JP2006274538A - Control unit of electric shutter - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To enable a smooth opening and closing operation of a shutter curtain by automatically correcting output through the ordinary opening and closing operation, even if a load fluctuates. <P>SOLUTION: This control unit comprises: a shutter driving means; an output control means for setting output with a predetermined margin against a load of the driving means as the output of the driving means; an overload detecting means for detecting the overload of the driving means; a number-of-times-of-operation storage means for storing the number of the times of the operations of the shutter; a number-of-cases-of-detection-of-overload storage means for storing the number of the cases of the detection of the overload by the overload detecting means; and an overload detection frequency computing means for computing an overload detection frequency from the number of the times of the operation of the shutter and the number of the cases of the detection of the overload. The output control means increases or decreases the output by using a frequency reference for determining the overload detection frequency. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

The present invention relates to an electric shutter control device.

In the shutter device, safety must be ensured so that no person is caught in the shutter curtain, and the opening / closing body is not damaged or deformed when the opening / closing body is caught in an obstacle. There is also a need to consider. In one system, obstacle detection when a person or an object is sandwiched between the opening and closing bodies is performed by detecting an overload of the driving means.

When obstacle detection is performed by overload detection, an output in which a predetermined margin is added to the load of the driving unit is set. The amount of addition here corresponds to so-called sensitivity of overload detection, and this sensitivity is important for both ensuring the original function of the opening / closing body for opening and closing the opening and ensuring the reliability of obstacle detection. This is because if the sensitivity is low, the reliability of obstacle detection is impaired, and if the sensitivity is too good, the opening / closing body detects an overload due to a slight load fluctuation and stops and opens and closes the opening. Because it loses.

However, since the load on the driving means changes due to secular changes such as wear and deformation of the shutter curtain and / or guide rail, the initial margin may not be obtained as it is used.

An object of the present invention is to enable a smooth opening / closing operation of a shutter curtain by automatically correcting an output through a normal opening / closing operation even when the load fluctuates.

The control device for the electric shutter employed by the present invention includes a shutter driving unit, an output control unit that outputs an output having a predetermined margin with respect to a load of the driving unit, and an overload of the driving unit. An overload detection means for storing, an operation count storage means for storing the number of shutter operations, an overload detection number storage means for storing the number of overload detections by the overload detection means, a shutter operation count and an overload detection count, Overload detection frequency calculating means for calculating an overload detection frequency from the output control means, and the output control means is configured to increase or decrease the output using a frequency reference for determining the overload detection frequency.

In a preferred aspect, the frequency criterion includes a first frequency criterion for increasing the output and a second frequency criterion for decreasing the output, and the frequency of the first frequency criterion is higher than the frequency of the second frequency criterion. Is also set larger. In one mode, the number of operations at the frequency of the second frequency criterion is set to be greater than the number of operations at the frequency of the first frequency criterion.

In a preferred aspect, after the overload detection frequency satisfies the first frequency criterion and the output of the driving unit is increased, the output control unit may be a case where the overload detection frequency satisfies the second frequency criterion. The output is not reduced. By doing so, priority is given to securing the original function of the opening / closing body, that is, opening / closing of the opening, and it is prevented as much as possible that the overload detection is performed unnecessarily and the opening / closing operation is stopped. .

In a preferred embodiment, the magnitude of the output that the output control means increases or decreases at a time is predetermined. In one aspect, a margin table having a plurality of ranks is prepared, and the increase or decrease of the output of the driving means is performed by increasing or decreasing the margin value by one rank. Therefore, when the overload detection frequency satisfies the first frequency criterion, the output is increased by increasing the margin by one rank, and when the overload detection frequency satisfies the second frequency criterion, the margin is decreased by one rank. To reduce the output. If the overload detection frequency satisfies the first frequency criterion after the margin has been increased by one rank, the increased margin is further increased to further increase the output of the driving means. Further, in one aspect, an upper limit and a lower limit of output correction are set. In an embodiment described later, the upper limit of output is “initially set value of margin + 3 ranks”, and the lower limit of output is “initially set value of margin”. -1 rank ".

In the present invention, since the output is corrected using the frequency criterion for determining the overload detection frequency, that is, the probability, the output is not changed inappropriately based on accidental overload detection. By providing a first frequency criterion for increasing the output and a second frequency criterion for decreasing the output, and setting the frequency of the first frequency criterion to be larger than the frequency of the second frequency criterion, stable output Can be corrected.

