JP5672082B2 - Motor control device, control device, motor drive device, image forming device, and voltage control program - Google Patents

Description

  The present invention relates to a motor control device, a control device, a motor drive device, an image forming apparatus, and a voltage control program.

  Conventionally, for the purpose of preventing damage due to overcurrent of a transistor or a motor driven by the transistor, the current flowing through the transistor is measured using a current detection resistor, and when the measured current exceeds a predetermined value, the input to the transistor A technique for preventing a large current from flowing through a transistor by turning off the signal for a certain time is known (see, for example, Patent Document 1).

  However, in the prior art as described above, only the drive current flowing through the transistor is considered, and the regenerative current flowing through the transistor is not considered when the excitation phase of the motor is switched. For this reason, in the conventional technology as described above, there is still a possibility that the transistor is damaged due to overcurrent due to the influence of the regenerative current flowing through the transistor.

  The present invention has been made in view of the above circumstances, and provides a motor control device, a control device, a motor drive device, an image forming apparatus, and a voltage control program that can prevent transistor damage due to overcurrent. Objective.

  In order to solve the above-described problems and achieve the object, a motor control device according to one aspect of the present invention is configured by switching a plurality of stators and a stator to be excited among the plurality of stators. A motor having a rotating rotor and a rotational position detecting means for detecting the rotational position of the rotor; a plurality of switching means for switching a stator to be excited by switching whether or not to pass current; and a power source The detection voltage output means for detecting the current flowing from the switching means to the switching means and outputting a detection voltage corresponding to the detected current, and the switching timing of the stator excited from the rotational position detected by the rotational position detection means The switching means for detecting the current is switched and the mode for reducing the current flowing to the switching means when the input detection voltage exceeds the limit voltage. Drive means, wherein the detection voltage output means can change the detection voltage, and the switching timing of the stator excited from the rotational position detected by the rotational position detection means And a control means for causing the detection voltage output means to increase the detection voltage for a certain period after detection.

  A motor control device according to another aspect of the present invention includes a plurality of stators, a rotor that rotates when a stator to be excited among the plurality of stators is switched, and rotation of the rotor. Rotation position detection means for detecting the position, a plurality of switching means for switching the stator to be excited by switching whether or not to flow current, and a current flowing from the power source to the switching means are detected. Detecting voltage output means for outputting a detection voltage corresponding to the detected current, and switching means for supplying current by detecting the switching timing of the stator to be excited from the rotational position detected by the rotational position detecting means. And a motor drive unit that reduces the current flowing through the switching unit when the input detection voltage exceeds a limit voltage. The detection voltage output means can change the detection voltage, and the motor driving means detects the switching timing of the stator excited from the rotational position detected by the rotational position detection means. A change period in which the detection voltage is increased from the switching timing is detected, and the detection voltage output unit is caused to increase the detection voltage during the change period.

  Further, a control device according to another aspect of the present invention includes a plurality of stators, a rotor that rotates when a stator to be excited among the plurality of stators is switched, and a rotational position of the rotor. Detecting a current flowing from the power source to the switching means, a plurality of switching means for switching the stator to be excited by switching whether or not to flow current, A detection voltage output unit that outputs a detection voltage corresponding to the detected current and a switching unit that detects the switching timing of the stator that is excited from the rotational position detected by the rotational position detection unit and switches the current are switched. And a motor drive means for reducing the current flowing through the switching means when the input detection voltage becomes equal to or higher than the limit voltage. Detecting the switching timing of the stator excited from the rotational position detected by the rotational position detecting means, and detecting the detection voltage output means capable of changing the detected voltage for a certain period after detection. The voltage is increased.

  A motor driving device according to another aspect of the present invention includes a plurality of stators, a rotor that rotates when a stator to be excited among the plurality of stators is switched, and rotation of the rotor. Rotation position detection means for detecting the position, a plurality of switching means for switching the stator to be excited by switching whether or not to flow current, and a current flowing from the power source to the switching means are detected. A detection voltage output means for outputting a detection voltage corresponding to the detected current, and a motor drive device of a motor control device, wherein the stator is excited from the rotational position detected by the rotational position detection means. The switching means that detects the switching timing and switches the current is switched, and when the detected voltage exceeds the limit voltage, the current that flows through the switching means is reduced. Detecting a switching timing of a stator excited from the rotational position detected by the control means and the rotational position detecting means, and detecting a change period for increasing the detection voltage from the switching timing, the change period, The detection voltage output means capable of changing the detection voltage includes a change period detection means for increasing the detection voltage.

  An image forming apparatus according to another aspect of the invention includes the motor control device, the control device, or the motor drive device.

  In addition, a voltage control program according to another aspect of the present invention includes a plurality of stators, a rotor that rotates when a stator to be excited among the plurality of stators is switched, and rotation of the rotor. Rotation position detection means for detecting the position, a plurality of switching means for switching the stator to be excited by switching whether or not to flow current, and a current flowing from the power source to the switching means are detected. Detecting voltage output means for outputting a detection voltage corresponding to the detected current, and switching means for supplying current by detecting the switching timing of the stator to be excited from the rotational position detected by the rotational position detecting means. And a motor drive means for reducing the current flowing through the switching means when the input detection voltage exceeds a limit voltage. A timing detection step of detecting a switching timing of a stator excited from the rotational position detected by the rotational position detecting means, and a detection voltage for a certain period after the detection of the switching timing. And a voltage control step for causing the changeable detection voltage output means to increase the detection voltage.

  According to the present invention, the transistor can be prevented from being damaged due to overcurrent.

