DE102022004376A1 - Supply device - Google Patents

Abstract

Supply device for at least one hydraulic consumer, such as a working cylinder (10), with a fluid supply device (14) which is connected to a supply circuit (16) for the respective hydraulic consumer, with a control device (32) which controls the fluid supply to the respective hydraulic consumer, and with at least one regulating device (18) which regulates the fluid supply to at least one hydraulic consumer, characterized in that the fluid supply device (14) has at least two fluid pumps (40, 41, 43) which are connected with their respective output sides (50, 51, 53) to different inlets (60, 61, 63) of the respective regulating device (18) in such a way that the respective regulating device (18) releases an opening cross-section (70, 71, 73) which can be assigned to each fluid pump (40, 41, 43) to a low-pressure or return connection (68), and that the opening cross-sections (70, 71, 73) are different from each other with regard to a rule specification.

Description

The invention relates to a supply device for at least one hydraulic consumer, such as a working cylinder, with a fluid supply device which is connected to a supply circuit for the respective hydraulic consumer, with a control device which controls the fluid supply to the respective hydraulic consumer, and with at least one regulating device which regulates the fluid supply for at least one hydraulic consumer.

In the state of the art, a wide variety of control devices for hydraulic feed or fluid pumps are known, whereby such pumps are limited by the maximum displacement volume and the maximum possible drive speed, related to the geometric design or with regard to the achievable strength of moving pump elements.

For example, a state of the art according to the 1 a so-called directly controlled power regulator. Here, the volume flow provided is adapted to the required volume flow of the consumer by regulating the volume flow, e.g. via the swivel angle adjustment on the fluid pump. The pressure on the fluid pump is increased by the pressure drop via a metering orifice as part of a control device. The required power of the consumer corresponds to the power on the fluid pump plus a power loss via the aforementioned metering orifice. This well-known system solution is very energy efficient; however, the swivel angle pumps used are very expensive to purchase.

Overall, the known controller forms a so-called load-sensing controller (LS), which adapts the pump delivery or volume flow as well as the pump pressure to the power requirement of the hydraulic consumer, thereby reducing any power losses. The term load-sensing (LS) stands for "load-sensing", whereby the control system basically requires an LS pressure to function, so that a pump pressure that exceeds the actual consumer pressure is required.

2 shows an alternative solution in the state of the art and instead of an LS controller for a swivel angle pump, a circulating pressure compensator is used as a controller. In this system solution, the fluid pump always provides the maximum volume flow. The volume flow not required by the hydraulic consumer is discharged via the circulating pressure compensator to a low-pressure side or to the tank. This means that the power not required is converted into heat and is thus lost inefficiently.

This system solution is very cost-effective in terms of investment costs due to the inexpensive fluid pumps available, especially in the form of at least one fixed displacement pump; however, the operating costs are significantly higher because the consumer regularly demands larger quantities of fluid volumes at higher pressure than are actually consumed.

In the well-known system solution according to the 3 A circulation pressure compensator and a switching valve with two fluid pumps are also used. In this variant, the aim is to save energy by dividing the total volume flow between two feed or fluid pumps, during the control itself and by switching one fluid pump to pressureless circulation. For example, if the consumer is at a predefined, low speed, where less delivery volume is required, one of the two fluid pumps can be switched off completely. In this respect, the third system solution is more energy efficient than the variant according to the 2 and more cost-effective than the variant according to the 1 However, a control system with sensors and electrical control is required and thus the solution according to the 3 , in terms of investment costs, is more expensive than the solution according to the 2 . Switching the valve for pressureless circulation is also much more demanding in terms of control technology, since the pressure compensator as a controller is not firmly coupled to the control of the switching valve.

