ELECTRONIC LEVEL CONTROL DEVICE FOR AIR-SUSPENDED VEHICLES, METHOD AND CONTROL DEVICE FOR ELECTRONIC LEVEL CONTROL

Abstract

Disclosed is an electronic level control device for a vehicle having an air suspension system, for example a trailer vehicle having an air suspension system, the vehicle comprising a chassis having an axle and at least two wheels arranged on the axle, wherein an air spring is arranged between the axle and the chassis for at least one of the wheels, wherein an electronic control unit can initiate a level controlling procedure by actuating a solenoid valve, and wherein at least one capacitive level sensor is provided for the axle. The distance between the chassis and the at least one axle can be determined by the level sensor.

Claims

1-11. (canceled)

12. An electronic level control device for a vehicle having an air suspension system, said vehicle comprising a chassis having at least one axle, at least two wheels arranged on the at least one axle, and an air spring arranged between the at least one axle and the chassis for at least one of the at least two wheels, the electronic level control device comprising: an electronic control unit configured to initiate a level controlling procedure by actuating a solenoid valve of the air spring to supply compressed air to the air spring from a compressed air storage device and/or discharge compressed air from the air spring into the atmosphere so as to perform the level controlling procedure; and at least one capacitive level sensor comprising a variable capacitance; wherein said capacitive level sensor is configured to determine a distance between the chassis and the at least one axle based on the variable capacitance.

13. The electronic level control device as claimed in claim 12, wherein the at least one capacitive level sensor comprises a capacitor formed by the chassis and the at least one axle, wherein the capacitor has a variable electrical capacitance that varies depending upon the distance between the chassis and the at least one axle, and wherein the electronic control unit is configured to generate a control signal for actuating the solenoid valve based on a value of the variable electrical capacitance.

14. The electronic level control device as claimed in claim 13, wherein the electronic control unit comprises an electric circuit measuring the variable electrical capacitance of the capacitor, and wherein the electronic control unit is configured to generate the control signal for actuating the solenoid valve based on the measured variable electrical capacitance.

15. The electronic level control device as claimed in claim 13, further comprising an electric circuit integrated in the electronic control unit, said electric circuit comprising a DC voltage source, a charging resistor, and a time-voltage measuring unit.

16. The electronic level control device as claimed in claim 15, wherein the electric circuit is configured to: generate a square wave voltage; determine a time period that elapses between applying the square wave voltage and achieving a predetermined charging voltage value at the capacitor; and calculate a current capacitance of the capacitor by the formula:
C2=(R1/t1/C1).sup.1 wherein C2 is the current capacitance of the capacitor, R1 is a previously known electrical resistance of the charging resistor, t is the determined time period, and C1 is a constant capacitance of other capacitive elements connected in series to the capacitor.

17. The electronic level control device as claimed in claim 16, further comprising value pairs of different capacitance values of the capacitor and associated distance values between the chassis and the at least one axle, wherein the value pairs are stored in the electronic control unit, wherein the electronic control unit is configured to generate the control signal on one of the value pairs corresponding to the current capacitance.

18. The electronic level control device as claimed in claim 16, wherein the electronic control unit is configured to determine a current distance between the chassis and the at least one axle based on the current capacitance, and wherein the electronic control unit is configured to generate the control signal based on a comparison of the current distance to a desired distance stored in the electronic control unit.

19. The electronic level control device as claimed in claim 16, wherein the predetermined charging voltage value is 0.67 times the square wave voltage.

20. The electronic level control device as claimed in claim 13, wherein a rotational speed sensor is arranged on the at least one axle for each of the at least two wheels and comprises a constant capacitive element connected in series to the capacitor.

