JPH0339786Y2 - - Google Patents

Description

[Detailed Description of the Invention] [Technical Field of the Invention] The present invention relates to an optical system drive device used in an image forming machine such as an electronic copying machine with a fixed document table.

[Technical background of the invention and its problems]

For example, an electronic copying machine with a fixed document table is provided with a drive device that reciprocates an optical system to scan a document placed on the document table. In this drive device, as shown in FIGS. 1 and 2, conventionally, a carriage b to which a mirror a is attached is movably installed between a pair of rails c and c. Further, a driving force transmission wire d is connected to one end of the carriage b. The carriage b is reciprocated by alternately connecting and disconnecting a plurality of clutches (not shown), for example, clutches for forward rotation and reverse rotation. However, due to the clutch connection-isolation operation,
For the carriage b, F=Mα (M is the carriage b
A force (mass of , α is its acceleration) is applied as an impact force to the rail c, and a force F・lw (lw is a force from the center of gravity G including the mirror a of the carriage b, etc.) to the rail c.
As a result of the moment (distance to Moreover,
When the clutch is isolated in order to stop the carriage b, an inertial force acts on the carriage b, so there are disadvantages such as the need to provide a brake mechanism.

Therefore, in recent years, prior to the present invention, an optical system driving device as shown in FIG. 3 has been proposed. That is, e in the figure is the first mirror, and f is the second mirror. A first mirror e is connected to a pair of rails i, i through a first carriage g, and a second mirror f is connected to a pair of rails i, i through a second carriage h, h.
It is supported so that it can move freely. A first pulley j is attached to the second carriage h, and a wire k is wound around the first pulley j. One end of this wire k is fixed via a spring l, and the middle part connects to the first pulley j, the second pulley m fixedly provided at one end of the rail i, and the other end of the rail i. A pulse motor n
drum o driven by and again said first
They are each successively stretched around a pulley j in a substantially U-shape, and the other end is fixed. Further, the first carriage g is connected between the pulley j of the wire k and the drum o. The drum o is driven by a pulse motor n, so that the first carriage g moves in the same direction at twice the speed of the second carriage h. Further, the pulse motor n is adapted to be controlled in terms of acceleration, deceleration, constant speed, etc.

According to such a configuration, the above-mentioned drawbacks can be eliminated. However, pulse motor n
The disadvantage is that vibrations are transmitted to the optical system by the step feed.

[Purpose of invention]

The present invention was developed based on the above circumstances, and its purpose is to provide an image forming machine that can obtain high-quality images by preventing as much as possible the vibrations caused by the step feed of the pulse motor. An object of the present invention is to provide an optical system driving device.

[Summary of the idea]

The present invention includes an optical system that moves relative to the original in order to scan the original, and an optical system that is provided to drive this optical system, with a step angle of 2 degrees or less, and at least 1000 PPS to 3000 PPS during original scanning of the optical system. A pulse motor driven at a rotation speed of The present invention is characterized by comprising a toothed belt having toothed portions made of an elastic material with a pitch of 3 mm or less and meshed with the pulley.

[Example of idea]

An embodiment of the present invention will be described below with reference to FIGS. 4 to 13. FIG. 4 shows an electronic copying machine as an image forming apparatus employing an optical system drive device according to the present invention, and 1 in the figure is a main body. A fixed document table 2 is provided at the top of the main body 1. Further, a photoreceptor 3 that rotates in the direction of the arrow at a predetermined speed is pivotally supported approximately at the center of the main body 1. A movable lamp 5 driven by an optical system drive device 4, which will be described later, and first, second, and third mirrors 6, 7, and 8 are fixed between the photoreceptor 3 and the document table 2. An optical system 12 is provided in which a lens mechanism 9 and a fourth mirror 10 are sequentially arranged in an optical path 11, and the optical system 12 irradiates the document placed on the document table 2 and directs the reflected light to the photoreceptor. 3 to form an image of the document. A developing device 13, a transfer device 14, a static eliminator 15, a cleaning device 16, and a charging device 17 are arranged in this order along the rotational direction of the photoreceptor 3 from this image forming position.
Further, a transfer paper conveyance path 18 is provided at the bottom of the main body 1, passing between the photoreceptor 3 and the transfer device 14.
This proximal end is connected to the first or second cassette 19, 2.
0 is connected to a paper feeding device 21 that independently feeds transfer paper, and the distal end faces a paper discharge tray 23 via a fixing device 22.

