Steering systems for vehicles, especially commercial vehicles

Abstract

The present invention relates to an electro-hydraulic steering system (100, 200, 300, 400) for vehicles, particularly commercial vehicles, and includes the following: The present invention relates to an electro-hydraulic steering system (100,200,300,400) comprising: -at least one steering gear (102), particularly a spindle-type steering gear, having at least one steering gear housing (104); and -at least one hydraulic assembly (106), particularly an electro-hydraulic assembly (106), which is directly or indirectly fixable to the steering gear housing (104) for supplying working fluid to the steering gear (102) and / or controlling the steering gear (102), wherein one or more components of the hydraulic assembly (106) are at least partially integrated within a housing block (110), and the hydraulic assembly (106) has at least one first hydraulic port (148) and at least one second hydraulic port (150) for supplying and / or controlling at least one external hydraulic component (152) with respect to the hydraulic assembly (106). Furthermore, the present invention relates to a vehicle, particularly a commercial vehicle, equipped with the steering system described above.

Description

Technical Field

[0001] The present invention relates to a vehicle, particularly an electro-hydraulic steering system for commercial vehicles. Further, the present invention relates to a vehicle equipped with an electro-hydraulic steering system, particularly a commercial vehicle.

[0002] In a conventional steering system for commercial vehicles, which is particularly configured in a distributed manner, large structural space requirements are generated by hydraulic elements such as filters and valves and / or control elements or actuators. Such structural space requirements have a negative impact on the output density, performance, and efficiency of the steering system. Also, in many vehicle concepts, particularly in the commercial vehicle field, the requirements for the steering force transmitted to the steering rod are increasing. Therefore, the above-mentioned low output density has an even more adverse effect when viewed from the perspective of the vehicle concept.

[0003] In the prior art, steering systems for vehicles, particularly for commercial vehicles, are already known.

[0004] According to that, in German Patent Application Publication No. 102016112332, a method for monitoring a closed-loop control block that drives and controls an actuator drive part, particularly the actuator drive part of a steering system, is shown.

[0005] The object of the present invention is to develop an electro-hydraulic steering system in the form described at the beginning in an advantageous manner. In particular, this system has a higher output density, has a lower energy requirement, and is further developed so that it can be configured more simply and with fewer components and / or pipelines.

[0006] This object is solved by an electro-hydraulic steering system according to the invention having the features of claim 1. According to this, an electro-hydraulic steering system for a vehicle, particularly for a commercial vehicle, comprising the following: - at least one steering gear provided with at least one steering gear housing, particularly a spindle type steering gear, and - comprising at least one hydraulic assembly, particularly an electro-hydraulic assembly, for supplying working fluid to the steering gear and / or controlling the steering gear, which can be fixed directly or indirectly to the steering gear housing, Here, one or more components of the hydraulic assembly are integrated at least partially within the housing block. Here, it is envisioned that an electro-hydraulic steering system for a vehicle is provided, wherein the hydraulic assembly has at least one first hydraulic port and at least one second hydraulic port for supplying and / or controlling at least one external hydraulic assembly with respect to the hydraulic assembly.

[0007] The present invention is based on the following fundamental consideration: that one or more components of a hydraulic assembly may be integrated at least partially within a single housing block. This allows for a very high power density within the housing block, thereby eliminating elasticity (and consequently inertia) and additional sources of failure within the steering system. It may also be assumed that all components of the hydraulic assembly may be integrated within the housing block. It should be understood that this type of integration does not intend to require one or more components to be structurally and completely integrated or embedded within the housing block (for example, in the case of a switching valve, the valve stem and certain ports may be integrated, but the control or operating area and possibly external ports may be located outside the housing block or flanged into the housing block). The housing block may be configured such that the necessary holes, conduits, wall structures, etc. for one or more components are introduced into a block-whole material, thereby forming the housing block. The housing block may be manufactured as a block-whole material (e.g., aluminum alloy) manufactured as a single unit. Furthermore, the hydraulic assembly may have (according to a further aspect of the basic considerations of the present invention) at least one first hydraulic port and at least one second hydraulic port. This simplifies the pre-installation of the steering system and the final installation on the vehicle, and the system architecture or system integration may also be carried out individually and freely.

[0008] External hydraulic components may be components of an electro-hydraulic steering system, and may be configured in particular as a steering booster hydraulic cylinder in the form of a differential hydraulic cylinder. This configuration allows for the provision of additional steering force, which is particularly advantageous in heavy commercial vehicle applications (e.g., commercial vehicles with two front axles, or towing machines where the front load is particularly large). Furthermore, the differential cylinder has a high power density even with short piston rod travel distances, thereby saving a large amount of structural space.

[0009] Furthermore, in the installed state, it is conceivable that the first hydraulic port is connected to at least one rod-side working chamber of the steering booster hydraulic cylinder, and the second hydraulic port is connected to at least one piston-end-side working chamber of the steering booster hydraulic cylinder. This connection allows for a highly variable and reciprocal local arrangement configuration between the steering gear or hydraulic assembly and the steering booster hydraulic cylinder. This allows the steering system to be adapted to various variations of commercial vehicles. A conventional hydraulic pipeline can be used as the connecting element between the hydraulic assembly and the steering booster hydraulic cylinder, thus providing a simple and inexpensive solution.

[0010] The hydraulic assembly may have at least one first hydraulic subassembly and at least one second hydraulic subassembly, which may be integrated at least partially within a first subhousing block and a second subhousing block, or together within a housing block. The first and second hydraulic subassemblies may be understood as separate assemblies, differing at least in their functional and / or structural components. Because the first and second hydraulic subassemblies are based on different primary functions, their functional separation is significant and advantageous in terms of the steering system's most unambiguous driving strategy. Nevertheless, structural and / or functional coupling of the two subhousing blocks may be at least partially advantageous in terms of optimized structural space requirements. Two alternatives may be considered: firstly, the housing block may have a first subhousing block and a second subhousing block. This configuration allows for a two-part housing block configuration based on first and second sub-housing blocks, and consequently, a variable configuration of the first and second hydraulic subassemblies. For this purpose, the first and second sub-housing blocks can be fixed to each other (e.g., by screwing, welding, or similar suitable methods). Alternatively, the first and second sub-housing blocks may be integrated within a single housing block, for example, in a one-piece configuration.

[0011] Furthermore, the first hydraulic subassembly may include at least one hydraulic pump, at least one working fluid tank, and at least one electric motor for driving the hydraulic pump, which is capable of supplying and / or controlling working fluid to the steering gear. By integrating at least partially the hydraulic pump within the first subhousing block, the flow path for its supply and drive control from the pump to the steering gear can be shortened, thereby enabling the steering gear to be driven, controlled, and supplied with working fluid (formed, for example, as a hydraulic fluid suitable for the steering gear) more quickly, more accurately, and with less pipeline loss. In addition, this can reduce the required structural space while simultaneously increasing power density.

[0012] In addition, the first hydraulic subassembly may be envisioned to have at least one first conduit connected to at least one first working chamber of the steering gear housing, to which working fluid can be supplied and / or controlled using a hydraulic pump. Furthermore, the first hydraulic subassembly may have at least one second conduit connected to at least one second working chamber of the steering gear housing, to which working fluid can be supplied and / or controlled using a hydraulic pump. By providing the first and second conduits inside the first subhousing block, the respective conduit lengths of the first and second conduits become very short, thereby enabling the steering gear to be driven, controlled, and supplied with hydraulic fluid more quickly, more accurately, and with less conduit loss. Alternatively, the first and second conduits can be provided directly in the block (e.g., as holes, grooves, or other recesses), thereby enabling a very simple configuration of the conduits and reducing conduit elasticity.

