Fan drive system

Abstract

The present invention discloses a hydraulic fan system and a method for controlling the speed of the hydraulic fan system. The fan system includes a fan operated by a hydraulic motor, and the hydraulic motor is driven by a variable displacement hydraulic pump including a displacement volume adjustment element. The tilt angle of the displacement volume adjustment element can be adjusted by controlling the tilt current supplied to an electronic displacement control unit. The hydraulic fan system further includes means for determining the volume flow rate of the pump and a control unit. The control unit includes: a fan speed calculation unit for calculating the fan speed according to the determined volume flow rate, and a fan speed error determination unit for determining a fan speed error by comparing the calculated fan speed with the fan speed set by a fan speed setting means. The control unit can supply an adjusted tilt current to the electronic displacement control unit so as to adjust the tilt angle of the displacement volume adjustment means, such that the volume flow rate can be adjusted to reduce the fan speed error.

Description

Technical Field

[0001] The present invention relates to a method for controlling the speed of a hydraulic fan system and to a hydraulic fan system. Background Art

[0002] Hydraulic fan systems are widely used in the field of work machines, for example, in road sweeping devices. These vehicles are typically propelled by an internal combustion engine that drives a hydraulic pump. The hydraulic pump is hydraulically connected to a hydraulic motor, which, for example, drives a fan to generate an air flow through a suction device of the vehicle.

[0003] In the prior art, hydraulic fan systems are typically equipped with hydraulic means for controlling the speed of the fan. These hydraulic control means generally provide poor efficiency and only offer limited options for controlling the fan speed, and these hydraulic control means are pressure-controlled (load-dependent), which means that once the suction fan or the grille covering the suction fan becomes blocked, the fan speed will increase until sufficient air flow is regained. This can have negative consequences as the fan may accelerate to overspeed, which can lead to damage to the fan. To prevent such fan overspeed, a hydraulic orifice or valve can be arranged in the hydraulic circuit between the pump and the motor, which reduces the pressure at the motor inlet once the hydraulic flow exceeds a certain limit. If the motor inlet pressure is reduced by this valve, there is an efficiency loss, making the efficiency of today's fan drive systems rather low. Additionally, the current operating state of a fan drive system according to the prior art is not monitored, leaving the machine operator with no knowledge of the machine's working performance and unable to identify potential hazards, such as a blockage of the fan grille during operation of the machine. Summary of the Invention

[0004] Accordingly, an object of the present invention is to provide a hydraulic fan drive system that is capable of controlling the fan speed independently of the hydraulic fluid flow in the associated circuit. This control increases the efficiency of the fan drive system as hydraulic losses can be reduced. Additionally, controlling the fan speed independently of the fluid flow prevents damage to the hydraulic fan system. Another object of the present invention is to provide a method for controlling the speed of a hydraulic fan system and to provide a hydraulic fan system that is capable of sending notifications regarding the current state of and originating from the hydraulic fan system to the machine operator. The system of the present invention may also be capable of identifying fault conditions, such as blockages of major system components.

[0005] The hydraulic fan system according to the present invention includes a fan operated by a hydraulic motor. The hydraulic motor is driven by a variable displacement hydraulic pump, which includes a displacement volume regulating element, the tilt angle of which can be controlled by a tilt current supplied to an electronic displacement control unit (EDC). In the context of the present invention, the tilt current, also referred to as the pump current or pump control current, is the current supplied to a tilt angle regulating device that is capable of setting the tilt angle, wherein the magnitude of the tilt current supplied to the tilt angle regulating device determines the tilt angle.

[0006] A method for controlling the speed of a hydraulic fan system includes the following repeating steps:

[0007] In a first step a), the operating parameters of the pump are measured to determine the volumetric flow rate of the pump. For example, by means for measuring at least the rotational speed of the pump and the tilt angle of the displacement volume regulating element, or by other equivalent variables, the operating parameters of the pump are measured to determine the volumetric flow rate of the pump. In addition to the rotational speed of the pump and the tilt angle of the displacement volume regulating element, the volumetric flow rate of the pump can be determined, for example, by measuring the suction power and the pressure difference between the pump inlet and the pump outlet of the pump. However, measuring or determining other equivalent variables to determine the volumetric flow rate is common knowledge to those skilled in the art.

[0008] In a second step b), the fan speed is calculated based on the volumetric flow rate determined in step a) using an equation representing the fan system. These equations can be physical equations, for example, state space matrices or models used as digital twins of the hydraulic fan system. The equations can also be used in the form of a neural network, which assigns a value of the fan speed to the input value of the volumetric flow rate after having received training data in the form of, for example, measured values from a real or ideal model hydraulic fan system.

