Patent Publication Number: US-2022234650-A1

Title: Steering system of engineering vehicle and backhoe loader

Description:
CROSS-REFERENCE TO RELATED APPLICATIONS 
     This disclosure is based on and claims priority to Chinese Patent Application No. 202010845049.2, entitled “Steering System of Engineering Vehicle and Backhoe Loader”, filed on Aug. 20, 2020, which is hereby incorporated by reference in its entirety. 
     FIELD 
     The present disclosure relates to the field of engineering vehicle, in particular to a steering system of an engineering vehicle, and a backhoe loader. 
     BACKGROUND 
     A wheeled engineering vehicle has a heavy body and large tire size, and often runs on roads of the construction site where the use conditions are harsh, the steering resistance is large, and frequent steering is required. Thus, the purpose of light and convenient manipulation and rapid steering will be difficult to achieve if a mechanical steering system is used therefor. To reduce a driver&#39;s fatigue, most engineering vehicles use a hydraulic power steering system. A full hydraulic steering system, as a type of hydraulic power steering system, has the characteristics of light and convenient steering operations, stable work, and convenient layout of the whole vehicle, and is widely used in medium and low speed wheeled engineering vehicles. In recent years, it has been increasingly applied to backhoe loaders and other models. 
     During use of a backhoe loader equipped with a full hydraulic steering system, a driver needs to perform steering operations frequently. However, currently, a backhoe loader product has no automatic return function. Furthermore, due to a full hydraulic steering mode, a steering wheel of the backhoe loader cannot achieve the limit of end points of turning left and right, which makes it difficult for the driver to determine the direction and position of the backhoe loader. He can perceive whether the steering wheel has returned and what angle the steering wheel is at only by observing a traveling path of the vehicle during a steering operation, which is not conducive to reducing the driver&#39;s operation intensity. 
     SUMMARY 
     An object of the present disclosure is to provide a steering system of an engineering vehicle, and a backhoe loader, to improve light and convenient manipulation of the steering system. 
     A first aspect of the present disclosure provides a steering system of an engineering vehicle, including: 
     a direction control device including a steering wheel, a steering cylinder and steerable wheels, the steering cylinder being in transmission connection with the steering wheel and the steerable wheels; 
     a displacement sensor configured to detect a piston displacement of the steering cylinder; 
     a return motor in transmission connection with the steerable wheels to drive the steerable wheels to return; and 
     a controller in signal connection with the displacement sensor and the return motor, and configured to output a control signal according to the piston displacement detected by the displacement sensor to manipulate the return motor to drive the steerable wheels to return. 
     According to some embodiments of the present disclosure, the direction control device further includes: 
     a hydraulic pump; and 
     a full hydraulic steering device, with an oil inlet and an oil return port of the full hydraulic steering device being respectively connected with an oil outlet of the hydraulic pump and a hydraulic oil tank, and two steering oil ports of the full hydraulic steering device being respectively connected with two working oil ports of the steering cylinder. 
     According to some embodiments of the present disclosure, the full hydraulic steering device is a load-sensitive full hydraulic steering device, and the direction control device further includes a priority valve arranged between the hydraulic pump and full hydraulic steering device. 
     According to some embodiments of the present disclosure, the direction control device further includes: 
     a steering shaft, the steering shaft being fixedly connected to the steering wheel, the steering shaft being in transmission connection with the full hydraulic steering device, and the return motor being in transmission connection with the steering shaft; and 
     a steering tube arranged rotatably with respect to the steering shaft. 
     According to some embodiments of the present disclosure, the steering system further includes a return transmission mechanism, the return transmission mechanism including: 
     a first gear fixedly connected with the steering shaft; and 
     a second gear in transmission connection with the return motor and the first gear. 
     According to some embodiments of the present disclosure, the direction control device further includes link mechanisms arranged between the steering cylinder and the steerable wheels. 
     According to some embodiments of the present disclosure, the displacement sensor is provided on the steering cylinder. 
     According to some embodiments of the present disclosure, the steering system further includes a display device in signal connection with the controller, the display device being configured to display the piston displacement of the steering cylinder and/or display a rotation angle of the steerable wheels calculated according to the piston displacement of the steering cylinder. 
     According to some embodiments of the present disclosure, the steering system further includes a holder fixedly connected to the steering tube, the return motor and the controller being mounted to the holder. 
     According to some embodiments of the present disclosure, the controller is configured to, when an absolute value of the piston displacement of the steering cylinder gradually decreases, manipulate the return motor to be energized until a piston of the steering cylinder moves to a middle position of the steering cylinder and the steerable wheels return. 
