JPH0588532A - Image forming device - Google Patents

Abstract

PURPOSE:To provide the image forming device which can increase the electrification potential of a toner recovering roller, can effectively prevent the generation of unequal images and fogging and decreases the wear degree of a member for triboelectrification. CONSTITUTION:This image forming device is disposed with the toner recovering roller 22 formed of an insulator 22c in at least the outer peripheral part near the working position of an image carrying member 1 and a developing roller 14. The member 23c for triboelectrification triboelectrifying the outer peripheral surface of the toner recovering roller 22 to the polarity reverse from the polarity of a toner is provided in such a manner that the member comes into contact with the outer peripheral surface of the toner recovering roller 22. The toner recovering roller 22 is intermittently and rotationally driven at a speed having an acceleration.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a copying machine, a printer,
The present invention relates to an image forming apparatus such as a facsimile.

[0002]

2. Description of the Related Art As a copying machine, an electrode composed of a metallic rotating roller is provided on the downstream side of the developing roller of a developing device in the rotating direction, and a bias voltage is applied to this electrode to generate an electric field between the developing roller and the electrode. A device has been already developed in which the toner remaining on the surface of the developing roller after the toner is supplied to the photosensitive drum and the floating toner are attracted to the electrodes to prevent the occurrence of image unevenness and fog (Actual Publication No. 1-5776).
See Japanese Patent Publication No. 3).

[0003]

The above-mentioned conventional device has the following problems. (A) A power supply for applying a bias voltage to the electrodes is required, which is costly.

(B) In order to supply a voltage to the metal rotating roller electrode, a terminal such as a brush must be used, the bias tends to become unstable, and the terminal must be replaced regularly.

(C) When the power of the machine is turned off immediately after the machine is stopped or immediately after the copying is finished, or when the front door of the copying machine is opened due to a recording paper jam or the like, the electrodes are not biased and float. Toner cannot be attracted to the electrodes.

(D) Since the metal rotary roller electrode has a high thermal conductivity, when the temperature changes during replacement, dew condensation occurs on the surface of the metal rotary roller electrode and adheres to the metal rotary roller electrode. The toner melts, and the melted toner is collected by the developing device, which adversely affects the toner.

Therefore, in order to solve these problems,
In order to frictionally charge the outer peripheral surface of the toner collecting roller with a polarity opposite to that of the toner, the applicant arranges a toner collecting roller at least having an outer peripheral portion formed of an insulating material near the position where the image carrier and the developing roller act. An image forming apparatus for frictionally charging the toner collecting roller has been developed by providing the triboelectric charging member of (1) in contact with the outer peripheral surface of the toner collecting roller.

The present invention relates to an improvement of the above-mentioned image forming apparatus developed by the present applicant, which can increase the charge potential of the toner collecting roller and effectively prevent the occurrence of image unevenness and fogging. It is an object of the present invention to provide an image forming apparatus that is capable of reducing the wear of the triboelectrification member.

[0009]

SUMMARY OF THE INVENTION In an image forming apparatus according to the present invention, a toner recovery roller having at least an outer peripheral portion formed of an insulating material is disposed near an operating position of an image carrier and a developing roller, and the toner recovery roller is provided. A frictional charging member for frictionally charging the outer peripheral surface with a polarity opposite to that of the toner is provided in contact with the outer peripheral surface of the toner collecting roller, and the toner collecting roller is driven to rotate intermittently and at a speed having acceleration. It is characterized by

The image bearing member includes a photosensitive drum, a photosensitive belt, a dielectric drum and the like. As the toner collecting roller, one in which the entire toner collecting roller is formed of an insulating material, one formed of a metal roller main body and an insulating layer formed on the outer peripheral surface of the metal roller main body, and the like are used.

The frictional charging member for frictionally charging the outer peripheral surface of the toner collecting roller to the opposite polarity to the toner may be used as a toner scraping member for scraping off the toner attracted and adhered to the toner collecting roller.

A drive mechanism for intermittently rotating the toner recovery roller at a speed having an acceleration is, for example, attached to the shaft of the toner recovery roller and integrally with the toner recovery roller in one rotation direction. Regarding the other rotation direction, the lever rotates idly with respect to the toner collecting roller, the cam that rotates at a constant speed in a predetermined direction and rotates the lever, and the lever always rotates in the direction idling with respect to the toner collecting roller. A drive mechanism is used that includes a biasing means that biases the lever against the cam.

