METHOD FOR COMPENSATING FOR TOLERANCES, PLAY AND ELASTICITY IN A MOTOR-DRIVEN HYDRAULIC VALVE

Abstract

Techniques involve detecting a mechanical play (W.sub.s) in a system having a hydraulic valve and a valve drive for driving the hydraulic valve. A valve slide, which is driven by the valve drive of the hydraulic valve, is clamped with at least one return spring which is designed, in the case of a de-energized valve drive, to push the valve slide from any arbitrary valve slide position back into a neutral position of the valve slide.

Claims

1. A method for detecting a mechanical play (W.sub.s) in a system having a hydraulic valve and a valve drive for driving the hydraulic valve, wherein a valve slide, which is driven by the valve drive, of the hydraulic valve is clamped with at least one return spring which is designed, in the case of a deenergized valve drive, to push the valve slide from any arbitrary valve slide position back into a neutral position of the valve slide, comprising the following steps: a) moving the valve slide by the valve drive in a first direction (R.sub.1) up to a first valve slide position (P.sub.1) outside a neutral position; b) reducing the current at the valve drive such that the valve slide is moved by the return spring in a second direction (R.sub.2) counter to the first direction (R.sub.1) back into the neutral position; c) moving the valve slide by the valve drive further in the second direction (R.sub.2) up to a defined second position (P.sub.2d) outside the neutral position and determining a first path (W.sub.1) from the neutral position to the defined second position (P.sub.2d); d) reducing the current at the valve drive such that the valve slide is moved by the return spring in the first direction (R.sub.1) back into the neutral position; e) moving the valve slide by the valve drive in the second direction (R.sub.2) up to the defined second position (P.sub.2d) outside the neutral position and determining a second path (W.sub.1s) from the neutral position to the defined second position (P.sub.2d); and f) calculating the play (W.sub.s) as difference between the second path and the first path.

2. The method as claimed in claim 1, wherein the neutral position of the valve slide is a neutral position region which extends from a first neutral position end position (N.sub.1end) up to a second neutral position end position (N.sub.2end), and wherein, in step b), the valve slide is pressed by the return spring into the second neutral position end position (N.sub.2end) and, in step d), the valve slide is pressed by the return spring into the first neutral position end position (N.sub.1end).

3. The method as claimed in claim 1, wherein the neutral position of the valve slide is arranged within an overlapping region between two opening points (P.sub.1o, P.sub.2o) of the hydraulic valve, and wherein hydraulic lines of the hydraulic valve are closed if the valve slide position lies within the overlap-ping region and an opening of hydraulic lines begins at the two opening points (P.sub.1o, P.sub.2o).

4. The method as claimed in claim 3, wherein, in step a), a defined safe path (W.sub.d) is travelled which is shorter than a distance (a) between a neutral position end position (N.sub.1end, N.sub.2end) and the corresponding opening point (P.sub.1o, P.sub.2o) of the hydraulic valve.

5. The method as claimed in claim 3, wherein the first position (P.sub.1) moved to in step a) and/or the defined second position (P.sub.2d) moved to are arranged within the overlapping region of the valve slide.

6. The method as claimed in claim 1, wherein the valve drive has a stepper motor, and wherein a measurement of paths (W) in the method occurs by counting steps of the stepper motor.

7. The method as claimed in claim 1, wherein method steps a) to f) are carried out during an initial commissioning of the system and/or during a recommissioning of the system after a repair or maintenance and at least the play (W.sub.s) calculated in step f) and, where appropriate, also further values are stored in a control device for operating the system and are then available for the operation of the system.

8. The method as claimed in claim 1, wherein the defined second position (P.sub.2d) moved to in step c) and step e) is an opening point (P.sub.2o) of the hydraulic valve which, in step c) and step e), is detected on the basis of a hydraulic property in the hydraulic valve and/or in a hydraulic system connected to the hydraulic valve.

