JP4364875B2 - Humidity sensor failure detection apparatus and image forming apparatus - Google Patents

Description

  The present invention relates to a failure detection device that detects a failure of an impedance change type humidity sensor and an image forming apparatus including the failure detection device. In particular, the present invention relates to a copying machine, a printer, a facsimile machine, an Internet facsimile machine, which is an apparatus for forming an image on recording paper, and a multifunction machine having any one of these functions.

  In an image forming apparatus such as a copying machine that forms an image on recording paper by an electrophotographic method, the amount of toner adhering to the recording paper changes as the humidity changes, thereby forming an image desired by the user. May not be possible.

Conventionally, various proposals have been disclosed in order to solve the above problems. For example, an image forming apparatus in which a humidity sensor is provided and image forming conditions (transfer conditions and the like) are set according to the measurement results has been proposed (see Patent Document 1).
JP 2005-134413 A

  However, even when a failure such as a disconnection occurs in the humidity sensor provided in the image forming apparatus, the image forming conditions are set according to the detection result of the humidity sensor, so the image quality may deteriorate. It was. For example, when the humidity sensor is disconnected (or short-circuited) and the humidity is detected to be 100% (or 0%) and the corresponding extreme image forming conditions are set, the above problem is further increased. Realize. Here, for convenience, the relative humidity is simply referred to as humidity.

  SUMMARY An advantage of some aspects of the invention is that it provides a failure detection device that detects a failure of an impedance change type humidity sensor and an image forming apparatus including the failure detection device.

  In order to achieve the above object, a failure detection device for a humidity sensor according to claim 1 is a failure detection device for detecting a failure of an impedance change type humidity sensor, which is set to a predetermined size and has a positive polarity. First voltage generating means for generating a first voltage that is a rectangular wave, second voltage generating means that is set to the predetermined magnitude and generates a second voltage that is a rectangular wave having a negative polarity, and the humidity The first voltage is applied to one end of the sensor, the second voltage is applied to the other end of the humidity sensor via the first resistor, and the voltage generated at both ends of the first resistor. A humidity measuring means for measuring humidity by measuring a certain first detection voltage, and when the first detection voltage satisfies a predetermined condition, the first voltage is applied to one end of the humidity sensor; Ground the other end of the humidity sensor, The serial second detection voltage is a voltage generated across the first resistor is measured, it is characterized in that it comprises a determination means for determining failure of the humidity sensor based on the value.

  The humidity sensor failure detection device according to claim 2 is the humidity sensor failure detection device according to claim 1, wherein the predetermined condition is a first threshold value in which the first detection voltage is preset. It is characterized by being less than or exceeding a preset second threshold value.

  The humidity sensor failure detection device according to claim 3 is the humidity sensor failure detection device according to claim 1 or 2, wherein the determination means includes the second detection voltage and the first detection voltage. When the absolute value of the difference between the two is less than a preset third threshold value, it is determined that the humidity sensor has failed.

  The humidity sensor failure detection device according to claim 4 is the humidity sensor failure detection device according to any one of claims 1 to 3, wherein the humidity sensor is a capacitive polymer. It is a film humidity sensor.

  An image forming apparatus according to a fifth aspect is detected by the humidity sensor failure detection apparatus according to any one of the first to fourth aspects, a printing unit that forms an image on a recording sheet, and the humidity sensor. And a condition setting means for setting an operating condition of the printing means based on the humidity.

  The image forming apparatus according to claim 6 is the image forming apparatus according to claim 5, wherein the humidity is set to a predetermined humidity when it is determined by the failure detection device that the humidity sensor has failed. Provided with a setting means, and when it is determined by the failure detection device that the humidity sensor has failed, the condition setting means sets the operating condition of the printing means based on the humidity set by the humidity setting means. It is characterized by doing.

