Electro-hydraulic steering assist device for a vehicle

Abstract

The electrohydraulic steering assist device (105) for a vehicle (100) includes a hydraulic pump (110), a drive unit (115), a first working line (120), a second working line (125), and a heat exchanger unit (130). The hydraulic pump (110) is configured to pump hydraulic oil to a first pump outlet (135) of the hydraulic pump (110) in a first turning direction and to a second pump outlet (140) of the hydraulic pump (110) in a second turning direction. The drive unit (115) is coupled to the hydraulic pump (110) and configured to selectively drive the hydraulic pump (110) in the first turning direction or the second turning direction. The first working line (120) is configured to fluidly connect the first pump outlet (135) to a first working chamber (145), the first working chamber (145) being adapted to move a piston (160) in a first direction (165), the piston (160) being connectable to a steering rod (150) of a steering (155). The heat exchanger unit (130) is configured to transfer heat (180) generated during operation of the drive (115) to at least one of the working lines (120, 125) for heating hydraulic oil flowing through the working lines (120, 125).

Description

[Technical field]

[0001] The present approach relates to an electro-hydraulic steering assist system for a vehicle.

[0002] A hydraulic power steering system (HPS) for large commercial vehicles includes a block steering, piping, a hydraulic oil pump, and a hydraulic oil surge tank. In this case, the hydraulic pump is continuously driven by the internal combustion engine. By constantly circulating the hydraulic oil, the hydraulic oil is always sufficiently regulated in temperature, and therefore the block steering is continuously sufficiently heated.

[0003] Against this background, the problem of the present approach is to provide an improved electro-hydraulic steering assist system for a vehicle.

[0004] This problem is solved by an electrohydraulic steering assist device having the features of device claim 1.

[0005] The advantage that can be achieved by the presented approach is that an electrohydraulic steering assist is provided which functions separately from the internal combustion engine or the electric motor of the vehicle, but which nevertheless provides heating of the hydraulic oil of the steering assist.

[0006] The electrohydraulic steering assist device for a vehicle includes a hydraulic pump, a drive, a first working line, a second working line, and a heat exchanger unit. The hydraulic pump is configured to pump hydraulic oil to a first pump outlet of the hydraulic pump in a first pivoting direction and to a second pump outlet of the hydraulic pump in a second pivoting direction. The drive is coupled to the hydraulic pump and configured to selectively drive the hydraulic pump in the first pivoting direction or the second pivoting direction. The first working line is configured to fluidly connect the first pump outlet to a first working chamber, where the first working chamber is suitable for moving a piston connectable to a steering rod of the steering in a first direction. The second working line is configured to fluidly connect the second pump outlet to the second working chamber, where the second working chamber is suitable for moving a piston connectable to a steering rod of the steering in a second direction opposite to the first direction. The heat exchanger unit is configured to transfer heat generated during operation of the drive to at least one of the working lines for heating hydraulic oil flowing through the working lines.

[0007] These electrohydraulic steering assists can be used, for example, for vehicle steering in commercial vehicles with axle loads of up to 8 tonnes. The steering assists are equipped with so-called "EPS" (Electronic Power Steering) steering assists based on the electrohydraulic principle. Such EPS steering is characterised by an intermittent operating characteristic, i.e. the hydraulic oil present in the hydraulic circuit of the steering is pumped by the pump unit only when the steering is moved, i.e. according to the "Power on Demand" principle. If the steering is not actuated, the hydraulic oil remains stationary and so is the motor-pump unit, which consists of the hydraulic pump and the drive. Steering assists of this kind can be used, for example, in electric commercial vehicles without an internal combustion engine, in order to function as a "Power on Demand" steering system, or to realise automated driving requests autonomously and without driver intervention, for example by driver assistance systems such as DAS / ADAS (levels 1-2) and HAD (levels 3-5). Due to the intermittent oil transport and the associated cooling of the hydraulic oil, it is necessary to preheat the hydraulic oil. The electrohydraulic steering assist device presented herein therefore advantageously allows, by virtue of the provision of a heat exchanger unit, to utilise the waste heat generated by the drive for heating the hydraulic oil.

[0008] The heat exchanger unit may comprise a heating device for heating the hydraulic oil flowing through at least one working line, which allows the hydraulic oil to be actively heated. To heat the working line, the heating device may be in direct contact with the working line, or may penetrate into the inner space of the working line in order to directly heat the hydraulic oil itself.

