JP2628508B2 - Motor overcurrent detection device - Google Patents

Description

The present invention relates to a device for detecting an abnormality of an electric drive source such as an electric motor used for driving an in-vehicle device, for example. In particular, the present invention relates to a device that monitors a current flowing through an electric drive source and detects whether there is an abnormality.

[Related Art] In drive control of an electric motor, it is necessary to detect whether or not the motor is locked. That is, if a load exceeding the driving torque generated by the electric motor is applied to the motor, the motor is energized in a stopped (locked) state, and may overheat, burn out, or cause a fire. . In order to eliminate this kind of inconvenience, it is necessary to detect the presence or absence of the motor lock, and to stop the motor when the lock occurs.

As a method for detecting the lock of the electric motor, the following is conventionally known.

(A) The current flowing through the armature of the electric motor is detected, the level of the current is compared with a predetermined reference level (fixed level), and the presence or absence of lock is detected based on the result of the comparison.

(B) detecting a current flowing through the armature of the electric motor, and comparing the level of the current with a predetermined reference level; The reference level changes in proportion to the power supply voltage applied to the electric motor.

[Problems to be Solved by the Invention] The graph of FIG. 5a is a graph for explaining the characteristics of the method (a), and the power supply voltage Vb and the detected current level Vm
The relationship with A is shown. The current flowing through the motor changes according to the magnitude of the load on the motor. However, if the power supply voltage is equal to or higher than a predetermined value, the current does not change even if the power supply voltage changes. Therefore, when the motor is performing a steady operation, the level VmA becomes the steady level Vm0. The reference level Vref is
As shown in FIG. 5a, the level is set to a level slightly larger than the steady level Vm0. When the load on the motor increases and an overcurrent flows, VmA> Vref, and the motor lock is detected. However, the actual motor lock occurs at VmA
Is a time (in the area shown by hatching) larger than the straight line C1 shown in FIG. 5a. Therefore, in the method (a), there is a lock undetectable region, and when the power supply voltage is low, even if the motor is locked, it cannot be detected.

The graph in FIG. 5b is a graph for explaining the characteristics of the method (b), and shows the relationship between the power supply voltage Vb and the detected current level VmB. As can be seen from FIG. 5b, (b)
In the method (1), the reference level Vref is set so as to increase in proportion to the power supply voltage Vb and to be slightly lower than the level determined by the straight line C1. Therefore, there is no lock undetectable area in the method (b). However, the power applied to the electric motor increases in proportion to the power supply voltage. As the power increases, the amount of heat generated by the electric motor increases. In other words, even if the current level is in the region where the motor does not lock,
If it is higher than the steady level, the amount of heat generated by the motor increases in a region where the power supply voltage is high, and the same problem as in the case of occurrence of motor lock occurs.

SUMMARY OF THE INVENTION It is an object of the present invention to provide an overcurrent detection device for a motor that can detect the presence or absence of operation lock regardless of the magnitude of a power supply voltage and can detect the presence or absence of abnormal heat generation when unlocked.

[Structure of the Invention] [Means for Solving the Problems] In order to achieve the above object, in the present invention, when the power supply voltage is equal to or lower than a predetermined value, the level changes in proportion to the power supply voltage, When the power supply voltage exceeds the predetermined value, a reference signal having a substantially constant level is generated irrespective of the power supply voltage, and the level of the reference signal is compared with a level corresponding to the current flowing through the motor to determine an overcurrent. Identify the presence or absence of

[Operation] Since the current level at which the motor lock occurs changes in proportion to the power supply voltage, when only the motor lock is detected, the reference level to be compared with the current level is set as in the method (b) described above. Then, it may be changed in proportion to the power supply voltage.

On the other hand, even if the power supply voltage increases, the level of the current flowing through the motor is constant. The driving torque of the motor increases as the power supply voltage increases. However, the maximum value of the magnitude of the load applied to the motor is substantially constant except when an abnormality occurs. Therefore, the maximum value of the current in the steady state is constant, and if the lock of the motor is ignored, the reference level of the current for identifying the presence or absence of the abnormal load may be a fixed level.

The motor enters the locked state when the load applied to the motor becomes larger than the driving torque of the motor.
Therefore, assuming that the magnitude of the load in a steady state is constant, when the power supply voltage becomes equal to or lower than the predetermined value Vt, the driving torque becomes smaller than the load and the motor locks, and when the power supply voltage exceeds Vt, the lock is disabled. Does not occur. Conversely, when the power supply voltage is equal to or lower than the predetermined value Vt, the motor may be locked even if the load is steady.

