Abstract:
A damping system, in particular in the form of a hydraulic cabin spring system, has at least one hydraulically triggerable actuating part ( 20 ) and has at least one hydraulic accumulator ( 26 ) connected to the actuating part ( 20 ). By a proportional throttle valve ( 10 ), proportional damping for the actuating part ( 20 ) is achieved. Variable proportional damping which can react to events in a manner specific to the user can be implemented.

Description:
FIELD OF THE INVENTION 
     The present invention relates to a damping system, in particular in the form of a hydraulic cabin spring. The system has at least one hydraulically triggerable actuating part and at least one hydraulic accumulator connected to the actuating part. 
     BACKGROUND OF THE INVENTION 
     Damping or spring systems are readily available in the market in a plurality of embodiments. In addition to a cabin spring system for vehicles, other hydraulically triggerable actuating parts can be designed with damping, such as, for example, hydraulic motors for drive units. In the known solutions, to obtain uniform or constant damping, high control effort is necessary to detect the hydraulic state of the respectively triggerable actuating part and/or its position using correspondingly designed sensors. 
     SUMMARY OF THE INVENTION 
     An object of the present invention is to provide a simplified damping system allowing variable adjustment of constant damping ratios with few insert parts and components. 
     This object is basically achieved by a damping system where proportional damping for the respective actuating part of the damping system is achieved by a proportional throttle valve providing the only fluid communication between the actuating part and an accumulator. Variable proportional damping can be accomplished, compared to current solutions with constant damping, having the advantage of being able to react to events depending on the situation and in a manner specific to the user. By using the proportional throttle valve, it is possible to variably choke the respectively hydraulically triggerable actuating part with only one triggering process without hysteresis phenomena occurring in the actual damping process. This arrangement could adversely affect triggering precision. Compared to known solutions, the damping system according to the present invention also requires less control effort and only little space. The damping system solution according to the present invention can also be economically implemented and reliably operated. 
     In one especially preferred embodiment of the damping system according to the present invention, the proportional throttle valve interworks with nonreturn valves and, via the nonreturn valves, the trigger side of the actuating part not being damped can accept oil from the hydraulic accumulator, counteracting the danger of cavitation in the hydraulic circuit, as otherwise often occurs in the prior art damping systems. In an especially advantageous manner, cavitation is avoided where the proportional throttle valve with the nonreturn valves forms a type of hydraulic rectifier circuit. 
     The damping system according to the present invention can be used in particular for the hydraulic cabin spring system of a work vehicle, such as construction machinery or the like, in which the triggerable actuating part is formed from a hydraulic power or cushioning cylinder. The ratio of the opening cross sections of the proportional valve can then be made uniform depending on the area ratios of the power cylinder (piston to ring area) over the entire valve stroke. The ratio of the opening cross sections is equal to the area ratio of the piston area to the ring area. Consequently, for the same valve position, the deflection and rebound motion is uniformly damped, since the volumetric flow changes uniformly depending on the cylinder areas. 
     Other objects, advantages and salient features of the present invention will become apparent from the following detailed description, which, taken in conjunction with the annexed drawings, discloses preferred embodiments of the present invention. 
    
    
     
       BRIEF DESCRIPTION OF THE DRAWINGS 
       Referring to the drawings which form a part of this disclosure: 
         FIG. 1  is a hydraulic operating and circuit diagram of the basic structure of a proportional throttle valve in use in the unactuated and actuated positions according to an exemplary embodiment of the present invention; 
         FIGS. 2 and 3  are hydraulic operating and circuit diagrams of the deflection and rebound process in a hydraulic power cylinder used for a cabin spring system according to a first exemplary embodiment of the present invention; 
         FIG. 4  is a hydraulic operating and circuit diagram of the hydraulic power cylinder used for the cabin spring system of  FIGS. 2 and 3 , but with nonreturn valves integrated in the housing of the proportional throttle valve according to a second exemplary embodiment of the present invention, 
         FIGS. 5 and 6  are hydraulic operating and circuit diagrams of the deflection and rebound process in a damping system according to a third exemplary embodiment of the present invention in a corresponding representation to the embodiment in  FIGS. 2 and 3 . 
     
