EP4273398A1 - Calibration method of a hydraulic pump control system - Google Patents
Calibration method of a hydraulic pump control system Download PDFInfo
- Publication number
- EP4273398A1 EP4273398A1 EP23170277.0A EP23170277A EP4273398A1 EP 4273398 A1 EP4273398 A1 EP 4273398A1 EP 23170277 A EP23170277 A EP 23170277A EP 4273398 A1 EP4273398 A1 EP 4273398A1
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- EP
- European Patent Office
- Prior art keywords
- hydraulic pump
- pressure
- value
- current intensity
- control pressure
- Prior art date
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- 238000000034 method Methods 0.000 title claims abstract description 37
- 230000002706 hydrostatic effect Effects 0.000 claims abstract description 16
- 238000006073 displacement reaction Methods 0.000 claims abstract description 14
- 230000001419 dependent effect Effects 0.000 claims abstract description 10
- 230000009467 reduction Effects 0.000 claims abstract description 5
- 230000000903 blocking effect Effects 0.000 claims description 24
- 230000001105 regulatory effect Effects 0.000 claims description 13
- 238000004364 calculation method Methods 0.000 claims description 6
- 239000012530 fluid Substances 0.000 claims description 5
- 238000004590 computer program Methods 0.000 claims description 4
- 230000035945 sensitivity Effects 0.000 description 14
- 230000010355 oscillation Effects 0.000 description 6
- 238000010586 diagram Methods 0.000 description 4
- 230000008859 change Effects 0.000 description 2
- 238000010276 construction Methods 0.000 description 2
- 230000001276 controlling effect Effects 0.000 description 2
- 238000004519 manufacturing process Methods 0.000 description 2
- 238000012986 modification Methods 0.000 description 2
- 230000004048 modification Effects 0.000 description 2
- 241001465754 Metazoa Species 0.000 description 1
- 230000033228 biological regulation Effects 0.000 description 1
- 238000005065 mining Methods 0.000 description 1
- 230000008569 process Effects 0.000 description 1
- 230000004044 response Effects 0.000 description 1
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Classifications
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B51/00—Testing machines, pumps, or pumping installations
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B1/00—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders
- F04B1/12—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders having cylinder axes coaxial with, or parallel or inclined to, main shaft axis
- F04B1/26—Control
- F04B1/28—Control of machines or pumps with stationary cylinders
- F04B1/29—Control of machines or pumps with stationary cylinders by varying the relative positions of a swash plate and a cylinder block
- F04B1/295—Control of machines or pumps with stationary cylinders by varying the relative positions of a swash plate and a cylinder block by changing the inclination of the swash plate
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B1/00—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders
- F04B1/12—Multi-cylinder machines or pumps characterised by number or arrangement of cylinders having cylinder axes coaxial with, or parallel or inclined to, main shaft axis
- F04B1/26—Control
- F04B1/30—Control of machines or pumps with rotary cylinder blocks
- F04B1/32—Control of machines or pumps with rotary cylinder blocks by varying the relative positions of a swash plate and a cylinder block
- F04B1/324—Control of machines or pumps with rotary cylinder blocks by varying the relative positions of a swash plate and a cylinder block by changing the inclination of the swash plate
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
- F04B49/002—Hydraulic systems to change the pump delivery
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
- F04B49/08—Regulating by delivery pressure
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
- F04B49/20—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00 by changing the driving speed
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B49/00—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00
- F04B49/22—Control, e.g. of pump delivery, or pump pressure of, or safety measures for, machines, pumps, or pumping installations, not otherwise provided for, or of interest apart from, groups F04B1/00 - F04B47/00 by means of valves
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04B—POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS
- F04B2205/00—Fluid parameters
- F04B2205/04—Pressure in the outlet chamber
Definitions
- the present invention relates to the field of a method for calibrating the control system of a hydraulic pump for a hydrostatic drive system, a computing unit adapted to perform such a method, an operating machine includes such a computing unit, a computer program that induces a computing unit to perform such a method, and a readable storage medium on which such a program is stored.
- ET pumps load-sensitive axial-piston tilting-plate hydraulic pumps
- ET pumps load-sensitive axial-piston tilting-plate hydraulic pumps
- Such pumps presented the characteristic that an increase in load tends to decrease the pump's tilt angle. Therefore, if, for example, the operating machine starts a climb, the load that the machine has to support will go up. This will then cause the pump's angle of inclination to decrease.
- the sensitivity of the pump to the specific load defines the driving behavior of the machine, especially with regard to pressure/power control and load dependence during constant speed driving.
