JP7269016B2 - Drive device and image forming device - Google Patents

Description

The present invention relates to a driving device suitable for image forming apparatuses such as electrophotographic copiers and electrophotographic printers.

In an electrophotographic image forming apparatus, a laser beam is used to form an electrostatic latent image on a photosensitive drum, which is a photosensitive member. The electrostatic latent image is developed as a toner image, and the toner image is transferred onto a sheet. form an image. In such an image forming apparatus, unevenness in the rotation speed of the photosensitive drum causes poor image quality. Therefore, it is necessary to suppress unevenness in the rotation speed of the photosensitive drum as much as possible in order to improve image quality.

On the other hand, in Patent Document 1, the rotation speed of a gear downstream of a pinion gear attached to a motor that drives the photosensitive drum is detected, and the rotation speed of the photosensitive drum is feedback-controlled based on the detection result. configuration is described. With such a configuration, since the rotation speed control of the photosensitive drum is not affected by the shaft vibration of the motor and the eccentricity of the pinion gear, the accuracy of the rotation speed control of the photosensitive drum is improved.

JP 2011-27933 A

However, in the configuration described in Patent Document 1, the eccentricity and shape deflection of the gear whose rotation speed is to be detected affects the rotation speed control of the photosensitive drum. Therefore, the rotation speed control of the photosensitive drum, which is the driven body, is deteriorated, and there is a possibility that an image defect may occur.

Therefore, the present invention has been made in view of such a situation, and is capable of suppressing deterioration in accuracy of rotation speed control of a driven body due to eccentricity and shape deflection of a gear whose rotation speed is to be detected. It is an object of the present invention to provide a driving device capable of

A representative configuration of the drive device according to the present invention for achieving the above object is a motor having a first gear attached to a rotating shaft and applying a rotational driving force to a driven body; A second gear that is attached and rotates when the rotational driving force of the motor is transmitted through the first gear meshes with the second gear or a third gear that rotates in conjunction with the second gear. a fourth gear; a fifth gear that meshes with the fourth gear and has the same shape as the fourth gear;
a speed detecting means for detecting the rotational speed of the fifth gear; and a control section for controlling the motor based on the detection result of the speed detecting means to control the rotational speed of the driven body, In the 4th gear, the rotation angle from the meshing position with respect to the 2nd gear or the 3rd gear to the meshing position with respect to the 5th gear is α, and the meshing position of the 4th gear with respect to the 2nd gear or the 3rd gear. the phase of the position of the corresponding portion of the fifth gear corresponding to the predetermined portion, and the phase of the engagement position of the fifth gear with respect to the fourth gear when the predetermined portion of the fourth gear is positioned at , the angular velocity of the fourth gear is ω, and the time is t, sin(ωt−α)−sin(ωt)−sin(ωt+β)=0 The fourth gear and the fifth gear are arranged.

Advantageous Effects of Invention According to the present invention, in a driving device, it is possible to suppress a decrease in the accuracy of rotational speed control of a driven body due to eccentricity or shape deflection of a gear whose rotational speed is to be detected.

1 is a schematic cross-sectional view of an image forming apparatus; FIG. 1 is a schematic diagram of a drive; FIG. FIG. 4 is a schematic diagram of another configuration of the driving device; It is a graph which shows the result of a comparative test. It is a schematic diagram of the drive device concerning a modification. 1 is a schematic diagram of a drive; FIG. 4 is a graph showing variations in rotation speed of a rotation detection gear and a pinion gear; 1 is a schematic diagram of a drive; FIG.

(First embodiment)
<Image forming apparatus>
Hereinafter, the overall configuration of an image forming apparatus including a driving device according to the first embodiment of the present invention will be described together with the operation during image formation with reference to the drawings.

FIG. 1 is a schematic cross-sectional view of the image forming apparatus A. As shown in FIG. As shown in FIG. 1, the image forming apparatus A includes an image forming section for transferring a toner image onto a sheet, a sheet feeding section for feeding the sheet toward the image forming section, and a fixing section for fixing the toner image on the sheet. Prepare.

The image forming section includes a process cartridge 60 that can be attached to and detached from the apparatus main body of the image forming apparatus A, an optical scanning device 70, a transfer roller 31, and the like. The process cartridge 60 also includes a photosensitive drum 61 as a photosensitive member, a charging roller 62, a developing device 63, and the like.

Next, the image forming operation will be described. 2 receives an image forming job signal, the sheets S stacked and accommodated in the sheet stacking section 10 are sent to the image forming section by the feeding roller 11 and the conveying roller 20 for image formation.

