JP3250342B2 - 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 device for controlling the driving and stopping of a motor capable of rotating in both forward and reverse directions, such as a brushless DC motor or a brushed DC motor.

[0002]

2. Description of the Related Art A drive control device for controlling the driving and stopping of a motor capable of rotating in both forward and reverse directions, such as a brushless DC motor, receives at least a drive command signal, a stop command signal, and a maximum current limit value setting signal as inputs. When a drive command signal is given, a drive current whose magnitude is limited to a limit value less than a limit value given by a maximum current limit value setting signal is supplied to the armature, and when a stop command signal is given, a predetermined method is used. The armature current is controlled so as to apply a brake to the motor.

In many cases, the drive control unit receives a speed instruction signal in addition to the above-mentioned signal, and controls the magnitude of the armature current so as to rotate the motor at the speed indicated by the speed instruction signal. Control.

[0004] In this type of driving device, a method of applying a plucking brake and a method of applying a short brake are often employed as methods for applying a brake to an electric motor. In the case of the plucking brake,
When a stop command is given, the motor is braked by supplying a braking current for generating a rotational torque in a direction that reverses the rotation direction of the motor to the armature. In the case of a short brake, when the stop command is given, the power supply to the motor is stopped, and at the same time, the armature coil is short-circuited so that the back electromotive force of the armature coil is consumed in the coil. Braking the motor.

Curves (a) and (c) of FIG. 2 show deceleration characteristics (changes of the rotation speed N with respect to time t) when the electric motor is braked by the plucking brake and the short brake. The curve d in FIG. 2 shows the deceleration characteristics when the armature current is set to zero when the stop command is given and the armature current is left as it is (in a free-off state).

[0006]

In the above-described electric motor control device, when a plucking brake is applied to the electric motor, a braking current corresponding to the maximum current limit value flows through the electric motor. In the conventional motor control device, the maximum current limit value is set solely from the viewpoint of protecting the motor during operation, so the maximum current limit value is literally set to a value close to the maximum value of the drive current that can flow through the motor. It had been. Therefore, when the plucking brake is applied, a very large braking current flows through the electric motor, and the number of revolutions rapidly decreases as shown by a curve a in FIG. If the rotation speed is rapidly reduced in this way, a mechanical shock during braking is large, which may adversely affect the load. In the conventional motor control device that applies the plucking brake when the motor stops, the braking current during the plucking brake is determined by the maximum current limit value during the operation of the motor, so the deceleration characteristics during braking can be adjusted. Therefore, it was not possible to meet the demand for obtaining relatively moderate deceleration characteristics.

[0007] If a short brake is adopted, FIG.
As shown by curve C, the number of revolutions can be gradually reduced, but in this case, there is a problem that it is not possible to meet the demand for further increasing the deceleration rate.

An object of the present invention is to provide a motor control device which can arbitrarily set a deceleration characteristic when the motor stops.

[0009]

According to the present invention, at least a drive command signal, a stop command signal, and a current limit value setting signal are input, and when a drive command signal is given, a limit given by the current limit value setting signal is provided. A drive current whose maximum value is limited to a value less than or equal to the value is supplied to the armature, and when a stop command signal is given, a braking current that generates a rotational torque in a direction of reversing the rotation direction of the motor is reduced to a value equal to or less than the limit value. The present invention relates to a motor control device including a drive control unit that supplies the motor to the armature while limiting the above.

In the present invention, when the stop command signal is given, the current limit value is changed in response to the stop command signal so that the limit value of the braking current is switched to the limit value for braking adapted to the desired braking characteristic. A current limit value switching circuit for switching a value setting signal is provided.

[0011]

As described above, when the current limit value switching circuit for switching the current limit value in response to the stop command signal is provided, the braking current limit value is set arbitrarily when the stop command is given. Can be switched to the
By appropriately setting the braking limit value, it is possible to obtain an arbitrary deceleration characteristic between a deceleration characteristic by a plucking brake in which the rotation speed drops rapidly and a deceleration characteristic by a short brake in which the rotation speed drops slowly. Can meet various needs.

[0012]

FIG. 1 schematically shows the configuration of an embodiment to which the present invention is applied when controlling a three-phase brushless DC motor. In FIG. 1, reference numeral 1 denotes a brushless DC motor, which is a rotor having three-phase armature coils Lu to Lw wound around three salient pole portions of an armature core and a two-pole magnet field, respectively. (Not shown)). Although not shown, three position detectors, such as Hall ICs, are provided at intervals of 120 degrees along the circumferential direction of the rotor, and these position detectors are provided with polarities (N poles) of the magnetic poles of the rotor. To the S-pole) to detect the position of the rotor for each of the three-phase armature coils of the U-phase, V-phase and W-phase to generate position detection signals eu, ev and ew.

