Method for determining switching position of direct-controlled hydraulic valve, method for controlling direct-controlled hydraulic valve, hydraulic valve and hydraulic system

Abstract

A method is provided for determining the switching position of a direct-controlled hydraulic valve 11 having a valve element 12 and a solenoid 13 having a coil S and an armature A. A control unit 14 associated with the hydraulic valve 11 applies a coil current in a coil S of the solenoid 13, said coil current consisting of an actuation current and a measurement current profile superimposed on the actuation current. The applied coil current is recorded as a current curve, a compensation characteristic value and a position characteristic value are determined on the basis of the current curve, and the switching position of the hydraulic valve 11 is calculated from the compensation characteristic value and the position characteristic value.

Description

Technical Field

[0001] The invention relates to a method for determining a switching position of a directly controlled hydraulic valve, a method for controlling a directly controlled hydraulic valve, a hydraulic valve and a hydraulic system. Background Art

[0002] In the case of a directly controlled (i.e. electromagnetically actuated) hydraulic valve, the valve element of the hydraulic valve is coupled to the armature of the solenoid of the hydraulic valve so as to move together with the armature between different switching positions of the hydraulic valve. This coupling can, for example, consist of a fixed connection between the armature and the valve element, or of a valve tappet firmly connected to the armature and resting against the valve element. By energizing the coil of the solenoid, the armature and the valve element are moved between different switching positions against the force of a reset element (usually a reset spring). The movement of the valve element between the different switching positions blocks or releases at least one connection of the hydraulic valve. Consequently, the volume flow of hydraulic fluid through the hydraulic valve depends on the switching position of the valve element. The valve element can be a valve piston or a valve seat element.

[0003] The variable switching position of the valve element generates a variable opening cross-section of the hydraulic valve, which in turn provides a variable volume flow through the hydraulic valve. To this end, a controlled actuating current is applied to the coil of the solenoid, on which the switching position of the hydraulic valve depends. However, the actual switching position of the hydraulic valve also depends on other boundary conditions (disturbance variables), such as friction- and / or temperature-related hysteresis effects, the system pressure of the higher-level hydraulic system, and the ambient or system temperature, which can all influence the properties of the solenoid.

[0004] In order to be able to adjust the volume flow provided by such directly controlled hydraulic valves as precisely and reproducibly as possible, it is therefore desirable to compensate for such disturbance variables as much as possible. This compensation is usually achieved by providing a dedicated position sensor that measures the actual current switching position of the hydraulic valve, i.e., the switching position of the valve element and / or armature. Based on this measured switching position, downstream position control can then be performed to control the volume flow provided by the hydraulic valve.

[0005] However, such dedicated position sensors for detecting the switching position of hydraulic valves are generally complex components, the use of which increases costs, increases the required installation space, increases complexity, and thus increases the likelihood of malfunction of the entire system.

[0006] DE 10 2022 202 224 A1 further discloses a method for determining the switching position of a directly controlled hydraulic valve having two solenoids for actuating a valve element on a respectively non-actuated solenoid. Summary of the Invention

[0007] Against this background, it is an object of the present invention to provide an improved possibility for controlling a volume flow via a directly controlled hydraulic valve, which can also be applied to directly controlled hydraulic valves having only a single solenoid for actuating the valve element.

[0008] The problem is first solved by a method for determining the switching position of a directly controlled hydraulic valve according to claim 1. The hydraulic valve comprises a valve element and a solenoid having an armature and a coil. The armature is coupled to the valve element so as to move together with the valve element between different switching positions. The method is executed by a control unit associated with the hydraulic valve and comprises the following steps:

[0009] - applying a coil current to the coil of the solenoid, wherein the coil current is composed of an actuation current and a measurement current curve superimposed on the actuation current;

[0010] - Record the applied coil current over time to form a current curve;

[0011] - determining a compensation characteristic value of the hydraulic valve based on the recorded current curve;

[0012] - determining a position characteristic value of the hydraulic valve based on the recorded current curve; and

[0013] - calculating the switching position of the hydraulic valve based on the compensation characteristic value and the position characteristic value.