[0013] Alternatively, the hydraulic pump may be configured as a bidirectional hydraulic pump having first and second discharge directions, connected to a first and second pipeline, in which case the hydraulic pump is configured to pressurize the first pipeline according to the first discharge direction and the second pipeline according to the second discharge direction. A bidirectional pump is particularly advantageous for this application because the steering gear piston needs to be pressurized in various directions symmetrically on both sides, especially on its respective end faces and the two working chambers formed therein, in order to generate steering force assistance. Each end face has the same hydraulic working surface. By reversing their rotational directions, the discharge direction of the hydraulic pump changes automatically for functional reasons, and thus pressurizing and driving control of the two working chambers of the steering gear can be performed very easily via the first and second pipelines. Thus, this configuration results in a highly efficient pump-steering gear configuration for appropriately adapted applications in steering gears. Furthermore, since the discharge direction depends only on the rotational direction, very simple drive control by an electric motor is also possible.

[0014] The second hydraulic subassembly may further have at least one first main conduit and at least one second main conduit, in which case the first main conduit is connected to the first conduit of the first hydraulic subassembly, and in which case the second main conduit is connected to the second conduit of the first hydraulic subassembly. By connecting the first main conduit to the first conduit and the second main conduit to the second conduit, precise, logical, and unique parallel or parallel drive control and pressurization of the steering gear and the steering booster hydraulic cylinder is achieved, thereby very easily and efficiently solving the parallel and parallel drive control of these two components.

[0015] In this context, the first main conduit may open to a first port, in which case at least one first switching valve may be located within the first main conduit. Thus, the second main conduit may open to a second port, in which case at least one second switching valve may be located within the second main conduit. This configuration makes it possible to directly connect the first and second main conduits to the rod-side working chamber and the piston-end-side working chamber of the steering booster hydraulic cylinder. Furthermore, by providing the first and second hydraulic ports, a very simple interface can be obtained that enables highly variable coupling between the second hydraulic subassembly and the steering booster hydraulic cylinder.

[0016] Furthermore, the first and second switching valves may each be configured as pipe rupture safety valves. These valves are provided as one of several safety levels and are used in particular in the event of a pipe rupture or leak between the first and second hydraulic ports and the steering booster hydraulic cylinder. These valves are designed to move to the shut-off position when the flow rate passing through them (which increases, for example, due to a pipe rupture) exceeds a defined limit, thereby automatically shutting off the first and / or second main lines. This prevents a complete pressure drop in the entire steering system, particularly in the first and second subassemblies, and thus ensures continued pressure supply to the first hydraulic subassembly if it remains intact. Even if hydraulic assistance from the hydraulic pump is no longer possible in the first subassembly, mechanical steering by the steering gear and steering shaft remains maintained as a last resort.

[0017] Furthermore, the second hydraulic subassembly is assumed to have at least one return line connected to the first main line and / or the second main line and opening to the working fluid tank. Since the steering booster hydraulic cylinder is configured as a differential cylinder, the rod-side working chamber of the steering booster hydraulic cylinder has a different hydraulic surface than the piston-end-side working chamber of the steering booster hydraulic cylinder, resulting in asymmetrical outflow and inflow velocities according to the piston's travel distance. The problem lies particularly in the pressurization or drive control of the rod-side working chamber, so that a first mass flow rate flows into this rod-side working chamber, and accordingly, a second mass flow rate greater than the first mass flow rate flows out from the piston-end-side working chamber. As a result of this mass flow rate difference without a return line, the hydraulic pump will be supplied with more mass flow rate (via the second main line and the second line) than is pushed out from the output side to the first line, which could lead to a dangerous blockage in the steering system. For this reason, a separate return line is provided to ensure that any excess difference in mass flow rate is discharged into the working fluid tank. In the reverse case (pressurization or drive control of the piston end side working chamber via a second main line), this type of risk does not occur. This is because the hydraulic pump is supplied with a mass flow rate that is less than what is pushed out from the output side, and therefore only the working fluid reflection decreases in the hydraulic tank, which can be resolved by sufficient tank capacity.

[0018] In addition, at least one hydraulic filter element may be placed within the return line. Integrating the hydraulic filter element into the second hydraulic subassembly has the advantage that the assembly can be very easily extended for further functionality. This is because the hydraulic filter element can be very easily integrated into the existing return line anyway, thereby filtering the working fluid (particularly as hydraulic fluid configured and specialized for steering gears) in a very simple manner.

[0019] According to one embodiment, the return pipeline may be branched from the second main pipeline. In particular, the return pipeline may be branched exclusively from the second main pipeline. This switching configuration saves at least one additional switching valve and one section of the return pipeline, thereby reducing the complexity of the system and the number of required components. This also enhances the safety of the system.

[0020] Furthermore, it may be assumed that at least one return switching valve is located in the return pipeline, and that the return switching valve has at least one control input side connected to the first main pipeline via at least one control pipeline. In this switching logic, the return switching valve is configured to open only when the first main pipeline is pressurized, thereby switching the return switching valve to the pass position using the control input side. Therefore, the working fluid can flow from the second main pipeline into the return pipeline as defined, and the aforementioned hydraulic blockage does not occur. In the case of the reverse pressurization (the second main pipeline is pressurized), the return switching valve remains in its stationary or shut-off position. This is because the first main pipeline is not pressurized, and therefore the control input side is not pressurized, and the return switching valve is not driven. This shut-off position is very important because otherwise, the pressurized working fluid would be directly supplied again from the second main pipeline to the return pipeline, making it impossible to drive the steering booster hydraulic cylinder.

[0021] Furthermore, it may be assumed that at least one check valve is provided in the second main pipeline. The check valve plays an important safety function when the rod-side working chamber of the steering booster hydraulic cylinder is pressurized. This is because the working fluid, flowing from the piston-end-side working chamber of the steering booster hydraulic cylinder to the second main pipeline at an increased mass flow rate (see above description), is prevented from flowing from the second main pipeline into the second pipeline of the first hydraulic subassembly, and instead can flow as defined into the return pipeline, and further supply from the return pipeline to the working fluid tank.

[0022] An electrohydraulic steering system may further have at least one pressure and / or volume compensating vessel connected to the working fluid tank. The working fluid is subject to some temperature fluctuations in the volume used in the steering system, and these temperature fluctuations lead to changes in the total volume of the working fluid. A key reason for the temperature fluctuations is the asymmetric inflow and outflow velocities of the differential cylinder. Therefore, based on the nearly incompressible nature of the working fluid within the normal pressure range for the steering gear, it is possible to compensate for any volume increase or decrease due to temperature. Pressure and / or volume compensating vessels are known systems with this kind of function and are therefore particularly advantageous to use in this context.

[0023] In further embodiments, at least one third switching valve, particularly in the form of a 3-port 2-way switching valve, may be located within the first main line. Accordingly, at least one fourth switching valve, particularly in the form of a 3-port 2-way switching valve, may be located within the second main line. The third and fourth switching valves advantageously enable further functionality within the second hydraulic subassembly. Furthermore, a check valve in the second main line can be omitted, which simplifies the system structure of the second main line.

[0024] Furthermore, it is conceivable that the third switching valve has a return port connected to the return line, and the fourth switching valve also has a return port connected to the return line. In addition to the further functionality described above, this configuration includes the fact that the working fluid is not returned directly to the pump, but rather, the inflow and outflow of the working fluid is supplied directly to the tank via the third or fourth switching valve and the return line, regardless of the operating direction of the steering booster hydraulic cylinder. Thus, the first and second lines of the first hydraulic subassembly and the first and second main lines of the second hydraulic subassembly are subjected to less pressure fluctuations, which has a positive effect on the lifespan and drive controllability of the assembly.

