Pump unit and electrohydraulic steering system

Abstract

The invention relates to a pump unit (100), in particular for an electrohydraulic steering system, having at least one drive unit (110), at least one pump (120), at least one housing unit (130) and at least one drive shaft unit (140), wherein at least one fluid connection between an external face of the housing unit (130), in particular at least one hydraulic fluid connection (144) of the housing unit (130), and the hydraulic tank (136), preferably formed within the housing unit (130), can be provided via the housing unit (130) and / or the drive shaft unit (140). The invention also relates to an electrohydraulic steering system (1000).

Description

[0001] DESCRIPTION

[0002] Pump unit and electro-hydraulic steering system

[0003] The present invention relates to a pump unit and an electro-hydraulic steering system for a vehicle, in particular for a commercial vehicle, with such a pump unit.

[0004] Electro-hydraulic steering systems are generally known in the art. However, during rapid steering maneuvers, such as quick evasive maneuvers, maintaining sufficient pressure in the piston chambers of a vehicle equipped with such a system can pose a challenge, particularly at low operating temperatures. This can slow down the response of the electro-hydraulic steering system and / or impair steering behavior in general.

[0005] Oil exhibits particularly high viscosity at low (operating) temperatures, for example, from approximately -40°C to -20°C. Immediately after commissioning the steering system and its associated components, such as oil pumps and wet-rotor motors, such low temperatures lead to significant viscous friction within the system.

[0006] Due to these frictional forces and losses, such strong viscous friction also results in a slower (fluid) pressure build-up, especially during rapid changes in the direction of rotation of a (bidirectionally acting) hydraulic pump. Furthermore, other components of the steering system, such as electronic control units, can also be affected by such low operating temperatures.

[0007] Furthermore, it should be considered that excessively high operating temperatures, for example from approximately 60°C to 110°C, can also impair the operation of an electro-hydraulic steering system, for example by leading to overheating of the electronic control unit or an increase in electric motor losses. In contrast, within a preferred operating temperature range of approximately -20°C to 60°C, a sufficiently suitable fluid pressure build-up, a suitable efficiency of the electric motor, and the proper functionality of all other components, such as a (functionally and spatially) associated control unit, can be ensured.

[0008] The object of the present invention is to provide a pump unit that enables efficient, rapid, and continuous adjustment of a suitable operating temperature, in particular by providing control and / or regulation of the temperature conditions, by means of the hydraulic fluid for temperature control of the components of the pump unit, and preferably also of components of an associated electro-hydraulic steering system. Furthermore, the object of the present invention is to provide an electro-hydraulic steering system incorporating such a pump unit.

[0009] This problem is solved according to the invention by a pump unit according to independent claim 1 and with respect to the steering system by the subject matter according to claim 12. Preferred embodiments are specified in the dependent claims.

[0010] According to the present invention, a pump unit, particularly for an electro-hydraulic steering system, is provided with at least one drive unit, in particular an electric motor with a stator and a rotor, at least one pump, at least one housing unit, and at least one drive shaft unit, wherein the housing unit is provided for accommodating the drive unit, the pump, for at least partial accommodating the drive shaft unit, and for forming a hydraulic tank for a hydraulic fluid. The at least one drive unit, in particular the rotor, is coupled or can be coupled to the at least one pump via the at least one drive shaft unit, so that the pump can be driven by means of the drive unit.At least one fluid connection between an outer surface of the housing unit, in particular at least one hydraulic fluid connection of the housing unit, and the hydraulic tank, preferably formed within the housing unit, can be provided via the housing unit and / or the drive shaft unit.

[0011] Preferably, a fluid connection can be provided from an outside of the housing unit to the inside of the housing unit or to the hydraulic tank of the housing unit.

[0012] The invention is based on the fundamental idea that a hydraulic fluid or operating / temperature control fluid, such as the oil of the electro-hydraulic steering system, can be introduced into or returned to the pump unit for short-term and long-term temperature control.

[0013] In its cold state, the high viscosity of a hydraulic fluid such as oil leads to high frictional forces and thus to a reduced efficiency of the pump unit or drive unit. The present invention allows such additional frictional forces to be prevented by briefly warming or heating the hydraulic fluid. This enables the drive unit of the pump unit to be operated with a higher efficiency, for example, by reducing the current draw of an electric motor used as the drive unit.

[0014] In terms of energy recovery, the hydraulic fluid, in particular the oil of an electro-hydraulic steering system, can be heated by the pump unit when in operation and can contribute to the temperature control of the pump unit by means of targeted recirculation into the housing unit.

[0015] In particular, after just a few pump revolutions, the (pumped) hydraulic fluid can reach a temperature increase of approximately 20°C. This volume of heated hydraulic fluid can be used to further heat the rest of the pump unit, including the remaining hydraulic fluid, the drive unit, an associated control unit, and the like. According to the present invention, the oil can be introduced from the pump into the housing unit via the drive shaft unit and / or returned there to effect heat transfer.

[0016] Accordingly, the pump unit can preferably be used in such a way that a suitable fluid connection between an outer surface of the pump unit's housing and the hydraulic tank inside the housing unit can be established or provided. By circulating a (comparatively) small volume of fluid within the pump unit, a temperature control effect for energy recovery can be achieved quickly and efficiently.

[0017] Preferably, to supply such a preferred fluid connection within the pump unit with hydraulic fluid, a valve device can be provided in an associated electro-hydraulic steering system, for example in the sense of a proportional valve, a select-low valve, an on / off valve, at least one throttle unit and / or the like.

[0018] In this way, the hydraulic fluid or oil, which heats up briefly, especially directly after the pump unit is switched on, can be returned to the pump unit to create a temperature control effect and to efficiently set an operating temperature range of the pump unit.

[0019] In particular, the resulting (hydraulic) losses can be used for energy recovery, for example to heat the pump, the drive unit, and / or a control unit of the pump unit. Furthermore, the hydraulic fluid or oil can provide a cooling effect, especially during continuous operation of the pump unit, to prevent overheating of the pump unit and, for example, its associated control unit.

[0020] The present invention provides an efficient short-term and long-term temperature control effect to ensure a suitable operating temperature range and to guarantee improved efficiency and optimized service life of the pump unit and the associated steering system.

[0021] Furthermore, the steering feel for the user can also be improved in the application of the associated electro-hydraulic steering system by temporarily overcoming or avoiding the highly viscous properties of the hydraulic fluid, even in the case of a cold start of the associated vehicle, through targeted and efficient temperature control of the hydraulic fluid.

[0022] For the purposes of the present invention, a hydraulic fluid can be understood to be a fluid such as oil, which is intended for the operation of a pump unit or an electro-hydraulic steering system and / or can produce a temperature control effect, i.e., in particular a heating effect and / or a cooling effect.

