Patent Publication Number: US-2010125394-A1

Title: Vehicle With A Loader

Description:
FIELD OF THE INVENTION 
     The invention herein relates to a vehicle with a loader device, such as a tractor with a front end loader, wherein the loader comprises a loader boom, and furthermore has a hydraulic system for raising and lowering the loader boom, a hydraulic suspension system for cushioning the loader boom, and a control unit for controlling the suspension system. 
     BACKGROUND OF THE INVENTION 
     Suspension systems for loaders on vehicles, in particular for front-end loaders on agricultural tractors, are known and are provided by many manufacturers as a feature which enhances the comfort of the operator and increases productivity. Suspension systems of this type are generally of a hydraulic design and are based upon an interaction between one or more hydraulic accumulators and the hydraulic cylinders actuating the loader. The suspension systems are further designed in such a manner that they can be switched on and off via a switching valve, wherein switching on and off generally takes place manually and is carried out individually by the vehicle operator depending on the application requirements. For this purpose, for example, the vehicle cab can be provided with an activating switch which is used to control a corresponding switching valve which, in turn, blocks or releases the hydraulic accumulator(s), the switching valves are customarily designed as electromagnetic switching valves. However, it is frequently disadvantageous, particularly during operation when stationary, that the suspension system is activated, since the response behavior of the loader is falsified when the suspension system is activated. The vehicle driver either has to accept these disadvantages or has to remember to deactivate or switch off the suspension system before carrying out the corresponding operations. 
     SUMMARY OF THE INVENTION 
     It is therefore an object of the invention providing a vehicle and loader of the type mentioned at the beginning, by means of which the aforementioned problems are overcome. 
     According to the invention, a vehicle and loader of the type mentioned at the beginning has a control unit which is designed in such a manner that the suspension system of the loader can be controlled as a function of a control variable representing a vehicle speed. It is thus possible, for example, for the suspension system to be activated or deactivated automatically when the vehicle is stationary or when a predetermined threshold value for a vehicle speed is reached, without the vehicle driver having to operate a switch to control the suspension system. In this case, the variable representing the vehicle speed can be generated, for example, by a speed or rotational speed sensor and passed to the control unit. The variable representing the vehicle speed can further be derived from any variable physically connected to vehicle speed and passed on to the control unit. It is also possible to provide an electronic bus system, for example a CAN BUS system, which automatically delivers the required vehicle speed control variables to the control unit. The control unit then generates a corresponding control signal which is used for controlling a switching valve activating (or deactivating) the suspension system. 
     In a preferred embodiment of the invention, the control unit is designed in such a manner that the suspension system is switched on when a threshold value, which can be predetermined for the control unit, for the vehicle speed is exceeded. In this case, when a control variable representing the threshold value for the driving speed is reached, the control unit generates a control signal which switches on the suspension system or which controls the control valve activating the suspension system such that the suspension system for the loader is activated. 
     In another embodiment of the invention, the control unit is designed in such a manner that the suspension system is switched off when a threshold value, which can be predetermined for the control unit, for the vehicle speed is fallen short of. In this case, when a control variable representing the threshold value for the driving speed is reached, the control unit generates a control signal that either switches off the suspension system or controls the control valve activating the suspension system such that the suspension system for the loader is deactivated. 
     An input device is preferably provided on the vehicle, with which the threshold value for the vehicle speed can be predetermined for the control unit. Via the input device, the vehicle driver can input or set the threshold speed value at which the control unit is to trigger or generate the corresponding control signal in order to control the suspension system. 
     Preferably, by way of the input device, an operating mode for activating or deactivating the suspension system can be selected such that manual control of the suspension system is permitted via an activating switch for the suspension system. 
     In another embodiment of the invention, the suspension system comprises electronically controllable damping means by which damping of the suspension system can be varied, and the damping means can be controlled as a function of the control variable representing the vehicle speed. The damping means can be designed as an electronically adjustable throttle valve by which the cushioning rate or damping rate of the suspension system can be varied by, for example, the cross section of the line leading to a hydraulic accumulator of the suspension system being reduced or increased. 
