JP3265767B2 - Motor control device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a motor control having a protection function for preventing a motor coil and components of a drive circuit from being damaged when the motor is mechanically restrained by a heavy load or the like. It concerns the device.

[0002]

2. Description of the Related Art When a rotating electric motor is supplied with a driving current through a predetermined driving circuit and stops in a mechanically restrained state due to a heavy load or the like, an excessive current flows through an armature coil. The child coil is burned out, or a component (for example, a switching element) of the drive circuit is damaged. Conventionally, in order to prevent such a situation from occurring, a fuse is inserted into a drive circuit of the motor, and the fuse is blown when an excessive current flows when the motor is in a restrained state. The supply of the drive current to the motor is stopped to protect the motor and the drive circuit.

[0003]

When a motor is protected by using a fuse as in the prior art, if the capacity of the fuse is not set properly, the fuse can be operated even in an overload state which is permissible for a certain period of time. There is a problem that it is difficult to set the capacity of the fuse because the motor stops due to fusing.

[0004] Further, even if a constrained state occurs in the electric motor, it may be allowed to continue to supply the driving current if the constrained state is short, so that the electric motor is only allowed when the constrained time exceeds a predetermined length. It is preferable to stop the drive of the motor, but if a fuse is used, the restraint time cannot be managed, so there is a problem that the motor stops even if the restraint state continues for a short time. Was. In this case, it is conceivable to set the capacity of the fuse to a relatively large value. However, if the capacity of the fuse is set to a relatively large value, the motor and its driving circuit may not be properly protected.

In the case of using a fuse, it is necessary to replace the fuse when it is blown, so that it is inevitable that maintenance becomes troublesome.

An object of the present invention is to provide a motor control device having a constraint protection function capable of properly protecting a motor in a constraint state without using a fuse.

[0007]

A motor control device according to the present invention has a control terminal for inputting a control signal having a first level and a second level. A motor drive for controlling a drive circuit of a motor so as to allow a drive current to be supplied to the motor when supplied and to prohibit supply of the drive current when a second level control signal is supplied. A control circuit and a timer signal having a circuit constant adjusted to output a timer signal for a first time by being triggered each time a rotation command signal for commanding to rotate the motor is input. A generation circuit, a rotation detection pulse generator for generating a rotation detection pulse whose generation period is shortened in accordance with an increase in the rotation speed of the electric motor, and a second time shorter than the first time when triggered. The retriggerable multivibrator is adjusted to output a rotation detection signal of a predetermined level only during the period, and is triggered each time a rotation detection pulse is given, and either a timer signal or a rotation detection signal is generated. And a control signal generating circuit for generating a second level control signal when both the timer signal and the rotation detection signal have disappeared. The above timer signal
The signal generator generates a timer signal by adjusting the circuit constants.
Is configured to be able to adjust the time width. Further, the length of the second time is set to be equal to or longer than the generation cycle of the rotation detection pulse Vp when the rotation speed of the electric motor reaches the set value.

In the present invention, a clear signal is supplied to a clear terminal of the multivibrator in order to inhibit the retriggerable multivibrator from generating a rotation detection signal when both the timer signal and the rotation detection signal have disappeared. It is preferable to provide a circuit for providing the same.

[0009]

In the above-described motor control device, when the rotation speed of the motor reaches the set value while the timer signal is generated after the start, and when the motor is rotating at the rotation speed equal to or higher than the set value, Since the control signal is at the first level, the motor drive control circuit allows the drive current to be provided to the motor. Therefore, the electric motor rotates without any trouble.

If the rotation speed of the motor cannot exceed the set value while the timer signal is generated due to the motor being restrained by a heavy load or the like, the control signal becomes the second level. The supply of the drive current to the motor is stopped, and the motor and its drive circuit are protected.

[0011] With the above configuration, the restraint time for performing the protection operation can be managed by adjusting the time width of the timer signal. Therefore, the protection of the electric motor and its drive circuit in the restrained state can be properly performed. Can be planned.

