Contactor system and contactor control method

Abstract

To achieve both inhibiting a contactor 6 from causing opening erroneous actuation due to a coil temperature rise and inhibiting cost increase, when closing the contactor 6.SOLUTION: A contactor system 1 comprises: a contactor 6 that is provided on a first power supply path 4 connecting a power supply 2 and a load 5 and has a normal-open type movable contact 13 for selectively turning on and off the first power supply path 4 and an electromagnetic coil 14 for driving the movable contact 13; a contactor drive circuit 15 that is electrically connected to the electromagnetic coil 14 and drives the contactor 6; a current sensor 19 for detecting drive current flowing from the contactor drive circuit 15 to the electromagnetic coil 14; and an ECU 10 for controlling the contactor drive circuit 15. The ECU 10 estimates a coil temperature of the electromagnetic coil 14 on the basis of a current detection value detected by the current sensor 19.SELECTED DRAWING: Figure 1

Description

[Technical Field]

[0001] The present invention relates to a contactor system and a contactor control method. [Background technology]

[0002] In recent years, efforts to realize a low-carbon or carbon-free society have become more active, and research and development into electrification technologies is being conducted in order to reduce CO2 emissions and improve energy efficiency in vehicles. In order to improve the driving performance of electric vehicles, it is important to provide a stable power supply from the power source to loads such as electric motors and inverters.

[0003] A contactor is provided in the power supply path to prevent excessive power from being supplied to the load if some abnormality occurs in the electric circuit, and a smoothing capacitor is provided in the power supply path to smooth the power supplied to the load.

[0004] For example, Patent Document 1 discloses a converter system in which a main contactor is provided in a power supply path from a battery to a DC / DC converter, which is a load, and a smoothing capacitor is connected in parallel to the load. This system includes a pre-charge contactor connected in parallel to the main contactor via a resistor, voltage sensors that detect the voltages of the battery and the capacitor, respectively, a current sensor that detects the current flowing from the battery to the load, and a control unit. The control unit controls pre-charging of the capacitor by opening and closing the pre-charge contactor, and also controls the opening and closing of the main contactor. The control unit determines that pre-charging is complete when the value detected by the current sensor is equal to or less than a threshold current. [Prior art documents] [Patent documents]

[0005] [Patent Document 1] Patent No. 7120072 Summary of the Invention [Problem to be solved by the invention]

[0006] However, with the above-mentioned conventional technology, when the contactor is in a closed state, an excessive rise in coil temperature can increase the coil resistance, causing an insufficient applied voltage, which can lead to a malfunction in which the contactor opens. While it is conceivable to provide a thermistor in the contactor to monitor the coil temperature and prevent the contactor from malfunctioning and opening, configuring the contactor system in this way would significantly increase the cost of the contactor system.

[0007] In view of the above background, the present invention aims to simultaneously prevent the contactor from malfunctioning and opening due to an increase in coil temperature when the contactor is closed, and to prevent an increase in the cost of the contactor system. [Means for solving the problem]

[0008] In order to solve the above-mentioned problems, one aspect of the present invention is a contactor system (1), comprising: a contactor (6) provided in a power supply path (4) connecting a power source (2) and a load (5), the contactor having a normally open movable contactor (13) for selectively connecting or disconnecting the power supply path and an electromagnetic coil (14) for driving the movable contactor; a contactor drive circuit (15) electrically connected to the electromagnetic coil and driving the contactor; a current sensor (19) for detecting a contactor drive current flowing from the contactor drive circuit to the electromagnetic coil; and a control device (10) for controlling the contactor drive circuit to apply a voltage to the electromagnetic coil to close the contactor and stop applying the voltage to the electromagnetic coil to open the contactor, and the control device is configured to estimate (ST6) a coil temperature (T) of the electromagnetic coil based on a current detection value detected by the current sensor.

[0009] According to this aspect, the control device estimates the coil temperature of the electromagnetic coil based on the current detection value detected by the current sensor, so that open malfunction of the contactor can be suppressed without providing a thermistor in the contactor.

