JP2002202368A - Imaging apparatus - Google Patents

Abstract

PROBLEM TO BE SOLVED: To realize to make an image carrier exert a high resolution and a high image quality by detecting a rotational speed of the image carrier highly accurately and inexpensively. SOLUTION: A surface velocity of the image carrier 1 is detected with the use of a detector provided with a transmitter S for transmitting ultrasonic waves fs to a surface of the image carrier 1, and a receiver O for receiving reflected waves fo reflected at the surface of the image carrier 1. Accordingly, to rotate the image carrier 1 highly accurately is realized, and the detection is enabled stably at all times without being affected by toner contamination, slide flaws or the like at an observation face of the image carrier 1.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus having an image carrier such as a photosensitive drum for electrophotography, and more particularly, to detecting a rotation speed of an image carrier and detecting an image based on the detected value. The present invention relates to an image forming apparatus that controls rotation of a carrier.

[0002]

2. Description of the Related Art Hitherto, in an image forming apparatus, the rotation of a drum of an image carrier has been detected by a rotary encoder, and the unevenness of speed has been feedback-controlled, thereby improving the quality of a printed image. However, since the rotary encoder detects the rotation of the drum shaft, it cannot detect the speed fluctuation of the photoconductor surface due to the eccentricity of the drum, and the misalignment between the drum rotation center and the encoder shaft core causes a speed error. Further, since the image carrier is attached to and detached from the apparatus at the time of maintenance replacement, a speed error occurs due to the accuracy of the detachable chucking mechanism.

Further, in order to perform highly accurate detection in such a system, a high-resolution rotary encoder is required, so that it cannot be realized at low cost. For example, in order to detect a speed fluctuation frequency component up to 200 Hz with a φ30 drum of 100 mm / s, 1000 pu1s /
rev is required, and an expensive rotary encoder is required.

As a method for solving such a problem, Japanese Unexamined Patent Publication No. Hei 8-160829 discloses a method of detecting a drum speed using a laser Doppler velocimeter, thereby enabling highly accurate speed detection of an image carrier. Techniques are disclosed.

[0005]

SUMMARY OF THE INVENTION Incidentally, Japanese Patent Application Laid-Open No.
According to drum speed detection using a laser Doppler velocimeter disclosed in Japanese Patent No. 160829, a method using reflection of laser light is used. In this case, the detection signal drops out and becomes uncontrollable. Further, when the surface of the photoconductor is measured, a malfunction is likely to occur because the reflectance of the photoconductor itself is low.

The present invention has been made in view of such circumstances, and can detect the rotation speed of an image carrier with high accuracy and at low cost, and realize high resolution and high image quality of the image carrier. It is an object of the present invention to provide an image forming apparatus capable of performing such operations.

[0007]

SUMMARY OF THE INVENTION The present invention relates to an image forming apparatus provided with a drum-shaped image carrier and a driving means for rotating the image carrier. It is characterized in that the detector is configured to detect the surface velocity of the image carrier by a detector that receives a reflected wave reflected on the surface of the image carrier.

[0008] According to the image forming apparatus of the present invention, the ultrasonic wave is transmitted to the surface of the image carrier, and the reflected wave reflected on the surface of the image carrier is detected by the detector. Since the speed of the surface is detected, the rotation speed of the image carrier can be detected with high accuracy. Thus, the rotation of the image carrier such as a photosensitive drum for electrophotography can be made highly accurate, and high resolution and high image quality can be achieved. Moreover,
Since the rotational speed is detected by a detector using ultrasonic waves, stable speed detection can be realized without being affected by toner contamination, sliding scratches, etc. on the observation surface (surface) of the image carrier. it can.

Further, since ultrasonic waves are used for detecting the rotation speed of the image carrier, there is no need to dispose the detector on the normal line of the observation surface of the image carrier, and the detector is used for observing the image carrier. It can be arranged at an angle to the normal of the surface. This increases the degree of freedom in the installation location of the detector, and can suppress an increase in the size of the image forming apparatus.