Therefore, when the power supply voltage is equal to or lower than Vt, the level corrected in proportion to the power supply voltage is used to detect the motor lock, and when the power supply voltage exceeds Vt, it is determined whether the current is at a level corresponding to a steady load. In order to perform detection, a predetermined fixed level may be set as a reference level. As a result, there is no lock undetectable region in a region where the power supply voltage is low, and it is possible to detect an overload in the unlocked state in a region where the power supply voltage is high.

The boundary between the region in which the reference level is changed in proportion to the power supply voltage and the region in which the reference level is set to a fixed level, that is, the transition level (corresponding to Vt) in the power supply voltage, depends on the driving torque generated in the motor and the motor. The power supply voltage may be set to a level obtained by adding a predetermined margin level to the power supply voltage at the time when the maximum value of the load applied in the steady state matches.

In general, in overcurrent detection, in order to eliminate the influence of noise or the like, overcurrent is not detected when the time during which the detected current exceeds the threshold level is short, and the overcurrent is continued when the time continues for a predetermined time or more. Is to be detected.

However, the cause of the occurrence of the abnormality is different between the abnormality when the motor is locked and the abnormality when the load exceeds the steady level. Therefore, it is determined whether or not the comparison result between the detected current level and the reference level is appropriate. The time required for each differs. Therefore, in a preferred embodiment of the present invention, it is determined whether or not the comparison result between the detected current level and the reference level is valid according to whether the power supply voltage exists in the larger or smaller area with the transition level as a boundary. Change the time limit. That is, a time period suitable for each is set according to the cause of the abnormality to be detected. Thereby, erroneous detection of abnormalities and detection delay can be eliminated.

Other objects and features of the present invention will become apparent from the following description of embodiments with reference to the drawings.

[Embodiment] FIG. 2 shows a configuration of a type of vehicle height adjusting apparatus for implementing the present invention. Referring to FIG. 2, 1FL, 1FR, 1R
L and 1RR denote front left, front right, rear left and rear right wheel suspensions, respectively. These suspension devices are provided with an air spring, and by introducing / discharging air into / from the air chamber of the air spring,
The distance between the wheels and the vehicle body, that is, the vehicle height is adjusted. The vehicle height sensor 2 detects the distance between the vehicle body and the chassis to identify the vehicle height.

The microcomputer 10 receives a signal from the vehicle height sensor 2 and determines whether the current vehicle height is high, appropriate or low with respect to the target vehicle height. If the current vehicle height is high, the microcomputer 10 discharges air from the air chamber of the air spring. To lower the vehicle height, and if low, introduce air into the air chamber to increase the vehicle height.

That is, when discharging the air, the signal SG3 is set to the low level L.
And the exhaust solenoid valve 3 is opened. When the solenoid valve 3 opens,
The air in the air chamber of the air spring is released to the atmosphere through the dryer 4 and the solenoid valve 3, so that the amount of air in the air chamber decreases and the vehicle height decreases. When introducing air, signal SG4
Is set to the low level L and the relay 5 is energized. When the relay 5 is energized, its electrical contacts close, power is supplied to the electric motor 6, and the electric motor 6 is driven. Electric motor 6
Drives the air compressor 7. The air compressor 7 introduces air from the atmosphere via the input port 8 and the check valve 9, and supplies the compressed air to the air chamber of the air spring via the dryer 4. As a result, the amount of air in the air chamber of the air spring increases, and the vehicle height increases.
11 is a relief valve.

One end of an electrode of the electric motor that drives the air compressor 7 is connected to the plus terminal of the on-vehicle battery 12 via an electrical contact of the relay 5, and the other end is grounded via a resistor R1. The resistor R1 is provided for detecting a current flowing through the armature of the electric motor 6. That is, a voltage proportional to the current flowing through the electric motor 6 appears between the two terminals of the resistor R1. This voltage is applied to the overcurrent detection circuit 20. Two signals SG1 and SG2 output from the overcurrent detection circuit 20 are applied to the input port of the microcomputer 10.

FIG. 3 shows a specific configuration of the overcurrent detection circuit 20 shown in FIG. Please refer to FIG. An analog signal SG5 corresponding to the current level of the electric motor 6 is applied to the positive input terminal of the operational amplifier OP1 via the resistors R2 and R3.
The operational amplifier OP1 is configured as an analog comparator, and includes a reference voltage Vref applied to a minus input terminal of the OP1 and a voltage VSG of a signal SG5 applied to a plus input terminal of the OP1.
Compare with m.

