CN113700692A

CN113700692A - Method for calibrating a continuously variable valve that can be regulated in an electrically proportional manner

Info

Publication number: CN113700692A
Application number: CN202110545641.5A
Authority: CN
Inventors: W·福特; B·塞莱斯; S·奥施曼
Original assignee: Robert Bosch GmbH
Current assignee: Robert Bosch GmbH
Priority date: 2020-05-20
Filing date: 2021-05-19
Publication date: 2021-11-26
Also published as: DE102020206343A1; KR20210144592A

Abstract

The invention relates to a method for calibrating a continuous valve arranged in a hydraulic system and adjustable in proportion to an actuation signal of an electronic control unit. According to the invention, the method comprises the following method steps: 1) regulating the pump pressure to a preset pressure with the continuous valve closed; 2) detecting a value at least for the displacement of the hydraulic pump; 3) starting from an initial actuation signal, the actuation signal of the continuous valve is changed, in particular increased, until a difference is detected, which corresponds to a predefined volume flow, between the current pump volume flow and the predefined pump volume flow in the case of a closed flow cross section of the continuous valve; 4) the offset of the actuating signal is determined by comparing the actuating signal of the continuous valve, which is detected when a predetermined volume flow is reached, with a theoretical actuating signal.

Description

Method for calibrating a continuously variable valve that can be regulated in an electrically proportional manner

Technical Field

The invention relates to a method for calibrating a continuous valve that can be adjusted proportionally to a control signal of an electronic control unit, said calibration taking into account the offset of the control signal in the following operating points: the working point has a predetermined pressure difference above the continuous valve and a predetermined volume flow through the continuous valve. Usually such continuous valves can be actuated directly electrically or electrohydraulic by means of proportional electromagnets. For example, after installation on a mobile work machine (e.g., an excavator), during operation, pressurized fluid can be supplied to the hydraulic consumers via such a continuous valve from the pressure connection of the hydraulic pump, the displacement of which, which can be detected with respect to its value, can be set and the pump pressure of which can be regulated.

Background

For manufacturing reasons, the continuously variable valve which can be adjusted in an electrically proportional manner has a divergence in the flow cross-section characteristic curve relative to the current through the proportional electromagnet. Typically the series divergence (serinstretuung) of the successive valves is present at a substantially constant offset of the steering signal. In other words, the control signal has a fixed value for the desired flow cross section, which is smaller or larger than the theoretical value. It is known to measure the manufactured continuous valve in order to compensate for the manufacturing divergence and to store in the controller the characteristic curve of the continuous valve which is manipulated by the electronic controller. Alternatively, the continuity valve is set in manufacture so as to reduce divergence. Both processing methods involve high costs. In addition, the control unit and the continuous valve controlled by the control unit are fixedly associated with each other. This makes subsequent replacement of the continuity valve difficult.

If the control unit itself recognizes how large the deviation of the actuating signal of the individual sequential valves is within the divergence width and generates and stores the individual characteristic curves of the sequential valves, the effort for taking into account the divergence or for constraining the divergence itself can be avoided or at least reduced and the subsequent exchange of sequential valves can be simplified.

A method for this is known from US 2017262001 a 1. It is proposed therein that a defined delivery quantity of the hydraulic pump first flows via a calibration metering orifice having a known flow cross section to the tank and then, with the calibration metering orifice closed, flows through the continuity valve, and that the actuating signal for the continuity valve is changed until the pressure drop across the continuity valve is as great as the previous pressure drop across the calibration metering orifice. The pump pressure and thus the pressure upstream of the calibrated orifice is detected by a pressure sensor. At the same throughflow rate and the same pressure drop, the throughflow cross section of the continuous valve is then as large as the throughflow cross section of the calibrated metering orifice, so that an operating point is known which has a specific value of the control signal and a specific value of the throughflow cross section which is linked to the specific value of the control signal. If a profile of the valve characteristic is known, in addition to the offset itself, the valve characteristic is shifted in such a way that: so that the operating point is located on the valve characteristic curve.

For the implementation of the method known from US 2017262001 a1, it is necessary to calibrate the orifice. This represents increased expenditure even if the calibrated metering orifice is integrated into a continuously adjustable bypass valve present in the hydraulic system, by means of which the pressure medium can be discharged from the pressure connection of the hydraulic pump to a tank. According to US 2017262001 a1, such a bypass valve has a rest position which is assumed by the action of a compression spring and in which there is a calibrated throughflow cross section from the pressure connection of the hydraulic pump to the tank, which is used as a calibration metering orifice. The bypass valve can be brought from the rest position by means of a proportional electromagnet via a position in which it is closed and there is no flow cross section from the hydraulic pump to the tank into the following positions: in these positions, flow cross sections of different sizes are provided. This means that in the closed position of the bypass valve the proportional solenoid is energized. If a currentless closed position with the bypass valve is desired, a second electromagnet may be required, by means of which the bypass valve can be brought into the following position: in this position, the calibrated flow cross section is opened.

Disclosure of Invention

The invention is therefore based on the object of specifying a method with which a continuity valve can be calibrated in a simple manner within the hydraulic system (which is a component of the hydraulic system) by means of an electronic control unit.

For a continuous valve arranged within the hydraulic system described at the outset, this object is achieved by a method having the method steps according to the invention.