Through EP 2 399 861 B1 a hydrostatic drive system of a mobile work machine is known, in particular an industrial truck, with a working hydraulic system and a hydraulic fluid pump for supplying the working hydraulic system, wherein the fluid pump is driven by a drive machine, in particular an internal combustion engine, and is designed as a fluid pump with an adjustable delivery volume, wherein a delivery line leading from the variable displacement pump to the working hydraulic system is assigned a pressure compensator, which is designed as an input pressure compensator of the working hydraulic system and is arranged in a return line branching off from the delivery line to a container and is designed as a control valve throttling in the intermediate position with a blocking position and a flow position, wherein the pressure compensator is controlled by the delivery pressure of the fluid pump in the delivery line in the direction of the Flow position and is acted upon by a spring as well as the highest load pressure of the controlled consumers of the working hydraulics in the direction of the blocking position, wherein a heat exchanger device for cooling the pressure medium of the drive system is arranged in the return line, wherein by changing the delivery volume of the variable displacement pump, the pressure medium volume flow flowing through the heat exchanger device is adapted to the cooling power requirement of the drive system.

A variable displacement pump with an adjustable delivery volume is therefore used to supply the working hydraulics, whereby a corresponding change and thus adjustment of the delivery volume of the variable displacement pump allows the pressure medium volume flow in the return line of the pressure compensator through the heat exchanger device to be adapted to the cooling power requirement and thus the required cooling power. Depending on the required cooling power, the delivery volume of the variable displacement pump can be increased or decreased.

Based on this prior art, the invention is based on the object of improving the known solutions, in particular to create a supply device that is as cost-effective as possible and is energy-efficient and stable during operation. This object is achieved by a supply device with the features of patent claim 1 in its entirety.

Because, according to the characterizing part of claim 1, the fluid supply device has at least two fluid pumps, which are connected with their respective output sides to different inputs of the respective control device in such a way that the respective control device releases a variable opening cross-section that can be assigned to each fluid pump to a low-pressure or return connection, and because the opening cross-sections that are set in operation are different from one another in relation to a control specification, on the one hand, in contrast to swivel angle pumps, inexpensive constant pumps such as gear pumps can be used and, on the other hand, no special load-sensing controllers are required, such as directly controlled power controllers. The total power can also be adapted to the power actually required by the respective consumer using structurally simple control and regulation means. In this way, the fluid pumps are connected to a circulation pressure compensator in the form of the control device, with the fluid path of one pump being released as a secondary pump to the low-pressure side or to the tank and the fluid path of the other fluid pump serving as a permanent pump for the fluid supply. Overall, it is a structurally simple, self-regulating and robust supply device solution.

In a preferred embodiment of the supply device according to the invention, it is provided that the control device has a control valve with a control housing and a control piston that can be moved longitudinally therein, and that the control housing has several fluid inlets, each of which can be assigned a fluid pump. In this way, the control device is implemented as part of an overall block valve solution, although it is also possible to divide the overall block into individual functions with individual valves.

In a further particularly preferred embodiment of the supply device according to the invention, it is provided that the individual opening cross-sections of control edges in the control piston and control housing are limited in pairs and that as the distance between the control edges of a pair increases, depending on the respective travel position of the control piston in the control housing in one direction, the associated opening cross-section increases accordingly. In this case, one control edge is predetermined by the housing geometry of the control housing and the adjacent control edge of a pair is predetermined by the geometry of the control piston. In this way, a type of cascading is achieved in a control-technically advantageous manner, in which one opening cross-section is already visibly opened, while in the sequence a subsequent opening cross-section is opened to a lesser extent or is still completely closed. Thanks to the control or regulating edge geometry mentioned, the power supply for the hydraulic consumer is ensured in every case of need.

In a further preferred embodiment of the supply device, it is provided that the control piston is acted upon on its opposite end faces by an energy store, such as a compression spring, and on the other hand by the fluid pressure at the input of the control device. As a result, the control piston is in a balanced basic position within the control housing and can react quickly to changing control pressures on its opposite end faces and carry out the aforementioned cascading with different opening cross sections.

In a further preferred embodiment of the supply device, it is provided that the control piston together with the control housing defines individual fluid spaces, each of which is separated by a Diameter reduction in the control piston is also formed and that when the opening cross sections are closed, the fluid spaces are exclusively connected to the low-pressure or return connection and when the opening cross sections are released, they are also in fluid communication with the fluid supply device. Preferably, it is further provided that each inlet for a fluid pump in the control housing opens into an associated fluid channel, which opens into an associated fluid space when the opening cross sections are released. In this way, the control housing with its control piston can be constructed modularly, so that in addition to the originally intended two constant pumps, three or more constant pumps can also be used as part of the fluid supply device.