- Load sensitivity is an inherent characteristic of the pump itself, and it is known that it is basically impossible to make a series of pumps having the same sensitivity during production. In order to ensure the same driving performance of the machines, several methods have been realized that allow the pump to be used regardless of the degree of sensitivity of the pump just out of production:
- the goal is to provide a method for solving these problems without having to resort to additional components or having particularly complex control systems.
- the present invention relates to a control method the features listed in claim 1.
- vehicle is used to refer to any man-driven (or even remotely operated) mechanical means of transporting people, animals or things, whether circulating on the road or usable off the road, such as at construction sites, quarries or mining operations, etc.
- a vehicle may be, for example, a construction machine such as a bulldozer.
- a vehicle is defined as any vehicle capable of performing vehicle displacement.
- FIG. 1 shows a hydraulic diagram of a traction system with respect to which a calibration method may be used according to a form of embodiment of the present invention. Only the components essential to the invention are described.
- the system has a casing 1 on which two working connections A, B are formed to which a working line (not shown) of a closed circuit is connected respectively, for example one or more hydraulic motors may be connected to said working connections A, B.
- a drive system is formed for a mobile working machine (not shown), such as a bulldozer.
- the axial piston pump 12 is made with an oblique disc 2 (also referred to more generally as an oblique element) whose angle of oscillation ⁇ pmp can be set by means of an adjusting unit 4, so as to go to adjust the displacement of the pump itself.
- a double-action regulating cylinder 6 is used for this purpose, which has a first chamber 8 1 of the regulating pressure and a second chamber 8 2 of the regulating pressure acting in the opposite direction to the first chamber.
- a first control pressure p st1 acts in the first chamber of the control pressure 8 1 in the direction of an increase in the oscillation angle ⁇ pmp and thus in the direction of an increase in pump displacement 12.
- a second control pressure p st2 in the second chamber 8 2 acts in the direction of a decrease in the oscillation angle ⁇ pmp and thus in the direction of a decrease in pump displacement 12.
- a difference in control pressure ⁇ pst can be defined given by the difference of the first and second control pressures p st1 , p st2 , this difference in control pressure ⁇ pst by definition always acts in the direction of an increase in the oscillation angle ⁇ pmp and thus in the displacement itself.
- Drive shaft 10 Via a drive shaft 10 of the axial piston pump, its drive unit is driven and in addition also a feed pump 14.
- Drive shaft 10 can be driven by a diesel engine (not shown) or alternatively also by an electric motor and rotates with a variable number of revolutions. This number of revolutions acts together with the control pressure difference in the direction of an increase in the oscillation angle ⁇ pmp .
- axial piston pump shown feeds through its working ports A, B numerous traction motors of the mobile work machine, in case of forward travel B must be thought of as a high pressure port, so that the channel connected with working port B is identified with high pressure HD, while the other channel connected with working port A is identified with reduced pressure ND.
- the high pressure HD which is also referred to as working pressure, acts in the direction of a reduction in the oscillation angle ⁇ pmp .
- the two control pressures are controlled by two pressure reducing valves 18 1 , 18 2 . These respectively have an electric magnet a, b, which via a respective electrical line 20 1 , 20 2 is connected with the electronic control unit 16.
- the two pressure reduction valves 18 1 , 18 2 are designed so that the respective control pressure p st1 , p st2 is proportional to the respective current intensity.
- the two pressure reducing valves 18 1 , 18 2 are fed on the inlet side via a supply pressure line 22 from the supply pump 14.
- the system shown in Figure 1 can be adjusted in two different modes.
- the first mode is shown in patent application DE 10 2018 210 694 A1 .
- Figure 3 of that document for the calculation of regulation pressures, it is necessary to go to the pump characteristic curve that describes the degree of pump sensitivity depending on the pump discharge pressure. This curve is shown in Figure 3 with reference number 32. It is clear, however, that this curve is specific to the pump itself, and therefore, for pumps having a slightly different sensitivity, this curve would not provide a particularly accurate value of the degree of sensitivity.
- Such a method includes the following steps: Defining at least a first state of the hydrostatic drive system at which said calibration is to be performed, wherein said first state comprises one or more operating conditions, wherein each operating condition comprises a hydraulic pump discharge pressure value 12;
- Such a state at which this calibration is carried out could be a blocked state at which said hydraulic motor is braked or at which the flow rate of fluid passing through said hydraulic pump 12 is reduced to a volume close to zero so that said hydraulic pump 12 delivers only enough volume in this first state to cover losses along said hydrostatic drive system.
- the circuit diagram shown in Figure 2 is used to determine the control pressure p st1 , p st2 or current intensity or a quantity dependent on them.