  An image forming apparatus according to claim 7 is the image forming apparatus according to claim 6, further comprising a humidity storage unit that stores humidity detected by the humidity sensor, wherein the humidity setting unit includes the failure detection unit. The apparatus determines whether or not the humidity sensor has failed at the timing when the main power is turned on, and when it is determined that the humidity sensor has not failed, the humidity detected by the humidity sensor is determined. The humidity is stored in the humidity storage unit, and when it is determined that the humidity sensor has failed, the humidity stored in the humidity storage unit is read and set.

  According to the failure detection apparatus for a humidity sensor according to claim 1, a first voltage which is set to a predetermined magnitude and has a positive rectangular wave is applied to one end of the humidity sensor, and the humidity sensor A second voltage, which is set to a predetermined magnitude and has a negative polarity and is a rectangular wave, is applied to the other end of the first terminal via the first resistor, and is a voltage generated at both ends of the first resistor. The humidity is measured by measuring the detection voltage. When the measured first detection voltage satisfies a predetermined condition, the first voltage is applied to one end of the humidity sensor, the other end of the humidity sensor is grounded, and both ends of the first resistor are connected. Since the second detection voltage, which is a generated voltage, is measured and the failure of the humidity sensor is determined based on the measured value, the failure of the humidity sensor can be accurately detected.

  That is, in the humidity sensor, when a failure such as a short circuit or disconnection occurs, the first detection voltage detected when the humidity is 100% (or 0%) is measured as the first detection voltage. It is difficult to determine the failure of the humidity sensor based on the detected voltage. However, as described above, if the second detection voltage detected with the other end of the humidity sensor being grounded is used, a more detailed determination can be made, so that the failure of the humidity sensor is accurately detected. is there.

  According to the failure detection apparatus for the humidity sensor according to claim 2, the predetermined condition is that the first detection voltage is less than a preset first threshold value or exceeds a preset second threshold value. Therefore, it is possible to easily determine whether or not to perform a failure sensor failure determination process.

  According to the humidity sensor failure detection device according to claim 3, when the absolute value of the difference between the second detection voltage and the first detection voltage is less than a preset third threshold, the humidity sensor fails. Therefore, it is possible to accurately detect a failure of the humidity sensor with a simple process.

  That is, when a failure such as a short circuit or disconnection occurs in the humidity sensor, the first voltage is applied to one end of the humidity sensor and the second voltage is applied to the other end of the humidity sensor. The first detection voltage, which is a voltage generated at both ends of the first resistor, and the first voltage is applied to one end of the humidity sensor, and the other end of the humidity sensor is grounded. This is because the second detection voltage, which is a voltage generated at both ends of the resistor, has substantially the same value.

  According to the failure detection apparatus for a humidity sensor according to claim 4, since the humidity sensor is a capacitive polymer film humidity sensor, the first voltage and the second voltage that are rectangular waves are applied to both ends. Thus, since the humidity sensor apparently functions as a resistance, the first detection voltage and the second detection voltage are easily detected.

  According to an image forming apparatus of a fifth aspect of the present invention, the humidity sensor failure detection device according to any one of the first to fourth aspects of the present invention is provided, on the recording paper based on the humidity detected by the humidity sensor. Since the operating conditions of the printing means for forming an image are set, it is possible to set appropriate operating conditions for the printing means.

  According to the image forming apparatus of the sixth aspect, when it is determined that the humidity sensor is out of order, the operation condition of the printing unit is set based on the humidity set by the humidity setting unit. By configuring the humidity setting means to set an appropriate humidity, it is possible to set an appropriate operating condition of the printing means even when the humidity sensor is out of order.

  According to the image forming apparatus of the seventh aspect, it is determined whether or not the humidity sensor is malfunctioning at the timing when the main power is turned on, and when it is determined that the humidity sensor is not malfunctioning, The humidity detected by the sensor is set, the humidity is stored in the humidity storage means, and when it is determined that the humidity sensor is malfunctioning, the humidity stored in the humidity storage means is read and set. Is done. Therefore, when it is determined that the humidity sensor has failed, the measured humidity is set at the timing when the main power supply is turned on immediately before the humidity sensor fails. Therefore, it is possible to set appropriate operating conditions for the printing means.

