Method for actuating a longitudinal slide valve, and hydraulic system

Abstract

The invention relates to a method for actuating a longitudinal slide valve (1) having an electromagnetically actuated longitudinal slide (2) which is loaded by a spring force and which is movable back and forth between two end positions (5, 7) defined by mechanical stops and at least one intermediate position (6). In order to improve the actuation of the longitudinal slide valve (1), the longitudinal slide (2) is actuated with a decaying superimposed vibration when its intermediate position (6) is actuated, such that the longitudinal slide (2) is deliberately excited into additional movements which are used to quickly and precisely bring the longitudinal slide (2) into its intermediate position (6) when undesired frictional forces occur between moving and stationary valve components.

Description

[0001] Method for controlling a longitudinal slide valve and hydraulic system

[0002] The invention relates to a method for controlling a linear slide valve with an electromagnetically controlled and spring-actuated linear slide, which is movable back and forth between two end positions defined by mechanical stops and at least one intermediate position. The invention further relates to a hydraulic system in a drive train of a motor vehicle with such a linear slide valve.

[0003] German patent application DE 10 2009 010 131 A1 discloses a linear slide valve with a linear slide that is movable back and forth between different switching positions in a valve housing having multiple ports, wherein the linear slide is designed as a flat slide and is movably mounted back and forth in a substantially cuboid receiving space recessed in a linear slide receiving body. German patent application DE 43 16 759 A1 discloses a hydraulic / pneumatic control valve with impulse magnets as actuators, wherein a continuous control function can be achieved by controlling the actuators via a suitably dimensioned digital controller, wherein the actuators, controlled by PWM signals, are controlled by a pulse control signal with variable pulse height, pulse duration, and pulse frequency.

[0004] The object of the invention is to improve the control of a longitudinal slide valve with an electromagnetically controlled longitudinal slide actuated by a spring force, which can be moved back and forth between two end positions defined by mechanical stops and at least one intermediate position.

[0005] The problem is solved in a method for controlling a linear slide valve with an electromagnetically actuated and spring-loaded linear slide, which is movable back and forth between two end positions defined by mechanical stops and at least one intermediate position, by applying a decaying superimposed oscillation to the linear slide when it is being actuated to its intermediate position. This oscillation causes the linear slide to be selectively excited to additional movements. These movements serve to quickly and precisely move the linear slide into its intermediate position when undesirable frictional forces occur between moving and stationary valve components. The linear slide valve is preferably designed as a directional control valve with at least three switching positions. The three switching positions comprise the previously described defined end positions and at least one intermediate position.If the linear slide valve has only three switching positions, the intermediate position can also be referred to as the middle position. The intermediate position must be maintained within narrow limits by a force equilibrium between an electromagnet, energized with a control current to actuate the linear slide, and a spring mechanism that provides the spring force. This equilibrium is disturbed during operation of the linear slide valve by the inherently undesirable frictional forces. Considerations carried out within the scope of the present invention revealed that simply superimposing a superimposed oscillation is not effective for various reasons. However, the inherently undesirable frictional forces during operation of the linear slide valve can be overcome very effectively by means of a preferably rapidly decaying superimposed oscillation.

[0006] A preferred embodiment of the method is characterized in that a maximum actuating current for the intermediate position is significantly smaller than a first actuating current for a first end position of the linear slide valve, and a minimum actuating current for the intermediate position is significantly larger than a second actuating current for a second end position of the linear slide valve. This reliably prevents unintentional switching of the linear slide valve to one of its end positions during operation.

[0007] Another preferred embodiment of the method is characterized in that the longitudinal slide valve is assigned to a hydraulically actuated component in the drivetrain of an automobile. The hydraulically actuated component is, for example, a hydraulically actuated disconnect clutch or a hydraulically actuated parking lock. The hydraulically actuated component with the longitudinal slide valve is particularly advantageously arranged in the drivetrain of an automobile with an e-axle.

