The invention relates to a hydraulic system having a plurality of hydraulic consumers and having a plurality of load-sensing valves for setting the pumping capacity of the hydraulic pump. The invention further relates to a method for controlling a hydraulic system.
In a hydraulic system of this kind, the delivery pressure of the hydraulic pump is set at a value greater than the maximum current load pressure required by one of the hydraulic consumers under the control of the load-sensing valves. For consumers with a lower current load pressure, the hydraulic pressure is reduced by pressure-maintaining valves.
The pressure reduction means that capacity is lost in the form of so-called compensation losses. The compensation losses are particularly pronounced when consumers with a low volume flow requirement and high load pressure and consumers with a high volume flow requirement and low load pressure are combined with one another in the hydraulic system.
The problem addressed by the invention is that of introducing a hydraulic system and an associated method, so that the compensation losses can be kept smaller. Starting from the aforementioned prior art, the problem is solved using the features of the independent claims. Advantageous embodiments are indicated in the dependent claims.
In the case of the hydraulic system according to the invention, an allocation unit is arranged between the hydraulic pump and the hydraulic consumers, which allocation unit defines a first hydraulic path between the hydraulic pump and the hydraulic consumers in a first switching state and a second hydraulic path between the hydraulic pump and the hydraulic consumers in a second switching state. The system comprises a controller which processes a state value of a hydraulic consumer as an input variable and which determines a control signal for the switching state of the allocation unit.
The invention has recognized that by means of a controller of the allocation unit which depends on the current state of the hydraulic consumers, it is possible for the hydraulic paths between the hydraulic pump and the hydraulic consumers to be selectively adapted to requirements.
A state value of a hydraulic consumer is a variable which represents the current operating state of the hydraulic consumer. In particular, the state value may relate to the current load pressure of the hydraulic consumer.
Taking account of the state value, the controller can determine a control signal for the switching state of the allocation unit. The control signal can be transmitted to the allocation unit. The allocation unit can be set to a switching state that corresponds to the control signal.
A hydraulic path denotes a path via which a hydraulic consumer is supplied by a hydraulic pump. A hydraulic path within the meaning of the invention generally extends from a hydraulic pump via a load-sensing valve to a hydraulic consumer. A load-sensing valve has the function of setting the pumping capacity of the hydraulic pump depending on the current operating state of the hydraulic consumers. In particular, the load-sensing valve may be designed to set the delivery pressure of the hydraulic pump to a value which is greater by a predefined pressure difference than the maximum load pressure of a consumer supplied by the hydraulic pump. The load-sensing valves may be configured as proportional valves. It is also possible for the plurality of load-sensing valves to comprise one or multiple proportional valves and/or one or multiple constant flow valves (flow control valves).
In one embodiment, the allocation unit is arranged between a plurality of load-sensing valves and a plurality of hydraulic consumers. The switching states of the allocation unit can be defined in such a manner that in the first switching state a first hydraulic consumer is supplied by a first load-sensing valve and in the second switching state a second hydraulic consumer is supplied by the first load-sensing valve. This may apply to any combinations of load-sensing valves and hydraulic consumers.
The allocation unit may be configured in such a manner that in the first switching state a first group of hydraulic consumers is supplied by a first load-sensing valve and in the second state a second group of hydraulic consumers is supplied by the first load-sensing valve. The allocation unit and/or the controller may be configured in such a manner that any group of hydraulic consumers can be assigned at random to each load-sensing valve. It is also possible for certain allocations to be allowed, while other allocations are precluded from the outset. In a preferred embodiment, the allocation unit is set up in such a manner that a load-sensing valve in each switching state supplies precisely one hydraulic consumer. There is therefore a first switching state of the allocation unit, in which a load-sensing valve supplies precisely one first hydraulic consumer, and a second switching state, in which the load-sensing valve supplies precisely one second hydraulic consumer.
The switching states of the allocation unit can be defined in such a manner that each hydraulic consumer is supplied by precisely one load-sensing valve. It is also possible for one or multiple hydraulic consumers to be supplied by a load-sensing valve in a first switching state and by more than one load-sensing valve in a second switching state. The connection of multiple load-sensing valves to a hydraulic consumer may be sensible if a load-sensing valve which supplies a volume flow sufficient for routine operating states of the hydraulic consumer has been allocated to a hydraulic consumer beforehand. By connecting a second load-sensing valve to the hydraulic consumer, the operating speed of the hydraulic consumer can be increased temporarily. In other words, the volume flow supplied to a hydraulic consumer can be increased while the valve size remains the same and/or the individual load-sensing valve can be made smaller, wherein the volume flow is temporarily increased by connecting a second load-sensing valve.
If the hydraulic consumer is used to fold a boom of a concrete pump, for example, the normal operating speed can be defined by the fact that when the boom is extended, the tip of the boom should not exceed a particular speed. By connecting a second load-sensing valve to the hydraulic consumer, when the boom is folded in, a higher operating speed can be facil-itated.