[0014] According to the present invention, the solenoid of a hydraulic valve is not only acted upon by the actuating current to switch the hydraulic valve. Instead, a measured current curve is superimposed on the actuating current, and the coil current applied to the solenoid's coil is measured, representing a combination of the actuating current and the measured current curve. In other words, the actuating current and the measured current curve are simultaneously applied to the solenoid's coil and recorded together as a current curve. A compensation characteristic value and a position characteristic value are determined from the recorded current curve to calculate the hydraulic valve's actual current switching position. By superimposing the measured current curve on the actuating current and detecting the applied coil current, the hydraulic valve's switching position can also be determined at the actuating solenoid of the hydraulic valve. This enables precise position or volume flow control, even in the case of directly controlled hydraulic valves with only a single solenoid actuating the valve element, without the need for a dedicated position sensor in the form of a separate component. The method according to the present invention can save both cost and installation space, and improve the reliability of systems using hydraulic valves, as fewer system components are required overall.

[0015] The term "determining" as used herein includes one or more process steps, such as controlling, measuring and / or calculating, in order to determine a corresponding value. System-defined values ​​may also be used for determination.

[0016] In particular, the control unit comprises a current sensor for measuring the current in the coil of the solenoid and a solenoid control unit which controls the actuation of the solenoid in a generally known manner by means of a supply voltage.The control unit is in particular an electronic control unit.

[0017] Preferably, the measuring current curve has a maximum measuring amplitude that is dependent on the current actuating current. In particular, the measuring current curve has a variable measuring amplitude that is dependent on the actuating amplitude of the current actuating current. In particular, the current actuating current is detected separately and the maximum measuring amplitude is set as a function of the detected current actuating current. It should be noted that brief current peaks that are higher than the set maximum measuring amplitude may also occur, but due to the short duration of these current peaks and the inertia of the entire system, they do not lead to significant movements of the valve element for the volume flow flowing through the hydraulic valve. For hydraulic valves in which there is a particularly large amplitude difference between the minimum actuating current and the maximum actuating current, the variable maximum measuring amplitude can be used to ensure that the amplitude of the measuring current curve is not lost in the actuating amplitude of the actuating current.

[0018] Preferably, the measured current curve has a maximum measured amplitude that corresponds to the dither amplitude. In particular, the dither amplitude reaches 20% of the actuation amplitude of the current actuation current of the solenoid. The use of dither signals is known, for example, in the field of continuous hydraulic valves. Here, a rectangular alternating current signal (dither frequency) with a low amplitude (dither amplitude) is superimposed on the direct actuation current in order to vibrate the valve element of the continuous hydraulic valve, thereby avoiding static friction and reducing hysteresis effects. Therefore, in abstract terms, the dither amplitude of the hydraulic valve corresponds to an amplitude that causes a slight movement of the valve element, which amplitude is particularly higher than the minimum actuation current of the hydraulic valve. The fact that the maximum measured amplitude "corresponds to the dither amplitude" should also be understood to mean that brief current peaks that are higher than the dither amplitude may also occur, but due to the short duration of these current peaks and the inertia of the entire system, they do not lead to significant movement of the valve element for the volume flow flowing through the hydraulic valve. In particular, the measured current curve can therefore have a maximum measured amplitude that is higher than the minimum actuating current of the hydraulic valve and even result in a slight movement of the valve element, which, however, has no significant effect on the switching position of the hydraulic valve. It is also conceivable that the measured current curve has a measuring frequency that corresponds to the dithering frequency.

[0019] Preferably, the compensation characteristic value of the hydraulic valve is a temperature-dependent compensation characteristic value of the solenoid. In particular, the temperature-dependent compensation characteristic value of the solenoid is the resistance of the solenoid coil, in particular the copper resistance, which is determined during a holding interval of the measured current curve, during which the measured amplitude remains constant. Alternatively, the temperature-dependent compensation characteristic value of the solenoid is the current rise rate in the recorded current curve, which is determined during a rising interval of the measured current curve, during which the measured amplitude increases. This allows temperature dependencies to be taken into account and compensated for when determining the switching position of the hydraulic valve.

