JPH0749640A - Electrophotographic device - Google Patents

Abstract

PURPOSE:To reduce cost, to save power, and to make a device small in size and light in weight by switching torque generated in a main motor in the case of initial rotation so that it may be large for a previously set time and small after the lapse of a set time on condition that a photoreceptor drum is detected to be new. CONSTITUTION:When a new drum unit 1 is attached to a main body 6 and a power source is turned on or a cover 7 is closed, a new drum unit exchanging detector 50 detects that the drum unit is new, so that a life counter 9 is cleared to zero. Since the attached drum unit 1 is new, the photoreceptor drum 2 directly comes in contact with a developing roller 4A not through a toner T layer. When the means 50 detects that it is new, generated torque switching control means 31 and 32 allow the main motor 2M to rotate at a high current value so as to switch the generated torque of the motor 2M to the large one. When the set time elapses, the control means 31 and 32 allow the main motor 2M to rotate at a low current so as to switch the torque to the small one.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an electrophotographic apparatus in which a photosensitive drum rotatably driven by a main motor and a developing roller are arranged in contact with each other so as to form a predetermined nip.

[0002]

2. Description of the Related Art FIG. 6 shows a schematic structure of an electrophotographic apparatus.
In FIG. 6, reference numeral 1 denotes a drum unit, which includes a photosensitive drum 2, a waste toner box 3, a developing device 4 (developing roller 4A, toner supply roller 4B), which form a process means together with a charging device and a transfer device, integrally with a case 5. It is built in. The drum unit 1 can be attached to and detached from the main body 6 in the direction of the arrow Y by opening the cover 7. Further, the photosensitive drum 3, the developing roller 4A, the toner supply roller 4B, the conveying roller and the like are rotationally driven by a main motor 2M including a DC servo motor and a stepping motor.
Therefore, the main motor 2M, its drive circuit, and the power supply device 100 are selected so as to generate a torque according to the maximum load in consideration of the condition that the developing device 4 is full of toner and that the paper is being conveyed. ing.

Thus, when the sheet is fed from the right side to the left side in the mounted state shown by the solid line in FIG. 6, the electrostatic image is transferred when passing below the photosensitive drum 2, and the image is formed on the sheet. Can be printed. Then, the electrophotographic (printed image) can be reliably fixed on the sheet by passing the fixing device 8 in the left direction. The control unit 20 controls the entire drive. Further, the power supply device 100 generates and outputs a control power supply (DC5V), a drive power supply (DC24V), and the like.

From the viewpoint of ensuring clear printing, the life of the photosensitive drum 2 is regulated by the printing operation time, generally the number of printing sheets. In this connection, the capacity of the waste toner box 3 is selected so that it will be full when the life of the photosensitive drum 2 is reached, and the developing device 4 is also replaced. For this reason, consumable items including the photosensitive drum 2, the waste toner box 3, the developing device 4, etc. are integrally incorporated in the case 5.

A drum life management unit (9, 50) is provided in order to properly manage the replacement time depending on the life of the drum unit 1. That is, for example, a life counter 9 for counting the number of print sheets is provided in the main body 6 and the drum unit 1 is replaced when the count value obtained by the life counter 9 reaches a predetermined value. Further, the life counter 9 is formed so as to be cleared to zero when the drum unit 1 is mounted on the main body 6, that is, when the new replacement detector 50 detects that the new photosensitive drum 2 has been replaced. There is. Further, a fusing element (for example, a fuse resistor) is installed in the drum unit 1 (case 5), and the fusing element is fused after the new replacement detector 50 detects a new replacement, so that the drum unit 1 that has been used once is not reattached. The one formed in the above has also been previously proposed.

In the electrophotographic apparatus, particularly in the case of the developing method using the non-magnetic one-component toner (T), the peripheral surface of the developing roller 4A is made of conductive urethane rubber and the photosensitive drum 2 is formed. The contact is arranged in the pressed state, as shown in FIG.
There is a nip having a predetermined width N as shown in FIG. Therefore, the torque generated by the main motor 2M is
It is largely selected to overcome the frictional resistance due to this nip.

