JP2012205428A - Inverter device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an inverter device which can promptly discharge electric charges stored in a smoothing capacitor when discharge is required in the case where an abnormality occurs on a circuit.SOLUTION: An inverter device 20 includes: a smoothing capacitor 23 installed in a circuit 29 for electrically connecting a battery 10 with a converter 22 and connected in parallel to the battery 10; a first resistance 24 installed in the circuit 29; a second resistance 32 having a resistance value smaller than that of the first resistance 24 installed in the circuit 29; a capacitor voltage reading circuit 26 detecting a voltage value of the smoothing capacitor 23; and an inverter device control part 27 controlling the circuit 29 so that electric charges stored in the smoothing capacitor 23 are forcedly discharged to the second resistance 32 when a detection result by the capacitor voltage reading circuit 26 becomes a predetermined voltage value V or lower which is lower than a voltage value of the battery 10 required for traveling of an electric vehicle 1.

Description

  The present invention relates to an inverter device that controls electric power supplied to an electric motor.

About.

  In an electric vehicle or a hybrid electric vehicle, a battery device is connected to an electric motor via an inverter device. The inverter device changes the direct current supplied from the battery device to an alternating current and supplies it to the electric motor.

  The battery device includes a contactor capable of releasing electrical connection with the inverter device. When the main switch of the electric vehicle or the hybrid electric vehicle is turned off, the electrical connection between the battery device and the inverter device is released by turning off the contactor. In a state where the main switch is turned on, the contactor is turned on, and therefore the battery device and the inverter device are electrically connected.

  The inverter device includes a smoothing capacitor. Even when the contactor is turned off and the electrical connection between the battery device and the inverter device is released, a high voltage charge is stored in the smoothing capacitor. For this reason, the inverter device includes a forced discharge circuit for discharging the electric charge stored in the smoothing capacitor when the contactor is turned off.

  On the other hand, a technique for operating a forced discharge circuit when a vehicle collision is detected has been proposed (see, for example, Patent Document 1).

  However, the technique disclosed in Patent Document 1 is a technique for operating a forced discharge circuit when a collision is detected. For this reason, depending on the extent of the collision, it is conceivable that the communication line for transmitting information indicating the collision to the inverter device side is damaged. In this case, since the forced discharge circuit does not operate, a state where a high voltage charge is stored in the smoothing capacitor is maintained.

  For this reason, in the inverter device, a technique for always discharging the charge in the smoothing capacitor using a resistor has been proposed. By always discharging the charge in the smoothing capacitor using the resistance value, the charge in the smoothing capacitor can be discharged even when the forced discharge circuit does not operate.

JP 2010-193691 A

  However, when the resistor is always discharged, the electric charge is always discharged even when the electric vehicle is running, which causes a reduction in the capacity of the battery. Therefore, by increasing the resistance value of the resistor, The discharge speed is slow. For this reason, when the forced discharge circuit is not driven, the time until the charges of the smoothing capacitor are completely discharged becomes longer.

  An object of the present invention is to provide an inverter device that can quickly discharge the electric charge stored in a smoothing capacitor when an abnormality occurs on a circuit and should be discharged.

  An inverter device according to a first aspect of the present invention is an inverter device that converts a direct current supplied from a battery mounted on a vehicle into an alternating current by a converter and supplies the alternating current to an electric motor, the battery, the converter, And a capacitor connected in parallel with the battery, a first resistor provided in the circuit, and a second resistor having a resistance value smaller than that of the first resistor provided in the circuit. And the voltage detection means for detecting the voltage value of the capacitor, and when the detection result of the voltage detection means falls below a predetermined voltage value lower than the voltage value of the battery required for running the vehicle, Control means for controlling the circuit to forcibly discharge the generated charge to the second resistor.

  According to a second aspect of the present invention, there is provided the inverter device according to the first aspect, wherein the circuit further comprises a connection / disconnection means for connecting / disconnecting the electrical connection between the capacitor and the second resistor. Controls connection / disconnection switching of means.

  According to a third aspect of the present invention, there is provided an inverter device according to the first or second aspect, wherein the control means discharges the capacitor with only the first resistor, and the voltage of the capacitor over time. A map showing a drop in value is provided, and when the second resistor is forcibly discharged, the slope of the voltage drop of the capacitor is the same as the slope of the voltage drop when the predetermined voltage value in the map The charge stored in the capacitor is forcibly discharged to the second resistor.

  The inverter device according to a fourth aspect of the present invention is the inverter device according to any one of the first to third aspects, wherein the control means, the capacitor, and the first resistor, The second resistor is accommodated in one case.