- a current speed n of hydraulic pump 12 and a selected direction of travel T are determined.
- the speed n hydraulic pump 12 is calculated from a speed n Eng of the drive motor (such as an electric or diesel motor).
- the speed n or n Eng is filtered by means of a filter element PT1 and then serves as an input variable on one side of a control element with a (so-called) characteristic curve Q 100 and on the other side of a control element with a (so-called) blocking characteristic curve 120.
- the blocking condition corresponds to a condition in which said hydraulic motor is braked or at which the flow rate of fluid passing through said hydraulic pump 12 is reduced to a volume close to zero so that said hydraulic pump 12 delivers only enough volume to cover losses along said hydrostatic drive system.
- the blocking characteristic curve 120 is a curve describing the control pressure p Block (which is nothing but the control pressure p st1 , p st2 described above, at a blocking condition) required as a function of the speed of the drive motor or hydraulic pump 12.
- the Q condition corresponds to a condition in which hydraulic pump 12 delivers a maximum flow rate, at which the flow rate of fluid passing through said hydraulic pump 12 is increased to a maximum value.
- characteristic curve Q 100 is a curve that describes the control pressure p Q (which is nothing but the control pressure p st1 , p st2 described above, at a maximum flow condition) required as a function of the speed of the drive motor or hydraulic pump 12.
- Both characteristic curves 100, 120 are monotonically increasing functions that define a respective control pressure p Block , p Q as a function of speed n and n Eng , respectively.
- control pressures p Block , p Q are the input variables of an interpolation element with an interpolation function 140.
- the interpolation function 140 defines the resultant control pressure pst for the two pressure reducing valves 8 1 , 8 2 , which according to the invention (at least over an average range of speed n or n Eng ) is a combination of the control pressure p Q of the Q characteristic 100 and the control pressure p Block of the block characteristic 120.
- this interpolation function depends on the tilt angle ⁇ pmp of the hydraulic pump 12. At a tilt angle ⁇ pmp of 0°, the control pressure pst corresponds to the control pressure p Block , and at a maximum tilt angle ⁇ pmp , the control pressure pst corresponds to the control pressure p Q .
- the resulting control pressure pst is also equal to the control pressure p Block for low tilt angles ⁇ pmp and the control pressure p Q for high tilt angles ⁇ pmp .
- the combination of the two control pressures p Block , p Q is used to determine the control pressure pst, where the values of the two control pressures p Block , p Q are weighted more or less depending on the value of the tilt angle of the hydraulic pump 12.
- the method includes the following steps:
- This method includes the following steps: Defining at least a first state of said hydrostatic drive system at which said calibration is to be performed, wherein said first state comprises one or more operating conditions, wherein each operating condition comprises a discharge pressure value of said hydraulic pump (12);
- the inventor has found that it is particularly advantageous if that first state coincides with the locked state since that condition is very easy to achieve and therefore such calibration can be done particularly easily.
- this process is repeated for two operating conditions each containing a discharge pressure, so that there are two different points to be used for correction.
- a first operating condition comprises a discharge pressure value of said hydraulic pump 12 corresponding to a maximum usable pressure in said hydrostatic drive system, wherein said discharge pressure in said first operating condition is preferably between 400 and 500 bar, even more preferably being 450 bar.
- a second operating condition comprises a discharge pressure value of said hydraulic pump 12 preferably being between 150 and 300 bar, even more preferably being equal to 200 bar, wherein said discharge pressure of said second operating condition preferably corresponds to the discharge pressure of said hydraulic pump 12 in a maximum flow condition.
- the calibration method includes the following steps:
- the present invention further describes a computational unit adapted to perform a method according to any of the preceding claims.
- present description includes a computer program that induces a computing unit to perform a method as described in the present invention.
- Also described is a readable storage medium comprising the computer program stored thereon described above.
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- Engineering & Computer Science (AREA)
- Mechanical Engineering (AREA)
- General Engineering & Computer Science (AREA)
- Fluid-Pressure Circuits (AREA)
Abstract
a. Define at least a first state of said hydrostatic drive system at which said calibration is to be performed, wherein said first state comprises one or more operating conditions, wherein each operating condition comprises a discharge pressure value of said hydraulic pump (12);
b. Measure the value of said first current intensity (I1) and/or said first control pressure required to arrive at each operating condition;
c. Compare the value of said first current intensity (I1) and/or said first control pressure with a reference value of each operating condition;
d. Correct said function according to the comparison made at said step c.
