JP2001318574A - Image forming device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide an image forming device equipped with a means for efficiently cooling, with low power consumption, a high voltage conversion circuit variably outputting high voltage required to form an image. SOLUTION: By input of a PWM: pulse width modulation signal 7, an output conversion part 2 turns on/off a transistor 3 and drives the transformer of a conversion part so as to output high voltage. The transistor 3 and the transformer of the conversion part are forcibly cooled by a fan in accordance with the operation state of the high voltage conversion circuit. By using a PWM output ON-signal 6 generated synchronously with the output of the PWM signal 7 over the output period of the signal 7 in a CPU1 as a control signal for a transistor 5 and turning on the transistor 5 in the output period, a fan motor 4 is driven. Thus failures caused by the absence of cooling means are eliminated.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an image forming apparatus (for example, a laser beam printer, a copying machine, etc.) using a high-voltage power supply, and more particularly, to a heating section of a high-voltage power supply (for example, a drive in a high-voltage conversion circuit). Transiters and transformers)
The present invention relates to an image forming apparatus provided with a unit for efficiently cooling the image forming apparatus with low power consumption or a unit for releasing heat generated in a heat generating unit.

[0002]

2. Description of the Related Art In an image forming apparatus such as a laser beam printer or a copying machine, it is necessary to cool a formatter (laser driving circuit) or a low-voltage power supply as a component of the apparatus in order to prevent an obstacle due to heat generated by the apparatus itself. Conventionally, a cooling fan has been used for this purpose. In addition, when cooling using a fan is actually performed, it is required to minimize noise of the fan and power consumption for driving the fan, and proposals have been made for that. In order to prevent the cooling fan from operating unnecessarily, it controls the number of rotations of the cooling fan according to the change in the load current of the circuit that generates heat, and operates the cooling fan efficiently. It is considered that a certain effect can be obtained.

[0003]

However, when the method of controlling the number of rotations of the cooling fan in accordance with the change of the load current of the formatter (laser drive circuit) or the low-voltage power supply exemplified above is adopted, the circuit to be applied is adopted. Although the cooling efficiency of the part is improved, the heat dissipation from other peripheral boards, especially the heat-generating part of the high-voltage power supply is not considered. There is a possibility that a situation in which the fan stops may occur, and the temperature condition of the entire cabin is not always perfect. In other words, heat radiation from the high-voltage power supply requires a corresponding heat radiation means and cooling means. However, the conventional example has no equipment for this purpose, and it is insufficient to adjust the temperature conditions in the entire machine.

SUMMARY OF THE INVENTION The present invention has been made in view of the above-mentioned problems of the prior art, and has as its object to reduce the power consumption of a high-voltage power supply provided with a high-voltage conversion circuit for outputting a high voltage required for image formation. The present invention provides an image forming apparatus (for example, a laser beam printer or the like) provided with a means for efficiently cooling the apparatus or a means for releasing heat generated by the high-voltage power supply.
Also, means for cooling the high-voltage power supply or heat generated by the high-voltage power supply so as to maintain a predetermined temperature condition in response to a change in the operating state of the high-voltage conversion circuit that outputs a high voltage or a change in the surrounding temperature state. An object of the present invention is to provide an image forming apparatus provided with a means for discharging the image.

[0005]

According to a first aspect of the present invention, there is provided an image forming apparatus having a high-voltage power supply having a high-voltage conversion circuit, a cooling means for cooling the high-voltage power supply, and the cooling means being provided with a high-voltage conversion circuit. An image forming apparatus is provided with a cooling control unit that is driven in synchronization with the above operation.

According to a second aspect of the present invention, in the image forming apparatus according to the first aspect, the cooling control means relies on a control signal generated by turning on a period during which an operation signal is input to the high-voltage conversion circuit. It is characterized in that the cooling means is controlled on / off.

According to a third aspect of the present invention, in the image forming apparatus according to the first aspect, when the output of the high-voltage conversion circuit is variable depending on the duty of the operation pulse signal, The driving of the cooling means is controlled depending on the duty of the signal.

According to a fourth aspect of the present invention, in an image forming apparatus having a high-voltage power supply having a high-voltage conversion circuit, a cooling unit for cooling the high-voltage conversion circuit, and the cooling unit is provided in accordance with an ambient temperature of the high-voltage conversion circuit. An image forming apparatus, comprising: a cooling control unit that is driven by a motor.

According to a fifth aspect of the present invention, in the image forming apparatus according to any one of the first to fourth aspects, the cooling means comprises a motor and a fan driven by the motor. .

