JP2007232817A - Rotary drive unit and color image forming apparatus using the same - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To precisely control the rotating operation of a rotation shaft in a rotary driving device which controls the rotating speed of a driving motor by detecting the rotating speed of a rotator via a plurality of sensors, even when any of the plurality of sensors fails. <P>SOLUTION: In the rotary drive unit 1, a detection unit 100 includes a fault detection section 9 which detects faults of the plurality of sensors S1 and S2 on the basis of pulse trains output from the sensors S1 and S2 via a rotary encoder 3 and an averaging unit 12 which computes the average speed of the rotary shaft 2 by using only a pulse train output from a normal sensor, and the rotary drive unit 1 controls driving of the driving motor 15 via a control circuit 13 so that the average speed approximates to a command speed. <P>COPYRIGHT: (C)2007,JPO&INPIT

Description

  The present invention relates to a rotational drive device that detects the rotational speed of a rotating body through a sensor and controls the rotational speed of a drive motor so that the detected rotational speed becomes a command speed, and in particular, to detect the rotational speed. The present invention relates to a rotary drive device that includes a plurality of sensors and includes fail software that can control the rotational speed of a rotating body even if any of these sensors fails, and a color image forming apparatus that includes the rotary drive device.

  Conventionally, an encoder that outputs a pulse signal in synchronization with the rotation of the rotating shaft is mounted on the rotating shaft that receives the driving motor and the driving force, and this pulse signal is detected to determine the rotational speed and angle of the rotating shaft. There is a rotary drive device that includes a control device that detects and controls the rotational speed of the drive motor so that the detected rotational speed becomes a command speed.

  In this case, the encoder is generally constituted by a disk-shaped rotating body having a plurality of identification codes along the circumferential direction, and a sensor provided to face the identification codes of the rotating body, and the rotating body rotates. The sensor is configured to rotate integrally with the shaft, and with the rotation of the rotating body, the sensor sequentially detects a plurality of identification codes and outputs a pulse signal.

  In addition, even if an eccentricity occurs between the rotating body and the rotating shaft, a plurality of sensors are provided along the circumferential direction of the rotating shaft so that the influence of the eccentricity can be canceled and the rotational speed of the rotating shaft can be detected with high accuracy. A rotation drive device is known in which an average value of rotational speeds detected by a plurality of sensors is calculated and the average value is obtained as the rotational speed of the rotary shaft (see, for example, Patent Documents 1 and 2). .

  Some image forming apparatuses including a photosensitive drum include the above-described rotation driving device in order to control the rotational speed of the photosensitive drum (see, for example, Patent Document 3).

Further, the color image forming apparatus includes a plurality of photosensitive drums associated with each color such as black, yellow, cyan, and magenta, and a plurality of drive motors that are paired with the photosensitive drums, and each photosensitive drum is provided with There is one in which the rotation speed is detected by an encoder and the rotation speed is controlled (for example, see Patent Document 4).
Japanese Unexamined Patent Publication No. 57-34785 JP-A-10-215593 JP-A-10-215593 Japanese Patent Laid-Open No. 9-1463292

  However, according to the rotational drive device including a plurality of sensors as in Patent Documents 1, 2, and 3, the failure rate of the sensor increases with the increase in the number of sensors, and the malfunctioning sensor is mixed to drive accuracy. There was a risk of damage. For example, when a malfunctioning sensor is mixed, the rotational speed of the rotary shaft becomes excessive or uneven in the rotational speed of the rotary shaft. As a result, the system using this rotational drive device operates smoothly. Could not be maintained, and there was a risk of failure and stoppage.

  Further, as disclosed in Patent Document 4, in particular, according to a color image forming apparatus including an encoder that detects a speed for each of a plurality of photosensitive drums, the sensor is provided for the number of photosensitive drums. If there is a failure, the rotational speed of the photosensitive drum may become excessive, or the rotational speed of the photosensitive drum may become uneven, which may significantly impair the accuracy and quality of the image.