[0007]

By the way, such electrophotographic apparatuses are no exception, and there is a strong demand for cost reduction, power consumption reduction, and size and weight reduction. Therefore,
If the capacity of the main motor 2M can be reduced or the generated torque during operation can be suppressed to be small, not only the main motor 2M but also its drive circuit and the power supply device 100 can be reduced in size and capacity.

An object of the present invention is to provide an electrophotographic apparatus capable of achieving cost reduction, power saving, size reduction and weight reduction by suppressing the torque generated by the main motor to a small value.

[0009]

In an electrophotographic apparatus, a main motor 2M is installed to detect whether or not paper remains in a conveyance path inside the apparatus when the power is turned on or the cover is closed. A so-called initial rotation process is provided in which the rotary drive is performed for a preset time. At this time, the photosensitive drum 2 and the developing roller 4A are rotated as well as the conveying roller. Therefore, when the initial rotation is completed, the toner T having a thickness of, for example, 30 μm is also present in the nip having the width N as shown in FIG. 8B, so that the frictional resistance between the photosensitive drum 2 and the developing roller 4A. Will be very small.

However, conventionally, as is conventionally known, as shown in FIG. 7, there is no distinction between the initial rotation (Int.), The subsequent warm-up, and the printing operation (Nom.) After the time t1. Is driven by the maximum current In that can generate the maximum torque.

However, the same initial rotation (In
t. 8A, the case where the photosensitive drum 2 and the developing roller 4A are in direct contact with each other without the toner T layer as shown in FIG. 8A, and the case where the toner T layer is provided as shown in FIG. 8B. There may be a case of indirect contact through. In the case of (B), the frictional resistance is small, but in the case of (A), it is relatively large.
Here, the two and 4A shown in the same (A) are in the state of being in direct contact with each other only in the initial rotation immediately after the drum unit 1, that is, the photosensitive drum 2 and the developing roller and 4A are replaced with new ones. . Moreover, this first
The initial rotation time T of the second time is an extremely short time that can be ignored when compared with the length of the printing operation time until the replacement time due to the life of the photosensitive drum 2.

The present invention pays attention to such peculiar technical matters and increases the torque generated by the main motor 2M only when the photosensitive drum 2 and the developing roller 4A are in direct contact with each other without the toner T layer, and other than that. At the time of, it is configured so that it can be made smaller.

That is, the electrophotographic apparatus according to the present invention is
In an electrophotographic apparatus in which a photosensitive drum rotatably driven by a main motor and a developing roller are arranged in contact with each other so as to form a predetermined nip, a torque generated by the main motor is formed so that the torque can be switched between large and small. A new product detecting means for detecting replacement with a new one, and a preset time for the torque generated by the main motor at the time of initial rotation on condition that the photosensitive drum is detected as a new one by the new detecting means. The present invention is characterized in that a generated torque switching control means for switching only a large value inside and a small value after a set time has elapsed is provided.

[0014]

In the case of the present invention having the above-mentioned structure, the generated torque switching control means largely switches the generated torque of the main motor at the time of initial rotation immediately after the photosensitive drum replaced by the new product detecting means is detected as being new. . Therefore, the photosensitive drum and the developing roller are in direct contact with each other without interposing the toner layer, and can rotate smoothly even if the frictional resistance is large.
Further, due to this initial rotation, a toner layer is formed between the photosensitive drum and the developing roller. Thus, when the preset set time has elapsed, the generated torque switching control means switches the generated torque of the main motor to a small value. In this case, since the photosensitive drum and the developing roller are in indirect contact with each other via the toner layer, the frictional resistance is very small.
Even if the generated torque is small, smooth printing operation can be performed. At the same time, power consumption is small.