According to a sixth aspect of the present invention, there is provided an image forming apparatus having a high-voltage power supply having a high-voltage conversion circuit, wherein a radiating means for cooling the high-voltage power supply by an airflow generated by a radiating hole provided in a member to which the high-voltage power supply is fixed. An image forming apparatus comprising:

According to a seventh aspect of the present invention, there is provided the image forming apparatus according to the sixth aspect, further comprising means for closing the heat radiation hole.

According to an eighth aspect of the present invention, there is provided the image forming apparatus according to the seventh aspect, further comprising means for controlling use / non-use of the means for closing the heat radiation hole.

According to a ninth aspect of the present invention, in the image forming apparatus according to the eighth aspect, the means for controlling the use / non-use of the means for closing the heat radiating hole is controlled according to the presence or absence of the image forming operation. It is characterized by operating.

According to a tenth aspect of the present invention, in the image forming apparatus according to the eighth or ninth aspect, the means for controlling the use / non-use of the means for closing the heat radiating hole is controlled according to the ambient temperature of the high voltage power supply. The operation is characterized by

[0015]

DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described based on the following embodiments shown in the accompanying drawings. In the first embodiment, a cooling means (a cooling fan in this embodiment) is operated according to the operation of the high-voltage conversion circuit. FIG. 1 shows a circuit configuration of the embodiment. As shown in FIG. 1, the circuit configuration includes a CPU 1 that controls the entire system (control system of the image forming apparatus), an output conversion unit 2 that performs conversion for outputting a high voltage, and a pulse width modulation from the CPU 1. (Hereinafter referred to as “PWM: Pulse_Width_Modulation”) The signal 3 is used as a control signal to directly drive the output conversion unit 2, the fan motor 4 for cooling the high-voltage conversion circuit having the above configuration, and the PWM signal 7 are synchronized. And a transistor 5 for directly driving the fan motor 4 using the PWM output ON signal 6 as a control signal.

The operation of the circuit shown in FIG. 1 will be described. The output conversion unit 2 in the high-voltage conversion circuit drives the transformer of the output conversion unit 2 with a drive element (in this embodiment, the transistor 3) in response to the input of the PWM signal 7, and outputs a high voltage. Output is PW
It changes according to the duty of the M signal 7 (DUTY: ratio between ON and OFF periods). The operation of such a high-voltage conversion circuit is basically the same as the existing technology, and will not be described in detail here.
In the present embodiment, the heat generating portion of the high-voltage conversion circuit is forcibly cooled by the fan motor 4. The main components to be cooled are, for example, a high-voltage output drive element (in this embodiment, a transistor 3) and an output conversion unit 2 (for example, a transformer). Further, a control circuit for the fan motor 4 is provided to perform the cooling operation according to the operation state of the high-voltage conversion circuit. This is because the power supply to the fan motor 4 is controlled by the switching of the transistor 5. The operation of the fan motor 4 will be described. The CPU 1 generates the PWM output ON signal 6 in synchronism with the output of the PWM signal 7 over the output period. That is, the PWM output ON signal 6 is a PW having a duty set to make the output of the output converter 2 a desired voltage.
The fan motor 4 turns on the transistor 5 by using the PWM output ON signal 6 as a control signal as a drive trigger of the transistor 5 as a signal that continues the ON state during the output period of the M signal 7.
Then, it is driven by supplying the power of the power supply (see FIG. 3).

The cooling operation of this embodiment will be described with reference to the flow chart of FIG. 2. Explaining the presence or absence of the output of the PWM signal 7 (in the example of FIG. 1, the transistor 5 is turned on by the presence / absence of the PWM output ON signal 6). / Corresponding to non-communication) (S
21) If there is an output, a drive current is supplied from a power supply to the fan motor 4 to drive the motor (S22); otherwise, the motor is not driven. The signal appearing in this operation will be described with reference to the signal timing chart of FIG. 3. The signal (PWM output ON signal 6) during the period when the PWM signal 7 is output and the FA
It can be seen that the NON signals are synchronized. As a result, the fan motor 4 is turned on at the same time as the high voltage output, and the fan motor 4 stops at the same time as the high voltage output stops.

Here, referring to the mounting position of the fan motor 4, it is assumed that this motor exclusively performs cooling of the high-voltage conversion circuit, and is provided separately from the fan motor that cools around the fixing unit. In other words, according to the conventional method, cooling including heat of the fixing unit is performed by one fan motor, and cooling of a substrate that generates heat, such as a high-voltage conversion circuit, is generally performed by natural air cooling. In the present invention, it is provided exclusively. Therefore, it is possible to perform a cooling operation suitable for each of the fan motor dedicated to the fixing unit and the fan motor dedicated to the high-voltage conversion circuit. Depending on the shape of the model, the mounting location can be set to the side of the main body (a type used for cooling a general fixing unit). Note that the fan motor 4 may also cool an adjacent heat generating board (for example, a power supply unit). However, in this case, the control is synchronized with the output ON / OFF of the high voltage conversion circuit.
The cooling of the heating part of the high-voltage conversion circuit is mainly performed. O of fan motor 4 synchronized with output ON / OFF of high voltage conversion circuit
By performing N / OFF control, low power consumption and high cooling efficiency can be achieved. For example, if a system that operates at the same time as turning on the power is used, it immediately becomes overcooled (supercooled)
This raises the concern that power consumption increases, but it is also possible to avoid such unnecessary operations.