The fluid pressure required always corresponds to the load pressure when the respective fluid pump is needed.

Preferably, it is further provided that a fluid channel in the form of a central channel is connected to the respective hydraulic consumer via a fluid connection and that the other fluid channels of the same type open into the central channel counter to the effect of a check valve. By arranging a central channel in the control housing, almost any fluid volumes and fluid pressures originating from constant pumps can be guided decoupled from one another within the control housing, which in turn accommodates the control behavior of the supply device as a whole. Preferably, a branch line opens into the central channel behind the respective check valve, which leads to the other end face of the control piston, which is opposite the end face with the energy storage device.

In a further preferred embodiment of the supply device according to the invention, it is provided that a branch channel opens into the central channel behind the respective check valve, which leads to the other end face of the control piston, which is opposite the end face with the energy storage device and receives the fluid pressure from the control device.

In a further preferred embodiment of the supply device according to the invention, it is provided that an adjustable measuring orifice is connected as part of the control device in a fluid connection to the hydraulic consumer and that a pump line originating from one of the constant pumps opens into this fluid connection between this measuring orifice and the control device.

The supply device according to the invention can be used in a particularly advantageous manner for open hydraulic circuits; but there are also useful applications in the context of closed circuits (not shown).

• 1, 2 und 3 Lösungen im Stand der Technik unter Einsatz einer Schwenkwinkelpumpe, einer Umlaufdruckwaage sowie einer Umlaufdruckwaage mit zwei Schaltventilen; und
• 4 und 5 die wesentlichen Komponenten der erfindungsgemäßen Versorgungsvorrichtung mit drei Konstantpumpen, in einem Ausgangs- bzw. Betriebszustand.

In the following, the supply device according to the invention is explained in more detail using an embodiment according to the drawing. In a basic and not to scale representation in the form of hydraulic circuit diagrams, the

• 1 , 2 and 3 State-of-the-art solutions using a swivel angle pump, a circulating pressure compensator and a circulating pressure compensator with two switching valves; and
• 4 and 5 the essential components of the supply device according to the invention with three fixed pumps, in an initial or operating state.

The 1 shows a supply device in the prior art for at least one hydraulic consumer, here in the form of a conventional working cylinder 10, which is designed as a so-called differential cylinder and is provided with a piston-rod unit 12, which is guided in a cylinder housing 11 in a correspondingly controlled manner so as to be longitudinally movable, wherein according to the illustration according to the 1 the piston-rod unit 12 occupies a middle position in the housing 11. The corresponding structure of working cylinders 10 is usual, so that it will not be discussed in more detail here. The supply device also has a fluid supply device, designated as a whole by 14, which is connected to a supply circuit 16 for the hydraulic consumer shown. Furthermore, there is a control device, designated as a whole by 18, which controls the fluid supply to the respective hydraulic consumer in the form of the working cylinder 10.

The fluid supply device 14 has a swivel angle pump 20 of conventional design, which, during operation, takes fluid from a storage tank 22. The swivel angle pump 20 is driven in the usual way by a motor M, which can also be an electric motor of conventional design. A directly controlled power regulator is used as part of the control device 18 to control the swivel angle pump 20. ler 24. In the housing 25 of the power regulator 24 shown there is at least one adjusting spring 26, which cooperates with an adjusting piston 28 to deflect the swivel angle pump 20. The possible deflection positions of the adjusting piston 28 under the influence of the respective adjusting spring 26 are shown in 1 with a double arrow and at the ends of the arrow representation there is a plus and a minus sign to show the deflection position for an increased volume flow or a reduced volume flow. The volume flow is thus regulated and the power is generated at the consumer or at the working cylinder 10.

