DE102019130837B3 - Method for regenerating a dryer of an air suspension system of an electric vehicle and an air suspension system - Google Patents

Abstract

The invention relates to a method for regenerating a dryer (6) of an air suspension system of an electric vehicle, the method having a regeneration cycle with the following successive partial cycles (1, 2, 3): - filling a pressure accumulator (7) to a target pressure, - releasing the pressure accumulator (7) to a pressure that is lower than the target pressure, the vented air flowing through the dryer (6), - refilling of the pressure accumulator (7) to the target pressure, the regeneration cycle being triggered by charging the electric vehicle. The invention also relates to an air suspension system for an electric vehicle, having a compressor (5), a pressure accumulator (7), a dryer (6) and an electronic control unit.

Description

• - Füllen eines Druckspeichers auf einen Zieldruck,
• - Ablassen des Druckspeichers auf einen, gegenüber dem Zieldruck erniedrigten Druck, wobei die abgelassene Luft den Trockner durchströmt,
• - Wiederbefüllen des Druckspeichers auf den Zieldruck.

The present invention relates to a method for regenerating a dryer of an air suspension system of an electric vehicle, the method having a regeneration cycle with the following successive partial cycles:

• - Filling a pressure accumulator to a target pressure,
• - Discharge of the pressure accumulator to a pressure that is lower than the target pressure, with the discharged air flowing through the dryer,
• - Refilling the pressure accumulator to the target pressure.

The present invention further relates to an air suspension system for an electric vehicle, having a compressor, a pressure accumulator, a dryer and an electronic control unit.

Air suspension systems in vehicles serve on the one hand, together with the vibration damping system, to absorb the forces and shocks that occur during driving and also allow level control through which the vehicle body is kept at a constant vehicle level, i.e. at a certain ground clearance above the road. The air suspension system is operated with ambient air, which is compressed to the required system pressure by a compressor and fed to a pressure accumulator. When operating the air suspension system, it must be avoided that the moisture contained in the air condenses in the system and forms icing at correspondingly low temperatures. In order to prevent the humidity from freezing in an operating range from -40 ° C to +50 ° C, moisture is removed from the ambient air with the aid of an air dryer. The dryer absorbs moisture from the air flowing into the air suspension system and, conversely, releases moisture to the air flowing out when it is drained.

In order to ensure sufficient removal of moisture from the dryer, a corresponding volume flow of the air flowing in and out is necessary. If long-lasting draining processes occur due to insufficient level control cycles during vehicle operation, the volume flow required for humidity control will not be achieved. The moisture content in the dryer rises to saturation or supersaturation and thus impairs the ability of the dryer to absorb further moisture. This can also lead to an increase in air humidity in the air springs, which, particularly in cold regions, creates the risk that icing, for example of the valves, will result in a vehicle failure.

In order to regenerate the dryer, ie to remove the increased moisture from the dryer, specific draining and refilling processes of the pressure accumulator must be carried out. The air only flows through the dryer without affecting the level control inherent in the system. Methods for regulating the humidity of a dryer are, for example, from DE 10 2009 038 600 A1 and the DE 31 39 682 A1 known. Such a regeneration cycle with draining and refilling processes of the pressure accumulator requires energy to operate the compressor. In the case of electric vehicles in particular, such regeneration cycles are at the expense of the range of the vehicle due to the electrical energy used.

Against this background, the task arises of providing a regeneration method for an air suspension system of an electric vehicle, by means of which the range of the electric vehicle is impaired as little as possible.

To achieve the object, a method according to claim 1 and an air suspension system for an electric vehicle according to claim 7 are proposed. In the method according to the invention, by releasing the pressure accumulator, a relatively high volume flow is temporarily produced through the dryer, so that the moisture in the dryer can be absorbed and transported away by the outflowing air. In addition to the relative humidity of the air flowing through the dryer, the regeneration effect is essentially determined by the volume flow and the total amount of discharged air. In order to remove the moisture from the dryer as completely as possible, it is advantageous if a larger amount of air to be released is available. For this purpose, the pressure accumulator is first filled to a target pressure in the first partial cycle. The target pressure preferably corresponds to the operating pressure that is required for the operation of the air suspension system when driving.

