JP5113395B2 - Dynamic brake device for motor - Google Patents

Description

  The present invention relates to a motor dynamic brake device for emergency stop of a shaft or the like.

  FIG. 1 shows a configuration of an example of a conventional dynamic brake device for a motor described in FIG.

  This device stops a servo motor 34 in a motor drive circuit that drives and controls the servo motor 34 with a transistor module 33 that is an inverter constituted by switching elements 21 to 26 and flywheel diodes 27 to 32 made of transistors. is there. The transistor module 33 is applied with the output of the AC power source converted to DC by the converter and smoothed by the smoothing capacitor 35, and PWM-modulated with a three-phase AC voltage and applied to the servo motor 34. In the transistor module 33, the transistors 21 to 26 are connected in series one by one, and the series circuit is connected in parallel to the DC power source (at both ends of the capacitor 35), and the pair of transistors 21 and 22, 23 and 24, 25 26 are mutually turned on / off and turned off / on to PWM modulate the output of the DC power supply. The dynamic brake device of this circuit is constituted by a photocoupler 44 comprising diodes 35 to 37, an energy consuming resistor 38, a transistor 39, resistors 40 and 41, a light emitting diode 42 and a phototransistor 43. The diodes 35 to 37 are flyers. A three-phase full-wave rectifier circuit is configured together with the wheel diodes 28, 30 and 32. This three-phase full-wave rectifier circuit may be configured using flywheel diodes 27, 29, and 31.

  During normal operation, the dynamic brake device enters a non-operating state when a dynamic brake (DB) operation stop signal is input via the photocoupler 44 and the transistor 39 is turned off. In the event of a power failure or emergency, the transistors 21 to 26 of the transistor module 33 are turned off, the DB operation stop signal is turned off, the servo motor 34 continues to rotate due to the inertia force of the load 45, and the power lines A and B of the servo motor 34 , C generates a voltage due to the back electromotive force of the servo motor 34. This voltage is rectified by a three-phase full-wave rectifier circuit composed of diodes 35 to 37 and flywheel diodes 28, 30, and 32, and is consumed by an energy consumption resistor 38. It is hung and stops.

  Further, as similar to the present invention, Patent Document 2 describes a multi-axis drive device that switches from deceleration by a predetermined deceleration pattern to deceleration by a dynamic brake at the time of an emergency stop. When printing for one pass is completed, supply of braking current to the CR motor that moves the head in the main scanning direction is started, and when the rotation speed of the CR motor is reduced to a predetermined speed, the CR motor is supplied. The recording apparatus is described in which the supply of the braking current is stopped and switched to the dynamic brake, and the supply of the drive current to the LF motor for paper feeding is started.

Japanese Patent Laid-Open No. 1-209973 (FIG. 1) JP 2006-218895 A JP-A-9-183262

  However, in the conventional dynamic brake device described in Patent Document 1, since the dynamic brake current is suppressed by the energy consuming resistor 38, the brake torque generated in the motor 34 during the dynamic brake operation is reduced and the braking effect is weak. Become. Therefore, there is a problem that the time until the motor 34 is stopped becomes long.

  In order to enhance the effectiveness of the dynamic brake and shorten the stop time, (1) the energy consumption resistor 38 and the resistor 40 are removed and short-circuited respectively, or (2) the dynamic brake is controlled by the base current of the transistors 27 to 32. In this case, that is, when the current is not suppressed, as shown by an arrow A in FIG. 2 (measured waveform), a phenomenon occurs in which the dynamic brake current becomes excessive immediately after the dynamic brake is activated. As a result, there are problems such as breakage of the power element, demagnetization of the motor magnet, and occurrence of mechanical damage due to an excessive torque shock caused by excessive dynamic brake current flowing.

Here, an excessive current generated immediately after the dynamic brake is operated will be described. Current waveform when excessive current flows immediately after the dynamic brake is activated (Fig. 3) and current waveform when excessive current is not flowing (steady state after a certain time has elapsed since the dynamic brake is activated) (Fig. 4) are compared, and the 1/2 period (Fig. 3 in T / 2) time t ₂ elapsed, the magnitude i ₁ of excessive current C immediately after exercising dynamic brake, have an excessive current flows it can be seen that big the i ₂ compared to approximately 2 times the size of the current E in the absence. Normally, in a coil load such as a motor, the phase of the current (I) is delayed by 90 ° with respect to the phase of the voltage (V) as shown in FIG. However, as shown in FIG. 3, the motor current immediately after applying the dynamic brake is 0, and the relationship between the normal voltage and current phase difference is broken. As a result, an excessive voltage is temporarily applied to the coil, and as a result, an excessive current i ₂ flows temporarily.

Specifically, this current can be obtained from the hatched portions B and D (motor induced voltage) of the voltage (V) in FIGS. 3 and 4 by using the following equation as R << ωL.
Δi = {e (average value) × Δt} / L (phase) (1)
Here, Δi: current [A] of hatched portions C and E
e: Average voltage [V] of hatched portions B and D (e = 2√2Ve / π)
Δt: period of hatched portions B and D L: inductance [mH]

Here, the values of L and e are set to L = 3.1 [mH] and e = 133 [V], and the current i ₁ immediately after the dynamic brake is activated using the equation (1) and an excessive current are flowing. When the current i ₂ when there is no power (steady state after a certain time has elapsed since the dynamic brake is applied) is calculated, i ₁ is 45.6 [A] and i ₂ is 23.2 [A].

