JPH10214017A - Driver protection unit for image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a driver protection unit of an image forming device which can accurately respond to variation in load current and protect a driver against thermal destruction due to overloading without stopping image forming operation. SOLUTION: A current detection resistance 13 detects the total load current of a driver array part 23 where transistors(TR) 10a to 10d which supply currents to load coils 2L, 3L, 8L, and 9L for a paper feed clutch, a relay clutch, a brush motor, and a dehumidifying heater. A comparator 14 compares the obtained current value with a reference current value; when the detected current value exceeds the reference current value, the logical value of the signal at the output terminal of the comparator 14 becomes '0', the signal at the output terminal of an AND element 20 becomes '0'< and the TR 10d turns off to cut off the current supply to the dehumidifying heater which is low in priority as to the image forming operation, thereby preventing the driver array part 23 from thermally breaking down without stopping the image forming operation.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

[0001] 1. Field of the Invention [0002] The present invention relates to a driver protection unit for an image forming apparatus, which is incorporated in the image forming apparatus and protects a driver that supplies a current to a load.

[0002]

2. Description of the Related Art In an image forming apparatus such as a copying machine, a driver drives a load such as a main motor, a brush motor, various clutches, and a fixing heater. Therefore, if the required current value changes over a wide range, the load may change significantly due to aging or operating conditions, and the load current from the driver will exceed the allowable value, causing the driver to overheat. Thermal breakdown may occur.

In order to solve such a problem, Japanese Patent Application Laid-Open No. 60-57867 discloses that a cooling fan and a load connected in parallel to the cooling fan are cut off by a restraining current of the cooling fan. A safety device of a copying machine that indirectly notifies a user of an abnormality of the copying machine is disclosed.

Japanese Unexamined Patent Publication No. Sho 60-204289 discloses that a load current of a motor is detected, A / D converted and input to a CPU, and when the load current value is abnormal, the CPU displays an error on a display. An apparatus for diagnosing an accident of a copying apparatus for performing the above is disclosed. Further, it has been proposed to detect the temperature of a package of a driver in an image forming apparatus, and to manage the temperature in the casing of the copying machine based on the detected temperature.

[0005]

SUMMARY OF THE INVENTION Japanese Patent Application Laid-Open No. Sho 60-5786
In the method disclosed in Japanese Patent Application Laid-Open No. 7-107, the cooling fan and the load connected in parallel to the cooling fan are cut off by the constrained current of the cooling fan. There is a problem that the operation rate of the system decreases.

Further, the method disclosed in Japanese Patent Application Laid-Open No. 60-204289 has a drawback that an appropriate process is not always executed by a user who has confirmed the display of an abnormality.

Further, in a system in which the temperature of a package of a driver in an image forming apparatus is detected and the temperature of the inside of the housing of the copying machine is controlled based on the detected temperature, a sudden change in current value due to a sudden change in load and temperature There is a time lag between the detection and the detection, and there is a problem that prompt response cannot be performed.

The present invention has been made in view of the current situation of protection of a driver against a change in load current of an image forming apparatus as described above, and an object of the present invention is to appropriately cope with a change in load current. An object of the present invention is to provide a driver protection unit of an image forming apparatus capable of protecting a driver from thermal destruction due to overload without stopping an image forming operation.

[0009]

According to a first aspect of the present invention, there is provided a driver protection unit for an image forming apparatus, which is incorporated in the image forming apparatus and protects a driver supplying a current to a load. A driver array unit that supplies currents to a plurality of types of loads, a current detection unit that detects a total load current supplied from the driver array unit, and a reference current value detected by the current detection unit. A current comparing unit that compares the detected current value with the reference current value. If the current comparing unit determines that the detected current value has exceeded the reference current value, the low priority of the image forming operation is low among the plurality of types of loads. Control means for interrupting the supply of current to the load.

[0010] Similarly, in order to achieve the above object, the invention according to claim 2 is different from the invention according to claim 1 in that the reference current changing means for changing the reference current value according to the environmental temperature is provided. It is characterized by being provided.

According to a third aspect of the present invention, there is provided an image forming apparatus according to the first or second aspect, wherein the detected current value is equal to the reference current value. Alarm means for alarming that the vehicle has exceeded the threshold is provided.

