation flow of a modified example of the motor drive device according to the first embodiment of the present disclosure; FIG. 4 is a block diagram showing a motor drive device according to a second embodiment of the present disclosure; FIG. 5 is a flowchart showing an operation flow of the motor drive device according to the second embodiment of the present disclosure; and FIG. 6 is a flowchart showing an operation flow of a modified example of the motor drive device according to the second embodiment of the present disclosure.

[0007] A motor drive device for estimating the temperature of a component according to an embodiment will be described below with reference to the drawings. In the following description, components having the same or similar functions are designated by the same reference numerals. Duplicate descriptions of these components may be omitted. The scale of the drawings has been adjusted appropriately to facilitate understanding. In the following description, the term "motor" refers to a motor that serves as a drive source for a machine (e.g., a robot or machine tool) in which the motor drive device is installed, and is driven by the motor drive device. Meanwhile, a "fan motor" refers to a motor that drives a cooling fan for cooling components within the motor drive device.

[0008] First Embodiment of the Present Disclosure FIG. 1 is a block diagram showing a motor drive device according to a first embodiment of the present disclosure.

[0009] A motor drive device 1 according to a first embodiment of the present disclosure drives a motor 2 for operating a machine (e.g., a robot or a machine tool) in which the motor drive device is installed. The motor drive device 1 includes a motor drive unit 11, a current detection unit 12, an atmospheric pressure information input unit 13, an air temperature information input unit 14, a setting unit 15, and a temperature estimation unit 16. The motor drive device 1 also includes an atmospheric pressure sensor 17 that detects the air pressure outside the motor drive unit 11, and a temperature sensor 18 that detects the air temperature outside the motor drive unit 11. Although not shown here, the motor drive device 1 also includes a power supply, measuring devices, input devices, display devices, cooling devices, and other circuits.

[0010] The motor drive unit 11 supplies a current to the motor 2 to drive the motor 2 .

[0011] The motor drive unit 11 may be one that includes an inverter, one that includes a rectifier, or one that includes an inverter and a rectifier integrated together.

[0012] The inverter in the motor drive unit 11 consists of a semiconductor switching element and a full-bridge circuit of diodes connected in anti-parallel to the element. A diode rectification type rectifier consists of a full-bridge circuit of diodes. A rectifier with a power regeneration function consists of a semiconductor switching element and a full-bridge circuit of diodes connected in anti-parallel to the element. The semiconductor switching elements and diodes that handle high voltages and large currents and are provided in the inverter and rectifier provided in the motor drive unit 11 are called power semiconductors. Examples of semiconductor switching elements include IGBTs, FETs, thyristors, GTOs, and transistors, but other semiconductor elements may also be used. Power semiconductors generate heat when they are conductive or operating.

[0013] A smoothing capacitor is provided between the rectifier and the inverter in the motor drive unit 11. The smoothing capacitor is installed to smooth the voltage after rectification by the rectifier, and generates heat when a current is supplied to the motor 2.

[0014] As described above, the motor drive unit 11 includes heat-generating components such as power semiconductors and smoothing capacitors. In each embodiment of the present disclosure, such heat-generating components are the targets of temperature estimation.

[0015] The current detection unit 12 detects the value of the current supplied from the motor drive unit 11 to the motor 2. Data relating to the current value detected by the current detection unit 12 is sent to the motor drive unit 11 and used to control the rotation of the motor 2. Data relating to the current value detected by the current detection unit 12 is also sent to the temperature estimation unit 16 and used in component temperature estimation processing.

[0016] An atmospheric pressure sensor 17 is connected to the atmospheric pressure information input unit 13. The atmospheric pressure value outside the motor drive unit 11 detected by the atmospheric pressure sensor 17 is input to the atmospheric pressure information input unit 13. The atmospheric pressure sensor 17 is provided outside the motor drive device 1. Alternatively, an operator may input the atmospheric pressure value to the atmospheric pressure information input unit 13 using an input device. Data relating to the atmospheric pressure value input to the atmospheric pressure information input unit 13 is sent to the setting unit 15.

[0017] A temperature sensor 18 is connected to the temperature information input unit 14. The value of the temperature outside the motor drive unit 11 detected by the temperature sensor 18 is input to the temperature information input unit 14. The temperature sensor 18 is provided outside the motor drive device 1. Alternatively, an operator may input the temperature value to the temperature information input unit 14 using an input device. Data related to the temperature value input to the temperature information input unit 14 is sent to the temperature estimation unit 16.

