Method for tightening a screw connection by means of an impact screwdriver having a variable speed electric drive motor

US6167606A · kind A · utility

Assignee

• Robert Bosch GmbH · DE

Inventors

• Gerold Mueller · Ulm, DE
• Peter Wolf · Wiesbaden, DE
• Heinz Veitinger · Murrhardt, DE

Key dates

• Filing date: Dec 15, 1995
• Grant date: Jan 2, 2001
• Expiry date: Dec 15, 2015

Classification

• Technology area (CPC Y): Emerging Cross-Sectional Technologies
• CPC primary: Y10T29/49766
• WIPO field: Machine tools
• WIPO sector: Mechanical engineering

Abstract

The screwdriving device (9) according to the invention has a control device (22) which uses a sensor system (18) to determine a characteristic variable (K) which characterizes a screwdriving moment (M.sub.v) of the screw connection (10) and/or an emitted moment (M) of the impact screwdriver, during or after at least one pulse emission from the impact screwdriver to the screw connection, and defines a drive variable, for example a required drive speed (n) for the next impulse emission, as a function of the determined characteristic variable (K.sub.i). In this case, the drive variable (n) is initially set to a value which corresponds to a value (K.sub.0) to be expected of the characteristic variable (K) and its magnitude is in any case less than a desired value (K.sub.req) for the final screw connection state. This prevents the desired screwdriving moment being exceeded even after the first impulse emission in the event of unfavorable screwdriving conditions. Instead of this, the desired final screw connection state is approached step by step, in a controlled manner.