FIG. 1 is a configuration diagram illustrating an example of a conventional motor control device. FIG. 2 is an explanatory diagram of an example of a drive current limiting method. FIG. 3 is a path diagram illustrating an example of a path of a current flowing through the transistor when the W-U phase is excited. FIG. 4 is a path diagram illustrating an example of a path of a current flowing through the transistor when the excitation phase is switched from the WU phase to the WV phase. FIG. 5 is a timing chart showing an example of the Hall signal and the current flowing through the transistor before and after the excitation phase is switched from the WU phase to the WV phase. FIG. 6 is a configuration diagram illustrating an example of the motor control device of the first embodiment. FIG. 7 is a timing chart illustrating an example of the Hall signal and the current flowing through the transistor before and after the excitation phase is switched from the WU phase to the WV phase in the first embodiment. FIG. 8 is a flowchart illustrating an example of a motor control operation of the motor control device according to the first embodiment. FIG. 9 is a configuration diagram illustrating an example of the motor control device of the second embodiment. FIG. 10 is a flowchart illustrating an example of a motor control operation of the motor control device according to the second embodiment. FIG. 11 is a configuration diagram illustrating an example of the motor control device of the third embodiment. FIG. 12 is a circuit diagram illustrating an example of a change period detection unit according to the third embodiment. FIG. 13 is a flowchart illustrating a motor control operation example of the motor control device of the third embodiment. FIG. 14 is a configuration diagram illustrating an example of an image forming apparatus according to the fourth embodiment.

  Hereinafter, embodiments of a motor control device, a control device, a motor drive device, an image forming apparatus, and a voltage control program according to the present invention will be described in detail with reference to the accompanying drawings. The motor control devices described in the following embodiments are applied to, for example, image forming apparatuses such as multifunction peripherals, copiers, printing apparatuses, scanner apparatuses, and facsimile apparatuses, but are not limited thereto. The multi-function device has at least two functions among a copying function, a printing function, a scanner function, and a facsimile function.

  In the motor control devices of the following embodiments, the current flowing through the transistor is set to be equal to or lower than the rated current in consideration of not only the drive current flowing through the transistor but also the regenerative current.

  First, an example of a conventional motor control device will be described as a comparative example before the motor control devices of the following embodiments are described.

  FIG. 1 is a configuration diagram illustrating an example of a conventional motor control device 1. As shown in FIG. 1, the motor control device 1 includes a brushless DC motor 10, transistors 20 a to 20 f, a drive current detection resistor 30, a main control device 40, and a pre-driver 50.

  The brushless DC motor 10 is a so-called non-commutator motor, and includes stator windings 11a to 11c, a rotor 12, and Hall elements 13a to 13c. The stator windings 11a to 11c are each composed of a U-phase to a W-phase, and a phase in which a drive current flows by a transistor 20a to 20f described later, that is, an excitation phase (excited among the stator windings 11a to 11c). The rotor 12 that is a magnet is rotated by switching the stator winding. The hall elements 13a to 13c detect the rotation position (rotation angle) of the rotor 12. Specifically, the Hall elements 13a to 13c use the Hall effect to output Hall signals HALL_U to HALL_W that indicate whether or not a predetermined position of the rotor 12 is detected to the pre-driver 50 described later. .

  The emitter terminals of the transistors 20a to 20c are connected to the collector terminals of the transistors 20d to 20f, respectively. The connection part of the transistor 20a and the transistor 20d is connected to the stator winding 11a (U phase), and the connection part of the transistor 20b and the transistor 20e is connected to the stator winding 11b (V phase). The connection portion 20f is connected to the stator winding 11c (W phase). Each of the transistors 20a to 20f is switched on / off by a pre-driver 50 described later, thereby switching whether or not the drive current from the power source 5 is supplied. Thereby, the transistors 20a to 20f switch the phase of the brushless DC motor 10 through which the drive current flows, that is, the excitation phase of the brushless DC motor 10 (the stator winding to be excited among the stator windings 11a to 11c). Thus, the transistors 20a to 20f function as an inverter circuit.

  The drive current detection resistor 30 is connected to the emitter terminals of the transistors 20d to 20f, detects a drive current flowing from at least one of the transistors 20a to 20f from the power supply 5, and detects a detection voltage corresponding to the detected drive current later. Is output to the pre-driver 50.

  The main controller 40 outputs an input PWM (Pulse Width Modulation) signal to a pre-driver 50 described later. For example, a CPU (Central Processing Unit), a ROM (Read Only Memory), and a RAM (Random Access Memory) It is a computer with etc.

  The pre-driver 50 includes a comparator 51 and an output unit 52. The pre-driver 50 has W +, V +, U +, W−, V−, and U− terminals connected to the transistors 20c, 20b, 20a, 20f, 20e, and 20d, respectively.

A detection voltage corresponding to the drive current detected by the drive current detection resistor 30 is applied to the V _sense terminal of the comparator 51, and a limit voltage corresponding to the current limit value of the drive current is applied to the V _clamp terminal of the comparator 51. . Here, the current limit value is an upper limit value of the rated current. The comparator 51 _compares the limit voltage according to the detected voltage and the _{V clamp} terminal according to _{V sense terminal,} if the limit voltage above the detection voltage is applied to the _{V sense} terminal, and outputs a drive current limit signal to the output unit 52 .

  The output unit 52 detects the switching timing of the excitation phase of the brushless DC motor 10 from the Hall signals input from the Hall elements 13a to 13c, and the W +, V +, U +, W−, V−, and U of the pre-driver 50 are detected. It is determined from which terminal of the terminal the output PWM signal corresponding to the input PWM signal input from the main controller 40 is output, and the output PWM signal is output from the determined terminal. As a result, the output unit 52 switches the excitation phase of the brushless DC motor 10 by switching on / off the transistors 20a to 20f and switching the transistors 20a to 20f through which the drive current from the power source 5 flows. 12 is rotated (the brushless DC motor 10 is driven).

  Further, when the drive current limit signal is input from the comparator 51, the output unit 52 limits the drive current flowing from the power source to the transistors 20a to 20f. FIG. 2 is an explanatory diagram of an example of a drive current limiting method. In the example shown in FIG. 2, when the drive current limit signal is input from the comparator 51, that is, when the drive current detected by the drive current detection resistor 30 exceeds the current limit value, the output unit 52 outputs the input PWM signal. The output of the corresponding output PWM signal is stopped, and the DUTY of the output PWM signal is made smaller than the input PWM signal. As a result, the output unit 52 reduces the drive current flowing through the transistors 20a to 20f to make the drive current equal to or lower than the rated current. The output unit 52 is configured such that when the DUTY of the input PWM signal becomes large and the drive current becomes equal to or greater than the current limit value, for example, when the rotation of the rotor 12 is started (when driving of the brushless DC motor 10 is started). Limit drive current.

