Flexible pump assembly for use in fan drive

Abstract

The invention relates to a pump assembly, the displacement of which can be continuously adjusted by means of a dual-acting control cylinder having a first and a second control chamber, each of which is assigned a first or a second receiving bore. According to the invention, a pressure regulating valve in the form of a built-in valve is mounted in one of the first or second receiving bores, a 3 / 2 passage switching valve in the form of a built-in valve is mounted in the other second or first receiving bore, the pressure regulating valve and the 3 / 2 passage switching valve are each electrically adjustable, and each of the pressure regulating valve and the 3 / 2 passage switching valve is connected to a control device. Wherein a nominal delivery pressure difference can be specified for the control device, and wherein the control device is configured in such a way that the control device adjusts the displacement by actuating the pressure regulating valve and the 3 / 2 passage switching valve in such a way that the difference between the first and second actual pressures approaches the nominal delivery pressure difference.

Description

Technical Field

[0001] The invention relates to a pump assembly according to the preamble of claim 1. Background Art

[0002] The data sheet "Axial Piston Variable-Control Pump A4VG Series 35" (order number RD92035; edition 12 February 2020) of Bosch Rexroth AG discloses a pump assembly in the form of an axial piston machine in a swash plate design, the displacement of which can be adjusted across a zero position by means of a double-acting control cylinder, so that the delivery direction can be reversed simply by adjusting the swivel cradle while the drive rotation direction remains the same. In the ET control, the two control chambers of the control cylinder are each connected to a pressure regulating valve in the form of a pressure reducing valve. In the event of a failure of the electric control, it is not possible to clearly determine which displacement is present or to set the zero displacement.

[0003] This behavior is undesirable for hydraulic fan drives, where the fan should normally rotate at maximum speed in the event of a failure of the electric control (fail-safe behavior).

[0004] DE 102010020528 A1 describes a fan drive having a closed hydraulic circuit which essentially comprises the axial piston machine described above. The regulating cylinder is here controlled by a pressure regulating valve in the form of a pressure reducing valve with an increasing or positive characteristic curve and by a 4 / 2-way switching valve, wherein the two regulating valves can be electrically adjusted separately. The switching is designed so that in the event of a failure of the electrical control, the axial piston machine automatically sets the maximum displacement in terms of value, so that the two fan impellers rotate as quickly as possible.

[0005] Furthermore, the switching is designed so that the current at the pressure regulating valve does not need to be adjusted in a step-like manner at the zero crossing of the regulating pressure difference. At the zero crossing, the corresponding regulating current drops to zero and then rises again, wherein only the 4 / 2-way switching valve is switched in a step-like manner.

[0006] The disadvantage of this control is that a special valve block is required for the regulating valve, which is specially matched to the fan drive. If other behaviors are desired instead of the above-mentioned failsafe behavior, the valve block must be changed. Summary of the invention

[0007] The invention has the advantage that the known axial piston machine can be implemented only with control valves available from the catalog, so that the above-mentioned failsafe behavior is achieved. At the same time, a large number of drive variants can be realized by suitable selection of the control direction and the installation location of the two control valves, without requiring a special mechanical design compared to the known catalog components. Only the program of the control device or its variable control variable must be adapted to the selected control valve arrangement.

[0008] According to claim 1, it is proposed that a pressure regulating valve in the form of an integrated valve is installed in one, the first or the second receiving hole, wherein a 3 / 2-way switching valve in the form of an integrated valve is installed in the other, the second or the first receiving hole, wherein the pressure regulating valve and the 3 / 2-way switching valve are each electrically adjustable, wherein they are each connected to a control device, wherein a setpoint delivery pressure difference can be predefined for the control device, wherein the control device is set up in such a way that it adjusts the displacement by controlling the pressure regulating valve and the 3 / 2-way switching valve in such a way that the difference formed by the first and the second actual pressure approaches the setpoint delivery pressure difference.

[0009] The pump assembly is preferably operated with a pressure fluid, which is preferably a liquid and in particular a hydraulic oil at most. The pump assembly preferably comprises an axial piston machine of a swash plate structure, wherein the swing cradle can swing around the swing axis by means of an adjusting cylinder, wherein the swing cradle is coupled to the adjusting piston movement of the adjusting cylinder, wherein the adjusting piston defines the first and second adjusting chambers. The swing axis preferably intersects the rotation axis of the drive shaft at a right angle. The two control kidney-shaped parts of the axial piston machine are preferably mirror-symmetrical to each other and mirror-symmetrical to the plane containing the rotation axis and the swing axis. The surfaces of the first and second adjusting chambers that act in hydraulic terms are preferably the same size. At least one hydraulic motor is preferably in a drive connection with the assigned fan impeller, preferably in a direct drive connection at most. The first and second receiving holes can be provided with internal threads respectively, and the pressure regulating valve or the 3 / 2-way switching valve can be screwed into the internal threads, wherein the two internal threads are particularly identical in terms of thread diameter and pitch. The pressure regulating valve and / or the 3 / 2-way switching valve can preferably be electrically adjusted by means of an actuating magnet. The pressure regulating valve is preferably configured as a pressure reducing valve. The first and / or second receiving opening is preferably each arranged on a housing of the pump component.

