DESC:TECHNICAL FIELD
[0001] The present disclosure generally relates to stabilization of a vehicle while steering the vehicle, and particularly relates to managing steering effort based on speed of the vehicle while steering.
BACKGROUND
[0002] In situations like low speed cornering, vehicle parking, and driving in hilly areas and in tight spaces, driving of heavy duty vehicle such as heavy duty truck, is very difficult due to a larger wheelbase and track width of the heavy duty vehicle. Hence there is a requirement of a mechanism which results in less turning radius.
[0003] Further, all wheel steering system is employed in such heavy duty vehicles to achieve better maneuverability at low speeds, to reduce the turning circle radius of the vehicle, and to manage the steering effort of driver or operator of the heavy duty vehicles. Some attempts on design and development of all wheel steering 4x4 passenger car were made. Further, typically, to reduce Turning Circle Diameter (TCD) of any vehicle either the wheel base is reduced or the wheel cut angles are increased. However, by reducing turning circle diameter, turning clearance circle diameter (TCCD) will be more which is a more practical way to determine mobility of the vehicle in hilly terrain. Further, increasing wheel cut angles beyond certain level is impossible considering the structural limitations. Furthermore, reducing wheel base compromises over-hang of the vehicle that puts the payload carrying and distribution ability at risk.
[0004] Further, the current heavy duty vehicles include only one pair of axles steerable, which are the front axles. The axles at the rear are not steerable, the rear axles follow the motion of the front axles. The front axles are capable of steering as per the requirement of the driver but the rear axles are not manufactured to curb this drawback, the rear axles are manufactured to be rigid and can only be moved in a straight motion. The incapability of the rear axles to steer makes it difficult for the vehicle to take sharp turns.
[0005] Hence there is a requirement of a solution that overcomes the above mentioned issues. More specifically, there lies a need for an all-wheel steering for an 8x8 heavy duty truck, for example, a 32t weight class & 11m length was never attempted.

SUMMARY
[0006] This summary is provided to introduce a selection of concepts in a simplified format that are further described in the detailed description of the present disclosure. This summary is not intended to identify key or essential inventive concepts of the claimed subject matter, nor is it intended for determining the scope of the claimed subject matter. In accordance with the purposes of the disclosure, the present disclosure as embodied and broadly described herein, describes method and system for controlling steering of rear wheels in a vehicle.
[0007] In accordance with some example embodiments of the inventive concepts, a method for controlling steering of rear wheels in a vehicle is disclosed. The method includes facilitating by an ECU controlled valve, flow of oil to rear steering circuit for regulating the steering effort at a steering wheel while steering. The method further includes receiving at the ECU, speed of the vehicle from a speedometer of the vehicle connected to the ECU. The method also includes the ECU to compare the speed of the vehicle with a pre-determined threshold speed range and limiting the flow of oil to a predetermined value by the ECU controlled valve when the speed of the vehicle is observed greater than the pre-determined threshold speed. Also, the method further includes regulating the flow of oil when the speed of the vehicle is restored below the pre-determined threshold speed.
[0008] In accordance with some example embodiments of the inventive concepts, a system for controlling steering of rear wheels of a vehicle is disclosed. The system includes two pair of steerable axles attached to front and rear of the vehicles. The system further includes a shaft constituted by a number of sub-shafts attached to one another through a number of joints. Furthermore, a first end of the shaft is attached to the first or front steering gearbox and a second end of the shaft of is attached to the second or rear steering gearbox. The first gearbox connects with a first cylinder to steer front pair of axles and the second gearbox connects with a second cylinder to steer rear pair of axles. Further, the system also includes a flow control valve (FCV) electronically controlled by an ECU for controlling the flow of oil to rear steering circuit by limiting and regulating the flow of oil by the ECU based on a vehicle speed to increase / decrease the steering effort needed at steering wheel.
[0009] These aspects and advantages will be more clearly understood from the following detailed description taken in conjunction with the accompanying drawings and claims.
