System for filling a pressure medium accumulator

A method of filling a pressure medium accumulator with a housing having an inner space that is subdivided into two chambers by a metallic pleated bellows used as a media-separating element. The first chamber thereof is filled with a gas and the second chamber is filled with a liquid pressure medium. The bottom valve is provided in a hydraulic port, its closing member being operable by the media-separating element. The valve permits filling of the second chamber with fluid and prevents a complete evacuation of the second chamber. To enable reliable filling of the above-mentioned chambers with corresponding media without damaging the pleated bellows, the method includes the steps of evacuating the second chamber, filling the second chamber with pressure medium and filling the first chamber with a gas.

TECHNICAL FIELD

The present invention generally relates to a system for filling a pressure medium accumulator and more particularly relates to a method of filling a pressure medium accumulator with a housing having an inner space that is subdivided into two chambers by a metallic pleated bellows used as a media-separating element.

BACKGROUND OF THE INVENTION

International patent application WO 00/31420 discloses a pressure medium accumulator of this general type. Movement of the pleated bellows causes the closing member of the bottom valve to adopt a position where it carries out the function of a hydraulic piston. The reliability of operation is considerably enhanced because this arrangement reliably prevents damage to the bottom valve and an inadvertent escape of pressure medium. However, the above-mentioned publication does not provide any way for reliably filling the chambers referred to above without damaging the pleated bellows.

BRIEF SUMMARY OF THE INVENTION

Therefore, an object of the present invention is to disclose a method as well as a device for filling a pressure medium accumulator of the above-mentioned type, ensuring that the pleated bellows is permanently in a pressure-balanced condition.

According to the present invention, this object is achieved by the combination of the following process steps:a) evacuation of the second chamberb) filling of the second chamber with pressure mediumc) filling the gas into the first chamber.

To render the idea of the invention more precise, arrangements are made for the second chamber to be filled with a defined pressure medium volume that corresponds to the system requirements for a determined temperature, according to which the first chamber is filled with a corresponding, previously calculated gas volume to compensate for the geometrical tolerances.

In a device for implementing the method of the invention, there is provision of means for evacuating the second chamber, means for filling the second chamber with pressure medium, as well as means for filling the gas into the first chamber.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Now referring toFIG. 1, the pressure medium accumulator that is to be filled according to the invention method has a housing1with an interior that is subdivided by a media-separating element2into two pressure compartments or chambers3,4. The media-separating element2is preferably formed by a thin-walled metallic pleated bellows, which is pressure-tightly connected to a cover8closing the housing1, on the one hand, and closed by means of a plate9, on the other hand. The interior of the pleated bellows2forms the first chamber3which can be filled with a gas generally under high pressure through a filling connection10provided in the cover8. In the bottom part of the housing1, a hydraulic port5is designed in which a bottom valve6is arranged whose closing member7projects into the second chamber4. The bottom valve6is preferably designed so that it permits filling of the second chamber4with a pressurized liquid pressure medium, e.g. brake fluid, on the one hand, and prevents complete evacuation of the second chamber4, on the other hand. Besides, the first chamber3houses a compression spring11which is compressed between the cover8and the previously mentioned plate9and, thus, biases the pleated bellows2in the direction of the bottom valve6. This ensures that the hydraulic pressure prevailing in the second chamber4is always higher than the gas pressure prevailing in the first chamber3.

Further, a sensor device carrying reference numeral12for sensing the movement of the media-separating element2is arranged in the first chamber3filled with gas. Sensor device12which may e.g. be designed as an inductive distance sensor represents an independent assembly that can be mounted into an opening provided in cover8.

The drawing also shows a schematic view of a device used to fill the pressure medium accumulator described above with corresponding pressure media. The illustrated device is substantially composed of the following components:a) a first supply line13which is connected to the above-mentioned first chamber3, on the one hand, and to a pressure gas source not shown, on the other hand,b) a second supply line14which is connected to the above-mentioned second chamber4, on the one hand, and either to a pressure medium source not shown or a vacuum source15, on the other hand,c) a mechanism16for mechanically opening or keeping open the bottom valve6, said mechanism being adapted to be introduced into the previously mentioned hydraulic connection5, andd) a shut-off valve17,18inserted in the second supply line14and respectively associated with the pressure medium source and the vacuum source15.

It is suitable to arrange for a first pressure sensor19to monitor the pressure medium filling pressure, a second pressure sensor20for monitoring the level of the vacuum generated by the vacuum source15, and a distance sensor21for monitoring the movement of the mechanism16for mechanically opening or keeping open the bottom valve6.

Before the filling operation commences that will be explained hereinbelow, it shall be assumed that the above-mentioned plate9is positioned on a first stop (e.g. on the bottom of housing1) under the effect of compression spring11, and that the bottom valve6is closed. A signal value of the distance sensor12which is determined and stored corresponds to this initial condition. The determined signal value is later used in operation to detect defects at the bottom valve6. To achieve the same effect in a design without the above-mentioned compression spring11, low pressure (e.g. compressed air up to 2 bar) is applied to the first chamber3.

After the device16which may e.g. be configured as a metallic pin has opened the bottom valve6, the second supply line14(by way of opening the associated shut-off valve18) is connected to the vacuum source15and the second chamber4evacuated. After the evacuation the second chamber4is filled completely with a pressure medium provided herefor, preferably brake fluid under low pressure, with the pleated bellows2being compressed by a small extent. Subsequently, the compression spring11or the gas pressure acting in the first chamber3causes a slow outflow of the excess pressure medium volume until the bottom valve6closes. Because the closing member7of the bottom valve, the plate9closing the pleated bellows2, and the distance sensor12are in contact with each other, the signal value of the distance sensor12, at which the bottom valve6closes, may be determined and stored.

A defined pressure medium volume is replenished which corresponds to the system-induced minimum requirements and represents e.g. the volume value that ensures a proper functioning of the pressure medium accumulator at the temperature of 120° C. This causes compression of the pleated bellows2or, respectively, a movement of the plate9closing it in an upward direction until a defined position to which a third signal value of the distance sensor12corresponds. The signal value is again determined and stored.

Subsequently, pressure medium is replenished until the plate9reaches a mechanical stop not shown, that is e.g. arranged in the first chamber3. Again, a signal value of the distance sensor12which is determined and stored corresponds to this top position of the (compressed) pleated bellows2. The mentioned signal value is especially appropriate in preventing destruction of the pleated bellows2.

After the signal value corresponding to the top position has been acquired, the replenished pressure medium volume is again bled until the position adjusted by replenishment of the defined pressure medium volume has been reached. In this position, the first chamber3is filled with a suitable gas by way of the first supply line13, whereafter the above-mentioned filling connection10is closed. Subsequently, the pressure medium that remained in the accumulator is bled until the bottom valve6closes. The filling operation is now terminated, and the accumulator with the determined signal values can be delivered.