JPS6289017A - Surface shake self-diagnostic optical deflector - Google Patents

Abstract

PURPOSE:To obtain images of high quality for a long time and to extend the life of a laser printer or the like by measuring always the extent of surface shake of a polygonal mirror during operation and adjusting a prepressure so that said extent is within a prescribed value range if the measured value exceeds prescribed value. CONSTITUTION:When a polygonal mirror 1 is rotated by a motor 2, an area S between electrodes is changed, and the electrostatic capacity C between the mirror 1 and a sensor electrode 4 is changed because an inter-electrode gap (g) is changed by surface shake of the mirror 1. Consequently, an electric charge Q stored in the capacity C is changed, and the quantity of electricity corresponding to a variation DELTAQ flows as a current. This variation is changed in accordance with the change of the area S and the gap (g). In a ball bearing prepressure adjusting mechanism part 3, the measured signal of the extent of surface shake is used as a prepressure adjusting signal. If the extent of surface shake exceeds the prescribed value, the prepressure adjusting signal is generated to drive a solenoid 14. A pinion 13 is moved thereby to change the position where a rack 12 and the pinion 13 are engaged with each other. Thus, the extent of surface shake is so adjusted that it is within the prescribed extent range.

Description

[Detailed description of the invention] lack of skill This invention is applicable to laser printers and digital copying machines.

The present invention relates to the improvement of an optical deflector equipped with a polygon mirror, which is suitable for use in facsimiles and other types of optical information processing equipment and optical measuring instruments equipped with a laser deflector. Self-diagnosis of surface runout that prevents jitter in the sub-scanning direction and extends the life of the optical deflector by measuring and automatically correcting it so that it always stays within the specified value range. Related to type optical deflector.

More specifically, a capacitive sensor is installed, and the output signal is used to adjust the suppression force in the axial direction of the rotation axis of the polygon mirror, and to control the speed of the motor. Regarding a deflection self-diagnosis type optical deflector.

Conventional technology rights have traditionally included laser deflectors for laser printers, laser deflectors for digital copiers, laser deflectors for facsimile machines,
Alternatively, various optical information processing devices such as image scanners of PO8 terminals, 3-eye III devices that inspect the presence or absence of scratches on banknotes and iron plates, and various optical measuring devices such as length measuring devices, etc. Light deflection 2 using a polygon mirror (polygon mirror) to deflect laser light used for reading and writing g-images, or for inspecting for scratches.
:÷ is provided.

An optical deflector using this polygon mirror has a high deflection speed and can continuously deflect light, so it can record information at high speed and with high precision. You can do things like pick up items.

In image output devices using such laser beam deflectors, such as laser printers, image jitter in the sub-scanning direction due to surface deflection of the polygon mirror is particularly problematic.

The surface wobbling of the polygon mirror in this optical deflector is caused by changes in the bearing portion over time.

For example, in the case of a ball bearing type, changes in the suppressing force against the steel balls inside the five-ball bearing, changes in the amount of air gap between the outer diameter of the bearing and the bearing case, etc. have a large influence.

For this reason, conventional single-ball bearing type optical deflectors have been provided with a preload adjustment mechanism that applies preload in the direction of the rotation axis of the bearing. However, such adjustment of the P pressure adjustment mechanism is not particularly performed except during periodic inspections or when a failure occurs.

Therefore, in conventional optical deflectors, firstly, the bearing part changes over time, resulting in increased surface wobbling.For example, in the case of a laser printer, when used for a long period of time, jitter occurs on the image in the sub-scanning direction. , the image quality will deteriorate.

Second, noise and vibration increase as the bearing portion changes over time.

Third, when the above problems occur, ultimately,
This causes the first inconvenience, which makes the laser printer inoperable and poses a major obstacle to realizing a longer service life.

Further, in conventional optical deflectors, an FG (frequency generator) is provided to drive and control a motor that rotates a polygon mirror, but in most cases, an electromagnetic induction type FG is employed.

As a result, the output level depends on the rotation speed,
Another drawback was that it could not be used in low-speed deflectors.

By the way, which conventional optical deflectors can self-diagnose such mirror surface deflection?

Doesn't exist.