[0012]

BEST MODE FOR CARRYING OUT THE INVENTION

[First Embodiment] FIG. 1 shows a first embodiment of the present invention.
This will be described with reference to FIG. FIG. 1 is a circuit diagram showing a configuration of a main part of the present embodiment, FIG. 2 is an explanatory diagram showing a state of arrangement of a load member related to the present embodiment in a housing of an image forming apparatus, and FIG. FIG. 10 is an explanatory diagram of a change in reference current value due to a change in environmental temperature in the embodiment.

In the present embodiment, as shown in FIG. 2, a timing belt 7 is wound around a main motor 1 for driving a load in a housing C of the image forming apparatus. Paper feed clutch 2, relay clutch 3, and registration clutch 4 for carrying
Sprockets 5 and 6 for transmitting the driving force of the main motor 1 are provided. Further, a brush motor 8 for driving the developing unit and a dehumidifying heater 9 for forming a high quality image by skipping the moisture of the transfer paper on which the image is transferred are provided in the housing C.

In the main part of this embodiment, as shown in FIG. 1, a control unit 18 for controlling the whole operation includes a storage unit 19 for storing various data on the control operation, and a current for the load. Is connected to the driver array unit 23 that supplies the data. The driver array unit 23 has a configuration in which transistors 10a to 10d are arranged in a package 11, and the control unit 18 provides the bases of the transistors 10a, 10b, and 10c with the transistors 10a, 10b, and 10c.
c are forward-biased drive signals fa and f, respectively.
b and fc can be applied.

An AND element 20 is connected between the base of the transistor 10d and the control unit 18, and a drive signal fd for biasing the transistor 10d in the forward direction is connected to one input terminal of the AND element 20 so as to be applied. AND
The output terminal of element 20 is connected to the base of transistor 10d.

On the other hand, between the load power supply terminal t1 and the collectors of the transistors 10a, 10b, 10c and 10d, a load winding 2L of the paper feed clutch 2, a load winding 3L of the relay clutch 3, and a load winding of the brush motor 8 are provided. Line 8L, dehumidification heater 9
Are connected to each other, and the transistor 1
The emitters 0a, 10b, 10c, and 10d are connected to each other, and a current detection resistor 13 is connected between the connection point and the ground.

The current detecting resistor 13 and the transistor 10
The connection point between the emitters a to 10d is connected to the inverting input terminal of the comparator 14 via the resistor 21R. A capacitor 21C is connected between the inverting input terminal of the comparator 14 and the ground. Form the smoothing circuit 21.

A resistor 15 and a thermistor 16 are connected in series between the terminal t2 of the reference power supply of the voltage Vcc and the ground, and a resistor 24 and a Zener diode 17 are connected in series with the resistor 15 and the thermistor 16. Are connected in parallel, the connection point between the resistor 15 and the thermistor 16 is connected to the non-inverting input terminal of the comparator 14, and the output terminal of the comparator 14 is connected to the other input terminal of the AND element 20. ing.

Here, the thermistor 16 has a temperature characteristic as shown in FIG. 3 with respect to the ambient temperature. When the ambient temperature rises with the reference voltage Vcc applied, the resistance value decreases. When the current increases and the environmental temperature decreases, the resistance value increases and the current decreases. Therefore, when the environmental temperature increases, the input voltage value to the non-inverting input terminal of the comparator 14 decreases, and when the environmental temperature decreases, The configuration is such that the input voltage value to the non-inverting input terminal of the comparator 14 increases.

The operation of this embodiment having such a configuration will be described. When the image forming operation of the image forming apparatus is started,
A control signal is output from the control unit 18 to drive the main motor 1, the brush motor 8, the paper feed clutch 2, the relay clutch 3, and the registration clutch 4 and the dehumidifying heater 9 is turned on. As a result, an increase in the humidity of the transfer paper used for image formation is prevented.

As described above, when the image forming operation proceeds and the load is in a normal state, the driving signals fa, fb, and fc from the control unit 18 cause the transistors 10a,
10b and 10c are respectively biased in the forward direction, and a collector current flows through the transistors 10a to 10c, so that the load winding 2L of the feed clutch 2, the load winding 3L of the relay clutch 3, and the load winding 8L of the brush motor 8 , A normal load current flows, and the image forming operation proceeds.

In this normal load state, a predetermined total load current programmed in advance flows through the current detection resistor 13, and a predetermined load voltage VL based on the total load current is generated at both ends of the current detection resistor 13. Then, the load voltage VL is input to the inverting input terminal of the comparator 14. On the other hand, the non-inverting input terminal of the comparator 14 has a resistance value of the resistor 15 and the resistance value of the thermistor 16 as R1 and R2, respectively, and a reference current Is = V based on the voltage Vcc applied to the terminal t2.
cc / (R1 + R2), the reference voltage Vs = Vcc
R2 / (R1 + R2) is input.

