JP5517064B2 - Motor rotation judgment method - Google Patents

Description

  The present invention relates to a motor rotation determination method, and more particularly to a motor rotation determination method for accurately determining that a motor stops.

  2. Description of the Related Art Conventionally, electric vehicles, hybrid vehicles, fuel cell vehicles, and the like have been developed as electric vehicles that are vehicles equipped with a motor as a power source. Then, when an accident occurs in the electric vehicle (at the time of a collision), in the inverter used in the motor drive circuit, the charge accumulated in the capacitor inside the inverter is discharged for safety.

  In the motor drive circuit, a discharge resistor is provided to discharge the electric charge accumulated in the capacitor. However, forcibly discharging with an inverter element has been studied in order to discharge in a shorter time. That is, one of the six elements of the inverter is completely turned on, and the element of the arm facing the completely turned on element is turned on in the middle (hereinafter referred to as half-on). In other words, the current value is controlled by using the element as a resistor.

  Here, if one of the six elements of the inverter is completely turned on and the motor is rotating, a large current flows through the motor drive circuit due to the influence of the electromotive force generated in the motor. there is a possibility. As a result, the element may be destroyed and the electric wire and the motor winding may be overheated. Furthermore, there is a possibility that the voltage of the capacitor does not drop for a long time and the discharging element is overheated.

  On the other hand, Patent Document 1 discloses a method of determining a stop state of a motor when discharging electric charges accumulated in a capacitor. Specifically, by controlling on / off of the semiconductor switching elements constituting the inverter circuit, the motor winding is short-circuited, and the value of the current flowing in the motor winding in the short-circuited state is referred to twice or more. . And when the electric current value referred in multiple times corresponds, it determines with the rotation of a motor having stopped.

Japanese Patent No. 4434636

  However, in the motor stop determination method described in Patent Document 1, since it is necessary to short-circuit the motor winding for a long time in order to refer to the value of the current flowing in the motor winding more than once, sudden braking is applied to the vehicle. May occur or each element in the motor drive circuit may be destroyed. Furthermore, since all the windings are short-circuited and a current sensor for detecting the value of the current flowing through the windings is required, there is a problem that the circuit scale becomes large.

  Therefore, an object of the present invention is to accurately determine that the motor has stopped, and then discharge the electric charge accumulated in the capacitor to prevent sudden braking in the vehicle and It is to provide a motor rotation determination method capable of suppressing the drive circuit from overheating.

  In order to achieve the above object, a motor drive circuit of the present invention is a motor drive circuit for driving a motor, and is a switching in which a DC power supply for supplying electric power for driving the motor and two switching elements are connected in series. An inverter circuit configured by arranging three units in parallel, converting electric power output from the DC power source into an AC current and outputting it to the motor, and a capacitor connected in parallel between the DC power source and the inverter circuit; And a control unit for controlling the discharge process for discharging the electric charge accumulated in the capacitor, each phase of the motor is connected to two switching elements in each switching unit, and the discharge process is performed by the control unit. At the start of the started discharge process, one of the two switching elements is turned on and the discharge process is started. When the current flowing through the turned-on switching element within a first time from the time exceeds a motor stop threshold value indicating that the motor is in a stopped state, the turned-on switching element is turned off and During the first time, when the current flowing through the turned-on switching element is equal to or less than the motor stop threshold, the other switching element of the two switching elements is half-on.

  Preferably, when the current flowing through the turned-on switching element exceeds the motor stop threshold within the second time from the elapse of the first time, the turned-on switching element is turned off, and the first time When the current flowing through the turned-on switching element is less than or equal to the motor stop threshold continuously for the second time from the elapsed time, the other switching element of the two switching elements is half-on.

  Further, preferably, first, when the discharge process is started by the control unit, 0 is set in the first time.

  In addition, in order to achieve the above object, each process performed by each configuration of the motor drive circuit of the present invention described above can be regarded as a motor drive method that provides a series of process procedures. This method is provided in the form of a program for causing a computer to execute a series of processing procedures. This program may be installed in a computer in a form recorded on a computer-readable recording medium.

  As described above, according to the motor rotation determination method of the present invention, it is accurately determined that the motor has stopped, and then sudden braking is generated in the vehicle by discharging the charge accumulated in the capacitor. While preventing, it can suppress that a motor drive circuit overheats.