Description
- The present invention relates to the field of a method for calibrating the control system of a hydraulic pump for a hydrostatic drive system, a computing unit adapted to perform such a method, an operating machine includes such a computing unit, a computer program that induces a computing unit to perform such a method, and a readable storage medium on which such a program is stored.
- In hydraulic traction drives, load-sensitive axial-piston tilting-plate hydraulic pumps (so-called ET pumps) in a closed loop are usually used. Such pumps presented the characteristic that an increase in load tends to decrease the pump's tilt angle. Therefore, if, for example, the operating machine starts a climb, the load that the machine has to support will go up. This will then cause the pump's angle of inclination to decrease.
- Among other things, the sensitivity of the pump to the specific load defines the driving behavior of the machine, especially with regard to pressure/power control and load dependence during constant speed driving.
- Load sensitivity is an inherent characteristic of the pump itself, and it is known that it is basically impossible to make a series of pumps having the same sensitivity during production. In order to ensure the same driving performance of the machines, several methods have been realized that allow the pump to be used regardless of the degree of sensitivity of the pump just out of production:
- I. Adjustment of the pump by means of a torque screw to ensure the same load sensitivity;
- II. Closed-loop control circuits that can adjust pressure and/or swing angle and thus compensate for tolerances.
- However, the approach(s) described above have the disadvantage of being associated with increased costs that are due to additional components, adjustment procedures, or additional sensors.
- The goal, therefore, is to provide a method for solving these problems without having to resort to additional components or having particularly complex control systems.
- The present invention relates to a control method the features listed in
claim 1. - By means of the method described in
claim 1, it is effectively possible to regulate the hydraulic pump independently of the sensitivity of the pump. Such a method is applicable in any type of pump control method, either in terms of controlling the pump based on the speed of the pump itself or the drive motor and or controlling the pump based on a desired speed of the pump itself. - Preferable forms of implementation are indicated in the dependent claims.
- The present invention will be described with reference to the appended figures in which the same reference numerals and/or marks indicate the same and/or similar and/or corresponding parts of the system.
-
Figure 1 shows a hydraulic diagram of a propulsion of an operating machine according to a scheme known from the state of the art; -
Figure 2 shows a function to calculate the first current intensity and/or the first control pressure as a function of a rotational speed of the drive motor or a quantity dependent on it and based on the angle of inclination of the pump; -
Figure 3a and 3b show the characteristic curve of two pumps having two different load sensitivities. - In the following, the present invention is described by reference to particular forms of embodiment as illustrated in the accompanying drawing plates. However, the present invention is not limited to the particular forms of embodiment described in the following detailed description and depicted in the figures, but rather the forms of embodiment described simply exemplify the various aspects of the present invention, the scope of which is defined by the claims. Further modifications and variations of the present invention will appear clear to the person in the art.
- In this description, the term vehicle is used to refer to any man-driven (or even remotely operated) mechanical means of transporting people, animals or things, whether circulating on the road or usable off the road, such as at construction sites, quarries or mining operations, etc. Thus an example of a vehicle may be, for example, a construction machine such as a bulldozer. In general, a vehicle is defined as any vehicle capable of performing vehicle displacement.
-
Figure 1 shows a hydraulic diagram of a traction system with respect to which a calibration method may be used according to a form of embodiment of the present invention. Only the components essential to the invention are described. The system has acasing 1 on which two working connections A, B are formed to which a working line (not shown) of a closed circuit is connected respectively, for example one or more hydraulic motors may be connected to said working connections A, B. In this way a drive system is formed for a mobile working machine (not shown), such as a bulldozer. - The
axial piston pump 12 is made with an oblique disc 2 (also referred to more generally as an oblique element) whose angle of oscillation αpmp can be set by means of an adjusting unit 4, so as to go to adjust the displacement of the pump itself. A double-action regulating cylinder 6 is used for this purpose, which has a first chamber 81 of the regulating pressure and a second chamber 82 of the regulating pressure acting in the opposite direction to the first chamber. - A first control pressure pst1 acts in the first chamber of the control pressure 81 in the direction of an increase in the oscillation angle αpmp and thus in the direction of an increase in
pump displacement 12. In the opposite direction to this, a second control pressure pst2 in the second chamber 82 acts in the direction of a decrease in the oscillation angle αpmp and thus in the direction of a decrease inpump displacement 12. In this way, a difference in control pressure Δpst can be defined given by the difference of the first and second control pressures pst1, pst2, this difference in control pressure Δpst by definition always acts in the direction of an increase in the oscillation angle αpmp and thus in the displacement itself. - Via a
