JPH10234130A - Motor lock prevention circuit - Google Patents

Abstract

PROBLEM TO BE SOLVED: To protect a motor, even under a low speed semi-locked state generating no overcurrent by setting first and second reference values appropriately, in order to make a decision whether or not a motor is locked based on the current and the rpm. SOLUTION: If a current value, detected upon elapse of a predetermined time after receiving a rotation command signal, exceeds a first reference set value and a detected rpm is lower than a second reference set value, a decision is made that a motor has been locked, and a lock protection is executed. Since the output from an AND circuit 24 goes to H and the output from a NAND circuit 25 goes to L, inverted input S to a latch circuit 26 goes 0 and an inverted input R goes to 1. Consequently, an inverted output Q is set and a power interrupt signal is outputted. That signal is inputted to the reset terminal of a brushless control IC 27 which is thereby reset, and a protective action for preventing conduction takes place.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

The present invention relates to a motor lock protection circuit device.

[0002]

2. Description of the Related Art As a protection circuit for preventing energization when a motor is locked, for example, there is a protection circuit as shown in FIG. This circuit shows a case where the present invention is applied to a drive control circuit of a brushless DC motor. The current is converted into a voltage by a resistor R1 for detecting the current, and this voltage is compared with a reference voltage 2 by a comparator 1. When the conversion voltage becomes equal to or higher than the reference voltage 2, the switching element (MOS type field effect transistor, hereinafter referred to as "MOSFE")
T ") is turned off and the motor coil 5
The current flowing through is limited. Reference voltage 2
Is set in advance to a voltage value corresponding to the value of the overcurrent to be detected. Therefore, when the motor is locked and an overcurrent flows, the energization is automatically stopped.
The control circuit 3 is configured using, for example, a commercially available dedicated IC. Also, a resistor R2 and a capacitor C
Constitutes a filter.

[0003]

However, in such a conventional protection circuit, when the overcurrent state is eliminated, the switching element 4 is turned on again to perform an operation for keeping the current constant. There is a possibility that a constant current may continue to flow while the motor is locked. in this case,
Since the wind does not flow when the motor is locked, for example, the heat sink of the MOSFET 4 is not cooled, and
The SFET 4 may be damaged.

In the above-mentioned protection circuit, the current is limited only at the upper limit, that is, only the overcurrent is limited. In the case where the motor is rotating at a low speed (during low rotation), current is not prevented because of a low current, and protection cannot be performed. In other words, when the motor is completely locked, the motor is not rotating, and therefore an overcurrent tends to flow.However, although a foreign object is trapped in the motor, the motor is completely locked. When the motor is not rotating (semi-locked state), the motor continues to rotate at a speed lower than the target speed, but a current larger than the normal current value but smaller than the overcurrent flows. Will be. Such a semi-locked state is more likely to subsequently transition to a fully locked state,
Since the current continues to flow in the state itself, there may be cases where protection is required as in the case of the completely locked state.

SUMMARY OF THE INVENTION The present invention has been made in view of the above problems in protection when the motor is locked, and can compensate for an overload at low rotation of the motor. It is an object of the present invention to provide a motor lock protection circuit device capable of holding the operation until the operation is performed.

[0006]

In order to achieve the above object, according to the present invention, there is provided a motor lock protection circuit device for preventing energization when a motor is locked. Current detection means for detecting a current, rotation number detection means for detecting the rotation number of the motor, and after a predetermined time has elapsed from the input of the rotation command signal, the output of the current detection means is equal to or more than a first reference value. ,
And a stop signal output means for outputting a signal to stop energization when an output of the rotation speed detection means is equal to or less than a second reference value.

According to the present invention, the current detecting means detects a current flowing in a circuit for driving the motor, and the rotational speed detecting means detects the rotational speed of the motor. The stop signal output means is
A signal for stopping the energization when the output of the current detection means is equal to or more than the first reference value and the output of the rotation number detection means is equal to or less than the second reference value after a predetermined time has elapsed since the input of the rotation command signal. Is output. That is, since it is determined whether or not the motor is in the locked state (overload state) based on the current and the number of rotations, if the first and second reference values are appropriately set, the half-locked state at the time of low rotation where overcurrent does not occur is obtained. In some cases, protection is possible.

