Fan drive system

Abstract

A hydraulic fan system and a method for controlling the speed of the hydraulic fan system. The fan system comprises a fan operated by a hydraulic motor driven by a hydraulic variable displacement pump comprising a displacement volume adjustment element. The tilt angle of the displacement volume adjustment element can be adjusted by controlling a ramp current supplied to an electronic displacement control unit. The hydraulic fan system further comprises a means for determining a volumetric flow rate of the pump and a control unit including a signal connection to the means for determining the volumetric flow rate of the pump, a signal connection to a fan speed setting device, a fan speed calculation unit for calculating a fan speed from the determined volumetric flow rate, and a fan speed error determination unit for determining a fan speed error by comparing the calculated fan speed with a fan speed set by the fan speed setting device. The control unit can supply an adapted ramp current to the electronic displacement control unit to adjust the tilt angle of the displacement volume adjustment device, whereby the volumetric flow rate can be adapted to reduce the fan speed error, an ideal ramp current value being derived from the calculated fan speed, and a safety action is performed to prevent damage to the fan when the difference between the ideal ramp current value and the adapted ramp current is greater than a ramp current threshold.

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 sweepers. These vehicles are often propelled by an internal combustion engine that drives a hydraulic pump. The hydraulic pump is hydraulically connected to a hydraulic motor that drives a fan, for example, to generate an air flow through a suction device of the vehicle.

[0003] In the prior art, hydraulic fan systems often include hydraulic means for controlling the speed of the fan. These hydraulic control means are usually inefficient, and the options for controlling the fan speed are limited and pressure-controlled (load-dependent), which means that when the suction fan or the grille covering the suction fan is blocked, the fan speed increases until sufficient air flow is restored. This can potentially lead to negative consequences as the fan may accelerate to an excessive speed that can cause damage to the fan. To prevent such fan overspeeds, a hydraulic orifice or valve can be placed in the hydraulic circuit between the pump and the motor, and the valve reduces the pressure at the motor inlet when the hydraulic flow exceeds a certain limit. When the motor inlet pressure is reduced by such a valve, an efficiency loss occurs and the efficiency of today's fan drive systems is significantly degraded. Furthermore, the current operating state of fan drive systems according to the prior art is not monitored, so the machine operator has no insight into the working operations of the machine and cannot identify potential hazards, such as blockages of the fan grille during machine operation.

[0004] For example, U.S. Patent Application Publication No. 2009 / 0025661A1 discloses a drive system for a cooling fan of a working machine. The rotational speed of the cooling fan is controlled to an optimal speed depending on the cooling water temperature. Lower and upper limiters are used to calculate a target displacement angle, which is then used to calculate a target control current.

[0005] U.S. Patent Application Publication No. 2011 / 0011356A1 describes a device for controlling a cooling fan. The cooling fan is driven by a hydraulic motor supplied by a hydraulic pump. Depending on various measurements taken, the supply to the hydraulic motor is adjusted by a volume flow regulator. A target flow control device sets a target value for the flow rate supplied to the hydraulic motor.

[0006] U.S. Patent Application Publication No. 2011 / 0293439A1 discloses a device for reducing volumetric flow loss of pressurized hydraulic fluid when the rotational speed of a cooling fan is increased to a target rotational speed. For this purpose, in particular, acceleration characteristics are provided, which are predetermined by an acceleration characteristic setting unit based on the rotational speed of the cooling fan. [Overview of the Initiative] [Problems that the invention aims to solve]

[0007] Therefore, an object of the present invention is to provide a hydraulic fan drive system capable of controlling the fan speed independently of the working fluid flow of the associated circuit. Such control can reduce hydraulic losses and thus improve the efficiency of the fan drive system. Furthermore, fan speed control independent of 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 a hydraulic fan system capable of transmitting notifications about the current state, derived from the current state of the hydraulic fan system, to the machine operator. The system of the present invention is also capable of identifying fault conditions, such as clogging of a major system component. [Means for solving the problem]

[0008] The object of the present invention is solved by the method for controlling the (rotational) speed of the hydraulic fan system described in claim 1, and by the hydraulic fan system described in claim 8.

[0009] The hydraulic fan system according to the present invention comprises a fan operated by a hydraulic motor. The hydraulic motor is driven by a hydraulic variable displacement pump having a displacement volume adjustment element whose tilt angle is controllable by a gradient current supplied to an electronic displacement control unit (EDC). In the sense of the present invention, the gradient current, also called the pump current or pump control current, is a current supplied to a tilt angle adjustment means capable of setting the tilt angle, and the magnitude of the gradient current supplied to the tilt angle adjustment means determines the tilt angle.