[0023] Furthermore, the drive shaft unit can be provided as a continuous drive shaft or a multi-section drive shaft within the pump unit to allow the drive unit to conveniently drive the pump. In particular, a multi-section drive shaft can be provided with a pump section and a drive unit section, wherein the pump section and the drive unit section can be joined together by force-fit and / or positive locking.

[0024] The pump unit according to the invention makes it advantageously possible to set a suitable operating temperature in the short and long term.

[0025] According to a preferred embodiment, the drive shaft unit is provided at least partially as a hollow shaft to form at least one fluid channel, wherein at least one fluid outlet opening is provided along a circumference of the drive shaft unit, so that at least one fluid connection to the housing unit, in particular to the hydraulic tank of the housing unit, can be provided along the at least one hydraulic fluid connection, the at least one fluid channel and the at least one fluid outlet opening of the drive shaft unit.

[0026] The drive shaft can therefore be used or designed as a fluid channel to provide a fluid connection between the outside of the housing unit, in particular a hydraulic fluid connection, and the hydraulic tank inside the housing unit. The fluid connection between the outside and the hydraulic tank can be understood as being at least partially integral.

[0027] In a preferred embodiment, the drive shaft unit is provided as a hollow shaft open at least on one side, with a fluid inlet opening, wherein the fluid inlet opening is in fluid communication with the hydraulic fluid connection of the housing unit. Alternatively, the drive shaft unit can have at least one fluid inlet opening along its circumference, wherein the at least one fluid inlet opening is in fluid communication with the hydraulic fluid connection of the housing unit.

[0028] Accordingly, the fluid inlet opening of the hollow shaft, which is open on at least one side, can preferably be in essentially direct fluid connection with the hydraulic fluid connection of the housing unit.

[0029] According to another variant, a continuous flow of hydraulic fluid into the partially hollow drive shaft unit can be provided. In this case, the drive shaft can be completely arranged and concealed within the housing unit, particularly in indirect fluid communication with the hydraulic fluid connection of the housing unit.

[0030] In a preferred embodiment, a plurality of fluid openings are formed along a circumference of the drive shaft unit, wherein the plurality of fluid openings are preferably formed in a first area along a first end side of the drive unit and / or in a second area along a second end side of the drive unit, in particular of the rotor of the electric motor.

[0031] According to this, by rotating the drive shaft unit during normal operation, the hydraulic fluid can escape from the drive shaft unit in a circumferential direction and be transferred into the hydraulic tank, inside the housing unit of the pump unit.

[0032] Furthermore, the rotation of the drive shaft unit and the circumferential leakage of the hydraulic fluid can result in additional energy input into the hydraulic fluid, including through internal frictional forces.

[0033] It is possible to briefly heat the hydraulic fluid to achieve a suitable operating temperature.

[0034] According to a further preferred embodiment, at least one pressure relief opening is formed at the end of the drive shaft unit facing away from the pump, wherein the at least one pressure relief opening is formed radially at the end of the drive shaft unit facing away from the pump and / or the drive shaft unit is designed as a hollow shaft open at both ends.

[0035] The drive shaft unit can be designed with a pressure relief opening to achieve axial force compensation.

[0036] According to a preferred embodiment, the housing unit has at least one hydraulic fluid connection with a fluid channel, wherein the at least one hydraulic fluid connection provides a fluid connection to the hydraulic tank in the housing unit indirectly or directly via the associated fluid channel.

[0037] In particular, as an alternative or supplement to the at least partial design of the drive shaft unit as a hollow shaft, the housing unit itself can be provided with at least one fluid channel for the expedient provision of a fluid connection in accordance with the invention. In particular, it is provided that the hydraulic fluid connection is formed in combination with a fluid channel within the housing unit or a wall of the housing unit.

[0038] In this way, in accordance with the present invention, an integral fluid connection can be provided between an outer surface of the pump unit or its housing unit and the internal hydraulic tank.

[0039] According to a further preferred embodiment, the housing unit has at least one first housing part for forming the hydraulic tank and for receiving the drive unit, wherein the drive unit is preferably arranged in the hydraulic tank.

[0040] According to a preferred embodiment, the housing unit has at least one second housing part for receiving the pump, wherein the second housing part has at least one first pump fluid port and one second pump fluid port, preferably along an outside of the housing unit, for supplying and / or drawing in hydraulic fluid by means of the pump.

[0041] In a further preferred embodiment, the housing unit has at least a second housing part for receiving the pump, wherein the second housing part has at least a third pump fluid connection and a fourth pump fluid connection, preferably each with a check valve, so that a fluid connection between the hydraulic tank and the pump or from the hydraulic tank to the pump can be provided via the third and / or fourth pump fluid connection, at least temporarily, in particular the temperature control fluid from the hydraulic tank in the first housing part can be drawn in by the pump in the second housing part.

[0042] Accordingly, the housing unit can be provided in two parts, with the drive unit, preferably an electric motor, being arranged directly inside the hydraulic tank of the first housing part. In accordance with the invention, the hydraulic tank can be understood as being integrally formed within the pump unit or the first housing part of the housing unit.

[0043] Furthermore, the first and second housing parts are preferably flanged or connected to each other in a fluid-tight manner.

[0044] A fluid circuit can be provided within the housing unit, allowing hydraulic fluid to flow via the hydraulic fluid port and fluid channel into the hydraulic tank. Furthermore, return flow to the pump of the pump unit is possible via the third and fourth pump fluid ports, preferably with appropriately arranged check valves.

[0045] In parallel to the internal circulation of the hydraulic fluid via the hydraulic tank, the pump can act as a bidirectional pump using the first and second pump fluid ports, whereby one of the first and second pump fluid ports can act as the pressure-side outlet and suction-side inlet of the pump, respectively, particularly in fluid connection with a steering gear of an electro-hydraulic steering system.

[0046] According to a further embodiment of the present invention, the pump unit has at least one control unit, wherein the control unit is arranged on the housing unit, in particular the first housing part, in such a way that a temperature transfer between the control unit and the hydraulic fluid in the hydraulic tank is possible.

[0047] An efficient and advantageous temperature control of the pump unit, in particular by means of the hydraulic tank within the housing unit, can therefore also exert a heat transfer or temperature control effect on the (spatially and functionally) associated control unit, in order to provide a suitable operating temperature.

[0048] According to a preferred embodiment, at least one fluid rotor disk, preferably with at least one disk rib, is provided along the drive shaft unit at longitudinal ends of the drive unit, in particular at longitudinal ends of the rotor, and / or in the area of ​​the at least one fluid opening, so that the hydraulic fluid can be transferred from the fluid channel, along the at least one fluid opening and the fluid rotor disk into the hydraulic tank.

[0049] The rotor, with at least one disc rib, ensures proper mixing of the hydraulic fluid during introduction into and within the hydraulic tank. Furthermore, additional heat energy, generated from friction, can be introduced into the hydraulic fluid, thus further reducing the warm-up time of the hydraulic fluid during commissioning of the pump unit or an associated electro-hydraulic steering system.