Next, a second embodiment will be described. The second embodiment is another example of operating a cooling means (in this embodiment, a cooling fan) in accordance with the operation of the high-voltage conversion circuit, and FIG. 4 shows a circuit configuration of the second embodiment. The circuit configuration of this embodiment is basically the same as that of the first embodiment shown in FIG. 1, except that a fan motor 4 for cooling the high-voltage conversion circuit is provided.
This embodiment is different from the first embodiment in that the control signal applied to the transistor 5 for driving the fan is a branch signal from the PWM signal 7 (the PWM branch signal 8 for driving the fan motor 4). Others are CPU1
An output conversion unit 2 that performs conversion for outputting a high voltage;
The first embodiment includes a transistor 3 for directly driving the output conversion unit 2 using the PWM signal 7 as a control signal, a fan motor 4 for cooling the high-voltage conversion circuit, and a transistor 5 for directly driving the fan motor 4. The same shall apply.

The operation of the circuit shown in FIG. 4 will be described. here,
The operation of the fan motor 4 which is different from the first embodiment will be described, and other overlapping parts will be omitted. In this embodiment, the output of the PWM signal 7 generated in the CPU 1 for driving the output converter 2, that is, the output of the output converter 2 is desired as a control signal for operating the transistor 5 for driving the fan motor 4. Set to the voltage of
A PWM branch signal 8 (see FIG. 6) obtained by branching a PWM signal 7 having a duty is used. Assuming that the PWM branch signal 8 is a control signal, the power of the power supply is supplied to the fan motor 4 by performing an operation in which the transistor 5 is turned on during the ON period of the PWM branch signal 8 and turned off during the OFF period. Drive. Therefore, the fan motor 4 is driven with a power proportional to the PWM DUTY of the PWM branch signal 8, and the rotation of the fan motor 4 can be changed according to the high voltage output, that is, the amount of heat generated.

Referring to the flow of FIG. 5, the cooling operation of this embodiment will be described. Whether the PWM signal 7 (that is, the PWM branch signal 8) is an ON output (in the example of FIG. It is determined whether or not the transistor 5 is turned on / off by the ON / OFF of the signal 8) (S51). If there is an output, power is supplied from a power supply to the fan motor 4 to drive the motor (step S51). S52) If no, the motor is not driven. The signals appearing in this operation will be described with reference to the signal timing diagram of FIG.
At the same time that the signal 7 is generated, the PWM branch signal 8 during that period
Is supplied to the fan motor 4 and the fan motor 4 is also driven in synchronization with the high voltage output, that is, the FANON signal is synchronized. This allows the fan motor 4
Is also turned on, and power is supplied according to the PWMDUTY, and the high-voltage output stops, and the fan motor 4 also stops at the same time. As described above, since the FAN drive input (average power) changes due to the PWM DUTY and the rotation of the fan motor 4 is controlled,
By changing the PWM DUTY and increasing the high voltage output, the PWM
As the duty changes, the average power supplied to the motor increases, and the cooling function increases.

Next, a third embodiment will be described. In the third embodiment, a cooling means (a cooling fan in this embodiment) is operated in accordance with the temperature state of the high-voltage conversion circuit. FIG. 7 shows an embodiment of the control circuit. As shown in FIG. 7, the circuit configuration includes an operational amplifier 9 as a comparator, a pair of voltage dividing resistors 10 for generating a negative input voltage of the operational amplifier 9, and a positive voltage input resistor for generating a positive input voltage of the operational amplifier 9. And a voltage dividing resistor 12 for determining a voltage dividing resistance ratio between the thermistor 11 and the thermistor 11, a fan motor 4 for cooling the high voltage conversion circuit, and a transistor 5 for directly driving the fan motor 4. .