The supply circuit 16 has a connecting line 30 between the output of the swivel angle pump 20 and the piston-side inlet of the cylinder housing 11 of the working cylinder 10. A measuring orifice 33, the free cross-section of which is adjustable, is connected to the corresponding connecting line 30 as part of a control device 32, with which the free volume flow in the direction of the working cylinder 10 and thus its travel speed can be specified, in particular when the piston-rod unit 12 is extended. A control line 34 is connected between the measuring orifice 33 and the fluid inlet of the working cylinder 10, the other free end of which opens into the (spring) housing 25 of the power regulator 24 with the respective adjusting spring 26. On the piston-rod side with the adjusting piston 28 of the power regulator 24, a further control line 36 is connected, which opens into the connecting line 30 on the output side of the swivel angle pump 20. Preferably, the solution after the 1 (not shown), as for the 2 shown, a return line 35 to the tank 22, with a further orifice or throttle 48, wherein the return line 35 is connected to the control line 34 and otherwise has no further branch, such as the branch in 2 which leads to the valve 42 in the form of a pressure compensator.

Overall, the known solution according to the 1 a so-called load-sensing regulator, which adapts the pump delivery or volume flow to the power requirement of the hydraulic consumer in the form of the working cylinder 10. Furthermore, the control line 34 has an orifice or throttle 38 with a fixed, free throttle cross-section in the direction of the power regulator 24 to generate a pressure drop.

To better understand the solutions shown in the figures, a fictitious working example is used. The investment costs are to be determined based on the purchase price and the operating costs based on the power P = p(pressure) * Q(volume flow). For the sake of simplicity, it is assumed for the exemplary embodiments that there is only one load that corresponds to a pressure at the consumer or at the working cylinder 10 of 100 bar. Consequently, the power at the consumer is proportional to the volume flow at the consumer. The power of the fluid supply results from the pressure p and the volume flow Q after the respective fluid pump. The variable displacement or swivel angle pump 20 should be able to provide a maximum flow rate of 100 l/min, with around 50 l/min being required on the consumer side at the working cylinder 10. The required power of the consumer 10 then corresponds to the power at the fluid pump 20 plus the power loss via the metering orifice 33. This results in a discharge pressure at the pump 20 of 110 bar, composed of the 100 bar at the consumer 10 and the 10 bar at the metering orifice 33. The volume flow of the fluid pump 20 is Qpump = Qconsumer.

$$\text{P}=5.500\left(\text{Einheiten nicht umgerechnet}\right)\text{; sonst P}\left(\text{kW}\right)=\text{p}\left(\text{bar}\right)\text{*Q}\left(\text{l/min}\right)\text{/600}$$

This leads to an overall view for the engine M as follows $$\text{P}=\text{QPump}\left(50\text{l/min}\right)*\text{p}\left(110\text{bar}\right)$$

$$\text{P}=\mathrm{5,500}\left(\text{Units not converted}\right)\text{; otherwise P}\left(\text{kW}\right)=\text{p}\left(\text{bar}\right)\text{*Q}\left(\text{l/min}\right)\text{/600}$$

Therefore, the solution can be 1 can be considered to be very energy efficient, but the swivel angle pumps 20 used are the most expensive pumps that can currently be used here.

The 2 relates to another known solution in the prior art, whereby the previously described hydraulic components of the same design are given the same reference numerals and the statements made so far also apply to the modified embodiment according to the 2 . In contrast to the well-known solution according to the 1 The supply device indicates the 2 a constant pump 40, for example in the form of a gear pump, which in turn is driven by a motor M, for example in the form of an electric motor.

