JP3933126B2 - Vehicle overload prevention device - Google Patents

Description

  The present invention relates to an overload prevention device for a vehicle including a motor driven using a plurality of switching elements, and more particularly, to a switching element that drives a motor when the vehicle is locked on an uphill. The present invention relates to an overload prevention device for a vehicle that prevents an overcurrent from being damaged.

An electric vehicle driven by a motor may not start if the accelerator is depressed for a while when climbing. That is, the electric vehicle starts running when the motor generates a predetermined output torque according to the amount of depression of the accelerator, and the motor generates an output torque larger than the running resistance against the vehicle. In the depressed state, the motor output torque is small, and when the running resistance against the vehicle is large, such as during climbing, the motor is in the locked state, and when the motor is in the locked state (ie, the phase of the stator and rotor is constant). Thus, the current flows continuously only to the specific switching element supplying the current to the motor. If the motor lock state continues for a long time, the temperature of a specific switching element to which current is continuously supplied rises, and if the resistance value of the element (for example, about 100 degrees to 200 degrees) is exceeded, the element is destroyed by heat. There was a problem that. As a conventional technique for preventing such switching element destruction of the motor, there is a technique for limiting the output of the motor (current supplied to the element) for temperature protection of the switching element (see Patent Document 1). .
In addition, as a conventional technique of an overheat protection device such as a power converter, a method of reducing a load by changing a carrier frequency of an element, a method of reducing a torque (energization current) by estimating a temperature, and the like have been proposed (Patent Document 2,). (See 3, 4). In conventional technologies such as reducing the current that flows through the element at the time of locking to prevent thermal destruction of the element, the field of the motor is lowered and the responsiveness is deteriorated, or the torque is reduced as the current value is lowered. There is a problem that the motor torque is not generated according to the accelerator opening because the current is reduced.
Furthermore, as a prior art, there is a method in which when the energization current is reduced and the reverse rotation (the motor starts to move) is started, the energization pattern is sequentially changed to generate a torque when it coincides with the energization phase (see Patent Document 5). ). In the above, since the energization pattern is changed after the torque in the reverse direction is generated while reducing the energization current, there is a problem that the acceleration increases depending on the slope of the slope.
Japanese Patent Laid-Open No. 11-215687 (paragraphs 0007-0008, FIG. 2) Japanese Patent Laid-Open No. 9-70195 (paragraph 0004, FIG. 3) Japanese Patent Laid-Open No. 10-164703 (paragraph 0009, FIG. 3) Japanese Patent Laid-Open No. 10-210790 (paragraph 0015, FIG. 4) JP 2001-177905 A (paragraph 0004, FIG. 4)

  An object of the present invention is to provide a vehicle overload prevention device (element protection device) that solves the above-described problems of the prior art.

An overload prevention device for a vehicle according to the present invention includes:
A vehicle overload prevention device including a motor driven by an alternating current obtained by converting a direct current by a plurality of switching elements,
Acceleration request detection means (circuit) for detecting a driver acceleration request (accelerator opening);
Motor rotation speed detection means (circuit) for detecting the rotation speed of the motor;
A lock state determination unit that determines whether or not the vehicle is locked based on the driver acceleration request detected by the acceleration request unit and the motor rotation speed detected by the motor rotation speed detection unit;
When it is determined that the lock state is determined to be in the lock state, the current supply target element is forcibly commutated between the plurality of switching elements , that is, switched (the phase of the stator / rotor and the like) Element commutation control means (circuit) forcibly switching energization to each element regardless of the motor rotation speed;
It is characterized by comprising.

