Steering system for a vehicle, in particular a utility vehicle

Abstract

The present invention relates to an electrohydraulic steering system (100) for a vehicle, in particular a utility vehicle, comprising: - at least one steering gear (102), in particular a spindle steering gear; - at least one first hydraulic, in particular electrohydraulic assembly (106), by means of which the steering gear (102) can be supplied with hydraulic fluid and / or controlled; - at least one second hydraulic, in particular electrohydraulic assembly (108) which can be connected to the steering gear (102); - at least one operating parameter-detecting device (113) for detecting at least one detectable assembly operating parameter of the first and / or the second hydraulic assembly (106, 108); and – at least one operating parameter-determining device (115), the operating parameter-determining device (115) being designed and / or configured to determine and / or estimate, on the basis of at least one detectable assembly operating parameter, at least one further assembly operating parameter of the first and / or the second hydraulic assembly (106, 108) in the form of a determinable assembly operating parameter. The present invention further relates to a vehicle, in particular a utility vehicle, having an above-described steering system.

Description

[0001] DESCRIPTION

[0002] Steering system for a vehicle, in particular a commercial vehicle

[0003] The present invention relates to an electrohydraulic steering system for a vehicle, in particular a commercial vehicle. Furthermore, the present invention relates to a vehicle with this electrohydraulic steering system.

[0004] In conventional steering systems for commercial vehicles, hydraulic elements or components such as sensors, filters, valves, and / or control elements such as actuators in the form of the steering gear create complex systems that negatively impact system efficiency and reliability. Steering systems for vehicles, especially commercial vehicles, are already known in the state of the art.

[0005] GB 2383433 A, for example, shows a hydraulic delivery device, e.g., a power steering pump, which has a flow control valve between the pump and the supply and return lines. The valve comprises a valve piston with a drilled, throttled extension that can be moved against the preload force of the valve spring to open the delivery chamber to the return flow. The spring is mounted in a single- or multi-part valve housing between the valve piston and a drilled, throttled adjusting piston, and its preload can be adjusted via the adjusting piston.

[0006] It is the object of the present invention to further develop an electro-hydraulic steering system of the type mentioned at the outset in an advantageous manner, in particular to the effect that this system is constructed in a simpler and more efficient manner, is more cost-effective and is less susceptible to errors.

[0007] This object is achieved according to the invention by an electro-hydraulic steering system having the features of claim 1. According to this, an electro-hydraulic steering system is provided for a vehicle, in particular a commercial vehicle, which has the following:

[0008] - at least one steering gear, in particular a spindle steering gear; - at least one first hydraulic, in particular electro-hydraulic, assembly, by means of which the steering gear can be supplied with hydraulic fluid and / or controlled;

[0009] - at least one second hydraulic, in particular electro-hydraulic, assembly which can be connected to the steering gear;

[0010] - at least one operating parameter detection device for detecting at least one detectable assembly operating parameter of the first and / or second hydraulic assembly; and

[0011] - at least one operating parameter determination device, wherein the operating parameter determination device is designed and / or configured to determine and / or estimate at least one further assembly operating parameter of the first and / or second hydraulic assembly in the form of a determinable assembly operating parameter on the basis of at least one detectable assembly operating parameter.

[0012] The invention is based on the fundamental idea that an operating parameter determination device is provided, by means of which an operating parameter of the first and / or second hydraulic assembly can be determined and estimated by processing a detectable operating parameter transmitted to it by the operating parameter detection device, e.g., as an input variable. This determination or estimation has the advantage that fewer assembly operating parameters actually need to be detected by sensors, so that the operating parameter detection device can be constructed more simply because it has fewer corresponding sensors or is connected to fewer of these. This reduces the overall number of components in the steering system, with the further advantages of reducing susceptibility to errors and system complexity, while still recording all important or critical assembly operating parameters (such as pressures, temperatures, switching states of the valves, etc.).) can still be determined. A detectable assembly operating parameter can be understood in particular as an assembly operating parameter that can actually be directly detected by means of a corresponding sensor device, wherein the sensor device can be part of the operating parameter detection device or can be connected to it. Accordingly, a determinable assembly operating parameter can be understood in particular as an assembly operating parameter that can be determined or estimated by means of the operating parameter determination device, wherein one or more detectable assembly operating parameters can serve as input variables on the basis of which the determinable assembly operating parameter can then be determined or estimated accordingly.The first and second hydraulic assemblies are to be understood as separate assemblies, differing in at least one function and / or structural component. The steering gear can also be a component of the first or second hydraulic assembly.