[0025] Furthermore, according to the present invention, a vehicle, particularly a commercial vehicle, equipped with at least one electro-hydraulic steering system as described above is envisaged. All advantages and technical effects that can be obtained in relation to the steering system according to the present invention can be applied to the vehicle according to the present invention, individually or in combination. This vehicle may particularly be a commercial vehicle.

[0026] Further details and advantages of the present invention will be explained in more detail here based on the embodiments shown in the drawings.

Brief Description of the Drawings

[0027] [Figure 1] FIG. 1 is a schematic diagram showing the switching arrangement configuration of a first embodiment of a steering system 100 according to the present invention. [Figure 2] FIG. 2 is a schematic diagram showing the switching arrangement configuration of a second embodiment of a steering system according to the present invention. [Figure 3] FIG. 3 is a schematic diagram showing the switching arrangement configuration of a third embodiment of a steering system according to the present invention. [Figure 4] FIG. 4 is a schematic diagram showing the switching arrangement configuration of a fourth embodiment of a steering system according to the present invention.

[0028] FIG. 1 shows a schematic diagram of the switching arrangement configuration of a first embodiment of a steering system 100 according to the present invention.

[0029] The electro-hydraulic steering system 100 for a commercial vehicle has a steering gear 102 in the form of a spindle-type steering gear 102, and this steering gear 102 also has a steering gear housing 104.

[0030] The spindle-type steering gear 102 may particularly be configured as a ball-circulation type spindle-type steering gear, and in this case, other gear systems are also conceivable.

[0031] The electro-hydraulic steering system 100 further comprises a hydraulic assembly 106, which is fixed directly or indirectly to the steering gear housing 104.

[0032] This hydraulic assembly 106 is configured in the form of an electro-hydraulic assembly 106.

[0033] As shown in Figure 1, the hydraulic assembly 106 has, as subassemblies, a first hydraulic subassembly 106.1 and a second hydraulic subassembly 106.2.

[0034] Furthermore, the electro-hydraulic steering system 100 also has a further hydraulic assembly that is fixed to the steering gear housing 104.

[0035] This additional hydraulic assembly can also be configured as an electro-hydraulic assembly.

[0036] Direct fastening of the hydraulic assembly 106 and further hydraulic assemblies to the steering gear housing 104 is possible via corresponding flange connections, which are not shown in the schematic diagram of Figure 1.

[0037] However, the attachment of the hydraulic assembly 106 and any further hydraulic assemblies to the steering gear housing 104 can also be achieved indirectly through other components of the steering system, although these are not shown in the schematic diagram of Figure 1.

[0038] As shown in Figure 1, several components of the hydraulic assembly 106 are integrated, at least partially, within the housing block 110.

[0039] Accordingly, several components of the first hydraulic subassembly 106.1 may be integrated, at least partially, within the first subhousing block 110.1.

[0040] Therefore, several components of the second hydraulic subassembly 106.2 may be integrated, at least partially, within the second subhousing block 110.2.

[0041] The first sub-housing block 110.1 and the second sub-housing block 110.2 are configured as structurally separate blocks and are blocked from each other by corresponding connecting parts, as shown in Figure 1.

[0042] Alternatively, the first and second hydraulic subassemblies 106.1 and 106.2 may also be integrated together within the housing block 110, which then constitutes a common valve block 110.

[0043] Further components of the hydraulic assembly are integrated, at least partially, within an additional housing block.

[0044] The housing block 110 and the further housing blocks are structurally separate blocks and are fixed to various points in the steering gear housing 104.

[0045] For example, the housing block 110 and the further housing block may be fixed in the steering gear housing 104 at opposing locations (i.e., oriented 180° apart from each other).

[0046] Similarly, the housing block 110 and the further housing block may be fixed in the steering gear housing 104 at orientations of 90° or 270° relative to each other.

[0047] According to an alternative configuration of the housing block for the steering system 100, (though not shown in Figure 1) multiple components of the hydraulic assembly 106 and further hydraulic assemblies may be integrated, at least partially, within a single common housing block.

[0048] Next, the common housing block may have a housing block 110 (composed of first and second sub-housing blocks 110.1, 110.2) and a further housing block, or it may consist of these two blocks 110, or alternatively, it may be configured as a single housing block (made of the same material as the entire block).

[0049] In addition, the steering system 100 includes an electronic open-loop control and / or closed-loop control device 114 for open-loop and / or closed-loop control of the first and second hydraulic subassemblies 106.1, 106.2 and further assemblies (the necessary electrical lines for this are not shown in Figure 1).

[0050] As a component, the first hydraulic subassembly 106.1 includes, in particular, a working fluid tank 117, a hydraulic pump 116, and an electric motor M for driving the hydraulic pump 116, which allows the working fluid to be supplied to and controlled for the steering gear 102.

[0051] The working fluid is configured as a hydraulic oil suitable for or specialized for steering gears.

[0052] The hydraulic pump 116 is configured as a double-acting or bidirectional hydraulic pump having a first and a second discharge direction.

[0053] The first hydraulic subassembly 106.1 further includes a first conduit 118 connected to a first working chamber 122 of the steering gear housing 104.

[0054] The first hydraulic subassembly 106.1 further includes a second conduit 120 connected to a second working chamber 124 of the steering gear housing 104.

[0055] As can be seen in Figure 1, the hydraulic pump 116 is connected to the first pipeline 118 and the second pipeline 120.

[0056] Alternatively, instead of the above configuration, a single, simple-to-operate hydraulic pump may be provided, connected to the first and second pipelines 118 and 120 via a corresponding switching valve (not shown in Figure 1), and this hydraulic pump may be connected to the first and second pipelines 118 and 120 according to the switching logic.

[0057] Alternatively, two hydraulic pumps may be provided, in which case each pump may be assigned to or connected to either the first or second pipeline 118,120.

[0058] According to Figure 1, the first conduit 118 extends from the first pressure output side of the hydraulic pump 116 to a port in the steering gear housing 104 that opens into the first working chamber 122.

[0059] The second conduit 120 extends from the second pressure output side of the hydraulic pump 116 to a port in the steering gear housing 104 that opens into the second working chamber 124.

[0060] One hydraulic filter element may be placed in each of the first pipeline 118 and the second pipeline 120.

[0061] Furthermore, as shown in Figure 1, a pressure sensor is located within the first pipeline 118.

[0062] Furthermore, a pressure sensor and a temperature sensor are located within the second pipeline 120.

[0063] Additionally or alternatively, a temperature sensor may be located within the first conduit 118.

[0064] As previously mentioned, the first hydraulic subassembly 106.1 includes a working fluid tank 117 which may be fully or partially integrated within the housing block 110 or flange-fixed to the housing block 110.

[0065] The working fluid tank 117 may simply be integrated entirely or partially within the first sub-housing block 110.1 or flange-fixed to the first sub-housing block 110.1.

[0066] The hydraulic tank is only shown schematically based on Figure 1, and therefore it is possible that the hydraulic pump 116 is integrated into the tank.

[0067] Alternatively or additionally, the electric motor, hydraulic tank, and hydraulic pump 116 may be flange-fixed to each other and connected via appropriate piping (not shown in Figure 1).

[0068] The hydraulic tank is further equipped with pressure and temperature sensors to monitor the pressure and temperature of the hydraulic fluid inside the tank.

[0069] A further hydraulic assembly is configured as a backup assembly and is connected to the steering gear 102 in the event of an error in the steering system 100.

