JP4093057B2 - Control device for electric motor for vehicle - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a control device for a vehicular electric motor that converts a DC current into a plurality of phases of AC power by a switching element and is driven by the AC power, and more particularly to an overcurrent in a switching element that drives the motor. The present invention relates to the prevention of overload of an electric motor that prevents a motor from flowing and being damaged.
[0002]
[Prior art]
[Patent Document 1]
JP, 11-215687, A In an electric vehicle, there is a possibility that it may become a balance state of driving force by electric motor torque and retreating force by gravity, or a slow speed driving due to insufficient depression of the accelerator pedal when climbing uphill. In that case, the current that flows in one of the three phases of the motor may be up to twice as large as the other phases, and the current concentrates on a specific switching element of the inverter, causing a rapid temperature rise. The switching element may be thermally destroyed.
Conventionally, in order to prevent thermal destruction of the inverter switching element in such a locked state of the motor or in ultra-low speed rotation, the locked state of the motor is detected from the temperature rise of the switching element and the rotational speed of the motor, and the output current is limited. It is considered to shift the rotation angle of the rotor of the electric motor by stopping the output or changing the phase (see Patent Document 1).
[0003]
[Problems to be solved by the invention]
According to this prior art, when it is detected that the motor is in the locked state, the torque of the motor is reduced and the rotation angle of the rotor is shifted to change the phase. By energizing a switching element that is not in an overheated state from the switching element, a large torque can be generated and the locked state can be released.
[0004]
However, even if the electric motor is started to rotate using a switching element that is not in an overheated state, torque is generated again by the switching element that is in an overheated state, and the overheated state continues.
In order to solve the above-described problems, an object of the present invention is to provide a control device for a motor for a vehicle that can prevent the motor from being locked and can avoid the overheating state of the switching element.
[0005]
[Means for Solving the Problems]
For this reason, the present invention provides an inverter that controls driving power supplied to an electric motor provided in a vehicle, and a first request for calculating a first torque request value for the electric motor based on an accelerator operation amount of the driver. A torque calculation means, a rotation speed detection means for detecting the rotation speed of the electric motor, and a determination that the first torque request value is not less than a predetermined torque value and the rotation speed of the electric motor is not more than the predetermined first rotation speed; Determining means for performing, second request torque calculating means for calculating a second torque request value based on a predetermined second rotation speed greater than the first rotation speed, and the first torque request value being the predetermined torque If the torque value is less than or equal to the first rotation speed, the inverter is controlled based on the first torque request value, and the first torque request value is greater than or equal to the predetermined torque value and the motor The rotation speed is equal to or higher than the first rotation speed. If it includes an inverter control means for controlling the inverter based on the second torque request value has a temperature detecting means for detecting a temperature of the inverter, the second requested torque calculation means, the last said second Based on the torque request value and the temperature of the inverter, the rotation speed calculating means for calculating the third rotation speed of the electric motor that does not overheat the inverter, the third rotation speed and the second rotation speed are compared, and the larger rotation speed The second torque request value for this time is calculated based on the number of revolutions selected by the revolution number selection means.
[0006]
【The invention's effect】
According to the present invention, the inverter control means causes the first torque request value corresponding to the accelerator opening calculated by the first request torque calculation means to be less than the predetermined torque value or the rotation speed from the rotation speed detection means to be a predetermined first speed. If the rotation speed is greater than 1, the inverter is controlled based on the first torque request value, the first torque request value is greater than or equal to a predetermined torque value, and the rotation speed from the rotation speed detection means is a predetermined first speed. If it is equal to or lower than the rotational speed, it is determined that there is a possibility that the electric motor may be locked due to insufficient depression of the accelerator, and the second speed based on a predetermined second rotational speed greater than the predetermined first rotational speed is determined. Since the inverter is controlled by generating a second torque request value that is greater than the first torque request value calculated by the required torque calculation means, it is possible to prevent the electric motor from being locked.
As a result, the current concentrates on the one-phase switching element of the inverter, and the possibility that the switching element is thermally destroyed is reduced.
[0007]
DETAILED DESCRIPTION OF THE INVENTION
Embodiments of the present invention will be described below.
FIG. 1 is a block diagram of a control device for a vehicle motor.
An accelerator opening detection unit 1 that detects the accelerator opening is connected to the motor control unit 20, and a control signal corresponding to the accelerator opening signal is output from the motor control unit 20 to the inverter 8, and the inverter 8 is connected to the motor control unit 20. The drive control of the electric motor 9 is performed by controlling the electric power to the electric motor 9 based on the control signal from.
The inverter 8 is provided with an inverter temperature detection unit 10 that detects the temperature (hereinafter referred to as inverter temperature) TI of the switching elements constituting the inverter 8, and a signal of the inverter temperature TI is input to the motor control unit 20.
The electric motor 9 is provided with an electric motor rotational speed detection unit 11 that detects the rotational speed, and a signal of the rotational speed ω is input to the electric motor control unit 20.
The motor control unit 20 is constituted by a microcomputer.
[0008]
The configuration of the motor control unit 20 will be described in more detail.
The motor control unit 20 includes a torque request value calculation unit 2, a rotation speed command generation unit 3, a rotation speed command restriction processing unit 4, a torque command value calculation unit 5, a torque command value selection unit 6, an inverter control unit 7, and a rotation speed command. It consists of a lower limit calculator 12.
The accelerator opening signal from the accelerator opening detector 1 is input to the torque request value calculator 2. The torque request value calculation unit 2 calculates the torque request value τ 1 based on the torque request value calculation unit 2 and outputs the torque request value τ 1 to the rotation speed command generation unit 3 and the torque command value selection unit 6.
A signal of the inverter temperature TI from the inverter temperature detector 10 is input to the rotation speed command lower limit calculator 12.
A signal of the rotational speed ω of the electric motor 9 from the electric motor rotational speed detection unit 11 is input to the rotational speed command generation unit 3, the torque command value calculation unit 5, and the torque command value selection unit 6.
[0009]
The rotation speed command generation unit 3 compares the rotation speed ω input from the motor rotation speed detection unit 11 with the built-in predetermined rotation speed ωo, and uses the torque request value τ1 and the built-in predetermined torque value τo. In comparison, when ω ≦ ωo and τ1 ≧ τo, the torque command value switching flag Lτ = 1 is set. When ω> ωo or τ1 <τo, the torque command value switching flag Lτ = 0 is set. Output to the selector 6.
Further, when the torque command value switching flag Lτ = 1, the rotational speed command generation unit 3 sets a predetermined provisional target rotational speed ω1 incorporated as the rotational speed command value and outputs it to the rotational speed command restriction processing unit 4 To do.
[0010]
The predetermined rotational speed ωo is a rotational speed of approximately 0 rpm, and the predetermined torque value τo is a torque value required when the vehicle starts at a creep speed on a normal flat ground.
The temporary target rotational speed ω1 is a predetermined rotational speed that can prevent overheating of the switching element of the inverter 8, and is, for example, the rotational speed of the electric motor that generates a creep speed when the vehicle starts.
[0011]
The rotation speed command limit processing unit 4 compares the provisional target rotation speed ω1 with a rotation speed command lower limit value ωL output from a rotation speed command lower limit value calculation unit 12 described later, and selects the larger value to rotate. It is set as a numerical command value ω 2 and is output to the torque command value calculation unit 5 and the torque command value selection unit 6.
The torque command value calculation unit 5 calculates a torque command value τ2 necessary for increasing the rotation speed of the motor in the uphill state, for example, by PI calculation from the deviation between the rotation speed command value ω2 and the current rotation speed ω of the motor 9. The torque command value selection unit 6 and the rotation speed command lower limit value calculation unit 12 are output.
[0012]
The rotational speed command lower limit value calculation unit 12 is a motor of the motor 9 in which the switching element of the inverter 8 does not overheat based on the torque command value τ 2 output from the torque command value calculation unit 5 and the inverter temperature TI output from the inverter temperature detection unit 10. The minimum rotational speed is calculated and output to the above-described rotational speed command restriction processing unit 4 as the rotational speed command lower limit value ωL.
[0013]
When the torque command value switching flag Lτ = 0, the torque command value selection unit 6 performs the torque request value τ1 from the torque request value calculation unit 2 as the torque command value τc output to the inverter control unit 7 as normal torque control. The torque request value τ1 is selected from the torque command value τ2 from the torque command value calculation unit 5.
[0014]
Further, when the torque command value switching flag Lτ = 1 and ω <ω2, the torque command value selection unit 6 performs the torque command value τc as the torque command value τc as torque control for preventing the inverter temperature from rising due to the locked state of the motor. τ2 is selected and output to the inverter control unit 7.
When the torque command value switching flag Lτ = 1 and the relationship between the rotational speed ω of the electric motor 9 and the rotational speed command value ω2 is ω ≧ ω2, it is determined that the torque control for preventing the inverter overheating is completed, and the torque command value switching flag Lτ is reset to 0, and the torque request value τ1 is selected as the torque command value τc to be output to the inverter control unit 7.
The inverter control unit 7 outputs a signal for controlling the switching element of the inverter 8 to the inverter 8 based on the input torque command value τc.
[0015]
In the rotational speed command lower limit calculation unit 12, the rotational speed command lower limit value ωL is obtained from the torque command value τ2 and the inverter temperature TI as follows.
In the case of a three-phase current value with a large peak current value, in order to prevent the inverter temperature TI from rising excessively, the allowable time that can be continuously passed through the switching element for one phase is short. It is necessary to shorten the cycle (that is, increase the rotation speed of the electric motor 9).
When the peak current value is low, the amount of heat generated by the switching element is small, so that the energization cycle can be lengthened. That is, the low rotation speed of the electric motor 9 can be allowed.
[0016]
Since the peak current value flowing through the switching element can be predicted from the torque command value output to the inverter control unit 7, the extent to which the inverter temperature TI rises within a predetermined time after receiving the torque command value τ2 can be predicted. If the current inverter temperature TI, which is the base temperature, is known, the minimum number of revolutions necessary to prevent the inverter temperature TI from exceeding a predetermined value due to heat generated by energization can be found.
Therefore, the relationship between the minimum number of revolutions of the motor 9 at which the inverter temperature TI using the torque command value and the inverter temperature TI as parameters is determined in advance through experiments or the like, and the revolution number command lower limit calculation unit 12 By having data in the form of a map such as a lookup method, the rotational speed command lower limit value ωL can be easily obtained from the torque command value and the inverter temperature TI.
[0017]
The operation of this embodiment will be described below.
2 and 3 are diagrams showing a flow of control for preventing overheating of the inverter performed by the motor control unit.
The driver depresses the accelerator pedal to start the vehicle on a slope. The accelerator opening detector 1 outputs an accelerator opening signal to the torque request value calculator 2, and the torque request value calculator 2 outputs the signal as the torque request value τ1.
Further, the motor rotation speed detection unit 11 outputs the rotation speed ω of the motor 9 and the inverter temperature detection unit 10 outputs the inverter temperature TI of the inverter 8 to the motor control unit 20 every moment.
[0018]
In step 101, the rotational speed command generator 3 confirms whether the rotational speed ω of the electric motor 9 is equal to or smaller than a predetermined value ωo and the torque request value τ1 is equal to or larger than the predetermined value τo.
When the rotational speed ω is equal to or smaller than the predetermined value ωo and the torque request value τ1 is equal to or larger than the predetermined value τo, the process proceeds to step 102, where the torque command value switching flag Lτ = 1 is set. Otherwise, the process proceeds to step 111, where the torque command value switching flag Lτ = 0 is set.
[0019]
The flow to step 102 is that the rotational speed ω of the electric motor 9 is lower than the creep speed of the vehicle, even though the driver is stepping on the accelerator to a degree equal to or greater than the accelerator opening corresponding to the start of the vehicle on a normal flat ground ( In order to avoid the occurrence of the locked state of the electric motor 9 when the rotational speed command generation unit 3 detects that the rotational speed is substantially zero), the driving state of the vehicle is maintained with the amount of depression of the driver's accelerator pedal, and the inverter 8 This means that the control enters a state in which a state in which a current flows only through a single-phase switching element is avoided.
The flow to step 111 means normal torque control in which the rotational speed ω of the electric motor increases according to the amount of depression of the accelerator pedal and the vehicle starts to move.
[0020]
In step 103, the rotational speed command generator 3 sets a predetermined temporary target rotational speed ω1 as a rotational speed command value candidate for preventing the inverter 8 from overheating.
In step 104, the rotational speed command lower limit calculation unit 12 reads the inverter temperature TI from the inverter temperature detection unit 10.
In step 105, the rotation speed command lower limit value calculation unit 12 reads the previous torque command value τ 2 from the torque command value calculation unit 5. Immediately after entering the flow of step 102, the torque command value τ2 in the torque command value calculation unit 5 is undefined, and in this case, the torque request value τ1 is substituted.
[0021]
In step 106, the rotational speed command lower limit value calculation unit 12 obtains the rotational speed command lower limit value ωL, which is the minimum rotational speed of the motor 9 that is allowed to prevent overheating of the inverter 8 corresponding to the previous torque command value τ2 and the inverter temperature TI. Obtained from the built-in data and output to the rotational speed command restriction processing unit 4.