[0008] Another preferred embodiment of the method is characterized in that a mean value of the decaying superimposed oscillation corresponds to a target current value of the intermediate position. This ensures that the longitudinal slide in the longitudinal slide valve assumes its intermediate position after the decay of the superimposed oscillation.

[0009] Another preferred embodiment of the method is characterized in that the decaying superimposed oscillation has at least three extreme values ​​before reaching its mean value. This number of extreme values, in combination with a frequency at which the linear slide valve is actuated, has proven advantageous with regard to desired switching times. The frequency at which the linear slide valve is actuated is preferably between forty and one hundred Hertz. Thus, in combination with the claimed number of at least three extreme values, switching times in the millisecond range can be achieved with the linear slide valve.

[0010] Another preferred embodiment of the method is characterized in that the linear slide valve is designed as a directional control valve with at least three ports. The linear slide valve is, for example, designed as a 4 / 3-way valve with four ports and three switching positions. Of course, the claimed method can also be applied to directional control valves that have more than one intermediate position and more than three or four ports.

[0011] Another preferred embodiment of the method is characterized in that the decaying superposition oscillation is implemented as a decaying sine wave. The decaying sine wave can decay linearly or, for example, hyperbolically.

[0012] Another preferred embodiment of the method is characterized in that the longitudinal slide is movably mounted in a valve housing which has several ports, wherein a travel window for adjustment movements of the longitudinal slide between its switching positions is less than one millimeter. The claimed method allows the longitudinal slide to be moved into its intermediate position quickly and reliably, even with very small adjustment movements.

[0013] Another preferred embodiment of the method is characterized in that the control of the linear slide valve is superimposed with strong current amplitudes only when the setpoint changes, in order to set the linear slide in motion. Once the setpoint current is reached, the superimposed amplitude is rapidly reduced to smaller values ​​or zero.

[0014] The problem described above can also be solved by a hydraulic system in the drivetrain of a motor vehicle with a longitudinal slide valve, which is controlled according to a previously described method. The hydraulic system is preferably assigned to a drivetrain with an e-axle, which includes, for example, an electric motor and advantageously also a transmission.

[0015] The claimed method preferably takes place in a control unit via which the longitudinal slide valve is controlled according to the claimed method. A corresponding program code is, for example, stored in a computer program product that is installed in the control unit.

[0016] Further advantages, features, and details of the invention will become apparent from the following description, in which various exemplary embodiments are described in detail with reference to the drawing. The drawing shows:

[0017] Figure 1 shows a schematic representation of an electromagnetically controlled longitudinal slide valve designed as a 4 / 3-way valve;

[0018] Figure 2 is a Cartesian coordinate diagram with an x-axis on which a current for controlling a linear slide valve in Figure 1 is plotted, and with a y-axis on which a path of a linear slide of the linear slide valve is plotted; and Figures 3 to 5 are three Cartesian coordinate diagrams in which different current profiles for controlling the linear slide valve from Figure 1 are plotted over time.

[0019] Figure 1 schematically depicts a linear slide valve 1 designed as a 4 / 3-way valve with a linear slide 2. A control symbol 3 in Figure 1 indicates that the linear slide 2 of the linear slide valve 1 is electromagnetically actuated. A spring symbol indicates a spring 4 that holds the linear slide 2 in one of its end positions.

[0020] The longitudinal slide valve 1 comprises three switching positions 5, 6, 7, which the longitudinal slide 2 can assume during operation of the longitudinal slide valve 1. Using these switching positions 5 to 7, a component (not shown) in a hydraulic system of an automobile's powertrain can be hydraulically actuated.

[0021] For hydraulic actuation, for example a preferably double-acting hydraulic cylinder is used, which can be pressurized with hydraulic pressure via four ports 8, 9, 10, 11 of the longitudinal slide valve 1 in a defined manner in order to effect, maintain or terminate a desired hydraulic actuation of the component.

[0022] Switching positions 5 and 7 of the longitudinal slide valve 1 are end positions achieved by mechanical stops. Switching position 6 is an intermediate position of the longitudinal slide valve 2, achieved by energizing an electromagnet.