[0070] Alternatively or additionally, a further hydraulic assembly may be connected to the steering gear 102 when the steering system 100 is inactive.

[0071] Here, "connection" can be understood to mean that a continuous flow path is provided between the working chambers 122 and 124 of the steering gear 102 via an additional hydraulic assembly.

[0072] Further hydraulic assemblies include, among other components, a hydraulic filter element and a backup switching valve.

[0073] The hydraulic filter element and the backup switching valve form a single series circuit.

[0074] The hydraulic filter element is located upstream of the backup switching valve.

[0075] A pressure sensor for monitoring the filter state and a bypass check valve or filter check valve may be arranged in parallel with the hydraulic filter element.

[0076] The pressure sensor may be configured as a differential pressure sensor, or alternatively, as two separate pressure sensors or pressure switches with configurable trigger thresholds (not shown in Figure 1).

[0077] The aforementioned pressure sensor, the additional sensors of the first hydraulic subassembly 106.1, and the electric motor M are connected to the electronic open-loop control and / or closed-loop control device 114 via corresponding conduits (not shown in Figure 1).

[0078] Further hydraulic assemblies have further first conduits and further second conduits.

[0079] A further first conduit is connected to the first working chamber 122 of the steering gear housing 104.

[0080] Accordingly, a further second conduit is connected to a second working chamber 124 of the steering gear housing 104.

[0081] The switching position of the backup switching valve is assigned to the flow position when it is inactive or in an error state.

[0082] Therefore, the first work chamber 122 and the second work chamber 124 are connected via further first and further second piping, as well as via a hydraulic filter element and a backup switching valve.

[0083] A further hydraulic assembly comprises a bridge circuit having four external branches and one bridge branch, in which case the four external branches are interconnected via four external nodes.

[0084] A bridge branch is also constructed from a series circuit consisting of a hydraulic filter element and a backup switching valve.

[0085] Therefore, the first work chamber 122 and the second work chamber 124 are connected to each other via further first and further second conduits, as well as via the bridge circuit 234.

[0086] For this purpose, the bridge circuit is connected to a further first conduit and a further second conduit using a second external node.

[0087] The bridge branch is also connected to two further external nodes of the bridge circuit, and they are not connected to the further first and second conduits.

[0088] A hydraulic filter element may be placed in each of the further first and further second conduits 118,120.

[0089] The backup switching valve is configured as a 2-port, 2-way solenoid valve and has a switching plunger and an electromagnetic coil for operating the switching plunger. In this case, a change in the switching position of the switching plunger triggers an induced voltage in the electromagnetic coil.

[0090] In addition to the first hydraulic subassembly 106.1 and further hydraulic assemblies, the steering system 100 also has a second subassembly 106.2, the structure of which will be described in more detail below.

[0091] Generally, the hydraulic assembly 106, or more specifically the second hydraulic subassembly 106.2, has a first hydraulic port 148 and a second hydraulic port 150 for supplying and / or controlling external hydraulic components 152 with respect to the hydraulic assembly 106.

[0092] The external hydraulic component 152 is a component of the electro-hydraulic steering system 100 and is configured as a steering booster hydraulic cylinder 152.

[0093] The steering booster hydraulic cylinder 152 is configured as a differential hydraulic cylinder, as shown in Figure 1.

[0094] In the installed state, the first hydraulic port 148 is connected to the rod-side working chamber of the steering booster hydraulic cylinder 152.

[0095] Therefore, the second hydraulic port 150 is connected to the piston end side working chamber of the steering booster hydraulic cylinder 152.

[0096] The second hydraulic subassembly 106.2 further includes a first main conduit 154 and a second main conduit 156.

[0097] The first main pipeline 154 is connected to the first pipeline 118 of the first hydraulic subassembly 106.1, as shown in Figure 1.

[0098] Therefore, the second main pipeline 156 is connected to the second pipeline 120 of the first hydraulic subassembly 106.1.

[0099] The first main pipeline 154 opens into the first port 148, or the first port 148 forms the end of the first main pipeline 154, to which the hydraulic pipeline of the steering booster hydraulic cylinder 152 can be detachably connected.

[0100] A first switching valve 158 is located within the first main pipeline 154.

[0101] The second main conduit 156 opens to the second port 150, or the port 150 forms the end of the second main conduit 156, to which further hydraulic lines of the steering booster hydraulic cylinder 152 can be detachably connected.

[0102] A second switching valve 160 is located within the second main pipeline 156.

[0103] The first switching valve 158 and the second switching valve 160 are each configured as pipe rupture safety valves.

[0104] In addition, the second hydraulic subassembly 106.2 may generally have a return line 162 that is connected to the first main line 154 and / or the second main line 156 and opens to the working fluid tank 117.

[0105] Within the return pipeline 162, a hydraulic filter element may be located (not shown in Figure 1) along with a bypass check valve and a differential pressure sensor, each arranged in parallel for this purpose.

[0106] According to this first embodiment, the return pipeline 162 is connected, in particular, exclusively to the second main pipeline 156.

[0107] In other words, the return pipeline 162 branches off exclusively from the second main pipeline 156.

[0108] A return switching valve 164 is located within the return pipeline 162, and this return switching valve 164 has a control input side that is connected to the first main pipeline 154 via a control pipeline 166.

[0109] A check valve 168 is also located within the second main pipeline 156.

[0110] The electrohydraulic steering system 100 further includes at least one pressure and / or volume compensation vessel 170 connected to the working fluid tank 117.

[0111] Furthermore, according to the present invention, a commercial vehicle is envisioned that is equipped with the electro-hydraulic steering system 100 described above (although not shown in Figure 1).

[0112] The functions of the steering system 100 according to the present invention can be described as follows.

[0113] The hydraulic pump 116 essentially supplies working fluid to the steering gear 102.

[0114] Furthermore, the steering gear 102 can be controlled based on its bidirectional configuration with respect to the hydraulic pump 116.

[0115] More precisely, the first working chamber 122 can be supplied with and controlled by the first conduit 118, because the first conduit 118 connects the working chamber 122 to the hydraulic pump 116.

[0116] Accordingly, the second working chamber 124 can be supplied with and controlled by the second conduit 120, because the second conduit 120 connects the working chamber 124 to the hydraulic pump 116.

[0117] This control is achieved by pressurizing either the first working chamber 122 or the second working chamber 124 of the steering gear by the hydraulic pump 116 (but not both simultaneously).

[0118] Therefore, the hydraulic pump 116 is configured such that the first pipeline 118 is pressurized according to the first discharge direction, and the second pipeline 120 is pressurized according to the second discharge direction.

[0119] As soon as the hydraulic pump 116 is driven by the electric motor M (for example, clockwise), the hydraulic pump 116 pressurizes the first pipeline 118, which extends to the first working chamber 122, according to its first discharge direction.

[0120] Therefore, the hydraulic pump 116 and the steering gear 102 are connected to each other via the first conduit 118, and the port of the steering gear 102 that is connected to the first conduit 118 and opens to the first work chamber 122 is pressurized.

[0121] Accordingly, the pressure is increased in the first working chamber 122, forcing the piston to shift linearly. This is because a lower pressure prevails in the opposing second working chamber 124, thereby achieving steering assistance via the steering output shaft.

[0122] Therefore, the pressure in the opposing second working chamber 124 is lower because this working chamber 124 is connected to the tank via the second pipeline 120 and (not shown in Figure 1) a corresponding return pipeline.

[0123] Therefore, the hydraulic fluid can flow back into the tank from the second working chamber 124.

[0124] In this regard, it is important to understand that the hydraulic pump 116 is always driven in only one direction of rotation, and therefore only the first or second pipeline 118, 120 can always be pressurized.