[0020] Preferably, the position characteristic value of the hydraulic valve is a temperature- and inductance-dependent position characteristic value of the solenoid. In particular, the temperature- and inductance-dependent position characteristic value of the solenoid is the current drop rate in the recorded current curve, determined during a decay interval of the measured current curve, during which the measured amplitude decreases. Temperature dependence can be compensated for by offsetting the compensation characteristic value. The inductance of the solenoid depends in particular on the position of the armature within the coil, so that the position of the armature within the coil and, therefore, the switching position of the hydraulic valve can be calculated based on the inductive dependence of the position characteristic value.

[0021] Furthermore, a solution to the problem is provided by a method for controlling a directly controlled hydraulic valve. The hydraulic valve includes a valve element and a solenoid having an armature and a coil. The armature is coupled to the valve element to move together with the valve element between different switching positions. The method is executed by a control unit associated with the hydraulic valve and includes the following steps:

[0022] - determining the switching position of the hydraulic valve by the method for determining the switching position of a hydraulic valve described above; and

[0023] - controlling the switching position of the hydraulic valve based on the determined switching position.

[0024] By controlling the switching position of the hydraulic valve, the flow rate through the hydraulic valve can be controlled. Thus, according to the present invention, a position or volume flow control for the hydraulic valve is implemented, for which the use of a separate position sensor in the form of a separate component is no longer necessary. This position or volume flow control can also be used for directly controlled hydraulic valves having only a single solenoid for actuating the valve element.

[0025] Furthermore, a solution to the problem is provided by a hydraulic valve having a valve element and a solenoid having an armature and a coil. The armature is coupled to the valve element so as to move therewith between different switching positions. The hydraulic valve further includes an integrated control unit configured to execute one of the above-described methods for determining the switching position of a directly controlled hydraulic valve and for controlling the directly controlled hydraulic valve.

[0026] Furthermore, a hydraulic system having a hydraulic valve solves the problem. The hydraulic valve includes a valve element and a solenoid having an armature and a coil. The armature is coupled to the valve element to move together with the valve element between different switching positions. The hydraulic system further includes a control unit associated with the hydraulic valve, the control unit being configured to execute one of the above-described methods for determining the switching position of a directly controlled hydraulic valve and for controlling the directly controlled hydraulic valve. Preferably, the control unit is integrated into the hydraulic valve. BRIEF DESCRIPTION OF THE DRAWINGS

[0027] The present invention is explained in more detail below with reference to the embodiments shown in the accompanying drawings. The drawings schematically show:

[0028] Figure 1 A hydraulic system having a directly controlled hydraulic valve according to an exemplary embodiment of the present invention;

[0029] Figure 2 Flowchart of the method according to the present invention;

[0030] Figure 3 a graph showing a first measured current curve; and

[0031] Figure 4 Graph showing a second measured current curve. DETAILED DESCRIPTION

[0032] Figure 1 A hydraulic system 10 according to an exemplary embodiment of the present invention is shown. The hydraulic system has a directly controlled hydraulic valve 11 and an electronic control unit 14 associated with the hydraulic valve 11. The hydraulic valve 11 comprises a valve element 12, a solenoid 13, and a return element 15, which is schematically illustrated here as a return spring. The hydraulic valve 11 is a directly controlled proportional 2 / 2-way seat valve. In this embodiment, the valve element 12 is a valve closing element that, in the closed switching position of the hydraulic valve 11, abuts against a seat in the housing of the hydraulic valve 11 and blocks the two connections of the hydraulic valve 11 from each other, preventing hydraulic fluid from flowing through the hydraulic valve 11.

[0033] The solenoid 13 includes a coil S and an armature A. By energizing the coil S of the solenoid 13 with an actuating current, the armature A of the solenoid 13 overcomes the restoring force of the restoring element 15 and moves together with the valve element 12. The armature A is coupled to the valve element 12 to move between different switching positions of the hydraulic valve 11. Depending on the actuating amplitude of the actuating current, the hydraulic valve 11 can be continuously moved into different switching positions between its closed switching position and its fully open switching position, and a variable volume flow of hydraulic fluid can be provided through the hydraulic valve 11.