In the second partial cycle, the pressure accumulator filled in the first partial cycle is released and the released air is passed through the dryer. The pressure accumulator is drained to a pressure that is lower than the target pressure. The reduced pressure can, for example, be equal to the ambient pressure, which corresponds to a complete discharge of the pressure accumulator. Alternatively, the reduced pressure can also be increased compared to the ambient pressure, for example because the discharge speed decreases as the ambient pressure approaches or the subsequent partial cycle of refilling is otherwise too long would last. It is also possible that the pressure, which is lower than the target pressure, corresponds, for example, to 90%, 80%, 70%, 60%, 50%, 40%, 30% or 20% of the target pressure. It is also conceivable, for example, that the shortening of the draining process and the refilling process achieved by a value of 50%, 60%, 70%, 80% or 90% is compensated for by carrying out several regeneration cycles that have been shortened in this way in order to achieve as complete dehumidification as possible of the dryer. The discharge speed and thus the flow rate through the dryer is preferably selected such that the moisture in the dryer is reduced as quickly and as efficiently as possible. At high flow rates, the air flowing through is only in contact with the interior of the dryer for a correspondingly short period of time and can therefore possibly only absorb part of the maximum possible amount of moisture. At low flow rates, on the other hand, the removal of moisture takes place very slowly. The discharge speed is preferably set up in such a way that, on the one hand, the amount of moisture removed per volume of air discharged is maximized and, on the other hand, the duration of the discharge process is aligned with the time required for the charging process. In the third sub-cycle, the pressure accumulator is refilled to the target pressure. The regeneration cycle can be carried out several times if necessary. The third partial cycle, which concludes the preceding regeneration cycle, simultaneously plays the role of the first partial cycle of the subsequent regeneration cycle. Preferably, the regeneration cycle is repeated until the desired amount of moisture has been removed from the dryer.

In order not to reduce the range of the electric vehicle due to the energy consumption during regeneration, the regeneration cycle is triggered according to the invention by charging the electric vehicle. In this way, at least part of the regeneration cycle or a first part of several successive regeneration cycles is carried out during the charging process. The electrical energy stored at the end of the charging process therefore advantageously does not flow into the regeneration process, or flows only slightly, so that the range of the electric vehicle is not unnecessarily reduced. If the loading process is ended or aborted during the partial cycle of filling the pressure accumulator or the partial cycle of refilling the pressure accumulator, this preferably does not lead to an abortion of the corresponding partial cycle. This ensures that the pressure accumulator is completely filled to the target pressure in spite of the completed or aborted charging process.

According to an advantageous embodiment of the invention, the partial cycle of draining the pressure accumulator is only carried out during an active charging process. In this way, it is advantageously prevented that the partial cycle of draining the pressure accumulator is carried out after the charging process has already been terminated or aborted. If the regeneration cycle is started when charging is recognized and the first partial cycle of filling the pressure accumulator is carried out to the target pressure, termination or abortion of the charging process preferably leads to the first partial cycle being completed completely, but not starting the second partial cycle. In this way, it is advantageously ensured that the electrical energy stored at the end of the charging process is not used unnecessarily and is available as completely as possible for the range of the electric vehicle.

According to the invention, the regeneration cycle is triggered when there is a need for regeneration. The need for regeneration is determined with the help of sensor data, and a model-based calculation can also be incorporated. The requirement is preferably determined as a function of a model-supported and sensor-supported function. For example, statistically collected information or empirical values, such as the average regeneration frequency, can be included in the model-supported function. When the air suspension system is in operation, the volume flows when the pressure accumulator is being filled and drained are preferably recorded by the associated control and regulation unit, and the probability of a need for regeneration being determined therefrom. The need for regeneration is preferably registered by the value of a system variable, for example in the control and regulation unit. The need for regeneration is preferably reset only after the regeneration cycle has been completed or the plurality of regeneration cycles necessary for dehumidification have been completed. For example, this resetting can consist of resetting the corresponding value of the system variable. A new determination of the regeneration requirement is preferably started after the regeneration requirement has been reset. If the regeneration cycle or the plurality of regeneration cycles necessary for dehumidification is not carried out completely, the effect that the regeneration cycle or the plurality of regeneration cycles is completely restarted during the next charging process.

According to the invention, a determination of the regeneration requirement comprises a measurement of a dryer air humidity inside the dryer. In this way, the need for regeneration can advantageously be measured by directly measuring the Determine the dryer air humidity. The regeneration requirement can be determined using the current value of the dryer air humidity. Alternatively, the time of the next need for regeneration can also be predicted by extrapolating the time course of the dryer air humidity.

