Method for adapting the pressure of a hydraulic pump of a travel drive

Abstract

The invention relates to a method for adapting a pressure (p) of a hydraulic pump (2) of a travel drive (1), wherein the travel drive is provided with a hydraulic pump (2) for a pressure medium supply of a hydraulic motor (78) of the travel drive (1), which can be coupled to an output device (80), wherein the pressure (p) generated by the hydraulic pump (2) is adjusted by means of an influence on an adjustment pressure (p a , p b ), wherein the method comprises the following steps: a) calculating a maximum permissible adjustment pressure (p p , p p ) in consideration of a stroke volume (V p ) of the hydraulic pump (2) or a variable (a p ) representing the stroke volume (V amax ), a rotational speed (n bmax ) of the hydraulic pump (2) and a maximum permissible pressure (pmax) of the hydraulic pump (2); b) detecting a currently generated pressure (p) of the hydraulic pump (2); c) comparing the currently generated pressure (p) of the hydraulic pump (2) with the maximum permissible pressure (pmax); and d) adapting the maximum permissible adjustment pressure (p max , p amax ) in consideration of a difference between the currently generated pressure (p) of the hydraulic pump (2) and the maximum permissible pressure (p bmax ) in such a way that a learning factor, which is a parameter of a pump characteristic or a pump characteristic curve or a calculation rule, is corrected.

Description

Technical Field

[0001] The present invention relates to a method for adapting the pressure of a hydraulic pump to a driving device, and more preferably to a method for learning parameters of pump characteristics or pump characteristic curves or calculation rules for adapting the pressure of a hydraulic pump to a driving device. Background Technology

[0002] Hydrostatic drive systems for mobile machinery are known, in which a hydraulic pump and one or more hydraulic motors are interconnected in a closed hydraulic circuit. The hydraulic pump is driven by an internal combustion engine (e.g., a diesel engine), and the hydraulic motors ultimately drive the mobile machinery, for example, through corresponding wheels.

[0003] The hydraulic pump of such a driving device is typically adjustable in terms of its transport volume. Therefore, for example, at a constant speed of the internal combustion engine, the volumetric flow rate transported by the hydraulic pump can be changed in a closed loop, and thus it is possible to adapt to the output speed of the hydraulic motor or wheel, i.e., the travel speed of the moving machine.

[0004] Hydrostatic axial piston pumps are primarily installed in the drive systems of construction machinery. Part of their function is to limit the maximum permissible pressure. This is necessary for primarily limiting torque and also for limiting the maximum permissible pressure of components.

[0005] In addition to using destructive pressure relief valves (where the pump's volumetric flow rate is diverted to the storage tank), hydraulically controlled pressure regulating valves are also used. These valves limit high pressures, at which they reduce the pump's regulating pressure, and thus the pump reduces its discharge volume.

[0006] If the pump is electronically controlled, a “closed-loop” pressure regulator or a controlled, calibrated solution is sometimes used, as disclosed in patent application DE 10 2018 210685 A1.

[0007] The corresponding methods have several drawbacks.

[0008] Pressure relief valves result in high losses and subsequent heat loads, which correspond to additional costs. Furthermore, pressure relief valves can only preset a fixed pressure.

[0009] Hydraulic mechanical pressure cut-off regulators, especially under existing electrical control, incur additional costs and are temperature-dependent, suffering from tolerance and drift characteristics. Furthermore, the design of highly dynamic and stable characteristics is extremely complex and can only be preset to a fixed pressure.

[0010] The calibrated, electronically controlled solution is temperature-dependent and suffers from tolerance and drift characteristics, and can only be preset to a fixed pressure.

[0011] The electronic “closed-loop” regulator disclosed in DE 10 2018 210685 A1 has the following disadvantages:

[0012] The design of highly dynamic and stable characteristics is complex;

[0013] • This typically leads to high resource consumption on the controller and is complex and difficult to integrate with external controllers. Summary of the Invention

[0014] In contrast, the objective of this invention is to provide a method for eliminating the aforementioned disadvantages.