BRIEF DESCRIPTION OF THE DRAWINGS
[0010] FIG. 1a illustrates a system for controlling steering of rear wheels in a vehicle, in accordance with an embodiment of the present invention;
[0011] FIG. 1b illustrates a circuit architecture of the system for controlling the steering of the vehicle;
[0012] FIG. 2 illustrates a schematic block diagram of an ECU for controlling the steering of the rear wheels of the vehicle;
[0013] FIG. 3a illustrates a permanent mechanical connection in accordance with the embodiment of the present invention;
[0014] FIG. 3b illustrates the gear box as shown in the FIG. 3a;
[0015] FIG. 3c and Fig. 3d illustrate a T-L Mitre Box and a Z- Mitre Box used in the system of the present invention; and
[0016] FIG. 3e illustrates a front and a rear steering cylinder as shown in the Fig. 3a;
[0017] FIG. 4 illustrates flow diagram of a method for controlling the steering of the rear wheels of the vehicle, in accordance with some example embodiments of the inventive concepts;
[0018] Fig.5 illustrates a system depicting the engagement of the ECU with a flow controlled valve (FCV) for controlling the flow of oil to rear circuit of the vehicle;
[0019] Fig. 6 illustrates an example reference for a relation between speed of the vehicle and flow of oil in accordance with some example embodiments of the inventive concepts; and
[0020] Fig. 7 illustrates a system implemented in the vehicle according to one or more embodiments of the present invention.
[0021] Further, skilled artisans will appreciate that elements in the drawings are illustrated for simplicity and may not have been necessarily been drawn to scale. For example, the flow charts illustrate the method in terms of the most prominent steps involved to help to improve understanding of aspects of the present invention. Furthermore, in terms of the construction of the device, one or more components of the device may have been represented in the drawings by conventional symbols, and the drawings may show only those specific details that are pertinent to understanding the embodiments of the present invention so as not to obscure the drawings with details that will be readily apparent to those of ordinary skill in the art having benefit of the description herein.

DETAILED DESCRIPTION
[0022] For the purpose of promoting an understanding of the principles of the invention, reference will now be made to the embodiment illustrated in the drawings and specific language will be used to describe the same. It will nevertheless be understood that no limitation of the scope of the invention is thereby intended, such alterations and further modifications in the illustrated system, and such further applications of the principles of the invention as illustrated therein being contemplated as would normally occur to one skilled in the art to which the invention relates.
[0023] It will be understood by those skilled in the art that the foregoing general description and the following detailed description are explanatory of the invention and are not intended to be restrictive thereof.
[0024] Reference throughout this specification to “an aspect”, “another aspect” or similar language means that a particular feature, structure, or characteristic described in connection with the embodiment is included in at least one embodiment of the present invention. Thus, appearances of the phrase “in an embodiment”, “in another embodiment” and similar language throughout this specification may, but do not necessarily, all refer to the same embodiment.
[0025] The terms "comprises", "comprising", or any other variations thereof, are intended to cover a non-exclusive inclusion, such that a process or method that comprises a list of steps does not include only those steps but may include other steps not expressly listed or inherent to such process or method. Similarly, one or more devices or sub-systems or elements or structures or components proceeded by "comprises... a" does not, without more constraints, preclude the existence of other devices or other sub-systems or other elements or other structures or other components or additional devices or additional sub-systems or additional elements or additional structures or additional components.
[0026] Unless otherwise defined, all technical and scientific terms used herein have the same meaning as commonly understood by one of ordinary skilled in the art to which this invention belongs. The system, methods, and examples provided herein are illustrative only and not intended to be limiting.
[0027] For the sake of clarity, the first digit of a reference numeral of each component of the present disclosure is indicative of the Figure number, in which the corresponding component is shown. For example, reference numerals starting with digit “1” are shown at least in Figure 1. Similarly, reference numerals starting with digit “2” are shown at least in Figure 2, and so on and so forth.
[0028] Embodiments of the present subject matter are described below in detail with reference to the accompanying drawings.
[0029] While specific language has been used to describe the present disclosure, any limitations arising on account thereto, are not intended. As would be apparent to a person in the art, various working modifications may be made to the method in order to implement the inventive concepts as taught herein. The drawings and the foregoing description give examples of embodiments. Those skilled in the art will appreciate that the described elements may well be combined into a single functional element. Alternatively, certain elements may be split into multiple functional elements. Elements from one embodiment may be added to another embodiment. Clearly, the present disclosure may be otherwise variously embodied, and practiced within the scope of the following claims.
