Valve system for a vehicle with PWM damping signal

Abstract

The invention relates to a valve system for a vehicle, comprising a closing element (1), an electric actuator (3), and a counteracting spring (5), and a control unit for controlling the electric actuator (3) by means of a PWM signal, wherein: for an actuator-driven direction of movement of the closing element (1), a PWM signal with a plurality of drive pulses (7) with a respective duty cycle above a predefined upper limit; for a spring-driven direction of movement of the closing element (1), a PWM signal with a plurality of drive pulses (7) with a respective duty cycle below a predefined lower limit; and at several points in time within the PWM signal: between drive pulses (7) with a duty cycle above the upper limit, one or more successive damping pulses (9) with a duty cycle below the upper limit.and between drive pulses (7) with a duty cycle below the lower limit, one or more successive damping pulses (9) with a duty cycle above the lower limit.

Description

[0001] The invention relates to a valve system for a vehicle, and to a method for designing a control unit for a valve system for a vehicle.

[0002] Electrically actuated valves used in motor vehicles typically comprise a closing element, such as a valve tappet, a seal, and an actuator for adjusting the closing element. In simple valves, this actuator has an electromagnet that, when an electric current is applied, generates a magnetic field to exert a force on the closing element, thus moving it in one direction. In the other direction, a spring usually exerts a force to achieve the opposite movement of the closing element without energizing the electromagnet. Such valves therefore typically have two positions: open and closed. Depending on the design, it is optionally possible to have either "open" or "closed" as the default position without an applied electric current. Modern motor vehicles typically have a large number of valves installed. They usually serve to regulate fluid flow.This could include coolant, intake air, tank venting, or other things.

[0003] The approach described above makes it very simple and cost-effective to manufacture reliably closing, electrically switchable valves. No linear motor or other complex electrical actuator is required; only a mechanical spring and an electromagnet are needed. However, a disadvantage of these designs is that these valves typically exhibit very poor acoustic and vibration characteristics. To ensure reliable opening and closing throughout their entire service life in all operating ranges, the forces required for opening and closing must be significantly over-engineered. Furthermore, when the electromagnet is electrically energized, the closing element is accelerated until it impacts a stop.The acceleration of the closing element tends to increase during movement, as the magnetic field strength of the actuator's electromagnet acting on the closing element increases with decreasing distance. At the moment of impact at the end position, the closing element therefore reaches its highest speed. The same applies when the electromagnet is switched off. Then, the closing element is continuously accelerated by the pre-tensioned mechanical spring throughout its entire travel. At the moment of impact at the other end position, the valve again reaches its maximum speed. These impacts, occurring each time the valve switches, generate impulses that are perceptible acoustically and through vibrations, and which can impair the comfort of passengers in a vehicle in which the valve is installed.

[0004] In this context, DE 199 08 899 A1 relates to an electromagnetic valve with an armature pre-tensioned by a return spring towards a first end position, in which a plunger assumes a first valve switching position, comprising a control circuit with a first device with which, by activation, the electromagnetic valve is supplied with a damping current which is directed and dimensioned in such a way that a stop of the armature against the first end position is dampened or avoided.

[0005] According to DE 199 08 899 A1, control of the valve system by a pulse width modulated (PWM) signal is also known.

[0006] The object of the invention is to mitigate these above-mentioned negative effects, such as force impulses of a valve closing element against an end stop, in an alternative way, and without having to measure an electrical quantity at the electromagnet to actuate the closing element.

[0007] The invention is defined by the features of the independent claims. Advantageous further developments and embodiments are the subject of the dependent claims.

[0008] A first aspect of the invention relates to a valve system for a vehicle, comprising a closing element which is movable between a closing position and a releasing position, as well as comprising an electric actuator coupled to the closing element and a spring coupled to the closing element and opposing the electric actuator, and comprising a control unit for controlling the electric actuator by means of a PWM signal, characterized in that the control unit is designed to - to specify a PWM signal with a multitude of drive pulses with a respective duty cycle above a predefined upper limit for an actuator-driven movement direction of the closing element between the positions, - to specify a PWM signal with a multitude of drive pulses with a respective duty cycle below a predefined lower limit for a spring-driven movement direction of the closing element between the positions, and at several times in the PWM signal: - between drive pulses with a duty cycle above the upper limit, one or more successive damping pulses with a duty cycle below the upper limit, and - to provide one or more successive damping pulses with a duty cycle above the lower limit between drive pulses with a duty cycle below the lower limit.

