Saxomat

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Representation of the Saxomat control box (pneumatic valve control):

1 - electromagnet;
2 - solenoid operated valve;
3 - check valve;
4 - pressure reducer;
5 - pressure control valve (negative pressure);
A - vacuum chamber;
B - overflow area;
C - ambient pressure .

The valve is activated, the clutch is open

Under the name Saxomat , derived from the manufacturer's name Fichtel & Sachs , an electro-pneumatic clutch was offered from 1956 (initially for DKW) until the end of the 1960s, which was used, for example, in vehicles from the manufacturers Borgward , DKW , Fiat, Lancia, Opel , Saab or VW was available.

The Saxomat was available from 1959 in the Opel Rekord P1 as the " Olymat ". As early as August 1957, Daimler-Benz offered the Hydrak, which was available in the Mercedes 219 sedan for a surcharge of DM 450  and, unlike the Saxomat, had a hydraulic start-up clutch. NSU used a similar system in the Ro 80.

The Saxomat could not really establish itself on the market. This is attributed to the unreliability of the system and the difficult adjustability, which also led to the fact that many vehicles were upgraded to a normal manual transmission. Start-up comfort and imprecise maneuvering were often criticized. This technology also sometimes proved to be vulnerable.

technology

The Saxomat was a further development of the F&S roller centrifugal clutch and was intended to be a cost-effective alternative to the automatic transmission . In terms of price, the Saxomat was between a normal manual and an automatic transmission.

Essentially, the Saxomat works with two clutches connected in series and one freewheel :

  • The centrifugal roller clutch is closed depending on the engine speed. Above the idling speed (950..1000 / min) this clutch closes so that the full torque can be transmitted at around 1500 / min.
  • However, the centrifugal clutch only works in pulling mode (when engine torque is to be transferred to the drive axle); a freewheel is connected in parallel to it, which bypasses it in pushing mode.
  • If the accelerator is removed, the engine brakes up to idle speed, because in overrun mode the drag torque of the drive axle remains connected to the transmission via the freewheel operated in the reverse direction, although the centrifugal clutch has released.
  • Because the centrifugal clutch is bypassed by the freewheel, the vehicle can be parked both uphill with reverse gear engaged and downhill with forward gear engaged. Towing is also possible.

In principle, you can start up in any gear with the starting clutch, but in higher gears the time increases until the speed of 1500 rpm. has been reached and the clutch wear increases.

Regardless of this, the power flow can be separated with a second clutch so that a gear change is possible even at higher speeds:

  • If the selector lever provided with a switch is touched, this second clutch opens with the aid of a vacuum unit. The vacuum unit is connected to the intake manifold of the engine via a solenoid valve.
  • If the selector lever is released, the solenoid valve switches off, air can slowly flow back into the can and the clutch closes again.
  • The coupling process is controlled correspondingly smoothly by throttling the air flowing back. The delay is variable and depends on whether and how much the driver accelerates.
  • The more the driver accelerates, the faster the clutch closes. This is to prevent the engine from revving up without load.

The freewheel has no influence on the second clutch, so that this clutch can always separate the power flow.

See also

literature

  • Eckhard Kirchner: Power transmission in vehicle transmissions . Springer-Verlag, 2007, ISBN 978-3-540-35288-4 , chap. 1.2 "History of Vehicle Transmissions".
  • Keller, H .: "The fully automatic clutch 'Saxomat'" in the Automobiltechnischen Zeitschrift (ATZ) 59 (1951) pp. 212-214.
  • Patent DE1027530 : Speed- dependent clutch, in particular centrifugal clutch with a disconnect clutch operated by foot or external force, especially for motor vehicles. Registered on March 16, 1955 , published on April 3, 1958 , applicant: Fichtel & Sachs AG, Schweinfurt / M., Inventor: Richard Binder, Schweinfurt. ‌

Web links

Individual evidence

  1. ↑ word brand of ZF Friedrichshafen AG, DPMA register number DD623601 ; Nice class 23: Couplings, coupling parts, parts for operating clutches; Gearboxes, especially gearboxes
  2. ↑ Harald Naunheimer, Bernd Bertsche, Gisbert Lechner, "Vehicle transmission", Springer-Verlag Berlin Heidelberg, 2nd edition 2007, ISBN 978-3-540-30625-2
  3. ↑ Heiner Bubb, Klaus Bengler, Rainer E. Grünen, Mark Vollrath "Automobilergonomie", Springer Fachmedien Wiesbaden 2015, ISBN 978-3-8348-1890-4 , section 1.4.2