According to the present invention, when a wheel falls into a locked state (including an ultra-low speed state) on a muddy road, sandy ground, snowy road, etc., when climbing a hill, an excessive response to a specific switching element in response to a driver acceleration request. It is possible to prevent the current from being continuously supplied (beyond the withstand capability of the element) and being destroyed by heat by “forced commutation (switching) ”. In this configuration, while the current value is not reduced and the element's thermal countermeasures are taken by “forced commutation (switching) ” that is independent of the motor phase, the current within the element's tolerance can be supplied, so the torque is greatly affected. It is possible to prevent thermal destruction of the element without giving the resistance. Therefore, the response of the motor torque can be improved compared to the prior art. Furthermore, since the current value is not reduced in this configuration, there is also a merit that a sense of incongruity does not easily occur between the accelerator opening of the driver and the motor torque. That is, when the current value is reduced as in the prior art, the current value is once reduced (that is, the torque is reduced), and when the lock state is exited, a situation occurs in which the current value is returned to the current value corresponding to the accelerator opening at that time ( That is, the torque rises), and since there is a delay in the rise of the current value due to such a series of current value changes (that is, torque changes), the driver feels that the acceleration is insufficient. According to “ Switching ”, it is possible to minimize the deterioration of the acceleration deficiency. Furthermore, there is an advantage that the service life of each element becomes longer by applying such heat countermeasures to the element.

Moreover, the vehicle overload prevention device according to the present invention comprises:
The element commutation control means switches the energization pattern for the plurality of switching elements to at least one other energization pattern, and forcibly switches with the other energization pattern.

Furthermore, the overload prevention device for a vehicle according to the present invention includes:
At the time of switching the energization pattern, a current component that contributes to torque (for example, the q axis) is limited.
It is characterized by that.

Furthermore, the overload prevention device for a vehicle according to the present invention includes:
Motor rotation speed detection means (sensor) for detecting motor rotation speed, current value detection means (sensor) for detecting motor current value, or acceleration request detection means (circuit) for detecting driver acceleration request (accelerator opening) )
The lock state determination means refers to a predetermined tolerance map in which an allowable time according to a motor current value or an accelerator opening is defined when the rotation speed of the motor is equal to or lower than a predetermined speed. Determine if there is,
It is characterized by that.

Furthermore, the overload prevention device for a vehicle according to the present invention includes:
The allowable time is shortened as the motor current value increases.
It is characterized by that.

Furthermore, the overload prevention device for a vehicle according to the present invention includes:
The cycle for forcibly switching the current supply target element, that is, the commutation period (period for sequentially switching the current supply to each element) is delayed as the motor current value increases.
It is characterized by that.

Furthermore, the overload prevention device for a vehicle according to the present invention includes:
Temperature detecting means (temperature sensor) for detecting the temperature of each of the plurality of switching elements,
When the rotation speed of the motor is equal to or lower than a predetermined speed, the lock state determination means determines whether or not the lock state is based on whether or not the temperature detected by the temperature detection means is equal to or higher than a predetermined temperature. ,
It is characterized by that.

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.
FIG. 1 is a diagram showing a circuit configuration of a motor control device for an electric vehicle suitable for incorporating an overload prevention device for an electric vehicle (vehicle) according to an embodiment of the present invention.
As shown in the figure, the motor control device has a motor 5 for running an electric vehicle, and the motor 5 is generated by switching DC power from the in-vehicle battery 1 by an inverter circuit 4. The three-phase AC power is supplied to operate. DC power from the battery 1 is supplied to the inverter circuit 4 via the switch 2, and a capacitor 3 is connected to both ends of the inverter circuit 4. Note that the battery 1 can be replaced with a DC generator, that is, an alternator, in the case of a vehicle.

The inverter circuit 4 is composed of six switching elements T1 to T6 made of, for example, an IGBT, a power transistor, a thyristor, and the like, and protective diodes D1 to D6 connected in parallel to the switching elements T1 to T6, respectively. The switching elements T1 to T6 are controlled by the motor controller 12. The switching elements T1 to T6 are mounted on a cooling fin (not shown), and a temperature detecting thermistor 6 for detecting the temperature Ts of the fin is mounted on the switching element cooling fin. The cooling fin temperature Ts detected at 6 is supplied to the motor controller 12.
For example, when the motor is continuously operated, currents of various values are intermittently supplied to each element, so that each element has some heat accumulation. If a temperature sensor is used as in this configuration, it is possible to more effectively prevent the thermal destruction of each element in consideration of the influence of the accumulated heat.