[0015] According to one embodiment of the present invention, a method for adapting the pressure of a hydraulic pump for a driving device is provided, wherein the driving device is provided with a hydraulic pump coupled to a drive motor for supplying pressure medium to a hydraulic motor of the driving device that can be coupled to an output device, wherein the hydraulic pump has an adjusting cylinder with at least one cylinder space and a stroke volume adjustable by the adjusting cylinder, and is provided with at least one electrically operable pressure valve, the cylinder space being able to be loaded with an adjusting pressure through the pressure valve to perform an adjusting function, and has means for adjusting the pressure of the hydraulic pump by means of influencing the adjusting pressure, wherein the pressure can be controlled, wherein the method includes the following steps:

[0016] a) Calculate the maximum permissible regulating pressure, taking into account the stroke volume of the hydraulic pump or a parameter representing that stroke volume, the speed of the hydraulic pump, and the maximum permissible pressure of the hydraulic pump.

[0017] b) Detect the current pressure of the hydraulic pump;

[0018] c) Compare the current pressure of the hydraulic pump with the maximum permissible pressure;

[0019] d) Adjust the maximum permissible regulating pressure by taking into account the difference between the current pressure and the maximum pressure of the hydraulic pump.

[0020] According to one embodiment of the present invention, a method is provided for adapting the pressure of a hydraulic pump in a driving device, wherein the driving device is equipped with a hydraulic pump for supplying pressure medium to a hydraulic motor of the driving device that can be coupled to an output device, wherein the pressure generated by the hydraulic pump can be adjusted by means of influencing the regulating pressure.

[0021] The method includes the following steps:

[0022] a) Calculate the maximum permissible regulating pressure, taking into account the stroke volume of the hydraulic pump or a parameter representing that stroke volume, the speed of the hydraulic pump, and the maximum permissible pressure of the hydraulic pump.

[0023] b) Detect the current pressure generated by the hydraulic pump;

[0024] c) Compare the current pressure generated by the hydraulic pump with the maximum permissible pressure; and

[0025] d) Taking into account the difference between the current pressure of the hydraulic pump and the maximum permissible pressure, the pressure is adjusted by modifying the learning factor, which is preferably a parameter of the pump characteristic or pump characteristic curve or calculation rule.

[0026] This solution is particularly advantageous because it can always be adapted to the characteristics of the hydraulic pump by adjusting the learning factor. This is because the regulating pressure can be calculated by taking into account the learning factor corrected in the previous cycle.

[0027] According to one embodiment of the present invention, a method is provided in which the learning factor is learned in step d.

[0028] According to one embodiment of the present invention, a method is provided, wherein the method further includes the following steps:

[0029] e) Compare the maximum permissible regulating pressure adapted in step d with the regulating pressure calculated taking into account the driver's expectations and independent of the maximum permissible pressure of the hydraulic pump;

[0030] f) The hydraulic pump is controlled using the smaller of the regulating pressure calculated taking into account the driver's expectations and independent of the maximum permissible pressure of the hydraulic pump.

[0031] According to one embodiment of the present invention, a method is provided in which a preset condition is checked between steps b and c; wherein, when the preset condition is met, step c is executed.

[0032] According to one embodiment of the present invention, a method is provided in which one of the preset conditions is that the absolute value of the difference between the current pressure of the hydraulic pump and the maximum permissible pressure is greater than a preset value.

[0033] According to one embodiment of the present invention, a method is provided in which one of the preset conditions is that, for a preset time window, the absolute value of the difference between the current pressure of the hydraulic pump and the maximum permissible pressure is greater than a preset value.

[0034] According to one embodiment of the present invention, a method is provided in which, in step e, the learning factor is modified multiplicatively or additively.

[0035] According to one embodiment of the invention, a method is provided in which, when the current pressure of the hydraulic pump is higher than the maximum permissible pressure, the learning factor is corrected downward during the aforementioned step d.

[0036] According to one embodiment of the invention, a method is provided in which, during step d, the learning factor is corrected upward when the current pressure of the hydraulic pump is less than the maximum permissible pressure and preferably other conditions are in effect (e.g., a control value lower than that desired by the driver).