[0015]

Embodiments of the present invention will be described below with reference to the drawings. As shown in FIG. 1, the electrophotographic apparatus (10) includes a control unit 20 and an engine unit (engine controller 30 and engine 40), forms a torque generated by the main motor 2M so that the torque can be switched between large and small, and detects a new product. Means (50)
And the generated torque switching control means (31, 32) are provided, and the generated torque is large during the initial rotation in which the photosensitive drum 2 and the developing roller 4A directly contact each other without the toner T layer, and indirectly contact via the toner T layer. When it does, the generated torque is made small and is automatically switched.

The engine 40 has the same structure as that shown in the conventional example (FIG. 6), and has a nip of width N as shown in FIG. Has been done. The nip width N is set to 4.5 mm, and the toner T layer is formed to a thickness of 30 μm.
Further, the torque (kg · cm) required to overcome the frictional resistance between the photosensitive drum 2 and the developing roller 4A is 4k when the two and 4A are in direct contact as shown in FIG.
2 in the case of indirect contact via the toner T layer at g · cm
It is kg · cm. The influence of the thickness of the toner T is small. Further, if the amount of toner in the developing device 4 is large, the load on the toner supply roller 4B increases, so that the torque generated by the main motor 2M must be qualitatively increased. However, the increase is very small as shown in FIG. The amount of fluctuation depending on whether or not the paper is being conveyed is also very small.
Therefore, it is understood that the load fluctuation that affects the torque generated by the main motor 2M is most often due to the difference in the contact state between the photosensitive drum 2 and the developing roller 4A.

Now, as shown in FIG. 1, the control section 20 controls C
PU 21, ROM 22, RAM 23, video data conversion chip 24, EEP ROM 25, interface 2
When receiving the print data PDS from the host computer 100 including the data Nos. 6, 27, etc., the print data PDS is converted into video data VDS of bitmap data and transmitted to the engine controller 30. A paper size designation, a print sheet number designation, and the like are transmitted together with the video data VDS.

The engine controller 30 has a CPU 3
1, the ROM 32, the RAM 33, the input / output port 34, the interface 36, etc., and drives and controls the engine 40 by a proper amount at a proper time based on the video data VDS received from the control unit 20. The engine 40 is the same as the conventional example (FIG. 6) as described above, and is provided with a drum life management unit of the photosensitive drum 2 including a new replacement detector 50 and a life counter 9.

This drum life management unit determines whether the drum unit 1 (photosensitive drum 2, developing roller 4A, etc.) replaced when the drum unit 1 is mounted on the main body 6 is new, and when it is determined to be new. Life counter 9
Is cleared to zero, and thereafter the number of print sheets counted by the life counter 9 is monitored to manage the life of the photosensitive drum 2.

That is, a resistance fuse is stored in the drum unit 1, and the resistance fuse and the new replacement detector 50 are electrically connected when the drum unit 1 is mounted on the main body 6. When the resistance fuse is normal, the new replacement detector 50 determines that the drum unit 1 is new and clears the life counter 9 to zero. After that, a current is passed to blow the resistance fuse. On the other hand, if the resistance fuse is blown, it is determined that the resistance fuse is not new, and the life counter 9 is not cleared.

The main motor 2M has a power supply unit 10
It is formed of a stepping motor which uses DC 24 V generated and output at 0 as a drive power source, and is rotation-controlled by the drive circuit 60 shown in FIG. The drive circuit 60 includes a motor phase switching latch circuit 6 bus-connected to the engine controller 30.
1 and a motor current control data circuit 62, a D / A converter 63, and a constant current control circuit 64, and a motor phase switching signal that regulates a rotation direction and a rotation speed from the motor phase switching latch circuit 61 to the constant current circuit 64. Ph is input. Further, the motor current control data circuit 52 is a CPU
The torque value data Tq input from 31 is input to the D / A converter 63, and is converted into an analog signal by the D / A converter 63. That is, the current value I is set in the constant current control circuit 64.

Here, it is understood that the generated torque of the main motor 2M can be switched between large and small. In the case of this embodiment, as shown in FIG. 3, initial rotation (In
t. ), A large current value Ii (for example, 1 A) is set to generate a large torque Tqi, and a small torque Tq is generated during warm-up and printing operation (Nom.) After time t1.
n for generating a small current value In (for example, 0.
6A) can be set.