[0018] The setting unit 15 sets the heat generation coefficients of the components of the motor drive unit 11 and the time constant of the transfer function of the first-order lag system according to the value of the atmospheric pressure input to the atmospheric pressure information input unit 13. The heat generation coefficients of the components and the time constant of the transfer function of the first-order lag system are set for each component whose temperature is to be estimated. Therefore, if the component or atmospheric pressure value differs, the heat generation coefficients and the time constant of the transfer function of the first-order lag system may differ.

[0019] In general, the heat generation coefficient of a component tends to increase as the atmospheric pressure decreases. Furthermore, the time constant of the transfer function of the first-order lag system, which represents the change in heat, tends to increase as the atmospheric pressure decreases. Therefore, in the first embodiment of the present disclosure and the second embodiment described below, the setting unit 15 sets the heat generation coefficient to a larger value as the atmospheric pressure value input to the atmospheric pressure information input unit 13 decreases, and sets the time constant to a larger value as the atmospheric pressure value decreases. Data related to the heat generation coefficient of the component and the time constant of the transfer function of the first-order lag system, which are set by the setting unit 15, are sent to the temperature estimation unit 16.

[0020] The setting unit 15 may determine, for example, based on a predefined table or formula, the values ​​to which the heat generation coefficients of components and the time constants of the transfer functions of the first-order lag systems are set in response to the atmospheric pressure values ​​input to the atmospheric pressure information input unit 13. Such tables or formulas used in the setting process by the setting unit 15 should be prepared by conducting experiments or computer simulations before the motor drive device 1 is put into operation. For example, the actual heat generation coefficients and time constants at each of a plurality of atmospheric pressure values ​​are obtained through experiments or computer simulations. The results obtained through the experiments or computer simulations can be used to understand the tendency of how much the heat generation coefficients and time constants decrease with decreasing atmospheric pressure. Then, based on the results obtained through the experiments or computer simulations, a table or formula is created that indicates "how much the heat generation coefficients and time constants should be increased with decreasing atmospheric pressure." This table or formula indicates the relationship that "the lower the atmospheric pressure value, the larger the heat generation coefficients and time constants." The table specifies a one-to-one relationship between atmospheric pressure values ​​and heat generation coefficients and time constants. The formula is defined as a function of the heat generation coefficient relative to the atmospheric pressure value and a function of the time constant relative to the atmospheric pressure value. Linear approximation or the least squares method may be used to create the formula. The created table or formula is stored in memory so that it can be used in the setting process of the setting unit 15.

[0021] The setting unit 15 sets the heat generation coefficient of the components of the motor drive unit 11 and the time constant of the transfer function of the first-order lag system according to the value of atmospheric pressure input to the atmospheric pressure information input unit 13, by referring to a table showing the relationship that "the lower the atmospheric pressure value, the larger the heat generation coefficient and time constant" or according to a formula showing the relationship that "the lower the atmospheric pressure value, the larger the heat generation coefficient and time constant".

[0022] The temperature estimation unit 16 calculates an estimated component temperature value based on a value obtained by multiplying the heat generation coefficient set by the setting unit 15, the value of the current detected by the current detection unit 12, and a transfer function having a time constant set by the setting unit 15, and the air temperature value input to the air temperature information input unit 14. The estimated component temperature value is calculated for each component whose temperature is to be estimated. As such, in this embodiment, there is no need to provide a thermometer for each component to monitor the temperature of the component.

[0023] The current value I(t) detected by the current detection unit 12 is a variable that changes with time t. When the estimated component temperature value is Tc(t) and the air temperature value input to the air temperature information input unit 14 is Ta(t), the difference ΔT(t) between the estimated component temperature value Tc(t) and the air temperature is defined as shown in Equation 1.

[0024]

[0025] In the Laplace domain, ΔT(s) can be expressed as Equation 2, which is the value obtained by multiplying the heat generation coefficient K set by the setting unit 15, the current value I(s) detected by the current detection unit 12, and the transfer function G(s) of the first-order lag system.

[0026]

[0027] In Equation 2, I(s) is obtained by Laplace transforming I(t). The transfer function G(s) of the first-order lag system can be expressed by Equation 3. The time constant T uses a value set by the setting unit 15.