  According to the present invention, it is possible to provide an inverter device that can quickly discharge the electric charge stored in the smoothing capacitor when an abnormality occurs on the circuit and should be discharged.

Schematic which shows an electric vehicle provided with the inverter apparatus of the 1st Embodiment of this invention. A change in the voltage value of the charge stored in the smoothing capacitor when the charge stored in the smoothing capacitor shown in FIG. 1 is discharged using only the first resistor, The graph which shows the change of the voltage value of the electric charge which the smoothing capacitor stores when it discharges using resistance of. The flowchart which shows operation | movement of the inverter apparatus shown by FIG. The graph which shows the change of the voltage value of the electric charge which the smoothing capacitor shown in FIG. 1 accumulates. Schematic which shows an electric vehicle provided with the inverter apparatus of the 2nd Embodiment of this invention. The map with which the control part for inverter apparatuses shown in FIG. 5 is provided. The flowchart which shows operation | movement of the inverter apparatus shown in FIG. The graph which shows the detection result of the capacitor voltage reading circuit which the control part for inverter apparatuses shown in FIG. 5 has recorded. The graph which shows the detection result of the capacitor voltage reading circuit which the control part for inverter apparatuses shown in FIG. 5 has recorded. The flowchart which shows operation | movement of the inverter apparatus which concerns on the 3rd Embodiment of this invention. The flowchart which shows operation | movement of the inverter apparatus which concerns on the other example of the 3rd Embodiment of this invention.

  An inverter device according to a first embodiment of the present invention will be described with reference to FIGS. FIG. 1 is a schematic diagram illustrating an electric vehicle 1 including the inverter device 20 of the present embodiment. As shown in FIG. 1, the electric vehicle 1 includes a pair of front wheels 2, a pair of rear wheels 3, an electric motor 4, a speed reducer 5, a battery 10, an inverter device 20, and a main control unit 40. I have. The electric vehicle 1 is an example of a vehicle referred to in the present invention.

  The electric motor 4 is electrically connected to the battery 10 via the inverter device 20. The electric motor 4 is rotated by electric power supplied from the battery 10. The speed reducer 5 is connected to the output shaft of the electric motor 4, and reduces the rotational speed of the output shaft of the electric motor 4 and transmits it to the rear wheel 3.

  The battery 10 includes a battery main body 11 configured by connecting a plurality of battery cells in series, and a contactor 12. The battery body 11 is electrically connected to the inverter device 20 through the contactor 12. The battery body 11 is a part that stores electric power in the battery 10. When the contactor 12 is in the on state, the electrical connection between the battery body 11 and the inverter device 20 is maintained. In the off state, the electrical connection between the battery body 11 and the inverter device 20 is released.

  The inverter device 20 includes a case 21, a converter 22, a smoothing capacitor 23, a first resistor 24, a forced discharge unit 25, a capacitor voltage reading circuit 26, an inverter device control unit 27, and a power supply 28. It has. Converter 22, smoothing capacitor 23, first resistor 24, forced discharge unit 25, capacitor voltage reading circuit 26, inverter device control unit 27, and power supply 28 are housed in case 21. Yes.

The converter 22 is formed by connecting a parallel circuit of a switching element 30 and a diode 31 in a three-phase bridge configuration. The diode 31 converts the direct current supplied from the battery 10 into an alternating current and supplies it to the electric motor 4.

  The smoothing capacitor 23 is connected in parallel to the converter 22 in a circuit 29 that electrically connects the battery 10 and the converter 22. The first resistor 24 is connected in parallel to the converter 22 in the circuit 29.

  The forced discharge unit 25 includes a second resistor 32, a switching element (connecting / disconnecting means) 33, and a forced discharge drive circuit 34. The second resistor 32 and the switching element 33 are connected in series with each other. A device in which the second resistor 32 and the switching element 33 are connected in series is connected in parallel to the converter 22 in the circuit 29.

  The forced discharge drive circuit 34 drives the switching element 33. When the switching element 33 is driven, the second resistor 32 is electrically connected to the circuit 29, and therefore current flows. When the switching element 33 is not driven, no current flows through the second resistor 32. The switching element 33 is an example of the connection / disconnection means referred to in the present invention.

  Here, the first resistor 24 and the second resistor 32 will be specifically described. The resistance value of the second resistor 32 is smaller than the resistance value of the first resistor 24. FIG. 2 shows the change in the voltage value of the charge stored in the smoothing capacitor 23 when the charge stored in the smoothing capacitor 23 is discharged using only the first resistor 24, and the charge stored in the smoothing capacitor 23. The graph shows the change in the voltage value of the charge stored in the smoothing capacitor 23 when discharged using the first and second resistors 24 and 32. In FIG. 2, reference numeral 70 is attached to a line indicating a change when only the first resistor 24 is used. Reference numeral 71 denotes a line indicating a change when the first and second resistors 24 and 32 are used.