  In order to detect the driving current of each phase when the motor 5 is driven by each switching element T1 to T6 of the inverter circuit 4, the connection line between each switching element T1 to T6 and the motor 5 is formed of a current transformer or the like. Current sensors 7, 8, 9 are provided, and output currents Iu, Iv, Iw of the inverter circuit 4 supplied to the motor 5 are detected by the current sensors 7, 8, 9 and supplied to the motor controller 12.

  The motor 5 is provided with a magnetic pole sensor 10 and a rotation speed sensor 11. The magnetic pole sensor 10 detects the magnetic pole position θ of the motor 5, the rotational speed sensor 11 detects the motor rotational speed N of the motor 5, and each detected value is supplied to the motor control 12.

The motor controller 12 includes, for example, a microcomputer and its peripheral components. The vehicle controller shown in FIG. 3 generates a motor torque command value Tc based on information such as the accelerator opening, and supplies the motor torque command value Tc to the motor 5 according to the motor torque command value Tc. The three-phase currents Iu, Iv, and Iw to be controlled are controlled. Conventionally, for example, when an electric vehicle enters a locked state on an uphill, for example, the motor torque is decreased by a predetermined value to change the phase region of the motor, thereby performing a control operation to release the locked state. The current value is reduced to such an extent that the element is not destroyed. Further, the motor controller 12 controls the switching 2 to supply DC power from the battery 1 to the inverter circuit 4.
The vehicle overload prevention device of the present invention is preferably implemented in a form incorporated in such a motor controller 12.

FIG. 2 is a block diagram showing the basic components of a vehicle overload prevention device according to an embodiment of the present invention.
As shown in the figure, the vehicle 20 includes a battery 22, an inverter 24 having a plurality of switching elements 23 for converting a direct current from the battery into an alternating current, and a motor 26 driven by the alternating current from the inverter. The overload prevention device 30 according to the present invention is in a locked state by a lock state determination means (circuit) 32 for determining a lock state in which the motor does not substantially rotate when a driver acceleration request is made, and a lock state determination means 32. If determined, element commutation control means (circuit) 34 for forcibly commutating (switching) the current supply target element among the plurality of switching elements 23 in the inverter 24 is provided. Hereinafter, the present invention will be described in more detail with reference to a more detailed circuit configuration.

  FIG. 4 is a flowchart showing the processing procedure of the overload prevention apparatus according to one aspect of the present invention. With reference to this figure, the effect | action of this invention in a structure like FIG. 1 is demonstrated. As shown in the figure, first, in order to check whether or not the electric vehicle is in a locked state, a first predetermined motor rotation such as a motor rotation speed N of the motor 5 detected by the rotation speed sensor 11 is 100 rpm, for example. It is checked whether or not the speed is smaller than the speed Np1 (step S11). If the motor rotational speed N is smaller than the first predetermined motor rotational speed Np1, the motor current Ic is larger than the motor current predetermined value Ip. (Step S13), and when the motor current Ic is larger than the motor current predetermined value Ip, it is determined that the motor 5 of the electric vehicle is in a locked state including an ultra-low rotational speed state. For example, when the motor is locked, the predetermined motor current value Ip causes the maximum current that the switching element can continuously allow to the motor 5 from one switching element in the inverter circuit 4 to output the output torque of the motor 5. A value obtained from the accelerator opening, for example, 200A.

  On the other hand, if it is determined in step S11 that the motor rotation speed N is not smaller than the first predetermined motor rotation speed Np1, the process proceeds to step S41, and the motor rotation speed N is set to a second predetermined value such as 120 rpm. It is checked whether or not the motor rotational speed Np2 or less. If so, the lock flag is set to 0 (step S43), indicating that it is not locked, and the process proceeds to step S21. If not, the process proceeds directly to step S21. As described above, in the present embodiment, two motor rotation speeds Np1 and Np2 are provided as motor rotation speeds used for determination of the locked state of the motor, and a hysteresis of, for example, 20 rpm width is given to the motor rotation speed. Chattering that switches the state judgments violently is prevented.

  If it is determined in step S13 that the accelerator opening degree Ac is not greater than the accelerator opening predetermined value Ap, the process proceeds to step S45, where it is checked whether or not this state has continued for a predetermined time. Is determined not to be in the locked state, the lock flag is set to 0 (step S47), the process proceeds to step S21, and if the predetermined time is not continued, the process proceeds directly to step S21.