[0013] Furthermore, it can be provided that the first hydraulic assembly has at least one hydraulic pump and at least one electric motor for driving the hydraulic pump, wherein the operating parameter detection device is designed and / or configured to detect at least one motor operating parameter of the electric motor and / or at least one pump operating parameter of the hydraulic pump, and wherein the operating parameter determination device is designed and / or configured to determine and / or estimate at least one determinable assembly operating parameter of the first and / or second hydraulic assembly based at least on the detected motor operating parameter and / or pump operating parameter. The detection of the motor operating parameter can be carried out relatively simply and efficiently, so that the detection of this parameter is advantageous.Furthermore, certain motor operating parameters can be highly informative with respect to other assembly operating parameters, making it advantageous to record this parameter, which also applies to the pump operating parameters. Motor operating parameters and pump operating parameters can be specific operating parameters of the first hydraulic assembly.

[0014] The motor operating parameter(s) may include at least one electric motor current and / or at least one electric motor voltage and / or at least one motor speed and / or at least one motor power and / or at least one motor torque. Since these motor operating parameters can be highly informative with respect to other, particularly determinable, assembly operating parameters of the first and / or second hydraulic assembly, recording this or these parameters is advantageous.

[0015] Furthermore, the pump operating parameter(s) may include at least one volume flow of the hydraulic fluid and / or at least one mass flow of the hydraulic fluid and / or at least one pump speed. Since these pump operating parameters can also be highly informative with respect to other, particularly determinable, assembly operating parameters of the first and / or second hydraulic assembly, the recording of this or these parameters is also advantageous. The hydraulic fluid can be embodied as a hydraulic oil suitable for steering gears.

[0016] In addition, it is conceivable that the detectable assembly operating parameter(s) comprise(s) at least a temperature of the hydraulic fluid in the first hydraulic assembly and / or at least a pressure of the hydraulic fluid in the first hydraulic assembly. For system safety, knowledge of the pressure in the first hydraulic assembly can be particularly advantageous because it is in this assembly that pressure is generated and this pressure is therefore a critical system variable. Based on this knowledge, the operation of the first hydraulic assembly can be reliably monitored, so that the detection of this operating parameter is particularly advantageous, which incidentally also applies to the detection of the temperature of the hydraulic fluid. In addition, the temperature detection can be particularly advantageous because it forms the basis for determining orEstimation of many other determinable assembly operating parameters is possible, so that the temperature recording can also provide a high level of information about other, in particular determinable, assembly operating parameters of the first and / or second hydraulic assembly.

[0017] The detectable assembly operating parameter(s) can further comprise at least a temperature of the hydraulic fluid in the second hydraulic assembly and / or at least a pressure of the hydraulic fluid in the second hydraulic assembly. Knowledge of the pressure in the second hydraulic assembly can also be advantageous for system safety, because system-relevant components can also be arranged in this assembly. Based on this knowledge, the operation of the second hydraulic assembly can be reliably monitored, so that the detection of this operating parameter can be particularly advantageous, which incidentally also applies to the detection of the temperature of the hydraulic fluid. In addition, the temperature detection is particularly advantageous because it forms the basis for determining orEstimation of many other determinable assembly operating parameters, so that the temperature recording also enables a high degree of informative value of other, in particular determinable, assembly operating parameters of the first and / or second hydraulic assembly.

[0018] It may also be advantageous for the determinable assembly operating parameter(s) to include at least a pressure of the hydraulic fluid in the second hydraulic assembly. Advantageously, a pressure of the hydraulic fluid in the second hydraulic assembly can be determined or estimated as described above, so that the sensory detection of the pressure of the hydraulic fluid in the second hydraulic assembly can be omitted, thus eliminating components such as sensors and corresponding lines.

[0019] System complexity and the number of components are reduced, while the pressure in the second hydraulic assembly is still predictable, even if not actually in a directly measured form.

[0020] The second hydraulic assembly can be designed as a backup assembly and can have at least one hydraulic filter element and at least one backup switching valve. Firstly, the backup assembly can ensure the steerability of the steering system even in the event of a total failure of the first hydraulic assembly, as it creates a short circuit between the two working chambers of the steering gear, such that the hydraulic fluid can be moved between these two chambers, which further ensures steering capability. The integration of the hydraulic filter element in the backup assembly is further advantageous in that the infrastructure already existing due to the second hydraulic assembly can be assigned additional functions. During the inactive phases of the steering system, the hydraulic fluid (as specified or required for the steering gear) can thus be cleaned very efficiently.suitable hydraulic oil) via the second hydraulic assembly by opening the backup switching valve. This pressurises the second assembly from the first assembly via the intermediate steering gear, making the hydraulic fluid filterable. This design is particularly advantageous because it takes advantage of the fact that there are repeatedly inactive phases during which the steering system does not require any steering assistance from the steering gear. However, because steering assistance is requested at any time (particularly during manual steering movements), the hydraulic pump of the first hydraulic assembly should always be kept in active operation so that this active operation can also be used for filtering. This eliminates the need for an additional flushing valve or flushing pump, allowing the steering system to be constructed even more simply, lighter, and more cost-effectively.

[0021] Alternatively, it can also be provided that the steering gear is not connected or mounted between the first and second modules and accordingly the first and second modules are directly connected to each other or are fastened to each other and are fastened to the steering gear as a complete module.