[0050] According to a secondary aspect of the invention, an electro-hydraulic steering system for a vehicle, in particular for a commercial vehicle, is provided with at least one pump unit according to the invention.

[0051] In a preferred embodiment, the electro-hydraulic steering system further comprises:

[0052] - at least one steering gear, in particular a screw steering gear;

[0053] - at least one first line through which the steering gear can be supplied with hydraulic fluid and / or controlled;

[0054] - at least one second line through which the steering gear can be supplied with hydraulic fluid and / or controlled;

[0055] - at least one hydraulic tank; and

[0056] - at least one valve assembly connected or connectable to the first line and / or the second line, in particular a 3 / 3-way solenoid valve assembly, a 3 / 2-way solenoid valve assembly, an on / off valve assembly, a low-pressure valve assembly and / or at least one throttle unit for connecting the first and / or second line to the at least one hydraulic tank as required, wherein the at least one pump unit is connected or connectable to the steering gear via the first and second lines and wherein a fluid connection between the hydraulic tank of the pump unit and the valve assembly can be provided directly or indirectly via a return line.

[0057] In particular, the hydraulic tank of the pump unit can be connected or connectable to the valve assembly directly or indirectly via a return line, especially in the sense of connecting the return line to the hydraulic fluid connection of the pump unit along the housing unit.

[0058] According to a further preferred embodiment, the first line provides a fluid connection between the at least one pump unit, the at least one valve assembly, and at least one first pressure port of the steering gear. The second line provides a fluid connection between the at least one pump unit, the at least one valve assembly, and at least one second pressure port of the steering gear. The steering gear can be supplied with hydraulic fluid in different directions via the first and second pressure ports.

[0059] According to a preferred embodiment, a return line check valve and / or a filter device is provided along the return line, so that a fluid connection from the valve device to the hydraulic fluid connection of the pump unit can be provided.

[0060] This arrangement has the advantage that the filter unit does not need to be located on the high-pressure side, but can be positioned on the low-pressure side in the return line to the hydraulic tank. Consequently, the filter can be mechanically less robust and structurally simpler, as it is not subjected to such high pressures. As a result, cost savings can also be achieved with this type of filter design.

[0061] Therefore, the pump unit and its connection to the valve assembly allow for advantageous temperature control of the hydraulic fluid in accordance with the invention. In particular, the hydraulic fluid can be heated within the pump unit for short periods and then transferred to or returned to the hydraulic circuit of the steering system, i.e., also to the steering gear, in order to enable appropriate temperature control of the steering system components.

[0062] All the advantages and technical effects achievable in connection with the pump unit according to the invention can also apply individually or in combination to the steering system according to the invention.

[0063] Further details and advantages of the present invention will now be explained in more detail with reference to the exemplary embodiments shown in the schematic drawings.

[0064] They show:

[0065] Fig. 1 shows a sectional view of a first embodiment of a pump unit;

[0066] Fig. 2 shows another sectional view of a second embodiment of a pump unit;

[0067] Fig. 3 shows a perspective view of individual components of the embodiment according to Fig. 2;

[0068] Fig. 4 shows a sectional view of a third embodiment of a pump unit;

[0069] Fig. 5 shows a sectional view of a fourth embodiment of a pump unit;

[0070] Fig. 6 shows a circuit arrangement according to a first embodiment of a steering system; Fig. 7 shows a circuit arrangement according to a second embodiment of a steering system;

[0071] Fig. 8 shows a circuit arrangement according to a third embodiment of a steering system; and

[0072] Fig. 9 shows a circuit arrangement according to a fourth embodiment of a steering system.

[0073] Fig. 1 shows a sectional view of a first embodiment of a pump unit 100.

[0074] According to Fig. 1, the pump unit 100 has a housing unit 130 in which an electric motor 110 as a drive unit, a pump 120 and a drive shaft unit 140 are arranged. In addition, a hydraulic tank 136 is formed inside the housing unit 130 for holding hydraulic fluid such as oil.

[0075] According to the embodiment shown in Fig. 1, the housing unit 130 can comprise a first housing part 132 with the drive unit or electric motor 110 and the hydraulic tank 136. The pump 120 can be arranged in a second housing part 134.

[0076] An associated control unit 160 can be arranged or attached to the first housing part 132 as part of the housing unit 130 in a housing 162 (of the control unit 160).

[0077] In particular, the control unit 160 can be coupled to the first housing part with a large surface area or with maximum surface coverage and / or with a heat-conducting element to enable efficient heat transfer or an efficient temperature control effect. The first housing part 132 forms a hydraulic tank 136 in which the electric motor 110 with a stator 112 and a rotor 114 is arranged. The electric motor 110 can be designed as a wet-rotor motor, as shown in Fig. 1.

[0078] The first and second housing parts 132; 134 are preferably fluid-tightly connected or arranged together, in particular so that a hydraulic circuit can be provided. In particular, the first housing part 132 can be open on one side or have an opening at the transition to the second housing part 134 to allow a fluid connection between the first and second housing parts 132; 134.

[0079] Within the first housing part 132, in particular along the one-sided opening of the first housing part 132, a bearing unit 170 with a drive shaft unit bearing 172 and at least one bearing unit fluid channel 174 can be provided to provide a fluid connection from the hydraulic tank 136 to the second housing part 134.

[0080] The housing unit 130 can be configured, preferably in multiple parts, with the first housing part 132, the second housing part 134, the housing of the control unit 162, and the bearing unit 170. Furthermore, individual components of the housing unit 130 can be formed as a single unit, either individually or together. For example, the first housing part 132 and the bearing unit 170 can be formed as a single unit.

[0081] The second housing part 134 has a first and second pump fluid port 151; 152 along its outer surface, each of which can function as a pressure-side or suction-side pump fluid port. The pump 120 arranged inside the second housing part 134 can thus be configured as a unidirectional or a bidirectional pump.

[0082] A hydraulic fluid connection 144 is provided along the outer surface of the second housing part 134. According to Fig. 1, the hydraulic fluid connection 144 is separate from the first and second pump fluid connections 151 and 152. Furthermore, the second housing part 134, as shown in Fig. 1, has a third and a fourth pump fluid connection 153 and 154, each with a check valve 1118 and 1120, respectively. The check valves are arranged within the third and fourth pump fluid connections 153 and 154 such that the pump 120 is prevented from pumping hydraulic fluid on the pressure side via the third and fourth pump fluid connections 153 and 154.

[0083] Furthermore, the pump unit 100 includes the drive shaft unit 140, which extends within the first and second housing parts 132; 134 as shown in Fig. 1.