     According to some embodiments of the present disclosure, the steering system further includes a control switch in signal connection with the controller, the control switch being configured to switch steering modes of the steering system. 
     According to some embodiments of the present disclosure, the controller is configured to, when the control switch is turned on, manipulate the return motor to be energized until a piston of the steering cylinder moves to the middle position and the steerable wheels return. 
     A second aspect of the present disclosure provides a backhoe loader including the steering system in the first aspect of the present disclosure. 
     In the steering system of an engineering vehicle and the a backhoe loader provided by the present disclosure, the controller outputs a control signal to the return motor according to the piston displacement of the steering cylinder detected by the displacement sensor to manipulate the return motor to drive the steerable wheels to automatically return, which is beneficial to improving light and convenient manipulation of the steering system. 
     Other features and advantages of the present disclosure will become apparent from the following detailed description of exemplary embodiments of the present disclosure with reference to the accompanying drawings. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Drawings illustrated herein are used for providing further understanding of the present disclosure and form part of the present application, and illustrative embodiments of the present disclosure and description thereof are intended for explaining instead of improperly limiting the present disclosure. In the drawings: 
         FIG. 1  is a structure diagram of a steering system of some embodiments of the present disclosure. 
     
    
    
     DETAILED DESCRIPTION OF THE EMBODIMENTS 
     Technical solutions in the embodiments will be described below clearly and completely in conjunction with the accompanying drawings in the embodiments of the present disclosure. Obviously, the described embodiments are only part of, instead of all of embodiments of the present disclosure. The following description of at least one exemplary embodiment is actually only illustrative, and in no way serves as any limitation to the present disclosure and its application or use. Based on the embodiments of the present disclosure, all of other embodiments obtained by a person of ordinary skill in the art without creative work should fall into the protection scope of the present disclosure. 
     Unless specifically stated otherwise, the relative arrangement of components and steps, numerical expressions and numerical values set forth in these embodiments do not limit the scope of the present disclosure. Furthermore, it should be understood that, for ease of description, the sizes of various parts shown in the drawings are not drawn in accordance with actual proportional relationships. Technologies, methods, and devices known to those of ordinary skill in the related art may be not discussed in detail, but where appropriate, the technologies, methods, and device should be regarded as part of the specification as granted. In all examples shown and discussed here, any specific value should be interpreted as merely exemplary, rather than as a limitation. Therefore, other examples of an exemplary embodiment may have different values. It should be noted that similar reference numerals and letters denote similar items in the following drawings, so once a certain item is defined in one drawing, it does not need to be further discussed in subsequent drawings. 
     In the description of the present disclosure, it should be understood that the use of terms such as “first” and “second” to define parts and components is only for the convenience of distinguishing the corresponding parts and components. Unless otherwise stated, the above terms have no special meanings, and therefore cannot be understood as limitations on the protection scope of the present disclosure. 
     In description of the present disclosure, it should be understood that orientation or position relations denoted by terms such as “front”, “rear”, “upper”, “lower”, “left”, “right”, “transverse”, “longitudinal”, “vertical”, “horizontal”, “top” and “bottom” are generally orientation or position relations illustrated based on the drawings, and are merely for the convenience of describing the present disclosure and simplifying description, and unless stated to the contrary, such terms do not indicate or imply the denoted devices or elements must have specific orientations or be constructed and operated in specific orientations, and thus cannot be understood as limiting the protection scope of the present disclosure; and orientation terms “inner” and “outer” refer to the inside and outside with respect to the contour of each component itself. 
     As shown in  FIG. 1 , some embodiments of the present disclosure provide a steering system of an engineering vehicle, including a direction control device, a displacement sensor  14 , a return motor  9  and a controller  4 . 
     The direction control device includes a steering wheel  5 , a steering cylinder  12  and steerable wheels  16 , the steering cylinder  12  being in transmission connection with the steering wheel  5  and the steerable wheels  16 . The displacement sensor  14  is configured to detect a piston displacement of the steering cylinder  12 . The return motor  9  is in transmission connection with the steerable wheels  16  to drive the steerable wheels  16  to return. The controller  4  is in signal connection with the displacement sensor  14  and the return motor  9 , and the controller  4  is configured to output a control signal according to the piston displacement detected by the displacement sensor  14  to manipulate the return motor  9  to drive the steerable wheels  16  to return. 
     In the steering system of an engineering vehicle provided by the embodiments of the present disclosure, the controller outputs a control signal to the return motor according to the piston displacement of the steering cylinder detected by the displacement sensor to manipulate the return motor to drive the steerable wheels to automatically return, which is beneficial to improving light and convenient manipulation of the steering system, and there is no need to provide a sensing device such as a steerable wheel angle sensor or steering wheel torque sensor. 
