ELECTRO-HYDRAULIC STEERING ASSISTANCE DEVICE FOR A VEHICLE

Description

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

[0002] Hydraulic power steering (HPS) systems for heavy commercial vehicles consist of a steering unit, hydraulic piping, a hydraulic pump, and a hydraulic oil reservoir. The hydraulic pump is continuously driven by the combustion engine. This constant circulation of hydraulic oil ensures it remains at a sufficiently warm temperature, thus keeping the steering unit consistently warm.

[0003] US 2011 / 190986 A1 discloses a steering system for a vehicle with a hydraulic pump and a motor, the waste heat of which is used to heat a working medium.

[0004] JP 2008 273361 A discloses a steering system for a vehicle with a hydraulic pump and a motor.

[0005] DE 10 2007 053263 A1 discloses a steering system for a vehicle with a hydraulic pump and a motor.

[0006] Against this background, the task of the present approach is to create an improved electro-hydraulic power steering device for a vehicle.

[0007] This problem is solved by an electro-hydraulic steering support device with the features of device claim 1.

[0008] The advantages achievable with the presented approach are that an electro-hydraulic power steering device is created which operates decoupled from a combustion engine or electric motor of a vehicle, while still resulting in heating of the hydraulic oil of the power steering device.

[0009] An electro-hydraulic power steering device for a vehicle comprises a hydraulic pump, a drive unit, 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 in a first direction of rotation and to a second pump outlet in a second direction of rotation. The drive unit is coupled to the hydraulic pump and is configured to drive the hydraulic pump selectively in either the first or second direction of rotation. The first working line is configured to fluidically connect the first pump outlet to a first working chamber, the first working chamber being suitable for moving a piston, which can be coupled to a steering rod, in a first direction.The second working line is designed to fluidically connect the second pump outlet to a second working chamber, the second working chamber being suitable for moving the piston, which can be coupled to the steering rod, in a second direction opposite to the first. The heat exchanger unit is designed to transfer heat generated during operation of the drive to at least one of the working lines in order to heat the hydraulic oil flowing through the working line.

[0010] This electro-hydraulic power steering system is suitable for use in commercial vehicles, for example, with an axle load of up to eight tons. The system is equipped with an "EPS" (Electronic Power Steering) system based on an electro-hydraulic principle. Such an EPS system is characterized by discontinuous operation; that is, the hydraulic fluid in the steering system's hydraulic circuit is only circulated by a pump unit during steering movements, thus operating on the "power on demand" principle. When no steering is required, the hydraulic fluid remains stationary, as does the motor-pump unit consisting of the hydraulic pump and drive. This type of power steering system can be used to function as a "power on demand" steering system, for example, in electrified commercial vehicles without an internal combustion engine, or to meet automated driving requirements, such as...Driver assistance systems such as DAS / ADAS (Level 1-2) and HAD (Level 3-5) can implement these functions independently without driver intervention. Due to intermittent oil demand and the associated cooling of the hydraulic oil, preheating of the hydraulic oil is necessary. The electro-hydraulic power steering device presented here is therefore advantageously able to utilize waste heat generated by the drive system to warm the hydraulic oil, thanks to its heat exchanger unit.

[0011] The heat exchanger unit can include a heating element for warming the hydraulic oil flowing through at least one working line. This provides a means of actively heating the hydraulic oil. The heating element can be in direct contact with the working line or extend into an interior space of the working line to directly heat the hydraulic oil itself. The hydraulic pump is designed as a bidirectional pump. This allows the hydraulic oil to be pumped / suctioned in two directions, depending on the required steering assistance.

[0012] According to one embodiment, the steering assist device can also include the steering mechanism with the steering rod, the piston, the first working chamber, and the second working chamber. The steering mechanism can be a block steering system. Thus, a complete steering system is created. The block steering system can also be designed to be coupled to a steering wheel.

[0013] The first and second working chambers are fluidically connected to each other by means of a switchable valve, for example a solenoid valve, or are designed to be connectable. This creates a continuous hydraulic oil circuit, which enables heating of the entire circuit even with only one heat exchanger unit.

[0014] The first working line can be arranged around the drive on at least one drive side, and additionally or alternatively, the second working line can be arranged around the drive on the opposite drive side. This ensures ideal heat transfer from the drive to the nearby working line(s). The drive can include a radial flux machine.

[0015] It is further advantageous if, according to one embodiment, the power steering device has a motor housing in which the drive unit and, additionally or alternatively, the hydraulic pump are housed. Ideally, the motor housing should be made of a thermally conductive material. This facilitates heat transfer via the material to at least one working line.

[0016] The heat exchanger unit can be located outside the engine housing. In this case, it is not necessary to integrate the heat exchanger unit into the engine housing. Alternatively, the heat exchanger unit can be integrated into the engine housing. This allows for a compact design and high heat transfer efficiency.

[0017] Examples of the approach presented here are explained in more detail in the following description with reference to the figures. These show: Fig. 1 a schematic representation of a vehicle with an electro-hydraulic power steering device according to an exemplary embodiment; and Fig. 2 a perspective view of an electro-hydraulic power steering device according to an exemplary embodiment.

