JP5621960B2 - Motor drive device and image forming apparatus - Google Patents

Description

  The present invention relates to a motor driving device that outputs a current without waveform distortion in a motor driving device that applies a pulse width modulation (PWM) voltage to a coil terminal of a motor to rotationally drive a multiphase motor. The present invention relates to an apparatus and an image forming apparatus using the apparatus.

  In the fields of home appliances, office automation equipment, and vehicle motors, non-commutator motors that perform commutation by means of electrical circuits using switching elements, such as brushless motors and induction motors, are widely used to drive motors. Switching of bridge circuit based on pulse width modulated signal obtained by comparing terminal voltage command value changing in sine wave and carrier wave such as triangular wave to obtain terminal voltage waveform of approximate sine wave A method of driving an element and controlling a terminal output voltage and frequency is known.

  FIG. 13 shows a configuration of a motor driving device that drives a motor by applying a PWM voltage to a coil terminal of the motor. The multiphase motor 1 is composed of three phases of U phase, V phase, and W phase, and is connected to the bridge circuit 2 at each coil terminal of U phase, V phase, and W phase.

  As shown in FIG. 2, the bridge circuit 2 is configured by connecting the upper arm 21 in which the switching element 25 and the diode 26 are connected in parallel and the lower arm 22 having the same configuration in a three-phase connection. The switching element is driven by gate signals UH, VH, WH, UL, VL, WL, applies a PWM voltage to the coil of the multiphase motor 1, supplies a drive current to the coil, Rotating drive.

  The PWM means 3 is a sine wave or a sine wave approximate waveform having a phase difference between three phases with a virtual 0 as the center of amplitude shown in FIG. 3, and is a voltage command value to be applied to each coil terminal. The terminal voltage command values (Vu *, Vv *, Vw *) and the carrier wave Vc are compared to perform pulse width modulation to generate PWM signals (Upwm, Vpwm, Wpwm).

  The gate signal generating means 5 inserts a switching element short-circuit prevention period (dead time) in accordance with the PWM signal, and the gate signal of the switching element of the upper arm 21 and the switching element of the lower arm 22 of each phase. Gate signals (UH, VH, WH, UL, VL, WL) are generated.

Detailed operations of the PWM means 3 and the gate signal generating means 5 will be described with reference to FIG.
First, the operation of the PWM means 3 will be described. The carrier wave Vc shown in the first stage of FIG. 14 is a triangular wave having a predetermined PWM cycle and has an amplitude from the ground GND to the power supply voltage Vcc. The terminal voltage command value Vu * is a virtual zero between the power supply voltage Vcc and the ground GND. The terminal voltage command value Vu * and the carrier wave Vc are compared to generate the PWM signal Upwm shown in the second stage of FIG.

  Next, the operation of the gate signal generating means 5 will be described. As shown in the third and fourth stages of FIG. 14, the upper arm 21 is a signal whose rising edge is delayed by td with respect to the PWM signal Upwm. The switching device gate signal UH is generated. Further, the PWM signal Upwm is inverted, and the gate signal UL of the lower arm 22 which is a signal obtained by delaying the rising edge (falling portion in Upwm) by td is generated. The td is a short-circuit prevention section (dead time) provided for the purpose of preventing a short circuit between the switching elements of the upper arm and the lower arm. The other V-phase and W-phase operations are the same, and the above is the description of the motor drive device.

Next, current waveform distortion in the motor driving device will be described.
First, taking the U phase as an example, for the ON / OFF states of the gate signals UH and UL, as shown in FIG. , UH: OFF / UL: OFF section is named Dead and section. It should be noted that the combination of UH: ON / UL: ON does not exist in practice because it causes a short circuit and destroys the switching element.

  Here, the direction of the current flowing through the coil and the current path will be described. First, taking the U phase as an example, the voltage at the point where the bridge circuit 2 and the coil of the multiphase motor 1 are connected is defined as the terminal voltage Vu. Furthermore, the current flowing through the coil of the multiphase motor 1 is defined as a coil current iu, and the direction flowing from the bridge circuit 2 to the coil is defined as a positive value of the coil current iu.