  Further, the horizontal axis in FIG. 2 indicates the passage of time. The horizontal axis indicates that time elapses along the arrow x. The vertical axis represents the voltage value of the charge stored in the smoothing capacitor 23. The vertical axis indicates that the voltage value increases as it proceeds along the arrow y.

  As shown in FIG. 2, when the first and second resistors 24 and 32 are used, all charges stored in the smoothing capacitor 23 are discharged after time t1 from the start of discharge. That is, the voltage value becomes zero. In the case where only the first resistor 24 is used, all charges stored in the smoothing capacitor 23 are discharged after time t2 after the discharge is started. Time t2 is greater than time t1.

  As shown in FIG. 1, the capacitor voltage reading circuit 26 is connected to both ends of the smoothing capacitor 23 in the circuit 29 and detects the voltage value of the electric charge stored in the smoothing capacitor 23.

  The inverter device control unit 27 is connected to the converter 22, the forced discharge drive circuit 34, the capacitor voltage reading circuit 26, and the main control unit 40. The inverter device control unit 27 controls the converter 22 based on an output torque command output from the main control unit 40 described later, and controls the current supplied to the electric motor 4. Specifically, the inverter device control unit 27 is connected to each switching element 30 constituting the converter 22 and controls each switching element 30.

  When receiving the forced discharge command from the main control unit 40, the inverter device control unit 27 controls the forced discharge drive circuit 34 to drive the switching element 33 so that a current flows through the second resistor 32. The inverter device control unit 27 transmits the output result of the capacitor voltage reading circuit 26.

  Further, the inverter device control unit 27 drives the forced discharge drive circuit 34 when the voltage value of the electric charge stored in the smoothing capacitor 23 becomes equal to or lower than the predetermined value V. The predetermined value V mentioned here is an example of the predetermined value referred to in the present invention. In particular, it is preferable that the predetermined value V is a value lower than the voltage of the battery 10 required for traveling of the vehicle. As a result, the battery 10 and the smoothing capacitor 23 maintain a voltage of a predetermined value V or more during normal vehicle travel, and suitable discharge is possible without being accidentally forcibly discharged during normal vehicle travel. .

 The main control unit 40 performs overall control of the electric vehicle 1. One of the functions of the main control unit 40 is control of the output of the electric motor 4. The main control unit 40 issues an output torque command to the inverter device control unit 27 based on the detection result of the accelerator sensor 42 that detects the depression amount of the accelerator pedal 41. As described above, when receiving the output torque command from the main control unit 40, the inverter device control unit 27 converts the converter to control the current supplied to the electric motor 4 so as to output the torque corresponding to the command. 22 is controlled.

  Further, the main control unit 40 controls the operation of the contactor 12 of the battery 10. When the main switch of the electric vehicle 1 is turned on, the main control unit 40 sets the contactor 12 in a connected state so as to supply current from the battery 10 to the inverter device 20. When the main switch is off, the main control unit 40 places the contactor 12 in a disconnected state so that no current is supplied from the battery 10 to the inverter device 20.

  The state in which the main switch of the electric vehicle 1 is turned on is a state in which the electric vehicle 1 is operated to supply electric current to the electric motor 4 so that the electric vehicle 1 can run when the accelerator pedal 41 is depressed. . For example, the key is inserted into the key cylinder on the electric vehicle 1 side and further rotated to the on position. In the case of the push button type, the push button is pushed to travel. The state in which the main switch is turned off is a state in which the key is rotated to the off position in order to stop the supply of current to the electric motor 4. In the case of the push button type, the push button is pressed to stop the supply of current to the electric motor 4.

  Further, when the main switch is turned off, the main control unit 40 outputs a forced discharge command to the inverter device control unit 27. As described above, when receiving the forced discharge command from the main control unit 40, the inverter device control unit 27 drives and switches the forced discharge drive circuit 34 to forcibly discharge the charge stored in the smoothing capacitor 23. The element 33 is turned on so that a current flows through the second resistor 32.

  Next, an example of the operation of the inverter device 20 will be described. FIG. 3 is a flowchart showing an example of the operation of the inverter device 20. The inverter device control unit 27 is in an operable state when the main control unit 40 is in an operable state, and therefore can receive a signal from the main control unit 40. The main control unit 40 becomes operable when the electric system of the electric vehicle 1 is turned on. For this reason, the inverter device control unit 27 can operate even when the main switch is in the OFF state.