    
    
     DETAILED DESCRIPTION OF THE INVENTION 
       FIG. 1  shows a proportional throttle valve  10  interconnecting the ports  1 ,  2  and  3  to carry fluid. The two integrated chokes  12 ,  14 , depending on the application, can have the same free opening cross section, but also can have different cross sections. The proportional throttle valve  10  is completely closed in the base position (de-energized) or has a definable initial throttling cross section. Proportionally to the adjustment path, proportional throttle valve  10  clears a visibly increasing fluid cross section. The possibility also exists for the valve  10  in the base position (de-energized) to be completely opened and then to be proportionally closed over the adjustment path. To trigger the proportional throttle valve  10 , an electromagnetic actuator  16  is used. The proportional throttle valve  10  can be returned into its initial position shown in  FIG. 1  via a reset spring  18 . The representation of the proportional throttle valve  10  shown in  FIG. 1  is modified in  FIGS. 2 to 4  in that only the chokes  12 ,  14  are shown to emphasize the proportional adjustment nature of the valve  10  in this way. 
       FIG. 2  shows the basic circuit of the damping system according to the present invention. In particular, the damping system is in the form of a hydraulic cabin spring system. Since these spring systems are conventionally known, only those parts in the present invention that differ from the prior art will be detailed here. The cabin or other vehicle structure is coupled to a hydraulically triggerable actuating part  20  in the form of a hydraulic power cylinder with a piston part  22  and a rod part  24 . This actuating part in the form of a power cylinder is generally dynamically connected to an individual wheel or wheel set (not shown) of a work vehicle. The hydraulic actuating part  20  in terms of its fundamental function need not be limited to hydraulic power or cushioning cylinders. Other hydraulic means can be used here with components which can be triggered in two opposite directions, such as, for example, hydraulic motors (not shown). 
     With the damping system according to the present invention, the “spring system” for a hydraulic motor in its work use could also be implemented. This system, for example, can play a part in elevator cars or for forklifts of any type. For the actuating part  20 , a hydraulic accumulator  26  is preferably formed from a diaphragm accumulator which is conventional in this field. This hydraulic accumulator  26  has a separating diaphragm  28  which separates the gas side  30  of the accumulator from its fluid side  32 . The hydraulic accumulator  26  can be pretensioned accordingly depending on the fluid pressure on its gas side  30  and then in this respect forms an energy storage device for stored hydraulic energy. The port  3  of the proportional throttle valve  10  is connected to the fluid side  32  of the hydraulic accumulator  26  such that fluid communication between the actuating part and the accumulator is only through the proportional throttle valve. Between the hydraulic accumulator  26  and the proportional throttle valve  10 , a branch point  34  is formed into which fluid lines  36  and  38  discharge with spring-loaded nonreturn valves  40  and  42  assuming their blocking position in the direction to the fluid side  32  of the hydraulic accumulator  26 . The fluid line  36  furthermore discharges to the rod side of the power cylinder  20  and the fluid line  38  discharges into the assigned piston space of the cylinder  20 . Assigned fluid lines  48 ,  50  discharge into the ports  1  and  2  of the valve  10  via other branch sites  44  and  46 . 
       FIG. 2  shows the fluid-carrying situation for deflection, i.e., in the direction of  FIG. 2 , the piston part  22  and rod part  24  move down according to the arrow representation for the actuating part  20 . The further broken-line arrows depict the approximate fluid path or flow in the hydraulic circuit of the damping system. Hydraulic energy is delivered into the hydraulic accumulator  26 , in which fluid is displaced to the fluid side  32  thereof. Furthermore, in the deflection process shown in  FIG. 2 , the upper nonreturn valve  40  is opened and the nonreturn valve  42  is closed. The fluid displaced from the piston space by the piston part  22  is then routed via the choke  14  of the valve  10  in the direction to the accumulator  26 . 
       FIG. 3  in turn shows the rebound process in the opposite direction. The fluid displaced on the rod side travels or flows via the choke  12  into the afterflow circuit for the piston side of the cushioning cylinder  20  when the nonreturn valve  42  is opened and the nonreturn valve  40  is closed on the rod side. The fluid displaced from the cylinder  20  then takes the afterflow path to the piston side of the cylinder. This extension and rebound process of the piston part  22  and rod part  24  viewed in the direction of  FIG. 3  is supported toward the top by the hydraulic accumulator  26 . 
