Method for detecting overload condition, overload monitoring system and elevator

Abstract

The invention relates to a method for detecting an overload condition of an elevator car (1) of an elevator (100), the method comprising: obtaining current car load information from a load weighing device (2) arranged to weigh a current car load, preferably when the elevator car (1) stands at a landing floor in an elevator shaft (3), and determining whether the current car load information satisfies one or more overload criteria; and generating a signal indicative of an overload condition of the elevator car (1) if the car load information meets one or more of the overload criteria. The method further includes obtaining information of at least one operating parameter of the elevator (100) and adjusting one or more of the overload criterion or the car load information based on the information of at least one operating parameter of the elevator (100). The invention also relates to an overload monitoring system (S) and an elevator (100) implementing the method.

Description

Technical Field

[0001] The invention relates to detecting an overload of an elevator car. An elevator is in particular an elevator for transporting passengers and / or goods. Background Art

[0002] The elevator system is manufactured to have a rated load, and the operation of the elevator system should not be allowed if the load in the elevator car (hereinafter referred to as the car load) is too large. In order to obtain the car load information, the elevator system is provided with a load weighing device (LWD) to measure the elevator car load, for example, from a component connected to the car force transmission. For example, the load weighing device can measure the car load by sensing the tension of one or more suspension ropes of the elevator. The control system can determine whether the current car load information meets at least one overload standard, such as exceeding the overload threshold. Typically, the control system compares the obtained car load information (such as the measured current car load value) with the overload threshold to determine whether to allow the elevator operation to be started.

[0003] A disadvantage of the known elevators is that it is difficult to make the elevator available close to its full transport capacity and the probability of false alarms is low. It has been noted that some elevators are sensitive to false alarms of overload conditions when the load in the car is close to the rated load. This is taken into account, for example, by setting the overload threshold to be higher than the rated load of the elevator system, with sufficient margin so that false alarms of overload conditions can be prevented from being triggered. Summary of the invention

[0004] The object of the present invention is to introduce an improved solution for detecting an overload condition of an elevator car with improved accuracy. This may mean that even with a small overload threshold margin, false alarms of an overload condition may be avoided. By means of the present invention, an overload situation may already be detected, in which the overload of the elevator car is smaller than before, which improves elevator safety.

[0005] It is an object of the present invention to introduce an improved solution by which one or more of the above-mentioned problems of the prior art and / or the disadvantages discussed or hinted at elsewhere in the specification may be alleviated.

[0006] In particular, embodiments are described that can at least partially eliminate the effects of changes in the mobility of the elevator car from overload detection. Such changes may be due to many things during the life of the elevator. For example, aging, wear or degradation of components (e.g. guide shoes or guide rollers) or the occurrence of lubrication problems or slight changes in the positioning, surface properties or shape of the guide rails (e.g. bulges) may change, generally reduce, the mobility of the elevator car.

[0007] A new method for detecting an overload condition of an elevator car of an elevator is proposed. The method comprises obtaining current car load information from a load weighing device, the load weighing device being arranged to weigh the current car load, preferably when the elevator car is standing at a landing floor in the elevator shaft, and determining whether the current car load information meets one or more overload criteria; and generating a signal indicating an overload condition of the elevator car if the car load information meets one or more of the overload criteria.

[0008] The method further comprises obtaining information of at least one operating parameter of the elevator and adjusting one or more of the one or more overload criteria or the car load information based on the information of at least one operating parameter of the elevator.

[0009] With this solution one or more of the above mentioned objects may be promoted.The adaptation in particular provides for a dynamic nature in overload monitoring and the possibility to take into account operating parameters of the elevator which are not constant and / or may change during the elevator life.

[0010] In a preferred embodiment, the operating parameter is friction or any parameter suitable for indicating the resistance to movement acting directly on the car. Thus, factors affecting the mobility of the car can be taken into account and used as a basis for adjustments. For example, if the car movement is more restricted than before, for example if the friction Fr increases, the load weighing device indicates a lower car load value than before for the same amount of load in the elevator car. This problem can be overcome by adjusting one or more of the overload criteria or the car load information as described above.

[0011] In a preferred embodiment, said information on at least one operating parameter of the elevator comprises the magnitude of friction or of a parameter suitable for indicating the resistance to movement acting directly on the car.

[0012] In a preferred embodiment, the method comprises determining a current car load value based on said car load information, and said one or more criteria comprises that the current car load value exceeds at least one threshold value.

[0013] In a preferred embodiment, adjusting one or more criteria includes changing a threshold value to a new value based on information of at least one operating parameter.

[0014] In a preferred embodiment, when changing the threshold, if the information of at least one operating parameter obtained indicates that the resistance to movement directly acting on the car has increased, the threshold is changed to a lower value, and / or if the information of at least one operating parameter obtained indicates that the resistance to movement directly acting on the car has decreased, the threshold is changed to a higher value.

[0015] In a preferred embodiment, information on operating parameters is obtained during movement of the car.

[0016] In a preferred embodiment, the load weighing device is arranged to sense the tension of one or more suspension ropes suspending the elevator car.

[0017] In a preferred embodiment, said determining comprises reading a memory storing said one or more criteria for an overload condition of the elevator car.

[0018] In a preferred embodiment, adjusting the criteria includes accessing a memory storing the one or more criteria for an overload condition of the elevator car and changing the one or more criteria.

[0019] In a preferred embodiment, obtaining information of at least one operating parameter of the elevator comprises moving the car upwards and downwards and measuring motor parameters such as current of a motor of a traction machine of the elevator, preferably during movement in both said directions.

[0020] In a preferred embodiment, each movement of the car upwards and downwards is performed at a constant speed, which is preferably slow, preferably slower than 0.5 m / s, more preferably slower than 0.2 m / s.

[0021] In a preferred embodiment, each movement of the car up and down is performed while the car is empty.

[0022] In a preferred embodiment, information of at least one operating parameter of the elevator is obtained calculating the magnitude of friction or any parameter suitable for indicating the resistance to movement acting directly on the car, preferably based on measurements of motor parameters, preferably motor current.

[0023] In a preferred embodiment, said calculating comprises calculating the difference between measurements of a motor parameter, preferably calculating the difference between the current measured during the upward movement and the current measured during the downward movement.

[0024] In a preferred embodiment, the method comprises weighing the current car load, in particular by means of a load weighing device, preferably when the elevator car is at a landing floor in the elevator shaft. Preferably, the weighing is performed when the elevator car is at a landing floor in the elevator shaft and one or more brakes of the traction machine are in a braking state.

[0025] A new elevator overload monitoring system is also proposed, comprising a load weighing device, which is particularly arranged to weigh the current car load, preferably when the elevator car of the elevator is standing at a landing floor in the elevator shaft; and a control system. The control system is configured to perform a method as defined anywhere above or in any of the claims of the present application.

[0026] Preferred further details of the overload monitoring system are presented below, which can be combined with the overload monitoring system alone or in any combination.

[0027] In a preferred embodiment, the control system is configured to obtain car load information from a load weighing device; and determine whether the current car load information meets one or more overload criteria; and if the car load information meets the overload criteria, generate a signal indicating an elevator car overload condition; and obtain information on at least an operating parameter of the elevator during elevator operation, and adjust at least one of the one or more overload criteria and the car load information based on the information on the at least one operating parameter.

[0028] In a preferred embodiment, the control system is configured to perform any step of the method described above or any step of any claim of the present application.

[0029] In a preferred embodiment, the control system comprises a memory storing one or more criteria for an overload condition of the elevator car, or the control system is configured to read and / or change the contents of such a memory.

[0030] In a preferred embodiment, the control system is connected to a traction machine comprising a motor and a drive wheel that engages one or more hoisting ropes of the elevator.

[0031] In a preferred embodiment, the control system includes at least one electronic processing unit (e.g., a microprocessor unit) configured (e.g., programmed) to perform one or more of the following steps: determining whether the current car load information meets one or more overload criteria, generating a signal, obtaining information of at least one operating parameter of the elevator, and adjusting.

[0032] A new elevator is also proposed, comprising an elevator car and an overload monitoring system as defined anywhere above or in any claim of the present application.

[0033] Preferred further details of the elevator have been introduced above with reference to the method and the overload monitoring system. Preferred further details of the elevator will be further introduced below. Preferably, the further details can be combined with the elevator alone or in any combination.

[0034] In a preferred embodiment, the control system is configured to control movement of the elevator car in the elevator shaft.