[0009] In step c), a fan speed error value is determined by comparing the calculated fan speed in step b) with a fan speed setpoint. The fan speed setpoint can be preset not only by an operator, but also by a control unit. The fan speed setpoint can also be set through a mechanical interface, whereby the mechanical movement of the fan speed setting device is converted into an electrical signal representing the fan speed setpoint. Then this electrical signal can be compared with the electrical signal representing the calculated fan speed.

[0010] In step d), the tilt current is adjusted, which is supplied to the electronic displacement control unit to adjust the tilt angle of the displacement volume adjustment element. Thereby, the tilt angle of the displacement volume adjustment element is adjusted so that the fan speed error can be reduced. There are many different solutions for how the tilt current can cause the adjustment of the tilt angle of the displacement volume adjustment element. For example, the tilt current can be supplied to a solenoid, which, for example, acts on a swashplate used as the displacement volume adjustment element to tilt the swashplate and thus adjust the tilt angle. If the tilt angle of the displacement volume adjustment element is changed in one direction such that the fan speed error is reduced, the fan speed of the hydraulically operated fan will approach the fan speed setpoint. This ensures the stable operating performance of the hydraulic fan system.

[0011] In step e), assuming ideal performance of the fan system, an ideal tilt current is derived from the fan speed calculated in step b). This ideal tilt current represents the current that should be supplied to the electronic displacement control device (EDC) in order to operate the fan at a certain speed when the hydraulic fan system operates under ideal conditions (i.e., without the influence of disturbances, or at least without the influence of unpredictable disturbances).

[0012] In step f), if the difference between the ideal tilt current and the tilt current adjusted in step d) is higher than a predefined tilt current threshold, a safety-related function / action is performed to prevent damage to the fan, such as preventing the fan from overspeeding. If the ideal tilt current deviates significantly from the adjusted tilt current, disturbances may occur during the operation of the hydraulic fan system.

[0013] In this case, it is preferable to perform certain safety-related actions resulting from the operation under the influence of disturbances; for example, by sending a warning message to the control interface, or by shutting down the system to avoid severe damage to the hydraulic fan system or the fan (blades), certain safety-related actions resulting from the operation under the influence of disturbances are performed. By defining the magnitude of the deviation threshold, the system operator can choose between setting a rather low threshold or defining a higher threshold that results in a more disturbance-resistant system performance, and this rather low threshold will already cause a safety action when the difference between the ideal tilt current and the supplied tilt current is low.

[0014] In one embodiment of the present invention, additional steps e) and f) are at least partially executed in time parallel (simultaneously) with steps c) and d). In the context of the present invention, the phrase "in time parallel" or simultaneously is not limited to executing steps c) and e) in parallel and then steps d) and f). "In time parallel" will be considered to be substantially in parallel in time, which means that for example steps c), e) and f) can be executed simultaneously with the previously mentioned steps, and as an alternative option. However, a person skilled in the art can apply different working sequences to the implemented steps, for example execute step c), then step e), then step f) and finally step d). All sequences of steps c) to f) that start after step b) and end before the method according to the present invention starts again with step a) are covered by the concept of the present invention.

[0015] In another embodiment of the present invention, a speed error threshold can be defined. By doing so, a threshold level can be set, and if the fan speed error exceeds this threshold level, an action is taken. Here, one can consider starting the tilt current adjustment or performing a safety action as mentioned before. By defining the magnitude of the speed error threshold, the sensitivity of the hydraulic fan system to disturbances can be set; the smaller the speed error threshold, the higher the sensitivity of the method for controlling the speed of the hydraulic fan system.

[0016] The method according to the present invention can be applied to controlling a hydraulic fan drive system in which a hydraulic pump and / or a hydraulic motor operates in an open or closed hydraulic circuit. The arrangement of the same or alternative types of additional hydraulic components in the hydraulic circuit of the fan system to provide additional functions and / or safety features for the hydraulic fan system is also covered by the present invention.

[0017] The method according to the present invention can be applied to a hydraulic pump and / or a hydraulic motor in which the displacement volume regulating element is a swash plate or a yoke. In other words, the method can also be applied to an axial piston pump or motor, or a swash plate pump or motor.

[0018] In one embodiment of the present invention, a shut-off valve can be hydraulically arranged between the pump and the motor. The shut-off valve includes a first safety position and a second operating position. In the first safety position, the hydraulic fluid flow between the pump and the motor is reduced or even interrupted, ultimately until the motor speed decreases to a stop, and in the second operating position, the pump and the motor are hydraulically connected to operate the fan.

