Unit having at least one piston with an associated piston spring

1. An apparatus comprising:

a housing having a cavity therein and which at least in regions is configured as a bore in which at least one piston and one piston spring associated with the piston are received;

wherein the piston spring in the bore when activating the piston in the operation of the apparatus is compressed by the piston;

wherein an assembly unit which comprises the piston and the piston spring is provided for assembling the piston having the piston spring in the apparatus;

wherein the piston spring is configured from a magnetic or magnetizable material, the piston is configured from a non-magnetic material; and

wherein the piston spring in the assembly unit is held on the piston by a magnetic field.

2. The apparatus as claimed in claim 1 , wherein the magnetic field is generated by a magnetic element which is disposed in an assembly tool, wherein the piston when assembling is positioned between the magnetic element and the piston spring.

3. The apparatus as claimed in claim 2 , wherein the assembly tool is removed from the apparatus incorporating the assembly unit in the apparatus.

4. The apparatus as claimed in claim 1 , wherein the piston is designed so as to be substantially sleeve-shaped having a base and a tubular wall, wherein an internal side of the wall and an internal side of the base in the piston delimit a piston interior space, and the piston spring at least in regions is disposed in the piston interior space.

5. The apparatus as claimed in claim 2 , wherein the magnetic element for assembling is positioned in the region of the external side of the base such that the piston spring is pressed against the internal side of the base by the magnetic field.

6. The apparatus as claimed in claim 1 , wherein the piston spring has a loose clearance fit in relation to the piston.

7. The apparatus as claimed in claim 1 , wherein the piston spring is disposed so as to be coaxial with the piston.

8. The apparatus according to claim 4 , wherein an appendage for centering the piston spring which projects into the piston interior space is disposed on the internal side of the base, wherein the appendage at least in regions possesses a conical external contour portion, and wherein the piston spring has a clearance fit in relation to the appendage.

9. The apparatus as claimed in claim 2 , wherein the magnetic element is configured as a permanent magnet.

10. The apparatus as claimed in claim 2 , wherein the magnetic element configured as a solenoid, the magnetic field of the latter being present in an activated state of the magnetic element and not being present or not being present to a sufficient extent in a deactivated state of the magnetic element.

11. The apparatus as claimed in claim 1 , wherein the apparatus is designed as a master brake cylinder for a motor vehicle brake system.

12. The apparatus as claimed in claim 11 , wherein the master brake cylinder is configured in a tandem construction having at least two first pistons which are disposed coaxially behind one another and have the associated first piston spring and second pistons having the associated second piston spring, wherein at least one piston having the associated piston spring is provided as the assembly unit.

13. The apparatus as claimed in claim 1 , wherein the piston spring is configured from a ferromagnetic material.

14. An assembly tool for assembling a housing having a cavity therein and which at least in regions is configured as a bore in which at least one piston and one piston spring associated with the piston are received;

wherein the piston spring in the bore when activating the piston in the operation of the apparatus is compressed by the piston;

wherein an assembly unit which comprises the piston and the piston spring is provided for assembling the piston having the piston spring in the apparatus;

wherein the piston spring is configured from a magnetic or magnetizable material, the piston is configured from a non-magnetic material; and

wherein the piston spring in the assembly unit is held on the piston by a magnetic field, wherein the assembly tool for physically linking the piston to the assembly tool has an interface and at least one magnetic element in the region of the interface.

15. The method as recited in claim 14 , wherein the piston spring is configured from a magnetic or magnetizable material, and the piston is configured from a non-magnetic material, the method further comprising:

forming an assembly unit in that the piston conjointly with a piston spring which is spatially aligned with said piston is placed in a magnetic field of the assembly tool at a provided interface between the piston and the assembly tool;

introducing the assembly unit into the cavity in the housing of the apparatus; and

separating the assembly tool from the piston.

16. The method as recited in claim 14 , wherein the piston spring is configured from a magnetizable material.

17. The method as recited in claim 14 , wherein the piston spring is configured from a ferromagnetic material.