9. The method as claimed in claim 8, wherein, after step e), the following step is carried out: g) moving the valve slide in the first direction up to a defined first position (P.sub.1d); and wherein the defined second position (P.sub.2d) moved to in step c) and step e) and the defined first position (P.sub.1d) moved to in step g) are each opening points (P.sub.1o, P.sub.2o) of the hydraulic valve which, in steps c), e) and g), are detected on the basis of a hydraulic property in the hydraulic valve and/or in a hydraulic system connected to the hydraulic valve.

10. The method as claimed in claim 1, wherein the defined second position (P.sub.2d) moved to in step c) and step e) is defined by a spring force of the return spring of the hydraulic valve, and wherein the spring force is detected in the valve drive in step c) and in step e).

11. The method as claimed in claim 1, wherein the defined second position (P.sub.2d) moved to in step c) and step e) is detected in that the valve drive is controlled with a reduced drive current and a valve slide position which can be achieved with this drive current is the second defined position (P.sub.2d).

12. The method as claimed in claim 1, wherein the defined second position (P.sub.2d) moved to in step c) and step e) is detected on the occurrence of a step loss which occurs on a stepper motor of the valve drive and which is detected with a step loss detection configured therefor in a control device of the valve drive.

13. The method as claimed in claim 1, wherein method steps a) to f) are carried out during a renewed commissioning of the system after an initial commissioning of the system and/or after a recommissioning of the system after a repair or maintenance and parameters determined with method steps a) to f) are compared with parameters which are stored in a control device and which have been determined during a previous implementation of method steps a) to f), and, on the basis of this comparison, wear of the system consisting of hydraulic valve and valve drive is determined.

14. A system having a hydraulic valve and a valve drive, which is configured for carrying out the method as claimed claim 1.

15. A control device for a system as claimed in claim 14, which is configured for carrying out the method.

16. A method for operating a system having a hydraulic valve and a valve drive for driving the hydraulic valve, wherein a play (W.sub.s) exists between the valve drive and the valve slide, and wherein at least one last drive direction (R) and the play (W.sub.s) are stored as variables in a control device for controlling the actuation of the valve slide and are taken into consideration during actuation of the valve slide with the valve drive.

Description

[0061] The invention and the technical field of the invention will be described in more detail below on the basis of the figures. The figures show preferred exemplary embodiments, to which the invention is not limited. It should be noted in particular that the figures and in particular the dimensional relationships illustrated in the figures are only schematic. In the figures:

[0062] FIG. 1 schematically shows a system consisting of hydraulic valve and valve drive;

[0063] FIGS. 2a, 2b and 2c show a valve slide with return spring in various valve slide positions:

[0064] FIG. 3 shows a first flow diagram of the method described; and

[0065] FIG. 4 shows a second flow diagram of the method described.

[0066] FIG. 1 schematically shows a system 3 having a hydraulic valve 1 and a valve drive 5 for driving the hydraulic valve 1. The hydraulic valve 1 preferably has a first outlet A and a second outlet B and is in particular configured to selectively provide pressurized hydraulic liquid at the first outlet A or at the second outlet B and then to receive it again at the respective other outlet B, A and channel it back to a tank (not shown here). The hydraulic valve 1 preferably has a pressure connection P at which the hydraulic valve 1 is provided with pressurized hydraulic liquid from a hydraulic supply 17. Moreover, the hydraulic valve 1 has a tank connection T at which hydraulic liquid flowing back from the respective other outlet B, A can be discharged.

[0067] The hydraulic valve 1 preferably has a valve block 14, in which hydraulic lines 9 are provided, for example as bores, and a valve slide 2 which can be moved back and forth in an axial direction in a control bore 22 and can assume various valve slide positions 7 there. On the valve slide 2 there are preferably provided control structures 13 which can be configured, for example, as cutouts and which, depending on the valve slide position 7, produce or close passages between individual hydraulic lines 9 and thus control the provision of hydraulic liquid at the outlets A, B.