[0030] Fig. 1a illustrates a system 100a of the present invention. The system 100a includes controlling simultaneous steering of front and rear wheels in a vehicle 102. In an example embodiment, the vehicle 102 is a heavy duty truck such as an 8x8 vehicle, or the like. The vehicle 102 includes two pairs of steerable axles 104, a shaft 106 and an ECU 108. The two pairs of steerable axles 104 are attached at front and rear of the vehicle 102 for providing the vehicle 102 with a stable steer-ability while in motion.
[0031] The system 100a further includes a pair of steering gear boxes 112 attached to one another through the shaft 106. The shaft 106 is present to provide a linkage between front and rear of the vehicle 102. The shaft 106 includes a first end 106-1 and a second end 106-2. The first end 106-1 is attached to a front steering gearbox 112-1 at front of the vehicle 102 and the second end 106-2 is attached to a rear steering gearbox 112-2 at rear of the vehicle 102. The shaft 106 constitutes of a number of sub-shafts 110 attached to one another. In an example embodiment, the shaft 106 includes at least two sub-shafts 110. In another embodiment, the shaft 106 may constitute of more than two sub-shafts based on the size of the vehicle 102.
[0032] The system 100a further includes a pair of mitre boxes 114 to attach the steering gear boxes 112 to the shaft 106 from the first end 106-1 and the second end 106-2. A first mitre box 114-1 attaches the front steering gear box 112-1 to the first end 106-1 and a second mitre box 114-2 attaches the rear steering gear box 112-2 to the second end 106-2. The steering gear boxes 112 are further attached to the steerable axles 104-1 and 104-2 through mechanical linkages and a pair of steering cylinders 116.
[0033] Each of the steering gear boxes 112 powers the steering cylinders 116. A first steering cylinder 116-1 attached to the front steering gear box 112-1 together steers the front pair of axles 104-1 through the mechanical linkages utilizing fluid power aid. Fluid through a flow controlled valve (FCV) 118 to a steering second cylinder 116-2 attached to the rear steering gear box 112-2 together steers the rear pair of axles 104-2 through mechanical linkages and the fluid power aid.
[0034] The ECU 108 is present to control the steer-ability of the rear wheels by monitoring speed of the vehicle 102. The ECU 108 monitors the speed of the vehicle 102 and manages the flow of fluid through the FCV 118 to rear steering circuit based on the speed of the vehicle 102. The ECU controls operation of the FCV 118 to manage flow of the fluid to the rear steering circuit.
[0035] Fig. 1b illustrates a circuit architecture 100b of the system elements pertaining to working of the system 100a. The circuitry architecture 100a includes an oil reservoir 120 with a filter 122. The oil reservoir 120 is present to provide oil to the front steering gearbox 112-1 and the rear steering gear box 112-2. The oil reservoir 120 is connected to a tandem gear pump 124. The tandem gear pump 124 is present to pump the oil to the front steering gearbox 112-1 and the rear steering gearbox 112-2 from the oil reservoir 120.
[0036] In an implementation, a tandem Steering pump is installed on the power-source, for example, an engine, of the vehicle used to power a front and the rear steering circuit. The flow to the rear steering circuit through the FCV 118 is controlled by the ECU 108. A flow path to the front steering circuit is however separate.
[0037] Each of the pair of the steering gearboxes 112 includes a pressure relief valve 126, an input shaft 128, an integrated pilot valve 130 and an output shaft 132. The pressure relief valve 126 in each of the steering gearboxes 112 is present to control the pressure in the steering gearboxes 112 for preventing an over process of the steering gearboxes 112 and a subsequent failure in the steering gearboxes 112. In an example embodiment, the input shafts 128 of the steering gearboxes 112 are in connection to the steering wheel inside a cabin of the vehicle 102 and transmits a steering wheel input by an operator to the steering gearbox 112 through the shaft 106. When the power reaches inside of the steering gearboxes 112, each gear receives the power and the output shafts 132 transmit the power from the steering gearboxes 112 to the wheels of the vehicle 102. The power reaches the wheels of the vehicle 102 through the mechanical linkage present on the steerable axles 104 and with power assistance from the fluid flow from the steering gearboxes 112 to the steering cylinders 116.