[0019] In step f), if the difference between the provided tilt current and the ideal tilt current, or the fan speed error, is higher than a predefined tilt current threshold or higher than a predefined speed error threshold, the shut-off valve can be switched from the operating position to the safe position. For example, the thresholds are defined to prevent damage to the fan due to fan overspeed. A possible embodiment of a functional safety action is to switch the shut-off valve from the operating position to the safe position. Depending on the desired application, the shut-off valve can be a two-way valve or a proportional valve. If the shut-off valve is a two-way valve, the switching of the shut-off valve from its operating position to its safe position will disconnect the hydraulic pump from the hydraulic motor and thus shut down the hydraulic motor, which in turn causes the fan to stop / stand still. If the shut-off valve is a proportional valve, the switching from the operating position to the safe position will result in a lower pressure at the motor inlet, reducing the torque and speed of the fan. This may eventually cause the valve to reach its closed position, where the fan speed also decreases until the fan stops.

[0020] An additional or alternative function of switching the shut-off valve in step f) if the difference between the provided tilt current and the ideal tilt current, or the fan speed error, is higher than the corresponding predefined threshold is to send a warning message to the operator, and / or to the control interface, and / or to the user interface of the fan system, and / or to the work machine to which the fan system is installed. After receiving this warning, the system operator or the control interface can perform additional safety actions to eliminate the disturbance and thus readjust the system performance towards the ideal system performance. According to the invention, other safety measures can also be performed, such as an electric shutdown of the machine, reducing the engine speed, or starting a cleaning of the suction system or the air intake grille in order to eliminate the disturbance. Those skilled in the art know many other ways of performing safety actions to respectively maintain the system performance and prevent damage to the fan or the hydraulic fan system.

[0021] The adjustment of the tilt current in step d) can be calculated using a P-type controller, a PI-type controller, a PID-type controller, a fuzzy controller or a predictive controller or a similar type of linear or non-linear controller based on the fan speed error. Those skilled in the art will select an appropriate control architecture depending on the application and the available computing power. The parameters of any of the above controllers can be adjusted in order to obtain a rather rapid controller response or alternatively in order to obtain a slow controller response. The invention also covers the application of computational intelligence methods such as, for example, neural networks, or the application of predictive controllers.

[0022] The ideal swash current can be derived in step e) from a look-up table, matrix, function or similar data structure that assigns values of the ideal swash current to each calculated value of the fan speed. The data structure can be established using measurement values obtained from simulations or experiments, using the hydraulic fan system of the present invention or the results of model-based calculations using the hydraulic fan system. The data structure can represent not only the ideal system performance but also include the average disturbances that affect the ideal system performance. The second option slows down / limits the response of the safety system of the present invention to disturbances other than these average / usual disturbances.

[0023] The hydraulic fan system according to the present invention includes a fan operated by a hydraulic motor. The fan and the motor can be connected, for example, by a shaft and / or a gearbox or similar components that transfer the torque generated by the hydraulic motor to the fan. The system also includes a variable displacement hydraulic pump for driving the hydraulic motor, the variable displacement hydraulic pump including a displacement volume regulating element that can be swashed, wherein the swash angle can be adjusted by controlling the swash current supplied to an electronic displacement control unit. The variable displacement pump and the hydraulic motor are hydraulically connected such that the hydraulic pressure at the pump outlet is transferred to the inlet of the hydraulic motor. The displacement volume regulating element can be, for example, a swash plate that can be swashed such that the volume flow rate and / or the displacement volume of the variable displacement pump can be adjusted. The swash angle can be changed by controlling, for example, the swash current supplied to an electronic displacement control device, which can be, for example, a solenoid, which acts on the displacement volume regulating element to change its swash angle, and thus the electronic displacement control device causes a change in the volume flow rate through the variable displacement pump. The hydraulic fan system also includes means for determining the volume flow rate of the pump. Since there are various methods for determining the volume flow rate of the pump that are obvious to those skilled in the art, those skilled in the art will select an appropriate solution for the selected application.

[0024] In another embodiment, the hydraulic fan system further includes a control unit. The control unit includes one signal connection connected to the means for determining the volume flow rate of the pump and another signal connection connected to the means for setting the fan speed. As described above, the means for determining the volume flow rate of the pump, such as a rotational speed sensor and a swash angle measurement sensor, can be selected from a wide range of devices. The means for setting the fan speed can be, for example, a control interface or a joystick. The two signal connections are not limited to any physical limitations, i.e., the connection can be established by wires or as a wireless connection, and / or the connection can be a bus system or any other communication structure.

[0025] The control unit further includes a fan speed calculation unit for calculating the fan speed based on the determined volume flow rate. The fan speed calculation unit may include means for storing calculation rules and / or measured values based on which the fan speed can be determined. The control unit further includes a fan speed error determination unit for determining the fan speed error by comparing the calculated fan speed with the fan speed set by the fan speed setting means. Based on this comparison, the control unit supplies an adjusted tilt current to the displacement volume control unit so that the volume flow rate can be adjusted to reduce the fan speed error. As previously mentioned, the displacement volume of the variable displacement hydraulic pump or the volume flow rate is adjusted by adjusting the tilt current supplied to the displacement control unit of the pump or motor unit.