[0084] In particular, the drive shaft unit 140 extends from the electric motor 110 or the rotor 114 to the pump 120 to enable the pump 120 to be driven. The drive shaft unit is preferably mounted within the first housing part 132 on both sides of the electric motor 110, in particular by the bearing unit 170.

[0085] According to the embodiment shown in Fig. 1, the drive shaft unit 140 projects beyond the electric motor 110 or the rotor 114 and extends to the hydraulic fluid connection 144 of the housing unit 130 or the second housing part 134.

[0086] The drive shaft unit 140 can be provided as a multi-part drive shaft unit 140 according to Fig. 1, comprising a pump section and a drive section. The pump section and the drive section can be expediently connected to each other.

[0087] In the embodiment shown in Fig. 1, the drive shaft unit 140 is designed as a hollow shaft open at least on one side. The drive shaft unit 140 has a fluid channel 142 that opens into the fluid inlet opening 145 at one longitudinal end of the drive shaft unit 140. A pressure relief opening 148 can be provided at one longitudinal end of the drive shaft unit 140 opposite the fluid inlet opening 145. In this sense, the drive shaft unit 140 according to Fig. 1 can be understood as a hollow shaft open at both ends.

[0088] The pressure relief opening 148 can be provided or configured in combination with a sensor unit 118, for example, an angular velocity sensor. The sensor unit 118 can be arranged or attached to the longitudinal end of the drive shaft unit 140 opposite the pump.

[0089] A plurality of fluid outlet openings 146 are provided along one circumference of the drive shaft unit 140. According to Fig. 1, the fluid outlet openings 146 are located in the region of the end faces of the electric motor 110 or the rotor 114 and in the region of the first housing part 132.

[0090] In particular, the fluid outlet openings 146 are distributed along the circumference of the drive shaft unit 140 in such a way that the hydraulic fluid from the fluid channel 142 of the hollow shaft-like drive shaft unit 140 can enter the hydraulic tank 136, formed by the first housing part 132, on both sides of the electric motor 110.

[0091] According to Fig. 1, the hydraulic fluid can be conveyed from the hydraulic fluid connection 144 along the outside of the housing unit 130 via the drive shaft unit 140, in particular the fluid inlet opening 145, the fluid channel 142 and the fluid outlet openings 146, to the hydraulic tank 136 inside the housing unit 130 or the first housing part 132.

[0092] The drive shaft unit 140 forms a fluid connection between the outside of the housing unit 130 and the hydraulic tank 136 inside the housing unit 130.

[0093] Furthermore, the fluid rotor disc with the disc ribs 117 can be designed to be matched to the fluid outlet openings 146 of the drive shaft unit 140 in such a way that an advantageous distribution of the hydraulic fluid and an advantageous energy input into the hydraulic fluid can take place during the transfer into the hydraulic tank 136.

[0094] In particular, a plurality of preferably at least partially radially extending disk ribs 117 can be formed in the circumferential direction of the fluid rotor disk 116 (see Fig. 3).

[0095] If the hydraulic fluid has been transferred into the hydraulic tank 136, a return to the pump 120 can take place via the bearing unit 170 and the third or fourth pump fluid connection 153; 154, as shown in Fig. 1.

[0096] In particular, the pump 120 can draw the hydraulic fluid from the hydraulic tank 136 via the at least one bearing unit fluid channel 174 of the bearing unit 170 in the opening direction of the check valves 1118; 1120.

[0097] Within the pump unit 100 or the housing unit 130 of the pump unit 100, a hydraulic fluid circuit can be implemented, in particular along the drive shaft unit 140, the hydraulic tank 136, the bearing unit 170 and the second housing part 134 with the third or fourth fluid connection 153; 154 as well as the pump 120, for the pressure-side delivery of hydraulic fluid via the first and / or second pump fluid connection 151; 152.

[0098] Fig. 2 shows a further sectional view of a second embodiment of a pump unit 100. Furthermore, Fig. 3 illustrates a perspective view of individual components of the embodiment according to Fig. 2. The differences compared to the embodiment described above will be discussed in detail below.

[0099] In contrast to the embodiment shown in Fig. 1, Figs. 2 and 3 show that the drive shaft unit 140 is designed as a hollow shaft open at one end. In particular, the drive shaft unit 140, as shown in Fig. 2, has the fluid inlet opening 145 in essentially direct fluid connection or in essentially direct contact with the hydraulic fluid connection 144 of the housing unit 130.

[0100] A pressure relief opening 148 can be formed on the longitudinal end of the drive shaft unit 140 facing away from the pump 120 by means of a through-hole in the radial direction of the drive shaft unit 140, as shown in Fig. 2.

[0101] The sensor unit 180, for example an angular velocity sensor, can be arranged or attached to the drive shaft unit 140 at its longitudinal end as shown in Fig. 2.

[0102] Fig. 4 shows a sectional view of a third embodiment of a pump unit 100. The differences compared to the embodiments described above will be discussed in detail below.

[0103] As shown in Fig. 4, it is particularly intended that the housing unit 130 or the second housing part 134 does not have a separately designed hydraulic fluid connection 144.

[0104] As shown in Fig. 4, the hydraulic fluid connection 144 is designed in the form of, or in combination with, the first and / or second pump fluid connection 151 ; 152.

[0105] The drive shaft unit 140 is shown in Fig. 4 as a hollow shaft open at both ends. According to the embodiment shown in Fig. 4, the drive shaft unit 140 can also be used as a hollow shaft open at one end.

[0106] The drive shaft unit 140 has in the area of ​​the second housing part 134 or in the

[0107] The area of ​​the pump 120 has at least one fluid inlet opening 145 on its circumference, preferably a plurality of fluid inlet openings 145 arranged distributed around the circumference.

[0108] Hydraulic fluid can enter the fluid channel 142 of the drive shaft unit 140 from the first or second pump fluid connection 151 ; 152 of the second housing part 134 via at least one fluid inlet opening 145 and be directed or transferred via the fluid outlet openings 146 into the hydraulic tank 136.

[0109] Fig. 5 shows a sectional view of a fourth embodiment of a pump unit 100. The differences compared to the embodiments described above will be discussed in detail below.

[0110] In contrast to the embodiment shown in Fig. 1, the design of the drive shaft unit 140 as a solid material is shown in Fig. 5.

[0111] The second housing part 134 has at least one, or according to Fig. 2 at least two, hydraulic fluid connections 144, each of which is formed in combination with a fluid channel 142.

[0112] According to Fig. 5, the fluid channel 142 runs from the respective hydraulic fluid connection 144 through the wall of the second housing part 134, in particular past the pump 120.

[0113] The fluid channel 142 can open into or be in fluid contact with at least one bearing unit fluid channel 174 of the bearing unit 170 at the interface between the first and second housing parts 132; 134.