[0022] The determinable assembly operating parameter(s) may include at least an inlet pressure and / or outlet pressure of the hydraulic fluid at the hydraulic filter element. Monitoring the inlet pressure and / or outlet pressure at the hydraulic filter element is important because knowledge of this pressure allows statements to be made about the operating state of the hydraulic filter element. Therefore, this pressure is a system-critical variable that should be monitored. By determining or estimating the inlet pressure and / or outlet pressure of the hydraulic fluid at the hydraulic filter element, a pressure sensor (e.g., in the form of a differential pressure sensor) can be omitted, allowing the second assembly to be constructed in a simpler and more reliable manner.

[0023] The operating parameter determination device can further be designed and / or configured to determine and / or estimate at least one inlet and / or outlet pressure at the hydraulic filter element based at least on the electric motor current, the volume flow of the hydraulic fluid, and the temperature of the hydraulic fluid, and in particular the pump speed and / or the motor speed. In particular, the electric motor current, the volume flow of the hydraulic fluid, and the temperature of the hydraulic fluid are elementary parameters for determining or estimating the inlet and / or outlet pressure at the hydraulic filter element, so that their provision is particularly advantageous. In particular, the volume flow of the hydraulic fluid is an operating parameter that is preferably not detected or measured, but is determined or derived based on the measured pump speed.

[0024] Furthermore, it can be provided that the operating parameter determination device is designed and / or configured to determine and / or estimate a filter operating state, in particular wear state or load state, of the hydraulic filter element at least on the basis of the inlet and / or outlet pressure at the hydraulic filter element. Monitoring the filter state is very important for the functionality of the steering system, as this has a direct influence on the system reliability of the steering system and is therefore a critical system variable. Determining or estimating the inlet pressure and / or outlet pressure at the hydraulic filter element provides a very simple and advantageous option, since knowledge of this pressure allows reliable and yet easily implemented statements to be made about the operating state of the hydraulic filter element. Determining or estimating the inlet pressure and / or outlet pressure at the hydraulic filter element can be particularly advantageous.Estimation of the inlet pressure at the hydraulic filter element.

[0025] Furthermore, it is conceivable that a parameter model is implemented in the operating parameter determination device, by means of which the operating parameter determination device is designed and / or configured to determine and / or estimate at least one assembly operating parameter of the first and / or second hydraulic assembly, at least based on a detectable operating parameter as an input variable. By means of this parameter model, an even better, more precise, and more flexible determination or estimation of at least one assembly operating parameter of the first and / or second hydraulic assembly is possible, since the parameter model can be flexibly adapted to the boundary conditions of the steering system. Furthermore, it is conceivable that circuit diagram data assigned to a hydraulic circuit arrangement of components and lines of the first hydraulic assembly and the second hydraulic assembly are implemented in the parameter model.By means of this circuit diagram data, an even improved, more precise and more flexible determination or estimation of at least one determinable assembly operating parameter of the first and / or second hydraulic assembly is possible, since the circuit diagram data enable an even more detailed modeling of the boundary conditions of the steering system.

[0026] Furthermore, according to the invention, a vehicle is provided, in particular a commercial vehicle, with at least one electro-hydraulic steering system as described above.

[0027] All advantages and technical effects achievable in connection with the steering system according to the invention can also apply, individually or in combination, to the vehicle according to the invention. The vehicle can be designed, in particular, as a commercial vehicle.

[0028] Further details and advantages of the invention will now be explained in more detail with reference to the embodiment shown in the drawing.

[0029] It shows:

[0030] Fig. 1 is a schematic representation of a circuit arrangement of an embodiment of a steering system according to the invention.

[0031] Fig. 1 shows a schematic representation of a circuit arrangement of an embodiment of a steering system 100 according to the invention.

[0032] The electro-hydraulic steering system 100 for a commercial vehicle has a steering gear 102 in the form of a spindle steering gear 102, which in turn has a steering gear housing 104.

[0033] The spindle steering gear 102 can be configured as a recirculating ball screw steering gear, although other types of gears are also conceivable. The electro-hydraulic steering system 100 further comprises a first hydraulic assembly 106, which is attached to the steering gear housing 104.

[0034] The first hydraulic assembly 106 is designed in the form of an electro-hydraulic assembly 106.

[0035] The electro-hydraulic steering system 100 also has a second hydraulic assembly 108 which is attached to the steering gear housing 104.

[0036] The second hydraulic assembly 108 is designed as an electro-hydraulic assembly 108.

[0037] The fastening of the first and second hydraulic assemblies 106, 108 to the steering gear housing 104 can be realized via corresponding flange connections, which, however, are not shown in the schematic representation of Fig. 1.

[0038] Several components of the first hydraulic assembly 106 can be at least partially integrated into a first housing block 110 (made of solid block material as the starting structure).

[0039] Accordingly, several components of the second hydraulic assembly 108 can also be at least partially integrated into a second housing block 112 (made of solid block material as the starting structure).