drive shaft 10 of the axial piston pump, its drive unit is driven and in addition also afeed pump 14.Drive shaft 10 can be driven by a diesel engine (not shown) or alternatively also by an electric motor and rotates with a variable number of revolutions. This number of revolutions acts together with the control pressure difference in the direction of an increase in the oscillation angle αpmp. - If the axial piston pump shown feeds through its working ports A, B numerous traction motors of the mobile work machine, in case of forward travel B must be thought of as a high pressure port, so that the channel connected with working port B is identified with high pressure HD, while the other channel connected with working port A is identified with reduced pressure ND. The high pressure HD, which is also referred to as working pressure, acts in the direction of a reduction in the oscillation angle αpmp. These relationships are called axial piston pump characteristic and are stored in an
electronic control unit 16 in the form of formulas and/or as characteristic diagrams and/or characteristic lines or more ingenerally functions. - The two control pressures are controlled by two pressure reducing valves 181, 182. These respectively have an electric magnet a, b, which via a respective electrical line 201, 202 is connected with the
electronic control unit 16. The two pressure reduction valves 181, 182 are designed so that the respective control pressure pst1, pst2 is proportional to the respective current intensity. - The two pressure reducing valves 181, 182 are fed on the inlet side via a
supply pressure line 22 from thesupply pump 14. - The system shown in
Figure 1 can be adjusted in two different modes. - The first mode is shown in
patent application DE 10 2018 210 694 A1 . In that document, it is shown how the pump is adjusted, based on a desired speed of the operating machine. As shown inFigure 3 of that document, for the calculation of regulation pressures, it is necessary to go to the pump characteristic curve that describes the degree of pump sensitivity depending on the pump discharge pressure. This curve is shown inFigure 3 with reference number 32. It is clear, however, that this curve is specific to the pump itself, and therefore, for pumps having a slightly different sensitivity, this curve would not provide a particularly accurate value of the degree of sensitivity. - The inventor has discovered that it is possible to carry out a method of calibrating the pump using software, instead of going directly to adjust the calibration of the pump itself. Such a method includes the following steps:
Defining at least a first state of the hydrostatic drive system at which said calibration is to be performed, wherein said first state comprises one or more operating conditions, wherein each operating condition comprises a hydraulic pumpdischarge pressure value 12; - a. Measure the value of said first current intensity and/or said first control pressure pst1, pst2 required to arrive at each operating condition;
- b. Compare the value of said first current intensity and/or said first control pressure pst1, pst2 with a reference value of each operating condition;
- c. Correct the sub-function describing the pump sensitivity based on the pump discharge pressure of the pump according to the comparison made at said step c.
- With this method of calibration, it is actually possible to go in and correct the degree of sensitivity of the pump without going in and changing the physical characteristics of the pump itself (as was done until now). Such a state at which this calibration is carried out could be a blocked state at which said hydraulic motor is braked or at which the flow rate of fluid passing through said
hydraulic pump 12 is reduced to a volume close to zero so that saidhydraulic pump 12 delivers only enough volume in this first state to cover losses along said hydrostatic drive system. - The second mode is shown in
patent application DE 10 2020 207 284 A1 and will be briefly summarized here with reference toFigure 2 . - The circuit diagram shown in
Figure 2 is used to determine the control pressure pst1, pst2 or current intensity or a quantity dependent on them. First, a current speed n ofhydraulic pump 12 and a selected direction of travel T are determined. The speed nhydraulic pump 12 is calculated from a speed nEng of the drive motor (such as an electric or diesel motor). The speed n or nEng is filtered by means of a filter element PT1 and then serves as an input variable on one side of a control element with a (so-called)characteristic curve Q 100 and on the other side of a control element with a (so-called) blockingcharacteristic curve 120. - The blocking condition corresponds to a condition in which said hydraulic motor is braked or at which the flow rate of fluid passing through said
hydraulic pump 12 is reduced to a volume close to zero so that saidhydraulic pump 12 delivers only enough volume to cover losses along said hydrostatic drive system. - Therefore, the blocking
characteristic curve 120 is a curve describing the control pressure pBlock (which is nothing but the control pressure pst1, pst2 described above, at a blocking condition) required as a function of the speed of the drive motor orhydraulic pump 12. - The Q condition corresponds to a condition in which
hydraulic pump 12 delivers a maximum flow rate, at which the flow rate of fluid passing through saidhydraulic pump 12 is increased to a maximum value. - Therefore,
characteristic curve Q 100 is a curve that describes the control pressure pQ (which is nothing but the control pressure pst1, pst2 described above, at a maximum flow condition) required as a function of the speed of the drive motor orhydraulic pump 12. - Both
characteristic curves - These two control pressures pBlock, pQ are the input variables of an interpolation element with an