  At this time, the current path and the terminal voltage Vu in the case of the positive / negative of the coil current iu and the ON / OFF state of the gate signal will be described with reference to FIGS. 16 and 17, the switching elements are illustrated as ideal switches in order to illustrate the ON / OFF states of the switching elements.

  First, the case where the coil current iu is positive will be described with reference to FIG. The influence of the voltage drop due to the on-resistance of the switching element and the forward voltage drop of the diode is not specified. The same applies thereafter. In the case of the above-mentioned Hon, the current flows from the power source to the coil through the switching element of the upper arm 21. At this time, the terminal voltage Vu becomes Vcc. In the case of the Dead, the current flows from the ground to the coil through the diode of the lower arm 22. At this time, the terminal voltage Vu becomes GND. In the case of Lon, the current flows from the ground to the coil through the switching element of the lower arm 22. At this time, the terminal voltage Vu becomes GND.

  Next, the case where the coil current iu is negative will be described with reference to FIG. In the case of Hon, the current flows from the coil through the switching element of the upper arm 21 to the power source. At this time, the terminal voltage Vu becomes Vcc. In the case of the Dead, the current flows from the coil through the diode of the upper arm 21 to the power source. At this time, the terminal voltage Vu becomes Vcc. In the case of Lon, the current flows from the coil through the switching element of the lower arm 22 to the ground. At this time, the terminal voltage Vu becomes GND.

The above is the description of the direction of current flowing through the coil and the current path.
Next, FIG. 14 shows an error between the terminal voltage command value Vu * and the actual terminal voltage Vu using the coil current iu and the change in the value of the terminal voltage Vu with respect to the ON / OFF state of the switching element. First, when the coil current iu is positive, as shown in the fifth stage of FIG. 14, the terminal voltage Vu is applied smaller than the terminal voltage command value by td corresponding to the short-circuit prevention section. On the other hand, when the coil current iu is negative, the terminal voltage Vu is largely applied to the terminal voltage command value by td corresponding to the short-circuit prevention section, as shown in the sixth stage of FIG.

  As described above, due to the voltage error between the terminal voltage command value Vu * and the terminal voltage Vu which is pulse-width modulated and actually applied to the coil terminal, the coil current as shown in the left diagram of FIG. Distortion occurs.

Here, the technique shown in FIG. 18 is widely known for the current waveform distortion. The current detection means 4 detects three-phase coil currents iu, iv and iw. Based on the detected coil current, the voltage compensation means 6 compensates for the error with respect to the terminal voltage command values Vu *, Vv *, and Vw *. FIG. 19 shows the operation of the voltage compensation means 6 taking the U phase as an example. If the detected coil current iu is positive, the correction value ΔV is added to the terminal voltage command value Vu *, and if iu is negative, the correction value ΔV is subtracted from the terminal voltage Vv * to obtain a terminal voltage command value Vu after voltage compensation. Output to the PWM means 3 as * '. However, the correction value ΔV is a value represented by Formula 01, and is a value determined by the power supply voltage Vcc, the length td of the short-circuit prevention section, and the length tpwm of the PWM cycle. Δ is the symbol that appears at the beginning of Equation 1 below.
Is used instead.

  However, in the above prior art, the correction value ΔV is a constant value and needs to be adjusted in accordance with the change of the parameter. On the other hand, for example, as disclosed in Patent Document 1, an error is detected by taking a difference between the terminal voltage command value or the PWM signal and the terminal voltage, and the error is reduced to zero by a compensator configured by an integrator. A method is known in which a control signal is generated such that the control signal is added to the terminal voltage command value. "

The mathematical formula for calculating the voltage compensation value in the prior art is as follows.

  By the way, the conventional technology compensates for the error between the terminal voltage command value and the terminal voltage caused by the short-circuit prevention section by adding or subtracting the compensation value to the terminal voltage command value, so that the terminal voltage command value is the voltage output of the circuit. If it is at the end of the possible range, it may be out of the output range and error compensation may not be performed normally.

