Patent Application
20220088940
This application is based upon and claims the benefit of priority from Japanese Patent Application No. 2020-158961, filed Sep. 23, 2020, the entire contents of which are incorporated herein by reference.
Embodiments described herein relate generally to a motor control device and a thermal printer.
Conventionally, in an electronic apparatus with a motor, the motor is controlled so as not to exceed some rated temperature that corresponds to a usage limit temperature for the motor. In such an electronic apparatus, the temperature of the motor is detected by a temperature sensor, such as a thermistor, and when the detected temperature reaches or exceeds a predetermined temperature, the motor is stopped.
A thermal printer with a sheet conveyance motor is known. In such a thermal printer, a temperature sensor is generally attached to the sheet conveyance motor via a heat conductive member. The temperature sensor is electrically connected to a circuit board. The motor is stopped when the temperature detected by the temperature sensor reaches or exceeds a predetermined temperature. There has also been known a configuration of a thermal printer in which the temperature sensor is directly attached to the motor rather than via a heat conductive member. In such a case, the temperature sensor and the circuit board can be connected by a flexible substrate board.
According to such conventional techniques, the temperature of the motor is detected by a temperature sensor that is off the circuit board by some distance. Therefore, it is necessary to connect the temperature sensor to the circuit board via a flexible substrate board or the like, which causes an increase in cost of the thermal printer.
In general, according to one embodiment, a motor driving device includes a first substrate, a motor drive circuit, a first temperature sensor, a second temperature sensor, and a controller. The first substrate is connected to a motor via a first wiring. The motor drive circuit is provided on the first substrate. The first temperature sensor is provided on the substrate and detects a first temperature of the motor drive circuit. The second temperature sensor detects a second temperature of an ambient environment where the motor is being used. The controller controls the motor drive circuit based on the first temperature from the first temperature sensor and the second temperature from the second temperature sensor.
Certain example embodiments of a motor control device and a thermal printer will be described with reference to the accompanying drawings. In the example embodiments, a motor control device or a motor driving device for a paper conveyance motor of a thermal printer will be described as one example of a control device in an electronic apparatus, but the present disclosure is not limited thereto.
The housing 10 includes a main body 11, a cover 12, a display/operation unit 13, and a bumper 14. The main body 11 includes a sheet storage portion having an open upper surface. The sheet storage portion detachably stores a sheet P (see
The cover 12 is rotatably and pivotally supported by a rear end part 15 of the main body 11. The cover 12 rotates to open and close the upper surface opening of the sheet storage portion. As shown in
The display/operation unit 13 includes a power switch 21, a paper feed button 22 for a user to instruct paper feed or the like, a pause button 23 for a user to instruct pause of paper feed or the like, an indicator 24 for notifying a user of the state of the battery, and a display unit 25 formed of, for example, a Liquid Crystal Display (LCD) or the like.
The bumper 14 is provided at each of four corners of the main body 11 and protrudes outward from the main body 11. The bumper 14 is made of an elastic material such as rubber. For example, when a user drops the thermal printer 1 while carrying the thermal printer 1, the bumper 14 functions as a cushioning material to prevent the housing 10 from being damaged.
The thermal head 30 is accommodated in the main body 11 of the housing 10. The thermal head 30 is, for example, a line thermal head having a plurality of heat generation elements arranged in a line in a main scanning direction perpendicular to a conveyance direction of the sheet P indicated by an arrow in
The platen 40 is formed in a roller shape and is attached to the cover 12. The platen 40 is provided at a position where the platen 40 is pressed against the thermal head 30 in a state where the cover 12 is closed. A driven gear that rotates integrally with the platen 40 is provided on one end side in the axial direction of the platen 40. The main body 11 is provided with a driving gear driven by the motor 50 at a position corresponding to the driven gear. The driven gear meshes with the driving gear when the cover 12 is closed. Accordingly, the platen 40 is rotationally driven by the motor 50 in a state where the cover 12 is closed and conveys the sheet P in the direction of the arrow shown in
The motor 50 is, for example, a permanent magnet (PM) motor using one or more permanent magnets as a rotor and rotates the platen 40 to convey the sheet P in the thermal printer 1. The first wiring 51 includes, for example, a plurality of wires and cables and causes a necessary current to flow to the motor 50.