The operation of the circuit shown in FIG. 7 will be described. The high-voltage conversion circuit, not shown in FIG. 7, is the same as that of the above-described embodiment, and generally drives a transformer of an output conversion unit with a driving element (transistor) by input of a PWM signal to output a high voltage. The operation of such a high-voltage conversion circuit is basically the same as the existing technology, and will not be described in detail here. In the present invention, the heat generating portion in the high-voltage conversion circuit is forcibly cooled by the fan motor 4. The main components to be cooled are, for example, a transistor 5 which is a high-voltage output drive element, a transformer of an output converter, and the like. The cooling operation in this example is performed according to the temperature state of the high-voltage conversion circuit. For this purpose, a thermistor 11 whose resistance value changes with temperature is provided at an appropriate position where a temperature change due to heat generated from the high-voltage conversion circuit is provided, and a circuit for detecting the heat generation state of the high-voltage conversion circuit is provided. And a control circuit for the fan motor 4 for driving the fan motor 4.

The operating conditions of the control circuit shown in FIG. 7 are, for example, when the temperature exceeds 50.degree.
Is driven. FIG. 9 shows the temperature characteristic of the thermistor 11 used in the control circuit. The characteristic shown in FIG. 9 is 1.2 kΩ at 60 ° C. Therefore, the voltage dividing resistor 12 for generating the + side input voltage in this control circuit is set to 1
If it is determined to be kΩ, the resistance value of the thermistor 11 is 60 ° C.
At the time of the operation, the division resistance ratio becomes 1.2 kΩ.
(Thermistor 11): 1 (voltage dividing resistor 12), and the + side input voltage of the operational amplifier 9 becomes about 13V. On the other hand, if the resistance value of each of the pair of voltage dividing resistors 10 for generating the negative input voltage is determined to be 1 kΩ, the voltage dividing resistance ratio is 1: 1 and the negative input voltage of the operational amplifier 9 is 12 V. . Therefore, as an input state to the operational amplifier 9 operating as a comparator, the + side input voltage becomes larger than the − side input voltage, and the comparator output becomes 5V, and this output is applied to the transistor 5 to which the control signal is applied. ON
Then, the fan motor 4 is driven.

Referring to the flow chart of FIG. 8, the cooling operation of this embodiment will be described. A voltage that changes according to the temperature state of the high-voltage conversion circuit is compared with a reference voltage. Then, it is determined whether or not the reference voltage has been exceeded (S81). In this step, in the circuit of this embodiment, one output terminal of the resistor bridge having one side as the thermistor 11 is connected to the + input of the operational amplifier 9 operating as a comparator, and the other output terminal is connected to the-input, When the temperature state of the conversion circuit exceeds the set value and the + input voltage becomes larger than the − input voltage, the operation of the operational amplifier 9 to output a predetermined voltage is performed. S
As a result of the judgment at 81, if the temperature rise of the high-voltage conversion circuit is confirmed (the operational amplifier 9 outputs a predetermined voltage), power is supplied from the power supply to the fan motor 4 to drive the fan motor 4 (S82); Do not drive the motor. In the operation of the above-described embodiment, the transistor 5 is turned on by using a predetermined voltage output from the operational amplifier 9 as a control signal as a drive trigger of the transistor 5, so that power is supplied from the power supply to the fan motor 4 and the fan motor 4 is turned on. Drive.

Next, a fourth embodiment will be described. In this embodiment, cooling of the high-voltage power supply is efficiently performed by providing a dedicated radiator for releasing heat generated in the high-voltage conversion circuit of the high-voltage power supply. Here, the heat radiating holes are provided in the sheet metal holding the high-voltage conversion circuit, and FIGS. 10 and 11 show the configuration of the embodiment. FIG. 10 is a schematic diagram showing a laser beam printer to which the present invention is applied, together with an arrangement state of a built-in high-voltage power supply. The configuration of the laser beam printer of this embodiment is not particularly different from the existing laser beam printer except for the configuration related to the heat radiation means of the high-voltage power supply. The high-voltage power supply itself is composed of an existing circuit as in the above-described embodiment (see FIG. 1), and the output conversion unit in the high-voltage conversion circuit operates a switching element such as a transistor in response to input of a PWM signal to perform output conversion. It drives the transformer of the unit to output a high voltage, and the high voltage output changes according to the duty of the PWM signal. As shown in FIG. 10, the laser beam printer 22 includes a paper feed cassette 28 for supplying paper 21 used for image formation (the paper 21 output after image formation is shown in FIG. 10). When the paper runs out, the user pulls out the paper cassette 28 and replenishes the cassette case with paper. In the apparatus of the present embodiment, the sheet metal 2 is placed at a position in the apparatus main body adjacent to the upper part of the case of the paper feed cassette 28 for taking out and feeding paper.
3, a high-voltage power supply 24 having a high-voltage conversion circuit provided on a substrate is fixed on a sheet metal 23.