  Therefore, the present invention provides a rotary drive device that detects the rotational speed of a rotating body through a plurality of sensors and controls the rotational speed of a drive motor, and even if a malfunction occurs in any of the plurality of sensors, The rotation operation is accurately controlled, and further, in a color image forming apparatus including a plurality of photosensitive drums and their rotation driving devices, the reliability of the detection unit for detecting the rotation speed of the photosensitive drums is improved, and the accuracy and quality are improved. The object is to obtain a good color image.

  In order to achieve this object, the invention according to claim 1 is characterized in that a drive motor that rotates a rotation shaft to be controlled based on a command speed, and a rotation motor that is connected to the rotation shaft and rotates integrally with the rotation shaft. A rotating body provided with a plurality of identification codes at equal intervals along the circumferential direction coaxial with the rotating shaft, and equally divided along the circumferential direction of the rotating body, with the rotation of the rotating body A plurality of sensors that sequentially detect the identification code and output a pulse train; and a plurality of pulse trains output from the plurality of sensors to calculate an average rotational speed of the rotating body, and the average rotational speed is A speed control means for controlling the rotational speed of the drive motor so as to achieve a command speed; and a failure detection means for detecting a failure of each sensor based on a pulse train output from the plurality of sensors. Control means Based on the detection result of said failure detecting means, wherein the failure mode auxiliary means for driving the drive motor is provided with only the pulse train output from the normal sensor.

  According to the rotation driving device of claim 1, the average rotation speed of the rotating body is calculated using a plurality of pulse trains output from a plurality of sensors, and the average rotation speed is driven so as to become the command speed. A speed control means for controlling the rotational speed of the motor; and a failure detection means for detecting a failure of each sensor based on a pulse train output from a plurality of sensors. The speed control means includes a detection result of the failure detection means. The failure mode auxiliary means for driving the drive motor using only the pulse train output from the normal sensor is provided based on the rotation speed of the drive motor even if any of the plurality of sensors fails. The rotation operation of the rotary shaft can be accurately controlled without causing excessive rotation or uneven rotation speed. It can maintain a smooth operation.

  According to a first aspect of the present invention, in the rotary drive device according to the second aspect of the invention, the failure detection means detects a change in the rise and fall of the pulse in each of the pulse trains of the plurality of sensors. If at least one cycle of any one of the pulse trains of the plurality of sensors is configured so that a sensor that does not output a pulse rise or fall is detected as a failure from other sensors, one cycle of one sensor As a reference, it is possible to detect the presence or absence of a failure of the other sensor and to coordinate the operations of a plurality of sensors.

  Further, in the rotary drive device according to claim 1 or 2, as in the invention according to claim 3, the failure mode auxiliary means is a pulse train output from a normal sensor among the plurality of sensors. By replacing either of these with the pulse train of the sensor detected as a failure, the rotational speed of the rotating shaft can be detected with high accuracy without adding the pulse train output from the failed sensor.

  In addition, the rotary drive device according to any one of claims 1 to 3, as in the invention according to claim 4, is an initialization unit that initializes a previous detection result every time the failure detection unit is activated. If the sensor failure is a temporary factor and returns to normal, the sensor can be added to the normal sensor group again to detect the rotational speed of the rotating shaft with high accuracy.

  In addition, the rotary drive device according to any one of claims 1 to 4 is a display that indicates the failure when the failure detection means detects a failure of the sensor, as in the invention according to claim 5. By providing the means, the operator can easily detect the presence or absence of a sensor failure, and can quickly cope with the failure.

  Next, the invention described in claim 6 is a rotary drive device that includes a plurality of photosensitive drums corresponding to each of a plurality of colors, and rotationally drives the plurality of photosensitive drums. Any one of the above-mentioned rotational drive devices is provided.

  According to the color image forming apparatus of the sixth aspect, since the rotational driving device according to any one of the first to fifth aspects is provided as a rotational driving device for rotationally driving the photosensitive drum, the photosensitive drum is provided. Even if one of the sensors that detect the rotation speed of the sensor malfunctions, the rotation speed of the photosensitive drum can be controlled accurately without causing the rotation speed of the drive motor to become excessive or uneven in the rotation speed. And an image with good accuracy and quality can be formed.