Reference numeral 2 denotes a switch circuit for turning on and off a drive current supplied to the armature coils Lu to Lw from a DC power source such as a battery (not shown). This switch circuit includes an NPN transistor T as a bridge-connected switch element.
u, Tv, Tw and Tx, Ty, Tz, and diodes Du, D connected in anti-parallel between transistors Tu, Tv, Tw and the collectors and emitters of Tx, Ty, Tz, respectively.
v, Dz and Dx, Dy, Dz, and a current detection resistor Ri having a sufficiently small resistance value is connected in series with the switch circuit 2.

Reference numeral 3 denotes a drive control unit formed as an IC. The drive control unit receives an input terminal to which the position detection signals eu, ev, ew are inputted, and a rotation direction command signal Vd for designating a rotation direction of the motor. Rotation direction command input terminal DIR to be input
A drive stop command input terminal 3a to which the drive command signal Cr and the stop command signal Cs are input, and a current limit value setting signal V
a current limit value setting signal input terminal 3b to which imax is input;
A current detection signal input terminal 3c to which a current detection signal Vi obtained at both ends of the current detection resistor Ri is input, an instruction speed signal input terminal 3d to which an instruction speed signal Vno for giving an instruction speed of the motor is input, and an attachment to the motor. A rotation speed detection signal input terminal 3e to which a rotation speed detection signal Vn obtained from the obtained rotation speed detector is input, and transistors Tu, Tv, T
It has output terminals 3u, 3v, 3w and 3x, 3y, 3z connected to respective bases of w and Tx, Ty, Tz.

The rotation direction command signal Vd is, for example, a DC signal having a zero level or a high level.
When d is at the zero level and at the high level, it indicates that the motor is to be rotated in one direction and the other direction, respectively.

The current limit value setting signal Vimax is a voltage signal for giving a current limit value, and the signal Vimax is proportional to the current limit value.

The drive command signal Cr is a signal of a zero level (ground level), and the stop command signal Cs is a signal of a high level.

The drive controller 3 controls the transistors Tu to T according to the position detection signals eu to ew and the rotation direction command signal Vd.
w and one of the transistors Tx to Tz are turned on, and the armature coils Lu to L are supplied from a DC power supply (not shown) such as a battery through the switch circuit 2.
A drive current is passed through w to rotate the rotor in the rotation direction specified by the rotation direction command signal Vd.

The drive control unit 3 compares the rotation speed detection signal Vn with the commanded speed signal Vno to calculate the difference between the motor's rotation speed and the commanded speed, and sends the difference to the motor to reduce the difference to zero. A certain drive current is calculated, and a signal applied to the bases of the transistors Tu to Tw is subjected to PWM control so that a drive current of the calculated magnitude flows.

The drive control unit also compares the current detection signal Vi with the current limit value setting signal Vimax to determine the current detection signal V
The drive current is controlled so that i does not exceed the current limit value setting signal Vimax.

In this embodiment, when the stop command signal Cs is given, the current limit value of the braking current is switched to the braking time limit value suitable for the desired braking characteristic. A current limit value switching circuit 4 for switching the magnitude of the limit value setting signal Vimax is provided.

The current limit value switching circuit 4 shown in the figure is connected to a resistor R1 whose one end is connected to an output terminal of a DC constant voltage power supply (not shown) that outputs a DC constant voltage Vcc, and is connected between the other end of the resistor R1 and the ground. A resistor R3 having one end connected to a connection point of the resistors R1 and R2, a PNP transistor Tr1 having an emitter connected to one end of the resistor R1, and a collector connected to the other end of the resistor R3, and a transistor Tr1. A resistor R4 connected between the emitter and the base of the transistor T
The resistor R5 has one end connected to the base of r1. The voltage at both ends of the resistor R2 is input to the drive control unit 3 as a current limit value setting signal Vimax. The other end of the resistor R5 is connected to the drive stop command input terminal 3a, and the drive command signal Cr and the stop command signal Cs are input to both the drive stop command input terminal 3a and the current limit value switching circuit 4.