[0028]

[0029] By performing an inverse Laplace transform on ΔT(s) obtained by Equation 2, ΔT(t) can be obtained, which is the difference between the estimated temperature value Tc(t) in the time domain and the air temperature Ta(t). Then, by substituting the difference ΔT(t) and the air temperature value Ta(t) input to the air temperature information input unit 14 into Equation 1, the estimated temperature value Tc(t) of the part in the time domain can be obtained.

[0030] If the current supplied from the motor drive unit 11 to the motor 2 is a constant value that does not change over time, the estimated temperature of the component may be calculated based on Equation 4. In Equation 4, the estimated temperature of the component at time t is Tc, the temperature value input to the temperature information input unit 14 is Ta, the heat generation coefficient set by the setting unit 15 is K, and the time constant set by the setting unit 15 is T.

[0031]

[0032] Data relating to the estimated temperature values ​​of the components calculated by the temperature estimator 16 is sent to the motor driver 11 .

[0033] The motor drive unit 11 controls to stop the motor 2 when the estimated temperature value of the component calculated by the temperature estimator 16 exceeds a predetermined threshold. If the estimated temperature value of a component becomes relatively high, it can be said that the component is generating heat, and there is a high possibility of a malfunction occurring. Therefore, the motor drive unit 11 controls to stop the motor 2 when the estimated temperature value of the component calculated by the temperature estimator 16 exceeds a predetermined threshold. Examples of processing to stop the motor 2 by the motor drive unit 11 include processing to cut off the current supplied from the motor drive unit 11 to the motor 2, and processing to apply regenerative braking, dynamic braking, or mechanical braking to the motor 2 by the motor drive unit 11.

[0034] Furthermore, as a modification of the first embodiment of the present disclosure and the second embodiment described below, the motor drive unit 11 may control the current supplied to the motor 2 so as to decrease as the estimated component temperature calculated by the temperature estimator 16 increases. The motor drive unit 11 normally supplies a predetermined current to the motor 2. However, if the estimated component temperature increases to a certain extent, the component is likely to generate heat, increasing the likelihood of a malfunction. Therefore, in this modification, if the estimated component temperature calculated by the temperature estimator 16 exceeds a predetermined threshold, the motor drive unit 11 supplies a current smaller than the normal current supplied to the motor 2. In this case, the current is reduced as the estimated component temperature calculated by the temperature estimator 16 increases. This reduces the heat generated by the components inside the motor drive unit 11, thereby preventing overheating and malfunction of the components.

[0035] The threshold value used in the above-described processing by the motor drive unit 11 is set to, for example, a value several percent to several tens of percent lower than the heat resistance temperature of the component. Note that the numerical values ​​given here are merely examples, and other numerical values ​​may also be used. Note that the threshold value may be stored in a rewritable storage unit (not shown) and rewritable by an external device, which allows the threshold value to be changed to an appropriate value as needed even after it has been set.

[0036] The estimated temperature values ​​of the components calculated by temperature estimator 16 may be displayed on, for example, a display device (not shown). Examples of display devices include a standalone display device, a display device attached to motor drive device 1, a display device attached to a higher-level control device (e.g., a robot controller or a numerical control device) to which motor drive device 1 is connected, and a display device attached to a personal computer or a mobile terminal.

[0037] FIG. 2 is a flowchart showing the operation flow of the motor drive device according to the first embodiment of the present disclosure.

[0038] In a state in which the motor 2 is driven by a current being supplied from the motor drive unit 11 based on a predefined operation program, first, in step S101, the current detection unit 12 detects the value of the current being supplied from the motor drive unit 11 to the motor 2. Data relating to the current value detected by the current detection unit 12 is sent to the motor drive unit 11 and the temperature estimation unit 16.

[0039] In step S102, the value of the atmospheric pressure outside the motor drive unit 11, detected by the atmospheric pressure sensor 17, is input to the atmospheric pressure information input unit 13. The data relating to the atmospheric pressure value input to the atmospheric pressure information input unit 13 is sent to the setting unit 15.

[0040] In step S103, the value of the temperature outside the motor drive unit 11, detected by the temperature sensor 18, is input to the temperature information input unit 14. The data relating to the temperature value input to the temperature information input unit 14 is sent to the temperature estimation unit 16.

[0041] The order of the processes in steps S101 to S103 may be reversed, or two or all of the processes in steps S101 to S103 may be executed simultaneously.