     The embodiment as illustrated in  FIGS. 2 and 3  shows that the ratio of the opening cross sections of the chokes  12  and  14  of the proportional throttle valve  10  is uniform depending on the area ratio of the cylinder (piston area to ring area) for the actuating part  20  over the entire stroke of the valve  10 . The ratio of the opening cross sections for the chokes  12 ,  14  accordingly is equal to the area ratio of the piston to the ring area from the piston part  22  to the rod part  24 . Consequently, for the same valve position the deflection and rebound motion is uniformly damped, as shown, since the volumetric flow can change uniformly depending on the cylinder areas. Via the nonreturn valves  40 ,  42  the respective cylinder side (piston part  22  or rod part  24 ) which is not being damped can accept oil from the hydraulic accumulator  26 , as a result of which the danger of cavitation in the circuit of the damping system is prevented. 
     In the modified or second embodiment as shown in  FIG. 4 , the nonreturn valves  40 ,  42  are connected in a parallel configuration to the assignable chokes  14 ,  12 . By using the respective integrated nonreturn valves  40 ,  42 , additional fluid lines can be dispensed with and the proportional throttle valve  10  can be connected directly via the fluid lines  48 ,  50  to the rod side or piston side of the actuating part  20  in the form of the power cylinder. 
     The modified or third embodiment shown in  FIGS. 5 and 6  is explained only to the extent it differs significantly from the preceding embodiments.  FIG. 5  shows a deflection process, comparable to  FIG. 2 .  FIG. 6  shows a rebound process comparable to  FIG. 3 . The proportional throttle valve  10  includes only one choke  14 . The parallel choke  12  located in the secondary branch is not necessary in the embodiment shown in  FIGS. 5 and 6 . Instead, two additional nonreturn valves  52  and  54  are used. The pairs of nonreturn vales  40 ,  42  and  52 ,  54  are interconnected in the manner of a hydraulic rectifier circuit together with the proportional throttle valve  10 . The fluid lines  48  and  50  connected to the actuating part  20  each discharge between two adjacent nonreturn valves  42  and  54  and  40  and  52 . In the opening direction the nonreturn valves  52  and  54  are placed on the connection side  2  of the valve  10  via the corresponding fluid lines  56 . Conversely, the port  3  is connected in turn to the hydraulic accumulator  26  to carry fluid. The port  1  provided in the secondary branch shown in the embodiment in  FIGS. 2 to 4  is omitted for this purpose. 
     For the deflection process as shown in  FIG. 5 , the nonreturn valves  40  and  54  located in different fluid branches are opened. The other nonreturn valves  42  and  52  are closed. In deflection, the required damping takes place via the choke  14 . In the rebound process shown in  FIG. 6 , the nonreturn valves  42  and  52  are then opened while the nonreturn valves  40  and  52  are closed. Rebound takes place supported by the fluid discharge on the fluid side  32  of the hydraulic accumulator  26 . 
     With the damping system according to the exemplary embodiment of the present invention shown in  FIGS. 5 and 6 , the oil to be damped is always routed through the proportional throttle valve  10 . Via the respective nonreturn valves the power cylinder  20  can reroute oil without loss on the side which is not to be damped. Accordingly, only the pressure side is ever damped, regardless of the direction of motion on the actuating part  20 . By the nonreturn valves the danger of cavitation on the respective draft side of the actuating part  20  is prevented. If in the embodiment shown in  FIGS. 2 to 4  the same damping is to take place in both directions by the proportional throttle valve  10 , the free opening cross section of choke  12  must be smaller than that of choke  14 . 
     The damping system solution according to the present invention for a power cylinder (actuating part  20 ) manages with only one proportional throttle valve  10 . This arrangement helps facilitate rapid and dedicated triggering. In particular the control effort can be greatly reduced. The damping system according to the present invention is also reliable in operation and requires little installation space. Due to the small number of components, an economical implementation is possible. 
     While various embodiments have been chosen to illustrate the invention, it will be understood by those skilled in the art that various changes and modifications can be made therein without departing from the scope of the invention as defined in the appended claims.