     Preferably, one or more regulating values for the damping means can be input by the input device, said regulating values being used by the control unit as a function of the control variable representing the vehicle speed in order to control the damping means. Thus, different predetermined damping rates can also be adjusted as a function of the vehicle speed or controlled by the control unit such that, for example, the damping rate of the suspension system is increased as vehicle speeds increase. Depending on the application, however, the damping may also be reduced as vehicle speeds increase. In this case, the regulating values for the damping rates may preferably be input into the input device in the form of individual regulating values or else in the form of a damping curve as a function of the vehicle speed such that the damping can also be continuously and infinitely variably matched to the vehicle speed. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       The invention is described and explained in more detail below with reference to the accompanying drawings wherein: 
         FIG. 1  is a schematic side view of a vehicle according to the invention in the form of a tractor with a loader; and, 
         FIG. 2  is a schematic circuit diagram of a hydraulic suspension system for the loader device of  FIG. 1 . 
     
    
    
     DESCRIPTION OF THE PREFERRED EMBODIMENT 
       FIG. 1  shows a vehicle  10  in the form of an agricultural tractor which is equipped with a loader  12 . The loader  12  is designed as a front-end loader. The vehicle  10  has a vehicle frame  14  to which a bracket  16  for the attachment of the loader  12  is fastened. Further, the vehicle  10  comprises a vehicle cab  17 . 
     The loader  12  comprises a mast  18  with which the loader is connected to the bracket  16 . Further, the loader  12  comprises a loader boom  20  which is equipped with an implement  22  in the form of a loading bucket  24 . The implement  22  is designed as a loading bucket  24  here only by way of example. Other implements  22 , for example a loading fork or a gripper, may, also be used. 
     A respective hydraulic cylinder  26  extends on both sides between the loader boom  20  and mast  18 , the hydraulic cylinder being actuatable by means of a hydraulic system  28  in order to raise and lower the loader boom  20 . 
     The hydraulic system  28  for raising and lowering the loader boom  20  is illustrated in  FIG. 2  with reference to a schematic hydraulic circuit diagram. 
     The hydraulic system  28  comprises a hydraulic tank  30 , a hydraulic pump  32 , a main control valve  34 , one or more hydraulic cylinders  26 , a switching valve  36  and a hydraulic accumulator  38 . A pressure-limiting device  40  is also provided. 
     The main control valve  34  is designed as a 4/3-way directional control valve with a central locking position and connects the hydraulic cylinder  26  to the hydraulic pump  32  and the hydraulic tank  30 , the hydraulic cylinder  26  being designed as a double-action hydraulic cylinder  26  with a chamber  42  on the lifting side (piston side) and a chamber  44  on the lowering side (rod side). It is also possible in this case for the hydraulic cylinder to be designed such that it acts on one side, and therefore the chamber on the lowering side is omitted. 
     In a first switching position, the raising position  46 , the raising function is triggered by the chamber  42  on the lifting side being connected to the hydraulic pump  32  and it being possible for the hydraulic oil to flow out of the chamber  44  on the lowering side into the hydraulic tank  30 . The loader boom  20  can be raised in the raising position  46 . 
     In a second switching position, the retaining position  48 , the retaining function is triggered by the chambers  42 ,  44  on the lifting side and lowering side being separated from the hydraulic pump  32  and hydraulic tank  30  wherein it is not possible for hydraulic oil to flow from the hydraulic pump  32  to the hydraulic cylinder  26  or from the hydraulic cylinder  26  to the hydraulic tank  30 . With the retaining position  48 , the loader boom  20  can be retained in a corresponding pivoted position. 
     In a third switching position, the lowering position  50 , lowering function is triggered by the chamber  42  on the lowering side being connected to the hydraulic pump  32  and it being possible for the hydraulic oil to flow out of the chamber  44  on the lifting side into the hydraulic tank  30 . The loader boom  20  can be lowered in the lowering position  50 . 
     The individual switching positions can be selected by the vehicle driver, for example, via a manual control lever  52  or joystick. 