[0040] However, it is also alternatively conceivable that the first hydraulic assembly 106 and the second hydraulic assembly 108 can each be integrated in a first and second assembly housing.

[0041] The first and second housing blocks 110, 112 may be formed as structurally separate blocks as shown in Fig. 1 and may be attached at different locations on the steering gear housing 104. For example, the first and second housing blocks 110, 112 may be attached at opposite locations on the steering gear housing 104 (i.e., at a 180° angle to each other).

[0042] It is also conceivable that the first and second housing blocks 110, 112 can also be attached to the steering gear housing 104 in a 90° or 270° orientation to each other.

[0043] According to an alternative design of the housing block of the steering system 100, one or more components of the first hydraulic assembly 106 and the second hydraulic assembly 108 can also be at least partially integrated into a common housing block (not shown in Fig. 1).

[0044] The common housing block can comprise the first housing block 110 and the second housing block 112 or can be constructed from these two blocks 110, 112 or alternatively can be designed as a one-piece housing block (made of solid block material as the starting structure).

[0045] However, it is also alternatively conceivable that the first hydraulic assembly 106 and the second hydraulic assembly 108 can each be integrated in a common assembly housing.

[0046] The steering system 100 further comprises an operating parameter detection device 113 for detecting one or more detectable assembly operating parameters of the first and second hydraulic assemblies 106, 108.

[0047] Furthermore, the steering system 100 has an electronic control and / or regulating device 114 for controlling and / or regulating the first and second hydraulic assemblies 106, 108.

[0048] In addition, the steering system 100 comprises an operating parameter determination device 115. The devices 113, 114 and 115 are shown without connecting lines in Fig. 1, wherein these devices 113, 114 and 115 are connected or connectable to the corresponding components of the first and second hydraulic assemblies 106, 108 via connecting lines.

[0049] Furthermore, it is conceivable that the operating parameter detection device 113 and the operating parameter determination device 115 can be combined into a common device.

[0050] Alternatively, it can also be provided that the operating parameter detection device 113 and / or the operating parameter determination device 115 are part of the electronic control and / or regulating device 114.

[0051] The first hydraulic assembly 106 comprises a hydraulic pump 116 and an electric motor M for driving the hydraulic pump 116.

[0052] The hydraulic pump 116 is designed as a double-acting or bidirectional hydraulic pump with a first and second delivery direction.

[0053] Alternatively, it may also be conceivable that only a single-acting hydraulic pump is provided and is connected to the first and second lines 118, 120 via a corresponding switching valve (not shown in Fig. 1), which connects the hydraulic pump 116 to the first or second line 118, 120 depending on the switching logic.

[0054] Alternatively, it may also be conceivable that two hydraulic pumps can be provided, with one pump each being assigned to or connected to the first and second lines 118, 120.

[0055] The first hydraulic assembly 106 further includes a first line 118 connected to a first working chamber 122 of the steering gear housing 104. The first hydraulic assembly 106 correspondingly includes a second line 120 connected to a second working chamber 124 of the steering gear housing 104.

[0056] According to Fig. 1 it can be seen that the hydraulic pump 116 is connected to the first line 118 and to the second line 120.

[0057] The first line 118 consequently extends from a first pressure outlet of the hydraulic pump 116 to a connection of the steering gear housing 104, which opens into the first working chamber 122.

[0058] The second line 120 extends accordingly from a second pressure outlet of the hydraulic pump 116 to a connection of the steering gear housing 104, which opens into the second working chamber 124.

[0059] A hydraulic filter element can be arranged in each of the first and second lines 118, 120.

[0060] In addition, according to Fig. 1, a pressure sensor is arranged in the first line 118.

[0061] Furthermore, a pressure sensor and a temperature sensor are arranged in the second line 120.

[0062] Additionally or alternatively, it is conceivable that a temperature sensor is arranged in the first line 118.

[0063] The first hydraulic assembly 106 further comprises a hydraulic tank, which may be fully or partially integrated into the first housing block 110.

[0064] Alternatively, it is also conceivable that the hydraulic tank is flanged to the first housing block 110.

[0065] The hydraulic tank is shown only schematically in Fig. 1, so it is also conceivable that the hydraulic pump 116 is integrated into the tank. Alternatively or additionally, it is also conceivable that the electric motor, the hydraulic tank, and the hydraulic pump 116 are flanged together and connected via corresponding lines (not shown in Fig. 1).

[0066] The hydraulic tank is also assigned a pressure sensor and a temperature sensor to monitor the pressure and temperature of the hydraulic oil in the tank.

[0067] The second hydraulic assembly 108 is designed as a backup assembly and is connected to the steering gear 102 in a fault condition of the steering system 100.

[0068] Alternatively or additionally, the second hydraulic assembly 108 may be connected to the steering gear 102 in the form of a hydraulic flow connection in an inactive state of the steering system 100.