21. A method for electronic level control of a vehicle having an air suspension system, said vehicle comprising a chassis having at least one axle, two wheels arranged on the at least one axle, and an air spring for at least one of the wheels arranged between the at least one axle and the chassis, the method comprising: initiating, by an electronic control unit, a level controlling procedure comprising one of: supplying compressed air to the air spring from a compressed air storage device; or discharging compressed air from the air spring into the atmosphere; determining a capacitance of a capacitor, said capacitance being variable in dependence upon a distance between the at least one axle and the chassis, wherein the chassis together with the at least one axle forms the capacitor; and generating a control signal for actuating a solenoid valve to initiate the level controlling procedure based on the determined capacitance.

22. The method as claimed in claim 21, further comprising: generating a square wave voltage by an electric circuit, wherein the electric circuit comprises a DC voltage source, a charging resistor, and a time-voltage measuring unit; and determining, using the electric circuit, a time period that elapses between applying the square wave voltage and achieving a predetermined charging voltage value at the capacitor; wherein determining the capacitance of the capacitor comprises calculating a current capacitance of the capacitor by the formula:
C2=(R1/t1/C1).sup.1 wherein C2 is the current capacitance of the capacitor, R1 is a previously known electrical resistance of the charging resistor, t is the determined time period, and C1 is a constant capacitance of other capacitive elements connected in series to the capacitor.

23. The method as claimed in claim 22, further comprising adjusting the distance between the chassis and that least one axle based upon value pairs stored by the electronic control unit for the current capacitance and an associated distance value.

24. The method as claimed in claim 22, further comprising determining a current distance between the chassis and the at least one axle based on the current capacitance, wherein the control signal is based on a comparison of the current distance to a desired distance stored in the electronic control unit.

25. The method as claimed in claim 22, further comprising calibrating the electronic control unit by: measuring the constant capacitance of other capacitive elements connected in series to the capacitor by measuring the constant capacitance of a rotational speed sensor connected in series to the capacitor, and storing the value of the measured constant capacitance in the electronic control unit; and measuring the value of the capacitance of the capacitor at different distance values between the at least one axle and the chassis, and storing the capacitance and distance values as value pairs in the electronic control unit.

26. The method as claimed in claim 22, wherein the predetermined charging voltage value is 0.67 times the square wave voltage.

27. The method as claimed in claim 21, wherein the vehicle comprises at least one other axle, wherein initiating the level controlling procedure comprises initiating a simultaneous level controlling procedure for both axles of the vehicle based on the determined capacitance.

Description

BRIEF DESCRIPTION OF THE DRAWINGS

[0030] The invention is described in greater detail below with reference to the accompanying figures, in which:

[0031] FIG. 1 is a sectional schematic view of a vehicle having an axle and an air suspension system,

[0032] FIG. 2 illustrates schematically the electrical capacitance C2 of a capacitor that is formed by the chassis and an axle of the vehicle having an air suspension system, the electrical capacitance C2 depending upon the distance D between the chassis and axle,

[0033] FIG. 3 is a schematic diagram of a circuit for measuring the distance-dependent electrical capacitance C2,

[0034] FIG. 4 is a diagram of the charging voltage curve over the time t at the capacitor that is formed by the chassis and the axle, and

[0035] FIG. 5 is a schematic diagram of a circuit for measuring the distance-dependent electrical capacitance C2 of the capacitor that is formed by the chassis and the axle, with the use of a rotational speed sensor for a wheel on the axle of the vehicle having an air suspension system.