[0026] The control unit may include a controller for calculating the tilt current supplied to the electronic displacement control unit based on the determined fan speed error. For example, by applying a control architecture such as a PI-type or PID-type controller, the adjustment of the current can be obtained directly or indirectly from the fan speed error. If a computer or a microcontroller is used as the control unit, the fan speed calculation unit, the fan speed error determination unit, and the fan grille clogging detection unit may be designed as separate computers or devices according to the concept of the present invention, or may be designed as units sharing the same computer and / or microcontroller and / or device according to the concept of the present invention.

[0027] The control unit may further include a fan grille clogging detection unit for performing functional safety actions in the case where, for example, the fan grille is clogged with dirt or debris. These actions can prevent damage to the fan caused by, for example, fan overspeed. If the difference between the adjusted tilt current and the ideal tilt current derived from the calculated fan speed, i.e., the fan speed error, is higher than a predefined threshold, safety-critical actions can be performed. If the tilt current and the ideal tilt current are significantly different, a fault may occur in the hydraulic fan system. The ideal tilt current represents the tilt current that would be necessary if the operating system were under ideal or optimal conditions. The actions that can be caused by the fan grille clogging detection unit can be critical to safety, and these actions are, for example: shutting down the fan system, sending a notification, reducing the fan torque or fan speed, changing the relevant calculation parameters (i.e., the parameters responsible for calculating the tilt current based on the fan speed error), or similar safety-critical measures.

[0028] The fan grille blockage detection unit according to the present invention can be able to hydraulically switch the shut-off valve arranged between the hydraulic pump and the hydraulic motor. The shut-off valve includes an operating position and a safety position. In the operating position, the pump and the motor are hydraulically connected, and in the safety position, the hydraulic connection between the pump and the motor is interrupted. The shut-off valve can be implemented as a two-position valve having the two above-mentioned positions, or as a proportional valve, in which the fluid connection between the pump and the motor is fully opened in the operating position of the shut-off valve, and the more the shut-off valve is switched towards its safety position, the more gradually the fluid connection between the pump and the motor decreases. The fan grille blockage detection unit can switch the shut-off valve by, for example, applying hydraulic pressure to the shut-off valve spool or by acting on the shut-off valve spool by means of a solenoid when the difference between the adjusted tilt current and the ideal tilt current or the fan speed error is higher than a predefined threshold for the fan speed error.

[0029] According to another embodiment of the concept of the present invention, the shut-off valve can additionally include a spring that forces the shut-off valve into its safety position. During operation, only when the difference between the supplied / adjusted tilt current and the ideal tilt current or the fan speed error is lower than the corresponding predefined threshold for the tilt current or the fan speed error, the fan grille blockage detection unit forces the shut-off valve into its operating position against the force of the spring or by the fan grille blockage detection unit providing a signal to resist the force of the spring. Alternatively or in addition to being able to switch the shut-off valve, if the difference between the supplied tilt current and the ideal tilt current or the fan speed error is higher than the corresponding predefined threshold, the blockage detection unit can also be able to send a warning message or notification or other signal to the operator, to the control interface or the user interface of the fan system or to the device in which the fan system is installed.

[0030] As mentioned before, there are many options available to those skilled in the art when determining the volumetric flow rate of the pump. The volumetric flow rate can be directly measured by a flow sensor, or indirectly measured by measuring other parameters that can be used to calculate the volumetric flow rate. For example, the volumetric flow rate can be calculated based on the rotational speed of the pump measured by a rotational speed sensor and based on the displacement tilt angle of the pump measured by a tilt angle sensor.

[0031] The measured values and / or calculation results can be stored in a storage unit for accessible use for error detection condition monitoring, predictive maintenance or similar purposes. In particular, the values of the volumetric flow rate, the fan speed, the fan speed error, the tilt current and / or the ideal tilt current are of particular interest because they allow an assertion about the current wear state of the system or about disturbances such as dirt or debris that clog the fan grille and affect the system.

[0032] According to the present invention, the displacement volume adjusting element of the hydraulic motor and / or pump can be a swash plate or a yoke. In other words, an inclined shaft pump or motor or a swash plate pump or motor can be used.

[0033] The hydraulic fan system of the present invention can be used as a hydraulic suction or blowing system, or as a hydraulic ventilation device in a hydraulic work vehicle or machine. The hydraulic work vehicle can be, for example, a road sweeping device or a road / channel maintenance vehicle or a snow removal vehicle. Description of the Drawings

[0034] The present invention, generally described above, will now be described in further detail with the aid of the drawings, in which preferred embodiments and preferred design possibilities are shown. However, these preferred embodiments do not limit the scope of the concept of the present invention. The preferred embodiments shown can be combined with each other without departing from the spirit of the present invention. In addition, modifications within the knowledge and capabilities of those skilled in the relevant technical field can be made without departing from the spirit of the present invention. In the figures:

[0035] Figure 1 A hydraulic diagram of a hydraulic fan system according to the present invention is shown;

[0036] Figure 2 A flowchart of a method for controlling the speed of a hydraulic fan system according to the present invention is shown; and

[0037] Figure 3 A schematic diagram of a control unit according to the present invention is shown. Detailed Description of the Invention

[0038] Figure 1 A hydraulic fan system 1 according to the present invention is shown. The hydraulic fan system 1 includes a fan 25 which is connected to a hydraulic motor 20 via a shaft and / or a gear arrangement. The outlet of the hydraulic motor 20 is connected to a hydraulic tank 5 via a motor outlet line 24. A hydraulic pump 10 with variable displacement is hydraulically connected to the tank 5 via a pump suction line 14. The pump outlet is connected to a shut-off valve 30 via a pump pressure line 16, wherein the outlet of the shut-off valve 30 is hydraulically connected to a motor inlet line 22 which can transmit hydraulic pressure to the inlet line 22 of the hydraulic motor 20.

[0039] The shut-off valve 30 includes a safety position 32 (also referred to as a closed position) and an operating position 34. If the spring 38 is not counteracted by the force exerted by the shut-off valve actuator 36, the spring 38 holds the shut-off valve 30 in the closed / safety position 32 of the shut-off valve 30. Figure 1The shut-off valve 30 shown in the is designed as a two-position valve, which can be switched between a safety position 32 and an operating position 34. In the safety position 32, the pump pressure line 16 and the motor inlet line 22 are hydraulically disconnected, while in the operating position 34, the pump pressure line 16 and the motor inlet line 22 are hydraulically connected. However, the shut-off valve 30 can also be designed as a proportional valve providing an opening that can be reduced in proportion to the force of the shut-off valve actuator 36. The shut-off valve actuator 36 is connected to a control unit 40 via a safety action signal connection 35, which control unit 40 is able to send a safety action signal 52 (see Figure 2 and Figure 3 ).

[0040] The hydraulic pump 10 comprises a displacement volume adjustment element 15 to control a volume flow 19 of the pump 10. The volume flow 19 of the pump 10 is determined by a rotation speed sensor 17 and an inclination angle sensor 18, which are connected to a control unit 40 via a volume flow signal connection 41. The control unit 40 is also capable of sending a tilting current 12 to an electronic displacement control unit (EDC) connected to the displacement volume adjustment element 15. The tilting angle of the displacement volume adjustment element 15 is set depending on the tilting current 12.

[0041] Figure 2 A flow chart showing a method for controlling the speed of a hydraulic fan system 1, which is exemplarily shown in FIG. Figure 1 The method comprises steps a) to d) and steps e) to f). The method can be applied to control a hydraulic system including a blower 25, which is operated by a hydraulic motor 20 driven by a variable displacement hydraulic pump 10. The variable displacement hydraulic pump 10 comprises a displacement volume adjustment element 15 (e.g. a swash plate or a yoke), the inclination angle 13 of which is controlled by an inclination current 12 supplied to the EDC. Figure 2 The method according to the invention shown comprises the following steps which are repeatedly and / or periodically performed (see Figure 1 System components in (

[0042] Step a):

[0043] The volumetric flow rate 19 of the hydraulic pump 10 is determined by measuring the operating parameters of the hydraulic system. The volumetric flow rate 19 of the pump 10 can be determined, for example, by means for measuring the rotational speed 11 of the pump 10 and the tilt angle 13 of the displacement volume regulating element 15. Since the tilt angle 13 of the displacement volume regulating element 15 directly affects the displacement volume of the hydraulic pump 10, in this example, the volumetric flow rate 19 of the pump 10 can be calculated by multiplying the rotational speed 11 of the pump 10 by the displacement volume per revolution of the pump 10. Alternatively, the volumetric flow rate of the pump 10 can be measured more directly using a volumetric flow rate sensor, which can be installed in the hydraulic line 16 connecting the pump outlet to the motor inlet line 22.

[0044] Step b):

[0045] Using the equation representing the fan system 1, calculate the fan speed 45 based on the volumetric flow rate 19 in step a). This equation represents the technical correlation between the volumetric flow rate 19 and the fan speed 45, and can be derived by creating a physical model of the hydraulic fan system 1 or by training a neural network using training data suitable for assigning values of the fan speed 45 to corresponding values of the volumetric flow rate 19, where the training data is measured, for example, during the operation of the hydraulic fan system 1.

[0046] Step c):

[0047] Determine the fan speed error 48 by comparing the calculated fan speed 45 in step b) with the fan speed setpoint 43 set by the fan speed setting device 47, for example, according to the operator input. This comparison is performed, for example, by subtracting the fan speed value 45 calculated in step b) from the fan speed setpoint 43.