If a circuit for providing a clear signal to a clear terminal of the retriggerable multivibrator when both the timer signal and the rotation detection signal are extinguished is provided, it is possible to detect when the motor is locked. In addition, since the control signal can be held at the second level, a chattering phenomenon in which the control signal becomes the first level or the second level occurs, and the motor exhibits an unstable behavior. Can be prevented.

[0013]

1 shows an embodiment of the present invention. In FIG. 1, reference numeral 1 denotes a control terminal CTR to which a binary control signal Vc having a first level and a second level is inputted. A motor drive control circuit having a terminal to which the rotation command signal Vs is input is a motor drive circuit 2 controlled by the motor drive control circuit 1. The motor drive control circuit 1 supplies a drive current to the motor when the first level control signal is supplied, and prohibits the supply of the drive current to the motor when the second control signal is supplied. To control the motor drive circuit 2.
In this embodiment, it is assumed that the control signal has two levels, a high level and a low level, and the high level and the low level are the first level and the second level, respectively. Hereinafter, the high level of the binary signal is called H level, and the low level is L level.
Let's call it a level.

In this embodiment, it is assumed that the motor is a three-phase brushless DC motor. When the motor is a three-phase brushless DC motor, the motor drive circuit 2 is, for example, a known inverter circuit in which six switch elements, such as FETs, are connected in a three-phase bridge.
Is such that when the H-level rotation command signal Vs is supplied and the H-level control signal Vc is supplied, the excitation phase of the motor is switched according to the position of the rotor magnetic pole detected by the position sensor. And control signals eu and e for controlling on / off of each switch element of the drive circuit 2.
Generates v, ew, ex, ey and ez. As the motor drive control circuit 1, a commercially available integrated circuit (IC) can be used.

3 is triggered each time a rotation command signal for commanding to rotate the motor is input, and is triggered by a first time T.
This is a timer signal generating circuit that outputs a timer signal during the period of 1. For this embodiment, this timer signal generating circuit is composed of a retriggerable multivibrator M1 formed as an IC.
A rotation command signal Vs is given from a rotation command generation circuit 4 to a trigger input terminal A of the retriggerable multivibrator M1, and a trigger input terminal B is grounded. A power supply voltage Vcc is applied to the Q bar terminal of the retriggerable multivibrator M1 through a resistor R3. At time t1, as shown in FIG. 2A, an H level rotation command is applied to a trigger input terminal A of the multivibrator M1. When the signal Vs is applied, a timer signal Vt (FIG. 2B) that holds the L level for the first time T1 is obtained at the Q bar output terminal. The retriggerable multivibrator M1 is externally provided with a time adjustment resistor R1 and a capacitor C1. By adjusting a time constant determined by the resistor R1 and the capacitor C1, the length of the first time T1 can be reduced. It can be adjusted appropriately. The clear terminal CLR of the retriggerable multivibrator M1 is kept at the H level (the state in which the multivibrator M1 is not cleared) by receiving a voltage Vcc from a power supply (not shown).

The rotation command generating circuit 4 is composed of a circuit for outputting a voltage of a certain level through a switch, a CPU constituting a control device for controlling the electric motor, and the like.
As shown in FIG. 3A, a rotation command signal Vs having an H level or an L level is generated. The up edge of this signal Vs is a rotation command signal, and the down edge is a stop command signal.

Reference numeral 5 denotes a rotation detection pulse generator for generating a rotation detection pulse Vp whose generation period becomes shorter as the rotation speed of the motor increases, as shown in FIG. 2D. Consists of, for example, a photo-interrupter-type encoder attached to a rotating shaft of a motor.