[0009] The PWM signal is characterized by a switching between a first and second amplitude of electrical voltage at a defined frequency. However, the variable and crucial factor for the control signal, which serves as the output value of the control unit, is the relative holding time of the second amplitude in each frequency step. This relative holding time is referred to as the duty cycle. To generate a PWM signal with a continuous voltage equal to the second amplitude, the duty cycle is set to 100%. Conversely, to generate a PWM signal with a continuous voltage equal to the first amplitude, the duty cycle is set to 0%. Depending on the percentage of the duty cycle, the resulting average, and therefore effective, amplitude of the electrical voltage, which serves as the relevant PWM signal, will be a value between the first and second amplitudes.Assuming a switching frequency of 2000 Hz, then a switching cycle lasts 1 / 2000 s = 0.5 ms. A duty cycle of 80% would therefore have the upper amplitude (e.g., 12V) for 0.4 ms and the lower amplitude (e.g., 0V) for 0.1 ms.

[0010] The spring, with its spring force, and the force of the actuator, resulting from the current supplied to the electrical actuator, are opposing forces. If the force of the actuator exceeds the spring force, the locking element is held in a first position – this requires a corresponding electrical current in the actuator. If the current is sufficiently reduced, the spring force exceeds the force of the electrical actuator, and the locking element is moved from a first position to a second position and held there. The opposite movement is possible, correspondingly, if the force of the electrical actuator is increased from a low to a higher force, until the spring force is overcome.

[0011] A control unit regulates the current supply to the electrical actuator. This is achieved using a PWM signal, the operation of which is described above. The higher the duty cycle in the PWM signal, the higher the effective amplitude of the electrical control voltage at the control unit, which drives the electrical actuator. Depending on this control voltage, the electrical actuator is supplied with a specific current, which in turn causes the electrical actuator to exert a force.

[0012] There are two limit values: if the duty cycle exceeds an upper limit, the control voltage in the PWM signal is sufficiently high to generate a sufficiently high force from the electrical actuator and, as explained above, to overcome the spring force. In such a case, the locking element is moved in an actuator-driven direction. Similarly, a lower limit value for the duty cycle is considered, below which the effective control voltage in the PWM signal is so low that the spring force exceeds the force exerted by the electrical actuator, thereby causing spring-driven movement of the locking element.

[0013] This effect is achieved by the control unit being designed to provide a PWM signal with a multitude of drive pulses with a respective duty cycle above a predefined upper limit for an actuator-driven movement direction of the closing element between the positions, and to provide a PWM signal with a multitude of drive pulses with a respective duty cycle below a predefined lower limit for a spring-driven movement direction of the closing element between the positions.

[0014] These steps of the control unit alone would, however, cause a continuously accelerated, actuator-driven movement of the locking element whenever the duty cycle exceeds the upper limit. This would result in a harsh impact when the locking element reaches its end stop, generating significant noise. Similarly, the spring-driven movement of the locking element would behave as follows if the duty cycle remains consistently below the lower limit, as the spring force would cause a continuous increase in the locking element's speed until it reaches its end stop.

[0015] To avoid this problem, a pulse with a neutral or even braking effect is mixed into the PWM signal, at least for a certain period, during the PWM signal that generates the movement of the locking element. This prevents the movement of the locking element from accelerating further near the end stop. Therefore, in the case of actuator-driven movement of the locking element, the force exerted by the electric actuator towards the end stop is slightly reduced, while in the case of spring-driven movement, it is slightly increased towards the opposite end stop to counteract the spring force. This reduces the speed at which the locking element strikes the respective end stop compared to the unmodified version described above.

[0016] This is achieved by inserting or replacing pulses that are oriented in the same direction as the current movement of the locking element and thus accelerate it further, by introducing individual pulses that have a neutral or even braking effect. The control unit makes the following adjustments to the PWM signal at several points in time: - between drive pulses with a duty cycle above the upper limit, one or more successive damping pulses with a duty cycle below the upper limit, and - between drive pulses with a duty cycle below the lower limit, one or more successive damping pulses with a duty cycle above the lower limit are specified.