  In addition, when the power supply voltage, the length of the short-circuit prevention section (time), and the value of the PWM cycle change, the voltage error also changes, so there is a problem that it is necessary to change the compensation value in accordance with the change. In order to automatically change the compensation value, if it is configured with an analog circuit, it requires a large number of amplifiers that make up a terminal voltage command and terminal voltage comparison and a voltage error compensator, and is configured with a digital circuit. Then, it is necessary to use voltage value detection means such as an A / D converter, which causes an increase in cost.

  Therefore, in the present invention, when the terminal voltage command value is in the vicinity of the output limit value, there is no problem of exceeding the output range due to correction, even if the short-circuit prevention time, the PWM cycle, and the power supply voltage value change, It is an object of the present invention to provide a motor drive device that can compensate for the above error without adjusting a compensation value and that can realize these functions at low cost.

Among the motor driving devices according to the present invention, the motor driving device according to claim 1 is connected to the coil terminal of the multiphase motor, and the switching element and the diode are connected in parallel, respectively, and the pair of the upper arm and the lower arm is connected in a plurality of phases. The PWM circuit for generating a PWM signal by pulse width modulating the terminal voltage command value to be applied to the coil terminals of each phase of the multiphase motor, and the coils of each phase of the multiphase motor. Current detection means for detecting a current value, and a gate signal generation means for generating a gate signal of each phase switching element in the bridge circuit according to a predetermined switching element drive logic from the PWM signal from the PWM means, The switching element for each phase of the plurality of multiphase motors according to the gate signal generation means according to the coil current value of each phase detected by the current detection means. The motor drive device for selecting the dynamic logic,
The gate signal generating means includes
In the phase detected by the current detection means that current flows from the bridge circuit toward the coil of the multiphase motor, a short-circuit prevention section is provided between the switching element of the upper arm and the switching element of the lower arm. Select the switching element drive logic to be complementarily driven,
In the phase detected when a current flows from the coil of the multiphase motor toward the bridge circuit, switching element driving logic for driving only the switching element of the lower arm is selected .

In the motor drive device according to the second aspect , the multi-phase motor is a three-phase motor, and the terminal voltage command value is two-phase modulated.

In the motor drive device according to the third aspect , the current detection means detects only the direction of the coil current of each phase of the multiphase motor.

According to a fourth aspect of the present invention, there is provided an image forming apparatus comprising the motor driving device according to any one of the first to third aspects.

An image forming apparatus according to a fifth aspect of the present invention is a tandem type full-color image forming apparatus.

  According to the present invention, in the compensation for the error that causes the current waveform distortion, the correction value is not added to or subtracted from the terminal voltage command value. Therefore, when the terminal voltage command value is close to the output limit value, the output range is corrected. The problem of exceeding the limit does not occur. In addition, even if the short-circuit prevention time, PWM cycle, and power supply voltage values change, the above error can be compensated without adjusting the compensation value, and no terminal voltage detection means is required. There is an effect that can be realized.

  In addition, according to the present invention, in various image forming apparatuses, a motor that is rotationally driven provided in each part of the apparatus can be driven without distortion due to the coil current, and torque fluctuations generated by the motor can be reduced, and noise and vibration can be reduced. And can be driven precisely. Therefore, high-quality image formation can be performed with low noise, and furthermore, high-precision paper conveyance can be performed with low noise and low vibration. Of course, it is possible to read a document image with high quality and low noise.