The rotation detection pulse Vp is input to the trigger signal input terminal A of the retriggerable multivibrator M2. The trigger input terminal B of the retriggerable multivibrator M2 is grounded, and the power supply voltage Vcc is applied to the Q bar output terminal through a resistor R4. The retriggerable multivibrator M2 is triggered every time the H-level rotation detection pulse Vp is supplied, and its L-bar output terminal is set at L level for a second time T2 as shown in FIG.
The rotation detection signal Vn for maintaining the level is output.

A resistor R2 and a capacitor C2 are externally connected to the retriggerable multivibrator M2. By adjusting a time constant determined by the resistor R2 and the capacitor C2, the length of the second time T2 can be appropriately adjusted. It can be adjusted.

In the present invention, the second time T2 is the first time T2.
Of the rotation detection pulse Vp when the rotation speed of the motor reaches a set value, which is sufficiently shorter than the time T1
o or more (To ≦ T2 << T1). Therefore, as shown in FIG. 2 (D), when the rotation speed of the electric motor exceeds the set value at time t2, the retriggerable multivibrator is retriggered at intervals shorter than the second time T2. As shown in FIG. 2 (E), the rotation detection signal Vn obtained at the Q-bar output terminal of the retriggerable multivibrator M2 keeps the L level (when it is detected that the motor is rotating at the set speed or more). State)
It becomes.

The timer signal Vt and the rotation detection signal Vn are input to the control signal generation circuit 6. The control signal generating circuit 6 includes NAND circuits NAND1 and NAN.
D2, the inverter INV, the resistors R5 to R7, and the capacitor C3, and when one of the timer signal Vt and the rotation detection signal Vn is generated (V
When one or both of t and Vn are at L level, an H level control signal Vc is applied to the control terminal CTR of the motor drive control circuit 1, and when both the timer signal Vt and the rotation detection signal Vn disappear (Vt). And V
When both n are at H level), it detects that the electric motor is in the locked state, and applies an L level control signal Vc to the control terminal CTR.

The reset signal Vr from the reset signal generation circuit 7 is supplied to the NAND circuit NAND2 of the control signal generation circuit 6. The reset signal Vr is shown in FIG.
As shown in (F), the reset signal V is an L level signal.
When r is given, the control signal Vc is unconditionally set to L level to stop the motor, and the drive control circuit 1 is returned to the initial state.

In this embodiment, the NAND circuit NAND1
Is output to the clear input terminal CLR of the retriggerable multivibrator M2, and when the output of the NAND circuit NAND1 goes low, the output of the Q bar output terminal of the multivibrator M2 goes high unconditionally. It has become.

In the embodiment shown in FIG. 1, the timer signal Vt, the rotation detection signal Vn, the output signal Va of the NAND circuit NAND1, and the output signal Vb of the NAND circuit NAND2 when no reset signal is supplied (when Vr is at the H level). And the output signal (control signal) Vc of the inverter INV
Is shown in Table 1.

[0025]

[Table 1] Table 2 shows a truth table of Vt, Vn, Va, Vb, and Vc when a reset signal is applied (when Vr becomes L level).

[0026]

[Table 2] The operation of the above embodiment will be described below with reference to FIG. FIG.
It is assumed that an H-level rotation command signal Vs is supplied at time t1 as shown in FIG. This rotation command signal V
s is inputted to the trigger input terminal A of the retriggerable multivibrator M1 and is also given to the motor drive control circuit 1. When the rotation command signal Vs becomes H level at time t1, as shown in FIG. 2B, the retriggerable multivibrator M1 outputs a timer signal Vt holding its L level to the Q bar terminal for the first time T1. Occurs. When the low-level timer signal Vt is generated, the output Va of the NAND circuit NAND1 goes high as shown in FIG. 2C. When the output Va of NAND1 becomes H level, FIG.
As shown in (G), the output Vb of the NAND circuit NAND2 becomes L level, and as shown in FIG.
The NV output signal (control signal) Vc becomes H level. Therefore, the motor drive control circuit 1 is
To supply the control signals eu to ew and ex to ez to start the motor.