     Further, the chamber  42  on the lifting side of the hydraulic cylinder  26  is connected to the switching valve  36  which is designed as an electronically controllable 2/2-way directional control valve. It has a pass-through position  54  and a closed position  56 . The switching valve  36  connects the chamber  42  on the lifting side to the hydraulic accumulator  38  via a line  58 , the chamber  42  on the lifting side being connected to the hydraulic accumulator  38  in the pass-through position  54  and being separated therefrom in the closed position  56 . By means of corresponding control or switching of the switching valve  36 , a hydraulic suspension system for the hydraulic cylinder  26  is therefore activated or deactivated by the chamber  42  on the lifting side being connected to the hydraulic accumulator  38  or being separated therefrom. In the activated state, i.e. in the pass-through position  54  of the switching valve  36 , hydraulic oil can flow under load out of the chamber  42  on the lifting side into the hydraulic accumulator  38  and can flow out therefrom back again into the chamber  42  on the lifting side such that a cushioning function for the hydraulic cylinder  26  or for the loader boom  20  is produced. 
     The hydraulic system  28  further comprises an electronic control unit  60 , an activating switch  62 , a speed sensor  64  and an input device  66 . 
     The electronic control unit  60  can be arranged both in the vehicle  10  and on the loader  12  itself. It can also be designed as part of an electronic control unit which is already present in any case on the vehicle  10 , or can be implemented there. 
     The speed sensor can be designed as any sensor representing the speed of the vehicle  10 , in particular as a rotation speed sensor which is arranged in the drive train or on the drive axles of the vehicle  10 . It is also conceivable to tap off a speed signal from a CAN BUS system which is present and pass said signal to the control unit  60 . 
     The electronic control unit  60  is connected to the activating switch  62  for activating the hydraulic suspension system, to a speed sensor  64  for detecting or recording the driving speed or for recording a variable representing the driving speed, and to the input device  66  for inputting regulating variables and threshold values and for selecting one or more operating modes. 
     The activating switch  62  and the input device  66  are preferably arranged in the vehicle cab  17  where they can be operated or actuated by a vehicle driver. 
     Actuation of the activating switch  62  can lead to the hydraulic suspension system of the hydraulic system being activated. The electronic control unit  60  then generates a corresponding control signal and switches the switching valve  36  into the pass-through position  54 . Further, one or more threshold values, upon the reaching of which a control signal for controlling the switching valve is to be generated, are preset or stored in the control unit  60 . When the hydraulic suspension system is activated and switched on (the switching valve  36  is in the pass-through position  54 ), the sensor signals or sensor signal variables supplied by the speed sensor  64  are compared with the threshold value stored in the control unit  60 . If the driving speed decreases and reaches the preset threshold value, the control unit  60  generates a corresponding control signal which switches the switching valve  36  into its closed position  56  and therefore deactivates or switches off the hydraulic suspension system. If the vehicle then accelerates again and the driving speed increases again, when the preset threshold value is reached a corresponding control signal is in turn generated by the electronic control unit  60  and the switching valve  36  is switched again into its pass-through position  54  and therefore the hydraulic suspension system is activated or switched on again. 
     The abovementioned threshold values can be selected freely here by the vehicle driver and input via the input device  66  and stored in the control unit  60 . Additionally, a corresponding operating mode can be selected in the input device  66 , said operating mode permitting the electronic control unit  60  to be operated without automatic control that is dependent on the driving speed. If this mode is activated, the suspension system can be activated or deactivated manually via the activating switch  62  irrespective of the driving speed or irrespective of a driving speed signal. 
     In an expanded exemplary embodiment, a throttle device in the form of a throttle valve  68  is provided. The throttle valve  68  is arranged in the line  58  between the switching valve  36  and the hydraulic accumulator  38  and is controlled via the electronic control unit  60  likewise in accordance with predetermined desired values or regulating variables. Depending on the control signal, which can be generated by the control unit  60  as a function of the driving speed, a pass-through cross section of the throttle valve  68  and therefore the damping of the hydraulic suspension system can be varied electronically as a function of the driving speed. 
     For example, the throttle cross section of the throttle valve  68  can be reduced as the driving speed increases, thus producing harder cushioning (greater damping of the suspension system). Similarly, the throttle cross section can also be increased automatically as the driving speed decreases, thus producing softer cushioning (lower damping of the suspension system). The regulating values or regulating variables required for this can be input by the vehicle driver in the input device  66  and stored. A damping function can be selected or deselected via the operating modes. Damping curves as a function of vehicle speed can also be stored, the damping curves making it possible to select different damping characteristics for different operating states. 
     Having described the preferred embodiment, it will become apparent that various modifications can be made without departing from the scope of the invention as defined in the accompanying claims.