JPH0449688B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to an image recording apparatus, and more particularly to an image recording apparatus that records images digitally, such as a laser beam printer or a digital copying machine.

With the advancement and spread of digital information processing technology, digital image recording devices, such as laser beam printers (hereinafter referred to as LBPs), process images using digital signals and obtain hard copies from those signals.
Furthermore, digital copying machines have been attracting particular attention in recent years.

FIG. 1 shows the structure of an optical system for scanning an image in an LBP as an example of such an image recording device. In FIG. 1, a rotating polygon mirror (hereinafter referred to as
A system is shown in which the original 4 is scanned through a lens 3 by deflecting the light by a polygon (referred to as a polygon). Such an optical system is characterized in that it is capable of faster processing than other scanning methods.

In the laser optical scanning system as described above, the drive motor, such as a scanner motor, which rotates the polygon 2 at high speed is the only movable unit and one of the most important components. Therefore, especially in LBPs whose mission is high-speed processing, the drive motor is required to meet various strict conditions such as short start-up time, low power consumption, and long bearing life. for example,
If you want to perform higher-speed processing, it is natural that the scanner motor as a drive motor will be required to rotate at a higher speed, but the faster the operating range is set, the higher the rotation speed will be. The rise time until reaching the operating area becomes proportionally longer, resulting in a longer waiting time until recording can be performed, which reduces the value of the product.

Conventionally, attempts have been made to solve this problem by increasing the power applied to the scanner motor, but with this method, for example, when trying to reduce the startup time by half, it depends on the rotation speed of the operating range. However, approximately twice to four times as much power is required, resulting in an increase in power consumption or a rise in temperature inside the device due to heat generated by the motor. In addition, in large LBPs, etc., a method is adopted in which the motor is kept rotating in the operating range even when it is not in use, but in this case, expensive hydrodynamic bearings that require extremely precise machining and assembly are used. This made it difficult to miniaturize the bearing, and it was impossible to avoid generating noise because it was constantly being rotated.

The present invention has been made in view of the above points, and an object of the present invention is to provide an image recording device having a small and inexpensive scanner motor drive device that consumes less power, generates less heat, and has low operating noise. do.

In order to achieve the above object, the present invention includes a scanner motor that rotationally drives a rotating polygon mirror for deflecting a laser beam, a detection means that detects the number of rotations of the scanner motor, and a scanner motor that rotationally drives a rotating polygon mirror for deflecting a laser beam. an oscillating means for generating a signal of a reference frequency corresponding to a predetermined number of rotations of the mirror, and comparing the phase of the detection signal from the detection means with the phase of the signal of the reference frequency; and control means for controlling the scanner motor, and the control means controls the scanner motor based on a comparison result between the phase of the detection signal and the phase of the reference frequency signal during image recording, and when the image recording is stopped. In order to rotationally drive the rotating polygon mirror at a rotation speed lower than the predetermined rotation speed necessary for recording the image, without being based on the comparison result between the phase of the detection signal and the phase of the reference frequency signal, A configuration was adopted to control the scanner motor.

Hereinafter, the present invention will be explained in detail based on embodiments shown in the drawings. However, in the following drawings, the same or corresponding parts are denoted by the same reference numerals, and the explanation thereof will be omitted.

Figure 2 shows a cross-sectional view of the structure of a scanner motor for driving polygons such as LBP. As for the structure of the motor itself, a Hall element 10 is provided opposite the rotor magnet 8, and a stator 9 is further provided around the rotor magnet 8.
It constitutes a so-called DC Hall motor. A polygon 2, high-precision bearings 7 and 11, and a rotor magnet 8 are fixed to a rotating shaft 12 of the motor, and a preload is applied to the bearing 11 by a spring 13 to maintain rotational accuracy. Furthermore, in order to control rotational unevenness, a pattern is printed on the outer periphery of a balance ring 15 fixed to the rotating shaft 12, and a reflective sensor 14 reads the pattern.
A tachometer generator is provided, and the rotational speed of the motor is controlled according to the output signal.

However, in the present invention, the scanner motor is not limited to the above DC Hall motor.
AC hysteresis motors or DC brush motors can also be used.