[0114] According to Fig. 5, a fluid connection between the outside of the pump unit 100 and the hydraulic tank 136 inside the housing unit 130 can therefore be provided via the hydraulic fluid connections 144, the fluid channels 142 along the second housing unit 134, and the bearing unit fluid channels 174. Fig. 6 shows a schematic representation of a circuit arrangement according to a first embodiment of a steering system 1000.

[0115] In particular, it is intended that the steering system 1000 shown can be used with a pump unit 100 according to the embodiments described above. The pump unit 100 is shown here in Fig. 6, as well as in the following Figs. 7 to 9, only as an example.

[0116] The electro-hydraulic steering system 1000 for a commercial vehicle has a steering gear 1102 in the form of a spindle steering gear 102.

[0117] The screw steering gear 1102 can be designed as a ball screw steering gear, although other types of gears are also conceivable.

[0118] The electro-hydraulic steering system 1000 further includes a first line 1104 through which the steering gear 1102 can be supplied with hydraulic fluid and controlled.

[0119] Accordingly, the electro-hydraulic steering system 1000 has a second line 1106 through which the steering gear 1102 can also be supplied with hydraulic fluid and controlled.

[0120] Furthermore, the steering system 1000 includes a valve assembly 1108. The valve assembly 1108 can, in particular, be designed as a 3 / 3-way solenoid valve assembly, an on / off valve assembly, or a low-pressure valve assembly.

[0121] The valve assembly 108 is connected on the input side to the first line 104 and also on the input side to the second line 106.

[0122] According to Fig. 6, the valve assembly 1108 is also connected, or can be connected, on its output side via a return line 1120 of the steering system 1000 to the pump unit 100, in particular to the housing unit 130 of the pump unit 100. According to Fig. 6, the return line 1120 can be connected to the hydraulic fluid connection 144 of the housing unit 130 of the pump unit 100.

[0123] The valve device 1108 can therefore transfer or forward a hydraulic fluid to the pump unit 100 and into the hydraulic tank 136, in particular in the sense of the invention for efficient temperature control of the hydraulic fluid, for example during the initial commissioning of the electro-hydraulic steering system 1000.

[0124] Furthermore, the valve device can be provided, for example, for pressure reduction in the first line 1104 and / or the second line 1106.

[0125] The valve assembly 1108 can be actuated, preferably electromagnetically, by means of a control unit not shown in the figures, which can be assigned to or associated with the steering system 1000. Alternatively, the valve assembly can be provided as a passively acting (low-pressure) valve assembly that can be conditionally controlled by means of a pilot pressure (see Fig. 6, dashed lines).

[0126] Furthermore, the pump unit 100 is connected to the first and second lines 1104, 1106.

[0127] The pump unit 100 can be designed as a double-acting hydraulic pump, so that depending on the direction of rotation either the first line 1104 or the second line 1106 can be printed.

[0128] Alternatively, it is also conceivable that only a single-acting hydraulic pump is provided and connected via a corresponding switching valve (not shown in the figures) to the first and second lines 1104; 1106, which, depending on the switching logic, connects the hydraulic pump to either the first or the second line 1104; 1106. Alternatively, it is also conceivable that two pump units 100 are provided, with one pump unit 100 each being assigned to or connected with the first and second lines 1104, 1106, respectively.

[0129] The pump unit 100 in Fig. 6 can be connected to the steering gear 1102 via the first line 1104 and, alternatively, via the second line 1106, so that the actual connection depends on a direction control of the pump unit 100.

[0130] Such control can be effected by a control unit that is assigned to or associated with the steering system 1000 and is not shown in the figures.

[0131] As can be seen in Fig. 6, the hydraulic tank 136 is symbolically shown within the pump or housing unit 100; 130, in the sense of an integrated design of the hydraulic tank 136 within the housing unit 130, as described in the preceding embodiments of a pump unit 100 according to the invention.

[0132] According to Fig. 6, the first line 1104 and the second line 1106 are connected to the hydraulic tank 136 via the check valves 1118; 1120 of the third / fourth pump fluid connections 153; 154 (not explicitly illustrated in Fig. 6).

[0133] The two check valves 1118; 1120 can be arranged in such a way that hydraulic fluid can be supplied from the hydraulic tank 136 to the pump 120 via the check valves 1118; 1120, while preventing backflow towards the hydraulic tank 136.

[0134] The first check valve 1118 and the second check valve 1120 can also serve and / or function as suction valves in this case.

[0135] Advantageously, pressure build-up, in particular pressure build-up controllable or controlled via a control unit assignable to or associated with the steering system 1000, for example the one already mentioned, can thus occur under the influence, preferably with the support, of the suction valves. In other words, the first and second check valves 1118; 1120 can support the pump 120 in a pressure build-up, in particular along the first or second line up to the steering gear 1102.

[0136] As can be seen in Fig. 6, the pump unit 100 can also include a temperature sensor 1122 and a pressure sensor 1124, which can be arranged, for example, inside the hydraulic tank 136. Alternatively, an arrangement along, for example, the at least one fluid channel 142 is also conceivable.

[0137] It is understood that the temperature sensor 1122 and the pressure sensor 1124 can be connected or linked to the control unit 160 of the pump unit 100 and / or to a control unit that can be assigned or associated with the steering system 1000, for example the control unit already mentioned above, for controlling an operation and / or partial operation of the steering system 1000 via signal technology.

[0138] The function of the steering system 1000 according to the embodiment shown in Fig. 6 can be described as follows:

[0139] As soon as the pump 120 is driven by the drive unit or the electric motor 110 (e.g. counterclockwise), it can pressurize the section of the first line 1104, which extends to the steering gear 1102 and to a first connection 1128 of the valve assembly 1108, with hydraulic fluid pressure.

[0140] With regard to the short-term and / or long-term temperature control of the hydraulic fluid during commissioning or continuous operation of the electro-hydraulic steering system 1000, the hydraulic fluid can be circulated by means of the pump unit 100 and via the valve device 1108 along the return line 1112.

[0141] In particular, the pump 120 can deliver the hydraulic fluid via the first or second pump fluid connection 151; 152 along the first or second line 1104; 1106 to the valve assembly 1108 with the inlet connections 1128; 1130. Using the valve assembly 1108, the hydraulic fluid can be returned via the return line 1112 directly to the pump unit and the hydraulic fluid connection 144 to return to the hydraulic tank 136.

[0142] The valve assembly 1108 enables a short-circuit circulation of the hydraulic fluid through the hydraulic tank 136 of the pump unit 100. This allows the operating temperature of the hydraulic fluid to be set quickly, or the temperature of the pump unit 100 and other components of the steering system 1000 to be controlled.

[0143] In particular, efficiency can be increased and the operating temperature of the pump unit 100 can be appropriately set by circulating only the smallest possible volume of hydraulic fluid via the short-circuited fluid connection along the valve assembly 1108 and by increasing or adjusting the fluid temperature primarily within the pump unit 100.