  As described above, in the conventional motor control device 1, the drive current flowing through the transistors 20a to 20f is suppressed to the current limit value or less, so that the drive current is set to the rated current or less. However, the current flowing through the transistors 20a to 20f includes not only the drive current but also a regenerative current that is generated when the excitation phase is switched. For this reason, in the conventional motor control device 1, even if the drive current flowing through the transistors 20a to 20f is kept below the current limit value, the total current (drive current + regenerative current) flowing through the transistors 20a to 20f due to the effect of the regenerative current. Exceeds the rated current, and the transistors 20a to 20f may be damaged due to overcurrent. Hereinafter, the influence of the regenerative current will be specifically described.

  FIG. 3 is a path diagram illustrating an example of a path of a current flowing through the transistors 20a to 20f when the W-U phase is excited. FIG. 4 illustrates the excitation phase from the W-U phase to the W-V phase. It is a route diagram showing an example of a route of current which flows into transistors 20a-20f when it switches. In the example shown in FIGS. 3 and 4, for the brushless DC motor 10, only the stator windings 11 a to 11 c and the hall elements 13 a to 13 c are shown.

  As shown in FIG. 3, when the excitation phase is the WU phase (when the transistors 20c and 20d are turned on), the drive current (WU) 71 is supplied from the power source 5, the transistor 20c, and the stator winding 11c. (W phase), the stator winding 11a (U phase), and the transistor 20d. As shown in FIG. 4, when the transistor 20d is turned off, the transistor 20e is turned on, and the excitation phase is switched from the WU phase to the WV phase (when the transistors 20c and 20e are turned on). The drive current (W-V) 72 flows through the path of the power source 5, the transistor 20c, the stator winding 11c (W phase), the stator winding 11b (V phase), and the transistor 20e. In addition, as shown in FIG. 4, when the excitation phase is switched from the WU phase to the WV phase, the current stored in the stator windings 11a and 11c due to the excitation of the WU phase. However, the regenerative current 73 circulates through the path of the stator winding 11c (W phase), the stator winding 11a (U phase), the transistor 20a, and the transistor 20c. As shown in FIG. 4, the regenerative current 73 does not flow through any of the transistors 20 d to 20 f, and thus the drive current detection resistor 30 cannot detect the regenerative current 73.

  FIG. 5 is a timing chart showing an example of the Hall signal and the current flowing through the transistor 20c before and after the excitation phase is switched from the WU phase to the WV phase. In the example shown in FIG. 5, the broken line 81 indicates the switching timing of the excitation phase from the WU phase to the WV phase. Specifically, the excitation phase is switched from the WU phase to the WV phase by the pre-driver 50 at the timing when the hall signals HALL_U to HALL_W are switched from Low, High, and High to Low, Low, and High, respectively. Further, the period from the broken line 81 to the broken line 82 indicates the period during which the regenerative current flows through the transistor 20c.

  As shown in FIG. 5, when the excitation phase is switched from the WU phase to the WV phase, the drive current (WU) flowing through the transistor 20c becomes 0 and the drive current (WV) flowing through the transistor 20c. Gradually increases and a regenerative current flowing through the transistor 20c is generated and gradually decreases. As a result, while the regenerative current flows through the transistor 20c, the total current (drive current (W−U) + drive current (W−V) + regenerative current) flowing through the transistor 20c exceeds the current limit value. The total current flowing through the transistor 20c exceeds the rated current, and the transistor 20c may be damaged due to overcurrent.

  As described above, in the conventional motor control device 1, even if the drive current flowing through the transistors 20a to 20f is suppressed to the current limit value or less, any of the transistors 20a to 20f is affected by the regenerative current when the excitation phase is switched. There is a possibility that the total current (driving current + regenerative current) that flows will exceed the rated current, and the transistor may be damaged by overcurrent.

  For this reason, the motor control devices of the following embodiments virtually increase the drive current flowing through the transistors by increasing the detection voltage when switching the excitation phase of the motor. That is, even if the drive current flowing through the transistor does not actually reach the current limit value, the drive current flowing through the transistor is reduced by making the pre-driver sense that the drive current has reached the current limit value. As a result, when the excitation phase of the motor is switched, the total current flowing through the transistor (drive current + regenerative current) can be reduced below the rated current even if the regenerative current flows in the transistor, and the transistor current due to overcurrent can be reduced. Breakage can be prevented.

(First embodiment)
In the first embodiment, an example will be described in which the main control device and the drive current detection device increase the detection voltage when switching the excitation phase of the motor.

  FIG. 6 is a configuration diagram illustrating an example of the motor control device 101 according to the first embodiment. As shown in FIG. 6, the motor control device 101 is different from the conventional motor control device 1 in that the configuration of the main control device 140 and the drive current detection device 130 are further provided. In the following description, differences from the conventional motor control device 1 will be mainly described, and components having the same functions as those of the conventional motor control device 1 are denoted by the same names and symbols as those of the conventional motor control device 1. A description thereof will be omitted. In other words, the brushless DC motor 10 (an example of a motor), the transistors 20a to 20f (an example of a plurality of switching units), and the pre-driver 50 (an example of a motor driving unit) included in the motor control device 101 are conventional motor control devices. 1 has the same function as that of FIG. In FIG. 6, only the stator windings 11 a to 11 c (an example of a plurality of stators) and the hall elements 13 a to 13 c (an example of rotational position detection means) are shown for the brushless DC motor 10.

The main control device 140 (an example of the control means and the control device) detects the excitation phase switching timing from the rotational position of the rotor 12 detected by the Hall elements 13a to 13c, and changes the detection voltage for a certain period after detection. The detection voltage applied to the V _sense terminal of the comparator 51 of the pre-driver 50 is increased in the possible drive current detection device 130 (an example of detection voltage output means).

Main controller 140 includes a timing detection unit 141 and an instruction signal output unit 142. Further, main controller 140 has a V _{mode enable} terminal that outputs an instruction signal.

