EP4658548A1

EP4658548A1 - Electrohydraulic steering system with a safety assist configuration

Info

Publication number: EP4658548A1
Application number: EP23836626.4A
Authority: EP
Inventors: R.J. Marotta; Derek MUFF; Jonah LEASON; Elijah J. WARTGOW
Original assignee: Parker Hannifin Corp
Current assignee: Parker Hannifin Corp
Priority date: 2023-01-31
Filing date: 2023-11-22
Publication date: 2025-12-10
Also published as: WO2024163036A1

Abstract

An example electrohydraulic steering system includes: electrohydraulic power unit comprising an electric motor driving a pump; a steering unit that steers a vehicle; and an emergency steering unit including: an accumulator, and a solenoid valve that operates in: (i) a first state in which the solenoid valve allows fluid flow from the pump to the accumulator to charge the accumulator while preventing backflow from the accumulator, and (ii) a second state when a failure occurs that prevents the pump from providing fluid flow to the steering unit, wherein the solenoid valve allows fluid discharged from the accumulator to be provided to the steering unit to allow the vehicle to be steered to a safe position.

Description

Electrohydraulic Steering System with a Safety Assist Configuration

CROSS REFERENCE TO RELATED APPLICATION

[0001] The present application claims priority to U.S. Provisional Patent Application No. 63/482,312, filed on January 31, 2023, and U.S. Provisional Patent Application No. 63/509,067, filed on June 20, 2023, the entire contents of all of which are herein incorporated by reference as if fully set forth in this description.

BACKGROUND

[0002] Hydraulic steering is used in many vehicles. Recently, the electrification trend in on-road vehicles has led to the use of electrohydraulic power units to generate hydraulic steering fluid flow separately from the propulsion system of the vehicle.

[0003] An example electrohydraulic power steering system (eHPS) may include a high voltage source that drives an electric motor, which in turn drives a hydraulic pump to provide steering fluid flow/pressure. This fluid energy is then directed to a steering control unit where it is converted to linear motion to turn the vehicle wheels at the operator’s command.

[0004] One drawback of such steering system is that if the primary source of steering fluid fails (e.g. loss of high voltage power, mechanical failure, electric motor or pump failure, etc.), the vehicle might become not steerable or difficult to steer, which might be a safety issue. It may thus be desirable to introduce redundancy in the steering system such that in the case of a failure, the operator can steer the vehicle to a safe position.

[0005] For electrified vehicles, a backup battery could be used to provide such a redundancy. However, the substantial added cost of a battery and the complexity associated with its integration in the steering system may be prohibitive. Additionally, a battery backup alone might not always be sufficient. For instance, in the case of a pump failure, a backup battery might not help steer the vehicle in the absence of a redundant pump.

[0006] It may thus be desirable to provide a redundant source of steering fluid for a period of time in the case of a failure to allow the operator to make a controlled maneuver to a safe position. It is with respect to these and other considerations that the disclosure made herein is presented.

SUMMARY

[0007] The present disclosure describes implementations that relate to an electrohydraulic steering system with a safety assist configuration.

[0008] In a first example implementation, the present disclosure describes an electro-hydraulic steering system including: an electrohydraulic power unit having an electric motor driving a pump; a steering unit having a directional control valve and a hydraulic cylinder that steers a vehicle, wherein during a normal steering operation mode, the pump provides fluid flow to the directional control valve, which controls fluid flow to and from the hydraulic cylinder to steer the vehicle; and an emergency steering unit having: an accumulator, and a solenoid valve that operates in: (i) a first state in which the solenoid valve allows fluid flow from the pump to the accumulator to charge the accumulator while preventing backflow from the accumulator, and (ii) a second state when a failure occurs that prevents the pump from providing fluid flow to the steering unit, wherein the solenoid valve allows fluid discharged from the accumulator to be provided to the steering unit to allow the vehicle to be steered to a safe position.

[0009] In a second example implementation, the present disclosure describes the electrohydraulic steering system of the first example implementation, wherein an assembly integrates the accumulator having a housing with a manifold formed as a cap mounted to an end of the housing. The manifold has a valve cavity and a plurality of ports to fluidly couple the electrohydraulic power unit and the steering unit to the assembly, and the solenoid valve is disposed in the valve cavity of the manifold.

[0010] In a third example implementation, the present disclosure describes a method of operating the electrohydraulic steering system of the first or second example implementations. [0011] The foregoing summary is illustrative only and is not intended to be in any way limiting. In addition to the illustrative aspects, implementations, and features described above, further aspects, implementations, and features will become apparent by reference to the figures and the following detailed description.

BRIEF DESCRIPTION OF THE FIGURES

[0012] Figure 1 illustrates a hydraulic schematic of an electrohydraulic steering system, in accordance with an example implementation.

[0013] Figure 2 illustrates a hydraulic schematic of the electrohydraulic steering system of Figure 1 when configured to steer a vehicle without charging an accumulator, in accordance with an example implementation.

[0014] Figure 3 illustrates a hydraulic schematic of the electrohydraulic steering system of Figure 1 during charging an accumulator, in accordance with an example implementation.

[0015] Figure 4 is a graph showing variation of pressure level within an accumulator and fluid flow rate to the accumulator, in accordance with an example implementation.

[0016] Figure 5 illustrates a hydraulic schematic of the electrohydraulic steering system of Figure 1 during normal steering operation where an accumulator is in standby mode, in accordance with an example implementation.

[0017] Figure 6 illustrates a hydraulic schematic of the electrohydraulic steering system of Figure 1 during an emergency condition, in accordance with an example implementation.

[0018] Figure 7 is a graph showing variation of pressure level within an accumulator and fluid flow rate discharged from the accumulator, in accordance with an example implementation.

[0019] Figure 8 illustrates a hydraulic schematic of an electrohydraulic steering system with a variable orifice, in accordance with an example implementation.

[0020] Figure 9 illustrates a perspective view of an assembly, in accordance with an example implementation. [0021] Figure 10 is a flowchart of a method of an electrohydraulic steering system, in accordance with an example implementation.

DETAILED DESCRIPTION

[0022] Disclosed herein are systems and methods associated with an electrohydraulic steering system having a safety /emergency assist configuration that involves storing backup hydraulic energy downstream of a pump. Such stored hydraulic energy can be used as a redundant source of steering fluid in the case of any upstream failure causing a lack of supply of steering fluid flow. With this redundancy configuration, the Automotive Safety Integrity Level (ASIL) rating (per ISO 26262) of the vehicle can be enhanced with minimal impact to the vehicle architecture, cost, and complexity.