In the above embodiment, a zero-level drive command signal Cr is input to the drive stop command input terminal 3a of the drive control unit 3.
Is applied, the transistor Tr1 conducts, so that the resistor R3 is connected in parallel to both ends of the resistor R1 through the transistor Tr1. At this time, the large voltage divided by the voltage dividing circuit constituted by the parallel circuit of the resistors R1 and R3 and the series circuit of the resistor R2 is input to the drive control unit 3 as the current limit value setting signal Vimax. The limit value is set to a large value, and as shown in FIG. 2, the rotation speed of the electric motor rapidly increases and reaches the designated rotation speed.

Drive stop command input terminal 3a of drive control unit 3
Is supplied with a high-level stop command signal Cs, the drive control unit 3 reverses the phase sequence of the signal supplied to the transistor of the switch circuit 2 to generate a rotational torque in a direction to reverse the rotational direction of the motor. The current is supplied to the motor as a braking current. At this time, since the transistor Tr1 is turned off, the resistor R3 is disconnected from the resistor R1, and the current limit value setting signal Vim obtained at both ends of the resistor R2.
ax decreases. Therefore, a braking current limited to a value lower than the maximum current limit value during operation flows to the electric motor, and the electric motor gradually reduces its rotation speed and stops. Resistance R3
As shown by curve B in FIG. 2, the deceleration characteristic between the deceleration characteristic by the plucking brake (curve a) and the deceleration characteristic by the short brake (curve C) is appropriately set as shown in curve b of FIG. Properties can be obtained.
By using a variable resistor as the resistor R3, the braking characteristics can be adjusted arbitrarily.

FIG. 3 shows another embodiment of the present invention. In this embodiment, an NPN transistor is used as the transistor Tr1. With the configuration as shown in FIG. 3, when the drive command signal Cr is given, the transistor Tr1 is turned off, the current limit value setting signal Vimax becomes small, and when the stop command signal Cs is given, the transistor Tr1 becomes conductive. As a result, the current limit value setting signal Vimax becomes large, and as shown in FIG. 4, a characteristic is obtained in which the rotation speed rises relatively slowly at the time of start-up and sharply drops at the time of stoppage.

In each of the above embodiments, the drive command signal Cr is a zero level signal and the stop command signal Cs is a high level signal. However, in the embodiment of FIG. 1, the drive command signal Cr is a high level signal. When the stop command signal Cs is a zero level signal, the characteristics shown in FIG. 4 are obtained.
When the drive command signal Cr is a high-level signal and the stop command signal Cs is a zero-level signal in the embodiment of FIG. 3, a characteristic as shown by a curve B in FIG. 2 is obtained.

In the above embodiment, a case where a brushless DC motor is controlled has been described as an example. However, the present invention can be applied to a case where a DC motor having a brush is controlled.

[0028]

As described above, according to the present invention, since the current limit value switching circuit for switching the current limit value in response to the stop command signal is provided, the braking current is limited when the stop command is given. The value can be switched to an arbitrarily set braking limit value. Therefore, by appropriately setting the braking time limit value, an arbitrary deceleration characteristic between the deceleration characteristic due to the plucking brake in which the rotational speed decreases rapidly and the deceleration characteristic due to the short brake in which the rotational speed decreases gradually is set. There is an advantage that it can be obtained and can meet various needs.

[Brief description of the drawings]

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

FIG. 2 is a diagram showing a comparison between a deceleration characteristic obtained by an embodiment of the present invention and a deceleration characteristic obtained by a conventional example.

FIG. 3 is a circuit diagram showing a circuit configuration of a main part of another embodiment of the present invention.

FIG. 4 is a diagram showing deceleration characteristics obtained by the embodiment of FIG. 3;

[Explanation of symbols]

 Reference Signs List 1 brushless DC motor 2 switch circuit 3 drive control unit 3a drive stop command input terminal 3b current limit value setting signal input terminal 3c current detection signal input terminal 3d instruction speed signal input terminal 3e rotation speed detection signal input terminal 4 current limit value switching circuit Tr1 transistor R1 to R5 resistance

──────────────────────────────────────────────────続 き Continued on front page (58) Field surveyed (Int.Cl. ⁷ , DB name) H02P 6/24

Claims (1)

(57) [Claims] When a drive command signal is given by inputting at least a drive command signal, a stop command signal, and a current limit value setting signal, the maximum value is limited to a limit value given by the current limit value setting signal. The driving current is supplied to the armature, and when a stop command signal is given, the magnitude of the braking current that generates a rotational torque in the direction of reversing the rotational direction of the motor is limited to the limit value or less to the armature. An electric motor control device including a drive control unit for supplying, when the stop command signal is given, the stop command is changed to a braking time limit value that matches a desired braking characteristic. A motor control device comprising: a current limit value switching circuit that switches the current limit value setting signal in response to a signal.