The pump pressure is therefore regulated to a predetermined pressure with the continuous valve closed. A value is detected at least for the displacement of the hydraulic pump. This can also be achieved by: detecting a control signal for a control device of the hydraulic pump, the displacement being derived from the control signal, and the displacement itself being unknown or at least not precisely known. Axial piston pumps in the form of swash plate or inclined shaft arrangements are now commonly used as hydraulic pumps. Wherein the displacement is given by a swing angle of a swash plate or by a swing angle of a drum, taking into consideration the size and number of the axial pistons. Starting from an initial actuation signal, the actuation signal of the continuous valve is changed until a difference is detected between the current pump volume flow and the given pump volume flow in the case of a closed flow cross section of the continuous valve, which corresponds to the predefined volume flow.

The method according to the invention can be further designed in an advantageous manner.

In principle, it is conceivable to start with a high initial actuation signal, i.e. a high starting current and thus a wide open continuous valve, and to reduce the actuation signal until the hydraulic pump delivers a predefined volume flow. It is particularly preferred, however, to increase the actuating signal of the continuous valve from an initial actuating signal, at which the continuous valve is closed. As long as the continuous valve is closed despite the increase of the control signal, the delivery rate of the hydraulic pump is not changed. Once the continuity valve begins to open, a volume flow can flow through the continuity valve. This pressure regulation causes the displacement of the hydraulic pump to be increased, thus maintaining the preset pressure. The actuation signal for the continuous valve is further increased until a difference is reached, which corresponds to the predefined volume flow, between a current pump volume flow, which is determined by a current displacement and a current rotational speed of the hydraulic pump, and a pump volume flow, which is predefined by the displacement and the rotational speed of the hydraulic pump before the flow cross section of the continuous valve is opened. The volume flow flowing through the continuous valve is therefore equal to the change in the volume flow delivered by the hydraulic pump. Even when the volume flow delivered by the hydraulic pump with the continuous valve open and the current volume flow are not accurately determined, the change in the volume flow can be detected very accurately in comparison with the absolute value of the volume flow. Inaccuracies along the same direction and of at least almost the same magnitude do not play a role in the difference. The volume flow through the continuous valve can thus be determined without additional mechanical effort. Finally, the deviation of the actuating signal is determined by comparing the actuating signal of the continuous valve, which is detected when the predefined volume flow is reached, with a theoretical actuating signal. The individual method steps are automatically executed by the electronic control unit after a start signal, wherein the individual method steps are automatically executed by the electronic control unit in a very short time in the range of one second at least since the continuous valve starts to open.

In principle, it is conceivable for the regulating and control device of the hydraulic pump to comprise a pressure regulator, which can also be adjusted if necessary, and for the pump pressure for pressure control to be fed back hydraulically. It appears simpler, however, that the pump pressure can be detected by a pressure sensor, the electrical output signal of which, which serves to regulate the pump pressure to the preset pressure, is used by the electronic controller or by an electronic device mounted directly above the hydraulic pump, a so-called on-board electronic device.

It can be provided that the displacement of the hydraulic pump is detected by a displacement sensor using an electrical output signal and is therefore conducted back electrically. The supply and discharge of the pressurized fluid to and from the adjusting piston system of the hydraulic pump can then be effected by a simple electrically actuated directional control valve, for example by a proportional adjustable directional control valve with three hydraulic connections. Wherein the control signal for the directional valve is derived from the difference between the desired displacement and the displacement detected by the displacement sensor. If the desired displacement is present, the directional valve is in the following modulated position: in this control position, the valve connection connected to the control chamber of the control piston system is blocked with a small positive or negative coverage against the pressure connection and against the tank connection. After moving out of the regulating position, the pressure fluid of the regulating chamber flows to or from the regulating chamber, and the displacement volume is changed.

The displacement of the hydraulic pump can also be adjusted proportionally to the electric pump actuation signal. Reference is then made to the (EP-) regulation of the electrokinetic ratio. The position of an element (for example the swashplate) which determines the displacement of the hydraulic pump is guided back to the valve piston of the control valve as a force by a feedback spring. A proportional electromagnet acts on the valve piston, in opposition to the force of the feedback spring, whose force depends on the magnitude of the current flowing through it. If the spring force is as great as the magnetic force, the control valve is in a control position in which the compensation of the leakage is abandoned and the pressure fluid flows neither into nor out of the control chamber. The displacement of the hydraulic pump does not change. If the magnetic force increases or decreases due to a change in the current flowing through the electromagnet, the force balance at the valve piston is disturbed and the valve piston moves out of the regulating position. When pressure fluid flows into or out of the control chamber, the swash plate changes its position until there is again a balance between the force of the feedback spring and the magnetic force, which changes with the position of the swash plate. In EP control, the value of the pump control signal can thus be used to determine: the determined difference between the current pump volume flow and the pump volume flow before the opening of the flow cross section is achieved, and the value of the pump actuation signal is calculated taking into account the value of the pump actuation signal before the displacement is increased and the predefined determined pump volume flow difference. The pump actuation signal is here a current flowing through the proportional electromagnet.

The continuous valve is preferably a valve with exactly two connections, which is thus an adjustable throttle valve from the functional point of view.

In principle, it is conceivable that the rotational speed of the hydraulic pump changes when the method is performed. The pump volume flow at the beginning of the opening of the continuous valve is then derived from the displacement volume present at this point in time and from the rotational speed present at this point in time. The current displacement and the current rotational speed are used to derive the pump volume flow that should be present during an increase of the actuation signal of the continuous valve, so that the pump volume flow must be continuously calculated during a change in rotational speed until a predefined difference between the current pump volume flow and the pump volume flow that exists when the continuous valve begins to open is reached.

