U.S. patent application number 09/725670 was filed with the patent office on 2001-05-31 for method for controlling a motor roller.
This patent application is currently assigned to ITOH ELECTRIC CO., LTD.. Invention is credited to Fukata, Shigeki, Itoh, Kazuo, Tachibana, Toshiyuki.
Application Number | 20010002099 09/725670 |
Document ID | / |
Family ID | 18332474 |
Filed Date | 2001-05-31 |
United States Patent
Application |
20010002099 |
Kind Code |
A1 |
Itoh, Kazuo ; et
al. |
May 31, 2001 |
Method for controlling a motor roller
Abstract
A motor driver for drive-controlling a brushless motor being
provided with a delay circuit that detects the motor pulse. When a
stop signal is inputted, a transistor is activated, which in turn
activates an electric brake to brake the brushless motor, while at
the same time, the motor pulse detected by the motor driver is
inputted to the delay circuit. After the stop signal is inputted,
the motor pulse declines, which is detected by the delay circuit to
activate the electromagnetic brake. The delay circuit is provided
on the driver substrate for the motor driver.
Inventors: |
Itoh, Kazuo; (Kasai, JP)
; Tachibana, Toshiyuki; (Himeji, JP) ; Fukata,
Shigeki; (Kasai, JP) |
Correspondence
Address: |
KODA & ANDROLIA
SUITE 3850
2029 CENTURY PARK EAST
LOS ANGELES
CA
90067-3024
US
|
Assignee: |
ITOH ELECTRIC CO., LTD.
|
Family ID: |
18332474 |
Appl. No.: |
09/725670 |
Filed: |
November 29, 2000 |
Current U.S.
Class: |
318/727 ;
318/728 |
Current CPC
Class: |
H02P 3/04 20130101; B65G
13/075 20130101; B65G 23/08 20130101; H02P 6/24 20130101; B65G
39/02 20130101 |
Class at
Publication: |
318/727 ;
318/728 |
International
Class: |
H02P 001/24; H02P
001/42; H02P 003/18 |
Foreign Application Data
Date |
Code |
Application Number |
Nov 30, 1999 |
JP |
1999-339,967 |
Claims
1. A method for controlling a motor roller powered by a brushless
motor, in which the motor roller has a built-in electromagnetic
brake, and the motor has a drive-controlling device provided with a
delay circuit, characterized in that the motor pulse rate detected
by a motor driver is inputted to the delay circuit, and the decline
of the motor pulse rate after a stop signal has been inputted is
detected at the delay circuit to activate the electromagnetic
brake.
Description
BACKGROUND OF THE INVENTION
[0001] 1. Field of the Invention
[0002] The present invention relates to a method for controlling a
motor roller, which is powered by a brushless motor equipped with a
brake mechanism. Such a motor roller is effectively used for a
conveyor, in particular, a conveyor that is repeatedly switched on
and off.
[0003] 2. Prior Art
[0004] A motor roller for a conveyor is usually stopped by an
electric brake. What is stopped, however, is only the rotation of
the motor roller itself. The conveyor itself can be moved easily by
an external force, etc. On the other hand, in a mechanism in which
the conveyor is stopped mechanically using an electromagnetic brake
only, the brake pad is subjected to friction, which causes abrasion
and shortens the life of the brake pad. In order to solve these
problems, a number of methods have been devised to increase the
electric brake power. Another method that has been devised for
ensuring the stopping position uses both an electric inverter brake
and a physical electromagnetic brake. In such a conventional method
for controlling a motor roller for a conveyor using both an
electric brake and an electromagnetic brake, the electric brake and
the electromagnetic brake are activated at the same time.
[0005] In the conventional method in which an electric brake and an
electromagnetic brake are activated at the same time, the
electromagnetic brake is activated at high speed. This causes the
brake parts to wear out quickly, shortening the life of the motor
roller. On the other hand, adding an independent delay circuit in
order to delay the activation timing of the electromagnetic brake
with respect to the activation of the electric brake increases the
cost.
BRIEF SUMMARY OF THE INVENTION
[0006] The present invention aims at solving these problems
associated with the conventional methods by using a simple method
to delay the activation timing of the electromagnetic brake until
after the revolution of the brushless motor is reduced, thereby
providing an economical motor roller that can be used over an
extended period of time because the brake parts wear less.
[0007] To achieve the above object, a motor roller powered by a
brushless motor is provided with a built-in electromagnetic brake,
and a delay circuit is provided in a drive-controlling device for
the motor. The delay circuit uses the motor pulse detected by a
motor driver. When a stop signal is inputted, the motor pulse rate
declines. This decline of the motor pulse rate is detected to
activate an electromagnetic brake. Because the motor pulse can be
detected by the motor driver, it is sufficient to mount the delay
circuit for activating the electromagnetic brake on the driver
substrate of the motor driver; there is no need to provide a
special delay circuit device.
BRIEF DESCRIPTION OF THE SEVERAL VIEWS OF THE DRAWINGS
[0008] FIG. 1 is a block diagram showing the control method of the
delay circuit; and
[0009] FIG. 2 is a longitudinal section view of the motor
roller.
DETAILED DESCRIPTION OF THE INVENTION
[0010] An embodiment of the motor roller of the present invention
will now be described with reference to the accompanying
drawings.