[0017] Both the drive pulses and the damping pulses are pulses of the PWM signal. The terms "drive" and "damping" simply describe the effect of these pulses – in the case of drive pulses, they are aligned with a desired direction of movement and thus have an accelerating effect; in the case of damping pulses, they counteract a current movement by braking it.

[0018] Advantageously, the upper limit of the duty cycle is predetermined such that all duty cycles above this limit result in an actuator-driven and accelerated movement of the locking element. The upper limit is, in particular, the duty cycle of PWM pulses below which a complete change of position is not achieved by the actuator-driven movement. Similarly, the lower limit of the duty cycle is advantageously predetermined such that all duty cycles below this limit result in a spring-driven complete change of position of the locking element, while duty cycles above this limit result in no movement or incomplete movement of the locking element.

[0019] Advantageously, a PWM signal can be generated to reduce the end-stop velocity of the closing element and thus the force pulses at the end stops, whether at an end stop reached by spring force or by the force of the electric actuator, without having to measure an electrical current at the electromagnet of the electric actuator. This simplifies the control of the valve system, as the predefined and unchanged PWM signal can be played continuously without requiring a special control circuit. Therefore, no modifications to the valve system hardware or the valve system's control electronics are necessary. Only minor software changes are required to significantly reduce the end-stop pulses.

[0020] According to an advantageous embodiment, the control unit is designed to generate drive pulses and / or damping pulses with a duty cycle that are each a distance from a respective limit value.

[0021] The specific spacing of this embodiment takes into account the fact that the upper and lower limits depend on various factors over time. For example, temperature changes, aging, corrosion, manufacturing variations, fluctuations in the electrical supply, etc., can lead to different or time-changing limits.

[0022] According to another advantageous embodiment, the control unit is designed to perform several functions at different times: - between drive pulses with a duty cycle above the upper limit, one or more successive damping pulses with a duty cycle below the lower limit, and - to provide one or more successive damping pulses with a duty cycle above the upper limit between drive pulses with a duty cycle below the lower limit.

[0023] While the introduction of such damping pulses between drive pulses with a duty cycle above the upper limit, which have a duty cycle below the upper limit, reduces, keeps constant, or only slightly decelerates the acceleration of the closing element's movement, such damping pulses below the lower limit are always decelerating, since this constitutes the definition, or at least the estimation, of the lower limit. The same applies to the introduction of such damping pulses between drive pulses with a duty cycle below the lower limit, which are above the upper limit, and thus clearly counteract the spring-driven movement, since they would tend to cause an actuator-driven movement if applied long enough, instead of merely acting as a diverting force.

[0024] According to a further advantageous embodiment, the control unit is designed to specify the drive pulses and the damping pulses in the same sequence with respect to the respective number and sequence of drive pulses and damping pulses.

[0025] If the drive pulses and damping pulses follow each other in the same number and sequence, a uniform pattern is generated in the PWM signal. However, this can be detrimental if this pattern includes an excitation frequency that triggers unfavorable resonances or produces an undesirable acoustic effect.

[0026] According to a further advantageous embodiment, the control unit is designed to specify the drive pulses and the damping pulses in different sequences with respect to the respective number and / or sequence of drive pulses and damping pulses.

[0027] If the drive pulses and damping pulses are specified in different sequences with respect to the respective number and / or order of drive and damping pulses, a pattern with a richer excitation spectrum is created. In other words, several frequencies in the PWM signal act as excitation, but each of these frequencies with a lower amplitude. This makes it easier to avoid individual, narrow excitations of resonances.

[0028] According to a further advantageous embodiment, the control unit is designed to specify a predetermined pattern in the number and sequence of drive pulses and damping pulses.

[0029] According to this embodiment, i.e., the use of a predetermined pattern, there is determinism and a constant sequence between drive pulses and damping pulses.

[0030] According to a further advantageous embodiment, the control unit is designed to specify the damping pulses only after a first predetermined time period, starting from the control unit's movement input of the closing element.