[0068] Preferably, the valve slide 2, the control structures 13 formed thereon and the hydraulic lines 9 are formed in such a way that, during a movement of the valve slide 2 in a first direction R1, a first outlet A opens from a first opening point (not explicitly shown here) and, during a further movement in the direction R1, is then opened ever further in order to be able to set a provided volumetric flow of hydraulic liquid at the first outlet A by means of the valve slide position 7. Preferably, the valve slide 2, the control structures 13 formed thereon and the hydraulic lines 9 are further formed in such a way that, during a movement of the valve slide 2 in a second direction R2, a second outlet B opens from a second opening point (not explicitly shown here) and, during a further movement in direction R2, is then opened ever further in order to be able to set a provided volumetric flow of hydraulic liquid at the second outlet B by means of the valve slide position 7.

[0069] Preferably, the valve slide 2, the control structures 13 formed thereon and the hydraulic lines 9 are formed in such a way that an overlapping region 8 exists between the valve slide positions 7 at the first opening point and at the second opening point. For valve slide positions 7 within this overlapping region 8, both outlets A and B are preferably closed and hydraulic liquid is not provided at either of the outlets A, B.

[0070] Preferably, the valve slide 2 is braced with a return spring 6. The return spring 6 is preferably configured in such a way that the valve slide 2 is moved back into a neutral position 4 by the spring from any arbitrary valve slide position 7 if the valve drive 5 is not driven or is de-energized. The return spring 6 is preferably double-clamped and pushes the valve slide 2 back into the neutral position 4 by deflection in both directions R1, R2. The precise mode of operation of the return spring 6 will be explained in more detail below on the basis of FIGS. 2a, 2b and 2c.

[0071] The system 3 with the hydraulic valve 1 and the valve drive 5 serves, for example, to supply a hydraulic system 12 with hydraulic liquid from the hydraulic supply 17. The hydraulic system 12 can comprise, for example, a differential cylinder 18 whose chambers can be connected to the connections A and B. The differential cylinder 18 can then be controlled by the system 3.

[0072] The valve drive 5 is preferably connected to the valve slide 2 and configured to actuate the valve slide 2. The valve drive 5 can have, for example, a stepper motor 10 which, via a gear mechanism 15, generates a linear movement which is transmitted to the valve slide 2. The gear mechanism 15 can comprise, for example, a rack (schematically indicated here) and toothed wheels. A play in the valve drive 5 or between the valve drive 5 and the valve slide 2 is caused, for example, by tolerances within the gear mechanism 15 and in particular, for example, by tolerances between racks and toothed wheels of the gear mechanism 15.

[0073] Preferably, the system 3 has a control device 11 which is connected to the stepper motor 10 and which, to actuate the stepper motor 10, controls the latter. The control device 11 is preferably configured to monitor the operation of the valve drive 5. For this purpose, sensors 16, which are connected to the control device 11, can be provided in the valve drive 5. The control device 11 is preferably also configured to monitor the operation of the hydraulic valve 1. For this purpose, sensors 16, which are connected to the control device 11, can be provided, for example, on the outlets A, B.

[0074] For the operating principle of the described method, the valve slide position 7 and the effect of the return spring 6 on the valve slide position 7 are highly relevant. They are somewhat explained here on the basis of FIGS. 2a, 2b and 2c. FIGS. 2a, 2b and 2c each show the double clamping of the valve slide 2 with the return spring 6. The valve slide 2 preferably has two shoulders 25 which are clamped with the return spring 6 in a clamping device 23. Particularly preferably, there are movable transmission elements 24 which are each pressed against the shoulders 25 and the counter-holding structures 26 of the clamping device 23 by the return spring 6.

[0075] In FIG. 2a, the valve slide 2 is shown in a neutral position 4. The valve slide position 7 here corresponds to the neutral position 4. The return spring 6 is under tension and clamps the valve slide 2 or its shoulders 25 in both directions with a pre-tensioning force.

[0076] FIG. 2b then shows a deflection of the valve slide position 7 in the second direction R2. FIG. 2c shows a deflection of the valve slide position 7 in the first direction R1. Owing to the type of clamping device 23, the return spring 6 is compressed equally in both directions R1, R2 and there results a spring force which drives the valve slide 2 back into the neutral position 4 according to FIG. 2a.