[0037] According to one embodiment of the invention, a method is provided in which, during step d, the learning factor is corrected upward when the current pressure of the hydraulic pump is less than the maximum permissible pressure and the maximum permissible regulating pressure is less than the control pressure calculated taking into account the driver's expectations and independent of the maximum permissible pressure of the hydraulic pump.

[0038] According to one embodiment of the present invention, a method is provided in which the learning factor is reset during vehicle calibration.

[0039] According to one embodiment of the present invention, a method is provided in which a diagnostic message is generated when the difference between the learning factor before and after correction is greater than a preset value.

[0040] According to one embodiment of the present invention, a method is provided in which, in step d, the currently generated and detected pressures are filtered to take into account pressure dynamics.

[0041] According to one embodiment of the invention, a method is provided in which the maximum permissible pressure of the hydraulic pump is different for traction operation and towing operation or braking operation. Attached Figure Description

[0042] The present invention is described with reference to the accompanying drawings, wherein like reference numerals refer to like and / or similar and / or corresponding parts of the system. Wherein:

[0043] Figure 1 The diagram shows the hydraulic piping of a hydrostatic driving drive system according to the prior art.

[0044] Figure 2 It shows according to Figure 1 The characteristics of hydrostatic driving drive system, and

[0045] Figure 3A more detailed block diagram of a method for controlling hydrostatic driving devices according to prior art is shown.

[0046] Figure 4 A simplified block diagram is shown of a method for adapting the pressure of a hydraulic pump for a driving drive device according to an embodiment of the present invention. Detailed Implementation

[0047] The invention will now be described with reference to specific embodiments shown in the accompanying drawings. However, the invention is not limited to the particular embodiments described in the following detailed description and shown in the drawings; rather, the described embodiments only illustrate some aspects of the invention, the scope of which is defined by the claims.

[0048] Further modifications and variations of the present invention will be apparent to those skilled in the art. Therefore, this specification includes all modifications and / or variations of the present invention, and the scope of protection of the present invention is defined by the claims.

[0049] according to Figure 1 The hydrostatic driving device 1 includes a hydraulic pump 2, which is fluidly connected to a hydraulic motor (not shown) in a closed hydraulic circuit via working lines 4 and 6 for supplying pressure medium to the hydraulic motor. Here, the hydraulic pump 2 is coupled to a drive motor (not shown) via a drive shaft 8 to transmit torque. This coupling does not involve speed change, thus the drive motor and the hydraulic pump 2 rotate at the same speed.

[0050] Hydraulic pump 2 is designed as an axial piston pump with a tilting disc structure, capable of operating in both directions of rotation, and can operate not only as a pump but also as a motor. This hydraulic pump has an adjustable discharge volume V. P And an adjustment device 10 designed as a double-acting hydraulic cylinder.

[0051] The hydraulic cylinder 10 has a first cylinder chamber 12 and a second cylinder chamber 14 that reacts with the first cylinder chamber. The first cylinder chamber 12 is connected to the output of a first pressure reducing valve 18 via a first regulating pressure line 16. The latter is connected to a control pressure line 20, which can be connected to a control pressure connector p. S It is supplied with a control pressure medium via a feed pump 22, which is located on the same drive shaft 8 as the hydraulic pump 2.

[0052] Similarly, the second cylinder chamber 14 is connected to the second pressure reducing valve 26 via the second regulating pressure line 24, which is connected to the control pressure line 20. The pressure reducing valves 18 and 26 are electromagnetically actuated, wherein the regulating pressure p generated in the corresponding regulating pressure line 16 or 24... a or p bAccording to the valve characteristic curve and the control current I of electromagnet a or b a Or I b Proportional. Through electromagnetic control of pressure reducing valves 18 and 26, it is possible to control the current I by a preset value. a I b To control the regulating pressure p of cylinder chambers 12 and 14 a p b For this purpose, the electromagnets a and b of the pressure reducing valves 18 and 26 are connected to the electronic control unit 32 via corresponding signal lines 28 or 30.