     In some embodiments, the direction control device further includes a hydraulic pump  15  and a full hydraulic steering device  1 . An oil inlet and an oil return port of the full hydraulic steering device  1  are respectively connected with an oil outlet of the hydraulic pump  15  and a hydraulic oil tank  17 , and a first steering oil port A and a second steering oil port B of the full hydraulic steering device  1  are respectively connected with two working oil ports of the steering cylinder  12 . 
     In some embodiments, the full hydraulic steering device  1  is a load-sensitive full hydraulic steering device, and the direction control device further includes a priority valve  2  arranged between the hydraulic pump  15  and full hydraulic steering device  1 . The hydraulic pump  15  may supply oil to a steering circuit and working circuit of the engineering vehicle. The load-sensitive full hydraulic steering device and priority valve  2  may preferentially provide a flow output from the hydraulic pump  15  to the steering circuit according to requirement of the steering circuit to ensure the demand of performing a steering action without being influenced by a load pressure and a steering wheel speed, so that the steering action is smooth and reliable, and the remaining flow of the hydraulic pump  15  is provided to the working circuit. 
     As shown in  FIG. 1 , an oil inlet P2 of the priority valve  2  is connected to the oil outlet of the hydraulic pump; a first oil outlet CF of the priority valve  2  is connected to an oil inlet P1 of the load-sensitive full hydraulic steering device, and the flow output from the hydraulic pump  15  is preferentially provided to the steering circuit where the load-sensitive full hydraulic steering device is located, through the first oil outlet CF of priority valve  2 ; a second oil outlet EF of priority valve  2  is connected to the working circuit of the engineering vehicle; and a control oil port LS2 of the priority valve  2  is connected to a control oil port LS1 of the load-sensitive full hydraulic steering device. 
     In some embodiments, the direction control device further includes a steering shaft  6  and a steering tube  7 . The steering shaft  6  is fixedly connected to the steering wheel  5 , such as being fixedly connected to the steering wheel  5  through a spline structure provided on the steering wheel  5 . The steering shaft  6  is in transmission connection with the full hydraulic steering device  1 , such as being mounted to the full hydraulic steering device  1  through a spline structure provided on the steering shaft  6 . The return motor  9  is in transmission connection with the steerable wheels  6 . The steering tube  7  is arranged rotatably with respect to the steering shaft  6 . 
     In some embodiments, the steering system further includes a return transmission mechanism, which may be a gear transmission mechanism, and the return transmission mechanism includes a first gear  3  and a second gear  10 . The first gear  3  is fixedly connected to the steering shaft  6 . For example, the first gear  3  may be mounted to the steering shaft  6  in a flat key fit manner. The second gear  10  is in transmission connection with the return motor  9 , and the second gear  10  is in transmission connection with the first gear  3 . As shown in  FIG. 1 , the first gear  3  and the second gear  10  directly engaged. 
     In some embodiments, the direction control device further includes link mechanisms  13  arranged between the steering cylinder  12  and the steerable wheels  16 . As shown in  FIG. 1 , the steering cylinder  12  is a double-acting cylinder; both ends of the piston of the steering cylinder  12  are provided with piston rods; one ends of the two link mechanisms  13  arranged on two sides of the steering cylinder are connected to the two piston rods on both ends of a piston of the steering cylinder  12  by universal joints, and the other ends of the two link mechanisms  13  are connected to the steerable wheels  16 ; and the link mechanisms  13  and the piston rods of the steering cylinder  12  form a steering trapezoidal structure of the steering system. 
     In some embodiments, the displacement sensor  14  is provided on the steering cylinder  12 . For example, it may be arranged inside or outside the steering cylinder  12  as a built-in or external displacement sensor. 
     In some embodiments, the steering system further includes a display device  11  in signal connection with the controller  4 , the display device  11  being configured to display the piston displacement of the steering cylinder  12  and/or display a rotation angle of the steerable wheels  16  calculated according to the piston displacement of the steering cylinder  12 . The display device  11  may be a separate display, or it may also be integrated in a display panel of a cab of the engineering vehicle. The display device  11  is provided to facilitate a driver of the engineering vehicle observing a steering state of the steerable wheels  16  through data displayed by the display device  11  and then quickly determining whether the steerable wheels  16  have return. 
     In some embodiments, the steering system further includes a holder  8  fixedly connected to the steering tube  7 , the return motor  9  and the controller  4  being mounted to the holder  8 . 