If, on the other hand, the rotational speed of the hydraulic pump is at least approximately constant during a change of the actuation signal for the continuous valve, the value of the displacement can be calculated using the rotational speed, and furthermore a predefined difference in the pump volume flow and thus a predefined value of the volume flow flowing through the continuous valve is achieved. It is only necessary to observe the value of the displacement as well and the volume flow need not be calculated continuously. This value of the displacement can thus be derived from the values of the displacement and the rotational speed during method steps one and two.

When during the execution of method step three the pressure fluid flows to the hydraulic consumer whose load pressure is known or can be estimated, the method is possible without a special design of the hydraulic system. Then no additional valve is required: the valve enables the quantity of pressure fluid flowing through the continuous valve to flow to the tank. For example, when calibrating the associated continuity valve, the boom and bucket of the excavator equipment can be freely suspended, so that the load pressure is zero. The pressure difference over the continuous valve is thus equal to the preset pressure. During the calibration process a certain amount of pressure fluid flows to the stick cylinder and to the bucket cylinder, so that their positions and thus also the load pressure change. However, the method can be carried out very quickly, so that the inflowing pressure fluid volume is small. The pressure difference is also only included in the volume flow in its root. During the execution of the method, the boom can be placed on the ground by means of the stick and the bucket.

It is also conceivable to measure the load pressure and to set the setpoint pressure, to which the hydraulic pump is controlled, above the load pressure by a predefined difference in each case.

The hydraulic consumers on mobile work machines are usually double-acting hydraulic cylinders, for which the control of the continuous valves to be calibrated is primarily provided. Then there is a main control valve in addition to the continuous valve for each hydraulic cylinder, with which the direction of movement of the hydraulic consumers can be controlled, but volume flow throttling is also possible. The main control valve has two consumer connections in fluid connection with the hydraulic consumers, a supply connection in fluid connection with the continuity valve, and a tank connection. It is particularly advantageous here if, during the method steps one to three, the low-load side of the hydraulic consumer is fluidically connected to the continuous valve via the main control valve. The method can then be performed in the following cases: in this case, the pressure on the side of the hydraulic cylinder opposite to the load side is zero or close to zero.

The hydraulic system, within which the continuous valve to be calibrated is arranged, may also comprise a continuously adjustable bypass valve, with which the flow cross section between the pressure connection of the hydraulic pump and the tank can be controlled. Even when the main control valve is of the kind having a closed intermediate position, load sensing (lastfuhligkeit) can thereby be obtained in accordance with a control manner of the hydraulic consumer, which is referred to as positive control. In the neutral position, a defined amount of pressure fluid (for example 30 l/min) flows from the hydraulic pump via the bypass valve to the tank. If a hydraulic consumer is actuated, the main control valve, the continuous valve and the bypass valve are actuated and their valve pistons are displaced proportionally to the magnitude of the actuating signal. This reduces the flow cross section of the bypass valve and simultaneously opens the flow cross sections at the main control valve and at the continuous valve. At the same time, the pump is proportionally swung outward. Once the pump pressure is greater than the load pressure, oil flows to a consumer. Advantageously, the bypass valve is opened during the method steps one to three. The bypass valve is set to such a throughflow cross section that is constant during calibration: so that the delivery rate of the hydraulic pump during the method steps one to three can set the pump pressure to a predetermined pressure. A too large flow cross section of the bypass valve can result in the preset pressure not being reached even with the maximum displacement of the hydraulic pump.

In the drawings, a hydraulic system with a continuous valve to be calibrated is shown, together with different diagrams of the time profile with the following quantities: the current, the throughflow cross section, the pump pressure and the delivery volume of the hydraulic pump during the execution of the example of the method according to the invention. The invention will now be further explained with the aid of said figures.

Drawings

In which is shown:

fig. 1 shows a circuit diagram of a hydraulic system which is shown in a simplified manner only with hydraulic cylinders and corresponding valves, wherein the hydraulic system is in an initial state;

FIG. 2 shows a circuit diagram of a modulation pump having a setting of an electrical proportion of displacement that can be used in the hydraulic system according to FIG. 1;

fig. 3 shows three graphs with a representation of the different variables at successive valves, namely: a predetermined pressure difference; current-an electromagnet with which to operate the continuous valve to be calibrated; and a volume flow flowing through the continuous valve during a time during which the method according to the invention is performed;

fig. 4 shows four graphs with an illustration of additional variables in the initial state and in successive phases of the time during which the method according to the invention is carried out;

fig. 5 shows a circuit diagram according to fig. 1 in a state during a first time period when a method for calibration is carried out;

fig. 6 shows a circuit diagram according to fig. 1 in a state during a second time period when the method for calibration is performed;

fig. 7 shows a circuit diagram according to fig. 1 in a state during a third time period when the method for calibration is performed; and is

Fig. 8 shows a circuit diagram of a control pump which can be used in the hydraulic system according to fig. 1, in which a set displacement can be detected by means of a pivot angle sensor.

Detailed Description

The hydraulic system according to fig. 1 comprises a double-acting hydraulic cylinder 15 designed as a differential cylinder, which is used, for example, to move components of a boom, and which has a cylinder housing 16, from whose inner chamber a piston 17 (from which a piston rod 18 projects on one side) divides into a piston rod-distal cylinder chamber 19 and a piston rod-side cylinder chamber 20.