When the motor rotates, the rotation detection pulse generator 5 generates a rotation detection pulse Vp as shown in FIG. When the rotation detection pulse Vp is generated, the retriggerable multivibrator M2 is triggered, and the potential at the Q-bar output terminal thereof becomes L level for the second time T2 (the rotation detection signal Vn is generated). If the rotation speed of the motor exceeds the set value at time t2, the multivibrator is retriggered while the multivibrator M2 is generating the rotation detection signal Vn, so that the output of the Q bar terminal of the multivibrator M2 is output. Keeps the L level, and the rotation detection signal Vn is continuously generated.

At time t3, when the rotation command signal Vs is set to L level and a stop command is given, the motor drive control circuit 1
Since the supply of the drive current to the motor is stopped, the rotation speed of the motor decreases. At time t4, when the rotation speed becomes lower than the set value, retriggerable multivibrator M
2 is no longer retriggered, so that at time t4 (t4 -t3
When .ltoreq.T2, the output of the Q bar terminal of the multivibrator M2 goes high (the rotation detection signal Vn disappears), and the output Va of the NAND circuit NAND1 goes low. Accordingly, the output Vb of the NAND circuit NAND2 goes high, the output Vc (control signal) of the inverter INV goes low, and the motor drive control circuit 1 outputs the control signals eu to.
The output of ew and ex to ez is stopped. NAND circuit NA
When the output Va of ND1 goes low, the retriggerable multivibrator M2 is cleared, so that the output of the Q-bar terminal of the multivibrator M2 is unconditionally kept high. Therefore, for example, even if the rotor of the motor is rotated by an external force and the rotation detection pulse Vp is generated, the Q bar output of the multivibrator M2 is maintained at the H level, the rotation detection signal Vn is not generated, and the control signal Vc is set to the H level. Never level.

At time t6, it is assumed that the rotation command signal Vs goes high again and a start command is given. At this time, it is assumed that the electric motor cannot be rotated due to the heavy load. It is also assumed that the rotation detection pulse generator 5 enters a state of continuously generating an H level signal at time t6. This state is, for example, a state in which the light-receiving element of the photo-interrupter constituting the rotation detection pulse generator 5 is still receiving light because the rotor of the motor slightly moves only at the moment when the start command is given. .

When the rotation command signal Vs goes high at time t6, the multivibrator M1 generates a timer signal Vt. At this time, the retriggerable multivibrator M2 generates the rotation detection signal Vn only for the second time T2, but the motor is not rotating and the rotation detection pulse Vp
Does not occur (in this example, the trigger input of the multivibrator M2 is kept at the H level), and the output of the Q bar terminal of the multivibrator M2 becomes the H level when the second time T2 has elapsed from the time t6. become. While the timer signal Vt is being generated, the NAND circuit NAND
1 output Va becomes H level, and the control signal Vc
Becomes H level, but the motor is in a stopped state because it is in a restrained state. When the timer signal Vt disappears at time t7, the output signal Va of the NAND circuit NAND1 becomes L
Level (the motor's restraint state is detected)
The control signal Vc becomes L level, and the motor drive control circuit 1 stops outputting the control signals eu to ew and ex to ez to inhibit the drive current from being supplied to the motor. Accordingly, by appropriately setting the time T1 during which the timer signal Va is generated, it is possible to prevent the coil of the motor from burning when the motor is in the locked state, and to protect the motor by the short-time locking. Can be prevented from working.

In this embodiment, when the restraint state of the motor is detected and the output of the NAND circuit NAND1 goes low, the multivibrator M2 is cleared and the output of the Q bar terminal of the multivibrator M2 goes high. And the control signal Vc is held at the L level, so that even if the rotor of the motor moves to generate a rotation detection pulse, the motor is not energized. Therefore, it is possible to prevent the motor from exhibiting an unstable behavior due to a chattering phenomenon in which the level of the control signal changes when the restrained state is detected.