[0069] Connected here is to be understood as meaning that a continuous flow path is provided between the working chambers 122, 124 of the steering gear via the second hydraulic assembly 108.

[0070] The second hydraulic assembly 108 includes, among other components, a hydraulic filter element 126 and a backup switching valve 128.

[0071] The hydraulic filter element 126 and the backup switching valve 128 form a series circuit.

[0072] The hydraulic filter element 126 is arranged upstream of the backup switching valve 128.

[0073] A pressure sensor 144 for monitoring the filter condition and a bypass check valve or filter check valve 146 can be arranged parallel to the hydraulic filter element 126, although this arrangement can only be provided optionally. The pressure sensor can be designed as a differential pressure sensor or, alternatively, as two individual pressure sensors or pressure switches with an adjustable pressure trigger threshold.

[0074] The pressure sensors and temperature sensors of the first hydraulic assembly 106 and the pressure sensor 144 of the second hydraulic assembly 108 explained above can be components of the operating parameter detection device 113 or can be connected to it via corresponding signal lines.

[0075] The pressure sensor 144 described above and the electric motor M are further connected to the electronic control and / or regulating device 114 via corresponding lines.

[0076] Furthermore, the second hydraulic assembly 108 has a further first line 130 and a further second line 132.

[0077] The further first line 130 is connected to the first working chamber 122 of the steering gear housing 104.

[0078] Accordingly, the further second line 132 is connected to the second working chamber 124 of the steering gear housing 104.

[0079] As shown in Fig. 1, the backup switching valve 128 is switched to the pass-through position in the inactivity or fault state.

[0080] Accordingly, the first working chamber 122 and the second working chamber 124 are connected via the further first and further second lines 130, 132 as well as via the hydraulic filter element 126 and the backup switching valve 128.

[0081] According to Fig. 1, the second hydraulic assembly 108 also has a bridge circuit 134 comprising four outer branches 136 and one bridge branch 138, wherein the four outer branches 136 are connected to one another via four outer nodes 140. The bridge branch 138, in turn, is formed by the series connection with the hydraulic filter element 126 and the backup switching valve 128.

[0082] Accordingly, the first working chamber 122 and the second working chamber 124 are connected to one another via the further first and further second lines 130, 132 and via the bridge circuit 134.

[0083] For this purpose, the bridge circuit 134 is connected to the further first line 130 and the further second line 132 by means of two external nodes 140.

[0084] The bridge branch 138, in turn, is connected to those two further external nodes 140 of the bridge circuit which are not connected to the further first and second lines 130, 132.

[0085] A further hydraulic filter element can be arranged in each of the further first and further second lines 118, 120.

[0086] The backup switching valve 128 is designed as a 2 / 2-way solenoid valve and has a switching plunger and a solenoid coil for actuating the switching plunger, wherein a change in the switching position of the switching plunger triggers an induced voltage in the solenoid coil.

[0087] Furthermore, according to the invention, a commercial vehicle is provided (not shown in Fig. 1) which has the electro-hydraulic steering system 100 as described above.

[0088] The function of the steering system 100 according to the invention can now be described as follows:

[0089] The function of the operating parameter detection device 113 and the operating parameter determination device 115 is initially as follows: According to the basic idea of ​​the invention, the operating parameter determination device 115 is designed and / or configured to determine and / or estimate at least one further assembly operating parameter of the first and / or second hydraulic assembly 106, 108 in the form of a determinable assembly operating parameter on the basis of at least one detectable assembly operating parameter.

[0090] Detectable assembly operating parameters are in particular those operating parameters that can be recorded by sensors or by means of the operating parameter recording device.

[0091] The detectable assembly operating parameter(s) includes / include a temperature of the hydraulic fluid in the first hydraulic assembly 106 and / or a pressure of the hydraulic fluid in the first hydraulic assembly 106.

[0092] Alternatively, the detectable assembly operating parameter(s) may include a temperature of the hydraulic fluid in the second hydraulic assembly 108 and / or a pressure of the hydraulic fluid in the second hydraulic assembly 108.

[0093] Accordingly, determinable assembly operating parameters are in particular those operating parameters that can be determined or estimated on the basis of the detectable assembly operating parameter(s) (which can thus serve as input variables) of the operating parameter determination device.

[0094] A determinable assembly operating parameter includes a pressure of the hydraulic fluid in the second hydraulic assembly 108.

[0095] Preferably, the determinable assembly operating parameter includes an inlet pressure of the hydraulic fluid at the hydraulic filter element 126.

[0096] Alternatively or additionally, the determinable assembly operating parameter includes the output pressure of the hydraulic fluid at the hydraulic filter element 126. Further alternatively or additionally, the determinable assembly operating parameter includes the inlet pressure and the outlet pressure of the hydraulic fluid at the hydraulic filter element 126.

[0097] Furthermore, the operating parameter detection device 113 is designed and / or configured to detect a motor operating parameter of the electric motor M and / or a pump operating parameter of the hydraulic pump 116.