[0023] Figure 1 illustrates a hydraulic schematic of an electrohydraulic steering system 100, in accordance with an example implementation. The electrohydraulic steering system 100 includes an electrohydraulic power unit 102 having an electric motor 104 driving a pump 106 (e.g., a variable displacement hydraulic pump). As an example for illustration, the electric motor 104 can drive the pump 106 at a rotational speed between zero and 2000 revolutions per minute (RPM), and the pump 106 may have a displacement of 8.3 cubic centimeter per revolution (cm³/rev).

[0024] The electrohydraulic power unit 102 can also have a fluid reservoir 108 (e.g., a tank) containing steering fluid at a low pressure (e.g., atmospheric pressure). The pump 106 is configured to draw fluid from the fluid reservoir 108 and generate fluid flow to other components of the electrohydraulic steering system 100.

[0025] The electrohydraulic power unit 102 can also have a pressure relief valve 110. The pressure relief valve 110 is a valve used to control or limit the pressure in the electrohydraulic steering system 100. Pressure might otherwise build up and can cause some components or fluid lines to fail. If pressure level in the electrohydraulic steering system 100 exceeds a threshold pressure value, such as 208 bar or 3000 pounds per square inch, the pressure relief valve 110 opens to form a fluid path for fluid from the pump 106 to the fluid reservoir 108 to relieve pressure in the electrohydraulic steering system 100.

[0026] In some examples, the electrohydraulic power unit 102 can include a pump pressure sensor 112 that indicates pressure level at an outlet of the pump 106. For example, the pump pressure sensor 112 can provide pump sensor information indicative of the pressure level at the outlet port of the pump 106.

[0027] The electrohydraulic steering system 100 includes a steering unit 114 having a directional control valve 116 and a hydraulic cylinder 118. The hydraulic cylinder 118 has a piston 120, the linear motion of which steers the wheels of a vehicle. A piston head of the piston 120 divides an internal chamber of the hydraulic cylinder into a first chamber 101 and a second chamber 103.

[0028] In the example implementation of Figure 1, the directional control valve 116 can be a three- position, four-way valve, and is configured to control fluid flow to and from the chambers 101, 103 of the hydraulic cylinder 118. In an example, the directional control valve 116 has an inlet port 105, a return port 107 fluidly coupled to the fluid reservoir 108 via an orifice 109, a first workport 111 fluidly coupled to the first chamber 101, and a second workport 113 fluidly coupled to the second chamber 103.

[0029] In an example, the directional control valve 116 can be as spool type valve having a spool that is axially-movable within a bore in a valve body of the directional control valve 116. When the spool is in an unactuated or neutral position, the spool allows the ports of the directional control valve 116 to be connected to each other, and thus connected to the fluid reservoir 108. This way, if the pump 106 provides fluid to the directional control valve 116 while the directional control valve 116 is unactuated (e.g., the driver is not steering the vehicle), fluid flows to the fluid reservoir

108 via the orifice 109. [0030] The directional control valve 116 can be electrically, fluidically, or manually actuated, for example. When the directional control valve 116 is actuated to operate in a first state (e.g., the spool shifts in a first direction), the inlet port 105 is fluidly coupled to the first workport 111, and the second workport 113 is fluidly coupled to the return port 107. In this first state, the directional control valve 116 directs fluid flow received at the inlet port 105 to the first workport 111, then to the first chamber 101, causing the piston 120 to move in a first direction (e.g., to the right in Figure 1) and steer the vehicle in a corresponding direction. Fluid discharged from the second chamber 103 flows to the second workport 113, then to the return port 107, then to the fluid reservoir 108 via the orifice 109.

[0031] When the directional control valve 116 is actuated to operate in a second state (e.g., the spool shifts in a second direction), the inlet port 105 is fluidly coupled to the second workport 113, and the first workport 111 is fluidly coupled to the return port 107. In this second state, the directional control valve 116 directs fluid flow received at the inlet port 105 to the second workport 113, then to the second chamber 103, causing the piston 120 to move in a second direction (e.g., to the left in Figure 1) and steer the vehicle in a corresponding direction. Fluid discharged from the first chamber 101 flows to the first workport 111, then to the return port 107, then to the fluid reservoir 108 via the orifice 109.

[0032] The fluid reservoir 108 is drawn in two different locations in the figures to reduce visual clutter in the drawings. However, it should be understood that the vehicle or the electrohydraulic steering system 100 can have one fluid reservoir.

[0033] Also, the implementation of the directional control valve 116 as a three position, four-way spool valve is an example implementation for illustration only, and is not limiting. Operations of the directional control valve 116 can be implemented via many configurations including multiple cartridge valves in a manifold, a valve assembly having multiple valves, etc.

[0034] The electrohydraulic steering system 100 further includes a redundant or emergency steering unit 122. The emergency steering unit 122 includes a first check valve 124 that prevents back flow into the pump 106. In examples, the first check valve 124 can be part of the electrohydraulic power unit 102.

[0035] The emergency steering unit 122 further includes an accumulator 126 configured as an emergency source of fluid flow and pressure in the case of a failure in the electrohydraulic power unit 102. As an example for illustration, the accumulator 126 can be a piston-type accumulator. Other types of accumulator (e.g., bladder or diaphragm type accumulator) could be used, however. The accumulator 126, for example, can include a cylindrical housing or vessel that is divided into two chambers by a movable piston, bladder, or diaphragm. One chamber is filled with hydraulic fluid, while the other chamber is filled with a compressible gas, such as nitrogen. As hydraulic fluid enters the accumulator 126, it compresses the gas, thereby increasing the pressure of hydraulic fluid within the accumulator 126.

[0036] The accumulator 126 is configured to have a capacity that is sufficient to operate the steering unit 114 for a particular period of time in the case of emergency. As an example for illustration, the accumulator 126 may have a storage capacity of 0.6 gallons or (2271.25 cm³).