[0010] A method for controlling the speed of a hydraulic fan system includes the following iterative steps:

[0011] In the first step a), the operating parameters of the pump are measured, for example, by means of measuring at least the rotational speed of the pump and the inclination angle of the displacement volume adjustment element, or by other comparable variables, in order to determine the volumetric flow rate of the pump. In addition to the rotational speed of the pump and the inclination angle of the displacement volume adjustment element, the volumetric flow rate of the pump may be determined, for example, by measuring the suction force and the pressure difference between the pump inlet and the pump outlet. However, it is common sense for those skilled in the art to measure or determine other comparable variables in order to determine the volumetric flow rate.

[0012] In the second step b), the fan speed is calculated based on the volumetric flow rate determined in step a) using equations representing the fan system. These equations can be physical equations, for example, a state-space matrix or model that acts as a digital twin of the hydraulic fan system. The equations may also be used in the form of a neural network, which, for example, receives training data in the form of measurements from a real or idealized model of a hydraulic fan system and then assigns fan speed values ​​to input values ​​for volumetric flow rates.

[0013] In step c), the fan speed error value is determined by comparing the fan speed calculated in step b) with the fan speed setpoint. The fan speed setpoint can be preset by the operator, or it can be set by the control unit. The fan speed setpoint can also be set by a mechanical interface, where the mechanical movement of the fan speed setting device is converted into an electrical signal representing the fan speed setpoint. This electrical signal can then be compared with the electrical signal representing the calculated fan speed.

[0014] In step d), the gradient current supplied to the electronic displacement control unit to adjust the tilt angle of the displacement volume adjustment element is adapted. This adjusts the tilt angle of the displacement volume adjustment element so that the fan speed error can be reduced. Many different solutions are available for how the gradient current adjusts the tilt angle of the displacement volume adjustment element. For example, the gradient current could be supplied to a solenoid acting on the swash plate, which in turn acts as a displacement volume adjustment element to tilt the swash plate and, as a result, adjust the tilt angle. When the tilt angle of the displacement volume adjustment element changes in a direction that reduces the fan speed error, the fan speed of the hydraulically operated fan approaches the fan speed setpoint. This ensures stable operation of the hydraulic fan system.

[0015] In step e), the ideal gradient current is derived from the calculated fan speed in step b), which assumes ideal operation of the fan system. This ideal gradient current represents the current that must be supplied to the electronic displacement control (EDC) to operate the fan at a specific speed when the hydraulic fan system is operating under ideal conditions, i.e., without the influence of disturbances, or at least without the influence of unpredictable disturbances.

[0016] In step f), if the difference between the ideal gradient current and the gradient current adapted in step d) is greater than a predefined gradient current threshold, safety-related functions / actions are performed to prevent fan damage, for example, to prevent the fan from overspeeding. If the ideal gradient current deviates significantly from the adapted gradient current, a disturbance may be occurring during the operation of the hydraulic fan system.

[0017] In this case, it may be preferable to perform certain safety-related actions resulting from 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 fan (blades). By defining the magnitude of the deviation threshold, the system operator may choose to either set a fairly low threshold that immediately invokes a safety action when the difference between the ideal gradient current and the provided gradient current is small, or define a larger threshold that leads to system operation that tolerates more disturbances.

[0018] In one embodiment of the present invention, additional steps e) and f) are performed at least partially in parallel (concurrently) with steps c) and d). In the context of the present invention, the terms “in parallel” or “concurrently” are not limited to performing steps c) and e) in parallel, and then steps d) and f). “In parallel” means that steps c), e), and f) can be performed concurrently with the preceding ones, and that they are treated as substantially parallel in time, and as alternative options. However, those skilled in the art may apply different working orders to the embodied steps, for example, performing step c), then step e), then step f), and finally step d). All orders of steps c) through f) that begin after step b) and end before starting the method according to the present invention again in step a) are encompassed in the concept of the present invention.

[0019] In another embodiment of the present invention, a speed error threshold can be defined. By doing so, a threshold level can be set to deal with the case when the fan speed error exceeds this threshold level. Here, one might consider initiating gradient current adaptation or taking the safety action described above. 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 more sensitive the method for controlling the speed of the hydraulic fan system is.

[0020] The method according to the present invention can be applied to control a hydraulic fan drive system in which a hydraulic pump and / or hydraulic motor operates in an open hydraulic circuit or a closed hydraulic circuit. The invention also includes arranging additional hydraulic components of the same or alternative types in the hydraulic circuit of a fan system to provide additional functions and / or safety features to the hydraulic fan system.

