Increasing the dither signal of a pressure controller

Abstract

A method for controlling a pressure regulator (22) of a transmission (16) comprises: energizing a magnet (24) of the pressure regulator (22) with a current such that an armature (26) of the pressure regulator (22) is moved to adjust a valve (28) of the pressure regulator (22), the current having a dither signal for preventing sticking of the armature (26); measuring the current and determining an induction of the magnet (24) from the measured current; and, if the induction exceeds a threshold, determining that the armature (26) is stuck and increasing an amplitude of the dither signal.

Description

The invention relates to a method, a computer program, a computer-readable medium and a transmission controller for controlling a pressure regulator of a transmission. The invention further relates to the transmission.Many automatic transmissions have hydraulic components that are moved by increasing and decreasing a pressure of the hydraulic fluid. For example, the closing and opening of a clutch or the shifting between gears can take place via hydraulic components. These hydraulic components are actuated by pressure regulators. Normally, the pressure regulator comprises a valve that is opened and closed via an armature in a solenoid. The magnet is electrically controlled, wherein a dither signal is superimposed on the current signal, which dither signal reduces the so-called stick-slip effect. In the case of the stick-slip effect, the armature slides in its guide with small jerks, since the static friction is higher than the sliding friction. The dither intensity is selected to be only so high that the stick-slip effect is reduced. Too high a dither intensity may cause the automatic transmission to become acoustically conspicuous, since the frequency and amplitude of the dither signal may oscillate the drive train.In the case of pressure regulators running for a longer time, the adhesion and sliding friction properties can change as a result of wear, with the result that the valves can become fixed in spite of the dither signal when the actuation is constant. As a result, the pressure can no longer be regulated as desired.US 2018 / 0 080 568 A1 discloses a pressure regulator having an armature and an electromagnet moving the armature. A current for the magnet is superimposed with a dither signal in order to avoid a sticking of the armature.DE 10 2017 202 076 A1 describes a method for adapting parameters for a dither signal for an electromagnetic actuator, wherein a movement of the armature is determined from a measured current and voltage profile, a characteristic variable is determined from the movement, and if the characteristic variable deviates from a setpoint value, the parameters of the dither signal are adjusted accordingly.It is an object of the invention to extend the lifetime of pressure regulators in a transmission and to reduce failures of such pressure regulators.This object is achieved by the subject matter of the independent claims. Further embodiments of the invention will become apparent from the dependent claims and from the following description.One aspect of the invention relates to a method for controlling a pressure regulator of a transmission. The method can be carried out automatically by a controller of the transmission or a transmission controller. The pressure regulator comprises a valve which can be opened and closed in an electromagnet via an armature. If the magnet is energized, the armature is pulled into the magnet and the valve is actuated. A spring element can move the armature back into an initial position counter to the force of the magnet.According to one embodiment, the method comprises: energizing an electromagnet of the pressure regulator with a current or current signal such that the armature of the pressure regulator is moved for adjusting the valve of the pressure regulator, wherein the current has a dither signal for preventing adhesion of the armature. For example, the pressure regulator is configured to regulate a pressure with the valve in proportion to this flow. The current or a magnitude of the current whose main component is a sliding current signal is adjusted by the transmission controller according to a desired pressure provided by the valve. To the main component, a dither signal having substantially smaller amplitude (about less than 5%) but substantially higher frequency (about more than 100 times higher) is added. The dither signal may be an AC signal having a predetermined frequency and amplitude selected for the pressure regulator by design. The frequency and amplitude are selected such that the dither motion imparted to the armature prevents an stick-slip effect, but does not produce any appreciable transmission to the transmission.According to an embodiment, the method further comprises: measuring the current through the magnet and determining an induction of the magnet from the measured current. The transmission control is designed to determine a current or current intensity through the magnet and optionally a voltage at the magnet. This can be done with corresponding sensors. An induction or self-induction of the magnet can be determined from a comparison of the setpoint current with the measured actual current over time and / or by a phase shift between current and voltage over time. A corresponding calculation can be carried out by the transmission controller, which then provides a (digital) induction signal over time.According to an embodiment, the method further comprises: determining that the anchor is stuck, and / or increasing an amplitude of the dither signal if the induction exceeds a threshold value. The induction of the magnet increases when the armature does not move. When a current is applied to the magnet which cannot be converted at the valve, an induction is produced by the force on the valve slide in the magnet which presses against the fixed valve.By comparing the induction with a threshold value, it can be established in such a way that the armature is seated, i.e. does not move, although it should move. In this case, the anchor adheres to its guide due to stiction. It is to be understood that exceeding the swelling represents the locking of the sticking. When the induction reaches the threshold value, the amplitude of the dither signal is increased and thus an increased magnetic force is generated via the dither functionality, which revirates the valve free again.The induction threshold may be a fixed value stored in