  First, an operation when a forced discharge command is received from the main control unit 40 will be described. In the electric vehicle 1, a direct current is supplied from the battery 10 to the inverter device 20 when the main switch is on and the vehicle is running. The main control unit 40 outputs an output torque command to the inverter device control unit 27 based on the output signal of the accelerator sensor 42. The inverter device control unit 27 controls the converter 22 based on the output torque command received from the main control unit 40.

  In step ST <b> 1, the inverter device control unit 27 determines whether a forced discharge command is received from the main control unit 40. If it is determined that the forced discharge command has not been received, the process proceeds to step ST2.

  In step ST2, the inverter device control unit 27 determines whether or not the voltage value of the electric charge stored in the smoothing capacitor 23 is equal to or less than a predetermined value V. When the contactor 12 is in the on state, the battery 10 and the inverter device 20 are electrically connected, so that a current is supplied to the smoothing capacitor 23. The smoothing capacitor 23 is always discharged by the first resistor 24. However, since the current is supplied from the battery 10 as described above, the voltage value of the electric charge stored in the smoothing capacitor 23 is always the voltage value of the battery 10. It becomes the same value. The inverter device control unit 27 determines that the voltage value of the charge stored in the smoothing capacitor 23 is not the predetermined value V. Then, the process returns to step ST1. When the contactor 12 is on, steps ST1 and ST2 are repeated.

  For example, when the driver turns off the main switch because the electric vehicle 1 arrives at the destination, the main control unit 40 turns off the contactor 12. As a result, the electrical connection between the battery body 11 and the inverter device 20 is released, so that no current is supplied from the battery body 11 to the smoothing capacitor 23. Further, the main control unit 40 outputs a forced discharge command to the inverter device control unit 27. When receiving the forced discharge command in step ST1, the inverter device control unit 27 proceeds to step ST3.

  In step ST <b> 3, the inverter device control unit 27 drives the forced discharge drive circuit 34. By driving the forced discharge drive circuit 34, the switching element 33 of the forced discharge unit 25 is turned on, and a current flows through the second resistor 32. When the current flows through the second resistor 32, the charge stored in the smoothing capacitor 23 is discharged by flowing through the first and second resistors 24 and 32. Then, the process proceeds to step ST4.

  In step ST4, the inverter device control unit 27 determines whether or not the voltage value of the charge stored in the smoothing capacitor 23 is zero. Specifically, the inverter device control unit 27 uses the detection value of the capacitor voltage reading circuit 26.

  As shown in FIG. 2, when discharging using the first and second resistors 24 and 32, all of the electric charge stored in the smoothing capacitor 23 is discharged after time t <b> 1 after the switching element 33 is turned on, Therefore, the voltage value becomes zero. Until the voltage value of the electric charge stored in the smoothing capacitor 23 becomes zero, the operations of steps ST3 and ST4 are repeated. When the voltage value of the charge stored in the smoothing capacitor 23 becomes zero, the process proceeds from step ST4 to step ST5.

  In step ST5, the inverter device control unit 27 stops the driving of the forced discharge driving circuit 34 and stops its operation.

  Next, an operation when the voltage value of the electric charge stored in the smoothing capacitor 23 becomes a predetermined value V or less in a state where the forced discharge command from the main control unit 40 has not been received will be described. For example, this operation is performed when, for example, the electric vehicle 1 collides with a wall or the like and the circuit for connecting the battery 10 and the inverter device 20 is disconnected, or the main control unit 40 and the inverter device control unit 27 are connected. This is performed with the signal line 50 to be cut off. When the signal line 50 is disconnected, the inverter device control unit 27 cannot receive the forced discharge command output from the main control unit 40. For this reason, the inverter device control unit 27 repeats the operations of steps ST1 and ST2.

  Normally, when the signal line 50 is disconnected, the contactor 12 is turned off. As a result, the supply of current to the smoothing capacitor 23 is stopped. Furthermore, the electric charge stored in the smoothing capacitor 23 is discharged by the first resistor 24. As a result, the voltage value of the charge stored in the smoothing capacitor 23 gradually decreases.

  When detecting that the voltage value of the electric charge stored in the smoothing capacitor 23 has reached the predetermined value V in step ST2, the inverter device control unit 27 is in a state where no current is supplied from the battery 10 and is forcibly discharged. It is determined that it is in a state. Then, the process proceeds to step ST3. By proceeding to step ST3, forced discharge is performed.