[0042] In step S104, the setting unit 15 sets the heat generation coefficients of the components of the motor drive unit 11 and the time constant of the transfer function of the first-order lag system according to the value of atmospheric pressure input to the atmospheric pressure information input unit 13. The setting unit 15 sets the heat generation coefficient to a larger value the lower the value of atmospheric pressure input to the atmospheric pressure information input unit 13. The setting unit 15 also sets the time constant to a larger value the lower the value of atmospheric pressure input to the atmospheric pressure information input unit 13. Data related to the heat generation coefficients of the components and the time constant of the transfer function of the first-order lag system set by the setting unit 15 is sent to the temperature estimator 16.

[0043] In step S105, the temperature estimation unit 16 calculates an estimated component temperature value based on a value obtained by multiplying the heat generation coefficient set by the setting unit 15, the value of the current detected by the current detection unit 12, and a transfer function having a time constant set by the setting unit 15, and the air temperature value input to the air temperature information input unit 14. The estimated component temperature value is calculated for each component whose temperature is to be estimated. Data related to the estimated component temperature value calculated by the temperature estimation unit 16 is sent to the motor drive unit 11. Furthermore, the data related to the estimated component temperature value calculated by the temperature estimation unit 16 may be sent to a display device.

[0044] In step S106, the motor drive unit 11 determines whether the estimated temperature value of the component calculated by the temperature estimator 16 exceeds a predetermined threshold value.

[0045] If it is determined in step S106 that the estimated temperature value does not exceed the threshold value, in step S107, the motor drive unit 11 supplies a predetermined current to the motor 2 as usual, and then the process returns to step S101.

[0046] If it is determined in step S106 that the estimated temperature value exceeds the threshold value, then in step S108, the motor driving unit 11 performs processing to stop the motor 2. Thereafter, the processing ends.

[0047] The processes of steps S101 to S108 are repeatedly executed at predetermined intervals.

[0048] 3 is a flowchart showing an operation flow of a modified example of the motor drive device according to the first embodiment of the present disclosure. In this modified example, when the estimated temperature value of a component calculated by the temperature estimator 16 exceeds a predetermined threshold, the motor drive unit 11 performs control such that the current supplied to the motor 2 is reduced as the estimated temperature value increases.

[0049] Steps S201 to S206 correspond to steps S101 to S106 in FIG. 2, respectively.

[0050] In step S206, the motor drive unit 11 determines whether the estimated temperature value of the component calculated by the temperature estimator 16 exceeds a predetermined threshold value.

[0051] If it is determined in step S206 that the estimated temperature value does not exceed the threshold value, in step S207, the motor drive unit 11 supplies a predetermined current to the motor 2 as usual, and then the process returns to step S201.

[0052] If it is determined in step S206 that the estimated temperature value exceeds the threshold, then in step S208, the motor drive unit 11 causes a current smaller than the normal current to be supplied to the motor 2. Here, the motor drive unit 11 causes the current supplied from the motor drive unit 11 to the motor 2 to decrease as the estimated temperature value of the component calculated by the temperature estimator 16 increases. Thereafter, the process returns to step S201. The motor drive unit 11 continues to supply a current smaller than normal to the motor 2 until it is no longer determined in step S206 that the estimated temperature value has exceeded the threshold. However, if it is no longer determined in step S206 that the estimated temperature value has exceeded the threshold, the motor drive unit 11 returns to supplying the predetermined current to the motor 2 as normal.

[0053] Second Embodiment of the Present Disclosure FIG. 4 is a block diagram showing a motor drive device according to a second embodiment of the present disclosure.

[0054] The second embodiment of the present disclosure changes the rotation speed of the cooling fan 19 for cooling the component in accordance with the estimated temperature value of the component calculated by the temperature estimator 16 .

[0055] A motor drive device 1 according to a second embodiment of the present disclosure includes a motor drive unit 11, a current detection unit 12, an atmospheric pressure information input unit 13, an air temperature information input unit 14, a setting unit 15, a temperature estimation unit 16, a cooling fan 19, and a cooling fan control unit 20. The motor drive device 1 also includes an air pressure sensor 17 that detects the air pressure outside the motor drive unit 11, and a temperature sensor 18 that detects the air temperature outside the motor drive unit 11. Although not shown here, the motor drive device 1 also includes measuring devices, input devices, display devices, and other circuits.

[0056] The motor drive unit 11, current detection unit 12, atmospheric pressure information input unit 13, temperature information input unit 14, setting unit 15, temperature estimation unit 16, atmospheric pressure sensor 17, and temperature sensor 18 are as described with reference to Figure 1.