A preferred example of the electric opening / closing body for construction will be described based on an electric shutter device. In FIG. 1, a shutter device installed in a building opening includes a shutter curtain 1, a winding shaft 2 to which the upper end of the shutter curtain 1 is connected, and an opening / closing device 3 that drives the winding shaft 2 to open and close. . The opening / closing machine 3 has a stepping motor 4 as a driving means, and the rotation shaft of the stepping motor 4 and the winding shaft 2 are connected by transmission to transmit the rotation of the rotation shaft of the stepping motor 4 to the winding shaft 2. Thus, the winding shaft 1 is rotated forward and backward to wind the shutter curtain 1 around the winding shaft 2, or it is fed out from the winding shaft 2 to guide the shutter curtain 1 to the left and right guide rails 5 to open the opening. Open and close.

The opening / closing drive of the shutter device is performed by a command from the switch box 6. A command from the switch box 6 is transmitted to the switch 3 via the control unit 7. The switch box 6 is provided with push button type operation switches PBU, PBS and PBD for raising, lowering and stopping. When the up button PBU is pressed, a shutter up signal is transmitted to the open / close control circuit of the control unit 7, a motor drive current is supplied to the motor 4 of the open / close machine 3, and the motor 4 rotates to wind the shutter curtain 1. Take up around the take-up shaft 2. When the lowering button PBD is pressed, a shutter lowering signal is transmitted to the opening / closing control circuit of the control unit 7, a motor driving current is supplied to the motor 4 of the opening / closing machine 3, the motor 4 rotates, and the shutter curtain 1 is wound. It is fed out from the take-up shaft 2. When the stop button PBS is pressed, a stop signal is transmitted to the open / close control circuit of the control unit 7, the supply of the motor drive current to the motor 4 is interrupted, and the rotation of the motor 4 is stopped.

The control unit (control unit) 7 includes a microcomputer, and the microcomputer includes a CPU and a storage unit, and an IC memory constituting the storage unit further includes a ROM and a RAM (at least of the IC memory). Some are non-volatile memories such as EPROM, EEPROM, non-volatile RAM). The driving of the stepping motor 4 is controlled by a microcomputer. That is, the stepping motor outputs a predetermined driving torque (switch output) by sending a predetermined driving current controlled by the microcomputer to the motor. In the present invention, the value of the drive current supplied to the motor is controlled in accordance with the position of the shutter curtain (shutter curtain feed amount).

A rotary encoder (not shown) is attached to the rotating shaft of the motor 4 constituting the opening / closing machine 3, and counts the number of pulses output according to the rotation of the rotating shaft. The nonvolatile movement memory of the microcomputer stores the maximum movement amount of the shutter curtain, counts pulses output from the rotary encoder with the upper limit position or the lower limit position as the origin position, and stores them in the RAM. When the count value matches the value corresponding to the origin position and the value corresponding to the maximum movement amount, it is determined that the upper and lower limit positions have been reached, and the drive current supply to the motor is stopped. The data of the origin position is stored in the microcomputer RAM by operating the setting switch by stopping the shutter curtain at the upper limit position or the lower limit position when the shutter is installed in the building opening. Further, the rotational speed and rotational speed of the rotating shaft of the motor can be calculated by the rotary encoder.

The rotary encoder constitutes a shutter curtain position detection means, and can detect the position of the shutter curtain based on the counted number of pulses. The rotary encoder attached to the rotation shaft of the motor counts the number of pulses output according to the rotation of the rotation shaft by the counting means, and stores the count value in the storage unit. By counting the pulses output from the rotary encoder with the upper limit position or lower limit position of the shutter curtain as the origin position and storing them in the storage unit, the position of the shutter curtain is detected by the count value. The data of the origin position is stored in the microcomputer RAM by operating the setting switch by stopping the shutter curtain at the upper limit position or the lower limit position when the shutter is installed in the building opening.