[0125] When the rotation direction of the hydraulic pump 116 is reversed, the above-described relationships or cases proceed in the reverse order, as described below.

[0126] As soon as the hydraulic pump 116 is driven by the electric motor M (for example, counterclockwise), the hydraulic pump 116 pressurizes the second pipeline 120, which extends to the second working chamber 124, according to the second discharge direction.

[0127] Therefore, the hydraulic pump 116 and the steering gear 102 are interconnected via a second conduit 120, and the port of the steering gear 102, which is connected to the second conduit 120 and opens to the second work chamber 124, is pressurized.

[0128] Consequently, the pressure in the second working chamber 124 increases, forcing the piston to shift linearly. This is because a lower pressure prevails in the opposing first working chamber 122, thereby achieving steering assistance via the steering output shaft.

[0129] Therefore, the pressure in the opposing first working chamber 122 is lower because this working chamber 122 is connected to the tank via the first pipeline 118 and (not shown in Figure 1) a corresponding return pipeline.

[0130] Therefore, the hydraulic fluid can flow back into the tank from the first working chamber 122.

[0131] In this regard, it is important to understand that the hydraulic pump 116 is always driven in only one direction of rotation, and therefore only the first or second pipeline 118, 120 can always be pressurized.

[0132] The functions of the steering system 100 described above are explained according to the normal operating state, while the following function descriptions describe the non-operating or error state of the system.

[0133] In this state, the backup switching valve is positioned in the flow switching position.

[0134] This position allows for uninterrupted flow from the first work chamber 122 to the second work chamber 124 via further first and second conduits and bridge circuits.

[0135] The direction of flow of the working fluid depends on the pressure gradient between the first working chamber 122 and the second working chamber 124.

[0136] The pressure gradient can only be generated by manual steering movement of the steering input shaft, which is shown to the left of the second working chamber 124 in Figure 1, in which case the steering input shaft may be located in a different position.

[0137] This is because the rotation of the steering shaft takes into account the linear shift movement of the steering gear piston via the internal spindle (in this case, no pressurization by the hydraulic pump 116 is performed), and in this case, this case is assigned to an error state.

[0138] Alternatively, the pressure gradient can be formed by selective pressurization of the first or second working chambers 122,124 by the hydraulic pump 116, as described above, in which case this case is assigned to the non-operating state of the steering system.

[0139] In this case, since the steering system operates normally, the backup switching valve is driven and controlled by the open-loop control and / or closed-loop control device, thereby switching to the pass position.

[0140] Non-operational status refers to a state where the steering system is not functioning, that is, a commercial vehicle is currently stationary or is moving but will not require steering assistance in the future in terms of time series.

[0141] In other words, the future steering assistance of the steering system (and consequently, the non-pressurization of the steering gear 102) cannot be estimated with a specific probability.

[0142] In this state, further functional assignments of additional assemblies of the hydraulic fluid filtration configuration can be advantageously utilized.

[0143] This is because the hydraulic pump 116 needs to be operating almost continuously so that the driver can perceive a certain steering resistance sensation, because steering assistance can only be generated quickly enough if the hydraulic pump is already operating.

[0144] Therefore, the pump operation in a non-operating state can be utilized to pressurize one of the two working chambers 122, 124, but the pressurization must be below a pressure threshold (made possible by the system's inertia and friction) that does not initiate actual steering assistance.

[0145] Since the filter element is located within the backup assembly, it can filter the hydraulic fluid very efficiently in terms of energy.

[0146] If the pressure inside the first working chamber 122 is higher than that inside the second working chamber 124, then, based on that, in the flow path that continues to the further assembly, or in the following components: - A first further pipeline (and possibly a hydraulic filter within that pipeline), - External node connecting the bridge circuit and further first conduits, - Permeable external branch in the direction of flow (uniquely determined by the arrangement of check valves), -Bridge branch with hydraulic filter element and backup switching valve, - A bridge branch is connected to an external node connected to a second pipeline, a further external branch that is permeable in the direction of flow, -A second pipeline, - Second working chamber 124, A flow of hydraulic fluid occurs through this passage.

[0147] If the pressure inside the second working chamber 124 is higher than that inside the first working chamber 122, then, based on that, in the flow path that continues to the further assembly, or in the following components: - A second pipeline (and possibly a hydraulic filter within that pipeline), - An external node connecting the bridge circuit to a second conduit, - Permeable external branch in the direction of flow (uniquely determined by the arrangement of check valves), -Bridge branch with hydraulic filter element and backup switching valve, - A bridge branch is connected to an external node connected to a further first conduit, a further external branch that is permeable in the direction of flow, - Further first pipeline, - First working chamber 122, A flow of hydraulic fluid occurs through this passage.

[0148] The two aforementioned flow paths enable the cleaning of the hydraulic fluid via the hydraulic filter element, which is the main filter element.

[0149] To that extent, the hydraulic fluid can be cleaned very efficiently when the steering system 100 is not in operation. This is because the pressure required for this is far less than the pressure required for steering assistance, and therefore no additional pumps or valves are needed.

[0150] This filtering pressure must remain below a pressure threshold, so as not to lead to any operation that would cause the steering gear piston to trigger actual steering motion.

[0151] However, since cleaning below the aforementioned threshold is quite possible based on friction and inertia within the steering system, cleaning via the hydraulic filter element will be very efficient when the steering system 100 is not in operation.

[0152] The function of the first hydraulic subassembly 106.1 was described above in conjunction with that of further hydraulic assemblies.

[0153] Here, the function of the first hydraulic subassembly 106.1 is described together with that of the second hydraulic subassembly 106.2.

[0154] According to the first discharge direction, the hydraulic pump 116 pressurizes a first conduit 118 that extends to a first working chamber 122, where it operates the steering gear piston, and immediately thereafter steering assistance is transmitted to the steering rod (not shown in Figure 1).

[0155] Simultaneously, the first main pipeline 154 is also pressurized, based on the fact that the first main pipeline 154 is connected to the first pipeline 118.

[0156] Under normal operating conditions, the first switching valve 158 switches to the position shown in Figure 1, thereby pressurizing the rod-side working chamber of the steering booster hydraulic cylinder 152 via the first port 148.

[0157] As a result, the hydraulic cylinder piston shifts toward the working chamber at the piston end, thereby pushing the working fluid out of this working chamber.

[0158] Similarly, the rod of the hydraulic cylinder piston is connected to the steering rod, so that an additional or amplified steering force is generated.

[0159] In other words, by providing the steering booster hydraulic cylinder 152, an additional hydraulic surface is provided, which, in combination with the existing hydraulic pressure, can perform additional work that is transmitted to the steering rod as amplified steering force.

[0160] Next, the working fluid is pushed into the second main conduit 156 through the second port 150 and then flows through the second switching valve 160 and the return switching valve 164 to the return conduit 162.

[0161] A check valve 168 located in the second main conduit 156 prevents the backflow of the working fluid into the second conduit 120 (of the first hydraulic subassembly 106.1).

[0162] According to this switching logic, the return switching valve 164 switches to the flow position based on the pressurized first main pipe 154 (not shown in Figure 1). This is because the pressurized first main pipe 154 pressurizes the control pipe 166, which in turn switches the return switching valve 164 to its flow position.

[0163] Next, the working fluid is returned to the working fluid tank 117 from the return pipe 162.

[0164] Since the steering booster hydraulic cylinder 152 is configured as a differential cylinder, the rod-side working chamber of the steering booster hydraulic cylinder 152 has a different hydraulic operating surface than the piston-end-side working chamber. As a result, asymmetrical outflow and inflow velocities or mass flow rates occur depending on the control logic.