[0010] Advantageous developments and refinements of the invention are described in the dependent claims.

[0011] It can be provided that in the control device it can be set in which of the two receiving openings, namely the first and the second receiving opening, the pressure regulating valve or the 3 / 2-way switching valve is to be installed, wherein the control device is set up in such a way that this setting is taken into account when actuating the pressure regulating valve and when actuating the 3 / 2-way switching valve. The aforementioned consideration is preferably carried out within the scope of the case differentiation and within the scope of the calculation of the various cases, namely the zero case, the positive case and the negative case. The consideration is preferably carried out only there at most. This is possible because in reference to Figure 2 and 3 In the calculation sequence described, a setpoint control differential pressure is used as an intermediate value, wherein the setpoint control differential pressure is independent of the adjustable configuration of the control valve.

[0012] A rotation speed sensor can be provided, with which the actual rotation speed of the drive shaft can be measured, wherein the control device is set up such that when the pressure regulating valve is actuated and when the 3 / 2-way switching valve is actuated, only the actual rotation speed and the first and second actual pressures are taken into account as actual values ​​measured in continuous operation. This particularly cost-effective sensor arrangement is possible in particular because a setpoint delivery pressure difference is predefined as a command variable for the control device.

[0013] It can be provided that the control device implements a pilot control, with which the regulation is superimposed. As a result, the pump assembly reacts quickly to changes in the setpoint delivery pressure difference, while the setpoint delivery pressure difference is still achieved very accurately.

[0014] It can be provided that it can be set in the control device whether the pressure regulating valve actually used has a rising characteristic curve or a falling characteristic curve, wherein the control device is set up in such a way that this setting is taken into account when actuating the pressure regulating valve. For a rising characteristic curve or a positive characteristic curve, the pressure at the outlet of the pressure regulating valve rises approximately proportionally to the current in the actuating magnet. For a falling characteristic curve or a negative characteristic curve, the relationship is approximately inversely proportional. The mentioned considerations are preferably carried out within the scope of an inverse model of the pressure regulating valve, wherein the considerations are preferably carried out only there at most. The inverse model of the pressure regulating valve is preferably selected as a function of the mentioned regulation. This is possible because in reference to Figure 2 and 3 In the calculation sequence described, the first and second control pressures are used as intermediate values, wherein these intermediate values ​​are independent of the characteristic curve of the pressure control valve.

[0015] It can be provided that the 3 / 2-way switching valve is preloaded into a first position by means of a return spring, wherein the 3 / 2-way switching valve can be switched into a second position by means of an assigned operating magnet, wherein the relevant first or second regulating chamber can be optionally connected either to a control inlet fluid or to a control return fluid by switching the 3 / 2-way switching valve, wherein it can be set in the control device whether the 3 / 2-way switching valve actually used establishes a fluid connection between the assigned regulating chamber, that is, the first or second regulating chamber and the control inlet or the control return in the first position, wherein the control device is set up in such a way that this setting is taken into account when actuating the 3 / 2-way switching valve. The mentioned considerations are preferably carried out within the scope of an inverse model of the 3 / 2-way switching valve, wherein the considerations are preferably carried out only there at most. The inverse model of the 3 / 2-way switching valve is preferably selected depending on the mentioned settings. This is possible because in reference to Figure 2 and 3 In the calculation sequence described, the first and second actuating pressures are used as intermediate values, wherein the intermediate value is independent of the switching function of the 3 / 2-way switching valve.

[0016] It can be provided that the pressure regulating valve has a rising characteristic curve, wherein the 3 / 2-way switching valve establishes a connection to the control inlet in a first position. This is a possibility for implementing the failsafe behavior of the fan drive explained at the outset.

[0017] It can be provided that the pressure regulating valve has a falling characteristic curve, wherein the 3 / 2-way switching valve establishes a connection to the control return in a first position. This is another possibility for implementing the failsafe behavior of the fan drive explained at the outset.