In order to open and close the shutter curtain with the switch, the output of the switch (drive torque of the motor) needs to exceed the load of the switch determined by the shutter moment, but the shutter curtain is rotated by rotating the winding shaft. When the shutter is moved up and down, the shutter moment is the amount that the shutter curtain is unwound from the take-up shaft during the process from the fully open state to the fully closed state and the process from the fully closed state to the fully open state. (In this specification, a load that changes with time due to the amount of extension of the shutter curtain when the shutter curtain is opened and closed is referred to as a shutter moment). The shutter moment when the shutter curtain is opened and closed is determined by the balance between the shutter curtain feed amount and the spring built in the take-up shaft, so the load changes depending on the shutter curtain feed amount that changes when the shutter curtain opens and closes. become.

The shutter moment, which is a load that changes when the shutter curtain is opened and closed, is monitored and detected over time, and a predetermined margin (this margin is referred to as an offset amount in this specification) is added to the detected load. The output of the stepping motor is controlled so as to obtain the output of the value switch (the lowest output that can be driven). The motor output is controlled by controlling the drive torque by controlling the drive current supplied to the motor. Then, when the load applied to the motor exceeds a preset minimum driveable output, the stepping motor is stepped out to stop the opening / closing drive of the shutter curtain.

Load information (shutter moment) that changes by monitoring and detecting the load over time from the fully open state of the shutter curtain to the fully closed state and from the fully closed state to the fully open state is acquired and stored in the storage unit. . The load when the shutter curtain is raised and the load when the shutter curtain is lowered are acquired and stored independently of each other. In one aspect, the current value is stored in the storage unit as equivalent to the load determined by the shutter moment by detecting the fluctuation of the load using the current detection device. Although the load is equivalent to the current value, the relationship between the drive current and the torque is determined by the motor used, and therefore the load torque can be calculated if the drive current is known. The load detection by the current detection device is performed for each opening operation and one closing operation, and the load stored in the storage unit is updated. The offset amount selected in advance is added to the load value of the load during operation and the load during descent operation. In general, the amount of offset added to the load is the same during the ascending operation and the descending operation of the shutter curtain, but the offset amounts of the two may be different.

The amount of offset added to the detected load is such that the driving torque (load detected at a certain time + offset amount) does not fall below the torque when the shutter curtain is normally opened and closed, and there is an obstacle on the moving shutter curtain. The magnitude of the load acting on the switch when it hits is set to a value that exceeds the drive torque (the load detected at a certain time + the offset amount). That is, in the overload state, the offset amount is set to such a value that the load exceeds the driving torque and the stepping motor constituting the switch is stepped out. In a specific aspect, the offset amount is set as a current value, and a current value obtained by adding the offset amount to a current value equivalent to the detected load is supplied to the motor as a drive current. By doing so, overload detection is performed by stepping out the stepping motor at the time of overload, and when the motor steps out, the rotation of the rotating shaft stops and the shutter curtain opening / closing drive stops. When the shutter curtain is opened and closed, the drive current is determined over time (every predetermined timing) based on a preset offset amount and a current value equivalent to the detected load. The offset amount is set to such a value that the motor output becomes the lowest output that can be driven according to the shutter moment, which is a load that varies depending on the opening / closing amount of the shutter curtain. The offset amount determines a margin such that the motor is driven without stepping out in a slight load change that may occur during normal use (for example, a slight load that acts on the shutter curtain due to a slight wind). The offset amount directly affects the detection sensitivity of overload detection, and the offset amount may be updated as necessary in the process of opening / closing the shutter curtain. In one embodiment, the offset amount is stored as a table in the ROM of the microcomputer, and an appropriate offset amount is selected from the table.

Here, since the output of the opening / closing machine required for opening and closing the shutter curtain varies depending on the size of the shutter, the appropriate motor driving current value varies depending on the shutter size. In general, if the shutter size is large, a correspondingly large driving current is required, and if the shutter size is small, a correspondingly small driving current is sufficient. In addition, in order to open and close the shutter curtain with an opening / closing device, the output of the opening / closing device (motor driving torque) must exceed the shutter moment that is the load, but the output margin (offset amount) with respect to the shutter moment is also There is an appropriate amount depending on the shutter size.