  Hereinafter, an example of an image forming apparatus according to the present invention will be described with reference to the drawings. FIG. 1 is a block diagram showing an example of a schematic configuration of an image forming apparatus according to the present invention. Here, the case where the image forming apparatus is a copying machine will be described. However, the image forming apparatus may be another image forming apparatus (for example, a facsimile, an Internet facsimile, a printer, a multifunction machine, etc.) that forms an image on recording paper. Good. As shown in FIG. 1, the copying machine 1 includes an image generation unit 11, a control unit 12, a display unit 13, an operation unit 14, a print processing unit 15, and a humidity detection unit 16.

  The image generation unit 11 reads an image formed on a document and generates document image information, and includes a reading unit 111 and an ADF 112. The reading unit 111 illuminates a document to be read and reads reflected light with a CCD (Charge Coupled Devices) or the like to generate document image information. An ADF (Automatic Document Feeder) 112 conveys a document to a document reading position of the reading unit 111.

  The control unit 12 (corresponding to a part of the failure detection apparatus) controls the operation of the entire copying machine 1, and includes a CPU (Central Processing Unit) 121, a RAM (Random Access Memory) 122, and an illustration not shown. ROM (Read Only Memory).

  The display unit 13 includes an LCD (Liquid Crystal Display), an LED (Light Emitting Diode), and the like, and displays setting information, guidance information, message information, and the like so as to be visible to the user based on instructions from the control unit 12 (CPU 121). To do.

  The operation unit 14 receives an operation input from the user, generates operation input information corresponding to the received operation input, and outputs the operation input information to the control unit 12 (CPU 121). The operation unit 14 includes, for example, various buttons such as a numeric keypad and a start button, and a touch panel formed integrally with the LCD disposed in the display unit 13.

  The print processing unit 15 (corresponding to a part of the printing means) forms an image (here, an image corresponding to the image information generated by the image generation unit 11) on a recording paper by electrophotography. A developing unit 151, a photosensitive unit 152, and the like. The developing unit 151 forms an electrostatic latent image corresponding to the original image generated by reading the image formed on the original on the surface of the photosensitive drum with a laser beam or the like, and adds toner to the formed electrostatic latent image. To form a toner image. The photosensitive unit 152 includes a photosensitive drum. First, the surface of the photosensitive drum is substantially uniformly charged by a charging roller, and then, toner is attached to the electrostatic latent image corresponding to the original image by the developing unit 151. An image is formed, and the toner image is further transferred onto a recording sheet by a transfer roller.

  The humidity detection unit 16 (corresponding to a part of the failure detection apparatus) detects the humidity (or the humidity of the outside air) inside the copying machine 1, and includes a humidity sensor 161, a humidity measurement circuit 162, and the like. Yes. The humidity sensor 161 is an impedance change type humidity sensor disposed at an appropriate position in the air path in the vicinity of the intake fan of the copier 1. Here, the humidity sensor 161 is a capacitance-type high sensor described later with reference to FIG. It is a molecular film humidity sensor. The humidity measuring circuit 162 (corresponding to a part of the humidity measuring means) is a circuit connected to the humidity sensor 161 in order to detect humidity (or determine whether the humidity sensor 161 has failed). The configuration of the humidity measurement circuit 162 will be described later with reference to FIG.

  FIG. 2 is a functional configuration diagram illustrating an example of the control unit 12. The CPU 121 functionally includes a first voltage generation unit 121a, a second voltage generation unit 121b, a humidity measurement unit 121c, a determination unit 121d, a humidity setting unit 121e, a condition setting unit 121f, and a print control unit 121g, and a RAM 122. Is functionally provided with a humidity storage unit 122a. The failure determination device according to the present invention includes a first voltage generation unit 121a, a second voltage generation unit 121b, a humidity measurement unit 121c and a determination unit 121d of the CPU 121, and the humidity detection unit 16 described above.