Thus, the drive circuit 60 and the power supply device 1
00 (24 VDC) can have about half the capacity of the conventional example in terms of current resistance and heat resistance. Therefore, it is possible to significantly reduce costs, reduce size and weight, and save power during printing operation.

Here, the new article detecting means is constructed so as to also serve as the new article replacement detector 50 of the life management unit, and the result of detection of new article or non-new article is in the RAM 33.
Is formed in the work area.

The initial rotation (In
t. ) Period, that is, the set time T is stored in the RAM 32 in advance. Further, in this embodiment, the torque value data Tq (the large torque data Tq) for setting the large current value Ii and the small current value In in the constant current control circuit 64.
i, small torque data Tqn) are also stored in the ROM 32.

The generated torque switching control means detects that the photosensitive drum 2 is new by the new article detecting means (50) (S in FIG. 2).
If the torque generated by the main motor 2M at the time of initial rotation is increased during the preset time T and is set small after the elapse of the preset time T (YES in ST13) on condition that it has been performed (YES in T10), CPU
31 and ROM 32, and ST11 and ST of FIG.
14 is executed.

That is, when it is determined that the product is new (YES in ST10), the CPU 31 reads the large torque data Tqi stored in the ROM 32, outputs it to the motor current control data circuit 62, and outputs it to the constant current control circuit 64. Current Ii
Is set (ST11). Then, the initial rotation (S
T12) is performed for the set time T and ends (ST13).
YES), this time the small torque data Tqn is read from the ROM 32, output to the motor current control circuit 62, and the small current In is set in the constant current control circuit 64 (ST14).

Next, the operation of this embodiment will be described. Figure 6
When the new drum unit 1 is attached to the main body 6 and the power is turned on or the cover 7 is closed, the new replacement detector 50 is detected as a new product and the life counter 9 is cleared to zero. Then, the fuse resistance in the drum unit 1 is blown. Therefore, even if the drum unit 1 is reloaded thereafter, it will not be detected as a new one.

Since the drum unit 1 thus mounted is new, the photosensitive drum 2 and the developing roller 4A are in direct contact with each other without the toner T layer, as shown in FIG. 8 (A). Here, when the new article detecting means (50) detects that the article is new (YES in ST10 of FIG. 2),
The generated torque switching control means (31, 32) has a large current value Ii (for example, 1 A) as shown in FIG.
Is rotated to switch the generated torque to the large torque Tqi (ST11).

Therefore, the first initial rotation (In
t. At this time, even if the photosensitive drum 2 and the developing roller 4A are in direct contact with each other and the frictional resistance is large, the photosensitive drum 2 and the like can be smoothly rotated (ST12). Then, when the set time T elapses (YES in ST13), the generated torque switching control means (31, 32) causes the small current In shown in FIG. 3 (for example,
At 0.6 A), the main motor 2M is rotated to switch to a small torque Tqn (ST14). At this stage, since the toner T layer is interposed between the photosensitive drum 2 and the developing roller 4A as shown in FIG. 8B, the frictional resistance is halved, so that the toner can smoothly rotate even with a small torque Tqn. . That is, the conventional example (Ii) shown by the chain double-dashed line in FIG.
Power consumption can be significantly reduced.

Further, since a large torque Tqi is not applied to the light load, the noise is low. If it is not new (ST
No of 10) makes the generated torque of the main motor 2M a small torque Tqn from the beginning. That is, this operation is performed from the second time onward.

Thus, the CPU 31 causes the worming up (ST15), and receives the print command from the control unit 20 at the subsequent time t1 (YES in ST16).
Then, the engine 40 is drive-controlled to perform printing processing. In addition,
When the printing process is completed and then the power is turned on again to perform the initial rotation again, since the NO determination is made in ST10 this time, the small torque Tqn may remain.