[0023] In practice, reaching the intermediate position 6 is considerably more difficult than reaching the defined end positions 5 and 7, for example due to the unavoidable occurrence of hysteresis. This includes, in part, magnetic hysteresis of the electromagnet.

[0024] A second component of the hysteresis, while undesirable in itself, is unavoidable due to mechanical friction between the armature of the electromagnet and the longitudinal slide 2 within a valve housing (not shown). This friction is subject to considerable variation between individual components due to numerous tolerances, such as surface finish, diameter, orientation, etc. Furthermore, the friction also varies over time.

[0025] This is due, for example, to the fact that friction is reduced by the break-in period. Alternatively or additionally, friction is increased, for example, by contamination or surface damage such as scratches.

[0026] Frictional forces caused by friction always oppose the movement of the longitudinal slide 2. Since, even with a known setpoint step, for example from a zero position to a neutral position, it is not reliably known whether and how much overshoot occurs in the position of the longitudinal slide 2, the direction of the frictional force, i.e., its sign, is also unpredictable.

[0027] It is proposed that, when the setpoint changes, for example due to friction, the longitudinal slide valve 1 be superimposed with strong current amplitudes in order to set it into targeted movement. Once the desired setpoint current is reached, the superimposed amplitude is then rapidly reduced to smaller values ​​or zero.

[0028] Figure 2 shows a Cartesian coordinate diagram with an x-axis 15, on which a current 22 for controlling the linear slide valve 1 in Figure 1 is plotted in a suitable current unit. On a y-axis 16, a displacement of the linear slide 2 of the linear slide valve 1 in Figure 1 is plotted in a suitable displacement unit.

[0029] The longitudinal slide 2 of the longitudinal slide valve 1 in Figure 1, also referred to as the valve slide, is held against a first stop by the force of the spring 4 up to a current 21, forming the switching position 7. As the current increases, the force of the electromagnet 3 increases and pushes the valve slide or longitudinal slide 2 further against the spring force between 21 and 22 towards the second stop, which is reached at 22 and defines the switching position 5. Between these points, the path via the current follows a curve 20, which here, for example, is almost linear. To achieve the permissible travel range 24 of the switching position 6 from Figure 1, a current range 23 is theoretically available.

[0030] However, when friction and magnetic hysteresis are taken into account, curves 25 for increasing current and 26 for decreasing current differ, which considerably complicates maintaining range 24 during operation of the longitudinal slide valve 1. While the magnetic hysteresis acts systematically and reproducibly against the flow change and can therefore be maintained in the target flow, the direction and magnitude of the friction, as previously described, are unpredictable.

[0031] Even with a clearly increasing current from zero to a current designated h in Figures 3 to 5, the longitudinal slider 2 can overshoot once or several times, as indicated in Figure 3 by different curves 31, 32 and 33.

[0032] Furthermore, as indicated in Figure 3 by the different paths 31 to 33, the longitudinal slide 2 can enter its target position 30 either from above or from below. Depending on the last movement before coming to a standstill, the remaining frictional force acts in one direction or the other, thus distorting the achieved position in an unpredictable way.

[0033] One way to reduce friction effects is to superimpose an oscillation 41 onto the current h designed for the target position, as indicated in Figure 4. The oscillation 41 in Figure 4 has a constant amplitude 42, which is sufficient to keep the frictional longitudinal slide 2 in continuous motion around its target position 6 in Figure 2, so that the frictional forces act alternately positively and negatively. This ensures that the effect of the frictional forces cancels out on average, meaning that the longitudinal slide 2, on average, accurately reaches the desired position 6 in Figure 2.

[0034] However, the excitation 41 in Figure 4, which is sufficiently dimensioned for highly frictional specimens, unfortunately also leads to large slide movements in less stiff valves, which, although the position 6 is hit well on average, cause the longitudinal slide 2 to repeatedly swing out of the permissible range 24, which can lead to temporary unauthorized hydraulic connections or hydraulic interruptions.