In the image forming section, the surface of the photosensitive drum 61 in contact with the charging roller 62 is charged by applying a bias to the charging roller 62 . After that, a laser beam is emitted from the optical scanning device 70, and the photosensitive drum 61, which is a photosensitive member and a driven member, is irradiated with the laser beam according to image information. As a result, the potential of the photosensitive drum 61, which is both a photosensitive member and a driven member, is partially lowered, and an electrostatic latent image corresponding to image information is formed on the surface of the photosensitive drum 61. FIG.

Next, a bias is applied to the developing sleeve 64 provided in the developing device 63 to cause toner to adhere from the developing sleeve 64 to the electrostatic latent image formed on the surface of the photosensitive drum 61 . As a result, a toner image corresponding to the image information is formed on the surface of the photosensitive drum 61 which is both a photosensitive member and a driven member, and the toner image is carried on the surface of the photosensitive drum 61 .

Next, the toner image carried on the photosensitive drum 61 is sent to a transfer nip portion formed by the photosensitive drum 61 and the transfer roller 31 . When the toner image reaches the transfer nip portion, a bias having a polarity opposite to the charging polarity of the toner is applied to the transfer roller 31 to transfer the toner image onto the sheet S. FIG.

After that, the sheet S having the toner image transferred thereon is sent to the fixing device 40, and heated and pressurized in the process of passing through the fixing nip portion of the fixing device 40, so that the toner image is thermally melted and thermally fixed to the sheet S. . After that, the sheet S is discharged to the discharge section 51 by the discharge rollers 50 .

<Driving device>
Next, the driving device 4 for rotating the photosensitive drum 61, which is both a photosensitive member and a driven member, will be described.

FIG. 2 is a schematic diagram of the drive device 4 . As shown in FIG. 2 , the drive device 4 includes a motor 21 as a drive source and a pinion gear 22 as a first gear attached to a rotating shaft 21 a of the motor 21 . Further, a photoreceptor gear 23 as a second gear attached to the rotating shaft 61a of the photoreceptor drum 61, a pinion gear 22 as a first gear, and a third gear meshing with the photoreceptor gear 23 as a second gear. A first idler gear 25 is provided. The first idler gear 25 as the third gear is a two-stage gear that rotates in conjunction with the pinion gear 22 by the rotational driving force of the motor 21 .

Further, the driving device 4 includes a second idler gear 26 as a fourth gear that meshes with the first idler gear 25, a rotation detection gear 24 as a fifth gear that meshes with the second idler gear 26, and rotation of the rotation detection gear 24. It has a rotation detection sensor 27 as speed detection means for detecting speed. Since the second idler gear 26 as the fourth gear and the rotation detection gear 24 as the fifth gear are members of the same shape formed by the same mold, both have the same amplitude and period during rotation. . Note that C4 shown in FIG. 2 is the rotation center of the rotation detection gear 24 . Also, the first idler gear 25 and the rotation detection gear 24 are not meshed.

The second idler gear 26 as the fourth gear and the rotation detection gear 24 as the fifth gear are provided with ribs 24a, 26a for visually recognizing the phase during assembly. In order to stabilize the rotation speed, the rotation detection gear 24 is loaded by the frictional force of a spring (not shown) or a torque limiter (not shown). The structure for visually recognizing the phase is not limited to the ribs 24a and 26a, and may be, for example, a stamp or a hole.

A rotation detection sensor 27 as speed detection means detects the rotation speed of the rotation detection gear 24 via a flag (not shown). In this embodiment, the flag (not shown) is a code wheel that rotates together with the rotation detection gear 24 . The rotation detection sensor 27 as speed detection means is a photointerrupter fixed to a frame (not shown) and having a light emitting element and a light receiving element, and detects interruption of light when a flag (not shown) passes between the two elements. do. Note that the rotation detection gear 24 and the flag may be integrally formed.

The drive device 4 also includes a controller 28 having a CPU and a memory, and a motor driver 29 that supplies a drive current to the motor 21 according to the control of the controller 28 . A detection result of the rotation speed of the rotation detection gear 24 by the rotation detection sensor 27 as detection means is input to the control unit 28 . The control unit 28 compares this detection result with the target rotational speed, and transmits an acceleration signal and a deceleration signal to the motor driver 29 .

The motor driver 29 supplies drive current to the motor 21 according to the transmitted signal. When a drive current is supplied to the motor 21, the rotating shaft 21a of the motor 21 rotates, and accordingly the pinion gear 22 as the first gear rotates. The rotational driving force of the motor 21 is transmitted to the photoreceptor gear 23 as the second gear through the pinion gear 22 as the first gear and the first idler gear 25 as the third gear, thereby rotating the photoreceptor drum 61. The shaft 61a rotates. As the rotating shaft 61a of the photosensitive drum 61 rotates, the photosensitive drum 61 rotates. The controller 28 thus performs feedback control so that the rotational speed of the photosensitive drum 61 reaches the target rotational speed.