[0165] When pressurizing or controlling the drive of the rod-side working chamber as described above, a first mass flow rate flows into the rod-side working chamber, while a second mass flow rate, which is greater than the first mass flow rate, flows out from the piston-end side working chamber (based on a larger hydraulic pressure surface).

[0166] As a result of this mass flow rate difference, without the return line 162, the hydraulic pump 116 may receive a greater mass flow rate (via the second line 120) than is pushed from the output side into the first line 118, which could lead to a risk of blockage in the steering system 100.

[0167] For this reason, a separate return pipe 162 is provided, which reliably discharges any excess difference in mass flow rate to the working fluid tank 117.

[0168] This difference in mass flow rate increases the temperature of the working fluid, which in turn causes pressure and volume changes within the working fluid, and these changes are reliably compensated for using the pressure and volume compensation vessel 170 connected to the working fluid tank 117.

[0169] In the opposite case (pressurization or drive control of the piston end side working chamber via the second main pipeline 156), the risk of this type of blockage is not as great. This is because the hydraulic pump 116 is supplied with a mass flow rate that is less than the mass flow rate pushed from the output side into the second pipeline 120 via the first pipeline 118.

[0170] Therefore, the amount of working fluid reflected in the hydraulic tank 117 decreases, but this can be resolved by having a sufficient tank capacity.

[0171] Furthermore, a hydraulic filter element may be located within the return pipe 162 (not shown in Figure 1), thereby filtering the working fluid when the first pipe 118 of the first subassembly 106.1 is pressurized under normal operating and / or non-operating conditions (see the description of the pressurization function of the first and second pipes 118,120 above).

[0172] In this configuration, the hydraulic filter element can be omitted, and in this case, it may be considered that two hydraulic filter elements may be provided instead.

[0173] Figure 2 shows a schematic diagram of the switching arrangement configuration of a second embodiment of the steering system 200 according to the present invention.

[0174] The second embodiment has substantially the same characteristics as the first embodiment, and in this case, the differences in structural characteristics will be explained below.

[0175] Components of the second embodiment, configured to substantially correspond to components of the first embodiment, have the same reference numerals.

[0176] According to Figure 2, a third switching valve 272, in the form of a 3-port 2-way switching valve, is located within the first main conduit 154.

[0177] Furthermore, a fourth switching valve 274, in the form of a 3-port 2-way switching valve, is located within the second main conduit 156.

[0178] The third switching valve 272 and the fourth switching valve 274 each have one return port connected to the return pipeline 162.

[0179] The functions of the second embodiment of the first hydraulic subassembly 106.1 and the second hydraulic subassembly 106.2 are described below.

[0180] According to the second discharge direction, the hydraulic pump 116 extends to the second working chamber 124, where it pressurizes the second conduit 120 that operates the steering gear piston, and immediately thereafter steering assistance is transmitted to the steering rod (not shown in Figure 2).

[0181] At the same time, based on the connection between the second main pipeline 156 and the second pipeline 120, the second main pipeline 156 is also pressurized.

[0182] Under normal operating conditions, the second switching valve 160 switches to the position shown in Figure 2, in which case the fourth switching valve 274 switches to the flow position for the second main conduit 156, which is not shown in Figure 2.

[0183] In these switching positions of the switching valves 160 and 274, the piston end side working chamber of the steering booster hydraulic cylinder 152 is pressurized via the second port 150.

[0184] As a result, the hydraulic cylinder piston shifts toward the rod-side working chamber (which is consequently reduced in size), thereby pushing the working fluid out of this working chamber.

[0185] Similarly, the rod of the hydraulic cylinder piston is connected to the steering rod, so that an additional or amplified steering force is generated.

[0186] In other words, by providing the steering booster hydraulic cylinder 152, an additional hydraulic surface is provided, which, in combination with the existing hydraulic pressure, can perform additional work that is transmitted to the steering rod as amplified steering force.

[0187] Next, the working fluid is pushed into the first main conduit 154 through the first port 148 and then flows through the first switching valve 158 and the third switching valve 272 to the return conduit 162.

[0188] The third switching valve 272 switches to the flow position for the return pipeline 162 based on the first main pipeline 154, which is not pressurized, according to the switching logic.

[0189] This is because the unpressurized first main line 154 does not pressurize the control input side of the third switching valve 272, thereby connecting the first main line 154 (the section between the third switching valve 272 and the first port 148) and the return line 162 to each other.

[0190] Next, the working fluid is returned to the working fluid tank 117 from the return pipe 162.

[0191] Since the steering booster hydraulic cylinder 152 is configured as a differential cylinder, the rod-side working chamber of the steering booster hydraulic cylinder 152 has a different hydraulic operating surface than the piston-end-side working chamber. As a result, asymmetrical outflow and inflow velocities or mass flow rates occur depending on the control logic.

[0192] When pressurizing or controlling the drive of the piston end side work chamber as described above, a second mass flow rate flows into the piston end side work chamber (from the second main line 156), while a corresponding amount of the first mass flow rate, which is less than the second mass flow rate, flows out from the rod side work chamber.

[0193] However, according to the second embodiment, the two main lines 154 and 156 are connected symmetrically to the return guide line 162 via switching valves 272 and 274, so that the difference in mass flow rate is reliably discharged to the working fluid tank 117, regardless of whether the first main line 154 or the second main line 156 is pressurized.

[0194] Furthermore, a hydraulic filter element (not shown in Figure 2) may be placed in the return pipe 162, thereby filtering the working fluid when the first pipe 118 or the second pipe 120 of the first subassembly 106.1 is pressurized (see the description of the pressurization function of the first and second pipes 118 and 120 above).

[0195] In this case, the hydraulic filter elements within the hydraulic assembly can be omitted, and it may be considered that two hydraulic filter elements may be provided instead.

[0196] In the reverse case (i.e., when the first conduit 118 and the first main conduit 154 are pressurized), the second hydraulic subassembly 106.2 operates with a strictly reversed switching logic (based on the symmetrical arrangement of components and conduits within the second hydraulic subassembly 106.2).

[0197] Figure 3 shows a schematic diagram of the switching arrangement configuration of a third embodiment of the steering system 300 according to the present invention.

[0198] Figure 3 shows only the second hydraulic subassembly 206.2, in which case the first hydraulic subassembly 106.1, the steering gear 102, and further hydraulic assemblies correspond to the hydraulic assemblies in Figures 1 and 2.

[0199] A third embodiment of the second hydraulic subassembly 206.2 has substantially the same structural and / or functional features as the second embodiment of the second hydraulic subassembly 106.2, as follows:

[0200] The second hydraulic subassembly 206.2 has a first main conduit 154 and a second main conduit 156.

[0201] The first main conduit 154 is connected to the first conduit 118 of the first hydraulic subassembly 106.1, and accordingly, the second main conduit 156 is connected to the second conduit 120 of the first hydraulic subassembly 106.1 (see Figure 1).

[0202] The first main pipeline 154 opens into the first port 148, or the first port 148 forms the end of the first main pipeline 154, to which the hydraulic pipeline of the steering booster hydraulic cylinder 152 can be detachably connected.

[0203] A first switching valve 158 is located within the first main conduit 154 (see Figure 1).

[0204] The second main conduit 156 opens to the second port 150, or the port 150 forms the end of the second main conduit 156, to which further hydraulic lines for the steering booster hydraulic cylinder 152 can be detachably connected.

[0205] A second switching valve 160 is located within the second main pipeline 156 (see Figure 1).

[0206] The first switching valve 158 and the second switching valve 160 are each formed as pipe rupture safety valves.