  Further, according to the color image forming apparatus of the sixth aspect, when a failure of each sensor is detected based on the pulse train output from the plurality of sensors, as in the seventh aspect of the invention, By providing the display means for displaying the failure or the communication means for communicating the failure, the operator can easily detect the presence or absence of the sensor failure and promptly prevent the image from being damaged in the case of the failure. I can deal with it. At this time, a communication means for communicating the failure may be provided together with a display means for displaying the failure.

  The rotational drive device of the present invention outputs the speed control means for controlling the rotational speed of the drive motor and the plurality of sensors so that the average rotational speed of the rotating body obtained through the plurality of sensors becomes the command speed. Failure detection means for detecting failure of each sensor based on the pulse train, and the speed control means uses only the pulse train output from the normal sensor based on the detection result of the failure detection means, and the drive motor Failure mode auxiliary means for driving the rotating shaft, even if any of the plurality of sensors fails, the rotational speed of the drive motor does not become excessive or uneven in the rotational speed. The rotation operation of the system can be controlled with high accuracy, and as a result, the smooth operation of the system using the rotation drive device can be maintained.

  Further, in the rotational drive device of the present invention, the failure detection means detects a change in the rise and fall of the pulse in each of the pulse trains of the plurality of sensors, and at least one cycle of any pulse train of the plurality of sensors, If a sensor that does not output a pulse rise or fall is detected as a failure from other sensors, the presence or absence of a failure of the other sensor can be detected based on one cycle of one sensor. The operations of the sensors can cooperate with each other.

  Further, the rotary drive device of the present invention is configured such that the failure mode auxiliary means replaces one of the pul trains output from a normal sensor among a plurality of sensors with a pulse train of the sensor detected as a failure. Therefore, when calculating the average rotation speed of the rotating body, the average speed of the rotating body can be accurately detected without adding a pulse train output from the failed sensor.

  In addition, since the rotation drive device of the present invention includes an initialization unit that initializes the previous detection result every time the failure detection unit is activated, the sensor failure is a temporary factor and returns to normal. In this case, this sensor can be added to the normal sensor group again to control the rotation operation of the rotary shaft with high accuracy.

  In addition, since the rotation drive device of the present invention includes an output means for displaying a signal indicating a failure state when the failure detection means detects a failure of the sensor, the operator can easily detect the presence or absence of the sensor failure. Can be dealt with promptly in case of failure.

  Next, the color image forming apparatus of the present invention is provided with the rotation drive device according to any one of claims 1 to 5 as a rotation drive device for rotating and driving the photosensitive drum. Even if one of the sensors that detect the failure occurs, the rotational operation of the photosensitive drum can be accurately controlled without causing the rotational speed of the drive motor to be excessive or uneven. An image with good accuracy and quality can be formed.

  The color image forming apparatus of the present invention further includes a display unit for displaying a failure or a communication unit for communicating the failure when a failure of each sensor is detected based on a pulse train output from a plurality of sensors. Therefore, the operator can easily detect the presence or absence of a sensor failure, and can quickly cope with the failure so as not to damage the image. At this time, the convenience can be further improved by providing the communication means for communicating the failure together with the display means for displaying the failure.

  Next, a driving device 1 according to an embodiment of the present invention will be described with reference to the drawings. FIG. 1 is a circuit block diagram of a rotary drive device of the present invention, and FIG. 2 is a circuit diagram of a failure detection unit in FIG.

  As shown in FIG. 1, the rotary drive device 1 decelerates via an operation unit 17 for an operator to input various command signals, a drive motor 15 that rotates the rotary shaft 2 of the speed reducer 16, and a rotary encoder 3. The detection unit 100 that detects the rotation speed of the rotary shaft 2 of the machine 16, and the rotation speed of the drive motor 15 is adjusted so that the rotation speed detected via the detection unit 100 becomes the command speed input via the operation unit 17. A control circuit 13 to be controlled is provided.