[0037] The emergency steering unit 122 can also have an accumulator pressure sensor 128 configured to provide accumulator sensor information indicative of pressure level of fluid stored in the accumulator 126. For example, the accumulator pressure sensor 128 can provide sensor information indicative of the pressure level of fluid stored in the accumulator 126. In some examples, the pump pressure sensor 112 at the outlet of the pump 106 can also be included in the emergency steering unit 122.

[0038] The emergency steering unit 122 includes a first solenoid valve 130 that is fluidly coupled to the accumulator 126, and the first solenoid valve 130 controls fluid flow to and from the accumulator 126. The emergency steering unit 122 can further include a combination of a second check valve 132 disposed in parallel with an orifice 134. The second check valve 132 is disposed downstream of the first check valve 124 and upstream of the first solenoid valve 130 when fluid is being provided from the pump 106 to the accumulator 126 as described below with respect to Figure 3.

[0039] In an example, the orifice 134 may be more restrictive than the second check valve 132 such that fluid provided to the accumulator 126 flows through the second check valve 132 as a path of least resistance compared to a path through the orifice 134. As an example for illustration, the orifice 134 can have a diameter of 0.063 inches. Further, although the orifice 134 is depicted as a fixed orifice in Figure 1, in other example implementations, the orifice 134 can be made as a variable orifice that can be tuned to achieve a particular profile for flow and pressure of fluid discharged from the accumulator 126 and provided to the steering unit 114, as described below with respect to Figure 8.

[0040] In an example, the emergency steering unit 122 includes a second solenoid valve 136. However, as explained below, the electrohydraulic steering system 100 is operable without the second solenoid valve 136. As depicted, the second solenoid valve 136 is disposed downstream from the electrohydraulic power unit 102 and upstream of the steering unit 114.

[0041] In the example implementation of Figure 1, both the first solenoid valve 130 and the second solenoid valve 136 are normally-open valves (e.g., both valves are open when unactuated). When a solenoid of either solenoid valve is energized via an electric command signal, the respective solenoid valve is actuated to a closed position to block fluid flow, at least in one direction.

[0042] For example, when the first solenoid valve 130 is actuated (when its solenoid is energized), the first solenoid valve 130 allows fluid flow to the accumulator 126, but prevents fluid flow from the accumulator 126. When the second solenoid valve 136 is actuated (when its solenoid is energized), the second solenoid valve 136 prevents fluid flow to the steering unit 114, and thus disables steering the vehicle.

[0043] The electrohydraulic steering system 100 further includes a controller 138. The controller 138 can include one or more processors or microprocessors and may include data storage (e.g., memory, transitory computer-readable medium, non-transitory computer-readable medium, etc.). The data storage may have stored thereon instructions that, when executed by the one or more processors of the controller 138, cause the controller 138 to perform operations described herein.

[0044] The controller 138 can receive sensor information from various sensors such as the pressure sensors 112, 128, and other inputs (e.g., commands from a vehicle controller). The controller 138 can then responsively actuate the first solenoid valve 130, the second solenoid valve 136, the electric motor 104, etc. to operate the electrohydraulic steering system 100 in a particular state. The controller 138 is not shown in Figures 2, 3, 5, 6 described below to reduce visual clutter in the drawings, but it should be understood that the controller 138 provides commands to the electrically actuated components in the modes of operation described below.

[0045] Figure 2 illustrates a hydraulic schematic of the electrohydraulic steering system 100 when configured to steer the vehicle without charging the accumulator 126, in accordance with an example implementation. In this mode of operation, the electric motor 104 drives the pump 106 (e g., at 1000 RPM) so the pump 106 can provide fluid to the steering unit 114. Also, the second solenoid valve 136 is unactuated, and is thus in an open state as depicted in Figure 2.

[0046] Fluid flows from the pump 106 through the first check valve 124, then through the second solenoid valve 136, to the steering unit 114. The directional control valve 116, which may be actuated by the driver of the vehicle, controls fluid flow to the hydraulic cylinder 118, which in turn steers the vehicle.

[0047] If the directional control valve 116 is not actuated (e.g., no steering wheel movement by the operator), fluid from the pump 106 is provided to the fluid reservoir 108 via the orifice 109. In this case, a pressure level of fluid provided by the pump 106 can be low (e.g., 3.5 bar). If the directional control valve 116 is actuated, fluid from the pump 106 is provided through the directional control valve 116 to the hydraulic cylinder 118, and fluid discharged from the hydraulic cylinder 118 is provided to the fluid reservoir 108 via the orifice 109. In this case, fluid provided by the pump 106 can be a high pressure fluid (e.g., up to the pressure setting of the pressure relief valve 110) to enable steering of the vehicle.

[0048] The accumulator 126 is configured as an emergency source of hydraulic energy. To operate as a source of fluid, the accumulator 126 is first charged with fluid from the pump 106 to store hydraulic energy in the accumulator 126. The accumulator 126 can, for example, be charged at start-up of the vehicle.

[0049] Figure 3 illustrates a hydraulic schematic of the electrohydraulic steering system 100 during charging the accumulator 126, in accordance with an example implementation. To charge the accumulator 126, the second solenoid valve 136 can be actuated (e.g., its solenoid is energized), causing the second solenoid valve 136 to block the fluid path to the steering unit 114. The first solenoid valve 130 is also actuated to allow fluid flow to the accumulator 126, while blocking backflow from the accumulator 126. In this mode, the electric motor 104 can drive the pump 106 at 2000 RPM, for example.

[0050] As the second solenoid valve 136 blocks fluid, fluid is directed from the pump 106 through the first check valve 124, then through the second check valve 132, then through the first solenoid valve 130, which is in the actuated state, to the accumulator 126. Fluid continues to flow into the accumulator 126, and pressure level of fluid in the accumulator 126 thus continues to increase, until total system pressure reaches the setting of the pressure relief valve 110, for example.

[0051] Figure 4 is a graph 200 showing variation of pressure level within the accumulator 126 and fluid flow rate to the accumulator 126, in accordance with an example. The x-axis represents time, and the y-axis represents both the flow rate of fluid provided to the accumulator 126 and pressure of fluid within the accumulator 126. Line 202 shows variation of pressure in bar, and line 204 shows variation of fluid flow rate to the accumulator 126 in liters per minute (L/min) during the charging mode of Figure 3.

[0052] As an example for illustration, in this mode of operation, the accumulator 126 can be charged until its pressure level as indicated by the accumulator pressure sensor 128 reaches 208.5 bar as shown in Figure 4. In this state, the accumulator 126 may store about 1064 cm³ of fluid volume, for example. The charging process can take 3-4 seconds when the electric motor 104 is driving the pump 106 at 2000 RPM, for example.

[0053] Figure 5 illustrates a hydraulic schematic of the electrohydraulic steering system 100 during normal steering operation mode where the accumulator 126 is in standby mode, in accordance with an example implementation. In this mode of operation, the pump 106 is configured to provide steering fluid to the steering unit 114 as described above with respect to Figure 2. As an example, the electric motor 104 can drive the pump 106 at 1000 RPM, and the pump 106 can provide fluid to the steering unit 114.

[0054] In this mode, the accumulator 126 is charged and is in standby mode in case a failure occurs. As an example, the accumulator 126 can be charged with 1064 cm³ of fluid volume at a pressure level of 208 bar as mentioned above.

[0055] If leakages occurs from the accumulator 126 overtime, and pressure level of fluid in the accumulator 126 may fall below a threshold value, the electrohydraulic power unit 102 can be used to “top off’ the accumulator 126. Particularly, the first solenoid valve 130 can be energized to allow a portion of fluid from the pump 106 to flow through the first check valve 124, then through the first solenoid valve 130 to the accumulator 126 until the desired pressure level of fluid in the accumulator 126 is reached. This way, the accumulator 126 remains ready to replace the pump 106 as a source of fluid flow in the case of an emergency or failure.

[0056] Figure 6 illustrates a hydraulic schematic of the electrohydraulic steering system 100 during an emergency condition, in accordance with an example implementation. If the electric system, the electric motor 104, or the pump 106 fails, the pump 106 might not be able to provide fluid flow to the steering unit 114. As mentioned above, the first solenoid valve 130 and the second solenoid valve 136 are normally open valves, and thus if electric power is lost as a possible mode of failure, they operate in their normally open position. If electric power has not failed, the controller 138 of the electrohydraulic steering system 100 removes any electric signals provided to the solenoid valves 130, 136 to ensure they operate in the normally-open state.

[0057] In this emergency mode of operation, fluid is allowed to be discharged from the accumulator 126 to flow through the first solenoid valve 130, through the orifice 134, through the second solenoid valve 136, and then to the steering unit 114. Notably, the first check valve 124 prevents backflow to the pump 106 during this emergency steering mode

[0058] Figure 7 illustrates a graph 300 showing variation of pressure level within the accumulator 126 and fluid flow rate discharged from the accumulator 126, in accordance with an example. Similar to Figure 4, the x-axis represents time, and the y-axis represents both the flow rate and pressure level of fluid discharged from the accumulator 126. Line 302 shows variation of pressure in bar, and line 304 shows variation of fluid flow rate discharged from the accumulator 126 in L/min during the emergency steering mode of Figure 6.

[0059] The accumulator 126 can supply fluid flow to the steering unit 114 to enable the driver to steer the vehicle to a safe position. As indicated by the lines 302, 304 in Figure 7, as the accumulator 126 supplies fluid, fluid volume and pressure inside the accumulator 126 decrease. For example, the pressure level can decrease from about 208 bar to 138 bar, and fluid volume can decrease from 1064 cm³ to about 455 cm³ in 2.5 seconds.

[0060] In an example, the controller 138 of the electrohydraulic steering system 100 can determine when to operate the first solenoid valve 130 in the open state (unactuated state) to operate the electrohydraulic steering system 100 in the emergency mode based on pressure levels indicated by the pressure sensors 112, 128. For instance, if the pump pressure sensor 112 indicates that there is no pressure (e.g., 0 bar pressure level) at the outlet of the pump 106, then a failure may have occurred (e.g., electric power is lost, the electric motor 104 or the pump 106 has failed, etc.). If the accumulator pressure sensor 128 indicates that the accumulator 126 is sufficiently charged (fluid is stored therein at a pressure level above a threshold value), the controller 138 can then unactuate the first solenoid valve 130 to operate the electrohydraulic steering system 100 in the emergency mode. [0061] In the example where electric power is lost, the first solenoid valve 130 operates in the open state regardless of any commands, and the electrohydraulic steering system 100 is operable in the emergency state. Notably, the use of the first solenoid valve 130 in the closed state when actuated (when its solenoid is energized) allows the accumulator 126 to be charged and recharged even if the second solenoid valve 136 is not used in the electrohydraulic steering system 100. As such, the electrohydraulic steering system 100 is operable without the second solenoid valve 136.

[0062] The controller 138 of the electrohydraulic steering system 100 can be integrated into the electrohydraulic steering system 100 or can be a separate controller (e.g., a controller of the vehicle). Also, several additional control logic aspects can be implemented by the controller 138 of the electrohydraulic steering system 100. For instance, the controller 138 can be configured to control the electrohydraulic steering system 100 (e.g., control actuation of the electric motor 104, the first solenoid valve 130, and the second solenoid valve 136) to provide assistive steering in some circumstances or limit steering power in others.

[0063] Further, in an example, the electrohydraulic steering system 100 can be configured to be tunable to match a weight of the vehicle. For instance, the controller 138 can be used to control flow rate and pressure level of fluid discharged from the accumulator 126 based on a particular configuration of the vehicle (e.g., weight of the vehicle).

[0064] In an example, by varying the size of the orifice 134, the flow profile or characteristics (e.g., pressure level and duration of flow) of fluid discharged from the accumulator 126 can be adjusted to be suitable for the weight of the vehicle. In one example, the size of the orifice can be dynamically changed to adjust the flow characteristics from the accumulator 126 dynamically based on vehicle weight, speed, or operator preference. [0065] Figure 8 illustrates a hydraulic schematic of the electrohydraulic steering system 100 with a variable orifice 140, in accordance with an example implementation. As depicted in Figure 8, the orifice 134 (fixed orifice) is replaced with the variable orifice 140.

[0066] The variable orifice 140 can be implemented in various ways. For example, the variable orifice 140 can be implemented via a needle valve that is mechanically, fluidically, or electrically actuated. In another example, the variable orifice 140 can be implemented via a proportional two- way, two-position valve that is manually, fluidically, or electrically actuated. In the examples where the variable orifice 140 is implemented via an electrically-actuated device (e.g., a solenoid valve), the controller 138 provides a command signal thereto to adjust the opening or size of the variable orifice 140 as desired.