The figure which shows the structure in Example 1 of this invention. The figure which shows the structure of the upper arm in a bridge circuit The figure which shows the example of a waveform of terminal voltage command value in Example 1 and a prior art Diagram showing definition of U-phase coil current and terminal voltage The figure which shows the structure of the electric current detection means in Example 1. The figure which shows PWM, a gate signal, and a terminal voltage in Example 1 when a coil current is positive The figure which shows PWM, a gate signal, and a terminal voltage in Example 1 when a coil current is negative The figure which shows the structure in Example 2. The figure which shows the example of a waveform of the terminal voltage command value by which 2 phase modulation was carried out in Example 2. The figure which shows the structure of the electric current detection means in Example 2. FIG. The figure which shows PWM, a gate signal, and a terminal voltage in Example 2 when a coil current flows to a positive direction The figure which shows PWM, a gate signal, and a terminal voltage in Example 2 when a coil current flows to a negative direction The figure which shows an apparatus structure in a prior art. Diagram showing PWM, gate signal generation, and terminal voltage error in the prior art The figure which shows the definition of ON / OFF state (State) of each switching element Diagram showing the state and current path when the coil current is positive Diagram showing the state and current path when the coil current is negative The figure which shows the example of an apparatus structure provided with voltage error compensation in a prior art. 18 is a diagram showing a configuration example of voltage compensation means in FIG. The figure which shows the waveform distortion of a coil current, and the effect of this invention A diagram showing a tandem-type full-color apparatus configured as a copying apparatus with an image reading unit

  The present invention applies a pulse width modulated voltage according to a terminal voltage command value to a coil terminal of a multiphase motor, and drives a motor in a motor driving device that drives the motor. The coil current is detected so that a voltage error does not occur, and the switching element drive logic of each phase is selectively switched according to the sign of the coil current of each phase. With this configuration, the compensation value is not added to or subtracted from the terminal voltage command value in the compensation for the above-mentioned error that causes current waveform distortion.Therefore, when the terminal voltage command value is near the output limit value, the output exceeds the output range due to the correction. There will be no problem. Even if the short-circuit prevention time, the PWM cycle, and the power supply voltage change, the above error can be compensated without adjusting the compensation value. In addition, since the terminal voltage detecting means is not necessary, the above function can be realized at low cost.

  Further, in the present invention, since the terminal voltage command value is two-phase modulated so that any one phase is always zero, one phase always stops switching. As a result, the number of switching operations is reduced, and switching loss can be reduced. In addition, since only the voltage difference between the coil terminals, which is effective for passing current through the coil, becomes the terminal voltage command value, if the power supply voltage is the same, a larger voltage difference between the terminals than in the case of three-phase modulation is generated. In addition, a larger current can flow.

  Further, in order to automatically eliminate the distortion of the current with the configuration with one switching element driving logic, it is necessary to provide a large number of amplifiers or A / D converters. By having a drive logic and switching the plurality of switching element drive logics according to the direction of the current flowing in the coils of each phase, without providing separate members such as an amplifier and an A / D converter, The distortion of the current flowing in the coil can be eliminated automatically.

  In addition, this invention can be comprised so that only the direction of a coil current may be detected using cheap components, such as a comparator. Therefore, a voltage comparison and a plurality of amplifiers constituting a compensator are not required if configured with an analog circuit, and an A / D converter is not required if configured with a digital circuit, and the motor driving device according to the present invention can be made inexpensive. Can be realized.

  In the image forming apparatus according to the present invention, various motors of each part of the apparatus can be driven without distortion by the coil current. As a result, torque fluctuations generated by the motor are reduced, and it becomes possible to drive with low noise, low vibration, and precision. Therefore, high-quality image formation can be performed with low noise, high-precision paper conveyance can be performed with low noise and low vibration, and document image reading can also be performed with high quality and low noise.

<Example 1>
Embodiments of the present invention will be described below with reference to the drawings. However, the description of the parts common to the above-described conventional technology is omitted.

  FIG. 1 is a circuit diagram showing a configuration of an apparatus according to Embodiment 1 of the present invention. As shown in FIG. 5, the current detection means 4 includes an A / D converter 41, detects current for two phases, outputs coil current value data d_iu and d_iv for two phases, From the coil current value data d_iu and d_iv, the calculation means 42 outputs the remaining one-phase coil current value data d_iw.

  The gate signal generating means 5 selectively switches the switching element driving logic for each phase according to the coil current value data, and outputs the gate signals UH, VH, WH, UL, VL, WL.