The storage unit of the control unit 7 stores a table of initial drive current values (determined by initial Vref [mV]) and offset amounts respectively corresponding to a plurality of types of shutters having different sizes. FIG. 3 is a table illustrating the relationship between the shutter size, the drive current value, and the offset amount, and shows initial drive current values and offset amounts corresponding to nine types of shutter sizes. If the shutter size is large, the offset amount is set to be large correspondingly, and rank 5 is standard (default) in eight ranks. When it is desired to adjust the load detection sensitivity, the offset amount can be adjusted in eight steps by the combination of the selection of three dip switches provided in the motor control device. For example, when three dip switches are OFF, OFF, and OFF, they are rank 1, and when they are OFF, OFF, and ON, they are rank 2. If you want to change the offset amount in the low sensitivity direction, select Nos. 1-4, and if you want to change the offset amount in the high sensitivity direction, select Nos. 6-8.

Then, a load (shutter moment) that changes depending on the amount of shutter curtain being sent during the opening / closing operation of the shutter curtain is acquired over time by the load detection unit configured by the current detection device, and is stored in the storage unit (RAM). . Based on the detected shutter moment (current value) and a preset offset amount (current value), the drive current supplied to the motor of the switch is determined every predetermined timing (1.7 seconds), and a predetermined drive torque ( Output) is output every predetermined timing (1.7 seconds) to drive the shutter curtain to open and close. The load determined by the shutter moment is updated by detecting each time the shutter curtain is opened and closed, and the latest load value is stored in the storage unit (RAM). The drive current is controlled using the latest load value and the selected offset amount. Controlling the driving current at every predetermined timing (1.7 seconds) means that the position that the shutter curtain can take when opening and closing is divided into a plurality of sections, and the driving current is controlled for each section according to the position of the shutter curtain. Means that. That is, a range corresponding to the amount of movement of the shutter curtain in 1.7 seconds constitutes each section.

In a normal opening / closing operation of the shutter curtain, the load does not exceed the output of the motor, so that the shutter curtain is driven to open / close with a driving torque output by a predetermined driving current. If an obstacle hits the shutter curtain when the shutter curtain is opened and closed, the load acting on the shutter curtain exceeds the motor output and the stepping motor steps out. When the stepping motor steps out, the rotation of the motor rotation shaft stops, so that the shutter curtain opening / closing drive stops. That is, the overload state is automatically detected when the stepping motor steps out.

For the opening / closing drive control of the shutter curtain after detecting the overload state, the stepping motor step-out is detected by the step-out detecting means. The stepping motor step-out is in a state in which the rotation of the motor is not synchronized with the input pulse. Therefore, the stepping motor is detected by detecting the rotation of the motor rotation shaft with the rotary encoder and the presence or absence of the output pulse of the encoder. Can be detected. As a processing procedure when a stepping motor step-out is detected, in one aspect, the motor driving current supplied to the motor is cut off to completely stop the motor. In another aspect, after the motor is completely stopped or after a step-out is detected, a motor driving current that reverses the shutter curtain is supplied to the motor for a predetermined time, and the shutter curtain is moved for a predetermined time. Reverse operation is performed, and then the motor is stopped. Here, in the present specification, the description is based mainly on the driving means including the stepping motor, but the driving means and overload detection applied to the present invention are limited to the stepping motor and the stepping motor step-out. Other DC motors, AC motors, etc. can be used, and other overload detection means such as a change in motor current value, a decrease in motor rotation speed (change in pulse interval from the encoder) ), An overload condition may be detected.

The present invention includes a control unit that corrects the output with respect to a fluctuating load, and corrects the output by correcting the amount of margin (offset amount) added to the load of the driving unit. The shutter control device according to the present invention includes a shutter driving unit, an output control unit that outputs an output having a predetermined margin with respect to a load of the driving unit, and an overload that detects an overload of the driving unit. The load detection means, the operation count storage means for storing the number of shutter operations, the overload detection number storage means for storing the number of overload detections by the overload detection means, and the shutter operation count and the overload detection count. Overload detection frequency calculating means for calculating the load detection frequency. The output control means controls the output using the first frequency criterion and the second frequency criterion for determining the frequency of overload detection, and the frequency of the first frequency criterion is set larger than the frequency of the second frequency criterion. The output of the driving means is increased when the overload detection frequency is equal to or higher than the frequency of the first frequency reference, and the output is decreased when the overload detection frequency is equal to or lower than the frequency of the second frequency reference. After the overload detection frequency satisfies the first frequency criterion and increases the output of the driving means, if the overload detection frequency is equal to or higher than the frequency of the first frequency reference, the increased output of the driving means is further increased. It is configured as follows. After the overload detection frequency satisfies the first frequency criterion and increases the output of the driving means, the output is not decreased even if the overload detection frequency satisfies the second frequency criterion.