[0067] In examples, vehicles can be classified based on their gross weight. For example, a class 5 truck may be characterized by a front axle capable of handling a load of 8000 pounds. A class 8 truck on the other hand can have an axle capable of handling a load of 14,000 pounds, for example. Thus, the front axle of different vehicles may be subjected to different loads.

[0068] The electrohydraulic steering system 100 may be configured to handle steering of vehicles of different classifications or weights by adjusting the size of the variable orifice 140. For example, for a higher weight class vehicle, the variable orifice 140 may be opened more than for a lower weight class vehicle. This way, a higher flow rate and higher pressure fluid may be provided from the accumulator 126 in an emergency to the steering unit 114 to enable steering the vehicle with the larger weights. In this case, the accumulator 126 may discharge its stored fluid energy in a short period of time.

[0069] Conversely, for a smaller weight vehicle, the variable orifice 140 may be made more restrictive, and therefore the accumulator 126 may provide fluid to the steering unit 114 at a lower pressure and smaller flow rate. Further, in this case, and the accumulator 126 may discharge its stored fluid energy in a comparatively longer period of time.

[0070] As such, the controller 138 may adjust the opening of the variable orifice 140 in an inversely related manner with respect to the gross weight of the vehicle. The larger the gross weight of the vehicle, the less restrictive the variable orifice 140 and vice versa.

[0071] In some examples, several components of the electrohydraulic steering system 100 can be integrated into a manifold. In an example implementation, such manifold can be integrated into the accumulator 126. For instance, the cap of the accumulator 126 can be formed as a manifold that integrates various components of the electrohydraulic steering system 100. This implementation may advantageously save space, have fewer potential leak or failure points, and reduce cost.

[0072] Figure 9 illustrates a perspective view of an assembly 400, in according to an example implementation. The assembly 400 may include at least some of the components of the emergency steering unit 122.

[0073] The assembly 400 includes the accumulator 126 having a housing 401 that is generally cylindrical. A cap of the accumulator 126 is formed as a manifold 402 that is crimped into the housing 401 of the accumulator 126, as depicted in Figure 9. In other examples, the cap (the manifold 402) can be threaded into the housing 401.

[0074] This configuration reduces the installation space of the electrohydraulic steering system 100, and may reduce the number of fluid lines (e.g., hoses, tubes, etc.) and fittings, thereby enhancing reliability of the electrohydraulic steering system 100. [0075] The manifold 402 can have a first valve cavity that receives the first solenoid valve 130 and a second valve cavity that receives the second solenoid valve 136. For instance, the first solenoid valve 130 and the second solenoid valve 136 can be screwed into their respective cavity in the manifold 402 (the cap of the accumulator 126).

[0076] The manifold 402 can also include various ports that connect various components of the electrohydraulic steering system 100 to the manifold 402. For example, the manifold 402 includes a port 404 and a port 406, wherein one of the ports 404, 406 may be an inlet port providing charge fluid to the accumulator 126, and the other is an outlet port for discharging fluid from the accumulator 126.

[0077] Other components can further be integrated within the manifold 402 such as the second check valve 132 and the orifice 134 (or the variable orifice 140). In another example, the manifold 402 can also include the pump pressure sensor 112 and/or the accumulator pressure sensor 128. The manifold 402 further includes fluid passages formed therein to fluidly couple the components of the electrohydraulic steering system 100, based on actuation state of the first solenoid valve 130 and the second solenoid valve 136.

[0078] Figure 10 is a flowchart of a method 500 of operating the electrohydraulic steering system 100, in accordance with an example implementation. For example, the method 500 can be implemented by the controller 138, for example.

[0079] The method 500 may include one or more operations, or actions as illustrated by one or more of blocks 502-506. Although the blocks are illustrated in a sequential order, these blocks may in some instances be performed in parallel, and/or in a different order than those described herein. Also, the various blocks may be combined into fewer blocks, divided into additional blocks, and/or removed based upon the desired implementation. [0080] In addition, for the method 500 and other processes and operations disclosed herein, the flowchart shows operation of one possible implementation of present examples. In this regard, each block may represent a module, a segment, or a portion of program code, which includes one or more instructions executable by a processor (e g., a processor of the controller 138) for implementing specific logical operations or steps in the process. The program code may be stored on any type of computer readable medium or memory, for example, such as a storage device including a disk or hard drive. The computer readable medium may include a non-transitory computer readable medium or memory, for example, such as computer-readable media that stores data for short periods of time like register memory, processor cache and Random Access Memory (RAM). The computer readable medium may also include non-transitory media or memory, such as secondary or persistent long term storage, like read only memory (ROM), optical or magnetic disks, compact-disc read only memory (CD-ROM), for example. The computer readable media may also be any other volatile or non-volatile storage systems. The computer readable medium may be considered a computer readable storage medium, a tangible storage device, or other article of manufacture, for example. In addition, for the method 500 and other processes and operations disclosed herein, one or more blocks in Figure 10 may represent circuitry or digital logic that is arranged to perform the specific logical operations in the process.

[0081] At block 502, the method 500 includes actuating, by the controller 138, the first solenoid valve 130 of the electrohydraulic steering system 100 having (i) the electrohydraulic power unit 102 having the electric motor 104 driving the pump 106, (ii) the steering unit 114 that steers a vehicle, and (iii) the emergency steering unit 122 having the accumulator 126, wherein actuating the first solenoid valve 130 allows fluid flow from the pump 106 to the accumulator 126 to charge the accumulator 126 while preventing backflow from the accumulator 126. [0082] At block 504, the method 500 includes detecting, by the controller 138, an emergency state that prevents the pump 106 from providing fluid flow to the steering unit 114. For example, the controller 138 can detect loss of electric power or voltage to the electric motor 104, failure of the electric motor 104 or the pump 106 (e.g., as indicated by a pressure level at the outlet of the pump 106 being zero or below a threshold value), etc.

[0083] At block 506, the method 500 includes responsive to detecting the emergency state, operating the first solenoid valve 130 in an unactuated state, causing the first solenoid valve 130 to allow fluid to be discharged from the accumulator 126 to be provided to the steering unit 114 to allow the vehicle to be steered to a safe position.