In the embodiment according to the 2 a circulating pressure compensator 42 is used as a regulator. The two opposing control sides of the circulating pressure compensator 42 are acted upon by the spring force of a compression spring 44 and together with this the pressure acts in the part of the control line 34 which is guided via the further throttle 38. On the opposite side, the control pressure of the constant pump 40 is applied on its output side via a further control line 46. The simplified drawing of the circulating pressure compensator 42 is shown in the 2 shown in its blocked position, in which a fluid connection 31 between the connecting line 30 and a return line 35 is blocked, which opens into the storage tank 22 on the outlet side. Furthermore, a further, third orifice or throttle 48 is connected in the corresponding branch with the return line 35. In the controlled state, the circulating pressure compensator 42 keeps the pressure difference across the measuring orifice 33 constant and when the measuring orifice 33 is completely closed, the pressure compensator 42 is fully open and there is a largely pressure-free circulation of the volume flow conveyed by the pump 40 in the direction of the fluid storage tank 22. In this respect, however, there is always at least a pressure corresponding to the spring force of the compression spring 44 in the system.

With this solution after the 2 the pump 40 always provides the maximum volume flow and the volume flow not required by the consumer 10 is discharged to the tank 22 via the circulation pressure compensator 42. This means that unused power is converted into heat, which is not very energy efficient.

As a working example for the solution according to the 2 A constant flow rate of 100 l/min should be available at the output side of pump 40, with the consumer again requiring 50 l/min.

also $$\text{P}=11.000\left(\text{Einheiten nicht umgerechnet}\right).$$

This results in an output pressure of 1 10 bar for the fluid pump 40, formed from the assumed 100 bar at the consumer and the 10 bar at the metering orifice 33. The volume flow of the pump 40 corresponds to Qpump = Qmax, with an overall consideration for the motor M as follows: $$\text{P}=\text{QPump}\left(100\text{l/min}\right)*\text{p}\left(110\text{bar}\right);\text{so}$$

so $$\text{P}=\mathrm{11,000}\left(\text{Units not converted}\right).$$

The solution after the 2 The investment costs are very low due to the inexpensive fluid pumps 40. However, the operating costs are significantly higher if, as in the case shown, only 50 l/min at 110 bar are required, but 100 l/min are actually consumed at 110 bar.

The 3 shows another solution in the state of the art. Here, too, the same components as described above are shown with the same reference numerals and the statements made so far also apply to the solution according to the 3 The solution is comparable to the 2 constructed, whereby a further, second constant pump 41 is used, which is driven together with the first constant pump 40 by the motor M. On the output side of the further constant pump 41, a switching valve 49 is connected, which is electromagnetically actuated, reset in an initial position by means of a compression spring 45, its 3 shown initial position. The 3/2-way valve is connected to the return line 35, which is connected at one end to the outlet side of the pressure compensator 42 and at its other end opens into the storage tank 22.

In this variant after the 3 An attempt is made to save energy by dividing the total volume flow of 100 l/min between two fluid pumps 40, 41, with each fluid pump 40 or 41 delivering a constant 500 l/min, and by using a control system and the possible switching of one fluid pump 41 into pressure-free circulation using the switching valve 49 in the position shown. If, due to the speed of the consumer or the working cylinder 10, less than the preset delivery volume of 50 l/min is required at the consumer, one pump, in this case the fluid pump 41, can be switched off. If more volume is required at the consumer, the valve 49 is switched and fluid flows from the pump 41 to the consumer via the lines 65 and 30.

At exactly 50 l/min the solution is after the 3 according to the fictitious example as efficient as the solution according to the 1 For all volume flows at the consumer > 50 l/min, the performance is determined according to the solution according to the 2 to P = 11,000. For all volume flows at the consumer < 50 l/min, the output corresponds to the solution according to the 2 , divided by two, giving P = 5500.

Therefore, the solution according to the 3 more energy efficient than the solution according to 2 and more cost-effective than the solution according to 1 However, a control system with sensors and electrical control is required, which is 3 is not reproduced and therefore the solution according to the 3 more expensive in terms of investment costs than the solution according to the 2 . The switching of the valve 49 for the pressureless circulation is also more demanding in terms of control technology, since the pressure compensator 42 as a controller is not firmly coupled to the control of the switching valve 49.

With this in mind, an inventive solution will now be described based on the 4 and 5 which is almost as energy efficient as the solution according to the 3 and almost as cost-effective as the solution according to 2 .

Again, the same hydraulic components as shown above are identified with the same reference numerals in the 1 to 3 reproduced and also in this respect the previous statements then apply to the inventive solution according to the 4 and 5 .