Therefore, many of the above-mentioned disadvantages caused by aging of the bearing portion still remain unresolved, and there are disadvantages such as occurrence of jitter in the sub-scanning direction and shortening of the life of the optical deflector.

Therefore, the surface deflection self-diagnosis type optical deflector of the present invention solves such inconveniences caused by the surface deflection of the polygon mirror in conventional optical deflectors, and detects when the surface deflection amount exceeds the specified value range. By adjusting the suppression force in the direction of the rotation axis of the bearing, the amount of surface runout of the polygon mirror is always within the specified range, allowing stable operation with little image jitter and long service life. The object of the present invention is to realize an optical deflector according to the present invention, and also to provide an optical deflector suitable for low-speed operation.

Structure Therefore, in the surface runout self-diagnosis type optical deflector of the present invention, the +? 7
An I capacitance type sensor is provided, and the suppression force in the axial direction of the rotation axis of the polygon mirror is automatically adjusted based on the output signal of this capacitance type sensor.

Furthermore, the output signal of this capacitive sensor allows
The rotation speed of the motor is controlled.

Next, regarding the surface deflection self-diagnosis type optical deflector of this invention, 1.
Examples thereof will be described in detail with reference to the drawings.

Figures 1 (1) to (3) are diagrams showing the configuration of essential parts of an embodiment of the surface deflection self-diagnosis type optical deflector of the present invention, and Figure 5 (1) is a top view of the mirror. 2) is side view 1 (
3) is a low voltage circuit showing the connection state of a capacitive sensor. In the drawing, l is a polygon mirror, 2 is a motor, 3 is a ball bearing preload adjustment mechanism, 4 is a sensor electrode for a capacitive sensor, and 1 is the radius of the inscribed circle of the polygon mirror l.

r2 is the radius of the circumscribed circle, g is the gap between poles, C is the capacitance of the capacitive sensor, ■ is DC? Ii source voltage voltage.

FIGS. 1 (1) to (3) show the case where a one-ball bearing type is used as the bearing portion of the polygon mirror.

The polygon mirror 1 is a polygon mirror as shown in the top view in FIG. 1(1), and not only its mirror surface but also its side surfaces are precisely machined.

The motor 2 is supported by a ball bearing type bearing.
The polygon mirror 1 is rotationally driven to deflect the laser beam.

The ball bearing preload adjustment mechanism 3 has a function of adjusting the pressing force in the axial direction of the rotating shaft of the polygon mirror 1.

The sensor electrode 4 for the capacitive sensor is shown in FIG.
) and (2), it is disposed at a position facing the non-mirror surface of the polygon mirror l and near the circumference of the inner and outer circumscribed circles of the polygon mirror l.

First, regarding the capacitance type sensor, under normal conditions, it is installed at a position with a gap gear g, as shown in Figure 1 (2), and in the equal low circuit shown in Figure 1 (3). As shown, the electrode 4 of the capacitive sensor is connected to the + side of the liI current gV, and the polygon mirror 1 is connected to one side of the DC power supply V.

As shown in the circuit diagram of FIG. 1(3), when the sensor electrode 4 is connected, a capacitance C is formed between the polygon mirror 1 and the sensor electrode 4.

This capacitance ic is C=εS/g (1
) Here, ε: dielectric constant S: area between electrodes g: gap between electrodes.

When the polygon mirror 1 is rotated by the motor 2, the area S between the electrodes changes, and the polygon mirror 1
Since the gap g between the electrodes also changes due to the surface runout, the capacitance C changes as is clear from the above equation (1).

Therefore, the charge Q stored in the capacitance changes depending on the area S between the electrodes and the surface deflection of the polygon mirror 1. In other words, the amount of change Δ in this charge Q
An amount of electricity equal to Q flows as a current.

In this case, the periodicity of the amount of change ΔQ in the charge Q is cursed as the period of the number of faces of the precisely manufactured polygon mirror 1 and the period of one rotation due to surface wobbling.

Then, the signal of the period of the number of planes, that is, the signal of the number of planes component, is
Since it corresponds to the rotation speed of the polygon mirror 1, it can be used for controlling the rotation of the motor 2.