[0010] In the above aspect, the control device may calculate the resistance of the electromagnetic coil based on the voltage applied to the electromagnetic coil and the detected current value, and estimate the coil temperature of the electromagnetic coil based on the resistance.

[0011] According to this aspect, the control device can accurately estimate the coil temperature of the electromagnetic coil based on the resistance of the coil.

[0012] In the above aspect, the control device may estimate the coil temperature by referring to a map showing a relationship between the resistance and the coil temperature.

[0013] According to this aspect, the control device can accurately estimate the coil temperature of the electromagnetic coil without performing complex calculations.

[0014] In the above aspect, if the coil temperature exceeds a preset first threshold temperature (Tth1) (ST15: Yes), the control device may increase the voltage applied to the electromagnetic coil (ST9).

[0015] According to this aspect, it is possible to suppress the contactor from malfunctioning and opening in response to an increase in the coil temperature while maintaining continuity in the power supply path.

[0016] In the above aspect, the control device may control the contactor drive circuit to stop applying the voltage to the electromagnetic coil (ST11) when the coil temperature exceeds a predetermined second threshold temperature (Tth2) (ST17: Yes).

[0017] According to this aspect, the contactor can be opened and the power supply path can be cut off before an open malfunction of the contactor occurs due to an increase in the coil temperature.

[0018] In the above aspect, the control device may control the contactor drive circuit to stop applying the voltage to the electromagnetic coil (ST11) when the coil temperature exceeds a second threshold temperature (Tth2) that is higher than the preset first threshold temperature (ST17: Yes).

[0019] According to this aspect, the electrical continuity of the power supply path is maintained while suppressing the contactor from malfunctioning to open in response to an increase in coil temperature, and when the coil temperature becomes higher, the power supply path is cut off to reliably prevent the contactor from malfunctioning to open.

[0020] Another aspect of the present invention for solving the above-mentioned problems is a contactor control method in a contactor system (1), the contactor system including: a contactor (6) provided in a power supply path (4) connecting a power source (2) and a load (5), the contactor having a normally open movable contact (13) for selectively conducting / cutting off the power supply path and an electromagnetic coil (14) for driving the movable contact; a contactor drive circuit (15) electrically connected to the electromagnetic coil for driving the contactor; and a current sensor (19) that detects a contactor drive current flowing through the electromagnetic coil. The contactor control method controls the contactor drive circuit so that a voltage is applied to the electromagnetic coil when the contactor is closed and the application of voltage to the electromagnetic coil is stopped when the contactor is opened, estimates a coil temperature (T) of the electromagnetic coil based on a current detection value detected by the current sensor (ST6), and controls the contactor drive circuit in accordance with the coil temperature (ST4, ST9, ST11).

[0021] According to this aspect, the control device estimates the coil temperature of the electromagnetic coil based on the current detection value detected by the current sensor, so that open malfunction of the contactor can be suppressed without providing a thermistor in the contactor.

[0022] In the above aspect, the contactor control method may control the contactor drive circuit so that, when the coil temperature exceeds a predetermined first threshold temperature (Tth1) (ST15: Yes), the applied voltage to the electromagnetic coil is increased (ST9).

[0023] According to this aspect, it is possible to suppress the contactor from malfunctioning and opening in response to an increase in the coil temperature while maintaining continuity in the power supply path.

[0024] In the above aspect, the contactor control method may control the contactor drive circuit so that, when the coil temperature exceeds a predetermined second threshold temperature (Tth2) (ST17: Yes), the application of voltage to the electromagnetic coil is stopped (ST11).

[0025] According to this aspect, the contactor can be opened and the power supply path can be cut off before an open malfunction of the contactor occurs due to an increase in the coil temperature.

[0026] In the above aspect, the contactor control method may control the contactor drive circuit so that, when the coil temperature exceeds a second threshold temperature (Tth2) that is higher than the preset first threshold temperature (ST17: Yes), the application of voltage to the electromagnetic coil is stopped (ST11).