[0098] The motor operating parameter(s) may include an electric motor current and / or an electric motor voltage and / or a motor speed and / or at least one motor power and / or at least one motor torque.

[0099] Accordingly, the pump operating parameter(s) may include a volume flow of the hydraulic fluid and / or a mass flow of the hydraulic fluid and / or a pump speed.

[0100] The operating parameter determination device 115 can also determine the electric motor power by multiplying the electric motor current and the electric motor voltage or the motor torque by a motor speed or motor angular velocity.

[0101] Furthermore, the operating parameter determination device 115 is in turn designed and / or configured to determine and / or estimate a determinable assembly operating parameter of the first and / or second hydraulic assembly 106, 108 on the basis of the detected engine operating parameter and / or pump operating parameter.

[0102] More specifically, the operating parameter determination device 115 is configured and / or set up to determine and / or estimate the inlet pressure at the hydraulic filter element 126 based on the electric motor current, the volume flow of the hydraulic fluid, and the temperature of the hydraulic fluid. Alternatively, the operating parameter determination device 115 can be configured and / or set up to determine and / or estimate the inlet and outlet pressure at the hydraulic filter element based on the electric motor current, the volume flow of the hydraulic fluid, and the temperature of the hydraulic fluid.

[0103] The operating parameter determination device 115 is further designed and / or configured to determine and / or estimate a filter operating state in the form of a wear state or loading state of the hydraulic filter element 126 based on the inlet pressure at the hydraulic filter element 126.

[0104] Alternatively, the operating parameter determination device 115 may further be designed and / or configured to determine and / or estimate the filter operating state in the form of the wear state or loading state of the hydraulic filter element 126 based on the inlet and outlet pressure at the hydraulic filter element 126.

[0105] Furthermore, a parameter model is implemented in the operating parameter determination device 115, by means of which the operating parameter determination device 115 is designed and / or configured to determine and / or estimate a corresponding assembly operating parameter of the second hydraulic assembly 108 on the basis of one or more detectable operating parameters as described above as an input variable.

[0106] Circuit diagram data are implemented in the parameter model, whereby in particular the circuit diagram arrangement according to Fig. 1 can be implemented as described above.

[0107] Accordingly, the circuit diagram data of the hydraulic circuit arrangement are assigned to components and lines of the first hydraulic assembly 106 and the second hydraulic assembly 108 according to Fig. 1, which are stored in the operating parameter determination device 115 using a digital circuit diagram model. The function of the operating parameter detection device 113 and the operating parameter determination device 115 in connection with the hydraulic circuit arrangement shown in Fig. 1 is as follows:

[0108] The steering gear 102 can be supplied with hydraulic fluid via the hydraulic pump 116.

[0109] In addition, the steering gear 102 can be controlled by the hydraulic pump 116 due to its different delivery directions.

[0110] More precisely, the first working chamber 122 can be supplied with hydraulic fluid and controlled by the first line 118, since the first line connects this working chamber 122 to the hydraulic pump 116.

[0111] Accordingly, the second working chamber 124 can be supplied with hydraulic fluid and controlled through the second line 120, since the second line connects this working chamber 124 to the hydraulic pump 116.

[0112] The control is effected by the hydraulic pump 116 pressurizing either the first working chamber 122 or the second working chamber 124 of the steering gear - but not both at the same time.

[0113] The hydraulic pump 116 is therefore configured to pressurize the first line 118 according to the first conveying direction and to pressurize the second line 120 according to the second conveying direction.

[0114] As soon as the hydraulic pump 116 is driven by the electric motor M (e.g. clockwise), it pressurizes the first line 118, which extends to the first working chamber 122, according to a first conveying direction.

[0115] Consequently, the hydraulic pump 116 and the steering gear 102 are connected to each other via the first line 118, and the connection of the steering gear 102 connected to the first line 118 and leading into the first working chamber 122 is pressurized. The pressure in the first working chamber 122 then increases, and the piston is forced into a linear displacement movement, since a lower pressure prevails in the opposite, second working chamber 124, thus achieving steering assistance.

[0116] The pressure in the opposite second working chamber 124 is lower because this working chamber 124 is connected to the tank via the second line 120 and a corresponding return line (not shown in Fig. 1).

[0117] Accordingly, the hydraulic oil can flow back from the second working chamber 124 into the tank.

[0118] It is important to understand in this context that the hydraulic pump 116 is always driven in only one direction of rotation and therefore only the first or the second line 118, 120 can be pressurized.

[0119] If the direction of rotation of the hydraulic pump 130 is reversed, the previously described relationship or case occurs in exactly the reverse order, as described below:

[0120] As soon as the hydraulic pump 116 is driven by the electric motor M (e.g. counterclockwise), it pressurizes the second line 120, which extends to the second working chamber 124, according to a second conveying direction.

[0121] Consequently, the hydraulic pump 116 and the steering gear 102 are connected to each other via the second line 120, and the connection of the steering gear 102 connected to the second line 120 and opening into the second working chamber 124 is pressurized.