[0144] Furthermore, the pressure build-up for the application of steering assistance can be carried out using the present steering system 1000 as described below:

[0145] During the pressure build-up for the application of steering assistance, the hydraulic pump 120 can be supported by the second check valve 1120, which acts as a suction valve, particularly when a sufficient negative pressure is generated by the pump 120 along the second line 1106 and the second pump fluid port 152, which leads to the opening of the second check valve 1120.

[0146] Consequently, the pump 120 and the steering gear 1102 are connected to each other via the first line 1104 and the connection of the steering gear 102 connected to the first line 1104 is printed.

[0147] Subsequently, the pressure in the assigned first pressure chamber of the steering gear 1102 increases, and the piston is forced into a displacement movement because the pressure in the opposite, second pressure chamber is lower, thus achieving steering assistance. In this sense, the second pressure chamber can be understood as a low-pressure chamber.

[0148] The pressure in the opposite second pressure chamber is therefore lower because the connection of the steering gear 1102 is connected to the return line 1112 via the section of the second line 1106 and via the valve assembly 1108.

[0149] In this case, the hydraulic fluid is displaced from the opposite, second pressure chamber and via the valve device 1108 into the return line 1112 and then fed back to the hydraulic tank 136 of the pump unit 100 via the return line 1112.

[0150] A rapid return of the hydraulic fluid can be initiated, for example, if the operating pressure in the first line 1104 is higher compared to the operating pressure in the second line 1106 and the second line 1106 is connected to the return line 1112 by means of the at least partially controllable valve device 1108.

[0151] The second line 1106 can thus be connected to the return line 1112 depending on the pressure difference between the first line 1104 and the second line 1106 and the actuable valve device 1108, preferably by means of the electromagnetically actuated valve device 1108.

[0152] This enables a rapid pressure relief phase in the pressure chamber of the steering gear 1102 connected to the second line 1106, and thus the response behavior of the steering system 1000 can be improved, preferably enabling a faster system response and a better steering feel.

[0153] It should be understood that the pump 120 can preferably only be driven in one direction of rotation, and therefore only the first or the second line 1104, 1106 can be pressurized at any given time. In the case described above, the first line 1104 is consequently pressurized by the hydraulic pump 120, whereas the second line 1106 is not pressurized, at least in the section between the pump 120 and the steering gear 1102 and / or the valve assembly 1108.

[0154] If the direction of rotation of pump 120 is reversed, the previously described relationship or case occurs in exactly the opposite way, as described below:

[0155] As soon as the pump 120 is driven by the drive unit or the electric motor 110 (now clockwise), it prints the section of the second line 1106, which extends to the steering gear 1102 and to a second connection 1130 of the valve assembly 1108.

[0156] During pressure build-up, the pump 120 is supported by the first check valve 1118, which acts as a suction valve.

[0157] Consequently, the pump 120 and the steering gear 1102 are now connected to each other via the second line 1106 and the connection of the steering gear 1102 connected to the second line 1106 is printed.

[0158] As a result, the pressure in the associated second pressure chamber of the steering gear 1102 increases, and the piston is forced into a displacement movement because the pressure in the opposite first pressure chamber is now lower, thus achieving steering assistance. In this case, the first pressure chamber of the steering gear 1102 can be considered a low-pressure chamber.

[0159] The pressure in the opposite first pressure chamber is therefore lower because the connection of the steering gear 1102 is connected to the return line 1112 via the section of the first line and via the valve assembly 1108.

[0160] In this case, the hydraulic fluid is displaced from the opposite, first pressure chamber and directed via the valve assembly 1108 into the return line 1112 and then fed back to the pump unit 100 with the hydraulic tank 136 via the return line 1112.

[0161] In this case, a rapid return of the hydraulic fluid can be initiated if the operating pressure in the second line 1106 is higher compared to the operating pressure in the first line 1104 and the first line 1104 is connected to the return line 1112 by means of the at least partially controllable valve device 1108.

[0162] The first line 1104 can be connected to the return line 1112 depending on the pressure difference between the first line 1104 and the second line 1106 by means of the actuable valve device 1108, preferably by means of the at least partially actively controllable valve device 1108.

[0163] This enables a rapid pressure relief phase in the pressure chamber of the steering gear 1102 connected to the first line 1104, and thus the response behavior of the steering system 1000 can be improved, preferably enabling a faster system response and a better steering feel.

[0164] It should be understood that the pump 120 is preferably always driven in only one direction of rotation and therefore only the first or the second line 1104; 1106 can be printed on at any given time.

[0165] In the second case described above, the second line 1106 is therefore printed by the (hydraulic) pump 120, whereas the first line 1104 is not printed, at least in the section between pump 120 and steering gear 1102 and / or valve assembly 1108.

[0166] The pressure in the first or second line 1104; 1106 can be used, at least partially, as a (pre-)control pressure for the valve assembly 1108 (see Fig. 6, dashed lines to the valve assembly 1108) to enable a pressure reduction in the other line 1106; 1104 and the corresponding pressure chamber. This advantageously allows for a rapid pressure relief phase in the pressure chamber and consequently accelerates the response of the entire steering system. This operating behavior can also be further enhanced and accelerated by at least partially controlled actuation of the valve assembly 1108, thus further improving the system dynamics and response accuracy of the valve assembly 1108 and ultimately of the steering system 1000.

[0167] In summary, it should also be noted that, depending on the direction of rotation of the pump, either the first or the second line 1104; 1106 is printed, so that the steering gear 1102 is preferably always printed by only one of the lines 1104; 1106 and thus the other line 1104, 1106 (which is not printed) can be connected or is connected to the return line 1112 via the valve device 1108.

[0168] Since the piston displacement direction of the piston in the steering gear 1102 also changes depending on the steering direction, the control / pressure of the steering gear 1102 via the first line 1104 or the second line 1106 also changes accordingly. By enabling a rapid pressure reduction by means of the valve assembly 1108, the piston displacement direction can also be carried out quickly, and a fast and dynamic change of steering direction can be achieved.

[0169] Figure 7 shows a circuit arrangement according to a second embodiment of a steering system 1000. The differences compared to the embodiment described above will be discussed in detail below.

[0170] In particular, a valve assembly 1108 in the form of a 3 / 3-way solenoid valve is provided according to Fig. 7.

[0171] In this sense, the (re-)circulation of hydraulic fluid by means of the pump 120, via the valve assembly 1108 and the hydraulic tank 136 of the pump unit 100, can be controlled and / or regulated as required. Likewise, as shown in Fig. 7, pressure build-up or pressure reduction can be selectively adjusted with or via the valve assembly 1108.

[0172] Fig. 8 shows a circuit arrangement according to a third embodiment of a steering system 1000. The differences compared to the embodiments described above will be discussed in detail below.