In one aspect, the first frequency criterion is “whether the number of obstacle detections is four or more in 60 shutter operations”, and the frequency of the first frequency criterion is 4/60. The first frequency criterion is satisfied when the number of operations stored in the operation number storage unit is 60 or less and the number of detections stored in the obstacle detection number storage unit is 4 or more. For example, in 60 shutter operations, if the number of obstacle detections is 5, the first frequency standard is satisfied, but if the number of obstacle detections is 3, the first frequency standard is not satisfied.

The second frequency criterion is “whether there was less than one obstacle detection in 180 shutter operations, ie, there was no obstacle detection”, and the frequency of the second frequency criterion is 1/180. The second frequency criterion is satisfied when the number of operations stored in the operation number storage unit is 180 or more and the number of detections stored in the obstacle detection number storage unit is 0. For example, in the 180 shutter operations, if the number of obstacle detections is one, the second frequency criterion is not satisfied, and the second frequency criterion is satisfied only when the number of obstacle detections is zero.

In the above, the frequency of the first frequency reference is 4/60, the frequency of the second frequency reference is 1/180, and the frequency of the first frequency reference is set larger than the frequency of the second frequency reference. Furthermore, the number of operations (180 times) at the frequency of the second frequency criterion is set to be larger than the number of operations (60 times) at the frequency of the first frequency criterion. Specific numerical values of the frequency of the first frequency reference and the frequency of the second frequency reference are not limited to those described above, and can be selected as appropriate depending on the type of the shutter device and the count mode of the number of shutter operations. In one aspect of the method of counting the number of shutter operations, “one descent” and “one up” are each regarded as one operation. For example, if the shutter has a height of 2 m and is opened by intermittent operation every 50 cm from fully closed to fully open, 4 operations are performed. In addition, when the shutter has a height of 2 m and is opened / closed by intermittent operation every 50 cm from fully closed to fully open, there are 8 operations. The method of counting the number of times of the shutter operation is not limited to this, and it is only necessary to set an appropriate frequency reference according to the number of operations even in other counting methods. Also, for reasons such as inspection, it is desirable not to count the first predetermined number of times (for example, 20 times) after power-on as the number of operations.

An embodiment of controlling the shutter curtain according to the present invention will be described. FIG. 4 is a flowchart showing offset amount correction. As a basic control method, when the first frequency criterion is satisfied, the offset amount (margin) is increased by one rank, but the margin to be increased is up to three ranks. After the offset amount becomes “initial value of offset amount + 3 ranks”, even if the first frequency criterion is satisfied, the rank is not further increased. When the second frequency standard is satisfied, the offset amount (margin) is lowered by one rank, but when the offset amount is reduced, it is limited to one rank. After “offset amount initial setting value—1 rank”, even if the second frequency criterion is satisfied, the rank is not lowered any further. Therefore, in this embodiment, the offset amount after correction can be in the range from “offset amount initial setting value−1” to “offset amount initial setting value + 3”. In addition, after the first frequency criterion is satisfied and the output of the driving unit is increased, the output is not decreased even when the second frequency criterion is satisfied. The increase / decrease in the offset amount is performed according to the table shown in FIG. 3, but a correction table may be provided separately. In one aspect, the offset amount table is provided separately for the shutter curtain raising and the shutter curtain lowering, and the amount of one rank of the offset is set larger in the case of the ascending operation than in the case of the descending operation. Has been. In one embodiment, the offset amount is corrected simultaneously in the ascending operation and the descending operation. However, the offset amount may be corrected independently for each ascending operation and every descending operation.

First, symbols in the flowchart of FIG. 4 will be described.
N1: A symbol representing the number of opening and closing operations for the first frequency reference.
N2: A symbol representing the number of opening and closing operations for the second frequency reference.
K: A symbol representing the number of obstacle detections. “K = 0” represents initialization or initialization of the number of detections.
M: A symbol indicating how many ranks have been raised or lowered from the initially set offset amount. “M = 0” represents an initial setting; “M = + 1” represents one rank increase in the offset amount from the initial setting; “M = −1” represents one rank decrease in the offset amount from the initial setting.
F: A symbol indicating whether the offset amount has been increased by one rank.

