Patent Application
20100300086
The invention relates to a hydraulic control arrangement for pressure medium supply of hydraulic consumers, and to a distribution valve section for such a control arrangement.
Such hydraulic control arrangements are, for instance, used in mobile hydraulics. In forestry, for instance, machinery components carried by an all-terrain working equipment are used which are adapted to perform suboperations of timber harvesting such as felling, debranching, decorticating, collecting, depositing. So-called harvesters are used to separate the lumber from the stem, to debranch it, to cut it in, and to collect the lumber cut to size. A harvester head employed for this purpose and supported at a crane of the working equipment comprises grabs, feed rolls, and a saw for felling, moving, debranching, and cutting the lumber to size. All these components are actuated hydraulically, wherein the controlling is usually performed through a mobile control block of the working equipment.
Such a control arrangement is frequently designed as an LS system, wherein a load-sensing variable displacement pump is adjusted as a function of the highest load pressure of the simultaneously actuated hydraulic consumers by an LS pump regulator such that the pump pressure always ranges by a predetermined Δp above the highest load pressure of the consumers. The pressure medium volume flow to the individual consumers of the harvester head is adjusted via a respective distribution valve section of the mobile control block, wherein this distribution valve section usually comprises an adjustable metering aperture—formed by a proportionately adjustable distribution valve—and an LS or LUDV pressure compensation valve.
The harvester head of a forestry machine is a product equipped with many functions in which the device components required for the many functions are accommodated in a narrow space and are therefore to be dimensioned as small as possible. The hydraulic valves required for the control of the hydraulic consumers at a harvester head, which are usually accommodated directly on the harvester head, should require as little space as possible.
If one intends to make a cut with a chain saw, for instance, for cutting felled trunks of a tree to size, the saw will have to be taken to maximum speed prior to entering the lumber so as to pass through the trunk as quickly as possible at chain speed as high as possible. Since harvesters predominantly harvest smallwood that is sawn through relatively quickly, the time required for powering up the saw to high speed has a noticeable influence on the time required for a cut.
If—given the space available for accommodation—the valve is large enough, the flow rate may be increased in that one has the pressure difference become larger than usual via a metering aperture by influencing, for instance, an individual compensation valve assigned to the distribution valve. The variable displacement pump must, of course, be adjusted or must have been adjusted from the outset such that it also supplies the amount of pressure medium causing the larger pressure difference.
A large amount of pressure medium, i.e. a high speed or rotational frequency of the hydraulic consumer, for instance, the chain saw at the harvester head, and high dynamics, i.e. a quick swiveling out of the variable displacement pump is achieved—in particular also with hydraulic consumers whose load pressure depends on their speed or rotational frequency—if the signaling line to the pump regulator is connected with the supply line to the distribution valve, i.e. a pressure increased vis-à-vis the load pressure, in particular also the pump pressure itself, is reported to the pump regulator.
Such an arbitrary increase of the pressure reported to the LS pump regulator may, for instance, be caused by means of a control arrangement described in DE 199 30 618 A1 or in DE 37 13 824 A1. In these known solutions, for increasing the pressure reported to the LS pump regulator, a separate valve is provided via which the LS line that usually carries the load pressure and that is connected with the LS pump regulator is impacted with the pump pressure, so that the pump, on actuation of the separate valve, goes to maximum pressure and hence a hydraulic consumer may be operated with high dynamics. This means that in these known solutions the corresponding consumer is controlled by a constant pressure system.
It is a disadvantage of this known solution that considerable effort with respect to device technology effort is required since an external valve is necessary for supplying the pump pressure to the LS pump regulator.
Contrary to this, it is an object of the invention to provide a hydraulic control arrangement and a distribution valve section by which a hydraulic consumer is controllable with high dynamics.
In accordance with the invention, the hydraulic control arrangement comprises, for supplying pressure medium to hydraulic consumers, a load-sensing variable displacement pump the adjustment of which is modifiable by an LS pump regulator as a function of a signaling pressure in a signaling line. The control arrangement comprises a distribution valve with a valve gate via which a metering aperture is adapted to be controlled, said metering aperture being arranged in the pressure medium flow path between a supply line supplied by the pump and a consumer line leading to the consumer. The signaling line is adapted to be impacted with a signaling pressure that is increased vis-à-vis the load pressure of the consumer by connecting it with the supply line. In accordance with the invention, this is effected in that the signaling line is adapted to be connected with the supply line by shifting the valve gate. The distribution valve section according to the invention which is suited for such a hydraulic control arrangement is designed appropriately.