[0009] The hydraulic pump can be configured as a bidirectional hydraulic pump, so that hydraulic oil can be pumped / sucked in two directions depending on the required steering assist.

[0010] According to one embodiment, the steering assist device may also have a steering with a steering rod, a piston, a first working chamber and a second working chamber. The steering may be a block steering. Thus, a comprehensive steering system is provided. The block steering may further be formed to be connectable with a steering wheel.

[0011] The first and second working chambers can be fluidly connected to one another via a switchable valve, e.g. a solenoid valve, or can be made fluidly connectable, thus providing a consistent hydraulic oil circuit that allows for heating in the entire circuit with only one heat exchanger unit.

[0012] The first working line can be arranged around the drive on at least one drive side of the drive, and additionally or alternatively the second working line can be arranged around the drive on the opposite drive side. In this way, an ideal heat transfer from the drive to the nearby working line is ensured. The drive can include a radial flux machine.

[0013] It is furthermore advantageous if the steering assist device according to one embodiment has a motor housing in which the drive and additionally or alternatively the hydraulic pump are accommodated. The motor housing can ideally have a heat-conducting material, in which case heat transfer via the material to the at least one working line is promoted.

[0014] The heat exchanger unit can be arranged outside the motor housing, in which case it does not have to be accommodated in the motor housing, or alternatively it is integrated into the motor housing. This makes it possible to achieve a compact design and high heat transfer.

[0015] Examples of the approaches presented herein are explained in detail in the following description with reference to the drawings. [Brief description of the drawings]

[0016] [Figure 1] 1 is a schematic diagram illustrating a vehicle equipped with an electrohydraulic steering assist device according to one embodiment. [Diagram 2] FIG. 1 is a perspective view of an electrohydraulic steering assist device according to one embodiment.

[0017] In the following description of the preferred embodiment of the present approach, the same or similar reference numerals are used for elements that are illustrated in different figures and function similarly without repeating the description of those elements.

[0018] FIG. 1 shows a schematic diagram of a vehicle 100 equipped with an electro-hydraulic steering assist device 105 according to one embodiment.

[0019] By way of example only, the electrohydraulic steering assist device 105 according to this embodiment is accommodated in or on a vehicle 100, which according to this embodiment is configured as a commercial vehicle, for example with an axle load of up to 8 tonnes. The vehicle 100 according to one embodiment is an electrified or highly automated vehicle 100.

[0020] The electrohydraulic steering assist device 105 comprises a hydraulic pump 110, a drive 115, a first working line 120, a second working line 125 and a heat exchanger unit 130. The hydraulic pump 110 is configured to pump hydraulic oil to a first pump outlet 135 of the hydraulic pump 110 in a first turning direction and to a second pump outlet 140 of the hydraulic pump 110 in a second turning direction. The hydraulic pump 110 is thus a pump with an adjustable volume flow rate. The drive 115 is coupled to the hydraulic pump 110 and configured to selectively drive the hydraulic pump 110 in the first turning direction or the second turning direction. The first working line 120 is configured to fluidly connect the first pump outlet 135 to the first working chamber 145, whereby the first working chamber 145 is suitable for moving a piston 160 connectable to a steering rod 150 of the steering 155 in a first direction 165. The second working line 125 is configured to fluidly connect the second pump outlet 140 to the second working chamber 170, whereby the second working chamber 170 is suitable for moving a piston 160 connectable to a steering rod 150 of the steering 155 in a second direction 175 opposite to the first direction 165. The heat exchanger unit 130 is configured to transfer heat 180 generated during operation of the drive 115 to at least one of the working lines 120, 125 for the purpose of heating hydraulic oil flowing through the working lines 120, 125.

[0021] According to the embodiment, the steering assist device 105 further comprises a steering 155 with a steering rod 150, a piston 160, a first working chamber 145 and a second working chamber 170, and / or a motor housing 182. The steering 155 is a block steering according to the embodiment. In the motor housing 182, according to the embodiment, the drive 115 and / or the hydraulic pump 110 are accommodated. According to the embodiment, the motor housing 182 comprises a thermally conductive material. According to one embodiment, the heat exchanger unit 130 is arranged outside the motor housing 182. Alternatively, the heat exchanger unit 130 is arranged in the motor housing 182, for example integrated in the motor housing 182. According to the embodiment, the heat exchanger unit 130 optionally comprises a heating device 185 for heating the hydraulic oil flowing through at least one working line 120, 125. The heating device 185 is according to the present embodiment in or in contact with the first working line 120 or around the first working line 120. The heat exchanger unit 130 is according to the present embodiment arranged at the level of the drive part 115. For example, the heat exchanger unit 130 is connected to the motor housing 182 for thermal conduction, either directly or via a thermal bridge. According to one embodiment, the heat exchanger unit 130 is integrated into the motor housing 182.