[0038] In the present invention, an input shaft 128-2 of the rear steering gearbox 112-2 receives the power from the steering wheel inside the cabin through the mitre boxes 114 and the shaft 106. A second output shaft 132-2 attached to the rear steering gearbox 112-2 transmits the power to the rear wheels of the vehicle 102 through the mechanical linkage present on the rear steerable axles 104-2 and with power assistance from the oil flow from the steering gearbox 112-2 to the steering cylinder 116-2.
[0039] A rear hydraulic subsystem 134 is managed by the ECU 108, sensing the speed of the vehicle and comparing the speed with a pre-determined speed range and regulating the flow to the rear circuit 134 through the FCV 118.
[0040] Fig. 2 illustrates a schematic block diagram of the ECU 108 for controlling oil flow to steering of the rear wheels of the vehicle 102. In an example embodiment, the ECU 108 may be a single processing unit or a number of units, all of which could include multiple computing units.
[0041] Typically, the ECU 108 includes a processor 202 coupled to a memory 204, data 206, a receiver 208. The processor 202, the memory 204, the data 206 and the receiver 208 may be communicatively coupled to one another. The data 206 may serve, amongst other things, as a repository for storing data processed, received, and/or generated by the ECU 108. The data 206 may be received from the speedometer of the vehicle 102. Among other capabilities, the ECU 108 may be configured to fetch and/or execute computer-readable instructions and/or data (e.g., the Service data) stored in the memory 204.
[0042] The ECU 108 is capable of controlling flow of oil to the second steering cylinder 116-2 to manage the power assistance in steering of the rear wheels of the vehicle 102 by controlling the FCV 118. The oil is stored in a reservoir 210 present in the vehicle 102. The ECU 108 limits and regulates the flow of oil by the FCV 118. The regulation of the oil flow is based on the speed of the vehicle 102 detected by the speedometer and received by the ECU 108.
[0043] In an example embodiment, the ECU 108 is capable of communicating with the speedometer of the vehicle 102 through the receiver 208 by hard wire or CAN communication. The receiver 208 receives speed of the vehicle 102 from the speedometer. The speed of the vehicle 102 is stored in the memory 204. The processor 202 coupled to the memory 204 runs a comparison program to process the speed of the vehicle 102. The processor 202 compares the speed of the vehicle 102 with a pre-determined threshold speed range. The pre-determined threshold speed is stored in the memory 204 along with the speed of the vehicle 102.
[0044] When the speed of the vehicle 102 is above the pre-determined threshold speed, the ECU 108 limits the flow of the oil towards the second steerable axles 104-2 by regulating the FCV 118.
[0045] In an example embodiment, the pre-determined threshold speed of the vehicle 102 may be based on the size of the vehicle 102 for allowing a balance and stable steer of the vehicle 102, when steering at sharp turns. In another embodiment, the pre-determined threshold speed of the vehicle 102 may be based upon maximum speed of the vehicle 102.
[0046] The memory 204 may include the data 206. The data 206 may be the data processed, received, and/or generated by the ECU 108.
[0047] Fig. 3a illustrates a system 300 for a permanent mechanical connection between the first steerable axles 104-1 and the second steerable axles 104-2 and the steering wheel inside the cabin in accordance with the embodiment of the present invention. In an example embodiment, the mechanical connection between the pair of steerable axles 104 is present to steer the second steerable axles 104-2 based on an input through the steering wheel in the cabin by an operator. The shaft 106 in the system 300 is present to provide a linkage between the front & rear steerable axles 104-1 and 104-2.
[0048] The shaft 106 constitutes of a number of sub-shafts 110 attached to one another. In an example embodiment, the shaft 106 includes three sub-shafts 110. The sub-shafts 110 are attached to one another through a number of joints 302. In an example embodiment, each of the joints 302 may be an universal joint (UJ), a double universal joint (DUJ) or the like. The steer-ability of the shaft 106 provides stable steering of the vehicle 102 by allowing the second steerable axles 104-2 to steer along the first steerable axles 104-1 and the shaft 106. The pair of steering gear boxes 112 is attached to the shaft 106 at the first end 106-1 and the second end 106-2 through the pair of mitre boxes 114. The steering gear boxes 112 are further attached to the steerable axles 104-1 and 104-2 through the mechanical linkages & the steerable cylinders 116.
