EP2982868B1

EP2982868B1 - Hydraulic system and method for controlling hydraulic systems

Info

Publication number: EP2982868B1
Application number: EP15179397.3A
Authority: EP
Inventors: Francesco PADOAN
Original assignee: Padoan Srl
Current assignee: Padoan Srl
Priority date: 2014-08-06
Filing date: 2015-07-31
Publication date: 2019-03-20
Anticipated expiration: 2035-07-31
Also published as: ES2731799T3; EP2982868A1; PL2982868T3

Description

The present invention refers in general to an apparatus and a method for the control of hydraulic systems. More particularly, the present invention refers to an apparatus and a method for hydraulic systems used in vehicles with tipper, said apparatus and method being suitable to check the need for maintenance of the aforesaid systems.
As for any mechanical system, also in the case of hydraulic systems for vehicles with tipper, a regular routine maintenance reduces the need of having to perform extraordinary maintenance interventions in the case of any breakage in the system so as to avoid, as much as possible, significant costs of repair and unwanted non-use time of the vehicle.
The choice of the more proper moment to carry out the routine maintenance is rather complex since the systems according to known art do not supply any parameters or data reliable and useful for this purpose; consequently, there is a risk that the maintenance be performed too soon involving an at least partially useless expense, or a risk that the maintenance be performed too late causing breakages in the system involving unwanted costs.
Currently, the choice of the more proper moment to carry out the ordinary maintenance is made by using two different methods.
The first method is to fix a time limit within which the controls and operations of the ordinary maintenance must be carried out. However, this method does not take into account the use of varying intensity of the vehicle; in fact, on the one hand there may be vehicles that are used continuously for 24 hours a day and for very short distances, for example those employed in the mine with many cycles of loading and unloading in the day; on the other hand, there may be much less stressed vehicles which are used in the loading and unloading operations only a few times a day, for example vehicle that have to make longer distances.
Thus, the needs for maintenance of the hydraulic system of vehicles such as those previously mentioned are very different. However, if a method based on deadlines is used, such vehicles have to be subject, paradoxically, to the same maintenance plan.
A second method for determining the time when performing routine maintenance involves the insertion of a clogging sensor in the filter of the hydraulic system.
However, this second method allows to intervene only in relation to the state of the filter. Also should be emphasized that the signaling of the filter may be strongly influenced by factors such as the viscosity and temperature of oil and the flow rate. Consequently, this second method may carry out incorrect signals in addition to being limited.
Furthermore, in light of the relative ineffectiveness of the known methods described above, the operators very often tend not to take any maintenance plan and expect that the system itself shows signs of malfunction so as to intervene.
However, this approach implies that when the vehicle stops for some failure, there is the need of emergency measures to minimize the period of immobilization of the vehicle. In addition, the damages are often substantial and the costs for labor and spare parts required are also considerable.
The issue in question is also strongly felt by supplier companies and vendor companies of the hydraulic systems and vehicles since giving a determined warranty period may expose to a risk difficult to assess if the intensity of use of the vehicle is not known.
Known apparatus and method for the control of hydraulic systems are disclosed by the patent document EP 1 150 019 A1 . An aim and function of the present invention is to provide an apparatus and a method that allow to determine, with good reasonableness, when carrying out the routine maintenance operations on a hydraulic system for vehicles with tipper.
Another aim of the present invention is to provide an apparatus and a method that allow to refer the need for maintenance of the hydraulic system of a vehicle with tipper to a parameter that is as objective as possible.
Another aim of the invention is to provide an apparatus and a method that allow to establish the use of the hydraulic system of a vehicle with tipper so as to determine if and when performing the routine maintenance of the hydraulic system.
The above-mentioned aims and other aims are reached through a hydraulic system comprising a controlling apparatus, an oil reservoir and a hydraulic cylinder with a rod movable in a liner, said cylinder being configurable from a retracted position in which the rod is withdrawn into the liner to an extended position in which the rod is completely out of the liner. For example, the hydraulic system may be the hydraulic system of a vehicle provided with a tipper that may be lifted by a hydraulic cylinder.
The controlling apparatus comprises detecting means that detect the extended position of the hydraulic cylinder, said detecting means being connected to a control unit adapted to count the number of times in which the cylinder is in its extended position.
Through this configuration, the detecting means detect the position of the cylinder and the control unit analyzes the information collected by the detecting means and is able to ascertain when the hydraulic system has carried out a working cycle corresponding to the transition from a more or less retracted position to a totally extended position. Accordingly, the control unit is able to count the number of working cycles and to compare this number with a preset number representing the work that the hydraulic system can perform before having to carry out routine maintenance tasks. The hydraulic system according to the invention is characterized by the fact that the detecting means detecting the extended position comprise a first level sensor positioned inside the reservoir at such a height as to identify the absence in the reservoir of a quantity of liquid equal to that necessary to position the cylinder in its extended position.
Besides, in the apparatus according to the invention, detecting means are comprised to detect the retracted position of the hydraulic cylinder, said detecting means being suitably connected to the control unit which can count the number of times in which the cylinder passes from the retracted position to the extended position.
Advantageously, the detecting means may comprise a second level sensor positioned inside the reservoir above the first level sensor at a height equal to that identified by the volume of oil necessary for the hydraulic cylinder to pass from the retracted position to the extended position.
In other words, the detecting means, which can be one or more level sensors, are arranged inside the reservoir, in a safe and stable position so as to avoid unwanted position variations of the sensors, which could distort the counting of the cycle numbers.
Furthermore, through this position, the sensors are protected from impacts or from the action of dirt and bad weather, which are not remote possibilities in the case of vehicles with tripper.
Advantageously, a temperature sensor can be included in the control apparatus preferably in correspondence of the level sensors, inside the reservoir, so as to provide more information to the control unit and therefore to the operator.
Besides, also a data communication module can be included in the control apparatus and is connected to the control unit so as to send to a third party the information detected and analyzed by the control unit. In this way, the maintenance request can be sent automatically.
Advantageously, a flow meter can be included in the control apparatus and is mounted in a conduit of the hydraulic system and is adapted to measure the amount of oil moved continuously according to a same direction so that the hydraulic cylinder can be moved from the retracted position to the extended position.
Also in this way, it is possible to detect the completion of a working cycle and therefore, the control unit is able to count the number of working cycles carried out and to compare this number with the number of working cycles for which the ordinary maintenance is deemed necessary.
In addition, the aims and advantages of the invention are reached through a control method for a hydraulic system comprising a reservoir containing oil and connected to a hydraulic cylinder with a rod movable in a liner, said cylinder being configurable from a retracted position in which the rod is withdrawn into the liner to an extended position in which the rod is completely out of the liner, and vice versa.
This control method comprises the following phases:

counting the number of times in which the cylinder is configured in an extended position;
comparing, in continuous, the number of times previously measured, with a number preset in the design and testing phases of the hydraulic system, said preset number being representative of the work that the hydraulic system is capable to perform before having to perform routine maintenance operations.

Accordingly, this method allows to know the real utilization of the hydraulic system regardless of its age.
In this way, it is also possible to meet the requirement of optimally managing the warranty of the components of the system: indeed, giving a determined warranty period exposes to a risk difficult to assess if the intensity of use of the vehicle is not known.
In the method according to the invention, an objective reference, that is the number of lifting cycles, is utilized regardless of the starting position of the cylinder, more or less retracted; it is thus possible to determine a warranty period subject to a maximum number of cycles, otherwise it is possible to take the time parameter instead of the parameter relative to the number of cycles. The control method according to the invention is characterized by the fact that the counting of the number of times in which the cylinder is configured in an extended position is performed by counting the number of times in which the oil in the reservoir reaches a first level.
The aforesaid first level corresponds to a height of the liquid left in the reservoir such as to ascertain the absence in the reservoir of an amount of liquid equal to the amount that is necessary to position the cylinder in the extended position.
Besides, the method according to the invention may provide that the number of times in which the cylinder is configured in an extended position is actually counted if said extended position is reached starting from a retracted position of the cylinder. Essentially, the lifting cycle is counted only if it is complete that is, when there is the passage from a retracted position to an extended position.
Advantageously, the control method according to the invention may provide that the counting of the number of times in which the cylinder moves from a retracted position to an extended position, that is the number of the lifting cycles, is performed by counting the number of times in which the oil in the reservoir passes to the first level starting from a second level which is higher than the first level.
In this way, it is possible to determine the variation of the oil volume inside the reservoir and, therefore, the amount of oil released from the reservoir. By appropriately setting the first level and the second level inside the reservoir so that the amount of outgoing oil, included between the two levels, is equal to the amount necessary to complete a lifting cycle, it is possible to verify the completion of a working cycle of the hydraulic system.
By counting the number of cycles and comparing this number with a preset number it is possible to determine the moment when it is preferable to carry out the maintenance of the hydraulic system.
In order to perform the measurements, the first level reached by the oil may be measured by means of a first level sensor disposed at a first height in the reservoir above the height of the first level and adapted to signalize the absence of oil in the reservoir at the height in which it is placed.
In this way, the first sensor verifies whether the oil level is lower than a determined height, which means that an amount of oil has been released from the reservoir which corresponds to the amount of oil required to complete a working cycle or lifting cycle.
Likewise, in order to perform the desired measurements, the second level reached by the oil may be measured by means of a second level sensor disposed at a second height in the reservoir lower than the height of the second level and adapted to signalize the presence of oil in the reservoir at the height in which it is placed.
In this way, the second sensor verifies whether the oil level is higher than a determined height, which means that an amount of oil has returned to the reservoir, which corresponds to the amount of oil required to complete a working cycle or lifting cycle.
Furthermore, the second sensor has the function to indicate the presence of a sufficient amount of oil in the reservoir to ensure a correct operation the hydraulic system.