[0013]

In the image forming apparatus according to the present invention, when the toner collecting roller is rotated, the friction charging member and the insulating outer peripheral surface of the toner collecting roller rub against each other, so that the insulating outer peripheral surface of the toner collecting roller is opposite to the toner. It is triboelectrically charged. Since the toner collecting roller is driven to rotate intermittently and at a speed having acceleration, the charging potential of the toner collecting roller becomes higher than that when the toner collecting roller is rotated at a constant speed, and after the toner collecting roller stops. Also, the degree of attenuation of the charging potential at is also moderate.

Therefore, toner scattered from the developing roller or floating toner when the machine is turned off immediately after the machine is stopped or immediately after the copying is finished, or when the front door of the copying machine is opened due to a recording paper jam or the like is used as the toner. Effectively sucked and attached to the collection roller.

Further, since at least the outer peripheral portion of the toner collecting roller is formed of an insulator, it is
Condensation does not occur on the surface of the toner collecting roller, and the toner is not adversely affected.

In the case where the frictional charging sheet for frictionally charging the outer peripheral surface of the toner collecting roller to the opposite polarity to the toner also serves as the toner scraping member for scraping off the toner attracted and adhered to the toner collecting roller. The toner adhering to the toner collecting roller is scraped off by the triboelectric charging member and returned to the developing device, for example.

[0017]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a copying machine will be described below with reference to the drawings.

FIG. 1 shows an image forming section of a copying machine.

Around the photosensitive drum 1, along the rotation direction thereof (direction shown by arrow A in FIG. 1), a charger 2 for charging the photosensitive layer on the surface of the photosensitive drum, is formed on the photosensitive layer. A developing device 3 for making the electrostatic latent image noticeable as a toner image, a recording paper guide path 4 for guiding the recording paper to the photoconductor drum 1, and a transfer for transferring the toner image formed on the photosensitive layer to the recording paper. An electric discharger 5, a separating electric discharger 6 for separating the recording paper from the photosensitive drum 1, and a cleaning device 7 for removing the toner remaining on the photosensitive drum 1 after transfer are arranged.

In the housing 11 of the developing device 3, a developing spiral 12, a stirring roller 13 and a developing roller 14 are provided.
Are arranged. A toner recovery unit 20 is attached to the housing 11 of the developing device 3.

2 to 4 show the toner collecting unit 20.

In the following description, the front means the left side of FIG. 3, and the rear means the right side of FIG.

The toner collecting unit 20 includes a frame 21.
And a toner collecting roller 22 rotatably attached to the frame 21, and a toner scraping / friction charging unit 23 attached to the frame 21.

The frame 21 is composed of a base portion 21a extending in the length direction of the developing roller 14 and a pair of bearing portions 21b formed at both ends of the base portion 21a. The base portion 21 a has an upper wall 31 that is substantially parallel to the lower wall of the housing 11 of the developing device 3.
And a lower wall 32 behind the upper wall 31 and substantially parallel to the upper wall 31, and a connecting wall 33 connecting the upper wall 31 and the lower wall 32. The upper wall 31 is provided with a plurality of elongated screw insertion slots 34 in the front and rear at predetermined intervals in the length direction. Elongated elongated holes 35 for screw insertion are also formed in front and rear of both ends of the lower wall 32.

The bearing portion 21b is formed from both ends of the upper wall 31,
Each bearing 2 is provided so as to project upward and forward.
A synthetic resin bearing 24 is attached to 1b in a penetrating state. Each bearing part 24 has two oval parts 24a.
And 24b, and both oval parts 24a and 24b
Are joined so that their major axes form a 90 degree angle. The oval-shaped portion 24a inside each bearing portion 24 is fitted into the oval-shaped holes 25 formed in both bearing portions 21b.

The toner collecting roller 22 is the photosensitive drum 1
And the developing roller 14 between the developing roller 14 and the developing roller 14 are arranged on the downstream side in the rotation direction of the developing roller 14 (the direction indicated by the arrow B in FIG. 1).
The toner collecting roller 22 has an insulating layer 2 on the entire outer peripheral surface of a metal roller body 22a having a shaft portion 22b having a small diameter at both ends.
2c is formed by coating. The material of the roller body 22a is, for example, non-magnetic stainless steel. As a material for the insulating layer 22c, a nylon resin (for example, trade name Asahi Pla Coat ARM-
900) and other synthetic resins are used.