<Gear arrangement>
Next, the arrangement of the second idler gear 26 and the rotation detection gear 24 will be described.

In the rotation speed control of the photosensitive drum 61, if the rotation detection gear 24, which is the gear for speed detection, has eccentricity or deviation in shape, the rotation speed of the rotation detection gear 24 becomes uneven. Accuracy of the rotation speed control of the photosensitive drum 61 is degraded. Therefore, by arranging the second idler gear 26 as the fourth gear and the rotation detection gear 24 as the fifth gear as described below, the photosensitive drum caused by the eccentricity and shape deflection of the rotation detection gear 24 can be 61 to suppress the deterioration of the accuracy of the rotation speed control.

First, the angular velocity of the second idler gear 26 at the meshing position between the first idler gear 25 and the second idler gear 26 is considered. Let V25 [mm/s] be the peripheral velocity of the first idler gear 25, r26 [mm] be the radius of the second idler gear 26, ω26 [rad/s] be the angular velocity, and t [s] be the time.

Here, since the radius of the second idler gear 26 includes eccentricity and shape runout components, the runout component Asin(ωt) [mm] is added to the ideal radius r1 [mm] without eccentricity and shape runout. can be thought of as That is, r26=r1+A sin(ωt). Also, since the first idler gear 25 and the second idler gear 26 are meshed, the circumferential speeds of both at the meshing position are the same. Therefore, the angular velocity ω26 of the second idler gear 26 can be obtained from the following equation (1).

(Formula 1)

Next, consider the peripheral speed of the second idler gear 26 at the meshing position between the second idler gear 26 and the rotation detecting gear 24 . Let V26 [mm/s] be the circumferential velocity of the second idler gear 26 at the meshing position, and α be the rotation angle from the meshing position of the second idler gear 26 with respect to the first idler gear 25 to the meshing position with respect to the rotation detection gear 24 . At this time, V26 can be obtained from the following equation 2.

(Formula 2)

Next, the angular velocity of the rotation detection gear 24 at the meshing position between the second idler gear 26 and the rotation detection gear 24 will be considered. Assume that the radius of the rotation detection gear 24 is r24 [mm] and the angular velocity is ω24 [rad/s]. As described above, since the rotation detection gear 24 has the same shape as the second idler gear 26, it can be considered that they have the same radius. That is, if the phase difference between the meshing position of the second idler gear 26 with respect to the first idler gear 25 and the meshing position of the rotation detection gear 24 with respect to the second idler gear 26 is β, then r24=r1+A sin(ω26t+β). Also, since the first idler gear 25 and the second idler gear 26 are meshed, the peripheral speeds of both at the meshing position are the same. Therefore, the angular velocity ω24 of the rotation detection gear 24 can be obtained from the following equation (3).

(Formula 3)

Next, consider a case where the rotation detection gear 24 has no eccentricity or shape deflection and the angular velocity of the rotation detection gear 24 is constant. The angular velocity of the rotation detection gear 24 at this time can be represented by V25/r1. Here, the difference value of the angular velocities between when the rotation detection gear 24 has eccentricity and shape deflection and when it does not can be obtained from the following equation 4.

In the denominator {(r1+Asin(ω26t)}{r1+Asin(ω26t+β) in the following equation 4, since A2 is minute with respect to r12 and r1A, r1(r1+Asin(ω26t)+Asin(ω26t-β ), that is, A is an error component and is very small with respect to r1, so the approximation is performed as described above.

(Formula 4)

Here, the second idler gear 26 and the rotation detection gear 24 are arranged by setting the angles α and β so that sin(ω26t−α)−sin(ω26t)−sin(ω26t+β)=0 in Equation 4. As a result, the eccentricity of the rotation detection gear 24 and the vibration component of the shape can be almost cancelled. In other words, the eccentricity and shape deflection components of the rotation detection gear 24 are not necessarily sinusoidal waves. Since they fluctuate with the same amplitude, they can be almost cancelled.

In this embodiment, sin(ω26t−α)−sin(ω26t)−sin(ω26t+β)=0 is satisfied when α=60° and β=240° or when α=300° and β=120°. be Therefore, the second idler gear 26 and the rotation detection gear 24 are arranged with the angles α and β set to α=60° and β=240°. The angles α and β are adjusted while visually checking the ribs 24a and 26a.