After the cause of the restriction of the motor is removed, the motor is started by supplying the H-level rotation command signal Vs again.

In the above embodiment, the rotation detection pulse generator 5 continuously generates an H-level signal when the restraint state occurs at time t6. When the output holds L level,
Since the output of the Q bar terminal of the retriggerable multivibrator M2 holds the H level, it is possible to detect the restraint state at the time when the first time T1 has elapsed and perform the protection operation in the same manner as described above.

When the motor does not maintain a completely stopped state in the constrained state, but is rotating at a rotation speed lower than the set rotation speed, the retriggerable multivibrator M2 operates after the first time T1 has elapsed. However, since the trigger is not retriggered, the output of the NAND circuit NAND1 goes low when the output of the Q-bar terminal of the retriggerable multivibrator M2 goes high after the first time T1 has elapsed. It is detected that there is.

In the above embodiment, the timer signal Vt is an L-level signal and the rotation detection signal Vn is also an L-level signal. The levels of these signals depend on the logic circuit configuration of the control signal generation circuit 6. Can be changed as appropriate. Also, the levels of the rotation command signal Vs and the control signal Vc can be appropriately changed according to the configuration of the IC.

In the above embodiment, the timer signal generation circuit 3
Was constituted by retriggerable multivibrator M1, this timer signal generating circuit may be a circuit for generating a timer signal a predetermined time width when triggered, other such conventional monostable multivibrator suitable The timer signal generation circuit 3 can be configured by a circuit.

[0037]

As described above, according to the present invention, by adjusting the time width of the timer signal, it is possible to manage the constraint time for performing the protection operation. There is an advantage that the protection of the device can be properly achieved.

According to the second aspect of the present invention, a circuit for providing a clear signal to the clear terminal of the retriggerable multivibrator when both the timer signal and the rotation detection signal have disappeared is provided, so that the motor is in the locked state. Since the control signal is held at the second level when it is detected that the control signal has reached the threshold, the level of the control signal changes when a stop command is given or when the restraint state is detected. This prevents the motor from exhibiting unstable behavior due to a phenomenon.

[Brief description of the drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is a waveform diagram showing signal waveforms at various parts in FIG.

[Explanation of symbols]

 Reference Signs List 1 motor drive control circuit 2 motor drive circuit 3 timer signal generation circuit 4 rotation command generation circuit 5 rotation detection pulse generator 6 control signal generation circuit M1, M2 retriggerable multivibrator NAND1, NAND2 NAND circuit INV inverter

Claims (2)

(57) [Claims] A control terminal for receiving a control signal having a first level and a second level is provided, and when the control signal is at the first level, a drive current is supplied to the motor. A motor drive control circuit for controlling the drive circuit of the motor so as to prohibit supply of the drive current to the motor when the control signal is at the second level; and a rotation command signal for commanding the motor to rotate. A timer signal generating circuit in which a circuit constant is adjusted so that a timer signal is output for a first time by being triggered each time a signal is input, and a rotation detection in which the generation cycle is shortened in accordance with an increase in the rotation speed of the motor A rotation detection pulse generator that generates a pulse, and is adjusted so as to output a rotation detection signal of a predetermined level only during a second time shorter than the first time when triggered. A retriggerable multivibrator that is triggered each time the rotation detection pulse is given; and the first level control signal when either the timer signal or the rotation detection signal is generated. A control signal generation circuit for generating the second level control signal when both the timer signal and the rotation detection signal have disappeared, wherein the timer signal generation circuit adjusts a circuit constant.
The time width of the timer signal can be adjusted.
Is the length of the second time, the motor control unit the rotational speed of the motor is set to more than generation cycle of the rotation detection pulse Vp when it reaches the set value. 2. A circuit for providing a clear signal to a clear terminal of the retriggerable multivibrator to inhibit the retriggerable multivibrator from generating a rotation detection signal when both the timer signal and the rotation detection signal have disappeared. The motor control device according to claim 1, further comprising: