JP2001037296A - Driver - Google Patents

Abstract

PROBLEM TO BE SOLVED: To reduce starting time drivingly connecting the rotating shaft of a first motor driving an object-to-be-driven and the rotating shaft of a second motor which has a driving torque larger than that of the first motor at the time of starting the object-to-be driven, and releasing driving connection before the object-to-be-driven is rotated uniformly. SOLUTION: A rotary shaft 36 of a DC motor 34 of a first motor and a rotary shaft 37 of a pulse motor 35 of a second motor are connected at the time of starting. A polygon mirror 32 of an object to be driven is driven by the pulse motor 35 of the second motor which has a larger driving torque to increase rotational speed in a short time. The connection of both rotating shafts 36, 37 are released before they are uniformly rotated. The polygon mirror 32 of the object-to-be-driven is driven by the DC motor 34 of the first motor which has a smaller driving torque, and accelerated to a prescribed speed at a high speed. The starting time of the motor is reduced, thus it is possible to prevent the productivity of image formation from being lowered, and prevent generation of noise and electric noise.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a driving apparatus for rotating a driven object, and more particularly, to using two motors having different driving torques as driving sources and driving these two motor shafts. The present invention relates to a drive device for shortening the startup time of a driven object by appropriately connecting and disconnecting by a switching unit.

[0002]

2. Description of the Related Art Hitherto, high speed has been promoted in image forming processing of a copying machine, a printer and the like. Accordingly, there is a demand for a high-speed electrostatic latent image writing operation by a scanning writing optical system used in an exposure process for image formation. In order to speed up this electrostatic latent image writing operation, scanning is performed by reflecting light from an exposure light source such as a semiconductor laser and writing an electrostatic latent image corresponding to a desired image on a photoconductor. What is necessary is just to drive the polygon mirror to rotate at high speed, that is, to increase the speed of the drive motor that drives to rotate the polygon mirror.

[0003] However, if the speed of the drive motor of the polygon mirror (hereinafter referred to as a motor) is increased, the start-up time of the motor (the time required for the motor to reach a predetermined constant speed from a stopped state) becomes longer. Because, in order to increase the number of rotations of the motor, it is necessary to suppress the generation of the armature voltage during rotation of the motor by, for example, suppressing the inductance of the motor coil.
This is because it takes time for the rotation speed of the motor to increase. The length of the motor start-up time greatly affects the length of the first copy time, the productivity of the image forming apparatus, and the like.

As a method for solving the above problem, it is known that a polygon mirror is rotated even during non-image formation so that an electrostatic latent image can be written at any time. It is not preferable because of problems such as life and motor noise. Regarding the life of the bearing, if a special fluid bearing structure such as an air bearing is adopted, a tentative solution can be found, but the cost is increased. Furthermore, since the special fluid bearing has low durability against intermittent operation, the rotation of the motor cannot be stopped even during non-image formation, and the motor noise cannot be eliminated.

In the invention described in Japanese Patent Application Laid-Open No. 8-31838, two sets of coils are provided in the motor for start-up and for steady-state rotation, and the start-up time of the motor is shortened by performing appropriate switching. By performing the low-speed rotation operation in advance even during the sleep / stand-by state of the motor, the first copy time is further reduced. However, according to the present invention, a plurality of windings are provided in the same coil yoke, and the winding volume allocated to one coil is reduced. For this reason, desired rotation characteristics cannot be sufficiently obtained, and the motor must be increased in size to obtain the desired rotation characteristics. Furthermore, the switching control of the coil in the rotating motor has a problem that the circuit configuration becomes complicated because it is necessary to suppress a phenomenon such as generation of electric noise due to load energy or the like.

[0006]

SUMMARY OF THE INVENTION The present invention solves the above-mentioned problems such as a reduction in productivity of image formation due to a prolonged motor start-up time, noise, a driving load on the motor, and electric noise in the motor. It is intended to solve the problem with a simple configuration.

[0007]

According to one aspect of the present invention, there is provided a driving apparatus for driving a driven object to a predetermined speed and then driving the driven object at a constant speed at the predetermined speed. , A first motor for driving a driven object, a second motor having a larger driving torque than the first motor, and a rotation axis of the first motor and a rotation axis of the second motor at the start of activation of the driven object. And a drive switching means for releasing the drive connection before the driven object is rotated at a constant speed.

In the present invention, the drive switching means connects the rotating shaft of the first motor and the rotating shaft of the second motor at the start of startup, so that the driven object is driven by the second motor having a large driving torque. It is driven and increases the rotation speed in a short time. Since the two rotating shafts are disconnected before being rotated at a constant speed, the driven object is driven by the first motor having a small driving torque and accelerates at a high speed to a predetermined speed. Further, since the two rotating shafts are connected and released before the driven object is rotated at a constant speed, the second motor does not become a driving load on the first motor, and electric noise or the like in the first motor is generated. Can be reduced. As described above, the startup time of the driven object can be reduced.

Further, according to a second aspect of the present invention, in the driving device according to the first aspect, the drive switching means is configured to connect the drive when the rotation speed of the first motor becomes higher than the rotation speed of the second motor. It is characterized by releasing.

According to the present invention, after the rotation speed of the first motor becomes larger than the rotation speed of the second motor, the second motor does not become a load on the first motor, and the load of the driven object is further increased. Startup time can be reduced.

Further, according to a third aspect of the present invention, in the driving device according to the first or second aspect, the first motor is a DC motor and the second motor is a pulse motor. .

In the present invention, a DC motor capable of high-speed rotation is used as the first motor having a small torque. In addition, the second motor has better responsiveness to input energy than the DC motor, and the torque at the time of low-speed rotation is larger,
In addition, by using a pulse motor having a characteristic that the drive transmission loss is small with respect to the same drive current, the start can be started smoothly and quickly.

Further, according to a fourth aspect of the present invention, in the driving device according to the first to third aspects, the driven object is a polygon mirror, and the polygon mirror is supported by a rotation shaft of the first motor. It is characterized by having.

According to the present invention, it is possible to reduce the start-up time of a polygon mirror used for forming an electrostatic latent image in an image forming exposure process by a copying machine, a printer, or the like.
The productivity of image formation is increased.

Further, the invention according to claim 5 of the present application is a DC motor for driving a driven object, a pulse motor having a larger driving torque than the DC motor, and a rotation of the DC motor at the start of starting the driven object. A drive device, comprising: drive connection between a shaft and a rotation shaft of a pulse motor; and drive switching means for releasing the drive connection before the driven object is completely started.

According to the present invention, when the driven object is started to be driven, the drive switching means has a small torque and a DC motor capable of high-speed rotation, and has excellent responsiveness to input energy as compared with the DC motor. Since the respective rotating shafts of the pulse motor having the characteristic that the torque at the time of the low-speed rotation is large and the drive transmission loss for the same drive current is small are connected to each other, the startup time of the driven object can be reduced. Further, in order to release the drive connection of the two rotating shafts before the driven object is completely started,
The pulse motor does not become a driving load on the DC motor, and the occurrence of electric noise and the like in the DC motor can be reduced.

Further, according to a sixth aspect of the present invention, in the driving device according to the seventh aspect, the drive switching means includes a drive switch.
The drive connection release is performed when the rotation speed of C becomes higher than the rotation speed of the pulse motor.

According to the present invention, after the rotation speed of the DC motor becomes higher than the rotation speed of the pulse motor, the pulse motor does not become a load on the DC motor, and the startup time of the driven object can be further reduced. I can do it.

According to a seventh aspect of the present invention, in the driving device according to the fifth or sixth aspect, the driven object is a polygon mirror, and the polygon mirror is a D mirror.
It is characterized by being supported by the rotating shaft of a C motor.

According to the present invention, the start-up time of the polygon mirror used for forming an electrostatic latent image in an image forming exposure process by a copying machine, a printer or the like can be shortened.
The productivity of image formation is increased.

[0021]

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

FIG. 1 is a side sectional view of an image forming apparatus 100 provided with a drive device according to the present invention in a scanning writing optical system. A corona charger 2, a developing device 4, a transfer device 5, a fixing device 6, and a toner remaining on the photoreceptor 1 are provided around the photoreceptor 1 rotatable in the direction of the arrow in FIG. A cleaning device 7 for removal, a laser optical system 3 having a driving device according to the present invention, and the like are provided.

The laser optical system 3 shown in FIG. 2 comprises a laser light source 31, a polygon mirror 32, and a lens optical system (fθ lens, collimator lens, etc.) 33. The polygon mirror 32 is a rotating mirror having a hexagonal shape.
The laser beam emitted from 1 is reflected and scans the surface of the photoconductor 1. The lens 33 corrects the curvature at both ends of the scanning surface. The driving device according to the present invention is provided to rotationally drive the polygon mirror 32.

A plurality of paper feed cassettes 8 and 9 are provided below the image forming apparatus 100 to store recording paper. The paper feed rollers 10 and 11 pick up the recording paper one by one and send it to the timing roller 12. The timing roller 12 temporarily stops the recording paper conveyed from the paper feed cassettes 8 and 9 and sends the recording paper to the transfer device 5 in synchronization with the rotating photoconductor 1 carrying the toner image.

Since the principle of image formation by the electrophotographic method is well known, it is simply described. Image information obtained by reading the reflected light of the original with a CCD is first converted into an electric signal. This electric signal is converted into an optical signal through an image processing unit, an image memory unit and the like (not shown), and emitted from the laser light source 31 of the laser optical system 3. The laser beam is scanned by the polygon mirror 32 on the surface of the photoconductor 1 charged by the corona charger 2. In this way, an electrostatic latent image is formed on the photoreceptor 1, and the electrostatic latent image is developed by the developing device 4 to obtain a visible image. Next, the visible image is transferred to the recording paper conveyed from the paper feed cassettes 8 and 9 by the transfer device 5 and then fixed by heating by the fixing device 6. The recording paper carrying the desired visible image is finally discharged to the discharge tray 13. On the other hand, the photoconductor 1 returns to the initial state after being processed by the cleaning device 7. By repeating this series of processes, continuous image formation becomes possible.

Next, the operation sequence of the present invention will be described with reference to FIG. In FIG. 3A, the horizontal axis represents the time elapsed since the user operated the image formation start key, and the vertical axis represents the rotation speed of the photoconductor 1. In FIG. 3B, the horizontal axis represents the time elapsed since the user operated the image formation start key, as in FIG. 3A. The vertical axis indicates the rotation speed of the polygon mirror 32. In FIG. 3C, the horizontal axis indicates the time elapsed since the user operated the image formation start key, as in FIG. 3A. The vertical axis indicates the position of the recording paper moving from the paper feed roller 10 (or 11) via the timing roller 12 to the transfer device 5.

In order for the laser optical system 3 having the driving device according to the present invention to start irradiating the photosensitive member 1, the photosensitive member 1 must have reached a predetermined number of revolutions P, and the polygon mirror 32 has to be rotated.
Must reach a predetermined constant speed Q, and the recording paper must be at a predetermined position.

When the image formation start key is operated by the user, a motor for driving the photosensitive member 1, a motor for driving the paper feed roller 10 (or 11) for conveying the recording paper, and the present invention for driving the polygon mirror 32 are provided. A drive motor required for image formation, such as a drive device (hereinafter, referred to as a polygon motor), starts to be activated. When the photoconductor 1 reaches a predetermined constant speed P, the conveyance of the recording paper from the paper feed cassette 8 (or 9) by the paper feed roller 10 (or 11) starts. When the recording paper reaches the timing roller 12,
After the charging, exposure, and development processes, the operation is temporarily stopped in order to obtain synchronization with the photoconductor 1 carrying the toner image on the surface. After the synchronization is obtained, the conveyance of the recording sheet is restarted, and the recording sheet moves to the transfer device 5.

FIG. 3B shows a conventional polygon motor.
The start-up time is long as indicated by the solid line and the dashed line. That is, it takes time until the rotation speed of the polygon motor reaches the constant speed rotation speed Q. Accordingly, the time during which the recording paper stops at the timing roller 12 becomes longer, and the productivity of the image forming apparatus decreases.

According to the polygon motor of the present invention, the start-up time is short as shown by the broken line in FIG. That is, the time required for the rotation speed of the polygon motor to reach the predetermined constant speed rotation speed Q is short. Therefore, in order to obtain synchronization with the photoreceptor 1, no time is required for the recording paper to stop at the timing roller 12, and high productivity can be secured.

Next, the configuration of a polygon motor which is a driving device according to the present invention will be described. FIG. 4 is a half sectional view of the polygon motor according to the present invention.

The polygon motor comprises a DC motor 34 having a small driving torque and a pulse motor 3 having a large driving torque.
Consists of five. The pulse motor 35 is a motor that receives an electric pulse and outputs a mechanical angle corresponding to the number of pulses.
Excellent response to input and low drive transmission loss.

Each of the motors 34 and 35 has a DC motor rotating shaft 36 and a pulse motor rotating shaft 37, respectively. The one-way bearing 38 as a drive switching means is provided through one end of the DC motor rotation shaft 36 and one end of the pulse motor rotation shaft 37, and connects and disconnects the two motor rotation shafts 36 and 37. The polygon mirror 32
The other end of the DC motor rotating shaft 36 is rotatably held.

When the polygon mirror 32 is activated, the one-way bearing 38 causes the mirror 32 to be driven to rotate by a motor having the larger rotation speed of the DC motor 34 and the rotation speed of the pulse motor 35.

Immediately after start-up, the responsiveness to input energy is excellent, the torque at low speed rotation is large,
In addition, the pulse motor 35 having a small drive transmission loss with respect to the drive current smoothly and quickly increases the rotation speed, and the rotation speed of the pulse motor 35 becomes larger than the rotation speed of the DC motor 34. Therefore, the polygon mirror 32 and the DC motor 34
Starts rotational driving by the pulse motor 35. In other words, the DC motor rotating shaft 36 and the pulse motor rotating shaft 37 are drivingly connected by the one-way bearing 38. The pulse motor 35 has excellent responsiveness to input energy as compared with the DC motor, has a large torque at low speed rotation, and Since the drive transmission loss for the drive current is small,
The rotation speed of the polygon mirror 32 can be increased in a short time. The pulse motor 35 can sufficiently increase the rotation speed of the polygon mirror 32 by one pulse of the pulse rate. Therefore, the starting time T by the pulse motor 35
Is approximately T = 1 / pulse rate.

Actually, a polygon mirror 32 having a diameter of 60 mm
Is started at a pulse rate of 300 pps using a pulse motor having a step angle of 7.5 degrees, the time T becomes about 3 ms.
ec, the rotation speed of the polygon mirror 32 at this time was 375 rpm, and the acceleration was 40 G.

The rotation speed of the pulse motor 35 having a large driving torque reaches a limit at a certain point and stops the acceleration. On the other hand, the DC motor 3 that has been rotationally driven by the pulse motor 35
4 has the same acceleration as the pulse motor 35, and at this time, the rotation speed of the DC motor 34 is
Exceeds the number of revolutions. The DC motor rotating shaft 36 and the pulse motor rotating shaft 37 are driven by the one-way bearing 38.
Is released, and the polygon mirror 32 is rotationally driven by the DC motor. By this drive connection release, the pulse motor 35 does not become a load of the DC motor 34 that continues to accelerate, and the polygon mirror 32 continues to accelerate efficiently to a predetermined constant speed Q, completing the startup.

According to the above-described configuration, simple problems can be avoided without causing problems such as a decrease in productivity of image formation due to a long start-up time of the polygon motor, noise, a driving load on the motor, and electric noise in the motor. With this configuration, the startup time of the polygon motor can be reduced.

In this embodiment, the one-way bearing 38 is used as the drive switching means, but the invention is not limited to this. An electromagnetic clutch or the like may be used as long as it can freely control connection and release of connection.

[0040]

As described above, according to the first aspect of the present invention, at the start of the start-up by the drive switching means, the rotating shaft of the first motor and the rotating shaft of the second motor are connected. The driven object is driven by the second motor having a large driving torque, and increases the rotation speed in a short time. Since the two rotating shafts are disconnected before being rotated at a constant speed, the driven object is driven by the first motor having a small driving torque and accelerates at a high speed to a predetermined speed. Further, since the two rotating shafts are connected and released before the driven object is rotated at a constant speed, the second motor does not become a driving load on the first motor, and electric noise or the like in the first motor is generated. Can be reduced. As described above, the startup time of the driven object can be reduced.

Further, according to the invention of claim 2 of the present application, after the rotation speed of the first motor becomes higher than the rotation speed of the second motor, the second motor does not become a load on the first motor. Further, the startup time of the driven object can be further reduced.

Further, according to the invention of claim 3 of the present application, a DC motor capable of high-speed rotation drive is used for the first motor having a small torque, and the second motor has a higher responsiveness to input energy than the DC motor. By using a pulse motor which is excellent in torque, has a large torque at the time of low-speed rotation, and has a small drive transmission loss with respect to the same drive current, the start can be started smoothly and promptly.

Further, according to the invention of claim 4 of the present application, it is possible to shorten the start-up time of the polygon mirror used for forming the electrostatic latent image in the image forming exposure process by a copying machine, a printer or the like. Increases productivity.

Further, according to the invention according to claim 5 of the present application, when the start of the driven object is started by the drive switching means, a DC motor having a small torque and capable of high-speed rotation and an input compared with the DC motor are provided. Excellent response to energy, high torque at low-speed rotation, and low drive transmission loss for the same drive current. it can. In addition, since the drive shafts are released from the drive connection before the driven object is completely started, the pulse motor does not become a driving load on the DC motor, and the generation of electric noise and the like in the DC motor can be reduced.

Further, according to the invention of claim 6 of the present application, after the rotation speed of the DC motor becomes higher than the rotation speed of the pulse motor, the pulse motor does not become a load on the DC motor, and the load is further increased. The startup time of the drive target can be reduced.

Further, according to the invention of claim 7 of the present application, it is possible to reduce the start-up time of the polygon mirror used for forming the electrostatic latent image in the image forming exposure process by a copying machine, a printer or the like. Increases productivity.

[Brief description of the drawings]

FIG. 1 is a side sectional view of an image forming apparatus provided with a driving device according to the present invention.

FIG. 2 is a schematic diagram of a laser optical system.

FIG. 3 is an operation sequence of the present invention.

FIG. 4 is a half sectional view of a driving device according to the present invention.

[Explanation of symbols]

 31: Laser light source 32: Polygon mirror 33: Lens 34: DC motor 35: Pulse motor 36: DC motor rotation axis 37: Pulse motor rotation axis 38: One-way bearing

Continued on the front page F-term (reference) 2H045 AA13 AA54 CA33 CA53 5H001 AA02 AB02 AB09 AD00 5H303 AA27 AA28 CC04 DD01 DD03 DD19 EE04 EE08 JJ01 KK21 KK35 5H572 AA13 AA20 BB04 BB05 BB10 DD07 DD08 EE03 FF01 FF03

Claims (7)

[Claims] 1. A driving device for driving a driven object at a constant speed at a predetermined speed after accelerating the driven object to a predetermined speed, and a first motor for driving the driven object, and a driving torque larger than the first motor. At the start of activation of the second motor and the driven object, the drive connection between the rotation axis of the first motor and the rotation axis of the second motor is performed, and the drive connection release is performed before the driven object is rotated at a constant speed. And a drive switching means for performing the driving. 2. The drive device according to claim 1, wherein the drive switching unit performs the drive connection release when the rotation speed of the first motor becomes higher than the rotation speed of the second motor. . 3. The method according to claim 2, wherein the first motor is a DC motor, and the second motor is a pulse motor.
The drive device according to claim 1 or 2. 4. The driving device according to claim 1, wherein the driven object is a polygon mirror, and the polygon mirror is supported by a rotation shaft of a first motor. 5. A DC motor for driving a driven object,
A drive connection between the pulse motor having a larger driving torque than the DC motor and the rotation axis of the DC motor and the rotation axis of the pulse motor when starting the driven object is started, and the driving is performed before the driven object is completely started. A drive device comprising: a drive switching unit that performs connection release. 6. The drive switching unit according to claim 5, wherein the drive switching unit performs the drive connection release when the rotation speed of the DC motor becomes higher than the rotation speed of the pulse motor.
The driving device as described. 7. The driving device according to claim 5, wherein the driven object is a polygon mirror, and the polygon mirror is supported on a rotating shaft of a DC motor.