Method for operating a floor cleaning machine

Abstract

A method for operating a floor cleaning machine (1) is presented and described, wherein the floor cleaning machine (1) has a cleaning fluid reservoir (17), a dirty fluid reservoir (33), and a chassis (5) for moving the floor cleaning machine (1) over a floor surface (7) to be cleaned, wherein the floor cleaning machine (1) has a cleaning device (9) with cleaning elements (11) configured to engage with the floor surface (7) to be cleaned, wherein the method comprises the following steps: - moving the floor cleaning machine (1) over a floor surface (7) to be cleaned, - during movement, measuring the quantity of cleaning fluid supplied to the cleaning device (11) from the cleaning fluid reservoir (17) within a first time interval, - during movement, measuring the quantity of dirty fluid,which is discharged from the dirty liquid intake device (47) to the dirty liquid container (33) within a second time interval, - comparing the detected quantity of cleaning liquid with a first threshold value, - comparing the detected quantity of dirty liquid with a second threshold value, - outputting a first error signal if the detected quantity of cleaning liquid is greater than the first threshold value and the detected quantity of dirty liquid is less than the second threshold value.

Description

[0001] The present invention relates to a method for operating a floor cleaning machine, wherein the floor cleaning machine has a cleaning fluid container, a dirty fluid container, and a chassis for moving the floor cleaning machine over a floor surface to be cleaned. Furthermore, the floor cleaning machine has a cleaning device with cleaning elements configured to engage with the floor surface to be cleaned, as well as a dirty fluid receiving device connected to the dirty fluid container for discharging dirty fluid from the dirty fluid receiving device to the dirty fluid container and configured to receive dirty fluid from the floor surface to be cleaned. Furthermore, the present invention relates to a floor cleaning machine configured to carry out such a method.

[0002] Such floor cleaning machines are known from the prior art, for example from CN108937749. During operation of such machines, cleaning fluid, such as fresh water, is applied from the cleaning fluid container to the floor to be cleaned by means of the cleaning device. The cleaning elements engage with the floor surface to loosen dirt from it in cooperation with the cleaning fluid. With the aid of the dirty fluid collection device, which can be designed, for example, as a suction cup, the previously applied cleaning fluid, which is laden with dirt after the cleaning elements engage with the floor surface, thus becoming dirty fluid, is collected again and transferred to the dirty fluid container.

[0003] These scrubber-dryers can be hand-held or ride-on. They can also be designed as autonomous cleaning robots, meaning no operator is directly monitoring their operation.

[0004] However, the following problems may occur when operating such machines.

[0005] If cleaning fluid is applied to the floor to be cleaned but the dirty fluid collection system is not functioning reliably, dirt-laden cleaning fluid, i.e., dirty fluid, will remain on the floor to be cleaned. This poses a safety risk, as it increases the risk of slipping on the floor. Furthermore, the desired cleaning result will not be achieved.

[0006] In addition, such floor cleaning machines often have a suction device such as a suction turbine driven by an electric motor. This creates an air flow from the dirty liquid collection device, which can then be designed as a squeegee, for example, to the dirty liquid container. This air flow entrains dirty liquid in the collection device and conveys it into the dirty liquid container. If the motor current of the electric motor drops while the voltage remains constant, this can usually have two causes. First, it is possible that the connection between the dirty liquid collection device and the dirty liquid container is blocked, meaning that there is no longer any air flow from the dirty liquid collection device into the dirty liquid container. This means that the suction device has to convey less air, thus reducing the motor current.So there is an error.

[0007] Alternatively, there may be so much liquid in the dirty fluid collection device that ambient air is prevented from entering the device, which also prevents airflow. However, this is not a fault; rather, this condition is resolved when the liquid in the collection device has been drawn into the dirty fluid container due to the negative pressure. However, the two previously described cases cannot be distinguished from the motor current measurement alone. In particular, it is not possible to determine whether a fault exists or not based on this.

[0008] Based on the prior art, the present invention is therefore based on the object of providing a method for operating a floor cleaning machine and such a machine with which errors can be reliably detected during operation.

