| 摘要 |
The invention relates to a resistance welding machine in which workpieces to be welded together can be pressed together with a defined force by means of an electrically controlled hydraulic cylinder (18), which is configured as a differential cylinder having a high ratio F2/F1 of the piston surface (34) used for feed driving, represented by the value F2, to the smaller counter surface (27) of the drive piston (26), represented by the value F1. To control the drive an electrically controlled servo-control valve is provided for which works by mechanical actual-position feedback. To supply the hydraulic cylinder (18) with pressure a pressure accumulator (29) which can be charged with a high pressure Ph and a pressure accumulator (33) which can be charged with a lower pressure Pn are provided for. Before triggering the welding current Is the lower pressure Pn is injected into the drive-pressure chamber (36) of the hydraulic cylinder (18), which is defined over a large surface area. When the welding current pulse is triggered, and at least for the duration of said pulse, the high pressure Ph is injected. Both during feed operations, in which the workpieces support each other via welding projections and during a make-up operating mode due to the melting of the welding projection, said higher pressure Ph is injected into the drive-pressure chamber (28) defined over a small surface area.
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