[0018] A feed pump can be provided, which is in drive connection with the drive shaft, wherein the feed pump is fluidically connected to the control inlet on the outlet side, wherein a feed pressure limiting valve is provided, by means of which the pressure in the control inlet can be adjusted, wherein the control device is set up so that the adjustment of the feed pressure limiting valve is taken into account when the pressure regulating valve is actuated and when the 3 / 2-way switching valve is actuated. The feed pressure limiting valve can be fixedly adjusted, for example, with a locked adjusting screw, wherein this adjustment in the form of an adjustable parameter is taken into account in the control device. The feed pressure limiting valve can be electrically adjusted by means of an actuating magnet, wherein the feed pressure limiting valve is connected to the control device, wherein the control device takes into account the actual electrical adjustment of the feed pressure limiting valve. The aforementioned consideration is preferably carried out within the scope of an inverse model of the pressure regulating valve and within the scope of an inverse model of the 3 / 2-way switching valve, wherein the consideration is preferably carried out only there at most.

[0019] It can be provided that the first and / or second regulating chamber is permanently fluidically connected to the assigned first or second receiving opening via the respectively assigned first or second throttle valve. The speed for adjusting the displacement can be reliably limited upwards by the first and second throttle valves in order to protect the hydraulic motor and the fan from damage. The first and / or second throttle valves preferably each have a fixed flow resistance. The throttle valves are preferably designed in the form of separate inserts, which can be fixed, in particular screwed, into a fluid channel in the housing of the pump assembly.

[0020] It can be provided that the displacement can be adjusted continuously in such a way that the direction of the fluid flow between the first and second working connection can be reversed only by adjusting the adjusting cylinder while the direction of rotation of the drive shaft remains the same. The pump assembly according to the data sheet mentioned at the beginning has this operating behavior. Within the scope of the invention, this operating behavior can be used to reverse the delivery direction in the de-energized state by exchanging the pressure regulating valve with the 3 / 2-way switching valve, wherein the assigned regulation is set accordingly in the control device.

[0021] It goes without saying that the features mentioned above and still to be explained below can be used not only in the respectively specified combination but also in other combinations or alone, without departing from the scope of the present invention. BRIEF DESCRIPTION OF THE DRAWINGS

[0022] The present invention is described in detail below with the aid of the accompanying drawings.

[0023] Figure 1 A hydraulic circuit diagram of a pump assembly according to the present invention is shown;

[0024] Figure 2 A part of a control diagram for implementing the method according to the invention is shown;

[0025] Figure 3 Shows Figure 2 Another part of the regulation chart in;

[0026] Figure 4 A diagram illustrating an inverse model of a pressure regulating valve is shown;

[0027] Figure 5 A pump assembly according to the invention is shown according to a second embodiment. Figure 1 The corresponding hydraulic circuit diagram; and

[0028] Figure 6 A sectional view of the pressure regulating valve is shown together with the associated receiving opening. DETAILED DESCRIPTION

[0029] Figure 1The hydraulic circuit diagram of the pump assembly 10 according to the invention is shown. The pump assembly 10 comprises a main pump 18 and a feed pump 13, which are driven by a common drive shaft 19. The actual rotational speed n of the drive shaft 19 can be measured by means of a rotational speed sensor 70, which is preferably fixedly attached to the pump assembly 10.

[0030] The main pump 18 is designed as an axial piston, wherein its displacement can preferably be continuously adjusted by means of a pivotable swivel cradle. The swivel cradle is coupled to the control piston movement of a dual-acting control cylinder 20. The control cylinder 20 has a first and a second control chamber 21, 22, wherein the pressures therein (whose values ​​correspond to Figure 3 The first regulating chamber 21 is directly fluidically connected to a pressure regulating valve 30, which is preferably designed as a pressure reducing valve, wherein the pressure regulating valve can be electrically adjusted by means of an actuating magnet 31. The second regulating chamber 22 is directly fluidically connected to a 3 / 2-way switching valve 32, which can be electrically adjusted by means of an actuating magnet 33, wherein the actuating magnet is preloaded by means of a return spring 34 into a position in which the control inlet 15 is connected (so-called open position). The pressure regulating valve 30 and / or the 3 / 2-way switching valve 32+ are preferably respectively actuated by means of a pulse width modulated voltage, the duty cycle of which is selected so that, on average, a current is generated, the value of which corresponds to i_DRE or i3 / 2. For this purpose, preferably a digitally implemented current control loop is always used, which is preferably calculated by the control device 80 at most.

[0031] The pressure regulating valve 30 has a positive or rising characteristic curve, so that in its non-energized state, the low pressure in the control return port 16 exists in the first regulating chamber 21. The 3 / 2-way switching valve 32 is open when it is not energized, so that in its non-energized state, the high pressure in the control inlet 15 exists in the second regulating chamber 22. The current main pump 18 can be adjusted across the zero displacement. Correspondingly, in the non-energized state, as long as the drive shaft 19 rotates, the maximum displacement is set in numerical terms. The corresponding rotation direction is designed in this way so that the fan impeller 41 rotates according to the desired cooling air delivery direction. This behavior is welcome in most cases of fan drives in order to produce sufficient cooling of the internal combustion engine to be cooled even when the electric control fails.