[0021] The method according to the present invention may also be applied to hydraulic pumps and / or hydraulic motors, where the displacement volume adjustment element is a swash plate or yoke. In other words, the method can also be applied to swash-shaft or swash-plate pumps or motors.

[0022] In one embodiment of the present invention, a shut-off valve may be hydraulically positioned between the pump and the motor. The shut-off valve has a first safety position in which the flow of working fluid between the pump and the motor is reduced or even shut off until the motor speed is eventually reduced to a stop, and a second operating position in which the pump and motor are hydraulically connected to operate the fan.

[0023] In step f), if the difference between the provided gradient current and the ideal gradient current is greater than a predefined gradient current threshold, or if the fan speed error is greater 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 overspeed. One possible embodiment of functional safe operation is switching the shut-off valve from the operating position to the safe position. The shut-off valve can be a two-position valve or a proportional valve depending on the desired application. If the shut-off valve is a two-position valve, switching the shut-off valve from its operating position to its safe position disconnects the hydraulic pump from the hydraulic motor, and therefore stops the hydraulic motor, which then stops / quiets the fan. If the shut-off valve is a proportional valve, switching from the operating position to the safe position lowers the pressure at the motor inlet, reducing the fan torque and speed. This also reduces the fan speed until the valve is eventually moved to its closed position and stopped.

[0024] An additional or alternative function to the switching of the shut-off valve in step f) is to send a warning message to the operator and / or the control interface and / or the user interface of the fan system and / or the work machine to which the fan system is installed if the difference between the provided gradient current and the ideal gradient current, or the fan speed error, is greater than a corresponding predefined threshold. After receiving this warning notification, the system operator or control interface may perform additional safety actions to eliminate the disturbance, thereby readjusting the system operation to ideal system operation. According to the present invention, other safety measures may also be performed to eliminate the disturbance, such as electrically shutting down the machine, reducing the engine speed, or initiating cleaning of the intake system or intake grille. Those skilled in the art know of many other ways to perform safety actions to maintain system operation and prevent damage to the drive fan or hydraulic fan system, respectively.

[0025] The gradient current fit in step d) can be calculated based on the fan speed error using a P-, PI-, PID-, fuzzy, or predictive control device, or a similar type of linear or nonlinear control device. A suitable control architecture will be selected by those skilled in the art, depending on the available application and computing power. The parameters of any of the above-described control devices may be adjusted to obtain a fairly fast or, conversely, a slow control device response. For example, applications of computer intelligence methods, such as neural network or predictive control device applications, are also included in the present invention.

[0026] The ideal ramp current can, in step e), be derived from a reference table, matrix, function, or similar data structure that assigns a value of the ideal ramp current to all values of the calculated fan speed. The data structure may be set using measurement values obtained from simulations or experiments by means of the hydraulic fan system according to the invention or by using the results of model-based calculations of the hydraulic fan system. The data structure may not only represent ideal system operation but may also include average disturbances that affect ideal system operation. This second option slows down / limits the response of the safety system according to the invention to disturbances outside these average / normal disturbances.

[0027] The hydraulic fan system according to the invention comprises a fan actuated by a hydraulic motor. The fan and the motor can be connected, for example, by a shaft and / or a gearbox, or by a similar means for transmitting the torque generated by the hydraulic motor to the fan. The system further comprises a hydraulic variable displacement pump for driving the hydraulic motor, which comprises a tilting displacement adjustment element that can be tilted, and the tilt angle can be adjusted by controlling the ramp 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 transmitted to the inlet of the hydraulic motor. The displacement adjustment element can be, for example, a swash plate, which can be tilted so as to adjust the volumetric flow rate and / or the displacement volume of the variable displacement pump. The tilt angle can be changed, for example, by controlling the ramp current supplied to an electronic displacement control device, which can be, for example, a solenoid acting on the displacement adjustment element and thereby changing its tilt angle, thus resulting in a change in the volumetric flow rate through the variable displacement pump. The hydraulic fan system further comprises means for determining the volumetric flow rate of the pump. Since there are various methods for determining the volumetric flow rate of the pump that will be apparent to a person skilled in the art, the person skilled in the art will select the appropriate solution method for the selected application.

[0028] In a further embodiment, the hydraulic fan system further comprises a control unit. The control unit comprises another signal connection to means for determining the volumetric flow rate of the pump and a signal connection to a device for setting the fan speed. As described above, the means for determining the volumetric flow rate of the pump, for example, a rotational speed sensor and an inclination angle measurement sensor, can be selected from various devices. The fan speed setting device can be, for example, a control interface or a joystick. Neither of the signal connections is restricted by any physical constraints, that is, the connection can be established via a wire or as a wireless connection, and / or the connection can be a bus system or any other communication structure.