Further, a signal of one rotation period due to surface runout, that is, a signal whose amplitude is changed in accordance with the amount of surface runout of the polygon mirror 1, is a measurement signal of surface runout sludge, and can be used for preload adjustment.

Here, the relationship between the amount of change ΔQ in charge Q and the area S between the electrodes is expressed as follows: ΔQ=(εS/g)XΔS (2)
, corresponding to the change in the area S between the electrodes.

It can be seen that the amount of change ΔQ in charge ff1Q is varied.

Similarly, the relationship between the change layer ΔQ of charge Q and the gap g between electrodes is as follows.

ΔQ=(−εS/g”)X6g (3) It can be seen that the amount of change ΔQ in the amount of charge Q changes in response to a change in the gap g between electrodes.

First, a method for correcting surface wobbling will be explained.

FIG. 2 is a longitudinal cross-sectional view showing an embodiment of the main part configuration of the ball bearing preload adjustment mechanism 3 of the surface runout self-diagnosis type optical deflector of the present invention shown in FIGS. 1 (1) to (3). It is a front view.

In the drawing, 11 is a preload spring.

12 is a rack, 13 is a pinion, 14 is a solenoid, 1
5 is a spring member, 1G is a ball bearing case portion, and 17 is a case portion of a preload adjustment mechanism portion.

In the ball bearing preload adjustment mechanism 3 shown in FIG. 2, the above formula (
The measurement signal of the amount of surface runout as shown in 3) is used as the preload adjustment signal.

When the amount of surface runout exceeds a specified amount, a preload adjustment signal is generated and the solenoid 14 is actuated.

Solenoid 14 no Kakeru! The pinion 13 is moved by PIj, and the position where the rack 12 and the pinion 13 engage is changed, thereby adjusting the preload of the one-ball bearing portion.

In this way, in the surface deflection self-diagnosis type optical deflector of the present invention, a capacitance sensor is provided, and the amount of change ΔQ in the charge Q generated in response to the change in the gap between the poles, that is, the surface of the polygon mirror l is measured. A signal whose amplitude changes in accordance with the amount of runout is extracted, and when the amount of surface runout exceeds a specified amount, a preload adjustment signal is output to drive the preload adjustment mechanism 3, and the amount of surface runout is adjusted to the specified amount. Adjust to fit within the range.

In this way, the surface runout is self-diagnosed and the preload is automatically adjusted so that the amount of surface runout falls within the specified value, so an optical deflector with a long life can be obtained. Note that when the amount of one-plane runout does not fall within a specified value even after adjusting the preload due to long-term use, it is determined that the life of the optical deflector has come to an end.

FIG. 3 is a functional block diagram showing an example of a circuit configuration for extracting a surface number component signal and a one-rotation component signal in the surface runout self-diagnosis type optical deflector of the present invention.

Reference numerals in the drawings are the same as in FIG. 1, and 21 represents an amplifier circuit and 22 represents a filter circuit.

As already explained in relation to equation (1), a capacitive sensor, i.e. a sensor pole 4 and a polygon mirror l
The capacitance MC formed between the electrodes is the area S between the electrodes, and
It is changed in accordance with the change in the gap g between poles.

On the one hand, as shown in equation (2), it can be extracted as a signal of the period of the number of surfaces, that is, as a signal of the number of surfaces components, and on the other hand, as shown in equation (3),
It can be extracted as a rotation period signal, that is, a signal whose amplitude is changed in accordance with the amount of surface deflection of the polygon mirror 1.

Therefore, in the circuit shown in FIG. 3, the output of the capacitance type sensor formed between the sensor electrode 4 and the polygon mirror l is taken out by the amplifier circuit 21 and the filter circuit 22. Among these, the signal of one rotation component is
It is taken out as a surface runout amount meter a+q signal, and when it exceeds the specified value range, it is applied to the preload adjustment mechanism shown in FIG. 2 to adjust the preload.

On the other hand, since the signal of the single-plane number component corresponds to the rotational speed of the polygon mirror 1, it can be used for controlling the rotation of the motor 2.