[0032] The feed pump 13 can be designed as a vane pump, for example. It draws in pressure fluid from the tank 17 and delivers it on the one hand to the control inlet 15 and on the other hand via the feed valve 23 into the closed hydraulic circuit. Figure 1In FIG. 1 , all tank symbols 17 denote the same tank. The pressure fluid is preferably a liquid and at most preferably a hydraulic oil. The outlet of the feed pump 13 is connected to a feed pressure limiting valve 14. The delivery flow of the feed pump 13 is so great during the main operating time of the pump assembly 10 that the feed pressure limiting valve 14 is triggered, so that the pressure in the control flow inlet 15 is defined by adjusting the feed pressure limiting valve 14. The feed pressure limiting valve 14 is fixedly adjusted here, wherein an electrically adjustable feed pressure limiting valve (see Figure 5 ).

[0033] The first and second working interfaces 11; 12 of the main pump 18 or the pump assembly 10 are fluidically connected to the hydraulic motor 40 in the sense of a closed hydraulic circuit. The hydraulic motor 40 directly drives the fan impeller 41, which cools the cooling circuit of the internal combustion engine of a larger vehicle, especially a mobile working machine. The present invention is mainly configured for this application, wherein it can of course also be used for other applications. The rated delivery pressure difference explained below can be used as a regulating variable in a superimposed control loop (using this control loop to adjust the speed of the fan impeller 41). Here, it should preferably only use the first and second pressure sensors 71, 72 and the speed sensor 70, wherein other sensors are not mandatory. It goes without saying that, for example, a swivel angle sensor on the main pump 18 or another speed sensor on the hydraulic motor 40 can be used optionally to improve the operating behavior of the overall system.

[0034] A first actual pressure p_A at the first working port 11 can be measured by the first pressure sensor 71 , and a second actual pressure p_B at the second working port 12 can be measured by the second pressure sensor 72 .

[0035] Two feed valves 23 should be mentioned, via which pressure fluid can be conveyed from the feed pump 13 into the closed hydraulic circuit in order to compensate for leakages. It is conceivable to equip the pump assembly 10 with flushing valves, with which pressure fluid can be removed in a targeted manner from the closed hydraulic circuit over the aforementioned leakages, so that the pressure fluid there does not overheat. However, this risk is less in current fan drives.

[0036] The pump assembly 10 comprises a control device 80, which preferably comprises a programmable digital computer, in particular a microprocessor and / or an FPGA. On the inlet side, the first and second pressure sensors 71, 72 and the rotational speed sensor 70 are connected to the control device 80, so that the first and second actual pressures p_A, p_B and the actual rotational speed n are available for the calculation of the first and second regulating currents i_DRE, i_3 / 2 in the control device 80. On the outlet side, the operating magnets 31, 33 of the pressure regulating valve 30 and the 3 / 2-way switching valve 32 are connected to the control device 80.

[0037] In addition, it should be noted that the first and second throttle valves 83 and 84 are connected between the first or second regulating chamber 21, 22 and the assigned regulating valve 30 and 32. The first and second throttle valves 83 and 84 can reliably limit the speed for regulating the displacement upwards to protect the hydraulic motor 40 and the fan 41 from damage.

[0038] Figure 2 A part of a control diagram for implementing the method according to the invention is shown. Figure 2 The parts shown in the figure can be subjected to significant changes without departing from the scope of the invention. For example, only a precontrol with a trajectory planning filter 50 and an inverse model 51 of the pump assembly can be used. It is also conceivable to use only the regulator 52. In any case, an operational overall system is produced, in which Figure 2 The most expensive variant with the best operating characteristics is shown.

[0039] A setpoint delivery pressure difference dp_soll is externally predetermined for the pump assembly, wherein a difference from a first or second actual pressure p_A, p_B measured by means of the first and second pressure sensor is to be adjusted to the setpoint delivery pressure difference dp_soll.

[0040] In order to make this regulation as fast as possible, a precontrol is first provided, which is based on an inverse model 51 of the pump assembly. The following mathematical formula is described in the specification of DE 102019210003 A1, with which the behavior of a pump assembly in the form of an axial piston machine can be modeled. DE 102021200693 A1 describes a method with which a mathematical model of an axial piston machine can be determined empirically. All these models have in common that, in the case of a time profile of a delivery pressure difference that can actually be regulated and used as an input variable in a real pump assembly, the models only provide results that are then available when reversed.