[0031] The initiation of both an actuator-driven and a spring-driven movement of the locking element can be divided into two time periods: during the first period, no movement occurs because a magnetic field in the electrical actuator must first build up sufficiently. The movement then takes place in the subsequent second period. With this knowledge, a predetermined time period can be estimated, after which braking effects should ideally occur through the use of damping pulses, in order to achieve the fastest possible movement of the locking element while simultaneously reducing the force impulses at the end stops.

[0032] According to another advantageous embodiment, the control unit is designed to variably specify the duty cycle of the damping pulses.

[0033] By varying the duty cycle over the time course of the PWM signal, the net braking forces can be increased, for example, at an expected time shortly before the end stop. A person skilled in the art has numerous degrees of freedom here regarding how the damping pulses are mixed into the series of drive pulses, particularly with respect to the duty cycle and the overall intensity of the braking effects. Progressive timing can be incorporated into the sequence of driving and braking pulses with the aim of achieving the lowest possible speed before the end stop. In the actuator-driven direction, an attempt can initially be made to maximize damping. This can be achieved either by introducing as many braking pulses as possible (as many pulses as possible with a duty cycle below the upper duty cycle threshold), by introducing braking pulses with the lowest possible duty cycle (e.g., even zero duty cycle), or a combination of both.Ideally, the valve switches very quietly in this case of strong damping. In the worst case, the valve does not switch at all. Then, the progressive nature of the signal results in fewer damping pulses being introduced in the following period, or in the lower duty cycles no longer being as low, thus reducing the damping effect. If the valve has already switched, no further noise should occur, as the valve is then already at its end stop. The progressive signal (reduction of braking pulses over time) can continue until, after some time, no more braking pulses are received. This ensures reliable valve switching. Furthermore, switching occurs at the optimal time with regard to maximum damping and thus minimum final velocity of the valve stem. This progressive nature can be used in both directions of valve stem movement.Progressiveness can be adjusted by changing the duty cycle level, as well as by changing the number of successive damping or actuation pulses. In particular, the actuation or damping effect of each pulse can be adjusted via the duty cycle level. Progressiveness can be set in both the timing and the duty cycle level. This ensures optimal damping when opening and closing the valve over a wide operating range.

[0034] Using the example of switching the valve by a magnetic force against a spring force, the following example with 4 time ranges results: (1) Initially, no current flows and consequently the spring force keeps the valve closed; the magnetic force is zero. (2) If the valve is to be switched, the duty cycle is directly increased to a value just below the sound threshold. The aim is a rapid increase in the current through the coil and thus a rapid build-up of the magnetic field, without, however, switching the valve yet. Alternatively, a duty cycle of 100% would also be possible to achieve a faster magnetic field build-up. In that case, however, the time duration (2) must be chosen conservatively short so that no premature switching occurs. (3) Alternating duty cycles below and above the switching threshold (where several actuation and / or damping pulses can follow one another) ensures that damping pulses occur during the valve travel, thereby reducing the valve tappet speed. This requires a sufficiently high switching frequency. The pulse length must be significantly shorter than the valve travel time so that at least one braking pulse occurs within the valve travel time. Furthermore, the signal should exhibit a certain degree of progressiveness. The damping should be continuously reduced over time. The goal is to achieve switching with maximum possible damping. Despite tolerances and operational influences, a well-damped switching process can be achieved through progressive damping reduction.Progressive damping can be achieved by continuously increasing the lower and upper duty cycles. Furthermore, the pulse sequence can be selected to output increasingly more drive pulses and fewer damping pulses. The goal is to start with slightly excessive damping and gradually reduce it. This ensures the valve switches at the maximum possible damping. Since this damping is unknown beforehand due to variations and tolerances, it is approximated in this way. (4) After a certain period of time, a duty cycle of 100% is set. This ensures that reliable switching is achieved in every case.