According to the invention, a determination of the regeneration requirement comprises a measurement of an ambient air humidity in the vicinity of the electric vehicle. At low humidity, more precisely, at low relative humidity, the dryer can be regenerated in a particularly efficient manner, while ambient air with high relative humidity gives off a relatively large amount of moisture to the dryer when it is filled, which is only given back to the air flowing through when it is drained must, so that the efficiency of the regeneration is reduced. The measurement of the ambient air humidity is preferably combined with a model-based determination of the regeneration requirement. In the case of increased air humidity, when the air suspension system is in operation, the dryer must absorb a greater amount of moisture from the ambient air flowing in, so that the dryer needs to be regenerated more quickly. By means of suitable modeling of this relationship, it is advantageously possible to make a prediction about the time span to be expected until a need for regeneration occurs, which can be related, for example, to the charge state of the vehicle. In this way, the expected regeneration requirement and the expected charging requirement can be used to match the times of the regeneration cycles to the charging times.

According to an advantageous embodiment of the invention, the regeneration requirement is determined at time intervals or essentially continuously. In the simplest case, the requirement can be determined at constant time intervals, but it is also possible that the time intervals increase or decrease depending on the time that has passed since the last regeneration cycle. It is also conceivable that the frequency with which the needs are determined depends on additional data from model-based calculations or sensor data. The determination of the need for regeneration is preferably carried out by the control and regulation unit.

According to an advantageous embodiment of the invention, when there is a need for regeneration, the determination of the need for regeneration is blocked. In this way, it can advantageously be avoided that new determinations of need are carried out when a need for regeneration has already been effectively recognized. By blocking the determination of the need, the need for regeneration remains until the next regeneration cycle is carried out.

According to an advantageous embodiment of the invention, the blocking of the determination of the regeneration requirement is lifted as soon as the pressure accumulator has been completely drained to the pressure that is lower than the target pressure. This ensures that the draining process necessary for dehumidifying the dryer is carried out in full at least once before a new requirement determination is started. It is also possible that the determination of the regeneration requirement is only blocked when the number of regeneration cycles required for dehumidification has been carried out.

According to an advantageous embodiment of the invention, the regeneration cycle is controlled by a software component of the electric vehicle. Such functional software components (Software Component, SWC) are modular components of the software architecture of a vehicle, each of which is separate from one another and from the basic software. Both the determination of the need for a regeneration cycle and the regeneration cycle itself are preferably controlled by a software component of the electric vehicle. For this purpose, the software component preferably receives signals via the runtime environment (RTE) about the charging status and particularly preferably additional signals such as, for example, the ambient air humidity and / or the dryer air humidity. The charging status, the ambient air humidity and / or the dryer air humidity can be stored as values of a local variable of the software component and the requirement determination or control of the regeneration cycle can be carried out on the basis of these variables. The software component preferably forms the permissible release from the input signals or causes the regeneration function to be aborted. The dryer regeneration is preferably triggered by a start signal for the regeneration cycle after loading has been recognized. The software component preferably controls the filling of the pressure reservoir to the target pressure independently.

Another object of the invention is an air spring system according to claim 7. The same advantages can be achieved in the air spring system as have already been described in connection with the method according to the invention. The advantageous configurations and features discussed with regard to the method can also be used in the air spring system.

• 1 den Transportweg der in ein Luftfedersystem ein- und ausströmenden Luft in einem schematischen Blockdiagramm;
• 2 die Teilzyklen des erfindungsgemäßen Verfahrens in einem schematischen Blockdiagramm.

In the following, further advantageous features and details of the invention are to be explained with reference to the exemplary embodiments shown in the drawings. Herein shows:

• 1 the transport path of the air flowing in and out of an air suspension system in a schematic block diagram;
• 2 the partial cycles of the method according to the invention in a schematic block diagram.

In the 1 the transport path of the air flowing into and out of an air suspension system is shown schematically. Such a course of the air flow can, for example, also be generated within the scope of an embodiment of the method according to the invention. The ambient air 4th , which has a certain relative humidity, is fed to the air suspension system, where it is initially supplied by a compressor 5 is compressed to an increased pressure. The compressed air flows through the dryer 6th where part of the moisture it contains is extracted from the air. In this embodiment of the air suspension system, the dryer is 6th arranged behind the compressor with respect to the inflowing air. By the one in the compressor 5 When compression takes place, the relative humidity increases, ie the tendency of the air to give off moisture increases. This allows the compressed air in the dryer 6th the moisture can be removed more easily or in larger quantities. With this arrangement between the compressor 5 and dryer 6th however, it is only one possible implementation. The method according to the invention and the system according to the invention can be implemented both with this and with alternative arrangements.