[0022] The first working chamber 145 and the second working chamber 170 are fluidly connected or fluidly connectable to one another via a switchable valve 190, here for example a solenoid valve. The first working line 120 is arranged around the drive 115 on at least one drive side of the drive 115 and / or the second working line 125 is arranged around the drive 115 on the opposite drive side. The drive 115 comprises a radial flux machine according to the embodiment.

[0023] The steering assist device 105 presented here advantageously comprises an internal heating unit for an electrohydraulic "Electronic Power Steering" steering gear, or "EPS steering gear" for short.

[0024] The EPS steering assist device 105 follows a fully integrated plug-and-play approach, where the hydraulic oil circuit is separated from the vehicle drive, such as the internal combustion engine or the electric motor of the vehicle 100, and is mounted in a block steering as a compact drive unit, see also FIG.

[0025] Due to the intermittent oil transport and the associated cooling of the hydraulic oil in the drive unit of the EPS steering assist device, a pre-heating of the hydraulic oil is required. The pre-heated hydraulic oil is advantageously distributed in the steering assist device 105 presented herein and uniformly heats it sufficiently. Thanks to the approach described herein, the generated thermal energy is transferred directly to the hydraulic oil. This is possible over an entire volume flow bandwidth and pressure bandwidth, according to the present embodiment over a volume flow bandwidth of 0-16 l / min and / or a pressure bandwidth of 0-180 bar. The heating of the hydraulic oil is important for a constant system stability and the associated steering feel.

[0026] As a heat source, the drive unit uses the drive 115 of the hydraulic pump 110, which drive 115 is a drive motor according to the embodiment. The drive motor is an electric motor, for example a radial flux machine or a radial flux motor. The waste heat of the drive 115 is utilized for the purpose of heating the hydraulic oil. By arranging the working lines 120, 125 formed as hydraulic lines at a distance from each other around the drive 115, the waste heat is transferred directly to the hydraulic medium during operation by thermal conduction of the housing material of the drive 115.

[0027] The steering assist device 105 fulfills the task of discharging the generated heat in the form of waste heat of the drive 115 to the hydraulic oil, which flows directly into the working chambers 145, 170 of the block steering. Such an arrangement allows the use of the waste heat of the motor to heat the oil during the assist operation, thus sufficiently warming up the entire steering assist device 105.

[0028] Furthermore, the steering assist device 105 according to this embodiment optionally comprises a switchable valve 190 connecting both working chambers 145, 170 of the steering 155. Thus, according to one embodiment, a heating function can be applied in which the coil of the drive 115 is used as a heating element (vehicle 100 in a stationary state from a relatively long stop time, e.g. parked after out of operation). The generated heat, according to one embodiment, is conducted to the hydraulic oil via the steering assist device 105 described herein and pumped in a circuit by the switchable valve 190 until a certain target temperature is reached that allows the vehicle 100 to start moving.

[0029] Here, a simplified hydraulic circuit diagram of the bidirectional EPS steering assist device 105 is shown in a schematic manner. The heat exchanger unit 130 in the form of an integrated thermal unit is arranged to reject waste heat to the first working line 120 for temperature regulation of the hydraulic oil. When the first working line 120 is in a pressure operation state, the hydraulic oil is conveyed directly into the first working chamber 145 and moves the piston 160 to the right according to the driver's request for assistance. During the suction operation of the first working line 120, heat is rejected by the suctioned oil from the first working line 120 and transferred to the second working chamber 170 via the second working line 125. In this case, the second working line 125 is in a pressure operation state. The approach presented here states that the provision of the heat exchanger unit 130 allows the waste heat of the radial flux motor to be directly brought to the working lines 120, 125. The hydraulic oil is thus heated and the oil viscosity becomes thinner and more uniform, improving system performance.