[0035] In a preferred embodiment, the elevator comprises suspension ropes for suspending the elevator car.

[0036] In a preferred embodiment of the method, the overload monitoring system or the elevator, the operating parameter is friction or any parameter suitable for indicating the resistance to movement acting directly on the car.

[0037] In a preferred embodiment of the method, the overload monitoring system or the elevator, the car is arranged to be guided by one or more guide rails.

[0038] In a preferred embodiment of the method, the overload monitoring system or the elevator, the car comprises one or more guide members which are supported in horizontal direction from one or more guide rails.

[0039] In a preferred embodiment of the method, the overload monitoring system or the elevator, the load weighing device is arranged to sense the tension of one or more suspension ropes suspending the elevator car.

[0040] In a preferred embodiment of the method, the overload monitoring system or the elevator, the load weighing device is arranged in connection with a rope anchor, which fixes the ends of the one or more suspension ropes to a fixed base. The fixed base may be a structure, for example, of a building, or a structure, for example, in a shaft or a car. This may depend on the type of elevator, for example its lifting ratio. Preferably, the car is suspended by a rope anchor. The load weighing device is preferably such that it is arranged to measure one or more forces exerted on the rope anchor by the one or more suspension ropes. For this purpose, it preferably comprises one or more force sensors, but alternative sensors may also be used.

[0041] In a preferred embodiment of the method, the overload monitoring system or the elevator, the load weighing device is connected to one or more suspension ropes of the elevator car so that at least a part of the force generated by the load of the elevator car is transferred to the load weighing device via the one or more suspension ropes.

[0042] In a preferred embodiment of the method, the overload monitoring system or the elevator, the load weighing device is arranged to measure a force which is transmitted to the load weighing device via the one or more suspension ropes.

[0043] In a preferred embodiment of the method, the overload monitoring system or the elevator, the overload monitoring system (such as preferably the control system thereof) preferably comprises at least one sensor for sensing an operating parameter of the elevator, in particular during movement of the elevator car. The sensor is preferably a current sensor measuring the current of the motor of the traction machine.

[0044] Typically, the car preferably comprises an interior in which passengers and / or cargo can be transported. The car preferably also comprises one or more doors through which the interior can be opened and closed. The doors are preferably automatic doors, whereby the elevator solution can provide comfortable and safe elevator use. BRIEF DESCRIPTION OF THE DRAWINGS

[0045] In the following, the present invention will be described in more detail by way of examples and with reference to the accompanying drawings, in which:

[0046] Figure 1An elevator and an overload monitoring system are shown which implement a method according to an embodiment at a moment of normal transport use, while the elevator is available for loading.

[0047] Figure 2 The present invention shows the time at which the step for obtaining information on at least one operating parameter of the elevator is performed. Figure 1 Elevator and overload monitoring system. DETAILED DESCRIPTION

[0048] Figure 1 An elevator 100 according to an embodiment is shown. The elevator 100 comprises an elevator car 1 located in an elevator shaft 3 and an overload monitoring system S according to an embodiment. Figure 1 The elevator 100 is shown at a moment of normal transport use, while the elevator is available for loading and for this purpose stands at a landing level F in the elevator shaft 3 .

[0049] The overload monitoring system S of the elevator 100 comprises a load weighing device 2, which is particularly arranged to weigh the current car load when the elevator car 1 of the elevator 100 stands at a landing floor in the elevator shaft 3; and a control system 10. In the embodiment shown, the control system 10 is connected to a traction machine 5, which comprises a motor 5a and a drive wheel 5b engaging one or more hoisting ropes 4. The motor 5a is particularly preferably an electric motor, such as, for example, a permanent magnet motor. For example, the motor 5a can preferably be controlled by an elevator controller included in the control system.

[0050] The overload monitoring system S is configured to perform a method for detecting an overload condition of an elevator car 1 of an elevator 100 according to an embodiment.

[0051] The method comprises, in particular during normal transport use when the elevator car 1 is available for loading, obtaining current car load information from a load weighing device 2, which is arranged to weigh the current car load when the elevator car 1 is standing at a landing floor in the elevator shaft 3, and determining whether the current car load information meets one or more overload criteria; and if the car load information meets the overload criteria, generating a signal indicating an overload condition of the elevator car 1. Thus, when the elevator car 1 is available for loading, the loading state of the car 1 is monitored.

[0052] exist Figure 1 In a preferred embodiment of the present invention, the load weighing device 2 is arranged to sense the tension of one or more suspension ropes 4 of the elevator 100. Figure 1In a preferred embodiment of the invention, this is achieved in such a way that the load weighing device 2 is connected to one or more suspension ropes 4 of the elevator car, so that at least a part of the force generated by the load of the elevator car is transferred to the load weighing device 2 via the one or more suspension ropes 4. The load weighing device 2 is schematically shown and is arranged to be connected to a rope anchor 6, which fixes the ends of the one or more suspension ropes 4 to a fixed base (not shown). The car 1 is suspended by the rope anchor 6. The load weighing device 2 is preferably such that it comprises one or more force sensors, such as strain sensors, which are arranged to measure one or more forces exerted by the one or more suspension ropes 4 on the rope anchor 6.

[0053] The method comprises obtaining information of at least one operating parameter of the elevator 100. In a preferred embodiment, the above operating parameter is the friction force Fr. The friction force is the resistance to movement acting directly on the car 1. The friction force may be caused, for example, by the guide members 9 of the elevator car 1 moving along the guide rails 8 of the elevator 100. Alternatively, the operating parameter may be any other parameter suitable for indicating the resistance to movement acting directly on the car 1. Preferred steps related to the step of obtaining information are already described in Figure 2 and will be described in more detail later.

[0054] After obtaining the information of at least one operating parameter of the elevator 100, the method comprises adjusting one or more of said overload criterion or alternatively said car load information based on the information of at least one operating parameter of the elevator 100. Such an adjustment provides for a dynamic nature of the overload detection and the possibility to take into account operating parameters of the elevator which are not constant and / or are difficult to predict and / or may change during the life of the elevator.

[0055] Adjustment of one or more of the overload criteria provides a simple way to provide correction capability into overload detection, since one or more criteria are generally easy to adjust. As described above, the car load information can also be adjusted based on information of at least one operating parameter of the elevator 100. Adjusting the car load information provides a correction to the car load information, which can effectively eliminate errors in the car load information caused by, for example, increased friction. This translates into better accuracy of the car load information, and adjustment of the criteria is not necessary, although it is still possible. In this method, it is necessary to adjust the car load information or, alternatively, one or more of the one or more overload criteria based on the information of at least one operating parameter of the elevator 100, but both of them can be adjusted.

[0056] As mentioned above, the operating parameter is preferably the friction force Fr, which is a parameter suitable for indicating the resistance to movement acting directly on the car 1. Therefore, factors affecting the mobility of the car 1 can be taken into account and used as the basis for adjustment. Alternatively, the operating parameter can be any other parameter suitable for indicating the resistance to movement acting directly on the car 1. Adjustment based on any of these alternatives is advantageous because changes in the mobility of the car 1 may reduce the accuracy of the load weighing. This is particularly the case when the load weighing device 2 is arranged to sense directly or indirectly the tension of one or more suspension ropes 4 suspending the elevator car 1. That is, if the movement of the car is not free but is resisted, for example, by friction, the force is not transmitted from the car 1 only via the ropes 4, but other structures of the elevator provide some load-bearing or braking action on the car as friction. Therefore, it is possible that the vertical force of the load is not completely and unaffected by the friction force. Transfer to the hoisting rope 4, and therefore the load in the car 1 cannot be accurately sensed by the weighing device 2. If a change is detected in said friction force Fr or any other parameter suitable for indicating the resistance to movement acting directly on the car 1, adjustments should be made.

[0057] In a preferred embodiment, said information of at least one operating parameter of the elevator 100 comprises the magnitude (such as its value) of the friction force Fr or the magnitude (such as its value) of any parameter suitable for indicating the resistance to movement acting directly on the car.

[0058] After the adjustment, continue the normal transportation use of the elevator.

[0059] The above-mentioned acquisition of information of at least one operating parameter of the elevator 100 can generally be implemented in different ways. Figure 2 In the preferred embodiment shown, this step includes moving the car 1 upwards and downwards, such as Figure 2 As shown by arrow A in . Thus, it is convenient to collect information indicating parameters of the resistance to movement of the car 1 (e.g. preferably the friction force). The method preferably includes measuring motor parameters, i.e. parameters of the motor 5a of the traction machine 5 of the elevator 100, during movement in both directions. The motor parameter is particularly preferably the current of the motor of the traction machine 5 of the elevator 100.

[0060] In order to collect information on parameters indicative of the resistance to movement of the car 1, the overload monitoring system S, such as preferably its control system 10, preferably comprises at least one sensor for sensing an operating parameter of the elevator 100 during the movement of the elevator car 1. The sensor is preferably a current sensor measuring the current of the motor 5a of the traction machine 5.

[0061] In a preferred embodiment, each movement of the car upwards and downwards is performed at a constant speed, which is preferably slow, preferably slower than 0.5 m / s, more preferably slower than 0.2 m / s.

[0062] In a preferred embodiment, each movement of the car upwards and downwards is performed while the car 1 is empty or alternatively has a constant load.

[0063] In a preferred embodiment, obtaining information of at least one operating parameter of the elevator 100 comprises calculating the magnitude of the friction force Fr or any parameter suitable for indicating the resistance to movement acting directly on the car based on measurements of motor parameters, preferably measured current.

[0064] Preferably, the calculation comprises calculating the difference between the measurements of the motor parameters, preferably calculating the difference between the current measured during upward movement and the current measured during downward movement. When friction forces act on the elevator car 1 in two opposite directions of movement of the car 1, the force / current generated by the friction forces can be calculated, for example, by calculating current up - current down.

[0065] In a preferred embodiment, the method includes determining a current car load value based on the car load information, and the one or more criteria include the current car load value exceeding at least one threshold. The determination includes reading a memory storing one or more criteria for an overload condition of the elevator car.

[0066] On the other hand, adjusting one or more criteria comprises accessing a memory storing one or more criteria for an overload condition of the elevator car, and changing said one or more criteria. Adjusting one or more criteria comprises in particular changing a threshold value (limit value) to a new value based on information of at least one operating parameter, such as based on the magnitude of the friction force Fr or the magnitude of a parameter suitable for indicating the resistance to movement acting directly on the car 1. The new value may be higher or lower than the previous value. In a preferred embodiment, when changing the threshold value, if the information of at least one operating parameter obtained indicates that the resistance to movement acting directly on the car 1 has risen, then preferably more particularly if the magnitude of the friction force Fr or some other parameter suitable for indicating the resistance to movement acting directly on the car 1 is higher than before, for example higher than its earlier magnitude stored in the memory of the control system 10, then the value is changed to a lower value, and if the information of at least one operating parameter obtained indicates that the resistance to movement acting directly on the car 1 has decreased, then vice versa. Then, the method preferably comprises comparing the information of at least one operating parameter obtained with a reference, for example by comparing the magnitude of the friction force Fr or some other parameter suitable for indicating the resistance to movement acting directly on the car 1 with its reference magnitude stored in the memory of the control system 10.

[0067] exist Figure 1 In a preferred embodiment, the overload monitoring system S of the elevator comprises a load weighing device 2, which is arranged to weigh the current car load when the elevator car 1 of the elevator 100 stands at a landing floor in the elevator shaft 3; and a control system 10, which is configured to perform the method as described anywhere above. Therefore, the control system 10 is configured to obtain car load information from the load weighing device 2; and determine whether the current car load information meets one or more overload criteria; and if the car load information meets the overload criteria, generate a signal indicating an overload condition of the elevator car 1. The control system 10 is also configured to obtain information on at least operating parameters of the elevator 100, and adjust at least one of the one or more overload criteria and the car load information based on the information on at least one operating parameter. The structure of the monitoring system S is as previously referred to. Figure 1 and Figure 2 Likewise, the monitoring system S is configured to perform as previously described with reference to Figure 1 and Figure 2 Describe the steps of the method.

[0068] It is generally preferred that the control system 10 preferably includes a memory storing one or more criteria for an overload condition of an elevator car, or that the control system 10 is configured to read and / or change the contents of such a memory.

[0069] It is generally preferred that the control system 10 is configured to control the movement of the elevator car 1 in the elevator shaft 3 .