[0041] However, the set delivery pressure difference dp_soll can have a step-like change that cannot occur in the actual delivery pressure difference, because this actual delivery pressure difference can only change continuously. Therefore, before the set delivery pressure difference dp_soll is delivered to the inverse model 51 of the pump component, it is first delivered to the trajectory planning filter 50. The trajectory planning filter 50 is a low-pass filter with a fixed limit frequency in the simplest case. As a result, the mentioned steps can be eliminated in a simple manner. However, it is preferred to use the trajectory planning filter 50 disclosed in DE 102019210003 A1, with which the power capacity of the pump component can be utilized as best as possible, so as to achieve a particularly fast approach to the set delivery pressure difference dp_soll within the scope of the pre-control.

[0042] In addition to the modified setpoint delivery pressure difference, the measured values ​​of the sensor, that is, the actual rotational speed n of the drive shaft and the first and second actual pressures p_A, p_B, are also supplied to the inverse model 51 of the pump assembly to calculate the model 51. As a result, the inverse model 51 of the pump assembly provides a setpoint control pressure difference dpX_setpoint, which must be set theoretically, in order to achieve a quicker approach of the actual delivery pressure difference to the target delivery pressure difference dp_setpoint. It goes without saying that this theoretical value does not perfectly correspond to the actual situation. Therefore, the control 50 is superimposed on the precontrol.

[0043] The manipulated variable of the regulator 52 is here a further setpoint differential pressure which is additively superimposed 54 on the pilot-controlled setpoint differential pressure to obtain dpX_setpoint. It is conceivable to use the manipulated variable of the regulator 52 at a suitable point in the inverse model 51 of the pump assembly to improve the control behavior.

[0044] On the inlet side of the regulator 52, the actual delivery pressure difference is first calculated 55 as the difference 53 formed by the first and second actual pressures p_A, P_B. The control deviation is generated from the difference 53 formed by the setpoint delivery pressure difference dp_setpoint and the actual delivery pressure difference. The control deviation is supplied to the regulator 52, which is preferably designed as a continuous linear regulator, in particular as a PID regulator. The regulator 52 is preferably calculated in a time-discrete manner.

[0045] Figure 3 Shows Figure 2 Another part of the adjustment chart in . Figure 2 and 3 The interface forms the setpoint regulating pressure difference dpX_soll.

[0046] In the scope of the invention, control valves are used in particular, namely pressure regulating valves and 3 / 2-way switching valves. This selection has significant advantages for fan drives, since different fan variants common on the market can be realized with the same components. In particular, it is possible to freely select on which side of the control cylinder the pressure regulating valve should be arranged, with the 3 / 2-way switching valve being arranged on the other side. This advantage is exchanged for the disadvantage that the control behavior of the control valve has a significant discontinuity for a set regulating pressure difference dpX_set equal to zero, which relates to the two control valves. Therefore, the current control valve cannot be used with conventional purely hydraulic control devices, even if the control valve can be hydraulically actuated.

[0047] The aforementioned discontinuity is taken into account by distinguishing between three cases, namely a zero case 60, a positive case 61 and a negative case 62. In the zero case 60, the setpoint differential pressure dpX_setpoint is essentially zero, wherein the case should also be detected in which, due to position inaccuracies, it cannot be reliably determined whether the actual setpoint differential pressure is positive or negative.

[0048] In the positive case 61, the setpoint control pressure difference dpX_setpoint is positive, wherein there is no zero case 60. In the positive case 61, the second control chamber is connected to the control return via the 3 / 2-way switching valve, so that essentially zero pressure exists in the second control chamber. Figure 1 For the pressure regulating valve shown in FIG. 1 , which has a positive characteristic curve, the current i_DRE increases approximately proportionally to the desired setpoint regulating pressure dpX_set. The corresponding relationship is Figure 4 Shown in.

[0049] In the negative case 62, the setpoint differential pressure dpX_setpoint is negative, wherein there is no zero case. In this case, the second control chamber is connected to the control inlet via the 3 / 2-way switching valve, so that a high pressure prevails in the second control chamber, wherein this pressure simultaneously defines the maximum pressure that can be set with the pressure regulating valve. Figure 1 For the pressure regulating valve shown in FIG. 1 , which has a rising characteristic curve, the current i_DRE decreases approximately inversely proportionally to the value of the desired setpoint control pressure difference dpX_setpoint.

[0050] In the zero condition 60, the two zero adjustments of the control valve (at Figure 1 Either the two control chambers can be connected to the control flow inlet, or the two control chambers (in Figure 1In the figure, the reference numerals 21, 22) can be connected to the control return port. In both cases of zero regulation, an effective zero pressure acts on the regulating piston. Theoretically, the pressure regulating valve should not be adjusted to an intermediate value. However, this is unavoidable in practice, especially when there is a changeover from the positive situation 61 to the negative situation 62 or vice versa (zero crossing). This problem is addressed in that the corresponding changeover is only carried out when it is actually necessary, and the changeover is then carried out particularly quickly.