[0048] Step d):

[0049] Adjust the tilt current 12 supplied to the electronic displacement control unit (EDC) to regulate the tilt angle 13 of the displacement volume regulating element 15 such that the fan speed error 48 is reduced. In other words, the tilt current 12 is calculated based on the fan speed error 48 determined in step c) and is sent to the electronic displacement control unit (EDC) to regulate the tilt angle 13 of the displacement volume regulating element 15 (e.g., swash plate or yoke). Thereby, the volumetric flow rate 19 of the pump 10 is increased or decreased.

[0050] The tilt current 12 can be supplied to a solenoid acting on the displacement volume regulating element 15, thereby setting the tilt angle 13 of the displacement volume regulating element 15 in proportion to the tilt current.

[0051] Assume that the fan speed setpoint 43 is higher than the calculated fan speed 45. The tilt current 12 can be adjusted in a direction such that the tilt angle of the displacement volume adjustment element 15 increases, which results in an increase in the volume flow rate 19 of the pump 10 and thus a higher calculated fan speed 45. Therefore, if a proportional controller (P-controller) is installed, for example, the fan speed error 48 between the fan speed setpoint 43 and the calculated fan speed 45 is reduced, and the fan speed error 48 is multiplied by a constant factor to determine the tilt current 12. However, those skilled in the art know various types of controllers suitable for calculating the tilt current adjustment based on the fan speed error 48.

[0052] As Figure 2 shown, steps e) and f) are performed substantially simultaneously with steps c) and d). In step e), the ideal tilt current is derived from the calculated fan speed 45, assuming that the fan system 1 has ideal performance. Starting from the calculated fan speed 45 in step e), the ideal tilt current value 55 is determined by, for example, means of a look-up table, matrix, or similar method that describes the relationship between the fan speed and the tilt current under ideal conditions. This means that for each calculated fan speed 45, an ideal tilt current value 55 can be associated. Here, different physical models or disturbances can be considered at a theoretical level.

[0053] In the following step f), the ideal tilt current value 55 determined in step e) is compared with the tilt current value 12 adjusted in step d), and the ideal tilt current value 55 determined in step e) is supplied to the electronic displacement control device EDC. If the difference between the two currents is higher than a predefined threshold, a safety action 52 is performed to prevent damage to the fan 25, for example, due to fan overspeed. If, for example, the volume flow rate 19 or pressure in the inlet line 22 of the hydraulic motor 20 causes the pressure drop across the hydraulic motor 20 or the volume flow rate 19 through the hydraulic motor 20 to be too high, fan overspeed may occur. This results in a very high torque and / or rotational speed on the shaft connecting the fan 25 to the hydraulic motor 20.

[0054] The predefined threshold can define how quickly the hydraulic fan system 1 reacts to deviations from this ideal performance. The higher the predefined threshold is set, the slower or more delayed (smoother) the system will react to disturbances, which results in an increase or decrease in the delivered tilt current compared to the ideal tilt current.

[0055] Figure 3 shows a schematic diagram of the control unit 40 according to the invention. In Figure 3Among them, the solid arrows represent the physical connections outside the control unit 40. Among these, the dashed lines represent the communication parameters within the control unit 40. These communication parameters can be shared via the physical connections, but can also be virtually exchanged between the subunits of the control unit 40. The control unit 40 includes a volumetric flow signal connection 41. Sensors 17, 18 for determining the rotational speed 11 of the pump 10 and the tilt angle 13 of the displacement volume regulating element 15 are connected to the control unit 40 via this volumetric flow signal connection 41. The control unit 40 further includes a fan speed setpoint signal connection 42. The fan speed setpoint signal connection 42 is used to receive a fan speed setpoint 43 from a control interface or a similar fan speed setting device 47. The sensor signals 17 and 18 sent via the signal connection 41 are processed in a fan speed calculation unit 44. The fan speed calculation unit 44 calculates a fan speed 45 based on the sensor signals 17 and 18. The calculated fan speed 45 is internally distributed to a fan speed error determination unit 46 and a fan grille clogging detection unit 50. The fan speed error determination unit 46 can determine a fan speed error 48 by comparing the calculated fan speed 45 with the fan speed setpoint 43. Based on the fan speed error 48, the controller 60 supplies an adjusted tilt current 12 to the electronic displacement control unit EDC via a tilt current line 49 as an output of the control unit 40.

[0056] The fan grille clogging detection unit 50 can perform a functional safety action 52. This functional safety action 52 can be sent as an output of the control unit 40, or can be processed inside the control unit 40 to adjust the calculation of the tilt current 12 based on the fan speed error 48 executed by the controller 60. The fan grille clogging detection unit 50 selects and calculates which safety-critical action should be performed based on the calculated tilt current 12 and the calculated fan speed 45. Among them, the fan grille clogging detection unit 50 can derive an ideal tilt current 55 from the calculated fan speed 45 in order to compare this ideal tilt current 55 with the tilt current 12 supplied to the electronic displacement control unit EDC.