The hydraulic system according to fig. 1 furthermore comprises a hydraulic pump 25 which can be set on one side between a minimum and a maximum value with respect to the displacement of the hydraulic pump by means of a setting device 24, is designed as an axial piston pump in the form of a swash plate and can be driven, for example, by a diesel engine. The hydraulic cylinders 15 and, as a rule, further hydraulic cylinders or hydraulic motors, which are not shown, can be supplied with pressure fluid individually or also simultaneously by the hydraulic pump 25. The hydraulic pump 25 draws pressure fluid from a tank 26 and discharges it via a pressure connection 27 into a pump line 28. The rotation speed of the hydraulic pump 25 is detected by a rotation speed sensor 23.

The inflow and outflow of pressure fluid to and from the hydraulic cylinder 15 is controlled by a valve system, the individual valves of which are combined to form a valve disk 29, which can be constructed as a control block together with other valve disks of the same or similar construction. The valve system, to which the main valve 30 belongs, determines the following directions: the piston rod 18 of the hydraulic cylinder 15 moves in this direction; and having a consumer connection 31 in fluid connection with the chamber 19 of said hydraulic cylinder 15; and the master valve has a consumer connection 32 in fluid connection with the chamber 20 of the hydraulic cylinder; and the main valve has a pump connection 33 for which said hydraulic pump 25 is able to deliver a fluid under pressure; and has two tank connections 34 from which the pressure fluid can flow out into the tank 26. The control slide, not shown in detail, of the main valve 30, under the action of the two return springs 35 assumes the intermediate position shown in fig. 1, in which the connections of the main valve are blocked with respect to each other. It can therefore also be said that the valve disk has a blocked intermediate position (Closed-Center-steuerscheib). By means of two pressure control valves, each of which can be set by a proportional electromagnet 36, the control slide can be set proportionally continuously from the intermediate position to one side or the other side in relation to the control signal. On movement in one direction, the consumer connection 31 and thus the cylinder chamber 19 open towards the pump connection 33 and the consumer connection 32 and thus the cylinder chamber 20 open towards the tank connection 34, so that pressure fluid delivered by the hydraulic pump can flow towards the cylinder chamber 19 and pressure fluid can flow away from the cylinder chamber 20 to the tank 26. When the control slide moves out of the neutral position in the opposite direction, the consumer connection 32 and therefore the cylinder chamber 20 open towards the pump connection 33 and the consumer connection 31 and therefore the cylinder chamber 20 open towards the tank connection 34, so that pressure fluid delivered by the hydraulic pump can flow towards the cylinder chamber 20 and pressure fluid can flow away from the cylinder chamber 19 to the tank 26.

Between the pressure connection 27 of the hydraulic pump 25 and the pump connection 33 of the main valve 30, a continuous valve 40 is arranged, which is adjustable in proportion to the actuating signal and has two working connections 41 and 42, wherein the inlet connection 41 is fluidically connected to the pump line 28 and the outlet connection 42 is fluidically connected to the pump connection 33 of the main valve 30. Under the action of the return spring 43, the continuity valve 40 assumes a rest position in which it blocks the two working connections from each other. The continuous valve 40 can be continuously adjusted from a rest position up to a maximum open position. When the valve is adjusted out of the rest position, the flow cross section through the continuous valve becomes increasingly larger to a maximum value. The adjustment is effected electro-hydraulically by means of a pilot valve (pilotpilot) which can be adjusted by a proportional electromagnet 44, so that the throughflow cross section of the continuous valve 40 is ultimately dependent on the signal with which the proportional electromagnet 44 is actuated and thus the current flowing through it. When the pressure at the connection 42 of the continuity valve is higher than the pressure at the connection 41, i.e. higher than the pump pressure in the pump line 28, the continuity valve 40 additionally acts as a load holding valve and closes.

A continuously adjustable bypass valve 50 is connected to the pump line 28, by means of which bypass valve pressure fluid can flow directly out of the pump line 28 to the tank 26. Under the action of the return spring 51, the bypass valve 50 assumes a rest position in which a maximum throughflow cross section between the pump line 28 and the tank 26 is open. The bypass valve 50 can be adjusted from the rest position into a closed position with a continuously decreasing flow cross section, in which no more pressurized fluid can flow from the pump line to the tank via the bypass valve. A proportional electromagnet 52 is used for the adjustment.

The pressure in the pump line is detected by a pressure sensor 54.

The direction and speed with which the piston and the piston rod of the hydraulic cylinder are to be moved can be predetermined using the electrical input device 55. The electrical signal of the input device 55 is supplied via an electrical line 56 to an electronic control unit 57 with a microcontroller, which in addition receives an electrical signal from the rotational speed sensor 23 via an electrical line 53, which electrical signal represents the rotational speed of the hydraulic pump 25; and the electronic controller obtains an electrical signal from the pressure sensor 54 via electrical lead 58 that is indicative of the pressure in the pump line 28, i.e., the pump pressure. The two proportional electromagnets 36 of the main valve 30, the proportional electromagnet 44 of the continuous valve 40, the proportional electromagnet 52 of the bypass valve 50 and the proportional electromagnet 59 of the regulating device 24 for regulating the displacement of the hydraulic pump 25 are connected to an electronic control 57 via

electrical lines

61, 62, 63, 64 and 65 and are energized by the electronic control as a function of the signals of the input device 55, as a function of the state of the hydraulic system and as a function of the actuation of the method for calibrating the continuous valve 40.

The displacement of the hydraulic pump 25 is configured by the control device 24, which is shown in more detail in fig. 2, according to an electric proportional (EP-) control with an overlapping maximum pressure control. However, in the case of a signal containing the pressure sensor 54, it is also possible to control the pressure below the maximum pressure. The regulating device 24 comprises a regulating piston 73 which is linearly displaceable and which delimits a regulating chamber 74, to which a pressure medium can flow and from which a pressure medium can be pressed out by means of two regulating valves, if controlled by these regulating valves. Under the effect of the pressure prevailing in the adjustment chamber 74, the adjustment piston 73 bears against the swash plate 75 and attempts to adjust the swash plate 75 in the direction of reducing the displacement.

A counter spring (gegenelder) 76 acts in the opposite direction on the swash plate 75, which, unlike the one shown in the circuit diagram according to fig. 2, does not act directly on the adjusting piston 73, but on the swash plate 75. The effect of the counter spring on the adjusting piston necessitates a positive connection between the adjusting piston and the swash plate in both adjustment directions.

A control valve 78, which serves as a pressure control and has a control piston 79 for controlling the pump pressure, more precisely for limiting the pump pressure, is formed on the flange face of the pump housing 77, which is shown in a dash-dot line. The control piston 79 is acted upon by a settable control spring 80 in the direction of a rest position, which is shown in fig. 2 and can be adjusted continuously from the rest position. The control piston forms, together with a housing, not shown in detail, a two-position, three-way directional valve which can be adjusted proportionally.

The control valve 78 has a pressure connection P, a control connection a and a tank connection T in the mounting surface with which it rests on the flange surface. The pressure connection P is fluidly connected via a bore in the pump housing 77 to a high pressure passage leading to the pressure connection 27 of the hydraulic pump 25. The tank connection is connected to the interior of the pump housing 77 via a bore in the pump housing and is connected to the tank via a leak connection of the pump housing in a manner not shown in detail. The control connection a is connected to an adjusting chamber bore, in which the adjusting piston 73 is guided in a movable manner, via a bore in the pump housing 77. The control valve 78 allows the pressure medium to be supplied directly from the pressure connection P to the regulating chamber 74 via the control connection a or to be discharged from the regulating chamber to the tank connection T.

The control piston 79 of the pressure regulator 78 is acted upon by the pump pressure against a control spring 80.

In the rest position of the pressure regulator 78, its control port a is connected to the tank port T, so that the pressure medium can be displaced out of the adjustment chamber 74 by means of the counter spring 76. Thereby increasing the displacement of the regulating pump. If the pump pressure is so high: so that it exceeds the pressure of the regulating spring 80, etc., the regulating piston 79 of the pressure regulator 78 is moved out of its rest position, so that pressure fluid can be delivered from the pressure connection 27 of the hydraulic pump 25 to the regulating chamber 74 via the pressure regulator and the displacement of the hydraulic pump is reduced.

The fluid path does not lead directly from the control connection a of the pressure regulator 78 to the adjustment chamber 74. Rather, a control valve 81, which can be actuated proportionally by the proportional electromagnet 59, is also inserted into the control chamber bore as an insert cartridge (einbaupitatron) and delimits the control chamber 74 on the side opposite the control piston 73, into the fluid path. The control valve 81 (also referred to as EP regulator as desired) has a pressure connection directly connected to the high-pressure side of the hydraulic pump 25, an inert connection connected to the control connection a of the pressure regulator 78, and a regulating chamber connection connected to the regulating chamber 74. The control piston 82 of the control valve 81 is acted upon by the force of a feedback spring 83 clamped between the control piston 82 and the control piston 73 in the direction of a rest position, in which the control chamber connection is connected to the pressure connection of the control valve 81. The force of the feedback spring depends on the position of the adjusting piston 73 and thus on the position of the swash plate 75. The proportional electromagnet 59 can move the control piston 82 against the feedback spring 83 into a position in which the adjustment chamber connection is connected to the inert connection and further to the pressure connection P or the tank connection T of the pressure regulator via the control connection a of the pressure regulator 78. The control piston 82 is pressure-balanced with respect to the pressure prevailing in the adjusting chamber 74. The pressure prevailing in the adjustment chamber therefore does not exert the resulting force on the regulating piston 82. When the force exerted by the feedback spring 83 is as great as the force of the proportional electromagnet 59, the regulating piston takes up a regulating position. Since the force exerted by the feedback spring 83 depends on the position of the swashplate 75, the determined angle of oscillation of the swashplate 75 is regulated in proportion to the current flowing through the proportional electromagnet 59. The control valve 81 thus effects a regulation of the electrical ratio of the hydraulic pump 25.

In the variant of the electric proportional control shown in fig. 2, the control valve 81 has a third position, into which it enters in the event of a loss of control signal. The hydraulic pump is set to maximum displacement when the control signal is lost.

Fig. 3 shows three graphs which show an exemplary deviation of the characteristic curve of the continuous valve 40 from the theoretical characteristic curve. The uppermost diagram shows the pressure exerted on the continuous valve over a time range for which a specific value is predefined, i.e. for example a working point pressure of 50 bar. According to the middle diagram, the control signal for the continuous valve 40, i.e. the current flowing through the proportional electromagnet 44, increases in a ramp-like manner over a time range. In the lowermost diagram, the theoretical volume flow through the continuous valve 40 is shown by dashed lines, and the actual volume flow through the continuous valve is shown by solid lines, as is the volume flow that occurs during a ramp-like increase in the current. Additionally, the working point volume flow is plotted, for example, at 10 l/min. In principle, at a predefined operating point pressure, at time T1, an operating point volume flow should be reached at the rated current I1 flowing through proportional electromagnet 44. Since the manufacturing-related deviation causes the continuous valve 40 to open later, the operating point volume flow is only reached at a later time T2 at a higher current value I2 than the current value I1. The difference between the current value I2 and the current value I1 is the current offset which is acquired in the hydraulic system by the electronic controller 57 individually for each successive valve 40 by the calibration procedure according to the invention.