Here, the amount of charge Q stored in the capacitive sensor is
The relationship between capacitance C1 and DC power supply voltage V is expressed as follows: Q=CXV (4)
becomes.

As is clear from this equation (4) and the previous equation (1),
The amount of change ΔQ in the amount of charge Q is theoretically a signal that does not depend on one frequency, and is a signal that does not depend on the number of rotations.

Therefore, this electrostatic 8-type sensor also functions as a frequency generator, so there is no need to provide a special FG mechanism, and its output is an FG multiplier signal that is unrelated to the motor rotation speed. Therefore, it can also be used to control the rotation of a slow polarizer.

In addition, in the circuit of FIG. 3, the amplifier circuit 21 and the filter circuit 2
The connection position with 2 may be reversed.

In the above embodiments, a ball bearing type optical deflector has been described, but a hydrostatic air bearing type can also be implemented in the same manner.

FIG. 4 is a vertical cross-sectional view showing the main part configuration of the preload adjustment mechanism of the air/magnetic bearing type optical deflector, which is another embodiment of the surface deflection self-diagnosis type optical deflector of the present invention. In the drawing, 31 is a fixed shaft, 3+a is its air supply hole, 32 is a first permanent magnet constituting a thrust bearing, 33 is piping,
34 is a pneumatic pressure adjusting means, 35 is an air pump, 36 is an air 11
adjustment means; 41 is a rotor; 41a is a flange thereof;
42 is a polygon mirror, 43 is a second permanent magnet that constitutes a thrust bearing, 44 is a rotor magnet assembly of the motor section,
51 is a lower housing, 52 is an excitation coil of the motor section,
53 indicates an upper case.

The surface deflection self-diagnosis type optical deflector shown in FIG. 4 uses a radial bearing to operate the rotor 41 using air pressure supplied from the air pressure adjustment means 34, the air pump 35, etc. to the air supply hole 31a of the fixed shaft 3I. A magnetic magnet is provided with a static air bearing that holds the rotor 41 in a predetermined position, and as a thrust bearing, it is composed of first and second permanent magnets that are opposed with the same polarity and hold the rotor 41 in a predetermined position by a repulsive force. Equipped with bearings.

In the case of such an optical deflector with an air/magnetic bearing, if the diameter of the air supply hole 31a of the fixed shaft 3 becomes small due to fine dust etc. after long-term operation, and the bearing rigidity decreases, the single-ball bearing type As in the case, the surface deflection of the polygon mirror 42 increases.

Therefore, as in the case of Fig. 1, a capacitance type sensor is installed to extract the surface runout measurement signal, and when it exceeds the specified value range, it outputs a preload adjustment signal and adjusts the air pressure. The means 34 and air volume adjusting means 36 are operated to adjust air pressure, air volume, etc.

By adjusting the air pressure, air volume, etc., the bearing rigidity is increased, and the surface runout of the polygon mirror 42 is automatically controlled within the specified value range.

As explained in detail above, in the surface runout self-diagnosis type optical deflector of the present invention, an electrostatic A capacitive sensor is provided, and the suppressing force in the axial direction of the rotation axis of the polygon mirror is automatically adjusted based on the output signal of this electrostatic 8-rat sensor.

- As an example, when the rotation axis of the polygon mirror is of a ball bearing type, a preload adjustment mechanism is provided, and the magnitude of the preload applied from the preload adjustment mechanism is adjusted according to the output signal of a capacitance type sensor. , the amount of surface deflection of the polygon mirror is controlled to be within a specified value range.

As another example, when the rotation axis of the polygon mirror is of an air bearing type, an air amount/air pressure adjustment means for the air bearing is provided, and the air amount/air pressure adjustment means is adjusted based on the output signal of the capacitance type sensor. By adjusting the air volume, air pressure, etc. output from the polygon mirror, the amount of image taken by the polygon mirror is controlled to be within a specified value range.

Furthermore, in addition to simply controlling the surface runout, the output signal of this capacitance type sensor is used to control the rotational speed of the motor.

Therefore, according to the surface deflection self-diagnosis type optical deflector of the present invention, the amount of surface deflection of the polygon mirror is always measured during operation of the optical deflector, and when the amount of surface deflection exceeds a specified value, the amount of surface deflection is measured. , the preload is adjusted so that it falls within the specified value range.