By arranging the second idler gear 26 and the rotation detection gear 24 with the angles α and β determined in this way, the eccentricity and shape deflection components of the rotation detection gear 24, which is the gear whose rotational speed is to be detected, can be eliminated. almost can be cancelled. Therefore, in the driving device 4, it is possible to suppress deterioration in the accuracy of the rotation speed control of the photosensitive drum 61 due to the eccentricity and shape deflection of the rotation detection gear 24, which is the gear whose rotation speed is to be detected.

In this embodiment, the phase of the engagement position of the rotation detection gear 24 with respect to the second idler gear 26 is shifted clockwise by 240 degrees from the phase of the engagement position of the second idler gear 26 with respect to the first idler gear 25. . However, as shown in FIG. 3, it may be configured to displace 240 degrees in the counterclockwise direction.

Although it is desirable that the angles α and β are set to the angles described above, if α and β are determined so as to satisfy the following Equation 5, the eccentricity of the rotation detection gear 24 and the vibration of the shape of the rotation detection gear 24 will cause exposure to light. It is possible to suppress a decrease in the accuracy of rotational speed control of the drum 61 .

(Formula 5)
cos(α+β)+cos(α)−cos(β)>1

This expression 5 is an expression comparing the configuration of this embodiment with the following configuration. That is, the configuration of this embodiment and the second idler gear 26 are not provided, and the rotation detection gear 24 is arranged at the position of the second idler gear 26, and based on the rotation speed of the rotation detection gear 24 detected by the rotation detection sensor 27, It is a formula comparing configurations in which the control unit 28 controls the motor 21 . Equation 5 is derived from the condition that Equation 4 is smaller than Equation 1. That is, the following formula 6 is solved.

(Formula 6)

In addition, the larger the value of Equation 5, the greater the effect of suppressing the deterioration of the accuracy of the rotation speed control of the photosensitive drum 61. sometimes takes a maximum value of 1.5. Therefore, if α = 60° (or 300°) and β = 240° (or 120°) cannot be set due to gear arrangement restrictions, the angles α and β are determined so as to satisfy Equation 5, It is possible to suppress a decrease in the accuracy of rotational speed control of the photosensitive drum 61 .

Moreover, the second idler gear 26 preferably has a configuration in which it meshes with a gear that is not decelerating from the pinion gear 22 . Furthermore, it is preferable that the number of teeth of the second idler gear 26 and the rotation detection gear 24 is as small as possible. This is because when the rotation speed of the rotation detection gear 24 is low, the accuracy of rotation detection of the rotation detection gear 24 is lowered.

Further, the angle θ between the straight line connecting the rotation center C1 of the pinion gear 22 and the rotation center C2 of the first idler gear 25 and the straight line connecting the rotation center C3 of the second idler gear 26 and the rotation center C2 of the first idler gear 25 is preferably as small as possible. This is to reduce the phase difference between the phase when driving force is transmitted from the pinion gear 22 and the phase when driving force is transmitted to the second idler gear 26 in the first idler gear 25 . As a result, the eccentric component during one rotation of the first idler gear 25 as the third gear can be reduced in the rotational speed control of the photosensitive drum 61 . It is also possible to set θ to approximately 0° by, for example, widening the tooth width of the first idler gear 25 as the third gear.

<Comparative experiment>
Next, the results of comparative experiments comparing changes in the angular velocity of the rotation detection gear 24 between the configuration of the comparative example and the configuration of the present embodiment will be described. Here, in the configuration of the comparative example, the second idler gear 26 is not provided, the rotation detection gear 24 is arranged at the position of the second idler gear 26, and the rotational speed of the rotation detection gear 24 detected by the rotation detection sensor 27 is detected. , the control unit 28 controls the motor 21 .

FIG. 4(a) is a graph showing the results of the comparative test. FIG. 4(b) is a graph showing fluctuations in rotational speed during one rotation of the rotation detection gear 24 and the second idler gear 26 according to this embodiment. Here, in the graph shown in FIG. 4B, the rotation speed of the second idler gear 26 indicates the rotation speed at the meshing position of the second idler gear 26 with the rotation detection gear 24 . The rotation speed of the rotation detection gear 24 indicates the rotation speed at the detection position of the rotation detection sensor 27 in the rotation detection gear 24 .