Further, by using ultrasonic waves for detecting the rotational speed of the image carrier, it is possible to detect even if the speed observation surface of the image carrier is rough, and it is possible to detect the surface other than the photosensitive surface of the image carrier. The location can be a speed observation surface, and the installation position of the detector can be the longitudinal end of the image carrier. As a result, it is possible to suppress an increase in the size of the image forming apparatus, and it is possible to realize highly accurate speed detection at low cost.

In the image forming apparatus of the present invention, if the phase of the reflected wave from the surface of the image carrier is detected, the detector can be constituted by a simpler circuit, and the speed can be detected with high accuracy. It can be realized at low cost.

In the image forming apparatus of the present invention, if the speed fluctuation is detected from the fluctuation of the phase of the reflected wave, the influence of the change in the sound speed due to the surrounding environment such as temperature and humidity can be reduced, and the image carrier can be reduced. The reliability of the speed detection value can be improved.

In the image forming apparatus of the present invention, it is preferable that the transmission wave of the detector is an intermittent pulse. If the intermittent pulse is used, the phase shift from the reception wave can be easily recognized, and high accuracy can be achieved. Speed detection can be realized at low cost.

In the image forming apparatus according to the present invention, if a window (mask processing) is applied to the received wave received by the detector, only the period permitted by the window can be used as an effective signal, and As a result, the reliability of the speed detection value of the image carrier can be increased.

In the image forming apparatus according to the present invention, the speed of the image carrier is controlled by PLL control, and a phase signal detector for obtaining a phase signal for performing the PLL control is provided. Thus, the PLL control of the image carrier can be easily realized, and the problem of the accumulated error generated only by the velocity signal due to the Doppler effect can be solved. As a result, the rotation of the image carrier can be further improved, and a higher resolution and higher quality image can be obtained.

In the image forming apparatus of the present invention, the angle of the tangent of the center of the reflection position of the image carrier to the surface of the image carrier from the vertical direction is n degrees, and the tangent of the center of the transmission wave (center of the transmitter) and the center of the reflection position. Is θs, and the angle between the center of the received wave (the center of the receiver) and the tangent of the center of the reflection position is θo degrees. When n ≦ θs ≦ n + 90, n ≦ θo ≦ n + 90.
Or, when n + 90 ≦ θs ≦ n + 180, n + 90
If ≤θo ≤n + 180, and the installation positions of the transmitter and the receiver (or the transmitting element and the receiving element) constituting the detector are in the same quadrant, the received wave with respect to the transmitted wave can be received with high sensitivity.

In the image forming apparatus of the present invention, if the transmitting element for transmitting the ultrasonic wave to the surface of the image carrier and the receiving element for receiving the reflected wave reflected on the surface of the image carrier are used, The detector can be reduced in size and the number of parts can be reduced, and the size of the image forming apparatus can be suppressed.

[0018]

Embodiments of the present invention will be described below with reference to the drawings.

FIG. 1 is a perspective view schematically showing the main structure of the image forming apparatus of the present invention.

The image forming apparatus of this embodiment includes a drum-shaped image carrier 1, a drum motor 3 for rotating the image carrier 1, and an encoder 2 for detecting the rotation speed of the image carrier 1.

As a surface speed detecting system for detecting the surface speed of the image carrier 1, a transmitter S for irradiating the surface (observation surface) of the image carrier 1 with an ultrasonic wave, and a reflection at the surface of the image carrier 1 A receiver O for detecting the reflected wave is provided, and in this surface velocity detection system, the rotation speed of the image carrier 1 is detected by the Doppler effect of the ultrasonic reflected sound, thereby realizing highly accurate detection. are doing. The specific method will be described below.

First, in the configuration of FIG. 1, the transmitter S
Ultrasonic waves of the reference frequency fs are irradiated on the observation surface of the image carrier 1, and the reflected wave from the observation surface is received by the receiver O. The frequency of the received wave fo is a frequency obtained by adding the Doppler effect to the transmitted wave fs when the surface of the image carrier 1 which is the observation surface is moving (rotating) at the speed V.

The general formula based on the Doppler effect is as follows.