  As a result of the determination in steps S11 and S13, if it is determined that the motor 5 is in the locked state, whether or not the lock flag indicating that the motor 5 is in the locked state is 0, that is, the motor 5 is currently in the locked state. Is checked (step S15). In the locked state, a timer value corresponding to the motor current is set based on a predetermined tolerance map (FIG. 6). This timer value is set to a value that reduces the temperature of the element when the switching pattern is changed based on the maximum torque value according to the accelerator opening and the energization time according to the current at that time. The energization time is stored as a timer value (that is, lock time Tr or allowable time).

At this time, the commutation ( switching ) time Ti is set. As shown in FIG. 8, basically, the larger the motor current, the longer the commutation ( switching ) time, thereby suppressing the heat rise of the element due to the excessive current. Then, the lock flag is set to 1 (step S19), indicating that it is currently locked, and the process proceeds to step S21.

  In step S21, it is checked whether or not the lock flag is 1, and it is determined whether or not the lock flag is set. If the lock state is not set, the process is terminated. If the lock flag is 1 and the lock state is set, a process of subtracting a predetermined value C from the current timer value is performed. (Step S23) The predetermined value C is set to a value that subtracts the calculation time required for the current calculation from the previous calculation.

  Then, it is determined whether or not this value has become 0 (step S25). When the value has become 0, a drive frequency based on Ti is obtained and change of the energization pattern is started (S27). If the value is not 0, the process is terminated as it is. When obtaining the energization pattern, the maximum torque is output so that the torque direction at that time is the same as the current direction.

Assuming that Q1-Q6-Q2 is currently energized in FIG. 1 (Q1 to Q6 are not shown) , for example, Q1-16-Q2, Q1-Q3-Q2, Q4-Q3 sequentially -Change to Q2, Q4-Q3-Q5, Q4-Q6-Q5 and finally return to Q1-Q6- Q2 . When switching the energization pattern, the Q axis of the current value for generating torque is set to 0 to prevent the generation of torque. After returning to the original position, or after performing commutation ( switching ) for a predetermined commutation ( switching ) time, the lock flag is returned to 0 (S29) and the process is terminated.
As in this configuration, by switching the energization pattern, other elements (for example, q1-q6-q2) that are supplied with current in the energization pattern at the time of locking other elements (for example, q1-q6-q2) (for example, q4-q3-q5) can also supply current. In other words, evenly flowing current to each element makes it possible to cool the element earlier and prevent thermal destruction of the element more effectively.
Further, when the energization pattern is changed, the current component contributing to the torque (for example, the q axis) is limited to change the energization pattern, so that a torque different from the accelerator operation is generated and the driver feels uncomfortable. Can be prevented. Note that since the switching of the energization pattern is a short time, the torque is reduced for a short time. For example, even on a slope, the car does not proceed against the intention.
Thus, the time during which current flows through each element per unit time is reduced. Therefore, as the motor current value increases, the commutation cycle is delayed, that is, the cycle in which one element is a current supply target is delayed, thereby suppressing the temperature rise of each element. That is, by slowing the commutation period (period for forcibly switching the current supply target element ), the total time during which current flows through one element per unit time is reduced, and the element whose temperature has risen is more easily cooled. Therefore, it is possible to escape from the temperature zone where there is a risk of element destruction at an early stage.

  FIG. 5 is a flowchart showing a modification of the processing procedure of the overload prevention apparatus according to the present invention. The processing procedure is almost the same as in FIG. 5 except for steps S13, S17, and S29 in FIG. In this modification, as shown in step S13A, the locked state is determined based on the motor current value instead of the accelerator opening. Then, as shown in step S17A, a timer value (that is, a lock time or an allowable time) corresponding to the motor current value is set based on a predetermined tolerance map (FIG. 7). A drive frequency based on Ti is obtained (S26), and the change of the energization pattern is started (S27). If the value is not 0, the process is terminated as it is.