[0051] For this purpose, all four conceivable cases of the first and second control pressures p_DRE, p_3 / 2 are preferably calculated continuously and quasi-simultaneously or provided as a constant in the case of zero control, wherein it is only determined within the scope of the case distinction 63 which of the four cases is used for actuating the control valve (in Figure 1 30; 32).

[0052] If there is clearly a positive or negative case 61, 62, then this case distinction 63 is simple. It becomes difficult if a zero crossing occurs. It is conceivable here that the setpoint control pressure difference dpX_set should be set in a step-like manner across zero. In this subcase, a simple case distinction between positive and negative cases 61; 62 already leads to the desired result, wherein the discontinuity caused by the control system does not interfere with the discontinuous adjustment of the setpoint control pressure difference dpX_set.

[0053] If a zero crossing occurs within the scope of a continuous control of the setpoint differential pressure dpX_set, it is possible to predict when the theoretical zero crossing will occur by observing the derivative of the setpoint differential pressure over time. A zero control is then set for a short period of time before the theoretical zero crossing, which does not require a step-like adjustment of the control valve. The setpoint differential pressure dpX_set continues to be observed during the zero situation 60. If the zero situation 60 is clearly left in the sense of a zero crossing, another zero control is set in a step-like manner.

[0054] The inverse model 64 of the pressure regulating valve is used to determine the first regulating current i_DRE required to set the desired pressure. Figure 4 , which is simply the valve characteristic curve. However, it is also conceivable to use a dynamic model that takes into account how quickly the pressure regulating valve reacts to changes in the first regulating current i_DRE. Due to the particularly fast regulation expected in the zero case 60, a dynamic inverse model 64 is advantageous.

[0055] The second regulating current i_3 / 2 required for setting the desired pressure is determined by the inverse model 65 of the 3 / 2-way switching valve. Due to the basic switching characteristics, only two cases can be distinguished here in principle. In one case, i_3 / 2 is equal to zero. In the other case, i_3 / 2 is as large as possible, without the possibility of a corresponding actuating magnet (in Figure 1 Overheating of the 3 / 2-way switching valve (reference numeral 33 in the figure). It is conceivable to set a second control current i_3 / 2 that is greater during the switching time period than in the subsequent time period, in which the 3 / 2-way switching valve is only supposed to maintain its position. This allows, on the one hand, a fast switching to be achieved, while on the other hand, the current consumption and the risk of overheating are minimized.

[0056] Figure 4 A diagram is shown which illustrates an inverse model of a pressure regulating valve. This is a static model in the form of a valve characteristic curve. The (average) current in the actuating magnet is plotted on the horizontal axis, the pressure at the outlet of the pressure regulating valve being plotted on the vertical axis. The pressure regulating valve is preferably designed in such a way that it has at least a monotonic characteristic curve. This ensures the unambiguous reversibility of the model. If a first regulating pressure p_DRE is predetermined, there is only one possible first regulating current i_DRE which is to be set for this purpose.

[0057] The current characteristic curve is approximately linear. Within the scope of the preferred digital control, the current approximation quality is adequate without any problems, since the remaining nonlinearities are compensated by the inverse model without having to worry about technical disadvantages.

[0058] Figure 5 A pump assembly 10 ′ according to the invention is shown according to a second embodiment. Figure 1 The second embodiment is the same as the one described below except for the differences described below. Figures 1 to 3 The first embodiment of the present invention is identically configured, so that in this respect reference is made to the Figures 1 to 3 explanation.

[0059] In a second embodiment, a pressure regulating valve 30 is assigned to the second regulating chamber 22, wherein a 3 / 2-way switching valve 32 is assigned to the first regulating chamber 21. In addition, a pressure regulating valve 30 with a falling characteristic curve is used. In the de-energized state, the pressure regulating valve connects the pressure in the control inlet 15 to the second regulating chamber 22. In order to achieve the desired fail-safe behavior, the 3 / 2-way switching valve 31 is designed so that in the de-energized state it connects the first regulating chamber 21 to the control return 16. In the de-energized state, the first and second embodiments are identical in terms of the flow direction between the first and second working connections 11; 12, since in both cases the second regulating chamber 22 conducts a higher pressure.

[0060] If the flow direction between the first and second working interfaces 11; 12 is to be reversed in the de-energized state, not only Figure 1 In and Figure 5 In each case, both regulating valves 30; 32 must be interchanged, wherein the regulation should be adjusted accordingly in the control device 80. It is utilized here that the delivery direction of the pump assembly can only be reversed by adjusting the displacement.