[0027] According to this aspect, the electrical continuity of the power supply path is maintained while suppressing the contactor from malfunctioning to open in response to an increase in coil temperature, and when the coil temperature becomes higher, the power supply path is cut off to reliably prevent the contactor from malfunctioning to open. [Effects of the Invention]

[0028] According to the above aspect, when the contactor is closed, it is possible to prevent the contactor from malfunctioning and opening due to an increase in coil temperature. [Brief explanation of the drawings]

[0029] [Figure 1] FIG. 1 is a block diagram showing a functional configuration of a converter system including a contactor system according to an embodiment. [Figure 2] A map showing the correlation between coil resistance and coil temperature [Figure 3] Flow diagram showing the contactor control procedure by the ECU [Figure 4] FIG. 1 is a block diagram showing a functional configuration of a converter system according to a comparative example. DETAILED DESCRIPTION OF THE INVENTION

[0030] Hereinafter, a contactor system according to an embodiment of the present invention will be described in detail with reference to the drawings. The following embodiment will be described as an example in which the present invention is applied to an automobile. The automobile may be any of a hybrid car, a fuel cell car, an electric car, etc.

[0031] Fig. 1 is a block diagram showing the functional configuration of a converter system 1 including a contactor system according to an embodiment. As shown in Fig. 1, the converter system 1 includes a power source 2, a load 3, and a first power supply path 4 (4A, 4B) connecting the power source 2 and the load 3. A converter 5 is provided on the first power supply path 4, i.e., between the power source 2 and the load 3 on the first power supply path 4, and contactors 6 (6A, 6B) are provided on the first power supply path 4 between the converter 5 and the load 3. In other words, the converter system 1 can also be said to be a contactor system including a contactor 6.

[0032] The power supply 2 is configured by a power supply device mounted on the vehicle. The power supply device may be a battery fixed to the vehicle, a portable battery configured to be removable from the vehicle, a fuel cell, etc. The battery may be a lithium-ion battery, a nickel-metal hydride battery, etc. The power supply 2 is a DC power supply that outputs DC power and supplies the DC power to the converter 5.

[0033] The load 3 is, for example, a traction motor or inverter of an automobile. The traction motor may be an AC motor or a DC motor equipped with a permanent magnet. If the traction motor is an AC motor, the load 3 includes the traction motor and an inverter. The traction motor functions as a traction motor when the automobile is powered and as a generator when the automobile is braking.

[0034] The inverter may be configured as, for example, a three-phase bridge inverter. When the vehicle is powered, DC power is supplied to the inverter from the power source 2 via the converter 5. The inverter converts the DC power into three-phase AC power and supplies the AC power to the traction motor. When the traction motor is driven, the drive wheels are rotated and the vehicle moves.

[0035] The converter 5 is a DC / DC converter and includes an ECU 10 (Electronic Control Unit; an example of an electronic control device). In the converter 5, a capacitor for smoothing the output voltage is connected in parallel with the load 3. The ECU 10 controls the converter 5 to boost the DC power supplied from the power supply 2. The ECU 10 adjusts the output voltage to be applied to the load 3 to a desired value, thereby adjusting the drive current supplied to the load 3 via the first power supply path 4.

[0036] On the other hand, when braking while the vehicle is running, the inverter performs regenerative operation to cause the traction motor to function as a generator, converting AC power generated by the traction motor into DC power. The high-voltage DC power converted by the inverter is stepped down via converter 5 and supplied to power source 2. This charges power source 2. ECU 10 adjusts the charging voltage to be applied to power source 2 to a desired value, thereby adjusting the charging current supplied to power source 2.

[0037] The ECU 10 is a computer equipped with a processor (a processing unit such as a CPU or MPU) and a memory (a storage unit such as a ROM or RAM), and configured to execute various processes required for controlling the converter 5, etc. The ECU 10 is programmed so that the processor reads necessary data and software from the memory in accordance with execution commands from an external device such as an input device, and executes predetermined arithmetic processing in accordance with the software. The ECU 10 may be configured as a single piece of hardware, or may be configured as a unit consisting of multiple pieces of hardware.