The comparator 14 compares the load current VL with the reference voltage Vs. If Vs> VL, the logical value of the signal at the output terminal of the comparator 14 becomes "1", and the output terminal of the AND element 20 Becomes logical "1" and a forward bias is also applied to the transistor 10d, so that the load winding 9L of the dehumidifying heater 9 is loaded.
Also, the image forming operation proceeds with a normal load current flowing.

When the load on the brush motor 8 increases and the load current flowing through the load winding 8L of the brush motor 8 increases due to an increase in frictional force due to aging, for example, from the normal load state, the current detection resistor 13 , A load voltage VL1> VL higher than a predetermined load voltage VL is generated at both ends of the current detection resistor 13, and this load voltage VL1 is input to the non-inverting input terminal of the comparator 14. You.

Therefore, when the load voltage reaches a value satisfying the condition of VL1> Vs, the logical value of the signal at the output terminal of the comparator 14 becomes "0" and the logical value of the signal at the output terminal of the AND element 20 becomes "0". ", And the transistor 10d is biased in the reverse direction, so that no current flows through the load winding 9L of the dehumidification heater 9 and the operation of the dehumidification heater 9 stops.

As described above, in this embodiment, when the total load current exceeds a predetermined value due to, for example, an increase in the load current flowing through the load winding 8L of the brush motor 8, the priority is low in the image forming operation. The operation of the dehumidification heater 9 is stopped, and the transfer sheet is not dehumidified, but the image forming operation is continued without being stopped.
3 is prevented from being thermally damaged.

The maintenance process is performed after the end of a series of image forming operations, so that the brush motor 8
When the load current flowing through the load winding 8L returns to a predetermined normal value, a bias is again applied to the transistor 10d in the forward direction during the next image forming operation, and the load current flows through the dehumidification heater 9 so that the dehumidification heater 9 Is driven again, and the drive array unit 23 returns to the normal load current supply operation.

In this case, in this embodiment, the environmental temperature rises and the resistance of the thermistor 16 becomes, for example, Rh (Rh
<R2), the reference voltage Vs becomes Vs1 (Vs1
<Vs), the condition for increasing the total load current when the operation of the dehumidifying heater 9 is stopped becomes severe, and the condition for lowering the heat radiation efficiency from the package 11 in a high environmental temperature state is compensated for. 23 is properly prevented from thermal destruction.

Further, when the environmental temperature decreases, the thermistor 16
Increases, for example, to Rc (Rc> R2).
Since the reference voltage Vs rises to Vs2 (Vs2> Vs), the condition for increasing the total load current when the operation of the dehumidifying heater 9 is stopped is moderated, and the condition for increasing the heat radiation efficiency from the package 11 in a low environmental temperature state. Correspondingly, the drive array unit 23 is operated under an efficient operation in which the allowable load current is increased.
The thermal destruction of the steel is properly prevented.

As described above, according to the present embodiment, the allowable value of the total load current supplied by the driver array 23 is set in response to the heat radiation efficiency from the package 11 of the drive array unit 23 based on the environmental temperature. When the total load current exceeds the set allowable value, the transistor 10
A reverse bias is applied to d, the priority of the image forming operation is low, and the dehumidifying heater 9, which is not necessarily required for basic image formation, is stopped, and the image forming operation is not stopped, thereby reducing the operation rate of the apparatus. Thus, it is possible to prevent the thermal destruction of the drive array unit 23. Further, in the present embodiment, accurate control is performed without sending a feedback signal to the control unit 18, the configuration is simple, the manufacturing cost is not increased, and the load is properly adjusted in accordance with the environmental temperature. The current can be set to prevent the driver array unit 23 from being thermally destroyed.

[Second Embodiment] A second embodiment of the present invention will be described with reference to FIG. FIG. 4 is a circuit diagram showing a configuration of the present embodiment.

In this embodiment, as shown in FIG. 4, an increase in the total load current from a predetermined reference value by the comparator 14 is different from that of the first embodiment already described with reference to FIG. When detected, the display unit 25 for displaying an abnormal increase in the load current of the driver array unit 23 is connected to the control unit 18, and the output terminal of the comparator 14 is connected to the control unit 18. The configuration of the other parts of the present embodiment is the same as that of the first embodiment already described, and therefore will not be described repeatedly.