Although not shown in FIG. 10, as a heat radiating means, a heat radiating hole is provided on a sheet metal 23 to which a high-voltage power supply 24 is fixed, and a heat radiating hole is provided on the sheet metal 23 so as to be slidable along the plate surface. An attached sheet metal 25 and means for sliding it are provided. In this case, the heat-dissipating sheet metal 25 may be provided on any of the upper and lower surfaces of the sheet metal 23. FIG. 11 shows the details of the structure of the sheet metal 23 and the sheet metal 25 with the heat radiating holes slidably provided along the plate surface, and the relationship between the two sheet metals. The high-voltage power supply 24 is fixed to the one sheet metal 23 as described above. However, as shown in FIG. 11A, heat radiation for releasing heat generated from the high-voltage power supply 24 by ventilation to a part of the plate is performed. A hole 231 is provided. Here, the heat radiating holes 231 are provided with two rows of unit heat radiating holes formed by arranging a plurality of heat radiating holes 231 at predetermined intervals. As shown in FIG. 11 (B),
When the heat radiating holes 251 are provided in correspondence with the heat radiating holes 231 of the sheet metal 23 and the heat radiating holes 231 and 251 of both the sheet metals are overlapped, the state in which both the heat radiating holes 231 and 251 match and the air can be ventilated is provided. Is closed so that the air cannot be ventilated (see FIGS. 11D and 11E). When the surfaces of the sheet metal 23 and the sheet metal 25 with the heat radiation holes are overlapped, FIG.
The state shown in FIG. In this case, the sheet metal 2
The sliding direction of 5 is the direction shown by the arrow in the figure. A guide is required as a means for regulating the movement of the sheet metal 25 with the heat radiating holes in the direction of the arrow, and this is processed by processing a part of the sheet metal 23 (for example, a rail bent to L) or separately prepared. It is configured by attaching parts (not shown), and the end faces A, A (FIG.
(See (B) and (C)). FIG. 11 (D),
(E) shows a relative positional relationship between the two metal plates due to sliding of the stacked metal plates 25 with the heat radiation holes in a sectional view including both the heat radiation holes. FIG. 11 (D) shows a state in which the two sheet metals are just alternated and are covered, and in this state, ventilation is not possible through the sheet metal. At this time, the high-voltage power supply 24 is cut off from the outside. For example, even if the sheet cassette 28 is pulled out and tries to come in contact with the outside,
Make contact impossible. FIG. 11E shows a state in which ventilation is performed through the sheet metal and heat can be released.

The operation of the heat radiating means will be described. In this embodiment, the sheet metal 25 with the heat radiating holes can be slid so as to take a ventilation state and a cutoff state. Originally, simply providing a heat radiating hole in the sheet metal 23 (always providing a ventilation state) can increase the heat radiation efficiency as compared with a case where no heat radiating hole is provided. That is, the present invention is not limited to the forced cooling by the dedicated fan of the first to third embodiments, but is also effective in the case of the conventional cooling method (a method in which a fan dedicated to the high-voltage power supply is not provided). Here, the significance of sliding the metal plate 25 with the heat radiating holes is that, in addition to being able to change the ventilation state in the apparatus, it is possible to prevent external contact with the high-voltage power supply 24 when the shut-off state is taken.
In order to realize these, in this embodiment, a shut-off state is set when the image forming operation is not performed, and a ventilation state is set when the image forming operation is performed. As an example, the sheet metal with heat radiating holes 25 is moved in conjunction with the insertion and removal of the sheet cassette 28. As an embodying means, an elastic body (preferably a contraction spring, see a contraction spring 27 in FIG. 13) is acted on the sheet metal 25 with the heat radiating hole to cause the sheet metal 25 to be deviated, and the end of the sheet metal 25 with the heat radiating hole in the moving direction. Is bent into L, for example,
A mechanism for abutting a projection or the like provided on a part of 8. By this mechanism, when the sheet cassette 28 is pulled out, the contact with the sheet metal 25 with the heat radiating holes is released, so that the sheet metal 25 is cut off by the function of the elastic body (FIG. 11D). When the paper cassette 28 is set back, the sheet metal 25 is brought into contact with the sheet metal 25 with heat radiating holes and is moved against the force of the elastic body to be in a ventilation state (FIG. 11E). As described above, in the present embodiment, when the sheet cassette 28 is pulled out, the ventilation state is changed from the ventilation state to the cutoff state, so that the danger of touching the high voltage power supply 24 can be eliminated. Since the drive elements (transistors) and output converters (transformers) provided in the power supply circuit are directly cooled by the function of the heat radiating means, it is conventionally used for cooling the fixing unit. Effective cooling is also possible with a cooling fan motor that has not been provided. Also, by using the cooling means using the fan described in the above embodiment together with the heat radiation operation, the high-voltage power supply 24 can be cooled more effectively.