[0207] The first main pipeline 154 has a first check valve 376 between the connection point in the first pipeline 118 (see Figure 1) and the first switching valve 158.

[0208] Accordingly, the second main pipeline 156 has a second check valve 378 between the connection point in the second pipeline 120 (see Figure 2) and the second switching valve 160.

[0209] As described above, the third embodiment of the second hydraulic subassembly 206.2 has substantially the same structural and / or functional characteristics as the second embodiment of the second hydraulic subassembly 106.2, in which case the following structural and / or functional differences should be shown.

[0210] A first branch return pipe 380 branches off between the first switching valve 158 and the first check valve 376.

[0211] Accordingly, a second branch return pipe 382 branches off between the second switching valve 160 and the second check valve 378.

[0212] According to Figure 3, the second hydraulic subassembly 206.2 further includes a return switching valve 264.

[0213] This return switching valve 264 connects two branch return pipes 380 and 382 to a return pipe 162 that opens to the working fluid tank 117 (see Figure 1).

[0214] The return switching valve 264 is configured as a hydraulically operated 3-port 3-way switching valve and has correspondingly 3 switching positions.

[0215] Additionally or alternatively, the return switching valve 264 may be configured as an electrically and / or electro-hydraulically operable three-port three-way switching valve, having correspondingly these three switching positions.

[0216] In the intermediate position shown in Figure 3, the return switching valve 264 blocks both the two branched return pipes 380 and 382 and the return pipe 162 from each other, so no fluid communication is formed between these pipes.

[0217] The intermediate position of the return switching valve 264 is centered by a spring. That is, two springs positioned laterally and outward automatically place the return switching valve 264 in the intermediate position due to the spring stress of their respective springs when the pressures in the two branch return pipes 380 and 382 are the same.

[0218] The same pressure may exist in the two branched return pipes 380 and 382 when the steering system 300 is losing pressure or when the pressure in the pressurized steering system 300 is correspondingly the same.

[0219] At a first passing position not shown in Figure 3, the return switching valve 264 shuts off the second branch return pipeline 382 and thus connects the first branch return pipeline 380 to the return pipeline 162, thus creating a fluid communication between these two pipelines.

[0220] A first passing position, not shown in Figure 3, occurs when the pressure in the second branched return pipe 382 is higher than the pressure in the first branched return pipe 380.

[0221] In other words, the return switching valve 264 always connects the branch return pipes 380 and 382, ​​which are occupied by lower pressures, to the return pipe 162, and therefore, according to the first passing position, connects the first branch return pipe 380 to the return pipe 162 accordingly.

[0222] Accordingly, the return switching valve 264 also shuts off the first branch return pipeline 380 at a second passing position not shown in Figure 3, and thus connects the second branch return pipeline 382 to the return pipeline 162, thereby creating a fluid communication between these two pipelines.

[0223] This second passing position, also not shown in Figure 3, occurs when the pressure in the first branch return pipe 380 is higher than the pressure in the second branch return pipe 382.

[0224] In other words, the return switching valve 264 always connects the branch return pipes 380 and 382, ​​which are occupied by lower pressures, to the return pipe 162, and therefore, depending on the second passing position, connects the second branch return pipe 382 to the return pipe 162 accordingly.

[0225] Within the return pipeline 162, a hydraulic filter element may be located (not shown in Figure 3) together with a bypass check valve and a differential pressure sensor, each arranged in parallel for this purpose.

[0226] Furthermore, two additional connecting pipelines branch off from the return pipeline 162. In this case, the first connecting pipeline is connected to the first main pipeline 154, and the second connecting pipeline is connected to the second main pipeline 156.

[0227] Each of the first and second connecting conduits is equipped with one check valve.

[0228] Figure 4 shows a schematic diagram of the switching arrangement configuration of a fourth embodiment of the steering system 400 according to the present invention.

[0229] Figure 4 shows only the second hydraulic subassembly 306.2, in which case the first hydraulic subassembly 106.1, the steering gear 102, and further hydraulic assemblies correspond to the hydraulic assemblies in Figures 1 and 2.

[0230] A fourth embodiment of the second hydraulic subassembly 306.2 has substantially the same structural and / or functional features as the third embodiment of the second hydraulic subassembly 206.2, as follows:

[0231] The second hydraulic subassembly 306.2 similarly has a first main conduit 154 and a second main conduit 156.

[0232] The first main conduit 154 is connected to the first conduit 118 of the first hydraulic subassembly 106.1, and therefore the second main conduit 156 is connected to the second conduit 120 of the first hydraulic subassembly 106.1 (see Figure 1).

[0233] The first main pipeline 154 opens into the first port 148, or the first port 148 forms the end of the first main pipeline 154, to which the hydraulic pipeline of the steering booster hydraulic cylinder 152 can be detachably connected (see Figure 1).

[0234] A first switching valve 158 is also located within the first main conduit 154.

[0235] The second main pipeline 156 opens to the second port 150, as shown in Figure 4, or the port 150 forms the end of the second main pipeline 156, to which further hydraulic lines for the steering booster hydraulic cylinder 152 can be detachably connected (see also Figure 1).

[0236] A second switching valve 160 is located within the second main pipeline 156.

[0237] The first switching valve 158 and the second switching valve 160 are each configured as pipe rupture safety valves.

[0238] The first main pipeline 154 further has a first check valve 476 between the connection point in the first pipeline 118 (see Figure 1) and the first switching valve 158.

[0239] Accordingly, the second main pipeline 156 shown in Figure 4 has a second check valve 478 between the connection point in the second pipeline 120 (see Figure 1) and the second switching valve 160.

[0240] A first branch return pipe 480 branches off between the first switching valve 158 and the first check valve 476.

[0241] Accordingly, a second branch return pipe 482 branches off between the second switching valve 160 and the second check valve 478.

[0242] As described above, the fourth embodiment of the second hydraulic subassembly 306.2 has substantially the same structural and / or functional characteristics as the third embodiment of the second hydraulic subassembly 206.2, in which case the following structural and / or functional differences should be shown.

[0243] The first branched return pipe 480 and the second branched return pipe 482 each have corresponding ports opening into the return pipe 162, so the two branched return pipes 480 and 482 are connected to the return pipe 162 (see, for example, Figure 1) which opens into the working fluid tank 117.

[0244] In the first branched return pipeline 480, as shown in Figure 4, a first valve assembly is located, which consists of a controllable first check valve 484 and a pipeline section having an integrated throttling that extends parallel to the first check valve 484.

[0245] Accordingly, a second valve assembly is located within the second branch return pipeline 482, which comprises a controllable second check valve 486 and a pipeline section having an integrated throttling extending parallel to the check valve 486.

[0246] For the control of the first controllable check valve 484, the check valve 484 is connected to the second main pipeline 156 via a first control pipeline (dashed line diagram), in which case the first control pipeline branches between the second switching valve 160 and the second check valve 478.

[0247] The first controllable check valve 484 may be configured as a check valve that can be shut off and released, and may have various drive control states.

[0248] According to the first drive control state, the first controllable check valve 484 can be shut off if a pressure (exceeding a certain first control pressure threshold) is applied in the first control pipeline or the second main pipeline 156.

[0249] Furthermore, (according to the second drive control state) the first controllable check valve 484 may be assumed to be able to shut off if no pressure (below a certain control pressure threshold) is applied in the first control pipeline or the second main pipeline 156.

[0250] Accordingly, for the control of the second controllable check valve 486, the second check valve 486 is connected to the first main pipeline 154 via a second control pipeline (dashed line diagram), in which case the second control pipeline branches between the first switching valve 158 and the first check valve 476.