[0053] Furthermore, the hydrostatic driving drive 1 has a speed detection unit 34, through which the speed n of the hydraulic pump 2 can be detected. p And this is transmitted to the electronic control unit 32 via signal line 36. Similarly, the driving drive unit 1 has a speed detection unit (not shown) through which the speed n of the hydraulic motor can be detected. M And it is transmitted to the electronic control unit 32 via signal line 38.

[0054] To provide safety-related pressure protection for working lines 4 and 6 to prevent overload, the hydrostatic drive unit 1 is equipped with pressure relief valves 40, which are connected to the corresponding working lines 4 and 6. Both pressure relief valves 40 connect to the feed pressure line 44 via their output terminals, which is connected to the feed pump 22. The feed pressure line 44 is fluidly connected to the control pressure line 20 via a throttle valve 42. In response to the pressure relief valves, the pressure of the medium flowing into the feed pressure line 44 is reduced, thus minimizing energy loss compared to when pressure is reduced towards the storage tank T. The pressure relief valves 40 each have a feed-or-suction function in the form of check valves.

[0055] The hydrostatic driving device 1 can operate not only in traction operation but also in towing or braking operation. In traction operation, the hydraulic pump 2 operates in pump mode; in braking operation, the hydraulic pump operates in motor mode. Furthermore, the hydraulic pump 2 is reversible, meaning its discharge volume V... P The adjustment device 10 can be used to adjust the volume V to zero. P Adjustments are made on both sides of the intermediate position = 0. Therefore, it is possible to reverse the direction of travel while keeping the rotation direction of the drive shaft 8 and the drive unit (diesel engine) unchanged.

[0056] The electronic control unit 32 is connected via signal line 46 to an operator interface in the form of a drive pedal (not shown). Here, the driver transmits a speed request to the electronic control unit 32 via the drive pedal. This speed request can relate to both reverse and forward travel. If the drive pedal is actuated, this corresponds to the traction or pumping operation of the hydraulic pump 2; conversely, if the drive pedal is retracted, this corresponds to the braking or motoring operation of the hydraulic pump 2. Actuation of the drive pedal (not shown) also corresponds to the braking or motoring operation of the hydraulic pump 2.

[0057] The control unit is designed to perform corresponding operations based on the aforementioned manipulations. For selecting the direction of travel, the hydrostatic drive unit 1 also has an operable direction switch (not shown), which is signal-connected to the electronic control unit 32 via signal line 48. Control of the hydraulic pump 2 is performed within its reversible or irreversible adjustment range depending on its position, i.e., on one side or the other side of the middle position of the hydraulic pump 2's stroke volume. The following driving states are defined for further observation.

[0058] Forward movement and traction: via control current I a The first pressure reducing valve 18 is controlled by the control unit 32 via the first signal line 28, and the first regulating pressure p is used. a Pressure is applied to the first cylinder chamber 12 via the first regulating pressure line 16 and the first pressure reducing valve 18.

[0059] Forward movement and braking operation: via control current I b The second pressure reducing valve 26 is controlled by the control unit 32 via signal line 30, and the second regulating pressure p is used. b Pressure is applied to the second cylinder chamber 14 via the second regulating pressure line 24 and the second pressure reducing valve 26.

[0060] Reverse driving and traction operation: Pressure is applied to the second cylinder chamber 14 through chains 24, 26, 30, and 32.

[0061] Reverse driving and braking operation: Pressure is applied to the first cylinder chamber 12 through chains 16, 18, 28, and 32.

[0062] In the two illustrated embodiments of the hydrostatic driving device 1, the hydraulic pump 2 is designed such that the pressure p formed in the high-pressure working lines guiding the working lines 4, 6 is then effectively regulated by the pressure p. a or p bThe resistance, and its own decreasing direction, is effective. For this purpose, the hydraulic pump 2 has a structurally implemented regulating circuit. In the current case of the hydraulic pump 2, which is designed as an axial piston pump with a swashplate structure, this is achieved such that the control disc of the hydraulic pump 2 is arranged torsionally about the rotation axis of its cylinder drum. The inlet of the cylinder, connected to the pressure control disc with pressure (high pressure), is thus arranged asymmetrically about the pivot axis of the swashplate. The support of the working piston guided in the cylinder is also asymmetrically arranged at the end section of the swashplate. The supporting force, thus asymmetrically acting by the working piston, generates a torque at the swashplate that pivots in the opposite direction during pump operation and pivots outward during motor operation. As a result, a relationship appears in the form of a pump characteristic curve or a family of characteristic curves for the hydraulic pump 2, in which the relationship between the hydraulic pump 2 pressure p and the stroke volume V can be described. P and its rotational speed n p The corresponding regulating pressure p a P b These characteristic curves or families of characteristic curves are measured and stored in the electronic control unit 32 for processing, and in particular for performing the methods described later.