  Here, the CPU 121 reads out and executes a program stored in advance in a ROM or the like, whereby the first voltage generation unit 121a, the second voltage generation unit 121b, the humidity measurement unit 121c, the determination unit 121d, the humidity setting unit 121e, The RAM 122 functions as a functional unit such as the humidity storage unit 122a as well as a functional unit such as the condition setting unit 121f and the print control unit 121g. The humidity storage unit 122a (corresponding to temperature storage means) stores the humidity measured by the humidity sensor 161.

  Of the various data stored in the RAM 122 and ROM, data that can be stored in a removable recording medium is read by a driver such as a hard disk drive, an optical disk drive, a flexible disk drive, a silicon disk drive, or a cassette medium reader. In this case, the recording medium is, for example, a hard disk, an optical disk, a flexible disk, a CD, a DVD, a semiconductor memory, or the like.

  As shown in FIG. 3, the first voltage generator 121a (corresponding to the first voltage generator) is set to a predetermined magnitude (here, 5V), and the first voltage is a rectangular wave having a positive polarity. CLK1 is generated. The first voltage CLK1 is set to a predetermined duty ratio (here, 50%).

  As shown in FIG. 3, the second voltage generator 121b (corresponding to the second voltage generator) is set to a predetermined magnitude (here, 5V, which is the same as the first voltage CLK1), and has a negative polarity. The second voltage CLK2, which is a rectangular wave, is generated. Note that the second voltage CLK2 is set to the same duty ratio as the first voltage CLK1 (here, 50%).

  As shown in FIG. 4A, the humidity measuring unit 121c (corresponding to a part of the humidity measuring unit) is connected to the first voltage generating unit 121a at one end 161a of the humidity sensor 161 via the humidity measuring circuit 162. The second voltage CLK2 generated by the second voltage generator 121b is applied to the other end 161b of the humidity sensor 161 via the first resistor R1. The humidity is measured by measuring a first detection voltage Vm1, which is a voltage generated across the resistor R1.

  As shown in FIG. 4A, the determination unit 121d (corresponding to determination means) is connected to one end of the humidity sensor 161 when the first detection voltage Vm1 satisfies a predetermined condition via the humidity measurement circuit 162. 161a is applied with the first voltage CLK1 generated by the first voltage generator 121a, the other end 161b of the humidity sensor 161 is grounded via the resistor R1, and the voltage generated at both ends of the first resistor R1. A certain second detection voltage Vm2 is measured, and a failure of the humidity sensor 161 is determined based on the value.

  Here, the predetermined condition is that the first detection voltage Vm1 is less than a preset first threshold value VL (here, VL = 0.4V) or a preset second threshold value VH (here, , VHL = 4.6V) (see FIG. 7). Further, the determination unit 121d determines that the absolute value of the difference between the second detection voltage Vm2 and the first detection voltage Vm1 is less than a preset third threshold VS (here, VS = 0.02V). It is determined that the humidity sensor 161 has failed (see FIG. 7).

  FIG. 3 is a timing chart showing measurement timings of the first detection voltage Vm1 and the second detection voltage Vm2 by the humidity measurement unit 121c and the determination unit 121d. The measurement timings of the first voltage CLK1, the second voltage CLK2, and the first detection voltage Vm1 and the second detection voltage Vm2 are shown in order from the top of the figure. As shown in this figure, the first detection voltage Vm1 and the second detection voltage Vm2 are measured within a period (measurement period MT) in which the first voltage CLK1 is “High = 5V”.