[0029] The control unit further comprises a fan speed calculation unit for calculating the fan speed based on the determined volumetric flow rate. The fan speed calculation unit may comprise means for storing calculation rules and / or measured values on a basis on which the fan speed can be determined. The control unit further comprises a fan speed error determination unit for determining a fan speed error by comparing the calculated fan speed with the fan speed set by the fan speed setting device. Based on this comparison, the control unit can provide an adapted bias current to the displacement control unit of the displacement or hydraulic variable displacement pump, thereby adapting the volumetric flow rate to reduce the fan speed error. As described above, the volumetric flow rate of the displacement or hydraulic variable displacement pump is adapted by adjusting the bias current provided to the displacement control unit of the pump or motor unit.

[0030] The control unit may include a control device for calculating the gradient current provided / supplied to the electronic displacement control unit based on the determined fan speed error. This adaptation of the current can be derived directly or indirectly from the fan speed error, for example, by applying a control architecture, such as a PI or PID control device. When a computer or microcontroller is used as the control unit, the fan speed calculation unit, the fan speed error determination unit, and the fan grill clogging detection unit can be designed as separate computers or devices in accordance with the concept of the present invention, or as a unit sharing the same computer and / or microcontroller and / or device in accordance with the concept of the present invention.

[0031] The control unit may further include a fan grill clogging detection unit to perform functional safety actions, for example, if the fan grill becomes clogged with dust or debris. These actions can prevent fan damage, for example, by preventing the fan from overspeeding. If the difference between the adapted gradient current and the ideal gradient current derived from the calculated fan speed, i.e., the fan speed error, is greater than a predefined threshold, a critical safety action may be performed. A large difference between the gradient current and the ideal gradient current may indicate a malfunction in the hydraulic fan system. The ideal gradient current represents the gradient current that would be required if the system were operating under ideal or optimal conditions. Actions that may be triggered by the fan grill clogging detection unit may be critical safety measures, such as shutting down the fan system, sending a notification, reducing fan torque or fan speed, changing relevant calculation parameters, i.e., parameters for calculating the gradient current based on the fan speed error, or similar critical safety measures.

[0032] The fan grill clogging detection unit according to the present invention may be capable of switching a shut-off valve hydraulically positioned between a hydraulic pump and a hydraulic motor. The shut-off valve has an operating position in which the pump and motor are hydraulically connected and a safety position in which the hydraulic connection between the pump and motor is shut off. The shut-off valve may be implemented as a two-position valve having the two positions described above, or as a proportional valve, wherein the fluid connection between the pump and motor is fully open in the operating position of the shut-off valve and gradually decreases as the shut-off valve switches toward its safety position. The fan grill clogging detection unit may be able to switch the shut-off valve by, for example, applying water pressure to the shut-off valve spool, or by acting on the shut-off valve spool with a solenoid when the difference between the adapted gradient current and the ideal gradient current, or the fan speed error, is greater than a predefined threshold for the fan speed error.

[0033] According to another embodiment of the concept of the present invention, the shut-off valve may further comprise a spring that presses the shut-off valve to its safe position. During operation, the shut-off valve is pressed to its operating position by a fan grill clogging detection unit that acts against the force of the spring or provides a signal acting against the force of the spring only when the difference between the supplied / adjusted gradient current and the ideal gradient current, or the fan speed error, is less than a corresponding predetermined threshold for the gradient current or the fan speed error. Instead of or in addition to the shut-off valve being switchable, the clogging detection unit may be capable of transmitting 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 to which the fan system is mounted, if the difference between the supplied gradient current and the ideal gradient current or the fan speed error is greater than a corresponding predetermined threshold.

[0034] As described above, there are many options available to those skilled in the art when determining the volumetric flow rate of a pump. The volumetric flow rate can be measured directly by a flow sensor or indirectly by measuring other parameters that can be used to calculate the volumetric flow rate. For example, the volumetric flow rate can be calculated by an angle sensor based on the rotational speed of the pump, measured by a rotational speed sensor, and based on the displacement angle of the pump, which is also measured.

[0035] Measured and / or calculated values ​​can be stored in a memory unit for access for error detection state monitoring, predictive maintenance, or similar purposes. In particular, values ​​for volumetric flow rate, fan speed, fan speed error, gradient current, and / or ideal gradient current are of special interest because they provide conclusions about the current state of system wear or about disturbances affecting the system, such as dust or debris blocking the fan grille.