  FIG. 4 shows a change in the voltage value of the charge stored in the smoothing capacitor 23 due to the above operation. In FIG. 4, reference numeral 73 is attached to a line indicating a change in voltage value. The horizontal axis of FIG. 4 shows the passage of time as in FIG. The vertical axis indicates the voltage value of the charge provided in the smoothing capacitor 23 as in FIG.

  As shown in FIG. 4, after the contactor 12 is turned off, the process proceeds to step ST3 after the time t3 has elapsed and forced discharge is started. Until the time t <b> 3 elapses after the contactor 12 is turned off, the charge stored in the smoothing capacitor 23 is discharged using only the first resistor 24. After the elapse of time t3, the electric charge stored in the smoothing capacitor 23 is discharged using the first and second resistors 24 and 32.

  And the voltage value of the electric charge which the smoothing capacitor 23 stores becomes zero after the time t4 after the contactor 12 is turned off. Time t4 is smaller than time t2.

  In the inverter device 20 configured as described above, even when the forced discharge command cannot be received from the main control unit 40, the voltage value of the charge stored in the smoothing capacitor 23 is compared with the predetermined value V, and the smoothing capacitor 23 Since the forced discharge is performed when the voltage value of the stored charge is equal to or lower than the predetermined value, the charge stored in the smoothing capacitor 23 is quickly discharged. In other words, the charge stored in the smoothing capacitor can be discharged quickly when it should be discharged.

  In the inverter device 20, a power source 28 for operating the inverter device control unit 27 and an electric wire 51 that supplies power from the power source 28 to the inverter device control unit 27 are accommodated in the case 21. For this reason, even if the electric vehicle 1 crashes and the signal line 50 is disconnected as described above, the power supply to the inverter device control unit 27 is stopped by the case 21. Therefore, it becomes difficult for the forced discharge drive circuit 34 to be driven. For this reason, it can suppress that it becomes impossible to discharge the electric charge of the smoothing capacitor 23 rapidly.

  Further, the predetermined value V is set to a voltage lower than the voltage of the battery 10 required for traveling of the vehicle. For this reason, in the state where the contactor 12 is turned on, in other words, when the electric vehicle 1 is running, the voltage value of the electric charge stored in the smoothing capacitor 23 does not become the predetermined value V or less.

  For this reason, the forced discharge drive circuit 34 is not driven when it is not time for forced discharge, such as during travel of the electric vehicle 1.

  Next, an inverter device according to a second embodiment of the present invention will be described with reference to FIGS. In addition, the structure which has the same function as 1st Embodiment attaches | subjects the code | symbol same as 1st Embodiment, and abbreviate | omits description.

  In the present embodiment, an inverter device control unit 60 is used instead of the inverter device control unit 27. Except for the inverter device control unit 60, the second embodiment is the same as the first embodiment. The different points will be specifically described. The inverter device is denoted by reference numeral 20a. As described above, the inverter device 20a of the present embodiment is the same as the inverter device 20 of the first embodiment except for the inverter device control unit 60. The configuration of the electric vehicle 1 is the same as that of the first embodiment.

  FIG. 5 is a schematic diagram showing an electric vehicle 1 including the inverter device 20a of the present embodiment. The inverter device control unit 60 is connected to the converter 22, the forced discharge drive circuit 34, the capacitor voltage reading circuit 26, and the main control unit 40 in the same manner as the inverter device control unit 27 of the first embodiment. Has been.

  The inverter device controller 60 controls the converter 22 based on a command from the main controller 40 and controls the current supplied to the electric motor 4. Specifically, the inverter device control unit 60 is connected to each switching element 30 constituting the converter 22 and controls each switching element 30.

  When receiving the forced discharge command from the main control unit 40, the inverter device control unit 60 controls the forced discharge drive circuit 34 to drive the switching element 33 so that a current flows through the second resistor 32. The inverter device controller 60 transmits the detection result from the capacitor voltage reading circuit 26.

  Further, the inverter device control unit 60 always detects the voltage value of the charge stored in the smoothing capacitor 23, and always calculates the slope of the change in the voltage value. Here, the slope of the change in the voltage value is a value obtained by differentiating the detection result detected by the capacitor voltage reading circuit 26 with respect to time.

  As shown in FIG. 5, the inverter device control unit 60 includes a map group 61. FIG. 6 shows a map 62 that is a part of the map group 61. The map 62 shows the change in the voltage value of the charge stored in the smoothing capacitor 23 when the charge stored in the smoothing capacitor 23 is discharged using only the first resistor 24 when the contactor 12 is in the OFF state. The horizontal and vertical axes in FIG. 6 are the same as those in FIG. In FIG. 6, reference numeral 74 is attached to a line indicating a change in voltage value.