[0049] Fig. 3b illustrates the steering gear box 112 as shown in the Fig. 3a. The pair of steering gear boxes 112 is attached to the shaft 106 at the first end 106-1 and the second end 106-2.
[0050] Fig. 3c and Fig.3d illustrate different embodiments of the mitre box 114 of the system 300. In an example embodiment, the system 300 may include any of the mitre box 114 such as a T-L mitre box or a Z mitre box as shown in fig. 3c and 3d. In an example embodiment, the mitre box 114 functions as a connector for attaching the shaft 106 and the steering gearbox 112 with one another. The steering gearbox 112 attaches to one end of the mitre box 114 and the shaft 106 is attached to another end of the mitre box 114.
[0051] Fig. 3e illustrates the one of the pair of steering cylinders 116 of the system 300 of the present invention. In an example embodiment, the steering cylinders 116 are present to assist the steering of the steerable-axles 104 by the flow of oil from steering gear boxes 112. The cylinder 116-1 is connected to the front steering gearbox 112-1 and the second cylinder 116-2 is attached to the rear steering gearbox 112-2.
[0052] Fig. 4 illustrates a flow diagram for a method 400 for controlling flow of oil to rear wheels steering circuit of a vehicle, in accordance with the embodiment of the present invention. The method 400 may be implemented by the system 200 using components thereof and/or the processor 208 in the vehicle 102, as described above. In an embodiment, the method 400 may be executed by the ECU 108. Further, for the sake of brevity, details of the present disclosure that are explained in details in the description of Fig. 1 to Fig. 3a-3e are not explained in detail in the description of Fig. 4.
[0053] At block 402, the method 400 includes facilitating flow of oil to a rear steering circuit by an ECU through a flow controlled valve (FCV). The flow of oil is controlled in order to control the power assistance to steer the rear steerable-axles such as the rear-steerable axles 104-2 for efficient stability and balance of the vehicle 102.
[0054] At block 404, the method 400 includes receiving speed of the vehicle from a speedometer at the ECU 108. The speedometer is connected to the vehicle and senses the speed of the vehicle before transmitting the speed to the ECU 108.
[0055] At block 406, the method 400 includes comparing the speed received from the speedometer at the ECU with a pre-determined threshold speed range. The pre-determined threshold speed range of the vehicle is stored in a memory.
[0056] At block 408, the method 400 includes limiting the flow of oil by the FCV, when the speed of the vehicle is above the pre-determined threshold speed of the vehicle. The pre-determined threshold speed of the vehicle is based on the required balance and stability while steering the vehicle.
[0057] At block 410, the method 400 includes regulating the flow of oil when the speed of the vehicle is below the pre-determined threshold speed of the vehicle. By regulating the flow of oil towards the rear steerable axles 104-2, the power assistance to steer the rear steerable axles 104-2 is increased or decreased depending upon the vehicle speeds.
[0058] Fig. 5 illustrates a system 500 including the ECU 108 and the FCV 118 connected with one another to manage the flow of oil towards the rear steerable axles 104-2. In an example embodiment, the FCV 118 may be a solenoid operated valve. The FCV is electromechanically coupled to the ECU 108 and limits and regulates the flow of oil based on commands received from the ECU 108.
[0059] When the speed received by the ECU 108 is detected to be above the pre-determined threshold speed, the ECU 108 commands the FCV 118 to limit the oil flow towards the rear steerable axles 104-2.
[0060] The flow of oil is reduced to curb the power assistance for steering the rear steerable axles 104-2 and thereby increasing the manual steering effort needed at the steering wheel for allowing better stability and balance while steering the vehicle 102 at higher speeds. The flow of oil is increased to provide full power assistance for steering the rear steerable axles 104-2 and thereby reducing the manual steering effort needed at the steering wheel for allowing better steering of the vehicle 102 at lower speeds.
[0061] Overall, the ECU senses the speed of the vehicle & control the flow of oil to rear steering circuit based on the vehicle speed. Oil flow less to the rear circuit may be defined by less oil flow to the power steering gearbox which translates to the higher manual effort at the steering wheel inside the cabin. As a result, the same at least leads to vehicle stability & safety during high speed manoeuvring. For example, steering wheels feels hard at higher speed restricting the lateral or sidewise movement. At low-speed, the steering-wheel is soft & ensures the lowest-possible turning circle diameter (TCD).