  The functional configuration of the control unit 12 will be described using the configuration diagram of FIG. 2 again. The humidity setting unit 121e (corresponding to the humidity setting unit) sets a predetermined humidity when the determination unit 121d determines that the humidity sensor 161 has failed (= printing for the condition setting unit 121f). Output as humidity used to set the operating condition of the processing unit 15). Here, at the timing when the main power supply is turned on, the determination unit 121d determines whether or not the humidity sensor 161 has failed. When it is determined that the humidity sensor 161 has not failed, The humidity detected by the sensor 161 is set, and the humidity is stored in the humidity storage unit 122a. When it is determined that the humidity sensor 161 has failed, the humidity stored in the humidity storage unit 122a is read out. It is to set.

  The condition setting unit 121f (corresponding to the condition setting unit) sets the operating condition of the print processing unit 15 based on the humidity detected by the humidity sensor 161. Here, the operating condition of the print processing unit 15 corresponding to the humidity set by the humidity setting unit 121e is set based on the humidity detected by the humidity sensor 161.

  The print control unit 121g (corresponding to a part of the printing unit) controls the print processing unit 15 based on the operation condition set by the condition setting unit 121f to form an image on recording paper.

  FIG. 4 is a circuit diagram for explaining an example of the configuration of the humidity measurement circuit 162. (A) is a circuit diagram of the humidity measurement circuit 162, and (b) is a circuit diagram of an equivalent circuit of the humidity measurement circuit 162. As shown in (a), when the humidity is detected by the humidity measuring unit 121c, the humidity measuring circuit 162 has a first voltage generated by the first voltage generating unit 121a at one end 161a of the humidity sensor 161. The second voltage CLK2 generated by the second voltage generator 121b is applied to the other end 161b of the humidity sensor 161 via the first resistor R1 (the resistance value r1 of the resistor R1 is, for example, 30 kΩ). A first detection voltage Vm1, which is a voltage applied to both ends of the first resistor R1, is input to an A / D port (not shown) of the CPU 121.

  The humidity measuring circuit 162 applies the first voltage CLK1 generated by the first voltage generator 121a to one end 161a of the humidity sensor 161 when the determination unit 121d determines that the humidity sensor 161 has failed. The other end 161b of the humidity sensor 161 is grounded via the first resistor R1, and the second detection voltage Vm2 that is a voltage generated at both ends of the first resistor R1 is input to the A / D port of the CPU 121. Yes.

  Here, the first detection voltage Vm1 and the second detection voltage Vm2 have a resistance R2 (one end connected to the A / D port of the CPU 121 and the other end connected to the humidity sensor 161 side contact of the first resistance R1. The resistance value r2 of the resistor R2 is, for example, 1 kΩ, and a third resistor R3 whose one end is connected to a contact on the humidity sensor 161 side of the first resistor R1 and whose other end is grounded (the resistance value r3 of the resistor R3 is , For example, 1 MΩ), and a bypass composed of a capacitor C1 whose one end is connected to the A / D port side contact of the CPU 121 of the resistor R2 and whose other end is grounded (capacitance c1 of the capacitor C1 is, for example, 1000 pF) The data is input to the A / D port of the CPU 121 via the circuit.

  As shown in (b), the equivalent circuit (DC circuit) of the humidity measuring circuit 162 differs from the humidity measuring circuit 162 shown in (a) in the following points. The humidity sensor 161 functions as a variable resistor R (P) whose resistance value changes based on humidity. Between the contacts to which the first detection voltage Vm1 and the second detection voltage Vm2 are applied, this is equivalent to the application of the DC voltage Vcc1 (or DC voltage Vcc2) (here, one end is grounded, The voltage Vcc is applied to the other end). Here, the magnitude of the DC voltage Vcc1 is determined by the voltage values of the first voltage CLK1 and the second voltage CLK2, and the magnitude of the DC voltage Vcc2 is determined by the voltage value of the first voltage CLK1. Here, the magnitudes of the DC voltage Vcc1 and the DC voltage Vcc2 are approximately 5V.