  In FIG. 6, the voltage value of the charge provided in the smoothing capacitor 23 when the time is zero is the same value as the voltage value of the battery 10 when the contactor 12 is turned off. The voltage value of the battery 10 when the contactor 12 is turned off changes according to the SOC and the deterioration of the battery 10.

  The map group 61 is a set of maps indicating changes in the voltage value of the electric charge stored in the smoothing capacitor 23 with respect to various voltage values of the battery 10 when the contactor 12 is turned off. The various voltages mentioned here are values that the battery 10 can take. A map 62 shown in FIG. 6 is a part of the map group 61 described above. In other words, the map group 61 is a set of maps at the various voltage values shown as a map 62.

  Further, the inverter device control unit 60 includes information on the slope of the voltage drop indicated by each map of the map group 61. The information on the slope of the voltage drop is a value obtained by differentiating the voltage drop indicated by each map of the map group 61 with respect to time. More specifically, it is the slope of the line indicating the voltage change indicated by the map.

  Even when the inverter device control unit 60 does not receive the forced discharge command from the main control unit 40, the voltage value of the charge stored in the smoothing capacitor 23 is equal to or lower than the predetermined value V and becomes the predetermined value V. When the slope of the voltage drop is the same as the slope at the predetermined value V of each map of the map group 61, the forced discharge drive circuit 34 is driven.

  Next, the operation of the inverter device 20a will be described. FIG. 7 is a flowchart showing the operation of the inverter device 20a. The inverter device 20a further includes a step ST10 in addition to the operation of the inverter device 20 of the first embodiment. The operation in other steps is the same as that in the first embodiment.

  An operation when the voltage value of the electric charge stored in the smoothing capacitor 23 becomes a predetermined value V or less in a state where the forced discharge command from the main control unit 40 has not been received will be described. First, an operation in the case where the voltage value of the electric charge stored in the smoothing capacitor 23 instantaneously becomes a predetermined value V or less by suddenly depressing the accelerator pedal 41 to rapidly accelerate the electric vehicle 1 will be described.

  In this case, the inverter device control unit 60 determines that the detection result of the capacitor voltage reading circuit 26 is equal to or less than the predetermined value V, and proceeds to step ST10. In step ST10, the inverter device control unit 60 matches any one of the gradients when the detection result of the capacitor voltage reading circuit 26 is a predetermined voltage value of all the maps included in the inverter device control unit 60. It is determined whether or not.

  FIG. 8 shows the detection result of the capacitor voltage reading circuit 26 recorded by the inverter device controller 60. The horizontal and vertical axes are the same as in FIG. As shown in FIG. 8, in this operation, the voltage value of the electric charge stored in the smoothing capacitor 23 is drastically decreased due to the rapid depression of the accelerator pedal 41.

  In step ST10, the inverter device control unit 60 calculates the slope of the voltage change when the voltage value stored in the smoothing capacitor 23 becomes the predetermined value V. In FIG. 8, reference numeral 63 is attached to a line indicating a change in the voltage value of the charge stored in the smoothing capacitor 23. The inclination detected in step ST10 is the inclination of the line 63 at the predetermined voltage value. A line indicating the inclination is indicated by 64.

  A change in the voltage value of the smoothing capacitor 23 due to a sudden depression of the accelerator pedal 41 occurs abruptly. For this reason, the inclination of the line 64 is steep as shown in FIG. The voltage drop due to the first resistor 24 is more gradual than the voltage change of the smoothing capacitor 23 caused by the sudden depression of the accelerator pedal 41. In other words, the resistance value of the first resistor 24 is set so that the voltage drop due to the discharge using only the first resistor 24 is more gradual than the voltage drop of the smoothing capacitor 23 caused by the rapid accelerator pedal 41. ing. A change in voltage caused by a sudden depression of the accelerator pedal 41 can be obtained by experiments.

  Then, the inverter device control unit 60 is configured such that the slope of the voltage change at the predetermined voltage value of the smoothing capacitor 23 is the voltage at the predetermined voltage value of a plurality of maps included in all the map groups 61 included in the inverter device control unit 60. It is determined whether it is the same as any one of the slopes of the change.

  The inverter device control unit 60 determines that the slope 64 at the predetermined voltage value obtained from FIG. 8 does not match the slope at the predetermined voltage value of the plurality of maps included in the map group 61. Then, the process returns to step ST1.