     During traveling of the engineering vehicle, after performing a steering operation, the driver needs to operate the steering wheel  5  to cause the steerable wheels  16  to return. During traveling of the engineering vehicle, the steering system may determine an operation intention of the driver according to a change of the piston displacement of the steering cylinder  12  detected by the displacement sensor  14 . In the case where the driver is intended to cause the steerable wheels  16  to return, the steering system enables an automatic return function, thereby reducing the operation intensity of the driver and improving the manipulation comfort for the driver. 
     When an absolute value of the piston displacement of the steering cylinder  12  gradually increases or remains unchanged, it indicates that the driver is manipulating the steering wheel  5  to cause the steerable wheels  16  to turn, or the engineering vehicle is traveling in a straight line; and when the absolute value of the piston displacement of the steering cylinder  12  gradually decreases, it indicates that the driver has completed a steering operation and is operating the steering wheel  5  to cause the steerable wheels  16  to return. 
     To reduce the operation intensity of the driver and improve the manipulation comfort for the driver, in some embodiments, the controller  4  is configured to, when the absolute value of the piston displacement of the steering cylinder  12  gradually decreases, manipulate the return motor  9  to be energized until the piston of the steering cylinder  12  moves to the middle position and the steerable wheels  16  return. 
     A steering system of an engineering vehicle usually has multiple steering modes, such as two-wheel steering, four-wheel steering, and crab steering modes. When the engineering vehicle switches between the various steering modes, the piston of the steering cylinder  12  needs to return to the middle position such that the steerable wheels  16  return. 
     In some embodiments, the steering system further includes a control switch  18  in signal connection with the controller  4 , the control switch  18  being configured to switch steering modes of the steering system. 
     To quickly switch the steering modes of the steering system, in some embodiments, the controller  4  is configured to, when the control switch  18  is turned on, manipulate the return motor  9  to be energized until the piston of the steering cylinder  12  moves to the middle position and the steerable wheels  16  return. 
     According to the above configuration of the controller  4 , when the driver of the engineering vehicle operates the steering wheel  5  to cause the steerable wheels  16  to return or switches steering modes of the steering system, that is, when the absolute value of the piston displacement of the steering cylinder  12  gradually decreases or when the control switch for switching the steering modes of the steering system is turned on, the automatic return function of the steering system is enabled, and the controller  4  sends a control signal to the return motor  9  according to the piston displacement of the steering cylinder  12  detected by the displacement sensor  14 , and the return motor  9  is energized and works with a certain output speed and output torque to drive the steerable wheels  16  to return. 
     In some embodiments, the controller described above may be embodied as a general-purpose processor, a programmable logic controller (PLC), a digital signal processor (DSP), an application specific integrated circuit (ASIC), a field-programmable gate array (FPGA) or other programmable logic device, a discrete gate or transistor logic device, a discrete hardware component, or any appropriate combination thereof, for performing the functions described in the present disclosure. 
     The working principle of the steering system of an engineering vehicle according to some embodiments of the present disclosure will be further described below in conjunction with  FIG. 1 . 
     As shown in  FIG. 1 , the steering system of an engineering vehicle includes a direction control device, a displacement sensor  14 , a controller  4 , a holder  8 , a return transmission mechanism, a return motor  9 , a display device  11  and a control switch. 
     The direction control device includes a steering wheel  5 , a steering shaft  6 , a steering tube  7 , a hydraulic pump  15 , a priority valve  2 , a full hydraulic steering device  1 , a steering cylinder  12 , link mechanisms  13  and steerable wheels  16 . The steering wheel  5 , the steering shaft  6 , the full hydraulic steering device  1 , the steering cylinder  12 , the link mechanisms  13  and the steerable wheels  16  are successively in transmission connection to form a complete transmission chain. The hydraulic pump  15 , the priority valve  2 , the full hydraulic steering device  1  and the steering cylinder  12  are connected through a hydraulic pipeline via corresponding oil ports to form a steering circuit of the engineering vehicle. 
     The controller  4  is in signal connection with the displacement sensor  14 , the return motor  9 , the display device  11  and the control switch  18 . The displacement sensor  14  is provided on the steering cylinder  12  and may detect a piston displacement of the steering cylinder  12  in real time, and sends the detected piston displacement to the controller  4 . The control switch  18  is configured to switch steering modes of the steering system. The display device  11  is configured to display the piston displacement of the steering cylinder  12  and/or display a rotation angle of the steerable wheels  16  calculated according to the piston displacement of the steering cylinder  12 . 
     The return transmission mechanism includes a first gear  3  and a second gear  10  engaged with each other, the first gear  3  being mounted to the steering shaft  6 , and an output shaft of the return motor  9  being connected to the second gear  10 . 