[0077] FIGS. 3 and 4 then show two different embodiment variants of the described method, wherein the embodiment variant according to FIG. 3 is carried out, for example, during an initial commissioning of the system 3 or during a recommissioning after a maintenance or repair, and wherein the embodiment variant according to FIG. 4 can be carried out, for example, as an initializing function during any arbitrary commissioning (after an initial commissioning). First of all, common aspects of FIGS. 3 and 4 will be explained here. FIG. 3 will then be explained and then the explanation of FIG. 4 will build on the explanations for FIG. 3.

[0078] FIGS. 3 and 4 each show, plotted on a valve slide position axis 27, the valve slide positions 7 before and after the respective implementation of the individual method steps of the method, wherein the individual method steps each comprise movements of the valve slide 2, which are plotted as arrows. The sequence of method steps a) to g) is in each case represented with one below the other. In the upper part of FIGS. 3 and 4, a characteristic of the spring force 19 of the return spring 6 is in each case plotted schematically against the valve slide position 7. Also plotted schematically against the valve slide position 7 is a first volumetric flow 20 or a second volumetric flow 21 which is established at the outlets of the hydraulic valve 1 in a certain valve slide position 7. There can be seen a first opening point P.sub.1o, from which a first volumetric flow 20 is provided, and a second opening point P.sub.2o, from which a second volumetric flow 21 is provided. There is an overlapping region 8 between the first opening point P.sub.1o, and the second opening point P.sub.2o. No volumetric flows 20, 21 of hydraulic liquid are provided in present valve slide positions 7 within this overlapping region 8. There is a neutral position 4 within the overlapping region 8.

[0079] With regard to the neutral position, it should be pointed out that the diagrams according to FIGS. 3 and 4 each illustrate valve slide positions 7 with respect to the valve drive 5. As can be seen from FIGS. 2a and 2c, the valve slide 7 is preferably clamped with the return spring 6 in a defined and play-free manner. The neutral position 4 is therefore in theory, and with respect to the valve slide 2 itself, preferably a discrete, determined valve slide position 7.

[0080] However, owing to elasticities in the system 3, tolerances and, where appropriate, owing to a play in the valve drive 5, there results a play of the system 3 which means that, with respect to the valve drive 5, the neutral position 4 is a valve slide position region which extends from a first neutral position end position N.sub.1end up to a second neutral position end position N.sub.2end. The characteristic of the spring force 19 is also illustrated here with respect to the valve drive 5. It can be seen that the spring force 19 begins to act in each case in the neutral position end positions N.sub.1end and N.sub.2end. The double clamping of the return spring 6 according to FIG. 2a results in the pretensioning force 28 of the spring force 19, which has to be overcome at the neutral position end positions N.sub.1end and N.sub.2end. From there, during further deflection, the spring force 19 preferably further increases linearly or proportionally to the deflection.

[0081] According to FIG. 3, first of all, in step a), the valve slide 2 is moved in a first direction R.sub.1 and this direction R.sub.1 is preferably stored. Preferably, the movement which the valve slide 2 makes in step a) is firmly defined by its length. This is thus preferably a defined path W.sub.d which can be defined, for example, by a fixed number of steps of a stepper motor 10 of the valve drive 5. The starting position P.sub.a before the start of step a) is not precisely known. Since the valve was preferably de-energized before step a), it must lie within the neutral position 4. However, it is not precisely known where within the neutral position 4 the starting position P.sub.a lies. The length of the defined path W.sub.d is preferably fixed in such a way that it is in any case longer than the neutral position 4, with the result that the valve slide 2 is in any case moved out of the neutral position 4, and moreover preferably in any case shorter than a distance a between the respective neutral position end positions N.sub.1end, N.sub.2end and the opening point P.sub.1o then following in the respective direction R1. It can thus be ensured that the valve is here also not opened inadvertently. The result of the movement of the valve slide 2 in step a) is that the valve slide 2 is situated in a first valve slide position P1 between the opening point P.sub.1o and the neutral position end positions N.sub.1end, N.sub.2end.