  The drive motor 15 is composed of a pulse motor, and the amount of rotation is controlled by the number of pulses of the pulse train input via the control circuit 13. The detection unit 100 outputs the rotation amount for each predetermined cycle of the rotating shaft 2 instead of the pulse train, and the control circuit 13 sets the number of pulses of the pulse train input from the detection unit 100 to the number of pulses of the speed command value. The number of pulses in the pulse train input to the drive motor 15 is increased or decreased so as to approach.

  The rotary encoder 3 is arranged on the opposite side of the light receiving diodes 5 and 6 with the rotary plate 3a having a plurality of slits 3b arranged along the circumferential direction and the rotary plate 3a interposed therebetween, and projects light to the rotary plate 3a. It comprises light emitting diodes that emit light and light receiving diodes 5 and 6 that receive light projected from the light emitting diodes through the slit 3b, and the light receiving diodes 5 and 6 emit light as the drive motor 14 rotates. The generated light is used as a pulse signal, and a plurality of continuous pulse signals (so-called pulse trains) are output to the waveform generators 7 and 8. The control object in the present invention is the speed reducer 16, the rotating body in the present invention is the rotating plate 3a, the identification code in the present invention is the slit 3b, the sensor in the present invention is the light emitting diode and the light receiving diodes 5 and 6, and the speed control in the present invention. The means corresponds to the control circuit 13. Hereinafter, the light emitting diode and light receiving diode 5 on the S1 side are referred to as S1 sensors, and the light emitting diode and light receiving diode 6 on the S2 side are referred to as S2 sensors.

  Further, the pulse signal S1 output from the light receiving diode 5 is converted into a rectangular clock signal by the S1 waveform generator 7, and the pulse signal S2 output from the light receiving diode 6 is converted to a rectangular signal by the S2 waveform generator 8. It is converted into a shape clock signal.

  Next, the detection unit 100 detects a failure of the S1 sensor and the S2 sensor based on the clock signals input from the S1 waveform generator 7 and the S2 waveform generator 8, the S1 sensor, and the S2. Among the sensors, a multiplexer that outputs the pulse train output from the normal sensor to the averager 12 and outputs the pulse train output from the normal sensor to the averager 12 instead of the pulse train of the sensor detected as a failure. 10, 11 and a pair of pulse trains input at predetermined intervals via the multiplexers 10 and 11 are synthesized, and the number of pulses per sensor is averaged to obtain a pulse train having the average number of pulses. 13 and the like. The function of the failure detection means in the present invention is expressed by the failure detection unit 9.

  In the failure detection unit 9, the outputs o2 and o1 are set to signals of L (LOW) level by default. If there is no rise or fall of the pulse train of S2 during at least one cycle of the pulse train of S1, the output of o2 The output transitions to a signal of H (HIGH) level, and the output of o1 transitions to a signal of H level if there is no rise or fall of the pulse train of S1 during at least one period of the pulse train of S2.

  When the signal input from o1 is at the L level, the multiplexer 10 outputs the pulse train a input from the S1 waveform generator 7 to the averager 12, and when the signal input from o1 is at the H level. Outputs the pulse train b input from the S2 waveform generator 8 to the averager 12.

  On the other hand, when the signal input from o2 is at L level, the multiplexer 11 outputs the pulse train a input from the S2 waveform generator 8 to the averager 12, and the signal input from o2 is at H level. In some cases, the pulse train b input from the S1 waveform generator 7 is output to the averager 12.

  That is, the failure detection unit 9 selects the other sensor if there is no rise or fall of the pulse train output from the other sensor during one cycle of the pulse train output from one of the S1 sensor and S2 sensor. The pulse train output from the failed sensor is replaced with a pulse train output from another normal sensor and input to the averager 12. Note that the failure mode auxiliary means of the present invention exhibits its function by the failure detection unit 9.

  Next, the averager 12 synthesizes the respective pulse trains inputted via the multiplexer 10 and the multiplexer 11 for each predetermined period, detects their phase difference, and average pulse train having an average number of pulses. Is input to the control circuit 13.