[0034] The coil S is energized by a control unit 14 assigned to the hydraulic valve 11, which control unit is shown here as being separate from the hydraulic valve 11. The signal connection between the solenoid 13 of the hydraulic valve 11 and the control unit 14 is at Figure 1 However, it is also conceivable that the control unit 14 is integrated into the hydraulic valve 11 , for example in the housing of the solenoid 13 , and is thus connected in terms of signal technology to a higher-level control unit of the hydraulic system 10 .

[0035] Therefore, the control unit 14 actuates the hydraulic valve 11 via the solenoid 13 of the hydraulic valve 11. In addition, the control unit 14 is configured to execute the method according to the present invention for determining the switching position of the hydraulic valve 11. For this purpose, the control unit 14 superimposes a measured current curve on the actuation current for switching the hydraulic valve 11 and records the coil current applied to the coil S over time t, forming a current curve, as explained in detail below.

[0036] Figure 3 An exemplary first measured current curve MS1 is shown as a function of time t. Figure 3 In the first measured current curve MS1 in FIG, the measured amplitude IM increases during the ramp-up interval T1, T1' (times t1 to t2, t2') to reach a defined maximum measured amplitude IMmax. It remains at the maximum measured amplitude IMmax during the first hold interval T2, T2' (times t2, t2' to t3). Then, during the decay interval T3, T3' (times t3 to t4, t4'), the voltage used to generate the coil current is removed until the measured amplitude IM reaches a defined minimum measured amplitude IMmin. Finally, during the second hold interval T4, T4' (times t4, t4' to t5), the measured amplitude IM remains at the minimum measured amplitude IMmin. During the decay intervals T3, T3', no voltage is applied to the coil. Consequently, the coil current decreases from the defined maximum measured amplitude IMmax to the defined minimum measured amplitude IMmin during the free-running decay intervals T3, T3' and remains there until time t5. In this case, the time interval t1 to t5 corresponds to the dither period of the hydraulic valve 11.

[0037] The inductance of the coil S varies depending on the distance of the armature A inside the coil S (ie the current position of the valve element 12 ), which is why the length of the decay interval T3 , T3 ′ of the measured amplitude IM varies during free running. Figure 3 An example of a first decay interval T3 and a second decay interval T3' is shown, each of which represents the time required for the measured amplitude IM to fall from its defined maximum value IMmax to its defined minimum value IMmin. The longer second decay interval T3' ( Figure 3 The dashed curve in FIG3 corresponds to the case where the armature A is located further inside the coil S, that is, the inductance of the coil S is greater than that in the shorter decay interval T3 ( Figure 3 Therefore, the switching position of the hydraulic valve 11 can be obtained from the length of the decay intervals T3 and T3'. Figure 3 It is also shown that the length of the rising intervals T1 , T1 ′ also depends on the position of the armature A within the coil S.

[0038] In the present case, the dither signal is used to Figure 3 The first measurement current curve MS1 is used to measure the position of the armature A within the coil S. Accordingly, for all switching positions of the hydraulic valve 11 (the positions of the armature A within the coil S), the dither period from t1 to t5 is selected so that the decay intervals T3 and T3', during which the measured amplitude IM during free running decreases from the maximum measured amplitude IMmax to the minimum measured amplitude IMmin, are shorter than half the dither period from time t3 to time t5. This ensures that the switching position of the hydraulic valve 11 can be reliably determined using the dither signal.

[0039] Figure 4 An alternative second measuring current curve MS2 is shown which also alternates between a defined maximum measuring amplitude IMmax and a defined minimum measuring amplitude IMmin. Figure 4 In the second measurement current curve MS2, the measurement amplitude IM is not maintained at its maximum value IMmax, but directly switches to free running when the maximum measurement amplitude IMmax is reached. In addition, the measurement amplitude IM is not maintained when the minimum measurement amplitude IMmin is reached, but directly increases again to reach the maximum measurement amplitude IMmax. In the second measurement current curve MS2, the rise time of the measurement amplitude IM during the rise intervals T5 and T5' is also one of the parameters to be recorded. This rise time depends on the position of the armature A in the coil S, resulting in Figure 4 The first rising interval T5 ( Figure 4 The solid curve in the figure is shorter and the second rising interval T5' ( Figure 4 The dotted curve in the figure is longer. Figure 4 Similarly, there is a shorter first decay interval T6 and a longer second decay interval T6 '. As is generally known, the length of the rising interval T5 and the length of the decay interval T6 of the measured amplitude IM in the second measured current curve MS2 are measures of the position of the armature A in the coil S and the switching position of the hydraulic valve 11.