The fluid supply device 14 now has three fluid pumps 40, 41, 43, for example, each with a constant volume flow, on their associated output sides 50, 51, 53. In this respect, too, these are constant pumps, such as gear pumps, which are driven by a common drive, i.e. a motor M. An electric motor should again be used here with particular preference; however, other types of drive are also conceivable, for example drive by a diesel engine.

The respective output sides 50, 51, 53 are connected to various assigned inputs 60, 61, 63 of the control housing 64 of the control device 18 in such a way that a control piston 66 of the said control device 18, which is arranged longitudinally displaceably in the control housing 64, is controlled by a control pressure in front of and behind the metering orifice 33 of the control device 32 and releases an opening cross-section 70, 71, 73, which can be assigned to each fluid pump 40, 41, 43, to a tank or return connection 68, which in the direction of the 4 and 5 seen from the bottom side into the storage tank 22 via a corresponding connecting line. Since the 4 represents an initial state for the supply device, the relevant variable, partially released opening cross-sections 70, 71, 73 during operation of the supply device are only exemplary in the 5 Thus, in the operating position shown after the 5 the first opening cross-section 70 is closed, the further opening cross-section 71 is opened the widest and the third opening cross-section 73 is in a position between the widest opening position 71 and the closed position 70. In this respect, the opening cross-sections 70, 71, 73 which are set during operation are different from one another and in the initial position of the supply device according to the 3 completely closed. The description given here that one opening cross-section is more open than the other is correct if fluid pumps 40, 41, 43 of the same size are used. In fact, however, the design takes different pump sizes into account. In any case, in order to maintain a cascading arrangement, it is necessary that one opening cross-section opens before another.

As can be seen from the 4 and 5 The individual opening cross sections 70, 71, 73 are limited in pairs by circumferential control edges 74 on the control piston 66 and on the control housing 64, whereby in the 4 For the sake of simplicity, only the control edges of the housing 64 are designated 74. As the distance between the corresponding control edges 74 of a pair increases, the corresponding opening cross-section 70, 71, 73 also increases as shown in 5 shown. In the manner of a cascading system, an opening cross-section 70 is thus visibly opened during operation, with a subsequent opening cross-section 73 being opened to a lesser extent and the third opening cross-section 71 still being completely closed. It is understood that as the third opening cross-section 70 opens, the other two opening cross-sections 71, 73 accordingly increase in size in terms of their free cross-section. In order to maintain the individual opening cross-sections 70, 71, 73, the control piston 66 is acted upon on its opposite end faces on the one hand by an energy store, such as at least one compression spring 76, and the fluid pressure at point 96 in front of the inlet 78 of the respective hydraulic consumer and on the other hand at least partially by the fluid pressure of the fluid supply device 14, which will be explained in more detail below. In this respect, a connecting line 80 is guided between the connection point 96 and parts 82 of the control housing 64, which accommodate the respective compression spring 76 as well as parts of the longitudinally displaceable control piston 66.

The control piston 66, together with the control housing 64, at least partially delimits individual fluid chambers 84, which are each formed by a diameter reduction in the control piston 66. The stalt are with closed opening cross-sections 70, 71, 73 the fluid spaces 84 as shown in the 4 connected exclusively to the tank or return connection 68 and with approved opening cross-sections 70, 71, 73 as shown in the 5 additionally with the fluid supply device 14.