[0122] The pressure in the second working chamber 124 then increases and the piston is forced to perform a linear displacement movement, since there is now a lower pressure in the opposite, first working chamber 122, so that steering assistance is achieved.

[0123] The pressure in the opposite first working chamber 122 is lower because this working chamber 122 is connected to the tank via the first line 118 and a corresponding return line (not shown in Fig. 1).

[0124] Accordingly, the hydraulic oil can flow back from the first working chamber 122 into the tank.

[0125] It is important to understand in this context that the hydraulic pump 116 is always driven in only one direction of rotation and therefore only the first or the second line 118, 120 can be pressurized.

[0126] The above function of the steering system 100 has been described according to a normal operating state, with the following functional description explaining an inactivity state or fault state of the system:

[0127] In this state, the backup switching valve 128 is arranged in the passage switching position shown in Fig. 1.

[0128] This position enables an uninterrupted flow path from the first working chamber 122 to the second working chamber 124 via the further first and further second lines 130, 132 and via the bridge circuit 134.

[0129] The flow direction of the hydraulic oil depends on the pressure gradient between the first and second working chambers 122, 124.

[0130] The pressure gradient can either arise solely through a manual steering movement of the steering shaft, since the steering shaft provides the linear displacement of the steering gear piston (in this case, no pressure is applied by the hydraulic pump 116), in which case the fault condition is associated with the fault condition. Additionally or alternatively, the pressure gradient can be created, as described above, by the selective pressure applied to the first or second working chamber 122, 124 by the hydraulic pump 116, in which case the fault condition is associated with an inactivity state of the steering system.

[0131] Inactivity state is the state when the steering system is inactive, ie when either the commercial vehicle is not currently moving or the commercial vehicle is moving and no steering assistance will be required in the future.

[0132] In this case, the operating parameter detection device 113 can, as described above, detect the corresponding operating parameters of the first and second modules 106, 108 and transmit them to the operating parameter determination device.

[0133] In particular, the operating parameter determination device 115 can determine or estimate the inlet pressure at the hydraulic filter element 126 from the detected operating parameters and can use this to determine its wear or clogging state or loading state.

[0134] If the pressure in the first working chamber 122 is higher than in the second working chamber 124, the following flow path or hydraulic oil flow through the following components results:

[0135] - first additional line 130 (hydraulic filter in this line if necessary);

[0136] - external node 140 connecting the bridge circuit 134 and another first line 130;

[0137] - outer branch 136 permeable in the direction of flow (clearly defined by check valve arrangement);

[0138] - bridge branch 138, further outer branch 136 permeable in the flow direction, which connects the bridge branch 138 to the outer node 140 connected to the further second line 132;

[0139] - further second line 132; and second working chamber 124. If the pressure in the second working chamber 124 is greater than in the first working chamber 122, the following flow path or hydraulic oil flow through the following components results:

[0140] - further second line 132 (if necessary hydraulic filter in this line);

[0141] - external node 140 connecting the bridge circuit 134 and another second line 132;

[0142] - outer branch 136 permeable in the direction of flow (clearly defined by check valve arrangement);

[0143] - Bridge branch 138;

[0144] - further outer branch 136 which is permeable in the flow direction and which connects the bridge branch 138 to the outer node 140 connected to the further first line 130;

[0145] - further first line 130; and

[0146] - first workroom 122.

[0147] These two previously described flow paths enable the cleaning of the hydraulic oil via the hydraulic filter element 126, which is the main filter element.

[0148] In this respect, the hydraulic oil can be cleaned very efficiently when the steering system is inactive, since the pressures required for this are much lower than those required for steering assistance.

[0149] Because these cleaning pressures must not cause the steering gear piston to be actuated so strongly that this would trigger an actual steering movement or steering assistance, the pressures must remain below a corresponding pressure threshold.

[0150] However, due to friction and inertia in the steering system, cleaning below the previously described pressure threshold is quite possible, so that in the event of future inactivity of the steering system 100, cleaning via the hydraulic filter element 126 is very efficient.