In this embodiment, the load on the brush motor 8 increases due to an increase in frictional force due to, for example, aging during the image forming operation, and the load winding 8L of the brush motor 8 is increased.
When the load current flowing through the current detection resistor 13 increases, the total load current flowing through the current detection resistor 13 increases, and both ends of the current detection resistor 13 have a load voltage VL1> V higher than a predetermined load voltage VL.
L occurs, the load voltage VL1 is input to the non-inverting input terminal of the comparator 14, and if VL1> Vs, the logical value of the signal at the output terminal of the comparator 14 becomes "0", and the output terminal of the AND element 20 The logical value of the signal is “0”
As a result, the transistor 10d is biased in the reverse direction, and no current flows through the load winding 9L of the dehumidification heater 9, and the operation of the dehumidification heater 9 stops.

At the same time, the output signal of the comparator 14 is input to the control unit 18 and the output signal
The display unit 25 displays a message indicating an abnormal increase in the load current of the driver array unit 23 on the display unit 25. Other operations of the present embodiment are the same as the operations of the first embodiment already described, and therefore, will not be described repeatedly.

As described above, according to this embodiment, in addition to the effects obtained in the first embodiment already described,
When the load current of the driver array unit 23 abnormally increases, a message indicating that the load current of the driver array unit 23 abnormally increases is displayed on the display unit 25, so that the user can quickly detect the abnormal increase of the load current of the driver array unit 23. It is possible to quickly restore the driver array unit 23 to a normal operation state by quickly performing maintenance at an optimal time while avoiding a decrease in the operation rate of the device.

[0036]

According to the first aspect of the present invention, the total load current supplied from the driver array unit which supplies current to each of a plurality of types of loads is detected by the current detecting means, and the obtained current value is determined by the current value. The comparing means compares the detected current value with the reference current value and determines that the detected current value has exceeded the reference current value. Since the supply is interrupted, the driver supplying the current to the load can be protected from thermal damage due to overload without stopping the image forming operation and without reducing the operation rate of the image forming apparatus.

According to the second aspect of the invention, in addition to the effect obtained by the first aspect, the reference current value is changed by the reference current changing means in accordance with the environmental temperature. Under the adapted conditions, it is possible to appropriately control the interruption of the current supply to the load having a low priority in the image forming operation.

According to the third aspect of the present invention, in addition to the effects obtained by the first or second aspect, when the current detected by the current detecting means exceeds the reference current value, an alarm is issued by the alarm means. Since the alarm is issued, the user can quickly grasp the interruption of the current supply to the low-priority load, set the maintenance time, and more appropriately perform the image forming operation.

[Brief description of the drawings]

FIG. 1 is a circuit diagram showing a configuration of a main part of a first embodiment of the present invention.

FIG. 2 is an explanatory diagram showing an arrangement state of a load member related to the embodiment in a housing of the image forming apparatus.

FIG. 3 is an explanatory diagram of a change in reference current value due to a change in environmental temperature according to the embodiment.

FIG. 4 is a circuit diagram showing a configuration of a second exemplary embodiment of the present invention.

[Explanation of symbols]

 DESCRIPTION OF SYMBOLS 1 Main motor 2 Feeding clutch 3 Relay clutch 4 Registration clutch 5, 6 Sprocket 7 Timing belt 8 Brush motor 9 Dehumidifying heater 13 Current detection resistor 14 Comparator 15 Resistance 16 Thermistor 18 Control unit 19 Storage unit 20 AND element 23 Driver array unit

Claims (3)

[Claims] 1. A driver protection unit of an image forming apparatus, which is incorporated in an image forming apparatus and protects a driver that supplies a current to a load, a driver array unit that supplies a current to a plurality of types of loads, and the driver array. Current detection means for detecting a total load current supplied from the unit; current comparison means for comparing a detection current value detected by the current detection means with a reference current value; When it is determined that the reference current value is exceeded, among the plurality of types of loads,
And a control unit for interrupting a current supply to a load having a low priority in an image forming operation. 2. The image forming apparatus according to claim 1, further comprising: a reference current changing unit configured to change the reference current value in accordance with an environmental temperature with respect to the driver protection unit of the image forming apparatus. Driver protection unit for forming equipment. 3. The image forming apparatus according to claim 1, further comprising: a warning unit for warning that the detected current value exceeds the reference current value. Characteristic driver protection unit of an image forming apparatus.