[0063] exist Figure 2 The diagram shows a system with open-loop control, meaning it has a directly controlled discharge volume or stroke volume V. P The characteristics of hydraulic pump 2. Based on the discharge volume V P A pressure p, or more precisely, a pressure difference ΔP, is applied between working pipes 4 and 6. A first regulating pressure p is applied to the first cylinder chamber 12 as a parameter. a The first regulating pressure increases from the initial value of 0 / 0. The rated power P of the diesel drive engine... nomeng The dashed curve represents the power limit. The starting point of the description is the unoperated accelerator or drive pedal and the drive motor rotating at idle speed.

[0064] Following arrow 1, the operator first operates the drive pedal, thereby increasing the speed of the drive unit (diesel engine) from idle to rated speed. Correspondingly, the electronic control unit 32 generates a control signal or operating current l for the hydraulic pump 2, more precisely for the first pressure reducing valve 18 of the hydraulic pump, based on the diesel engine's speed. a .

[0065] As the rated speed of the drive motor is reached, the maximum travel speed of the travel drive unit 1 is obtained. Therefore, the first regulating pressure p a According to the storage of hydraulic pump 2 according to Figure 1 The family of characteristic curves in the electronic control unit 32 is improved. Since no load has yet been applied, the hydraulic pump 2 fully pivots out to its maximum stroke volume V.Pmax And provides its maximum volumetric flow rate Q at rated speed. max .

[0066] Due to the resulting driving resistance, a pressure or load pressure p is generated when traveling on a flat surface, for example, 250 bar. This process occurs... Figure 2 This is symbolically represented by an arrow denoted by the number 2. Following... Figure 2 The graph then reaches the curve P. nomeng Point Q is located on the axis. At this point, the first regulating pressure p is designed such that it operates at the rated speed. a This makes the hydraulic power pQ of hydraulic pump 2... max Corresponding to the rated power P nomeng .

[0067] If, for example, in the case of a wheel loader, the load at the drive unit 1 increases while traveling uphill or grappling gravel, then the pressure p increases. This is based on the previously mentioned design of the hydraulic pump 2 (where the working pressure p during forward travel in the traction operation of the hydraulic pump 2 is equal to the first regulating pressure p in the direction of decreasing stroke volume Vp). a (Counteracting pressure), pressure p causes the pivoting rocker arm of hydraulic pump 2 to pivot back, thereby slowing down the movement. First regulating pressure p a This remains unchanged during this period and corresponds to the travel volume V intersecting at point Q. P The linear curve (arrow 3) shows the simultaneous decrease of pressure p or pressure difference ΔP.

[0068] As of reaching the standard Figure 2 Point L in the chart represents the point where the maximum permissible pressure P is reached. max Or cut-off pressure or maximum permissible pressure difference ΔP max .

[0069] The task of the electronic control unit 32 is now to ensure that the limit P is not exceeded. max ΔP max Therefore, when the load increases further, the pressure p is not further increased; instead, it is achieved by the control unit 32 according to... Figure 1 The pressure reducing valve 18 is used to reduce the first regulating pressure p. a So that the pressure does not exceed p max Accordingly, according to Figure 2 Movement along the block-or-restraint curve, which is horizontal from point L with a constant pressure p max Or a constant pressure difference ΔP max Extending to the left. Therefore, if, for example, a maximum permissible pressure of, say, 450 bar is set in control unit 32... maxThen, the control unit 32 intervenes according to the pressure cutoff according to the present invention and withdraws the first regulating pressure p. a Therefore, even with further increases in load, it can prevent the maximum permissible pressure p from being exceeded. max .