Advantageously, in order to avoid false detections of the oil level and consequent wrong computations of the lifting cycles, for example due to the movement of the vehicle on which the hydraulic system to be controlled is arranged, the signaling of absence or presence of oil at the height of the first level sensor and/or the signaling of absence or presence of oil at the height of the second level sensor are considered reliable if said absence or presence of oil is detected for a continuous period of time exceeding a predetermined duration.
Further features and details of the invention may be better understood from the following description which is supplied by way of a non-restricting example as well as from the attached drawing, wherein:
Fig. 1 is a schematic side view in section of a control apparatus, according to the invention, of a hydraulic system, mounted on a reservoir for hydraulic systems during a first step of utilization of the system;
Fig. 2 is a schematic side view in section of the control system in Fig. 1, in a second step of utilization of the system and filing of the reservoir.
With reference to the attached drawing, number 10 denotes a controlling apparatus for a hydraulic system mounted, for example, on a vehicle with a tipper which is tipped up by means of a hydraulic cylinder.
The controlling apparatus 10, described in detail below, is mounted on a reservoir 12 containing hydraulic oil 14 that can reach different levels, for instance a first level denoted by reference number 16 in Figure 2 and a second level denoted by reference number 18 in Figure 1.
According to prior art, a delivery and return duct 20, represented schematically in the attached drawing, is mounted on the reservoir 12. This duct includes an inner conduit 22, connected through a box 24 to a delivery tube 26 and return tube 28 which are connected to the lifting cylinder that lifts the tipper.
Besides, other components such as a valve, an exhaust opening and other components are mounted on the reservoir 12 but these components have not been described, and nor illustrated in the drawing since all these components are realized according to prior art.
The controlling apparatus 10 comprises a first level sensor 30 and a second level sensor 32 which are connected to each other through a connecting rod 34 that transmits data. The level sensors are arranged rigidly inside the reservoir so that the sensors can not vary their position.
The first level sensor 30 is arranged in a position lower than the position of the second level sensor 32.
Besides, the rod 34 is connected to a connecting box 36 arranged on the outer surface of the reservoir 12 and connected through a connecting cable 38 to a control unit 40 provided with a display 42.
The controlling apparatus 10 according to the invention provides that the first level sensor 30 and the second level sensor 32 send to the control unit 40 the information regarding the presence or absence of oil in the reservoir in correspondence of the height of the two level sensors 30, 32.
Said information is sent to the control unit 40 through the connecting rod 34, the connecting box 36 and the connecting cable 38 which contain the electrical wiring allowing the data transmission.
The volume of oil included between a level slightly lower than the first level sensor 30 and a level slightly higher than the second level sensor 32 corresponds to the amount of oil required to carry out the lifting of the tipper arranged on the vehicle and represents, therefore, a working cycle.
In other words, when the reservoir 12 comprises an amount of oil that reaches the second level 18 as represented in Figure 1, the tipper rests on the vehicle frame. Thus, the reservoir 12 is filled completely with oil.
On the contrary, when the reservoir 12 comprises an amount of oil that reaches the first level 16 as represented in Figure 2, the tipper has reached the maximum lifting end from the vehicle frame. The oil missing in the reservoir 12 in Figure 1 in comparison to the oil contained in the reservoir 12 in Figure 2 is present in the hydraulic system, and in particular the missing oil is present in the cylinder allowing the tipper to be lifted.
Thus, the hydraulic system has completed a working cycle.
A working cycle is counted as follows:

at first the second level sensor 32 signalizes the presence of oil which, indeed, reaches the second level 18 which is higher than the height at which the second level sensor 32 is positioned;
then, the first level sensor 30 signalizes the absence of oil which, indeed, reaches the first level 16 which is lower than the height at which the first level sensor 30 is positioned.