[0061] In a second embodiment, the feed pressure limiting valve 14 can be electrically adjusted by means of a pilot valve 85. The pilot valve 85 is designed in the present case as an electrically adjustable pressure reducing valve, wherein its output pressure acts on the spring counterpart of the feed pressure limiting valve 14. As a result, when the pressure at the outlet of the pilot valve 85 increases, the triggering pressure of the feed pressure limiting valve 14 decreases. The pilot valve 85 is connected to the control device 80 on the outlet side, wherein the corresponding third regulating current i_speise or the assigned feed pressure is taken into account when actuating the pressure regulating valve 30 and the 3 / 2-way switching valve 32.

[0062] Figure 6 A sectional view of a pressure regulating valve 30 with the assigned first or second receiving opening 81; 82 is shown. The pressure regulating valve 30 is a pressure reducing valve known from the data sheet “Proportional pressure reducing valve, directly controlled, rising characteristic curve FTDRE 4K” (order number RD58038; edition 2.02.22) of Bosch Rexroth AG, which can be used within the scope of the present invention, wherein other types can also be used. This data sheet also indicates the assigned first or second receiving opening 81; 82 with all the dimensions required for production. A 3 / 2-way switching valve is also available for this receiving opening.

[0063] The pressure regulating valve 30 comprises an actuating magnet 31 which can act upon a control slide 86 of the pressure regulating valve 30 with an electrically adjustable magnetic force. A valve section 87 of the pressure regulating valve 30 is fixed in the associated first or second receiving opening 81; 82, wherein the valve section is screwed 88 therein.

[0064] The first or second throttle valve 83 ; 84 is preferably each designed in the form of a separate insert which is fixedly mounted, in particular screwed, on the bottom of the first or second receiving opening 81 ; 82 .

[0065] Finally, reference is made to a parallel patent application of the present patent applicant having the same priority date, which relates to further details of the pump assembly according to the invention.

[0066] List of reference numerals:

[0067] 10 Pump assembly (first embodiment)

[0068] 10' Pump assembly (second embodiment)