The optical system driving device 4 is constructed as shown in FIG. That is, a first carriage 24 to which the first mirror 6 is attached and a second carriage 25 to which the second and third mirrors 7 and 8 are attached are movably mounted on a pair of rails 26 and 26, respectively. has been done. Further, the first carriage 24 is connected to a first toothed belt 29 that is stretched around the first and second pulleys 27 and 28 so as to run endlessly along the rail 26. The pulley 27 is the rotating shaft 31 of the first pulse motor 30
installed on. Further, third and fourth pulleys 32 and 33 are fixed to the second carriage 25, and a wire 34 is stretched between these pulleys. This wire 34 has one end fixed, the other end fixed via a spring 35, and a midway portion connected to the first carriage 24.
Therefore, since the third and fourth pulleys 32 and 33 act as movable pulleys, the first carriage 24 moves in the same direction at twice the speed of the second carriage 25. There is.

The first pulse motor 30 has a step angle of 2
at least during copying, that is, when the optical system 12 scans the original using the 1-2 phase excitation method.
It is designed to be driven at 1000 to 3000 PPS (pulses per second).

As shown in FIGS. 6 to 9, the first toothed belt 29 has teeth 37 formed of an elastic material such as rubber based on a core wire 36 that maintains strength. The teeth 37 are formed into a substantially trapezoidal shape and are arranged at a pitch of 3 mm or less. And its surface reduces the coefficient of friction with the first pulley 27, all tooth cloth 3
Covered by 8. Further, the first pulley 27 is arranged so that the toothed belt 29 meshes with the toothed belt 29 in a normal bent state.
and from the first pulse motor 30 to the toothed belt 29
The number of teeth is set between 10 and 30 so that the driving force is transmitted at a predetermined transmission ratio. Note that if the number of teeth is 9 or less, the driving force cannot be transmitted smoothly, and if the number of teeth is 31 or more, the diameter of the pulley 27 becomes too large and driving becomes difficult. Also, the first
Since the toothed belt 29 and the first pulley 27 are involutely engaged with each other, it is preferable that the shape of the toothed portion 37 be close to an involute.

Thus, when the first pulse motor 30 is driven based on a predetermined pulse signal, the first pulleys 27 are each stepped by a predetermined angle. Then, the first toothed belt 29 is driven to run and move the first and second carriages 24, 25. At this time, since the teeth 37 of the first toothed belt 29 are made of an elastic material, even if the first pulley 27 is fed in steps, the vibration caused by this is absorbed by the teeth 37. . Therefore, vibrations caused by step feeding of the pulse motor 30 are not transmitted to the optical system 12, and a high quality image can be obtained.

Moreover, the pulse motor 30 with a step angle of 2 degrees or less is driven by a 1-2 phase excitation method, the pitch of the teeth 37 of the toothed belt 29 is set to 3 mm or less, and the number of teeth of the first pulley 27 is set to 10 to 10. By setting each to 30, sufficient resolution can be obtained for the copying machine, thereby preventing poor image quality. That is, to explain the relationship between the feed amount per step of the pulse motor 30 and the resolution, the resolution is as shown in FIGS. 10 and 11.
As shown in the figure, the resolution is often expressed in terms of the number of lines per 1 mm, and it is generally considered that a resolution of 4 lines per 1 mm is sufficient for copying machines. In order to obtain this resolution, the period between the optical system 12 and the photoreceptor 3 is an important factor, but in order to obtain a resolution of 4 lines per 1 mm, a simple calculation shows that P = 1/pitch per pitch.
It is good if one line can be identified at 4=0.25mm. However, as shown in FIG. 12, the pulse motor 30 has a vibration period for one pulse, so the resolution is affected by how many millimeters it moves per one pulse. In other words, it is sufficient to determine the reduction ratio from the pulse motor 30 so that the feed amount corresponding to one pulse is P=0.25 mm or less. Therefore, if the step angle of the pulse motor 30 is within 2 degrees, that is, 180 equal parts/rotation, the pitch of the first toothed belt 29 is 3 mm or less, and the number of teeth of the first pulley 27 is 30, then the number of teeth per step is 90／
It will feed 180=0.5mm. This is 0.25mm, which is half of the per pulse when driving with the 1-2 phase excitation method.
This corresponds to the minimum requirement for obtaining a resolution of 4 lines per mm. Therefore, by configuring as described above, a resolution of 4 lines per mm or more can be obtained.

Further, since the pulse motor 30 is driven at 1000 to 3000 PPS, good driving is achieved.
In other words, as shown in FIG. 13, the pulse motor 30 tends to be unstable at low speeds, and has an unstable region.
Occurs below 1000PPS. Furthermore, if the number of pulses per unit second is increased, the movement becomes smoother, but not only does the torque decrease, but also high frequencies characteristic of a pulse motor are generated. For this reason, it is desirable to drive at 1000 to 3000 PPS.