[0038] The ECU 10 also includes a voltage detection circuit 11 that detects the voltage output from the converter 5 to the first power supply path 4. The first power supply path 4 is configured with a positive power line 4A and a negative power line 4B. The voltage detection circuit 11 is connected to the positive power line 4A and the negative power line 4B of the first power supply path 4.

[0039] The ECU 10 stores a preset overvoltage threshold. If the detection result of the voltage detection circuit 11 exceeds the overvoltage threshold while the converter 5 is operating, the ECU 10 determines that an abnormality has occurred in the voltage output from the converter 5 to the load 3, and stops the converter 5. However, there is a predetermined delay between the time when the output voltage of the converter 5 exceeds the overvoltage threshold and the time when the converter 5 actually stops.

[0040] The contactors 6 are electromagnetic contactors for selectively conducting or interrupting the first power supply path 4, and two contactors 6 (hereinafter referred to as a first contactor 6A and a second contactor 6B) are provided in this embodiment. The first contactor 6A is provided on the positive power line 4A of the first power supply path 4, and the second contactor 6B is provided on the negative power line 4B of the first power supply path 4. Each contactor 6 includes a movable contactor 13 (contact) that selectively switches between an open state and a closed state, and an electromagnetic coil 14 that drives the movable contactor 13. Each contactor 6 is a normally open electromagnetic contactor in which the movable contactor 13 is in an open state when the electromagnetic coil 14 is not energized, thereby interrupting the first power supply path 4, and the movable contactor 13 is in a closed state when the electromagnetic coil 14 is energized, thereby conducting the first power supply path 4.

[0041] If the contactor 6 is provided in the first power supply path 4, a failure may occur in which the contactor 6 is stuck in the closed state. In this embodiment, since the contactor 6 includes the first contactor 6A and the second contactor 6B, even if one of the contactors 6 is stuck in the closed state, it is possible to stop the power supply to the load 3 by opening the other contactor 6.

[0042] Each contactor 6 is controlled by an ECU 10 of the converter 5. The ECU 10 has a first contactor drive circuit 15A that controls the first contactor 6A and a second contactor drive circuit 15B that drives the second contactor 6B. The first contactor drive circuit 15A is electrically connected to the electromagnetic coil 14 of the first contactor 6A via a first contactor power supply path 17A. The second contactor drive circuit 15B is electrically connected to the electromagnetic coil 14 of the second contactor 6B via a second contactor power supply path 17B. Each contactor 6 drive circuit applies a voltage to the electromagnetic coil 14 of the corresponding contactor 6 and controls the contactor drive current flowing through the electromagnetic coil 14, thereby driving the moving contactor 13 to open and close.

[0043] The ECU 10 also includes a first current sensor 19A that detects the contactor drive current flowing through the first contactor drive circuit 15A and a second current sensor 19B that detects the contactor drive current flowing through the second contactor drive circuit 15B. The first contactor drive circuit 15A supplies the contactor drive current to the electromagnetic coil 14 and closes the first contactor 6A when the converter 5 is operating, and opens the first contactor 6A without supplying the contactor drive current to the electromagnetic coil 14 when the converter 5 is stopped. The second contactor drive circuit 15B supplies the contactor drive current to the electromagnetic coil 14 and closes the second contactor 6B when the converter 5 is operating, and opens the second contactor 6B without supplying the contactor drive current to the electromagnetic coil 14 when the converter 5 is stopped.

[0044] During startup, the ECU 10 estimates the coil temperature T of the electromagnetic coil 14 of the first contactor 6A based on the first current detection value detected by the first current sensor 19A. Also, during startup, the ECU 10 estimates the coil temperature T of the electromagnetic coil 14 of the second contactor 6B based on the second current detection value detected by the second current sensor 19B.

[0045] In this way, the ECU 10 estimates the coil temperature T of the corresponding electromagnetic coil 14 based on the current detection value detected by each current sensor 19, so that it is possible to suppress open malfunction of the contactor 6 without providing a thermistor in each contactor 6.