Then, both shaft portions 2 of the toner collecting roller 22.
2b is rotatably inserted in the corresponding bearing 24.
A retainer 26 is fitted into the end of the one shaft 22b protruding from the bearing 24. At the end of the other shaft portion 22b protruding from the bearing 24, the lever 27 rotates integrally with the shaft portion 22b in one direction and idles with respect to the shaft portion 22b in the opposite direction. It is installed.

Toner scraping and friction charging unit 2
Reference numeral 3 denotes a sheet support member 23a having a trapezoidal cross section, which extends in the length direction of the developing roller 14 and whose front surface is inclined forward and obliquely upward.
A sheet 23c for toner scraping and tribocharging applied to the front surface of the sheet supporting member 23a through a reinforcing sheet 23b, and a sheet 23 for scraping toner and tribocharging.
c and a holding plate 23d for holding the reinforcing sheet 23b between the front surface of the sheet supporting member 23a and the reinforcing sheet 23b.

The seat support member 23a is applied to the lower surface of the upper wall 31 of the base portion 21b of the frame 21, and the frame 21 is fixed by the screw 36 inserted in the long hole 34 for screw insertion.
It is screwed to.

The sandwiching plate 23d is substantially L-shaped in transverse cross section, and comprises a fixing portion 37 along the lower surface of the seat supporting member 23a and a sandwiching portion 38 along the front surface of the seat supporting member 23a. Then, with the toner scraping and friction charging sheet 23c and the reinforcing sheet 23b sandwiched between the sandwiching portion 38 and the front surface of the sheet supporting member 23a, the fixing portion 37 is screwed to the sheet supporting member 23a with the screw 39. By
The toner scraping / triboelectric charging sheet 23c and the reinforcing sheet 23b are attached to the sheet supporting member 23a.

Toner scraping and friction charging sheet 23
The upper portion of c projects above the reinforcing sheet 23b and is in pressure contact with the toner collecting roller 22. Reinforcement sheet 23b
Is to reinforce the toner scraping / triboelectric charging sheet 23c. In consideration of the fact that both ends of the toner scraping / friction charging sheet 23c become weaker at the both ends than at the central part, the upper and lower widths of the both ends of the reinforcing sheet 23b are formed to be wide.

Toner scraping and friction charging sheet 23
c is a synthetic resin sheet such as a polyester sheet,
A conductive sheet (for example, a cast polycarbonate film (trade name KL3) containing special conductive carbon manufactured by Vantec Co., Ltd.) or the like is used. Reinforcement sheet 23
As b, a synthetic resin sheet such as a polyester sheet is used.

As described above, since the toner collecting roller 22 and the toner scraping / triboelectric charging sheet 23c are unitized, it is easy to replace them. Further, since the toner scraping / friction charging unit 23 is screwed to the frame 21 by the screw 36 inserted into the screw insertion long hole 34 of the frame 21, the toner collecting roller 22
The toner scraping / triboelectric charging sheet 23c can be accurately positioned by using a jig or the like when assembling the toner collecting unit 20. Therefore, the toner scraping / friction charging sheet 23c can be accurately positioned at a position where it is effective for scraping the toner from the toner collecting roller 22 and the pressure contact force is not too large.

5 to 7 show a mounting structure and a mounting method of the toner recovery unit 20 to the housing 11 of the developing device 3.

Bearing members 40 of the developing roller 14 are fixed to both end surfaces of the housing 11 of the developing device 3.
A keyhole-shaped notch 41 for fitting the bearing 24 for the toner collecting roller 22 of the toner collecting unit 20 is formed in the lower front end portion of both bearing members 40. This notch 4
1 is a narrow portion 41a of the opening and a circular portion 41 following the narrow portion 41a.
b. The width of the narrow portion 41a is formed slightly larger than the length of the minor axis of the oval portions 24a and 24b of the bearing 24. The diameter of the circular portion 41b is equal to that of the oval portion 2 of the bearing 24.
It is formed to be slightly longer than the length of the major axis of 4a and 24b.

The toner collecting unit 20 is attached to the housing 11
First, as shown in FIGS. 5 and 6, the oval-shaped portions 24b on the outside of each bearing 24 of the toner recovery unit 20 are aligned so that the major axis direction thereof coincides with the depth direction of the notch 41. Then, the notch 41 is fitted into the circular portion 41b from the narrow portion 41a.

Next, as shown in FIGS. 6 and 7, the toner recovery unit 20 is rotated counterclockwise by about 90 degrees about the shaft portion 22b, and the lower wall 32 of the base portion 21b of the frame 21 is moved to the housing 11. Apply to the outer surface of the lower wall.