Next, a fifth embodiment will be described. In this embodiment, the sliding of the sheet metal 25 with the heat radiating holes in the fourth embodiment is automatically operated according to the operation state of the apparatus main body. Note that, in this embodiment, the conditions are the same as those in the fourth embodiment, except for the newly added constituent elements described later, so that the detailed description of the overlapping parts will be omitted. FIG. 13 shows a configuration and operation explanatory diagram of the present embodiment. In the figure, the relation between the sheet metal 23 and the sheet metal 25 with heat radiating holes slidably mounted along the plate surface is basically the same as that of the fourth embodiment. Here, an elastic body (a contraction spring 27 in this embodiment) attached so that an elastic force acts between the sheet metal 25 with the heat dissipation hole and the driving means for sliding the sheet metal 25 with the heat dissipation hole. 26 (by an electromagnetic clutch in this embodiment). When the electromagnetic clutch 26 is operated, as shown in FIG. 13 (A), the sheet metal 25 with the heat radiating holes is moved against the spring force of the contraction spring 27, and from the cut-off state (FIG. 11 (D)) to the ventilation state (FIG. 11 (D)). FIG.
(E)). When the electromagnetic clutch 26 in the operating state is deactivated, the sheet metal 25 with the heat radiating holes returns to the original interrupted state (FIG. 11D) by the action of the contraction spring 27 as shown in FIG. 13B. .

The radiation operation controlled by the electromagnetic clutch 26 will be described below. FIG.
2 shows a flow of a heat dissipation operation controlled by the following. Referring to the flow of FIG. 12, the heat radiation operation of this embodiment will be described.
First, it is checked whether or not the power supply of the device main body is ON (S121). When the power is ON, the electromagnetic clutch 26 is operated (S122), and the sheet metal 25 with the heat radiating holes is moved to a ventilation state (FIG. 13A). In this state, it is determined whether the interlock is OFF (S12).
3). This is to check an interlock switch for operating a safety device of a device provided in many laser beam printers. When the interlock switch is turned off due to the opening of the door of the device in S123, the electromagnetic clutch 26 is turned off (S124). By turning off the electromagnetic clutch 26 as part of the operation of the safety device that works by turning off the interlock, the sheet metal 2
13 from the ventilation state (FIG. 13A) to the blocking state (FIG. 13A).
(B)), it is possible to eliminate the danger of touching the high-voltage power supply 24 through the heat-dissipating holes that have been opened when the ventilation state is maintained. Also, by using the cooling means using the fan described in the above embodiment together with the heat radiation operation, the high-voltage power supply 24 can be cooled more effectively.

Next, a sixth embodiment will be described. In the present embodiment, the heat radiating means (the heat radiating means (FIG. 13) shown in the fifth embodiment is applied) is operated according to the temperature state of the high voltage power supply 24, and FIG. 14 shows the embodiment. As a circuit configuration, as shown in FIG. 14, an operational amplifier 29 as a comparator, a pair of voltage-dividing resistors 30 for generating a negative input voltage of the operational amplifier 29, and a +
Thermistor 31 and Thermistor 3 for Generating Side Input Voltage
The operation of the voltage dividing resistor 32 for determining the voltage dividing resistance ratio to 1 and the heat dissipating means (see FIG. 13) similar to that described in the fifth embodiment for dissipating the heat generated by the high voltage power supply 24. And a transistor 35 for directly driving the electromagnetic clutch 26.

The operation of the circuit shown in FIG. 14 will be described. The heat radiation operation of this embodiment is performed according to the temperature state of the high-voltage power supply 24.
For this purpose, a thermistor 31 whose resistance value changes with temperature is provided at an appropriate position where a temperature change due to heat generated from the high voltage power supply 24 is provided, and a circuit for detecting the heat generation state of the high voltage power supply 24 is provided. A control circuit for the electromagnetic clutch 26 that drives the motor 26 is provided. As an operating condition of the control circuit shown in FIG. 14, for example, a case where the electromagnetic clutch 26 is driven when the temperature exceeds 50 ° C. is considered. FIG. 9 shows the temperature characteristic of the thermistor 31 used in the control circuit. The characteristic shown in FIG. 9 is 1.2 kΩ at 60 ° C. Therefore, if the voltage dividing resistor 32 for generating the + side input voltage in this control circuit is determined to be 1 kΩ, the resistance value of the thermistor 31 during operation at 60 ° C.
Since it is 2 kΩ, the voltage dividing resistance ratio is 1.2 (thermistor 1
1): 1 (voltage dividing resistor 12), and the operational amplifier 29
The side input voltage is about 13V. On the other hand, if the resistance value of each of the pair of voltage dividing resistors 30 for generating the negative input voltage is set to 1 kΩ, the voltage dividing resistance ratio is 1: 1 and the negative input voltage of the operational amplifier 29 is 12 V. . Therefore, as the input state to the operational amplifier 29, the + side input voltage becomes larger than the − side input voltage, and the comparator output becomes
When the voltage becomes 5 V, the output turns on the transistor 35 to which the control signal is applied, and the electromagnetic clutch 26 is driven.

