Patent Grant
7005824
The present application is related to, and claims priority from, Japanese patent application no. 2002-373953, filed on Dec. 25, 2002, the contents of which are incorporated herein by reference.
The present invention relates to shutter mechanisms for shutters, elevators, or the like, and in particular to improvement of the stopping control at the upper and lower limit positions of an object to be wound and unwound by using the detected magnitude of a load generated at a motor used to wind and unwind the object.
Shutter mechanisms such as the one disclosed in Japanese unexamined patent application 2002-332788 are equipped with a shutter main unit having multiple hinged plates, a drum around which the hinged plates are wound, a motor that rotates the drum, and a speed reduction mechanism. This type of shutter mechanism is typically installed at the top of entrances and exits of shops, factories, or the like, and the motor rotates the drum to open and close the entrance/exit by respectively winding and unwinding the hinged plates. In general terms, the shutter mechanism described herein, and particularly the stepping motor control apparatus, may be used for controlling any stepping motor used in an application requiring accurate bi-directional control of first and second stopping positions of an object that is moved thereby.
More specifically, the motor of the shutter mechanism is typically activated by the push of a button located on, for example, a wall inside the entrance/exit. When the button is pushed, a controller controls the current provided to the motor to thereby cause the motor to rotate the drum in a forward direction to unwind the shutter, to rotate the drum in the reverse direction to wind the shutter, or to stop. Furthermore, sensors detect the upper limit position for winding the shutter main unit and the lower limit position for unwinding the shutter main unit. The detection results are input into the controller, and the controller then stops the motor based on the detection results.
In a shutter mechanism such as the one described above, the motor rotor continues to rotate briefly due to inertia even after the controller stops the current to the motor. As a result, there is a time lag until the motor stops completely, reducing the precision of the position wherein the shutter main unit comes to rest. In addition, a shutter mechanism that includes the sensors for sensing the upper limit position for winding the shutter main unit and the lower limit position for unwinding the shutter main unit requires additional parts, and the assembly required to place the sensors in the location wherein the shutter mechanism will be used is complicated and time-consuming.
A brake mechanism can be provided on the drum, and a speed reduction mechanism may be connected to the drum through a clutch, in order to increase-the accuracy of the position where the shutter main unit comes to rest. However, such a brake mechanism would require an even higher number of parts, and would further increase the cost of manufacturing and assembly of the shutter mechanism.
In view of the above, it is an object of the present invention to provide a shutter mechanism that is capable of improving the accuracy of the position at which an object to be selectively wound and unwound (hereinafter object) stops, without increasing the number of parts or adding cost to the manufacture of the mechanism.
It is a further object of the present invention to provide a shutter mechanism wherein the upper and lower limit positions of the object to be wound and unwound can be easily set.
It is yet another object of the present invention to provide a stepping motor control apparatus with upper and lower limit stopping position control for a shutter mechanism including an object to be wound and unwound.
The shutter mechanism of the present invention is equipped with a drum including an object to be selectively wound and unwound, a stepping motor for rotating the drum, a driver for supplying a drive current to the stepping motor, a controller for supplying command pulses to the driver, a memory for storing control data for the controller, and a load magnitude detection circuit that detects the magnitude of a load on the stepping motor.
Because the shutter mechanism of the present invention includes a stepping motor as the motive source for the drum, it possible to control the speed and to immediately stop the stepping motor as soon as the controller issues the stop command. Consequently, it is possible to increase the stopping precision of the shutter mechanism without increasing the number of parts. In addition, because the load magnitude detection circuit detects the magnitude of the load on the stepping motor, the detection results thereof can be used to set the upper and lower limit positions for the object, and can be used to provide, for example, an emergency stop feature.
The structure of the shutter mechanism of the present invention is such that the load generated at the stepping motor increases when the object arrives at the upper limit position when wound, or at the lower level position when unwound, making it possible for the load magnitude detection circuit to detect that the object has arrived at the upper level position or at the lower level position by detecting the increase in the load.
Furthermore, the memory stores the number of command pulses to be output from the controller in order to move the object between the upper limit position and the lower limit position. This makes it possible for the controller to read out the number of command pulses stored by the memory, and to control the number of command pulses output to the driver. For example, even if the object is halted temporarily between the upper limit position and the lower limit position, it is still possible to stop the object at the upper limit position or at the lower limit position after restarting movement of the object.
The controller can set the number of command pulses stored in the memory and stop the output of the command pulses to the driver when the load magnitude detection circuit detects an increase in the magnitude of the load at the stepping motor. The controller can then subsequently restart the output of the command pulses to the driver, and cause the memory to store the number of output command pulses output up to the point that the load magnitude detection circuit detects an increase in the magnitude of the load at the stepping motor, after the output of the command pulses has been restarted. With this type of situation, the object is, for example, first wound to the upper limit position and then unwound to the lower limit position, and the number of pulses output by the controller in order to move the object from the upper limit position to the lower limit position is stored in the memory. As a result, it is possible to detect the arrival of the object at the upper or lower limit position by counting the number of corresponding command pulses output by the controller.