[0084] The method 500 can further include other steps to as described throughout herein. For example, as mentioned above with respect to Figure 8, the electrohydraulic steering system 100 may include the second check valve 132 disposed upstream from the first solenoid valve 130, and the variable orifice 140 disposed in parallel with the second check valve 132, wherein the second check valve allows fluid flow therethrough to the first solenoid valve 130 to allow the accumulator 126 to be charged, wherein fluid discharged from the accumulator 126 flows through the variable orifice 140 to the steering unit 114. In this case, the method may further include adjusting a size of the variable orifice 140 to change flow rate and pressure level of fluid provided from the accumulator 126 to the steering unit 114. Any of the other steps or operations described throughout herein can be included in the method 500.

[0085] The detailed description above describes various features and operations of the disclosed systems with reference to the accompanying figures. The illustrative implementations described herein are not meant to be limiting. Certain aspects of the disclosed systems can be arranged and combined in a wide variety of different configurations, all of which are contemplated herein. [0086] Further, unless context suggests otherwise, the features illustrated in each of the figures may be used in combination with one another. Thus, the figures should be generally viewed as component aspects of one or more overall implementations, with the understanding that not all illustrated features are necessary for each implementation.

[0087] Additionally, any enumeration of elements, blocks, or steps in this specification or the claims is for purposes of clarity. Thus, such enumeration should not be interpreted to require or imply that these elements, blocks, or steps adhere to a particular arrangement or are carried out in a particular order.

[0088] Further, devices or systems may be used or configured to perform functions presented in the figures. In some instances, components of the devices and/or systems may be configured to perform the functions such that the components are actually configured and structured (with hardware and/or software) to enable such performance. In other examples, components of the devices and/or systems may be arranged to be adapted to, capable of, or suited for performing the functions, such as when operated in a specific manner.

[0089] By the term “substantially” or “about” it is meant that the recited characteristic, parameter, or value need not be achieved exactly, but that deviations or variations, including for example, tolerances, measurement error, measurement accuracy limitations and other factors known to skill in the art, may occur in amounts that do not preclude the effect the characteristic was intended to provide.

[0090] The arrangements described herein are for purposes of example only. As such, those skilled in the art will appreciate that other arrangements and other elements (e.g., machines, interfaces, operations, orders, and groupings of operations, etc.) can be used instead, and some elements may be omitted altogether according to the desired results. Further, many of the elements that are described are functional entities that may be implemented as discrete or distributed components or in conjunction with other components, in any suitable combination and location.

[0091] While various aspects and implementations have been disclosed herein, other aspects and implementations will be apparent to those skilled in the art. The various aspects and implementations disclosed herein are for purposes of illustration and are not intended to be limiting, with the true scope being indicated by the following claims, along with the full scope of equivalents to which such claims are entitled. Also, the terminology used herein is for the purpose of describing particular implementations only, and is not intended to be limiting.

[0092] Embodiments of the present disclosure can thus relate to one of the enumerated example embodiments (EEEs) listed below.

[0093] EEE 1 is an electrohydraulic steering system comprising: an electrohydraulic power unit having an electric motor driving a pump; a steering unit having a directional control valve and a hydraulic cylinder that steers a vehicle, wherein during a normal steering operation mode, the pump provides fluid flow to the directional control valve, which controls fluid flow to and from the hydraulic cylinder to steer the vehicle; and an emergency steering unit having: an accumulator, and a solenoid valve that operates in: (i) a first state in which the solenoid valve allows fluid flow from the pump to the accumulator to charge the accumulator while preventing backflow from the accumulator, and (ii) a second state when a failure occurs that prevents the pump from providing fluid flow to the steering unit, wherein the solenoid valve allows fluid discharged from the accumulator to be provided to the steering unit to allow the vehicle to be steered to a safe position.

[0094] EEE 2 is the electrohydraulic steering system of EEE 1, further comprising: a check valve disposed at an outlet of the pump to prevent backflow to the pump when a failure occurs, thereby allowing fluid to be directed from the accumulator to the steering unit. [0095] EEE 3 is the electrohydraulic steering system of EEE 2, wherein the check valve is a first check valve, and wherein the emergency steering unit further comprises: a second check valve disposed downstream from the first check valve and upstream from the solenoid valve; and an orifice disposed in parallel with the second check valve, wherein the second check valve allows fluid flow therethrough to the solenoid valve to allow the accumulator to be charged, and wherein fluid discharged from the accumulator flows through the orifice to the steering unit.

[0096] EEE 4 is the electrohydraulic steering system of any of EEEs 1-3, wherein the solenoid valve is a first solenoid valve, and wherein the emergency steering unit further comprises: a second solenoid valve downstream of the electrohydraulic power unit and upstream of the steering unit, wherein the second solenoid valve operates in: (i) a first state in which the second solenoid valve allows fluid to flow to the steering unit, and (ii) a second state in which the second solenoid valve prevents fluid flow to the steering unit to direct fluid flow to the first solenoid valve to charge the accumulator.

[0097] EEE 5 is the electrohydraulic steering system of any of EEEs 1-4, further comprising: a pump pressure sensor that provides pump sensor information indicative of pressure level at an outlet of the pump; an accumulator pressure sensor that provides accumulator sensor information indicative of pressure level of fluid of the accumulator; and a controller that determines whether to operate the solenoid valve in the first state or the second state based on the pump sensor information and the accumulator sensor information.

[0098] EEE 6 is the electrohydraulic steering system of any of EEEs 1-5, wherein the emergency steering unit further comprises: a check valve disposed upstream from the solenoid valve; and an orifice disposed in parallel with the check valve, wherein the check valve allows fluid flow therethrough to the solenoid valve to allow the accumulator to be charged, and wherein fluid discharged from the accumulator flows through the orifice to the steering unit.

[0099] EEE 7 is the electrohydraulic steering system of EEE 6, wherein the orifice is a variable orifice.

[00100] EEE 8 is the electrohydraulic steering system of EEE 7, further comprising: a controller that adjusts a size of the variable orifice to change flow rate and pressure level of fluid provided from the accumulator to the steering unit.

[00101] EEE 9 is the electrohydraulic steering system of any of EEEs 1-8, wherein an assembly integrates the accumulator having a housing with a manifold formed as a cap mounted to an end of the housing. The manifold has a valve cavity and a plurality of ports to fluidly couple the electrohydraulic power unit and the steering unit to the assembly, and the solenoid valve is disposed in the valve cavity of the manifold.