According to a second aspect of the present invention, in the first aspect of the present invention, when the stop signal output means enters the state of outputting the stop signal, the stop signal output means keeps the state until a reset signal is input. It is characterized by holding.

In the present invention, when a stop signal is output, the stop signal output means holds the state until a reset signal is input. That is,
Once the protection operation starts, the protection operation continues to operate until reset.

The invention according to claim 3 is characterized in that, in the invention described in claim 1 or 2, the first reference value and the second reference value are predetermined constant values, respectively.

According to a fourth aspect of the present invention, in the first or second aspect of the invention, the first reference value and the second reference value are respectively changed according to a target rotation speed.

[0012]

Embodiments of the present invention will be described below with reference to the drawings. Here, the present invention is applied to a battery-cooling electric fan for cooling a battery mounted on an electric vehicle, and a brushless D fan.
An example using a C motor will be described.

FIG. 1 is a schematic configuration diagram of a brushless motor control system to which the present invention is applied. This brushless motor control system is of a three-phase type,
Magnet rotor 10 having a plurality of magnetized field magnets, and three .DELTA.-connected armature coils 1 which generate torque by interaction with the field.
1, three magnetic detection sensors (for example, Hall elements) 12 for detecting the position of the magnet rotor 10, and six switching elements (for example, MOS) for switching the phase while permitting energization to a predetermined armature coil 11.
FET 13, and a control circuit 14 that performs switching of the MOSFET 13 based on a signal from the Hall element 12 and controls energization to a predetermined amateur coil 11. The control circuit 14 is provided with a lock protection circuit 15 described later. The MOSFET 13 and the control circuit 14 are configured as one drive control circuit, for example, by a printed circuit board and electronic components (including a dedicated IC) mounted thereon. Further, the control circuit 14 includes a controller 1 for comprehensively controlling electric components of the electric vehicle.
6 are connected. From the controller 16 to the control circuit 1
4 is supplied with a brushless motor rotation command signal, and the control circuit 14 is supplied with a brushless motor rotation abnormality signal from the control circuit 14 to the controller 16. The rotation abnormality signal is output when a lock protection operation described later is activated, and the controller 16 that has received this signal displays the fact on a display unit (not shown), for example. Since the operating principle or driving principle of the brushless motor is well known, the description thereof is omitted.

FIG. 2 is a block diagram showing one configuration example of the lock protection circuit 15. As shown in FIG. This lock protection circuit 15
A current / voltage conversion circuit 20, a rotation speed detection circuit 21, a rotation command signal input circuit 22, a delay circuit 23, an AND circuit 24,
It comprises a NAND circuit 25, a latch circuit 26, and a brushless control IC 27. The current detection means is a current / voltage conversion circuit 20, the rotation number detection means is a rotation number detection circuit 21, and the stop signal output means is a rotation command signal input circuit 22, a delay circuit 23, an AND circuit 24, an NA
It is composed of an ND circuit 25 and a latch circuit 26, respectively.

The current / voltage conversion circuit 20 converts a current flowing through a circuit for driving a motor (see FIG. 1) into a voltage, and a predetermined reference voltage (corresponding to a set current value) preset as a first reference value. ), An H (high) signal is output when the detected current value (converted input voltage value) is larger than the set reference value, and L (high) when the detected current value is smaller than the set reference value. Low). Specifically, for example, like the circuit of FIG.
It comprises a current detection resistor connected to the drain of the OSFET 13, a resistor and a capacitor forming a filter, and a comparator for comparing an input voltage with a reference voltage. Here, the reference value for comparison is a current value when the fan speed is Lo (lowest speed), for example, 1.8 A
(Actually, a voltage value corresponding to this). Therefore, when the current flowing through the circuit exceeds 1.8 A, an H signal is output. The output terminal of the current / voltage conversion circuit 20 is connected to one input terminal of the AND circuit 24.

The rotation speed detection circuit 21 compares the rotation speed of the motor with a predetermined reference value as a second reference value, and when the detected rotation speed is smaller than the set reference value, the value of H is detected. It has a function of outputting a signal and outputting an L signal when the signal is equal to or larger than a set reference value. The rotation speed of the motor is obtained based on a signal from the Hall element 12.
Here, the reference value for comparison is that the fan speed is Lo.
The rotation speed in the case of (lowest speed), for example, 780 rpm is set. Therefore, the detected rotation speed is 78
0 rpm (that is, 0 to 780 rpm).
m) An H signal is output. The output terminal of the rotation speed detection circuit 21 is connected to the other input terminal of the AND circuit 24.