DETAILED DESCRIPTION

[0036] With reference to the figures, FIG. 1 illustrates schematically a section of a chassis 1 of a vehicle having air suspension system, in particular a trailer vehicle having an air suspension system. The chassis 1 is connected to at least one axle 2 via, respectively, one air spring 3 per vehicle wheel 14. Each of the vehicle wheels 14 comprises a tire 8 and a rim 9, with the result that the axle 2 and the chassis 1 are electrically insulated from the road or from roadway elements. A distance D of the axle 2 from the chassis 1 can be set by an electronic control unit 6 to desired values that can be predetermined. For this purpose, the control unit 6, after using information regarding the current distance D, transmits signals to a solenoid valve 4 that is arranged in a pneumatic connecting line 15 between a compressed air storage device 5 and the air springs 3. Depending upon the respective set desired level and in the case of fluctuations in the distance D, the solenoid valve supplies compressed air from the compressed air storage device 5 to the air springs 3 or discharges compressed air from the air springs 3 into the atmosphere. This level controlling procedure is normally performed automatically with reference to data and control programs that are stored in the electronic control unit 6, but it is also possible to provide an operating unit 7 that is operated manually and can be used to input desired data for the desired distance D into the control unit 6.

[0037] The electronic control unit 6 can be an engine control unit or, as in the present embodiment, an axle modulator. It is also possible to integrate an anti-lock system in such an engine control unit or in an axle modulator or also in an electronic brake system, and for this reason a rotational speed sensor 10 is provided on the axle 2 for each vehicle wheel 14. This rotational speed sensor 10 transmits rotational speed signals to an anti-lock system or an electronic brake system so as to actuate the wheel brakes in order to prevent the wheels locking when the service brake of the vehicle is actuated.

[0038] The diagram in accordance with FIG. 2 illustrates that the distance-dependent, and therefore variable, electrical capacitance C2 of a capacitor 13 that is formed by the chassis 1 and the axle 2 increases starting from a minimum value in the case of a maximum distance D1 of the axle 2 from the chassis 1 over an average value to a maximum value in the case of a minimum distance D2.

[0039] FIG. 3 illustrates a schematic diagram of a circuit S for measuring the variable capacitance C2 of the capacitor 13 that is formed by the chassis 1 and the axle 2 that is galvanically isolated from the chassis 1. A further capacitor 10 having a constant electrical capacitance C1 that can be measured in a known manner is connected in series to this capacitor 13, the further capacitor 10 being formed in this embodiment by the above-mentioned rotational speed sensor 10 for the vehicle wheel 14.

[0040] The capacitors that are connected in series, namely the capacitor that is formed by the rotational speed sensor 10 and that has the constant capacitance C1, and the capacitor 13 that is formed by the chassis 1 and the axle 2 and that has the distance-dependent capacitance C2, can be charged via a charging resistor R1 by a DC voltage source 11 that periodically generates a square wave voltage U1. A charging voltage curve U=f (t) in relation to this is illustrated in FIG. 4. As shown in FIG. 4, the increase of the charging voltage U does not occur instantaneously to the maximum value of the applied square wave voltage U1, but rather that a specific time period t from a point in time t0 to a point in time t1 is necessary to reach a predetermined charging voltage U2. At a later point in time t2, the charging voltage increase periodically drops to zero. Since the charging voltage U approaches the applied square wave voltage U1 in an asymptotic manner, only the period of time t between the point in time t0 of the start of the charging period of time and achieving a predetermined charging voltage value U2 is measured by a time-voltage measuring unit 12, the charging voltage value U2 amounting in this exemplary embodiment to 0.67 times the maximum voltage value of the applied square wave voltage U1. This value of the charging voltage U2=0.67*U1 represents a good compromise between a charging voltage value that can be measured comparatively effectively and a comparatively short measuring time.

[0041] The variable capacitance of the capacitor 13 that is formed by the chassis 1 and the axle 2 can be calculated using the formula C2=(R1/t1/C1).sup.(1), wherein R1 is the previously known electrical resistance [] of the charging resistor R1, t is the time period [s] prior to achieving the charging voltage U2=U1*0.67 [V], and C1 is the previously known constant capacitance [nF] of the rotational speed sensor 10. The voltage source 11, the time-voltage measuring unit 12 and the two series-connected capacitors 10, 13 that have a constant capacitance C1 or have a distance-dependent capacitance C2 lie respectively with a pole against the chassis 1, which forms the ground pole in the vehicle. The distance D between the chassis 1 and the axle 2 can be selected from a table that is stored in the control device 6 using the respective current value for the distance-dependent variable electrical capacitance C2, which is determined with the aid of the above-mentioned formula. This distance value D is then used by the control device 6 for the described actual value-desired value comparison, after which a control signal for the solenoid valve 4 is generated or not generated. The table having the value pairs for the distance D between the chassis 1 and the axle 2 and the associated value for the capacitance C2 can be set in a calibrating phase and stored in the control device 6.