The operation of the gate signal generating means 5 will be described with reference to FIGS. 6 and 7, taking the U phase as an example.
First, if the coil current value data d_iu detects that the coil current iu is positive, as shown in the third stage of FIG. 6, the signal delayed by the length td of the short-circuit prevention section with respect to the PWM signal Upwm. Is output as the gate signal UH of the switching element of the upper arm 21. Further, as shown in the fourth stage of FIG. 6, the signal falls in synchronization with the rise of the PWM signal Upwm, and rises with a delay of twice the length td of the short-circuit prevention section from the fall of the PWM signal Upwm. Is output as the gate signal UL of the switching element of the lower arm 22. At this time, as shown in the sixth stage of FIG. 6, the terminal voltage Vu is applied to the coil without excess or deficiency with respect to the PWM signal Upwm. That is, the terminal voltage Vu subjected to pulse width modulation has no error with respect to the terminal voltage command value.

  Next, when the coil current value d_iu detects that the coil current iu is negative, the gate signal UH of the switching element of the upper arm 21 is always set to Lo as shown in the third stage of FIG. That is, the switching element of the upper arm 21 is not driven while being OFF. Further, as shown in the fourth stage of FIG. 7, a signal obtained by inverting the PWM signal Upwm is output as the gate signal UL of the switching element of the lower arm 22.

  At this time, as shown in the sixth stage of FIG. 7, the terminal voltage Vu is applied to the coil without excess or deficiency with respect to the PWM signal Upwm. That is, the terminal voltage Vu subjected to pulse width modulation has no error with respect to the terminal voltage command value. At this time, the predetermined logic for generating the gate signals UH and UL based on the PWM signal Upwm corresponds to the switching element driving logic of the present invention, and the gate signal generating means 5 includes the two switching element driving logics. And switching the switching element drive logic based on the positive / negative of the coil current iu indicated by the detected coil current value data d_iu to generate the PWM signals UH and UL.

  The gate signal generation means 5 in this embodiment includes two switching element driving logics. However, when configured by a digital circuit, the addition of the switching element driving logics can be realized with a slight increase in circuit scale.

  As described above, the switching element driving logic for generating the gate signal of the switching element of the bridge circuit from the PWM signal in which the coil current of the multiphase motor is detected and the terminal voltage command value is subjected to pulse width modulation is detected. By switching appropriately according to the positive and negative of the terminal voltage, an error does not occur in the terminal voltage that is pulse width modulated with respect to the terminal voltage command value within one PWM period. Therefore, as shown in the right diagram of FIG. The torque fluctuation generated by the motor is reduced, and the motor drive with low noise and vibration is possible, and the power supply voltage, the length of the short-circuit prevention section, and the change of the PWM cycle are also There is no need for an adjustment process, and it is possible to prevent coil current distortion.

<Example 2>
Hereinafter, a second embodiment of the present invention will be described with reference to the drawings. However, the description of the parts in common with the prior art and the first embodiment is omitted.

  FIG. 8 is a diagram showing a device configuration in the present embodiment. As shown in the first stage of FIG. 11 and FIG. 12, the PWM means 3 has two-phase modulated coil terminals in which one of the three phases is always zero with the zero shown in FIG. 9 as the lower limit. The terminal voltage command value (Vu *, Vv *, Vw *), which is the voltage command value to be applied, is compared with the carrier wave Vc, which is a triangular wave with an amplitude from the ground GND to the power supply voltage Vcc, and pulse width modulation is performed. , PWM signals (Upwm, Vpwm, Wpwm) are generated.

  The two-phase modulated terminal voltage command values (Vu *, Vv *, Vw *) are effective only for the voltage difference between the coil terminals, which is effective for causing the current for driving the multiphase motor 1 to flow through the coil. Show.

  As shown in FIG. 10, the current detection means 4 uses a low-cost comparator 43 to set the three-phase coil currents iu, iv, iw to Hi if positive and Lo if negative, and to indicate the coil current direction signal of each phase. s_iu, s_iv, and s_iw are output.