interpolation function 140. Theinterpolation function 140 defines the resultant control pressure pst for the two pressure reducing valves 81, 82, which according to the invention (at least over an average range of speed n or nEng) is a combination of the control pressure pQ of the Q characteristic 100 and the control pressure pBlock of theblock characteristic 120. Furthermore, according to the invention, this interpolation function depends on the tilt angle αpmp of thehydraulic pump 12. At a tilt angle αpmp of 0°, the control pressure pst corresponds to the control pressure pBlock, and at a maximum tilt angle αpmp, the control pressure pst corresponds to the control pressure pQ. - In the example shown in the figure, the resulting control pressure pst is also equal to the control pressure pBlock for low tilt angles αpmp and the control pressure pQ for high tilt angles αpmp. At an intermediate range of the tilt angle αpmp, the combination of the two control pressures pBlock, pQ is used to determine the control pressure pst, where the values of the two control pressures pBlock, pQ are weighted more or less depending on the value of the tilt angle of the
hydraulic pump 12. - In summary, the method includes the following steps:
- Calculate on the basis of the rotational speed of the drive motor or said quantity dependent thereon a value of a blocking current intensity and/or a blocking control pressure, wherein said calculation is performed by means of a blocking subfunction (the blocking curve 120);
- Calculate on the basis of said rotational speed of the drive motor or of said magnitude dependent thereon a value of a flow rate current intensity and/or a flow rate control pressure, , wherein said calculation is made by means of a flow rate subfunction (the flow rate curve 100);
- obtain a current value of said angle of inclination αpmp of said inclined element 2 (e.g., by means of a flow rate balancing equation, then by calculation, or based on a sensor placed on the hydraulic pump),
- Calculate said first current intensity (I1) and/or said first control pressure based on said tilt angle αpmp, said blocking current intensity and/or said blocking control pressure, said flow rate current intensity and/or said flow rate control pressure, e.g., by
interpolation curve 140. - It is clear, however, that both
curves - In fact, as shown in
Figure 3 (which shows two characteristic curves of two different pumps) the characteristic curve of each pump varies considerably. If, for example, the curve on the left is taken, it can be seen that in order to realize a pressure delta of 300 bar at a tilt angle αpmp of 5 degrees, a much smaller change in current/control pressure psA is required than is needed psB for the pump whose characteristic is shown infigure 3b . Therefore, this different sensitivity with respect to a load change results in a significant difference in the response of the pump whose characteristic is shown infigure 3a compared with that shown infigure 3b . - The inventor discovered that it is possible to carry out a method of calibrating the pump via software, instead of going to directly adjust the calibration of the pump itself, allowing one to go to directly calibrate the 100, 120 curves. This method includes the following steps:
Defining at least a first state of said hydrostatic drive system at which said calibration is to be performed, wherein said first state comprises one or more operating conditions, wherein each operating condition comprises a discharge pressure value of said hydraulic pump (12); - a. Measure the value of said first current intensity (I1) and/or said first control pressure required to arrive at each operating condition;
- b. Compare the value of said first current intensity (I1) and/or said first control pressure with a reference value of each operating condition;
- c. Correct said function according to the comparison made at said step c.
- The inventor has found that it is particularly advantageous if that first state coincides with the locked state since that condition is very easy to achieve and therefore such calibration can be done particularly easily.
- The condition shown with psA and psB in
Figure 3 can be considered very close to a lockout condition because it is a particularly small angle of pump inclination. Therefore, according to the method described above, it will suffice to define at least one pressure (e.g., 400 bar) and see what current I or what control pressure pst is required to reach that pressure in such a locked state. This value will then be compared with a reference value. For example, in the case shown infigure 3 , if we assume that curve 3a represents the reference curve we will go and compare the current/pressure value needed to reach for example 400 bar infigure 3b and compare it with the reference value infigure 3a . This difference will then be used to go to correct the blocking curve. - According to a preferred form of realization, this process is repeated for two operating conditions each containing a discharge pressure, so that there are two different points to be used for correction.
- According to a preferred form of embodiment, a first operating condition comprises a discharge pressure value of said
hydraulic pump 12 corresponding to a maximum usable pressure in said hydrostatic drive system, wherein said discharge pressure in said first operating condition is preferably between 400 and 500 bar, even more preferably being 450 bar. Further, a second operating condition comprises a discharge pressure value of saidhydraulic pump 12 preferably being between 150 and 300 bar, even more preferably being equal to 200 bar, wherein said discharge pressure of said second operating condition preferably corresponds to the discharge pressure of saidhydraulic pump 12 in a maximum flow condition. - In addition, the calibration method includes the following steps:
- Correct said blocking sub-function (the curve 120) based on the comparison made against one or more reference values. Such correction may, for example, be made by calculating a ratio of the measured current/pressure value to the reference value and then multiplying the reference curve by that value;
- Correcting said flow sub-function (the 100 curve) on the basis of said correction of said blocking sub-function.