Next, FIG. 3 shows a first embodiment of the scanner motor drive device described above. In FIG. 3, the output of the tachogenerator 22 of the scanner motor 21 is input to a comparator 24.
Oscillators 23 and 31 are connected to generate two reference frequencies. The output of the comparator 24 is connected to the drive circuit 25.
The terminal 29 is configured to receive a power source for driving the scanner motor 21, and the terminal 30 is configured to receive a driving command from a CPU or the like of the main body of the recording apparatus.

The comparator 24 described above is configured to compare the output frequency of the tachogenerator 22 and the phase of the reference frequency output from the oscillators 23 and 31, and the drive circuit 25 is configured to perform a shift according to the comparison output of the comparator 24. The rotation speed of the scanner motor 21 is controlled by controlling the power supply of the scanner motor 21. In addition, the oscillators 23 and 31
When recording an image, for example, the oscillator 23 is used to provide a predetermined number of rotations necessary for image recording, and the oscillator 31 is used to provide a number of rotations when idling (for example, 1/2 during recording) when recording is not performed. It is assumed that the comparator 24 uses these two output frequencies by switching them in accordance with a rotation speed control signal synchronized with a drive command inputted from the terminal 32. However, the above-mentioned idling speed may be appropriately set by a person skilled in the art in consideration of bearing durability, power consumption, startup time, etc.

In the above configuration, when image recording is not performed and the oscillator 31 is enabled during the pause period, the oscillator 31 is enabled by the CPU of the main body, and the reference frequency of the oscillator 31 and the output frequency of the tachometer generator 22 are adjusted according to the comparison output of the comparator 24. By controlling the current applied to the scanner motor 21 by the drive circuit 25 so that the numbers coincide with each other, the scanner motor 21 is held in an idling state at a rotation speed that is approximately 1/2 of the predetermined rotation speed during image recording. Furthermore, when a drive command is input through the terminal 30, the oscillator 23 is enabled at the same time, and a similar operation increases the rotational speed of the scanner motor 21 to the rotational speed necessary for image recording.

With the above configuration, it is no longer necessary to start the scanner motor 21 from a state of 0 rotation speed, and if the idling speed is set to about 1/2, the start-up time is approximately 1/2 of the time when starting from a stopped state. /2, power consumption is 20-30%
The operating noise can be reduced by 15 to 25% compared to when the motor is constantly rotating in the operating range.

In the above configuration, two oscillators are provided to provide two frequencies, but these may be reduced to one, and a frequency divider or the like may be used to obtain the above frequencies. Further, the rotation speed control signal inputted to the comparator 24 from the terminal 32 can be based on the end of the recording operation of the main body of the image recording apparatus or the end of a standby signal such as auto-shut-off.

Next, FIG. 4 shows a second embodiment. The second embodiment described below is a simplified version of the first embodiment.

Generally, the rotation speed of a DC motor is uniquely determined by the applied current, so in the second embodiment, the idling rotation speed is determined by driving the scanner motor 21 by configuring the drive circuit 25 with a switching circuit 27 and a motor control circuit 28. When a command is input through the terminal 30, the required current required for idling is directly applied to the scanner motor 21, and only the rotational speed required for image recording is applied to the oscillator motor 21 as in the first embodiment (FIG. 3). 23 and comparator 2
The configuration is given by 4. Here, the rotational speed control command is sent to the switching circuit 2 via a terminal 32.
7 and is designed to control two rotational speeds.

With the above configuration, effects similar to those of the first embodiment can be obtained.

Furthermore, by modifying the second embodiment, a third embodiment is shown in FIG.
A configuration as shown as an example is also conceivable. In FIG. 5, a timer circuit 37 is connected to the switching circuit 27 of the embodiment shown in FIG. 4, and the scanner motor 21 is driven intermittently in accordance with the output of the timer circuit 37 during idling. This is because the rotational speed during idling does not need to be maintained very accurately, and when idling, the scanner motor 21 alternately repeats two states, a driving state and an inertial rotation state, due to this configuration. During this intermittent drive, the drive time is set so that the rotation speed during idling does not fall below the minimum rotation speed that allows a problem-free startup time even during inert rotation, and the rotation speed required for image recording is set. The motor control circuit 28 may drive the scanner motor 21 using the available applied power. The above configuration can further reduce power consumption when used in a device with large rotational inertia, such as a large polygon 2 to be driven.