[0082] Then, in step b), the valve drive 5 is deactivated or de-energized or the current present at the valve drive 5 is correspondingly reduced. Consequently, the return spring 6 moves the valve slide 2 counter to the first direction R.sub.1 in the second direction R.sub.2 back into the neutral position. Owing to its pretensioning, the return spring 6 accelerates the valve slide 2 to such an extent that the valve slide 2 is completely pushed through the neutral position 4 and passes within the neutral position 4 into the second neutral position end position N.sub.2end. From the first neutral position end position N.sub.1end, by comparison with the spring force 19 of the return spring 6, only relatively small frictional forces act on the valve slide 2, with the result that the movement of the valve slide 2 through the neutral position 4 occurs very reliably. At the second neutral position end position N.sub.2end there then acts the pretensioning force 28 of the return spring 6, which reliably stops the valve slide 2 there. After step b), the valve slide 2 is thus reliably situated in the second neutral position end position N.sub.2end.

[0083] In step c), the valve slide 2 is then moved in the direction R2 up to a defined second valve slide position P.sub.2d. This defined second valve slide position P.sub.2d has to be able to be determined in a reliable manner. This can occur in various ways. Here, it is proposed to use, as defined second valve slide position P.sub.2d, a second opening point P.sub.2o of the hydraulic valve 1. The second opening point P.sub.2o can, for example, be reliably detected in that a pressure occurs at a connection of the hydraulic valve 1, or a threshold value for a (small) volumetric flow of hydraulic liquid at the respective connection can be defined as opening point. The valve slide position 7 is actively monitored during the implementation of step c) and a movement of the valve slide 2 in step c) is stopped as soon as the defined second valve slide position P.sub.2d has been reached. A first path W1 of the valve slide 2 covered during step c) is determined. That is to say that this path is measured and stored in a control device 11. In the case that the valve drive 5 has a stepper motor 10, this can occur, for example, in that the steps of the stepper motor 10 from the second neutral position end position N.sub.2end to the defined second valve slide position P.sub.2d are stored.

[0084] Then, in step d), the valve drive 5 is deactivated or de-energized again or the current present at the valve drive 5 is correspondingly reduced. Consequently, the return spring 6 moves the valve slide 2 counter to the direction R.sub.1 back into the neutral position. Owing to its pretensioning, the return spring 6 accelerates the valve slide 2 to such an extent that the valve slide 2 is completely pushed through the neutral position 4 and passes within the neutral position 4 into the first neutral position end position N.sub.1end. From the first neutral position end position N.sub.1end, by comparison with the spring force 19 of the return spring 6, only relatively small frictional forces act on the valve slide 2, with the result that the movement of the valve slide 2 through the neutral position 4 occurs very reliably. At the first neutral position end position N.sub.1end there then acts the pretensioning force 28 of the return spring 6, which reliably stops the valve slide 2 there. After step d), the valve slide 2 is thus reliably situated in the first neutral position end position N.sub.1end.

[0085] In step e), the valve slide 2 is then moved in the direction R2 up to the defined second valve slide position P.sub.2d. Owing to the fact that this defined second valve slide position P.sub.2d is able to be reliably determined, it can be moved to in exactly the same way as already in step c).

[0086] The valve slide position 7 is also actively monitored during the implementation of step e) and a movement of the valve slide 2 in step e) is stopped as soon as the defined second valve slide position P.sub.2d has been reached. A second path W.sub.1s of the valve slide 2 covered during step e) is determined. That is to say that this path is measured and stored in a control device 11. In the case that the valve drive 5 has a stepper motor 10, this can occur, for example, in that the steps of the stepper motor 10 from the second neutral position end position N.sub.1end to the defined second valve slide position P.sub.2d are stored.

[0087] The second path W.sub.1s and the first path W1 are then present as values. In step f), the play W.sub.s can be calculated as difference of the second path W.sub.1s and of the first path W.sub.1.