  The timing detector 141 detects the excitation phase switching timing from the rotational position of the rotor 12 detected by the Hall elements 13a to 13c. Specifically, hall signals HALL_U to HALL_W (an example of a position detection signal) are input to the timing detection unit 141 from the hall elements 13a to 13c, respectively. The timing detection unit 141 switches from the predetermined position detection state in which the predetermined position of the rotor 12 is detected to the predetermined position non-detection state in which the predetermined position is not detected using the input hall signals HALL_U to HALL_W. In other words, a change from a predetermined position non-detection state to a predetermined position detection state is detected. For example, the timing detection unit 141 determines whether the Hall element 13b has not detected the predetermined position of the rotor 12 from the predetermined position detection state (HALL_V is High) in which the Hall element 13b has detected the predetermined position of the rotor 12. The switching to the position non-detection state (HALL_V is Low) is detected.

The instruction signal output unit 142 switches from the predetermined position detection state to the predetermined position non-detection state or from the predetermined position non-detection state to the predetermined position detection state when the timing detection unit 141 detects the switching timing. An instruction signal for instructing to increase the detection voltage when a change is detected, specifically, an instruction signal for instructing to change the resistance value to a second resistance value larger than the first resistance value, It outputs to the drive current detection apparatus 130 for a fixed period. The instruction signal output unit 142 sets the resistance value to the first resistance value by setting the V _{mode enable} terminal to High in the drive current detection device 130 in normal times (when the excitation phase is not switched). Instruct. When it is the excitation phase switching timing, the instruction signal output unit 142 changes the resistance value from the first resistance value to the second resistance value by changing the V _{mode enable} terminal from High to Low for a certain period. The drive current detection device 130 is instructed to change and increase the detection voltage. In this embodiment, since the period during which the regenerative current is generated is about 0.5 msec, the fixed period is set to 0.5 msec. However, the present invention is not limited to this, and the resistance value is changed from the first resistance value. Any period may be used as long as the total current (drive current + regenerative current) flowing through the transistors 20a to 20f can be made equal to or less than the current limit value by changing to the second resistance value and increasing the detection voltage.

When the instruction signal is not input from the instruction signal output unit 142, the drive current detection device 130 sets the resistance value as the first resistance value, and sets the resistance value while the instruction signal is input from the instruction signal output unit 142. By setting the resistance value to 2, the detection voltage applied to the V _sense terminal of the comparator 51 is increased while the instruction signal is being input. The drive current detection device 130 is realized by a voltage dividing circuit in the present embodiment, and includes a drive current detection resistor 30, resistors 131 to 133, and a transistor 134.

Specifically, when the V _{mode enable} terminal is set to High by the instruction signal output unit 142 and the transistor 134 is turned on, the driving current detection device 130 causes the driving current to flow through the transistor 134 and the resistance value is set. The first resistance value is used. Note that the first resistance value is expressed by Equation (1).

  R = R1 × Rs / (R1 + Rs) (1)

  Here, R is a resistance value (first resistance value) of the drive current detection device 130, Rs is a resistance value of the drive current detection resistor 30, and R1 is a resistance value of the resistor 131. Note that the potential difference between the collector and emitter of the transistor 134 is zero.

In addition, the drive current detection device 130 sets the resistance value to the second resistance without flowing the drive current to the transistor 134 by setting the V _{mode enable} terminal to Low by the instruction signal output unit 142 and switching the transistor 134 to OFF. Value. Note that the second resistance value is expressed by Equation (2).

  R = Rs (2)

Here, R is the resistance value (second resistance value) of the drive current detection device 130. Further, Equation (1) and (2), since the direction of the second resistance value (R in Equation (2)) is always Rs ² greater than the first resistance value (R in Equation (1)), the driving It can be seen that the detection voltage applied to the V _sense terminal of the comparator 51 increases by changing the resistance value of the current detection device 130 from the first resistance value to the second resistance value.

  FIG. 7 is a timing chart illustrating an example of the Hall signal and the current flowing through the transistor 20c before and after the excitation phase is switched from the WU phase to the WV phase in the first embodiment. In the example shown in FIG. 7, the period from the broken line 81 to the broken line 82, that is, the period during which the regenerative current flows through the transistor 20 c indicates a certain period during which the detection voltage is increased.

As shown in FIG. 7, when the excitation phase is switched from the W-U phase to the W-V phase, the resistance value of the drive current detection device 130 increases for a certain period, and the detection voltage applied to the V _sense terminal becomes the limit voltage for a certain period. Higher than. For this reason, the drive current (W-V) flowing through the transistor 20c is reduced, and the drive current (W-V) flowing through the transistor 20c is gradually increased as compared with the conventional motor control device 1. As a result, even if the regenerative current is flowing through the transistor 20c, the total current (drive current (W−U) + drive current (W−V) + regenerative current) flowing through the transistor 20c is less than the current limit value. That is, the current is less than the rated current, and the transistor 20c can be prevented from being damaged due to overcurrent.

  FIG. 8 is a flowchart illustrating an example of a procedure flow of a motor control operation of the motor control device 101 according to the first embodiment.

First, the instruction signal output unit 142 sets the V _{mode enable} terminal of the main control device 140 to High (step S100). As a result, the drive current detection device 130 causes the drive current to flow through the transistor 134 and sets the resistance value to the first resistance value.

  Subsequently, main controller 140 outputs an input PWM signal to pre-driver 50 to start driving brushless DC motor 10 (step S102).

Subsequently, when the timing detection unit 141 detects the excitation phase switching timing from the rotational position of the rotor 12 detected by the Hall elements 13a to 13c (YES in Step S104), the instruction signal output unit 142 The V _{mode enable} terminal of main controller 140 is set to Low (step S106). Thereby, the drive current detection device 130 does not pass the drive current through the transistor 134 and sets the resistance value to the second resistance value. As a result, the detection voltage applied to the V _sense terminal increases.