Reference voltage Vref is generated by resistors Ra, Rb, Rc and zener diode ZD. The resistors Ra, Rb, and Rc constitute a voltage divider, and generate a divided potential according to the voltage between the power supply line (Vb) and the ground line. The Zener diode ZD limits the voltage so that the potential at the connection point between the resistors Ra and Rb does not exceed a predetermined value. Therefore, the reference voltage Vref
As shown in FIG. 1, when the power supply voltage Vb is equal to or lower than the predetermined voltage Vbz, the power supply voltage Vb changes in proportion to the voltage Vb, and is maintained at a constant value when Vb exceeds Vbz.

The graph of FIG. 6 shows the load torque-rotation speed characteristics and the load torque-motor current characteristics of the electric motor 6 shown in FIG. The load torque applied to the electric motor 6 in the steady state is within a predetermined range. In this example,
The maximum value of the load torque in the steady state becomes Tmax. Therefore, considering the case where the load torque is constant at Tmax, it can be seen that when the power supply voltage Vb becomes about 10 V or less, the number of revolutions becomes 0 and the motor is locked. From FIG. 6, the current flowing through the motor is proportional to the load torque, and the load torque is Tm.
It can be seen that the current becomes Imax at the time of ax. That is, if the current exceeds Imax, it can be considered that the load is overloaded. The current Imax corresponds to Vm0 shown in FIG. 1 when converted into the level of the signal SG5 (Vm).

Therefore, in this embodiment, as shown in FIG. 1, in a region where the power supply voltage is equal to or higher than the predetermined voltage Vbz, the level of the reference voltage Vref is set to a constant value in order to detect the occurrence of an overload exceeding the load in a steady state. Set to Vr1. Therefore, in this area,
As long as no overload occurs, it can be seen that Vref> Vm0. In this case, the level Vr1 of the reference voltage Vref is determined by the Zener voltage Vz of the Zener diode ZD as shown in the following equation (1).

Vr1 = Vz · Rc / (Rb + Rc) (1) The power supply voltage Vb at the switching point of the characteristic curve of the reference voltage Vref
z is expressed by the following equation (2).

Vbz = Vz ・ (Ra + Rb + Rc) / (Rb + Rc) (2) In a region where the power supply voltage is equal to or lower than Vbz, the reference voltage Vref is expressed by the following equation (3).

Vref = Vb · Rc / (Ra + Rb + Rc) (3) Therefore, in this region, the reference voltage Vref is determined by the resistors Ra and R
It is determined by the voltage dividing ratio of the resistive voltage divider composed of b and Rc and the power supply voltage. Also, as is clear from FIG. 1, in this region, the level of Vref is slightly lower than the level indicated by the straight line C1 indicating the boundary between the motor lock region and the unlock region. The reference voltage Vref and the straight line C1 are both the power supply voltage.
It can be seen that there is a proportional relationship with Vb. Therefore, when the electric motor 6 approaches the locked state, Vm> Vref. In this case, even if the magnitude of the load is within the range of the steady level, if the power supply voltage Vb is abnormally low, Vm0> V
ref and the current is considered abnormal. Conversely, even when the power supply voltage Vb is abnormally low, if the magnitude of the load at that time is extremely small, there is no possibility that the motor will be locked, so the current level is not regarded as abnormal.

FIG. 3 is referred to again. When the current level is normal, that is, when Vm <Vref, the output level of the operational amplifier OP1 becomes low level L, and via the diode D1 and the resistor R6,
A low level L is applied to the base terminal of the transistor Q1,
Since Q1 is turned off, the signal SG1 output from the collector terminal of Q1 becomes high level H. When the current level becomes abnormal, that is, when Vm> Vref, the output level of the operational amplifier OP1 is inverted to the high level H, and the high level H is applied to the base terminal of the transistor Q1 via the diode D1 and the resistor R6. , The transistor Q1 turns on, and the signal SG1 output from the collector terminal of Q1 goes low.

On the other hand, when the power supply voltage Vb is equal to or lower than Vbz, the resistors Ra and Rb
Since the voltage between the connection point and the ground is equal to or less than the Zener voltage of the Zener diode ZD, almost no current flows through the Zener diode ZD, and therefore the voltage drop across the resistor Ra is very small. In this case, the transistor Q2 turns off, the transistor Q3 turns off, and the signal SG2 goes high. When the power supply voltage Vb exceeds Vbz, the voltage between the connection point of the resistors Ra and Rb and the ground exceeds the Zener voltage of the Zener diode ZD. The descent increases. In this case, the transistor Q2 turns on, Q3 turns on, and the signal SG2 goes low.