[0057] Data relating to the estimated temperature values ​​of the components calculated by the temperature estimator 16 is sent to the cooling fan controller 20 and the motor driver 11 .

[0058] The cooling fan 19 is provided to cool the heat-generating components and the heat sink to which the components are connected. A fan motor (not shown) is connected to the cooling fan 19, and the cooling fan 19 rotates in response to the rotation of the fan motor.

[0059] The cooling fan control unit 20 controls the rotation of the fan motor in accordance with the temperature estimated value calculated by the temperature estimator 16, thereby controlling the rotation of the cooling fan 19. The higher the estimated temperature value of a component calculated by the temperature estimator 16, the higher the rotation speed of the cooling fan 19 for cooling the component. The higher the rotation speed of the cooling fan 19, the greater the cooling effect on the component.

[0060] The cooling fan control unit 20 controls the rotation of the fan motor, for example, based on PI control or PID control, using a rotation speed command indicating the rotation speed at which the fan motor driving the cooling fan 19 should be rotated in response to an estimated component temperature value and the actual rotation speed of the fan motor. The cooling fan control unit 20 may determine, for example, the value of the rotation speed command set in response to the estimated component temperature value based on a predefined table or formula. Such a table or formula used in the rotation control process by the cooling fan control unit 20 should be prepared by conducting experiments or computer simulations before the motor drive device 1 is put into operation. For example, the actual temperatures (or temperature drop widths) of the components when the fan motor rotates the cooling fan 19 at multiple rotation speeds are obtained through experiments or computer simulations. The results obtained through experiments or computer simulations can be used to understand the trends in the rotation speed of the cooling fan 19 and the actual temperatures (or temperature drop widths) of the components at those times. Then, based on the results obtained by this experiment or computer simulation, a table or formula is created that indicates "at what rotation speed the fan motor that drives the cooling fan 19 should rotate in relation to the estimated temperature value of the component." The table or formula indicates the relationship that "the higher the estimated temperature value, the larger the rotation speed command." The table defines a one-to-one relationship between the estimated temperature value and the rotation speed command. The formula is defined as a function of the rotation speed command relative to the estimated temperature value. Note that linear approximation or the least squares method may be used when creating the formula. The created table or formula is stored in memory so that it can be used in the rotation control process in the cooling fan control unit 20.

[0061] FIG. 5 is a flowchart showing the operation flow of the motor drive device according to the second embodiment of the present disclosure.

[0062] In a state in which the motor 2 is driven by a current being supplied from the motor drive unit 11 based on a predefined operation program, first, in step S301, the current detection unit 12 detects the value of the current being supplied from the motor drive unit 11 to the motor 2. Data relating to the current value detected by the current detection unit 12 is sent to the motor drive unit 11 and the temperature estimation unit 16.

[0063] In step S302, the value of the atmospheric pressure outside the motor drive unit 11, detected by the atmospheric pressure sensor 17, is input to the atmospheric pressure information input unit 13. The data relating to the atmospheric pressure value input to the atmospheric pressure information input unit 13 is sent to the setting unit 15.

[0064] In step S303, the value of the temperature outside the motor drive unit 11, detected by the temperature sensor 18, is input to the temperature information input unit 14. The data relating to the temperature value input to the temperature information input unit 14 is sent to the temperature estimation unit 16.

[0065] Steps S301 to S303 may be executed in a reverse order, or two or all of steps S301 to S303 may be executed simultaneously.

[0066] In step S304, the setting unit 15 sets the heat generation coefficients of the components of the motor drive unit 11 and the time constant of the transfer function of the first-order lag system according to the value of atmospheric pressure input to the atmospheric pressure information input unit 13. The setting unit 15 sets the heat generation coefficient to a larger value the lower the value of atmospheric pressure input to the atmospheric pressure information input unit 13, and sets the time constant to a larger value the lower the value of atmospheric pressure. Data related to the heat generation coefficients of the components and the time constant of the transfer function of the first-order lag system set by the setting unit 15 is sent to the temperature estimating unit 16.

[0067] In step S305, the temperature estimation unit 16 calculates an estimated component temperature value based on a value obtained by multiplying the heat generation coefficient set by the setting unit 15, the value of the current detected by the current detection unit 12, and a transfer function having a time constant set by the setting unit 15, and the air temperature value input to the air temperature information input unit 14. The estimated component temperature value is calculated for each component whose temperature is to be estimated. Data related to the estimated component temperature value calculated by the temperature estimation unit 16 is sent to the motor drive unit 11 and the cooling fan control unit 20. The data related to the estimated component temperature value calculated by the temperature estimation unit 16 may also be sent to a display device.