[0040] The maximum measurement amplitude IMmax and the minimum measurement amplitude IMmin are variable for both the first measurement current curve MS1 and the second measurement current curve MS2 and are set by the control unit 14 as a function of the recorded current actuation current or its actuation amplitude. In particular, in the present embodiment, the control unit 14 sets the maximum measurement amplitude IMmax such that it corresponds to the dither amplitude of the hydraulic valve 11. Thus, Figure 3 and Figure 4 The periodic repetition of the measured current curves MS1 and MS2 shown in FIG and the resulting alternation between the maximum measured amplitude IMmax and the minimum measured amplitude IMmin constantly maintains slightly oscillatory movements of the valve element 12 of the hydraulic valve 11. These oscillatory movements prevent stiction of the valve element 12 and thus reduce hysteresis effects when switching the hydraulic valve 11.

[0041] refer to Figures 2 to 4 , a method according to the invention for determining the switching position of a hydraulic valve 11 is described below, which method is executed by the control unit 14 .

[0042] In step S1, a coil current is applied to the coil S of the solenoid 13, which coil current consists of an actuating current and a measurement current curve MS1, MS2 superimposed on the actuating current. In the present case, the actuating current is a controlled direct current for switching the hydraulic valve 11 to a switching position depending on the actuating current. As described above, Figure 3 An exemplary first measurement current curve MS1 is shown in FIG. Figure 4 An exemplary second measurement current curve MS2 is shown in . Thus, in the present case, the coil current applied to the coil S in step S1 is, in a first alternative, the sum of the actuation current for switching the hydraulic valve 11 and the first measurement current curve MS1, or, in a second alternative, the sum of the actuation current for switching the hydraulic valve 11 and the second measurement current curve MS2.

[0043] In step S2, the applied coil current is recorded over time by the control unit 14 to form a current curve. Step S2 occurs in parallel with the application of the coil current in step S1.

[0044] In step S3, the control unit 14 determines a compensation characteristic value for the hydraulic valve 11 based on the recorded current curve. In this case, the compensation characteristic value is a temperature-dependent compensation characteristic value. When using the first measurement current curve MS1, the temperature-dependent compensation characteristic value is the copper resistance of the coil S and is determined during the first holding intervals T2 and T2'. When using the second measurement current curve MS2, the temperature-dependent compensation parameter is the rate of rise of the coil current and is determined during the rising intervals T5 and T5' of the second measurement current curve MS2. The rate of rise of the coil current from the measurement current curve MS2 also depends on the position of the armature A in the coil S and the energization voltage. The voltage dependency is compensated in a known manner by back-testing the supply voltage, via which the control unit 14 actuates the solenoid 13.

[0045] In step S4, the control unit 14 determines the position characteristic value of the hydraulic valve 11 based on the recorded current curve. If both the first measured current curve MS1 and the second measured current curve MS2 are used, the position characteristic value is a temperature- and inductance-dependent position characteristic value, that is, the current decay rate of the coil current, and is determined during the decay intervals T3, T3' of the first measured current curve MS1 or during the decay intervals T6, T6' of the second measured current curve MS2.

[0046] In step S5, the control unit 14 calculates the current switching position of the hydraulic valve 11 based on the compensation characteristic value and the position characteristic value. The temperature dependency of the current decrease rate (position characteristic value) of the coil current is calculated using the determined copper resistance of the coil or the determined current increase rate (compensation characteristic value), thereby enabling accurate calculation of the current switching position of the hydraulic valve 11. Thus, both the coil S and the armature A of the solenoid 13 of the hydraulic valve 11 are used in parallel to actuate the valve element 12, and the switching position of the hydraulic valve 11 is determined based on the recorded current curve.

[0047] This allows the control unit 14 to control the switching position of the hydraulic valve 11 or the flow rate flowing through the hydraulic valve 11 based on the determined switching position in optional step S6 .