The instruction signal output unit 142 waits for a certain period to elapse (NO in step S108), and when the certain period elapses (YES in step S108), sets the V _{mode enable} terminal of the main controller 140 to High again (step S108). Step S110). As a result, the drive current detection device 130 causes the drive current to flow through the transistor 134 and sets the resistance value to the first resistance value again.

  If the timing detection unit 141 does not detect the excitation phase switching timing (NO in step S104), the processes in steps S106 to S110 are not performed.

  Then, while the brushless DC motor 10 is being driven by the main controller 140 (NO in step S112), that is, while the input PWM signal is being output to the pre-driver 50, the processes in steps S104 to S110 are repeated. When the main controller 140 stops the driving of the brushless DC motor 10 (YES in step S112), that is, when the output of the input PWM signal to the pre-driver 50 is finished, the processing is finished.

  As described above, in the motor control device of the first embodiment, the drive current flowing through the transistor is virtually increased by increasing the detection voltage when switching the excitation phase of the brushless DC motor. That is, even if the drive current flowing through the transistor does not actually reach the current limit value, the drive current flowing through the transistor is reduced by making the pre-driver sense that the drive current has reached the current limit value. Therefore, according to the motor control device of the first embodiment, when switching the excitation phase of the brushless DC motor, not only the drive current but also the regenerative current flows through the transistor, the total current (drive current + regenerative current) that flows through the transistor is the rated current. The transistor can be prevented from being damaged due to overcurrent.

(Second Embodiment)
In the second embodiment, an example in which the detection voltage is increased when the rotation speed of the rotor is equal to or lower than a predetermined speed when switching the excitation phase of the motor will be described.

  FIG. 9 is a configuration diagram illustrating an example of the motor control device 201 according to the second embodiment. As shown in FIG. 9, the motor control device 201 is different from the motor control device 101 of the first embodiment in that the configuration of the main control device 240 and an encoder 260 are further provided. In the following, differences from the motor control device 101 of the first embodiment will be mainly described, and components having functions similar to those of the motor control device 101 of the first embodiment will be described. The same names and symbols as those of the apparatus 101 are given, and the description thereof is omitted.

  The encoder 260 detects the rotational speed of the rotor 12 (not shown) of the brushless DC motor 10 and outputs it to the main controller 240.

  The main controller 240 includes a timing detection unit 141, an instruction signal output unit 242, and a rotation speed detection unit 243.

  The rotation speed detection unit 243 detects the rotation speed of the rotor 12 using the rotation speed of the rotor 12 input from the encoder 260.

  The instruction signal output unit 242 instructs to increase the detection voltage when the switching timing is detected by the timing detection unit 141 and the rotation speed of the rotor 12 detected by the rotation speed detection unit 243 is equal to or lower than a predetermined speed. The instruction signal is output to the drive current detector 130 for a certain period.

  The main controller 240 outputs the input PWM signal to the pre-driver 50 with DUTY corresponding to the rotational speed of the rotor 12 detected by the rotational speed detector 243. Here, it is assumed that the DUTY of the input PWM signal decreases as the rotational speed of the rotor 12 increases.

  FIG. 10 is a flowchart illustrating an example of a procedure flow of a motor control operation of the motor control device 201 according to the second embodiment.

  First, the processes in steps S200 to S204 are the same as the processes in steps S100 to S104 in FIG.

Subsequent to step S204, when the rotation speed of the rotor 12 detected by the rotation speed detection unit 243 is equal to or lower than the predetermined speed (YES in step S205), the instruction signal output unit 242 has a V _{mode enable} terminal of the main controller 240. Is set to Low (step S206).

  The subsequent processes in steps S208 and S210 are the same as the processes in steps S108 and S110 in FIG.

  If the rotational speed of the rotor 12 exceeds the predetermined speed (NO in step S205), the processes in steps S206 to S210 are not performed. If the timing detection unit 141 does not detect the excitation phase switching timing (NO in step S204), the processing in steps S205 to S210 is not performed.

  Then, while the brushless DC motor 10 is being driven by the main controller 240 (NO in step S212), that is, while the input PWM signal is being output to the pre-driver 50, the processes in steps S204 to S210 are repeated. When the main controller 240 stops driving the brushless DC motor 10 (YES in step S212), that is, when the output of the input PWM signal to the pre-driver 50 is terminated, the processing is terminated.

  As described above, in the motor control device of the second embodiment, when the excitation phase of the brushless DC motor is switched, only when the rotation speed of the rotor is equal to or lower than the predetermined speed, the detection voltage is increased to flow into the transistor. When the drive current is virtually increased and the rotation speed of the rotor exceeds a predetermined speed, the detection voltage is not increased and the drive current flowing through the transistor is not virtually increased.

  This is because when the rotation speed of the rotor exceeds a predetermined speed and the rotation speed of the rotor is sufficiently high, the DUTY of the input PWM signal becomes smaller than that at the start of rotation of the rotor, and the drive current flowing through the transistor is reduced. This is because the current limit value is sufficiently small, so that there is no risk of damage to the transistor even if a regenerative current flows through the transistor when switching the excitation phase.

  Therefore, according to the motor control device of the second embodiment, when the rotation speed of the rotor is equal to or lower than the predetermined speed, it is possible to prevent the transistor from being damaged due to an overcurrent. If it is, the acceleration and rotation unevenness of the rotor can be improved, and the brushless DC motor can be driven with high accuracy.

  In particular, also in the motor control device of the second embodiment, a certain period in which the detection voltage is increased when switching the excitation phase of the brushless DC motor is matched with the period (0.5 msec) in which the regenerative current is generated. As a result, the fixed period during which the detection voltage is increased can be minimized, so that it is possible to prevent the transistor from being damaged due to overcurrent while minimizing the decrease in the acceleration of the rotor and the deterioration of the rotation unevenness.

(Third embodiment)
In the third embodiment, an example will be described in which the pre-driver and the drive current detection device increase the detection voltage when switching the excitation phase of the motor.