[0070] It is generally preferred that the control system 10 is a local system physically near the elevator car, but may include remote units, for example the memory may be cloud storage.The control system 10 may preferably be or at least include a unit known as an elevator controller.

[0071] It is generally preferred that the control system 10 includes at least one electronic processing unit, such as a microprocessor unit, which is configured to, for example, be programmed to perform one or more of the following steps: determine whether the current car load information meets one or more overload criteria, generate a signal, obtain information of at least one operating parameter of the elevator 100, and adjust.

[0072] It is generally preferred that the car 1 is arranged to be guided by one or more guide rails 8. An elevator of this type may be exposed to variations in the friction or other resistance to movement acting directly on the car during its lifetime.

[0073] It is generally preferred that the car 1 comprises one or more guide members 9 , such as rollers or sliding guides, deriving support in the horizontal direction from one or more guide rails 8 .

[0074] It is generally preferred that the elevator 100 further comprises a counterweight 7 in the shaft 3 for generating an upward pulling force on the car 1. The counterweight is suspended by the hoisting ropes 4, in particular on the side of the drive sheave 5b opposite to the car 1.

[0075] It is generally preferred that the lift ratio of the car 1 and / or the counterweight 7 suspension also be different from the 2:1 shown in the example, for example 1:1 or 3:1.

[0076] Typically, the information of at least one operating parameter of the elevator 100 can be specific to a landing or generally specific to a location, and one or more criteria can be specific to a landing floor or generally specific to a location, which means that the method and system store one or more overload criteria separately for different landing floors / locations. In this case, obtaining the information of at least one operating parameter of the elevator 100 is also performed in a landing floor-specific manner or in a location-specific manner, respectively.

[0077] As mentioned above, the load weighing device 2 is arranged to weigh the current car load, preferably when the elevator car 1 stands at a landing floor in the elevator shaft 3. More specifically, this is preferably such that the load weighing device 2 is arranged to weigh the current car load, when the elevator car 1 stands at a landing floor in the elevator shaft 3 and one or more brakes of the traction machine 5 are in a braking state, in particular in a state in which it / they brake and / or prevent rotation of the traction machine and / or its drive wheel engaged with one or more hoisting ropes. For this purpose, the traction machine 5 preferably has one or more brakes for braking and / or preventing rotation of the traction machine and / or its drive wheel. The control system 10 (such as preferably its elevator controller) is preferably configured to control the one or more brakes.

[0078] Typically, the method includes weighing the current car load by the load weighing device 2, preferably when the elevator car 1 stands at a landing floor in the elevator shaft 3, more preferably when the elevator car 1 stands at a landing floor in the elevator shaft 3 and one or more brakes of the traction machine 5 are in a braking state.

[0079] In general, the signal indicating an overload condition of the elevator car 1 can be any type of signal suitable for indicating the overload condition, such as preferably indicating the overload condition to a person or an elevator controller. For example, the signal can be an alarm signal, an electrical signal, a visual signal or an acoustic signal, or any combination of two or more of these signals. A person in the car can react to the signal indicating the overload condition. When the signal is an electrical signal, it can be an electrical signal of an elevator controller (described elsewhere) for controlling the system 10, in response to which the elevator controller is preferably configured to cause the car to stop, such as by causing the braking of one or more brakes of the traction machine and / or by causing the rotation of the motor of the traction machine to stop.

[0080] As described above, the above-mentioned obtaining of information about at least one operating parameter of the elevator 100 can generally be implemented in different ways. Figure 2 In the preferred embodiment shown, this step includes moving the car 1 upwards and downwards, such as Figure 2 As shown by arrow A in . Thereby, it is possible to facilitate the collection of information of parameters indicating the movement resistance of the car 1 (such as preferably the friction force). As an alternative to the parameters measured for the two directions being motor parameters, the parameters used may be current car load values ​​determined based on car load information obtained during movement in the two directions. In this case, calculating the friction force magnitude (Fr) may include calculating the difference between the current car load value during upward movement and the current car load value during downward movement.

[0081] It should be understood that the above description and accompanying drawings are only intended to teach the best way to make and use the present invention known to the inventor. It is obvious to those skilled in the art that the inventive concept can be implemented in various ways. Therefore, as those skilled in the art understand in accordance with the above teachings, the above-described embodiments of the present invention may be modified or changed without departing from the present invention. Therefore, it should be understood that the present invention and its embodiments are not limited to the above-described examples, but may be varied within the scope of the claims.