[0173] According to the embodiment shown in Fig. 8, a valve assembly 1108 is provided in combination with a preceding first or second throttle unit 1142; 1144.

[0174] In particular, a first or second throttle unit 1142; 1144 is connected upstream of the valve device 1108 or the inlet-side first / second connection 1128; 1 ​​130 along the first or second line 1104; 1 106.

[0175] Fig. 9 illustrates a circuit arrangement according to a fourth embodiment of a steering system 1000. The differences compared to the embodiments described above will be discussed in detail below.

[0176] Compared to the embodiment in Fig. 6, the steering system 1000 according to Fig. 9 differs in particular in the arrangement of further check valves 1152; 1154 in the first line 1104 and the second line 1106 between the valve assembly 1108 and the pump unit 100.

[0177] The valve assembly is preferably provided without the possibility of imprinting a pilot pressure, as shown in Fig. 9 (see Fig. 6 - dashed lines).

[0178] Furthermore, as shown in Fig. 9, and in contrast to Fig. 6, a return line check valve 1114 and a filter assembly 1116 can be provided along the return line 1112 between the pump unit 100 and the valve assembly 1108. This arrangement has the advantage that the filter or filter assembly 1116 does not have to be located on the high-pressure side, but rather on the low-pressure side in the return line 1112.

[0179] Preferably, the return line check valve 1114 according to Fig. 9 is provided between the filter device 1116 and the valve device 1108.

[0180] In particular, the return line check valve 1114 can be arranged along the return line 1112 in such a way that an oil flow or oil leakage from the valve assembly 1108 via the filter assembly 1116 and the hydraulic fluid connection 144 into the hydraulic tank 136 is provided or enabled and an opposite backflow, i.e. via the filter assembly 1116 to the valve assembly 1108, can be prevented.

[0181] A third check valve 1152 can be arranged in the first line 1104 and a fourth check valve 1154 in the second line 1106, in particular between the valve assembly 108 or the steering gear 102 and the pump unit 100 or the pump 120, so that backflow to the pump unit 100 or suction of hydraulic fluid by the pump 120 can be prevented.

[0182] In the first and second lines 1104; 1106, two check valves 1118; 1120; 1152; 1154 can each be arranged, so that, depending on a direction of rotation or delivery of the pump 120, a targeted suction of hydraulic fluid from the hydraulic tank 136 is made possible.

[0183] The check valves 1118; 1120; 1152; 1154 prevent or stop the (hydraulic) pump 120 from drawing hydraulic fluid from the steering gear 1102 or the valve device 1108 along the first or second line 1104; 1106.

[0184] Furthermore, a separate backup valve 1160 can be provided, as shown in Fig. 9. Alternatively, such a backup valve 1160 can, for example, be integrated into the valve assembly 1108. As shown in Fig. 9, the backup valve 1160 can, on the one hand, be connected, at least indirectly, to the first line 1104 via the pressure chamber of the steering gear 1102 assigned to the first line 1104.

[0185] On the other hand, the backup valve 1160 can be indirectly connected to the second line 1106 via the respective pressure chamber of the steering gear 1102 assigned to the second line 1106.

[0186] The respective pressure chambers of the steering gear 102 can be connected and preferably short-circuited by means of the backup valve 1160, especially in an emergency situation or in the event of a fault.

[0187] This allows the safety and / or reliability of the steering system 1000 to be further improved, as the pressure chambers of the steering gear 1102 can be connected in an emergency situation, thereby ensuring a corresponding pressure reduction or pressure equalization and thus a steering function in terms of the mobility of the (hydraulic) piston in the steering gear at all times.

[0188] In a sense, the backup valve 1160 can thus form and / or enable a fault circuit that is not specifically indicated in the figures and / or function as such.

[0189] In an emergency, the backup valve 1160 can switch from its closed position to a through position in order to provide a fluid short circuit between the two pressure chambers of the steering gear 1102.

[0190] Furthermore, the backup device or the backup valve device, in particular the backup valve 1160, can be controlled or controlled via a control unit that can be assigned to or associated with the steering system 1000.

[0191] In summary, the present invention enables an advantageous

[0192] Pump unit 100 is provided, which allows effective and rapid temperature control of hydraulic fluid within an electro-hydraulic steering system and can thus ensure an optimal operating temperature range for the components of the pump unit, i.e. in particular the drive unit 110, the pump 120 and the associated control unit 160.

[0193] In particular, also in conjunction with the steering system 1000 according to the invention and the valve device 1108 provided therein, an appropriate (re-)circulation of comparatively small volumes of hydraulic fluid to and from the integrated hydraulic tank 136 within the housing unit 130 of the pump unit 100 can be provided in order to ensure a temperature control effect for the components even briefly after or during the initial commissioning.

[0194] Furthermore, the steering system 1000 allows further advantageous operating characteristics and operating modes by means of the valve assembly 1108, such as a rapid pressure reduction in the steering gear 1102 along the valve assembly 1108 to the hydraulic tank 136 of the pump unit 100.

[0195] REFERENCE MARK LIST

[0196] 100 pump units

[0197] 110 electric motor

[0198] 112 Stator

[0199] 114 Rotor

[0200] 116 Fluid rotor disc

[0201] 117 Disc rib

[0202] 118 Sensor unit

[0203] 120 pump

[0204] 130 Housing unit

[0205] 132 first housing part

[0206] 134 second housing part

[0207] 136 Hydraulic tank

[0208] 140 drive shaft unit

[0209] 142 Fluid channel

[0210] 144 Hydraulic fluid connection (of the housing unit)

[0211] 145 Fluid inlet opening (of the drive shaft unit)

[0212] 146 Fluid outlet opening

[0213] 148 Pressure relief opening

[0214] 151 First pump fluid connection

[0215] 152 second pump fluid connection

[0216] 153 third pump fluid connection

[0217] 154 fourth pump fluid connection

[0218] 160 control unit

[0219] 162 Control unit housing

[0220] 170 storage units

[0221] 172 Drive shaft unit bearing

[0222] 174 Storage unit fluid channel

[0223] 1000 Electro-hydraulic steering system

[0224] 1102 Steering gear

[0225] 1104 first line

[0226] 1106 second line 1108 valve assembly

[0227] 1112 Return line

[0228] 1114 Return line check valve

[0229] 1116 Filter unit 1118 First check valve

[0230] 1120 second check valve

[0231] 1122 Temperature sensor

[0232] 1124 Pressure sensor

[0233] 1128 first connection 1130 second connection

[0234] 1142 first throttle unit

[0235] 1144 second throttle unit

[0236] 1152 third check valve

[0237] 1154 fourth check valve 1160 backup valve

Claims

PATENT CLAIMS 1. Pump unit (100), in particular for an electro-hydraulic steering system, comprising at least one drive unit (110), in particular an electric motor (110) with a stator (112) and a rotor (114), at least one pump (120), at least one housing unit (130) and at least one drive shaft unit (140), wherein the housing unit (130) is provided for receiving the drive unit (110), the pump (120), for at least partial receiving of the drive shaft unit (140) and for forming a hydraulic tank (136) for a hydraulic fluid, wherein the at least one drive unit (110), in particular the rotor (114), is coupled or can be coupled to the at least one pump (120) via the at least one drive shaft unit (140), so that the pump (120) can be driven by means of the drive unit (110), wherein at least one fluid connection between an outer surface of the housing unit and / or the drive shaft unit (140) is provided via the housing unit (130) and / or the drive shaft unit (140). (130),in particular at least one hydraulic fluid connection (144) of the housing unit (130), and the hydraulic tank (136), preferably formed within the housing unit (130), can be provided.