[0046] Specifically, the ECU 10 calculates the resistance of the electromagnetic coil 14 based on the voltage applied to the electromagnetic coil 14 by each contactor drive circuit 15 and the current detection value detected by the corresponding current sensor 19. The ECU 10 then estimates the coil temperature T of the electromagnetic coil 14 based on the calculated resistance of the electromagnetic coil 14. By the ECU 10 estimating the coil temperature T based on the resistance of the electromagnetic coil 14 in this manner, the coil temperature T of the electromagnetic coil 14 can be accurately estimated.

[0047] In this embodiment, the ECU 10 estimates the coil temperature T by referring to a map showing the relationship between the resistance of the electromagnetic coil 14 and the coil temperature T. FIG. 2 is a map showing the correlation between the resistance of the electromagnetic coil 14 and the coil temperature T. As shown in FIG. 2, there is a predetermined relationship between the resistance of the electromagnetic coil 14 and the coil temperature T. Therefore, a map such as that shown in FIG. 2, which is created in advance based on experimental results, is stored in the memory of the ECU 10. The memory of the ECU 10 may also store multiple maps corresponding to factors other than the resistance of the electromagnetic coil 14 that affect the coil temperature T, such as the outside air temperature and the coolant temperature. The ECU 10 derives the coil temperature T from the resistance of the electromagnetic coil 14 by referring to this map. By estimating the coil temperature T by referring to the map in this manner, the ECU 10 can accurately estimate the coil temperature T of the electromagnetic coil 14 without performing complex calculations.

[0048] The ECU 10 then controls the first contactor drive circuit 15A, the second contactor drive circuit 15B, and the converter 5 based on these estimated coil temperatures T.

[0049] Next, the procedure for contactor control performed by the ECU 10 will be described with reference to Fig. 3. Fig. 3 is a flow diagram showing the procedure for contactor control by the ECU 10. Note that in Fig. 3, processes indicating judgments are indicated by hexagonal preparation symbols instead of diamond-shaped judgment symbols.

[0050] When the ECU 10 is started, it repeatedly executes the process shown in Fig. 3 at a predetermined control cycle. Since the ECU 10 performs the same control on both the first contactor 6A and the second contactor 6B, the first and second contactors will not be distinguished from each other and will be described below as the contactor 6.

[0051] Upon startup, the ECU 10 first acquires a mode stored in memory (step ST1). The mode refers to a drive mode of the contactor 6 that the ECU 10 sets according to an estimated coil temperature T, as will be described later, and there are three modes: a normal mode, a high temperature mode, and a stop mode. The normal mode is set in memory as the initial mode to be acquired after startup.

[0052] The ECU 10 determines whether the acquired mode is the normal mode (step ST2). If the acquired mode is the normal mode (ST2: Yes), the ECU 10 determines whether there is a drive command (step ST3). The drive command is a drive command issued by the driver operating the accelerator pedal or a drive command from a device that controls automatic driving.

[0053] If there is a drive command in step ST3 (Yes), the ECU 10 controls the contactor drive circuit 15 to apply a normal voltage to the electromagnetic coil 14 in order to close the contactor 6 (step ST4). The normal voltage is a voltage that is preset as a voltage required to close the movable contactor 13 when the temperature of the electromagnetic coil 14 is within an appropriate range.

[0054] Furthermore, the ECU 10 drives the converter 5 in a normal operation mode to drive the load 3 (step ST5). The normal operation mode is an operation mode in a normal state for driving the load 3 so as to output a driving force according to a drive command.

[0055] Next, the ECU 10 estimates the coil temperature T of the electromagnetic coil 14 (step ST6). As described above, the ECU 10 calculates the resistance of the electromagnetic coil 14 based on the voltage applied to the electromagnetic coil 14 and the current detection value detected by the current sensor 19, and the coil temperature T is estimated based on the calculated resistance. If there is no drive command (No) in step ST3, the ECU 10 performs the process of step ST6 without performing the processes of steps ST4 and ST5.