  Next, the detection unit 100 includes an activation switch 18 that activates or deactivates the operation of the failure detection unit 9 in the operation unit 17, and every time the failure detection unit 9 is activated via the activation switch 18. The signal levels of o1 and o2 held by the failure detection unit 9 are set to default (L level). That is, every time the failure detection unit 9 is activated, the detection unit 100 is configured to initialize a failure detection result in the previous driving operation even if a failure of the S1 sensor or the S2 sensor is detected previously. Note that the function of the initialization means of the present invention is expressed by the start switch 18.

  Further, when the outputs o1 and o2 of the failure detection unit 9 transition from the L level to the H level, a signal indicating the transition is transmitted from the failure detection unit 9 to the display unit 4 of the operation unit 17 and displayed on the display unit 4 Is done. That is, when the output o1 transits from the L level to the H level, the failure of the S1 sensor is displayed, and when the output o2 transits from the L level to the H level, the failure of the S2 sensor is displayed. The function of the display means in the rotary drive device of the present invention is expressed by the failure detection unit 9 and the display unit 4.

  Next, details of the failure detection unit 9 will be described with reference to FIG.

  As shown in FIG. 2, the failure detection unit 9 includes pulse rising edge detection units 20 and 22 that detect rising edges of the pulse trains of the S1 sensor and S2 sensor, and a pulse falling edge detection unit that detects the falling edge of the pulse train. 21 and 23, when the edge signal detected by the pulse rising edge detectors 20 and 22 and the pulse falling edge detectors 21 and 23 is input, and when the edge signal is input from at least one, the D-FF flip-flop 26, This is composed of OR gate circuits 24 and 25 for outputting a “clock enable signal” to 27 clock enable CEs, and D-FF Philip flops 26, 27, 28 and 29.

  The D-FF Philip flops 26, 27, 28, 29 operate in synchronism with CLOCK (which is an oscillator) 31, 32, 33, 34. Further, the output Q of the D-FF Philip flops 28 and 29 is initialized to the L (LOW) level every time the activation SW is turned on.

  In the D-FF Philip 26, the input data D when the clock signal of the CLOCK 31 changes from LOW to HIGH is transmitted to the output Q. In other cases, the output of the previous data is held.

  In the D-FF Philip 27, the input data D when the CLOCK 32 changes from LOW to HIGH is transmitted to the output Q. In other cases, the output of the previous data is held.

  In the D-FF Philip flop 28, if the signal output from the D-FF Philip flop 26 does not change during one cycle of the edge signal input from the pulse rising edge detector 22, the Q output transitions to the H level. If there is a change in the signal output from the D-FF Philip flop 26, the L level of the Q output is held.

  In the D-FF Philip flop 29, if the signal output from the D-FF Philip flop 27 does not change during one cycle of the edge signal input from the pulse rising edge detector 20, the Q output transitions to the H level. If there is a change in the signal output from the D-FF Philip flop 27, the L level of the Q output is held.

  Below, the effect of the rotary drive device 1 of the said Example is described.

  The rotation drive device 1 of the embodiment detects the average rotation speed of the rotating shaft 2 via the S1 sensor and the S2 sensor, and detects a failure of each sensor based on the pulse train output from the S1 sensor and the S2 sensor. Since the average pulse train is detected using only the pulses output from the normal sensor, the rotational speed of the drive motor 15 is excessive even if either the S1 sensor or the S2 sensor fails. Therefore, the rotational operation of the rotary shaft 2 can be accurately controlled without causing unevenness in the rotational speed and the smooth operation of the system using the rotational drive device 1 can be maintained. .

  Further, the rotary drive device 1 of the present embodiment detects the rise and fall of the pulse in each of the pulse trains of the S1 sensor and S2 sensor via the failure detection unit 9, and the pulse train of either sensor is detected. Since at least one cycle is configured to detect, as a failure, a sensor that does not output a rising or falling pulse from other sensors, the failure of the other sensor is based on one cycle of one sensor. The presence or absence of the sensor can be detected, and the operations of the two sensors can cooperate with each other.

  In addition, the rotation drive device 1 of the present embodiment detected any one of the pulse trains output from the normal sensors among the S1 sensor and the S2 sensor as a failure through the failure detection unit 9 and the multiplexers 10 and 11. Since it is configured to replace the pulse train of the sensor, the average speed of the rotating shaft 2 can be detected accurately without adding the pulse train output from the failed sensor when calculating the rotational speed of the rotating shaft 2. .