  As the current increases, the dynamic brake torque immediately after the dynamic brake is actuated as shown in FIG. 5 also increases, resulting in adverse effects such as the occurrence of mechanical damage due to the impact of excessive torque.

  The technique described in Patent Document 2 switches from deceleration by a predetermined deceleration pattern to deceleration by dynamic brake in the middle, and the technique described in Patent Document 3 is from deceleration by supplying a braking current to dynamic brake. However, none of them was related to switching of the dynamic brake current.

  The present invention has been made to solve the above-mentioned conventional problems, without breaking the dynamic brake stop time more than necessary, such as power element destruction, motor magnet demagnetization, mechanical damage due to excessive torque impact, etc. It is an issue to avoid the problem.

The present invention relates to a dynamic brake device that urgently stops a motor and applies a brake by PWM control that repeats on / off of at least a part of a switching element for controlling a brake current for a predetermined time after starting the operation of the dynamic brake. The dynamic brake current is controlled so as to weaken, and after a predetermined time has elapsed , all the switching elements are always fixed to on or off without performing the PWM control, and the dynamic brake current that should originally flow is controlled to flow. The above-mentioned problem is solved.

  According to the present invention, the dynamic brake current is weakened and the excessive dynamic brake current is prevented from flowing for a predetermined time after starting the dynamic brake operation, so that the dynamic brake stop time is extended more than necessary. Therefore, it is possible to avoid power element destruction, demagnetization of the motor magnet, mechanical damage due to excessive torque impact, and the like caused by excessive dynamic brake current flowing.

  Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings.

  An embodiment of the dynamic brake device of the present invention including an inverter circuit is shown in FIG. In the figure, 200 is a diode bridge, 201 is a smoothing capacitor, 202 is a transistor module comprising an inverter circuit, 203 is a servo motor, 204 is a motor control circuit, 205 is an abnormality detection circuit, 206 is a current detection circuit, and 207 is current detection. , 208 is a deceleration pattern table, 209 is a selector, 210 is a motor encoder, 211 is an emergency stop switch, and 212 is a host controller.

  In the above configuration, when a signal from the abnormality detection circuit 205 or the emergency stop switch 211 is detected, the deceleration pattern a stored in advance in the deceleration pattern table 208 is selected by the selector 209 and output to the motor control circuit 204. . The section in which the deceleration pattern a is selected is the section A shown in FIG. 5. In this section A, the current rapidly increases at the shaded portion, so the deceleration pattern a is set to a pattern that weakens the dynamic brake current. Yes. By weakening the current, as shown in FIG. 7, the torque in the shaded area in FIG. 5 can also be suppressed. However, if this deceleration pattern a is continued, the dynamic brake current that should flow originally (the value obtained by dividing the induced voltage by the impedance of the motor) is also weakened. Therefore, in section B after a certain period of time (section A) has elapsed, The stored deceleration pattern b is selected by the selector 209 and output to the motor control circuit 204. In this section B, since it is necessary to flow the dynamic brake current that should flow, the deceleration pattern b is set to a pattern that does not weaken the dynamic brake current. The state of torque when the present invention is implemented is shown in FIG.

  Here, the deceleration patterns a and b are specifically PWM patterns for driving the transistor module 202, and in the section A, the upper three transistors in FIG. The three transistors can have a deceleration pattern a in which braking is performed by PWM control by repeatedly turning on and off. On the other hand, in the section B, since the current is smaller than that in the section A, (1) the upper three transistors in FIG. 6 are always off, the lower three transistors are always on, or (2) the lower 3 One transistor is always off, and the upper three transistors are always on, so that the deceleration pattern b for applying the original dynamic brake without performing PWM control can be obtained.

  In addition, the time setting of the section A and the deceleration pattern a can be obtained experimentally and set. For example, by making the deceleration pattern a changeable from the host controller 212, for example, depending on the motor speed, the dynamic brake is effective when the motor speed is high, and the dynamic brake is weak when the motor speed is low. Thus, the optimum setting corresponding to the dynamic brake current can be performed.

  Further, not only one pattern a in the section A but also two or more deceleration patterns in the section A can be switched.

The circuit diagram which shows the structural example of the dynamic brake apparatus of the conventional motor described in patent document 1 Diagram showing excessive current during dynamic braking to explain conventional problems A diagram showing the current waveform when an excessive current flows immediately after the dynamic brake is activated. The figure which shows the current waveform when excessive current is not flowing The figure which shows the excessive brake torque immediately after operating the dynamic brake similarly The circuit diagram which shows the structure of embodiment of this invention The figure which shows an example of the torque change of the dynamic brake in the said embodiment.

Explanation of symbols

202 ... Transistor module 203 ... Servo motor 204 ... Motor control circuit 205 ... Abnormality detection circuit 208 ... Table 209 ... Selector 211 ... Emergency stop switch

Claims (1)

In the dynamic brake device that stops the motor urgently,
For a predetermined time after starting the operation of the dynamic brake, control is performed so as to weaken the dynamic brake current by applying a brake by PWM control that repeatedly turns on and off at least a part of the switching element for controlling the brake current,
A dynamic brake device for a motor, characterized in that after a predetermined time has elapsed , all the switching elements are always fixed to on or off without performing PWM control, and a dynamic brake current that should flow originally is supplied.

Images