[0030] In Fig. 2, a perspective view of an electrohydraulic steering assist device 105 according to an embodiment is shown. This steering assist device 105 can be the steering assist device 105 described in Fig. 1. The EPS steering assist device 105 follows a fully integrated plug-and-play approach. In this case, the hydraulic oil circuit is separated from the internal combustion engine or the electric motor of the vehicle 100 and is attached to the steering wheel 155 in the form of a block steering as a compact drive unit 200. The steering wheel 155 is further formed to couple with a steering wheel 205.

[0031] According to one embodiment, the steering assist device 105 further comprises a control device configured to output an activation signal configured to activate the drive unit and / or the hydraulic pump in response to a steering operation signal representative of an operation of the steering wheel 205, and / or configured to output a deactivation signal configured to deactivate the drive unit and / or the hydraulic pump in response to a steering stationary signal representative of a stationary state of the steering wheel 194. [Explanation of symbols]

[0032] 100 vehicles 105 Electro-hydraulic steering assist device 110 Hydraulic pump 115 Drive unit 120 First working line 125 Second working line 130 Heat Exchanger Unit 135 First pump outlet 140 Second pump outlet 145 First working chamber 150 Steering rod 155 Steering 160 Piston 165 First Direction 170 Second working chamber 175 Second Direction 180 fever 182 Motor housing 185 Heating device 190 Valves 200 Drive Unit 205 Steering Wheel

Claims

1. An electrohydraulic steering assist device (105) for a vehicle (100), said steering assist device (105) having the following features: a hydraulic pump (110) configured to pump hydraulic oil in a first pivotal direction to a first pump outlet (135) of the hydraulic pump (110) and in a second pivotal direction to a second pump outlet (140) of the hydraulic pump (110); a drive unit (115) coupled to the hydraulic pump (110), the drive unit (115) configured to selectively drive the hydraulic pump (110) in the first rotation direction or the second rotation direction; a first actuation conduit (120) is provided, the first actuation conduit (120) configured to fluidly connect said first pump outlet (135) to a first actuation chamber (145), said first actuation chamber (145) adapted to move a piston (160) connectable to a steering rod (150) of a steering (155) in a first direction (165); a second actuation conduit (125) is provided, the second actuation conduit (125) being configured to fluidly connect the second pump outlet (140) to a second actuation chamber (170), the second actuation chamber (170) being suitable for moving the piston (160) connectable to the steering rod (150) of the steering (155) in a second direction (175) opposite to the first direction (165); a heat exchanger unit (130) configured to transfer heat (180) generated during operation of the drive (115) to at least one of the working lines (120, 125) for heating the hydraulic oil flowing through the working lines (120, 125); a motor housing (182) is provided, and the drive unit (115) and / or the hydraulic pump (110) are accommodated in the motor housing (182); The drive unit (115) includes a radial flux machine. An electrohydraulic steering assist device (105) for a vehicle (100).

2. The steering assist device (105) of claim 1, wherein the heat exchanger unit (130) comprises a heating device (185) for heating the hydraulic oil flowing through at least one of the working lines (120, 125).

3. 3. The steering assist device (105) according to claim 1 or 2, wherein the hydraulic pump (110) is configured as a bidirectional hydraulic pump (110).

4. The steering assist device (105) according to any one of claims 1 to 3, further comprising a steering (155) comprising the steering rod (150), the piston (160), the first working chamber (145) and the second working chamber (170).

5. 5. The steering assist device (105) according to claim 1, wherein the first working chamber (145) and the second working chamber (170) are fluidly connected or configured to be fluidly connectable to each other via a switchable valve (190).

6. A steering assist device (105) according to any one of claims 1 to 5, wherein the first actuating conduit (120) is arranged around the drive unit (115) on at least one drive unit side of the drive unit (115) and / or the second actuating conduit (125) is arranged around the drive unit (115) on a drive unit side of the drive unit (115) opposite the drive unit side.

7. The steering assist device (105) according to any one of claims 1 to 6, wherein the motor housing (182) comprises a thermally conductive material.

8. The steering assist device (105) according to any one of claims 1 to 7, wherein the heat exchanger unit (130) is integrated and arranged within the motor housing (182).

9. A steering assist device (105) as described in claim 5, wherein the valve (190) is arranged in a circuit consisting of the working lines (120, 125), the first working chamber (145), the second working chamber (170) and the valve (190), enabling heating of the entire circuit by the heat exchanger unit (130) alone.

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