[0009] According to a first aspect of the present invention, this object is achieved by a method for operating a floor cleaning machine, wherein the floor cleaning machine has a cleaning liquid container, a dirty liquid container and a chassis for moving the floor cleaning machine over a floor surface to be cleaned, wherein the floor cleaning machine has a cleaning device with cleaning elements that are designed to engage with the floor surface to be cleaned, wherein the cleaning device is connected to the cleaning liquid container for supplying cleaning liquid to the cleaning device and is designed to apply cleaning liquid to the floor surface to be cleaned, wherein the floor cleaning machine has a dirty liquid receiving device,which is connected to the dirty liquid container for discharging dirty liquid from the dirty liquid receiving device to the dirty liquid container and is designed to receive dirty liquid from the floor surface to be cleaned, the method comprising the following steps: , Moving the floor cleaning machine over a floor area to be cleaned, during the movement detecting the amount of cleaning liquid that is supplied to the cleaning device from the cleaning liquid tank within a first time interval, during the movement detecting the amount of dirty liquid that is discharged from the dirty liquid receiving device to the dirty liquid tank within a second time interval, comparing the detected amount of cleaning liquid with a first threshold value, comparing the detected amount of dirty liquid with a second threshold value, outputting a first error signal if the detected amount of cleaning liquid is greater than the first threshold value and the detected amount of dirty liquid is less than the second threshold value.

[0010] In the method according to the invention, during operation, i.e. while the machine is moving over a floor surface to be cleaned, it is firstly detected whether cleaning fluid is being applied to the floor surface to be cleaned by means of the cleaning device. This is done by using a suitably designed device to record the applied quantity of cleaning fluid in a first time interval and compare it with a threshold value. The threshold value can be very low and can also be selected to be equal to zero. However, by comparing it with a threshold value other than zero, it is ensured that low measured values ​​from the device do not automatically lead to the conclusion that cleaning fluid is actually being applied to the floor surface via the cleaning device.

[0011] Furthermore, a further device records the quantity of dirty liquid that is removed from the dirty liquid receiving device and placed in the dirty liquid container during a second time interval.

[0012] The first and second time intervals can be congruent, meaning that the recording takes place at the same time, or the second time interval is later than the first time interval in order to take into account that cleaning fluid applied to the floor surface to be cleaned can only be taken up again by the dirty fluid collection device at a later time.

[0013] The detected amount of dirt fluid absorbed is compared with a second threshold, which can also be set very low or even zero. However, the threshold comparison also ensures that the artifacts described above do not occur.

[0014] Finally, in the method according to the invention, an error signal is output if, on the one hand, the quantity of cleaning fluid dispensed detected during the first time interval is above the threshold value and, on the other hand, the quantity of dirty fluid discharged detected during the second time interval is below the threshold value. It is thus detected that the dirty fluid collection device is not functioning reliably.

[0015] This is either displayed to a user based on the error signal, or the error signal is used to switch off any drive of the floor cleaning machine that may be present and which drives the chassis and moves the machine over the floor area to be cleaned.

[0016] The method according to the invention is particularly advantageous when used in conjunction with an autonomously operating floor cleaning machine, since in this case, a user cannot immediately detect that dirty liquid remains on the floor surface to be cleaned, and the user can then actively stop the cleaning cycle. In contrast to the prior art, a malfunction of the dirty liquid collection device is reliably detected automatically during operation.

[0017] In a preferred embodiment, the floor cleaning machine has a suction device which applies negative pressure to the dirty liquid tank and which has an electric drive motor which, during operation, is supplied with a voltage of a predetermined strength so that a supply current flows through the drive motor, wherein the strength of the supply current is detected in a third time interval, wherein the detected strength of the supply current is compared with a third threshold value, wherein the detected quantity of dirty liquid is compared with a fourth threshold value and wherein a second error signal is output if the detected strength of the supply current is less than the third threshold value and the detected quantity of dirty liquid is less than the fourth threshold value.

[0018] In this preferred embodiment of the method according to the invention, in addition to the motor current of the suction device, it is also detected whether dirty liquid is being conveyed into the dirty liquid container. Only if this is not the case is the second error signal issued. This obviously indicates a malfunction due to a blockage in the line between the dirty liquid intake device and the dirty liquid container.

[0019] However, if dirty liquid is still pumped into the dirty liquid container when the motor current is too low, the condition for the second error signal is not met, since there is obviously no malfunction, but rather the dirty liquid itself means that only a low or even no air flow needs to be pumped by the suction device, which also leads to a reduction in the motor current.

[0020] In this preferred embodiment, not only the motor current of the suction device alone is used to detect a malfunction, but this is done in combination with the detection of the quantity of dirty liquid pumped into the dirty liquid container.

[0021] At this point, it is pointed out that it is an independently inventive concept to record both the motor current of the suction device and the quantity of dirty liquid fed into the dirty liquid container in a time interval and then to output an error signal if both the quantity of dirty liquid fed and the motor current are below a predetermined threshold.

[0022] In particular, the floor cleaning machine can comprise a device configured to detect the amount of cleaning fluid supplied to the cleaning device from the cleaning fluid tank within a first time interval, as well as a device configured to detect the amount of dirty fluid discharged from the dirty fluid receiving device to the dirty fluid tank within a second time interval. Furthermore, a device configured to detect the strength of the supply current in a third time interval can preferably also be provided.

[0023] In a further preferred embodiment, the cleaning fluid container and the cleaning device are connected by a cleaning fluid line for supplying cleaning fluid, wherein a flow sensor is provided in the cleaning fluid line as a means for detecting the amount of cleaning fluid supplied in the first time interval. The use of a flow sensor in the line is a reliable way to detect the amount of cleaning fluid in question.

[0024] As an alternative to the flow sensor, or in addition thereto, it is also possible to provide a cleaning fluid pump in the cleaning fluid line, which is designed to detect the amount of cleaning fluid supplied to the cleaning device in the first time interval, so that the pump acts as a device for detecting the amount of cleaning fluid supplied to the cleaning device from the cleaning fluid tank within a first time interval. In this case, there is no need to provide another sensor in addition to the pump. If another sensor is provided, a redundant system is provided that remains functional even if one of the two devices for detecting the flow rate fails.

[0025] In a further preferred embodiment, a first device is provided for detecting the level in the cleaning fluid container, wherein the amount of cleaning fluid supplied in the first time interval is detected by the first device detecting a change in the level in the cleaning fluid container in the first time interval. In this case, the amount of cleaning fluid supplied to the cleaning device is determined by a change in the level in the cleaning fluid container. This can be implemented easily in terms of device technology. In particular, this can be achieved in that the first device for detecting the level in the cleaning fluid container has a float, wherein the change in its position in the first time interval is detected in order to thereby detect the amount of cleaning fluid supplied in the first time interval.

[0026] Furthermore, it is preferred if a second device is provided for detecting the level in the dirty liquid container, wherein the amount of cleaning liquid supplied in the first time interval is detected by detecting a change in the level in the dirty liquid container in the second time interval by the second device. Thus, in this preferred embodiment, the amount of dirty liquid discharged into the dirty liquid container is also determined from a change in the level therein. In this case, it is particularly preferred if the second device for detecting the level in the dirty liquid container is designed as a pressure sensor.

[0027] Finally, in a further aspect of the present invention, the above object is achieved by a floor cleaning machine which is designed to carry out the method according to the invention as described above.

[0028] The present invention is described below with reference to a drawing which merely represents a preferred embodiment, wherein Figure 1 shows a schematic sectional view of an embodiment of a floor cleaning machine according to the invention.

[0029] Figure 1 shows an embodiment of a floor cleaning machine 1 according to the invention, which is designed to carry out an embodiment of a method according to the invention for operating such a machine.

[0030] How Figure 1As can be seen, the floor cleaning machine 1 has a chassis 5 comprising a plurality of wheels 3, with which the floor cleaning machine 1 can be moved over a floor area 7 to be cleaned. In the exemplary embodiment shown here, the floor cleaning machine 1 has a drive 8 (not shown in more detail), with which the rear wheels 3 of the chassis 5 are driven, so that the floor cleaning machine 1 can move independently over the floor area 7 to be cleaned. In addition, the floor cleaning machine 1 shown here is designed as a so-called robot, ie it can move autonomously, without being guided by a user, over the floor area 7 to be cleaned and automatically detects obstacles and determines its course based on this.

[0031] However, the present invention is not limited to such robots, but can be applied to any type of floor cleaning machine 1, ie also to so-called ride-on machines or machines in which the user walks behind the machine.

[0032] What next Figure 1 As can be seen, the floor cleaning machine 1 has a cleaning device 9, which comprises a cleaning element 11, designed here as a rotating brush, which engages with the floor surface 7 to be cleaned during operation. The cleaning device 9 is also designed such that the cleaning element 11 can be raised relative to the floor surface 7 to be cleaned, so that the cleaning element 11 then does not engage with the floor surface 7 to be cleaned.

[0033] How to continue in Figure 1As can be seen, the cleaning device 9 has an outlet 13 which is connected via a cleaning fluid line 15 to a cleaning fluid container 17 which is accommodated in a housing 19 of the floor cleaning machine 1. A flow sensor 21 is provided in the cleaning fluid line 15, which forms a device with which the quantity of cleaning fluid flowing through the cleaning fluid line 15 in a time interval and supplied to the cleaning device 9 can be detected.

[0034] Furthermore, a pump 23 is provided in the cleaning fluid line, which is designed to convey cleaning fluid from the cleaning fluid container 17 to the outlet 13 and thus to the cleaning device 9. The pump 23 can preferably be designed such that it also detects the amount of cleaning fluid conveyed from the cleaning fluid container 17 to the outlet 13 in a time interval. This can be in addition to the flow sensor 21 or as an alternative thereto. If both the pump 23 and the flow sensor 21 can detect the amount conveyed per time interval, a redundant system is provided.

[0035] In addition to or in addition to the flow sensor 21 and the pump 23, a first device can be provided in the liquid container 17, which is designed to detect the height of the level 25 of the cleaning liquid in the cleaning liquid container 17. This device has a guide element 27, which extends essentially vertically in the cleaning liquid container 17 when the floor cleaning machine 1 is arranged on a horizontally extending floor surface 7 to be cleaned. A float 29, the position of which can be detected, is guided on the guide element 27. Based on the change in the position of the float 29 of this float device 27, 29 within a time interval, the amount of cleaning liquid that has been supplied to the cleaning device 9 during this time interval can then also be determined.

[0036] Finally, as an alternative to the flow sensor 21, the pump 23, or the float device 27, 29, or in addition thereto, a first pressure sensor 31 can be provided in the bottom region of the cleaning fluid tank 17, the signal of which is a measure of the gravitational pressure of the cleaning fluid in the cleaning fluid container 17. This makes it possible to determine or record the cleaning fluid supplied to the cleaning device 9 in a given time interval using this first pressure sensor 31.

[0037] Further in Figure 1It can be seen that the floor cleaning machine 1 also has a dirty liquid container 33 in the housing 19, the upper region of which is connected to the inlet of a suction device 35 driven by an electric motor 37, which in a preferred embodiment is a so-called suction turbine in which the electric motor 37 rotates a fan wheel. The suction device is designed to subject the dirty liquid container 33 to a negative pressure compared to the environment of the floor cleaning machine 1. Finally, the electric motor 37 is designed or provided with a corresponding device such that a signal can be generated which is a measure of the current consumed by the electric motor 37. A signal can therefore be generated which represents the level of motor current that the electric motor 37 consumes in a time interval.

[0038] Furthermore, Figure 1It can be seen that a second and a third pressure sensor 39, 41 are provided in the dirty liquid container 33. The second pressure sensor 39 is designed to detect the gravitational pressure of the dirty liquid in the bottom region of the dirty liquid container 33 and to generate a corresponding signal. The third pressure sensor detects the pressure above the level 43 of the dirty liquid in the dirty liquid container 33, since this pressure is lower than the ambient pressure due to the suction device 35. From the signals of the second and third pressure sensors 39, 41, the level 43 in the dirty liquid container 33 can then be determined in a manner known per se. Furthermore, the change in the level 43 and thus the amount of dirty liquid supplied to the dirty liquid container 33 in a time interval can also be determined.

[0039] At this point, it should be noted that the present invention is not limited to the level 43 in the dirty liquid container 33 and thus the amount of dirty liquid supplied in a time interval being determined by means of pressure sensors.

[0040] Alternative solutions such as the use of a float are also conceivable here.

[0041] What next Figure 1As can be seen, the upper region of the dirty liquid container 33 is connected via a dirty liquid line 45 to a dirty liquid receiving device 47, which in the preferred embodiment shown here is designed as a so-called suction foot. The suction foot has a front sealing lip 49, which has slots extending away from the floor surface 7 to be cleaned in the region where it rests against the floor surface 7, and a rear sealing lip 51 that is not slotted. The sealing lips 49, 51 and the suction foot extend essentially across the width of the floor cleaning machine 1, and the area between the sealing lips 49, 51 is connected to the dirty liquid container 33 via the dirty liquid line 45 and is thus subjected to a negative pressure when the suction device 35 is in operation.This negative pressure ensures that dirty liquid on the floor surface 7 to be cleaned is sucked into the dirty liquid container 33.

[0042] If the dirty fluid line 45 is blocked or if the space between the sealing lips 49, 51 of the dirty fluid suction device 47 is completely filled with dirty fluid, preventing ambient air from penetrating this space, the suction device 35 only needs to deliver a small amount of air to maintain the negative pressure in the dirty fluid container 33. As a result, in these situations, the motor current of the electric motor 37, which drives the suction device 35, is reduced compared to normal operation.

[0043] Finally, it can be seen that the floor cleaning machine 1 has a controller 53 which is connected via lines to the electric motor 37, the float device 27, 29, the pump 23, the flow sensor 21, the drive 7 and the pressure sensors 31, 39, 41, so that the aforementioned components can transmit their signals to the controller 53.

[0044] This signal connection makes it possible for the flow sensor 21, the pump 23, the float device 27, 29, and the first pressure sensor 31 to each transmit a signal to the controller 53, which is a measure of the amount of cleaning fluid supplied from the cleaning fluid container 17 to the outlet 13 and thus to the cleaning device 9 in a first time interval. Similarly, the second pressure sensor 39 and the third pressure sensor 41 can also transmit a signal to the controller 53, which is a measure of the amount of dirty fluid received by the dirty fluid receiving device 47 and discharged into the dirty fluid container 33 in a second time interval.

[0045] The previously described embodiment of a floor cleaning machine 1 can be operated in the manner described below.

[0046] The floor cleaning machine 1 is moved over the floor area 7 to be cleaned by means of the chassis 5 and the drive 8, whereby in the present case this occurs automatically and the control 53 also determines a route along which the floor cleaning machine 1 cleans the floor area 7 to be cleaned by means of sensors (not shown). In this process, cleaning fluid is continuously supplied from the cleaning fluid container 17 through the cleaning fluid line 15 into the area of ​​the cleaning device 9 by means of the pump 23. With the help of the driven cleaning element 11, dirt is then removed from the floor area to be cleaned, while the floor cleaning machine 1 is in Figure 1moved further to the right, so that the cleaning fluid laden with dirt and thus the dirty fluid reaches the area of ​​the dirt collection device 47. Parallel to the supply of cleaning fluid, the suction device 35 with the electric motor 37 connected to it is also in operation, so that a negative pressure is generated in the dirty fluid container 33. Due to this negative pressure, dirty fluid that reaches the area of ​​the dirty fluid collection device 47 and thus between the sealing lips 49, 51 is sucked out through the dirty fluid line 45 and discharged into the dirty fluid container 33, provided that the dirty fluid line 45 is not blocked or the dirt collection device 47 is not malfunctioning for some other reason.

[0047] While the floor cleaning machine 1 is moving over the floor surface 7 and while cleaning fluid is being applied and dirty fluid is being removed, the following steps are always carried out repeatedly.

[0048] During a first time interval, the amount of cleaning fluid applied to the floor surface 7 to be cleaned is detected using the flow sensor 21. As an alternative to the flow sensor 21, this can also be done using the pump 23, the float device 27, 29, or the first pressure sensor 31 in the manner already described. This amount is detected during the first time interval on the basis of the signal transmitted to the controller 53. The signal from the flow sensor 21, the pump 23, the float device 27, 29, and / or the first pressure sensor 31 can be integrated in the controller 53 during the first time interval, so that the integrated signal then serves as a measure of the cleaning fluid applied to the floor surface 7 to be cleaned during the first time interval.

[0049] Similarly, using the second and third pressure sensors 39, 41 and the signals generated by them, the amount of dirty fluid discharged into the dirty fluid container 33 during a second time interval is recorded. In this case, too, this amount can be determined by integrating the respective signals. In particular, the signal from the third pressure sensor 41 is subtracted from that from the second pressure sensor 39 to account for the effect of the negative pressure prevailing above the level 43 in the dirty fluid container 33.