The number of opening / closing operations is counted according to the up / down operation of the shutter curtain and stored in the operation number storage means (S1). The number of operations is counted in parallel with a count N1 for the number of times used for the first frequency reference (60 times) and a count N2 for the number of times used for the second frequency reference (180 times).

It is determined whether or not an obstacle is detected by the overload detection means (S2). If the obstacle detection is “present”, the obstacle detection count K is counted and stored in the overload detection number storage means (S3). When the obstacle detection is “present”, the number of opening / closing operations N2 is initialized by the first obstacle detection (S4). It is determined whether the number of opening / closing operations N1 has reached 60 (S5). When the number of opening / closing operations N1 does not reach 60, the process returns to S1.

When the opening / closing operation count N1 is 60, it is determined whether the obstacle detection count K has reached 4 (S6). When the obstacle detection count K is less than 4 (when the first frequency criterion is not satisfied), the open / close operation count N1 is initialized and the process returns to S1. When the obstacle detection count K is 4 times or more (when the first frequency criterion is satisfied), it is determined whether the offset amount is increased by 3 ranks from the initial setting (S7). If the offset amount has already increased by three ranks from the initial setting, the number of opening / closing operations N1 is initialized and the process returns to S1. If the offset amount has not been increased by three ranks from the initial setting, the output control means increases the offset amount by one rank (S8). When the offset amount is increased by one rank, “M = + 1” is stored in the storage unit (S9). When the offset amount is increased by one rank, F = 1 is displayed (S10).

If the obstacle detection is “none” in S2, it is determined whether the opening / closing operation has reached 180 times (S11). When the determination result of S11 reaches 180 times, it is determined whether the offset amount is lowered by one rank from the initial setting (S12). When the offset amount is lowered by one rank from the initial setting, the number of opening / closing operations N2 is initialized. If the offset amount has not been lowered by one rank from the initial setting, it is determined whether the offset amount has been increased (S13). If the offset amount has been increased, N2 is initialized. If the offset amount has never been raised, the output control means lowers the offset amount by one rank (S14). When the offset amount is lowered by one rank, “M = −1” is stored (S15). When the offset amount is lowered by 180 times of opening / closing operations, the number of opening / closing operations N2 is initialized.

If the determination result of S11 has not reached 180 times, it is determined whether the number of opening / closing operations N1 is already 60 times or more (S16). When the number of opening / closing operations N1 has not reached 60, the number of opening / closing operations N1 is counted, and when the number of opening / closing operations N1 exceeds 60, the counting of the number of opening / closing operations N1 is initialized.

The control device and method according to the present invention can be used for driving control of the shutter curtain in the shutter device.

It is the schematic which shows the whole structure of an electric shutter apparatus. It is a flowchart which shows control of the switch output concerning this invention. It is a table which shows a response | compatibility with an automatic recognition shutter size and offset amount (sensitivity of overload detection). It is a flowchart which shows correction | amendment of offset amount.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 Shutter curtain 2 Winding shaft 3 Opening / closing machine 4 Stepping motor 7 Control part

Claims (3)

Shutter driving means;
Output control means for making the output of the driving means an output having a predetermined margin with respect to the load of the driving means;
Overload detection means for detecting overload of the drive means;
An operation count storage means for storing the number of shutter operations;
An overload detection number storage means for storing the number of overload detections by the overload detection means;
An overload detection frequency calculating means for calculating an overload detection frequency from the number of shutter operations and the number of overload detections;
The output control means is configured to increase or decrease the output using a frequency reference for determining an overload detection frequency. 2. The frequency reference according to claim 1, wherein the frequency criterion includes a first frequency criterion for increasing the output and a second frequency criterion for decreasing the output, and the frequency of the first frequency criterion is the frequency of the second frequency criterion. An electric shutter control device characterized by being set larger than the above. 3. The output control unit according to claim 2, wherein the overload detection frequency satisfies the first frequency criterion and the output of the drive unit is increased and the overload detection frequency satisfies the second frequency criterion. A control device for an electric shutter, characterized in that the output is not lowered.

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