[0042] The detailed schematic circuit diagram in accordance with FIG. 5 illustrates the chassis 1, simplified as a bold line, the schematically illustrated axle 2, and also the vehicle wheel 14 that comprises the tire 8 and the rim 9. The capacitor 13 that is formed by the chassis 1 and the axle 2 and that has the distance-dependent capacitance C2 is marked schematically as an electronic component between the chassis 1 and the axle 2. The capacitor that is formed by the rotational speed sensor 10 and that has a constant capacitance C1 is connected via electrical lines to the electronic control unit 6. The electric circuit S is integrated into the control unit, the electric circuit S comprising, and optionally consisting of, the DC voltage source 11 for periodically generating a square wave voltage U1, the charging resistor R1 and the time-voltage measuring unit 12.

[0043] The procedure of periodically charging the capacitor 13 that is formed by the chassis 1 and the axle 2 and that has the distance-dependent capacitance C2 and the capacitor that is formed by the rotational speed sensor 10 and is connected in series to the capacitor 13 and that has the constant capacitance C1 is performed by the electronic control unit 6. Moreover, the electronic control unit 6 is configured to separate the speed signals of the rotational speed sensor 10 and the charging voltage signals of the electric circuit S from the DC voltage source 11, the time-voltage measuring unit 12 and the charging resistor R1 from one another for further processing. An algorithm is stored in the control unit 6 and, using the algorithm, the current value of the variable capacitance C2 of the capacitor 13 that is formed by the chassis 1 and the axle 2 can be determined in accordance with the previously mentioned formula, C2=(R1/t1/C1).sup.1 [nF].

[0044] Every time a measurement is performed, the capacitor 13 that is formed by the chassis 1 and the axle 2 and also the capacitor that is formed by the rotational speed sensor 10 are initially discharged, and the square wave voltage U1 is then applied after a short time periodically in the circuit S, with the result that it is possible in this manner to measure the period of time t prior to achieving a charging voltage having the value U2=U1*0.67 and also to calculate the respective current capacitance C2.

[0045] In order to correlate the distance D between the chassis 1 and the axle 2 with respect to the electrical capacitance C2 of the capacitor 13 that is formed by the chassis 1 and the axle 2 in a calibrating procedure, in the case of a vehicle that is at a standstill, measurements are performed by the circuit that is illustrated in FIG. 5 in the case of different distances D that are set between the chassis 1 and the axle 2. The respective period of time t prior to achieving the predetermined charging voltage value U2 is determined, subsequently the capacitance C2 is calculated using the formula C2=(R1/t1/C1).sup.1, and finally the associated value pairs of the distance D and capacitance C2 are input into the diagram in accordance with FIG. 2 or into a table in the control unit 9 and stored in the diagram or table.

[0046] In the example illustrated in FIG. 2, the maximum value of the capacitance amounts to C2=85 nF in the case of a distance D2=710 mm in the lowest position of the chassis 1 with respect to the axle 2. The minimum value of the capacitance C2=56 nF is achieved in the case of a maximum distance D=960 mm. In the case of an intermediate distance of D1=910 mm lying between the chassis 1 and the axle 2, a capacitance of C2=73 nF is determined. Intermediate values are interpolated and likewise stored.