[0036] According to the present invention, the displacement volume adjustment element of the hydraulic motor and / or pump can be a swash plate or a yoke. In other words, a swash plate pump or motor can be used.

[0037] The hydraulic fan system of the present invention may be used as a hydraulic suction or blowing system, or as a hydraulic exhaust device for a hydraulic work vehicle or machine. A hydraulic work vehicle could be, for example, a road sweeping device or road / path maintenance vehicle, or a snow removal vehicle.

[0038] As described above, the present invention as a whole is further detailed here with reference to the accompanying drawings illustrating preferred embodiments and possible designs. However, these preferred embodiments do not limit the scope of the idea of ​​the present invention. The shown preferred embodiments can be combined with one another without departing from the spirit of the invention. Furthermore, modifications within the scope of what is possible with the knowledge of those skilled in the art can be implemented without departing from the spirit of the invention. [Brief explanation of the drawing]

[0039] [Figure 1] The hydraulic pressure diagram of the hydraulic fan system according to the present invention is shown. [Figure 2] A flowchart of a method for controlling the speed of a hydraulic fan system according to the present invention is shown. [Figure 3] A schematic diagram of the control unit according to the present invention is shown. [Modes for carrying out the invention]

[0040] Figure 1 shows a hydraulic fan system 1 according to the present invention, comprising a fan 25 connected to a hydraulic motor 20 via a shaft and / or gear mechanism. The outlet of the hydraulic motor 20 is connected to a hydraulic tank 5 via a motor outlet line 24. A variable displacement hydraulic pump 10 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, and the outlet of the shut-off valve 30 is hydraulically connected to a motor inlet line 22, which is capable of transmitting hydraulic pressure to the inlet line 22 of the hydraulic motor 20.

[0041] The shut-off valve 30 has a safety position 32, also called the stop position, and an operating position 34. A spring 38 holds the shut-off valve 30 in its stop / safe position 32 unless counteracted by the force exerted by the shut-off valve actuator 36. The shut-off valve 30 shown in Figure 1 is designed as a two-position valve that can be switched between the safety position 32 and the operating position 34. In the safety position 32, the pump pressure line 16 and the motor inlet line 22 are hydraulically separated, 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 may also be designed as a proportional valve that provides an opening that can be reduced in proportion to the force exerted by the shut-off valve actuator 36. The shut-off valve actuator 36 is connected to a control unit 40 via a safety operation signal connection 35, which is capable of transmitting a safety operation signal 52 (see Figures 2 and 3).

[0042] The hydraulic pump 10 includes a displacement volume adjustment element 15 that controls the volumetric flow rate 19 of the pump 10. The volumetric flow rate 19 of the pump 10 is determined by a rotational speed sensor 17 and an inclination angle sensor 18 connected to a control unit 40 via a volumetric flow rate signal connection 41. The control unit 40 can further transmit an inclination current 12 to an electronic displacement control unit (EDC) connected to the displacement volume adjustment element 15. The inclination angle of the displacement volume adjustment element 15 is set according to the inclination current 12.

[0043] Figure 2 shows a flowchart of a method for controlling the speed of a hydraulic fan system 1, typically shown in Figure 1, and includes steps a) to d) and e) to f). The method can be applied to control a hydraulic system comprising a fan 25, which is actuated by a hydraulic motor 20 driven by a hydraulic variable displacement pump 10. The hydraulic variable displacement pump 10 comprises a displacement volume adjustment element 15, for example, a swash plate or yoke, whose inclination angle 13 is controlled by a gradient current 12 supplied to the EDC. The method according to the present invention, shown in Figure 2, includes the following steps, which are performed repeatedly and / or periodically (see Figure 1 for reference system elements).

[0044] Step a) 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 typically be determined by means for measuring the rotational speed 11 of the pump 10 and the inclination angle 13 of the displacement volume adjustment element 15. Since the inclination angle 13 of the displacement volume adjustment element 15 directly affects the displacement volume of the hydraulic pump 10, the volumetric flow rate 19 of the pump 10 can be calculated in this example 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 may be measured more directly using a volumetric flow sensor, which may be mounted on the hydraulic line 16 connecting the motor inlet line 22 to the pump outlet.

[0045] Step b) The fan speed 45 is calculated using an equation representing the fan system 1, based on the volumetric flow rate 19 in step a). The 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 suitable neural network for assigning the values ​​of the fan speed 45 to the corresponding values ​​of the volumetric flow rate 19, for example, with training data measured during the operation of the hydraulic fan system 1.