  FIG. 11 is a configuration diagram illustrating an example of a motor control device 301 according to the third embodiment. As shown in FIG. 11, the motor control device 301 is different from the conventional motor control device 1 in that the configuration of the pre-driver 350 and the drive current detection device 330 are further provided. In the following description, differences from the conventional motor control device 1 will be mainly described, and components having the same functions as those of the conventional motor control device 1 are denoted by the same names and symbols as those of the conventional motor control device 1. A description thereof will be omitted. In other words, the brushless DC motor 10 (an example of a motor), the transistors 20a to 20f (an example of a plurality of switching units), and the main controller 40 (an example of a control device) included in the motor control device 301 are conventional motor control devices. 1 has the same function as that of FIG. In FIG. 11, only the stator windings 11 a to 11 c (an example of a plurality of stators) and the hall elements 13 a to 13 c (an example of rotational position detection means) are shown for the brushless DC motor 10.

  The pre-driver 350 (an example of a motor driving unit and a motor driving device) includes a comparator 51, an output unit 52 (an example of a current control unit), and a change period detection unit 353. Note that the comparator 51 and the output unit 52 have the same functions as those of the conventional motor control device 1, and thus the description thereof is omitted.

The change period detection unit 353 detects the excitation phase switching timing from the rotational position of the rotor 12 detected by the Hall elements 13a to 13c, and detects the change period for increasing the detection voltage from the detected switching timing, In the detected change period, the detection voltage applied to the V _sense terminal of the comparator 51 of the pre-driver 350 is increased in the drive current detection device 330 (an example of detection voltage output means) that can change the detection voltage. Here, the change period is a fixed period in which the resistance value of the drive current detection device 330 is changed to a second resistance value larger than the first resistance value. That is, the change period detection unit 353 switches from the excitation phase switching timing, that is, the predetermined position detection state in which the predetermined position of the rotor 12 is detected to the predetermined position non-detection state in which the predetermined position is not detected, Alternatively, a predetermined period from the switching timing from the predetermined position non-detection state to the predetermined position detection state is detected as the change period. Specifically, hall signals HALL_U to HALL_W (an example of a position detection signal) are input to the change period detection unit 353 from the hall elements 13a to 13c, respectively. Then, the change period detection unit 353 branches each of the input hall signals HALL_U to HALL_W into two signals, inverts one of the branched signals so as to delay the change period, and performs a logical product with the other signal. Thus, the change period is detected, and a change period detection signal indicating that the change period is detected is output to the drive current detection device 330.

  FIG. 12 is a circuit diagram illustrating an example of the change period detection unit 353 according to the third embodiment. As illustrated in FIG. 12, the change period detection unit 353 includes a change period detection circuit including a resistor 354, a capacitor 355, and an AND circuit 356. It is assumed that the change period detection unit 353 has a change period detection circuit for each input hall signal.

  The hall signal input to the change period detection circuit is branched into two signals. Then, the resistor 354 and the capacitor 355 delay one of the branched signals so as to delay the change period. If the value of R × C is increased, the change period (delay) can be lengthened, and if the value of R × C is decreased, the change period (delay) can be shortened. Here, R is the resistance value of the resistor 354, and C is the capacitance of the capacitor 355. The AND circuit 356 receives an inverted signal and inputs the other branched signal, and obtains a logical product of the two input signals. The AND circuit 356 outputs a change period detection signal to the drive current detection device 330 when the obtained logical product is true.

The drive current detection device 330 increases the detection voltage during the change period detected by the change period detection unit 353. Specifically, when the change period detection signal is not input from the change period detection unit 353, the drive current detection device 330 sets the resistance value as the first resistance value and the change period detection signal is input from the change period detection unit 353. During this time, by setting the resistance value to the second resistance value, the detection voltage applied to the V _sense terminal of the comparator 51 is increased while the change period detection signal is input. As in the first embodiment, the drive current detection device 330 is realized by a voltage dividing circuit, and includes a drive current detection resistor 30, resistors 131 to 133, and a transistor 134.

  Specifically, when the change period detection signal is not input from the change period detection unit 353 and the transistor 134 is switched on, the drive current detection device 330 passes the drive current to the transistor 134 and sets the resistance value. 1 resistance value. Note that the first resistance value is expressed by the mathematical formula (1), as in the first embodiment.

  In addition, when the change period detection signal is input from the change period detection unit 353 and the transistor 134 is switched off, the drive current detection device 330 does not pass the drive current to the transistor 134 and the resistance value is set to the second resistance value. To do. Note that the second resistance value is expressed by Expression (2) as in the first embodiment.

  In the third embodiment, the timing chart of the Hall signal and the current flowing through the transistor 20c before and after the excitation phase is switched from the W-U phase to the W-V phase is the same as FIG. 7 of the first embodiment. Therefore, the description is omitted.

  FIG. 13 is a flowchart illustrating an example of a procedure flow of a motor control operation of the motor control device 301 according to the third embodiment.

  First, main controller 40 outputs an input PWM signal to pre-driver 350 to start driving brushless DC motor 10 (step S300). Note that before the start of driving the brushless DC motor 10, the change period detection unit 353 does not detect the change period and does not output a change period detection signal to the drive current detection device 330. For this reason, the drive current detection device 330 sets the resistance value to the first resistance value.

  Subsequently, when the change period detection unit 353 detects the change period from the rotational position of the rotor 12 detected by the Hall elements 13a to 13c (YES in Step S302), the change period detection signal to the drive current detection device 330 is detected. Output is started (step S304). Thereby, the drive current detection device 330 does not pass the drive current through the transistor 134 and sets the resistance value to the second resistance value.

  Then, the drive current detection device 330 waits for the end of the output of the change period detection signal (NO in step S306). When the output of the change period detection signal ends (YES in step S306), the drive current is supplied to the transistor 134 and the resistance The value is the first resistance value.

  When the change period is not detected by the change period detection unit 353 (NO in step S302), the processes in steps S304 to S306 are not performed.

  Then, while the brushless DC motor 10 is being driven by the main controller 40 (NO in step S308), that is, while the input PWM signal is being output to the pre-driver 350, the processes in steps S302 to S306 are repeated. When the main controller 40 stops driving the brushless DC motor 10 (YES in step S308), that is, when the output of the input PWM signal to the pre-driver 350 is completed, the processing is terminated.