the transmission controller. The amplitude can be increased by a fixed value, which is predetermined, for example, and / or which is stored in the transmission control. It may be that the amplitude is increased in proportion to the extent of the threshold value being exceeded by the induction.The method can be used to detect a sticking of the armature in a simple manner and to swing the armature free by increasing the dither intensity. It is not necessary to adapt parameters of the dither function and / or to provide tables for parameters adapted in this way.According to one embodiment, the amplitude of the dither signal is increased and decreased a plurality of times when the induction exceeds the threshold value. The amplitude of the dither signal can be increased only for a specific period of time. Thereafter, the amplitude of the dither signal is reset again to the original value or control value. If the induction should then still exceed the threshold value, the amplitude of the dither signal can be increased again. Repeating the rocking-free multiple times can increase the probability that the anchor will become detached from its guide.It is also additionally possible that, independently of the induction being exceeded by a threshold value, an increase and decrease of the amplitude of the dither signal is repeated cyclically in order to prevent the armature from becoming stuck.According to one embodiment, the amplitude of the dither signal is increased stepwise as long as the induction exceeds the threshold value. Another possibility is to increase the amplitude again and again, i.e. after predetermined time intervals, by an offset, so that the force of the electromagnet increases more and more. Intensifying the rocking-free can increase the probability that the anchor will become detached from its guide. Between the time intervals with the increased amplitude, the amplitude can also be reduced again, approximately to the control value.In addition to the rocking-free of the anchor when the anchor is locked, further measures can also be carried out which can reduce the stick-slip effect, so that renewed locking of the anchor is reduced.According to one embodiment, a full stroke is carried out several times with the armature of the pressure regulator if it has been determined that the induction exceeds a threshold value or the armature is seated. One measure for reducing the stick-slip effect is to perform a full stroke a plurality of times. A full stroke of the armature is a complete movement of the armature between a minimum position and a maximum position. The full stroke (approximately 2 mm) may be greater than a normal stroke (approximately 1 mm) that is maximally performed during normal operation of the pressure regulator. The increased static friction may be caused by metal chips or other abraded material between the anchor and its guide. In this case, the abrasive material is removed from the normal range of movement by the full stroke.According to one embodiment, the repeated full stroke takes place in a state of rest of the transmission. This can be the case when a vehicle in which the transmission is installed is stationary or the vehicle engine is off and / or the transmission is decoupled from the drive train.Further aspects of the invention relate to a computer program which, when executed on at least one processor, carries out the method according to one of the preceding claims, and to a computer-readable medium on which such a computer program is stored. The processor may be a processor of the transmission controller. A computer-readable medium can be a hard disk, a USB memory device, a RAM, a ROM, an EPROM or a FLASH memory. A computer readable medium may also be a data communication network, such as the Internet, that enables download of program code.Another aspect of the invention relates to a transmission controller for a transmission configured to perform the method as described herein. The transmission control can be integrated into the transmission, for example, as a printed circuit board.A further aspect of the invention relates to a transmission having a pressure regulator for regulating a pressure for an actuator of the transmission and a transmission control of this type. The transmission can be designed to set a transmission torque between the input side and the output side of the transmission by means of a plurality of gears. The transmission may also include one or more clutches to generate a slip between input and output sides of the transmission. These clutches and / or gears may be operated with pressure regulators as described herein. For this purpose, the transmission can comprise a hydraulic system with a hydraulic pump and a hydraulic tank, which provide a main pressure (approximately 20 bar) for the hydraulic components. For example, a pressure regulator may reduce the main pressure to a clutch pressure, approximately 0-20 bar.For example, the transmission is installed in a vehicle to transmit torque from an engine to wheels of the vehicle. The vehicle may be a car, truck or bus.It is to be understood that features of the method as described above and below may also be features of the transmission and vice versa.Exemplary embodiments of the invention are described in detail below with reference to the attached figures. FIG. 1 schematically shows a vehicle with a transmission according to an embodiment of the invention. FIG. 2 shows a flow chart for a method according to an embodiment of the invention.The reference numerals used in the figures and their significance are listed in summary form in the list of reference numerals. In principle, identical or similar parts are provided with the same reference numerals.FIG. 1 schematically shows a vehicle 10 having a drive train 12 with a drive motor 14 and a transmission 16. A drive torque of the drive motor 14, such as an electric motor or internal combustion engine, is transmitted to the transmission 16 and converted by the latter into an output torque. To this end, the transmission 16, which may be an automatic transmission, has various shift states and / or gears and associated gear ratios. The output torque is transmitted to wheels 18 of the vehicle 10. The adjusting or controlling of the transmission 16 is performed by a transmission controller 20 of the vehicle 10.Of the transmission 16, which may include a plurality of components, such as gear shifts and clutches, only one pressure regulator 22 is shown that is used to shift hydraulic components of the transmission 