- The present invention further describes a computational unit adapted to perform a method according to any of the preceding claims.
- Further, the present description includes a computer program that induces a computing unit to perform a method as described in the present invention.
- Also described is a readable storage medium comprising the computer program stored thereon described above.
- Although the present invention has been described with reference to the forms of embodiment described above, it is clear to the person skilled in the art that various modifications, variations, and improvements of the present invention in light of the teaching described above and within the scope of the appended claims are possible without departing from the subject matter and scope of protection of the invention.
- Finally, those areas that are believed to be known by experts in the field have not been described to avoid overshadowing the described invention unnecessarily.
- Accordingly, the invention is not limited to the forms of embodiment described above, but is only limited by the scope of protection of the appended claims.
Claims (12)
- Method for calibrating a hydraulic pump control system (12) for a hydrostatic drive system, wherein said hydrostatic drive system comprises said hydraulic pump (12), the rotation of which is ensured by a drive motor, and at least one hydraulic motor connected in a closed circuit to said hydraulic pump (12), wherein said hydraulic pump (12) has a regulating unit (4) for adjusting the displacement of said hydraulic pump, wherein said displacement is adjustable by adjusting a tilt angle (αpmp) of an inclined element (2), wherein said regulating unit (4) has a regulating cylinder (6) with a first regulating pressure chamber (81) in which, by means of a first valve (181) it is possible to set a first control pressure (pst1) which depends on a first current intensity (I1) of said first valve (181) and which is configured to influence the inclination (αpmp) of said inclined element (2), wherein said control unit (4) is configured in such a way that an increase in the delivery pressure of said hydraulic pump (2) tends to cause a reduction in the displacement of said hydraulic pump (12), said control system includes a function allowing to calculate said first current intensity (I1) and/or said first control pressure (pst1) as a function of a rotation speed of said drive motor or of a variable dependent thereon and on the basis of said tilt angle (αpmp); said method being characterized in that said function is calibrated and in that said calibration comprises said steps:a. Defining at least a first state of said hydrostatic drive system at which said calibration is to be performed, wherein said first state comprises one or more operating conditions, wherein each operating condition comprises a value of delivery pressure of said hydraulic pump (12);b. Measuring the value of said first current intensity (I1) and/or said first control pressure (pst1) required to reach each operating condition;c. Compare the value of said first current intensity (I1) and/or said first control pressure (pst1) with a reference value of each operating condition;d. Correcting said function according to the comparison made in said step c.
- Method according to claim 1, wherein said hydraulic pump is an axial piston pump.
- Method according to any one of claims 1 or 2, wherein said first state comprises at least two operating conditions.
- Method according to claim 3, wherein a first operating condition comprises a discharge pressure value of said hydraulic pump (12) corresponding to a maximum usable pressure in said hydrostatic traction system, wherein said discharge pressure in said first operating condition is preferably between 400 and 500 bar, even more preferably being equal to 450 bar, and wherein a second operating condition comprises a discharge pressure value of said hydraulic pump (12) preferably between 150 and 300 bar, even more preferably being equal to 200 bar.
- Method according to any one of claims 1 to 4, wherein said function comprises the following sub-functions:- Calculating, on the basis of said rotational speed of said drive motor or of said variable dependent thereon, a value of a blocking current intensity and/or a blocking control pressure (pBlock), wherein said blocking current intensity and/or said blocking control pressure (pBlock) correspond respectively to a hypothetical value of current and pressure which would be needed to regulate said hydraulic pump (12) in a blocking condition, at which said hydraulic motor is braked or at which the fluid flow rate passing through said hydraulic pump (12) is reduced to a volume close to zero, so that said hydraulic pump (12) delivers only a volume sufficient in this first state to cover losses along said hydrostatic drive system, wherein said calculation is performed by means of a blocking sub-function (120);- Calculating, on the basis of said rotational speed of said drive motor or of said variable dependent thereon, a value of a flow rate current intensity and/or of a flow rate control pressure (pQ), wherein said flow rate current intensity and/or said flow rate control pressure (pQ) correspond respectively to a hypothetical value of current and pressure which would be needed to regulate said hydraulic pump (12) in a condition of maximum flow of said hydraulic pump (12), at which the flow rate of fluid passing through said hydraulic pump (12) is increased until it reaches a maximum value, wherein said calculation is performed by means of a flow sub-function (100);- obtaining a current value of said tilt angle (αpmp) of said inclined element (2),- Calculating said first current intensity (I1) and/or said first control pressure based on said tilt angle (αpmp), said blocking current intensity and/or said blocking control pressure, said flow current intensity and/or said flow control pressure.