The signals SG1 and SG2 are applied to the input port of the microcomputer 10, as shown in FIG. Therefore, the microcomputer 10 can know whether the current flowing through the electric motor 6 is abnormal and whether the power supply voltage is equal to or lower than Vbz.

In FIG. 3, IC1 is a stabilized voltage Vcc.
This is an integrated circuit that has the function of a regulator that generates (+ 5V).

FIG. 4 schematically shows the operation of the microcomputer 10 shown in FIG. This will be described with reference to FIG. When the power is turned on, an initialization process is executed to clear memories, flags, ports, and the like (step 1). In step 2, the state of the prohibition flag Fdis is checked. This flag is cleared to 0 by the initialization processing.

If the prohibition flag Fdis is 0, the process proceeds to step 3. In step 3, the vehicle height information SG0 output from the vehicle height sensor 2 is input, and the vehicle height at that time is identified. Next, the current control state is identified. That is, in step 4, it is checked whether or not the vehicle height reduction control is being performed with reference to the flag FE. If the vehicle height reduction control is not being performed, it is checked in step 5 whether or not the vehicle height raising control is being performed with reference to the flag FC. If the vehicle height raising control is not being performed, it is further determined in step 6 whether the current vehicle height is lower than the target vehicle height range. If not, step 7 further determines whether the current vehicle height is higher than the target vehicle height range.

When it is detected in step 4 that the vehicle height reduction control is being performed, the process proceeds to step 9. In step 9, it is determined whether or not the current vehicle height is higher than the target vehicle height range. When the current vehicle height is within the target vehicle height range, the routine proceeds to step 10, closes the exhaust electromagnetic valve 3, and clears the vehicle height reduction control flag FE to zero.

If it is detected in step 5 that the vehicle height raising control is being performed, the process proceeds to step 21. In step 21, the state of the abnormal current signal SG1 is referred to. If SG1 is at the low level L, that is, Vm> Vref, the process proceeds to step 12, otherwise, the process proceeds to step 22. In step 22, the timer TM is stopped and the count value is cleared.

In step 12, the timer flag Ftm is referred. In the initial state, the flag Ftm is 0. When Ftm is 0, the process proceeds to step S13. In step 13, the flag Ftm is set to 1, the timer TM is started, and the routine proceeds to step 14.

In step 14, the state of the signal SG2 is referred to. When SG2 is H, that is, when the power supply voltage Vb is equal to or lower than Vbz, the process proceeds to step 15, and otherwise, the process proceeds to step 17. In step 15, the count value of the timer TM is compared with a predetermined fixed value T1. If TM> T1, it is considered that the current of the motor 6 is abnormal, the prohibition flag Fdis is set to 1, and the routine proceeds to step 20. In step 17, the count value of the timer TM is compared with a predetermined fixed value T2. And if TM> T2,
It is considered that the current of the motor 6 is abnormal, and the prohibition flag Fdis
Is set to 1 and the process proceeds to step 20.

If no abnormality is detected, the process proceeds to step 19. Steps
At 19, it is determined whether or not the current vehicle height is lower than the target vehicle height.
When the current vehicle height is within the target vehicle height range, the process proceeds to step 20.

In step 20, the signal SG4 is set to the high level H to turn off the relay 5, thereby stopping the energization of the electric motor 6 and stopping the driving of the compressor 7. Then, the vehicle height increasing control flag FC is cleared to 0.

When an abnormality is detected, the prohibition flag Fdis becomes 1,
After the drive of the electric motor 6 is stopped, the process does not proceed from the process of step 2, and the subsequent operation is prohibited.

An abnormality is detected when the duration during which the signal SG1 is at the abnormal level L exceeds the time determined by T1 or T2. This time is automatically switched according to the state of signal SG2. That is, when SG2 is at a high level H, the target of the abnormality detection is whether or not the motor 6 is locked, and when SG2 is at a low level L, the target of the abnormality detection is a large load of the motor 6 at a steady state or higher. It depends on the cause of the abnormality, and the state of SG2 is determined. When the motor locks, even if the power supply voltage increases slightly, the motor will not start again, so when detecting the motor lock, if the current reaches an abnormal level, it will take a relatively short time. It is preferable to regard it as abnormal. On the other hand, in the case of an abnormality where the load becomes steady or higher, the cause of the abnormality may disappear within a relatively short time. Is preferred.