16. The pressure regulator includes an electromagnet 24, an armature 26 and a valve 28. the armature 26 is guided in a guide in the magnet 24 and / or valve 28 and is reciprocated by the magnet in this guide, opening or closing the valve 28. To adjust the force of the magnet 24 on the armature 26, the controller 20 energizes the magnet with a current that can be adjusted according to the desired valve opening (i.e., fully closed to fully open). The pressure regulator 22 may be configured to regulate a pressure with the valve 28 in proportion to the flow. A direct current component of the current controls the valve opening.In order to prevent a stick-slip effect between armature 26 and its guidance, a dither signal is added to the DC component, which dither signal is, for example, an AC signal having an amplitude substantially smaller than the DC component, but having a substantially higher frequency. The dither signal leads to a dither movement of the armature 26, so that no static friction can arise between the armature 26 and its guide.FIG. 2 shows a method for controlling the pressure regulator 22, which can be automatically carried out by the controller 20. The controller 20 can have, for example, a processor on which the method is executed as a computer program. The computer program can be stored in a memory of the controller 20.In step S 10, the transmission controller 20 energizes the magnet 24 of the pressure regulator 22 with a current such that the armature 26 is moved to adjust the valve 28. In this case, a direct current component of the current is set in such a way that the valve is moved into the desired open position. Furthermore, a dither signal is impressed on the current, which is intended to prevent adhesion of the armature 26. As described further above, the amplitude and frequency of the dither signal are selected such that no undesired oscillations arise in the drive train 12.In step S 12, the transmission controller 20 receives or determines a current through the magnet 24 and optionally a voltage across the magnet 24. The measured current and / or voltage may vary from the current and / or voltage set by the transmission controller 20 because the magnet 24 acts as a variable inductor depending on the position and movement of the armature.The transmission controller 20 determines an induction or self-induction of the magnet 24 from the measured current and optionally the measured voltage. The induction of the magnet 24 is a signal over time that can be determined by the transmission controller 20 at regular time steps.In step S 14, the transmission controller 20 compares the induction with a threshold value. This induction threshold may be a fixed value stored in the transmission controller 20.When the induction exceeds the threshold, the transmission controller 20 determines that the armature 26 is stuck. Based thereon, one or more actions are taken to release the anchor 26 from its guidance.One of these measures is to increase the amplitude of the dither signal. The amplitude can be increased by a fixed value, which is predetermined, for example, and / or which is stored in the transmission controller 20. It may be that the amplitude is increased in proportion to the extent of the threshold value being exceeded by the induction.This results in higher dithering forces acting on the armature 26, which can thus be released again.If the induction falls below the threshold value, the transmission control 20 establishes or assumes that the armature 26 is free again. In this case, the amplitude of the dither signal is set again to the normal value, i.e. the value that was set before increasing the amplitude of the dither signal.Furthermore, it may be that the increase of the amplitude of the dither signal takes place only for a predetermined time interval. That is, after the expiration of the time interval, the amplitude is set again to the normal value.It may be that when the induction exceeds the threshold, the amplitude of the dither signal is increased and decreased a plurality of times by the transmission controller 20. That is, the increase of the dither forces may be performed in a series of pulses. A pulse can be a time interval with an increased amplitude of the dither signal.Furthermore, it may be that the amplitude of the dither signal is increased stepwise by the transmission controller 20 as long as the induction exceeds the threshold value. For example, a sequence of more and more powerful pulses may be generated.If the transmission controller 20 has determined based on the induction that the armature 26 has become locked and even if this could be eliminated again by increasing the amplitude, the transmission controller 20 can store this in order to subsequently take further measures.In step S 16, if the transmission 16 has been placed in a rest state, for example, if the vehicle 10 is stationary and / or the engine 14 is stopped, and if the transmission controller 20 has stored that the armature 26 has become fixed, a full stroke of the armature 26 is carried out by the transmission controller 20.In particular, a full stroke can be carried out several times with the armature 26.A full stroke of the armature 26 is a complete movement of the armature between a minimum position and a maximum position. The increased stiction, which enhances the stick-slip effect, may be due to metal shavings or other debris between the anchor 26 and its guide. In this case, the abrasive material is removed from the normal range of movement by the full stroke.Additionally, it should be noted that "comprising" does not exclude other elements or steps and "a" or "an" does not exclude a plurality. It should also be noted that features or steps that have been described with reference to one of the above exemplary embodiments can also be used in combination with other features or steps of other exemplary embodiments described above. Reference signs in the claims should not be regarded as limiting.Reference numerals denote reference numerals10 Vehicle 12 Drive train 14 Drive motor 16 Transmission 18 Wheels 20 Controller 22 Pressure regulator 24 Electromagnet 26 Armature 28 ValveReferences included in the specificationThis list of documents cited by the applicant has been produced in an automated manner and is only included for the better information of the reader. The list is not part of the German patent application or utility model application. The DPMA does not take any adhesion for any faults or omissions.Patent Literature citedUS 2018 / 0 080 568 A1