- Method according to claim 5, wherein said first state coincides with said blocking condition.
- Method according to any one of claims 5 or 6, when dependent on claim 4, wherein said discharge pressure of said second operating condition corresponds to a value of the discharge pressure in said maximum flow condition.
- Method according to any one of claims 5 to 7, wherein said step d. comprises the following sub-steps:- Correcting said blocking sub-function (120) on the basis of said comparison of said step c.;- Correcting said flow sub-function (100) on the basis of said correction of said blocking sub-function (120).
- A data processing device comprising means for carrying out a method according to any one of the preceding claims.
- An operating machine comprising a hydrostatic drive system, wherein said hydrostatic drive system comprises said hydraulic pump (12), the rotation of which is ensured by a drive motor, and at least one hydraulic motor connected in a closed circuit to said hydraulic pump (12), wherein said hydraulic pump (12) has a regulating unit (4) for adjusting the displacement of said hydraulic pump, wherein said displacement is adjustable by adjusting a tilt angle (αpmp) of an inclined element (2), wherein said regulating unit (4) has a regulating cylinder (6) with a first regulating pressure chamber (81) in which, by means of a first valve (181) it is possible to set a first regulating pressure which depends on a first current intensity (I1) of the first valve (181) and which is configured to influence the inclination (αpmp) of said inclined element (2), wherein said regulating unit (4) is configured in such a way that an increase in the delivery pressure of the hydraulic pump (2) tends to cause a reduction in the displacement of the hydraulic pump (12), wherein said operating machine comprises a data processing device according to claim 9.
- A computer program comprising instructions which, when the program is executed by a computer, cause the computer to carry out the steps of the method of any of claims 1 to 8.
- A computer-readable storage medium comprising instructions which, when executed by a computer, cause the computer to carry out the steps of the method of any of claims 1 to 8.
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IT102022000008888A IT202200008888A1 (en) | 2022-05-03 | 2022-05-03 | Calibration method of the regulation system of a hydraulic pump |
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Citations (4)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE102018210694A1 (en) | 2018-06-29 | 2020-01-02 | Robert Bosch Gmbh | Hydrostatic axial piston pump for a hydrostatic drive |
US20200003303A1 (en) * | 2018-06-29 | 2020-01-02 | Robert Bosch Gmbh | Hydrostatic Traction Drive with a Pressure Cutoff and Method for Calibrating the Pressure Cutoff |
US20210025374A1 (en) * | 2019-07-26 | 2021-01-28 | Robert Bosch Gmbh | Hydraulic Pressurizing Medium Supply Assembly, and Method |
DE102020207284A1 (en) | 2020-06-10 | 2021-12-16 | Robert Bosch Gesellschaft mit beschränkter Haftung | Hydrostatic adjustable axial piston pump and drive train with an axial piston pump and method for controlling an axial piston pump |
-
2022
- 2022-05-03 IT IT102022000008888A patent/IT202200008888A1/en unknown
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- 2023-04-27 EP EP23170277.0A patent/EP4273398A1/en active Pending
Patent Citations (5)
Publication number | Priority date | Publication date | Assignee | Title |
---|---|---|---|---|
DE102018210694A1 (en) | 2018-06-29 | 2020-01-02 | Robert Bosch Gmbh | Hydrostatic axial piston pump for a hydrostatic drive |
US20200003206A1 (en) * | 2018-06-29 | 2020-01-02 | Robert Bosch Gmbh | Hydrostatic Axial Piston Pump for a Hydrostatic Traction Drive |
US20200003303A1 (en) * | 2018-06-29 | 2020-01-02 | Robert Bosch Gmbh | Hydrostatic Traction Drive with a Pressure Cutoff and Method for Calibrating the Pressure Cutoff |
US20210025374A1 (en) * | 2019-07-26 | 2021-01-28 | Robert Bosch Gmbh | Hydraulic Pressurizing Medium Supply Assembly, and Method |
DE102020207284A1 (en) | 2020-06-10 | 2021-12-16 | Robert Bosch Gesellschaft mit beschränkter Haftung | Hydrostatic adjustable axial piston pump and drive train with an axial piston pump and method for controlling an axial piston pump |
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