  Note that the drop in the voltage value of the smoothing capacitor 23 due to the sudden depression of the accelerator pedal 41 returns immediately. For this reason, as indicated by a two-dot chain line in FIG. 8, the voltage value of the smoothing capacitor 23 returns to the voltage value of the battery 10 immediately after it becomes equal to or less than the predetermined value V.

  Next, in a state where the forced discharge command from the main control unit 40 is not received, the contactor 12 is turned off, and the electric charge stored in the smoothing capacitor 23 is discharged only by the first resistor 24, so that the smoothing capacitor 23 The operation when the voltage value drops to a predetermined voltage will be described.

  FIG. 9 shows the voltage value of the smoothing capacitor 23 in this operation, that is, the detection result of the capacitor voltage reading circuit 26. The horizontal and vertical axes in FIG. 9 are the same as those in FIG. As shown in FIG. 9, the voltage value of the smoothing capacitor 23 gradually decreases after the contactor 12 is turned off.

  In step ST10, the inverter device controller 60 calculates the slope of the voltage change when the result of the capacitor reading circuit 26 reaches the predetermined value V. In FIG. 9, reference numeral 65 is attached to a line indicating the detection result of the capacitor reading circuit 26. Reference numeral 66 is given to a line indicating the inclination of the line 65 when the predetermined value V is reached.

  The inverter device control unit 60 determines whether or not the slope indicated by the reference numeral 66 is the same as any one of slopes at a predetermined voltage value of a plurality of maps included in the map group 61. The slope of the line 65 at the predetermined value V is the same as the slope of the predetermined value V of the map 62 shown in FIG. In FIG. 6, a line 67 indicating the slope at the predetermined value is enlarged and shown in the range F9. Then, the process proceeds to step ST3.

  In the present embodiment, the inverter device control unit 60 calculates the slope of the change in the voltage value of the smoothing capacitor 23, and the calculation result is the same as the slope when the map group 61 has a predetermined value of a plurality of maps. It is determined whether or not. If the determination results are the same, it is determined that it is time to forcibly discharge, and the forced discharge drive circuit 34 is driven. For this reason, in addition to the effect of the first embodiment, it is possible to determine with high accuracy whether or not it is time for forced discharge.

  Moreover, it can determine early that it is the state which should be forced-discharged. This point will be specifically described. In the present embodiment, the predetermined value V is set to a value smaller than the voltage of the battery 10 required for traveling of the vehicle in order to prevent the forced discharge drive circuit 34 from malfunctioning. For this reason, the predetermined voltage value is a relatively small value. However, as in this embodiment, since the determination is based on the slope of the voltage change, even if the predetermined voltage value is set to a large value, in other words, even if the voltage is higher than the voltage of the battery 10 required for traveling of the vehicle. When to discharge can be determined with high accuracy. For this reason, the time when forced discharge should be performed can be determined early.

  Next, an inverter device according to a third embodiment of the present invention will be described with reference to FIG. In addition, the structure which has the same function as 1st Embodiment attaches | subjects the code | symbol same as 1st Embodiment, and abbreviate | omits description. In the present embodiment, the operation of the inverter device control unit is different from that of the first embodiment. Specifically, it is different in that it further includes steps ST12, ST13, ST14, and ST15. Other operations of the inverter device control unit are the same as those in the first embodiment. For this reason, in this embodiment, the same code | symbol 27 as 1st Embodiment is attached | subjected to the control part for inverter apparatuses. Moreover, the structure of the electric vehicle 1 other than the inverter device control unit 27 in the inverter device 20 is the same as that of the first embodiment. The different points will be described.

  FIG. 10 is a flowchart showing the operation of the inverter device 20 of the present embodiment. As shown in FIG. 10, the inverter device 20 of the present embodiment further includes steps ST12, ST13, ST14 in addition to the operations shown in FIG. Other operations are the same as those in FIG.

  If the inverter device controller 27 determines in step ST2 that the voltage value of the smoothing capacitor 23 is equal to or less than the predetermined value V, the control unit 27 then proceeds to step ST12. The operation in step ST12 is the same as that in step ST3. In step ST12, the inverter device control unit 27 drives the forced discharge drive circuit 34. Then, the process proceeds to step ST13.

  Step ST13 is the same as step ST2. Based on the detection result of the capacitor voltage reading circuit 26, the inverter device control unit 27 determines whether or not the voltage value of the smoothing capacitor 23 is equal to or less than a predetermined value V. If it is equal to or less than the predetermined value V, the process proceeds to step ST14.