The hydraulic system according to the invention may comprise more than one hydraulic pump. Each hydraulic pump may be allocated precisely one load-sensing valve.
If the hydraulic system comprises more than one hydraulic pump, the invention opens up the possibility of a particular hydraulic consumer being temporarily supplied by a first hydraulic pump and temporarily by a second hydraulic pump. With the allocation unit according to the invention, a changeover can be made between the hydraulic paths in a suitable manner. In particular, the allocation unit may be designed in such a manner that the hydraulic consumers are assigned to the hydraulic pumps in groups, wherein the composition of the groups may vary depending on the switching state of the allocation unit.
In one embodiment of the invention, an allocation unit within the meaning of the invention is arranged between a plurality of hydraulic pumps and a plurality of load-sensing valves. The allocation unit may be provided, in addition or alternatively to the allocation unit, between the plurality of load-sensing valves and the plurality of hydraulic consumers. The different possibilities for hydraulic paths in the allocation unit correspond to the aforementioned possibilities.
If the hydraulic system comprises only one allocation unit between the load-sensing valves and the hydraulic consumers, but no allocation unit between the hydraulic pumps and the load-sensing valves, the possibility emerges of more than one hydraulic pump being temporarily connected to a hydraulic consumer. A corresponding effect can also be achieved if an allocation unit is only arranged between the hydraulic pumps and the load-sensing valves, but not between the load-sensing valves and the hydraulic consumers. If the hydraulic system comprises a first allocation unit which is arranged between the load-sensing valves and the consumers, and a second allocation unit which is arranged between the pumps and the load-sensing valves, the hydraulic paths between the hydraulic pump and the consumers can be particularly flexible in design.
The controller of the hydraulic system can be set up in such a manner that with the help of the state values of the hydraulic consumers it forms a first group of hydraulic consumers and a second group of hydraulic consumers. A group within the meaning of the invention may consist of individual hydraulic consumers. The groups may, for example, be defined in that with all hydraulic consumers in the first group the current load pressure lies below a threshold value, while with all hydraulic consumers in the second group the current load pressure lies above the threshold value. If the hydraulic consumers are sorted by load level and allocated to the hydraulic pumps, the compensation losses can be kept small. The composition of the groups can be dynamically adjusted depending on the current operating states of the hydraulic consumers. The controller can continuously check the operating state of the hydraulic consumers to this end and produce a control signal, where necessary, by means of which the switching state of the allocation unit is changed.
The controller may be designed to set the threshold value as a function of the operating state of the hydraulic consumers. For example, the load pressures of the hydraulic consumers can be observed in ascending order and the threshold value positioned between those adjacent load pressures which are spaced furthest apart from one another. If there is a subdi-vision into more than two groups, the threshold values can be positioned in the next smallest spacings.
In addition or alternatively, the controller can be designed to determine with the help of a suitable criterion whether load pressure oscillations occur in a hydraulic consumer. Fluc-tuations in load pressure may indicate that a mechanical oscillation has occurred in an element attached to the consumer. If an oscillation parameter is greater than a predetermined threshold value, the controller can generate a control requirement according to which the hydraulic consumer concerned is separated from other hydraulic consumers. In other words, if the allocation unit previously had a switching state in which the relevant hydraulic consumer was supplied jointly with other consumers, the allocation unit can be moved into another switching state in which the hydraulic consumer concerned is supplied by a hydraulic pump which is different from the other hydraulic consumers in the group hitherto. In this way, it is possible to prevent oscillations from being transmitted from one hydraulic consumer to other hydraulic consumers.
As a further input variable, the controller can take account of inputs by an operator. If the operating state of the hydraulic consumers changes according to an input by the operator, this can result in the previous switching state of the allocation unit no longer being optimal. The controller can process the operator input, in order to determine a new control requirement for the allocation unit. In a corresponding manner, the controller can process information on the global operating state of the hydraulic system as an input variable.
In addition to this, controller can make control requirements for the state of the load-sensing valves. In particular, the opening cross section of the load-sensing valves can be set under the control of the controller. The feedback between the load states of the hydraulic consumers and the pumping capacity of the hydraulic pump may take place on hydraulic paths. It is also possible for the load pressures to be detected electronically and for the hydraulic pumps to be electrically adjustable. The pumps can be activated by means of the controller in this case.
The consumers of the hydraulic system may, for example, be linear drives or rotational drives. The hydraulic system may be designed to drive elements of a concrete pump. The consumers of the hydraulic system may, for example, comprise a linear drive for folding a boom arm of a concrete pump and/or a rotational drive for driving a rotational movement of the boom arm. Moreover, the invention relates to a concrete pump with a plurality of hydraulic consumers in which the hydraulic consumers are elements of a hydraulic system of this kind.
