JP2732620B2 - Photoconductor drive unit - Google Patents

Description

Description: BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a photoconductor driving device for an electrostatic recording device.

2. Description of the Related Art In many cases, a photosensitive member of an electrostatic recording device such as an electrophotographic copying machine, a facsimile, or a laser printer is driven directly from a drive motor via a gear. In rare cases, a chain drive is employed. . However, in recent years, there has been an increasing demand for quietness of office automation equipment, and a photoconductor drum is driven from a drive motor using a urethane toothed belt (timing belt (prize name)) as a photoconductor drive transmission unit. Methods are being adopted.

FIG. 4 and FIG. 5 are views showing an example of a photoconductor driving device employing a toothed belt as a transmission means, in which a toothed pulley 2 directly connected to a photoconductor drum 1 and a driving motor shaft 3 are connected. A toothed belt 5 is stretched between the toothed pulley 4 and the photoreceptor drum 1 which rotates in the direction shown by the arrow in FIG.
Is driven to rotate.

A developing device 6 for visualizing an electrostatic latent image formed on the photoconductor is provided along the peripheral surface of the photoconductor drum 1, and the developing device is referred to as, for example, an S-NSP system. In a case where a method is adopted in which the developing roller is pressed against the photoconductor and the toner is transferred to the photoconductor to perform development, the developing unit 6 is slidable in the direction of coming into contact with and separating from the photoconductor. The developing roller 7 is urged in the direction of the photosensitive drum by springs 11 provided at both ends (in the axial direction of the photosensitive member), and is pressed against the photosensitive drum 1 with a force of, for example, 1 kgf. The electrostatic latent image formed on the photoconductor drum is developed by rotating the photoconductor drum 1 in a forward direction at a peripheral speed (for example, 2.25 times) higher than the peripheral speed of the photoconductor drum.

In order to determine the tension of the toothed belt 5 to a predetermined value, a tighter 8 is provided. FIGS. 6 and 7
As shown in detail in the figure, an idler 10 which is in contact with the outer peripheral surface on the loose side of the toothed belt 5 is provided near the free end, and is higher than the thickness of the tighter 8 in a hole provided at the opposite end, so that it can be loosely fitted into the hole. The shaft is rotatably supported by a shaft formed as a stepped screw 12 having a portion. One end is hooked near the point where the idler 10 is provided, and the other end is hooked at one point of the machine frame. The spun ring 9 urges the idler 10 in a direction in which the idler 10 comes into pressure contact with the outer peripheral surface of the toothed belt 5. Also, the idler 10 and the shaft 12 of the tightener 8
An arc-shaped long hole 8a centered on the shaft 12 is formed at a middle position between the hole and the hole, and a screw 13 with a flat seat is penetrated therethrough and screwed into a screw hole provided in the machine frame to tighten the tightener 8a. Can be fixed to the machine frame.

The conventional method of applying tension to the belt 5 with this device is as follows.
When the photosensitive drum 1 is not driven and the belt 5 is stopped, the screw 13 is loosened, and the tighter 8 is
7, the idler 10 is freely pressed against the belt 5, and as shown in FIG. 7, the belt 5 is pushed in at the position of the idler 10 and the screw 13 is tightened in a bent state. This is performed by fixing the tightener 8 to the machine frame.

When the photosensitive drum 1 is stationary, the tension on the tension side of the belt 5 and the tension on the slack side are equal, and a constant tension is applied by the tighter 8.

However, when the photosensitive drum 1 rotates and the developing roller 7 rotates at a higher peripheral speed, the belt 5
The tension on the tight side and the tension on the loose side are different. Further, when the developing roller is pressed against the photosensitive member and rotates at a higher peripheral speed than the photosensitive member, the balance between the tension on the tension side and the tension on the loose side is lost.

 This will be described with reference to FIG.

In general, when driving a rotating body, greater than the tension T _s in the loosening direction of the tension T _t of tight side Without load fluctuation to the driven object, since the difference is constant, the rotation unevenness does not occur .

Now, as described above, the developing roller 7 is pressed against the photosensitive drum 1, the photosensitive body is rolling at a peripheral speed v _1, rotates at a greater peripheral speed v ₂ than v ₁ and the developing roller 7 to the forward In this case, a frictional force f is generated between the photoreceptor drum 1 and the developing roller 7, and this force acts on the photoreceptor pulley 2 as a rotational driving force F due to friction and acts in the rotational direction.