  The operation in step ST14 is the same as that in step ST4. In step ST14, the inverter device control unit 27 determines whether or not the voltage value of the smoothing capacitor 23 is zero based on the detection result of the capacitor voltage reading circuit 26. If the voltage value of the smoothing capacitor 23 is not zero, the process returns to step ST12. If the voltage value of the smoothing capacitor 23 is zero, the process proceeds to step ST5.

  If the voltage value of the smoothing capacitor 23 temporarily becomes lower than the predetermined value V due to the sudden depression of the accelerator pedal 41 or the like, the voltage value of the smoothing capacitor 23 will be Return to the voltage value of 10. When the voltage value of the smoothing capacitor 23 starts to return to the voltage value of the battery 10 and becomes larger than the predetermined value V, in step ST13, it is determined that the voltage value of the smoothing capacitor 23 is not less than the predetermined value V, and the process proceeds to step ST15.

  In step ST15, the inverter device control unit 27 stops driving the forced discharge drive circuit 34. When the process in step ST15 is completed, the process returns to step ST1.

  In the present embodiment, in addition to the effects of the first embodiment, it is possible to determine with high accuracy whether or not it is time for forced discharge.

  Note that the operation steps of steps ST12, ST13, ST14, and ST15 described in the present embodiment may be included in the inverter device controller 60 of the second embodiment. FIG. 11 is a flowchart showing the operation when the inverter device control unit 60 of the second embodiment further includes the operation steps of steps ST12, ST13, ST14, and ST15. As shown in FIG. 11, in this case, when it is determined in step ST10 that the slope of the voltage drop is the same as the slope of the voltage drop on the map, the process proceeds to step ST12. In this case, in addition to the effect of the second embodiment, it can be determined with high accuracy whether or not forced discharge is to be performed.

  In the first and second embodiments, as an example of the predetermined value V, the voltage value is lower than the voltage of the battery 10 required for traveling of the vehicle. However, the predetermined value is a value that can be arbitrarily set. Another value may be set as the predetermined value.

  In the first and second embodiments, the inverter devices 20 and 20 a are mounted on the electric vehicle 1. The electric vehicle 1 does not include a drive source such as an engine other than the electric motor 4. Inverter devices 20 and 20a may be mounted on a hybrid electric vehicle including other drive units such as an engine in addition to electric motor 4.

  The present invention is not limited to the above-described embodiments as they are, and can be embodied by modifying the constituent elements without departing from the scope of the invention in the implementation stage. Various inventions can be formed by appropriately combining a plurality of constituent elements disclosed in the above-described embodiments. For example, you may delete some components from all the components shown by embodiment mentioned above. Furthermore, you may combine the component covering different embodiment suitably.

  DESCRIPTION OF SYMBOLS 1 ... Electric vehicle (vehicle), 10 ... Battery, 4 ... Electric motor (electric motor), 20 ... Inverter apparatus, 21 ... Case, 22 ... Converter, 23 ... Smoothing capacitor (capacitor), 24 ... First resistance, 26 ... Capacitor voltage reading circuit (voltage detection means), 27 ... Inverter device control unit (control means), 29 ... Circuit, 32 ... Second resistor, 33 ... Switching element (connection / disconnection means), 60 ... Inverter device control Part (control means), 61 ... map group, 62 ... map, V ... predetermined voltage value.

Claims (4)

An inverter device that converts a direct current supplied from a battery mounted on a vehicle into an alternating current by a converter and supplies the alternating current to an electric motor,
A capacitor provided in a circuit for electrically connecting the battery and the converter and connected in parallel with the battery;
A first resistor provided in the circuit;
A second resistor having a resistance value smaller than that of the first resistor provided in the circuit;
Voltage detection means for detecting the voltage value of the capacitor;
When the detection result of the voltage detection means becomes equal to or lower than a predetermined voltage value lower than the voltage value of the battery required for traveling of the vehicle, the electric charge stored in the capacitor is forced to the second resistor. An inverter device comprising: control means for controlling the circuit so as to be discharged. In the circuit, provided with a connection means for connecting and disconnecting the electrical connection between the capacitor and the second resistor,
The inverter device according to claim 1, wherein the control unit controls connection / disconnection switching of the connection / disconnection unit. The control means includes a map indicating a decrease in the voltage value of the capacitor over time when the capacitor is discharged only by the first resistor, and is forcibly discharged by the second resistor. And confirming whether or not the slope of the voltage drop of the capacitor is the same as the slope of the voltage drop when the predetermined voltage value in the map, the charge stored in the capacitor is The inverter device according to claim 1, wherein the resistor is forcibly discharged to the resistor. The control unit, the capacitor, the first resistor, and the second resistor are housed in one case. The inverter device described in the paragraph.

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