The invention relates to a filter device for filtering a hydraulic fluid comprising a housing having fluid through-openings for hydraulic fluid to be filtered to flow into the housing and for filtered hydraulic fluid to flow out of the housing, and having an assembly opening for inserting a filter element into the housing, the assembly opening being closable by a cover.
Such filter devices are used in different applications in hydraulic systems, in particular, in automotive machines such as, for example, construction machinery or agricultural machines. In particular, mineral oils for hydraulic systems can be filtered with such filter devices.
Filter devices of the kind mentioned at the outset are configured, in particular, as suction filters, as return filters or as return-suction filters. Suction filters are usually arranged upstream of a pump and are often installed in a storage tank for hydraulic fluid. Hydraulic fluid which is removed from the storage tank can be filtered by means of the suction filters, and the hydraulic fluid can then be supplied to the pump.
Return filters are usually arranged downstream of a hydraulic consumer, for example, a hydraulic cylinder. The hydraulic fluid flowing back into a storage tank can be filtered by means of these. Return filters are often also installed in the storage tank.
Return-suction filters assume the function of a return filter and a suction filter. By means of these, the hydraulic fluid flowing off from a hydraulic consumer can be filtered and then supplied to a pump. If the volumetric flow of the hydraulic fluid flowing off from the hydraulic consumer is greater than the volumetric flow delivered by the pump, i.e., in the case of an oversupply, the excess amount of hydraulic fluid flowing off can be filtered and then fed to a storage tank. If the volumetric flow flowing off from the hydraulic consumer is less than the volumetric flow delivered by the pump, i.e., in the case of an insufficient supply, hydraulic fluid can be taken from the storage tank and added to the filtered hydraulic fluid. To ensure that the filtered hydraulic fluid has a prescribable pressure level in the case of an oversupply, return-suction filters usually comprise a so-called pressurizing valve which only enables a flow connection to the storage tank when a prescribed pressure level is exceeded. Common return-suction filters additionally comprise a suction valve which in the case of an insufficient supply provides a flow connection from the storage tank to the clean side of the filter element.
The object of the present invention is to further develop a filter device of the kind mentioned at the outset such that it can be selectively configured in a cost-effective manner as suction filter, return filter or return-suction filter.