The figure which shows the motor drive circuit 100 which concerns on the 1st Embodiment of this invention. The flowchart which shows the flow of a process of the motor rotation determination method 200 which the motor drive circuit 100 which concerns on the 1st Embodiment of this invention performs. The flowchart which shows the flow of a process of the motor rotation determination method 300 which the motor drive circuit 100 which concerns on the 2nd Embodiment of this invention performs. The flowchart which shows the flow of the detailed process of motor rotation determination continuation method S310 which continues determination of whether the motor M1 is a stop state.

Hereinafter, embodiments of the present invention will be described with reference to the drawings.
<First Embodiment>
FIG. 1 is a diagram showing a motor drive circuit 100 according to the first embodiment of the present invention. In FIG. 1, the motor drive circuit 100 includes a battery B1, relays S1 and S2, a capacitor C1, an inverter I1, and a motor M1.

  The battery B1 is a high voltage battery for traveling, and applies a voltage to the capacitor C1 and the inverter I1 while the vehicle is traveling.

  Relays S1 and S2 are turned on while the vehicle is running and are in a conductive state.

  The capacitor C1 is a capacitor for stabilizing the power source of the inverter I1, and a voltage is applied by the battery B1 and the electric charge is accumulated during traveling of the vehicle.

  The motor M1 is a motor for driving the vehicle.

  Inverter I1 includes switching elements Q1 to Q6 and diodes D1 to D6 corresponding to switching elements Q1 to Q6, respectively.

  Here, when the vehicle has an accident (collision), in order to prevent a large current from flowing through the motor drive circuit 100, the relays S1 and S2 are turned off and the voltage applied by the battery B1 is cut off. The

  However, the electric charge accumulated while the vehicle is running remains in the capacitor C1, and generally, a resistor for discharging the accumulated electric charge is inserted in parallel. If the electric power consumed by the resistor is increased in order to discharge the accumulated electric charge in a short time, the electric power consumed during traveling of the vehicle increases, resulting in deterioration of fuel consumption. For this reason, the power (discharge current) consumed by the resistor cannot be set large, and it takes several minutes to discharge. In other words, it is difficult to discharge the accumulated charge in a short time, although it is necessary to prevent a large current from flowing through the motor drive circuit 100 when the vehicle has an accident (collision).

  Therefore, when the vehicle has an accident (collision), in order to discharge the accumulated electric charge in a shorter time and prevent a large current from flowing through the motor drive circuit 100, the switching elements Q1 to Q6 of the inverter I1. To discharge with a large current. As a result, when the vehicle has an accident (collision), the accumulated charge can be discharged in a shorter time.

  For example, when the vehicle has an accident (collision), in the motor drive circuit 100, the switching element Q2 is completely turned on, the switching element Q1 is turned on intermediately, and discharging is performed while controlling the current flowing through the motor M1 and the inverter I1. To do. Further, a shunt resistor is inserted into the emitter of the switching element Q2, and a current shunted from a part of the elements constituting the switching element Q2 is measured (such as a sense IGBT). Thus, the discharge current can be controlled by measuring the discharge current and controlling the gate voltage of the switching element Q1.

  However, even when the vehicle has an accident (collision), the vehicle may be traveling with repulsion. In this case, when the motor M1 is rotating and the switching element Q2 is completely turned on, the path from the diode D4 and the diode D6 to the switching element Q2 due to the influence of the electromotive force generated in the motor M1. Current flows (i1 in FIG. 1). And since the motor M1 is braked by the current i1, unintentional braking occurs in the vehicle, and the value of the current i1 may be about twice the current value during normal travel. There is a possibility of causing destruction of the element and burning of the electric wire.

  Here, since the electromotive force generated in the motor M1 is full-wave rectified via the diodes D1 to D6 and charges the capacitor C1, the electric charge accumulated in the capacitor C1 is forcibly discharged. However, the voltage of the capacitor C1 does not drop. In such a situation, if the discharge continues, the IGBT element consumes unexpected energy and overheats, and even if the vehicle stops thereafter, the charge accumulated in the capacitor C1 can no longer be discharged. End up.

  Further, when discharging the electric charge accumulated in the capacitor C1, it is necessary to control the current i2. However, a shunt resistor is inserted into the emitter of the switching element Q2, or a part of the elements constituting the switching element Q2 is shunted. In the method of measuring the current to be measured, the current i3 is measured. That is, since i3 = i1 + i2, if the current i1 exists due to the influence of the electromotive force generated in the motor M1, the current i2 cannot be accurately controlled.

