Method for detecting fault conditions during the venting of a printer or copier

Abstract

Method for detecting fault conditions during the venting of a printer or copier, in which exhaust air from an interior (12) of the printer (10) or copier is conveyed into the environment by means of a fan (28), wherein a pressure in the interior (12) is measured by means of a pressure sensor (24), and wherein, depending on the pressure determined by means of the pressure sensor (24), a fault condition in the ventilation is detected if this is the case, characterized in that a pressure profile is determined with the aid of the pressure sensor (24) arranged in the area of ​​a heating saddle (18), with the aid of which the negative pressure generated in the area of ​​the heating saddle (18) via a vacuum supply unit (22) is monitored, in order to determine the pressure profile in the area to monitor the negative pressure generated by the heating saddle (18), whereby the fan (28) is switched off during a predetermined first period and switched on during a predetermined second period during the determination of the pressure curve, and whereby a fault condition is inferred if the pressure curve, while the fan is switched on, does not fall below a preset threshold (36).

Description

[0001] The invention relates to a method for detecting fault conditions in the ventilation of a printer or copier, in which exhaust air from an interior of the printer or copier is conveyed into the environment by means of a fan.

[0002] Document US 2015 / 0168913 A1 discloses a printer with exhaust gas purification.

[0003] Document US 2015 / 0254958 A1 discloses a device for detecting clogged filters.

[0004] Publication US 2012 / 0285708 A1 discloses a fire protection device for a printer.

[0005] Document US 2003 / 0235635 A1 discloses a ventilation and cooling device for a 3D printer.

[0006] It is common practice for printers and copiers to be equipped with fans for ventilation. Specifically, an exhaust fan is used to ventilate the area around a fuser or drying unit, such as a heating plate, over which the paper web is heated as it passes. This ventilation is intended to prevent the release of volatile organic compounds (VOCs) and to remove moisture.

[0007] In well-known printers, dedicated evaluation units are used to check for fan failure, specifically either a tachometer signal evaluation of the fan's own tachometer signal or a fault contact. The tachometer signal evaluation has the disadvantage that it can only detect faults in the fan itself, and other faults that could also lead to insufficient ventilation, such as a blocked duct in which the fan is located, cannot be detected. Furthermore, only fans that support such tachometer signal evaluation can be used.

[0008] In contrast, with a fault contact, the problem is that a defective control circuit cannot be detected.

[0009] Furthermore, both methods have the disadvantage that they require additional sensors and evaluation electronics, which complicates the setup and control.

[0010] The object of the invention is to provide a method for detecting fault conditions during the venting of a printer or copier, with the help of which such fault conditions can be detected simply and reliably.

[0011] This problem is solved by a method having the features of claim 1. Advantageous embodiments of the invention are specified in the dependent claims.

[0012] According to the invention, a pressure sensor measures the pressure inside the printer or copier. Depending on the pressure determined by this pressure sensor, malfunctions in the venting system are then detected.

[0013] In particular, the pressure sensor measures the pressure drop when the fan is switched on. This is achieved by using the pressure sensor, located near the heating element, to monitor the vacuum generated by a vacuum supply unit in the heating element area. The pressure curve is then recorded to monitor the vacuum generated in this area. Provided the fan is functioning correctly and the duct in which it is located is not blocked, switching the fan on from standby will cause a pressure drop. If this pressure drop is less than a preset limit, there must be a problem with the venting system. In this case, an error message is generated and / or the printer is not started.

[0014] By using a pressure sensor, which serves, among other things, to detect possible fault conditions in a fan depending on the pressure drop, it is ensured that both faults of the fan itself and external faults can be reliably detected.

[0015] It is particularly advantageous if the pressure sensor is used to determine the pressure with the fan switched off and the pressure with the fan switched on. Furthermore, the difference between the two pressures is determined. If this difference is less than a preset limit, a fault condition is inferred.

[0016] Thus, by determining the pressure drop generated when the fan is switched on or the pressure increase generated when the fan is switched off, it can be easily determined whether the venting is working as intended or whether there is a fault.

[0017] For this purpose, the fan is operated at full speed, especially when switched on, so that the maximum pressure drop is determined and can be used as a basis for assessing the venting.

[0018] Furthermore, it is advantageous to determine a pressure profile using the pressure sensor, whereby the fan is switched off for a predetermined first period and switched on for a predetermined second period during the determination of the pressure profile. A fault condition is then inferred if the profile, while the fan is switched on, does not fall below a preset threshold value. This threshold value is specifically preset such that, assuming the venting system functions as intended, it would be undercut by the pressure drop generated when the fan is switched on.

[0019] In a particularly preferred embodiment, the pressure sensor used to monitor the vacuum at a fusing and / or drying unit, especially at a heating platen, of the printer or copier is employed. This has the advantage that a separate pressure sensor is not required; instead, the sensor already present for monitoring the vacuum at the heating platen can be used. Thus, no additional components are needed for monitoring the venting; only existing components can be used.

[0020] A pressure sensor is typically a differential pressure sensor. Alternatively, it can also be a relative pressure sensor or an absolute pressure sensor.

[0021] It is particularly advantageous if the previously described check of the pressure drop is carried out before each use of the printer or copier, and if the printer or copier is only put into operation if this check has shown that there is no fault condition.

[0022] Alternatively or additionally, the corresponding check can also be carried out regularly at predetermined intervals during operation or continuously.

[0023] Further features and advantages of the invention will become apparent from the following description, which explains the invention in more detail with reference to exemplary embodiments in conjunction with the accompanying figures.