As shown in FIG. 4A, the variation in angular velocity of the rotation detection gear 24 according to this embodiment is greatly reduced compared to the variation in angular velocity of the rotation detection gear 24 according to the comparative example. Specifically, the amplitude is reduced to about half. This is because, in the configuration of the present embodiment, by providing the second idler gear 26 and setting the angles α and β as described above, eccentricity and shape between the second idler gear 26 and the rotation detection gear 24 can occur. This is because the vibration component is canceled. That is, as shown in FIG. 4B, the second idler gear 26 and the rotation detection gear 24 have the same amplitude and are out of phase with each other by 180°. This is because the component was canceled. From such an experiment, it was confirmed that since fluctuations in the angular velocity of the rotation detection gear 24 are suppressed, the decrease in accuracy of the rotation speed control of the photosensitive drum 61 can be suppressed by the configuration of the present embodiment.

It should be noted that fluctuations in the circumferential speed of the second idler gear 26 are caused by eccentricity in one rotation period, and fluctuations in the angular velocity are caused by gear accuracy. Also, the fluctuation of the peripheral speed of the second idler gear 26 is the sum of the fluctuation of the angular speed and the fluctuation of the peripheral speed when the angular speed is assumed to be constant. The angular velocity of the rotation detection gear 24 is the sum of the angular velocity when the peripheral velocity of the rotation detection gear 24 is assumed to be constant and the fluctuation of the peripheral velocity of the second idler gear 26 .

<Modification>
Next, as a modified example of the first embodiment, a configuration of the drive device 4 that does not use the first idler gear 25 will be described.

FIG. 5 is a schematic diagram of a drive device 4 according to a modification. As shown in FIG. 5, the driving device 4 according to the modification meshes the pinion gear 22 with the photoreceptor gear 23 as the second gear, and on the downstream side of the photoreceptor gear 23, the second idler gear 26 and the photoreceptor gear are engaged. 23 are engaged.

Here, the rotation angle from the engagement position of the second idler gear 26 with respect to the photoreceptor gear 23 to the engagement position with respect to the rotation detection gear 24 is α'. The phase difference between the engagement position of the second idler gear 26 with respect to the photoreceptor gear 23 and the engagement position of the rotation detection gear 24 with respect to the second idler gear 26 is defined as β'. Let time be t, and rotation detection gear 24 be ω.

At this time, the rotation detecting gear 24 and the second idler gear 26 are arranged so that sin(ω26t−α′)−sin(ω26t)−sin(ω26t+β′)=0 is satisfied. As a result, the eccentricity of the rotation detection gear 24 and the vibration component of the shape can be almost cancelled. This is obtained by replacing α with α', β with β', and V25, which is the peripheral speed of the first idler gear 25, with V23, which is the peripheral speed of the photoreceptor gear 23, in Equations 1 to 4 of the first embodiment. be guided. Therefore, as in the first embodiment, in the driving device 4, the accuracy of the rotation speed control of the photosensitive drum 61 is lowered due to the eccentricity and shape deflection of the rotation detection gear 24, which is the gear whose rotation speed is to be detected. can be suppressed.

Although it is desirable to set the angles α' and β' to the angles described above, if α' and β' are determined so as to satisfy the following equation 7, the eccentricity of the rotation detecting gear 24 and the vibration of the shape can be prevented. Therefore, it is possible to suppress the deterioration in the accuracy of the rotation speed control of the photosensitive drum 61 caused by this. Equation 7 is obtained by replacing α with α' and β with β' in Equation 5 of the first embodiment.

(Formula 7)
cos(α'+β')+cos(α')-cos(β')>1

Further, the angle θ between the straight line connecting the rotation center C1 of the pinion gear 22 and the rotation center C5 of the photoreceptor gear 23 and the straight line connecting the rotation center C3 of the second idler gear 26 and the rotation center C5 of the photoreceptor gear 23 ' is preferably as small as possible. This is to reduce the phase difference between the phase when the driving force is transmitted from the pinion gear 22 and the phase when the driving force is transmitted to the second idler gear 26 in the photoreceptor gear 23 . As a result, the eccentric component during one rotation of the photoreceptor gear 23 can be reduced by controlling the rotation speed of the photoreceptor drum 61 . It is also possible to make .theta.' substantially 0.degree.

In the above-described first embodiment and modified example, feedback control is performed as control of the rotation speed of the photosensitive drum 61, but feedback control causes a loss in signal response time. Further, as described above, it is not possible to completely cancel the rotational speed fluctuations due to the eccentricity of the rotation detection gear 24 and the deflection of the shape. Therefore, in order to reduce the loss of response time, the motor 21 may be feedforward controlled.

Specifically, information that associates the phase of the rotation detection gear 24 with the value of the current for driving the motor 21 is stored in advance in a memory (not shown) as a storage unit of the control unit 28 . The current value for driving the motor 21 is a current value that can reduce the amount of deviation of the angular velocity of the rotation detection gear 24 detected by the rotation detection sensor 27 from the target velocity. Note that the value of this current is the value of the current that flows to the motor 21 to correct the eccentricity and shape deflection components of the pinion gear 22 and the first idler gear 25 that are arranged upstream of the rotation detection gear 24 in the gear train. Also a value. This information is measured by, for example, a rotary encoder, linear encoder, laser Doppler meter, or the like.