The memory may be a nonvolatile memory that stores the number of command pulses, making it possible for the controller to compare the number of command pulses output to the driver with the number of command pulses read out from the non-volatile memory. Consequently, it is possible to accurately stop the object at the upper limit position or the lower limit position. The non-volatile memory may be a non-volatile RAM, EPROM, one or more floppy disks, one or more hard disks, one or more magneto-optical disks, or other memory media capable of retaining stored data when the power is turned off. Using the configuration described above, it is possible to automatically set the upper limit position and the lower limit position of the object.
The controller may also be capable of stopping or reversing the motion of the object when the object moves between the upper limit position and the lower limit position and the magnitude of the load detected by the load magnitude detection circuit exceeds a preset value. For example, if there is an obstruction in the movement path of the object as the object is being unwound, the magnitude of the load will increase when the object strikes the obstruction. The controller then can either stop or reverse the direction of the object, thus preventing damage to the obstruction, the object and components of the shutter mechanism.
The driver used in the shutter mechanism of the present invention may be a chopper-type current source driver that outputs a chopper signal that chops out the square wave that is output by the driver. The chopper-type current source driver maintains the current to the stepping motor at a steady value using the chopper signal. In other words, the chopper signal will prevent an increase in the current that would otherwise occur when the magnitude of the load on the stepping motor increases. This type of chopper signal causes the square waves generated by the chopper-type current source driver to be chopped into a comb-tooth pattern. Consequently, the frequency of the output of the chopper signal increases in proportion to the magnitude of the load.
The load magnitude detection circuit is equipped with a waveform detector that detects and outputs the chopper signal, where the magnitude of the load is detected based on the waveform output from the waveform detector. The load magnitude detection circuit can be equipped with a filter that converts the waveform output from the waveform detector into a series of continuous pulses, making it possible for the magnitude of the load to be detected based on the width of the pulses output from the filter. Conversely, the load magnitude detection circuit can be equipped with a filter that converts the waveform signal output from the waveform detector into a voltage signal, making it possible to detect the magnitude of the load based on the voltage signal output from the filter.
The filter can be equipped with a capacitor having a capacitance that can be set in accordance with the desired shape of the pulses. For example, if the capacitance of the capacitor is relatively small, then the comb-tooth pattern of the chopper waveform can be made into a continuous series of pulses. Consequently, the controller is able to detect the magnitude of the load on the stepper motor based on the width of the pulses output from the filter.
Furthermore, if the capacitance is large, then the pulses, as described above, will be contiguous with one another, making it possible to produce a smooth waveform. Given this, if the filter is equipped with, for example, a comparator, the comparator can generate and output a signal to the controller if the voltage of the flat waveform exceeds a predetermined voltage that is set in the comparator or stored in the memory.
The waveform detector can be equipped between the coil and the power supply of the stepping motor, making it possible to detect the chopper signal. When the chopper signal and the square waves chopped into a comb-toothed pattern are output, the voltage of the drive current momentarily falls with the timing with which the chopper signal is output. The chopper signal can be detected as the collector current in an amplifier when the drop in the voltage is input as the base voltage of the amplifier. The waveform of this collective current is a comb-tooth pattern chopper waveform.
The accompanying figures, where like reference numerals refer to identical or functionally similar elements throughout the separate views and which together with the detailed description below, are incorporated in and form part of the specification, serve to further illustrate various embodiments and to explain various principles and advantages all in accordance with the present invention.
Referring now to the drawings in which like numbers reference like parts, a shutter mechanism according to a preferred exemplary embodiment of the present invention will be discussed.
Referring now to
As is shown in
Still referring to
The waveform generator circuit 50 includes a capacitor 51 and a comparator 52, along with resistors R4 and R5. The capacitor 51 and resistors R4, R5 effectively form a filter that causes the comb-tooth pattern collector current waveform (chopper waveform) output from the waveform detector as shown in
If the capacitance of the capacitor 51 is large, then the pulses will be contiguous with each other, forming flat waveforms of different voltages, as shown in
Referring again to
Manual setting of the upper and lower limit positions of the shutter 3 by the shutter mechanism described above will now be explained. First, when the DOWN switch 14b is operated, a signal indicative thereof is output to the microcomputer 10. This causes command pulses to be output from the microcomputer 10 to the current driver 20, and the control part 21 thereof outputs a square wave with the same width (time) as the command pulses to the amplifier 22. This square wave in turn causes emitter current to flow from the power supply 13 to the amplifier 22 to thereby supply the drive current to the coils C. Consequently, the output axle of the stepping motor 5 rotates to rotate the drum 2 and thus unwind the shutter 3. At this time, and each time a command pulse is output, the microcomputer 10 decrements the value in a register in the CPU 15.