Referring to the flow chart of FIG. 15, the heat radiating operation of this embodiment will be described. A voltage that changes according to the temperature state of the high-voltage power supply 24 is compared with a reference voltage. Then, it is determined whether or not the reference voltage has been exceeded (S151). In this step, in the circuit of this embodiment, one side is connected to the thermistor 31.
One output terminal of the resistive bridge is connected to the + input of the operational amplifier 29 operating as a comparator, and the other output terminal is connected to the-input, and the temperature state of the high voltage power supply 24 exceeds the set value and the + input voltage becomes-. When the input voltage becomes higher than the side input voltage, the operational amplifier 29 performs an operation of outputting a predetermined voltage. As a result of the determination in S151, when a rise in the temperature of the high-voltage power supply 24 is confirmed (the operational amplifier 29 outputs a predetermined voltage), power is supplied from the power supply to the electromagnetic clutch 26 to drive the sheet metal 25 with the heat radiation holes (S152). ), If there is no drive, do not drive. In the operation of this embodiment, a predetermined voltage output from the operational amplifier 29 is used as a control signal as a drive trigger of the transistor 35 to activate the transistor 35.
When turned on, the electromagnetic clutch 26 is driven by supplying power from a power supply. As described above, by operating the heat radiating means (applying the heat radiating means (FIG. 13) shown in the fifth embodiment) in accordance with the temperature state of the high-voltage power supply 24, the prior art which does not include a dedicated cooling means. In this case, it is possible to eliminate the overcooling or insufficient cooling caused in the above, and to cool the high-voltage power supply with low power consumption and high efficiency. Also, by using the cooling means using the fan described in the above embodiment together with the heat radiation operation, the high-voltage power supply 24 can be cooled more effectively.

[0034]

According to the present invention, the cooling means for cooling the high-voltage conversion circuit is driven in synchronization with the operation of the high-voltage conversion circuit, so that no dedicated cooling means is provided. In addition, supercooling and insufficient cooling that occur in the related art can be eliminated. (2) Effects corresponding to the second aspect of the invention In addition to the effect of the above (1), by controlling the cooling means on / off by an on signal generated during a period when the operation signal is input to the high voltage conversion circuit. Thus, the invention of claim 1 can be easily implemented, and the high-voltage conversion circuit can be efficiently cooled with low power consumption. (3) Effects corresponding to the third aspect of the invention In addition to the effect of the above (1), when the output is made variable by the duty of the operation pulse signal input to the high-voltage conversion circuit, the cooling means according to the duty of the operation pulse signal , The cooling capacity is made variable in accordance with the change in high-voltage output, that is, the amount of heat generation (for example, when a fan is used, the rotation of the fan is changed). Can be cooled. (4) Effects corresponding to the invention of claim 4 By driving the cooling means for cooling the high-voltage conversion circuit in accordance with the temperature around the high-pressure conversion circuit, the problem arises in the prior art which did not have a dedicated cooling means. It is possible to eliminate overcooling or insufficient cooling, and to cool the high-voltage conversion circuit with low power consumption and high efficiency. (5) Effects corresponding to the fifth aspect of the invention In addition to the effects of the above (1) to (4), the cooling means for cooling the high-voltage conversion circuit comprises a motor and a fan driven by the motor. Claims 1 to 3
The fifth invention can be easily and effectively implemented.

(6) According to the prior art which does not have a dedicated cooling means, by cooling the high-voltage power supply by an air flow generated by a heat radiation hole provided in a member to which the high-voltage power supply is fixed, The resulting insufficient cooling can be eliminated by simple means. (7) Effect corresponding to the seventh aspect of the invention In addition to the effect of the above (6), there is a danger that the high-voltage power supply 24 may be touched through the opened heat radiation hole when the heat radiation hole is left open. By providing the means for closing the heat radiating hole, this danger can be eliminated, and a device with higher safety can be provided. (8) Effect corresponding to the invention of claim 8 In addition to the effect of the above (7), in addition to the means for controlling the use / non-use of the means for closing the heat radiation hole, the operation of the apparatus main body, for example, the interlock OFF operation By setting the heat radiation hole in the cutoff state in accordance with the above, it is possible to eliminate the danger of touching the high voltage power supply 24 through the opened heat radiation hole as part of the operation of the safety device. (9) Effect corresponding to the ninth aspect of the invention In addition to the effect of the above (8), the means for controlling the use / non-use of the means for closing the heat radiation hole is operated according to the presence or absence of the image forming operation. Thus, the high-voltage power supply can be efficiently cooled with low power consumption. (10) Advantages Corresponding to the Tenth Invention In addition to the advantages (8) and (9), a means for controlling the use / non-use of the means for closing the heat radiating hole is provided according to the ambient temperature of the high voltage power supply. By operating, it is possible to eliminate the overcooling and the insufficient cooling caused in the prior art which did not include the exclusive cooling means, and it is possible to efficiently cool the high-voltage power supply with low power consumption.