[0018] In the following description of favorable embodiments of the present approach, the same or similar reference numerals are used for the elements shown in the various figures and which have a similar effect, without repeating these elements.

[0019] Fig. 1 Figure 1 shows a schematic representation of a vehicle 100 with an electro-hydraulic power steering device 105 according to an exemplary embodiment.

[0020] The electro-hydraulic power steering device 105 is shown, by way of example, on or in the vehicle 100 according to this embodiment, which, according to this embodiment, is designed as a commercial vehicle, for example with an axle load of up to eight tons. According to this embodiment, the vehicle 100 is an electrified or highly automated vehicle.

[0021] The electro-hydraulic power steering 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 direction of rotation and to a second pump outlet 140 of the hydraulic pump 110 in a second direction of rotation. The hydraulic pump 110 is therefore a pump with an adjustable flow rate. The drive 115 is coupled to the hydraulic pump 110 and is configured to drive the hydraulic pump 110 selectively in either the first or second direction of rotation.The first working line 120 is configured to fluidically connect the first pump outlet 135 to a first working chamber 145, wherein the first working chamber 145 is suitable for moving a piston 160, which can be coupled to a steering rod 150 of a steering mechanism 155, in a first direction 165. The second working line 125 is configured to fluidically connect the second pump outlet 140 to a second working chamber 170, wherein the second working chamber 170 is suitable for moving the piston 160, which can be coupled to the steering rod 150 of the steering mechanism 155, in a second direction 175 opposite to the first direction 165. The heat exchanger unit 130 is designed to transfer heat 180 generated during the operation of the drive 115 to at least one of the working lines 120, 125 in order to heat the hydraulic oil flowing through the working line 120, 125.

[0022] According to this embodiment, the steering assist device 105 further comprises the steering system 155 with the steering rod 150, the piston 160, the first working chamber 145 and the second working chamber 170, and / or a motor housing 182. According to this embodiment, the steering system 155 is a block steering system. According to this embodiment, the drive 115 and / or the hydraulic pump 110 are housed in the motor housing 182. According to this embodiment, the motor housing 182 is made of 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 inside the motor housing 182, for example, integrated into the motor housing 182. According to this embodiment, the heat exchanger unit 130 optionally has a heating device 185 for heating the hydraulic oil flowing through the at least one working line 120, 125.According to this embodiment, the heating device 185 is contacted in or on, or around, the first working line 120. According to this embodiment, the heat exchanger unit 130 is arranged at the level of the drive 115. For example, the heat exchanger unit 130 is connected directly or via a thermal bridge to the motor housing 182 for heat conduction. According to one embodiment, the heat exchanger unit 130 is integrated into the motor housing 182.

[0023] According to this embodiment, the first working chamber 145 and the second working chamber 170 are fluidically connected to each other by means of a switchable valve 190, here by way of example a solenoid valve, or are configured to be connectable. According to this embodiment, the first working line 120 is arranged around the drive 115 on at least one drive side and / or the second working line 125 is arranged around the drive 115 on a drive side opposite the drive side. According to this embodiment, the drive 115 comprises a radial flux machine.

[0024] The steering support device 105 presented here advantageously has an internal heating unit for an electro-hydraulic "Electronic Power Steering" steering gear, or "EPS steering gear" for short.

[0025] The EPS power steering device 105 follows a fully integrated plug-and-play approach. Here, the hydraulic oil circuit is decoupled from a vehicle drive system, such as an internal combustion engine or electric motor of the vehicle 100, and attached to the block steering system as a compact drive unit; see also [reference to relevant section]. Fig. 2 .

[0026] Due to intermittent oil demand and the associated cooling of the hydraulic oil in the drive unit of the EPS power steering system, it is necessary to preheat the hydraulic oil. The preheated hydraulic oil is advantageously distributed throughout the power steering system 105 presented here, thus heating it evenly. The approach described here transfers the generated heat energy directly into the hydraulic oil. This is possible across a full flow rate and pressure range, according to this embodiment, a flow rate range of 0 to 16 l / min and / or a pressure range of 0 to 180 bar. Heating the hydraulic oil is essential for consistent system stiffness and the associated steering feel.

[0027] The drive unit uses the drive 115 of the hydraulic pump 110 as its heat source, which, according to this embodiment, is a drive motor. In this embodiment, the drive motor is an electric motor, for example, a radial flux machine or a radial flux motor. The waste heat from the drive 115 is used to heat the hydraulic oil. Due to the spatial separation of the working lines 120, 125, which are designed as hydraulic lines, around the drive 115, the waste heat is transferred directly to the hydraulic fluid during operation via thermal conduction through the housing material of the drive 115.

[0028] The steering assist device 105 serves to transfer the heat generated as waste heat from the drive 115 to the hydraulic oil, which flows directly into the working chambers 145, 170 of the steering unit. This arrangement allows the engine's waste heat to be used to heat the oil and warm the entire steering assist device 105 during assist operation.