If the radius of the photoreceptor 1 is r and the radius of the pitch circle of the photoreceptor pulley 2 is R, then F = rf / R.

Due to the generation of the rotational driving force F, the balance between the tension side and the loose side of the toothed belt 5 for driving the photoreceptor is lost, and the photoreceptor cannot rotate at a constant speed even if the motor rotates at a constant speed. As a result, jitter occurs due to uneven rotation on the image.

The variation of the balance of the tension, the rotational driving force F of the acts in the rotational direction of the photosensitive member, when _{Δ (T t -T s) =} ΔT, △ T changes with time, slack side of the belt Then, the force F determined by the frictional force f was used as the energy source.
Self-excited vibration of T occurs. The self-excited vibration of ΔT also acts on the linear velocity v ₁ of the photoconductor, and the rotation unevenness of the photoconductor 1 causes the rotation unevenness at a specific period coincident with the self-excited vibration of ΔT. In general, in the case of self-excited vibration, the fluctuation period of ΔT is equal to the natural vibration of the system and appears as belt vibration, and the vibration frequency of the belt and the frequency of uneven rotation of the photoconductor detected by the encoder match. Has been confirmed.

Therefore, as in the conventional, if fixed in balance position determined the Taitona 8 in the initial tension in a state where the photosensitive member is stationary T _s =
Although the _{T t,} T _t> T _s next to the driving of the photosensitive member with the generation of torque loss, especially during startup becomes _{T t} "T _s.

Furthermore, as described above, when a forcing force due to friction acts on the photoreceptor, a fluctuation in tension occurs, so that stable rotation of the photoreceptor becomes impossible.

However, when the photosensitive body drive, if the value of T _t -T _s is a constant value, the rotation unevenness of the photoreceptor due to the fluctuation of the belt tension does not occur.

SUMMARY OF THE INVENTION The present invention has been made in consideration of the above-described problems of a photoconductor driving device that drives a photoconductor drum using a conventional toothed belt. Even when pressing in the forward direction at a peripheral speed greater than the peripheral speed, uneven rotation of the photoconductor due to fluctuations in the tension of the belt driving the photoconductor is suppressed, stable rotation is obtained, and jitter on the image is reduced. It is an object of the present invention to provide a photoconductor driving device capable of performing the following.

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention is to drive the photoreceptor with a toothed belt, and to adjust the tension of the belt by a position adjuster having an idler which is in pressure contact with the outer peripheral surface of the belt. In the photoconductor driving device of the electrostatic recording apparatus, the above-mentioned tighter is supported so as to be freely displaceable in a direction in which the idler comes into contact with and separates from the belt, and urges the tighter in a direction in which the above-mentioned idler comes into pressure contact with the above-mentioned belt. It has a spring, and the tightener is provided on the tight side and the loose side of the toothed belt.

Operation As described above, the tighter is provided on both the tension side and the loose side of the belt, and the tensioner is also displaceably urged in the direction of pressing the idler against the belt by a spring, so that the belt is attached to the belt on the belt tension side. Even in the case of occurrence of a blur, the tighter on the tension side follows the amount according to this amount, absorbs the vibration of the belt, and obtains stable rotation of the photoconductor.

Examples Hereinafter, examples of the present invention will be described in detail with reference to the drawings.

FIG. 1 is a diagram showing an embodiment in which the present invention is applied to the photoconductor driving device described in FIG. Therefore, members having the same functions will be described with the same reference numerals.

FIG. 2 and FIG. 3 are a front view and a sectional view of the tighter. The difference between the present embodiment and the conventional photoconductor driving device shown in FIGS. 4 to 7 is that a screw that passes through the arc-shaped long hole 8a of the tighter 8 and is screwed to the machine frame is different from the conventional device. A flat seat screw 13 is used. With this, the tighter is tightened by the spring 9 at the equilibrium position where the tensioner is pulled by the spring 9 and the idler 10 is pressed against the belt 5 while the photoconductor 1 is in a stationary state. However, in this embodiment,
As shown in FIG. 3, a stepped screw 14 is used as a screw that penetrates the frame 8a and is screwed to the machine frame. The height of the step portion of the stepped screw 14 is higher than the plate thickness of the tighter 8, and the diameter of the step portion is a diameter that can be loosely fitted into the elongated hole 8a. As the screw 12 serving as the rotation axis of the tighter, a stepped screw 12 which is higher than the plate thickness of the tighter 8 and is loosely fitted in a hole provided in the rotation center of the tighter is used. Can swing. Tightener 8 is spring 9
As a result, the idler 10 can be constantly pressed against the belt 5 with a constant pressing force.