[0068] In step S306, the cooling fan control unit 20 controls the rotation of the fan motor, thereby controlling the rotation of the cooling fan 19, in accordance with the estimated temperature value calculated by the temperature estimator 16. The higher the estimated temperature value calculated by the temperature estimator 16, the higher the rotation speed of the cooling fan control unit 20 causes the cooling fan 19 to rotate.

[0069] In step S307, the motor drive unit 11 determines whether the estimated temperature value of the component calculated by the temperature estimator 16 exceeds a predetermined threshold value.

[0070] If it is determined in step S307 that the estimated temperature value does not exceed the threshold value, in step S308, the motor drive unit 11 supplies a predetermined current to the motor 2 as usual, and then the process returns to step S301.

[0071] If it is determined in step S307 that the estimated temperature value exceeds the threshold value, in step S309, the motor driving unit 11 performs processing to stop the motor 2. Thereafter, the processing ends.

[0072] The processes of steps S301 to S309 are repeatedly executed at predetermined intervals.

[0073] 6 is a flowchart showing the operation flow of a modified example of the motor drive device according to the second embodiment of the present disclosure. In this modified example, when the estimated temperature value of a component calculated by the temperature estimator 16 exceeds a predetermined threshold, the motor drive unit 11 performs control such that the current supplied to the motor 2 is reduced as the estimated temperature value increases.

[0074] Steps S401 to S407 correspond to steps S301 to S307 in FIG. 5, respectively.

[0075] In step S407, the motor drive unit 11 determines whether the estimated temperature value of the component calculated by the temperature estimator 16 exceeds a predetermined threshold value.

[0076] If it is determined in step S407 that the estimated temperature value does not exceed the threshold value, in step S408, the motor drive unit 11 supplies a predetermined current to the motor 2 as usual, and then the process returns to step S401.

[0077] If it is determined in step S407 that the estimated temperature value exceeds the threshold, then in step S409, the motor drive unit 11 causes a current smaller than the normal current to be supplied to the motor 2. Here, the motor drive unit 11 causes the current supplied from the motor drive unit 11 to the motor 2 to decrease as the estimated component temperature value calculated by the temperature estimator 16 increases. Thereafter, the process returns to step S401. The motor drive unit 11 continues to supply a current smaller than normal to the motor 2 until it is no longer determined in step S407 that the estimated temperature value has exceeded the threshold. However, if it is no longer determined in step S407 that the estimated temperature value has exceeded the threshold, the motor drive unit 11 returns to supplying the predetermined current to the motor 2 as normal.

[0078] <Common Matters to the First and Second Embodiments of the Present Disclosure>

[0079] The motor drive device 1 includes at least one processor, which is an arithmetic processing device. Examples of the arithmetic processing device include an IC, an LSI, a CPU, an MPU, and a DSP. The arithmetic processing device is provided in a host control device or a mobile information terminal. The arithmetic processing device includes a control unit within the motor drive unit 11, a current detection unit 12, an atmospheric pressure information input unit 13, a temperature information input unit 14, a setting unit 15, a temperature estimation unit 16, a cooling fan control unit 20, and other processing units. Each of these units in the arithmetic processing device is a functional module implemented, for example, by a program executed on the processor. For example, if the control unit within the motor drive unit 11, the current detection unit 12, the atmospheric pressure information input unit 13, the temperature information input unit 14, the setting unit 15, the temperature estimation unit 16, the cooling fan control unit 20, and other processing units are implemented in a program format, the functions of each unit can be realized by operating the arithmetic processing device in accordance with the program. The programs for executing the processes in the control unit 11, current detection unit 12, atmospheric pressure information input unit 13, temperature information input unit 14, setting unit 15, temperature estimation unit 16, cooling fan control unit 20, and other processing units may be provided in the form of being recorded on a computer-readable recording medium such as a semiconductor memory, a magnetic recording medium, or an optical recording medium. Alternatively, the control unit 11, current detection unit 12, atmospheric pressure information input unit 13, temperature information input unit 14, setting unit 15, temperature estimation unit 16, cooling fan control unit 20, and other processing units may be realized as semiconductor integrated circuits into which programs for realizing the functions of each unit are written.