The rotation command signal input circuit 22 has a function of outputting an H signal when a rotation command signal is input from the controller 16. The output of the rotation command signal input circuit 22 is provided to the delay circuit 23 and the inverted reset input R of the latch circuit 26.

The delay circuit 23 includes a rotation command signal input circuit 2
2 has a function of delaying an input signal (particularly, an H signal) for a predetermined time. This is to cancel the lock protection operation for a certain period of time so that the lock protection circuit does not operate at the time of startup due to a large current at startup, low rotation (see FIG. 3), other noises, and the like. Therefore, it is preferable that the delay time is an appropriate time (depending on the motor specifications) which is longer than the time required to normally reach the set rotation speed (780 rpm) in a normal state after starting by inputting the rotation command signal. For example,
1 second or less). The output terminal of the delay circuit 23 is connected to one input terminal of the NAND circuit 25. The other input terminal of the NAND circuit 25 is connected to the output terminal of the AND circuit 24.

The latch circuit 26 is a circuit for holding (latching) data. Here, when a lock state of the motor is detected by a logic described later, a lock protection operation is started immediately and an energization stop signal is output. And resets the brushless control IC 27 to maintain the state. To release the hold, turn off the power
Or by setting the rotation command signal to L (that is, a motor stop command). Here, for example,
The latch circuit 26 is an asynchronous SR flip-flop (negative logic SR) having two NAND gates connected in tandem.
Latch). FIG. 4 shows a truth table representing the operation characteristics of the SR latch using the NAND gate. In this truth table, the inversion set input S and the inversion reset input R are not allowed to become 0 at the same time (inhibited state), and the output Q0 in the table is not allowed.
And the inverted output Q0 indicate a holding state, which indicates that the output state before the inverted input S = 1 and the inverted input R = 1 is held. Here, the inverted output Q of the latch circuit 26 is given to the reset terminal of the brushless control IC 27. Note that “0” in the truth table is the state of L,
“1” indicates the state of H, respectively.

The brushless control IC 27 is a commercially available dedicated IC for controlling a brushless motor, and is a main component of the control circuit 14. When the L signal is input to the reset terminal of the brushless control IC 27, the brushless control IC 27 stops energization and stops driving control of the motor.

Next, the operation of the lock protection circuit 15 will be described with reference to FIG. When a rotation command signal is output from the controller 16 to the control circuit 14 (H state) due to other conditions (for example, battery temperature) such as a switch operation of the occupant, the control circuit 14 (brushless control IC 27) The switching of the MOSFET 13 is performed based on the signal, and the energization control to the predetermined amateur coil 11 is started. Immediately after the start, a large current flows through the circuit, and if the circuit is in a normal state (unlocked state), the current gradually decreases to a current value corresponding to the specified target rotation speed and then stabilizes. On the other hand, when the motor is started, the motor starts to rotate. If the motor is in a normal state (unlocked state), the rotation speed gradually increases and stabilizes when the specified target rotation speed is reached. In such a normal state, the output of the current / voltage conversion circuit 20 becomes L, and
Since the output of the rotation speed detecting circuit 21 also becomes L, the output of the AND circuit 24 becomes L and the output of the NAND circuit 25 becomes H. Therefore, the inverting inputs S and R of the latch circuit 26 are both 1 (H), and the inverting output Q is in a stable reset state (state of 1), and the reset signal (energization stop signal) of the brushless control IC 27 is an output. Not done. That is, the lock protection operation is not performed. Since the output of the delay circuit 23 remains at L for a certain period of time after the rotation command signal is input, that is, after the start-up, A
Regardless of the output of the ND circuit 24, the output of the NAND circuit 25 becomes H, and the lock protection operation does not work.