At this time, the oval-shaped portion 24b of each bearing 24 also rotates about 90 degrees, and the minor axis direction thereof coincides with the depth direction of the notch 41, as shown in FIG. The oval portion 24b is in a state in which it does not come off from the circular portion 41b of the notch 41.

Thereafter, the screw 42 inserted in the screw insertion long hole 35 formed in the lower wall 32 of the frame 21 is screwed into the screw hole 43 formed in the lower wall of the housing 11 to collect the toner. The unit 20 is attached to the housing 11. The toner collecting roller 22
The metal roller body 22a is not grounded.

As described above, after the bearing 24 of the toner collecting unit 20 is fitted into the notch 41 formed in the bearing member 40 of the developing roller 14, the toner collecting unit 20 is
The toner collecting unit 20 can be attached to the developing device 3 by a simple operation such as rotating and screwing.

Further, the bearing 24 of the toner collecting unit 20
Is fixed to the notch 41 formed in the bearing member 40 of the developing roller 14, so that the distance between the toner collecting roller 22 and the developing roller 14 is accurately positioned.

Further, when the toner collecting unit 20 is attached to the developing device 3, the screw 36 for adjusting the position between the toner collecting roller 22 and the toner scraping / friction charging sheet 23c is located at a position where it cannot be operated. The screw 36 is not operated by mistake, and the good positional relationship between the toner collecting roller 22 and the toner scraping / triboelectric charging sheet 23c is maintained.

FIG. 8 shows a drive mechanism of the toner collecting roller 22.

On the outer surface side of one bearing member 40 of the developing roller 14, a gear 51 is fitted and fixed to one end of a shaft 14a of the developing roller 14. A gear 52 rotatably attached to the bearing member 40 meshes with the gear 51. A gear 53 rotatably attached to the bearing member 40 meshes with the gear 52. A substantially rectangular cam 54 having four concave curved surfaces on the outer periphery is fixed to the shaft of the gear 53.

One shaft portion 22b of the toner collecting roller 22
The lever 27 attached to the shaft rotates integrally with the shaft portion 22b in the direction indicated by the arrow E in FIG. 8 and idles with respect to the shaft portion 22b in the opposite direction. Then, the lever 27 causes the shaft portion 22b to move by the spring 55.
, The lever 27 is always urged in the direction opposite to the arrow E, and the tip of the lever 27 is pressed against the outer peripheral surface of the cam 54 by this urging force.

When the shaft 14a of the developing roller 14 is driven by a drive motor (not shown), the gear 51 rotates in the direction of arrow B, and the gear 52 accordingly rotates in the direction of arrow C. Further, as the gear 52 rotates, the gear 53 rotates in the direction of arrow D, and the cam 54 rotates in the same direction.

The lever 27 moves as the cam 54 rotates.
When the toner reciprocally swings within a certain angle range and rotates in the direction of arrow E, the toner recovery roller 22 is rotated in that direction.
That is, the toner collecting roller 22 intermittently rotates at a speed having a large acceleration.

9 to 11 show a state in which the toner scattered from the developing roller 14 is attracted by the toner collecting roller 22 and the attracted toner is returned to the developing device 3.

In these figures, arrows A, B and E
Indicates the rotation directions of the photosensitive drum 1, the developing roller 14, and the toner collecting roller 22.

As the toner collecting roller 22 rotates, the toner scraping / triboelectric charging sheet 23c rubs against the insulating layer 22c on the surface of the toner collecting roller 22, and as shown in FIG. The (-) charges move to the toner scraping / triboelectric charging sheet 23c, and the insulating layer 22c is positively (+) charged.

Since the toner has a negative polarity, FIG.
As shown in, the toner 50 scattered from the developing roller 14
Is attracted to the insulating layer 22c on the surface of the toner collecting roller 22 and adheres to the insulating layer 22c.

Insulating layer 22 on the surface of the toner collecting roller 22
As shown in FIG. 11, the toner 50 adhering to c is scraped off by the toner scraping / friction charging sheet 23c, and returned to the inside of the housing 11 of the developing device 3 by the ears of the developing roller 14.

The charge potential of the toner collecting roller 22 immediately becomes zero even when the power of the machine is turned off immediately after the machine is stopped or immediately after the copying is finished, or when the front door of the copying machine is opened due to a recording paper jam or the like. Since there is still some remaining,
Also in this case, the floating toner is sucked and adhered to the toner collecting roller 22 and returned to the housing 11 of the developing device 3.