  The gate signal generation means 5 selectively switches the switching element driving logic for each phase according to the coil current direction signal, and outputs the gate signals UH, VH, WH, UL, VL, WL. The operation of the gate signal generating means 5 will be described with reference to FIGS. 11 and 12, taking the U phase as an example.

  First, when the coil current direction signal s_iu is Hi, that is, when it is detected that the direction of the coil current iu is positive, as shown in the third row of FIG. The signal delayed by td is output as the gate signal UH of the switching element of the upper arm 21. Further, as shown in the fourth stage of FIG. 11, the signal falls in synchronization with the rise of the PWM signal Upwm, and rises with a delay of twice the length td of the short-circuit prevention section from the fall of the PWM signal Upwm. Is output as the gate signal UL of the switching element of the lower arm 22. At this time, as shown in the sixth stage of FIG. 11, the terminal voltage Vu is applied to the coil without excess or deficiency with respect to the PWM signal Upwm. That is, the terminal voltage Vu subjected to pulse width modulation has no error with respect to the terminal voltage command value.

  Next, when the coil current direction signal s_iu is Lo, that is, when the direction of the coil current iu is detected as negative, as shown in the third stage of FIG. 12, the gate signal UH of the switching element of the upper arm 21 is Always set to Lo. That is, the switching element of the upper arm 21 is not driven while being OFF. Further, as shown in the fourth stage of FIG. 12, a signal obtained by inverting the PWM signal Upwm is output as the gate signal UL of the switching element of the lower arm 22. At this time, as shown in the sixth stage of FIG. 12, the terminal voltage Vu is applied to the coil without excess or deficiency with respect to the PWM signal Upwm. That is, the terminal voltage Vu subjected to pulse width modulation has no error with respect to the terminal voltage command value. At this time, the predetermined logic for generating the gate signals UH and UL based on the PWM signal Upwm corresponds to the switching element driving logic of the present invention, and the gate signal generating means 5 includes the two switching element driving logics. And switching the switching element driving logic based on the detected Hi / Lo of the detected coil current direction signal s_iu to generate the PWM signals UH and UL.

  The gate signal generation means 5 in this embodiment includes two switching element drive logics. However, when configured by a digital circuit, the addition of the switching element drive logics can be realized with a slight increase in circuit scale.

  As described above, only the coil current direction of a multi-phase motor is detected using inexpensive components, and the terminal voltage command value subjected to two-phase modulation is converted from the pulse width modulated PWM signal to the gate signal of the switching element of the bridge circuit. The switching element driving logic that generates the above is configured to be appropriately switched according to the positive and negative of the detected coil current.

  Further, with the above configuration, if the power supply voltage is the same, the effective inter-coil terminal voltage can be increased and a larger coil current can be passed. Further, since no error occurs in the terminal voltage subjected to pulse width modulation with respect to the terminal voltage command value within one PWM period, no distortion of the coil current waveform occurs as shown in the right diagram of FIG. Reduces torque fluctuations, enables low noise and low vibration motor drive, and prevents coil current distortion with no need for adjustment process for changes in power supply voltage, short-circuit prevention interval, and PWM cycle It can respond to. Furthermore, an apparatus having the above effects can be configured at low cost.

<Example 3>
An example of an image forming apparatus to which the present invention is applied will be described.
The image forming apparatus shown in FIG. 21 is a so-called tandem type full-color apparatus, which is configured as a copying apparatus with an image reading unit. The copying apparatus of this example has an apparatus main body 310 mounted on a paper feed table 320, a scanner 330 is disposed at the top of the apparatus main body 310, and an automatic document feeder (ADF) 340 is further provided thereon. is there.

  Inside the scanner 330, a first traveling body 331 composed of an illumination light source and a mirror and a second traveling body 332 including a mirror are provided so as to be movable in parallel with the contact glass 333. The second traveling body 332 employs a known optical system that moves at half the speed of the first traveling body 331, and these traveling bodies 331 and 332 are stopped on the contact glass 332 while moving. Scan the original image. Reflected light from the original illuminated by the light source is imaged by a condenser lens 334 and taken into a solid-state imaging device 335 such as a CCD. The data is processed by the image processing unit of the copying apparatus main body.