In this solution, during controlling of the consumer and the adjustment of the pertinent metering aperture involved therewith, a higher pressure than the actual load pressure is signaled to the LS pump regulator, so that the pump is adjusted correspondingly and the pump pressure increases strongly vis-à-vis a solution in which only the current load pressure to the LS pump regulator is signaled, and thus it is possible to control the consumer with high dynamics. The hydraulic control arrangement then possibly operates during the controlling of the consumer as a constant pressure system with an artificially increased pressure signaled to the LS pump regulator. With the sole activation of the other consumers, the hydraulic control arrangement conventionally works as an LS system, wherein the LS variable displacement pump is then controlled as a function of the highest load pressure of these other consumers.
Another advantage of the solution according to the invention consists in that no external valve is required for applying the pump pressure since this application is integrated in the metering aperture assigned to the corresponding consumer.
In accordance with the invention it is preferred if the metering apertures are each formed by a distribution valve of a distribution valve section of a mobile control block, wherein each section has an LS connection adapted to be connected with the pump regulator via the signaling line. In the distribution valve section assigned to the constant pressure consumer, this LS connection is adapted to be connected with the supply line via a signaling channel.
In accordance with the invention it is preferred if an individual compensation valve is assigned at least to the distribution valve of the constant pressure consumer. It is preferably designed as an LS compensation valve that is impacted in opening direction by the pressure in the LS line and the force of a spring, and in closing direction by the pressure upstream of the metering aperture. This LS compensation valve is particularly advantageous if the signaling line is opened after a predetermined opening cross-section of the metering aperture only, so that the consumer is first of all supplied with pressure medium after an LS control, wherein the pressure medium volume flow across the metering aperture is kept constant by the LS compensation valve irrespective of the load pressure and the LS variable displacement pump is controlled as a function of the load pressure of this consumer. As soon as the metering aperture has reached the predetermined opening cross-section, the signaling line is opened and an increased pressure is correspondingly applied to the input of the LS pump regulator, so that the pump pressure increases correspondingly.
In a variant of the invention the LS compensation valve is designed with a load maintaining position in which, in the case of an undersaturation of the pump, it is not possible for the pressure medium volume flow to flow off from the distribution valve section assigned to the consumer.
For limiting the pump pressure, an LS pressure limiting valve used conventionally with LS systems and provided in the LS line may be used.
The control arrangement according to the invention is adapted to be designed in a particularly compact manner if the signaling channel is integrated in a valve gate of the distribution valve.
This integration of the signaling channel in the valve gate may, for instance, be performed in that it branches off from a connecting channel that connects a section of a consumer channel which is situated downstream of the metering aperture with the signaling line. In so doing, the signaling channel branches off between two nozzles, wherein a signaling nozzle is arranged in the signaling channel itself. By the latter nozzle and the nozzle positioned downstream of the metering aperture, a flow splitter is formed at which the higher signaling pressure is tapped.
In an alternative solution, a longitudinal bore of the valve gate is formed in the fluid path to the signaling line in which there opens a radial bore via which a pressure medium communication with the supply line is produced after a predetermined stroke of the valve gate.
A second radial bore of the valve gate may be provided whose opening cross-section is smaller than that of the first radial bore.
The hydraulic control arrangement according to the invention and the method according to the invention may be used in a particularly advantageous manner in mobile hydraulics, for instance, in a harvester head.
The LS distribution valve section in accordance with the invention is designed in correspondence with the foregoing embodiment.
In the following, a preferred embodiment of the invention will be explained in more detail by means of schematic drawings. There show:
a the circuit diagram of a variant of the distribution valve of
a a variant of the solution according to
In mobile working equipment, for instance, in a vehicle used in forestry with a harvester head carried on a crane, the pressure medium supply of the individual hydraulic consumers, e.g. of grabs, feed rolls, saws, or the hydraulic cylinders for adjusting the crane, is preferably performed via a plurality of LS mobile control blocks comprising a plurality of distribution valve sections which are each assigned to one of the afore-mentioned consumers.