  Further, since the rotary drive device 1 of the present embodiment is configured to initialize the previous detection result every time the failure detection unit 9 is activated via the activation switch 18, the failure of the S1 sensor or the S2 sensor Is a temporary factor and returns to normal, this sensor can be added to the normal sensor group again to control the rotation operation of the rotating shaft with high accuracy.

  Further, the rotation drive device 1 according to the present invention is configured to display a signal indicating a failure state on the display unit 4 when a failure of the S1 sensor or the S2 sensor is detected via the failure detection unit 9. Therefore, the operator can easily detect whether the S1 sensor or the S2 sensor has failed, and can quickly cope with the failure.

  Next, an embodiment of a color image forming apparatus provided with the rotary drive device 1 of the above embodiment will be described. FIG. 3 is a configuration diagram of the color image forming apparatus in the embodiment of the present invention, and FIG. 4 is a circuit block diagram showing a control system for rotational driving of the photosensitive drum in the color image forming apparatus of the embodiment.

  As shown in FIG. 3, the color image forming apparatus 37 according to the present embodiment is provided in a printer, a copier, or the like, and converts color images input from a personal computer or scanner into C (cyan), M (magenta), Y (yellow) and K (black) are converted into color data of four colors, and these four colors are printed on a recording paper P as a recording medium.

  The color image forming apparatus 37 is provided with a tray 50 for storing the recording paper P below the casing 38. The recording paper P is image-formed and discharged upward. Further, the color image forming apparatus 37 includes a communication unit 14 for communicating with other electronic devices such as a personal computer, an operation unit 17 operated by an operator, and the like.

  The color image forming apparatus 37 rotates on the basis of predetermined image data in accordance with an image of four color data from C (cyan), M (magenta), Y (yellow), and K (black), which will be described later. Photosensitive drums 43 </ b> C, 43 </ b> K, 43 </ b> M, and 43 </ b> Y that rotate by receiving the driving force of the driving device (101 in FIG. 2) are provided.

  As the photosensitive drums 43C, 43K, 43M, and 43Y are rotated, the photosensitive drums 43C, 43K, 43M, and 43Y are first uniformly charged positively by the stron type chargers 42C, 42K, 42M, and 42Y, and then the laser output units 40C, 40K, 40M, and 40Y. Exposure is performed by high-speed scanning, and an electrostatic image based on predetermined image data is formed.

  Next, toner of each color is supplied from the developing units 41C, 41K, 41M, and 14Y to the photosensitive drum, and at this time, electrostatic images formed on the surfaces of the photosensitive drums 43C, 43K, 43M, and 43Y, that is, laser light. Toner is supplied to an exposed portion where the potential is lowered due to exposure, and the image is visualized by being selectively carried.

  Further, below the photosensitive drums 43C, 43K, 43M, and 43Y, single-character transfer drums 44C, 44K, 44M, and 44Y are provided so as to sandwich the transfer belt 45, and these primary transfer drums pass through the transfer belt 45. As a result, the transfer belt 45 circulates around the primary transfer drums 44C, 44K, 44M, and 44Y and the conveying rollers 51, 52, and 53 by receiving the rotational force of the photosensitive drums 43C, 43K, 43M, and 43Y. At this time, the toner images carried on the photosensitive drums 43C, 43K, 43M, and 43Y are transferred to the transfer belt 45.

  On the other hand, the recording paper P is conveyed between the pair of secondary transfer drums 47, pressed onto the transfer belt 45, and the toner image transferred to the transfer belt 45 is transferred while passing through the secondary transfer drum 47. Further, the image is fixed by being heat-pressed by the fixing device 49.

  Next, in the color image forming apparatus 37, the rotation of the photosensitive drums 43C, 43K, 43M, and 43Y is controlled by the rotation driving device 101 shown in FIG. In this rotary drive device 1101, the same reference numerals are given to the same parts as those in the embodiment of the rotary drive device 1 described above, and the detailed description is omitted.