According to this embodiment, however, the generated torque of the main motor 2M is formed so that it can be switched between large and small, and the new product detecting means (50) and the generated torque switching control means (31,
32) is provided, the generated torque is large during the initial rotation in which the photosensitive drum 2 and the developing roller 4A are in direct contact with each other without the toner T layer, and the generated torque is small in the case of indirect contact through the toner T layer. Since the configuration is switched, the main motor 2M, the drive circuit 60, and the power supply device 100 can be reduced in size and weight, the cost can be reduced, and power can be saved during the printing operation.

Further, the initial rotation time (set time T) for rotating the main motor 2M with a large torque is very short as compared with the normal printing operation time for rotating with a small torque. Moreover, the diameter of the photosensitive drum 2 has become smaller and smaller. Therefore, since the set time T of the initial rotation can be set to, for example, several tens of seconds, the main motor 2M and the drive circuit 6
0, the power supply device (DC24V portion) 100 is for small torque, and it is possible to survive the temporary overload only once during the initial rotation, so that the size can be further reduced at a low cost.

Further, since there is no need to drive with a large torque generating power source under a light load, low noise operation can be performed.

Since the new article detecting means is also used as the new article replacement detector 50 of the drum life management unit,
Low cost and easy to embody.

Further, since the main motor 2M is formed of a stepping motor, and the drive circuit 60 includes the motor phase switching latch circuit 61 and the motor current control data circuit 62, the rotation speed and the generated torque can be set separately.
Even if the torque switching operation is performed, high-quality printing can be maintained without causing a slight defect in the formation of an electrostatic latent image on the photosensitive drum 2 or the sheet conveyance.

[0038]

According to the present invention, the generated torque of the main motor is formed so that it can be switched between large and small, a new product detecting means and a generated torque switching control means are provided, and the photosensitive drum and the developing roller do not have a toner layer therebetween. The generated torque is large when the initial rotation is in direct contact with the motor, and the generated torque is automatically changed to be small when the torque is indirectly contacted through the toner layer. Therefore, the main motor, drive circuit, and power supply are small and lightweight. It is possible to achieve higher efficiency and cost reduction, and to significantly reduce power consumption during printing operation. In addition, low noise driving is possible.

[Brief description of drawings]

FIG. 1 is a block diagram showing an embodiment of the present invention.

FIG. 2 is likewise a flowchart for explaining the switching operation.

FIG. 3 is also a diagram for explaining the generated torque switching operation.

FIG. 4 is a diagram for explaining the relationship between the thickness of the toner layer at the nip and the required torque.

FIG. 5 is a diagram for explaining the relationship between the amount of toner in the developing device and the required torque.

FIG. 6 is a side view for explaining a conventional example.

FIG. 7 is a diagram for explaining a conventional constant generated torque operation.

FIG. 8 is a diagram for explaining a contact state between a photosensitive drum and a developing roller in the present invention and a conventional example.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 drum unit 2 photosensitive drum 2M main motor 4 developing device 4A developing roller 4B toner supply roller 5 case 6 main body 9 life counter 10 electrophotographic device 20 control unit 30 engine controller 31 CPU (generated torque switching control means) 32 ROM (generated torque switching) Control means) 33 RAM 40 Engine 50 New article exchange detector (new article detection means) 60 Drive circuit 61 Motor phase switching latch circuit 62 Motor power supply control data circuit 63 D / A converter 64 Constant current control circuit T Set time

Claims (1)

[Claims] 1. An electrophotographic apparatus in which a photosensitive drum rotatably driven by a main motor and a developing roller are arranged in contact with each other so as to form a predetermined nip, and the torque generated by the main motor is formed so as to be switched between large and small. , The new drum detecting means for detecting that the photosensitive drum has been replaced with a new one, and the torque generated by the main motor at the time of initial rotation in advance on condition that the new photosensitive drum is detected by the new detecting means. An electrophotographic apparatus, comprising: a generated torque switching control unit that switches between a large value during a set set time and a small value after the set time has elapsed.