In accordance with the hydraulic control arrangement illustrated in
The continuously variable distribution valve 24 is, via a centering spring arrangement 26, biased in a basic position (0) in which the connections P, A, and B are locked. The load signaling line 18 is in this basic position (0) connected with the drain line 12. Via pilot valves (not illustrated) or via proportional magnets it is possible to shift a valve gate of the distribution valve 24 in the direction of the positions marked with (a).
In these positions the cross-section of the metering aperture 28 between the input connection P and the working connection A and a drain cross-section between the working connection B and the tank connection P are opened, so that pressure medium is adapted to flow, via the feed line 14, to the hydro motor 1 and to flow off to the tank T from the low pressure side thereof via the return line 16 and the distribution valve 24. In these positions (a) the connection to a load signaling chamber 30 which is merely indicated in
In accordance with the illustration in
The nozzles 36, 40, and 42 which are, as results from
For operation of the hydro motor 1, if it drives the chain saw at a harvester head, the distribution valve is usually deflected maximally in the direction of the positions designated with (a). At least in this position the nozzles 36 and 42 are open toward the connection P and the connection A of the distribution valve. Parallel to the metering aperture 28 a small amount of pressure medium flows from P to A via the nozzles 36 and 42. Between the two nozzles a pressure ranging between the pressure in P and the pressure in A will arise which is signaled to the load signaling channel 18 and to the pump regulator 8 via the nozzle 40. This in turn adjusts the pump 6 such that the pressure in P ranges by the pump Δp above the signaled pressure. That means that the pressure drop across the nozzle 36 is equal to the pump Δp. The amount of pressure medium flowing in the bypass to the metering aperture results from the flow rate cross-section of the nozzle 36 and the pressure drop across this nozzle, i.e. the pump Δp. This amount of pressure medium also flows over the nozzle 42 and generates a pressure drop which depends on the flow rate cross-section thereof. By selecting the flow rate cross-section of the nozzle 42 vis-à-vis the flow rate cross-section of the nozzle 36 it is thus possible to determine by how much the signaled pressure ranges above the pressure in A. If, for instance, the flow rate cross-section of the nozzle 42 is as large as the flow rate cross-section of the nozzle 26, the signaled pressure ranges by the pump Δp above the pressure in A. The variable displacement pump will then be adjusted to such a delivery rate (normal delivery rate without nozzle 36 multiplied by the root of 2) that it generates a pressure drop across the metering aperture 28 which is twice as large as the pump Δp. The variable displacement pump is, due to the pressure signaled to be increased vis-à-vis the load pressure in the connection A of the distribution valve, quickly adjusted to a high delivery rate, possibly to the maximum delivery rate, if this maximum delivery rate does not yet generate the pressure drop provided by the pump Δp and the flow rate cross-sections of the nozzles 36 and 42 via the metering aperture 28. The pump would remain below the maximum delivery rate if the pressure regulator with which an LS variable displacement pump is usually also equipped for maximum pressure safeguarding, or a pressure limiting valve connected to the load pressure signaling lines 18 or 22 would respond.
In the variant of the distribution valve 24 pursuant to
If, as in the variant pursuant to
If the distribution valve 24 is shifted to the positions marked with (b), the metering aperture 28 positioned between the input connection P and the working connection B will be opened and the pressure medium communication from the working connection A to the tank T will be opened, so that the hydro motor 1 is adapted to be driven with inverse direction of rotation. In these positions, the actual load pressure is tapped downstream of the metering aperture 28 and is signaled via the load signaling line 18, the two-way valve 20, and the LS line 22 to the LS pump regulator 8, so that the adjustment of the pump is performed as a function of the actual load pressure. On principle, however, the pump pressure may be signaled to the pump regulator 8 via a channel corresponding to the signaling channel 34 even if the distribution valve 24 is shifted in the direction (b), so that the pressure medium supply of the hydro motor 1 is also effected as a function of the pump pressure.