In fig. 4, the uppermost diagram shows the current which flows in the initial state a and during the different phases b, c, d and e of the calibration process through the proportional electromagnet 44 of the continuous valve 40, the proportional electromagnet 52 of the bypass valve 50, the proportional electromagnet 59 of the regulating device 24 and one of the proportional electromagnets 36 at the main valve 30. The curves are provided with the same reference numerals as the proportional electromagnets which are energized accordingly. The second diagram shows the pump volume flow from above in the initial state a and during the calibration phases b to e. The third diagram shows the flow cross sections of the

valves

30, 40 and 50 from above in the initial state and in different calibration phases. The curves are provided with the same reference numerals as the corresponding valves. The dashed line indicates the theoretical throughflow cross section of the continuous valve 40. And finally, the lowermost diagram shows the pump pressure in the initial state and during the calibration process, wherein in the present case the pump pressure during the calibration process is equal to the operating point pressure and regulated. Advantageously, the rotational speed of the hydraulic pump 25 is kept constant during the calibration process. This is taken as a starting point in the following.

In an initial state a (which is shown in fig. 1), the hydraulic system is in standby operation. The hydraulic pump 25 generates a standby volume flow which results from the energization of the proportional electromagnet 59 and flows through the opened bypass valve 50 into the tank 26. According to the uppermost diagram of fig. 4, the proportional electromagnet 52 of the bypass valve has been loaded with a certain current. The continuity valve 40 is closed, whereas according to the uppermost diagram of fig. 4 already a low current flows through the proportional electromagnet 44 of the continuity valve 40. The main valve 30 is located in its neutral position. No pressure regulation is activated for the hydraulic pump 25. The pump pressure is derived from the standby volume flow of the hydraulic pump 25 and the throughflow cross section of the bypass valve 50.

The calibration process starts in phase b. By energizing said proportional electromagnet 52 with a higher intensity and during a further phase to remain constantThe bypass valve 50 is set to this smaller throughflow cross section by energization in a defined manner, so that the operating point pressure to be controlled can be reached in the pump line 28. The hydraulic pump 25 is pressure-regulated to a predefined working point pressure by means of the pressure sensor 54 and the electronic control unit 57 and its regulating device 24, wherein the proportional electromagnet 59 is supplied with a current I1 that is increased compared to the initial phase a_Pumpe. Current value I1_PumpeStored by the electronic controller 57. The proportional electromagnet 36 of the main valve 30 is fully energized and remains fully energized during the calibration process, so that there is an open fluid connection from the continuous valve 40 to the hydraulic cylinder 15.

In phase b of the calibration process, the entire volume flow generated by the hydraulic pump 25 flows out via the bypass valve 50 to the tank 26.

Starting from the minimum current supply, in phase c of the calibration process, the current flowing through the proportional electromagnet 44 of the continuity valve 40 increases slowly, as is indicated in fig. 6 by the increasing lightning above the continuity valve 40. From the third diagram above fig. 4 it follows that: the continuity valve 40 has not been opened during phase c. In phase c, the volume flow of the hydraulic pump 25 is therefore the same as in phase b, as is also evident from the second diagram above fig. 4. Furthermore, the pump volume flow flows out via the bypass valve 50 to the tank 26.

Phase d of the calibration process begins when a current value is reached at the proportional electromagnet 44 of the continuous valve 40, at which the continuous valve begins to open. From this point in time, the volume flow can flow from the pump line 28 to the hydraulic cylinder 15 via the continuous valve 40 and via the main valve 30 which has opened since the start of phase b. Since the pressure fluid now flows away from the pump line not only via the bypass valve 50 but also via the continuous valve 40, the displacement of the hydraulic pump 25 is increased as a result of the pressure regulation in order to maintain the operating point pressure in the pump line. The larger the current flowing through the proportional electromagnet 44, the larger the flow cross section in the continuous valve 40, the larger the volume flow of the hydraulic pump, and the larger the current flowing through the proportional electromagnet 59 of the EP control device 24 of the hydraulic pump, which is necessary for generating the volume flow. The volume flow out of the bypass valve 50 to the tank does not change, since the flow cross section of the bypass valve and the pump pressure do not change.

At this time, the rotation speed of the hydraulic pump and the stored current value I1_PumpeThe current value I2 can be calculated_PumpeHow large is at the current value I2_PumpeThe operating point volumetric flow rate flows through the continuity valve 40. It is particularly advantageous here that the relationship between the displacement and the current through the proportional electromagnet 59 exhibits a linear relationship. The necessary displacement change is not dependent on the absolute displacement. Since the relationship between the working point volume flow through the continuous valve 40 and the change in the current at the hydraulic pump 25 necessary for this is now known, the change in the volume flow of the hydraulic pump corresponding to the working point volume flow through the continuous valve 40, and therefore the working volume flow, can be determined very accurately, starting from the pump volume flow which is unknown or inaccurate in phases b and c of the calibration process. For the acquisition of the working point volume flow, it is only necessary to know the change in the pump volume flow, whereas the absolute values of the volume flows in phases b and c of the calibration process do not have to be known.