[0080] The motor drive device 1 also includes at least one memory serving as a storage device. The memory includes various storage units within the motor drive unit 11. Examples of the memory include electrically erasable and recordable nonvolatile memory such as EEPROM (registered trademark), or high-speed read / write random access memory such as DRAM or SRAM. The storage unit may also include a hard disk drive (HDD) or solid state drive (SSD). The memory stores programs for operating the control unit, current detection unit 12, atmospheric pressure information input unit 13, temperature information input unit 14, setting unit 15, temperature estimation unit 16, cooling fan control unit 20, and other processing units within the motor drive unit 11. The memory also stores tables or formulas indicating "how much the heat generation coefficient and time constant should be increased depending on the degree of atmospheric pressure drop," which are used in the setting process by the setting unit 15. The memory also stores the heat generation coefficients of the components and the time constant of the transfer function of the first-order lag system, which are set by the setting unit 15. The memory also stores temperature estimates calculated by temperature estimator 16. The memory also stores a table or formula indicating "at what rotation speed the fan motor that drives cooling fan 19 should be rotated in response to the estimated temperature value of the component." The memory also stores various programs and data related to motor drive device 1.

[0081] As described above, according to the first and second embodiments of the present disclosure (including their modified examples, the same applies hereinafter), the temperature of components can be accurately estimated in a motor drive device.

[0082] A motor drive device requires a mechanism for monitoring the temperature of components to protect them from overheating. Installing a thermometer for each component that requires overheating protection, as in the past, increases costs and increases the mounting area. In contrast, according to the first and second embodiments of the present disclosure, it is not necessary to install a thermometer for each component, which allows for reduced cost and size of the motor drive device.

[0083] Furthermore, the heat generation coefficient of a component tends to increase as the atmospheric pressure decreases. Furthermore, the time constant of the transfer function of a first-order lag system that represents changes in heat tends to increase as the atmospheric pressure decreases. According to the first and second embodiments of the present disclosure, the estimated temperature of a component inside the motor drive unit is calculated taking into account the atmospheric pressure outside the motor drive unit, so that the estimated temperature can be calculated to be closer to the actual temperature of the component.

[0084] Furthermore, depending on the altitude of the location where the motor drive device is installed, the atmospheric pressure of the motor drive device may differ significantly from the atmospheric pressure assumed at the time of manufacture of the motor drive device. For example, it is said that the heat generation coefficient and time constant of a component located at an altitude of 1,000 m are approximately 10% smaller than those of a component located at an altitude of 0 m. Furthermore, atmospheric pressure also varies significantly depending on the weather at the location where the motor drive device is installed. For example, the difference in atmospheric pressure between high pressure on a sunny day and low pressure during bad weather such as a typhoon is significant. According to the first and second embodiments of the present disclosure, a temperature estimate is calculated taking into account the atmospheric pressure outside the motor drive unit, thereby enabling a highly accurate temperature estimate to be obtained under any atmospheric pressure. Furthermore, according to the first and second embodiments of the present disclosure, a highly accurate temperature estimate can be obtained, thereby enabling more appropriate overheat protection processing for components and preventing component failure due to heat generation. Furthermore, according to the first and second embodiments of the present disclosure, a highly accurate temperature estimate can be obtained, thereby maximizing the driving performance of the motor drive device under any atmospheric pressure.

[0085] Although the present disclosure has been described in detail above, the present disclosure is not limited to the individual embodiments described above. Various additions, substitutions, modifications, partial deletions, etc. are possible in these embodiments without departing from the gist of the present disclosure or the spirit of the present disclosure derived from the content of the claims and their equivalents. These embodiments can also be implemented in combination. For example, in the above-described embodiments, the order of each operation and the order of each process are shown as examples and are not limited to these. The same applies when numerical values ​​or mathematical expressions are used in the description of the above-described embodiments.

[0086] <Supplementary Notes> The following supplementary notes are further disclosed regarding the above embodiment.