As can be seen from the 4 and 5 further, each inlet 60, 61, 63 for a fluid pump 50, 51, 53 in the control housing 64 opens into an associated fluid channel 90, 91, 93, which opens into an adjacent fluid chamber 84 when the opening cross sections 70, 71, 73 are opened accordingly. One of the fluid channels, namely the fluid channel 90, forms a kind of central channel and is, as shown in the 4 and 5 in a vertical orientation in the control housing 64. The other fluid channels 91 and 93 open into the corresponding central channel 90 in an angular or arcuate design and lying one above the other, and at their other free end, like the channel 90, each open into an annular extension 94 in the control housing 64, along which the control piston 66 is guided. At the point where the fluid channels 91, 93 transition into the central channel 90, a spring-loaded check valve 86 is connected, which opens against the spring action as soon as the fluid pressure in the respective fluid channel 91, 93 is higher than the existing fluid pressure in the channel 90, against the spring action. Furthermore, a branch channel 88 leads from the central channel 90 below the two check valves 86 to the free front side of the control piston 66, which is opposite the opposite front side with the respective compression spring 76. Further fluid channels 95 are in fluid communication with the fluid channels 90, 91, 93 when the opening cross sections 70, 71, 73 are released and open out at the bottom into the tank or return connection 68, which is connected to the storage tank 22 in a fluid-carrying manner.

The measuring throttle 33 already introduced is connected between an output-side connection point 96 of the connecting line 80 and an input-side connection point 98 of a connecting line 100 to the first constant pump 50, which leads to the input side 60 of the control housing 64.

The supply device as shown in the illustration according to the 4 and 5 is used in an open circuit system and it is understood that the control housing 64 together with the control piston 66 are only shown in a very basic manner and details such as housing halves and housing end parts are ignored for the sake of better illustration.

The supply device can also be operated with only two constant pumps 50, 51 or 51, 53 and 50, 53, in which case one of the assignable fluid channels 90, 91, 93 can be omitted and it is also possible to control the respective hydraulic consumer with more than three constant pumps of the supply device, in which case more fluid channels and check valves must be provided accordingly.

To make a better comparison to the solution after the 3 In order to be able to produce the same pressure, the solution according to the invention is only compared insofar as two fluid pumps, as already explained, are to be used, which are connected to the circulation pressure compensator in the form of the control device 18 as a whole. The fluid path of one pump, which functions as a secondary pump, is released to the storage tank earlier than the fluid path of the other pump, which serves as a permanent pump. The additional check valve(s) 86 also generate a pressure loss, but this is in the lower range and, according to experience, is between 1 and 3 bar and is therefore to be considered low compared to the 110 bar at the consumer.

For the two pumps used, one fluid pump should have a delivery volume of 50 l/min and the other pump should also have a delivery volume of 50 l/min. For all volume flows at the consumer or at the working cylinder 10 greater than 50 l/min, control takes place via the control edge of the circulation pressure compensator assigned to the permanent pump. A control edge assigned to the secondary pump is adjusted to a larger opening cross-section and is therefore switched to the "pressure-free" circulation. The power requirement is then minimally worse than with the solution according to the 3 with switched valve 49, but significantly better than the solution according to the 2 The smaller the volume flow at the consumer, the more the power at the motor corresponds to the value P= 5500.

For all volume flows at the consumer greater than 50 l/min, the control edge of the circulation pressure compensator assigned to the auxiliary pump then regulates and the control edge assigned to the permanent pump is closed. The power requirement for this operating state then corresponds to the power requirement of the solution according to the 2 and/or the solution after the 3 , with the valve not switched; thus P=11000. The investment costs are, as shown, lower than with the solution according to the 3 , but slightly higher as in the solution after the 2 . Coordination of the two control circuits for the circulation pressure compensator 42 and the switching valve 49 is not necessary.

Independently of the previously described solutions with identical pumps 40, 41, 43 as shown in the 4 and 5 it makes sense to adapt the fluid pumps to typical operating conditions. This applies both to the size of the fluid pumps and to the order in which they are arranged. The respective opening cross-section on the circulation pressure compensator in the form of the control device 18 can also be adapted to the respective pump size. A large pump is described with G, a medium pump with M and a small pump with K, with the following combinations: GMK; MKG; KMG; KGM etc. With a supply device, as in the 4 and 5 described, can be comparable to the solutions in the state of the art according to the 1 to 3 If necessary, the hydraulic pump output of at least two fluid pumps for a hydraulic consumer can be kept constant by means of the circulating pressure compensator in the form of the control device 18, whereby power losses during pump operation are avoided, as is a delayed control behavior for the hydraulic consumer, even when it is subjected to a load. It is understood that the hydraulic consumer does not only have to consist of a single working cylinder 10, but that several actuators, including in the form of hydraulic motors, can form the hydraulic consumer.