The current value I2 is reached at the pump as soon as the current flowing through the proportional magnet 44 of the continuity valve 40 continues to increase at this point_PumpeThe final phase e of the calibration process is started. The controller 57 knows that the working point volume flow is now flowing through the continuity valve 40. Furthermore, the controller 57 knows how large the current flowing through the proportional electromagnet 44 of the continuity valve 40 is at the point in time at which the operating point volume flow flows through the continuity valve 40 and stores the current as a current value I2. At current value I2 and current value I1, at which current value I1 hour, the difference between the working point volume flow which should flow through the continuous valve 40 at a given working point pressure is the current offset. The current offsets are stored in the control 57 and the production-related deviations of the individual sequential valves 40 are corrected from the theoretical characteristic curve by adding the current offsets at each actuation signal to be sent to the proportional electromagnets 44 of the sequential valves 40 to the theoretical actuation signal, taking into account the sign of the current offsets.

It is advantageous for the method that the load pressure is as low as possible and is significantly lower than the operating point pressure in order to enable a volume flow to the hydraulic consumer. For the inflow of pressure fluid during the calibration process, a cylinder chamber with a lower load can be selected by means of the main valve. It is particularly advantageous to know the load pressure, for example by measuring or estimating from a known position of the kinematics. The regulated pump pressure can then be increased by the load pressure compared to the value at zero load pressure, so that a pressure difference corresponding to the operating point pressure is present across the continuous valve.

It is conceivable that the bypass valve 50 is kept closed during the calibration process. However, most hydraulic pumps have a mechanical stop for minimum displacement. In the initial state of phase a according to fig. 4, the standby volume flow, which is derived from the minimum displacement and rotational speed of the hydraulic pump, can flow out to the tank with little loss, and in phases b and c, a pressure below the maximum pressure can be regulated.

For the calibration of the valve according to the invention, a control pump with an EP control device is not necessarily required. Other adjustment means are also possible.

Fig. 8 thus shows a hydraulic pump in the form of an axial piston design, for which the displacement and in particular the displacement change is determined by means of a pivot angle sensor.

The adjusting device 24 shown in fig. 8 for adjusting the swash plate 75 of the pump 25 comprises: a single-acting adjusting piston 86 with which the swash plate can be pivoted in the sense of a reduced tilting position and thus a reduced displacement; and a single-acting counter-piston 87 which, together with a spring 88, is able to oscillate the swash plate in the sense of increasing the inclined position and thus the displacement, and whose active surface is smaller than that of the adjusting piston 86. The counter chamber 89 surrounding the counter piston 87 is continuously connected to the pressure connection 27 of the control pump 25, so that the counter piston is acted upon by the pump pressure.

The inflow and outflow of hydraulic oil to and from the adjusting chamber 90, into which the adjusting piston 86 is inserted, is controlled by a control valve 91, which is designed as a proportionally adjustable two-position three-way directional valve having: a pressure connection 92, which is connected to the pressure connection 27 of the control pump; and a tank fitting 93 in fluid connection with the interior of said pump housing 77 and therewith with said tank 26. The regulating valve 91 finally has a regulating chamber connection 94 which is in fluid connection with the regulating chamber 90. In the rest position of the control valve 91, which is assumed by the action of the compression spring 95, a large flow cross section exists between the adjustment chamber connection 94 and the tank connection 93. By means of a proportional electromagnet 96, the control valve 91 can be moved out of the rest position to different extents depending on the magnitude of the magnet current against the force of the compression spring 95. In the case of a certain magnitude of the current flowing through the proportional electromagnet 96, the control piston, not shown in detail, of the control valve 91 assumes a control position in which the control chamber port 94 is largely blocked with a small negative coverage relative to the pressure port 92 and relative to the tank port 93. In the regulating position, only a small amount of leakage flow from the regulating chamber is replaced. The inclined position of the swash plate 75 and thus the displacement of the regulating pump 25 is not changed. The current that then flows through the proportional electromagnet 96 is also referred to as neutral current.

If the current flowing through the proportional electromagnet 96 is reduced compared to the neutral current, the compression spring 95 is able to move the control piston from the control position into a position in which the control chamber connection 94 is opened towards the tank connection 93. The size of the current cross section depends on how large the difference between the neutral current and the current at the moment is. Hydraulic oil can now be displaced out of the adjustment chamber 90 via the adjustment chamber connection 94 and the tank connection 93, so that the tilting position of the swash plate 75 is increased. If the current flowing through the proportional electromagnet 96 is increased compared to the neutral current, it can move the control piston from the control position into a position in which the control chamber connection 94 is open toward the pressure connection 92. The size of the through-flow cross-section depends on how large the difference between the current and the neutral current at the moment is. It is now possible to let hydraulic oil flow from the pressure connection 27 of the regulating pump 25 into the adjusting chamber 90, so that the tilting position of the swash plate 75 is reduced.

In the regulating pump 25 according to fig. 8, the swivel angle of the swash plate 75 and thus the displacement is detected by a swivel angle sensor 97 serving as a displacement sensor which issues an electrical output signal to the electronic controller 57. The electronic controller compares the output signal of the pivot angle sensor 97, which corresponds to the actual value of the pivot angle, with a setpoint value and actuates the control valve 91 as a function of the difference between the setpoint value and the actual value of the pivot angle.

In the case of the control pump according to fig. 8, a pressure sensor 54 connected to the control unit 57 is also provided for detecting the pump pressure. This makes it possible to regulate the pump pressure. The signal from the pivot angle sensor 97 allows very accurate detection of the working point volume flow through the continuous valve 40, so that the calibration method according to the invention can also be carried out with the hydraulic pump according to fig. 8.