[0046] Step c) The fan speed error 48 is determined by comparing the calculated fan speed 45 from step b) with the fan speed setting value 43 set by the fan speed setting device 47, for example, according to the operator's input. The comparison is typically performed by subtracting the fan speed value 45 calculated in step b) from the fan speed setting value 43.

[0047] Step d) The gradient current 12 supplied to the electronic displacement control unit (EDC) is adapted to adjust the inclination angle 13 of the displacement volume adjustment element 15, thereby reducing the fan speed error 48. In other words, the gradient current 12 is calculated based on the fan speed error 48 determined in step c) and sent to the electronic displacement control unit (EDC) to adjust the inclination angle 13 of the displacement volume adjustment element 15, for example, the swash plate or yoke. This increases or decreases the volumetric flow rate 19 of the pump 10.

[0048] The gradient current 12 acts on the displacement volume adjustment element 15 and may be supplied to a solenoid that sets the inclination angle 13 of the displacement volume adjustment element 15 in proportion to the gradient current.

[0049] If the fan speed setting value 43 is greater than the calculated fan speed 45, the gradient current 12 may be adapted in a direction that increases the inclination angle of the displacement volume adjustment element 15, thereby increasing the volumetric flow rate 19 of the pump 10, and thus the calculated fan speed 45 becomes greater. Thus, the fan speed error 48 between the fan speed setting value 43 and the calculated fan speed 45 becomes smaller, and if a proportional control device (P control device) is installed, for example, the fan speed error 48 is multiplied by a constant coefficient to determine the gradient current 12. However, those skilled in the art know of various types of control devices that can be applied to calculate the gradient current adaptation based on the fan speed error 48.

[0050] As shown in Figure 2, steps e) and f) are performed approximately simultaneously with steps c) and d). In step e), the ideal gradient current is derived from the calculated fan speed 45, and the ideal operation of fan system 1 is estimated. Starting from the calculated fan speed 45 in step e), the ideal gradient current value 55 is determined with the help of, for example, a reference table, matrix, or a similar method that describes the relationship between fan speed and gradient current under ideal conditions. This means that an ideal gradient current value 55 can be associated with all calculated fan speeds 45. Here, different physical models or disturbances can be considered at a theoretical level.

[0051] In the next step f), the ideal gradient current value 55 determined in step e) is compared with the gradient current value 12 supplied to the electronic displacement control unit EDC after being adapted in step d). If the difference between the two currents is greater than a predefined threshold, a safety action 52 is performed, for example, to prevent damage to the fan 25 due to overspeeding. Overspeeding of the fan can occur, for example, with respect to the volumetric flow rate 19 or the pressure in the inlet line 22 of the hydraulic motor 20, if the pressure drop in the hydraulic motor 20 is very large, or if the volumetric flow rate 19 through the hydraulic motor 20 is very large. This results in very high torque and / or rotational speed on the shaft connecting the fan 25 to the hydraulic motor 20.

[0052] A predefined threshold can define how quickly the hydraulic fan system 1 responds to deviations from this ideal operation. The higher the predefined threshold is set, the slower or later (smoother) the system's response to disturbances will be, which will result in an increase or decrease in the supplied gradient current compared to the ideal gradient current.

[0053] Figure 3 shows a schematic diagram of the control unit 40 according to the present invention. In Figure 3, solid arrows represent physical connections of the control unit 40 to the outside, and dashed lines represent communication parameters within the control unit 40, which can be shared via physical connections but can also be virtually exchanged between subunits of the control unit 40. The control unit 40 includes a volume flow signal connection 41 through which sensors 17 and 18 for determining the rotational speed 11 of the pump 10 and the inclination angle 13 of the displacement volume adjustment element 15 are connected to the control unit 40. The control unit 40 further includes a fan speed setting signal connection 42 for receiving a fan speed setting value 43 from a control interface or similar fan speed setting device 47. The sensor signals 17 and 18 transmitted via the signal connection 41 are processed by a fan speed calculation unit 44, which calculates the fan speed 45 based on the sensor signals 17 and 18. The calculated fan speed 45 is internally distributed to the fan speed error determination unit 46 and the fan grill clogging detection unit 50. The fan speed error determination unit 46 can determine the fan speed error 48 by comparing the calculated fan speed 45 with the fan speed set value 43. Based on the fan speed error 48, the control device 60 provides / supplies a suitable gradient current 12 as the output of the control unit 40 to the electronic displacement control unit EDC via the gradient current line 49.

