JP2021026931A - Rotary switch switching position detection circuit, and image forming apparatus including the same - Google Patents

Abstract

To provide a rotary switch switching position detection circuit that can suitably clean contacts of a rotary switch, while reducing power consumption in detecting a switching position of the rotary switch, and an image forming apparatus including the same.SOLUTION: An image forming apparatus 10 comprises: a control unit 8; and a switching position detection unit 30. The switching position detection unit 30 has a first switching element 32, a second switching element 33, and a rotary switch 43. The control unit 8 inputs a gate signal only to the first switching element 32 until a prescribed condition determined in advance is satisfied to cause only the first switching element 32 to perform an ON operation. Meanwhile, the control unit 8 does not input the gate signal to the second switching element 33, that is, does not cause the second switching element 33 to perform the ON operation. Thus, the control unit 8 can detect a switching position of the rotary switch 43 until the prescribed condition is satisfied.SELECTED DRAWING: Figure 3

Description

The present invention relates to a switching position detection circuit that detects a switching position of a contact of a rotary switch.

The electrophotographic image forming apparatus is provided with a paper holding tray for holding the printing paper on which the image is formed. Any size of printing paper used by the user can be placed on the paper holding tray. The paper holding tray may be provided with a setting dial for setting the size of the placed printing paper. When the printing paper to be used is stored in the paper holding tray, the user operates the setting dial to set the setting dial at a position corresponding to the size of the printing paper to be used.

As the setting dial, one provided with a rotary switch capable of switching a plurality of contacts may be used. The contact point of the rotary switch is a portion that conducts or cuts off an electric current by contacting or disconnecting a conductor made of metal (metal conductor), and is configured such that the metal conductor physically contacts or disconnects. When the metal conductor used for the contact is left inactive for a long period of time, an oxide film is formed on the surface thereof by oxidation. This oxide film has a property (insulating property) that makes it difficult for current to pass through. On the other hand, the oxide film can be broken by passing a current equal to or higher than a predetermined value to the contact (see Patent Document 1). Therefore, in the circuit using the rotary switch, it is designed so that a current equal to or higher than the specified value flows through the contact when the metal conductor of the contact comes into contact with the contact. As a result, an arc discharge occurs at the time of contact with the metal conductor, so that the oxide film is destroyed and the oxide film of the contact is removed. That is, the contacts are cleaned. The destruction and removal of the oxide film in this way is referred to as a cleaning action or a refreshing action due to an arc discharge at the time of contact.

Japanese Unexamined Patent Publication No. 58-16651

By the way, the resistance value of the internal resistor of each electric circuit provided with the contact of the rotary switch is made different, a voltage dividing circuit is formed in the common line of each electric circuit, and the voltage value (voltage divided value) of the common line is formed. In the switching position detection circuit of the rotary switch that detects which contact is conducting based on the above, the current value in the electric circuit having the largest internal resistance is designed to be the specified value. However, in this case, in the switching position detection circuit, a current larger than the specified value flows in the electric circuit having the smallest internal resistance, and the power when the position of the setting dial is adjusted to the electric circuit. The amount of consumption increases.

An object of the present invention is to provide a rotary switch switching position detection circuit capable of suitably cleaning the contacts of the rotary switch while suppressing power consumption when detecting the switching position of the rotary switch, and an image forming apparatus including the same. To provide.

The switching position detecting device according to one aspect of the present invention is a switching position detecting device that detects the switching position of the rotary switch. The switching position detection device includes each of a plurality of metal contacts provided in the rotary switch, and is provided in each of the plurality of contact electric circuits to which a predetermined constant voltage is applied and each of the plurality of contact electric circuits. A resistor having a resistance value different for each of the plurality of contact electric circuits, a detection electric circuit having a detection resistor and a first switching element connected to a common line of the rotary switch, and a detection electric circuit connected in parallel to the detection electric circuit, the common The cleaning electric circuit having the cleaning resistor and the second switching element connected to the line, and either the first switching element or the second switching element is turned on until a predetermined predetermined condition is satisfied. A control unit that detects a switching position of the rotary switch based on the current value of the common line while the first switching element is on-operating is provided.

The image forming apparatus according to another aspect of the present invention is an image forming apparatus including the above-mentioned switching position detecting apparatus. In the image forming apparatus, the control unit receives the first condition when the image forming apparatus shifts from a power saving mode to a normal operation mode or when the power of the image forming apparatus is turned on, as the predetermined condition. The switching element is turned off and the second switching element is turned on.

According to the present invention, it is possible to suitably clean the contacts of the rotary switch while suppressing the power consumption at the time of detecting the switching position of the rotary switch.

FIG. 1 is a diagram showing a configuration of an image forming apparatus according to an embodiment of the present invention. FIG. 2 is a block diagram showing a configuration of an image forming apparatus. FIG. 3 is a circuit diagram showing a configuration of a switching position detection circuit included in the image forming apparatus.

Hereinafter, embodiments of the present invention will be described with reference to the drawings as appropriate. The following embodiments are merely examples that embody the present invention, and do not limit the technical scope of the present invention.

[Image forming device]
First, the configuration of the image forming apparatus 10 according to the embodiment of the present invention will be described with reference to FIG.

As shown in FIG. 1, the image forming apparatus 10 is an apparatus having at least a printing function, and is, for example, a color printer. The image forming apparatus 10 prints an image on printing paper, which is a sheet member, using a developer containing toner. A specific example of the image forming apparatus 10 is, for example, a printer, a copying machine, a facsimile, or a multifunction device having each of these functions. Further, although the image forming apparatus 10 can form a color image, it may be configured so that a monochrome image can be formed.

The image forming apparatus 10 includes a plurality of image forming units 4, an intermediate transfer unit 5, an exposure device 14, a secondary transfer device 15, a fixing device 16, and an operation display unit 9 having a touch panel, a liquid crystal display, and the like. , The control unit 8, the paper feed tray 17, the paper output tray 18, the manual feed tray 19 (an example of the paper holding tray of the present invention), the communication unit 20 (see FIG. 2), and the switching position detection unit 30. I have. These components are attached to the housing 11 that constitutes the outer frame (not shown), the inner frame, and the like of the image forming apparatus 10.

Each image forming unit 4 executes an image forming process (printing process) according to a so-called electrophotographic method based on image data read by a scanner (not shown) or a print job input through a communication unit 20. To do. Each image forming unit 4 includes a photoconductor drum 21, a charging device 22, a developing device 23, a primary transfer device 24, and the like. The surface of the photoconductor drum 21 is charged by the charging device 22, and the surface of the photoconductor drum 21 charged by the exposure device 14 is exposed and scanned. As a result, an electrostatic latent image is formed on the surface of the photoconductor drum 21. The developing device 23 develops the electrostatic latent image with toner. Then, the toner image on the photoconductor drum 21 is transferred by the primary transfer device 24 so as to be sequentially superimposed on the intermediate transfer belt 5A of the intermediate transfer unit 5.

The toner image transferred to the intermediate transfer belt 5A is transferred to the printing paper by the secondary transfer device 15, and then melt-fixed to the printing paper by the fixing device 16. The printing paper on which the toner image is fixed is further conveyed to the downstream side in the conveying direction, and is discharged and held in the tray-shaped output tray 18 arranged above the intermediate transfer unit 5.

In the present embodiment, the electrophotographic image forming unit 4 will be described as an example, but the image forming unit 4 is not limited to the electrophotographic type, and may be an inkjet recording type, or other than that. It may be the recording method or the printing method of.

A manual feed tray 19 rotatably supported by the housing 11 is provided on the right side surface of the housing 11. In addition, a paper feed tray 17 is provided at the bottom of the housing 11. A plurality of printing sheets of an arbitrary size are held in the bypass tray 19 and the paper feed tray 17.

The bypass tray 19 constitutes a part of the housing 11, and constitutes the right side surface of the housing 11 in a state of being closed to the housing 11 (the state shown by the broken line in FIG. 1). When the posture of the bypass tray 19 is changed to the state of being opened with respect to the housing 11 (the state shown by the solid line in FIG. 1), the manual feed tray 19 is supported in a posture of being slightly inclined diagonally upward as shown in FIG. .. That is, in the opened state, the manual feed tray 19 is gently inclined downward toward the downstream side in the feeding direction toward the inside of the housing 11. In this state, a plurality of sheets of printing paper can be placed on the upper surface of the manual feed tray 19. Further, when the manual feed tray 19 is opened with respect to the housing 11, a feed feed path 27 from the manual feed tray 19 to the vertical transport path 26 is formed.

With the bypass tray 19 opened, a paper feed roller 41 is provided on the tip side in the feeding direction. The paper feed roller 41 is rotationally driven to transport the printing paper placed on the manual feed tray 19 from the feed feed path 27 to the vertical transport path 26. The printing paper conveyed to the vertical transfer path 26 is sequentially discharged to the paper discharge tray 18 through the secondary transfer device 15 and the fixing device 16.

In the present embodiment, a setting dial 42 (an example of the operation input unit of the present invention, see FIG. 2) for setting the size of the printing paper held in the manual feed tray 19 is provided in the vicinity of the manual feed tray 19. .. The setting dial 42 is provided at a position where the user can operate the manual feed tray 19 in a state where the manual feed tray 19 is opened. For example, the setting dial 42 is provided on a portion of the manual feed tray 19 other than the paper mounting surface. Of course, it may be provided in the inner frame of the housing 11. The setting dial 42 has a rotatable dial-type operation unit, and the user operates and uses the operation unit of the setting dial 42 when placing the printing paper to be used on the manual feed tray 19. Set the setting dial 42 to the position corresponding to the size of the printing paper (the position of the display scale indicating the size).

The setting dial 42 includes a well-known rotary switch 43 having a plurality of contacts T1 to T6 (see FIG. 3). The setting dial 42 is connected to the rotary switch 43, and is configured so that the switching position of the rotary switch 43, that is, the contacts T1 to T6 can be switched by the operation of the operation unit.

The switching position detection unit 30 constitutes a part of the switching position detecting device of the present invention, and is used to detect the switching position of the rotary switch 43. In the present embodiment, the switching position detecting device of the present invention is realized by the switching position detecting unit 30 and the control unit 8. The switching position detection unit 30 is configured as an electric circuit including each contact T1 to T6 of the rotary switch 43. The rotary switch 43 is electrically connected to the control unit 8, and the control unit 8 can detect the switching position of the rotary switch 43 based on the partial pressure value described later obtained from the switching position detecting unit 30. ..

The control unit 8 comprehensively controls the image forming operation in the image forming apparatus 10. The control unit 8 is an example of the control unit of the present invention, and is configured as a control board on which a microcomputer having a CPU 81, a ROM 82, a RAM 83, and the like as main components is mounted. Further, the control unit 8 is also equipped with a control device such as a motor driver or a liquid crystal controller (not shown). The control unit 8 may be composed of an electronic circuit such as an integrated circuit (ASIC, DSP).

In the present embodiment, when the image data to be printed or the print job is input, the control unit 8 executes the image forming operation by the image forming unit 4, and at the required timing, the paper feed tray 17 designated in advance. Alternatively, the printing paper is fed from any of the manual feed trays 19. Further, the control unit 8 can detect the switching position of the rotary switch 43 and specify the size of the printing paper corresponding to the switching position.

Hereinafter, the switching position detection unit 30 will be described with reference to FIG. FIG. 3 is a circuit diagram showing a circuit configuration of the switching position detection unit 30.

As shown in FIG. 3, the switching position detection unit 30 determines the resistance values of the plurality of contact electric circuits L1 to L6 including the metal contacts T1 to T6 included in the rotary switch 43 and the resistance values of the respective contact electric circuits L1 to L6. It has a ladder resistance circuit 31 composed of a plurality of resistors R1 to R7 (an example of a resistor of the present invention), a detection electric circuit L11 having a first switching element 32, and a cleaning electric circuit L12 having a second switching element 33. ..

Each of the contact electric paths L1 to L6 is an electric path from the input terminal Vcc described later to the contact of the rotary switch 43. A plurality of metal contacts provided on the rotary switch 43 are connected to each of the contact electric circuits L1 to L6. That is, the contact T1 is connected to the contact electric line L1, the contact T2 is connected to the contact electric line L2, the contact T3 is connected to the contact electric line L3, and the contact T4 is connected to the contact electric line L4. The contact T5 is connected to the contact electric line L5, and the contact T6 is connected to the contact electric line L6. The contact electric lines L1 to L6 are connected to the ladder resistance circuit 31. A constant DC voltage is applied to the ladder resistance circuit 31 from a predetermined constant voltage source.

The ladder resistance circuit 31 is a circuit in which a plurality of resistors R1 to R7 are connected in series. In this embodiment, the resistors R1 to R7 have the same resistance value. A constant DC voltage is applied to the input terminal Vcc of the resistor R1 at one end of the ladder resistance circuit 31 from the constant voltage source. Further, the other end of the ladder resistance circuit 31 is grounded. In the ladder resistance circuit 31, the potential at each node of each resistor R1 to R7 differs depending on the voltage drop generated in each resistor R1 to R7.