Further, in order to determine the phase at the start of feedforward control, the rotation detection sensor 27 detects one rotation of the rotation detection gear 24 with respect to a flag (not shown) of the rotation detection gear 24. set up. For example, this detection unit makes the interval between one slit of the code wheel wider than that of the other slits, and detects one rotation at the timing when the rotation detection sensor 27 detects the slit for a long time. That is, the rotation detection sensor 27 is speed detection means for detecting the rotation speed of the rotation detection gear 24 and also phase detection means for detecting the phase of the rotation detection gear 24 .

The control unit 28 starts feedforward control at the timing when the rotation detection sensor 27 as phase detection means detects one rotation of the rotation detection gear 24 . The control unit 28 determines the current to be supplied to the motor 21 according to the phase detected by the rotation detection sensor 27 as phase detection means and information stored in a memory (not shown) as a storage unit. It controls the motor 21 via the driver 29 .

As a result, the loss of the signal response time is reduced, and the deterioration of the accuracy of the rotation speed control of the photosensitive drum 61 due to the eccentricity and shape deflection of the rotation detection gear 24, which is the gear whose rotation speed is to be detected, is prevented. can be suppressed.

(Second embodiment)
Next, a configuration of an image forming apparatus A including a driving device according to a second embodiment of the invention will be described. The same reference numerals are given to the portions whose description overlaps with that of the first embodiment, and the description thereof is omitted.

FIG. 6 is a schematic diagram of the driving device 4 according to this embodiment. As shown in FIG. 6, in this embodiment, the rotation detection gear 24 is meshed with the first idler gear 25 . The pinion gear 22 and the rotation detection gear 24 are members of the same shape formed by the same mold, and both are provided with ribs 24a and 22a for visually recognizing the phase during assembly. Other configurations are the same as those of the first embodiment.

In such a configuration, the phase of the engagement position of the pinion gear 22 with respect to the first idler gear 25 and the phase of the engagement position of the rotation detection gear 24 with respect to the first idler gear 25 are made the same. In other words, the phase difference between the pinion gear 22 and the rotation detection gear 24 is defined by a straight line connecting the rotation center C1 of the pinion gear 22 and the rotation center C2 of the first idler gear 25, and a rotation center C5 of the rotation detection gear 24 and the second It is made equal to the angle θ3 formed with the straight line connecting the rotation center C2 of the idler gear 25 .

As a result, when detecting the rotational speed of the rotation detection gear 24 , similar eccentricity and shape vibration components of the rotation detection gear 24 are added to the eccentricity and shape vibration components of the pinion gear 22 . That is, as shown in FIG. 7, the rotational speed fluctuation due to the eccentricity and shape deflection of the rotation detecting gear 24 is detected as a value twice the rotational speed fluctuation due to the pinion gear 22 eccentricity and profile deflection. reflected in

このような演算を行うことで、制御部は誤差成分の１／２を打ち消すように制御することができる。 Here, the control unit 28 performs control such that the fluctuation of the controlled object is canceled by 1/2. There are various control methods, but one example is a method of adjusting with a control gain. Normally, the control gain is adjusted and set to a value that can cancel out the variation, but in this embodiment, the control gain is made weaker than usual and set to a value that cancels out the variation by 1/2. As another method, there is a method of performing control after performing the following calculations when the motor driver 29 performs calculations. Assuming that the detected rotation speed is ω and the target rotation speed is ωc, the error information Δω given to the control unit is given as follows.

By performing such calculation, the control unit can perform control so as to cancel out 1/2 of the error component.

As a result, the eccentric component during one rotation of the rotation detecting gear 24 can be canceled. Note that the eccentricity of the pinion gear 22 and the vibration component of the shape are not affected by the rotation speed control because the rotation detection gear 24 on the downstream side of the pinion gear 22 is targeted for rotation speed detection.

Therefore, according to the configuration of the present embodiment, in the driving device 4, the accuracy of the rotation speed control of the photosensitive drum 61 is reduced due to the eccentricity and shape deflection of the rotation detection gear 24, which is the gear whose rotation speed is to be detected. Decrease can be suppressed.

Although one or more idler gears may be interposed between the photoreceptor gear 23 and the pinion gear 22, one idler gear is desirable in order to reduce control disturbances and improve accuracy. Alternatively, the photoreceptor gear 23 and the rotation detection gear 24 may be meshed without using a reduction gear.