[0035] Another aspect of the invention relates to a method for designing a control unit for a valve system for a vehicle, wherein the valve system has a closing element which is movable between a closing position and a releasing position, and has an electrical actuator coupled to the closing element and a spring coupled to the closing element and opposing the electrical actuator, wherein a duty cycle of a PWM signal for controlling the actuator is varied and the duty cycle at which the actuator overcomes the spring force and triggers an actuator-driven movement of the closing element is stored as the upper limit, and the duty cycle at which the spring force overcomes the force of the actuator and triggers a spring-driven movement of the closing element is set as the lower limit.wherein the upper limit and the lower limit are stored in the control unit in such a way that, - for an actuator-driven movement direction of the closing element between the positions, a PWM signal with a multitude of drive pulses with a duty cycle above the upper limit is specified, - for a spring-driven movement direction of the closing element between the positions, a PWM signal with a multitude of drive pulses with a duty cycle below the lower limit value is specified, and at several points in time during the course of the PWM signal: - between drive pulses with a duty cycle above the upper limit, one or more successive damping pulses with a duty cycle below the upper limit, and - between drive pulses with a duty cycle below the lower limit, one or more successive damping pulses with a duty cycle above the lower limit are specified.

[0036] Advantages and preferred further developments of the proposed method result from an analogous and substantive transfer of the above statements made in connection with the proposed valve system.

[0037] Further advantages, features and details will become apparent from the following description, in which - possibly with reference to the drawing - at least one embodiment is described in detail.

[0038] They show: Fig. 1: A valve system according to an embodiment of the invention. Fig. 2: A PWM signal with drive pulses and damping pulses according to an embodiment of the invention. Fig. 3: A PWM signal with drive pulses and damping pulses according to a further embodiment of the invention.

[0039] Fig. Figure 1 shows a valve system for a vehicle. A closing element 1, designed as a valve tappet, can be moved between a lower position, closing an opening, and an upper position, opening the opening. An electric actuator 3 generates a force on the closing element 1 when its coils are energized. The electric actuator 3 then exerts a force on the closing element 1, which pushes it upwards into the open position. However, this force is exerted against the force of a spring 5, so that with very little or no current at the electric actuator 3, the closing element 1 closes the opening. An alternative design in which the spring force 5 tends to push the closing element 1 into an open position would also be possible.A control unit is designed to control the electrical actuator 3 by means of a PWM signal and generates the PWM signal as follows, depending on the desired movement of the closing element 1:. - for an actuator-driven movement of the closing element 1: a plurality of drive pulses 7 with a respective duty cycle above a predefined upper limit; - for a spring-driven direction of movement of the closing element 1: a plurality of drive pulses 7 with a respective duty cycle below a predefined lower limit; and at several points in time within the PWM signal: - between drive pulses 7 with a duty cycle above the upper limit, one or more successive damping pulses 9 with a duty cycle below the upper limit, and - between drive pulses 7 with a duty cycle below the lower limit, one or more successive damping pulses 9 with a duty cycle above the lower limit.

[0040] Fig. Figure 2 shows an example PWM signal with a sequence of drive pulses 7 and damping pulses 9. Instead of every third drive pulse 7, which results in an accelerating movement of the closing element 1, a damping pulse 9 is regularly introduced. This sequence of drive pulses 7 and damping pulses 9 occurs at a predetermined frequency, for example 1000 Hz or 2000 Hz, and extends accordingly. For simplicity, in Figure 2, the frequency is shown as 1000 Hz or 2000 Hz. Fig. 2 only shows a section of the PWM signal.

[0041] Fig. Figure 3 shows another example PWM signal with a sequence of drive pulses 7 and damping pulses 9, in contrast to the one in Fig.In the sequence shown in Figure 2, an irregular sequence of drive pulses 7 and damping pulses 9 is provided in order to achieve a broadband excitation by electrical and mechanical frequencies at the valve system.

[0042] Although the invention has been further illustrated and explained in detail by means of preferred embodiments, the invention is not limited by the disclosed examples, and other variations can be derived from them by a person skilled in the art without departing from the scope of protection of the invention. It is therefore clear that a multitude of possible variations exist. It is also clear that the embodiments mentioned as examples are truly only examples and are not to be understood in any way as limiting, for example, the scope of protection, the possible applications, or the configuration of the invention.Rather, the preceding description and the description of the figures enable the person skilled in the art to implement the exemplary embodiments in concrete terms, whereby the person skilled in the art, with knowledge of the disclosed inventive concept, can make various changes, for example with regard to the function or the arrangement of individual elements mentioned in an exemplary embodiment, without leaving the scope of protection defined by the claims and their legal equivalents, such as further explanations in the description. QUOTES INCLUDED IN THE DESCRIPTION

