HK1020925A - Pneumatic suspension - Google Patents

Description

Air spring type suspension

The invention relates to an air spring suspension, in particular for motor vehicles, having a compressor which can be switched on and off as required and which is stopped for a long time during normal operation of the air spring suspension and only needs to be operated intermittently.

Air spring suspensions for motor vehicles are known in principle and are used in large numbers. On the pressure side of the compressor, a pneumatic pressure accumulator is generally provided, which constantly maintains a charging pressure from the compressor that is significantly higher than the operating pressure of the air spring device or the air spring bellows. Here, the compressor is generally operated only when the pressure accumulator has to be recharged, and the output power of the compressor can be lower than the maximum output power at the maximum energy consumption of the pneumatic spring suspension, since a sufficient pressure supply is always ensured by the pressure accumulator. DE3130874C2 shows such an air spring suspension with a compressor driven as required by an electric motor.

Furthermore, attempts have been made to dispense with pressure accumulators in the case of air spring suspensions and to supply the air spring assemblies or air spring bellows directly with compressed air from the compressor when required. This is possible in particular in the following cases: the charging of the air spring arrangement is changed substantially only when the vehicle body height is lowered or raised, and not during normal spring lifting.

The load-bearing capacity of the compressor must be adapted to the requirements concerned. During driving, there is no need to worry about overloading, since only slight changes in the body height or possibly small blow-by gases have to be taken into account.

However, there may be substantially different situations if the air spring suspension is capable of raising or lowering the vehicle when parked or is capable of maintaining the vehicle at a predetermined height independent of the vehicle load. In these cases, the compressor may be subjected to extreme loads, even due to improper utilization of the height variation capability.

It is therefore an object of the present invention to provide an advantageous compressor overload protection arrangement.

In the case of the air spring suspension type described above, this object is achieved in that: the control device for starting and stopping the compressor comprises a computer which calculates an estimated value of the operating temperature of the compressor and stops the compressor if the estimated value exceeds an upper limit value, and restarts or enables the compressor to be restarted if the estimated value is lower than a lower limit value.

The present invention is based on the general idea of: in the case of air spring suspensions of the type mentioned at the outset, the computer-assisted compressor control which is always desirable and necessary is arranged in such a way that the operating temperature of the compressor can be estimated from empirical values. Since the control device switches the compressor on and off, it "knows" the operating process of the compressor and thus also its load state. Furthermore, the estimated value can be determined sufficiently "carefully" so that the actual operating temperature of the compressor falls below the estimated value with a nearly positive probability.

It can be considered a particular advantage of the present invention that no additional sensors and additional signal inputs are required on the control system to monitor the operation of the compressor. Therefore, it is also unnecessary to consider the failure of these parts.

According to a preferred embodiment of the invention, a minimum value is predefined for the estimated value. The minimum value, e.g., 40 ℃, is based on the maximum expected ambient temperature of the vehicle, etc.

In addition, provision is made for: each final estimate increases by a predeterminable or predetermined temperature rise during compressor operation, the degree of increase being dependent on the magnitude of the final estimate. After a longer dwell time, i.e. when the temperature of the compressor has decreased to a lower temperature, the operating temperature increases significantly in a shorter time after the compressor has been started. Such temperature increases are slow in the region of typical operating temperatures of the compressor. This can be taken into account when the compressor is switched on in order to make the temperature rise that has to be calculated suitable.

During operation of the compressor, the estimated value increases at a predetermined or predeterminable positive rate of change.

When the compressor is stopped, the estimated value decreases at a predetermined or predeterminable negative rate of change.

This can be increased or decreased, for example, by the estimated value always being increased or decreased by a predetermined small temperature difference after a predeterminable time interval.

If the stop is detected, in particular by the operation of the shut-down device, the computer continues to operate for a predetermined time interval, for example 5 minutes, in order to be able to determine a current estimate of the compressor temperature and to take this estimate as an initial temperature value during the subsequent operation of the compressor. The calculation of the temperature is started with the above-mentioned, for example, predetermined minimum temperature value of 40 c only when the vehicle is stopped for a longer period of time.

With regard to further preferred features of the invention, reference is made to the claims and the following description of the figures, with the aid of which a preferred embodiment is described by way of example.

In the figures, the sole figure shows a partial representation of an air spring system in the form of a block diagram.

The air spring system, which is not shown in detail, has a compressor 1, which is driven by an electric motor 2. The electric motor 2 is automatically switched on and off by parameters via a computer-aided control circuit 3, which computer-aided control circuit 3 also operates the control mechanism (not shown) of the valve 4 of the air spring system.

On the input side, the control circuit 3 is connected to sensors 5, each sensor 5 detecting, for example, the vertical distance between the vehicle body and the wheel and thus the height, so that the control circuit 3 can set or maintain a desired height by comparison of the set value with the actual value, which is achieved by the control circuit 3 by appropriately activating and deactivating the electric motor 2 and thus the compressor 1 as required and by operating the valve 4 in a corresponding manner.

Furthermore, the control circuit 3 is connected on the input side to a manually operable command transmitter 6, which transmitter 6 can be mounted, for example, in the driver's position of the vehicle and/or on a door, for example a tailgate, and by its operation can predetermine a set height even when parking. Thus, it is possible to facilitate loading or unloading of the vehicle, for example, by raising or lowering the height of the vehicle body.

Finally, the control circuit 3 receives a signal as soon as the preferably electronic shut-down device 7 of the vehicle is activated.

Since the control circuit 3 "knows" the running time and the start and standstill of the electric motor 2 and the compressor 1, it is possible to determine an estimate of the operating temperature of the compressor 1 by means of a computer provided with the control circuit 3 using empirical values, as described at the outset.

In this way, overload protection of the compressor 1 is ensured without separate sensors being provided for this purpose and without special inputs being provided for these sensors on the control circuit 3.

Claims (6)

1. Air spring suspension, in particular for motor vehicles, provided with a compressor which can be switched on and off as required and which pauses for a long time during normal operation of the air spring suspension and only needs to operate intermittently, characterized in that: the control device (3) for starting and shutting down the compressor (1) comprises a computer which calculates an estimate of the operating temperature of the compressor (1) and shuts down the compressor if the estimate exceeds an upper limit value and starts or allows the compressor to be started if the estimate is below a lower limit value.

2. Air spring suspension according to claim 1, characterized in that: a minimum value is predetermined for the estimate.

3. Air spring suspension according to claim 1 or 2, characterized in that the last estimated values increase with a predetermined temperature rise when the compressor (1) is activated.

4. Air spring suspension according to one of claims 1 to 3, characterized in that the estimated value increases at a predetermined positive rate of change during operation of the compressor and decreases at a predetermined negative rate of change when the compressor is stopped.

5. Air spring suspension according to claim 4, characterized in that: the estimated value is always increased or decreased by a predetermined small temperature difference after a predetermined time interval.

6. Air spring suspension according to one of claims 1 to 5, characterized in that after parking the computer modifies the temperature estimate to the next time interval.