[0062] Fig. 6 illustrates an example dataset 600 including a number of vehicle speeds and corresponding amount of oil flow (in percentages) towards the second steerable axles 104-2. As depicted in the dataset 600, when the speed of the vehicle is low, the amount of oil flowing towards the second steerable axles 104-2 is high. The amount of oil flowing decreases gradually when the speed of the vehicle increases and when the speed of the vehicle is at above the highest limit depicted in the dataset 600, the flow of oil is shown to be minimum.
[0063] Fig. 7 illustrates a system 700 implemented in the vehicle 102, according to one or more embodiments of the present invention. The system 700 includes the steering state of the vehicle 102 by the broken lines and the non-steering state of the vehicle 102 by solid lines. In the steering state of the vehicle 102, a number of mechanical linkages or tie-rods L1, L2, L3 and L4 are shown in an extended configuration and are capable of allowing the vehicle 102 to steer. In the extended configurations of the mechanical linkages or the tie-rods L1, L2, L3 and L4, the second steerable axles 104-2 steers along the first steerable axles 104-1 providing the required balance and stability to the vehicle 102 while steering.
,CLAIMS:1. A method to control steering of rear wheels in a vehicle, the method comprising:
connecting a steering wheel, a front and a rear steering mechanism through a mechanical connection;
regulating, by an ECU controlled flow control valve (FCV), the flow of oil to rear steering mechanism;
receiving, at an ECU, speed of the vehicle from a speedometer of the vehicle connected to the ECU;
comparing, by the ECU, the speed of the vehicle with a pre-determined threshold speed range;
limiting the flow of oil by said ECU controlled FCV to the rear steering mechanism, when the speed of vehicle is observed greater than the pre-determined threshold speed; and
regulating the flow of oil to the rear steering mechanism when the speed of vehicle is restored below the pre-determined threshold speed.
2. The method according to claim 1, wherein said connecting comprises establishing a permanent mechanical connection between the steering wheel, the front & the rear steering mechanism to aid the steering of rear wheels even in case of hydraulic failure.
3. The method according to claim 1, wherein the flow of oil is managed through a flow control valve (FCV) controlled by the ECU.
4. The method according to claim 1, wherein the ECU limits the FCV to limit the flow of oil to a predetermined value when the speed of the vehicle is greater than the pre-determined threshold speed.
5. The method according to claim 3, wherein the flow of oil is at highest capacity when the speed of the vehicle is lower.
6. The method according to claim 1, wherein the vehicle is an 8x8 heavy duty truck.
7. A system to control steering of rear wheels of a vehicle, the system comprising:
at-least two pair of steerable axles attached to a front and a rear of the vehicles;
a shaft constituted by a plurality of sub-shafts attached to one another through a plurality of joints,;
a pair of steering gearboxes comprising a first and second steering gearbox, wherein a first gearbox is attached to the first end of the shaft through a first mitre box and the second gearbox is attached to the second end of the shaft through a second mitre box, wherein a first end of the shaft is attached to the first steering gearbox and a second end of the shaft is attached to the second steering gearbox, said pair of steering gear boxes comprising:
a first cylinder connected to the first gearbox to disperse oil;
a second cylinder connected to the second gearbox to disperse oil;
a tandem pump mounted to the power source to supply oil to front & rear steering circuit comprising the first and second gearboxes, respectively;
a flow control valve (FCV) electronically controlled by an ECU for controlling the flow of oil to the second gearbox which in turn to second cylinder, wherein said controlling by the FCV comprises limiting and regulating the flow of oil by the ECU to the second gearbox based on a vehicle speed to thereby increase or decrease the steering effort needed at the steering wheel.
8. The system according to claim 7, wherein the ECU receives speed of the vehicle from a speedometer of the vehicle connected to the ECU and compares the speed with a pre-determined threshold speed range.
9. The system according to claim 7, wherein the ECU limits the FCV when the speed of the vehicle is greater than the pre-determined threshold speed.
10. The system according to claim 9, wherein the flow of oil is at highest capacity when the speed of the vehicle is lower.
11. The system according to claim 7, wherein the vehicle is an 8x8 heavy duty truck.