Above are three examples using a DC Hall motor.
Although two embodiments have been shown, it goes without saying that the above configuration can also be applied to AC motors.
If the embodiment shown in the figure is applied to an AC motor 21 having a tachogenerator similar to that described above, a configuration as shown in FIG. 6 will be obtained. In FIG. 6, a known inverter circuit 33 for driving an AC motor is used in place of the drive circuit 25, and this inverter circuit 33 also has an oscillator 34 for providing a reference frequency for determining the rotation speed. , 35 are connected. In this configuration, for example, the rotation speed may be determined by the oscillator 34 during image recording and by the oscillator 35 during idling.

Furthermore, if an AC motor is used in the embodiment shown in FIG. 5, the configuration will be as shown in FIG. 7.
In this configuration, when recording an image, the oscillator 34 generates a predetermined number of revolutions necessary for image recording, and when idling, the oscillator 34 generates a predetermined number of rotations at a frequency corresponding to the same number of revolutions as for image recording, according to the set time of the timer circuit 37. The scanner motor 21 may be driven intermittently as in the embodiment shown.

As is clear from the above description, according to the present invention, there is provided a scanner motor that rotationally drives a rotating polygon mirror for deflecting a laser beam, a detection means that detects the number of rotations of the scanner motor, and a scanner motor that rotationally drives a rotating polygon mirror for deflecting a laser beam. an oscillating means for generating a signal of a reference frequency corresponding to a predetermined number of rotations of the rotating polygon mirror, and comparing the phase of the detection signal from the detection means with the phase of the signal of the reference frequency, and based on the comparison result. and control means for controlling the scanner motor based on a comparison result between the phase of the detection signal and the phase of the reference frequency signal during image recording, and the control means controls the scanner motor based on a comparison result between the phase of the detection signal and the phase of the signal of the reference frequency during image recording. When at rest, the rotating polygon mirror is driven to rotate at a rotation speed lower than the predetermined rotation speed required during image recording, without being based on a comparison result between the phase of the detection signal and the phase of the reference frequency signal. In order to achieve this, a configuration for controlling the scanner motor is adopted, so it can be easily and inexpensively implemented without using expensive parts such as hydrodynamic bearings, and the life of the component parts can be extended. The rise time during image recording is short, and the power required to accelerate the scanner motor is low, so power consumption is low.
It is possible to provide an image recording device that has various excellent advantages such as low heat generation and low operating noise.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram illustrating a document scanning method in a conventional image recording device, FIG. 2 is a sectional view of a DC Hall motor as an example of a scanner motor used in the image recording device of the present invention, and FIGS. FIG. 7 is a block diagram showing the structure of the scanner motor drive control circuit of the image recording apparatus of the present invention. 2...Polygon, 21...Scanner motor,
22...Tachometer generator, 23, 31, 34,
35... Oscillator, 24... Comparator, 25... Drive circuit, 27... Switching circuit, 28... Motor control circuit, 37... Timer circuit.

Claims (1)

[Scope of Claims] 1. A scanner motor that rotationally drives a rotating polygon mirror for deflecting a laser beam; a detection means that detects the rotation speed of the scanner motor; oscillation means for generating a signal at a corresponding reference frequency; and control means for comparing the phase of the detection signal from the detection means with the phase of the signal at the reference frequency and controlling the scanner motor based on the comparison result. The control means controls the scanner motor based on a comparison result between the phase of the detection signal and the phase of the reference frequency signal during image recording, and controls the detection signal when the image recording is stopped. controlling the scanner motor so as to rotate the rotating polygon mirror at a rotation speed lower than the predetermined rotation speed necessary for recording the image, without being based on a comparison result between the phase and the phase of the reference frequency signal; An image recording device characterized by: