JP2023068304A - Detector and image forming apparatus - Google Patents

Abstract

To reduce the number of necessary signal lines even for a substrate having one signal output circuit mounted thereon.SOLUTION: A detector has: a sensor substrate 411 that has mounted thereon an LED 404 and a phototransistor 405 that outputs a signal according to the state of reception of light from the LED 404; a master substrate 410 that has mounted thereon a CPU 120 that includes an input/output port; and signal lines 407, 408 that connect the sensor substrate 411 and the master substrate 410 with each other. The sensor substrate 411 has a capacitor 403, and a transistor 406 that is connected with the capacitor 403 and changed in its state by an output signal from the phototransistor 405, and when the phototransistor is turned on, electric charges accumulated in the capacitor 403 are discharged. In an output mode, the CPU 120 supplies a power supply voltage from the input/output port to the sensor substrate 411 through the signal line 407, and in an input mode, detects the state of reception of light from the phototransistor 405 based on the voltage of the capacitor 403 input to the input/output port through the signal line 407.SELECTED DRAWING: Figure 4

Description

The present invention relates to a detection device and an image forming device, and for example, to a substrate on which a photointerrupter is mounted.

Conventional electrophotographic image forming apparatuses that form images on recording paper have sensors to detect the presence or absence of recording paper, the position of the recording paper, and the open/close state of the cover of the image forming apparatus. It is used. Sensors often use a photointerrupter that detects state changes by arranging a light-emitting element and a light-receiving element facing each other, and blocking the light from the light-emitting element with a member interlocking with the detection target between them. .

When a photointerrupter is used as a sensor, it is necessary to place a light shielding member for shielding light from the light emitting element in the slit between the light emitting element and the light receiving element of the photointerrupter. Then, a link mechanism is provided to connect the detection member for detecting the detection target and the light shielding member so as to interlock with the movement of the detection target such as the cover or the recording paper described above, and the link mechanism detects the movement of the detection target according to the movement of the detection target. The light in the slit portion is blocked by moving the light blocking member through the . If the detection member and the sensor are separated from each other, the link mechanism becomes long, which may cause various structural problems. In such a case, the link mechanism may be shortened by mounting a photointerrupter, which is a sensor, on a small board (child board) and arranging it as a sensor board in the vicinity of the detection member.

For example, Patent Document 1 introduces a sensor in which a plurality of photointerrupters are mounted on a small substrate (child substrate). Originally, signal lines corresponding to the number of photointerrupters are required between the main board on which a CPU for controlling each photointerrupter provided on the subboard is installed and the subboard. Patent Document 1 proposes a configuration in which the number of signal lines is reduced to one by wired OR-connecting the outputs of each photointerrupter provided on a child board. In the method proposed in Patent Document 1, the CPU sequentially detects the output of each photointerrupter at a predetermined timing, which is similar to the case of detecting the output via the signal line connected to each photointerrupter. It is described that there is an effect.

Japanese Unexamined Patent Application Publication No. 2008-87908

In the above-described conventional system, five signal lines would normally be required for connecting the child board on which three photointerrupters are mounted and the main board on which the CPU is mounted. However, it can be done with three signal lines. That is, one signal line for supplying power supply voltage, one signal line for supplying ground potential (GND) as a reference potential, and three signal lines for outputting each photointerrupter, totaling five. Where three signal lines are required, three signal lines are sufficient. However, in the above-described conventional method, even in a sub-board on which only one photointerrupter is mounted, the power supply voltage, the ground, and the output of the photointerrupter are used in the same way as when three photointerrupters are mounted. 3 signal lines are required. Therefore, it is required to reduce the number of signal lines required even for a substrate on which one signal output circuit including a light emitting element and a switching element such as a photointerrupter is mounted.

SUMMARY OF THE INVENTION It is an object of the present invention to reduce the number of signal lines required even for a board on which one signal output circuit is mounted.

In order to solve the above problems, the present invention has the following configuration.

(1) A first substrate mounted with a light-emitting element and a light-receiving element that receives light emitted from the light-emitting element and outputs a different signal depending on the state of light reception; and an input/output port. and a connection line that connects the first substrate and the second substrate, wherein an electric charge is accumulated in the first substrate. and a switching element that is connected to the storage element and switches between an on state and an off state according to a signal output from the light receiving element, and when the switching element is in the on state, the storage element When the control unit operates in the output mode, the control unit supplies the power supply voltage from the input/output port to the first substrate through the connection line. is supplied, the storage element is charged by the power supply voltage supplied from the control unit, the light emitting element emits light by the power supply voltage, and when the control unit operates in the input mode, the light emitting element is Light is emitted by the voltage supplied from the storage element, and the control unit detects the light reception state of the light receiving element based on the voltage of the storage element input to the input/output port through the connection line. A detection device characterized by:

(2) A first substrate mounted with a light-emitting element and a switching element that switches between the light-emitting state and the extinguished state of the light-emitting element by being turned on or off, and a control unit provided with an input/output port. In a detection device having a mounted second substrate and a connection line connecting the first substrate and the second substrate, the first substrate is equipped with an electric storage element that accumulates electric charge. and when the switch element is turned on, the electric charge accumulated in the storage element is discharged. When the control section operates in the output mode, the control section is connected to a power supply voltage is supplied from the input/output port to the first substrate, the power storage element is charged by the power supply voltage supplied from the control unit, the light emitting element emits light by the power supply voltage, and When the control unit operates in the input mode, the control unit detects the ON state or the OFF state of the switch element based on the voltage of the storage element input to the input/output port via the connection line. A detection device characterized by:

(3) An image forming apparatus that performs an image forming operation on a recording material being conveyed along a conveying path, comprising the detection device according to (1), wherein the first substrate moves along the conveying path. An image forming apparatus, wherein the control unit detects the presence or absence of a recording material on the conveying path based on the light receiving state of the light receiving element.

(4) An image forming apparatus for forming an image on a recording material, comprising: a paper feeding unit on which the recording material is placed; and the detection device according to (1), wherein the first substrate is and wherein the control unit detects the presence or absence of the recording material placed on the paper supply unit based on the light receiving state of the light receiving element. .

(5) An image forming apparatus that performs an image forming operation on a recording material, comprising the detection device according to (2), wherein the control unit controls the power supply of the image forming apparatus based on the state of the switch element. from an ON state to an OFF state or from an OFF state to an ON state.

According to the present invention, it is possible to reduce the number of required signal lines even for a substrate on which one signal output circuit is mounted.

FIG. 2 is a cross-sectional view for explaining the configuration of the image forming apparatus of Examples 1 and 2; FIG. 2 is an external view for explaining the configuration of the sensor substrate of Example 1; FIG. 4 is a diagram for explaining the circuit configuration and connection method of a conventional substrate for comparison with the first embodiment; FIG. 4 is a diagram for explaining the circuit configuration and connection method of the substrate of Example 1; 4 is a flow chart showing a control sequence for controlling the sensors of the sensor board of the first embodiment; FIG. 10 is a diagram for explaining the circuit configuration and connection method of the substrate of Example 2;

BEST MODE FOR CARRYING OUT THE INVENTION Below, embodiments of the present invention will be described in detail with reference to the drawings.

[Configuration of Image Forming Apparatus]
FIG. 1 is a cross-sectional view for explaining the configuration of a monochrome laser printer 100 (hereinafter referred to as printer 100), which is an image forming apparatus to which Embodiment 1 is applied. In FIG. 1, an image forming unit that forms an image on a recording material P has a photosensitive drum 105 that is a photosensitive member, and a charging roller 107 that is a charging unit that charges the photosensitive drum 105 with a uniform potential. The image forming unit also has a laser scanner 102 which is an exposure unit that irradiates the surface of the photosensitive drum 105 with a laser beam 113 to form an electrostatic latent image. Further, the image forming unit has a developing roller 104 which is developing means for developing the electrostatic latent image formed on the photosensitive drum 105 with magnetic toner stored in the toner tank 103 to form a toner image. there is Incidentally, the developing blade 114 regulates the amount of toner on the developing roller 104 . Also, the waste toner tank 108 collects toner on the photosensitive drum 105 removed by the blade 118 . The CPU 120, which is a control unit, controls operations of the printer 100, which will be described later. For example, the CPU 120 controls the printer 100 according to various programs stored in a ROM (not shown), using a RAM (not shown) as a temporary work area, and performs an image forming operation.

The paper feed unit 101 feeds the stored recording material P to a conveying path 112 , and the fed recording material P passes through the conveying path 112 (on the conveying path) and is conveyed to the transfer roller 106 . A transfer roller 106, which is transfer means, transfers the toner image formed on the photosensitive drum 105 onto the recording material P. As shown in FIG. The fixing device 117 is a device for fixing the toner image transferred to the recording material P on the recording material P. The fixing roller 109 heats the toner image, and the fixing roller 109 is brought into contact with the fixing roller 109 to heat the recording material P passing therethrough. and a pressure roller 110 for pressing. The recording material P that has passed through the fixing device 117 is discharged and stacked on the discharge unit 111 . A recording material presence/absence sensor 116 detects the presence/absence of the recording material P accommodated in the paper feeding unit 101 . A recording material transport sensor 115 detects the leading edge of the recording material P fed from the paper feeding unit 101 to the transport path 112 in the transport direction.

[Image forming operation]
Next, an image forming operation of the printer 100 will be described. Upon receiving a print job from an external device (not shown) such as a personal computer, the CPU 120 of the printer 100 drives each roller in the device and starts the operation of the laser scanner 102 in order to form an image. The charging roller 107 is applied with a negative high voltage charging voltage from a power supply (not shown), contacts the photosensitive drum 105 rotating in the direction of the arrow (clockwise) in the figure, and is in contact with the surface of the photosensitive drum 105 . is charged to a uniform voltage. The laser scanner 102 emits laser light 113 according to image data included in the print job. The laser beam 113 emitted from the laser scanner 102 is applied to the photosensitive drum 105, and the charge of the portion of the photosensitive drum 105 irradiated with the laser beam 113 disappears, forming an electrostatic latent image. The developing roller 104 has a magnet inside, and when a developing voltage, which is a negative high voltage, is applied from a power supply (not shown), the magnetic toner in the toner tank 103 is attracted by magnetic force. The developing roller 104 rotates in the direction of the arrow (counterclockwise direction) in FIG. Developing blade 114 physically regulates the amount of toner, and toner is uniformly coated on developing roller 104 by electrostatic force with a potential difference of −300 V with respect to developing roller 104 .

On the other hand, according to an instruction from the CPU 120, the recording material P fed from the paper feeding unit 101 passes through the transport path 112 and is transported to the transfer nip formed by the contact between the transfer roller 106 and the photosensitive drum 105. FIG. A toner image formed on the photosensitive drum 105 is transferred to the recording material P by applying a transfer voltage, which is a positive high voltage, from a power supply (not shown) to the transfer roller 106 . The recording material P onto which the toner image has been transferred is conveyed to the fixing device 117 and conveyed to the fixing nip formed by the contact between the fixing roller 109 and the pressure roller 110 . A heater (not shown) is in contact with the fixing roller 109. At the fixing nip portion, the toner image is heated to, for example, several hundred degrees by the fixing roller 109, and pressed by the pressure roller 110, so that the toner image is unfixed. is fixed on the recording material P. Then, the recording material P on which the toner image is fixed is discharged to the discharge section 111 and stacked.

Even after the toner image is transferred onto the recording material P, some toner remains on the surface of the photosensitive drum 105 . Ideally, all the toner images should be transferred to the recording material P, but in reality the amount of charge that the toner has is not uniform, so that the toner remains on the photosensitive drum 105 when transferred to the recording material P. I have toner. Toner remaining on the photosensitive drum 105 is scraped off by the blade 118 brought into contact with the photosensitive drum 105 and collected in the waste toner tank 108 . As a result, toner is removed from the surface of the photosensitive drum 105, and the photosensitive drum 105 is again charged to a uniform potential by the charging roller 107, and the laser scanner 102 forms the next electrostatic latent image. The printer 100 executes a print job while repeating the image forming operation described above. Note that FIG. 1 is an example of an image forming apparatus, and the apparatus is not limited to a monochrome printer, and may be a color printer, for example.

[Recording Material Conveyance Sensor and Recording Material Presence/Absence Sensor]
Here, the recording material conveying sensor 115 and the recording material presence/absence sensor 116 will be described. The recording material conveying sensor 115 is arranged upstream of the transfer roller 106 in the conveying direction of the recording material P. As shown in FIG. The recording material transport sensor 115 can detect the arrival of the leading edge of the recording material P fed from the paper feeding unit 101, the presence or absence of the recording material P, and the passage of the trailing edge of the recording material P. When performing printing on the recording material P, the CPU 120 detects that the recording material P is normally fed from the paper feeding unit 101 , and the fed recording material P is conveyed to the transfer roller 106 . It is necessary to start image formation by the image forming unit in accordance with the timing of the image formation. Therefore, when the recording material transport sensor 115 detects that the recording material P fed from the paper feeding unit 101 has been transported, it is necessary to notify the CPU 120 without delay. The recording material conveying sensor 115 has a signal output circuit, which will be described later, and the signal output circuit outputs a signal indicating the detection result of the recording material P to the CPU 120 .

On the other hand, the recording material presence/absence sensor 116 is a sensor that detects the presence/absence of the recording material P accommodated and placed in the paper feeding unit 101 . Even if the print job is received, the CPU 120 does not perform the image forming operation if the recording material P is not present in the paper feed unit 101 based on the detection result of the recording material presence/absence sensor 116, and feeds the paper to the display unit (not shown). A message to replenish the recording material P is displayed on the unit 101 to prompt the user to replenish the recording material P. FIG. In the recording material transport sensor 115 , the speed at which the recording material P is detected is an important factor, but in the recording material presence/absence sensor 116 , the speed at which the recording material P is detected is not as important as the recording material transport sensor 115 . In terms of contrast.

As shown in FIG. 1, the recording material presence/absence sensor 116 and the recording material transport sensor 115 each comprise a small plate (hereinafter referred to as a lever) having a lever shape molded by molding. For example, when the recording material P fed from the paper feeding unit 101 is transported through the transport path 112, it contacts the lever of the recording material transport sensor 115 in the state indicated by the solid line in FIG. When the lever of the recording material conveying sensor 115 comes into contact with the conveyed recording material P, it rotates in the conveying direction of the recording material P, and retreats to a position (the position indicated by the dotted line in FIG. 1) where the conveying of the recording material P is not hindered. do. The lever of the recording material transport sensor 115 is connected to one end of a link mechanism that transmits the movement of the lever to a sensor (photointerrupter), which will be described later. lever). When the lever of the recording material conveying sensor 115 rotates, the flag rotates via the link mechanism and interrupts the slit portion of the sensor (photointerrupter). In the case of the recording material presence/absence sensor 116, as shown in FIG. and the state where the lever is not rotated, which is indicated by the dotted line. As with the recording material transport sensor 115, the recording material presence/absence sensor 116 is also triggered by a sensor (photointerrupter), which will be described later, via a link mechanism connected to a lever and a flag (light shielding lever). is detected.

[Configuration of sensor board]
FIG. 2 is an external perspective view for explaining the configuration of a substrate on which sensors (photointerrupters) for detecting the states of the levers of the recording material transport sensor 115 and the recording material presence/absence sensor 116 are mounted. Hereinafter, a board on which a sensor (photo interrupter) is mounted is referred to as a sensor board (also referred to as a child board). In FIG. 2, the sensor substrate 200 has a sensor substrate portion 201, a photointerrupter 202, and a hole 204 for mounting bundled wires (also called signal wires) connected to the parent substrate (see FIG. 4). A photointerrupter 202 is a sensor that detects the state of levers of the recording material conveying sensor 115 and the recording material presence/absence sensor 116 .

The photointerrupter 202, as shown in FIG. 2, has a "U" shape with two protrusions. Of the two protrusions, one protrusion is provided with a light emitting section that emits light, and the other protrusion is provided with a light receiving section that receives the light emitted from the light emitting section. A slit portion 203 is provided between the two protrusions. For example, when the lever of the recording material transport sensor 115 is rotated by the transported recording material P, the above-described link mechanism lowers (moves) the light shielding lever that blocks light from the light emitting unit to the slit portion 203, thereby moving the light emitting unit. block light from The light receiving section outputs different signals according to the light receiving state of the light emitted from the light emitting section. As a result, the photointerrupter 202 can detect the state of the lever of the recording material conveying sensor 115 . In this embodiment, the sensor substrate 200 is arranged near the recording material transport sensor 115 and the recording material presence/absence sensor 116 in order to shorten the length of the link mechanism.

[Conventional connection method between slave board and master board]
Next, a conventional method of connecting a sensor substrate and a parent substrate will be described for comparison with the present embodiment, which will be described later. FIG. 3 is a circuit diagram for explaining the circuit configuration of the parent board, the circuit configuration of the child board which is the sensor board, and the connection between the parent board and the child board in the case of the conventional connection method. In FIG. 3, the mother board 309 has a CPU 312 (central control unit) that controls the sensor board 310, and the sensor board 310 has a photointerrupter 308 as a sensor. The photointerrupter 308 has a light emitting diode (LED) 303 and a phototransistor 304 . The mother board 309 and the sensor board 310 are connected via signal lines 305, 306, and 307, which are three bundled lines indicated by dashed lines. Also, the power supply voltage Vcc is supplied to the CPU 312 of the mother board 309 . A power supply voltage Vcc of a parent substrate 309 is input to the anode terminal of a light emitting diode (LED) 303 of a photointerrupter 308 via a signal line 305 and a resistor 302 of a sensor substrate 310 . A cathode terminal of the LED 303 is grounded. The phototransistor 304 of the photointerrupter 308 of the sensor substrate 310 has a collector terminal connected to the I/O port 311 of the CPU 312 of the parent substrate 309 via the signal line 306, and an emitter terminal grounded. The I/O port 311 of the CPU 312 on the mother board 309 is connected to the power supply voltage Vcc through a resistor 301 . The ground potential (GND) of the parent substrate 309 is connected to the ground potential (GND) of the sensor substrate 310 via the signal line 307 .

In the conventional connection system shown in FIG. 3, the signal line 305 is used to supply the power supply voltage Vcc from the mother board 309 to the sensor board 310 to drive the LED 303 of the photointerrupter 308 . On the other hand, the CPU 312 of the mother board 309 uses the signal line 306 to detect the ON/OFF state of the phototransistor 304 of the photointerrupter 308 of the sensor board 310 . Furthermore, since a ground potential (GND) is required as a reference potential, a signal line 307 is provided for connecting the ground potential (GND) of the parent substrate 309 and the sensor substrate 310 . Therefore, in the conventional connection method, as shown in FIG. 3, even if there is only one photointerrupter 308 mounted on the sensor substrate 310, three signal lines are required to connect the master substrate 309 and the sensor substrate 310. FIG.

[Connection method between child board and parent board in Example 1]
Next, a method of connecting the sensor substrate and the parent substrate of this embodiment will be described. FIG. 4 is a circuit diagram for explaining the circuit configuration of the parent board, the circuit configuration of the child board which is the sensor board, and the connection between the parent board and the child board in the case of the connection method of this embodiment.

In FIG. 4, the mother board 410 has a CPU 120 (central control unit) (FIG. 1) that controls the sensor board 411. The sensor board 411 includes a photointerrupter 202, a transistor 406, a capacitor 403, resistors 401 and 402, which are sensors. have. The photointerrupter 202 has a light emitting diode (LED) 404 as a light emitting element and a phototransistor 405 as a light receiving element. Further, the mother substrate 410 and the sensor substrate 411 are connected via signal lines 407 and 408 which are bundles (connection lines). On the mother board 410 (second board), the signal line 407 is connected to an I/O port 412 that is an input/output terminal (input/output port) of the CPU 120 . Also, the power supply voltage Vcc is supplied to the CPU 120 . The signal line 408 is connected to ground potential (GND). Note that the sensor substrate 411, the parent substrate 410, and the signal lines 407 and 408 function as a detection device.

In the sensor substrate 411 (first substrate), the light emitting diode (LED) 404 of the photointerrupter 202 has an anode terminal connected to one end of the resistor 402 and a cathode terminal grounded. The other end of resistor 402 is connected to one end of resistor 401 . A phototransistor 405 of the photointerrupter 202 has a collector terminal connected to one end of the resistor 401 and an emitter terminal connected to the base terminal of the transistor 406 . A transistor 406, which is a switching element, has a collector terminal connected to one end of the resistor 401 and an emitter terminal grounded. A capacitor 403, which is a storage element, has one end connected to one end of the resistor 401 and the other end grounded. One end of the resistor 401 is connected to one end of the resistor 402, the collector terminal of the phototransistor 405 of the photointerrupter 202, the collector terminal of the transistor 406, and one end of the capacitor 403, and the other end of the resistor 401 is connected to the signal line 407. there is Also, the signal line 408 is connected to the ground potential (GND).

[Sensor control of child board of this embodiment]
In this embodiment, the signal line 408 is used to connect the ground potential (GND) of the parent board 410 and the ground potential (GND) of the sensor board 411 . On the other hand, the signal line 407 serves both as a supply of power supply voltage from the mother substrate 410 to the sensor substrate 411 and as a signal line for transmitting the sensor state from the sensor substrate 411 to the mother substrate 410 . Therefore, only two signal lines are required to connect the parent board 410 and the sensor board 411, which is a child board. The circuit operation of the circuit shown in FIG. 4 will be described below using the control sequence for the sensor substrate 411 by the CPU 120 shown in the flow chart.

FIG. 5 is a flowchart showing a control sequence for detecting the state of the photointerrupter 202, which is a sensor provided on the sensor substrate 411, by the CPU 120 provided on the mother substrate 410. FIG. The processing shown in FIG. 5 is started and executed by the CPU 120 when the power of the printer 100 is turned on. Note that the CPU 120 has a timer for measuring time. The I/O port 412 connected to the signal line 407 of the CPU 120 is a port capable of switching between an input port for inputting signals and an output port for outputting signals under the control of the CPU 120 .

At step (hereinafter referred to as S) 500, the CPU 120 sets the I/O port 412 connected to the signal line 407 to the output mode in order to use the I/O port 412 as an output port. In S<b>501 , the CPU 120 outputs a high level signal from the I/O port 412 . As a result, a voltage substantially equal to the power supply voltage Vcc supplied to the CPU 120 is output from the I/O port 412 of the CPU 120 and supplied to the sensor substrate 411 via the signal line 407 . In the sensor substrate 411 , the voltage supplied from the mother substrate 410 charges the capacitor 403 through the resistor 401 and is applied to the anode terminal of the LED 404 of the photointerrupter 202 through the resistor 402 . As a result, the LED 404 is brought into a conductive state, current flows through the LED 404, and the LED 404 lights up. At this time, since the CPU 120 uses the I/O port 412 as an output port, it cannot detect the state of the photointerrupter 202 as a sensor, that is, the ON/OFF state of the phototransistor 405 .

In S502, CPU 120 resets and starts the timer. In S503, CPU 120 refers to the timer to determine whether a predetermined time has elapsed. If the CPU 120 determines that the predetermined time has elapsed, the process proceeds to S504, and if it determines that the predetermined time has not elapsed, the CPU 120 returns the process to S503. For a predetermined period of time, the charge voltage of the capacitor 403 is raised by supplying the power supply voltage from the mother board 410 to the voltage that has been lowered due to the discharge of the voltage charged in the capacitor 403 of the sensor board 411 by the process described later. It's time for

In S504, the CPU 120 sets the I/O port 412 from the output mode to the input mode in order to use the I/O port 412 connected to the signal line 407 as an input port. As a result, the supply of the power supply voltage that has been supplied from the parent substrate 410 to the sensor substrate 411 via the signal line 407 is cut off. When the I/O port 412 of the CPU 120 is set as an input port, the I/O port 412 is set in a high impedance state when viewed from the outside. Therefore, the voltage charged in the capacitor 403 of the sensor board 411 does not flow out to the I/O port 412 of the CPU 120 via the signal line 407 . Even if the supply of the power supply voltage from the signal line 407 is interrupted, the LED 404 of the photointerrupter 202 can continue to be in a conductive state for a short time due to the voltage charged in the capacitor 403, and can continue to light. can. When the LED 404 is lit, the light emitted by the LED 404 is blocked by the above flag (not shown), and the phototransistor 405 is off, the voltage input to the I/O port 412 of the CPU 120 is as follows. become that way. That is, the input voltage of the I/O port 412 of the CPU 120 becomes a voltage (predetermined voltage or higher) obtained by subtracting the forward voltage of the LED 404 and the voltage drop due to the resistor 402 from the charged voltage of the capacitor 403 . On the other hand, when the light emitted by the LED 404 is not blocked while the LED 404 is lit and the phototransistor 405 is on, current flows through the base terminal of the transistor 406 . As a result, the transistor 406 is turned on, the charging voltage (accumulated charge) of the capacitor 403 is discharged via the transistor 406, and the voltage of the capacitor 403 is lowered. Then, when the charged voltage of the capacitor 403 drops and falls below the forward voltage of the LED 404 of the photointerrupter 202, the LED 404 becomes non-conductive and goes out. As a result, the phototransistor 405 of the photointerrupter 202 is turned off, no current flows to the base terminal of the transistor 406, the transistor 406 is also turned off, and the charging voltage of the capacitor 403 stops decreasing. As a result, when the phototransistor 405 of the photointerrupter 202 is on, the voltage input to the I/O port 412 of the CPU 120 is lower than when the phototransistor 405 is off.

In S<b>505 , the CPU 120 determines the ON/OFF state of the phototransistor 405 based on the obtained input voltage to the I/O port 412 . The difference in the voltage input to the I/O port 412 of the CPU 120 between when the phototransistor 405 of the photointerrupter 202 is on and when it is off depends on the resistance values used and the characteristics of the parts. Therefore, if the CPU 120 can clearly determine whether the voltage input to the I/O port 412 is high level or low level, the determination may be made using the input signal level. On the other hand, if the voltage difference between the high level and the low level of the voltage that the CPU 120 inputs to the I/O port 412 is small, it may be amplified by, for example, a general voltage doubler circuit, or an analog/digital (A/D) A digital converter converts the voltage value into a digital value and compares them. After completing the input voltage detection process of the I/O port 412, the CPU 120 returns to the process of S500, switches the I/O port 412 to the output mode again, and supplies power (supply of power supply voltage). As a result, the lowered charging voltage of the capacitor 403 of the sensor substrate 411 is restored, and the LED 404 of the photointerrupter 202 can continue to light up.

As described above, in this embodiment, a high-level voltage signal output from the I/O port 412 of the CPU 120 of the mother board 410 to the sensor board 411 is used as the power supply voltage in the sensor board 411 to charge the capacitor 403 . use. Then, the CPU 120 switches the I/O port 412 from the output mode to the input mode, cuts off the supply of the power supply voltage to the sensor substrate 411, and detects the photo sensor, which is a sensor, based on the voltage input to the I/O port 412. The ON/OFF state of the interrupter 202 is detected. In this way, in this embodiment, the power transmission line for supplying the power supply voltage and the signal line for notifying the state of the sensor are shared, thereby reducing the number of signal lines between the master substrate 410 and the sensor substrate 411. are doing. As a result, further cost reduction and space saving can be realized even for a sub-board on which only one photointerrupter is mounted.

When the I/O port 412 is switched from the output mode to the input mode, the power supply to the sensor substrate 411 is cut off and the voltage charged in the capacitor 403 drops. In order to suppress the voltage drop of the capacitor 403, it is necessary to sufficiently lengthen the time during which the I/O port 412 is set as an output port and shorten the time during which it is set as an input port. As a guideline, the time during which the I/O port 412 is set as an output port is set to be sufficient to fully charge the capacitor 403 on the sensor board 411, and the time during which the I/O port 412 is set as an input port. The time should be set as short as possible.

Regarding the cycle (processing time of S500 to S505 in FIG. 5) for setting the I/O port 412 as an output port and an input port, the sensor (here, the photointerrupter 202) installed on the sensor substrate 411 is the detection target. It is necessary to make it a detectable period according to For example, in the recording material transport sensor 115 of FIG. 1, when the recording material P transported from the paper feeding unit 101 contacts the lever and rotates the lever, the light shielding lever (not shown) moves via the link mechanism. When a light shielding lever (not shown) moves to the slit portion 203 of the photointerrupter 202 shown in FIG. 2 and the light emitted from the light emitting portion is shielded by the light shielding lever, the state of the photointerrupter 202 changes. . Therefore, the CPU 120 needs to detect the state change of the photointerrupter 202 without delay. In such a case, the CPU 120 responds by shortening the switching period between the output port and the input port of the I/O port 412 . However, if shortening the switching cycle of the I/O port 412 puts pressure on the processing capability of the CPU 120 or causes a detection delay even if the switching cycle is shortened, then this embodiment shown in FIG. It is better to use the configuration of the conventional system shown in FIG. 3 instead of the conventional system. Further, the image forming apparatus is also provided with a sensor such as the recording material presence/absence sensor 116 in FIG. 1, for which the speed and detection delay of detecting state change are not important factors. The method of this embodiment is particularly suitable for such a sensor, and in this case, the switching cycle of the I/O port 412 should be set to a long cycle that does not put pressure on CPU resources.

In the circuit configuration shown in FIG. 4, when the phototransistor 405 of the photointerrupter 202 of the sensor substrate 411 is on and off, the voltage input to the I/O port 412 of the CPU 120 of the mother substrate 410 is measured. I did an experiment. The specifications of each component used in the experiment are as follows. That is, the power supply voltage Vcc is 3.36 V (volt), the resistance values of the resistors 401 and 402 are 100Ω and 1 kΩ, respectively, and the capacitance of the capacitor 403 is 40 μF. Also, the time during which the I/O port 412 of the CPU 120 is set to the input mode is set to 40 μsec (microseconds), and the period for setting the I/O port 412 to the output port and input port is set to 20 msec (50 Hz). As a result of experiments with the circuit configuration described above, the voltage input to the I/O port 412 of the CPU 120 when the phototransistor 405 is on is 1.65 V, and the voltage input when the phototransistor 405 is off is 1.65V. The voltage applied was 2.60V. The voltage input to the I/O port 412 has a voltage difference of about 1 V (≈2.60 V-1.65 V) between when the phototransistor 405 is on and when it is off. , the off state can be detected. Also, while the I/O port 412 of the CPU 120 was set as the input port, the voltage of the capacitor 403 on the sensor board 411 dropped by about 6%, but the voltage drop was not significant. .

As described above, according to this embodiment, it is possible to reduce the number of required signal lines even for a board on which one signal output circuit is mounted.

In the first embodiment, an embodiment has been described in which the number of signal lines between the child board on which the sensor is mounted is reduced. In a second embodiment, an embodiment will be described in which the number of signal lines between a slave board on which a switch such as a power switch is mounted and a parent board on which a CPU is mounted is reduced. Note that the image forming apparatus in this embodiment is the same as the printer 100 in Embodiment 1, and the same devices and members are denoted by the same reference numerals as in Embodiment 1, and descriptions thereof are omitted here.

[Connection method between child board and parent board in this embodiment]
A method of connecting the sensor substrate and the mother substrate of this embodiment will be described. FIG. 6 is a circuit diagram for explaining the circuit configuration of the parent board, the circuit configuration of the child board which is the switch board, and the connection between the parent board and the child board in the case of the connection method of this embodiment.

In FIG. 6, a mother board 510 has a CPU 120 (central control unit) that controls a switch board 511, and the switch board 511 has a switch 505 which is a mechanical switch, a light emitting diode 504, a capacitor 503, and resistors 501 and 502. are doing. Also, the parent board 510 and the switch board 511 are connected via signal lines 507 and 508 . On the mother board 510 (second board), the signal line 507 is connected to an I/O port 512 that is an input/output terminal (input/output port) of the CPU 120 . Also, the power supply voltage Vcc is supplied to the CPU 120 . The signal line 508 is connected to ground potential (GND).

In the switch substrate 511 (first substrate), a light emitting diode (LED) 504 has an anode terminal connected to one end of a resistor 501 and a cathode terminal grounded. One end of the switch 505 is connected to one end of the resistor 501 and the other end of the switch 505 is connected to one end of the resistor 502 . Note that the other end of the resistor 502 is grounded. A capacitor 503 has one end connected to one end of the resistor 501 and the other end grounded. One end of the resistor 501 is connected to the anode terminal of the light emitting diode 504 , one end of the switch 505 and one end of the capacitor 503 , and the other end of the resistor 501 is connected to the signal line 507 . Also, the signal line 508 is connected to the ground potential (GND).

In this embodiment, the switch 505 is assumed to be a power switch with a pilot lamp commonly found in image forming apparatuses. Since the power switch used in the image forming apparatus is placed in a position that is easily accessible to the user, it is often placed away from the main control CPU 120 . Therefore, the child board on which the power switch is mounted is often a small board on which only the LED for the pilot lamp and the switch are mounted. Therefore, the present invention can be applied to the switch substrate 511 on which the power switch is mounted as well as the sensor substrate 411 on which only the photointerrupter is mounted as in the first embodiment. Therefore, in a second embodiment, an example in which a method similar to that of the first embodiment is applied to such a power switch board with a pilot lamp will be shown.

[Sensor control of child board of this embodiment]
In this embodiment, a connection method similar to that of the first embodiment is applied to a switch substrate 511 on which a switch 505, which is a power switch with a pilot lamp, which is a light emitting diode 504, is mounted. The circuit of the switch substrate 511 of this embodiment differs from the circuit of the sensor substrate 411 of the first embodiment in the following points. That is, the light-emitting diode (LED) 404 and phototransistor 405 in the photointerrupter 202 of the sensor substrate 411 are replaced with a light-emitting diode 504 and a switch 505 in the switch substrate 511, respectively, and the transistor 406 is eliminated. However, the basic circuit operation of the switch board 511 is the same as the circuit operation of the sensor board 411, and the circuit shown in FIG. will be described.

5 differs from the first embodiment, the process shown in FIG. 5 is activated when the power socket of the printer 100 shown in FIG. 1 is inserted into a power outlet and power is supplied from an AC power supply (not shown). and executed by the CPU 120. Note that the CPU 120 of the printer 100 is activated when the power socket is inserted into the power outlet, but the printer 100 does not operate as an image forming apparatus unless the power switch is turned on. The CPU 120 also has a timer for measuring time. The I/O port 512 connected to the signal line 507 of the CPU 120 is a port capable of switching between an input port for inputting signals and an output port for outputting signals under the control of the CPU 120 .

In S500, the CPU 120 sets the I/O port 512 to output mode in order to use the I/O port 512 connected to the signal line 507 as an output port. In S<b>501 , the CPU 120 outputs a high level signal from the I/O port 512 . As a result, a voltage substantially equal to the power supply voltage Vcc supplied to the CPU 120 is output from the I/O port 512 of the CPU 120 and supplied to the switch substrate 511 via the signal line 507 . In the switch board 511, the voltage supplied from the mother board 510 charges the capacitor 503 via the resistor 501 and is applied to the anode terminal of the LED 504, which is the pilot lamp. As a result, the LED 504 becomes conductive, current flows through the LED 504, and the LED 504 lights up. At this time, since the CPU 120 uses the I/O port 512 as an output port, the ON/OFF state of the switch 505 cannot be detected.