Since the apparatus of this embodiment has the above-described configuration, when the tension of the belt fluctuates, the tighter 8 is displaced in accordance with the amount. That is, when the frictional force increases, the belt 5 is pulled, so that the
It is displaced to the position pushed outward as shown by the broken line a in the figure. This position is a position where the frictional force + the initial tension of the belt and the load by the spring 9 of the tightener are balanced.

Conversely, when the frictional force is weakened, the tighter 8 moves inward of the belt loop, and comes to a position where it bites into the belt.

Thus, the tighter 8 is displaced in accordance with the frictional force, and the belt tension on the loose side is always maintained at a constant value T. As a result, the rotation unevenness of the photoconductor, which would otherwise be caused by the fluctuation of the belt tension, can be suppressed, and a stable rotation of the photoconductor can be obtained.

Further, in this embodiment, the idler 10 'is also pressed against the outer peripheral surface of the toothed belt 5 on the tight side thereof, and is urged by the spring 9' in the direction of pressing the idler against the belt 5, so as to rotate around the support shaft 12 '. Is provided with a tighter 8 'so as to be rotatable.

Therefore, when the tension on the tension side of the toothed belt 5 fluctuates, the tighter 8 'always moves to a position where the tension of the belt and the force of the spring 9' are balanced, and the tension on the tension side also changes. Can be kept constant even when the rotational driving force fluctuates.

In particular, when a tighter is provided only on the loose side of the belt, when the photoconductor is pressed against the developing roller and rotates in a forward direction at a higher peripheral speed than the photoconductor, a very large frictional force is applied. The belt on the tension side may bend and the photoreceptor cannot rotate stably. However, as described above, the idler can be displaced not only on the loose side of the belt but also on the tension side, and the idler presses against the belt with a spring. The biasing in the direction absorbs the amount of deflection, which is very effective in preventing tension fluctuation on the tension side.

The effect of the spring 9 'on the tighter 8' is ineffective unless it is smaller than that on the loose side. Specifically, it is appropriate to set the spring load of the tightener 8 to about 1/6 to 1/4.

As described above, according to the present invention, in addition to the above-described effects, the belt is bent on the tight side of the belt in addition to the above-described effects by providing the tightener not only on the loose side of the photoconductor driving belt but also on the tight side. Even if it occurs, it is absorbed, so that it absorbs the vibration of the belt caused by the fluctuation of the tension on the tension side, and contributes to the stable rotation of the photoconductor.

[Brief description of the drawings]

FIG. 1 is a front view showing an embodiment of the present invention, FIG. 2 is a front view of the tighter, FIG. 3 is a cross-sectional view thereof, FIG. FIGS. 6 and 7 are side views showing the structure near the drive belt, FIGS. 6 and 7 are front views illustrating the detailed structure and operation of the tighter, and FIG. 8 is an explanatory view illustrating the force acting on the belt. is there. DESCRIPTION OF SYMBOLS 1 ... Photoreceptor drum, 2 ... Photoreceptor pulley, 3 ... Drive motor shaft, 4 ... Motor pulley, 5 ... Toothed belt, 7 ... Developing roller, 8,8 '... Tightener, 8a ... Circular oblong hole, 9,9 '... Spring, 10,10' ... Idler, 12,12 '... Stepped screw (rotary shaft), 14 ... Stepped screw

Claims (2)

(57) [Claims] 1. A photoconductor driving apparatus for an electrostatic recording apparatus, wherein a photoconductor is driven by a toothed belt, and an idler that is in pressure contact with the outer peripheral surface of the belt is used to determine the tension of the bell by a position-adjustable tightener. The tighter is supported so as to be freely displaceable in a direction in which the idler comes into contact with and separates from the belt, and has a spring for urging the titler in a direction in which the idler comes into pressure contact with the belt. A photoconductor driving device provided on the tension side and the loose side of the photoconductor. 2. A driving device for a photosensitive member according to claim 1, wherein the spring of the tighter on the tension side is set to have a smaller load than the spring of the tighter on the loose side. apparatus.