QUOTES INCLUDED IN THE DESCRIPTION

This list of documents listed by the applicant was generated automatically and is included solely for the better information of the reader. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions.

Cited patent literature

• EP 2399861 B1 [0008]

Claims (11)

Supply device for at least one hydraulic consumer, such as a working cylinder (10), with a fluid supply device (14) which is connected to a supply circuit (16) for the respective hydraulic consumer, with a control device (32) which controls the fluid supply to the respective hydraulic consumer, and with at least one regulating device (18) which regulates the fluid supply for at least one hydraulic consumer, characterized in that the fluid supply device (14) has at least two fluid pumps (40, 41, 43) which are connected with their respective output sides (50, 51, 53) to different inputs (60, 61, 63) of the respective regulating device (18) in such a way that the respective regulating device (18) releases a variable opening cross-section (70, 71, 73) which can be assigned to each fluid pump (40, 41, 43) to a low-pressure or return connection (68), and that the opening cross-sections which are set in operation (70, 71, 73) are different from each other with respect to a control specification. Supply device according to Claim 1 , characterized in that the control device (18) has a control valve with a control housing (64) and a control piston (66) which can be moved longitudinally therein, and that the control housing (64) has a plurality of fluid inlets (60, 61, 65), each of which can be assigned a fluid pump (40, 41, 43). Supply device according to Claim 1 or 2 , characterized in that the individual opening cross-sections (70, 71, 73) of control edges (74) in the control piston (66) and control housing (64) are delimited in pairs and that with increasing the distance between the control edges (74) of a pair, depending on the respective travel position of the control piston (66) in the control housing (64) in one direction, the associated opening cross-section (70, 71, 73) increases accordingly. Supply device according to one of the preceding claims, characterized in that, in the manner of a cascading, an opening cross-section (71) is already visibly opened and an opening cross-section (73) following in the sequence is, in contrast, opened to a lesser extent or still completely closed (70). Supply device according to one of the preceding claims, characterized in that the control piston (66) is acted upon on its opposite end faces on the one hand by an energy store, such as a compression spring (76), and on the other hand by the fluid pressure at the inlet or outlet of the control device (32). Supply device according to one of the preceding claims, characterized in that the control piston (66) together with the control housing (66) delimits individual fluid spaces (84), which are each formed by a diameter reduction in the control piston (66), and that when the opening cross sections (70, 71, 73) are closed, the fluid spaces (84) are exclusively connected to the low-pressure or return connection (68) and when the opening cross sections (70, 71, 73) are released, they are additionally in fluid connection with the fluid supply device (14). Supply device according to one of the preceding claims, characterized in that each inlet (60, 61, 63) for a fluid pump (40, 41, 43) in the control housing (64) opens into an associated fluid channel (90, 91, 93) which opens into an associated fluid chamber (84) when the opening cross sections (70, 71, 73) are released. Supply device according to one of the preceding claims, characterized in that when the opening cross sections (70, 71, 73) are released, the respective fluid channel (90, 91, 93) opens via the assignable fluid space (84) into an adjacent further fluid channel (95) which leads to the low-pressure or return connection (68). Supply device according to one of the preceding claims, characterized in that a fluid channel (90) in the manner of a central channel is connected to the respective hydraulic consumer via a fluid connection and that the respective further fluid channels (91, 93) of the same type open into the central channel (90) counter to the action of a check valve (86). Supply device according to one of the preceding claims, characterized in that behind the respective check valve (86) a branch channel (88) opens into the central channel (90), which to the other end face of the control piston (66), which is opposite the end face with the energy storage device and receives the fluid pressure from the control device (32). Supply device according to one of the preceding claims, characterized in that an adjustable measuring throttle (33) as part of the control device (32) is connected into a fluid connection (16) to the hydraulic representative and that a pump line (100) originating from one of the constant pumps (40) opens into this fluid connection between this measuring throttle (33) and the control device (18).

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