However, after a lapse of a predetermined time from the input of the rotation command signal, the detected current value exceeds the set reference value (1.8 A) (the output of the current / voltage conversion circuit 20 is in the H state). If the detected value of the rotation speed is smaller than the set reference value (780 rpm) (the output of the rotation speed detection circuit 21 is H), the motor is in a locked state (including a half-locked state). And executes the lock protection operation. That is, in this case, the AND circuit 2
4 becomes H and the output of the NAND circuit 25 becomes L. Therefore, the inverted input S of the latch circuit 26 becomes 0 (L) and the inverted input R becomes 1 (H). Therefore, its inverted output Q
Becomes a set state (state of 0), and an energization stop signal (signal of L) is output. This stop signal is input to the reset terminal of the brushless control IC 27 (L input),
The brushless control IC 27 is reset. Thereby, the energization is stopped. That is, when the above condition (logic) is satisfied, the lock protection operation for stopping the energization is activated. This lock protection operation is maintained even when the inverting input S of the latch circuit 26 returns to 1 (H), that is, even when the condition of at least one of the current and the rotation speed is not satisfied. The release of the hold (transition from the set state to the reset state) is performed while the inverted input S of the latch circuit 26 is held at 1 (H) (the output of the NAND circuit 25 always becomes H by stopping the power supply).
This is executed by setting the inversion input R to 0 (L), that is, turning off the power or setting the rotation command signal to L (motor stop command) as described above.

For example, as shown by a broken line in FIG. 3, when a certain time has elapsed after the start and the current has increased beyond the reference value and the rotational speed has decreased below the reference value, the motor Is determined to be in a locked state (including a semi-locked state), and the above-described lock protection operation is performed. As described above, when the motor is completely locked (rotational speed = 0), an overcurrent flows, so that it is of course necessary to protect the motor. Even in the locked state (rotation speed ≠ 0),
Current continues to flow, but wind (cooling) due to motor rotation
Cannot be expected so much, and protection by a fuse cannot be expected.

FIG. 5 is a block diagram showing another example of the configuration of the lock protection circuit 15. As shown in FIG. The same parts as those in FIG. 2 are denoted by the same reference numerals, and the description thereof will be partially omitted. In the first embodiment shown in FIG. 2, the reference values for comparison are constant values, whereas in the second embodiment, they are changed according to the target rotation speed. Specifically, in the first embodiment, a reference value (threshold value) for comparing the current and the rotation speed is set based on the rotation speed of 780 rpm when the fan speed is Lo (minimum speed). However, in the second embodiment, the reference value (threshold) for comparing the current and the rotation speed is changed based on the target rotation speed included in the rotation command signal, and thus the entire range from the low rotation speed to the high rotation speed is changed. Over protection.

Therefore, here, as a configuration, for example, as compared with the first embodiment, the rotational speed / voltage conversion circuit 30 instead of the rotational speed detection circuit 21 and the two comparators 31 and 32 instead of the AND circuit 24 , A three-input NAND circuit 33 is provided instead of the two-input NAND circuit 25. The rotation speed / voltage conversion circuit 30 has a function of converting the rotation speed of the motor by the Hall element 12 into a voltage.
The output of the current / voltage conversion circuit 20 is given to the non-inverting input terminal (+) of the comparator 31, and the output of the rotation command signal input circuit 22 is given to its inverting input terminal (+). The output of the rotation command signal input circuit 22 is provided to the non-inverting input terminal (+) of the comparator 32, and the output of the rotation speed / voltage conversion circuit 30 is provided to the inverting input terminal (+). In this case, the rotation command signal input circuit 22 outputs the voltage value corresponding to the target rotation speed included in the rotation command signal to each of the comparators 31, 32.
Output function. Also, the NAND circuit 33
The outputs of the comparators 31 and 32 and the output of the delay circuit 23 are supplied to the three input terminals. In this case,
The current detection means is a current / voltage conversion circuit 20, the rotation number detection means is a rotation number / voltage conversion circuit 30, and the stop signal output means is a rotation command signal input circuit 22, a delay circuit 23, a comparator 31,
32, a NAND circuit 33, and a latch circuit 26.

When the detected current value (input voltage value) is larger than the current value (reference voltage value) corresponding to the specified target rotation speed, the comparator 31 sets H to A signal is output. In the comparator 32,
When the detected rotation speed does not reach the target rotation speed with reference to the specified target rotation speed, an H signal is output. Therefore, after a certain period of time has elapsed since the start-up, when the current is higher than the reference value and the number of revolutions is lower than the reference value, that is, the motor is in the locked state (including the half-locked state). If it is determined that there is, as in the case of the first embodiment, the NAND circuit 33
Becomes L, so that the lock protection operation described above is performed.