(Third Embodiment)
Next, a configuration of an image forming apparatus including a driving device according to a third embodiment of the invention will be described. The same reference numerals are given to the portions whose explanation overlaps with those of the first embodiment and the second embodiment, and explanations thereof are omitted.

FIG. 8 is a schematic diagram of the driving device 4 according to this embodiment. As shown in FIG. 8, in this embodiment, the number of teeth of the first idler gear 25 is an integral multiple of the number of teeth of the rotation detection gear 24, and the number of teeth of the photosensitive gear 23 is These three gears are configured to have integral multiples of the number of teeth, and these three gears are always rotated in a predetermined phase relationship.

A flag (not shown) of the rotation detection gear 24 is provided with a detection portion similar to that described above for the rotation detection sensor 27 to detect one rotation of the rotation detection gear 24 . Other mechanical configurations are the same as those of the second embodiment.

The controller 28 controls the rotational speed of the photosensitive drum 61 using both feedforward control and feedback control. A memory (not shown) as a storage unit in the control unit 28 stores the phase of the rotation detection gear 24 and a correction value for correcting the rotational speed of the rotation detection gear 24 detected by the rotation detection sensor 27. Associated information is stored in advance. This correction value is a correction value for correcting the eccentricity of the rotation detection gear 24 and the vibration component of the shape.

When controlling the rotation speed of the photosensitive drum 61, first, the rotation detection sensor 27, which is both speed detection means and phase detection means, detects one rotation of the rotation detection gear 24 as the third gear. Next, the control unit 28 detects the rotation speed of the rotation detection gear 24 detected by the rotation detection sensor 27 based on the phase of the rotation detection gear 24 and information stored in a memory (not shown) as a storage unit. to correct. Then, the motor 21 is feedback-controlled via the motor driver 29 so that the corrected rotational speed becomes the target speed.

When the rotation detection sensor 27 detects the rotation speed of the rotation detection gear 24 in this way, by correcting the eccentric component of the rotation detection gear 24 by feedforward control, unevenness in the rotation speed of the photosensitive drum 61 is reduced. can do. In addition, by performing feedback control according to the rotation speed of the rotation detection gear 24, which is a gear downstream of the pinion gear 22 in the gear train, the shaft runout of the motor 21 and the eccentric component of the pinion gear 22 can be corrected. can be done. Therefore, according to the configuration of the present embodiment, in the driving device 4, the accuracy of the rotation speed control of the photosensitive drum 61 is reduced due to the eccentricity and shape deflection of the rotation detection gear 24, which is the gear whose rotation speed is to be detected. Decrease can be suppressed.

In the present embodiment, when correcting the rotation speed of the rotation detection gear 24 detected by the rotation detection sensor 27 from the phase and the information in the memory, the controller 28 corrects the shaft runout and eccentricity of the photoreceptor gear 23 . A configuration may be adopted in which correction is performed in consideration of information regarding components. As a result, the shaft runout and eccentricity of the photoreceptor gear 23 are corrected, so that it is possible to further suppress the deterioration of the accuracy of the rotation speed control of the photoreceptor drum 61 .

Further, in this embodiment, the pinion gear 22 and the rotation detection gear 24 do not necessarily have the same shape. By setting the number of teeth of the pinion gear 22 and the number of teeth of the rotation detection gear 24 to be different and not to be integral multiples of each other, it becomes difficult to disturb the control.

In the first to third embodiments, spur gears are used as the pinion gear 22, the first idler gear 25, the second idler gear 26, and the rotation detection gear 24, but helical gears may be used. By using a helical gear, reducing the tooth module, or increasing the meshing face width, it is possible to reduce the transmission error at the meshing portion of each gear.

4... Drive device 21... Motor 21a... Rotating shaft (rotating shaft of motor)
22... Pinion gear (first gear)
23 Photoreceptor gear (second gear)
24 ... Rotation detection gear (fifth gear, third gear)
25... First idler gear (third gear)
26... Second idler gear (fourth gear)
27 Rotation detection sensor (speed detection means, phase detection means)
28... Control unit 61... Photosensitive drum (photosensitive member, driven member)
61a... Rotating shaft (rotating shaft of driven body)
A... Image forming apparatus