2. Pump unit (100) according to claim 1, characterized in that the drive shaft unit (140) is provided at least partially as a hollow shaft to form at least one fluid channel (142), wherein at least one fluid outlet opening (146) is provided along a circumference of the drive shaft unit (140), so that at least one fluid connection to the housing unit (130), in particular to the hydraulic tank (136) of the housing unit (130), can be provided along the at least one hydraulic fluid connection (144), the at least one fluid channel (142) and the at least one fluid outlet opening (146) of the drive shaft unit (140).

3. Pump unit (100) according to claim 1 or 2, characterized in that the drive shaft unit (140) is provided with a fluid inlet opening (145) as a hollow shaft open at least on one side, wherein the fluid inlet opening (145) is in fluid communication with the hydraulic fluid connection (144) of the housing unit, or the drive shaft unit (140) has at least one fluid inlet opening (145) along the circumference of the drive shaft unit (140), wherein the at least one fluid inlet opening (145) is in fluid communication with the hydraulic fluid connection (144) of the housing unit.

4. Pump unit (100) according to one of the preceding claims, characterized in that a plurality of fluid openings (146) are formed along a circumference of the drive shaft unit (140), wherein the plurality of fluid openings (146) are preferably formed in a first area along a first end side (116) of the drive unit (110) and / or in a second area along a second end side (118) of the drive unit (110), in particular of the rotor (114) of the electric motor (110).

5. Pump unit (100) according to one of the preceding claims, characterized in that at least one pressure relief opening (148) is formed at the end of the drive shaft unit (140) facing away from the pump (120), wherein the at least one pressure relief opening (148) is formed radially at the end of the drive shaft unit (140) facing away from the pump (120) and / or the drive shaft unit (140) is formed as a hollow shaft open at both ends.

6. Pump unit (100) according to claim 1, characterized in that the housing unit (130) has at least one hydraulic fluid connection (145) with a fluid channel (142), wherein the at least one hydraulic fluid connection (145) provides a fluid connection to the hydraulic tank (136) in the housing unit (130) indirectly or directly via the associated fluid channel.

7. Pump unit (100) according to one of the preceding claims, characterized in that the housing unit (130) has at least one first housing part (132) for forming the hydraulic tank (136) and for receiving the drive unit (110), wherein the drive unit (110) is preferably arranged in the hydraulic tank (136).

8. Pump unit (100) according to claim 6, characterized in that the housing unit (130) has at least one second housing part (134) for receiving the pump (120), wherein the second housing part (134) has at least one first pump fluid connection (151) and one second pump fluid connection (152), preferably along an outside of the housing unit (130), for providing and / or drawing in hydraulic fluid by means of the pump (120).

9. Pump unit (100) according to one of the preceding claims, characterized in that the housing unit (130) has at least one second housing part (134) for receiving the pump (120), wherein the second housing part (134) has at least one third pump fluid connection (153) and one fourth pump fluid connection (154), preferably each with a check valve (156), so that a fluid connection between the hydraulic tank (136) and the pump (120) can be provided via the third and / or fourth pump fluid connection (153; 154), at least temporarily, in particular the temperature control fluid from the hydraulic tank (136) in the first housing part (132) can be drawn in by the pump (120) in the second housing part (134).

10. Pump unit (100) according to one of the preceding claims, characterized in that the pump unit (100) has at least one control unit (160), wherein the control unit (160) is attached to the housing unit (130), in particular the first housing part (132), is arranged so that a temperature transfer between the control unit (160) and the hydraulic fluid in the hydraulic tank (136) can be provided.

11. Pump unit (100) according to one of the preceding claims, characterized in that at least one fluid rotor disk (116), preferably with at least one disk rib (117), is provided along the drive shaft unit (140) at longitudinal ends of the drive unit (110), in particular at longitudinal ends of the rotor (114), and / or in the area of ​​the at least one fluid opening (146), so that the hydraulic fluid can be transferred from the fluid channel (142), along the at least one fluid opening (146) and the fluid rotor disk (116) into the hydraulic tank (136).

12. Electro-hydraulic steering system (1000) for a vehicle, in particular for a commercial vehicle, comprising at least one pump unit (100) according to one of the preceding claims.

13. Electro-hydraulic steering system (1000) according to claim 10, characterized in that the electro-hydraulic steering system (1000) further comprises: - at least one steering gear (1102), in particular a screw steering gear; - at least one first line (1104) through which the steering gear (1102) can be supplied with hydraulic fluid and / or controlled; - at least one second line (1106) through which the steering gear (1102) can be supplied with hydraulic fluid and / or controlled; - at least one hydraulic tank (136); and - at least one valve assembly (1108) connected or connectable to the first line (1104) and / or the second line (1106), in particular a 3 / 3-way solenoid valve assembly, a 3 / 2-way solenoid valve assembly, an on / off valve assembly, a low-pressure valve assembly and / or at least one throttling unit for connecting the first and / or second line (1104; 1106) to the at least one hydraulic tank (136) at least as required, wherein at least one pump unit (100) is connected or connectable to the steering gear (1102) via the first and second lines (1104; 1106), wherein a fluid connection between the hydraulic tank (136) of the pump unit (100) and the valve assembly (1108) can be provided indirectly or directly via a return line (1112).

14. Electro-hydraulic steering system (1000) according to claim 13, characterized in that the first line (1104) provides a fluid connection between the at least one pump unit (100), the at least one valve assembly (1108) and at least one first pressure port of the steering gear (1102), wherein the second line (1106) provides a fluid connection between the at least one pump unit (100), the at least one valve assembly (1108) and at least one second pressure port of the steering gear (1102), wherein the steering gear (1102) can be supplied with hydraulic fluid in different directions via the first and second pressure ports.

15. Electro-hydraulic steering system (1000) according to claim 13 or 14, characterized in that a return line check valve (1114) and / or a filter device (1116) is provided along the return line (1112) so that a fluid connection from the valve device (1108) to the hydraulic fluid connection (144) of the pump unit (100) can be provided.

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