[0069] 11 First working interface

[0070] 12 Second working interface

[0071] 13 Feed pump

[0072] 14 Feed pressure limiting valve

[0073] 15 Control flow inlet

[0074] 16 Control reflux port

[0075] 17 Tanks

[0076] 18 Main pump

[0077] 19 Drive shaft

[0078] 20 Adjustment cylinder

[0079] 21. First conditioning room

[0080] 22 Second Conditioning Room

[0081] 23 Feed valve

[0082] 30 Pressure regulating valve

[0083] 31. Pressure regulating valve operating magnet

[0084] 32 3 / 2 way switching valve

[0085] 33 Actuating magnet for 3 / 2-way switching valve

[0086] 34 Return spring

[0087] 35 First Position

[0088] 36 Second position

[0089] 40 Hydraulic motor

[0090] 41 Fan impeller

[0091] 50 Trajectory Planning Filter

[0092] 51 Inverse model of axial piston machine

[0093] 52 Regulator

[0094] 53 Rated and actual value comparison

[0095] 54 Superposition of pre-control and regulation

[0096] 55 Determination of actual delivery pressure difference

[0097] 60 Zero Case

[0098] 61 Positive situation

[0099] 62 Negative situation

[0100] 63 Situation Distinction

[0101] 64 Inverse Model of Pressure Regulating Valve

[0102] 65 Inverse Model of 3 / 2-Way Switching Valve

[0103] 70 Speed ​​sensor

[0104] 71 First pressure sensor

[0105] 72 Second pressure sensor

[0106] 80 Control device

[0107] 81 First receiving hole

[0108] 82 Second receiving hole

[0109] 83 First Throttle Valve

[0110] 84 Second throttle valve

[0111] 85 Pilot control valve for feed pressure limiting valve

[0112] 86 Control slide valve for pressure regulating valve

[0113] 87 Valve section

[0114] 88 Threaded connection

[0115] dpX_soll Rated regulated pressure difference

[0116] dp_soll Rated delivery pressure difference

[0117] i_DRE First regulation current

[0118] i_3 / 2 Second regulation current

[0119] i_speise Third regulation current

[0120] p_A First actual pressure

[0121] p_B Second actual pressure

[0122] n Actual speed

[0123] p_DRE First regulation pressure

[0124] p_3 / 2 Second adjustment pressure

Claims

1. A pump assembly (10, 10') having a first and a second working connection (11; 12), to which at least one hydraulic motor (40) can be fluidically connected in the sense of a closed hydraulic circuit, wherein the pump assembly (10, 10') has a drive shaft (19), wherein a displacement of a pressure fluid is conveyed between the first and the other working connection (11; 12) during one complete rotation of the drive shaft (19), wherein the displacement can be continuously adjusted by means of a double-acting regulating cylinder (20) having a first and a second regulating chamber (21, 22), wherein a first or a second receiving bore (81; 82) is respectively assigned to the first and the second regulating chamber (21, 22). ), the receiving hole is respectively permanently connected to the associated first or second regulating chamber (21, 22) in fluidic connection, the first and second receiving holes (81; 82) being identically designed, wherein they are respectively designed for fixing the built-in valve, wherein a first pressure sensor (71) is provided, by means of which a first actual pressure (p_A) at the first working interface (11) can be measured, wherein a second pressure sensor (72) is provided, by means of which a second actual pressure (p_B) at the second working interface (12) can be measured, wherein a control device (80) is provided, to which the first and second pressure sensors (71, 72) are connected, It is characterized in that A pressure regulating valve (30) in the form of an integrated valve is installed in one, first or second receiving bore (81; 82), wherein a 3 / 2-way switching valve (32) in the form of an integrated valve is installed in the other, second or first receiving bore (82, 81), wherein the pressure regulating valve (30) and the 3 / 2-way switching valve (32) are each electrically adjustable, wherein they are each connected to a control device (80), wherein a setpoint delivery pressure difference (dp_setpoint) can be predefined for the control device (80), wherein the control device (80) is designed such that it adjusts the displacement by actuating the pressure regulating valve (30) and the 3 / 2-way switching valve (32) such that a difference between a first and a second actual pressure (p_A, p_B) approaches the setpoint delivery pressure difference (dp_setpoint).

2. The pump assembly (10, 10') according to claim 1, It is possible to set in the control device (80) which of the two receiving holes, namely the first and second receiving holes (81; 82), the pressure regulating valve (30) or the 3 / 2-way switching valve (32) is installed, wherein the control device (80) is set up so that this setting is taken into account when actuating the pressure regulating valve (30) and when actuating the 3 / 2-way switching valve (32).

3. Pump assembly (10, 10') according to any one of the preceding claims, A rotational speed sensor (70) is provided, with which the actual rotational speed (n) of the drive shaft (19) can be measured, wherein the control device (80) is configured such that when actuating the pressure regulating valve (30) and actuating the 3 / 2-way switching valve (32), only the actual rotational speed (n) and the first and second actual pressures (p_A, p_B) are taken into account as actual values ​​measured in continuous operation.

4. Pump assembly (10, 10') according to any one of the preceding claims, The control device (80) carries out a pilot control (51) which is superimposed on the regulation (52).

5. Pump assembly (10, 10') according to any one of the preceding claims, In the control device (80), it is possible to set whether the pressure regulating valve (30) actually used has a rising or falling characteristic curve, wherein the control device (80) is designed in such a way that this setting is taken into account when actuating the pressure regulating valve (30).

6. Pump assembly (10, 10') according to any one of the preceding claims, The 3 / 2-way switching valve (32) is preloaded into a first position (35) by means of a return spring (34), the 3 / 2-way switching valve can be switched into a second position (36) by means of an assigned actuating magnet (33), the associated first or second regulating chamber (21, 22) can be selectively connected to either a control inlet (15) or a control return port (16) by switching the 3 / 2-way switching valve (32), it being possible to set in the control device (80) whether the 3 / 2-way switching valve (32) actually used establishes a fluid connection between the assigned regulating chamber, i.e. the first or second regulating chamber (21, 22) and the control inlet (16) or the control return port (15) in the first position (35), the control device (80) being configured so that this setting is taken into account when actuating the 3 / 2-way switching valve (32).

7. Pump assembly (10) according to any one of the preceding claims, The pressure regulating valve (30) has a rising characteristic curve, wherein the 3 / 2-way switching valve (32) establishes a connection with the control flow inlet (15) in a first position (35).

8. The pump assembly (10') according to any one of claims 1 to 6, The pressure regulating valve (30) has a falling characteristic curve, wherein the 3 / 2-way switching valve (32) establishes a connection with a control return (16) in a first position (35).

9. Pump assembly (10, 10') according to any one of the preceding claims, A feed pump (13) is provided, which is in drive connection with a drive shaft (19), wherein the feed pump is fluidically connected to a control flow inlet (15) on the outlet side, wherein a feed pressure limiting valve (14) is provided, by means of which the pressure in the control flow inlet (15) can be adjusted, wherein the control device (80) is designed such that the adjustment of the feed pressure limiting valve (14) is taken into account when actuating the pressure regulating valve (30) and when actuating the 3 / 2-way switching valve (32).

10. Pump assembly (10, 10') according to any one of the preceding claims, The first and / or second regulating chamber (21, 22) is permanently fluidically connected to an associated first or second receiving opening (81; 82) via a respectively associated first or second throttle valve (83; 84).

11. Pump assembly (10, 10') according to any one of the preceding claims, The displacement is continuously adjustable in such a way that the direction of the fluid flow between the first and second working connections (11; 12) can be reversed merely by adjusting the adjustment cylinder (20) while the direction of rotation of the drive shaft (19) remains the same.

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