The main substrate 60 includes a motor driver Integrated Circuit (IC) 61, a first thermistor 62, a first terminal portion 63, and a second terminal portion 64. Although not specifically depicted, the main substrate 60 includes various electronic components necessary for controlling the thermal printer 1 in addition to a head drive circuit 65 (see
The motor driver IC 61 includes a circuit for driving the motor 50 and is one example of a motor drive circuit. Since the current corresponding to the current flowing through the motor 50 flows through the motor driver IC 61, a temperature rise due to current consumption of the motor driver IC 61 has a correlation with a temperature rise due to current consumption of the motor 50.
The first thermistor 62 is provided in the vicinity of the motor driver IC 61 and detects a temperature of the motor driver IC 61. The first thermistor 62 is an example of a first temperature sensor configured to detect a temperature of the motor drive circuit. Since the temperature rise of the motor driver IC 61 has a correlation with the temperature rise of the motor 50, the temperature of the motor 50 can be estimated based on the temperature detected by the first thermistor 62. Therefore, the first thermistor 62 indirectly detects the temperature of the motor 50.
The first terminal portion 63 is provided on one end side of the main substrate 60 and connects the main substrate 60 to the plurality of wires and cables of the first wiring 51 connected to the motor 50. The second terminal portion 64 is provided on another end side of the main substrate 60 and connects the main substrate 60 to the plurality of wires and cables of the second wiring 71 connected to the thermistor substrate 70.
The thermistor substrate 70 includes a second thermistor 72 and a terminal portion 73. The second thermistor 72 is provided on one end side of the thermistor substrate 70 and detects a temperature of an ambient environment of the motor driving device 2. The second thermistor 72 is an example of a second temperature sensor being provided in a housing of an electronic apparatus, such as the housing 10 of the thermal printer 1, and configured to detect a temperature of an ambient environment where a motor, such as the sheet conveyance motor 50, is being used. The terminal portion 73 is provided on another end side of the thermistor substrate 70 and connects the thermistor substrate 70 to the plurality of wires and cables of the second wiring 71 connected to the main substrate 60.
As time elapses after the motor 50 starts operating, both the temperature TM (of the motor 50) and the temperature TT (of the first thermistor 62) (and the temperature TD of the motor driver IC 61) gradually rise from the initial, ambient environment temperature. The temperature rise of the motor 50 has a correlation with that of the motor driver IC 61, and the gradient of the temperature rise of the motor 50 is greater than that of the motor driver IC 61. In this situation, the motor driving device 2 performs control such that the temperature TM does not reach or exceed a predetermined rated temperature T. Since the second thermistor 72 is provided at a position not readily affected by the temperature changes of either the motor 50 or the motor driver IC 61, the temperature TR as detected by the second thermistor 72 is substantially constant even when the motor 50 is being driven.
When the drive current flows through the motor driver IC 61, the temperature TT as detected by the first thermistor 62 rises. When the temperature TT reaches a temperature Y, which is a threshold, at time Q, the motor driving device 2 stops driving the motor 50. The threshold temperature Y is set to correspond to the temperature that will be detected by the first thermistor 62 when the temperature TM reaches near the rated temperature T of the motor 50. In other words, if the temperature TT reaches the threshold temperature Y, it can be estimated that the temperature TM has reached a temperature close to the rated temperature T. After the driving of the motor 50 is stopped, the temperature TM stops rising since the motor driving current no longer flows. Accordingly, the motor driving device 2 can control the motor 50 so that the temperature TM does not to reach or exceed the rated temperature T. According to this configuration, since it is not necessary to directly attach a temperature sensor to the motor 50, it is not necessary to use a flexible substrate or the like for connecting the temperature sensor for the motor 50 to the main substrate 60. This simplifies the configuration of the motor driving device 2.