Therefore, according to each of the above-described embodiments, it is not limited to the overcurrent as in the related art, but whether or not the lock state (overload state) is determined based on the current and the rotation speed. By setting the value appropriately, protection is possible even in the case of an overload state at the time of low rotation. This is extremely useful because a large current does not flow during low rotation and protection by a fuse cannot be expected.

According to each of the above embodiments, the latch circuit 26 is provided so that once the protection operation starts, the protection operation continues to operate unless the power is turned off or the rotation command signal is set to L. As described above, there is no possibility that the current continues to flow while the motor is locked, and the durability is improved.

Further, according to the second embodiment, since protection is applied in relation to the target rotation speed and the current value and the current rotation speed, the locking (overload) can be performed over a wide range from low rotation to high rotation. ) Protection can be provided.

Although the application to a system using a brushless DC motor has been described as an example, the present invention is not limited to this, and the lock protection according to the present invention can be applied to any motor control system. It is.

[0031]

As described above, according to the first aspect of the present invention, it is determined whether or not the lock state (overload state) based on the current and the number of revolutions, so that the first and second reference values can be appropriately set. By setting, it is possible to protect even in the case of a half-lock overload state at low rotation speed where no overcurrent occurs and protection by a fuse cannot be expected.

According to the second aspect of the invention, in addition to the effect of the first aspect of the invention, once the protection operation is started, the protection operation is continued until reset, so that the motor is locked as in the prior art. There is no danger that current will continue to flow as it is, and durability will be improved.

According to the third aspect of the invention, in addition to the effects of the first or second aspect, the first reference value and the second reference value
Since the reference values are each set to a constant value, the above effects can be enjoyed with a simpler configuration.

According to the fourth aspect, in addition to the effects of the first or second aspect, the first reference value and the second reference value are set.
Since the reference value is variable according to the target rotation speed,
Protection is provided based on the relationship between the target rotation speed, the current current value, and the rotation speed, and protection during locking (at the time of overload) can be performed over a wide range from low rotation to high rotation.

[Brief description of the drawings]

FIG. 1 is a schematic configuration diagram of a brushless motor control system to which the present invention is applied.

FIG. 2 is a block diagram showing one configuration example of a lock protection circuit shown in FIG. 1;

FIG. 3 is a time chart for explaining the operation of the circuit of FIG. 2;

FIG. 4 is a truth table of the latch circuit of FIG. 2;

FIG. 5 is a block diagram showing another configuration example of the lock protection circuit shown in FIG. 1;

FIG. 6 is a schematic configuration diagram illustrating an example of a lock protection circuit of a conventional brushless motor.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 10 ... Magnet rotor 11 ... Armature coil 12 ... Hall element 13 ... MOSFET 14 ... Control circuit 15 ... Lock protection circuit 16 ... Controller 20 ... Current / voltage conversion circuit (current detection means) 21 ... Rotation speed detection circuit (rotation speed detection means) 22 ... rotation command signal input circuit (stop signal output means) 23 ... delay circuit (stop signal output means) 24 ... AND circuit (stop signal output means) 25,33 ... NAND circuit (stop signal output means) 26 ... latch circuit (Stop signal output means) 27: brushless control IC 30: rotation speed / voltage conversion circuit (rotation speed detection means) 31, 32: comparator (stop signal output means)

Claims (4)

[Claims] 1. A motor lock protection circuit device for preventing energization when a motor is locked, a current detection means (20) for detecting a current flowing in a circuit for driving the motor, and detecting a rotation speed of the motor. A predetermined number of times after the input of the rotation command signal, the output of the current detection means (20) is greater than or equal to a first reference value, and
Stop signal output means (22, 23, 24, 25, 26) for outputting a signal to stop energization when the output of the rotation speed detection means (21) is equal to or less than a second reference value. Motor lock protection circuit device. 2. The apparatus according to claim 1, wherein the stop signal output means (26) holds the state until the reset signal is input when the stop signal is output. Motor lock protection circuit device. 3. The motor lock protection circuit device according to claim 1, wherein the first reference value and the second reference value are predetermined constant values, respectively. 4. The lock protection circuit device for a motor according to claim 1, wherein said first reference value and said second reference value are respectively changed according to a target rotation speed.