  Therefore, a method of discharging after the motor M1 is stopped while determining whether or not the motor M1 is stopped using the switching elements Q1 to Q6 of the inverter I1 will be described in detail below. FIG. 2 is a flowchart showing a process flow of the motor rotation determination method 200 executed by the motor drive circuit 100 according to the first embodiment of the present invention. In FIG. 2, the motor rotation determination method 200 includes steps S210 to S280. In steps S210 to S280, each element in the motor drive circuit 100 is controlled by a control unit (not shown) that controls each element. It is controlled.

  In step S210, the motor drive circuit 100 issues a discharge processing start instruction based on the occurrence of a vehicle accident (collision). Specifically, the motor drive circuit 100 detects, for example, an airbag deployment signal for deploying an airbag when the vehicle has an accident (collision), and commands to start discharging.

  In step S220, the motor drive circuit 100 starts a timer (not shown). When the motor speed decreases, the current flowing at the time of the short circuit decreases, so the timer value T1 is set based on the motor speed at which the current flowing at the time of the short circuit becomes sufficiently small. More specifically, the timer value T1 is set to a time of one rotation or more in electrical angle. Here, the electrical angle for one rotation means that when the winding is one set for three phases, the electrical angle is equal to the mechanical angle, and when the winding is shifted by two sets for three phases, Angle = mechanical angle × 2. Specifically, for example, when the motor speed is reduced to 120 rpm, the current flowing at the time of the short circuit is negligibly small. If the electrical angle = mechanical angle × 2, the electrical angle corresponds to one rotation. The time is 60 seconds / (120 × 2) rpm = 0.25 seconds. That is, the timer value T1 is set to 0.25 seconds or more.

  In step S230, the motor drive circuit 100 turns on the switching element of the lower arm in the inverter I1. Here, the switching element Q2 is turned on. At this time, if the motor M1 is rotating, a current (i1 = i3) due to electromotive force starts to flow. Then, the current due to the electromotive force is monitored.

  In step S240, it is determined whether or not the current due to the electromotive force is equal to or less than a motor stop threshold value indicating that the motor M1 is in a stopped state. If the current due to the electromotive force is less than or equal to the motor stop threshold, the process proceeds to step S250 (Yes in step S240), and if the current due to the electromotive force exceeds the motor stop threshold, the process proceeds to step S270 (step S270). Yes in S240).

  In step S250, the motor drive circuit 100 determines whether or not the timer value T1 of the timer started in step S220 has elapsed. When the timer value T1 has elapsed, the process proceeds to step S260 (Yes in step S250). On the other hand, when the timer value T1 has not elapsed, the process returns to step S240, and it is determined whether or not the current due to the electromotive force is equal to or less than the motor stop threshold (No in step S250).

  In other words, it is determined that the motor M1 is in the stopped state only when the current due to the electromotive force is equal to or less than the motor stop threshold within the timer value T1 of the timer started in step S220, and step S260. (Yes in step S250). On the other hand, if the current due to the electromotive force exceeds the motor stop threshold even within the timer value T1 of the timer started in step S220, it is determined that the motor M1 is not in a stopped state, and the process proceeds to step S270. (No in step S240).

  In step S260, the motor drive circuit 100 half-ONs the switching element of the upper arm in the inverter I1 in order to discharge the charge accumulated in the capacitor C1. Here, the switching element Q1, which is opposite to the switching element Q2, is half-on.

  In step S270, in the motor drive circuit 100, if the current due to the electromotive force exceeds the motor stop threshold even within the timer value T1 of the timer started in step S220, the motor M1 is rotating. The switching element Q2 turned on in step S230 is turned off.

  In step S280, the motor drive circuit 100 waits until the current due to the electromotive force decreases, and then returns to step S220.

  The motor stop threshold value indicating that the motor M1 is in a stopped state is so small that the braking generated in the vehicle is less than the allowable value and does not affect the current control for discharging the capacitor C1. Set it to a value.

  As described above, according to the motor drive circuit 100 and the motor rotation determination method 200 according to the first embodiment of the present invention, it is accurately determined that the motor M1 has stopped, and then the charge accumulated in the capacitor C1. Therefore, it is possible to prevent the motor drive circuit 100 from being overheated while preventing sudden braking in the vehicle.

  Further, the current value does not change suddenly due to the influence of the inductance of the motor M1. As a result, by measuring the current value and comparing the measured current value with the motor stop threshold value, the motor M1 can judge that the motor is stopped and shut off before the current value increases abnormally. It is.