  The rotation drive device 101 includes a detection unit 36 that detects the rotation speed of the photosensitive drums 43K, 43C, 43M, and 43Y. The detection unit 36 is connected to drive motors 15K, 15M, 15C, and 15Y, and the photosensitive drum 43K. , 43C, 43M, 43Y, rotary encoders 3Y, 3M, 3C, 3K for detecting the rotation amount are attached. At this time, the rotary encoders 3Y, 3M, 3C, and 3K are the same as the rotary encoder 3 described in the rotary drive device 1 of the above-described embodiment, and the S1 sensor is used to detect the rotation amount of the rotary plate 3a. And S2 sensor.

  Further, control circuits 13K, 13C, 13M, and 13Y having the same functions as those of the control circuit 13 of the rotary drive device 1 are connected to the drive motors 15K, 15M, 15C, and 15Y, respectively.

  The detection unit 36 does not have a rising or falling edge of the pulse train output from the other sensor between the one-cycle pulse trains output from one of the S1 sensor and the S2 sensor via the failure detection unit 9. The other sensor is detected as a failure, the pulse train output from the failed sensor is replaced with a pulse train output from another normal sensor, and input to the averager 12.

  Then, the averager 12 synthesizes the respective pulse trains input via the multiplexer 10 and the multiplexer 11 for each predetermined period, detects the phase difference between them, and obtains the average pulse train having the average number of pulses. Generated and input to the control circuits 13K, 13M, 13C, 13Y.

  Further, the color image forming apparatus 36 includes a display unit (liquid crystal display) 55 that displays whether or not the S1 sensor or S2 sensor has failed in the failure detection unit 9 and a communication unit 14 that communicates with other devices. Further, the operation unit 17 is provided with an invalid instruction key for invalidating a signal output from the sensor when the S1 sensor or the S2 sensor fails. When the operator turns on the invalid instruction key, the averager 12 generates a pulse train using only normal sensors.

  Hereinafter, the operational effects of the color image forming apparatus 37 of the above-described embodiment will be described.

  Since the color image forming apparatus 37 according to the embodiment includes the rotation driving device 101 that rotates and drives the photosensitive drums 43K, 43C, 43M, and 43Y, a plurality of rotation speeds of the photosensitive drums 43K, 43C, 43M, and 43Y are detected. Even if one of the sensors fails, the rotational speed of the photosensitive drums 43K, 43C, 43M, and 43Y can be accurately controlled without causing the rotational speed of the drive motor 15 to be excessive or uneven. And an image with good accuracy and quality can be formed.

In addition, the color image forming apparatus 37 according to the embodiment is configured such that when a failure of each sensor is detected based on the pulse train output from the S1 sensor and S2, the display unit 55 that displays the failure or communication that communicates the failure. Since the unit 14 is provided, the operator can easily detect the presence or absence of the sensor failure, and can quickly cope with the failure so as not to damage the image.
As mentioned above, although one Example of this invention was described, this invention is not limited to the said Example.

  For example, in order to detect the rotational speed of the rotating plate 3a in the rotary drive device 1 of the present embodiment, two S1 sensors and two S2 sensors are provided. Then, a change in the rise and fall of the pulse in each of the pulse trains of the plurality of sensors is detected, and the rise or fall of the pulse is detected from other sensors in at least one cycle of the pulse train of any of the plurality of sensors. A sensor that does not output a lowering may be detected as a failure.

  In addition, in the rotary drive device 1 of the present embodiment, one of the pulse trains output from the normal sensor among the S1 sensor and the S2 sensor is configured to be replaced with the pulse train of the sensor detected as a failure. When a sensor is detected, the operation of the malfunctioning sensor may be invalidated, and the pulse train output from the normal sensor may be averaged by the number of normal sensors and output to the control circuit.

  In the rotary drive device 1 of the present embodiment, the optical rotary encoder 3 having a plurality of slits 3b that transmit light to the rotating plate 3a is used. However, a magnetic encoder or an electrostatic encoder is used. May be.

  In the color image forming apparatus 37 of the present embodiment, the rotary encoders 3C, 3K, 3M, and 3Y are arranged on any rotation shaft of the drive motors 15, 15C, 15K, 15M, and 15Y and the photosensitive drums 43C, 43K, 43M, and 43Y. It may be fixed.