[0070] The following is a more detailed description of method 52, which is able to limit the maximum pressure p. max .

[0071] As already mentioned, the input parameter for this method is the obtained or estimated stroke volume V. P Or the corresponding pivot angle α of hydraulic pump 2 p Its rotational speed n p and the preset pressure limit or working pressure p max (450 bar in this case).

[0072] according to Figure 1 In the electronic control unit 32, for each pressure limit p max The system stores pump characteristics or pump performance curves, or calculation rules 82 for the operation of hydraulic pump 2 in traction operation (pump operation), and calculation rules 84 for the braking-or motor operation of hydraulic pump 2. Accordingly, the corresponding calculation rules related to pump speed n are described here. p and pump pivot angle α p (As a percentage of the maximum pivot angle) Related regulating pressure p a or p b Adjust pressure p a and p b Similarly, the maximum available control-or regulating pressure p in control pressure line 20 is used. smax The percentage is shown here. Here, a second regulating pressure p is set for the second regulating chamber 14 during motor operation. b The range extends from zero to -50%. The plus or minus sign indicates the different directions of pressure generated by the opposing forces of the regulating chambers 12 and 14.

[0073] Based on the current value n of the driving drive unit's operating status. p α p and p max According to method 52, the maximum permissible regulating pressure p for traction operation is first determined. amax and the maximum permissible regulating pressure p for braking operation bmax This is in the fixed limit p. max The process continues in new locations, because α p Especially during operation, it varies due to its load dependence. For traction operation, the required initial regulating pressure p is applied. a68The adjustment, the first regulatory pressure comes from the adjustment according to Figure 1 The operation of the driving pedal 68. Finally, the adjustment pressure and the calculated maximum permissible first adjustment pressure p are mentioned. amax The control unit 32 compares the values ​​and selects the smaller adjustment pressure in step 86.

[0074] In step 88, the maximum permissible second pressure p is used bmax To achieve a similar situation, the smaller regulating pressure selected from steps 86 and 88 is then multiplied by the maximum available regulating pressure p. smax Thus, the actual regulating pressure p is generated from the regulating pressure previously described as a percentage. a or p b The actual regulating pressure is input into the corresponding valve characteristic curve 90 or 92 for the pressure reducing valve 18 or 26, and then the corresponding control current I for controlling the pressure reducing valve 18 or 26 is obtained from this valve characteristic curve. a Or I b .

[0075] In this way, from the rotational speed n p Pivot angle α p Pump characteristic curves 82 and 84, maximum permissible pressure p, required regulating pressure p a68 The required regulating pressure p during normal operation can be obtained from the valve characteristic curves 90 and 92. a P b and the maximum permissible regulating pressure p amax P bmax Among them, the relatively small adjustment pressure leads to a control current l a l b If the output pressure p is adjusted according to the driver's desired output... a68 Above the limit p amax or p bmax Then the control current p is limited or cut off. a or p b .

[0076] In the methods described above, designing highly dynamic and stable properties is extremely complex. In particular, the difficulty lies in generating properties that can effectively limit p. max Δp max The pump characteristics or pump characteristic curves or calculation rules. In particular, the present invention can compensate for tolerances and control characteristic fluctuations with respect to temperature and aging characteristics, and dynamically adapt to the maximum allowable pressure.

[0077] Figure 4 A method according to an embodiment of the present invention is shown, which overcomes the above-mentioned problems.

[0078] The pump characteristics, or pump characteristic curve, or calculation rule (hereafter referred to as the "power characteristic curve"), depend on a learning factor, which is a parameter of the power characteristic curve. The learning factor can be applied to the power characteristic curve not only multiplicatively but also additively, thus allowing the power characteristic curve to be corrected upwards or downwards.

[0079] The first step 101 is similar to Figure 3 Step 52 is shown. Specifically, based on the current value n of the operating state of the driving drive unit. p α p and p max First, determine the maximum permissible regulating pressure p for traction operation. amax and the maximum permissible regulating pressure p for braking operation bmax .