[0050] The first time interval and the second time interval are preferably offset from each other in time such that the second time interval starts slightly later than the first time interval. However, it is also possible for the time intervals to run parallel. However, if the first alternative is used, this takes into account that, due to the movement of the floor cleaning machine 1, a certain time period must always elapse between the application of a certain amount of cleaning fluid and the removal of exactly this amount.

[0051] Finally, during the second time interval, the signal of the motor current of the electric motor 37 of the suction device 35 is also recorded, whereby this can also be done by integrating the current signal in the controller 53.

[0052] If the signal representing the amount of cleaning fluid applied is greater than a first threshold, this indicates that cleaning fluid is actually being applied to the floor surface 7 to be cleaned. If the amount of dirty fluid removed during the second time interval falls below a second threshold, an insufficient amount of dirty fluid is being removed even though cleaning fluid is being applied. Therefore, if the amount of cleaning fluid applied during the first time interval exceeds the first threshold and, during the test, the amount of dirty fluid removed during the second time interval falls below the second threshold, a malfunction has occurred, and the controller outputs a first error signal.Such a malfunction can be caused, for example, by the sealing lips 49, 51 of the dirty liquid collection device 47, designed as a squeegee, being worn, so that insufficient negative pressure is generated in the squeegee, or by the dirty liquid line 45 between the dirty liquid collection device 47 and the dirty liquid container 33 being torn or leaking. The error signal can, for example, be used to stop the drive 8 so that the floor cleaning machine 1 comes to a standstill. This prevents larger areas of the floor to be cleaned from being exposed to cleaning liquid without the dirty liquid being drained away again. Furthermore, the first error signal can be used to switch off the pump 23.

[0053] Furthermore, a check is performed to determine whether the amount of dirty fluid discharged during the second time interval, or the signal generated thereon, falls below a third threshold. If, at the same time, the motor current of the electric motor 37, or the signal generated thereon, falls below a fourth threshold, this indicates that either the dirty fluid line 45 or the dirty fluid receiving device 47 is blocked, preventing any dirty fluid from entering the dirty fluid container 33. This is also a malfunction, and in this case, the controller 53 generates a second error signal, which in turn can be used to stop the drive 8 and / or the pump 23.

[0054] However, if the motor current signal falls below the fourth threshold, but at the same time the signal for the amount of dirty fluid discharged during the second time interval is above the third threshold, this indicates that the dirty fluid receptacle 47 is completely filled with dirty fluid, so that no air flow can occur through the dirty fluid line 45. In this case, the low motor current is not associated with a malfunction, and no error signal is generated by the controller 53.

[0055] The exemplary embodiment of the operating method according to the invention for the floor cleaning machine 1 thus enables the reliable detection of malfunctions in which dirty liquid would remain on the floor surface 7 to be cleaned. Furthermore, the parallel detection of the motor current and the amount of dirty liquid discharged also enables the motor current signal of the electric motor 37 to be used for fault determination. List of reference symbols:

[0056] 1 Floor cleaning machine 3 Wheel 5 Chassis 7 Floor area to be cleaned 8 Drive 9 Cleaning device 11 Cleaning element 13 Outlet 15 Cleaning fluid line 17 Cleaning fluid container 19 Housing 21 Flow sensor 23 Pump 25 Cleaning fluid level 27 Guide element 29 Float 31 First pressure sensor 33 Dirty fluid container 35 Suction device 37 Electric motor 39 Second pressure sensor 41 Third pressure sensor 43 Dirty fluid level 45 Dirty fluid line 47 Dirty fluid intake device 49 Front sealing lip 51 Rear sealing lip 53 Control