The STOP switch 14c is operated when the bottom edge part of the shutter 3 has been lowered far enough to contact, for example, the floor. This stops the output of the command pulses from the microcomputer 10, and as a result the stepping motor 5 stops immediately. The RESET switch 14d is then operated to cause the memory 16 to be cleared and, at the same time, to clear the number of command pulses stored in the register of the CPU 15, thereby effectively storing the lower limit position of the shutter 3.
When the UP switch 14a is actuated the shutter 3 is wound onto the drum 2. During this winding operation, the value in the register of the CPU 15 is incremented each time a command pulse is output. When the lower edge of the shutter 1 arrives, for example, in the vicinity of the opening 1a of the housing 1, the STOP switch 14c is actuated to stop the winding of the shutter 3. Next, when the SET switch 14e is operated, the number of command pulses stored in the register is then stored in the memory 16, thereby effectively storing the upper limit position of the shutter 3 in the memory 15.
Automatic setting of the upper and lower limit positions of the shutter 3 by the shutter mechanism described above will now be explained. Initially, the DOWN switch 14b is automatically actuated to unwind the shutter 3 until the lower edge of the shutter 3 contacts the floor surface. This will cause the magnitude of the load on the stepper motor 5 to increase.
When the value for the elevated drive current decreases, the voltage across the load resistor R2 also decreases. This drop in voltage causes the base voltage for the amplifier 41 in the waveform detector 40 to drop to generate a collector current in the amplifier 41. This collector current assumes a comb-tooth pattern chopper waveform, shown in
Here the leftmost graphs under (1) in
The memory 16 of the microcomputer 10 stores a specific pulse width (time) or a specific voltage as a threshold value, and if the signal input from the load magnitude detection circuit 30 indicates that the threshold value has been exceeded, the microcomputer stops the outputting of the command pulses, thereby stopping the rotation of the stepping motor 5, and stopping the movement of the shutter 3. At this time, the microcomputer 10 also illuminates the LED 11.
In addition, the microcomputer 10 clears the contents of the memory 16 and, at the same time, clears the number of command pulses stored in the register of the CPU 15. Consequently, when the shutter 3 arrives at the lower limit position and the magnitude of the load on the stepping motor 5 increases, the lower limit position of the shutter 3 is stored in the memory 16 because the contents of the register in the CPU 15 and of the memory 16 are cleared.
Next, the UP switch 14a is automatically actuated to wind up the shutter 3. When this is the case, the value in the register of the CPU 16 is incremented each time the microcomputer 10 outputs a command pulse. When the bottom edge of the shutter 3 arrives in, for example, the vicinity of the opening 1a of the housing 1, a guard part 3b equipped at the bottom edge of the shutter 3 fits into the opening 1a of the housing 1, and the load on the stepping motor 5 increases. The microcomputer 10 stops outputting the command pulses in this case as well, in the same way as described above, thereby stopping the winding of the shutter 3. Furthermore, the microcomputer 10 stores into the memory 16 the number of command pulses stored in the register of the CPU 15. Consequently, when the shutter 3 arrives at the upper limit position and the magnitude of the load on the stepping motor 5 increases, the number of command pulses output in order to move the shutter 3 from the lower limit position to the upper limit position is stored in the memory 16 to thereby effectively store the upper limit position of the stutter 3.
It should be noted that the switches 14a–14e on the switchboard 14 can be implemented to enable, for example, manual setup, automatic setup, automatic operation, manual operation, or the like of the shutter mechanism.
After the upper limit position and lower limit position for the shutter 3 have been set, either manually or automatically, as shown above, operations to open and close the shutter are performed automatically. In other words, when the DOWN switch 14b is operated when the shutter 3 is at the upper limit position, the value in the register of the CPU 15 is decremented. The CPU 15 of the microcomputer 10 constantly references the value of the register, and stops outputting command pulses when the value reaches 0. This stops the shutter 3 at the lower limit position. When the UP switch 14a is actuated, the value in the register of the CPU 15 is incremented, and the CPU 15 compares the value of the register to the value stored in the memory 16. The microcomputer 15 stops outputting the command pulses when the value in the register becomes equal to the value in the memory 16, thereby stopping the shutter 3 at the upper limit position. Note that even if the shutter 3 is raised while it is in the process of being lowered, or if the converse occurs, the register switches from decrementing to incrementing (or the converse). Therefore, the shutter 3 will always stop at the upper limit position or the lower limit position.