[0047] By virtue of periodically applying the square wave voltage U1 to the capacitor that is formed by the rotational speed sensor 10 and that has the constant capacitance C1 and periodically applying the square wave voltage U1 to the capacitor 13 that is formed by the chassis 1 and the axle 2, is connected in series to the capacitor 10 and has the variable capacitance C2, it is possible to determine the charging time periods t that elapse prior to achieving the charging voltage U2=U1*0.67 and the current distance values D therefrom, and, in the case of a deviation from a selected desired value, perform corrections of the distance D by the electronic level controlling procedure.

[0048] FIGS. 1 to 5 are only schematic in order to illustrate the measuring principle that is the basic idea of the invention. The description of the principle provides the person skilled in the art with the information that he requires in order to construct the real electric circuits using his expertise and to program the function of the electronic control unit 6 to determine distance correcting values for the distance D in order to be able to perform the corresponding corrections by the electronic control unit 6.

[0049] The invention is not limited to vehicles having an air-suspension system, in particular trailer vehicles having an air suspension system and rigid axles 2, but rather the invention also relates to vehicles having an air suspension system with individual wheel suspension arrangements, by way of example passenger cars in which one distance measurement in accordance with the invention using a rotational speed sensor 10 is provided at each wheel suspension arrangement.

[0050] The contacting arrangement of the proposed measuring circuit is provided in the exemplary embodiments via the rotational speed sensor 10. It is assumed that the coupling between the electrical interior of the rotational speed sensor 10 and its housing is capacitive, with the result that the constant electrical capacitance C1 that is present there is connected in series to the capacitance C2 that varies depending upon the distance D and that is to be actually measured. Alternatively, the coupling between the electrical interior of the rotational speed sensor 10 and its housing is ohmic, wherein a device and a method can be used that are described in DE 10 2015 000 380 A1, assigned to the applicant, which is incorporated herein by reference in its entirety. In lieu of measuring the capacitance C2 that varies depending upon the distance D, optionally an impedance that varies depending upon the distance can be measured, the impedance optionally being capacitive or ohmic.

[0051] All the features mentioned in the above description of the figures, in the claims and in the description introduction can be used both individually as well as in an arbitrary combination with one another. The invention is consequently not limited to the described and claimed combinations of features, on the contrary all combinations of the features are to be considered as disclosed.

[0052] The terms comprising or comprise are used herein in their broadest sense to mean and encompass the notions of including, include, consist(ing) essentially of, and consist(ing) of. The use of for example, e.g., such as, and including to list illustrative examples does not limit to only the listed examples. Thus, for example or such as means for example, but not limited to or such as, but not limited to and encompasses other similar or equivalent examples. The term about as used herein serves to reasonably encompass or describe minor variations in numerical values measured by instrumental analysis or as a result of sample handling. Such minor variations may be in the order of 0-25, 0-10, 0-5, or 0-2.5, % of the numerical values. Further, The term about applies to both numerical values when associated with a range of values. Moreover, the term about may apply to numerical values even when not explicitly stated.

[0053] On an individual basis, each of the aforementioned applications for patent, patents, and/or patent application publications, is expressly incorporated herein by reference in its entirety in one or more non-limiting embodiments.

[0054] It is to be understood that the appended claims are not limited to express and particular compounds, compositions, or methods described in the detailed description, which may vary between particular embodiments which fall within the scope of the appended claims. With respect to any Markush groups relied upon herein for describing particular features or aspects of various embodiments, it is to be appreciated that different, special, and/or unexpected results may be obtained from each member of the respective Markush group independent from all other Markush members. Each member of a Markush group may be relied upon individually and or in combination and provides adequate support for specific embodiments within the scope of the appended claims.

[0055] The present invention has been described herein in an illustrative manner, and it is to be understood that the terminology which has been used is intended to be in the nature of words of description rather than of limitation. Many modifications and variations of the present invention are possible in light of the above teachings. The present invention may be practiced otherwise than as specifically described within the scope of the appended claims. The subject matter of all combinations of independent and dependent claims, both single and multiple dependent, is herein expressly contemplated.