[00102] For example, EEE 9 is an electrohydraulic steering system comprising: an electrohydraulic power unit having an electric motor driving a pump; a steering unit having a directional control valve and a hydraulic cylinder that steers a vehicle, wherein during a normal steering operation mode, the pump provides fluid flow to the directional control valve, which controls fluid flow to and from the hydraulic cylinder to steer the vehicle; and an assembly having: an accumulator having a housing and a cap mounted to an end of the housing, wherein the cap is formed as a manifold that has a valve cavity, and a plurality of ports to fluidly couple the electrohydraulic power unit and the steering unit to the assembly, and a solenoid valve disposed in the valve cavity of the manifold and operates in: (i) a first state in which the solenoid valve allows fluid flow from the pump to the accumulator to charge the accumulator while preventing backflow from the accumulator, and (ii) a second state when a failure occurs that prevents the pump from providing fluid flow to the steering unit, wherein the solenoid valve allows fluid discharged from the accumulator to be provided to the steering unit to allow the vehicle to be steered to a safe position.

[00103] EEE 10 is the electrohydraulic steering system of EEE 9, further comprising: a check valve disposed at an outlet of the pump to prevent backflow to the pump when a failure occurs, thereby allowing fluid to be directed from the accumulator to the steering unit.

[00104] EEE 11 is the electrohydraulic steering system of EEE 10, wherein the check valve is a first check valve, and wherein the electrohydraulic steering system further comprises: a second check valve disposed downstream from the first check valve and upstream from the solenoid valve; and an orifice disposed in parallel with the second check valve, wherein the second check valve allows fluid flow therethrough to the solenoid valve to allow the accumulator to be charged, and wherein fluid discharged from the accumulator flows through the orifice to the steering unit.

[00105] EEE 12 is the electrohydraulic steering system of EEE 11, wherein the second check valve and the orifice are disposed within the manifold.

[00106] EEE 13 is the electrohydraulic steering system of any of EEEs 9-12, wherein the valve cavity is a first valve cavity, wherein the solenoid valve is a first solenoid valve, wherein the manifold has a second valve cavity, and wherein the assembly further comprises: a second solenoid valve disposed in the second valve cavity, wherein the second solenoid valve operates in: (i) a first state in which the second solenoid valve allows fluid to flow to the steering unit, and (ii) a second state in which the second solenoid valve prevents fluid flow to the steering unit to direct fluid flow to the first solenoid valve to charge the accumulator. [00107] EEE 14 is the electrohydraulic steering system of any of EEEs 9-13, further comprising: a pump pressure sensor that provides pump sensor information indicative of pressure level at an outlet of the pump; an accumulator pressure sensor that provides accumulator sensor information indicative of pressure level of fluid of the accumulator; and a controller that determines whether to operate the solenoid valve in the first state or the second state based on the pump sensor information and the accumulator sensor information.

[00108] EEE 15 is the electrohydraulic steering system of EEE 14, wherein the pump pressure sensor and/or the accumulator pressure sensor are disposed in the manifold.

[00109] EEE 16 is the electrohydraulic steering system of any of EEEs 9-15, further comprising: a check valve disposed upstream from the solenoid valve; and an orifice disposed in parallel with the check valve, wherein the check valve allows fluid flow therethrough to the solenoid valve to allow the accumulator to be charged, and wherein fluid discharged from the accumulator flows through the orifice to the steering unit.

[00110] EEE 17 is the electrohydraulic steering system of EEE 16, wherein the orifice is a variable orifice, wherein the electrohydraulic steering system further comprises: a controller that adjusts a size of the variable orifice to change flow rate and pressure level of fluid provided from the accumulator to the steering unit.

[00111] EEE 18 is the electrohydraulic steering system of any of EEEs 16-17, wherein the check valve and the orifice are disposed in the manifold.

[00112] EEE 19 is a method of operating the electrohydraulic steering system of any of EEEs 1- 18. For example, the method includes actuating, by a controller, a solenoid valve of an electrohydraulic steering system having (i) an electrohydraulic power unit having an electric motor driving a pump, (ii) a steering unit that steers a vehicle, and (iii) an emergency steering unit having an accumulator, wherein actuating the solenoid valve allows fluid flow from the pump to the accumulator to charge the accumulator while preventing backflow from the accumulator; detecting, by the controller, an emergency state that prevents the pump from providing fluid flow to the steering unit; and responsive to detecting the emergency state, operating the solenoid valve in an unactuated state, causing the solenoid valve to allow fluid to be discharged from the accumulator to be provided to the steering unit to allow the vehicle to be steered to a safe position.

[00113] EEE 20 is the method of EEE 19, wherein the electrohydraulic steering system further comprises: a check valve disposed upstream from the solenoid valve, and a variable orifice disposed in parallel with the check valve, wherein the check valve allows fluid flow therethrough to the solenoid valve to allow the accumulator to be charged, wherein fluid discharged from the accumulator flows through the variable orifice to the steering unit, and wherein the method further comprises: adjusting a size of the variable orifice to change flow rate and pressure level of fluid provided from the accumulator to the steering unit.

Claims

CLAIMS What is claimed is:

1 . An electrohydraulic steering system comprising: an electrohydraulic power unit having an electric motor driving a pump; a steering unit having a directional control valve and a hydraulic cylinder that steers a vehicle, wherein during a normal steering operation mode, the pump provides fluid flow to the directional control valve, which controls fluid flow to and from the hydraulic cylinder to steer the vehicle; and an emergency steering unit having: an accumulator, and a solenoid valve that operates in: (i) a first state in which the solenoid valve allows fluid flow from the pump to the accumulator to charge the accumulator while preventing backflow from the accumulator, and (ii) a second state when a failure occurs that prevents the pump from providing fluid flow to the steering unit, wherein the solenoid valve allows fluid discharged from the accumulator to be provided to the steering unit to allow the vehicle to be steered to a safe position.

2. The electrohydraulic steering system of claim 1, further comprising: a check valve disposed at an outlet of the pump to prevent backflow to the pump when a failure occurs, thereby allowing fluid to be directed from the accumulator to the steering unit.

3. The electrohydraulic steering system of claim 2, wherein the check valve is a first check valve, and wherein the emergency steering unit further comprises: a second check valve disposed downstream from the first check valve and upstream from the solenoid valve; and an orifice disposed in parallel with the second check valve, wherein the second check valve allows fluid flow therethrough to the solenoid valve to allow the accumulator to be charged, and wherein fluid discharged from the accumulator flows through the orifice to the steering unit.