Claims

1. A method for detecting an overload condition of an elevator car (1) of an elevator (100), the method comprising: obtaining current car load information from a load weighing device (2), said load weighing device being arranged to weigh the current car load, preferably when said elevator car (1) is standing at a landing floor (F) in an elevator shaft (3), and determining whether the current car load information satisfies one or more overload criteria; and generating a signal indicating an overload condition of the elevator car (1) if the car load information satisfies one or more of the overload criteria, Characterized in that the method comprises: obtaining information on at least one operating parameter of the elevator (100), wherein the operating parameter is friction (Fr) or any parameter suitable for indicating the resistance to movement acting directly on the car (1), and One or more of the overload criteria or the car load information is adjusted based on the information of at least one operating parameter of the elevator (100).

2. A method according to claim 1, wherein the information on at least one operating parameter of the elevator (100) includes the magnitude of the friction force (Fr) or the magnitude of a parameter suitable for indicating the resistance to movement acting directly on the car (1).

3. A method according to any one of the preceding claims, wherein the method comprises determining a current car load value based on the car load information, and the one or more criteria comprise the current car load value exceeding at least one threshold value. The method of claim 3 , wherein adjusting the one or more criteria comprises changing the threshold to a new value based on the information of the at least one operating parameter.

5. The method according to claim 4, wherein: When changing the threshold value, if the information of at least one operating parameter obtained indicates that the movement resistance directly acting on the car (1) increases, the threshold value is changed to a lower value, and / or if the information of at least one operating parameter obtained indicates that the movement resistance directly acting on the car (1) decreases, the threshold value is changed to a higher value.

6. A method according to any one of the preceding claims, wherein: Obtaining information of at least one operating parameter of the elevator (100) comprises moving the car upwards and downwards and measuring motor parameters, such as preferably the current of a motor (5a) of a traction machine (5) of the elevator (100) during movement in both directions, wherein preferably, - each movement of the car upwards and downwards is performed at a constant speed, preferably a slow speed, preferably slower than 0.5 m / s, more preferably slower than 0.2 m / s; and / or - Each movement of the car up and down is performed when the car (1) is empty.

7. A method according to any one of the preceding claims, wherein: Obtaining information on at least one operating parameter of the elevator (100) comprises calculating the magnitude of the friction force (Fr) or any parameter suitable for indicating the resistance to movement acting directly on the car, preferably based on measurements of motor parameters, preferably based on measurements of motor current.

8. The method according to claim 7, wherein: The calculation comprises calculating the difference between measurements of a motor parameter, preferably calculating the difference between the current measured during the upward movement and the current measured during the downward movement.

9. An elevator overload monitoring system, comprising: A load weighing device (2), the load weighing device being arranged to weigh the current car load; as well as A control system (10) configured to perform a method according to any one of the preceding claims.

10. An elevator (100) comprising an elevator car (1) and an overload monitoring system (S) according to claim 9.

11. The method, the overload monitoring system (S) or the elevator (100) according to any one of the preceding claims, wherein: The operating parameter is friction (Fr) or any parameter suitable for indicating the resistance to movement acting directly on the car (1).

12. The method, the overload monitoring system (S) or the elevator (100) according to any one of the preceding claims, wherein: The load weighing device (2) is arranged to sense the tension of one or more suspension ropes (4) suspending the elevator car (1).

13. The method, the overload monitoring system (S) or the elevator (100) according to any one of the preceding claims, wherein: The load weighing device (2) is arranged in connection with a rope anchor (6) which fixes the end of one or more suspension ropes (4) of the elevator car (1) to a fixed base.

14. The method, the overload monitoring system (S) or the elevator (100) according to any one of the preceding claims, wherein: The load weighing device (2) is connected to one or more suspension ropes (4) of the elevator car so that at least a part of the force generated by the load of the elevator car is transmitted to the load weighing device (2) via the one or more suspension ropes (4).

15. The method, the overload monitoring system (S) or the elevator (100) according to any one of the preceding claims, wherein: The overload monitoring system (S) or the elevator (100), for example preferably the control system (10) thereof, comprises at least one sensor for sensing an operating parameter of the elevator (100).

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