In step 107, the rotational speed command restriction processing unit 4 confirms whether the rotational speed command lower limit value ωL is equal to or lower than the provisional target rotational speed ω1 that is a candidate for the rotational speed command value.
If ωL ≦ ω1, the routine proceeds to step 108, where the rotational speed command value ω2 = ω1, and if not, the routine proceeds to step 109, where the rotational speed command value ω2 = ωL, and the rotational speed command value ω2 It is output to the command value selector 6.
[0022]
At the beginning when the torque command value switching flag becomes Lτ = 1, the locked state or ultra-low speed rotation state of the motor 9 is hardly continued, so that the inverter temperature TI is not high and the rotation speed command lower limit value ωL is ωL ≦ ω1. Yes, the flow goes to step 108.
When the inverter temperature TI rises after the locked state or the ultra-low speed rotation state continues, the rotational speed command lower limit value ωL becomes ωL> ω1, and the flow to step 109 is performed.
Accordingly, as the electric motor 9 is kept in the locked state or the ultra-low speed rotation state, a larger value of the rotational speed command lower limit value ωL is calculated in step 106 and set in step 109 as the rotational speed command value ω2.
[0023]
After step 108 and step 109, the process proceeds to step 110.
In step 110, the torque command value calculation unit 5 calculates a new (current) torque command value τ2 by PI calculation from the deviation between the rotation speed ω of the electric motor 9 and the rotation speed command value ω2. The torque command value calculation unit 5 calculates a larger torque command value τ2 as the deviation between the rotational speed ω of the electric motor 9 and the rotational speed command value ω2 increases.
After step 110, the process proceeds to step 112.
In addition, it progresses to step 111 after step 101, and when it is set as torque command value switching flag Lτ = 0, it progresses to step 112.
[0024]
In step 112, the torque command value selection unit 6 confirms the state of torque control. That is, it is confirmed whether or not the torque command value switching flag Lτ = 1.
When the torque command value switching flag Lτ = 1, the routine proceeds to step 113, and otherwise, the routine proceeds to step 116.
In step 113, the torque command value selection unit 6 checks whether or not the rotational speed ω of the electric motor 9 is equal to or higher than the rotational speed command value ω2.
[0025]
When the rotational speed ω is less than the rotational speed command value ω2, the routine proceeds to step 114, where the value of the torque command value τ2 from the torque command value calculation section 5 is set as the torque command value τc to be output to the inverter control section 7. Proceed to
When the rotational speed ω is equal to or higher than the rotational speed command value ω2, the process proceeds to step 115, the torque command value switching flag Lτ is reset to 0, and the process proceeds to step 116.
[0026]
In step 116, the torque command value selection unit 6 sets the torque request value τ 1 from the torque request value calculation unit 2 as the torque command value τc to be output to the inverter control unit 7, and proceeds to step 117.
In step 117, the torque command value selection unit 6 outputs the torque command value τc to the inverter control unit 7, and the inverter control unit 7 controls the inverter 8 based on the input torque command value τc to drive and control the motor 9. .
As a result, in the case of torque control (Lτ = 1) for preventing the inverter temperature from rising, the electric motor 9 is driven with a target torque command value τ2 larger than the torque request value τ1 corresponding to the accelerator opening, and is released from the locked state. The rotational speed ω will increase in the direction of movement.
[0027]
In step 118, the torque command value selector 6 confirms the state of torque control.
When the torque command value switching flag Lτ = 1, the process returns to step 104 to continue the torque control for preventing the inverter temperature from rising.
When the torque command value switching flag Lτ = 0, a series of torque control for preventing the inverter temperature rise is completed. That is, when the flow of torque control for preventing the inverter temperature from rising is repeated and the rotational speed ω of the electric motor 9 becomes equal to or larger than ω2, the torque request value τ1 corresponding to the accelerator opening is set as the torque command value τc to the inverter 8. Then, torque control corresponding to the driver's accelerator operation is executed.
[0028]
The accelerator opening detection unit 1 and the torque request value calculation unit 2 of the present embodiment are the first request torque calculation unit of the present invention, the inverter temperature detection unit 10 is the temperature detection unit, and the motor rotation speed detection unit 11 is the rotation. Steps 101, 102 and 111 of the flow constitute determination means, steps 103 to 110 constitute second required torque calculation means, and steps 112 to 118 constitute inverter control means. In particular, steps 104, 105 and 106 constitute a rotation speed calculation means, and steps 107, 108 and 109 constitute a rotation speed selection means.