[0054] The fan grill clogging detection unit 50 is capable of performing functional safety actions 52, which can be transmitted as an output of the control unit 40, or processed internally within the control unit 40 to adapt the calculation of the gradient current 12 based on the fan speed error 48, which is performed by the control device 60. The fan grill clogging detection unit 50 selects and calculates which critical safety actions should be performed based on the calculated gradient current 12 and the calculated fan speed 45, and the fan grill clogging detection unit 50 is capable of deriving an ideal gradient current 55 from the calculated fan speed 45 in order to compare the ideal gradient current 55 with the gradient current 12 supplied to the electronic displacement control unit EDC.

[0055] If the supplied gradient current 12 is greater than a predetermined gradient current threshold and deviates from the ideal gradient current 55, the control unit 40 invokes critical safety actions, such as reducing the current supplied to the shut-off valve actuator 36 to reduce or close the hydraulic connection between the pump pressure line 16 and the motor inlet line 22, or reducing or shutting off the power supply to the electronic displacement control unit EDC to tilt the displacement volume adjustment element 15 backward, thereby reducing the volumetric flow rate to the hydraulic motor 20 via the motor inlet line 22.

[0056] From the above disclosure and the accompanying drawings and claims, it will be understood that the method and hydraulic fan system for controlling the speed of a hydraulic fan system according to the present invention offers many possibilities and advantages over the prior art. It will also be understood by those skilled in the art that further modifications and changes to the methods and hydraulic fan systems for controlling the speed of a hydraulic fan system known in the art may be made to the methods and hydraulic fan systems according to the present invention without departing from the spirit of the invention; therefore, all such modifications and changes are within the scope and inclusion of the claims. The above examples and embodiments are for illustrative purposes only, and it should be further understood that various modifications, changes, or combinations of embodiments suggested to those skilled in the art, taking them into consideration, are included in the spirit and scope of this application. [Explanation of symbols]

[0057] 1. Hydraulic fan system 5 tanks 10. Hydraulic pump 11. Rotational speed pump 12 Gradient current 13 Tilt angle 14 Pump suction line 15 Displacement volume adjustment element 16 Pump pressure lines 17. Rotation speed sensor 18 Angle Sensor 19 Volumetric flow rate 20 Hydraulic motor 22 Motor inlet line 24 Motor Outlet Line 25 Fans 30 Shut-off valve 32 Safety position 34 Operating position 35 Safety operation signal connection 36 Shut-off valve actuator 38 springs 40 Control Units 41 Volumetric flow rate signal connection 42. Fan speed setting signal connection 43 Fan speed setting 44 Fan Speed ​​Calculation Unit 45 Calculated fan speed 46 Fan Speed ​​Error Determination Unit 47 Fan speed setting device 48 Fan speed error 49. Gradient Current Line 50 Fan Grill Clogging Detection Unit 52 Safe operation 55 Ideal gradient current value 60 Control device EDC Electronic Displacement Control Unit

Claims

1. A method for controlling the speed of a hydraulic fan system (1) comprising a fan (25) operated by a hydraulic motor (20) driven by a hydraulic variable displacement pump (10) having a displacement volume adjustment element (15) that can adjust the tilt angle (13) by controlling a gradient current (12) supplied to an electronic displacement control unit (EDC), a) A step of determining the volumetric flow rate (19) of the pump (10) by measuring the operating parameters of the pump (10), b) A step of calculating the fan speed (45) based on the volumetric flow rate (19) determined in step a) using an equation that represents the physical correlation between the volumetric flow rate (19) and the fan speed (45), c) A step of determining a fan speed error (48) by comparing the calculated fan speed (45) from step b) with a fan speed setting value (43) provided by the input device (47), d) A step of adjusting the gradient current (12) supplied to the electronic displacement control unit (EDC) in order to adjust the tilt angle (13) of the displacement volume adjustment element (15) so as to reduce the fan speed error (48), wherein the adjustment of the gradient current is calculated based on the fan speed error (48) using a P-, PI-, PID-, fuzzy, or predictive control device (60), or a similar type of linear or nonlinear control device. This includes the iterative step, e) A step of deriving an ideal gradient current value (55) from the calculated fan speed (45) of step b), wherein the ideal gradient current value (55) is derived from a reference table, matrix, function, or similar data structure that assigns all values ​​of the calculated fan speed (45) to the ideal gradient current value (55), f) If the difference between the ideal gradient current value (55) derived in step e) and the adapted gradient current (12) adapted in step d) is greater than the gradient current threshold, the step of performing a safety operation (52) to prevent damage to the fan (25) and This is performed simultaneously with steps c) and d). method.

2. If the fan speed error (48) determined in step c) is greater than the speed error threshold, a safety action (52) is performed to prevent damage to the fan (25). The method according to claim 1.