From the equivalent circuit of FIG. 4B, the first detection voltage Vm1 and the second detection voltage Vm2 are obtained by the following equations (1) and (2), respectively.
Vm1 = Vcc1 × r1 ÷ (r1 + R (P)) (1)
Vm2 = Vcc2 × r1 ÷ (r1 + R (P)) (2)
The humidity measuring unit 121c detects the first detection voltage Vm1, obtains the resistance value R (P) of the humidity sensor 161 using the equation (1), and obtains the humidity corresponding to the resistance value from the sensor characteristics. (See FIG. 6). When the humidity sensor 161 is disconnected, it is assumed that the resistance value R (P) is infinite in the above formulas (1) and (2), and the first detection voltage Vm1 and the second detection voltage Vm2 are used. “0V” is required. Conversely, when the humidity sensor 161 is short-circuited, it is assumed that the resistance value R (P) is zero in the above equations (1) and (2), and the first detection voltage Vm1 and the second detection voltage Vm2 are used. “Vcc1, Vcc2 = 5V” is obtained. Accordingly, when the humidity sensor 161 is disconnected or short-circuited, the first detection voltage Vm1 and the second detection voltage Vm2 have substantially the same value, and therefore the difference between the first detection voltage Vm1 and the second detection voltage Vm2 It is possible to determine whether or not the humidity sensor 161 has failed based on whether or not the absolute value is equal to or less than the third threshold value VS.

  FIG. 5 is a configuration diagram illustrating an example of the configuration of the humidity sensor 161. The humidity sensor 161 includes a polymer film 161d sandwiched between a pair of electrode plates 161c and 161e. The electrode plates 161c and 161e are formed by depositing a metal such as copper, for example. Further, the humidity sensor 161 changes its dielectric constant as the polymer film 161d absorbs and releases moisture in the atmosphere, and the humidity sensor 161 (between the electrode plates 161c and 161e) has a capacitance. The humidity is measured by utilizing the change.

  FIG. 6 is a chart showing an example of the relationship between the first detection voltage Vm1 and the humidity. The humidity measuring unit 121c measures the humidity by obtaining the humidity corresponding to the measured first detection voltage Vm1 using the correspondence table shown in this figure. The higher the first detection voltage Vm1, the higher the humidity. For example, when the first detection voltage Vm1 is 2.5V, the humidity is 50%.

  FIG. 7 is a flowchart illustrating an example of the operation of the control unit 12. First, the humidity setting unit 121e determines whether or not it is the timing when the main power is turned on (S101). If it is determined that it is not the timing when the main power is turned on (NO in S101), the process is set to a standby state. If it is determined that it is time to turn on the main power supply (YES in S101), the humidity measurement unit 121c measures the first detection voltage Vm1 (S103).

  Then, the determination unit 121d determines whether the first detection voltage Vm1 is equal to or higher than the first threshold value VL and equal to or lower than the second threshold value VH (S105). If the first detection voltage Vm1 is not less than the first threshold VL and not more than the second threshold VH (YES in S105), the process proceeds to step S107. When it is determined that the first detection voltage Vm1 is not lower than the first threshold VL and not lower than the second threshold VH (less than the first threshold VL or higher than the second threshold VH) (S105) In NO), the determination unit 121d measures the second detection voltage Vm2 (S113). Then, it is determined whether or not the absolute value of the difference between the first detection voltage Vm1 and the second detection voltage Vm2 is equal to or less than the third threshold value VS (S115). If it is determined that the absolute value of the difference between the first detection voltage Vm1 and the second detection voltage Vm2 is equal to or less than the third threshold value VS (YES in S115), the process proceeds to step 117.

  When it is determined that the absolute value of the difference between the first detection voltage Vm1 and the second detection voltage Vm2 is not less than or equal to the third threshold VS (NO in S115), or in the case of YES in step S105, the determination unit 121d determines that the humidity sensor 161 has not failed, and the humidity setting unit 121e determines the humidity P1 corresponding to the first detection voltage Vm1 (S107). The humidity setting unit 121e stores the humidity P1 in the humidity storage unit 122a (S109), and the condition setting unit 121f sets the operating condition of the print processing unit 15 based on the humidity P1 (S111). Is terminated.