[0029] Furthermore, according to this embodiment, the steering assist device 105 optionally includes the switchable valve 190, which connects both working chambers 145, 170 of the steering system 155. Thus, according to one embodiment, a heating function can be used (vehicle 100 stationary after a prolonged period of inactivity, e.g., after being parked following a work break), in which the coils of the drive 115 are used as a heating element. According to one embodiment, the heat generated is introduced into the hydraulic oil via the steering assist device 105 described here and circulated by the switchable valve 190 until a specific target temperature is reached, enabling the vehicle 100 to be driven away.

[0030] A simplified hydraulic circuit diagram of a bidirectional EPS power steering device 105 is shown schematically here. The heat exchanger unit 130, in the form of an integrated heating unit, is designed to transfer waste heat to the first working line 120 for temperature control of the hydraulic oil. When the first working line 120 is operating under pressure, the hydraulic oil is transported directly into the first working chamber 145 and moves the piston 160 to the right, depending on the driver's desired level of assistance. When the first working line 120 is operating under suction, heat is transferred to the oil drawn from the first working line 120 and transferred via the second working line 125 into the second working chamber 170. In this case, the second working line 125 is operating under pressure. The approach presented here describes a way to transfer the waste heat from the radial flow motor directly into the working lines 120 and 125 using the heat exchanger unit 130.This heats up the hydraulic oil and improves the system's behavior through a lower and more uniform oil viscosity.

[0031] Fig. 2 Figure 1 shows a perspective view of an electro-hydraulic power steering device 105 according to an exemplary embodiment. This could be the device shown in Figure 105. Fig. 1 The described power steering device 105 is a fully integrated plug-and-play system. The hydraulic oil circuit is decoupled from the combustion engine or electric motor of the vehicle 100 and attached to the steering system 155 as a compact drive unit 200 in the form of a block steering system. The steering system 155 is also designed for coupling with a steering wheel 205.

[0032] According to one embodiment, the steering assistance device 105 further comprises a control unit configured to output an activation signal in response to a steering actuation signal representing an actuation of the steering wheel 205, which is configured to activate the drive and / or the hydraulic pump, and / or to output a deactivation signal in response to a steering rest signal representing a rest state of the steering wheel 194, which is configured to deactivate the drive and / or the hydraulic pump. REFERENCE MARK LIST

[0033] 100 Vehicle 105 Electro-hydraulic power steering device 110 Hydraulic pump 115 Drive 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 Heat 182 Motor housing 185 Heating device 190 Valve 200 Drive unit 205 Steering wheel

Claims

1. Electrohydraulic steering assistance device (105) for a vehicle (100), wherein the steering assistance device (105) has the following features: a bidirectional hydraulic pump (110) which is constructed to pump a hydraulic oil in a first rotation direction to a first pump outlet (135) of the hydraulic pump (110) and in a second rotation direction to a second pump outlet (140) of the hydraulic pump (110), a drive (115) which is coupled to the hydraulic pump (110) and which is constructed to drive the hydraulic pump (110) selectively in the first rotation direction or second rotation direction, a first working line (120) which is formed to fluidically connect the first pump outlet (135) to a first working chamber (145), wherein the first working chamber (145) is suitable for moving a piston (160) which can be coupled to a steering rod (150) of a steering system (155) in a first direction (165), a second working line (125) which is formed to fluidically connect the second pump outlet (140) to a second working chamber (170), wherein the second working chamber (170) is suitable for moving the piston (160) which can be coupled to the steering rod (150) of the steering system (155) in a second direction (175) opposed to the first direction (165), and a heat transmission unit (130) which is constructed to transmit heat (180) generated during operation of the drive (115) to at least one of the working lines (120, 125) in order to heat the hydraulic oil flowing through the working line (120, 125), wherein the first working chamber (145) and the second working chamber (170) are formed to be able to be fluidically connected to each other by means of a switchable valve (190), characterized in that the valve (190) is arranged in a circuit which comprises the working lines (120, 125), working chambers (145, 170) and the valve (190) in order to enable heating in the entire circuit only with the heat transmission unit (130).

2. Steering assistance device (105) according to claim 1, in which the heat transmission unit (130) has a heating apparatus (185) for heating the hydraulic oil flowing through the at least one working line (120, 125).

3. Steering assistance device (105) according to any one of the preceding claims, having the steering system (155) with the steering rod (150), the piston (160), the first working chamber (145) and the second working chamber (170).

4. Steering assistance device (105) according to any one of the preceding claims, in which the first working line (120) is arranged at least at one driving side of the drive (115) so as to extend around the drive (115) and / or the second drive line (125) is arranged at a drive side of the drive (115) opposite the drive side so as extend around the drive (115).

5. Steering assistance device (105) according to any one of the preceding claims, with a motor housing (182), in which the drive (115) and / or the hydraulic pump (110) is received.

6. Steering assistance device (105) according to claim 5, in which the motor housing (182) has a heat-conducting material.

7. Steering assistance device (105) according to either claim 5 or 6, in which the heat transmission unit (130) is arranged in a state integrated in the motor housing (182).

8. Steering assistance device (105) according to any one of the preceding claims, in which the drive (115) comprises a radial flux motor.