The control arrangement illustrated in
In the control arrangement illustrated in
In the case of a shifting to the positions designated with (a), the pressure existing between the nozzles 36 and 42 via the nozzle 40 and the load signaling line 18 is present at the control face of the compensation valve control piston which is effective in opening direction. The pressure upstream of the metering aperture 28 is, corresponding to the force of the spring 46, higher than the pressure acting on the opening side of the compensation valve 44, so that here, too, a large pressure drop across the metering aperture 28 is possible.
The control arrangements pursuant to
The circuit diagram of such an embodiment of a control arrangement with a so-called booster function is illustrated in
During the further shifting of the distribution valve 24, the positions designated with (a) are reached in which the signaling channel 34 with the signaling nozzle 36 is opened in the afore-described manner, so that the pressure prevailing between the two nozzles 36 and 42 is present in the load signaling line 18 and hence in the spring chamber of the LS compensation valve 44 and at the LS pump regulator 8, so that the variable displacement pump 6 swivels out further and a high pressure medium volume flow is supplied to the hydro motor 1. If the cross-section of the nozzle is substantially larger than the cross-section of the nozzle 42, the pump pressure is practically signaled to the LS pump regulator, so that the pump changes to maximum delivery rate.
As for the rest, the embodiment illustrated in
In the illustrated basic position the valve gate 52 of the distribution valve 24 blocks the pressure medium communication between the communication channel 56 carrying the pressure P′ downstream of the LS compensation valve 44 and the two working connections A, B of the distribution valve section 2. On controlling of either of the pilot valves 53, 55 the pressure medium communication to the hydro motor 1 is opened or closed, respectively, in the afore-described manner via control grooves 58 or 60, respectively. The load pressure present at the working connections A, B, i.e. the pressure downstream of the metering aperture 28 opened by the control edge 58 or 60 (see
To this extent, the structure of the distribution valve section 2 corresponds completely to the known solution. In the embodiment according to the invention, this known distribution valve section 2 has been modified such that, after a predetermined stroke of the valve gate 52 in terms of a communication of the channel 68 with the channel 56, at least one further radial bore 74 of the valve gate which opens in the longitudinal bore 62 at the inside is opened toward the channel 56. The radial bore 64 that forms, in the viewed actuation direction of the valve gate, the nozzle 42 of
To increase the cross-section of the nozzle 36, further radial bores positioned in the same radial plane may be distributed around the circumference of the valve gate. Ultimately, the pressure in the longitudinal bore 62 will be almost equal to the pressure in the channel 56.
In the case of a small stroke of the valve gate 52 (positions (c)), a sensitive controlling of the consumer is thus possible, while during further shifting to the positions (a) the consumer is supplied with a high pressure medium volume flow. If the sensitivity is not required, the bore 68 may be dispensed with. With one single small bore 74 it is then possible to take the pressure from the channel 56 to the longitudinal bore 62.
In the illustrated distribution valve section 2, the maximum load pressure may be limited by the LS pressure limiting valve 48 connected to the load pressure signaling chamber 32.
In the case of a shifting in the direction (b), the radial bore 74 remains closed vis-à-vis the channel 56. In a conventional manner, the load pressure at the working connection B is signaled via the bore 66 to the spring chamber of the LS compensation valve 44 and to the pump regulator 8. On principle, however, a second signaling bore might be effective then, so that the LS variable displacement pump 6 is also shifted in direction (b) in terms of an increase of the pressure medium volume flow.
With the distribution valve of
If the valve gate 52, viewed pursuant to
A hydraulic control arrangement and a method for pressure medium supply of hydraulic consumers are disclosed, comprising an LS pump which can be controlled by a pump regulator dependent on the highest load pressure of the consumers. The pressure medium volume flow to each consumer is adjusted using a metering aperture, wherein on controlling a consumer a higher pressure than the load pressure is signaled to the LS pump regulator, so that the LS pump is controlled according to the higher pressure rather than the low load pressure of said consumer.
| Number | Date | Country | Kind |
|---|---|---|---|
| 10 2007 055 377.5 | Nov 2007 | DE | national |
| Filing Document | Filing Date | Country | Kind | 371c Date |
|---|---|---|---|---|
| PCT/DE2008/001890 | 11/14/2008 | WO | 00 | 8/12/2010 |