[0035] Figure 5 illustrates how the previously described problem is circumvented by initially superimposing a large oscillation amplitude 51 only when a desired position change 50 occurs, for example, when moving from position 7 to position 6 in Figure 1. This amplitude is used to set the longitudinal slide in motion and maintain that motion, while the superimposed amplitudes decay again over a time interval 54. In this way, the longitudinal slide is set in motion as desired and moved to the target position 6, where it will come to rest with a decaying excitation amplitude due to the low sliding friction.

[0036] With the decaying superimposed oscillation 52, even stiff longitudinal slide valves 1 can be guided into their intermediate position 6 despite friction, without smooth-running valve examples continuously oscillating strongly around the target position due to the superimposition.

[0037] Advantageously, the frequency of the superposition is chosen to be significantly lower or higher than the natural frequency of the linear slide valve 1. It is also advantageous to choose the decay time 54 to be similar to or greater than the step response time of the linear slide valve 1.

[0038] An average value 53 of the decaying oscillation 52 advantageously corresponds to the control current e. A minimum actuating current for the intermediate position 6 is designated 55 in Figure 5. A maximum actuating current for the intermediate position 6 is designated 56 in Figure 5. List of reference symbols: Linear slide valve, linear slide, actuating symbol, spring, switching position, switching position, switching position, connection, connection, connection, connection, x-axis, y-axis, current profile, current, current range, permissible travel range, profile, target position 1, x-axis, y-axis, profile 1, oscillation, amplitude, desired position change 1, amplitude, decaying superimposed oscillation, average value - IQ - time span, minimum actuating current, maximum actuating current

Claims

Patent claims 1. Method for controlling a longitudinal slide valve (1) with an electromagnetically controlled longitudinal slide (2) actuated by a spring force, which is movable back and forth between two end positions (5, 7) defined by mechanical stops and at least one intermediate position (6), characterized in that the longitudinal slide (2) is actuated with a decaying superimposed oscillation (52) when its intermediate position (6) is actuated in such a way that the longitudinal slide (2) is specifically excited to additional movements which serve to bring the longitudinal slide (2) quickly and precisely into its intermediate position (6) when frictional forces occur between moving and stationary valve components that are undesirable in themselves.

2. Method according to claim 1, characterized in that a maximum actuating current (56) for the intermediate position (6) is significantly smaller than a first actuating current for a first end position (5) of the longitudinal slide valve (2), wherein a minimum actuating current (55) for the intermediate position (6) is significantly larger than a second actuating current for a second end position (7) of the longitudinal slide valve (2).

3. Method according to one of the preceding claims, characterized in that the longitudinal slide valve (1 ) is assigned to a hydraulically actuated component in a drive train of an automobile.

4. Method according to one of the preceding claims, characterized in that an average value (53) of the decaying superposition oscillation (52) corresponds to a target current value (h) of the intermediate position (6).

5. Method according to one of the preceding claims, characterized in that the decaying superposition oscillation (52) has at least three extreme values ​​before the decaying superposition oscillation (52) reaches the mean value (53).

6. Method according to one of the preceding claims, characterized in that the longitudinal slide valve (1) is designed as a directional control valve with at least three ports (8-11).

7. Method according to one of the preceding claims, characterized in that the decaying superposition oscillation (52) is considered as a decaying oscillation The sine curve is executed.

8. Method according to one of the preceding claims, characterized in that the longitudinal slide (2) is movably received in a valve housing which has several ports (8-11), wherein a travel window for adjustment paths of the longitudinal slide (2) between its switching positions (5, 6, 7) is less than one millimeter.

9. Method according to one of the preceding claims, characterized in that the control of the longitudinal slide valve (1) is superimposed with strong current amplitudes only when there is a change in the setpoint, in order to set the longitudinal slide (2) in motion.

10. Hydraulic system in a drive train of a motor vehicle with a longitudinal slide valve (1) which is controlled according to a method according to one of the preceding claims.

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