List of reference numerals

15 hydraulic cylinder

1615 Cylinder housing

1715 piston

1815 piston rod

1915 Cylinder Chamber distal to piston rod

2015 cylinder chamber on piston rod side

23 speed sensor

24 adjustment device

25 hydraulic pump

26 storage tank

2725 pressure joint

28 pump pipeline

29 valve disk

30 main valve

3130A consumer connector

3230 consumable connector

3330 pump connector

3430 tank fitting

35 return spring

36 proportion electromagnet

40 continuous valve

4140 working joint

4240 working joint

43 Return spring

44 ratio electromagnet

50 bypass valve

5150 Return spring

5250 proportional electromagnet

53 electric lead

54 pressure sensor

55 electric input device

56 electrical lead

57 electronic controller

58 electrical lead

59 proportional electromagnet at 25

61 electric lead

62 electric lead

63 electric lead

64 electric lead

65 electric lead

73 adjusting piston

74 adjustment chamber

7525 swash plate

76 spring back

77 Pump casing

78 regulating valve

7978 regulating piston

8078 regulating spring

81 regulating valve

8281 regulating and controlling piston

83 feedback spring

86 adjusting piston

87 paired piston

88 spring

89 paired chambers

90 adjustment chamber

91 regulating and controlling valve

9291 pressure joint

9391 tank connector

9491 regulating chamber joint

95 compression spring at 91

9691 ratio electromagnet

97 swing angle sensor.

Claims

1. Method for calibrating a continuous valve (40) arranged in a hydraulic system and adjustable in proportion to an actuation signal of an electronic control unit (57), said calibration taking into account a deviation of the actuation signal in an operating point having a predefined pressure difference across the continuous valve (40) and a predefined volume flow through the continuous valve (40), wherein a pressure fluid can be supplied by the continuous valve (40) from a pressure connection of a hydraulic pump (25) whose displacement, which can be detected in terms of its value, can be adjusted to a hydraulic consumer (15), and the pump pressure of which can be regulated, having the following method steps:

1) regulating the pump pressure to a preset pressure with the continuous valve (40) closed;

2) detecting a value at least for the displacement of the hydraulic pump (25);

3) starting from an initial actuation signal, the actuation signal of the continuous valve (40) is changed until a difference is detected between the current pump volume flow and the pump volume flow specified with the closed flow cross section of the continuous valve (40), said difference corresponding to the specified volume flow;

4) the deviation of the control signal is determined by comparing the control signal of the continuous valve (40), which is detected when the predefined volume flow is reached, with a theoretical control signal.

2. Method according to claim 1, wherein during method step three, the actuation signal of the continuous valve (40) is increased starting from an initial actuation signal, at which the continuous valve (40) is closed, until a difference is detected, corresponding to the predefined volume flow, between the current pump volume flow and the pump volume flow specified before the opening of the flow cross section of the continuous valve (40).

3. Method according to claim 1 or 2, wherein the pump pressure is detectable by a pressure sensor (54), the electrical output signal of which is used to regulate the pump pressure to the preset pressure.

4. A method according to claim 1, 2 or 3, wherein the displacement of the hydraulic pump (25) is detected by means of a displacement sensor (97).

5. A method according to claim 4, wherein the displacement of the hydraulic pump (25) is adjustable via an electrically operated directional control valve (91), by the delivery of pressure fluid to an adjusting device (24) and the discharge from the adjusting device (24), and wherein an operating signal for the directional control valve (91) is derived from the difference between the desired displacement and the displacement detected by a displacement sensor (97).

6. Method according to claim 3 or 4, wherein the displacement of the hydraulic pump (25) is adjustable proportionally to an electrical pump steering signal, and wherein by means of the value of the pump steering signal: the determined difference between the current pump volume flow and the pump volume flow before the opening of the flow cross section is achieved, and the value of the pump actuation signal is calculated taking into account the value of the pump actuation signal before the displacement is increased and the predefined determined pump volume flow difference.

7. Method according to the preceding claim, wherein the continuous valve (40) is a valve with exactly two joints.

8. Method according to the preceding claim, wherein the rotational speed of the hydraulic pump (25) is at least almost constant during the variation of the command signal for the continuous valve (40), and the following displacements are obtained from the values of the displacements and from the values of the rotational speed during method steps one and two: in the case of the displacement, a defined difference between the pump volume flows is achieved.

9. Method according to the preceding claim, wherein during the third method step pressure fluid is caused to flow to the hydraulic consumer (15), and wherein the load pressure of the hydraulic consumer (15) is known or can be estimated.

10. Method according to claim 9, wherein the preset pressure, to which the hydraulic pump (25) is regulated, is higher than the load pressure by a predetermined difference.

11. Method according to the preceding claim, wherein the hydraulic consumer (15) is a dual-acting hydraulic consumer, in particular a dual-acting hydraulic cylinder, and the direction of movement of the hydraulic consumer can be controlled by means of a main control valve (30) having two consumer connections (31, 32) in fluid connection with the hydraulic consumer, a supply connection (33) in fluid connection with the continuity valve (40), and a tank connection (34), and wherein the lower side of the load of the hydraulic consumer (15) is in fluid connection with the continuity valve (40) via the main control valve (30) at least during the method steps one to three.

12. Method according to the preceding claim, wherein the hydraulic system comprises a continuously adjustable bypass valve (50) with which the flow cross section between a pressure connection (27) of the hydraulic pump (25) and a tank (26) can be controlled, and wherein the bypass valve (50) is opened during the method steps one to three and is set to a flow cross section such that: so that the delivery rate by the hydraulic pump (25) during the method steps one to three can regulate the pump pressure to a predetermined pressure.