  As described above, also in the motor control device of the third embodiment, the drive current flowing through the transistor is virtually increased by increasing the detection voltage when switching the excitation phase of the brushless DC motor. That is, even if the drive current flowing through the transistor does not actually reach the current limit value, the drive current flowing through the transistor is reduced by making the pre-driver sense that the drive current has reached the current limit value. Therefore, also in the motor control device of the third embodiment, when switching the excitation phase of the brushless DC motor, not only the drive current but also the regenerative current flows through the transistor, the total current (drive current + regenerative current) that flows through the transistor is less than the rated current. And damage to the transistor due to overcurrent can be prevented.

(Fourth embodiment)
In the fourth embodiment, an image forming apparatus to which the motor control device described in the first to third embodiments is applied will be described.

  FIG. 14 is a configuration diagram illustrating an example of an image forming apparatus 501 according to the fourth embodiment. As illustrated in FIG. 14, the image forming apparatus 501 includes a scanner unit 510, a paper feed unit 520, an image forming unit 530, and a paper discharge unit 540.

  The scanner unit 510 reads image data from a document or the like.

  The paper feed unit 520 includes a paper feed tray 521 in which a plurality of transfer papers are stacked and stored, a paper feed roller 522 that feeds the transfer paper P positioned at the top of the paper feed tray 521, and a paper feed roller 522. A transfer roller 523 that transports the transfer paper P fed by the above to the image forming unit 530.

  The image forming unit 530 includes an intermediate transfer belt 531, an intermediate transfer roller 532 that moves the intermediate transfer belt 531 endlessly, and an image forming process (charging process, exposure process, development process, transfer process, cleaning process, and charge removal process). As a result, a toner image is formed based on the image data read by the scanner unit 510, and the formed toner image is transferred to the intermediate transfer belt 531. The photosensitive drum units 533K, 533M, 533C, and 533Y are transported from the transport roller 523. Registration roller 534 for feeding the transferred transfer paper P to the intermediate transfer belt 531, a secondary transfer roller 535 and a repulsive roller 536 for transferring the toner image transferred to the intermediate transfer belt 531 to the transfer paper P, and transfer to the transfer paper P A fixing unit 537 for fixing the processed image.

  The transfer sheet P on which the image is fixed is discharged to the paper discharge unit 540.

  The motor control device described in the first to fourth embodiments includes a paper feed roller 522, a transport roller 523, an intermediate transfer roller 532, a photosensitive unit 533K, 533M, 533C, 533Y roller, a registration roller 534, It is used as a drive source for driving the secondary transfer roller 535, the roller of the fixing unit 537, the roller of the paper discharge unit 540, and the like.

  The voltage control program executed by the main control device of the motor control device described in the first to second embodiments is provided by being incorporated in advance in a ROM or the like.

  The voltage control program executed by the main control device of the motor control device described in the first embodiment to the second embodiment is a file in an installable format or executable format, such as a CD-ROM, a flexible disk (FD), You may comprise so that it may record and provide on computer-readable storage media, such as CD-R and DVD.

  Furthermore, the voltage control program executed by the main controller of the motor controller described in the first embodiment to the second embodiment is stored on a computer connected to a network such as the Internet and downloaded via the network. You may comprise so that it may provide. The voltage control program executed by the main controller of the motor controller described in the first to second embodiments may be provided or distributed via a network such as the Internet.

  The voltage control program executed by the main control device of the motor control device described in the first embodiment to the second embodiment has a module configuration for realizing each part of the above-described main control device on a computer. As actual hardware, the CPU reads out the voltage control program from the ROM into the RAM and executes it, so that the above-described units are realized on the computer.

(Modification)
In addition, this invention is not limited to said each embodiment, A various deformation | transformation is possible. For example, in each of the above embodiments, a bipolar transistor has been described as an example, but the transistor has been described. However, the transistor is not limited thereto, and may be a field effect transistor (FET) or the like.

1, 101, 201, 301 Motor controller 10 Brushless DC motor 11a-11c Stator winding 12 Rotor 13a-13c Hall element 20a-20f Transistor 30 Drive current detection resistor 40, 140, 240 Main controller 50, 350 pre Driver 51 Comparator 52 Output unit 130, 330 Drive current detection device 131-133 Resistance 134 Transistor 141 Timing detection unit 142, 242 Instruction signal output unit 243 Rotational speed detection unit 260 Encoder 353 Change period detection unit 354 Resistance 355 Capacitor 356 AND circuit 501 Image forming apparatus 510 Scanner unit 520 Paper feed unit 521 Paper feed tray 522 Paper feed roller 523 Transport roller 530 Image forming unit 531 Intermediate transfer belt 532 Intermediate transfer roller Roller 533K, 533M, 533C, 533Y Photosensitive unit 534 Registration roller 535 Secondary transfer roller 536 Repulsive roller 537 Fixing unit 540 Paper discharge unit

JP-A-7-31826

Claims (14)