The control unit 40 has the function of processing the data detected by the first level sensor 30 and second level sensor 32 and sending the data to the display 42, installed in the interior compartment of the vehicle, so that the operator can verify the operational state of the hydraulic system as well as the number of cycles performed by the hydraulic system since the last maintenance.
In fact, on the base of the information sent by the two level sensors 30, 32, the control unit 40 has mainly the task of counting the number of working cycles carried out by the hydraulic plant and comparing this number with a number of cycles preset during the design and testing of the hydraulic system, representing the work that the hydraulic system can perform before performing the regular activity of ordinary maintenance.
In order to avoid any wrong computation of a working cycle, for example due to the shaking of the oil inside the reservoir during the running of the vehicle, the control unit 40, through a software filter, considers correct the level signal received when this signal is extended without interruption for a predetermined time interval, for example at least 30 seconds.
Moreover, a temperature transducer is mounted in the first level sensor 30 or in the second level sensor 32 or in both sensors. The data of the temperature transducer are collected and sent to the control unit 40 and display 42 so that the operator in the cab can be alerted of any non-optimal operating conditions.
Obviously, the level and temperature sensors may also be mounted on a side wall of the reservoir.
According to a first variant of the invention, relating to the operation of the control apparatus, a working cycle is counted when the first level sensor 30 signalizes the absence of oil for a predetermined continuous period regardless of whether the presence of oil has been previously signalized or not at the height of the second level 18 by the second level sensor 32.
In other words, a control method for controlling the hydraulic system provides the counting of a working cycle whenever the cylinder remains extended completely or extended for a predetermined length corresponding to the positioning of the first level sensor, for a preset duration, for instance 30 seconds, regardless of the length of the cylinder at the beginning of the extension phase.
The control apparatus according to the invention may provide other devices and/or features, described below, useful to supply an additional information to the user and/or to the installation companies of hydraulic systems.
The control unit can communicate with the vehicle electronics in order to receive information on the speed of the vehicle or revolutions of the engine, parameters useful to verify whether the hydraulic system has been properly.
The control unit can communicate with a communication module used to communicate and send data, such as a GSM module, a UMTS module or an LTE module in order to send messages requesting maintenance interventions or signalization of the vehicle position so as to facilitate the maintenance interventions.
The control unit may also provide for the storage and management of data collected on time scale so that a user can obtain information on the base of data collected from the various sensors, for example the number of cycles in the work shift, the oil temperature, and more.
According to another variant of the invention, counting of the working cycles performed by the hydraulic system of a vehicle with tipper may be done by positioning a sensor in the hydraulic cylinder controlling the lifting of the tipper. This sensor signals when the cylinder is at maximum extension and when the same cylinder is compacted so as to indicate the complete lifting and the complete lowering of the tipper, respectively.
Said information is managed by a control unit in a similar manner to what has been done by the control unit 40 previously described, according to a method which provides a full cycle when the cylinder goes from its retracted position to its fully extended position, or according to a method which provides a full cycle when the cylinder remains in its extended position for a determined time regardless of the configuration from which the cylinder begins to extend.
According to another variant of the invention, counting the working cycles carried out by the hydraulic system of a vehicle with tipper may be performed by utilizing a proximity sensor positioned on the vehicle tipper.
Said sensor signals when the tipper rests on the vehicle frame or not. A second proximity sensor may indicate also a complete lifting of the tipper if the same sensor has been properly positioned, for example near the hinge that constrains the tipper to the frame.
Also in this case, the information collected from the proximity sensors are sent to and analyzed by a control unit.
According to another variant of the invention, counting the working cycles carried out by the hydraulic system of a vehicle with tipper may be performed by means of a flow meter inserted in a tube of the hydraulic system so as to have an indication of the oil flow and operation of the hydraulic system.
In this case, the flow meter has to measure the amount of oil flowing in one direction in a conduit. This information is collected and managed by a control unit which compares continuously the data obtained with a predetermined amount of oil identifying the full filling of the cylinder for the lifting of the tipper and, therefore, a working cycle.
According to another variant of the invention, counting the working cycles carried out by the hydraulic system of a vehicle with tipper may be performed by means of a sensor disposed on a hydraulic distributor in order to know the displacements of a cursor and, therefore, the activations of the system for lifting the tipper.
According to another variant of the invention, counting the working cycles carried out by the hydraulic system of a vehicle with tipper may be performed by means of a pressure switch inserted in the hydraulic system and/or in a pneumatic system so as to know when the oil is under pressure to lift the tipper.
Besides, another variant of the invention for counting the working cycles carried out by the hydraulic system of a vehicle with tipper may provide the use of a sensor of power takeoff inserted so as to know when the hydraulic system is actuated to lift the tipper.
Variants are possible which are to be considered as included in the scope of protection; for example, in the case of the first embodiment of the invention, more than two level sensors can be mounted to monitor the various phases of a working cycle as concerns timing, temperatures and any parameters to be measured.
Finally, the communication of the sensors arranged in the reservoir according to the first embodiment of the invention or the communication of the various device according to the other embodiments of the invention, with the control unit or directly with the display, can be performed not only with cable, as described above, but also with wireless systems such as wi-fi.