[0004] DE 10 2017 202 076 A1

[0005]

Claims

A method of controlling a pressure regulator (22) of a transmission (16), the method comprising: energizing a current to a magnet (24) of the pressure regulator (22) such that an armature (26) of the pressure regulator (22) is moved to adjust a valve (28) of the pressure regulator (22), the current having a dither signal to avoid sticking of the armature (26); measuring the current and determining induction of the magnet (24) from the measured current; if the induction exceeds a threshold, determining that the armature (26) is stuck and increasing an amplitude of the dither signal.The method of claim 1, wherein when the induction exceeds the threshold, the amplitude of the dither signal is increased and decreased a plurality of times.Method according to claim 1 or 2, wherein the amplitude of the dither signal is increased stepwise as long as the induction exceeds the threshold value.Method according to one of the preceding claims, wherein, if it has been determined that the induction exceeds a threshold value or the armature (26) is stuck, a full stroke is carried out a plurality of times with the armature (26).Method according to Claim 4, wherein the repeated full stroke takes place in a state of rest of the transmission (16).The method of any preceding claim, wherein the pressure regulator (22) is configured to regulate a pressure with the valve (28) in proportion to the flow.A computer program which, when executed on at least one processor, performs the method of any preceding claim.A computer readable medium having stored thereon a computer program according to claim 7.A transmission controller (20) for a transmission (16) configured to perform the method of any preceding claim.A transmission (16) comprising: a pressure regulator (22) for regulating a pressure for an actuator of the transmission; a transmission controller (20) according to claim 9.

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