The moisture removed from the air can, for example, condense in the dryer and / or be absorbed by suitable material. The compressed and dried air flows from the dryer 6th in the pressure accumulator 7th , which acts as a pressure reservoir for the level control of the vehicle. When regulating the vehicle level, there is a reduction in the pressure in the pressure accumulator 7th required, air is released from the accumulator 7th drained and in turn flows through the dryer 6th . The from the becomes the pressure accumulator 7th flowing air in the dryer 6th released moisture is absorbed and the moist air is released back into the ambient air 4th submitted.

With a perfectly balanced moisture balance, the amount of moisture in the dryer would be 6th on average neither decrease nor increase. A complete balance between liquid absorption and release in the dryer 6th However, this could essentially only be achieved with a continuous and constant volume flow through the dryer 6th to reach. However, since the level control causes draining processes of different lengths, slower or faster, the moisture content in the dryer can be reduced 6th increase over time. Reaches the moisture content of the dryer 6th its saturation value, no more moisture can be absorbed from the incoming air and undried air flows into the pressure accumulator 7th and from there into the air springs. At correspondingly low temperatures, the moisture freezes there to ice and thus leads to impairments that can lead to vehicle failure.

In the 2 are the partial cycles 1 , 2 , 3 of the method according to the invention shown schematically. To the in the dryer 6th To remove any accumulated moisture, a regeneration cycle is performed when the EV is charged. Since electrical energy is used to carry out the regeneration cycle, in particular to operate the compressor 5 must be expended, when the regeneration according to the invention is triggered by the charging process, the electrical energy is at least partially already consumed during charging, so that, for example, after the vehicle battery has been fully charged, practically all of the stored energy is available for operating the vehicle and the range is advantageously maximized in this way.

In the first sub-cycle 1 becomes the accumulator 7th initially filled to a target pressure. In the following second partial cycle 2 the pressure accumulator is drained to a pressure that is lower than the target pressure. The vented air flows through the dryer 6th and takes it in the dryer 6th accumulated moisture. Then in the third sub-cycle 3 the pressure accumulator is refilled to the target pressure. The one through the sub-cycles 1 , 2 , 3 formed regeneration cycle can also be repeated several times until the moisture content of the dryer 6th has reached the desired value for further operation of the air suspension system.

The sub-cycles described above 1 , 2 , 3 are part of a method according to claim 1, which is suitable for operating an air suspension system according to claim 7.

Claims (7)

A method for regenerating a dryer (6) of an air suspension system of an electric vehicle, the method having a regeneration cycle with the following successive partial cycles (1, 2, 3): - Filling fine pressure accumulator (7) to a target pressure, - Discharge of the pressure accumulator (7) to a pressure that is lower than the target pressure, the released air flowing through the dryer (6), - Refilling of the pressure accumulator (7) to the target pressure, characterized in that the regeneration cycle is carried out by a charging process when there is a need for regeneration of the electric vehicle is triggered, a determination of the regeneration requirement comprising a measurement of a dryer air humidity inside the dryer (6) and a measurement of an ambient air humidity in the vicinity of the electric vehicle. Procedure according to Claim 1 , characterized in that the partial cycle (2) of draining the pressure accumulator (7) is only carried out during an active charging process. Method according to one of the preceding claims, characterized in that the regeneration requirement is determined at time intervals or essentially continuously. Method according to one of the preceding claims, characterized in that when there is a need for regeneration, the determination of the need for regeneration is blocked. Procedure according to Claim 4 , characterized in that the blocking of the determination of the regeneration requirement is lifted as soon as the pressure accumulator (7) has been completely drained to the pressure which is lower than the target pressure. Method according to one of the preceding claims, characterized in that the regeneration cycle is controlled by a software component of the electric vehicle. Air suspension system for an electric vehicle, comprising a compressor (5), a pressure accumulator (7), a dryer (6) and an electronic control unit, characterized in that the electronic control unit is configured in such a way that when the electric vehicle is charging, if there is a need for regeneration Regeneration cycle is triggered with the following successive partial cycles (1, 2, 3): - The compressor (5) is operated in such a way that the pressure accumulator (7) is filled to a target pressure, - the pressure accumulator (7) is set to one, opposite the Target pressure lowered pressure, with the discharged air flowing through a dryer (6), - the compressor (5) is operated in such a way that the pressure accumulator (7) is refilled to the target pressure, with a determination of the regeneration requirement a measurement of the dryer air humidity inside the Dryer (6) and a measurement of ambient air humidity in the vicinity of the electric vehicle includes.

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