[0000] This list of documents cited by the applicant was automatically generated and is included solely for the reader's convenience. The list is not part of the German patent or utility model application. The DPMA accepts no liability for any errors or omissions. Cited patent literature

[0000] DE 199 08 899 A1 [0004, 0005]

Claims

[1] Valve system for a vehicle, comprising a closing element (1) which is movable between a closing position and a releasing position, comprising an electric actuator (3) coupled to the closing element (1) and a spring (5) coupled to the closing element (1) and acting against the electric actuator (3), and comprising a control unit for controlling the electric actuator (3) by means of a PWM signal, characterized by that the control unit is designed to - to specify a PWM signal with a plurality of drive pulses (7) with a respective duty cycle above a predefined upper limit for an actuator-driven movement direction of the closing element (1) between the positions, - to specify a PWM signal with a plurality of drive pulses (7) with a respective duty cycle below a predefined lower limit value for a spring-driven movement direction of the closing element (1) between the positions, and at several times in the PWM signal: - between drive pulses (7) with a duty cycle above the upper limit, one or more successive damping pulses (9) with a duty cycle below the upper limit, and - to provide one or more successive damping pulses (9) with a duty cycle above the lower limit between drive pulses (7) with a duty cycle below the lower limit. [2] Valve system according to claim 1, wherein the control unit is configured to generate drive pulses (7) and / or damping pulses (9) with a duty cycle that are each a distance from a respective limit value. [3] Valve system according to one of the preceding claims, wherein the control unit is configured to: - between drive pulses (7) with a duty cycle above the upper limit, one or more successive damping pulses (9) with a duty cycle below the lower limit, and - to provide one or more successive damping pulses (9) with a duty cycle above the upper limit between drive pulses (7) with a duty cycle below the lower limit. [4] Valve system according to one of claims 1 to 3, wherein the control unit is configured to specify the drive pulses (7) and the damping pulses (9) in the same sequence with respect to the respective number and sequence of drive pulses (7) and damping pulses (9). [5] Valve system according to one of claims 1 to 3, wherein the control unit is configured to specify the drive pulses (7) and the damping pulses (9) in different sequences with respect to the respective number and / or sequence of drive pulses (7) and damping pulses (9). [6] Valve system according to claim 5, wherein the control unit is configured to specify a predetermined pattern in number and sequence of drive pulses (7) and damping pulses (9). [7] Valve system according to one of the preceding claims, wherein the control unit is configured to specify the damping pulses (9) only from a first predetermined time period starting from the control unit's movement of the closing element (1). [8] Valve system according to one of the preceding claims, wherein the control unit is configured to variably specify the duty cycle of the damping pulses (9). [9] Method for designing a control unit for a valve system for a vehicle, wherein the valve system has a closing element (1) which is movable between a closing and a releasing position, and has an electrical actuator (3) coupled to the closing element (1) and a spring (5) coupled to the closing element (1) and opposing the electrical actuator (3), wherein a duty cycle of a PWM signal for controlling the actuator (3) is varied and the duty cycle at which the actuator (3) overcomes the spring force and triggers an actuator-driven movement of the closing element (1) is stored as the upper limit, and the duty cycle at which the spring force overcomes the force of the actuator (3) and triggers a spring-driven movement of the closing element (1) is set as the lower limit,wherein the upper limit and the lower limit are stored in the control unit such that , - for an actuator-driven movement direction of the closing element (1) between the positions a PWM signal with a plurality of drive pulses (7) with a duty cycle above the upper limit is specified, - for a spring-driven movement direction of the closing element (1) between the positions a PWM signal with a plurality of drive pulses (7) with a duty cycle below the lower limit value is specified, and at several times during the course of the PWM signal: - between drive pulses (7) with a duty cycle above the upper limit, one or more successive damping pulses (9) with a duty cycle below the upper limit, and - between drive pulses (7) with a duty cycle below the lower limit, one or more successive damping pulses (9) with a duty cycle above the lower limit are specified.

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