The predetermined rotational speed ωo is the first rotational speed of the present invention, the temporary target rotational speed ω1 is the second rotational speed, the rotational speed command lower limit value ωL is the third rotational speed, and the torque request value τ1 is The torque command value τ 2 corresponds to the first torque request value and the second torque request value.
[0029]
As described above, according to the present embodiment, when the electric motor 9 starts in a locked state or enters an ultra-low speed rotation state due to an insufficient depression amount of the accelerator pedal when starting on a slope, the rotation speed command generation unit 3 The torque control to the inverter 8 is determined to determine the start of over-rise prevention torque control, and the rotation speed ω is set to ω1 or more, and the inverter temperature TI due to the temperature rise of a specific one-phase switching element due to one-phase conduction is The rising phenomenon can be avoided.
[0030]
In particular, since the temperature rise of the switching element has a correlation with the integral value during the energization time of the current flowing through the one-phase switching element, the rotation speed command lower limit calculator 12 reflects the current inverter temperature TI, and the rotation speed The command lower limit value ωL is calculated, and the rotational speed command restriction processing unit 4 compares the rotational speed command lower limit value ωL with the rotational speed ω1 and selects the higher rotational speed as the rotational speed command value ω2, so that the inverter temperature TI The possibility of reaching overtemperature is reduced.
That is, it is possible to prevent the vehicle from being locked when climbing up, and the possibility of torque reduction due to a decrease in the inverter output of the overtemperature protection function of the inverter 8 is reduced, so that the climbing can be performed smoothly.
[0031]
Even when the torque control flow for preventing the inverter temperature from rising due to the accelerator pedal depression is insufficient, if the rotational speed ω of the electric motor 9 exceeds the rotational speed command value ω2, that is, the vehicle starts moving, and the inverter temperature is excessively increased. When the rotation speed is avoidable, the torque command value selection unit 6 switches to normal torque control and controls the inverter 8 based on the torque request value τ1 corresponding to the accelerator opening. It can be done in a short time.
[Brief description of the drawings]
FIG. 1 is a diagram showing a configuration of a control device for a vehicle motor according to an embodiment of the present invention.
FIG. 2 is a flowchart showing the operation of the embodiment.
FIG. 3 is a flowchart showing the operation of the embodiment.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Accelerator opening degree detection part 2 Torque request value calculation part 3 Rotation speed command production | generation part 4 Rotation speed command limitation process part 5 Torque command value calculation part 6 Torque command value selection part 7 Inverter control part 8 Inverter 9 Electric motor 10 Inverter temperature detection part 11 Motor Rotational Speed Detection Unit 12 Rotational Speed Command Lower Limit Calculation Unit 20 Motor Control Unit

Claims (2)

An inverter that controls drive power supplied to an electric motor provided in the vehicle;
First request torque calculating means for calculating a first torque request value for the electric motor based on a driver's accelerator operation amount;
A rotational speed detection means for detecting the rotational speed of the electric motor;
Determination means for determining that the first torque request value is equal to or greater than a predetermined torque value and the rotation speed of the electric motor is equal to or less than a predetermined first rotation speed;
Second required torque calculation means for calculating a second torque request value based on a predetermined second rotation speed greater than the first rotation speed;
When the first torque request value is less than the predetermined torque value or the rotation speed of the electric motor is greater than the first rotation speed, the inverter is controlled based on the first torque request value, and the first An inverter control means for controlling the inverter based on the second torque request value when the torque request value of the motor is equal to or higher than the predetermined torque value and the rotational speed of the motor is equal to or lower than the first rotational speed ;
Temperature detecting means for detecting the temperature of the inverter;
The second required torque calculation means includes:
Based on the previous second torque request value and the temperature of the inverter, a rotation speed calculation means for calculating a third rotation speed of the electric motor in which the inverter does not overheat;
A rotation speed selection means for comparing the third rotation speed with the second rotation speed and selecting a larger rotation speed;
2. A control apparatus for a motor for a vehicle according to claim 1, wherein the current second torque request value is calculated based on the rotation speed selected by the rotation speed selection means . The inverter control means determines that the first torque request value is equal to or greater than the predetermined torque value and the rotation speed of the electric motor is equal to or less than the first rotation speed, and then the rotation speed is determined by the rotation speed selection means. If it is less than the selected rotational speed, the inverter is controlled based on the second torque request value;
2. The vehicle motor according to claim 1, wherein the inverter is controlled based on the first torque request value when the rotation speed of the electric motor is equal to or higher than the rotation speed selected by the rotation speed selection means. Control device.

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