The invention relates to a pressure supply device for the prioritized distribution of a volume flow, in particular in mobile machines, consisting of at least one main pump designed as a variable displacement pump, which can be controlled by load-sensing signals, a fixed displacement pump as an auxiliary pump, two pressure maintenance-type components, a system to be supplied primarily, in particular in the form of steering hydraulics, which emits a load-sensing signal, a system to be supplied secondarily, in particular in the form of power hydraulics, that emits a further load-sensing signal, and a further system to be supplied hydraulically, in particular in the form of brake hydraulics.
Pressure supply systems of this type are known and are mainly used in mobile machines, in particular agricultural tractors. During the operation of such devices, for many phases of operation not all of the existing systems have to be simultaneously supplied with full volume flow, i.e. there is no danger of an under-supply of safety-relevant systems, such as steering. However, when special or extreme work situations occur, for example during certain maneuvers, such as those performed during fieldwork when turning at the headland, wherein steering systems, power hydraulics and possibly braking systems request the maximum volume flow, an under-supply may possibly occur. In view of this, it is state of the art, cf. DE 10 2004 005 606 B3, to throttle the return of a non-prioritized load in the case of an under-supply of a prioritized load, such as a power steering system, to ensure sufficient fluid pressure for the prioritized load. Similar known solutions provide for the use of an additional auxiliary pump, which can be operated to support the prioritized system, in particular in the form of a power steering pump.
In view of this, the invention addresses the problem of providing a pressure supply device of the type mentioned above, which is characterized by an uninterrupted service and a particularly favorable operational behavior.
According to the present invention, this problem is solved by a pressure supply device having the features of claim 1 in its entirety.
Accordingly, the invention provides a main pump and an auxiliary pump in the form of a variable displacement pump or a fixed displacement pump and a first and a second pressure maintenance-type component. In this case, the assigned fluid circuit is designed such that the first pressure maintenance-type component is used for supplying the system to be primarily supplied, such as the steering system, and/or the further hydraulic system, such as a trailer brake, that the second pressure maintenance-type component is used for supplying the system to be primarily supplied and/or the system to be secondarily supplied and that the respective pressure maintenance-type components can be controlled by a load-sensing signal, referred to below abbreviated as LS signal, in such a way that the fixed displacement pump is also used to supply the system to be secondarily supplied. The fact that the auxiliary pump even in normal operating conditions, in which there is no LS signal signaling the under-supply of the system to be primarily to be supplied (steering system), is used as an additional supply to support the variable displacement pump, results in a particularly safe and energetically favorable performance of device according to the invention.
Advantageously, the arrangement is such that the main pump directly supplies the system secondarily to be supplied with hydraulic fluid, the pressure of which can be preset, wherein the LS signal for the main pump is received from a shuttle valve, which compares the respective LS signals of the systems to be primarily and secondarily supplied and transmits the LS signal having the higher pressure to the main pump to control the latter.
In particularly advantageous exemplary embodiments, the output of the auxiliary pump is connected to the input of the first pressure maintenance-type component, the spring-loaded control side of which is additionally pressurized by the LS pressure on the output side of the shuttle valve or an LS-pressure, which, branched-off from the shuttle valve, relays the LS signal of the load to be supplied secondarily to this control side of the first pressure maintenance-type component.
Additionally, the spring-loaded control side of the second pressure maintenance-type component is pressurized by the LS-pressure, which, branched-off upstream of the shuttle valve, transmits the LS signal of the load to be primarily supplied to this control side.
The arrangement is advantageously made such that the two pressure maintenance-type components are pressurized by the control pressure of the load to be primarily supplied at their further control side arranged opposite from one of the control sides or that the other control side of the first pressure maintenance-type component is pressurized by the control pressure of the load to be secondarily supplied and the control pressure of the load to be primarily supplied is applied to the further control side of the other pressure maintenance-type component.
A check valve, which opens in the direction of the load to be primarily supplied, is installed in a connecting line between the outputs of the second pressure maintenance-type component, which is routed between the load to be primarily supplied and the load to be secondarily supplied, or a check valve is installed between one of the outputs of the second pressure maintenance-type component and the system to be secondarily supplied, which check valve closes in the direction of the output of the second pressure maintenance-type component, wherein the tap of the LS signal for the first pressure maintenance-type component is located in the supply line to the system to be secondarily supplied between this check valve and the feed point of the main pump.
A further check valve is installed between the two inputs of the two pressure maintenance-type components or between the input of the first pressure maintenance-type component and the output of the second pressure maintenance-type component, wherein the further check valve opens in the direction of the second pressure maintenance-type component.
A further check valve is arranged between the input of the second pressure maintenance-type component and the system to be primarily supplied, which check valve opens in the direction of this system, wherein the control line for the other control side of the second pressure maintenance-type component opens between this further check valve and this system.