[0151] 100 electro-hydraulic steering system

[0152] 102 Steering gears, in particular spindle steering gears

[0153] 104 Steering gear housing

[0154] 106 first hydraulic, in particular electro-hydraulic, assembly

[0155] 108 second hydraulic, in particular electro-hydraulic, assembly

[0156] 110 first housing block

[0157] 112 second housing block

[0158] 113 Operating parameter recording device

[0159] 114 electronic control and / or regulating device

[0160] 115 Operating parameter determination device

[0161] 116 Hydraulic pump

[0162] 118 first line

[0163] 120 second line

[0164] 122 first workroom

[0165] 124 second workroom

[0166] 126 Hydraulic filter element

[0167] 128 Backup switching valve

[0168] 130 additional first lines

[0169] 132 additional second lines

[0170] 134 Bridge circuit

[0171] 136 Outer branch

[0172] 138 bridge branch

[0173] 140 outer nodes

[0174] 142 Check valve

[0175] 144 Pressure sensor

[0176] 146 Filter check valve

[0177] M electric motor

Claims

PATENT CLAIMS 1 . Electrohydraulic steering system (100) for a vehicle, in particular a commercial vehicle, comprising: - at least one steering gear (102), in particular spindle steering gear; - at least one first hydraulic, in particular electro-hydraulic, assembly (106) by means of which the steering gear (102) can be supplied with hydraulic fluid and / or controlled; - at least one second hydraulic, in particular electro-hydraulic, assembly (108) which can be connected to the steering gear (102); - at least one operating parameter detection device (113) for detecting at least one detectable assembly operating parameter of the first and / or second hydraulic assembly (106, 108); and - at least one operating parameter determination device (115), wherein the operating parameter determination device (115) is designed and / or configured to determine and / or estimate at least one further assembly operating parameter of the first and / or second hydraulic assembly (106, 108) in the form of a determinable assembly operating parameter on the basis of at least one detectable assembly operating parameter.

2. Electro-hydraulic steering system (100) according to claim 1, characterized in that the first hydraulic assembly (106) has at least one hydraulic pump (116) and at least one electric motor (M) for driving the hydraulic pump (116), wherein the operating parameter detection device (113) is designed and / or configured to detect at least one motor operating parameter of the electric motor (M) and / or at least one pump operating parameter of the hydraulic pump (116), and wherein the operating parameter determination device (115) is designed and / or configured to determine and / or estimate at least one determinable assembly operating parameter of the first and / or second hydraulic assembly (106, 108) at least on the basis of the detected motor operating parameter and / or pump operating parameter.

3. Electrohydraulic steering system (100) according to claim 2, characterized in that the motor operating parameter(s) comprises or comprise at least one electric motor current and / or at least one electric motor voltage and / or at least one motor speed and / or at least one motor power and / or at least one motor torque.

4. Electro-hydraulic steering system (100) according to claim 2 or claim 3, characterized in that the pump operating parameter(s) comprises or comprise at least one volume flow of the hydraulic fluid and / or at least one mass flow of the hydraulic fluid and / or at least one pump speed.

5. Electro-hydraulic steering system (100) according to one of the preceding claims, characterized in that the detectable assembly operating parameter(s) comprises or comprise at least one temperature of the hydraulic fluid in the first hydraulic assembly (106) and / or at least one pressure of the hydraulic fluid in the first hydraulic assembly (106).

6. Electro-hydraulic steering system (100) according to one of the preceding claims, characterized in that the detectable assembly operating parameter(s) comprises or comprise at least one temperature of the hydraulic fluid in the second hydraulic assembly (108) and / or at least one pressure of the hydraulic fluid in the second hydraulic assembly (108).

7. Electro-hydraulic steering system (100) according to one of the preceding claims, characterized in that the determinable assembly operating parameter(s) comprises or comprise at least a pressure of the hydraulic fluid in the second hydraulic assembly (108).

8. Electro-hydraulic steering system (100) according to one of the preceding claims, characterized in that the second hydraulic assembly (108) is designed as a backup assembly and has at least one hydraulic filter element (126) and at least one backup switching valve (128).

9. Electro-hydraulic steering system (100) according to claim 8, characterized in that the determinable assembly operating parameter(s) comprises or comprise at least one inlet pressure and / or outlet pressure of the hydraulic fluid at the hydraulic filter element (126).

10. Electro-hydraulic steering system (100) according to claim 8 or claim 9, characterized in that the operating parameter determination device (115) is designed and / or configured to determine and / or estimate at least one inlet and / or outlet pressure at the hydraulic filter element based at least on the electric motor current, the volume flow of the hydraulic fluid and the temperature of the hydraulic fluid, and in particular the pump speed and / or the motor speed.

11. Electro-hydraulic steering system (100) according to claim 10, characterized in that the operating parameter determination device (115) is designed and / or configured to determine and / or estimate a filter operating state, in particular wear state or loading state, of the hydraulic filter element (126) at least on the basis of the inlet and / or outlet pressure at the hydraulic filter element (126).

12. Electro-hydraulic steering system (100) according to one of the preceding claims, characterized in that a parameter model is implemented in the operating parameter determination device (115), by means of which parameter model the operating parameter determination device (115) is designed and / or configured to determine and / or estimate at least one assembly operating parameter of the first and / or second hydraulic assembly (106, 108) at least on the basis of a detectable operating parameter as an input variable.

13. Electro-hydraulic steering system (100) according to claim 12, characterized in that circuit diagram data are implemented in the parameter model, which are assigned to a hydraulic circuit arrangement of components and lines of the first hydraulic assembly (106) and the second hydraulic assembly (108).

14. Vehicle, in particular commercial vehicle, with at least one electro-hydraulic steering system (100) according to one of claims 1 to 13.

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