As a result, high-quality images with less jitter can be obtained over a long period of time, and the lifespan of laser printers and the like can be extended.

Furthermore, since the output signal of the capacitive sensor is an FG multiplied signal that does not depend on the rotation speed of the polygon mirror, that is, the frequency, the signal necessary for speed control can be obtained without installing a special FG mechanism inside. This simplifies the speed control mechanism and also makes it possible to control the rotation of the low-speed optical deflector, providing many excellent effects.

[Brief explanation of drawings]

Fig. 1 is a diagram showing the configuration of the main parts of an embodiment of the self-diagnosis type optical deflector for surface deflection according to the present invention.
1) is a top view of the mirror, Figure (2) is a side view, Figure (3) is an equivalent circuit showing the connection state of a capacitive sensor, and the varnish plate is the same as shown in Figures 1 (1) to (3). Regarding the surface runout self-diagnosis type optical deflector of the invention, the ball bearing preload adjustment mechanism part 3
A vertical cross-sectional view showing an embodiment of the configuration of essential parts -U is an example of a circuit configuration for extracting a signal of the number of surfaces and a signal of one rotation component in the surface runout self-diagnosis type optical deflector of the present invention. The functional block diagram illustrating the preload adjustment mechanism of the air/magnetic bearing type optical deflector is another embodiment of the surface deflection self-diagnosis type optical deflector of the present invention. It is a front view. In the drawing, l is a polygon mirror, 2 is a motor, 3 is a ball bearing preload adjustment mechanism, 4 is a sensor electrode for a capacitive sensor, 11 is a preload spring, 12 is a rack, 13 is a pinion, and 14 is a solenoid. 15 is a spring member, and 16 is a ball bearing case portion. 17 is a case part of the preload adjustment mechanism section, 21 is an amplifier circuit, 2
2 is a filter circuit; 31 is a fixed shaft; 31a is its air supply hole; 32 is a first permanent magnet that constitutes a thrust bearing;
33 is a pipe, 34 is a pneumatic pressure adjustment means, 35 is an air pump,
36 is a pneumatic pressure adjusting means, 111 is a rotor, 41a is a flange thereof, 42 is a polygon mirror, 43 is a second permanent magnet forming a thrust bearing, 44 is a rotor magnet assembly of the motor section, 51 is a lower part A housing, 52 is an excitation coil of the motor section, and 53 is an upper case. Patent applicant: Ricoh Co., Ltd. - Patent attorney: Toshitaka Kanyo

Claims (1)

[Claims] 1. In an optical deflector equipped with a polygon mirror rotated by a motor, the optical deflector is arranged opposite to a non-mirror surface of the polygon mirror and near the circumference of the inner and outer circumscribed circles of the polygon mirror. A surface deflection self-diagnosis type light comprising a capacitance type sensor, and adjusting the pressing force in the axial direction of the rotation axis of the polygon mirror according to the output signal of the capacitance type sensor. Deflector. 2. In the surface deflection self-diagnosis type optical deflector according to claim 1, when the rotation axis of the polygon mirror is of a ball bearing type, a preload adjustment mechanism is provided and the deflection is controlled by the output signal of the capacitive sensor. The surface deflection self-diagnosis type optical deflection device is characterized in that the surface deflection amount of the polygon mirror is controlled to be within a specified value range by adjusting the magnitude of the preload applied from the preload adjustment mechanism. vessel. 3. In the surface deflection self-diagnosis type optical deflector according to claim 1, when the rotation axis of the polygon mirror is of an air bearing type, means for adjusting the amount of air and air pressure of the air bearing is provided to adjust the capacitance. By adjusting the air volume, air pressure, etc. output from the air volume/air pressure adjusting means according to the output signal of the mold sensor, the surface deflection amount of the polygon mirror is kept within a specified value range. A surface deflection self-diagnosis type optical deflector characterized by control. 4. In the surface runout self-diagnosis type optical deflector according to claim 1, the output signal of the capacitance sensor allows
A surface deflection self-diagnostic optical deflector that controls the rotational speed of a motor.