The threshold or the threshold temperature Y can be predetermined based on the various components used in the thermal printer 1 and design conditions such as a current draw of the motor 50, a position of the first thermistor 62 with respect to the motor 50, and the like. For example, the threshold is set based on experimental data obtained by performing an experiment in which the thermal printer 1 is operated in a controlled ambient environment temperature.
The ambient environment temperature has less influence on the motor 50 than on the first thermistor 62. Therefore, the temperature TM of the motor 50 estimated from the temperature TT detected by the first thermistor 62 becomes higher than the actual temperature of the motor 50. Accordingly, when the temperature TT reaches the threshold temperature Y, the temperature TM is considerably lower than the rated temperature T. This way, even though the temperature TM of the motor 50 is still at an operable temperature, the operation of the motor 50 will be stopped to secure a sufficient safety margin.
Although the configuration of the motor driving device 2 can be simplified by controlling the driving of the motor 50 based on the temperature TT detected by the first thermistor 62 according to the present embodiment, there may be room for further improvement in terms of the operation performance of the thermal printer 1. In the thermal printer 1 according to another embodiment, in order to achieve the further improvement of the operation performance, a threshold correction is performed in which the threshold temperature of the first thermistor 62 is adjusted/changed according to the actual ambient environment temperature.
As shown in
When the temperature TT detected by the first thermistor 62 reaches the threshold temperature V, the motor driving device 2 stops driving the motor 50. At this time, the temperature TM of the motor 50 is closer to the rated temperature T. As a result, time QB from the start of operation to the stop of the motor 50 becomes longer than the time QA shown in
The control unit 100 functions as or can be a computer comprising a central processing unit (CPU) 101, a read-only memory (ROM) 102, and a random-access memory (RAM) 103. The CPU 101, the ROM 102, and the RAM 103 are connected to each other via the bus 140.
The CPU 101 controls operations of the thermal printer 1. The ROM 102 stores various programs such as a program used for driving the CPU 101 and various data. The RAM 103 is used as a work area of the CPU 101 and loads various programs and various date stored in the ROM 102 or the memory unit 110. The control unit 100 executes various control processes of the thermal printer 1 by operating the CPU 101 according to a control program stored in the ROM 102 or the memory unit 110 and expanded in the RAM 103.
The memory unit 110 is a storage device including a rewritable nonvolatile storage medium such as a hard disk drive (HDD), a solid-state memory (SSD), or a flash memory. The memory unit 110 includes a control program unit 111, a head energization table unit 112, and a threshold table unit 113. The control program unit 111 stores the control program for the operation of the thermal printer 1 and other various control programs as needed.
The head energizing table unit 112 stores a head energizing table.
The threshold table unit 113 stores a threshold table.
Returning to
The operation acceptance unit 1001 receives an operation signal from the display/operation unit 13. For example, the operation acceptance unit 1001 receives an operation signal corresponding to pressing or switching of the power switch 21, the paper feed button 22, the pause button 23, or the like as entered via the display/operation unit 13 by a user of the thermal printer 1.
The print acceptance unit 1002 receives a print instruction and print data corresponding to the print instruction from an external PC or the like. Once the print instruction and the print data are accepted, the control unit 100 performs the control process for printing. For example, the control unit 100 controls the thermal head 30 and the motor 50 to perform the printing based on the accepted print instruction and print data.
The acquisition unit 1003 acquires temperature information indicating a measured temperature from the first thermistor 62 and the second thermistor 72. For example, when the thermal printer 1 is powered on, temperature information is sent from both the first thermistor 62 and the second thermistor 72 to the acquisition unit 1003 at predetermined intervals. The temperature information from the first thermistor 62 and the second thermistor 72 is then used by the head control unit 1004 and the motor control unit 1005 for the printing control process.