  If YES in step S115, the humidity setting unit 121e reads the humidity P0 stored in the humidity storage unit 122a (S117). Then, the condition setting unit 121f sets the operating condition of the print processing unit 15 based on the humidity P0 (S119), and the process is terminated.

  In this way, the first voltage CLK1 generated by the first voltage generator 121a is applied to one end 161a of the humidity sensor 161, and the second voltage generator 121b generates the other end 161b of the humidity sensor 161. The applied second voltage CLK2 is applied through the first resistor R1, and the humidity is measured by measuring the first detection voltage Vm1, which is a voltage generated at both ends of the first resistor R1. When the first detection voltage Vm1 satisfies a predetermined condition, the first voltage CLK1 generated by the first voltage generator 121a is applied to one end 161a of the humidity sensor 161, and the humidity via the resistor R1. Since the other end 161b of the sensor 161 is grounded, the second detection voltage Vm2 that is a voltage generated at both ends of the first resistor R1 is measured, and the failure of the humidity sensor 161 is determined based on the value, the humidity sensor 161 failures can be accurately detected.

  Further, the condition (= predetermined condition) for determining to measure the second detection voltage Vm2 to determine the failure is the first detection voltage Vm1 being less than the preset first threshold value VL, or in advance Since the set second threshold value VH is exceeded, it is possible to easily determine whether or not to perform the failure determination process for the humidity sensor 161.

  In addition, when the absolute value of the difference between the second detection voltage Vm2 and the first detection voltage Vm1 is less than the preset third threshold VS, it is determined that the humidity sensor 161 has failed, A failure of the humidity sensor 161 can be accurately detected by simple processing.

  Further, since the operating condition of the print processing unit 15 that forms an image on the recording paper is set based on the humidity detected by the humidity sensor 161, it is possible to set an appropriate operating condition of the print processing unit 15.

  Furthermore, when it is determined that the humidity sensor 161 is malfunctioning, the operating condition of the print processing unit 15 is set based on the humidity set by the humidity setting unit 121e. By configuring so as to set the humidity, it is possible to set an appropriate operating condition of the print processing unit 15 even when the humidity sensor 161 is out of order.

  In addition, at the timing when the main power is turned on, it is determined whether or not the humidity sensor 161 has failed. When it is determined that the humidity sensor 161 has not failed, the humidity P1 detected by the humidity sensor 161 is determined. Is set, the humidity P1 is stored in the humidity storage unit 122a, and the humidity P0 stored in the humidity storage unit 122a is read and set when it is determined that the humidity sensor 161 has failed. The Therefore, when it is determined that the humidity sensor 161 has failed, the measured humidity P0 is set at the timing when the main power supply is turned on immediately before the humidity sensor 161 has failed. Therefore, the humidity sensor 161 has failed. Even in such a case, it is possible to set an appropriate operation condition of the print processing unit 15.

  The present invention can also be applied to the following forms.

  (A) In the present embodiment, the case where the first threshold value VL, the second threshold value VH, and the third threshold value VS are set in advance has been described, but a mode in which the user sets via the operation unit 14 may be used. . In this case, user convenience is improved.

  (B) In the present embodiment, the case where the humidity setting unit 121ef reads and sets the humidity stored in the humidity storage unit 122a when it is determined that the humidity sensor 161 has failed has been described. A mode in which the user sets an appropriate humidity via the unit 14 may be used. In this case, an appropriate humidity can be further set. Further, when the determination unit 121d determines that the humidity sensor 161 is out of order, a message to that effect may be output to the outside by voice or the like (or displayed on the display unit 13).