[0056] In step ST2, if the acquired mode is not the normal mode (No), it is determined whether the acquired mode is the high temperature mode (step ST7). If the acquired mode is the high temperature mode (ST7: Yes), the ECU 10 determines whether there is a drive command (step ST8). If there is a drive command (ST8: Yes), the ECU 10 controls the contactor drive circuit 15 to apply a high voltage to the electromagnetic coil 14 in order to close the contactor 6 (step ST9). The high voltage is a voltage that is preset as a voltage required to maintain the movable contactor 13 in a closed state when the coil temperature T is within a predetermined high temperature range corresponding to the high temperature mode, and is a voltage that is higher than the normal voltage.

[0057] Furthermore, the ECU 10 drives the converter 5 in the limited operation mode to drive the load 3 (step ST10). The limited operation mode is a limited operation mode for driving the load 3 by limiting the driving force to a predetermined value regardless of the drive command. When driving the converter 5 in the limited operation mode, the ECU 10 presents a warning to the driver indicating that the load 3 is being driven in the limited operation mode. The warning may be, for example, a warning lamp displayed on the instrument panel, a warning display on a multi-information display (MID), a warning buzzer, audio guidance, or the like.

[0058] Thereafter, the ECU 10 performs the process of step ST6. If there is no drive command in step ST8 (No), the ECU 10 performs the process of step ST6 without performing the processes of steps ST9 and ST10.

[0059] In step ST7, if the acquired mode is not the high temperature mode (No), that is, if the acquired mode is the stop mode, the ECU 10 stops applying voltage to the electromagnetic coil 14 regardless of whether a drive command is present (step ST11). This closes the contactor 6. The stop mode is a mode set when the coil temperature T is higher than a predetermined high temperature range and the drive of the load 3 should be stopped. Furthermore, the ECU 10 stops the drive of the converter 5 to stop the load 3 (step ST12). Thereafter, the ECU 10 performs the process of step ST6.

[0060] After estimating the coil temperature T in step ST6, the ECU 10 determines whether the coil temperature T exceeds the reference threshold temperature Tth0 (step ST13). If the coil temperature T does not exceed the reference threshold temperature Tth0 (ST13: No), the ECU 10 sets the mode stored in the memory to the normal mode (step ST14) and ends this routine.

[0061] If the coil temperature T exceeds the reference threshold temperature Tth0 in step ST13 (Yes), the ECU 10 determines whether the coil temperature T exceeds a first threshold temperature Tth1 (step ST15). The first threshold temperature Tth1 is a preset temperature at which the normal mode should be switched to the high temperature mode when the coil temperature T is rising, and is higher than the reference threshold temperature Tth0.

[0062] In step ST15, if the coil temperature T does not exceed the first threshold temperature Tth1 (No), the ECU 10 determines whether the current mode acquired in step ST1 is the normal mode (step ST16). If the current mode is the normal mode (ST16: Yes), the ECU 10 performs the process of step ST14 and sets the mode stored in the memory to the normal mode.

[0063] In step ST15, if the coil temperature T exceeds the first threshold temperature Tth1 (ST15: Yes), the ECU 10 determines whether the coil temperature T exceeds a second threshold temperature Tth2 (step ST17). The second threshold temperature Tth2 is a temperature that is preset as a temperature at which the load 3 should be stopped, and is higher than the first threshold temperature Tth1.

[0064] In step ST17, if the coil temperature T does not exceed the second threshold temperature Tth2 (No), the ECU 10 sets the mode stored in the memory to the high temperature mode (step ST18) and ends this routine. Also, in step ST16, if the current mode is not the normal mode (ST16: No), that is, if the current mode is the high temperature mode, the ECU 10 performs the process of step ST18 and sets the mode stored in the memory to the high temperature mode.