[0057] If the supplied tilt current 12 deviates from the ideal tilt current 55 by more than a predetermined tilt current threshold, the control unit 40 causes a safety-critical action, such as reducing the current supplied to the shut-off valve actuator 36 in order to reduce or close the hydraulic connection between the pump pressure line 16 and the motor inlet line 22, or reducing or interrupting the current supply to the electronic displacement control unit EDC in order to tilt the displacement volume regulating element 15 back, thereby reducing the volumetric flow via the motor inlet line 22 to the hydraulic motor 20.

[0058] From the above disclosure, the drawings and the claims, it will be understood that the method for controlling the speed of a hydraulic fan system and the hydraulic fan system according to the present invention offer many possibilities and advantages over the prior art. Those skilled in the relevant art will further understand that, without departing from the spirit of the present invention, further modifications and changes to the method and the hydraulic fan system for controlling the speed of a hydraulic fan system known in the art can be made to the method and the hydraulic fan system according to the present invention, and thus all such modifications and variations are within the scope of the claims and are covered by the claims. It should be further understood that the above examples and embodiments are for illustrative purposes only, and all various modifications, changes or combinations inspired by the above examples and embodiments to those skilled in the relevant art are included in the spirit and scope of the present application.

[0059] List of Reference Numerals

[0060] 1 Hydraulic fan system

[0061] 5 Tank

[0062] 10 Hydraulic pump

[0063] 11 Speed pump

[0064] 12 Tilting current

[0065] 13 Tilting angle

[0066] 14 Pump suction line

[0067] 15 Displacement volume regulating element

[0068] 16 Pump pressure line

[0069] 17 Speed sensor

[0070] 18 Angle sensor

[0071] 19 Volume flow rate

[0072] 20 Hydraulic motor

[0073] 22 Motor inlet line

[0074] 24 Motor outlet line

[0075] 25 Fan

[0076] 30 Shut-off valve

[0077] 32 Safe position

[0078] 34 Operating position

[0079] 35 Safe action signal connection

[0080] 36 Shut-off valve actuator

[0081] 38 Springs

[0082] 40 Control Unit

[0083] 41 Volume Flow Signal Connection

[0084] 42 Fan Speed Setpoint Signal Connection

[0085] 43 Fan Speed Setpoint

[0086] 44 Fan Speed Calculation Unit

[0087] 45 Calculated Fan Speed

[0088] 46 Fan Speed Error Determination Unit

[0089] 47 Fan Speed Setting Device

[0090] 48 Fan Speed Error

[0091] 49 Inclination Current Circuit

[0092] 50 Fan Grill Blockage Detection Unit

[0093] 52 Safety Action

[0094] 55 Ideal Inclination Current Value

[0095] 60 Controller

[0096] EDC Electronic Displacement Control Unit

Claims

1. A method for controlling the speed of a hydraulic fan system (1), the hydraulic fan system (1) comprising a fan (25) operated by a hydraulic motor (20), the hydraulic motor (20) being driven by a variable displacement hydraulic pump (10), the variable displacement hydraulic pump (10) comprising a displacement volume regulating element (15), the swash angle (13) of the displacement volume regulating element (15) being adjustable by controlling the swash current (12) supplied to an electronic displacement control unit (EDC), the method comprising the following repeating steps: a) determining the volumetric flow rate (19) of the pump (10) by measuring the operating parameters of the pump (10); b) using an equation representing the fan system (1), calculating the fan speed (45) based on the volumetric flow rate (19) determined in step a); c) determining a fan speed error (48) by comparing the calculated fan speed (45) of step b) with a fan speed setpoint (43) provided by an input device (47); d) adjusting the swash current (12) supplied to the electronic displacement control unit (EDC) to adjust the swash angle (13) of the displacement volume regulating element (15) such that the fan speed error (48) is reduced; wherein, the following steps are performed simultaneously with steps c) to d): e) deriving an ideal swash current value (55) from the calculated fan speed (45) of step b); f) if the difference between the ideal swash current value (55) derived in step e) and the adjusted swash current (12) adjusted in step d) is higher than a swash current threshold, performing a safety action (52) to prevent damage to the fan (25).

2. The method according to claim 1, wherein, if the fan speed error (48) determined in step c) is higher than a speed error threshold, a safety action (52) for preventing damage to the fan (25) is performed.

3. The method according to claim 1, wherein, in step f), a shut-off valve (30) is switched from an operating position (34) to a safety position (32), in the operating position (34), the pump (10) and the motor (20) are hydraulically connected, and in the safety position (32), the hydraulic connection between the pump (10) and the motor (20) is reduced or interrupted.

4. The method according to any one of claims 1 to 3, wherein, if the swash current threshold or the speed error threshold is exceeded, a warning signal is sent to an operator, to a control interface, or to a user interface of the fan system (1), or to a work machine comprising the fan system (1).