3. In step f), the shut-off valve (30) is switched from the operating position (34) in which the pump (10) and the motor (20) are hydraulically connected to the safety position (32) in which the hydraulic connection between the pump (10) and the motor (20) is reduced or shut off. The method according to claim 1 or 2.

4. When the gradient current threshold or the speed error threshold is exceeded, a warning signal is transmitted to the operator of the fan system (1) via the control interface or the user interface, or to the work machine hosting the fan system (1). The method according to any one of claims 1 to 3.

5. A hydraulic fan system (1), - A fan (25) operated by a hydraulic motor (20), - A variable-capacity hydraulic pump (10) for driving the hydraulic motor (20) includes a tiltable displacement volume adjustment element (15) whose tilt angle (13) can be adjusted by a control unit (40) that controls a gradient current (12) that can be supplied to an electronic displacement control device (EDC), - A fan speed setting device (47) for setting a fan speed setting value (43) according to an input command, - Means for determining the volumetric flow rate (19) of the pump (10) and Equipped with, The control unit (40) - A volume flow rate signal connection (41) to the means for determining the volume flow rate (19) of the pump (10), - Connection of the fan speed setting value signal to the electronic displacement control device (EDC) (42), - A fan speed calculation unit (44) for calculating the fan speed (45) based on the volumetric flow rate (19) determined above, - 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 setting value (43) set by the fan speed setting device (47) and Equipped with, The control unit (40) can adjust the gradient current (12) supplied to the electronic displacement control device (EDC) so that the tilt angle (13) can be adjusted to reduce the fan speed error (48). The matching of the gradient current is calculated based on the fan speed error (48) using a P-, PI-, PID-, fuzzy, or predictive control device (60), or a similar type of linear or nonlinear control device. The control unit (40) further comprises a fan grill clogging detection unit (50) which assigns an ideal gradient current value (55) to each calculated fan speed (45), compares the ideal gradient current value (55) to the gradient current (12) value adapted by the control unit (40), and performs a safety action (52) to prevent damage to the fan (25) if the difference between the ideal gradient current value (55) and the adapted gradient current value (12) is greater than a gradient current threshold, wherein the ideal gradient current value (55) is derived from a reference table, matrix, function, or similar data structure which assigns all values ​​of the calculated fan speed (45) to the ideal gradient current value (55). Hydraulic fan system (1).

6. If the fan speed error (48) determined by the fan speed error determination unit (46) is greater than the speed error threshold, the control unit (40) can perform a safety operation (52) to prevent damage to the fan (25). The hydraulic fan system (1) according to claim 5.

7. The fan grill blockage detection unit (50) can switch the shut-off valve (30) from a safe position (32) where the hydraulic connection between the pump (10) and the motor (20) is reduced or interrupted, to an operating position (34) where the pump (10) and the motor (20) are hydraulically connected when the gradient current threshold is not exceeded. The hydraulic fan system (1) according to claim 5 or 6.

8. If the gradient current threshold is not exceeded, the shut-off valve (30) is pressed to its operating position (34) by the fan grill blockage detection unit (50) against the force of the spring (38). The hydraulic fan system (1) according to claim 7.

9. When the gradient current threshold is exceeded, the fan grill clogging detection unit (50) can send a warning message to the operator of the fan system (1) via the control interface, user interface, or host device. A hydraulic fan system (1) according to any one of claims 5 to 8.

10. The volumetric 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 inclination angle (13) of the displacement volume adjustment element (15) measured by the inclination angle sensor (18). A hydraulic fan system (1) according to any one of claims 5 to 9.

11. The volumetric flow rate (19), fan speed (45), fan speed error (48), gradient current (12), and / or ideal gradient current value (55) are stored in a memory unit so that they can be accessed for error detection, condition monitoring, predictive maintenance, or similar purposes. A hydraulic fan system (1) according to any one of claims 5 to 10.

12. The pump (10) and the motor (20) operate in an open hydraulic circuit or a closed hydraulic circuit. A hydraulic fan system (1) according to any one of claims 5 to 11.

13. The aforementioned displacement volume adjustment element (15) is a swash plate or a yoke. A hydraulic fan system (1) according to any one of claims 5 to 12.

14. As a hydraulic suction or blowing system, or as a hydraulic exhaust system for a hydraulic work vehicle or machine, Use of the hydraulic fan system (1) according to any one of claims 5 to 13.

15. The aforementioned hydraulic work vehicle is a road cleaning device. Use of the hydraulic fan system (1) according to claim 14.

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