[0065] That is, when the drive mode of the contactor 6 is the high temperature mode and the coil temperature T is decreasing, a reference threshold temperature Tth0 lower than the first threshold temperature Tth1 is set as the temperature for canceling the high temperature mode and switching to the normal mode. By providing hysteresis to the threshold for canceling the high temperature mode in this way, hunting of the contactor drive mode is prevented.

[0066] In step ST17, if the coil temperature T exceeds the second threshold temperature Tth2 (Yes), the ECU 10 sets the mode stored in the memory to the stop mode (step ST19) and ends this routine. In the routine following this routine, the mode set in step ST14, step ST18, or step ST19 is read in step ST1 and acquired by the ECU 10.

[0067] In this manner, the ECU 10 of the converter system 1 controls the contactor 6. The operation and effects of the converter system 1 configured in this manner will be described later.

[0068] Before describing the operation and effects of the converter system 1 according to the embodiment, the configuration and operation of the converter system 1 according to a comparative example will be described.

[0069] 4 is a block diagram showing the functional configuration of a converter system 101 according to a comparative example. Elements that are the same as or similar to those in the converter system 1 according to the embodiment are given the same reference numerals. Explanations that overlap with those of the first embodiment will be omitted.

[0070] As shown in Fig. 4, this converter system 101 differs from the converter system 1 according to the embodiment in that it does not include the first current sensor 19A and the second current sensor 19B (see Fig. 1), but is otherwise configured similarly. Because this converter system 101 does not include the first current sensor 19A and the second current sensor 19B, it cannot detect the currents of the first contactor drive circuit 15A and the second contactor drive circuit 15B. In other words, the ECU 10 of the converter system 101 cannot detect the contactor drive currents flowing from the first contactor drive circuit 15A and the second contactor drive circuit 15B to the electromagnetic coils 14 of the corresponding contactors 6.

[0071] Therefore, in this converter system 101, the ECU 10 cannot estimate the temperature of the electromagnetic coil 14 based on the detection results of the first current sensor 19A and the second current sensor 19B detected during operation of the converter 5. Therefore, when the temperature of the electromagnetic coil 14 rises and the resistance of the electromagnetic coil 14 increases, there is a possibility that an open malfunction will occur, in which the contactor 6 opens.

[0072] 1 is configured such that, in step ST6 of FIG. 3, the ECU 10 estimates the coil temperature T of the electromagnetic coil 14 based on the current detection value detected by the current sensor 19. Therefore, even if the contactor 6 is not provided with a thermistor, the ECU 10 can suppress the open malfunction of the contactor 6. Furthermore, since there is no need to provide a thermistor in the contactor 6, it is possible to suppress both an increase in the cost of the converter system 1 and the suppression of the open malfunction of the contactor 6.

[0073] If the coil temperature T exceeds the preset first threshold temperature Tth1 in step ST15 (Yes), the ECU 10 sets the high temperature mode in step ST18, thereby increasing the voltage applied to the electromagnetic coil 14 in step ST9. As a result, the conduction of the first power supply path 4 is maintained, and the open malfunction of the contactor 6 due to the increase in the coil temperature T is suppressed.

[0074] If the coil temperature T exceeds the preset second threshold temperature Tth2 in step ST17 (Yes), the ECU 10 sets the stop mode in step ST19, and stops the application of voltage to the electromagnetic coil 14 in step ST11. Therefore, before an open malfunction of the contactor 6 occurs in response to an increase in the coil temperature T, the contactor 6 is opened and the first power supply path 4 is interrupted.

[0075] Furthermore, the second threshold temperature Tth2 is set higher than the first threshold temperature Tth1. If the coil temperature T exceeds the second threshold temperature Tth2 in step ST17 (Yes), the ECU 10 stops applying voltage to the electromagnetic coil 14 in step ST11. Therefore, the conduction of the first power supply path 4 is maintained while suppressing the malfunction of opening of the contactor 6 in response to an increase in the coil temperature T, and when the coil temperature T becomes higher, the first power supply path 4 is cut off, thereby reliably preventing the malfunction of opening of the contactor 6.