[0088] As a further improvement of the described method, FIG. 3 also shows that after step f), as step g), the valve slide 2 can also be moved back up to a first defined position which preferably corresponds to a first opening point P.sub.1o of the hydraulic valve 1. Preferably, the first opening point P.sub.1o can be defined in exactly the same way as the second opening point P.sub.2o. In step g), the valve slide 2 moves over the complete overlapping region 8 and covers the overlapping path W.sub.?. The overlapping path W.sub.? is preferably also determined during the implementation of the method. The first opening point P.sub.1o and the second opening point P.sub.2o are preferably stored in a control device 11 and they are preferably available for the operation of the system 3 with the hydraulic valve 1 and the valve drive 5.

[0089] The adapted embodiment variant of the described method that is illustrated in FIG. 4 substantially corresponds to the procedure according to FIG. 3. The key difference is that the defined second valve slide position P.sub.2d, which is in each case moved to in steps c) and e), does not coincide here with the second opening point P.sub.2o but deviates therefrom and is preferably situated further in front (within the overlapping region 8) in the second direction R.sub.2. Such a defined second valve slide position P.sub.2d can be characterized, for example, by a defined spring force 19 of the return spring 8. Such a defined second valve slide position P.sub.2d can, for example, be moved to in a targeted manner in that the valve drive 5 or a stepper motor 10 of the valve drive 5 is driven with a reduced drive current. Particularly preferably, a step loss detection of a stepper motor 10 can be used to determine such a defined second valve slide position P.sub.2d.

[0090] An advantage of using such a defined second valve slide position P.sub.2d, with respect to the defined second valve slide position P.sub.2d, as second opening point P.sub.1o according to FIG. 3, is for example that a play detection is possible without in fact volumetric flows of hydraulic liquid occurring at the hydraulic valve 1. For this reason, this embodiment variant of the method is, for example, particularly suitable for an initializing function for initializing a system 3 consisting of hydraulic valve 1 and valve drive 5 during each commissioning.

[0091] According to a particularly preferred embodiment variant, a play W.sub.1s determined during an initial commissioning (according to FIG. 3) can then also be compared with a play W.sub.1s determined during an arbitrary commissioning after initialization (according to FIG. 4). If the play has increased (W.sub.1s>W.sub.1s), it can be assumed that wear has occurred. If this wear lies in an intended range, stored parameters for the operation of the system 3 can be adapted and the further operation of the system 3 can occur as intended. If a smaller play than during the initial commissioning has been determined (W.sub.1s<W.sub.1s), it is possible, where appropriate, also to output an error message because a reduction in the present and predetermined play cannot occur.

[0092] The method described here has been used to describe a novel and very efficient approach for determining the play in systems 3 having a hydraulic valve 1 and valve drive 5.

LIST OF REFERENCE SIGNS

[0093] 1 Hydraulic valve [0094] 2 Valve slide [0095] 3 System [0096] 4 Neutral position [0097] 5 Valve drive [0098] 6 Return spring [0099] 7 Valve slide position [0100] 8 Overlapping region [0101] 9 Hydraulic line [0102] 10 Stepper motor [0103] 11 Control device [0104] 12 Hydraulic system [0105] 13 Control structure [0106] 14 Valve block [0107] 15 Gear mechanism [0108] 16 Sensors [0109] 17 Hydraulic supply [0110] 18 Differential cylinder [0111] 19 Spring force [0112] 20 First volumetric flow [0113] 21 Second volumetric flow [0114] 22 Control bore [0115] 23 Clamping device [0116] 24 Transmission element [0117] 25 Shoulder [0118] 26 Counter-holding structures [0119] 27 Valve slide position axis [0120] 28 Pretensioning force [0121] R.sub.1 First direction [0122] R.sub.2 Second direction [0123] P.sub.i First valve slide position [0124] P.sub.1d Defined first valve slide position [0125] P.sub.2d Defined second valve slide position [0126] P.sub.a Starting position [0127] W.sub.1 First path [0128] W.sub.1s Second path [0129] W.sub.s Play [0130] W.sub.? Overlapping path [0131] W.sub.d Defined path [0132] A First outlet [0133] B Second outlet [0134] P Pressure connection [0135] T Tank connection [0136] N.sub.1end First neutral position end position [0137] N.sub.2end Second neutral position end position [0138] P.sub.1o First opening point [0139] P.sub.2o Second opening point [0140] a Distance