[0080] In the next step 102, the pressure difference ΔP between working lines 4 and 6 is detected. Preferably, the generated and detected pressure p is filtered to account for pressure dynamics and ignore fluctuations.

[0081] If the current pressure p generated by hydraulic pump 2 is greater than or less than the maximum allowable pressure p max If this is the case, there is an indication that the power characteristic curve should be corrected (either because the currently generated voltage p is too high or too low). Therefore, it is possible that the corresponding maximum permissible regulating pressure P obtained for traction operation must be corrected. amax and the maximum permissible regulating pressure p for braking operation bmax .

[0082] However, additional conditions must be met in order to actually determine whether a correction is needed.

[0083] The first condition is that it is related to the maximum permissible pressure p. max Different generated pressures p are undesirable. In other words, it must be verified that the pressure p generated by the pump is compared with the maximum pressure p. max The difference lies not in the driver's expectations, but in the power characteristic curve, through which the maximum permissible adjustment pressure p for traction operation is calculated in step 101. amax and the maximum permissible regulating pressure p for braking operation bmax .

[0084] If this condition and any possible additional conditions described in the next paragraph are met, the learning factor is corrected upwards or downwards, and preferably, the learning factor is learned, thereby enabling the storage of corrections to the power characteristic curve. Specifically, the learning factor is permanently stored in the controller so that the learned factor is available upon restart.

[0085] Additional conditions may include the following:

[0086] • The current pressure p generated by hydraulic pump 2 and the maximum allowable pressure p max The absolute value of the difference between them is greater than the preset value; and / or

[0087] • For a preset time window, the current pressure p generated by hydraulic pump 2 and the maximum allowable pressure p max The absolute value of the difference between them is greater than the preset value; and / or

[0088] • The pump is blocked (estimated pump angle < defined value); and / or

[0089] • Other conditions known to those skilled in the art.

[0090] After correcting the learning factor, the maximum permissible regulating pressure p for traction operation is recalculated based on the new learning factor. amax and the maximum permissible regulating pressure p for braking operation bmax .

[0091] Then, adjust the pressure p amax and p bmax With the maximum available control pressure p smax Multiplying these, the actual regulating pressure p is thus derived from the previously expressed percentage regulating pressure. amax or p bmax .

[0092] In steps 103 and 104, parallel to steps 101 and 102, firstly, without considering the maximum pressure p... max In the case of considering the operation of the driving pedal 68, the maximum available control-or regulation pressure p in the control pressure line 20 is achieved. smax The percentage is used to calculate the regulating pressure p. a and p b (Step 103). Then, adjust the pressure p. a and p b With the maximum available control pressure p smax Multiplying these, the actual regulating pressure p is thus derived from the previously expressed percentage regulating pressure. a or p b .

[0093] In step 105, the values ​​of the regulating pressure from steps 102 and 104 are compared, and the minimum value for the regulating pressure is selected.

[0094] In step 106, these values ​​are fed into the corresponding valve characteristic curve 90 or 92 for pressure reducing valve 18 or 26, from which the corresponding control current I for controlling pressure reducing valve 18 or 26 is obtained. a Or I b .

[0095] about Figure 4 The described method is always effective during operation and can identify which driving states it can learn from. Here, the algorithm adapts to excessively low and high pressures in inertial operation (negative pressure) and traction operation (positive pressure).

[0096] Furthermore, the learning factors can be reset during vehicle calibration and can be corrected and learned again during driving operations.

[0097] In special cases where the difference between the learning factor before and after correction is greater than a preset value, a diagnostic message can be generated.

[0098] Although the present invention has been described with reference to the above embodiments, it will be apparent to those skilled in the art that various modifications, variations and improvements of the present invention can be implemented based on the above teachings and within the scope of the appended claims without departing from the protection scope of the present invention.

[0099] Even when discussing maximum pressure, it is clear that the maximum permissible pressure p of hydraulic pump 2 is for traction and towing or braking operations. max They are different.