Each of the contact electric circuits L1 to L6 is connected to each node of the resistors R1 to R7. That is, the contact electric circuit L1 is connected to the node between the resistor R1 and the resistor R2. The contact line L2 is at the node between the resistor R2 and the resistor R3, the contact line L3 is at the node between the resistor R3 and the resistor R4, and the contact line L4 is at the node between the resistor R4 and the resistor R5. L5 is connected to the node between the resistor R5 and the resistor R6, and the contact electric circuit L6 is connected to the node between the resistor R6 and the resistor R7. Therefore, each contact electric circuit L1 to L6 has a different resistance value depending on the number of resistors included between the input terminal Vcc and each contact electric circuit L1 to L6. That is, each contact electric circuit L1 to L6 has a resistor having a different resistance value for each of the plurality of contact electric circuits L1 to L6.

The rotary switch 43 has a common terminal TC that conducts with each of the plurality of contacts T1 to T6. By operating the setting dial 42 to switch the contacts of the rotary switch 43, the connection position between each contact and the common terminal TC can be switched. A common electric circuit Lc (common line) is connected between the common terminal TC and the output terminal Vout. The output terminal Vout is connected to the control unit 8, and the control unit 8 can detect the output voltage at the output terminal Vout.

One of the detection electric circuits L11 is connected to the common electric circuit Lc, and the other is grounded. The first switching element 32 is provided in the detection electric path L11. In the detection electric circuit L11, an internal resistor R11 (an example of the detection resistor of the present invention) is provided between the first switching element 32 and the common electric circuit Lc. In the present embodiment, the resistance value of the internal resistor R11 is set to a value larger than the resistance value of the internal resistor R12 described later.

The first switching element 32 is a FET or MOSFET, and is a switching element capable of dropping the voltage on the first switching element 32 side of the internal resistor R11 to the ground potential when it is turned on. If it has a switch function, for example, an open drain type comparator can be used instead of the first switching element 32.

When a HIGH level gate signal is input from the control unit 8 to the gate terminal of the first switching element 32, the first switching element 32 is turned on and the internal resistor R11 is connected to the ground potential. In this case, the voltage divided from the output terminal Vout based on the resistance value in any of the contact electric circuits connected to the common terminal Tc and the resistance value of the internal resistor R11 of the detection electric circuit L11 is output. The control unit 8 can determine which contact electric circuit is conducting, that is, which contact is conducting, based on the voltage value of the output voltage.

The cleaning electric line L12 is connected in parallel to the detection electric line L11. One of the cleaning electric circuits L12 is connected to the common electric circuit Lc, and the other is grounded. A second switching element 33 is provided in the cleaning electric circuit L12. In the cleaning electric circuit L12, an internal resistor R12 (an example of the cleaning resistor of the present invention) is provided between the second switching element 33 and the common electric circuit Lc.

In the present embodiment, the resistance value of the internal resistor R12 is a value determined based on the voltage value of the input voltage input to the input terminal Vcc, and the contacts are connected at any of the contacts T1 to T6. It is defined as an arc resistance value (an example of the first value of the present invention) at which an arc discharge can occur at times.

The second switching element 33 is a FET or MOSFET, and is a switching element capable of dropping the voltage on the second switching element 33 side of the internal resistor R12 to the ground potential when it is turned on. If it has a switch function, for example, an open drain type comparator can be used instead of the second switching element 33.

When a HIGH level gate signal is input from the control unit 8 to the gate terminal of the second switching element 33, the second switching element 33 is turned on and the internal resistor R12 is connected to the ground potential. As a result, an arc discharge occurs at the contacts of the conducting contact electric circuit, and the oxide film formed on the metal conductor of the contacts can be broken. That is, the arc discharge occurs at the time of contact with the metal conductor, so that the oxide film is destroyed, the oxide film of the contact is removed, and the contact is cleaned.

In the present embodiment, the control unit 8 turns on either the first switching element 32 or the second switching element 33 until a predetermined condition is satisfied. Then, while the first switching element 32 is on, the switching position of the rotary switch 43 is detected based on the current value of the common electric circuit Lc.

Specifically, the control unit 8 inputs the gate signal only to the first switching element 32, and turns on only the first switching element 32. During this time, the control unit 8 does not input the gate signal to the second switching element 33, that is, does not turn on the second switching element 33. Therefore, the control unit 8 can detect the switching position of the rotary switch 43 until the predetermined condition is satisfied. In this case, as described above, since the resistance value of the internal resistor R11 is set to a value larger than the arc resistance value, a current sufficient to generate an arc discharge does not flow at the contacts of the conducting contact electric circuit. .. Therefore, it is possible to suppress power consumption during detection of the switching position of the rotary switch 43.