[0011] FIG. 2 is a longitudinal section of a motor roller. This
motor roller includes a brushless motor 2 inside the outer casing
1. The rotation of the brushless motor 2 is transmitted to the
outer casing from the output part 2b by first reducing the rotation
of the rotor shaft 2a via the reduction gear 3. In other words, the
outer casing 1, which is linked to the rotor shaft, rotates with
respect to the fixed shaft 4, which is attached to one part of the
conveyor. Between the outer casing 1 and the fixed shaft 4, a
bearing 5 is mounted to smooth the rotation. Inside the outer
casing 1, there is a fixed case 6, which is provided with an
electromagnetic brake 7 so that the rotation of the rotor shaft 2a
can be physically stopped.
[0012] FIG. 2 also shows an enlarged view of a section of the
electromagnetic brake. This electromagnetic brake has an inner disk
8 at the tip of the rotor 2a. The inner disk 8 is sandwiched by an
outer disk 9, which is a fixed part, and an electromagnetic plate
10, which is movable in the axial direction. The electromagnetic
plate 10 is constantly pressed against the inner disk 8, which
functions as a brake pad, by a spring 11. When the inner disk 8 is
gripped by the outer disk 9 and the electromagnetic plate 10, a
braking condition takes effect.
[0013] The electromagnetic plate 10, which is movable in the axial
direction, is designed to be attracted by the electromagnetic coil
12 of the electromagnetic brake 7. When the electromagnetic coil 12
is not turned on, the electromagnetic brake works by the resilience
of the spring 11. When the electromagnetic coil 12 is turned on and
magnetic attraction is generated, the electromagnetic plate 10 is
attracted to the electromagnetic coil 12, resisting the resilience
of the spring 11, thereby releasing the brake.
[0014] FIG. 1 shows a schematic drawing of the
motor-roller-controlling device with the brushless motor 2 built
in. When the start switch of the conveyor is turned on, a start
signal is sent to a motor driver 13. Then an electric current runs
to the electromagnetic coil of the electromagnetic brake. This
releases the electromagnetic brake while at the same time powering
the brushless motor 2. The brushless motor 2 is rotated, and the
rotation is transmitted to the outer casing of the motor
roller.
[0015] When a stop signal is transmitted, a transistor is
activated, which in turn activates an electric brake to slow down
the brushless motor 2. Activation of an electric brake using a
transistor is a widely used technique in a brushless motor. The
motor pulse rate, which inevitably reflects the revolution of the
brushless motor 2, is fed back to the motor driver 13.
[0016] In this invention, the driver substrate 14, on which the
motor driver is mounted, is also provided with a delay circuit 15.
The delay circuit 15 uses the motor pulse rate fed back to the
motor driver to detect the decline of the motor pulse rate. In
other words, after detecting that the motor pulse rate has
sufficiently declined after the stop signal has been given, the
electric current to the electromagnetic coil 12 of the
electromagnetic brake 7 is cut off. When the electric current to
the electric magnetic coil 12 is cut off, the attraction of the
electromagnetic plate 10 by the electromagnetic coil is released,
and the electromagnetic plate 10 is pressed against the inner disk
8 by the resilience of the spring 11. In other words, the
electromagnetic brake 7 is activated, and the rotation of the
brushless motor 2 is completely stopped.
[0017] The delay circuit 15 may activate the electromagnetic brake
by either detecting the declining trend of the motor pulse or by
confirming the cessation of the motor pulse. In the method in which
the electromagnetic brake is activated when the declining trend of
the motor pulse is detected, the motor roller can be stopped in a
short period of time. According to this method, because the
electromagnetic brake is activated after the electric brake is
activated, the motor roller can be stopped with little shock,
making it possible to avoid sudden friction with the inner disk 8,
which is a friction part.
[0018] In the method in which the electromagnetic brake 7 is
activated when the motor pulse rate of the electromagnetic brake
becomes zero or very small, the time to a complete halt is
determined by the characteristic of the electric brake. In this
case, the time to a complete halt is longer than in the above case.
After the electromagnetic brake is activated and the brushless
motor is stopped, it is possible to prevent the motor roller or the
conveyor from moving unnecessarily. The abrasion of the inner disk
can also be reduced significantly.
[0019] The delay circuit 15 of the present invention need only
consist of a circuit that detects changes in the motor pulse rate
on the driver substrate 14 on which the motor driver is mounted,
and there is no need to install a timer, an electromagnetic valve
or other special delay circuits on the control board. This makes it
possible to embody the present invention simply and
inexpensively.
[0020] According to the method for controlling a motor roller
described in claim 1 of the present invention, in a motor roller
using both an electric brake and an electromagnetic brake, the
electromagnetic brake can be activated only after the electric
brake is activated and the revolution of the brushless motor is
sufficiently reduced. This minimizes the abrasion of the brake
parts. Accordingly, the present invention is quite effective for
use with a belt conveyor that needs to be switched on and off
frequently.
[0021] Because the delay circuit employed in the present invention
uses the motor pulse that is detected by the motor driver, the
present invention can be embodied by simply adding the delay
circuit to the motor substrate. Therefore, there is no need to
install a special delay circuit device, making it possible to
embody the present invention simply and inexpensively.
* * * * *