[0024] They show: Fig. 1. A schematic representation of a section of a printer; and Fig. 2. the progress of the pressure inside the printer when the fan is switched on.

[0025] In Fig. Figure 1 shows a schematic representation of a section of a printer 10.

[0026] Inside the interior 12 of the printer 10, a paper web 14 is transported in a transport direction P1 over several rollers, one of which is designated by reference numeral 16 for example. The paper web 14 is first guided past a heating saddle 18 and then past a cooling unit 20.

[0027] In the area of ​​the heating saddle 18, a vacuum supply unit 22 is arranged, with the help of which a vacuum is generated in the area of ​​the heating saddle 18, by means of which the paper web 14 is drawn to the heating saddle 18, so that the paper web 14 is securely in contact with the heating saddle 18.

[0028] Furthermore, a pressure sensor 24 is provided in the area of ​​the heating saddle 18, with the help of which the negative pressure generated via the vacuum supply unit 22 in the area of ​​the heating saddle 18 is monitored.

[0029] Furthermore, the printer 10 has a channel 26, at the end of which a fan 28 is arranged, with the help of which exhaust air from the interior 12 is transported out of the interior 12 in accordance with arrows P2, so that the printer 10 is ventilated.

[0030] During printer operation, malfunctions can occur that prevent proper venting. For example, fan 28 may fail and / or duct 26 may become blocked, in both cases preventing proper venting and potentially allowing volatile organic compounds (VOCs) to escape. Furthermore, the exhaust vent located after fan 28 may also be faulty. Additionally, the hardware control may be defective.

[0031] The planned venting is monitored using the pressure sensor 24, which serves to monitor the negative pressure supply at the heating saddle 18.

[0032] The detection of fault conditions during venting is carried out in particular by measuring the pressure drop that occurs when the fan 28, which was previously in the switched-off state, is switched on.

[0033] In Fig. Figure 2 shows a diagram of the pressure curve when the fan is switched on, both during normal operation and in a fault condition. An example pressure curve during normal operation is shown by the solid line 30, and the curve during a fault condition during venting is shown by the dashed line 32.

[0034] Initially, the fan 28 is switched off, so that a resting pressure 34 is determined using the pressure sensor 24. If the fan 28 is then switched on at full speed, there is initially a rapid pressure drop, so that the measured pressure decreases.

[0035] A threshold value of 36 is preset in the control unit of printer 10. During normal operation of the venting system, this threshold value is undercut, as shown by the solid line 30, from which it is concluded that the venting system is functioning correctly and no fault condition exists.

[0036] The threshold value can be determined manually, for example. Alternatively, the threshold value can also be determined automatically by the control system, for example by repeatedly measuring the pressure curve when the venting system is functioning correctly.

[0037] If, on the other hand, as shown by the dashed line 32, the pressure drop when the fan 28 is switched on is so small that the threshold value 36 is not exceeded, it is concluded that either the fan 28 must be defective or there is another fault in the venting, so that in particular an error message is issued and / or the printer is taken out of service or is not put into service in the first place.

[0038] Thus, the planned function of the venting of the printer 10 can be easily monitored via the existing pressure sensor 28 and the pressure profile determined by it when the fan 28 is switched on from standby mode.

[0039] In an alternative embodiment of the invention, instead of a pressure drop when the printer is switched on, a pressure increase when the fan 28 is switched off can also be used as a basis for monitoring the intended function and detecting fault conditions. Reference symbol list 10 printers 12 Interior 14 paper web 16 rolls 18 heated saddles 20 Cooling 22 Vacuum supply unit 24 pressure sensor 26 Channel 28 fans 30, 32 lines 34 Resting pressure 36 Threshold P1 direction P2 Exhaust air

Claims

[1] Method for detecting fault conditions during the venting of a printer or copier, in which exhaust air from an interior (12) of the printer (10) or copier is conveyed into the environment by means of a fan (28), wherein a pressure in the interior (12) is measured by means of a pressure sensor (24), and wherein, depending on the pressure determined by means of the pressure sensor (24), a fault condition in the ventilation is detected if this is the case, characterized by , that with the help of the pressure sensor (24) arranged in the area of ​​a heating saddle (18), with the help of which the vacuum generated in the area of ​​the heating saddle (18) via a vacuum supply unit (22) is monitored, a pressure profile is determined in order to determine the pressure in the area to monitor the negative pressure generated by the heating saddle (18), whereby the fan (28) is switched off during a predetermined first period and switched on during a predetermined second period during the determination of the pressure curve, and whereby a fault condition is inferred if the pressure curve, while the fan is switched on, does not fall below a preset threshold (36). [2] Method according to claim 1, wherein the pressure is determined with the aid of the pressure sensor (24) when the fan (28) is switched off, wherein the pressure is determined with the aid of the pressure sensor (24) when the fan (28) is switched on, and wherein an error condition is determined if the difference between the two determined pressures is less than a preset limit value. [3] Method according to claim 2, wherein the fan (28) is operated at full speed when switched on. [4] Method according to one of the preceding claims, wherein the pressure sensor (24) is a pressure sensor which is also used to monitor the vacuum at a fixing and / or drying unit (18) of the printer (10) or copier. [5] Method according to one of the preceding claims, wherein a differential pressure sensor is used as the pressure sensor (24). [6] Method according to one of the preceding claims, wherein the venting is checked for a fault condition before the respective commissioning of the printer (10) or copier.

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