Centrifugal governor
The centrifugal governor is a machine element that uses the centrifugal force to regulate the speed of a machine .
The centrifugal governor , already known from mill construction , was introduced into general mechanical engineering by James Watt in 1788 . James Watt used the governor to keep the working speed constant of the steam engine he had improved . The dimensioning (dynamics of the transient response , tendency to oscillation and control characteristics) of the centrifugal governor for this task was the hour of birth of modern, mathematical control technology .
Function and types
Weight as a counterforce
The early design for regulating steam engines was driven by a belt , it used weight as a restoring force. At rest, the throttle valve of the steam line to the steam engine is fully open. When the piston of the steam engine moves, the governor begins to turn. As a result of this rotation, the two weights (e.g. made of cast iron ) are pulled upwards and outwards against the force of gravity by centrifugal force . A joint and lever mechanism (see toggle lever ) actuates a throttle valve in the steam line of the machine, which reduces the supply of steam to the machine. The machine then runs more slowly until a stable state or a constant speed is achieved. This arrangement is an example of a control loop with negative feedback (the faster the machine runs, the less steam is made available to it). The problem with the construction is the drive belt: Is there no transmission of the speed signal from the shaft to the controller, e.g. B. by a broken drive belt, the controller opens the steam supply completely. The steam engine runs at maximum speed until it is either switched off in an emergency or destroys itself.
Spring as a counterforce
In order to achieve a position-independent function, springs were mostly used later as a restoring force.
Examples:
- Number switch (coll. Dial, which is only the visible control element of the number switch) on older telephones: in which the finger-hole disc (coll. Also dial) rotates back under centrifugal force to keep the pulse sequence of the dialing pulses constant; the controller works on a small drum brake .
- The spring mechanism of the gramophone , film camera , camera , music box
- Centrifugal governor with contacts on the armature shaft of DC motors (especially series motors ): the contacts release a series resistor via slip rings in the circuit and keep the speed constant. This maintains the high starting torque.
- In music boxes , the playback speed is regulated by means of a centrifugal regulator, in which the rubber weights act as a brake through friction on one of the regulator's bearing plates.
literature
- W. Kriesel , H. Rohr, A. Koch: History and future of measurement and automation technology. VDI-Verlag, Düsseldorf 1995, ISBN 3-18-150047-X .
- H. Töpfer , W. Kriesel : Small automation through devices without auxiliary energy. Automation technology series, Vol. 173. Verlag Technik, Berlin 1976, 2nd edition 1978.
- H. Töpfer, W. Kriesel: Functional units of automation technology - electrical, pneumatic, hydraulic. Verlag Technik Berlin, VDI-Verlag Düsseldorf 1977, 2nd edition 1978, 3rd edition 1980, 4th edition 1983, 5th edition 1988, ISBN 3-341-00290-1 .
Web links
Individual evidence
- ↑ James Clerk Maxwell: On Governors . In: Proceedings of the Royal Society of London , Vol. 16. London 1868, pp. 270-283