[0076] Although the description of the specific embodiment has been completed above, the present invention is not limited to the above embodiment and its modifications, and can be widely modified and implemented. For example, in the above embodiment, the load 3 is a motor or inverter for a vehicle, but the load 3 may be a drive device other than a vehicle, a drive unit of a moving body other than a vehicle, industrial machinery, or other electrical equipment. Furthermore, only one of the first contactor 6A and the second contactor 6B may be provided as the contactor 6. In this case, the ECU 10 only needs to be equipped with one corresponding current sensor 19. Furthermore, the specific configuration, arrangement, and quantity of each member and part may be modified as appropriate within the scope of the present invention. Meanwhile, not all of the components shown in the above embodiment are necessarily required, and may be selected as appropriate. [Explanation of symbols]

[0077] 1: Converter system 2: Power supply 3: Load 4: First power supply path 4A: Positive power line 4B: Negative power line 5: Converter 6: Contactor 6A: First contactor 6B: Second contactor 10: ECU (control unit) 11: Voltage detection circuit 13: Movable contact (normally open terminal) 14: Electromagnetic coil 15A: First contactor drive circuit 15B: Second contactor drive circuit 17A: First contactor power supply path 17B: Second contactor power supply path 19: Current sensor 19A: First current sensor 19B: Second current sensor 101: Converter System

Claims

1. a contactor provided in a power supply path connecting a power source and a load, the contactor having a normally open movable contact for selectively connecting and disconnecting the power supply path and an electromagnetic coil for driving the movable contact; a contactor drive circuit electrically connected to the electromagnetic coil and configured to drive the contactor; a current sensor that detects a contactor drive current flowing from the contactor drive circuit to the electromagnetic coil; a control device that controls the contactor drive circuit to apply a voltage to the electromagnetic coil to close the contactor and to stop applying a voltage to the electromagnetic coil to open the contactor; The control device estimates the coil temperature of the electromagnetic coil based on the current detection value detected by the current sensor, and increases the voltage applied to the electromagnetic coil when the coil temperature exceeds a predetermined first threshold temperature.

2. The contactor system according to claim 1 , wherein the control device calculates a resistance of the electromagnetic coil based on the voltage applied to the electromagnetic coil and the current detection value, and estimates the coil temperature of the electromagnetic coil based on the resistance.

3. The contactor system according to claim 2 , wherein the control device estimates the coil temperature by referring to a map showing a relationship between the resistance and the coil temperature.

4. The contactor system according to any one of claims 1 to 3, wherein the control device controls the contactor drive circuit to stop applying the voltage to the electromagnetic coil when the coil temperature exceeds a preset second threshold temperature.

5. The contactor system according to any one of claims 1 to 3, wherein the control device controls the contactor drive circuit to stop applying the voltage to the electromagnetic coil when the coil temperature exceeds a second threshold temperature that is higher than the first threshold temperature that is set in advance.

6. A contactor control method in a contactor system, comprising: The contactor system comprises: a contactor provided in a power supply path connecting a power source and a load, the contactor having a normally open movable contact for selectively connecting and disconnecting the power supply path and an electromagnetic coil for driving the movable contact; a contactor drive circuit electrically connected to the electromagnetic coil and configured to drive the contactor; a current sensor that detects a contactor drive current flowing from the contactor drive circuit to the electromagnetic coil, controlling the contactor drive circuit so that a voltage is applied to the electromagnetic coil when the contactor is closed and the application of the voltage to the electromagnetic coil is stopped when the contactor is opened; estimating a coil temperature of the electromagnetic coil based on a current detection value detected by the current sensor; controlling the contactor drive circuit in response to the coil temperature; A contactor control method comprising: controlling the contactor drive circuit to increase a voltage applied to the electromagnetic coil when the coil temperature exceeds a preset first threshold temperature.

7. 7. The contactor control method according to claim 6, further comprising controlling the contactor drive circuit to stop applying the voltage to the electromagnetic coil when the coil temperature exceeds a second threshold temperature that is higher than the first threshold temperature.

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