In this way, since the toner scattered and the floating toner can be collected from the developing roller 14, the occurrence of image unevenness and fog can be prevented. Since the outer peripheral surface of the toner collecting roller 22 is covered with the insulating layer 22c, dew condensation does not occur on the surface of the toner collecting roller due to temperature change, and the toner is not adversely affected.

FIG. 12 shows the charging potential [V] of the insulating layer 22c on the surface of the toner collecting roller 22 and the average rotation of the toner collecting roller 22 with respect to the average number of rotations of the toner collecting roller 22 (the number of rotations of the gear 53) [rpm]. The experimental data of the rise time [sec] of the charging potential immediately after the start of the rotation of the toner collecting roller 22 with respect to several [rpm] is shown. Figure 1
In FIG. 2, black circles indicate charging potential and white circles indicate rising time.

From this figure, it is understood that the higher the average number of revolutions of the toner collecting roller 22, the faster the rising speed of the charging potential immediately after the rotation of the toner collecting roller 22 starts and the higher the charging potential.

However, the higher the average number of rotations of the toner collecting roller 22, the higher the degree of wear of the toner scraping / friction charging sheet 23c. Therefore, the number of rotations of the gear 53 is preferably 20 to 70 [rpm]. ..

In this embodiment, the toner collecting roller 22
Is intermittently rotated by the cam 54 and the lever 27 at a speed having a large acceleration, so that the toner recovery roller 22 is rotated at a constant speed equal to the rotation speed of the gear 53. There is an advantage that the rising speed of the charging potential immediately after the start of the rotation becomes faster and the charging potential becomes higher.

For example, in this embodiment, the gear 53 is set to 60.
To obtain a charging potential that is substantially equal to the charging potential of the insulating layer 22c on the surface of the toner collecting roller 22 generated when rotating at [rpm] by rotating the toner collecting roller 22 at a constant speed, About 500 [rp
Therefore, the life of the toner scraping / tribocharging sheet 23c is shortened.

FIG. 13 shows how the toner recovery roller 22 and the toner scraping / friction charging sheet 23c are charged when a conductive sheet is used as the toner scraping / friction charging sheet 23c.

The outer surface of the insulating layer 22c on the surface of the toner recovery roller 22 is positive (+) due to the friction between the toner recovery roller 22 and the toner scraping / friction charging sheet 23c.
Is charged, and the inner surface side of the insulating layer 22c is negatively (−) charged,
The roller body 22a of the toner collecting roller 22 is positively (+) charged. Further, the toner scraping / triboelectric charging sheet 23c is negatively charged.

Toner scraping and frictional charging sheet 23
When a conductive sheet is used as c, the roller body 2
2a, the insulating layer 22c, and the toner scraping / friction charging sheet 23c are capacitors sandwiched between the roller body 22a and the toner scraping / friction charging sheet 23c in which the insulating layer 22c is a conductor. Make a structure.

Therefore, in this case, as compared with the case where an insulating sheet is used as the toner scraping / friction charging sheet 23c, charges are more likely to be accumulated in the insulating layer 22c, and the charging potential of the insulating layer 22c and The fall of the charging potential after the driving of the toner recovery roller 22 is stopped becomes gentle.

FIG. 14 shows the charging of the toner collecting roller 22 when a conductive sheet (cast-type polycarbonate film containing special conductive carbon manufactured by Vantec Co., Ltd. (trade name KL3)) is used as the toner scraping / friction charging sheet 23c. FIG. 15 shows the potentials of the toner collecting roller 22 when an insulating sheet (polyester sheet) is used as the toner scraping / friction charging sheet 23c.

In the above embodiment, the toner collecting roller 22
Is composed of a metal roller body 22a and an insulating layer 22c formed on the outer peripheral surface of the roller body 22a.
The entire toner recovery roller 22 may be made of an insulating material such as synthetic resin.

Further, in the above-described embodiment, a friction charging member for frictionally charging the outer peripheral surface of the toner collecting roller to the opposite polarity to the toner and a toner scraping member for scraping off the toner attracted and adhered to the toner collecting roller are provided. Are constituted by the same member (toner scraping and frictional charging sheet 23c), but the frictional charging member and the toner scraping member may be separately provided.