Fo = [(C−Vo) / (C−Vs)] · fs ··· s: sound source o: observer V: moving speed C: sound speed f:
From this equation, when the transmission wave fs is reflected on the surface of the image carrier 1 (FIG. 1), fo = [1 + V (COSθs + COSθo) / C)] fsV = C (fo / fs−1) / (COSθs + COSθo)... Here, the general formula of the sound speed C is as follows: C = 331.5 + 0.607 · T (m / s) T: Ambient temperature [° C.] (At 15 ° C., the sound speed C = 340 m
/ S). Therefore, by detecting the reception wave fo by the receiver O, the moving speed V of the image carrier 1 is obtained from the above equation.
Can be requested.

In the above-described detection method, the receiving wave fo is detected by the receiver O, and the moving speed V of the image carrier 1 is obtained based on the following equation. The method to be determined will be described with reference to FIG. FIG. 2 shows the transmission wave fs at the transmitter S and the reception wave fo at the receiver O.
It is a time chart.

As shown in FIG. 2, the received wave fo is formed with a phase shifted by t1, t2 or t3 with respect to the transmitted wave fs, and this phase shift is caused by the image carrier of FIG. It is determined by the moving speed of the body 1. Therefore, if the phase of the reception wave fo is detected by the receiver O and the phase fluctuation between the transmission wave fs and the reception wave fo is detected, the moving speed of the image carrier 1 can be obtained.

As described above, in order to easily detect the phase fluctuation between the transmission wave fs and the reception wave fo, the transmission wave fs may be an intermittent pulse as shown in FIG.

As shown in FIG. 2, there is a possibility that noise is mixed in the received wave fo, and when this noise is detected, the phase difference between the transmitted wave fs and the received wave fo is erroneously recognized. Therefore, a wind signal as shown in FIG. 2 is provided, and the logical product of the received wave fo and the wind signal and the transmitted wave f
If the phase difference from s is detected, the influence of noise can be suppressed.

Next, a system for controlling the moving speed of the image carrier 1 by PLL using the above surface speed detecting system will be described.
This will be described with reference to the block in FIG.

In the system shown in FIG. 3, a rotation signal of the image carrier 1 is detected by the encoder 2, and the detected value of the encoder 2 and the reference clock CL 2 are input to the PLL circuit 5. P
The output from the LL circuit 5 and the output from the counting circuit 6 are added and input to the drum motor drive circuit 4.

In the counting circuit 6, the phase difference between the transmitted and received waves between the transmitter S and the receiver O is recognized by the counting circuit 6 based on a window created from the reference clock CL1, and the speed of the moving speed of the image carrier 1 is determined. The difference is output.

Therefore, in the drum motor drive circuit 4, the phase difference between the moving speed of the image carrier 1 detected by the encoder 2 and the speed difference between the moving speeds detected by the transmitter S and the receiver O are calculated. The driving amount of the drum motor input to the drum motor driving circuit 4 is corrected as needed,
As a result, highly accurate rotation of the drum motor 3 can be realized.

Here, in the above embodiment, since the ultrasonic wave is used for detecting the speed of the image carrier 1, the transmission wave fs from the transmitter S in FIG. Only the part that is irregularly reflected on the observation surface needs to be received by the receiver O as the reception wave fo. Therefore, it is not necessary to install the transmitter S or the receiver O on the normal line of the observation surface of the image carrier 1. Absent.

If the observation surface of the moving speed of the image carrier 1 is a rough surface (the condition under which irregular reflection occurs is an uneven surface substantially equal to or greater than the reception wavelength), the transmission wave fs can be effectively irregularly reflected. Since it is possible, the installation location of the transmitter S and the receiver O can be accommodated in the same quadrant, and the degree of freedom in selecting the moving observation surface of the image carrier 1 increases.

In order to more effectively observe the moving speed of the image carrier 1 by the transmitter S and the receiver O, the installation positions of the transmitter S and the receiver O are expressed by the following equations. The same quadrant may be used. By satisfying such a condition, the reception wave fo with respect to the transmission wave fs can be received with high sensitivity.