[Brief description of the drawings]

FIG. 1 shows an embodiment of a drive control circuit for a fan that cools a high-voltage conversion circuit.

FIG. 2 shows a flow of a drive control operation of a fan for cooling a high-voltage conversion circuit.

FIG. 3 shows signals related to a drive control operation of a fan for cooling a high-voltage conversion circuit.

FIG. 4 shows another embodiment of a fan drive control circuit for cooling the high voltage conversion circuit.

FIG. 5 shows a flow of another drive control operation of the fan for cooling the high-voltage conversion circuit.

FIG. 6 shows signals related to another drive control operation of the fan for cooling the high-voltage conversion circuit.

FIG. 7 shows another embodiment of a fan drive control circuit for cooling the high-voltage conversion circuit.

8 shows a flow of a control operation by the drive control circuit for the fan shown in FIG. 7;

FIG. 9 shows temperature characteristics of a thermistor used in the cooling control circuits of FIGS. 7 and 14.

FIG. 10 is a schematic diagram showing a laser beam printer to which the present invention is applied, together with an arrangement state of a built-in high-voltage power supply.

FIG. 11 shows details of the structure of a sheet metal slidably provided along the sheet surface and a sheet metal with a heat radiating hole, and the relationship between the two sheet metals.

FIG. 12 shows a flow of a control operation of a radiator operated by an electromagnetic clutch.

FIG. 13 shows a configuration and an operation state of a heat radiating means operated by an electromagnetic clutch.

FIG. 14 shows an embodiment of a drive control circuit of an electromagnetic clutch for operating a heat radiation means of a high voltage power supply.

15 shows a flow of a control operation by the electromagnetic clutch drive control circuit shown in FIG.

[Explanation of symbols]

1. CPU, 2. Output converter,
3, 5, 35 ... transistor, 4 ... fan motor, 9, 29 ... operational amplifier (comparator), 10, 1
2, 30, 32 ... voltage dividing resistor, 11, 31 ... thermistor,
22 laser beam printer, 23
... Sheet metal, 24 ... High voltage power supply, 23
Reference numerals 1 and 251 represent heat dissipation holes, 25 a sheet metal having heat dissipation holes, 26 an electromagnetic clutch, 27 a contraction spring, and 28 a paper feed cassette.

Claims (10)

[Claims] 1. An image forming apparatus having a high-voltage power supply having a high-voltage conversion circuit, a cooling unit for cooling the high-voltage power supply, and a cooling control unit for driving the cooling unit in synchronization with the operation of the high-voltage conversion circuit. An image forming apparatus comprising: 2. The image forming apparatus according to claim 1, wherein the cooling control unit turns on the cooling unit in response to a control signal generated by turning on a period during which an operation signal is input to the high-voltage conversion circuit. An image forming apparatus characterized in that it is turned off. 3. The image forming apparatus according to claim 1, wherein the cooling control unit changes the output of the high-voltage conversion circuit according to the duty of the operation pulse signal. An image forming apparatus for controlling the driving of the cooling means. 4. An image forming apparatus having a high-voltage power supply having a high-voltage conversion circuit, a cooling unit for cooling the high-voltage conversion circuit, and a cooling control for driving the cooling unit in accordance with a peripheral temperature of the high-voltage conversion circuit. An image forming apparatus comprising: 5. The image forming apparatus according to claim 1, wherein said cooling means comprises a motor and a fan driven by said motor. 6. An image forming apparatus having a high-voltage power supply provided with a high-voltage conversion circuit, further comprising a radiator for cooling the high-voltage power supply by an airflow generated by a radiating hole provided in a member to which the high-voltage power supply is fixed. Image forming apparatus. 7. The image forming apparatus according to claim 6, further comprising: means for closing said heat radiation hole. 8. The image forming apparatus according to claim 7, further comprising means for controlling use / non-use of the means for closing the heat radiation hole. 9. The image forming apparatus according to claim 8, wherein the means for controlling use / non-use of the means for closing the heat radiating hole operates according to the presence or absence of the image forming operation. Image forming apparatus. 10. The image forming apparatus according to claim 8, wherein the means for controlling use / non-use of the means for closing the heat radiating hole operates according to the ambient temperature of the high voltage power supply. Characteristic image forming apparatus.