[0067]

According to the present invention, since the toner recovery roller is driven to rotate intermittently and at a speed having an acceleration, the charging potential of the toner recovery roller is higher than that when the toner recovery roller is rotated at a constant speed. Becomes higher, the degree of attenuation of the charging potential after the toner collecting roller is stopped becomes gentle.

Therefore, the toner scattered from the developing roller or the floating toner when the power of the machine is turned off immediately after the machine is stopped or immediately after the copying is finished, or when the front door of the copying machine is opened due to a recording paper jam or the like, is a toner. Effectively sucked and attached to the collection roller. As a result, it is possible to effectively prevent the occurrence of image unevenness and fogging.

Moreover, since it is not necessary to apply a bias voltage, the cost can be reduced. Further, the toner is not adversely affected by the temperature change or the like.

[Brief description of drawings]

FIG. 1 is a configuration diagram illustrating an image forming unit of a copying machine.

FIG. 2 is an enlarged perspective view showing a toner recovery unit.

FIG. 3 is an enlarged side view showing a toner recovery unit.

FIG. 4 is an enlarged cross-sectional view showing a toner collecting roller and a toner scraping / triboelectric charging unit.

FIG. 5 is an enlarged side view showing a method of attaching the toner recovery unit to the housing of the developing device.

FIG. 6 is an enlarged side view showing a method of attaching the toner recovery unit to the housing of the developing device.

FIG. 7 is an enlarged side view illustrating a method of attaching the toner recovery unit to the housing of the developing device.

FIG. 8 is an enlarged side view showing a drive mechanism of a toner recovery roller.

FIG. 9 is an explanatory diagram for explaining how the insulating layer on the surface of the toner collecting roller is charged by the friction between the toner collecting roller and the toner scraping and friction charging sheet.

FIG. 10 is an explanatory diagram for explaining how the toner scattered from the developing roller is sucked and attached to the insulating layer on the surface of the toner collecting roller.

FIG. 11 is an explanatory diagram for explaining a state in which the toner attached to the insulating layer on the surface of the toner collecting roller is scraped off by the toner scraping / triboelectric charging sheet and returned to the housing of the developing device. ..

FIG. 12 is a graph showing experimental data of the charging potential of the insulating layer on the surface of the toner collecting roller with respect to the average number of rotations of the toner collecting roller and the rise time of the charging potential immediately after the start of rotation of the toner collecting roller with respect to the average number of rotations of the toner collecting roller. Is.

FIG. 13 is a schematic diagram showing a charging state of a toner recovery roller and a toner scraping / friction charging sheet when a conductive sheet is used as the toner scraping / friction charging sheet.

FIG. 14 is a graph showing a charging potential of a toner collecting roller when a conductive sheet is used as a sheet for scraping toner and also for frictional charging.

FIG. 15 is a graph showing a charging potential of a toner recovery roller when an insulating sheet is used as a toner scraping / friction charging sheet.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Photoconductor drum 14 Development roller 22 Toner recovery roller 22a Roller body 22b Shaft part 22c Insulating layer 23c Toner scraping and friction charging sheet 27 Lever 54 Cam 55 Spring

Claims (5)

[Claims] 1. A toner collecting roller, at least an outer peripheral portion of which is formed of an insulating material, is arranged near the position where the image bearing member and the developing roller work, and the outer peripheral surface of the toner collecting roller is triboelectrically charged in a polarity opposite to that of the toner. The friction charging member is provided so as to contact the outer peripheral surface of the toner collecting roller, and the toner collecting roller is intermittently and rotationally driven at a speed having acceleration. 2. The image forming apparatus according to claim 1, wherein the toner collecting roller comprises a metal roller body and an insulating layer formed on an outer peripheral surface of the metal roller body. 3. The image forming apparatus according to claim 1, wherein the entire toner recovery roller is made of an insulating material. 4. The image forming apparatus according to claim 1, wherein the friction charging member also serves as a toner scraping member for scraping off the toner attracted and adhered to the toner collecting roller. 5. A lever mounted on the shaft of the toner collecting roller and rotating integrally with the toner collecting roller in one rotation direction and idling with respect to the toner collecting roller in the other rotation direction, and fixed in a predetermined direction. The roller driving mechanism including a cam that is rotated at a high speed and that rotates the lever, and a biasing unit that constantly biases the lever in a direction of idling with respect to the toner collecting roller and presses the lever against the cam, The image forming apparatus according to claim 1, wherein the collecting roller is intermittently and rotationally driven at a speed having an acceleration.