A motor having a plurality of stators, a rotor that rotates when a stator to be excited among the plurality of stators is switched, and a rotational position detecting unit that detects a rotational position of the rotor;
A plurality of switching means for switching the stator to be excited by switching whether or not to flow current;
Detection voltage output means for detecting a current flowing from the power source to the switching means and outputting a detection voltage corresponding to the detected current;
The switching means for supplying current by detecting the switching timing of the stator to be excited from the rotational position detected by the rotational position detection means is switched, and the switching is performed when the input detection voltage becomes a limit voltage or more. A motor control device comprising: motor driving means for reducing the current flowing through the means;
The detection voltage output means can change the detection voltage,
It further comprises control means for detecting the switching timing of the stator excited from the rotational position detected by the rotational position detecting means and causing the detection voltage output means to increase the detection voltage for a certain period after detection. A motor control device. The control means includes
Timing detection means for detecting the switching timing of the stator excited from the rotational position detected by the rotational position detection means;
An instruction signal output means for outputting an instruction signal for instructing to change the resistance value to a second resistance value larger than the first resistance value when the switching timing is detected;
2. The motor control device according to claim 1, wherein the detection voltage output unit changes the resistance value from the first resistance value to the second resistance value while the instruction signal is input.   The detection voltage output means is a voltage dividing circuit having a plurality of resistors and transistors, and the resistance value is changed from the first resistance value by not flowing a current to the transistor while the instruction signal is input. The motor control device according to claim 2, wherein the motor control device is changed to a second resistance value. A rotation speed detecting means for detecting the rotation speed of the rotor;
The instruction signal output means outputs the instruction signal for the predetermined period when the switching timing is detected and the rotation speed detected by the rotation speed detection means is a predetermined speed or less. Item 4. The motor control device according to Item 2 or 3. The rotational position detecting means outputs a position detection signal indicating whether or not a predetermined position of the rotor is detected;
The timing detection means switches from a predetermined position detection state in which the predetermined position of the rotor is detected to a predetermined position non-detection state in which the predetermined position is not detected by using the input position detection signal. Detecting a change from the predetermined position non-detection state to the predetermined position detection state,
The instruction signal output means is configured to detect the instruction when switching from the predetermined position detection state to the predetermined position non-detection state or switching from the predetermined position non-detection state to the predetermined position detection state is detected. 5. The motor control device according to claim 2, wherein a signal is output for the predetermined period. A motor having a plurality of stators, a rotor that rotates when a stator to be excited among the plurality of stators is switched, and a rotational position detecting unit that detects a rotational position of the rotor;
A plurality of switching means for switching the stator to be excited by switching whether or not to flow current;
Detection voltage output means for detecting a current flowing from the power source to the switching means and outputting a detection voltage corresponding to the detected current;
The switching means for supplying current by detecting the switching timing of the stator to be excited from the rotational position detected by the rotational position detection means is switched, and the switching is performed when the input detection voltage becomes a limit voltage or more. A motor control device comprising: motor driving means for reducing the current flowing through the means;
The detection voltage output means can change the detection voltage,
The motor driving means detects a switching timing of a stator excited from the rotational position detected by the rotational position detecting means, detects a change period in which the detection voltage is increased from the switching timing, and the change A motor control device characterized by causing the detection voltage output means to increase the detection voltage during a period. The motor driving means is
The switching means for supplying a current is detected by detecting the switching timing of the stator to be excited from the rotational position detected by the rotational position detecting means, and flows to the switching means when the detected voltage exceeds a limit voltage. Current control means for reducing the current;
A change period for detecting a switching timing of the stator excited from the rotational position detected by the rotational position detecting means and changing the resistance value from the switching timing to a second resistance value larger than the first resistance value. The change period detecting means for detecting and changing the resistance value from the first resistance value to the second resistance value in the detection voltage output means during the change period. Motor control device. The rotational position detecting means outputs a position detection signal indicating whether or not a predetermined position of the rotor is detected;
The change period detection means branches the input position detection signal into two signals, and inverts and inverts one of the branched signals so as to delay the change period, and obtains a logical product with the other signal. The motor control device according to claim 7, wherein the change period is detected. The change period detection means outputs a change period detection signal indicating that the change period is detected,
The said detection voltage output means changes the said resistance value from the said 1st resistance value to the said 2nd resistance value, while the said change period detection signal is input. Motor control device.   The detection voltage output means is a voltage dividing circuit having a plurality of resistors and transistors, and the resistance value is set to the first resistance value by not passing a current through the transistor while the change period detection signal is input. The motor control device according to claim 9, wherein the motor control device is changed to the second resistance value. A motor having a plurality of stators, a rotor that rotates when a stator to be excited among the plurality of stators is switched, and a rotational position detecting unit that detects a rotational position of the rotor;
A plurality of switching means for switching the stator to be excited by switching whether or not to flow current;
Detection voltage output means for detecting a current flowing from the power source to the switching means and outputting a detection voltage corresponding to the detected current;
The switching means for supplying current by detecting the switching timing of the stator to be excited from the rotational position detected by the rotational position detection means is switched, and the switching is performed when the input detection voltage becomes a limit voltage or more. A motor drive unit comprising a motor drive unit that reduces a current flowing through the unit,
Detecting the switching timing of the stator excited from the rotational position detected by the rotational position detection means, and increasing the detection voltage to the detection voltage output means capable of changing the detection voltage for a certain period after detection. A control device characterized by. A motor having a plurality of stators, a rotor that rotates when a stator to be excited among the plurality of stators is switched, and a rotational position detecting unit that detects a rotational position of the rotor;
A plurality of switching means for switching the stator to be excited by switching whether or not to flow current;
A motor drive device of a motor control device comprising: a detection voltage output means for detecting a current flowing from a power source to the switching means and outputting a detection voltage corresponding to the detected current,
The switching means for supplying a current is detected by detecting the switching timing of the stator to be excited from the rotational position detected by the rotational position detecting means, and flows to the switching means when the detected voltage exceeds a limit voltage. Current control means for reducing the current;
Detecting a switching timing of a stator excited from the rotational position detected by the rotational position detecting means, detecting a change period for increasing the detection voltage from the switching timing, and detecting the change period and the detection voltage. A motor drive device comprising: a change period detection means for increasing the detection voltage to the changeable detection voltage output means.   An image forming apparatus comprising the motor control device according to claim 1, the control device according to claim 11, or the motor drive device according to claim 12. A motor having a plurality of stators, a rotor that rotates when a stator to be excited among the plurality of stators is switched, and a rotational position detecting unit that detects a rotational position of the rotor;
A plurality of switching means for switching the stator to be excited by switching whether or not to flow current;
Detection voltage output means for detecting a current flowing from the power source to the switching means and outputting a detection voltage corresponding to the detected current;
The switching means for supplying current by detecting the switching timing of the stator to be excited from the rotational position detected by the rotational position detection means is switched, and the switching is performed when the input detection voltage becomes a limit voltage or more. Motor drive means for reducing the current flowing through the means, and a computer of the control device of the motor control device,
A timing detection step of detecting a switching timing of a stator excited from the rotational position detected by the rotational position detection means;
A voltage control step of causing the detection voltage output means capable of changing the detection voltage to increase the detection voltage for a certain period after the detection of the switching timing;
A voltage control program for executing

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