4. The electrohydraulic steering system of claim 1, wherein the solenoid valve is a first solenoid valve, and wherein the emergency steering unit further comprises: a second solenoid valve downstream of the electrohydraulic power unit and upstream of the steering unit, wherein the second solenoid valve operates in: (i) a first state in which the second solenoid valve allows fluid to flow to the steering unit, and (ii) a second state in which the second solenoid valve prevents fluid flow to the steering unit to direct fluid flow to the first solenoid valve to charge the accumulator.

5. The electrohydraulic steering system of claim 1, further comprising: a pump pressure sensor that provides pump sensor information indicative of pressure level at an outlet of the pump; an accumulator pressure sensor that provides accumulator sensor information indicative of pressure level of fluid of the accumulator; and a controller that determines whether to operate the solenoid valve in the first state or the second state based on the pump sensor information and the accumulator sensor information.

6. The electrohydraulic steering system of claim 1, wherein the emergency steering unit further comprises: a check valve disposed upstream from the solenoid valve; and an orifice disposed in parallel with the check valve, wherein the check valve allows fluid flow therethrough to the solenoid valve to allow the accumulator to be charged, and wherein fluid discharged from the accumulator flows through the orifice to the steering unit.

7. The electrohydraulic steering system of claim 6, wherein the orifice is a variable orifice.

8. The electrohydraulic steering system of claim 7, further comprising: a controller that adjusts a size of the variable orifice to change flow rate and pressure level of fluid provided from the accumulator to the steering unit.

9. An electrohydraulic steering system comprising: an electrohydraulic power unit having an electric motor driving a pump; a steering unit having a directional control valve and a hydraulic cylinder that steers a vehicle, wherein during a normal steering operation mode, the pump provides fluid flow to the directional control valve, which controls fluid flow to and from the hydraulic cylinder to steer the vehicle; and an assembly having: an accumulator having a housing and a cap mounted to an end of the housing, wherein the cap is formed as a manifold that has a valve cavity, and a plurality of ports to fluidly couple the electrohydraulic power unit and the steering unit to the assembly, and a solenoid valve disposed in the valve cavity of the manifold and operates in: (i) a first state in which the solenoid valve allows fluid flow from the pump to the accumulator to charge the accumulator while preventing backflow from the accumulator, and (ii) a second state when a failure occurs that prevents the pump from providing fluid flow to the steering unit, wherein the solenoid valve allows fluid discharged from the accumulator to be provided to the steering unit to allow the vehicle to be steered to a safe position.

10. The electrohydraulic steering system of claim 9, further comprising: a check valve disposed at an outlet of the pump to prevent backflow to the pump when a failure occurs, thereby allowing fluid to be directed from the accumulator to the steering unit.

11. The electrohydraulic steering system of claim 10, wherein the check valve is a first check valve, and wherein the electrohydraulic steering system further comprises: a second check valve disposed downstream from the first check valve and upstream from the solenoid valve; and an orifice disposed in parallel with the second check valve, wherein the second check valve allows fluid flow therethrough to the solenoid valve to allow the accumulator to be charged, and wherein fluid discharged from the accumulator flows through the orifice to the steering unit.

12. The electrohydraulic steering system of claim 11, wherein the second check valve and the orifice are disposed within the manifold.

13. The electrohydraulic steering system of claim 9, wherein the valve cavity is a first valve cavity, wherein the solenoid valve is a first solenoid valve, wherein the manifold has a second valve cavity, and wherein the assembly further comprises: a second solenoid valve disposed in the second valve cavity, wherein the second solenoid valve operates in: (i) a first state in which the second solenoid valve allows fluid to flow to the steering unit, and (ii) a second state in which the second solenoid valve prevents fluid flow to the steering unit to direct fluid flow to the first solenoid valve to charge the accumulator.

14. The electrohydraulic steering system of claim 9, further comprising: a pump pressure sensor that provides pump sensor information indicative of pressure level at an outlet of the pump; an accumulator pressure sensor that provides accumulator sensor information indicative of pressure level of fluid of the accumulator; and a controller that determines whether to operate the solenoid valve in the first state or the second state based on the pump sensor information and the accumulator sensor information.

15. The electrohydraulic steering system of claim 14, wherein the pump pressure sensor and/or the accumulator pressure sensor are disposed in the manifold.

16. The electrohydraulic steering system of claim 9, further comprising: a check valve disposed upstream from the solenoid valve; and an orifice disposed in parallel with the check valve, wherein the check valve allows fluid flow therethrough to the solenoid valve to allow the accumulator to be charged, and wherein fluid discharged from the accumulator flows through the orifice to the steering unit.

17. The electrohydraulic steering system of claim 16, wherein the orifice is a variable orifice, wherein the electrohydraulic steering system further comprises: a controller that adjusts a size of the variable orifice to change flow rate and pressure level of fluid provided from the accumulator to the steering unit.

18. The electrohydraulic steering system of claim 16, wherein the check valve and the orifice are disposed in the manifold.

19. A method comprising: actuating, by a controller, a solenoid valve of an electrohydraulic steering system having (i) an electrohydraulic power unit having an electric motor driving a pump, (ii) a steering unit that steers a vehicle, and (iii) an emergency steering unit having an accumulator, wherein actuating the solenoid valve allows fluid flow from the pump to the accumulator to charge the accumulator while preventing backflow from the accumulator; detecting, by the controller, an emergency state that prevents the pump from providing fluid flow to the steering unit; and responsive to detecting the emergency state, operating the solenoid valve in an unactuated state, causing the solenoid valve to allow fluid to be discharged from the accumulator to be provided to the steering unit to allow the vehicle to be steered to a safe position.

20. The method of claim 19, wherein the electrohydraulic steering system further comprises: a check valve disposed upstream from the solenoid valve, and a variable orifice disposed in parallel with the check valve, wherein the check valve allows fluid flow therethrough to the solenoid valve to allow the accumulator to be charged, wherein fluid discharged from the accumulator flows through the variable orifice to the steering unit, and wherein the method further comprises: adjusting a size of the variable orifice to change flow rate and pressure level of fluid provided from the accumulator to the steering unit.