Note that the drive device 4 is not limited to the above embodiment, and may be configured as shown in FIG. 14 or 15, for example. That is, in the embodiment shown in FIG. 14, the first mirror 6 is connected via the third carriages 39, 39, and the second and third mirrors 7, 8 are connected via the fourth carriages 40, 40, respectively. It is movably supported by a pair of rails 41, 41. Further, the third carriage 39 is connected to a second toothed belt 44 that is stretched around fifth and sixth pulleys 42 and 43 so as to run endlessly along the rail 41, and The carriage 40 is connected to a third toothed belt 47 that runs endlessly around the seventh and eighth pulleys 45 and 46 along the racele 41. Further, the fifth pulley 42 is connected to a rotating shaft 49 of a second pulse motor 48, and the seventh pulley 45 is connected to a rotating shaft 51 of a third pulse motor 50. Then, the rotational speeds of the second and third pulse motors 48, 50 and the number of teeth of the fifth and seventh pulleys 42, 45 are appropriately selected so that the third carriage 39 is twice as fast as the fourth carriage 40. They are designed to move at speed in the same direction. In the embodiment shown in FIG. 15, the fifth pulley 42 transfers the driving force from the second pulse motor 48 to the seventh pulley 4 through the first speed reduction mechanism 52.
5 transfers the driving force from the third pulse motor 50 to the second
The transmission speed is transmitted through the deceleration mechanism 53 of each of the two. Then, the rotational speeds of the second and third pulse motors 48 and 50 and the reduction ratios of the first and second reduction mechanisms 52 and 53 are appropriately selected so that the third carriage 39 is connected to the second
They are now moving in the same direction at twice the speed.

[Effect of idea]

As explained above, according to the present invention, an optical system that moves relative to the original in order to scan the original;
Since it is equipped with a pulse motor that drives this optical system, and a toothed belt that is provided to transmit the driving force of this pulse motor to the optical system and has teeth made of a substantially trapezoidal elastic body, Vibrations caused by the step feed of the pulse motor can be prevented as much as possible, and high-quality images can be obtained. Furthermore, the step angle of the pulse motor should be within 2 degrees, the tooth pitch of the toothed belt should be 3 mm or less, and the number of teeth on the pulley should be 10 to 10.
By setting each to 30, sufficient resolution can be obtained for the copying machine. Furthermore, the pulse motor
Since it is driven at 1000 to 3000 PPS, excellent effects such as good driving can be achieved.

[Brief explanation of the drawing]

FIG. 1 is a front view showing a conventional example, FIG. 2 is a plan view, FIG. 3 is a perspective view schematically showing a prior invention, and FIG. 4 is an electronic copy using an optical system drive device according to the present invention. Fig. 5 is a perspective view showing the optical system drive device of the same embodiment, Fig. 6 is a perspective view showing the toothed belt of the same embodiment, and Fig. 7 is a longitudinal side view of the same embodiment. Figure 8 is also a longitudinal front view,
FIG. 9 is a side view, FIGS. 10 and 11 are diagrams for explaining the resolution, FIG. 12 is a diagram showing the relationship between the rotation angle and time of the pulse motor, and FIG. 13 is a diagram showing the relationship between the rotation angle and time of the pulse motor. Relationship diagram with seconds,
FIG. 14 is a perspective view showing another embodiment, and FIG. 15 is a perspective view showing still another embodiment. 12... Optical system, 27... First pulley, 29... First toothed belt, 30... First pulse motor, 3
7... Tooth portion, 42... Fifth pulley, 44... Second toothed belt, 45... Seventh pulley, 47... Third toothed belt, 48... Second pulse motor, 50... Third toothed belt. pulse motor.

Claims (1)

[Claims for Utility Model Registration] An optical system that moves relative to the original in order to scan the original, and an optical system that is provided to drive this optical system and has a step angle of 2 degrees or less, and at least the optical system that scans the original. A pulse motor having a rotating shaft driven at 1000 to 3000 PPS by a 1-2 phase excitation method, and 10 to 30 motors fixed to the rotating shaft of the pulse motor and transmitting the driving force of the rotating shaft. The toothed belt is provided with a pulley having teeth, and a toothed belt that is stretched over and meshed with the teeth of the pulley and has teeth made of an approximately trapezoidal elastic body with a pitch of 3 mm or less. An optical system drive device for an image forming machine, characterized in that the optical system is fixed to a part of a belt.