The invention relates to a damping system, in particular in the form of a hydraulic cabin spring, having at least one hydraulically triggerable actuating part and having at least one hydraulic accumulator which is connected to the assignable actuating part.
Damping or spring systems such as these are freely available in the market in a plurality of embodiments, and in addition to a cabin spring system for vehicles, also 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 which detects the hydraulic state of the respectively triggerable actuating part and/or its position using correspondingly designed sensors.
On the basis of this prior art, the object of the invention is to make available with a simplified structure a damping system which allows variable adjustment of constant damping ratios with few insert parts and components. This object is achieved by a damping system with the features of claim 1 in its entirety.
In that, as specified in the characterizing part of claim 1, proportional damping for the respective actuating part of the damping system is achieved by means of a proportional throttle valve, variable proportional damping can be accomplished which, compared to current solutions with constant damping, has 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 could adversely affect triggering precision. Compared to known solutions, the damping system according to the invention also requires less control effort and only little space. The damping system solution according to the invention can also be economically implemented and reliably operated.
In one especially preferred embodiment of the damping system according to the invention, the proportional throttle valve interworks with nonreturn valves and, via the nonreturn valves, the trigger side of the actuating part which is not being damped can accept oil from the hydraulic accumulator, counteracting the danger of cavitation in the hydraulic circuit, as otherwise often occurs in solutions in the prior art. In an especially advantageous manner, cavitation is avoided in solutions in which the proportional throttle valve with the nonreturn valves forms a type of hydraulic rectifier circuit.
The damping system according to the 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. Thus the ratio of the opening cross sections of the proportional valve can 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 advantageous embodiments are the subject matter of the other dependent claims.
The damping system according to the invention will be detailed below using various embodiments as shown in the drawings. In the manner of hydraulic operating and circuit diagrams the figures show the following.
FIG. 1 shows the basic structure of a proportional throttle valve in use in the unactuated and actuated position;
FIGS. 2 and 3 show the deflection and rebound process in a hydraulic power cylinder, used for a cabin spring system;
FIG. 4 shows one version of the solution as shown in FIGS. 2 and 3 with nonreturn valves integrated in the housing of the proportional throttle valve,
FIGS. 5 and 6 show the deflection and rebound process in a modified damping system in a corresponding representation to the solution as shown in FIGS. 2 and 3.
FIG. 1 shows a proportional throttle valve 10 which interconnects 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 different cross sections. The proportional throttle valve 10 which is completely closed in the base position (de-energized) or has a definable initial throttling cross section, proportionally to the adjustment path clears a visibly increasing fluid cross section. But 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 and 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 as shown in FIG. 1 is modified in FIGS. 2 to 4 in that only the chokes 12, 14 are shown in order 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 invention. In particular, the damping system is made in the form of a hydraulic cabin spring system, these spring systems being conventionally known, so that only what is claimed in the invention which differs from the prior art will be detailed here. The indicated cabin or other vehicle structure is coupled to a hydraulically triggerable actuating part 20, here 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 moreover generally dynamically connected to an individual wheel or wheel set (not shown) of a work vehicle. The hydraulic actuating part 20 as such in terms of its fundamental function however need not be limited to hydraulic power or cushioning cylinders; rather other hydraulic means are 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 invention, the “spring system” for a hydraulic motor in its work use could therefore also be implemented; this for example can play a part in elevator cars or for forklifts of any type. Furthermore, for the actuating part 20 there is a hydraulic accumulator 26 which 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 and 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 and 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 which assume 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 looking at 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 then reproduce the approximate fluid path in the hydraulic circuit of the damping system, hydraulic energy being 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, so that the fluid which has been displaced from the piston space by means of the piston part 22 is 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 and the fluid which has been displaced on the rod side traveling 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, so that in this respect the fluid which has been displaced from the cylinder 20 choked 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 looking at FIG. 3 being 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 indicated 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 embodiment as shown in FIG. 4, the nonreturn valves 40, 42 are connected in a parallel configuration to the assignable chokes 14, 12 and 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 embodiment as shown in FIGS. 5 and 6 will now be explained only to the extent it differs significantly from the preceding embodiments. FIG. 5 shows in turn a deflection process, comparable to FIG. 2, and FIG. 6 shows a rebound process comparable to FIG. 3. The proportional throttle valve 10 this time is one with only one choke 14 and the parallel choke 12 located in the secondary branch is not necessary in the embodiment as shown in FIGS. 5 and 6. Instead, two additional nonreturn valves 52 and 54 are used there and 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 as 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 which are located in different fluid branches are opened, whereas the other nonreturn valves 42 and 52 are closed. In deflection in turn the required damping takes place via the choke 14. In the rebound process as shown in FIG. 6 the nonreturn valves 42 and 52 are then opened, whereas the nonreturn valves 40 and 52 are closed. Rebound takes place in turn supported by the fluid discharge on the fluid side 32 of the hydraulic accumulator 26.
With the damping system according to the invention as shown in FIGS. 5 and 6, the oil to be damped is always routed through the proportional throttle valve 10, and via the respectively assignable 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 means of the indicated nonreturn valves the danger of cavitation on the respective draft side of the actuating part 20 is prevented. If in the embodiment as shown in FIGS. 2 to 4 the same damping is to take place in both directions by means of 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 invention for a power cylinder (actuating part 20) manages with only one proportional throttle valve 10; this helps facilitate rapid and dedicated triggering. In particular the control effort can be greatly reduced. The damping system according to the invention is also reliable in operation and requires little installation space. Due to the small number of components moreover an economical implementation is possible.
Patent Application
20090045022