Claims

1. A method for operating a floor cleaning machine (i), the floor cleaning machine (i) having a cleaning fluid container (17), a dirty liquid container (33), and a chassis (5) for moving the floor cleaning machine (1) over a floor surface (7) to be cleaned, the floor cleaning machine (1) having a cleaning device (9) with cleaning elements (11) which are designed to engage with the floor surface (7) to be cleaned, the cleaning device (11) being connected to the cleaning fluid container (17) for supplying cleaning fluid to the cleaning device (11) and being designed to apply cleaning fluid to the floor surface (7) to be cleaned, the floor cleaning machine (1) having a dirty liquid receiving device (47) which is connected to the dirty liquid container (33) for discharging dirty liquid from the dirty liquid receiving device (47) to the latter and being designed to receive dirty liquid from the floor surface (7) to be cleaned, the method comprising the following steps: - moving the floor cleaning machine (1) over a floor surface (7) to be cleaned, characterized in that the method comprises the following further steps: - detecting the amount of cleaning fluid supplied from the cleaning fluid tank (17) to the cleaning device (11) during movement within a first time interval, - detecting the amount of dirty liquid which is discharged from the dirty liquid receiving device (47) to the dirty liquid container (33) during the movement within a second time interval, - comparing the detected amount of cleaning fluid with a first threshold value, - comparing the detected amount of dirty liquid with a second threshold value, - outputting a first error signal if the detected amount of cleaning fluid is greater than the first threshold and the detected amount of dirty liquid is less than the second threshold.

2. The method according to claim 1, wherein the floor cleaning machine (1) has a suction device (35) which applies negative pressure to the dirty liquid container (33) and which has an electric drive motor (37) which is supplied with a voltage of a predetermined strength during operation so that a supply current flows through the drive motor (37), wherein the strength of the supply current is recorded in a third time interval, wherein the detected strength of the supply current is compared with a third threshold value, wherein the detected amount of dirty liquid is compared with a fourth threshold value and wherein a second error signal is output when the detected strength of the supply current is less than the third threshold and the detected amount of dirty liquid is less than the fourth threshold.

3. The method according to claim 1 or 2, wherein the floor cleaning machine (1) has a device which is designed to detect the amount of cleaning fluid which is supplied from the cleaning fluid tank (17) to the cleaning device (11) within a first time interval, and wherein the floor cleaning machine (1) comprises a device which is designed to detect the quantity of dirty liquid which is discharged from the dirty liquid receiving device (47) to the dirty liquid container (33) within a second time interval.

4. The method according to claim 2 or 3, wherein the floor cleaning machine (1) comprises a device which is designed to detect the strength of the supply current in a third time interval.

5. The method according to any one or more of claims 1 to 4, wherein the chassis (5) of the floor cleaning machine (1) has a drive (8) which is designed to drive the chassis to move the floor cleaning machine (1) over the floor surface (7) to be cleaned and wherein the drive (8) is switched off when the first or second error signal is present.

6. The method according to any one or more of claims 1 to 5, wherein the floor cleaning machine (1) is designed as an autonomously driving floor cleaning machine (1).

7. The method according to any one or more of claims 1 to 6, wherein the cleaning fluid container (17) and the cleaning device (9) are connected by a cleaning fluid line (15) for supplying cleaning fluid and wherein a flow sensor (21) is provided in the cleaning fluid line (15) as a device for detecting the amount of cleaning fluid supplied in the first time interval.

8. The method according to any one or more of claims 1 to 7, wherein the cleaning fluid container (17) and the cleaning device (11) are connected by a cleaning fluid line (15) for supplying cleaning fluid and wherein a cleaning fluid pump (23) is provided in the cleaning fluid line (15), which is designed to detect the amount of cleaning fluid supplied to the cleaning device (11) in the first time interval, so that the pump (23) acts as a device for detecting the amount of cleaning fluid supplied from the cleaning fluid container (17) to the cleaning device (11) within a first time interval.

9. The method according to any one or more of claims 1 to 8, wherein a first device (27, 29) is provided for detecting the level (25) in the cleaning fluid container and wherein the amount of cleaning fluid supplied in the first time interval is detected by the first device by detecting a change in the level (25) in the cleaning fluid container (17) in the first time interval.

10. The method according to claim 9, wherein the first device (27, 29) for detecting the level (25) in the cleaning fluid container (17) comprises a float (29), wherein the change in the position thereof is detected in the first time interval to thereby detect the amount of cleaning fluid supplied in the first time interval.

11. The method according to any one or more of claims 1 to 10, wherein a second device for detecting the level (43) in the dirty liquid container (33) is provided and wherein the amount of cleaning fluid supplied in the first time interval is detected by the second device by detecting a change in the level (43) in the dirty liquid container (33) in the second time interval.

12. The method according to claim 11, wherein the second device for detecting the level (43) in the dirty liquid container is designed as a pressure sensor (39, 41).

13. A floor cleaning machine designed to carry out the method according to any one or more of claims 1 to 12.

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