[0100] Furthermore, in order not to unnecessarily obscure the described invention, areas that might be understood by those skilled in the art are not described herein.

[0101] Accordingly, the present invention is not limited to the specific illustrative embodiments, but only to the scope of protection of the appended claims.

Claims

1. Method for adapting the pressure (p) of a hydraulic pump (2) of a travel drive (1), wherein The driving device is equipped with a hydraulic pump (2) for supplying pressure medium to a hydraulic motor (78) of the driving device (1) that can be coupled to an output device (80), wherein the pressure can be adjusted by means of the hydraulic pump (2). a p b The method adjusts the pressure (p) generated by the hydraulic pump (2) by means of the influence of the hydraulic pump (2), characterized in that the method includes the following steps: a. Taking into account the stroke volume (V) of the hydraulic pump (2) p ) or represents the volume of the stroke (V) p The parameter (α) p The rotational speed (n) of the hydraulic pump (2) p ), and the maximum permissible pressure (p) of the hydraulic pump (2). max Under the condition of ), calculate the maximum permissible regulating pressure (p) amax p bmax ); b. Detect the current pressure (p) generated by the hydraulic pump (2); c. Compare the current pressure (p) generated by the hydraulic pump (2) with the maximum permissible pressure (p). max ) for comparison; and d. Taking into account the current pressure (p) of the hydraulic pump (2) and the maximum permissible pressure (p) max In the case of the difference between ), the maximum permissible regulating pressure (p) is adapted. amax p bmax The method is as follows: modify the learning factor, which is a parameter of the power characteristic curve of the hydraulic pump (2).

2. The method of claim 1, wherein, The learning factor is learned in step d.

3. The method of claim 1 or 2, wherein, The method further includes the following steps: e. The maximum permissible regulating pressure (p) adapted in step d. amax p bmax ) and the maximum permissible pressure (p) considering the driver's expectations and independent of the hydraulic pump (2). max The regulating pressure (p) calculated under the condition of a p b ) for comparison; f. Utilizing the maximum permissible pressure (p) that takes into account the driver's expectations and is independent of the hydraulic pump (2). max The regulating pressure (p) calculated under the condition of a p b ) and the maximum permissible regulating pressure (p amax p bmax The smaller value between ) is used to control the hydraulic pump.

4. The method according to claim 1 or 2, wherein, Between steps b and c, check whether a preset condition is met; wherein, if the preset condition is met, step c is executed.

5. The method of claim 4, wherein, One of the preset conditions is that the current pressure (p) of the hydraulic pump (2) is equal to the maximum allowable pressure (p). max The absolute value of the difference between the two is greater than the preset value.

6. The method of claim 5, wherein, One of the pre-set conditions is that the absolute value of the difference between the current pressure (p) of the hydraulic pump (2) and the maximum allowed pressure (p max ) is greater than a pre-set value for a pre-set time window.

7. The method of claim 3, wherein, In step e, the learning factor is modified multiplicatively or additively.

8. The method of claim 1 or 2, wherein, When the current pressure (p) of the hydraulic pump (2) is higher than the maximum allowable pressure (p) max When ), the learning factor is adjusted downwards during the mentioned step d.

9. The method of claim 1 or 2, wherein, When the current pressure (p) of the hydraulic pump (2) is less than the maximum allowable pressure (p) max And the maximum permissible regulating pressure (p) amax p bmax The pressure is less than the maximum permissible pressure (p) that takes into account the driver's expectations and is independent of the hydraulic pump (2). max The control pressure (p) calculated under the condition of a p b When ), the learning factor is adjusted upwards during the mentioned step d.

10. The method of claim 1 or 2, wherein, The learning factor is reset during vehicle calibration.

11. The method of claim 1 or 2, wherein, A diagnostic message is generated when the difference between the learning factor before and after the correction is greater than a preset value.

12. The method of claim 1 or 2, wherein, In step d, the currently generated and detected pressure (p) is filtered to take pressure dynamics into account.

13. The method of claim 1 or 2, wherein, The maximum permissible pressure (p max ) of the hydraulic pump (2) is different for traction operation and for towing operation or braking operation.

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