  In this embodiment, the switching element Q2 is turned on and the switching element Q1 is half-on. However, the present invention is not limited to this, and conversely, the switching element Q1 may be turned on and the switching element Q2 may be half-on. Absent.

<Second Embodiment>
In the second embodiment of the present invention, in the discharge processing state described in the first embodiment of the present invention, a motor rotation determination method that takes into account the case where the vehicle starts to move due to some cause such as a secondary damage collision. Will be described. Since the configuration of the motor drive circuit according to the second embodiment of the present invention is the same as the configuration of the motor drive circuit 100 shown in FIG. 1 in the first embodiment of the present invention, the motor drive circuit shown in FIG. By using 100, detailed description is omitted.

  FIG. 3 is a flowchart showing a process flow of the motor rotation determination method 300 executed by the motor drive circuit 100 according to the second embodiment of the present invention. In FIG. 3, motor rotation determination method 300 includes steps S210 to S250, steps S270 to S280, and step S310. In step S210 to step S250, step S270 to step S280, and step S310, each element in the motor drive circuit 100 is controlled by a control unit (not shown) that controls each element. In the flowchart shown in FIG. 3, the same processes as those in the flowchart shown in FIG. 2 described in the first embodiment of the present invention are denoted by the same reference numerals, and detailed description thereof is omitted. Hereinafter, in the present embodiment, differences from the first embodiment of the present invention will be described in detail.

  In step S250, the motor drive circuit 100 determines whether or not the timer value T1 of the timer started in step S220 has elapsed. When the timer value T1 has not elapsed, the process returns to step S240, and it is determined whether or not the current due to the electromotive force is equal to or less than the motor stop threshold (No in step S250). On the other hand, when the timer value T1 has elapsed, unlike the first embodiment of the present invention which has proceeded to the process of step S260, in the present embodiment, the process proceeds to the process of step S310 (Yes in step S250).

  In step S310, the motor drive circuit 100 continues to determine whether or not the motor M1 is in a stopped state. FIG. 4 is a flowchart showing a detailed process flow of the motor rotation determination continuation method S310 for continuing the determination of whether or not the motor M1 is in the stopped state. 4, the motor rotation determination continuation method S310 includes steps S311 to S315. In steps S311 to S315, each element in the motor drive circuit 100 is a control unit (not shown) that controls each element. Is controlled by.

  In step S311, the motor drive circuit 100 starts a cycle timer (not shown) that turns on and off the switching element of the upper arm in the inverter I1. More specifically, here, a cycle timer value T2, which is a cycle for turning on and off the switching element Q1, is set.

  In step S312, the motor drive circuit 100 sets a time for turning on the switching element of the upper arm in the inverter I1 described above. More specifically, an on time Ton that is a time for turning on the switching element Q1 is set here.

  In step S313, in the motor drive circuit 100, the switching element of the upper arm in the inverter I1 described above is half-on for the on-time Ton. More specifically, here, the switching element Q1 is half-on only for the on-time Ton set in step S312.

  In step S314, the motor drive circuit 100 determines whether or not the current i3 (= i1) is equal to or less than a motor stop threshold value indicating that the motor M1 is in a stopped state. If the current i3 is less than or equal to the motor stop threshold, the process proceeds to step S315 (Yes in step S313). If the current i3 exceeds the motor stop threshold, the process proceeds to step S270 shown in FIG. Yes at S314). In other words, when the switching element Q1 is in the on state (step S313), since it cannot be determined whether or not the motor M1 is in the stopped state, the current i3 is compared with the motor stop threshold after the on time Ton has elapsed. Thus, it is determined whether or not the motor M1 is in a stopped state.

  In step S315, the motor drive circuit 100 determines whether or not the cycle timer value T2 of the cycle timer activated in step S311 has elapsed. If the cycle timer value T2 has elapsed, the process returns to step S311 (Yes in step S315). On the other hand, when the period timer value T2 has not elapsed, the process returns to the process of step S314, and it is determined whether or not the current i3 (= i1) is equal to or less than the motor stop threshold (No in step S315).

  In other words, it is determined that the motor M1 is in a stopped state only when the current i3 (= i1) is not more than the motor stop threshold value within the cycle timer value T2 of the cycle timer started in step S311. Then, the process returns to step S311 (Yes in step S315). On the other hand, if the current i3 (= i1) exceeds the motor stop threshold even within the period timer value T2 of the period timer activated in step S311, it is determined that the motor M1 is not in the stop state, and FIG. The process proceeds to step S270 shown in FIG.