[0087] (Supplementary Note 1) A motor drive device 1 comprising: a motor drive unit 11 that supplies a current to motor 2 for driving motor 2; a current detection unit 12 that detects the value of the current supplied from motor drive unit 11 to motor 2; an atmospheric pressure information input unit 13 to which a value of atmospheric pressure outside motor drive unit 11 is input; an air temperature information input unit 14 to which a value of air temperature outside motor drive unit 11 is input; a setting unit 15 that sets a heat generation coefficient of a component of motor drive unit 11 and a time constant of a transfer function of a first-order lag system according to the value of atmospheric pressure; and a temperature estimation unit 16 that calculates an estimated temperature of the component based on the value of air temperature and a value obtained by multiplying the heat generation coefficient set by setting unit 15, the value of the current detected by current detection unit 12, and a transfer function having the time constant set by setting unit 15. (Supplementary Note 2) The motor drive device 1 according to Supplementary Note 1, wherein setting unit 15 sets the heat generation coefficient to a larger value the lower the value of atmospheric pressure, and sets the time constant to a larger value the lower the value of atmospheric pressure. (Supplementary Note 3) The motor drive device 1 according to Supplementary Note 1, further comprising a barometric pressure sensor 17 that detects the value of barometric pressure outside the motor drive unit 11, and the value of barometric pressure detected by the barometric pressure sensor 17 is input to the barometric pressure information input unit 13. (Supplementary Note 4) The motor drive device 1 according to Supplementary Note 1, further comprising a temperature sensor 18 that detects the value of air temperature outside the motor drive unit 11, and the value of air temperature detected by the temperature sensor 18 is input to the air temperature information input unit 14. (Supplementary Note 5) The motor drive device 1 according to any one of Supplements 1 to 4, further comprising: when the estimated temperature value exceeds a predetermined threshold, the motor drive unit 11 reduces the current supplied to the motor 2 the higher the estimated temperature value. (Supplementary Note 6) The motor drive device 1 according to any one of Supplements 1 to 4, further comprising: when the estimated temperature value exceeds a predetermined threshold, the motor drive unit 11 controls to stop the motor 2. (Appendix 7) The motor drive device 1 according to any one of Appendices 1 to 4, comprising: a cooling fan 19 for cooling components; and a cooling fan control unit 20 for controlling the rotation of the cooling fan 19, wherein the cooling fan control unit 20 rotates the cooling fan 19 at a higher rotation speed as the estimated temperature value is higher.

[0088] REFERENCE SIGNS LIST 1 Motor drive device 2 Motor 11 Motor drive section 12 Current detection section 13 Barometric pressure information input section 14 Air temperature information input section 15 Setting section 16 Temperature estimation section 17 Barometric pressure sensor 18 Temperature sensor 19 Cooling fan 20 Cooling fan control section

Claims

1. A motor drive device comprising: a motor drive unit that supplies a current to the motor for driving the motor; a current detection unit that detects the value of the current supplied from the motor drive unit to the motor; an atmospheric pressure information input unit to which a value of the atmospheric pressure outside the motor drive unit is input; an air temperature information input unit to which a value of the air temperature outside the motor drive unit is input; a setting unit that sets a heat coefficient of a component of the motor drive unit and a time constant of a transfer function of a first-order lag system in accordance with the value of the atmospheric pressure; and a temperature estimation unit that calculates an estimated temperature of the component based on the value obtained by multiplying the heat coefficient set by the setting unit, the value of the current detected by the current detection unit, and the transfer function having the time constant set by the setting unit, and the value of the air temperature.

2. The motor drive device according to claim 1, wherein the setting section sets the heat generation coefficient to a larger value as the atmospheric pressure value becomes lower, and sets the time constant to a larger value as the atmospheric pressure value becomes lower.

3. A motor drive device according to claim 1, further comprising an air pressure sensor for detecting an air pressure value outside the motor drive unit, the air pressure value detected by the air pressure sensor being input to the air pressure information input unit.

4. The motor drive device according to claim 1, further comprising a temperature sensor for detecting an air temperature outside the motor drive unit, the air temperature value detected by the temperature sensor being input to the air temperature information input unit.

5. A motor driving device according to any one of claims 1 to 4, wherein, when the estimated temperature value exceeds a predetermined threshold, the motor driving unit reduces the current supplied to the motor the higher the estimated temperature value is.

6. A motor drive device according to any one of claims 1 to 4, wherein the motor drive unit performs control to stop the motor when the estimated temperature value exceeds a predetermined threshold value.

7. A motor drive device as claimed in any one of claims 1 to 4, comprising: a cooling fan for cooling the component; and a cooling fan control unit that controls the rotation of the cooling fan, wherein the cooling fan control unit rotates the cooling fan at a higher rotation speed as the temperature estimate value becomes higher.

Images