Therefore, in this embodiment, T1 <T2 is set, the abnormality is detected in a relatively short time when detecting the lock of the motor, and the abnormality is detected in a relatively long time when the excessive load is detected. Is to be detected.

In the above-described embodiment, the occurrence of an abnormality is detected when the state in which the abnormal current is detected continues for a predetermined time. For example, the current level is detected before the comparator (OP1 in the embodiment). When the indicated signal (SG5 in the embodiment) is passed through a filter having a relatively large time constant, or when the level of the reference signal (Vref in the embodiment) has a sufficiently large margin with respect to the steady-state value of the current level May use the comparison result of the comparator directly as the presence or absence of an abnormality.

[Effects] As described above, according to the present invention, it is possible to reliably detect whether or not the motor is locked due to a decrease in the power supply voltage, irrespective of a change in the power supply voltage level. The presence or absence of abnormal heating of the motor caused by the load can also be reliably detected.

[Brief description of the drawings]

FIG. 1 is a graph showing a relationship among a power supply voltage Vb, a current-corresponding voltage Vm, a reference voltage Vref, and a motor lock region of an overcurrent detection circuit 20 embodying the present invention. FIG. 2 is a block diagram showing a schematic configuration of one type of vehicle height adjusting device. FIG. 3 is an electric circuit diagram showing a specific configuration of the overcurrent detection circuit of FIG. FIG. 4 is a flowchart showing an outline of the operation of the microcomputer 10 in FIG. 5a and 5b are graphs showing the relationship between the power supply voltage Vb, the current detection levels VmA, VmB, and the reference level Vref in the conventional overcurrent detection method. FIG. 6 is a graph showing the relationship between the load torque and the number of revolutions of the electric motor 6 used in the embodiment, and the relationship between the load torque and the current. 1FL, 1FR, 1RL, 1RR: Suspension device 2: Vehicle height sensor, 3: Exhaust solenoid valve 4: Dryer, 5: Relay 6: Electric motor (motor) 7: Compressor, 8: Input port 9: Check valve 10: Microcomputer (protection means) 11: relief valve, 12: on-board battery R1: resistor (current detection means) ZD: Zener diode Ra + Rb + Rc + ZD: (reference signal generation means) OP1: operational amplifier (comparison means)

Continuing from the front page (72) Inventor Toshiaki Hamada 2-1-1 Asahi-cho, Kariya-shi, Aichi Aisin Seiki Co., Ltd. (72) Inventor Masanori Hirose 1-Toyota-cho, Toyota-shi, Aichi Japan Examiner, Toyota Motor Corporation Keiichi Sugita (56) References Registered Utility Model 338742 (JP, Z1)

Claims (4)

(57) [Claims] A current detecting means for outputting an electric signal corresponding to a level of a current flowing through the motor; a means for detecting a power supply voltage applied to the motor; and a means for limiting the voltage, wherein the power supply voltage is a predetermined value. In the following cases, the level changes in proportion to the power supply voltage, and when the power supply voltage exceeds the predetermined value, outputs a reference signal having a substantially constant level irrespective of the power supply voltage. Comparing means for comparing the level of the electric signal output by the current detecting means with the level of the reference signal output by the reference signal generating means to identify the presence or absence of an overcurrent of the motor and to detect an abnormality; An overcurrent detection device for a motor, comprising: protection means for performing a predetermined protection process on control of the motor when the comparison means detects an abnormality. 2. The reference signal generating means according to claim 1, wherein said power supply voltage is a transition level obtained by adding a predetermined margin level to a level when a generated torque of said motor matches a magnitude of a load applied to said motor in a steady state. In the following cases, the level changes in proportion to the power supply voltage, and when the power supply voltage exceeds the transition level, outputs a reference signal having a substantially constant level irrespective of the power supply voltage. The overcurrent detection device for an electric motor according to the range (1). 3. The comparing means includes time limit means for counting a time during which a predetermined comparison result is continuously obtained. When the power supply voltage is equal to or lower than the transition level, the time means counts a first time limit. The overcurrent detection device for an electric motor according to claim 2, wherein an abnormality is detected, and when the power supply voltage exceeds the transition level, the time means counts the second time period to detect the abnormality. 4. The reference signal generating means according to claim 1, wherein said reference signal generating means includes a resistor voltage divider inserted between power supply lines and a Zener diode connected to a part of said resistor voltage divider. Item, Item (2) or (3).