Next, operation of the above described shutter mechanism in the presence of an obstruction, such as freight, in the path of the shutter 3 will be explained. In such a situation, the memory 16 in the microcomputer 10 has a specific pulse width (time) or a specific voltage stored as a threshold value so that if the signal input from the load magnitude detection circuit 30 indicates that the threshold value has been exceeded, the outputting of the command pulses is stopped to stop the movement of the shutter 3. This makes it possible to prevent in advance damage to the shutter 3 and the obstruction, as well as other components in the shutter mechanism.
Here the threshold value stored in the memory 16 may be different for the automatic setup from what it is for obstruction detection. For example, the threshold value may correspond to a relatively small increase in the magnitude of the load, as indicated by the exemplary pulses shown in FIG. 4A(2), for the automatic setup, while the threshold value can correspond to a relatively large increase in the magnitude of the load, as indicated by the exemplary pulses shown in FIG. 4A(3), during operation. In such a configuration, the load applied on the components of the shutter mechanism when the shutter 3 arrives at the upper limit position or the lower limit position during operation will be minimal. Also, this makes it possible to avoid problems such as the shutter 3 stopping unintentionally during operation due to increased resistance caused by, for example, rust or dirt adhering to guides that support the shutter 3.
Note that it is possible to reduce the load that is applied when the shutter 3 reaches the upper limit position or the lower limit position by stopping the output of the command pulses prior to reaching zero or the set value when the value of the register of the CPU 15 increments from zero to reach the set value, or when the value of the register decrements from the set value to reach zero.
Because the shutter mechanism of the present invention includes a stepping motor 5 the motive source for the drum 2, it is possible to control and stop the rotor of the stepping motor 5 at the same time that the output of command pulses from the microcomputer 5 is stopped. Consequently, it is possible to increase the precision with which the shutter 3 is stopped without the need for extra parts, such as sensors. Furthermore, because a load magnitude detection circuit 30 is provided to detect the magnitude of the load on the stepping motor 5, it is possible to use the detection results thereof to set the upper limit position and lower limit position for the shutter 3, and to use the detection results thereof in, for example, emergency stops.
In other words, because the number of command pulses stored in the memory 16 is reset when the load magnitude detection circuit 30 detects an increase in the magnitude of the load generated by the stepping motor 5, and the number of command pulses output to that point is stored in the memory 16 when the load magnitude detection circuit 12 detects an increase in the magnitude of the load generated by the stepping motor 5 after the outputting of the command pulses is restarted, the lower limit position and upper limit position of the shutter 3 can be set automatically.
The shutter mechanism of the present invention as described above also enables detection results of the load magnitude detection circuit 30 to set the upper limit position and the lower limit position automatically for the object to be selectively wound and unwound, and to use the results of the detection in, for example, emergency stops.
The shutter mechanism and stepping motor control apparatus of the present invention are useful in a wide variety of applications, such as in structures wherein the torque of a stepping motor acts on an object when unwinding the object, such as is the case with shutters. However, the shutter mechanism and stepping motor control apparatus of the present invention may also be applicable when the torque from the stepping motor does not act on objects, such as, for example, drapes, curtains, blinds, or the like. In addition, the shutter mechanism and stepping motor control apparatus of the present invention may also be applicable to structures that are essentially rigid, such as wire, in which case the torque acts on the object. The shutter mechanism and stepping motor control apparatus of the present invention may also be applicable to, for example, sign boards, lighting equipment, partitioning curtains, gondolas ridden by workers, and other winding devices wherein there is hoisting using wires, chains, and the like.
This disclosure is intended to explain how to fashion and use various embodiments in accordance with the invention rather than to limit the true, intended, and fair scope and spirit thereof. The foregoing description is not intended to be exhaustive or to limit the invention to the precise form disclosed. Modifications or variations are possible in light of the above teachings. The embodiment(s) was chosen and described to provide the best illustration of the principles of the invention and its practical application, and to enable one of ordinary skill in the art to utilize the invention in various embodiments and with various modifications as are suited to the particular use contemplated. All such modifications and variations are within the scope of the invention as determined by the appended claims, as may be amended during the pendency of this application for patent, and all equivalents thereof, when interpreted in accordance with the breadth to which they are fairly, legally, and equitably entitled.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2002-373953 | Dec 2002 | JP | national |
| Number | Name | Date | Kind |
|---|---|---|---|
| 4902953 | Kraft et al. | Feb 1990 | A |
| 5038087 | Archer et al. | Aug 1991 | A |
| 5467808 | Bell | Nov 1995 | A |
| 5751128 | Chalupa et al. | May 1998 | A |
| 5850131 | Wolfer et al. | Dec 1998 | A |
| 6060852 | Domel et al. | May 2000 | A |
| Number | Date | Country |
|---|---|---|
| 2313499 | Nov 1997 | GB |
| A-2000-60185 | Feb 2000 | JP |
| WO 0206622 | Jan 2002 | WO |
| Number | Date | Country | |
|---|---|---|---|
| 20040169487 A1 | Sep 2004 | US |