  As described above, according to the motor drive circuit 100 and the motor rotation determination method 300 according to the second embodiment of the present invention, in the discharge processing state described in the first embodiment of the present invention, a secondary operation is further performed. Considering the case where the vehicle starts to move due to some cause such as a collision of damage, since the process of the motor rotation determination continuation method S310 is executed, it is determined in step S313 that the motor M1 is not in a stopped state even during discharging. In this case, the process returns to step S220 again. Then, again, it is accurately determined that the motor M1 has stopped, and then the electric charge accumulated in the capacitor C1 is discharged (discharge is resumed), so that sudden braking is prevented from occurring in the vehicle, and It is possible to prevent the motor drive circuit 100 from overheating.

  Further, the current value does not change suddenly due to the influence of the inductance of the motor M1. As a result, by measuring the current value and comparing the measured current value with the motor stop threshold value, the motor M1 can judge that the motor is stopped and shut off before the current value increases abnormally. It is.

  Note that the current value does not change suddenly due to the influence of the inductance of the motor M1. That is, if the on-time Ton, which is the time to turn on the switching element Q1, is set to a time shorter than the switching cycle during normal running, the current value does not increase abnormally within the on-time Ton.

  Note that the timer value T1 may be set to 0 in order to discharge the charge accumulated in the capacitor C1 in a short time. In this case, after starting the discharge, there is a possibility of detecting that the motor M1 is rotating. However, when it is detected that the motor M1 is rotating, the discharging is temporarily stopped and the motor M1 is stopped. When there is no more current flowing, discharging can be resumed.

  Furthermore, the time for determining whether or not the motor M1 is in a stopped state may be changed between the first time and the second time and thereafter. Specifically, for the timer value T1, the first time is set to 0, and the second time and thereafter are set to a time for one rotation. In this case, when the discharge of the electric charge accumulated in the capacitor C1 is started early, on the other hand, when it is detected that the motor M1 is rotating after the discharge is started, the motor M1 is surely stopped. It can also be made.

  By the way, it is conceivable to control the start of discharge and the stop of discharge by determining the stop of the vehicle with a sensor and microcomputer of the vehicle. However, after the accident of the vehicle (after a collision), a microcomputer that requires a large amount of power As described in the first and second embodiments of the present invention, it is difficult to secure a power supply for the vehicle, and the vehicle sensor may not operate normally. It is effective to judge.

  The present invention can be applied to a motor drive circuit and a motor rotation determination method that accurately determine whether or not a motor is in a stopped state, and in particular, when a vehicle accident occurs (at the time of a collision), the motor is in a stopped state. This is useful when accurately determining whether or not there is.

DESCRIPTION OF SYMBOLS 100 Motor drive circuit B1 Battery C1 Capacitor S1, S2 Relay I1 Inverter Q1-Q6 Switching element D1-D6 Diode M1 Motor 200, 300 Motor rotation determination method S210-S280, S310 Each step in motor rotation determination method S311-S315 Motor rotation determination Each step in the continuation method

Claims (3)

A motor drive circuit for driving a motor,
A DC power supply for supplying electric power for driving the motor;
An inverter circuit configured by arranging three switching units connected in series with two switching elements in parallel, converting the power output from the DC power source into an AC current, and outputting the AC current to the motor;
A capacitor connected in parallel between the DC power source and the inverter circuit;
A controller for controlling a discharge process for discharging the charge accumulated in the capacitor,
Each phase of the motor is connected to two switching elements in each switching unit,
At the time when the discharge process is started by the control unit, one of the two switching elements is turned on,
When the current flowing through the turned-on switching element exceeds a motor stop threshold indicating that the motor is in a stopped state within a first time from the start of the discharge process, the turned-on switching element is turned off. And
If the current flowing through the turned-on switching element is less than or equal to the motor stop threshold continuously during the first time from the start of the discharge process, the other switching element of the two switching elements is half-on. A motor drive circuit, characterized in that If the current flowing through the turned-on switching element exceeds the motor stop threshold within a second time after the first time elapses, the turned-on switching element is turned off,
When the current flowing through the turned-on switching element is less than or equal to the motor stop threshold continuously during the second time from the elapse of the first time, the other switching element of the two switching elements The motor drive circuit according to claim 1, wherein the motor is half-on.   3. The motor drive circuit according to claim 2, wherein when the discharge process is started by the control unit, 0 is set in the first time. 4.

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