FIG. 6 shows an exemplary graph (a tolerance map) showing the relationship between the accelerator opening and the timer value. Similarly, FIG. 7 shows an exemplary graph (a tolerance map) showing the relationship between the motor current and the timer value. These figures show how long each switching element can withstand continuous current supply at each motor current value and accelerator opening when the motor is locked. It is determined whether or not a commutation operation is finally performed based on these tolerance maps that take into account the above.
According to this configuration, torque is continuously applied until each element reaches the maximum permissible time (capacity value) that can withstand continuous supply of the current value according to the motor current value and accelerator opening (that is, current). ). That is, it is possible to efficiently utilize the limit of the capability of the element, and as a result, it is possible to maximize the capability of the motor while avoiding the destruction of the element.

FIG. 8 is an exemplary graph showing the relationship between motor current and commutation ( switching ) time. As shown in the figure, it is assumed that the temperature rise of the element increases as the current value increases. Therefore, it is preferable to set the commutation ( switching ) time to be larger as the current value increases.

  Although the principle of the present invention has been described in various embodiments in the present specification, those skilled in the art can make various modifications and changes to the present invention based on the present disclosure, and these are also included in the present invention. Please note that For example, although an electric vehicle is cited as an example of a vehicle, the present invention is widely applied to various vehicles that use a motor as part or all of a driving force, such as a hybrid vehicle, a fuel cell vehicle, a motorcycle (such as an electric scooter), and a train. Applicable.

It is a figure which shows the circuit structure of the motor control apparatus of the electric vehicle to which the overload prevention apparatus of the electric vehicle concerning one embodiment of this invention is applied. 1 is a block diagram illustrating basic components of a vehicle overload prevention apparatus according to an embodiment of the present invention. It is a block diagram of a vehicle controller. It is a flowchart which shows the process sequence of the overload prevention apparatus by one actual condition aspect of this invention. It is a flowchart which shows the modification of the process sequence of the overload prevention apparatus by the one actual condition aspect of this invention. It is an example graph (withstand capability map) which shows the relationship between an accelerator opening and a timer value. It is an example graph (withstand capability map) which shows the relationship between a motor current and a timer value. It is an example graph which shows the relationship between a motor current and commutation time.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Battery 2 Switch 3 Capacitor 4 Inverter circuit 5 Motor 6 Temperature detection thermistor 7-9 Current sensor 10 Magnetic pole sensor 11 Rotational speed sensor 12 Motor controller T1-T6 Switching element 20 Vehicle 22 Battery 23 Switching element 24 Inverter 26 Motor 30 Overload Prevention device 32 Lock state determination means (circuit)
34 Element commutation control means (circuit)

Claims (7)

A vehicle overload prevention device including a motor driven by an alternating current obtained by converting a direct current by a plurality of switching elements,
Lock state determination means for determining whether or not the lock state based on the driver acceleration request and the rotation speed of the motor;
And when it is determined that the locked state, the plurality of forcedly switching element commutation control unit current supply target element between the switching element in the locked state determining means,
An overload prevention device characterized by comprising: The overload prevention device according to claim 1,
The element commutation control means switches the energization pattern for the plurality of switching elements to at least one other energization pattern,
An overload prevention device characterized by that. The overload prevention device according to claim 2,
When switching the energization pattern, the current component contributing to the torque is limited.
An overload prevention device characterized by that. In the overload prevention device according to any one of claims 1 to 3,
The lock state determination means refers to a predetermined tolerance map in which an allowable time according to a motor current value or an accelerator opening is defined when the rotation speed of the motor is equal to or lower than a predetermined speed. Determine if there is,
An overload prevention device characterized by that. The overload prevention device according to claim 4,
The allowable time is shortened as the motor current value increases.
An overload prevention device characterized by that. In the overload prevention device according to any one of claims 1 to 5,
The cycle for forcibly switching the current supply target element is slower as the motor current value is larger,
An overload prevention device characterized by that. In the overload prevention apparatus of any one of Claims 1-6,
A cooling fin attached to the plurality of switching elements ;
Further comprising temperature detecting means for detecting the temperature of the cooling fin ,
When the rotation speed of the motor is equal to or lower than a predetermined speed, the lock state determination means determines whether or not the lock state is based on whether or not the temperature detected by the temperature detection means is equal to or higher than a predetermined temperature. ,
An overload prevention device characterized by that.

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