In S502, CPU 120 resets and starts the timer. In S503, CPU 120 refers to the timer to determine whether a predetermined time has elapsed. If the CPU 120 determines that the predetermined time has elapsed, the process proceeds to S504, and if it determines that the predetermined time has not elapsed, the CPU 120 returns the process to S503. For a predetermined period of time, the charge voltage of the capacitor 503 is raised by supplying the power supply voltage from the main board 510 to the voltage that has been lowered due to the discharge of the voltage charged in the capacitor 503 of the switch board 511 by the process described later. It's time for

In S504, the CPU 120 sets the I/O port 512 from the output mode to the input mode in order to use the I/O port 512 connected to the signal line 507 as an input port. As a result, the power supply voltage supplied from the parent substrate 510 to the switch substrate 511 through the signal line 507 is cut off. When switch 505 is in the off state, the voltage input to I/O port 512 of CPU 120 is as follows. That is, the input voltage of the I/O port 512 of the CPU 120 becomes a voltage (predetermined voltage or higher) obtained by subtracting the forward voltage of the LED 504 from the charged voltage of the capacitor 503 . On the other hand, when the switch 505 is on, a current flows from the capacitor 503 through the switch 505 and the resistor 502, and no current flows to the LED 504. FIG. Therefore, the voltage input to the I/O port of the CPU 120 becomes a voltage close to 0V.

In S505, the CPU 120 detects the obtained voltage input to the I/O port 512 and determines whether the switch 505 is on or off. In the first embodiment, since the current that can flow through the phototransistor 405 of the photointerrupter 202 is small, the amplifying transistor 406 is necessary, but the switch 505 of the second embodiment has no such limitation. Therefore, the potential difference of the capacitor 503 can be made large between the on state and the off state of the switch 505 without an amplifying transistor. Note that the resistor 502 of the switch substrate 511 is a current limiting resistor that protects the switch 505 by limiting the current that flows when the switch 505 is pressed and turned on. After completing the input voltage detection process of the I/O port 512, the CPU 120 returns to the process of S500, switches the I/O port 512 to the output mode again, and supplies power (supply of power supply voltage). As a result, the lowered charging voltage of the capacitor 503 of the switch substrate 511 is restored, and the LED 504 can be lit.

In the circuit configuration shown in FIG. 6, an experiment was conducted to measure the voltage input to the I/O port 512 of the CPU 120 of the mother board 510 when the switch 505 of the switch board 511 was on and off. The specifications of each component used in the experiment are as follows. That is, the power supply voltage Vcc is 3.36 V (volt), the resistance values of the resistors 501 and 502 are 1 kΩ and 100 Ω, respectively, and the capacitance of the capacitor 503 is 1.0 μF. Also, the time during which the I/O port 512 of the CPU 120 is set to the input mode is set to 40 μsec (microseconds), and the period for setting the I/O port 512 to the output port and input port is set to 20 msec (50 Hz). As a result of experiments with the circuit configuration described above, the voltage input to the I/O port 512 of the CPU 120 when the switch 505 is on is 0.24 V, and the voltage input when the switch 505 is off is 0.24 V. was 1.67V. The voltage input to I/O port 512 has a voltage difference of about 1.4 V (≈1.67 V - 0.24 V) between when switch 505 is on and when switch 505 is off. , the off state can be detected. By detecting the on state and off state of the switch 505, the CPU 120 can, for example, shift the power of the image forming apparatus from an on state to an off state or from an off state to an on state.

In addition, in the circuit configuration of the switch substrate 511 shown in FIG. 6, current flows through the LED 504 while the switch 505 is not pressed, and the LED 504 is in a light emitting state. On the other hand, while the switch 505 is pressed, no current flows through the LED 504, so the LED 504 is turned off. The LED 504 is arranged as a pilot lamp or indicator for the switch 505, but is extinguished while the switch 505 is pressed. Even if the supply of power supply voltage from the signal line 507 is cut off, the LED 504 is turned on for a short time by the voltage charged in the capacitor 403 when the switch 505 is not pressed and in the OFF state. The state is maintained and can continue to be lit.

As described above, in this embodiment, the high-level voltage signal output from the I/O port 512 of the CPU 120 of the mother board 510 to the switch board 511 is charged to the capacitor 503 as the power supply voltage in the switch board 511 . use. Then, the CPU 120 switches the I/O port 512 from the output mode to the input mode, cuts off the power supply (power supply voltage supply) to the switch board 511, and based on the voltage input to the I/O port 512, The ON/OFF state of the switch 505 is detected. In this way, in this embodiment, the number of signal lines between the master board 510 and the switch board 511 is reduced by sharing the power transmission line for supplying the power supply voltage and the signal line for notifying the state of the switch. are doing. As a result, further cost reduction and space saving can be realized even for a sub-board on which only one photointerrupter is mounted.

Note that when the I/O port 512 is switched from the output mode to the input mode, power supply to the switch board 511 is interrupted and the voltage charged in the capacitor 503 drops. In order to suppress the voltage drop of the capacitor 503, even in the second embodiment, it is necessary to sufficiently lengthen the time during which the I/O port 512 is set as an output port and shorten the time during which it is set as an input port. . Also, the cycle (processing time of S500 to S505 in FIG. 5) for setting the I/O port 512 as an output port and an input port is also a cycle corresponding to the operation of pressing the switch 505 installed on the switch board 511. Just do it.

In addition, in Embodiments 1 and 2, a photointerrupter was used as an example of a signal output circuit having a light emitting element and a switch element, but the present invention is not limited to this. For example, a photoreflector may be used in which light is emitted from a light emitting element to an object to be detected, and light reflected by the object to be detected is received by a light receiving element as a switching element. For example, in the printer 100, a photoreflector may be used as a sensor for detecting toner density. Even when one photoreflector is mounted on the sensor substrate, the present invention can be applied to achieve the same effect.