  An intermediate transfer belt 301 is disposed almost at the center of the copying apparatus main body 310. Four image forming units 302 are arranged side by side along the upper side of the intermediate transfer belt 301. In each image forming unit 302, devices necessary for the electrophotographic process are arranged around the photosensitive drum 303.

  The intermediate transfer belt 301 is stretched around a plurality of support rollers so as to be able to rotate and convey clockwise in the drawing. Inside the intermediate transfer belt 301, a transfer roller as a primary transfer unit is disposed at a position facing the photosensitive drum 303 of each image forming unit.

  An exposure device 304 is disposed above each image forming unit 302. Write light from the exposure device 304 is applied to the photosensitive drum 303 of each image forming unit 302.

  A transfer conveying belt 305 is disposed below the intermediate transfer belt 301. One roller supporting the transfer conveyance belt 305 is configured as a secondary transfer roller, and secondarily transfers the image on the intermediate transfer belt 301 to a recording medium (transfer paper or the like).

  Further, a fixing device 306 is provided on the left side of the transfer conveyance belt 305. A paper discharge tray 307 is provided on the left side of the fixing device 306. A sheet reversing unit 308 is provided at the lowermost part of the apparatus main body 310. The paper feed table 320 is provided with two stages of paper feed cassettes 321 and 322.

  When copying using the color copying apparatus of the present embodiment, the original is set on the original table of the ADF 340 or the contact glass 333 of the scanner. Then, when a start switch provided on an operation panel (not shown) is pressed, the scanner is driven, and reflected light from the light source is reflected by a mirror to enter a reading sensor through an imaging lens (not shown) to read document information.

  Similarly, when a start switch provided on the operation panel is pressed, the intermediate transfer belt 301 is rotated and conveyed by a drive motor (not shown). At the same time, the photoconductors 303 are rotated in the individual image forming units 302 to form black, yellow, magenta, and cyan single color images on the photoconductors 303, respectively. These single color images are sequentially transferred onto the intermediate transfer belt 301 to form a composite color image.

  When the start switch is pressed, the paper is fed out from the paper feed table 320 and abuts against the registration roller 326 to be temporarily stopped.

  Then, the registration roller 326 is rotated in synchronization with the composite color image on the intermediate transfer belt 301, the sheet is fed between the intermediate transfer belt 301 and the transfer conveyance belt 305, and the image is transferred by the secondary transfer unit. Record a color image on paper. The paper after the image transfer is sent to the fixing device 306, where the toner image is fixed and discharged to the paper discharge tray 307.

  In the image forming apparatus, the configuration of the image forming unit is arbitrary, and the arrangement order of the color image forming units in the tandem method is arbitrary. In addition to the tandem type, a configuration in which a plurality of developing devices are arranged around a single photosensitive member, or a configuration using a revolver type developing device is also possible. The present invention can also be applied to a full color machine using three color toners, a multicolor machine using two color toners, or a monochrome apparatus. Of course, the image forming apparatus is not limited to a copying machine, but may be a printer, a facsimile machine, or a multifunction machine having a plurality of functions.

  In the third embodiment, it is needless to say that the motors for driving the various belts, the photoconductors, and the rollers can be driven by the motor driving devices shown in the first and second embodiments.

  As mentioned above, although this invention was demonstrated along the Example shown in figure, this invention is not limited to this. For example, motors that are effective according to the present invention include many non-commutator motors such as brushless DC motors and induction motors, so-called non-commutator motors. Therefore, the non-commutator motor to which the present invention is applicable is not limited to a specific one. Further, the present invention can be applied not only to the outer rotor type but also to the inner rotor type. The coil connection pattern is not limited to Y-shaped connection (star connection), and delta connection is also possible. The number of poles of the motor rotor is not limited to eight. An appropriate type of FG sensor as the speed detecting means can also be adopted.