Finally, a further check valve is installed between the supply line of the main pump and the input of the second pressure maintenance-type component, which opens in the direction of the second pressure maintenance-type component.
2/2-way pressure maintenance-type components or 3/2-way pressure maintenance-type components or a 2/2-way pressure maintenance-type component in combination with 3/2 pressure maintenance-type components can be used.
Below the invention is explained in detail with reference to exemplary embodiments shown in the drawing.
In the Figures:
In the figures, a main pump designed as a variable displacement pump is denoted by 2 and a fixed displacement pump used as an auxiliary pump is denoted by 4, both of which are fed from a storage tank 6. The output of the variable displacement pump 2 is directly connected to a load port PA via a pressure input P and a supply line 8, which load port is routed to a system to be secondarily supplied, such as power hydraulics. In all exemplary embodiments the output of the fixed displacement pump 4 is connected to an input a of a first pressure maintenance-type component DW1 via a pressure input P2. In the exemplary embodiment of
In
Based on the circuit of
The variable displacement pump 2 receives the highest load pressure reported in the system from the shuttle valve WV. The fixed displacement pump 4 is used as an additional supply to ensure a supply of the prioritized function (such as the steering system) and the OC function (in this case trailer brake) in case of failure of the variable displacement pump 2. Additional fixed displacement pumps may be provided as add-ons, each of which have a further pressure maintenance-type component (such as the pressure maintenance-type component DW1) to feed oil into the system if there is an additional volume flow demand of the overall system. The spring force of the pressure maintenance-type component springs 10 and 16 is lower than the control pressure difference of the variable displacement pump 2. If there is no under-supply of the loads at the load ports PL and PA, wherein the LS pressure of the respective loads is lower than the pressure effective at the load port by at least the control pressure difference, then the pressure maintenance-type component DW1 is switched against the force of the spring 10. Accordingly, there is no volume flow at the second pressure maintenance-type component DW2 to be divided. If necessary, any backflow of oil can be prevented by means of check valves at the load ports PL and PA. The load to be secondarily supplied at the load port PA is directly supplied via the supply line 8 of the variable displacement pump 2, and the load to be primarily supplied at the load port PL is supplied by the supply line 8 via the check valve RV3.
If there is an under-supply, wherein the working pressure at at least one of the loads is lower than the LS pressure feedback by the individual load plus the regulating pressure difference of the pump 2, then the balance of forces at the pressure maintenance-type component DW1 changes. In this way, the volume flow of the fixed displacement pump 4 is partially or completely transferred in the direction of the second pressure maintenance-type component DW2, and accordingly, the volume flow to supply the further system to be supplied is minimized. In all the exemplary embodiments shown, this is the volume flow which is routed from the output d of the first pressure maintenance-type component DW1 via an OC supply line 26 to the load port PB, to which, for example, a trailer brake is connected as an OC load.
The pressure maintenance-type component DW2 regulates the volume flow additionally provided by the fixed displacement pump 4 via the pressure maintenance-type component DW1, which is provided for the prioritized load (steering system at PL). Before an under-supply occurs at the prioritized load, the pressure maintenance-type component DW2 moves in the direction of the spring force and increases the volume flow flowing to the prioritized load. The check valve RV3 prevents the oil from flowing from the prioritized load to the power hydraulics at the load port PA. If the volume flow of the fixed displacement pump 4 is at least as great as the maximum volume flow at the prioritized load, no under-supply can occur. If the volume flow at the prioritized load is smaller than the rated volume flow of the fixed displacement pump 4, then part of the volume flow can also be supplied to the power hydraulics via the pressure maintenance-type components DW1 and DW2.
The exemplary embodiment of
If there is an under-supply at the LS loads, i.e. the working pressure at at least one of the loads PL, PA is lower than the LS pressure feedback by the individual load plus the regulating pressure difference of the pump 2, then the balance of forces changes at the pressure maintenance-type component DW1. The maximum LS pressure fed back via the shuttle valve WV plus the pressure equivalent force of the spring 10 are stronger than the pressure at the prioritized load PL, therefore, the pressure maintenance-type component DW1 is switched in the direction of the spring force. In this way, the volume flow of the fixed displacement pump 4 is partially or completely transferred in the direction of the check valve RV1, and accordingly, the volume flow to supply the OC load connected at the output PB is minimized. The pressure maintenance-type component DW2 regulates the volume flow additionally provided by the fixed displacement pump 4 via the check valve RV1, which is provided for the prioritized load (PL). Before an under-supply occurs at the prioritized load, the pressure maintenance-type component DW1 moves in the direction of the spring force and increases the volume flow flowing to the prioritized load via the check valve RV2.
In the exemplary embodiment of
In the example of
In the variant of
The circuit of
Number | Date | Country | Kind |
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10 2017 005 479.7 | Jun 2017 | DE | national |
Filing Document | Filing Date | Country | Kind |
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PCT/EP2018/064163 | 5/30/2018 | WO | 00 |