As described above, according to this embodiment, it is possible to reduce the number of required signal lines even for a board on which one signal output circuit is mounted.

120 CPUs
403 capacitor 404 LED
405 Phototransistor 406 Transistors 407, 408 Signal line 410 Mother board 411 Sensor board

Claims (14)

a first substrate mounted with a light-emitting element and a light-receiving element that receives light emitted from the light-emitting element and outputs a different signal according to a light-receiving state of the light;
a second board on which a control unit having an input/output port is mounted;
A detection device comprising a connection line that connects the first substrate and the second substrate,
The first substrate is equipped with a storage element that stores electric charge, and a switching element that is connected to the storage element and switches between an on state and an off state according to a signal output from the light receiving element, The electric charge accumulated in the storage element is discharged when the switching element is turned on, and
When the control unit operates in the output mode, the control unit supplies a power supply voltage from the input/output port to the first substrate through the connection line, and the storage element receives the voltage supplied from the control unit. While being charged by the power supply voltage, the light emitting element emits light by the power supply voltage,
When the control unit operates in the input mode, the light emitting element emits light according to the voltage supplied from the storage element, and the control unit controls the voltage of the storage element input to the input/output port through the connection line. , wherein the light receiving state of the light receiving element is detected based on the above. The light emitting element is a light emitting diode,
The light receiving element is a phototransistor,
the storage element is a capacitor,
the switching element is a transistor,
the connection line is connected to one end of the capacitor, the anode terminal of the light emitting diode, the collector terminal of the phototransistor, and the collector terminal of the transistor;
an emitter terminal of the phototransistor is connected to a base terminal of the transistor;
the other end of the capacitor, the cathode terminal of the light emitting diode, and the emitter terminal of the transistor are grounded;
When the control unit operates in the output mode, the control unit outputs a high-level signal from the input/output port through the connection line to supply power supply voltage to the first substrate. 2. A sensing device according to claim 1. 3. The detection device according to claim 1, wherein the light emitting element and the light receiving element are included in a photointerrupter. 3. The detection device according to claim 1, wherein the light-emitting element and the light-receiving element are included in a photoreflector. a first substrate on which a light-emitting element and a switching element that switches between a light-emitting state and an extinguished state of the light-emitting element by being turned on or off;
a second board on which a control unit having an input/output port is mounted;
A detection device comprising a connection line that connects the first substrate and the second substrate,
The first substrate is mounted with a storage element for accumulating electric charge, and when the switch element is turned on, the electric charge accumulated in the storage element is discharged,
When the control unit operates in the output mode, the control unit supplies a power supply voltage from the input/output port to the first substrate through the connection line, and the storage element receives the voltage supplied from the control unit. While being charged by the power supply voltage, the light emitting element emits light by the power supply voltage,
When the control unit operates in the input mode, the control unit determines the ON state or the OFF state of the switch element based on the voltage of the storage element input to the input/output port through the connection line. A detection device characterized by detecting. The light emitting element is a light emitting diode,
The switch element is a mechanical switch,
the storage element is a capacitor,
the connection line is connected to one end of the capacitor, the anode terminal of the light emitting diode, and one end of the mechanical switch;
The other end of the mechanical switch is connected to one end of the resistor,
the other end of the capacitor, the cathode terminal of the light emitting diode, and the other end of the resistor are grounded;
When the control unit operates in the output mode, the control unit outputs a high-level signal from the input/output port through the connection line to supply power supply voltage to the first substrate. 6. A sensing device according to claim 5. An image forming apparatus that performs an image forming operation on a recording material being conveyed along a conveying path,
Equipped with the detection device according to any one of claims 1 to 4,
The first substrate is arranged along the transport path,
The image forming apparatus, wherein the control section detects the presence or absence of the recording material on the conveying path based on the light receiving state of the light receiving element. When the voltage of the storage element input to the input/output port is lower than a predetermined voltage, the control section determines that the light receiving element is receiving light and there is no recording material on the conveying path. When the voltage of the storage element input to the input/output port is equal to or higher than a predetermined voltage, it is determined that the light receiving element is not receiving light and that there is a recording material on the conveying path. 8. The image forming apparatus according to claim 7, wherein: 9. The image forming apparatus according to claim 8, wherein the control unit operates in the input mode at a period in which the recording material conveyed on the conveying path can be detected. An image forming apparatus for forming an image on a recording material,
a paper feed unit on which the recording material is placed;
A detection device according to any one of claims 1 to 4;
with
The first substrate is arranged in the paper feeding unit,
The image forming apparatus according to claim 1, wherein the control section detects the presence or absence of the recording material placed on the paper feeding section based on the light receiving state of the light receiving element. When the voltage of the storage element input to the input/output port is lower than a predetermined voltage, the control section determines that the light receiving element is in a state of receiving light, and that the light receiving element is placed on the paper feeding section. When the voltage of the storage element input to the input/output port is equal to or higher than a predetermined voltage, the light-receiving element is in a state of not receiving light, and the recording material is fed to the paper feeding unit. 11. The image forming apparatus according to claim 10, wherein it is determined that there is no recording material placed. 8. The time during which the control unit operates in the input mode is the time until the voltage of the storage element becomes lower than a predetermined voltage when the light receiving element is in the ON state. 12. The image forming apparatus according to claim 1, 9, or 11. An image forming apparatus for forming an image on a recording material,
A detection device according to claim 5 or claim 6,
The image forming apparatus according to claim 1, wherein the control section shifts the power supply of the image forming apparatus from an on state to an off state or from an off state to an on state based on the state of the switch element. a photoreceptor on which a latent image is formed;
a developing means for developing the latent image with toner to form a toner image;
14. The image forming apparatus according to claim 7, further comprising transfer means for transferring the toner image formed by said developing means onto a recording material.

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