5. The method according to any one of claims 1 to 3, wherein, the swash current adjustment in step d) is calculated based on the fan speed error (48) using a P-type controller, a PI-type controller, a PID-type controller, a fuzzy controller or a predictive controller (60) or a linear or non-linear controller of a similar type.

6. The method according to any one of claims 1 to 3, wherein, the ideal tilt current value (55) in step e) is derived from a look-up table, matrix, function or similar data structure that maps each value of the calculated fan speed (45) to a value of the ideal tilt current (55).

7. A hydraulic fan system (1), comprising: a fan (25) operated by a hydraulic motor (20), a variable displacement hydraulic pump (10) for driving the hydraulic motor (20), the variable displacement hydraulic pump (10) including a tiltable displacement volume regulating element (15), the tilt angle (13) of the displacement volume regulating element (15) being adjustable by a control unit (40) controlling a tilt current (12), the tilt current (12) being supplyable to an electronic displacement control device (EDC); a fan speed setting device (47) for setting a fan speed set value (43) according to an input command; a device for determining the volume flow rate (19) of the pump (10); wherein the control unit (40) includes: a volume flow rate signal connection (41) connected to the device for determining the volume flow rate (19) of the pump (10), a fan speed set value signal connection (42) connected to the electronic displacement control device (EDC), a fan speed calculation unit (44) for calculating a fan speed (45) based on the determined volume flow rate (19), a fan speed error determination unit (46) for determining a fan speed error (48) by comparing the calculated fan speed (45) with the fan speed set value (43) set by the fan speed setting device (47), and wherein the control unit (40) is capable of adjusting the tilt current (12) supplied to the electronic displacement control device (EDC) such that the tilt angle (13) can be adjusted to reduce the fan speed error (48), wherein the control unit (40) further includes a fan grille blockage detection unit (50) for assigning an ideal tilt current value (55) to each calculated fan speed (45), comparing the ideal tilt current value (55) with the value of the tilt current (12) adjusted by the control unit (40), and if the difference between the ideal tilt current value (55) and the adjusted tilt current (12) value is higher than a tilt current threshold, the fan grille blockage detection unit (50) performs a safety action (52) for preventing damage to the fan (25).

8. The hydraulic fan system (1) according to claim 7, wherein, If the fan speed error (48) determined by the fan speed error determination unit (46) is higher than the speed error threshold, the control unit (40) can perform a safety action (52) to prevent damage to the fan (25).

9. The hydraulic fan system (1) according to claim 7, wherein, If the tilt current threshold is not exceeded, the fan grille blockage detection unit (50) can switch the shut-off valve (30) from the safety position (32), where the hydraulic connection between the pump (10) and the motor (20) is reduced or interrupted, to the operating position (34), where the pump (10) and the motor (20) are hydraulically connected.

10. The hydraulic fan system (1) according to claim 9, wherein, If the tilt current threshold is not exceeded, the fan grille blockage detection unit (50) forces the shut-off valve (30) into the operating position (34) of the shut-off valve (30) against the force of the spring (38).

11. The hydraulic fan system (1) according to any one of claims 7 to 10, wherein, If the tilt current threshold is exceeded, the fan blockage detection unit (50) can send a warning message to the operator, to the control interface or to the user interface of the fan system (1), or to the host device.

12. The hydraulic fan system (1) according to any one of claims 7 to 10, wherein, The volume flow rate (19) of the pump (10) is determined based on the rotational speed (11) of the pump (10) measured by the rotational speed sensor (17) and based on the tilt angle (13) of the displacement volume adjustment element (15) measured by the tilt angle sensor (18).

13. The hydraulic fan system (1) according to any one of claims 7 to 10, wherein, Values of the volume flow rate (19), fan speed (45), fan speed error (48), tilt current (12) and / or ideal tilt current (55) are stored in a memory unit so as to be accessible for error detection, condition monitoring, predictive maintenance or similar purposes.

14. The hydraulic fan system (1) according to any one of claims 7 to 10, wherein, The control unit (40) includes a controller (60) for calculating the tilt current (12).

15. The hydraulic fan system (1) according to claim 14, wherein, The controller (60) is a PI type controller.

16. The hydraulic fan system (1) according to any one of claims 7 to 10, wherein, The pump (10) and the motor (20) operate in an open or closed hydraulic circuit.

17. The hydraulic fan system (1) according to any one of claims 7 to 10, wherein, The displacement volume adjustment element (15) is a swash plate or a yoke.

18. Use of the hydraulic fan system (1) according to any one of claims 7 to 10 as a hydraulic suction or blowing system or as a hydraulic ventilation device in a hydraulic work vehicle or machine.

19. Use of the hydraulic fan system (1) according to claim 18, wherein, the hydraulic work vehicle is a road sweeping device.

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