[0048] Thus, a switching position and volume flow control for the hydraulic valve 11 is achieved which does not require the use of a dedicated position sensor and is also suitable for directly controlled hydraulic valves having only a single solenoid for actuating the hydraulic valve.

[0049] Appendix 10 Hydraulic system

[0050] 11 Direct-operated hydraulic valve

[0051] 12 valve element

[0052] 13 Solenoid

[0053] 14 Control Unit

[0054] 15 Reset element

[0055] A. Armature

[0056] IM measurement amplitude

[0057] IMmax Maximum measurement amplitude

[0058] IMmin minimum measurement amplitude

[0059] MS1 first measurement current curve

[0060] MS2 Second measurement current curve

[0061] S coil

[0062] Process steps S1 to S6

[0063] t time

[0064] Time points t1 to t5

[0065] T1, T1' rising interval of the first measured current curve T2, T2' first holding interval of the first measurement current curve T3, T3' decay interval of the first measured current curve T4, T4' second holding interval of the first measurement current curve T5, T5' rising interval of the second measured current curve T6, T6' decay interval of the second measurement current curve

Claims

1. A method for determining a switching position of a directly controlled hydraulic valve (11), the hydraulic valve (11) comprising a valve element (12) and a solenoid (13), the solenoid having an armature (A) and a coil (S), the armature (A) being coupled to the valve element (12) so as to move together with the valve element (12) between different switching positions, the method being executed by a control unit (14) associated with the hydraulic valve (11) and comprising the following steps: - applying a coil current to the coil (S) of the solenoid (13), wherein the coil current is composed of an actuating current and a measurement current curve (MS1, MS2) superimposed on the actuating current; - Recording the applied coil current over time (t) to form a current curve; - determining a compensation characteristic value of the hydraulic valve (11) based on the recorded current curve; - determining a position characteristic value of the hydraulic valve (11) based on the recorded current curve; as well as - calculating the switching position of the hydraulic valve (11) based on the compensation characteristic value and the position characteristic value.

2. The method according to claim 1, It is characterized by: The measurement current curves (MS1, MS2) have a maximum measurement amplitude (IMmax) which is dependent on the current actuation current.

3. The method according to any one of the preceding claims, It is characterized by: The measured current curves (MS1, MS2) have a maximum measured amplitude (IMmax) corresponding to the jitter amplitude.

4. The method according to any one of the preceding claims, It is characterized by: The compensation characteristic value of the hydraulic valve (11) is a temperature-dependent compensation characteristic value of the solenoid (13).

5. The method according to any one of the preceding claims, It is characterized by: The position characteristic value of the hydraulic valve (11) is a position characteristic value of the solenoid (13) that is related to temperature and inductance.

6. A method for controlling a directly controlled hydraulic valve (11), the hydraulic valve (11) comprising a valve element (12) and a solenoid (13), the solenoid having an armature (A) and a coil (S), the armature (A) being coupled to the valve element (12) so as to move together with the valve element (12) between different switching positions, the method being executed by a control unit (14) associated with the hydraulic valve (11) and comprising the following steps: - determining the switching position of the hydraulic valve (11) by a method according to any one of the preceding claims; and - controlling the switching position of the hydraulic valve (11) based on the determined switching position.

7. A hydraulic valve (11) having a valve element (12) and a solenoid (13), the solenoid having an armature (A) and a coil (S), wherein the armature (A) is coupled to the valve element (12) to move together with the valve element (12) between different switching positions, the hydraulic valve (11) further comprising an integrated control unit (14) configured to perform the method according to any of the preceding claims.

8. A hydraulic system (10) having a hydraulic valve (11), the hydraulic valve (11) comprising a valve element (12) and a solenoid (13), the solenoid having an armature (A) and a coil (S), the armature (A) being coupled to the valve element (12) so as to move together with the valve element (12) between different switching positions, the hydraulic system (10) further comprising a control unit (14) associated with the hydraulic valve (11) and configured to perform the method according to any one of claims 1 to 6.

9. The hydraulic system (10) according to claim 8, It is characterized by: The control unit (14) is integrated into the hydraulic valve (11).

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