Moreover, the invention relates to a method for controlling a hydraulic system in which a plurality of hydraulic consumers is supplied using a hydraulic pump and in which the pumping capacity of the hydraulic pump is set using a plurality of load-sensing valves. An allocation unit with which it is possible to switch between different hydraulic paths from the hydraulic pump to the hydraulic consumers is arranged between the hydraulic pump and the hydraulic consumers. A controller processes a state value of a hydraulic consumer as an input variable, in order to determine a control signal for the switching state of the allocation unit.
The method can be improved with further features which are described in connection with the hydraulic system according to the invention. The hydraulic system can be improved with further features which are described in connection with the method according to the invention.
The invention is described below by way of example with reference to the attached drawings with the help of advantageous embodiments. In the drawings:
A truck 14 shown in
The mobile concrete pump according to
The hydraulic consumers 23, 24, 25, 26 are operated by operator inputs. If the folded state of the boom arm 18 is to be changed, the corresponding input by the operator is converted into an operation of the linear drives 23, 24, 25. The same applies to a rotation of the boom arm 18 relative to the chassis.
In the prior art, the delivery pressure of the hydraulic pump is set by load-sensing valves in such a manner that it is slightly higher than the highest load pressure currently required by one of the hydraulic consumers 23, 24, 25, 26. For the remaining hydraulic consumers, the pressure is reduced by pressure-maintaining valves. The reduction in pressure results in capacity losses in the form of compensation losses which are particularly pronounced, according to
In
In the case of the exemplary embodiment shown in
A first allocation unit 36 is arranged between the load-sensing valves 33, 34, 35 and the hydraulic consumers 23, 24, 25. The allocation unit 36 comprises different switching states with which different hydraulic paths between the load-sensing valves 33, 34, 35 and the hydraulic consumers 23, 24, 25 can be made available. The switching states are defined in such a manner that each of the hydraulic consumers 23, 24, 25 can be connected to one of the load-sensing valves 33, 34, 35 individually or in arbitrary groups.
A second allocation unit 37 with which the hydraulic pumps 31, 32 and the load-sensing valves 33, 34, 35 can be connected to one another correspondingly in an arbitrary manner is arranged between the hydraulic pumps 31, 32 and the load-sensing valves 33, 34, 35.
The hydraulic system comprises a controller 38 which is coupled with a control unit 39 of the hydraulic system and a higher-level information system 44. The controller 38 receives information on the current load pressures of the hydraulic consumers 23, 24, 25 as input vari-ables via signal lines 40. Control signals can be sent to the first allocation unit 36, the load-sensing valves 33, 34, 35, and the second allocation unit 37 via control lines 41, 42, 43.
If the controller 38 receives notification via the signal lines 40 that, in accordance with the state depicted in
According to a different control approach, the controller 38 can evaluate load pressure data on oscillations received via the signal lines 40. If, for example, a state occurs in the first hydraulic consumer 23 in which the oscillation of the load pressure is greater than a predetermined threshold value, the controller 38 can form a group of the second and third hydraulic consumers 24, 25 and separate the first hydraulic consumer 23 from the group. By means of the control lines 41, 43, the allocation units 36, 37 can be activated in such a manner that the first hydraulic consumer 23 is connected to the first hydraulic pump 31 and the second and third hydraulic consumers 24, 25 are connected to the second hydraulic pump 32. By separating the first hydraulic consumer 23, the oscillations which occur in the case of this hydraulic consumer 23 are prevented from having detrimental effects on the other hydraulic consumers 24, 25.
A further control approach of the controller 38 involves determining a state in which two of the hydraulic consumers 23, 24, 25 are inoperative or only require a small capacity, while a rapid movement is required of a third hydraulic consumer. It can be seen in
In the controller 38, a plurality of control approaches can be realized in parallel. In order to avoid conflict, a hierarchy can be established between the control approaches. For example, the avoidance of oscillations can be given the highest priority. If all hydraulic consumers in the system are free of oscillations, the hydraulic consumers can be sorted into groups with the help of the current load pressures according to the next priority, in order to keep compensation losses low. In the third priority, multiple hydraulic pumps can be connected to one hydraulic consumer, in order to increase the operating speed.
Number | Date | Country | Kind |
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10 2018 117 949.9 | Jul 2018 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2019/070012 | 7/25/2019 | WO |
Publishing Document | Publishing Date | Country | Kind |
---|---|---|---|
WO2020/020997 | 1/30/2020 | WO | A |
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Entry |
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German Examination Report for Application No. 10 2018 117 949.9 filed Jul. 25, 2018 dated Apr. 3, 2019; 2 pgs. |
PCT International Research Report and Written Decision for International file No. PCT/EP2019/070012 filed Jul. 25, 2019, dated Oct. 23, 2019, 6 pgs. |
Number | Date | Country | |
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20210190103 A1 | Jun 2021 | US |