Claims

Hydraulic system comprising a controlling apparatus (10), a control unit (40) and a hydraulic cylinder with a rod movable in a liner, said cylinder being configurable from a retracted position in which the rod is withdrawn into the liner to an extended position in which the rod is completely out of the liner, said hydraulic system comprising an oil reservoir (12) containing oil (14), wherein the controlling apparatus comprises detecting means that detect the extended position of the hydraulic cylinder, said detecting means detecting the extended position being connected to the control unit (40) adapted to count the number of times in which the cylinder is in its extended position; characterized by the fact that the detecting means detecting the extended position comprise a first level sensor (30) positioned inside the reservoir (12) at such a height as to identify the absence in the reservoir of a quantity of oil equal to that necessary to position the cylinder in its extended position.
Hydraulic system according to the preceding claim, wherein detecting means (32) are comprised to detect the retracted position of the hydraulic cylinder, said detecting means (32) detecting the retracted position being connected to the control unit (40) adapted to count the number of times in which the cylinder passes from the retracted position to the extended position.
Hydraulic system according to the preceding claim, wherein the detecting means detecting the retracted position comprise a second level sensor (32) positioned inside the reservoir (12) above the first level sensor (30) at a height equal to that identified by the volume of oil necessary for the hydraulic cylinder to pass from the retracted position to the extended position.
Control method for a hydraulic system comprising a reservoir (12) containing oil (14) and connected to a hydraulic cylinder with a rod movable in a liner, said cylinder being configurable from a retracted position in which the rod is withdrawn into the liner to an extended position in which the rod is completely out of the liner, and vice versa, wherein the following phases are comprised:
- counting the number of times in which the cylinder is configured in an extended position;

- comparing, in continuous, the number of times previously measured, with a number preset in the design and testing phases of the hydraulic system, said preset number being representative of the work that the hydraulic system is capable to perform before having to perform routine maintenance operations;
said method been characterized by the fact that the counting of the number of times in which the cylinder is configured in an extended position is performed by counting the number of times in which the oil in the reservoir reaches a first level (16).
Control method according to claim 4, wherein the number of times in which the cylinder is configured in an extended position is counted if said extended position is reached starting from a retracted position of the cylinder.
Control method according to the preceding claim, wherein the counting of the number of times in which the cylinder moves from a retracted position to an extended position is performed by counting the number of times in which the oil in the reservoir passes to a first level (16) starting from a second level (18) which is higher than the first level (16).
Control method according to claim 4 or 6, wherein the first level (16) reached by the oil is measured by means of a first level sensor (30) disposed at a first height in the reservoir (12) higher than the height of the first level (16) and adapted to signal the absence of oil in the reservoir at the height in which it is placed.
Control method according to claim 6, wherein the second level (18) reached by the oil is measured by means of a second level sensor (32) disposed at a second height in the reservoir (12) lower than the height of the second level (18) and adapted to signal the presence of oil in the reservoir at the height in which it is placed.
Control method according to one of claims 7 or 8, wherein the signaling of absence or presence of oil at the height of the first level sensor (30) and/or at the height of the second level sensor (32) is considered reliable if said absence or presence of oil is detected for a continuous period of time exceeding a predetermined duration.