Claims (5)

a motor having a first gear attached to a rotating shaft and applying a rotational driving force to a driven body;
a second gear attached to a rotating shaft of a driven body and rotated by transmission of the rotational driving force of the motor via the first gear;
a fourth gear that meshes with the second gear or with a third gear that rotates in conjunction with the second gear;
a fifth gear meshing with the fourth gear, the fifth gear having the same shape as the fourth gear;
speed detection means for detecting the rotation speed of the fifth gear;
a control unit that controls the motor based on the detection result of the speed detection means and controls the rotational speed of the driven body;
with
Let α be a rotation angle of the fourth gear from the meshing position with respect to the second gear or the third gear to the meshing position with respect to the fifth gear,
position of the corresponding portion of the fifth gear corresponding to the predetermined portion when the predetermined portion of the fourth gear is positioned at the meshing position of the fourth gear with respect to the second gear or the third gear; β is the phase difference between the phase and the phase of the engagement position of the fifth gear with respect to the fourth gear,
When the angular velocity of the fourth gear is ω and the time is t,
sin(ωt−α)−sin(ωt)−sin(ωt+β)=0
A driving device characterized in that the fourth gear and the fifth gear are arranged so as to satisfy: a motor having a first gear attached to a rotating shaft and applying a rotational driving force to a driven body;
a second gear attached to a rotating shaft of a driven body and rotated by transmission of the rotational driving force of the motor via the first gear;
a fourth gear that meshes with the second gear or with a third gear that rotates in conjunction with the second gear;
a fifth gear meshing with the fourth gear, the fifth gear having the same shape as the fourth gear;
speed detection means for detecting the rotation speed of the fifth gear;
a control unit that controls the motor based on the detection result of the speed detection means and controls the rotational speed of the driven body;
with
Let α be a rotation angle of the fourth gear from the meshing position with respect to the second gear or the third gear to the meshing position with respect to the fifth gear,
position of the corresponding portion of the fifth gear corresponding to the predetermined portion when the predetermined portion of the fourth gear is positioned at the meshing position of the fourth gear with respect to the second gear or the third gear; When the phase difference between the phase and the phase of the engagement position of the fifth gear with respect to the fourth gear is β,
cos(α+β)+cos(α)−cos(β)>1
A driving device characterized in that the fourth gear and the fifth gear are arranged so as to satisfy: a motor having a first gear attached to a rotating shaft and applying a rotational driving force to a driven body;
a second gear attached to a rotating shaft of a driven body and rotated by transmission of the rotational driving force of the motor via the first gear;
a fourth gear that meshes with the second gear or with a third gear that rotates in conjunction with the second gear;
a fifth gear meshing with the fourth gear, the fifth gear having the same shape as the fourth gear;
phase detection means for detecting the phase of the fifth gear;
a storage unit that stores information that associates the phase of the fifth gear with the value of the current that drives the motor;
a control unit that controls the motor and the rotational speed of the driven body based on the phase detected by the phase detection means and the information stored in the storage unit;
with
Let α be a rotation angle of the fourth gear from the meshing position with respect to the second gear or the third gear to the meshing position with respect to the fifth gear,
position of the corresponding portion of the fifth gear corresponding to the predetermined portion when the predetermined portion of the fourth gear is positioned at the meshing position of the fourth gear with respect to the second gear or the third gear; β is the phase difference between the phase and the phase of the engagement position of the fifth gear with respect to the fourth gear,
When the angular velocity of the fourth gear is ω and the time is t,
sin(ωt−α)−sin(ωt)−sin(ωt+β)=0
A driving device characterized in that the fourth gear and the fifth gear are arranged so as to satisfy: a motor having a first gear attached to a rotating shaft and applying a rotational driving force to a driven body;
a second gear attached to a rotating shaft of a driven body and rotated by transmission of the rotational driving force of the motor via the first gear;
a fourth gear that meshes with the second gear or with a third gear that rotates in conjunction with the second gear;
a fifth gear meshing with the fourth gear, the fifth gear having the same shape as the fourth gear;
phase detection means for detecting the phase of the fifth gear;
a storage unit that stores information that associates the phase of the fifth gear with the value of the current that drives the motor;
a control unit that controls the motor and the rotational speed of the driven body based on the phase detected by the phase detection means and the information stored in the storage unit;
with
Let α be a rotation angle of the fourth gear from the meshing position with respect to the second gear or the third gear to the meshing position with respect to the fifth gear,
position of the corresponding portion of the fifth gear corresponding to the predetermined portion when the predetermined portion of the fourth gear is positioned at the meshing position of the fourth gear with respect to the second gear or the third gear; When the phase difference between the phase and the phase of the engagement position of the fifth gear with respect to the fourth gear is β,
cos(α+β)+cos(α)−cos(β)>1
A driving device characterized in that the fourth gear and the fifth gear are arranged so as to satisfy: a photoreceptor carrying a toner image;
The driving device according to any one of claims 1 to 4 , which rotates the photoreceptor;
An image forming apparatus comprising:

Images