It is a circuit block diagram of the rotational drive apparatus in the Example of this invention. It is a circuit diagram of the failure detection part in the same Example. 1 is a configuration diagram of a color image forming apparatus in an embodiment of the present invention. FIG. 2 is a circuit block diagram illustrating a control system for rotational driving of a photosensitive drum in the color image forming apparatus of the embodiment.

Explanation of symbols

  DESCRIPTION OF SYMBOLS 1,101 ... Rotary drive device, 2 ... Rotating shaft, 3, 3C, 3K, 3M, 3Y ... Rotary encoder, 3a ... Rotating plate, 3b ... Slit, 4,55 ... Display part, 5, 6 ... Light receiving sensor, 7 ... S1 waveform shaper, 8 ... S2 waveform generator, 9 ... failure detection unit, 10, 11 ... multiplexer, 12 ... averager, 13,13C, 13K, 13M, 13Y ... control circuit, 14 ... communication unit, 15 , 15C, 15K, 15M, 15Y ... drive motor, 16 ... reduction gear, 17 ... operation unit, 18 ... start switch, 20, 22 ... pulse rising edge detection unit, 21, 23 ... pulse falling edge detection unit, 24 , 25 ... OR gate circuit, 26, 27, 28, 29 ... D flop, 30 ... start switch, 31, 32, 33, 34 ... CLOCK (oscillator), 36 ... detector, 37 ... color image forming apparatus, 38 Case, 40C, 40K, 40M, 40Y ... laser output unit, 41C, 41K, 41M, 14Y ... developing unit, 42C, 42K, 42M, 42Y ... Stron type charger, 43C, 43K, 43M, 43Y ... photosensitive drum, 44C 44K, 44M, 44Y ... primary transfer drum, 45 ... transfer belt, 47 ... secondary transfer drum, 48 ... cleaner, 49 ... fixing device, 50 ... tray, 51, 52, 53 ... transport roller, 100 ... detector, P: Recording paper.

Claims (7)

A drive motor that rotates the rotating shaft to be controlled based on the command speed;
A rotating body connected to the rotating shaft and rotating integrally with the rotating shaft, and having a plurality of identification codes at equal intervals along a circumferential direction coaxial with the rotating shaft;
A plurality of sensors that are arranged in equal divisions along the circumferential direction of the rotating body, and that sequentially detect the identification code and output a pulse train as the rotating body rotates,
Speed control means for calculating an average rotation speed of the rotating body using a plurality of pulse trains output from the plurality of sensors and controlling the rotation speed of the drive motor so that the average rotation speed becomes the command speed. When,
Failure detection means for detecting failure of each sensor based on the pulse train output from the plurality of sensors;
With
The speed control means includes a failure mode auxiliary means for driving the drive motor using only a pulse train output from a normal sensor based on the detection result of the failure detection means.
Rotation drive device. The failure detection means detects a change in the rise and fall of a pulse in each of the pulse trains of the plurality of sensors, and from at least one cycle of any of the pulse trains of the plurality of sensors, the fault detection means Detecting a sensor that does not output start or stop as a failure,
The rotation drive device according to claim 1. The failure mode auxiliary means replaces one of the pulse trains output from a normal sensor among the plurality of sensors with a pulse train of a sensor detected as a failure.
The rotation drive device according to claim 1 or 2. An initialization means for initializing a previous detection result each time the failure detection means is activated;
The rotational drive apparatus in any one of Claims 1 thru | or 3.   The rotation drive device according to any one of claims 1 to 4, further comprising display means for indicating the failure when the failure detection means detects a failure of the sensor. A plurality of photosensitive drums associated with each of a plurality of colors;
The rotation drive device according to any one of claims 1 to 5 is provided as a rotation drive device that rotationally drives the plurality of photosensitive drums.
A color image forming apparatus. When a failure of each sensor is detected based on a pulse train output from the plurality of sensors, the display device displays a failure or a communication unit communicates the failure.
The color image forming apparatus according to claim 6.

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