  Furthermore, the motor drive control device of the present invention can be suitably applied to household appliances, OA equipment, etc., but the OA equipment can be applied to an image reading apparatus or the like in addition to the image forming apparatus described above. If used in an image forming apparatus, the motor that drives the rotation of each part of the apparatus can be driven without distortion due to the coil current, so that torque fluctuations generated by the motor can be reduced, and driving with low noise, low vibration, and precision can be achieved. Therefore, high-quality image formation can be performed with low noise. Further, highly accurate paper conveyance can be performed with low noise and low vibration. Alternatively, it is possible to read a document image with high quality and low noise.

1: multiphase motor 2: bridge circuit 21: upper arm 22: lower arm 25: switching element 26: diode 3: PWM means 4: current detecting means 41: AD converting means 42: calculating means 43: comparator 5: gate signal Generation means 6: voltage compensation means
Vu *, Vv *, Vw *: Terminal voltage command value (U phase, V phase, W phase)
Vu * ', Vv *', Vw * ': Terminal voltage command value after voltage compensation (U phase, V phase, W phase)
Vu, Vv, Vw: Terminal voltage (U phase, V phase, W phase)
Upwm, Vpwm, Wpwm: PWM signal (U phase, V phase, W phase)
UH, VH, WH: Gate signal (U-phase, V-phase, W-phase upper arm)
UL, VL, WL: Gate signal (U-phase, V-phase, W-phase lower arm)
iu, iv, iw: Coil current (U phase, V phase, W phase)
d_iu, d_iv, d_iw: Coil current value data (U phase, V phase, W phase)
s_iu, s_iv, s_iw: Coil current direction signal (U phase, V phase, W phase)
Vc: Carrier wave
td: Length of short-circuit prevention section Dead (dead time)
tpwm: PWM cycle length ΔV: Voltage compensation value (fixed value)
Vcc: Power supply voltage
GND: Ground
State: ON / OFF state of switching element for each phase
Hon: Section where only upper arm switching element is ON (lower arm is OFF)
Lon: The section where only the switching element of the lower arm is ON (the upper arm is OFF)
Dead: The zone where both upper and lower arm switching elements are OFF

JP-A 63-234878

Claims (5)

A bridge circuit connected to a coil terminal of a multiphase motor, each of which is connected in parallel with a switching element and a diode, and a pair of upper and lower arms connected in multiple phases;
PWM means for generating a PWM signal by pulse width modulating the terminal voltage command value to be applied to the coil terminals of each phase of the multiphase motor;
Current detection means for detecting a current value flowing in the coil of each phase of the multiphase motor;
From the PWM signal from the PWM means, a gate signal generating means for generating a gate signal of each phase switching element in the bridge circuit according to a predetermined switching element drive logic,
With
In the motor drive device in which the gate signal generation unit selects the switching element drive logic for each phase of the plurality of multiphase motors according to the coil current value of each phase detected by the current detection unit ,
The gate signal generating means includes
In the phase detected by the current detection means that current flows from the bridge circuit toward the coil of the multiphase motor, a short-circuit prevention section is provided between the switching element of the upper arm and the switching element of the lower arm. Select the switching element drive logic to be complementarily driven,
In the phase detected when current flows from the coil of the multiphase motor toward the bridge circuit, the switching element driving logic for driving only the switching element of the lower arm is selected.
The motor drive device characterized by the above-mentioned. The motor drive device according to claim 1,
The multi-phase motor is a three-phase motor,
The terminal voltage command value that is the two-phase modulation,
The motor drive device characterized by the above-mentioned. In the motor drive device according to claim 1 or 2,
Said current detecting means, you detect only the direction of the coil current of each phase of said multiphase motor,
The motor drive device characterized by the above-mentioned. An image forming apparatus comprising the motor drive device according to claim 1. 6. The image forming apparatus according to claim 5, wherein the image forming apparatus is a tandem type full-color image forming apparatus.