Further, the control unit 8 turns off the first switching element 32 and turns on the second switching element 33 when the predetermined condition is satisfied. In this case, a large current flows through the contacts of the conducting contact electric circuit, and an arc discharge occurs. Therefore, the contacts are cleaned at the timing when the predetermined condition is satisfied. After cleaning the contacts, the second switching element 33 is turned off, and only the first switching element 32 is turned on again to detect the switching position of the rotary switch 43.

Here, the predetermined condition may be, for example, a case where the image forming apparatus 10 shifts from the power saving mode to the normal operation mode, or a case where the power of the image forming apparatus 10 is turned on. In such a case, it is highly possible that the contacts T1 to T6 of the rotary switch 43 have been left unused for a long period of time, and the contacts T1 to T6 are oxidized to form an oxide film on the surface thereof to generate an electric current. There is a high possibility that it is difficult to pass through. Therefore, it is preferable to turn on only the second switching element 33 at such a timing to clean the contacts.

In the conventional rotary switch switching position detection circuit, the current value in the electric circuit having the largest internal resistance is designed to be the current value at which arc discharge can occur. Therefore, the current value in the electric circuit having the smallest internal resistance. A larger current would flow than that, which wasted a large amount of power. However, according to the switching position detection unit 30 and the control unit 8 of the present embodiment, as described above, the detection of the switching position of the rotary switch 43 requires a large current such that an arc discharge may occur at each of the contacts T1 to T6. Not flowing. Therefore, the power consumption at the time of detecting the switching position of the rotary switch 43 can be suppressed. Further, when the above-mentioned predetermined conditions are satisfied, the contacts of the rotary switch can be suitably cleaned, so that connection failure due to the oxide film can be prevented.

4: Image forming unit 5: Intermediate transfer unit 8: Control unit 10: Image forming device 17: Feed tray 18: Paper ejection tray 19: Manual feed tray 20: Communication unit 26: Vertical transport path 27: Feed feed path 30: Switching Position detection unit 31: Ladder resistance circuit 32: First switching element 33: Second switching element 41: Feed roller 42: Setting dial 43: Rotary switch L1-L6: Contact electric circuit L11: Detection electric circuit L12: Cleaning electric circuit Lc: Common Electric circuit R1-R7: Resistor R11: Internal resistor R12: Internal resistor T1-T6: Contact TC: Common terminal Tc: Common terminal Vcc: Input terminal Vout: Output terminal

Claims (5)

It is a switching position detection device that detects the switching position of the rotary switch.
A plurality of contact electric circuits including each of a plurality of metal contacts provided in the rotary switch and to which a predetermined constant voltage is applied, and
A resistor provided in each of the plurality of contact electric circuits and having a different resistance value for each of the plurality of contact electric circuits,
A detection electric circuit having a detection resistor and a first switching element connected to the common line of the rotary switch,
A cleaning circuit having a cleaning resistor and a second switching element connected in parallel to the detection circuit and connected to the common line, and a cleaning circuit.
Either one of the first switching element and the second switching element is turned on until a predetermined predetermined condition is satisfied, and the current value of the common line is used while the first switching element is turned on. A switching position detecting device including a control unit for detecting the switching position of the rotary switch. The resistance value of the cleaning resistor is set to a first value at which an arc discharge can occur when the contacts conduct with each other based on the constant voltage.
The switching position detection device according to claim 1, wherein the resistance value of the detection resistor is set to a value larger than the first value. The control unit turns on the first switching element until the predetermined condition is satisfied, turns off the first switching element when the predetermined condition is satisfied, and turns on the second switching element. The switching position detection device according to 1 or 2. An image forming apparatus including the switching position detecting apparatus according to any one of claims 1 to 3.
As the predetermined condition, the control unit turns off the first switching element when the image forming apparatus shifts from the power saving mode to the normal operation mode or when the power of the image forming apparatus is turned on. An image forming apparatus that turns on the second switching element. A paper holding tray that holds the paper on which the image is formed, and
An operation input unit connected to the rotary switch and capable of switching the switching position of the rotary switch is further provided.
The image forming apparatus according to claim 4, wherein the operation input unit has display scales indicating a plurality of sizes of the paper placed on the paper holding tray at positions corresponding to the switching positions.