     In the case where an automatic return function of the steering system is not enabled, the return motor  9  is in a power-off state, and the first gear  3 , the second gear  10  and the return motor  9  are in a follow-up state at this time. 
     When an absolute value of the piston displacement of the steering cylinder  12  gradually decreases or when the control switch for switching the steering modes of the steering system is turned on, the automatic return function of the steering system is enabled. The controller  4  sends a control signal to the return motor  9  according to the piston displacement detected by the displacement sensor  14 ; the return motor  9  provides a motive power required for the steerable wheels  16  to return, according to the control signal sent by the controller  4 , and successively drives the second gear  10 , the first gear  3  and the steering shaft  6 ; and the steering shaft  6  successively drives the full hydraulic steering device  1 , the steering cylinder  12 , the link mechanisms  13  and the steerable wheels  16 , and drives the steering wheel  5 , such that the steerable wheels  16  and the steering wheel  5  automatically return. 
     The piston displacement detected by the displacement sensor  14  is defined as follows: when the steerable wheels  16  are in a non-steering state, that is, when a piston of the steering cylinder  12  is in the middle position, the piston displacement detected by the displacement sensor  14  is 0; when the steerable wheels  16  are in a left steering state, the piston displacement detected by the displacement sensor  14  is a negative value; and when the steerable wheels  16  are in a right steering state, the piston displacement detected by the displacement sensor  14  is a positive value. 
     If the piston displacement detected by the displacement sensor  14  is a negative value, the controller  4  controls the return motor  9  to rotate clockwise at a constant speed to drive the second gear  10 , the first gear  3  and the steering shaft  6 , such that the steering wheel  5  rotates to the right and the piston displacement of the steering cylinder  12  gradually increases until the piston displacement becomes 0. 
     If the piston displacement detected by the displacement sensor  14  is a positive value, the controller  4  controls the return motor  9  to rotate counterclockwise at a constant speed to drive the second gear  10 , the first gear  3  and the steering shaft  6 , such that the steering wheel  5  rotates to the left and the piston displacement of the steering cylinder  12  gradually decreases until the piston displacement becomes 0. 
     If the piston displacement detected by the displacement sensor  14  is 0, indicating that the piston of the steering cylinder  12  is already in the middle position and the steerable wheels  16  have return, the controller  6  controls the return motor  9  to be de-energized, and the automatic return function of the steering system is disabled. 
     The steering system of an engineering vehicle of the embodiment of the present disclosure has at least one of the following advantages: 
     The steering system may, according to the driver&#39;s intention, enable the automatic return function when the driver operates the steering wheel to cause the steerable wheels to return or when he switches the steering modes of the steering system, which is beneficial to reducing the steering operation intensity of the driver. 
     When the automatic return function is disabled, the return motor and the return transmission mechanism are in a follow-up state, so that the steering resistance is not increased, which is beneficial to improving the light and convenient manipulation of the steering system, and to reducing the steering operation intensity of the driver. 
     The controller controls, according to the piston displacement of the steering cylinder, the return motor to drive the steering cylinder, which can achieve closed-loop control of the steering cylinder, so that the piston of the steering cylinder can be accurately positioned after the automatic return function is enabled, which is beneficial to reducing the deviation between an actual value of the piston position of the steering cylinder or the rotation angle of the vehicle wheels controlled by the steering wheel and an expected value thereof, caused by internal leakage of the steering cylinder. 
     The display device configured to display the piston displacement of the steering cylinder and/or the rotation angle of the steerable wheels calculated according to the piston displacement of the steering cylinder facilitates the driver quickly judging whether the steerable wheels has returned. 
     The steering system uses a piston displacement signal of the steering cylinder as a detection signal for the controller to manipulate the steerable wheels to automatically return, so there is no need to provide a sensing device such as a steerable wheel angle sensor or steering wheel torque sensor. 
     The steering system is compatible with a steering column structure commonly used in engineering vehicles, requires no additional installation space, and is suitable for installation in various engineering vehicles, which is conducive to popularization and application. 
     Some embodiments of the present disclosure further provide a backhoe loader including the aforementioned steering system. The backhoe loader provided by the embodiments of the present disclosure has the corresponding advantages of the aforementioned steering system. 
     Finally, it should be noted that the above embodiments are only used for describing rather than limiting the technical solutions of the present disclosure. Although the present disclosure is described in detail with reference to the preferred embodiments, those of ordinary skill in the art should understand that they still can make modifications to the specific implementations in the present disclosure or make equivalent substitutions to part of technical features thereof; and such modifications and equivalent substitutions should be encompassed within the technical solutions sought for protection in the present disclosure.