When n ≦ θs ≦ n + 90, n ≦ θo ≦ n + 90... Or when n + 90 ≦ θs ≦ n + 180, n + 90 ≦ θo ≦ n + 180. The angle θs: the angle between the center of the transmitter S and the tangent of the center of the reflection position of the image carrier 1 θo: the angle from the vertical direction of the tangent to the surface of the image carrier 1 θo: the center of the receiver O and the image carrier 1 An angle formed by a tangent line at the center of the reflection position of the following formulas is most effectively realized by integrating the transmitter S and the receiver O, or using a transmitter / receiver that combines the transmission element and the reception element. Method.

[0037]

As described above, according to the image forming apparatus of the present invention, the ultrasonic wave is transmitted to the surface of the image carrier, and the reflected wave reflected on the surface of the image carrier is received. Since the speed of the surface of the image carrier is detected by the detector, the rotational speed of the image carrier can be detected with high accuracy. Accordingly, the rotation of the image carrier such as a photosensitive drum for electrophotography can be improved with high accuracy, and high resolution and high image quality can be achieved. Moreover, since the rotational speed is detected by the detector using ultrasonic waves, stable speed detection can be realized without being affected by toner contamination, sliding scratches, etc. on the observation surface of the image carrier. .

[Brief description of the drawings]

FIG. 1 is a perspective view schematically showing a main structure of an embodiment of the present invention.

FIG. 2 is a time chart showing transmission / reception waveforms in the transmitter / receiver of FIG.

FIG. 3 shows the rotation of the image carrier as P in the embodiment of the present invention.
FIG. 2 is a block diagram illustrating a system configuration when performing LL control.

[Explanation of symbols]

 Reference Signs List 1 image carrier 2 encoder 3 drum motor 4 drum motor driving circuit 5 PLL circuit 6 counting circuit CL1 reference clock CL2 reference clock S transmitter O receiver fs transmission wave fo reception wave

 ──────────────────────────────────────────────────続 き Continuing on the front page (72) Inventor Masaki Saka 22-22, Nagaikecho, Abeno-ku, Osaka, Osaka Inside Sharp Corporation (72) Inventor Morita Akira 22-22, Nagaikecho, Abeno-ku, Osaka, Osaka F term (reference) 2H027 DA17 DE04 DE10 ED02 EE03 EE04 5J083 AA02 AB14 AC17 AD08 AE10 AF01 BA01 BE30 CA01

Claims (10)

[Claims] In an image forming apparatus including a drum-shaped image carrier and a driving unit for rotating the image carrier, an ultrasonic wave is transmitted to the surface of the image carrier, and the ultrasonic wave is reflected by the surface of the image carrier. An image forming apparatus configured to detect a surface velocity of an image carrier by a detector that receives a reflected wave. 2. The image forming apparatus according to claim 1, wherein the detector is configured to detect a phase of a reflected wave from a surface of the image carrier. 3. The image forming apparatus according to claim 2, wherein the detector is configured to detect a speed fluctuation from a phase fluctuation of a reflected wave. 4. The image forming apparatus according to claim 1, wherein a transmission wave of said detector is an intermittent pulse. 5. An image forming apparatus, wherein a window is applied to a received wave in the detector. 6. The image forming apparatus according to claim 1, wherein
An image forming apparatus which is configured to control the speed of an image carrier by PLL control and includes a phase signal detector for obtaining a phase signal when performing the PLL control. 7. The apparatus according to claim 1, wherein the detector is installed at an angle with respect to a normal to the surface of the image carrier.
The image forming apparatus as described in the above. 8. The image forming apparatus according to claim 1, wherein
The angle from the vertical direction of the tangent to the image carrier surface at the reflection position center of the image carrier is n degrees, the angle formed by the tangent between the transmission wave center and the reflection position center is θs, and the tangent between the reception wave center and the reflection position center is formed. When the angle is θo degrees, when n ≦ θs ≦ n + 90, n ≦ 90 ≦ θ when n ≦ θo ≦ n + 90 or n + 90 ≦ θs ≦ n + 180.
An image forming apparatus, wherein o ≦ n + 180. 9. The image forming apparatus according to claim 1, wherein the speed detection position on the surface of the image carrier is set to a rough surface. 10. The detector, wherein a transmitting element for transmitting an ultrasonic wave to the surface of the image carrier and a receiving element for receiving a reflected wave reflected on the surface of the image carrier are used in combination. The image forming apparatus according to claim 1.