[0251] The second controllable check valve 486 may be configured as a deactivatable check valve and may have various drive control states.

[0252] According to the first drive control state, the second controllable check valve 486 can be shut off if a pressure (exceeding a certain control pressure threshold) is applied in the second control pipeline or the first main pipeline 154.

[0253] Additionally, (according to the second drive control state) the second controllable check valve 486 may be shut off if no pressure (below a certain control pressure threshold) is applied in the second control pipeline or the first main pipeline 154.

[0254] Further within the return pipeline 162, a hydraulic filter element may be located (not shown in Figure 4) along with a bypass check valve and a differential pressure sensor, each arranged in parallel for this purpose.

[0255] Furthermore, two additional connecting pipelines branch off from the return pipeline 162. In this case, the first connecting pipeline is connected to the first main pipeline 154, and the second connecting pipeline is connected to the second main pipeline 156.

[0256] Each of the first and second connecting conduits is equipped with one check valve. [Explanation of Symbols]

[0257] 100 Electro-hydraulic steering system 102 Steering gears, especially spindle-type steering gears 104 Steering gear housing 106 Hydraulic, especially electro-hydraulic assemblies 106.1 First hydraulic subassembly 106.2 Second hydraulic subassembly 110 Housing Blocks 110.1 First sub-housing block 110.2 Second sub-housing block 114 Electronic open-loop control and / or closed-loop control device 116 Hydraulic pump 117 Working fluid tank 118 First pipeline 120 Second pipeline 122 First working chamber 124 Second working chamber 148 First hydraulic port 150 Second hydraulic port 152 External hydraulic components, steering booster hydraulic cylinder 154 First Main Pipeline 156 Second main pipeline 158 First switching valve 160 Second switching valve 162 Return pipeline 164 Return switching valve 166 Control pipeline 168 Check valve 170 Pressure and / or volume compensating vessel 200 Electro-hydraulic steering system 272 Third switching valve 274 Fourth switching valve 300 Electro-hydraulic steering system 206.2 Second hydraulic subassembly 264 Return switching valve 376 First check valve 378 Second check valve 380 First branch return pipeline 382 Second branch return pipeline 400 Electro-hydraulic steering system 306.2 Second hydraulic subassembly 476 First check valve 478 Second check valve 480 First branch return pipeline 482 Second branch return pipeline 484 First controllable check valve 486 Second controllable check valve M Electric Motor

Claims

1. Electro-hydraulic steering systems (100, 200, 300, 400) for vehicles, especially commercial vehicles, including the following: - At least one steering gear (102) having at least one steering gear housing (104), in particular a spindle-type steering gear, - comprising at least one hydraulic assembly (106), particularly an electro-hydraulic assembly (106), which can be fixed directly or indirectly to the steering gear housing (104) for supplying working fluid to the steering gear (102) and / or for controlling the steering gear (102), One or more components of the hydraulic assembly (106) are at least partially integrated within the housing block (110), An electro-hydraulic steering system (100, 200, 300, 400) wherein the hydraulic assembly (106) has at least one first hydraulic port (148) and at least one second hydraulic port (150) for supplying and / or controlling at least one external hydraulic component (152) with respect to the hydraulic assembly (106).

2. The external hydraulic component (152) is a component of the electro-hydraulic steering system (100, 200, 300, 400), and is configured in particular as a steering booster hydraulic cylinder (152) in the form of a differential hydraulic cylinder, according to claim 1 of the electro-hydraulic steering system (100, 200, 300, 400).

3. The electro-hydraulic steering system (100, 200, 300, 400) according to claim 2, wherein, in the installed state, the first hydraulic port (148) is connected to at least one rod-side working chamber of the steering booster hydraulic cylinder (152), and the second hydraulic port (150) is connected to at least one piston-end-side working chamber of the steering booster hydraulic cylinder (152).

4. The electro-hydraulic steering system (100, 200, 300, 400) according to any one of claims 1 to 3, wherein the hydraulic assembly (106) comprises at least one first hydraulic subassembly (106.1) and at least one second hydraulic subassembly (106.2), each at least partially integrated within a first sub-housing block (110.1) and a second sub-housing block (110.2), or together within the housing block (110).

5. The electro-hydraulic steering system (100, 200, 300, 400) according to claim 4, wherein the first hydraulic subassembly (106.1) comprises at least one hydraulic pump (116), at least one working fluid tank (117), and at least one electric motor (M) for driving the hydraulic pump (116) which is capable of supplying and / or controlling working fluid to the steering gear (102).

6. The electrohydraulic steering system (100, 200, 300, 400) according to claim 4 or 5, wherein the first hydraulic subassembly (106.1) has at least one first conduit (118) connected to at least one first work chamber (122) of the steering gear housing (104) and to which working fluid can be supplied and / or controlled using the hydraulic pump (116), and the first hydraulic subassembly (106.1) has at least one second conduit (120) connected to at least one second work chamber (124) of the steering gear housing (104) and to which working fluid can be supplied and / or controlled using the hydraulic pump (116).

7. The electrohydraulic steering system (100, 200, 300, 400) according to any one of claims 4 to 6, wherein the second hydraulic subassembly (106.2) has at least one first main conduit (154) and at least one second main conduit (156), the first main conduit (154) being connected to the first conduit (118) of the first hydraulic subassembly (106.1), and the second main conduit (156) being connected to the second conduit (120) of the first hydraulic subassembly (106.1).

8. The electrohydraulic steering system (100, 200, 300, 400) according to claim 7, wherein the first main conduit (154) opens to the first port (148) and at least one first switching valve (158) is located within the first main conduit (154), and the second main conduit (156) opens to the second port (150) and at least one second switching valve (160) is located within the second main conduit (156).

9. The electrohydraulic steering system (100, 200, 300, 400) according to claim 8, wherein the first switching valve (158) and the second switching valve (160) are each configured as pipe rupture safety valves.

10. The electrohydraulic steering system (100, 200, 300, 400) according to any one of claims 7 to 9, wherein the second hydraulic subassembly (106.2) has at least one return line (162) connected to the first main line (154) and / or the second main line (156) and opening to the working fluid tank (117).

11. The electrohydraulic steering system (100, 200, 300, 400) according to claim 10, wherein at least one hydraulic filter element is located in the return pipe (162).

12. The electrohydraulic steering system (100) according to claim 10 or 11, wherein the return pipeline (162) branches particularly exclusively from the second main pipeline (156).

13. The electrohydraulic steering system (100) according to claim 12, wherein at least one return switching valve (164) is located in the return line (162), and the return switching valve (164) has at least one control input side connected to the first main line (154) via at least one control line (166).

14. The electrohydraulic steering system (100) according to claim 12 or 13, wherein at least one check valve (168) is located within the second main pipeline (156).

15. The electrohydraulic steering system (100) according to any one of claims 12 to 14, wherein the electrohydraulic steering system (100) has at least one pressure and / or volume compensation vessel (170) connected to the working fluid tank (117).

16. An electrohydraulic steering system (200) according to any one of claims 7 to 11, wherein at least one third switching valve (272), particularly in the form of a three-port two-way switching valve, is located in the first main conduit (154), and at least one fourth switching valve (274), particularly in the form of a three-port two-way switching valve, is located in the second main conduit (156).

17. The electrohydraulic steering system (200) according to claim 16, wherein the third switching valve (272) has a return port connected to the return pipe (162), and the fourth switching valve (274) also has a return port connected to the return pipe (162).

18. A vehicle, particularly a commercial vehicle, comprising at least one electrohydraulic steering system (100, 200) according to any one of claims 1 to 17.

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