The head control unit 1004 controls a drive circuit that drives the thermal head 30 based on the output of the second temperature sensor. The head control unit 1004 is one example of a thermal head controller. For example, the head control unit 1004 controls the head drive circuit 65 to proceed with the printing based on the print data received by the print acceptance unit 1002, and controls the energization time of the heat generation elements based on the temperature information from the second thermistor 72. More specifically, when the print acceptance unit 1002 receives a print instruction and print data, the head control unit 1004 reads, from the head energization table unit 112 (see
The motor control unit 1005 controls a motor drive circuit that drives the motor 50 based on the outputs of both the first temperature sensor and the second temperature sensor. Specifically, the motor controller 1005 controls the motor driver IC 61 to convey the sheet P for printing based on the print data received by the print receiver 1002, and a comparison of the detected temperature from the first thermistor 62 to the threshold temperature that has been set based on the detected temperature from the second thermistor 72 according to the threshold table of the threshold table unit 11 (see
In the case where the temperature information from the first thermistor 62 indicates the temperature TT is equal to or higher than the threshold temperature, the motor control unit 1005 controls the motor driver IC 61 to stop the driving of the motor 50. After the motor 50 is stopped, if the temperature information from the first thermistor 62 indicates the detected temperature TT is now below the threshold, the motor control unit 1005 controls the motor driver IC 61 to resume driving the motor 50 after an elapse of a predetermined time. After the motor 50 is stopped, the driving of the motor 50 will generally not be immediately resumed even if the temperature TT decreases below the threshold. The driving of the motor 50 will be resumed only after the elapse of some predetermined time period after the that the temperature of the motor 50 has sufficiently decreased. This way, the motor 50 can be operated in a more stable state.
The threshold temperature to be used for the comparison to the temperature TT by the motor control unit 1005 may be set by the threshold setting unit 1006. That is, the threshold correction can be performed by the threshold setting unit 1006 where the threshold temperature will be changed according to the output from the second temperature sensor 72. For example, the threshold setting unit 1006 reads, from the threshold table unit 113 (or the threshold table stored therein), the threshold corresponding to one of the temperature ranges in which the detected temperature TR from the second thermistor 72 falls and sets the read threshold as the threshold to be used for the comparison with the detected temperature TT from the first thermistor 62. The threshold setting unit 1006 performs the threshold correction before the start of the printing.
First, the control unit 100 determines whether the print acceptance unit 1002 has accepted a print instruction together with print data from an external PC or the like via the communication I/F 130 (S1). If the print instruction has not been accepted (No in S1), the control unit 100 stays in a waiting state. When the print acceptance unit 1002 has received a print instruction (Yes in S1), the acquisition unit 1003 acquires the temperature information indicating the detected temperature in the housing 10 as the ambient environment temperature from the second thermistor 72 (S2).
Subsequently, the threshold setting unit 1006 reads, from the threshold table unit 113 (or the threshold table stored therein), the threshold (or the threshold temperature) corresponding to the detected temperature included in the temperature information from the second thermistors 72 and sets the read threshold as the threshold to be used for comparison with the detected temperature from the first thermistors 62 (S3). Then, the motor control unit 1005 controls the motor driver IC 61 to drive the motor 50 to convey the sheet P for printing based on the accepted print date (S4).
During the printing operation after the start of the motor 50, the motor control unit 1005 compares the temperature information acquired from the first thermistor 62 to the threshold temperature value set by the threshold setting unit 1006 (S5). The comparison can be performed at a predetermined interval, for example, every 30 seconds. When the temperature of the motor driver IC 61 is not below the threshold (No in S5), that is, when the temperature of the motor driver IC 61 reaches or exceeds the threshold, the motor control unit 1005 controls the motor driver IC 61 to stop the operation of the motor 50 (S6). Then, the control unit 100 returns to the S5 process.
In the process of S5, if the temperature information from the first thermistor 62 indicates the detected temperature is below the threshold (Yes in S5), the motor control unit 1005 then determines whether the motor 50 is presently being driven (e.g., being supplied with power) (S7).
If the motor 50 is being driven (Yes in S7), the control unit 100 next determines whether the printing job has finished (S8). For example, the control unit 100 determines whether the sheet P printed by the thermal head 30 has been discharged from the sheet discharge port 18 in order to determine the present status of the printing process. In a case where the printing has finished (Yes in S8), the control unit 100 ends the motor control processing for the print operation. In a case where the printing has not finished (No in S8), the control unit 100 returns to the process in S5.