  (C) In the present embodiment, the case where the humidity setting unit 121e causes the determination unit 121d to determine whether or not the humidity sensor 161 has failed at the timing when the main power is turned on has been described. Alternatively, the determination unit 121d may determine whether or not the humidity sensor 161 has failed at the above timing. For example, the humidity setting unit 121e may cause the determination unit 121d to determine whether or not the humidity sensor 161 has failed every predetermined period (for example, every hour).

FIG. 1 is a block diagram showing an example of a schematic configuration of an image forming apparatus according to the present invention. These are functional block diagrams which show an example of a control part. These are timing charts showing the measurement timing of the first detection voltage and the second detection voltage by the humidity measurement unit and the determination unit. These are circuit diagrams explaining an example of a structure of a humidity measurement circuit. These are block diagrams which show an example of a structure of a humidity sensor. These are graphs which show an example of the relationship between a 1st detection voltage and humidity. These are flowcharts which show an example of operation | movement of a control part.

Explanation of symbols

1 Copier 12 Control Unit 121 CPU (corresponding to a part of failure detection device)
121a First voltage generator (first voltage generator)
121b Second voltage generator (second voltage generator)
121c Humidity measurement part (part of humidity measurement means)
121d determination unit (determination means)
121e Humidity setting section (humidity setting means)
121f Condition setting unit (condition setting means)
121g Print control unit (part of printing means)
122 RAM (corresponds to a part of the failure detection device)
122a Temperature storage unit (temperature storage means)
15 Print processing part (part of printing means)
16 Humidity detector (corresponds to a part of failure detection device)
161 Humidity sensor 162 Humidity measurement circuit (corresponding to a part of humidity measurement means)

Claims (7)

A failure detection device for detecting a failure of an impedance change type humidity sensor,
First voltage generating means for generating a first voltage which is set to a predetermined magnitude and is a rectangular wave having a positive polarity;
Second voltage generating means for generating a second voltage which is set to the predetermined magnitude and is a rectangular wave having a negative polarity;
The first voltage is applied to one end of the humidity sensor, and the second voltage is applied to the other end of the humidity sensor via a first resistor, and is generated at both ends of the first resistor. Humidity measuring means for measuring humidity by measuring a first detection voltage, which is a voltage;
When the first detection voltage satisfies a predetermined condition, the first voltage is applied to one end of the humidity sensor, the other end of the humidity sensor is grounded, and generated at both ends of the first resistor. A humidity sensor failure detection device, comprising: a second detection voltage that is a voltage to be measured; and a determination unit that determines failure of the humidity sensor based on the second detection voltage.   2. The humidity sensor according to claim 1, wherein the predetermined condition is that the first detection voltage is less than a preset first threshold value or exceeds a preset second threshold value. Fault detection device.   The determination means determines that the humidity sensor has failed when an absolute value of a difference between the second detection voltage and the first detection voltage is less than a preset third threshold value. The failure detection device for a humidity sensor according to claim 1 or 2, characterized in that:   The humidity sensor failure detection device according to claim 1, wherein the humidity sensor is a capacitive polymer film humidity sensor. The humidity sensor failure detection device according to any one of claims 1 to 4,
Printing means for forming an image on recording paper;
An image forming apparatus comprising: a condition setting unit configured to set an operation condition of the printing unit based on the humidity detected by the humidity sensor. When it is determined by the failure detection device that the humidity sensor has failed, a humidity setting means for setting a predetermined humidity is provided,
The condition setting means sets the operating condition of the printing means based on the humidity set by the humidity setting means when it is determined by the failure detection device that the humidity sensor has failed. The image forming apparatus according to claim 5. Comprising humidity storage means for storing the humidity detected by the humidity sensor;
The humidity setting means, for the failure detection device,
At the timing when the main power is turned on, it is determined whether or not the humidity sensor has failed,
When it is determined that the humidity sensor has not failed, the humidity detected by the humidity sensor is set, and the humidity is stored in the humidity storage means,
The image forming apparatus according to claim 6, wherein the humidity stored in the humidity storage unit is read and set when it is determined that the humidity sensor has failed.

Images