After the S7 process, if the motor 50 is not presently being driven, that is, the motor 50 is in the stopped state, the control unit 100 next determines whether a predetermined time has elapsed since the motor 50 was stopped (S9). If the predetermined time has not yet elapsed (No in S9), the control unit 100 waits until the predetermined time elapses. If the predetermined time has elapsed (Yes in S9), the control unit 100 considers that the temperature of the motor 50 has decreased sufficiently and returns to the motor driving process of S4.
In this manner, every time a print instruction is received, the control unit 100 executes the motor control processing during the print operation. In some examples, the motor control processing need not be executed for every print instruction that is received but may instead be executed every time certain type of print data is printed or for a predetermined print range, for example every time a full page of data is printed.
The motor driving device 2 of the present embodiment includes a main substrate (or the main board) 60 connected to a motor 50 via a first wiring 51 and a thermistor substrate (or the thermistor board) 70 connected to the main substrate 60 via a second wiring 71. The motor driving device 2 incorporates, on the main substrate 60, the motor driver IC 61 for driving the motor 50 and the first thermistor 62 for detecting the temperature of the motor driver IC 61 as well as, on the thermistor substrate 70, the second thermistor 72 for detecting the temperature of the ambient environment where the motor 50 is being used. The motor driving device 2 may further incorporates the control unit 100 shown in
Further, the control unit 100 of the motor driving device 2 includes the motor control unit 1005 that stops the driving of the motor 50 in the case where the temperature detected by the first thermistor 62 reaches or exceeds the threshold, and the threshold setting unit 1006 that sets the threshold according to the output of the second thermistor 72. Therefore, the operable time of the motor 50 can be further extended even if the motor 50 is operated under various ambient environments with differing temperatures. This improves the operation performance of the motor 50 of the thermal printer 1.
These advantages achieved by the motor driving device 2 in connection with the motor 50, such as the sheet conveyance motor, can advance the overall performance of the thermal printer 1 according to the present embodiment. In other embodiments, the motor driving device 2 can be installed in other electronic apparatuses that include a motor or motors and achieve substantially the same advantages as those in the case of the thermal printer 1.
The control unit 100 of the motor driving device 2 installed in the thermal printer 1 includes a head control unit 1004 that controls the head drive circuit 65 of the thermal head 30 according to the output of the second thermistor 72, which is provided to set the threshold value for the first thermistor 62. This second thermistor 72 serves as both the temperature sensor for setting the threshold for the first thermistor 62 and the temperature sensor for controlling the driving of the thermal head 30. Therefore, the configuration of the thermal printer 1 can be simplified.
The threshold setting unit 1006 included in the control unit 100 sets the threshold for the first thermistor 62 before the printing operation, that is, before the driving of the thermal head 30 and the motor 50 starts. Therefore, in setting this threshold value, the second thermistor is less likely to be affected by heat generated by the thermal head 30 and the motor 50. Consequently, the ambient environment temperature can be detected more accurately by the second thermistor 72, and the control by the motor control unit 1005 can be performed more appropriately.
The control program executed by the thermal printer 1 may be recorded on a non-transitory computer-readable recording medium such as a CD-ROM. The program executed by the thermal printer 1 may be stored on a computer connected to a network, such as the Internet, and downloaded via the network, or may be accessed via the network, such as the Internet.
While certain embodiments have been described, these embodiments have been presented by way of example only and are not intended to limit the scope of the inventions. Indeed, the novel embodiments described herein may be embodied in a variety of other forms; furthermore, various omissions, substitutions and changes in the form of the embodiments described herein may be made without departing from the spirit of the inventions. The accompanying claims and their equivalents are intended to cover such forms or modifications as would fall within the scope and spirit of the inventions.
| Number | Date | Country | Kind |
|---|---|---|---|
| 2020-158961 | Sep 2020 | JP | national |
